WO2023033064A1 - Refractive index adjustment agent and use thereof - Google Patents

Abstract

Provided is a refractive index adjustment agent for adjusting the refractive index of adhesives, wherein this refractive index adjustment agent for adhesives is an organic compound comprising a structure having at least two substituents on a hub ring. This hub ring is a double bond-containing ring, and at least one of the at least two substituents is a substituent that has a double bond-containing ring.

Description

Refractive index modifier and its use

The present invention relates to a refractive index adjuster and an adhesive and adhesive sheet using the refractive index adjuster. This application claims priority based on Japanese Patent Application No. 2021-145046 filed on September 6, 2021, the entire contents of which are incorporated herein by reference.

In general, pressure-sensitive adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of easily adhering to adherends under pressure. Taking advantage of such properties, pressure-sensitive adhesives are widely used for the purposes of bonding, fixing, protection, etc. in various industrial fields such as home electric appliances, automobiles, various machines, electrical equipment, and electronic equipment. As an example of the application of adhesives, in display devices such as liquid crystal display devices and organic EL display devices, polarizing films, retardation films, cover window members, and other various light-transmitting members and other members are joined. The use to do is mentioned. Patent Documents 1 and 2 are cited as technical documents relating to pressure-sensitive adhesives for optical members.

Japanese Patent Application Publication No. 2014-169382 Japanese Patent Application Publication No. 2017-128732

Patent Documents 1 and 2 relate to a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer as a main component, wherein the (meth)acrylic acid ester polymer contains a predetermined amount of a monomer having a plurality of aromatic rings as a monomer unit. Thus, it is proposed that the obtained pressure-sensitive adhesive has a high refractive index (paragraph [0011], etc.). For example, among the materials to which adhesives are attached, such as optical members, there are materials with high refractive indices. It is known that reflection occurs at the interface due to By using an adhesive having a refractive index close to that of the high refractive index material as the adhesive used for joining the high refractive index material, the interface reflection can be prevented or suppressed. In addition, the refractive index of a general acrylic pressure-sensitive adhesive is usually about 1.47.

On the other hand, the refractive index of the material that can be the adherend of the adhesive varies, and the composition (type and content ratio) of the monomer units that make up the base polymer of the adhesive is designed according to the refractive index of each adherend. is not always efficient. For example, it would be beneficial to be able to adjust the refractive index of the pressure-sensitive adhesive using an additive component separate from the base polymer. Incidentally, Patent Documents 1 and 2 list a refractive index modifier as an example of an optional component that can be optionally added to the pressure-sensitive adhesive composition (paragraph [0054]). There is no description about the structure, and it is unknown whether it is an organic substance or an inorganic substance.

The present invention was created in view of the above circumstances, and an object of the present invention is to provide a refractive index adjuster for adjusting the refractive index of an adhesive. Another object of the present invention is to provide a pressure-sensitive adhesive containing the refractive index modifier. Another related object is to provide a compound useful as the refractive index modifier.

According to this specification, a refractive index adjuster for adhesives is provided. The refractive index modifier is an organic compound having a structure having two or more substituents on the hub ring. Here, the hub ring is a double bond-containing ring, and one or more of the two or more substituents are substituents having a double bond-containing ring. A compound that satisfies such structural requirements is used as a constituent component of an adhesive and is useful as a refractive index adjuster that appropriately adjusts the refractive index of the adhesive.

Techniques disclosed herein (includes a refractive index modifier, an adhesive composition containing the refractive index modifier, an adhesive containing the refractive index modifier, an adhesive sheet containing the adhesive, and the like; the same shall apply hereinafter) In some aspects of , the molecular weight of the refractive index modifier is less than 3,000. It is preferable that the molecular weight of the refractive index adjuster is less than 3000 from the viewpoint of ease of blending with the pressure-sensitive adhesive.

In some embodiments, two or more of the substituents on the hub ring of the refractive index modifier have a double bond-containing ring. A refractive index adjuster having such a structure can be used as a constituent component of an adhesive to efficiently adjust the refractive index of the adhesive (for example, to increase the refractive index).

In some embodiments, one or more of the substituents on the hub ring of the refractive index adjuster has two or more double bond-containing rings. A refractive index adjuster having such a structure can be used as a constituent component of an adhesive to efficiently adjust the refractive index of the adhesive (for example, to increase the refractive index).

（式（Ｉ）中、Ｘ^１，Ｘ^２およびＸ^３は、それぞれ独立に、－Ｏ－，－Ｓ－および－ＮＲ^４－からなる群から選択され、ここでＲ^４は水素原子またはアルキル基であり、
　Ｒ^１，Ｒ^２およびＲ^３のうち１つ以上は、それぞれ独立に、置換基を有していてもよいフェニル基および置換基を有していてもよいビフェニル基からなる群から選択される芳香環含有基であり、上記置換基はアルキル基、アルコキシ基またはシアノ基であり、
　Ｒ^１，Ｒ^２およびＲ^３のうち上記芳香環含有基が２つ以下である場合、残りは脂肪族炭化水素基または水素原子である。）；
で表されるトリアジン化合物であり得る。このような構造を有する屈折率調整剤は、粘着剤の構成成分として用いられて、該粘着剤の屈折率を好適に調整（例えば高屈折率化）することができる。 Preferred examples of the refractive index adjusters disclosed herein include those in which the hub ring is a triazine ring. For example, the refractive index modifier has the following formula (I):

(In formula (I), X ¹ , X ² and X ³ are each independently selected from the group consisting of —O—, —S— and —NR ⁴ —, where R ⁴ is a hydrogen atom or an alkyl group and
One or more of R ¹ , R ² and R ³ are each independently an aromatic selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group a ring-containing group, wherein the substituent is an alkyl group, an alkoxy group or a cyano group;
When the above aromatic ring-containing groups are two or less among R ¹ , R ² and R ³ , the rest are aliphatic hydrocarbon groups or hydrogen atoms. );
It may be a triazine compound represented by A refractive index adjuster having such a structure is used as a constituent component of an adhesive, and can suitably adjust the refractive index of the adhesive (for example, increase the refractive index).

According to this specification, a pressure-sensitive adhesive containing any one of the refractive index modifiers disclosed herein is provided. A pressure-sensitive adhesive having such a composition can exhibit a desired refractive index adjusted by the refractive index adjuster.

The adhesive disclosed herein preferably contains the refractive index adjuster and an acrylic polymer containing the aromatic ring-containing monomer (m1) as a monomer unit. A pressure-sensitive adhesive having such a composition can easily achieve a desired high refractive index (for example, a refractive index of 1.550 or more).

（式（Ｉ）中、Ｘ^１，Ｘ^２およびＸ^３は、それぞれ独立に、－Ｏ－，－Ｓ－および－ＮＲ^４－からなる群から選択され、ここでＲ^４は水素原子またはアルキル基であり、
　Ｒ^１，Ｒ^２，Ｒ^３のうち１つ以上は、それぞれ独立に、置換基を有していてもよいフェニル基および置換基を有していてもよいビフェニル基からなる群から選択される芳香環含有基であり、上記置換基はアルキル基、アルコキシ基またはシアノ基であり、
　Ｒ^１，Ｒ^２およびＲ^３のうち上記芳香環含有基が２つ以下である場合、残りは脂肪族炭化水素基または水素原子である。）；
で表される化合物が提供される。かかる化合物は、例えば屈折率調整剤（特に、粘着剤用の屈折率調整剤）として有用である。 According to this specification, the following formula (I):

(In formula (I), X ¹ , X ² and X ³ are each independently selected from the group consisting of —O—, —S— and —NR ⁴ —, where R ⁴ is a hydrogen atom or an alkyl group and
One or more of R ¹ , R ² , and R ³ are each independently an aromatic selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group a ring-containing group, wherein the substituent is an alkyl group, an alkoxy group or a cyano group;
When the above aromatic ring-containing groups are two or less among R ¹ , R ² and R ³ , the rest are aliphatic hydrocarbon groups or hydrogen atoms. );
A compound represented by is provided. Such compounds are useful, for example, as refractive index modifiers (in particular, refractive index modifiers for adhesives).

Any suitable combination of the elements described in this specification may also be included in the scope of the invention for which patent protection is sought by this patent application.

1 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to one embodiment; FIG. FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment; 1 is a ¹ H-NMR spectrum of compound A1 according to Synthesis Example 1. FIG. 1 is a ¹³ C-NMR spectrum of compound A1 according to Synthesis Example 1. FIG. 1 is a ¹ H-NMR spectrum of compound A2 according to Synthesis Example 2. FIG. 2 is a ¹³ C-NMR spectrum of compound A2 according to Synthesis Example 2. FIG. 1 is a ¹ H-NMR spectrum of compound A3 according to Synthesis Example 3. FIG. 2 is a ¹³ C-NMR spectrum of compound A3 according to Synthesis Example 3. FIG. 1 is an enlarged view showing a main part of the ¹ H-NMR spectrum of compound A4 according to Synthesis Example 4. FIG. FIG. 4 is an enlarged view showing the main part of the ¹³ C-NMR spectrum of compound A4 according to Synthesis Example 4; 1 is a ¹ H-NMR spectrum of compound A5 according to Synthesis Example 5. FIG. 2 is a ¹³ C-NMR spectrum of compound A5 according to Synthesis Example 5. FIG. 2 is a ¹ H-NMR spectrum of compound A6 according to Synthesis Example 6. FIG. 2 is a ¹³ C-NMR spectrum of compound A6 according to Synthesis Example 6. FIG. 1 is a ¹ H-NMR spectrum of compound A7 according to Synthesis Example 7. FIG. 2 is a ¹³ C-NMR spectrum of compound A7 according to Synthesis Example 7. FIG. 2 is a ¹ H-NMR spectrum of compound A8 according to Synthesis Example 8. FIG. 2 is a ¹³ C-NMR spectrum of compound A8 according to Synthesis Example 8. FIG.

Preferred embodiments of the present invention are described below. Matters other than those specifically referred to in this specification that are necessary for the implementation of the present invention are applicable based on the teaching of the implementation of the invention described in this specification and the common general knowledge at the time of filing. understandable to traders. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.
In the drawings below, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the embodiments described in the drawings are schematics for the purpose of clearly explaining the present invention and do not necessarily represent the size or scale of the products actually provided.

As used herein, the term "double bond-containing ring" is a concept that includes conjugated double bond-containing rings and non-conjugated double bond-containing rings, preferably at least one of an aromatic ring and a heterocyclic ring (heterocyclic ring). This is the corresponding ring. The heterocyclic ring may have a structure included in an aromatic ring (heteroaromatic ring), or may have a double bond-containing heterocyclic ring structure different from the aromatic ring. The heteroatoms included as ring-constituting atoms in the heterocyclic ring may be one or more selected from the group consisting of nitrogen (N), sulfur (S) and oxygen (O), for example. Specific non-limiting examples of the double bond-containing ring include a benzene ring; a condensed ring of a naphthalene ring, an indene ring, an azulene ring, anthracene ring, and a phenanthrene ring; heterocycles such as pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, oxazole ring, isoxazole ring, thiazole ring, thiophene ring; The double bond-containing ring may be a non-condensed ring (benzene ring, triazine ring, etc.) or a condensed ring. The condensed ring may have a structure in which one or more carbon rings and one or more heterocycles are condensed, such as a dinaphthothiophene structure or a benzotriazole structure.

Unless otherwise specified, the double bond-containing ring in this specification may or may not have one or more substituents on the ring-constituting atoms. In this specification, examples of "substituents" include alkyl groups (e.g., alkyl groups having 1 to 12 carbon atoms), aryl groups (phenyl groups, naphthyl groups, biphenyl groups, etc.), and has one or more acyclic substituents such as an alkyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyl group, an amino group, a monoalkylamino group, a dialkylamino group, or a cyano group. ), cycloalkyl group, hydroxyalkyl group, monoalkylamino group, dialkylamino group, glycidyl group, aralkyl group (for example, 1 to 12 carbon atoms, preferably 1 to 8 hydrogen atoms of an alkyl group The above are groups substituted with the above aryl groups), ethylenically unsaturated groups such as alkenyl groups (e.g. vinyl groups, allyl groups) and (meth)acryloyl groups, ether bonds in the middle of the chain structures of these groups , a group interposed by one or more bonds selected from the group consisting of a thioether bond and an ester bond (e.g., an ethoxyethyl group, an ethoxyethoxyethyl group, a phenoxyethyl group), one of the hydrogens bonded to carbon in these groups Groups partially or wholly substituted with halogen atoms (fluorine, chlorine, bromine, etc.) groups, groups having a heteroatom such as O, S, N at the end of the double bond-containing ring side of these groups (e.g. , an alkoxy group, an aryloxy group, a cycloalkyloxy group, a hydroxyalkyloxy group, a glycidyloxy group, an alkylthio group, a (meth)acryloyloxy group, When the heteroatom is N, the remaining valences of the N are hydrogen atoms or other substituents), hydroxyl groups, amino groups, cyano groups, halogen atoms (fluorine, chlorine, bromine atoms, etc.), etc., but are not limited thereto. Examples of the above substituents include those having a double bond-containing ring (e.g., aryl groups, aralkyl groups, groups having a heteroatom such as O, S, N, etc. at the end of these groups on the ring-constituting atom side). , and those that do not have a double bond-containing ring (eg, alkyl groups, alkoxy groups, alkylthio groups, etc.).

In this specification, the "base polymer" of the adhesive refers to the main component of the rubber-like polymer contained in the adhesive. The term "rubber-like polymer" refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

In this specification, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as "acrylic monomer". Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomeric units derived from an acrylic monomer. Typical examples of acrylic polymers include acrylic polymers in which more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of monomer components constituting the polymer are acrylic monomers.

Also, in this specification, the term "acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. Here, "(meth)acryloyl group" is meant to comprehensively refer to acryloyl groups and methacryloyl groups. Therefore, the concept of an acrylic monomer as used herein can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" means acrylic acid and methacrylic acid, and "(meth)acrylate" means acrylate and methacrylate, respectively. The same applies to other similar terms.

<Refractive index adjuster>
The refractive index adjuster disclosed by this specification is an organic compound having a structure having a hub ring and two or more substituents bonded to constituent atoms of the hub ring. Here, the hub ring is a double bond-containing ring, and at least one of the two or more substituents is a substituent having a double bond-containing ring. A compound that satisfies such structural requirements is used as a constituent component of an adhesive and is useful as a refractive index adjuster that adjusts the refractive index of the adhesive.

The refractive index modifier disclosed herein may be a non-polymer and has the structure described above (that is, a structure having a hub ring and two or more substituents bonded to constituent atoms of the hub ring). may be a polymer having two or more repeating units of When the refractive index modifier is a polymer, the number of repeating units in the polymer is, for example, 2 to 30 or 2 to 10, preferably 2 to 6, more preferably 2 to 4 (eg, 2 to 3 ).

The molecular weight of the refractive index modifier is not particularly limited, and can be appropriately selected within a range in which the intended function can be exhibited. The molecular weight of the refractive index modifier may be, for example, approximately less than 10,000, less than 7,000, less than 5,000, less than 3,500, or 3,000 or less. In some aspects, the molecular weight of the refractive index modifier is advantageously less than 3000, preferably less than 2000 or less than 2000, and less than 1500 or It is more preferably less than 1500, may be 1000 or less or less than 1000, may be 800 or less or less than 800, may be 700 or less or less than 700, or may be 650 or less or less than 650. Further, the molecular weight of the refractive index adjuster may be, for example, 150 or more, 200 or more, or 250 or more. In some embodiments, from the viewpoint of facilitating the function of adjusting the refractive index (for example, increasing the refractive index), the molecular weight of the refractive index adjusting agent is suitably 300 or more, preferably 350 or more. is preferably 400 or more, and may be 430 or more, 470 or more, 500 or more, or 550 or more. It is preferable that the molecular weight of the refractive index adjuster is not too low from the viewpoint of the heat resistance of the pressure-sensitive adhesive and the suppression of contamination of the adherend.

The molecular weight of the refractive index modifier is calculated based on the chemical structure when the refractive index modifier is a non-polymer or a polymer with a low degree of polymerization (for example, about 2- to 5-mers). Molecular weight or measurements using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) can be used. For polymers with a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When the nominal value of the molecular weight is provided by the manufacturer or the like, the nominal value can be adopted.

The hub ring in the refractive index adjuster disclosed herein is typically a double bond-containing ring corresponding to at least one of an aromatic ring and a heterocyclic ring (preferably heteroaromatic ring). The hub ring may be a non-condensed ring (single ring) or a condensed ring, but is preferably a non-condensed ring (eg, 3- to 8-membered ring, preferably 5- to 7-membered ring). In some preferred embodiments, the hub ring is a non-fused heteroaromatic ring. The number of heteroatoms contained as ring-constituting atoms in the heteroaromatic ring may be 1 or 2 or more, for example, 1-3. In some embodiments, heteroaromatic rings in which at least one of the heteroatoms contained as ring-constituting atoms is N are preferred, and heteroaromatic rings in which all of the above heteroatoms are N are more preferred. An example of a particularly preferred heteroaromatic ring is a triazine ring.

The number of substituents bonded to the ring-constituting atoms of the hub ring is typically 2 or more and the number of the ring-constituting atoms or less, for example, 3 or more and the number of the ring-constituting atoms or less. Among the above substituents, the number of substituents having a double bond-containing ring may be 1 or more, 2 or more, or 3 or more. Among the substituents, the number of substituents having no double bond-containing ring may be 0, may be 1 or more and the total number of the substituents −1 or less, or may be 1 or more and the total number of the substituents −2 It can be below. The total number of substituents refers to the total number of substituents bonded to the ring-constituting atoms of the hub ring, regardless of whether the substituents have a double bond-containing ring.

Of the substituents bonded to the ring-constituting atoms of the hub ring, those having a double bond-containing ring can contribute to improving the refractive index. Refractive index improvers according to some aspects have two or more substituents having a double bond-containing ring on the hub ring. A refractive index adjuster having such a structure can be used as a constituent component of an adhesive to efficiently adjust the refractive index of the adhesive (for example, to increase the refractive index).

In the above substituent having a double bond-containing ring, the number of double bond-containing rings possessed by the substituent may be 1, or 2 or more. Here, having two or more double bond-containing rings means having two or more double bond-containing rings that are not mutually condensed. Each double bond-containing ring may independently be a non-fused ring or a fused ring. Having a substituent having two or more double bond-containing rings on the hub ring can be advantageous from the viewpoint of improving the refractive index. Refractive index improvers according to some embodiments have one or more (preferably two or more, for example three) substituents having two or more double bond-containing rings on the hub ring. A refractive index adjuster having such a structure can be used as a constituent component of an adhesive to efficiently adjust the refractive index of the adhesive (for example, to increase the refractive index).

In the substituent having two or more double bond-containing rings, the two or more double bond-containing rings may be chemically bonded directly (i.e., without intervening other atoms), such as in a biphenyl structure. Alternatively, they may be linked via a linking group. The linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (eg, -O-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1). , a thiooxyalkylene group (such as a —S—(CH ₂ ) _n — group, where n is 1 to 3, preferably 1), a linear alkylene group (ie, a —(CH ₂ ) _n — group, where n is 1 to 6, preferably 1 to 3), —NR ⁴ — group (R ⁴ is a hydrogen atom or an alkyl group (eg, an alkyl group having 1 to 3 carbon atoms, preferably 1)), —NR ⁴ —( CH ₂ ) _n — group (where n is 1 to 3, preferably 1, and R ⁴ is a hydrogen atom or an alkyl group (eg, an alkyl group having 1 to 3 carbon atoms, preferably 1)), the above The oxyalkylene group, the thiooxyalkylene group, the straight-chain alkylene group, and the alkylene group in the —NR ⁴ —(CH ₂ ) _n — group may be a partially or completely halogenated group, and the like. The linking group may have an ester bond. The number of atoms of the linking group is, for example, 1 to 6, preferably 1 to 4, may be 1 to 2, may be 2, or may be 1. The number of atoms in the linking group refers to the minimum number of atoms required to reach from one double bond-containing ring to the other double bond-containing ring. For example, when the linking group consists of a linear alkylene group (ie, -(CH ₂ ) _n - group), the number n is the number of atoms in the linking group. Preferable substituents from the viewpoint of increasing the refractive index include substituents containing structures in which the two or more double bond-containing rings are directly chemically bonded or bonded via an oxy group or a thiooxy group. .

In some preferred embodiments, the above substituent having a double bond-containing ring is such that a heteroatom (e.g., O, S or N, preferably O or S) of the substituent is attached to a ring-constituting atom (e.g., carbon atoms). A compound having such a structure is preferable because it can be suitable for increasing the refractive index of the compound itself or a composition containing the compound. A heteroatom bonded to a ring-constituting atom of the hub ring may be a ring-constituting atom of the double bond-containing ring (heterocyclic ring) in the substituent having the double bond-containing ring. It may be an atom constituting a linking group connecting with the hub ring. Examples of the linking group include a thiooxy group, an oxyalkylene group (eg —O—(CH ₂ ) _n — group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (eg —S—( CH ₂ ) _n — group, where n is 1 to 3, preferably 1), —NR ⁴ — group, —NR ⁴ —(CH ₂ ) _n — group (n is 1 to 3, preferably 1, R ⁴ is a hydrogen atom or an alkyl group (eg, an alkyl group having 1 to 3 carbon atoms, preferably 1). The number of atoms of the linking group that connects the double bond-containing ring and the hub ring is, for example, 1 to 6, preferably 1 to 4, may be 1 to 2, may be 2, or may be 1. The number of atoms in the linking group means the minimum number of atoms required to reach the double bond-containing ring of the substituent from the hub ring.

The double bond-containing ring possessed by the substituent bonded to the ring-constituting atoms of the hub ring is typically a ring corresponding to at least one of an aromatic ring and a heterocyclic ring, preferably a non-condensed ring. The above double bond-containing ring has, on its ring-constituting atoms, one or more substituents other than the substituents bonded to the hub ring and the substituents bonded to other double bond-containing rings. may Examples of such substituents include alkyl groups, alkoxy groups, alkylthio groups, alkenyl groups, (meth)acryloyl groups, (meth)acryloyloxy groups, halogen atoms, hydroxyl groups, amino groups, monoalkylamino groups, dialkylamino groups. , acyclic substituents such as cyano groups; and substituents having non-double bond-containing rings such as cycloalkyl groups, cycloalkyloxy groups, and norbornyl groups. In the above alkyl group, alkoxy group, alkylthio group, alkenyl group, monoalkylamino group and dialkylamino group, the number of carbon atoms in the alkyl group contained in each group is, for example, 1 to 6, preferably 1 to 4. , may be 1 to 2, may be 2, or may be 1.

In some preferred embodiments, the double bond-containing ring of the substituents attached to the ring-constituting atoms of the hub ring is an aromatic ring (preferably a carbon aromatic ring, particularly preferably a benzene ring) with or without a substituent. is. For example, at least one (for example, 1, 2 or 3) of the ring-constituting atoms of the hub ring has the following formula (II):
—X(CH ₂ ) _n —Ar(Y) _m (II)
(In formula (II) above, X is selected from the group consisting of —O—, —S— and —NR ⁴ — (wherein R ⁴ is a hydrogen atom or an alkyl group), preferably —O— or —S -, n is 0 to 3, preferably 0 or 1, more preferably 0. Ar is an aromatic ring, preferably a carbon aromatic ring, particularly preferably a benzene ring, Y is , are substituents on the ring-constituting atoms of Ar and are each independently an alkyl group (eg, an alkyl group having 1 to 3 carbon atoms, preferably 1), a cyano group, a hydroxyl group, a phenyl group, a tolyl group, a xylyl group and a phenoxy group, m is 0 to 3, preferably 0 or 1, more preferably 1);
A compound having a structure in which a substituent represented by is bonded is preferable.

The refractive index adjuster disclosed herein may have only the substituents having the double bond-containing ring as the substituents bonded to the ring-constituting atoms of the hub ring. Such a structure allows more substituents having a double bond-containing ring to be bonded to the hub ring, and is suitable for increasing the refractive index. On the other hand, the refractive index modifier disclosed herein has a substituent having a double bond-containing ring and a substituent having no double bond-containing ring as substituents bonded to the ring-constituting atoms of the hub ring. You may have In some embodiments, having a substituent that does not have a double bond-containing ring on the hub ring can contribute to improving solubility in solvents and compatibility in adhesives.

In the embodiment in which at least one of the substituents bonded to the ring-constituting atoms of the hub ring is a substituent having no double bond-containing ring, each of the substituents having no double bond-containing ring is independently selected from, for example, alkyl group, cycloalkyl group, hydroxyalkyl group, alkoxy group (e.g. methoxy group, ethoxy group), hydroxyalkyloxy group, glycidyloxy group, alkylthio group (-S-C _n H _2n+1 group), monoalkylamino group, dialkylamino group, alkenyl group, (meth)acryloyl group, (meth)acryloyloxy group, one or more bonds selected from the group consisting of ether bond, thioether bond and ester bond intervening in the chain structure of these groups groups, groups in which some or all of the hydrogens bonded to carbon in these groups are replaced with halogen atoms (fluorine, chlorine, bromine, etc.), hydroxyl groups, amino groups, cyano groups or halogen atoms .

Among the above examples of substituents having no double bond-containing ring, those containing an alkyl group in the substituent (alkyl group, alkoxy group, alkylthio group, ethoxyethyl group, etc.), the carbon atom of each alkyl group The number is, for example, 1-12, preferably 2-12, 4-12 or 6-10 in some embodiments, and 1-6, 1-4 or 1-2 in some other embodiments. When the number of atoms in the alkyl group is 3 or more, the alkyl group may be linear or branched. Specific examples of branched alkyl groups include 2-ethylhexyl, isooctyl and isononyl groups.
Preferable examples of substituents having no double bond-containing ring include alkoxy groups (eg, alkoxy groups having 1 to 12, 1 to 8, 1 to 6, 1 to 4 or 1 to 2 carbon atoms) and alkylthio groups. (eg, an alkylthio group having 2 to 12, 4 to 12 or 6 to 10 carbon atoms).

Suitable examples of the refractive index modifier disclosed herein include triazine compounds represented by the following formula (I).

Here, in formula (I) above, X ¹ , X ² and X ³ are each independently selected from the group consisting of -O-, -S- and -NR ⁴ . Here, R ⁴ is a hydrogen atom or an alkyl group (eg, an alkyl group having 1 to 3 carbon atoms). One or more of R ¹ , R ² and R ³ are each independently an aromatic selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group It is a ring-containing group. When the above aromatic ring-containing groups are two or less among R ¹ , R ² and R ³ , the rest are aliphatic hydrocarbon groups or hydrogen atoms.

In the above formula (I), when the phenyl group or the biphenyl group has a substituent, the substituent is each independently an alkyl group (e.g., an alkyl group having 1 to 3 carbon atoms), an alkoxy group (e.g., , an alkoxy group having 1 to 3 carbon atoms) and a cyano group. The aliphatic hydrocarbon group is an alkyl group having 1 to 12, 1 to 8, 1 to 6, 1 to 4 or 1 to 2 carbon atoms, or an alkyl group having 2 to 12, 4 to 12 carbon atoms or An alkyl group of 6 to 10 is preferred.

In formula (I) above, X ¹ , X ² and X ³ may be the same or different. From the viewpoint of increasing the refractive index, it is advantageous that two or more of X ¹ , X ² and X ³ are selected from —O— and —S—, and preferred examples are X ¹ , X ² and compounds wherein all of X ³ are -O-, compounds wherein two or more of X ¹ , X ² and X ³ are -S-, compounds wherein all of X ¹ , X ² and X ³ are -S- , etc. Among them, compounds in which X ¹ , X ² and X ³ are all -S- are preferred.

In formula (I) above, R ¹ , R ² and R ³ may be the same or different. From the viewpoint of increasing the refractive index, R ¹ , R ² and ^{R 3 are all} preferably ^aromatic ring-containing groups. Preferably. Among them, compounds in which R ¹ , R ² and R ³ are all optionally substituted biphenyl groups (for example, R ¹ , R ² and R ³ are all unsubstituted biphenyl groups) compound) is particularly preferable from the viewpoint of increasing the refractive index. When one, two or three of R ¹ , R ² and R ³ are optionally substituted biphenyl groups, the biphenyl group is, from the viewpoint of ease of synthesis, 2-biphenyl or 4-biphenyl. Here, 2-biphenyl means that the corresponding X ¹ , X ² and X ³ are bonded to the 2-position (ortho-position) carbon of the biphenyl group, and 4-biphenyl means the corresponding X It means that ¹ , X ² and X ³ are bonded to the 4-position (para-position) carbon of the biphenyl group. Compounds in which R ¹ , R ² and R ³ in formula (I) are all 2-biphenyl groups are particularly preferred from the viewpoint of increasing the refractive index and solubility in solvents.

The compound represented by the above formula (I) includes, for example, commercially available halogenated triazine compounds (cyanuric chloride, 2-(4-cyanophenyl)amino-4,6-dichloro-1,3, 5-triazine, etc.) with an alcohol compound or a thiol compound depending on the structure of the target product.

The refractive index of the refractive index adjuster disclosed herein is not particularly limited as long as it can be blended with the pressure-sensitive adhesive to adjust the refractive index of the pressure-sensitive adhesive to a desired range. The refractive index of the refractive index modifier can be, for example, within the range of 1.500 to 2.000. In addition, the refractive index of the refractive index adjuster means the refractive index measured under conditions of a measurement temperature of 25° C. and a measurement wavelength of 594 nm. The refractive index of the refractive index modifier can be measured using a commercially available measurement device (for example, Prism Coupler, model "2010M" manufactured by Metricon).

In some embodiments, the refractive index of the refractive index modifier may be, for example, 1.530 or higher, suitably 1.550 or higher, and advantageously 1.560 or higher. It is preferably 0.580 or more, more preferably 1.590 or more. In some preferred embodiments, the refractive index of the refractive index modifier may be, for example, 1.600 or higher, 1.610 or higher, 1.630 or higher, or 1.650 or higher. may be 1.660 or more, 1.670 or more, 1.680 or more, 1.690 or more, or 1.700 or more. A refractive index adjuster having a higher refractive index can more efficiently exhibit the effect of increasing the refractive index by being blended into the pressure-sensitive adhesive. Further, from the viewpoint of ease of synthesis, cost, etc. of the refractive index modifier, in some embodiments, the refractive index of the refractive index modifier may be 1.900 or less, or 1.800 or less. It may be 1.780 or less, 1.750 or less, or 1.730 or less. In some embodiments of the refractive index adjusting agent disclosed herein, the refractive index of the refractive index adjusting agent is, for example, 1.590 or more and 1.750 or less, preferably 1.610 or more and 1.750 or less. , more preferably 1.640 or more and 1.750, may be 1.660 or more and 1.730 or less, or may be 1.680 or more and 1.730 or less.

The refractive index adjuster disclosed herein is preferably soluble in a solvent (typically an organic solvent) from the viewpoint of ease of blending with the adhesive. Here, soluble means that the refractive index modifier is at least 2% by weight (preferably 5% by weight or more, more preferably 10% by weight or more, still more preferably 20% by weight or more, and particularly preferably 40% by weight or more). It means that it is possible to prepare a solution containing at a concentration of For example, acetic acid esters such as ethyl acetate and butyl acetate; lower ketones such as acetone and methyl ethyl ketone (MEK); aromatic hydrocarbon solvents such as benzene and toluene); and MEK is particularly preferred.

In the refractive index modifier disclosed herein (for example, the triazine compound represented by the above formula (I)), advantageous structural features from the viewpoint of solubility in a solvent include (i) a non-planar shape; and (ii) non-rotational symmetry with respect to the hub ring. A compound that corresponds to either one or both of (i) and (ii) above is preferable. Preferred examples of the compound corresponding to (i) above include compound (A1) and compound (A4) described in Examples below. These compounds have a ball-like (non-planar) shape as a whole due to their molecular structure. Further, for example, the compound (A5) described in Examples described later is rotationally symmetrical (has a three-fold rotational axis), whereas the compound (A6) is non-rotationally symmetrical and corresponds to (ii) above. A compound that satisfies the above (i) and is rotationally symmetrical with respect to the hub ring is preferable because it can have a high refractive index and good solubility.

<Adhesive>
The adhesive disclosed herein is characterized by containing a refractive index modifier as described above. The type of the adhesive is not particularly limited. Adhesives, polyether-based adhesives, polyamide-based adhesives, fluorine-based adhesives, and the like may be used. The acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive having an acrylic polymer as a base polymer. The same applies to rubber-based and other pressure-sensitive adhesives. From the standpoint of ease of adjustment of adhesive properties, optical properties, and the like, acrylic pressure-sensitive adhesives are preferred in some embodiments.

The adhesive disclosed herein can be formed using an adhesive composition containing a refractive index modifier (typically, an adhesive composition containing at least a base polymer and a refractive index modifier). The form of the pressure-sensitive adhesive composition is not particularly limited. An active energy ray-curable pressure-sensitive adhesive composition prepared to form a pressure-sensitive adhesive, a water-dispersible pressure-sensitive adhesive composition in which the pressure-sensitive adhesive-forming component is dispersed in water, and is applied in a heat-melted state, and It can be in various forms, such as a hot-melt adhesive composition that forms an adhesive when cooled to a temperature. Although not particularly limited, the adhesive disclosed herein can be preferably formed using a solvent-type adhesive composition from the viewpoint of ease of blending of the refractive index adjuster. For solvent-borne adhesive compositions, typically the composition can be dried (preferably further crosslinked) to form the adhesive. In the active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive is typically formed by irradiating an active energy ray to promote a polymerization reaction and/or a cross-linking reaction. When it is necessary to dry the active energy ray-curable pressure-sensitive adhesive composition, it is preferable to irradiate the active energy ray after drying.

The content of the refractive index adjuster in the adhesive is not particularly limited, and can be set so as to obtain an adhesive having a desired refractive index. In some aspects, the amount of the refractive index modifier used relative to 100 parts by weight of the base polymer (for example, an acrylic polymer) of the pressure-sensitive adhesive can be, for example, 0.1 parts by weight or more, from the viewpoint of obtaining a higher use effect. It is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, may be 3 parts by weight or more, may be 5 parts by weight or more, may be 7 parts by weight or more, or may be 9 parts by weight or more. good. In addition, the amount of the refractive index modifier used with respect to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less, and from the viewpoint of easily obtaining good adhesive properties, it is advantageous to use it at 60 parts by weight or less. , 45 parts by weight or less, may be 30 parts by weight or less, may be 25 parts by weight or less, may be 20 parts by weight or less, or may be 15 parts by weight or less.

The absolute value of the difference between the refractive index n _a of the refractive index adjusting agent and the refractive index n _T of the adhesive containing the refractive index adjusting agent, that is, |n _a −n _T | (hereinafter also referred to as |Δn _A |). ) can be set to be greater than zero. In some embodiments, |Δn _A | is, for example, 0.010 or more, preferably 0.020 or more, more preferably 0.030 or more, may be 0.040 or more, or 0.040 or more. 060 or more, 0.080 or more, 0.100 or more, 0.150 or more, 0.200 or more, or 0.250 or more. It can be said that the refractive index modifier contributes more to the refractive index of the pressure-sensitive adhesive having a larger value of |Δn _A |. In some embodiments, |Δn _A | may be, for example, 0.500 or less, 0.400 or less, or 0 It may be less than 0.300, less than 0.250, less than 0.200, or less than 0.100. The relationship between the refractive index _na of the refractive index adjuster and the refractive index _nT of the pressure-sensitive adhesive may be na _{> nT} or _na < _nT . That is, 0<Δn _A or 0>Δn _A may be used. The refractive index adjuster disclosed herein can exhibit a higher refractive index than a general adhesive (for example, an _acrylic adhesive). It can be preferably used as a refractive index agent.

The absolute value of the difference between the refractive index n _a of the refractive index modifier and the refractive index n _b of the base polymer, that is, |n _b −n _a | (hereinafter also referred to as |Δn _B |) is greater than 0. is set to In some embodiments, |Δn _B | is, for example, 0.010 or greater, preferably 0.020 or greater, more preferably 0.035 or greater, may be 0.045 or greater, or 0.045 or greater. 065 or more, 0.075 or more, 0.090 or more, 0.100 or more, 0.150 or more, 0.200 or more, or 0.250 or more. By selecting the base polymer and the refractive index adjusting agent so that the value of |Δn _B | becomes larger, the refractive index adjusting effect of using the refractive index adjusting agent tends to be enhanced. Further, from the viewpoint of compatibility in the adhesive, transparency of the adhesive, and the like, |Δn _B | may be, for example, 0.550 or less, 0.450 or less, or 0.550 or less in some embodiments. It may be 350 or less, 0.300 or less, less than 0.250, less than 0.150, or less than 0.130. The relationship between the refractive index _na of the refractive index modifier and the refractive index _nb of the base polymer may be na _{> nb} or _na < _nb . That is, 0<Δn _B or 0>Δn _B may be used. Since the refractive index adjuster disclosed herein can exhibit a higher refractive index than a base polymer (e.g., an acrylic polymer) of a general adhesive, for example, 0<Δn _B , the adhesive can be preferably used as a refractive index increasing agent.

In the following, the adhesive disclosed herein will be further described using an acrylic adhesive as a main example, but the adhesive disclosed herein is not intended to be limited to the acrylic adhesive.

The pressure-sensitive adhesive according to some preferred embodiments is an acrylic pressure-sensitive adhesive that uses an acrylic polymer as a base polymer and contains an aromatic ring-containing monomer (m1) as a monomer component that constitutes the acrylic polymer. The refractive index adjuster disclosed herein can be used in a pressure-sensitive adhesive containing such a base polymer to effectively adjust the refractive index of the pressure-sensitive adhesive (for example, increase the refractive index). Here, in the present specification, the "monomer component constituting the acrylic polymer" is contained in the pressure-sensitive adhesive composition in the form of a preformed polymer (which may be an oligomer), or is an unpolymerized monomer. It means a monomer that constitutes a repeating unit of the acrylic polymer in the adhesive formed from the adhesive composition, regardless of the form contained in the adhesive composition. That is, the monomer component that constitutes the acrylic polymer may be contained in the pressure-sensitive adhesive composition in the form of a polymer, an unpolymerized product, or a partially polymerized product. From the viewpoint of ease of preparation of the pressure-sensitive adhesive composition, in some embodiments, substantially all of the monomer components constituting the acrylic polymer (for example, 95% by weight or more, preferably 99% by weight or more) are added to the polymer. A pressure-sensitive adhesive composition comprising the form is preferred.

(Monomer (m1))
A compound containing at least one aromatic ring and at least one ethylenically unsaturated group in one molecule is used as the monomer (m1). As the monomer (m1), such compounds can be used singly or in combination of two or more.

Examples of the ethylenically unsaturated groups include (meth)acryloyl groups, vinyl groups, and (meth)allyl groups. A (meth)acryloyl group is preferred from the viewpoint of polymerization reactivity, and an acryloyl group is more preferred from the viewpoint of flexibility and adhesiveness. From the viewpoint of the flexibility of the pressure-sensitive adhesive, as the monomer (m1), a compound having one ethylenically unsaturated group contained in one molecule (that is, a monofunctional monomer) is preferably used.

The number of aromatic rings contained in one molecule of the compound used as the monomer (m1) may be 1, or 2 or more. The upper limit of the number of aromatic rings is not particularly limited, and may be, for example, 16 or less. In some embodiments, the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, and 6 or less, from the viewpoint of ease of preparation of the pressure-sensitive adhesive composition, transparency of the pressure-sensitive adhesive, and the like. is more preferable, and may be 5 or less, 4 or less, 3 or less, or 2 or less.

The aromatic ring possessed by the compound used as the monomer (m1) is a benzene ring (which may be a benzene ring constituting part of a biphenyl structure or a fluorene structure); a naphthalene ring, an indene ring, an azulene ring, anthracene ring, and a phenanthrene ring. may be a carbocyclic ring such as a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring , a thiophene ring; and the like. The heteroatoms included as ring-constituting atoms in the above heterocycle may be one or more selected from the group consisting of nitrogen, sulfur and oxygen, for example. In some embodiments, the heteroatoms that make up the heterocycle can be one or both of nitrogen and sulfur. The monomer (m1) may have a structure in which one or more carbon rings and one or more heterocycles are condensed, such as a dinaphthothiophene structure.

The aromatic ring (preferably carbocyclic ring) may or may not have one or more substituents on the ring-constituting atoms. When having a substituent, the substituent includes an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (fluorine atom, chlorine atom, bromine atom, etc.), a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group. etc. are exemplified, but not limited to these. In substituents containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1-4, more preferably 1-3, and can be, for example, 1 or 2. In some embodiments, the aromatic ring has no substituents on ring-constituting atoms, or has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups and halogen atoms (e.g., bromine atoms). can be an aromatic ring having The expression that the aromatic ring of the monomer (m1) has a substituent on its ring-constituting atom means that the aromatic ring has a substituent other than a substituent having an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be directly bonded or may be bonded via a linking group. The linking group is, for example, an alkylene group, an oxyalkylene group, a poly(oxyalkylene) group, a phenyl group, an alkylphenyl group, an alkoxyphenyl group, or a structure in which one or more hydrogen atoms in these groups are substituted with hydroxyl groups. (eg, hydroxyalkylene group), oxy group (--O-- group), thiooxy group (--S-- group), and the like. In some embodiments, the aromatic ring and the ethylenically unsaturated group are directly attached or attached via a linking group selected from the group consisting of alkylene, oxyalkylene and poly(oxyalkylene) groups. Aromatic ring-containing monomers having a structure in which The number of carbon atoms in the alkylene group and the oxyalkylene group is preferably 1-4, more preferably 1-3, and can be, for example, 1 or 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group may be, for example, 2-3.

Examples of compounds that can be preferably employed as the monomer (m1) include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylate and the aromatic ring-containing vinyl compound can be used singly or in combination of two or more. One or two or more aromatic ring-containing (meth)acrylates and one or two or more aromatic ring-containing vinyl compounds may be used in combination.

In some embodiments, as the monomer (m1), a monomer having two or more aromatic rings (preferably carbocyclic rings) in one molecule can be used because a high refractive index-increasing effect is likely to be obtained. Examples of monomers having two or more aromatic rings in one molecule (monomers containing multiple aromatic rings) include monomers having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, and two or more non-condensed aromatic rings. Monomers having a structure in which rings are directly (that is, not via other atoms) chemically bonded, monomers having a condensed aromatic ring structure, monomers having a fluorene structure, monomers having a dinaphthothiophene structure, monomers having a dibenzothiophene structure , etc. The monomers containing multiple aromatic rings may be used singly or in combination of two or more.

The linking group is, for example, an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (eg, -O-(CH ₂ ) _n - group, where n is 1 to 3, preferably 1). , a thiooxyalkylene group (such as a —S—(CH ₂ ) _n — group, where n is 1 to 3, preferably 1), a linear alkylene group (ie, a —(CH ₂ ) _n — group, where n is 1 to 6, preferably 1 to 3), the above oxyalkylene group, the above thiooxyalkylene group and the above linear alkylene group in which the alkylene group is partially or completely halogenated, and the like. Preferred examples of the linking group from the viewpoint of the flexibility of the adhesive include an oxy group, a thiooxy group, an oxyalkylene group and a linear alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate (e.g., m-phenoxybenzyl (meth)acrylate), thiophenoxybenzyl (meth) Acrylate, benzylbenzyl (meth)acrylate and the like.

The monomer having a structure in which two or more non-fused aromatic rings are directly chemically bonded may be, for example, a biphenyl structure-containing (meth)acrylate, a triphenyl structure-containing (meth)acrylate, a vinyl group-containing biphenyl, or the like. Specific examples include o-phenylphenol (meth)acrylate and biphenylmethyl (meth)acrylate.

Examples of monomers having a condensed aromatic ring structure include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracene. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2 -(4-methoxy-1-naphthoxy)ethyl (meth)acrylate and the like.

Specific examples of the monomer having a fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene (meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (meth)acrylate. etc. Since the monomer having a fluorene structure includes a structural portion in which two benzene rings are directly chemically bonded, it is included in the concept of a monomer having a structure in which two or more non-fused aromatic rings are directly chemically bonded.

Examples of the monomer having a dinaphthothiophene structure include (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, (meth)allyl group-containing dinaphthothiophene, and the like. Specific examples include (meth)acryloyloxymethyldinaphthothiophene (for example, a compound having a structure in which CH ₂ CH(R ¹ )C(O)OCH ₂ — is bonded to the 5- or 6-position of the dinaphthothiophene ring. and R ¹ is a hydrogen atom or a methyl group.), (meth)acryloyloxyethyldinaphthothiophene (for example, at the 5- or 6-position of the dinaphthothiophene ring, CH ₂ CH(R ¹ )C(O) OCH(CH ₃ )— or a compound having a structure in which CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ — is bonded, where R ¹ is a hydrogen atom or a methyl group), vinyldinaphthothiophene (For example, compounds having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), (meth)allyloxydinaphthothiophene, and the like. Note that the monomer having a dinaphthothiophene structure is included in the concept of the monomer having a condensed aromatic ring structure by including a naphthalene structure and by having a structure in which a thiophene ring and two naphthalene structures are condensed. be.

Examples of the monomer having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophene, vinyl group-containing dibenzothiophene, and the like. A monomer having a dibenzothiophene structure is included in the concept of a monomer having a condensed aromatic ring structure because it has a structure in which a thiophene ring and two benzene rings are condensed.
Neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to structures in which two or more non-fused aromatic rings are directly chemically bonded.

In some preferred embodiments, a monomer having one aromatic ring (preferably carbocyclic ring) in one molecule is used as the monomer (m1). A monomer having one aromatic ring in one molecule (single aromatic ring-containing monomer) can be useful, for example, in improving the flexibility of the pressure-sensitive adhesive, adjusting the pressure-sensitive adhesive properties, improving the transparency, and the like. A single aromatic ring-containing monomer may be used alone or in combination of two or more. In some aspects, a monomer having one aromatic ring in one molecule may be used in combination with a monomer containing multiple aromatic rings from the viewpoint of improving the refractive index of the pressure-sensitive adhesive.

Examples of monomers having one aromatic ring in one molecule include benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate. 2-(4, 6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, 6-(4,6-dibromo-2-s- Butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecyl Bromine-substituted aromatic ring-containing (meth)acrylates such as phenyl acrylate; carbon aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, tert-butylstyrene; N-vinylpyridine, N-vinylpyrimidine, N - compounds having a vinyl substituent on a heteroaromatic ring, such as vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole;

As the monomer (m1), a monomer having a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the aromatic ring in various aromatic ring-containing monomers as described above may be used. A monomer having an oxyethylene chain interposed between an ethylenically unsaturated group and an aromatic ring in this manner can be understood as an ethoxylated product of the original monomer. The number of repeating oxyethylene units ( _{--CH.sub.2CH.sub.2O--} ) in _the oxyethylene chain is typically 1-4, preferably 1-3, more preferably 1-2, for example 1. Specific examples of ethoxylated aromatic ring-containing monomers include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol. di(meth)acrylate and the like.

The content of the monomer containing multiple aromatic rings in the monomer (m1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some aspects, the content of the monomer containing multiple aromatic rings in the monomer (m1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of facilitating obtaining a higher refractive index. , 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (m1) may be the multiple aromatic ring-containing monomer. That is, only one or two or more aromatic ring-containing monomers may be used as the monomer (m1). In some aspects, for example, considering the balance between high refractive index and flexibility (viscoelastic properties such as storage modulus), the content of the monomer containing multiple aromatic rings in the monomer (m1) is 100. It may be less than wt%, may be 98 wt% or less, may be 90 wt% or less, may be 80 wt% or less, may be 70 wt% or less, may be 65 wt% or less, or may be 50 wt% or less. , 25% by weight or less, or 10% by weight or less. The technology disclosed herein can also be practiced in a mode in which the content of the monomer containing multiple aromatic rings in the monomer (m1) is less than 5% by weight. A monomer containing multiple aromatic rings may not be used.

The content of the monomer containing multiple aromatic rings in the monomer component that constitutes the acrylic polymer is not particularly limited, and can be set according to the purpose. The content of the monomer containing multiple aromatic rings in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some aspects, from the viewpoint of facilitating the realization of a pressure-sensitive adhesive having a higher refractive index, the content of the monomer containing multiple aromatic rings in the monomer component may be, for example, more than 35% by weight, or 50% by weight. Advantageously, it is greater than, preferably greater than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 95% by weight or more. The content of the monomer containing multiple aromatic rings in the monomer component is advantageously about 99% by weight or less, preferably 98% by weight or less, in consideration of the balance between high refractive index and flexibility. , 96% by weight or less, preferably 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (e.g., transparency), the content of the monomer containing multiple aromatic rings in the monomer component may be 70% by weight or less, or 60% by weight. % by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technology disclosed herein can also be practiced in a mode in which the content of the monomer containing multiple aromatic rings in the monomer component is less than 3% by weight.

The content of the single aromatic ring-containing monomer in the monomer (m1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the single aromatic ring-containing monomer in the monomer (m1) may be, for example, 50% by weight or more, and is preferably 70% by weight or more from the viewpoint of facilitating obtaining a higher refractive index. , 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomer (m1) may be a single aromatic ring-containing monomer. That is, as the monomer (m1), only one or more monomers containing a single aromatic ring may be used. Further, in some aspects, for example, considering the balance between high refractive index and flexibility, the content of the monomer containing a single aromatic ring in the monomer (m1) may be less than 100% by weight, and may be less than 98% by weight. % or less, 90 wt% or less, 80 wt% or less, 70 wt% or less, 65 wt% or less, 50 wt% or less, 25 wt% or less, 10 wt% It can be below. The technology disclosed herein can also be practiced in a mode in which the content of the single aromatic ring-containing monomer in the monomer (m1) is less than 5% by weight. A single aromatic ring-containing monomer may not be used.

The content of the single aromatic ring-containing monomer in the monomer component constituting the acrylic polymer is not particularly limited, and can be set according to the purpose. The content of the single aromatic ring-containing monomer in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some aspects, from the viewpoint of facilitating the realization of a pressure-sensitive adhesive having a higher refractive index, the content of the single aromatic ring-containing monomer in the monomer component may be, for example, more than 35% by weight, or more than 50% by weight. is preferably 60% by weight or more, more preferably more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 95% by weight or more , or 98% by weight or more. The content of the single aromatic ring-containing monomer in the monomer component may be about 99% by weight or less, preferably 98% by weight or less, in consideration of the balance between high refractive index and flexibility. More preferably, it is 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less. In some embodiments, from the viewpoint of easily achieving higher adhesive properties and/or optical properties (e.g., transparency), the content of the monomer containing a single aromatic ring in the monomer component may be 70% by weight or less, or 60% by weight. % by weight or less, 50% by weight or less, 40% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technology disclosed herein can also be practiced in a mode in which the content of the single aromatic ring-containing monomer in the monomer component is less than 3% by weight.

In some aspects of the technology disclosed herein, a high refractive index monomer can be preferably employed as at least part of the monomer (m1). Here, "high refractive index monomer" refers to a monomer having a refractive index of, for example, approximately 1.510 or higher, preferably approximately 1.530 or higher, and more preferably approximately 1.550 or higher. Although the upper limit of the refractive index of the high refractive index monomer is not particularly limited, it is, for example, 3.000 or less from the viewpoint of ease of preparation of the pressure-sensitive adhesive composition and compatibility with flexibility suitable as a pressure-sensitive adhesive. It may be 0.500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less. The high refractive index monomers can be used singly or in combination of two or more.
The refractive index of the monomer is measured using an Abbe refractometer under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, model "DR-M4" manufactured by ATAGO or its equivalent can be used. If the manufacturer or the like provides the nominal value of the refractive index at 25° C., the nominal value can be adopted.

As the above-mentioned high refractive index monomer, those having a corresponding refractive index among the compounds included in the concept of the aromatic ring-containing monomer (m1) disclosed herein (e.g., the compounds and compound groups exemplified above) can be adopted as appropriate. Specific examples include m-phenoxybenzyl acrylate (refractive index: 1.566, homopolymer Tg: -35°C), 1-naphthylmethyl acrylate (refractive index: 1.595, homopolymer Tg: 31°C), Ethoxylated o-phenylphenol acrylate (repeating number of oxyethylene unit: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD20): 1.519, homopolymer Tg: 6°C), phenoxyethyl acrylate (Refractive index (nD20): 1.517, homopolymer Tg: 2 ° C.), phenoxydiethylene glycol acrylate (refractive index: 1.510, homopolymer Tg: -35 ° C.), 6-acryloyloxymethyldinaphthothiophene ( 6MDNTA, refractive index: 1.75), 6-methacryloyloxymethyldinaphthothiophene (6MDNTMA, refractive index: 1.726), 5-acryloyloxyethyldinaphthothiophene (5EDNTA, refractive index: 1.786), 6 - acryloyloxyethyldinaphthothiophene (6EDNTA, refractive index: 1.722), 6-vinyldinaphthothiophene (6VDNT, refractive index: 1.802), 5-vinyldinaphthothiophene (abbreviation: 5VDNT, refractive index: 1 .793), etc., but are not limited to these.

The content of the high refractive index monomer (that is, the aromatic ring-containing monomer having a refractive index of about 1.510 or higher, preferably about 1.530 or higher, more preferably about 1.550 or higher) in the monomer (m1) is particularly For example, it may be 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer (m1) may be, for example, 50% by weight or more, preferably 70% by weight or more, from the viewpoint of easily obtaining a higher refractive index. , 85% by weight or more, 90% by weight or more, or 95% by weight or more. Substantially 100% by weight of the monomers (m1) may be high refractive index monomers. Further, in some aspects, for example, from the viewpoint of achieving both high refractive index and flexibility in a well-balanced manner, the content of the high refractive index monomer in the monomer (m1) may be less than 100% by weight, and may be 98% by weight. % or less, 90 wt% or less, 80 wt% or less, or 65 wt% or less.

The content of the high refractive index monomer in the monomer component that constitutes the acrylic polymer is not particularly limited, and can be set according to the purpose. In addition, if necessary, it can be set in consideration of compatibility with adhesive properties (eg, adhesive strength, etc.) and/or optical properties (eg, total light transmittance, haze value, etc.). The content of the high refractive index monomer in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer component constituting the acrylic polymer may be, for example, more than 35% by weight, and from the viewpoint of facilitating obtaining a higher refractive index, it is more than 50% by weight. Advantageously, it is preferably greater than 70% by weight, it may be 75% by weight or more, it may be 85% by weight or more, it may be 90% by weight or more, it may be 95% by weight or more. The content of the high refractive index monomer in the monomer component is advantageously 99% by weight or less, preferably 98% by weight or less, from the viewpoint of achieving both a high refractive index and flexibility in a well-balanced manner. It is more preferably 96% by weight or less, 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less.

In some preferred embodiments, an aromatic ring-containing monomer having a homopolymer Tg of 10°C or lower (hereinafter sometimes referred to as "monomer L") is employed as at least part of the monomer (m1). The content of the aromatic ring-containing monomer (m1) in the monomer component (in particular, the aromatic ring-containing monomer (m1) corresponding to at least one of the above-described multiple aromatic ring-containing monomer, single aromatic ring-containing monomer, and high refractive index monomer) Although the storage elastic modulus G' of the pressure-sensitive adhesive generally tends to increase when increased, the increase in the storage elastic modulus G' can be suppressed by adopting the monomer L as part or all of the monomer (m1). can. Thereby, the refractive index can be improved while maintaining the flexibility suitable as an adhesive. The Tg of the monomer L may be, for example, 5° C. or lower, 0° C. or lower, −10° C. or lower, −20° C. or lower, or −25° C. or lower. The lower limit of Tg of monomer L is not particularly limited. Considering the balance with the effect of improving the refractive index, in some embodiments, the Tg of the monomer L may be -70°C or higher, -55°C or higher, or -45°C or higher. In some other embodiments, the Tg of monomer L may be, for example, −30° C. or higher, −10° C. or higher, 0° C. or higher, or 3° C. or higher. Monomer L can be used individually by 1 type or in combination of 2 or more types.

As the monomer L, a compound having a corresponding Tg is appropriately selected from compounds included in the concept of the aromatic ring-containing monomer (m1) disclosed herein (e.g., the compounds and compound groups exemplified above). be able to. Preferred examples of aromatic ring-containing monomers that can be used as monomer L include m-phenoxybenzyl acrylate (Tg of homopolymer: −35° C.), benzyl acrylate (Tg of homopolymer: 6° C.), phenoxyethyl acrylate (Tg of homopolymer: Tg: 2°C) and phenoxydiethylene glycol acrylate (Tg of homopolymer: -35°C).

The content of the monomer L in the monomer (m1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer L in the monomer (m1) may be, for example, 50% by weight or more, from the viewpoint of easily obtaining a pressure-sensitive adhesive having both a high refractive index and flexibility at a high level, From the viewpoint of lowering the elastic modulus, it is preferably 60% by weight or more, may be 70% by weight or more, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. good. Substantially 100% by weight of monomer (m1) may be monomer L. Further, in some aspects, for example, from the viewpoint of achieving both a high refractive index and flexibility in a well-balanced manner, the content of the monomer L in the monomer (m1) may be less than 100% by weight, and 98% by weight or less. may be 90% by weight or less, 80% by weight or less, or 65% by weight or less.

The content of the monomer L in the monomer component constituting the acrylic polymer may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some aspects, from the viewpoint of facilitating the production of a pressure-sensitive adhesive having both a high refractive index and flexibility at a high level, the content of the monomer L in the monomer component may be, for example, more than 35% by weight, and the refractive index From the viewpoint of improvement, it is advantageous to be more than 50% by weight, preferably more than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight. It can be more than that. From the viewpoint of achieving both a high refractive index and flexibility in a well-balanced manner, the content of the monomer L in the monomer component is advantageously about 99% by weight or less, preferably 98% by weight or less, and 96% by weight. More preferably, it is 93% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, or 75% by weight or less.

In some embodiments, the glass transition temperature Tg _m1 based on the composition of the monomer (m1) is suitably about 20° C. or lower, preferably 10° C. or lower, from the viewpoint of the flexibility of the adhesive. For example, it may be 5° C. or lower, 0° C. or lower, −10° C. or lower, −20° C. or lower, or −25° C. or lower. The lower limit of the glass transition temperature Tg _m1 is not particularly limited. In some aspects, the glass transition temperature Tg _m1 may be -70° C. or higher, -55° C. or higher, or -45° C. or higher, in consideration of the balance with the refractive index improvement effect. The technology disclosed herein can also be suitably practiced in embodiments in which the glass transition temperature Tg _m1 is, for example, −40° C. or higher, −35° C. or higher, −33° C. or higher, −30° C. or higher, or −25° C. or higher. In some other embodiments, the glass transition temperature Tg _m1 may be, for example, −10° C. or higher, 0° C. or higher, or 3° C. or higher.

Here, the glass transition temperature Tg _m1 based on the composition of the monomer (m1) is the Tg determined by the Fox formula described below based on the composition of only the monomer (m1) among the monomer components constituting the acrylic polymer. say. The glass transition temperature Tg _m1 is obtained by applying the Fox formula to only the monomer (m1) among the monomer components constituting the acrylic polymer, and the glass of the homopolymer of each aromatic ring-containing monomer used as the monomer (m1). It can be calculated from the transition temperature and the weight fraction of each aromatic ring-containing monomer in the total amount of the monomers (m1). In an embodiment using only one kind of monomer as the monomer (m1), the Tg of the homopolymer of the monomer and the glass transition temperature Tg _m1 match.

In some embodiments, the aromatic ring-containing monomer (m1) is a combination of monomer L (i.e., an aromatic ring-containing monomer whose homopolymer Tg is 10°C or lower) and monomer H whose Tg is higher than 10°C. can be used for The Tg of monomer H may be, for example, greater than 10°C, greater than 15°C, or greater than 20°C. By using the monomer L and the monomer H in combination, the adhesive having a high content of the aromatic ring-containing monomer (m1) in the monomer component has a high refractive index and is suitable for adhesion to the adherend. It is possible to achieve both flexibility and flexibility at a higher level. The usage ratio of the monomer L and the monomer H is not particularly limited and can be set so as to suitably exhibit such effects. For example, it is preferable to set the usage amount ratio of the monomer L and the monomer H so as to satisfy one of the glass transition temperatures Tg _m1 described above.

In some embodiments, the aromatic ring-containing monomer (m1) can be preferably selected from compounds that do not contain a structure (for example, a biphenyl structure) in which two or more non-fused aromatic rings are directly chemically bonded. For example, the content of a compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded is less than 5% by weight (more preferably less than 3% by weight, and may be 0% by weight). An acrylic polymer composed of is preferred. Restricting the amount of the compound containing a structure in which two or more non-fused aromatic rings are directly chemically bonded in this way is advantageous from the viewpoint of realizing a pressure-sensitive adhesive that achieves both a high refractive index and flexibility in a well-balanced manner. can be.

The content of the monomer (m1) in the monomer component constituting the acrylic polymer is not particularly limited, and depending on the purpose, for example, desired refractive index and elastic modulus, adhesion properties (e.g. adhesive strength), optical properties (e.g. All light transmittance, haze value, etc.) can be set so as to realize a pressure-sensitive adhesive having one or more. In some embodiments, the content of the monomer (m1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, and 70% by weight. % or more. In some preferred embodiments, the content of the monomer (m1) in the monomer component constituting the acrylic polymer may be, for example, more than 70% by weight, suitably 75% by weight or more, and has a higher refractive index. It is preferably 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more. The content of the monomer (m1) in the monomer component is typically less than 100% by weight, and from the viewpoint of achieving both a high refractive index and flexibility in a well-balanced manner, it is advantageously about 99% by weight or less. It is preferably 98% by weight or less, more preferably 96% by weight or less, may be 93% by weight or less, or may be 90% by weight or less. In some embodiments, the content of the monomer (m1) in the monomer component may be less than 90% by weight, and may be less than 85% by weight, from the viewpoint of facilitating the realization of higher adhesive properties and/or optical properties (e.g., transparency). % or less than 80% by weight.

(monomer (m2))
In some preferred embodiments, the monomer component constituting the acrylic polymer may further contain a monomer (m2) in addition to the monomer (m1). The monomer (m2) is a monomer corresponding to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxy group (carboxy group-containing monomer). The hydroxyl group-containing monomer is a compound having at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. The carboxy group-containing monomer is a compound containing at least one carboxy group and at least one ethylenically unsaturated group in one molecule. The monomer (m2) can be useful for introducing cross-linking points into the acrylic polymer and imparting appropriate cohesiveness to the pressure-sensitive adhesive. Monomer (m2) can be used individually by 1 type or in combination of 2 or more types. Monomer (m2) is typically a monomer containing no aromatic ring.

Examples of ethylenically unsaturated groups possessed by the monomer (m2) include (meth)acryloyl groups, vinyl groups, and (meth)allyl groups. A (meth)acryloyl group is preferred from the viewpoint of polymerization reactivity, and an acryloyl group is more preferred from the viewpoint of flexibility and adhesiveness. From the viewpoint of the flexibility of the pressure-sensitive adhesive, as the monomer (m2), a compound having one ethylenically unsaturated group contained in one molecule (that is, a monofunctional monomer) is preferably used.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meth) ) Hydroxy (meth)acrylates such as 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, etc. Examples include, but are not limited to, alkyl. Examples of hydroxyl group-containing monomers that can be preferably used include 4-hydroxybutyl acrylate (Tg: -40°C) and 2-hydroxyethyl acrylate (Tg: -15°C). From the viewpoint of improving flexibility in the room temperature range, 4-hydroxybutyl acrylate having a lower Tg is more preferable. In one preferred embodiment, 50 wt% or more (eg, greater than 50 wt%, greater than 70 wt%, or greater than 85 wt%) of monomer (m2) can be 4-hydroxybutyl acrylate. A hydroxyl-containing monomer can be used individually by 1 type or in combination of 2 or more types.

In some embodiments in which a hydroxyl-containing monomer is used as the monomer (m2), the hydroxyl-containing monomer may be one or more selected from compounds having no methacryloyl group. Preferred examples of hydroxyl group-containing monomers having no methacryloyl group include the various hydroxyalkyl acrylates described above. For example, more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomer used as the monomer (m2) is preferably hydroxyalkyl acrylate. The use of hydroxyalkyl acrylates can introduce hydroxy groups into the acrylic polymer that help provide cross-linking points and moderate cohesiveness, and at room temperature compared to using only the corresponding hydroxyalkyl methacrylates. It is easy to obtain an adhesive with good flexibility and adhesiveness in the area.

Examples of carboxy group-containing monomers include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate, as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, Examples include, but are not limited to, isocrotonic acid and the like. Examples of carboxy group-containing monomers that can be preferably used include acrylic acid and methacrylic acid. A carboxy group-containing monomer can be used individually by 1 type or in combination of 2 or more types. A hydroxyl group-containing monomer and a carboxy group-containing monomer may be used in combination.

The content of the monomer (m2) in the monomer component constituting the acrylic polymer is not particularly limited and can be set according to the purpose. In some embodiments, the content of the monomer (m2) can be, for example, 0.01 wt% or more, 0.1 wt% or more, or 0.5 wt% or more. From the viewpoint of obtaining a higher use effect, in some embodiments, the content of the monomer (m2) is preferably 1% by weight or more, may be 2% by weight or more, or may be 4% by weight or more. . The upper limit of the content of the monomer (m2) in the monomer component is set so that the sum with the content of the monomer (m1) does not exceed 100% by weight. In some embodiments, the content of the monomer (m2) is, for example, 30% by weight or less or 25% by weight or less. From the viewpoint of facilitating conversion, it is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, may be less than 10% by weight, or may be less than 7% by weight. . In some embodiments, the content of the monomer (m2) may be less than 5 wt%, less than 3 wt%, or 1.5 wt% or less.

The total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer may be, for example, 31% by weight or more, preferably 51% by weight or more, and may be 61% by weight or more. , 71% by weight or more. In some aspects, the total content of the monomer (m1) and the monomer (m2) in the monomer component constituting the acrylic polymer is, for example, 76% by weight from the viewpoint of favorably exhibiting the effects of these monomers. or more, preferably 81 wt% or more, 86 wt% or more, 91 wt% or more, 96 wt% or more, 99 wt% or more, substantially 100 wt% It's okay.

(monomer m3)
In some preferred embodiments, the monomer component constituting the acrylic polymer may further contain an alkyl (meth)acrylate (hereinafter also referred to as "monomer (m3)") in addition to the monomer (m1). Monomer (m3) can help improve the flexibility of the adhesive. It can also help improve the compatibility of additives in the adhesive and adhesive properties such as adhesive strength. Monomer (m3) can be used individually by 1 type or in combination of 2 or more types.

As the monomer (m3), an alkyl (meth)acrylate having a straight or branched chain alkyl group having 1 to 20 carbon atoms (ie, C _1-20 ) at the ester end can be preferably used. Specific examples of C _1-20 alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-(meth)acrylate, Butyl, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, (meth)acrylate ) heptyl acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, ( meth) isodecyl acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, (meth) ) heptadecyl acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like, but are not limited thereto.

In some embodiments, an alkyl (meth)acrylate having a homopolymer Tg of -20°C or lower (more preferably -40°C or lower, for example -50°C or lower) is preferably employed as at least part of the monomer (m3). can. Such low Tg alkyl (meth)acrylates can help reduce the elastic modulus of the pressure-sensitive adhesive. It can also help improve adhesive properties such as adhesive strength. The lower limit of the Tg of the alkyl (meth)acrylate is not particularly limited, and may be -85°C or higher, -75°C or higher, -65°C or higher, or -60°C or higher. Specific examples of the low Tg alkyl (meth)acrylate include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate (iNA), and the like.

In some embodiments using monomer (m3), it is preferred to use C _4-8 alkyl (meth)acrylate as monomer (m3). Among them, the use of C _4-8 alkyl acrylate is more preferable. The C _4-8 alkyl (meth)acrylates can be used singly or in combination of two or more. The use of C _4-8 alkyl (meth)acrylate tends to improve the flexibility of the pressure-sensitive adhesive and to provide good pressure-sensitive adhesive properties (adhesive strength, etc.). In the embodiment using C _4-8 alkyl (meth)acrylate as the monomer (m3), the proportion of C _4-8 alkyl (meth)acrylate in the alkyl (meth)acrylate contained in the monomer component is 30% by weight or more. is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, and may be substantially 100% by weight.

In some embodiments using monomer (m3), C _1-6 alkyl (meth)acrylates can be preferably used as monomer (m3). The use of C _1-6 alkyl (meth)acrylates allows the storage modulus in each temperature range to be adjusted. For example, it is possible to set the storage elastic modulus in the high temperature range to be relatively high, or to suppress an increase in the difference in storage elastic modulus between the low temperature range and the high temperature range. In addition, the C _1-6 alkyl (meth)acrylate tends to be excellent in copolymerizability with the monomer (m1). The C _1-6 alkyl (meth)acrylates can be used singly or in combination of two or more. The C _1-6 alkyl (meth)acrylate is preferably a C _1-6 alkyl acrylate, more preferably a C _2-6 alkyl acrylate, and still more preferably a C _4-6 alkyl acrylate. In some other aspects, the C _1-6 alkyl (meth)acrylate is preferably a C _1-4 alkyl (meth)acrylate, more preferably a C _2-4 alkyl (meth)acrylate, even more preferably is a C _2-4 alkyl acrylate. Preferred examples of C _1-6 alkyl (meth)acrylates include BA.

The content of C _1-6 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It can be more than that. In some embodiments, the content of the C _1-6 alkyl (meth)acrylate may be 10% by weight or more, or 15% by weight or more, from the viewpoint of lowering the elastic modulus, adhesive strength, etc. It may be 20% by weight or more, or 25% by weight or more (for example, 30% by weight or more). The upper limit of the C _1-6 alkyl (meth)acrylate content in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _1-6 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and 17% by weight. It is more preferably less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced in an embodiment that does not substantially use C _1-6 alkyl (meth)acrylates.

In some other embodiments using monomer (m3), C _7-12 alkyl (meth)acrylates can preferably be used as monomer (m3). Storage modulus can be favorably reduced by the use of C _7-12 alkyl (meth)acrylates. The C _7-12 alkyl (meth)acrylates may be used singly or in combination of two or more. The C _7-12 alkyl (meth)acrylates are preferably C _7-10 alkyl acrylates, more preferably C _7-9 alkyl acrylates, and even more preferably C ₈ alkyl acrylates. Suitable examples of C _7-12 alkyl (meth)acrylates include 2EHA.

The content of C _7-12 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight. It can be more than that. In some aspects, the content of the C _7-12 alkyl (meth)acrylate may be 10% by weight or more, or 15% by weight or more, from the viewpoint of lowering the elastic modulus, adhesive strength, etc. It may be 20% by weight or more, or 25% by weight or more (for example, 30% by weight or more). The upper limit of the C _7-12 alkyl (meth)acrylate content in the monomer component is, for example, less than 50% by weight, and may be less than 35% by weight. In some embodiments, from the viewpoint of maintaining a high refractive index, the content of the C _7-12 alkyl (meth)acrylate is, for example, 24% by weight or less, preferably less than 20% by weight, and 17% by weight. It is more preferably less than 12% by weight, less than 7% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can also be practiced in a manner substantially free of C _7-12 alkyl (meth)acrylates.

In some embodiments using the monomer (m3), at least part of the monomer (m3) is preferably an alkyl acrylate from the viewpoint of lowering the elastic modulus. The use of alkyl acrylates is also advantageous in terms of adhesive properties such as adhesive strength. For example, it is preferable that 50% by weight or more of the monomer (m3) is an alkyl acrylate, and the proportion of the alkyl acrylate in the monomer (m3) is more preferably 75% by weight or more, still more preferably 90% by weight or more, Substantially 100% by weight of the monomers (m3) may be alkyl acrylates. An embodiment in which only one or two or more alkyl acrylates are used as the monomer (m3) and no alkyl methacrylate is used may be used.

In the aspect in which the monomer component contains the monomer (m3) (alkyl (meth)acrylate), the content of the alkyl (meth)acrylate in the monomer component can be set so that the effect of use can be appropriately exhibited. In some aspects, the content of the alkyl (meth)acrylate may be, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 8% by weight or more. The upper limit of the content of the monomer (m3) in the monomer component is set so that the total content of the monomers (m1) and (m2) does not exceed 100% by weight, for example, less than 50% by weight, and 35% by weight. % may be less. In some embodiments, the content of the monomer (m3) can be, for example, 24% by weight or less. Since the refractive index of alkyl (meth)acrylate is generally relatively low, in order to increase the refractive index, the content of monomer (m3) in the monomer component is limited, and the content of monomer (m1) is increased relatively. It is advantageous to From this point of view, the content of the monomer (m3) is suitably less than 23% by weight of the monomer component, preferably less than 20% by weight, more preferably less than 17% by weight. It may be less than wt%, it may be less than 7 wt%, it may be less than 3 wt%, it may be less than 1 wt%. The technology disclosed herein can also be preferably practiced in a mode in which the monomer (m3) is not substantially used.

(other monomers)
The monomer component constituting the acrylic polymer may contain monomers other than the above monomers (m1), (m2) and (m3) (hereinafter referred to as "other monomers"), if necessary. The above-mentioned other monomers can be used, for example, for the purposes of adjusting the Tg of the acrylic polymer, adjusting the adhesive performance, improving the compatibility in the adhesive layer, and the like. These other monomers may be used singly or in combination of two or more.

Examples of the other monomers include monomers having functional groups other than hydroxyl groups and carboxy groups (functional group-containing monomers). For example, other monomers capable of improving the cohesive strength and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, and the like. In addition, amide group-containing monomers ( For example, (meth)acrylamide, N-methylol (meth)acrylamide, etc.), amino group-containing monomers (e.g., aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), nitrogen atom-containing rings Monomers having (e.g., N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), imide group-containing monomers, epoxy group-containing monomers, keto group-containing monomers, isocyanate group-containing monomers, alkoxysilyl group-containing monomers, etc. mentioned. Incidentally, among the monomers having a nitrogen atom-containing ring, some, such as N-vinyl-2-pyrrolidone, also correspond to amide group-containing monomers. The same applies to the relationship between the monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Other monomers that can be used other than the functional group-containing monomer include vinyl ester monomers such as vinyl acetate; non-aromatic ring-containing (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; ethylene, Olefin monomers such as butadiene and isobutylene; Chlorine-containing monomers such as vinyl chloride; Alkoxy group-containing monomers such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate; Vinyl ethers such as methyl vinyl ether system monomer; and the like. A preferred example of other monomers that can be used for the purpose of improving the flexibility of the pressure-sensitive adhesive is ethoxyethoxyethyl acrylate (also known as ethyl carbitol acrylate, Tg of homopolymer: -67°C).

When the above other monomers are used, the amount used is not particularly limited, and can be appropriately set within a range in which the total amount of the monomer components does not exceed 100% by weight. From the viewpoint of making it easier to exhibit the effect of improving the refractive index by using the monomer (m1), the content of the other monomer in the monomer component can be, for example, approximately 35% by weight or less, and approximately 25% by weight or less (for example, 0 ~25% by weight), approximately 20% by weight or less (for example, 0 to 20% by weight), and approximately 10% by weight or less (for example, 0 to 10% by weight). Preferably it is about 5% by weight or less, for example about 1% by weight or less. The technology disclosed herein can be preferably practiced in a mode in which the monomer component does not substantially contain the above-mentioned other monomers.

In some aspects, the monomer component that constitutes the acrylic polymer may have a composition in which the amount of the methacryloyl group-containing monomer used is suppressed to a predetermined amount or less. The amount of the methacryloyl group-containing monomer used in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. Restricting the amount of the methacryloyl group-containing monomer to be used in this way can be advantageous from the viewpoint of achieving a pressure-sensitive adhesive that achieves a good balance between flexibility and adhesiveness and a high refractive index. The monomer component that constitutes the acrylic polymer may have a composition that does not contain a methacryloyl group-containing monomer (for example, a composition that consists only of an acryloyl group-containing monomer).

In some aspects, the amount of the carboxy group-containing monomer used in the monomer component constituting the acrylic polymer is limited from the viewpoint of suppressing the coloring or discoloration (eg, yellowing) of the pressure-sensitive adhesive. The amount of the carboxy group-containing monomer used in the monomer component may be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, and 0 less than 0.05% by weight. The fact that the amount of the carboxy group-containing monomer used is limited in this way is due to the fact that metal materials that can be placed in contact with or in close proximity to the pressure-sensitive adhesive disclosed herein (for example, metal wiring that can be present on the adherend, It is also advantageous from the viewpoint of suppressing corrosion of metal films, etc.). The technology disclosed herein can be practiced in a mode in which the monomer component constituting the acrylic polymer does not contain a carboxy group-containing monomer.
For the same reason, in some embodiments, the monomer component constituting the acrylic polymer has an acidic functional group (including a carboxy group, a sulfonic acid group, a phosphoric acid group, etc.). preferably restricted. As the amount of the acidic functional group-containing monomer used in the monomer component of this embodiment, the above-described preferred amount of the carboxy group-containing monomer can be applied. The technology disclosed herein can be preferably practiced in an aspect in which the monomer component does not contain an acidic group-containing monomer (that is, an aspect in which the acrylic polymer is acid-free).

The refractive index of the acrylic polymer is, for example, 1.460 or higher, preferably 1.500 or higher, more preferably 1.530 or higher, still more preferably 1.550 or higher, and may be 1.560 or higher. , 1.570 or more, or 1.580 or more. The refractive index adjuster disclosed herein is preferably used for the purpose of increasing the refractive index of the pressure-sensitive adhesive by blending it into a pressure-sensitive adhesive whose base polymer is an acrylic polymer having a refractive index equal to or higher than a predetermined value. can be The upper limit of the refractive index of the acrylic polymer is not particularly limited. In some embodiments, the refractive index of the acrylic polymer is, for example, 1.700 or less, preferably 1.650 or less, or even 1.630 or less, from the viewpoint of adhesive properties and optical properties. It may be 610 or less, or 1.600 or less.

The refractive index of the base polymer is measured as the refractive index of the pressure-sensitive adhesive made from the base polymer. As used herein, the refractive index of an adhesive refers to the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the pressure-sensitive adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO or its equivalent is used. As a measurement sample, an adhesive layer made of an adhesive to be evaluated can be used. Specifically, the refractive index of the pressure-sensitive adhesive can be measured by the method described in Examples below.

In addition, the adhesive containing the refractive index modifier disclosed herein is based on an acrylic polymer composed of a monomer component containing a certain amount of the monomer (m1) (for example, 30% by weight or more of the monomer component) as described above. The base polymer is not limited to the acrylic pressure-sensitive adhesive used as a polymer, and for example, an acrylic polymer composed of a monomer component that does not contain the above monomer (m1) or has a relatively small content of the above monomer (m1) is used as the base polymer. An acrylic adhesive may be used. The pressure-sensitive adhesive containing the refractive index modifier disclosed herein is, for example:
The lower limit of the content of the monomer (m3) is 50% by weight, 60% by weight, 70% by weight or 80% by weight, and the upper limit is 99.9% by weight, 99.5% by weight, 98% by weight, 95% by weight. or 90% by weight;
The lower limit of the content of the monomer (m2) is 0.1% by weight, 0.5% by weight, 1% by weight, 2% by weight or 3% by weight, and the upper limit is 30% by weight, 20% by weight, 15% by weight. , 10%, 8% or 5% by weight;
As an optional component, the monomer (m1) is less than 30% by weight, 20% by weight or less, 10% by weight or less, or 5% by weight or less, and more than 0% by weight, 1% by weight or more, 3% by weight or more, 8% by weight or more , 12% by weight or more, or 18% by weight or more, or does not contain the monomer (m1);
As an optional component, the above other monomers are less than 30% by weight, 20% by weight or less, 10% by weight or less, or 5% by weight or less, and more than 0% by weight, 0.1% by weight or more, 0.5% by weight or more, 1% by weight % or more, 3 wt% or more, 8 wt% or more, 12 wt% or more, or 18 wt% or more, or no other monomer;
It may be an acrylic pressure-sensitive adhesive whose base polymer is an acrylic polymer composed of monomer components of the composition. The refractive index of the acrylic polymer may be, for example, less than 1.550, 1.530 or less, 1.510 or less, 1.490 or less, or 1.480 or less. The refractive index adjuster disclosed herein is also preferably used in a mode in which it is blended in a pressure-sensitive adhesive that uses an acrylic polymer having such a refractive index as a base polymer, and effectively adjusts the pressure-sensitive adhesive (typically can have a high refractive index). The lower limit of the refractive index of the acrylic polymer is not particularly limited. The refractive index of the acrylic polymer may be, for example, 1.400 or higher, 1.440 or higher, 1.460 or higher, or 1.470 or higher.

(Method for preparing acrylic polymer)
In the technique disclosed herein, the method for obtaining an acrylic polymer composed of such monomer components is not particularly limited, and solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, photopolymerization, etc. Various polymerization methods known as methods for synthesizing acrylic polymers can be appropriately employed. For example, a solution polymerization method can be preferably employed. The polymerization temperature at the time of solution polymerization can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc. ° C.).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetic esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane and the like Halogenated alkanes; lower alcohols such as isopropyl alcohol (e.g., monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or a mixed solvent of two or more kinds can be used.

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds. ; and the like. Still another example of the polymerization initiator is a redox initiator obtained by combining a peroxide and a reducing agent. A polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer component. ).

Various conventionally known chain transfer agents can be used for the above polymerization, if necessary. For example, mercaptans such as n-dodecylmercaptan, t-dodecylmercaptan, thioglycolic acid and α-thioglycerol can be used. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) may be used. Examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylstyrene, α-methylstyrene dimer, etc. styrenes; and the like. A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. When using a chain transfer agent, the amount used can be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer component.

(Glass transition temperature Tg _T of base polymer)
The monomer component constituting the base polymer (for example, acrylic polymer) of the pressure-sensitive adhesive disclosed herein preferably has a composition such that the glass transition temperature Tg _T based on the composition of the monomer component is about 15° C. or lower. In some embodiments, the glass temperature Tg _T is preferably 10° C. or lower, more preferably 5° C. or lower, even more preferably 1° C. or lower, and may be 0° C. or lower. In some other embodiments, the glass temperature Tg _T may be −10° C. or lower, −20° C. or lower, −25° C. or lower, −30° C. or lower, or −35° C. or lower. It's okay. A low glass transition temperature Tg _T can be advantageous from the viewpoint of lowering the elastic modulus of the pressure-sensitive adhesive. Also, the glass transition temperature Tg _T may be, for example, −80° C. or lower, −70° C. or higher, or −60° C. or higher. From the viewpoint of facilitating a high refractive index of the adhesive, in some embodiments, the glass transition temperature Tg _T is preferably -50°C or higher, more preferably -45°C or higher, and -40°C or higher. may In some preferred embodiments, the glass temperature Tg _T may be greater than -30°C, greater than -20°C, greater than -10°C, or greater than -5°C.

Here, the glass transition temperature Tg _T means the glass transition temperature determined by the Fox formula based on the composition of the above monomer components, unless otherwise specified. The Fox equation is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (weight-based copolymerization ratio), and Tgi is the homopolymer of the monomer i. represents the glass transition temperature (unit: K).
As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in known materials such as "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) is used. For monomers for which multiple values are listed in the above Polymer Handbook, the highest value is adopted. If the Tg of the homopolymer is not described in known documents, the value obtained by the measurement method described in Japanese Patent Application Publication No. 2007-51271 shall be used.

(Mw of base polymer)
^The weight-average molecular weight (Mw) of the base polymer ⁽ for example, an acrylic polymer) of the pressure-sensitive adhesive disclosed herein is not particularly limited. or more, or about 80×10 ⁴ or more. By using a base polymer having a Mw of a predetermined value or more, it is easy to obtain an appropriate cohesive force capable of exhibiting desired adhesive properties. The upper limit of Mw of the base polymer is, for example, about 500×10 ⁴ or less, and from the viewpoint of adhesion performance, about 400×10 ⁴ or less (more preferably about 150×10 ⁴ or less, for example about 130×10 ⁴ or less). A range is preferred.

Here, the Mw of the base polymer (for example, acrylic polymer) can be determined by gel permeation chromatography (GPC) in terms of polystyrene. Specifically, it can be obtained by measuring under the following conditions using a GPC measurement device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation).
[Measurement conditions for GPC]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10 μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: Product name "TSKgel SuperH-RC" 1 column (manufactured by Tosoh Corporation)
Detector: differential refractometer (RI)
Standard sample: Polystyrene

(crosslinking agent)
In the technology disclosed herein, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive may contain a cross-linking agent, if necessary, for the purpose of adjusting the cohesive force of the pressure-sensitive adhesive. As the cross-linking agent, a cross-linking agent known in the field of adhesives such as an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an aziridine-based cross-linking agent, an oxazoline-based cross-linking agent, a melamine-based resin, a metal chelate-based cross-linking agent, etc. can be used. can be done. Among them, isocyanate-based cross-linking agents and epoxy-based cross-linking agents can be preferably employed. Other examples of cross-linking agents include monomers having two or more ethylenically unsaturated groups in one molecule, ie, polyfunctional monomers. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

As the isocyanate-based cross-linking agent, an isocyanate compound having a functionality of 2 or more can be used. , cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis (isocyanatomethyl) alicyclic isocyanates such as cyclohexane; 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate ( XDI) and other aromatic isocyanates; modified polyisocyanates obtained by modifying the above isocyanate compounds with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds, etc.; mentioned. Examples of commercially available products include Takenate 300S, Takenate 500, Takenate 600, Takenate D165N, Takenate D178N (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidule T80, Sumidule L, Desmodur N3400 (Sumika Bayer Urethane Corporation), Millionate MR, Millionate MT, Coronate L, Coronate HL, Coronate HX (all manufactured by Tosoh Corporation), and the like. An isocyanate compound can be used individually by 1 type or in combination of 2 or more types. A bifunctional isocyanate compound and a trifunctional or higher isocyanate compound may be used in combination.

Epoxy cross-linking agents include, for example, bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylol. Propane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, Pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecane Diol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, epoxy acrylate , polyester acrylate, urethane acrylate, butyldiol (meth)acrylate, hexyldiol di(meth)acrylate, and the like. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The amount of the cross-linking agent (which may be a polyfunctional monomer) is not particularly limited, and is, for example, in the range of about 0.001 to 5.0 parts by weight per 100 parts by weight of the monomer component. can do. From the viewpoint of improving the adhesion to the adherend, in some embodiments, the amount of the cross-linking agent used is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less relative to 100 parts by weight of the monomer component. , 1.0 parts by weight or less, 0.5 parts by weight or less, or 0.2 parts by weight or less. Further, from the viewpoint of appropriately exhibiting the effect of using the cross-linking agent, in some embodiments, the amount of the cross-linking agent used relative to 100 parts by weight of the monomer component may be, for example, 0.005 parts by weight or more, and may be 0.01 part by weight. 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.4 parts by weight or more It's okay.

A cross-linking catalyst may be used to promote the cross-linking reaction more effectively. Examples of cross-linking catalysts include metallic cross-linking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, Nasem ferric, butyltin oxide, and dioctyltin dilaurate. Of these, tin-based cross-linking catalysts such as dioctyltin dilaurate are preferred. The amount of cross-linking catalyst used is not particularly limited. The amount of the cross-linking catalyst used relative to 100 parts by weight of the monomer component is, for example, about 0.0001 part by weight or more and 1 part by weight or less in consideration of the balance between the speed of the crosslinking reaction rate and the length of the pot life of the pressure-sensitive adhesive composition. and it is preferably in the range of 0.001 part by weight or more and 0.5 part by weight or less.

The adhesive composition can contain a compound that causes keto-enol tautomerism as a cross-linking retarder. This can achieve the effect of extending the pot life of the pressure-sensitive adhesive composition. For example, a compound that exhibits keto-enol tautomerism can be preferably used in a pressure-sensitive adhesive composition containing an isocyanate-based cross-linking agent. Various β-dicarbonyl compounds can be used as compounds that cause keto-enol tautomerism. For example, β-diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetic esters (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably employed. Compounds that cause keto-enol tautomerism can be used singly or in combination of two or more. The amount of the compound that causes keto-enol tautomerism can be, for example, 0.1 parts by weight or more and 20 parts by weight or less, or 0.5 parts by weight or more and 10 parts by weight or less, relative to 100 parts by weight of the monomer component. 1 part by weight or more and 5 parts by weight or less.

(High refractive index particles)
The adhesive disclosed herein can contain high refractive index particles as an optional component. Here, the high refractive index particles mean particles capable of increasing the refractive index of the pressure-sensitive adhesive by being contained in the pressure-sensitive adhesive. Hereinafter, the high refractive index particles may be referred to as "particles P _HRI ". HRI stands for high refractive index.

The particle _PHRI is, for example, 1.60 or higher, preferably 1.65 or higher, more preferably 1.70 or higher (1.80 or higher, 1.90 or higher, or even 2.00 or higher). ) may be used. The upper limit of the refractive index of the material constituting the particles P _HRI is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or 2.20 or less. It may be 2.00 or less. The refractive index of the material constituting the particle P _HRI was measured using a commercially available spectroscopic ellipsometer for a single layer film of the material (a film thickness that allows refractive index measurement) at a measurement wavelength of 589 nm and a measurement temperature of 25 ° C. is the refractive index measured under the conditions of As the spectroscopic ellipsometer, for example, the product name "EC-400" (manufactured by JA. Woolam) or its equivalent is used.

The type of particles P _HRI is not particularly limited, and one or more materials that can improve the refractive index of the adhesive are selected from metal particles, metal compound particles, organic particles, and organic-inorganic composite particles. can be selected and used. In some embodiments, as the particles _PHRI , inorganic oxides (for example, metal oxides) that can improve the refractive index of the pressure-sensitive adhesive sheet can be preferably used. Preferable examples of materials constituting the particles _PHRI include titania (titanium oxide, TiO ₂ ), zirconia (zirconium oxide, ZrO ₂ ), aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide ( Nb ₂ O ₅ , etc.) and other inorganic oxides (specifically, metal oxides). Particles composed of these inorganic oxides (for example, metal oxides) can be used singly or in combination of two or more. Among them, particles made of titania or zirconia are preferable, and particles made of zirconia are particularly preferable. As the metal particles, for example, iron-based, zinc-based, tungsten-based, and platinum-based materials can have a high refractive index. As the organic particles, particles made of resins such as styrene resins, phenol resins, polyester resins, and polycarbonate resins have a relatively high refractive index. Examples of the organic-inorganic composite particles include composites of the aforementioned inorganic material and organic material, inorganic particles coated with an organic material such as a resin, and the like. From the viewpoint of compatibility with the pressure-sensitive adhesive component, the particles _PHRI may be the above-mentioned organic or inorganic particles surface-treated with a surface-treating agent.

The average particle size of the particles _PHRI is not particularly limited, and particles having an appropriate size that can achieve the desired refractive index improvement by being contained in the pressure-sensitive adhesive can be used. The average particle size of the particles _PHRI can be, for example, about 1 nm or more, suitably about 5 nm or more. From the viewpoint of improving the refractive index and handling properties, the average particle size of the particles _PHRI is preferably approximately 10 nm or more, may be approximately 20 nm or more, or may be approximately 30 nm or more. Also, from the viewpoint of maintaining adhesive properties, etc., the upper limit of the average particle diameter is, for example, about 300 nm or less. It is about 50 nm or less, and may be about 35 nm or less (for example, about 25 nm or less).

The average particle diameter of the particles _PHRI refers to the volume average particle diameter _. It refers to the particle diameter at an integrated value of 50% (50% volume average particle diameter; hereinafter sometimes abbreviated as _D50 ). As the measuring device, for example, the product name "Microtrac MT3000II" manufactured by Microtrac Bell or its equivalent can be used.

The content of particle _PHRI in the adhesive is not particularly limited. The content of the particle _PHRI can vary depending on the desired refractive index. For example, the content of the particles _PHRI can be appropriately set in consideration of the required adhesion properties and the like so that the refractive index is equal to or greater than a predetermined value. In some embodiments, the content of particulate P _HRI in the adhesive can be, for example, approximately 75% by weight or less, and may be approximately 50% by weight or less, or approximately 30% by weight from the standpoint of adhesive properties and transparency. The following may be used. The lower limit of the particle _PHRI content is not particularly limited, and may be, for example, more than 0% by weight, 1% by weight or more, or 5% by weight or more. In some other embodiments, the content of particulate P _HRI in the adhesive is, for example, less than 10 wt%, may be less than 1 wt%, and may be less than 0.1 wt%. The techniques disclosed herein can be practiced in such a manner that the adhesive is substantially free of particulate _PHRI .

The content of particulate P _HRI in the adhesive can also be specified relative to the amount of base polymer contained in the adhesive. The content of the particles P _HRI can be, for example, about 100 parts by weight or less relative to 100 parts by weight of the base polymer. The following may be used. The lower limit of the particle P _HRI content relative to 100 parts by weight of the base polymer is not particularly limited, and may be, for example, more than 0 parts by weight, 1 part by weight or more, or 5 parts by weight or more. In some embodiments, the content of particulate P _HRI is, for example, less than 30 parts by weight, may be less than 10 parts by weight, may be less than 1 part by weight, and may be less than 0.2 parts by weight, based on 100 parts by weight of base polymer. It may be less than 1 part by weight.

(Plasticizer)
The adhesive disclosed herein may contain a plasticizer as an optional component. The use of a plasticizer can reduce the elastic modulus of the adhesive. In addition, in the form molded into a pressure-sensitive adhesive sheet, flexibility and conformability to deformation can be improved. As the plasticizer, an appropriate material that can contribute to lowering the elastic modulus of the pressure-sensitive adhesive can be used. A plasticizer can be used individually by 1 type or in combination of 2 or more types.

In some aspects, the plasticizer is preferably a compound that is liquid at 30°C. In this specification, the term “liquid” means exhibiting fluidity, and refers to a liquid as a substance state. Such compounds include compounds having a melting point of 30° C. or less. Since the plasticizer is liquid at 30° C., the plasticizing effect is preferably exhibited, and the elastic modulus of the pressure-sensitive adhesive can be effectively reduced. The plasticizer is preferably a compound that is liquid at 25°C, more preferably a compound that is liquid at 20°C.

From the viewpoint of suppressing a decrease in the refractive index of the pressure-sensitive adhesive due to blending a plasticizer, in some embodiments, the plasticizer is a compound having two or more double bond-containing rings in one molecule (however, the refractive index excluding compounds having structures corresponding to regulators) can be preferably used. The number of double bond-containing rings contained in the plasticizer is preferably 6 or less, may be 4 or less, or may be 3 or less, from the viewpoint of exhibiting a plasticizing effect.

The double bond-containing ring of the plasticizer may be a conjugated double bond-containing ring (typically an aromatic ring) or a non-conjugated double bond-containing ring. The plasticizer may have at least one ring selected from an aromatic ring and a heterocyclic ring (heterocyclic ring) as the double bond-containing ring. The double bond-containing ring (typically an aromatic ring, preferably a carbocyclic ring) may have one or more substituents on the ring-constituting atoms, or may have no substituents. good. In substituents containing carbon atoms, the number of carbon atoms contained in the substituent is preferably 1-4, more preferably 1-3, and can be, for example, 1 or 2. In some embodiments, the double bond-containing ring has no substituents on the ring atoms, alkyl groups, alkoxy groups, ethylenically unsaturated groups (e.g., (meth)acryloxy groups), hydroxy groups and hydroxy It may be an aromatic ring having one or more substituents selected from the group consisting of alkyl groups (preferably alkyl groups, alkoxy groups, and hydroxyalkyl groups).

In some embodiments, a compound having no ethylenically unsaturated group can be preferably employed as a plasticizer. As a result, deterioration of the pressure-sensitive adhesive composition due to heat or light (decrease in leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be enhanced. Employing a plasticizer that does not have an ethylenically unsaturated group means that, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the plasticizer, changes in elastic modulus, dimensional changes, and deformation ( It is also preferable from the viewpoint of suppressing the occurrence of warpage, waviness, etc.), optical distortion, and the like.

From the viewpoint of suppressing a decrease in the refractive index of the pressure-sensitive adhesive and achieving a low elastic modulus, in some embodiments, the refractive index is about 1.50 or more (preferably about 1.51 or more, more preferably about 1.53 or more , more preferably about 1.55 or higher) can be preferably used. A plasticizer having a refractive index of about 1.56 or higher, about 1.58 or higher, about 1.60 or higher, or about 1.62 or higher may be used. In some aspects, the refractive index of the plasticizer is suitably 2.50 or less, and 2.00 or less, from the viewpoint of ease of preparation of the pressure-sensitive adhesive composition, compatibility in the pressure-sensitive adhesive, and the like. and may be 1.90 or less, 1.80 or less, or 1.70 or less.
The refractive index of the plasticizer is measured using an Abbe refractometer under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. in the same manner as the refractive index of the monomer. If the manufacturer or the like provides the nominal value of the refractive index at 25° C., the nominal value can be adopted.

The molecular weight of the plasticizer is not particularly limited, but usually one with a molecular weight smaller than that of the base polymer is used. The molecular weight of the plasticizer is suitably 30,000 or less, advantageously 25,000 or less, and may be less than 10,000 (e.g., less than 5,000), from the viewpoint of facilitating the expression of the plasticizing effect. It may be less than 3000. In some embodiments, the molecular weight of the plasticizer is preferably 2000 or less, more preferably 1200 or less, even more preferably 900 or less, may be 600 or less, may be 500 or less, may be 400 or less, may be 300 It may be less than or equal to 250 or less (for example, 220 or less). It may be advantageous from the viewpoint of improving the compatibility in the pressure-sensitive adhesive layer that the molecular weight of the plasticizer is not too large. Further, the molecular weight of the plasticizer is suitably 100 or more, preferably 130 or more, more preferably 150 or more, more preferably 170 or more, from the viewpoint of easily exhibiting a sufficient plasticizing effect. , 200 or more, 220 or more, or 250 or more. It is preferable that the molecular weight of the plasticizer is not too low from the viewpoint of the heat resistance of the pressure-sensitive adhesive sheet and the suppression of contamination of the adherend.
As the molecular weight of the plasticizer, a molecular weight calculated based on the chemical structure is used. When the nominal value of the molecular weight is provided by the manufacturer or the like, the nominal value can be adopted.

In some aspects, an ethylene glycol-based compound having two or more double bond-containing rings in one molecule can be used as a plasticizer. The number of oxyethylene units (that is, —(C ₂ H ₄ O)—units) possessed by the ethylene glycol compound is, for example, 1 to 10, may be 1 to 6, or may be 2 to 4. The ethylene glycol-based compound has two or more non-fused double bond-containing rings containing oxyethylene units (for example, 1 to 10, preferably 1 to 6, typically 2 to 4 oxyethylene units) as linking groups. ) can be a compound having a structure linked via Such compounds may have one or more ester groups. Examples of the ethylene glycol-based compound include compounds having a structure in which two or more benzoic acids are linked to ethylene glycol, diethylene glycol, triethylene glycol or polyethylene glycol via an ester bond.

In some other embodiments, liquid rosins such as liquid rosin esters can be used as plasticizers. The above-mentioned liquid rosins (for example, liquid rosin esters) can correspond to compounds having the above-mentioned condensed double bond-containing ring structure.

Further, as other examples of plasticizers that can be used in the pressure-sensitive adhesive disclosed herein, known plasticizers other than the above (e.g., phthalate-based, terephthalate-based, adipic acid ester-based, adipic acid-based polyester , benzoic acid glycol ester, etc.) and plasticizing materials such as liquid camphenphenol.

The amount of plasticizer used is not particularly limited and can be set according to the purpose. From the viewpoint of reducing the elastic modulus of the adhesive, the amount of the plasticizer used relative to 100 parts by weight of the base polymer may be, for example, 1 part by weight or more, may be 10 parts by weight or more, or may be 15 parts by weight or more (for example, 15 parts by weight), 20 parts by weight or more, 30 parts by weight or more (for example, 30 parts by weight or more), 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 75 parts by weight or more, or 90 It may be more than parts by weight. In addition, from the viewpoint of achieving both a high refractive index and a low elastic modulus of the pressure-sensitive adhesive in a well-balanced manner, the amount of the plasticizer used with respect to 100 parts by weight of the base polymer is preferably about 200 parts by weight or less. It is preferably 120 parts by weight or less, more preferably 120 parts by weight or less, 100 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, 45 parts by weight or less, or 35 parts by weight. Part or less is acceptable.

(Additive (H _RO ))
The pressure-sensitive adhesive disclosed herein contains, as an optional additive, an organic material having a higher refractive index than the base polymer (excluding compounds having a structure corresponding to the above refractive index modifier). be able to. Hereinafter, such an organic material may be referred to as an "additive (H _RO )". Here, the above "H _RO " represents an organic material with a high refractive index (High Refractive index). By using the additive (H _RO ) and the refractive index adjuster in combination, it is possible to realize a pressure-sensitive adhesive that satisfactorily balances the refractive index and the pressure-sensitive adhesive properties (peel strength, flexibility, etc.). The organic materials used as additives (H _RO ) may be polymeric or non-polymeric. Moreover, it may or may not have a polymerizable functional group. In this specification, the additive (H _RO ) is defined as different from the compound used as the plasticizer described above. Therefore, the additive (H _RO ) is specifically not liquid at 30° C. (eg 25° C. or 20° C.). Additives (H _RO ) can be used singly or in combination of two or more.

The refractive index of the additive (H _RO ) is not limited to a specific range because it can be set within an appropriate range in relation to the refractive index of the base polymer. The refractive index of the additive (H _RO ) may be selected from a range, for example greater than 1.55, greater than 1.56 or greater than 1.57 and higher than the refractive index of the base polymer. From the viewpoint of increasing the refractive index of the adhesive, in some aspects, the refractive index of the additive (H _RO ) is advantageously 1.58 or more, preferably 1.60 or more, It is more preferably 1.63 or more, may be 1.65 or more, may be 1.70 or more, or may be 1.75 or more. The upper limit of the refractive index of the additive (H _RO ) is not particularly limited. 000 or less, 2.500 or less, 2.000 or less, 1.950 or less, 1.900 or less, or 1.850 or less.
The refractive index of the additive (H _RO ) is measured using an Abbe refractometer under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25° C. in the same manner as the refractive index of the monomer. If the manufacturer or the like provides the nominal value of the refractive index at 25° C., the nominal value can be adopted.

The molecular weight of the organic material used as the additive (H _RO ) is not particularly limited and can be selected depending on the purpose. From the viewpoint of achieving a good balance between the effect of increasing the refractive index and other properties (e.g., flexibility suitable for adhesives, optical properties such as haze), in some embodiments, the molecular weight of the additive (H _RO ) is suitably less than about 10000, preferably less than 5000, more preferably less than 3000 (e.g. less than 1000), may be less than 800, may be less than 600, may be less than 500, It may be less than 400. It may be advantageous from the viewpoint of improving the compatibility in the adhesive that the molecular weight of the additive (H _RO ) is not too large. Moreover, the molecular weight of the additive (H _RO ) may be, for example, 130 or more, or 150 or more. In some aspects, the molecular weight of the additive (H _RO ) is preferably 170 or more, more preferably 200 or more, more preferably 230, from the viewpoint of increasing the refractive index of the additive (H _RO ). 250 or more, 270 or more, 500 or more, 1000 or more, or 2000 or more. In some embodiments, a polymer with a molecular weight of about 1000 to 10000 (eg, 1000 or more and less than 5000) can be used as the additive (H _RO ).
The molecular weight of the additive (H _RO ) is calculated based on the chemical structure in the case of a non-polymer or a polymer with a low degree of polymerization (for example, about 2- to 5-mer), as in the case of the refractive index modifier. Molecular weights or measurements using MALDI-TOF-MS can be used. If the additive (H _RO ) is a polymer with a higher degree of polymerization, the weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. When the nominal value of the molecular weight is provided by the manufacturer or the like, the nominal value can be adopted.

Examples of organic materials that can be selected as the additive (H _RO ) include organic compounds having an aromatic ring, organic compounds having a heterocyclic ring (which may be an aromatic ring or a non-aromatic heterocyclic ring), and the like. including but not limited to:
The aromatic ring of the organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") used as the additive (H _RO ) is the same as the aromatic ring of the compound used as the monomer (m1). can be selected from
Examples of aromatic ring-containing compounds that can be used as additives (H _RO ) include: compounds that can be used as monomers (m1); oligomers that contain compounds that can be used as monomers (m1) as monomer units; monomers (m1 ), except for a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring-constituting atom) or a portion of the group that constitutes an ethylenically unsaturated group, a hydrogen atom or A compound having a structure substituted with a group having no ethylenically unsaturated group (e.g., hydroxyl group, amino group, halogen atom, alkyl group, alkoxy group, hydroxyalkyl group, hydroxyalkyloxy group, glycidyloxy group, etc.); Examples include, but are not limited to, those not falling under the refractive index modifiers and plasticizers disclosed herein.

In some embodiments, as the additive (H _RO ), an organic compound having two or more aromatic rings in one molecule (hereinafter referred to as "multiple aromatic ring-containing compound ”) can be preferably adopted. The compound containing multiple aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. Also, the compound containing multiple aromatic rings may be a polymer or a non-polymer. Further, the polymer is an oligomer (preferably an oligomer having a molecular weight of about 5,000 or less, more preferably about 1,000 or less, for example, a low polymer of about 2- to 5-mers) containing multiple aromatic ring-containing monomers as monomer units. obtain. The above oligomers are, for example: homopolymers of monomers containing multiple aromatic rings; copolymers of one or more monomers containing multiple aromatic rings; monomers containing one or more multiple aromatic rings and other monomers. a copolymer of; The above-mentioned other monomer may be an aromatic ring-containing monomer that does not correspond to a monomer containing multiple aromatic rings, a monomer having no aromatic ring, or a combination thereof.

In some aspects, a compound having no ethylenically unsaturated groups can be preferably employed as the additive (H _RO ). As a result, deterioration of the pressure-sensitive adhesive composition due to heat or light (decrease in leveling properties due to progression of gelation or increase in viscosity) can be suppressed, and storage stability can be enhanced. Employing an additive (H _RO ) that does not have an ethylenically unsaturated group prevents a dimensional change due to the reaction of the ethylenically unsaturated group in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the additive (H _RO ). It is also preferable from the viewpoint of suppressing deformation (warpage, waviness, etc.), generation of optical distortion, and the like.

The amount of the additive (H _RO ) used relative to 100 parts by weight of the base polymer (the total amount thereof when using multiple types of compounds) is not particularly limited as long as it exceeds 0 parts by weight, and is set according to the purpose. be able to. In some embodiments, the amount of the additive (H _RO ) used relative to 100 parts by weight of the base polymer can be, for example, 80 parts by weight or less to achieve a balance between increasing the refractive index of the adhesive and suppressing deterioration of adhesive properties. From the viewpoint of good compatibility, it is advantageous to use 60 parts by weight or less, preferably 45 parts by weight or less. In some aspects in which more emphasis is placed on adhesive properties and optical properties, the amount of the additive (H _RO ) used relative to 100 parts by weight of the base polymer may be, for example, 30 parts by weight or less, may be 20 parts by weight or less, or may be 15 parts by weight or less. It may be less than or equal to 10 parts by weight. In addition, from the viewpoint of increasing the refractive index of the adhesive, the amount of the additive (H _RO ) used relative to 100 parts by weight of the base polymer can be, for example, 1 part by weight or more, and is preferably 3 parts by weight or more. It is preferably 5 parts by weight or more, may be 7 parts by weight or more, may be 10 parts by weight or more, may be 15 parts by weight or more, or may be 20 parts by weight or more.

(Tackifier)
The adhesive disclosed herein may contain a tackifier. Tackifiers include rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, hydrocarbon-based tackifier resins, ketone-based tackifier resins, polyamide-based tackifier resins, epoxy-based tackifier resins, and elastomers. Known tackifying resins can be used, such as system tackifying resins. These can be used individually by 1 type or in combination of 2 or more types. The amount of the tackifying resin to be used is not particularly limited, and can be set so as to exhibit appropriate adhesive performance depending on the purpose and application. In some embodiments, from the viewpoint of refractive index and transparency, the amount of the tackifier to be used with respect to 100 parts by weight of the base polymer is suitably 30 parts by weight or less, preferably 10 parts by weight or less. , 5 parts by weight or less. The technology disclosed herein can be preferably practiced in a mode that does not use a tackifier.

(Other additives)
In addition, the pressure-sensitive adhesive disclosed herein includes leveling agents, softening agents, coloring agents (dyes, pigments, etc.), fillers, antistatic agents, anti-aging agents, ultraviolet Known additives that can be used in pressure-sensitive adhesives, such as absorbents, antioxidants, light stabilizers, preservatives, etc., may optionally be included. As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

(refractive index)
The refractive index of the pressure-sensitive adhesive disclosed herein is not particularly limited, and can be set depending on the purpose (for example, considering the refractive index of the adherend). The refractive index of the adhesive disclosed herein can be, for example, about 1.300 to 1.900 (preferably about 1.450 to 1.800). In some embodiments, the refractive index of the pressure-sensitive adhesive is higher than that of conventional general acrylic pressure-sensitive adhesives. According to the technology disclosed herein, a pressure-sensitive adhesive having a refractive index of, for example, 1.550 or more, a pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive can be provided. The refractive index of the pressure-sensitive adhesive is suitably 1.560 or more, preferably more than 1.570. In some embodiments, the adhesive may have a refractive index of 1.575 or higher, 1.580 or higher, or 1.585 or higher. A pressure-sensitive adhesive having such a refractive index can suitably suppress light reflection at the interface with an adherend in a mode of use in which it is attached to a material with a high refractive index. A preferable upper limit of the refractive index of the pressure-sensitive adhesive is not limited to a specific range because it may vary depending on the refractive index of the adherend and the like. It may be 650 or less, 1.620 or less, or 1.600 or less. The refractive index of the pressure-sensitive adhesive can be adjusted, for example, by the composition of the pressure-sensitive adhesive (for example, the type of base polymer, the type and amount of refractive index modifier used, and the presence or absence of other optional components).

In this specification, the refractive index of the adhesive refers to the refractive index of the surface (adhesive surface) of the adhesive. The refractive index of the pressure-sensitive adhesive can be measured using a commercially available refractive index measuring device (Abbe refractometer) under conditions of a measurement wavelength of 589 nm and a measurement temperature of 25°C. As the Abbe refractometer, for example, model "DR-M4" manufactured by ATAGO or its equivalent is used. As a measurement sample, an adhesive layer made of an adhesive to be evaluated can be used. Specifically, the refractive index of the pressure-sensitive adhesive can be measured by the method described in Examples below.

(Storage modulus G')
The storage elastic modulus G′ at 25° C. of the pressure-sensitive adhesive disclosed herein (hereinafter also referred to as “storage elastic modulus G′(25)”) is appropriately set according to the purpose of use, the mode of use, etc. is not limited to the range of The storage modulus G'(25) of the adhesive can be, for example, approximately 2000 kPa or less. In some embodiments, the storage elastic modulus G'(25) of the pressure-sensitive adhesive is advantageously approximately 1500 kPa or less, preferably 1000 kPa or less, from the viewpoint of ease of application to adherends and the like. , 800 kPa or less. In some embodiments, the storage elastic modulus G′(25) of the adhesive is about 650 kPa or less from the viewpoint of increasing the flexibility of the adhesive in the room temperature range (for example, 25° C.) and making it easier to adhere to the adherend. It is preferably 550 kPa or less, 450 kPa or less, 350 kPa or less, or 300 kPa or less. In some embodiments in which the stickability and flexibility in the room temperature range are more important, the storage modulus G'(25) of the adhesive may be, for example, less than 270 kPa, less than 250 kPa, less than 200 kPa, or less than 180 kPa. Well, less than 160 kPa (eg, less than 140 kPa). In some embodiments, the adhesive's storage modulus G'(25) may be less than 100 kPa, and may be less than 90 kPa. Although the lower limit of the storage modulus G'(25) of the adhesive is not particularly limited, it may be, for example, 30 kPa or more, 50 kPa or more, or 70 kPa or more from the viewpoint of workability and handleability. In some embodiments, in consideration of increasing the refractive index, the storage modulus G'(25) may be 100 kPa or more, 150 kPa or more, 200 kPa or more, 250 kPa or more, or 300 kPa or more, It may be 500 kPa or more, 600 kPa or more, or 700 kPa or more.

The storage elastic modulus G' at 50°C of the adhesive disclosed herein (hereinafter also referred to as "storage elastic modulus G'(50)") is not particularly limited, and may be, for example, less than 600 kPa. In some embodiments, the storage modulus G′(50) is suitably less than 400 kPa, preferably less than 250 kPa, may be less than 200 kPa, may be less than 150 kPa, may be less than 100 kPa, may be less than 70 kPa It may be less than 50 kPa, less than 38 kPa or less than 36 kPa. The pressure-sensitive adhesive having a limited storage elastic modulus G'(50) in this way can be easily enhanced in adhesion to the adherend by performing moderate heating as necessary. can improve adhesion to The lower limit of the storage modulus G'(50) of the adhesive is not particularly limited. In some embodiments, the storage modulus G'(50) may be, for example, 10 kPa or more, 15 kPa or more, 20 kPa or more, or 23 kPa or more, from the viewpoint of heat resistance properties of the adhesive. In some embodiments, the storage elastic modulus G'(50) of the pressure-sensitive adhesive may be 40 kPa or more, 70 kPa or more, or 120 kPa or more in consideration of increasing the refractive index. It may be 170 kPa or more.

In some embodiments of the adhesives disclosed herein, the adhesives are:
(a) a storage modulus G′(25) at 25° C. of 1500 kPa or less (preferably 1000 kPa or less, such as 550 kPa or less, 350 kPa or less or 180 kPa or less); and (b) a storage modulus G′(50) at 50° C. ) is less than 400 kPa (preferably less than 200 kPa, more preferably less than 150 kPa, such as less than 100 kPa or less than 50 kPa);
It is preferable to satisfy at least one of A pressure-sensitive adhesive that satisfies at least the above condition (a) is preferable from the viewpoint of adhesion to an adherend in a room temperature range (for example, 25° C.). A pressure-sensitive adhesive that satisfies at least the above condition (b) is preferable because the adhesiveness (adhesiveness) to the adherend can be easily improved by heating to a temperature slightly higher than room temperature. A pressure-sensitive adhesive that does not satisfy the above condition (a) but satisfies the above (b) has good reworkability (re-adhesion property) at the initial stage of application in the room temperature range, and can be reworked by heating to a temperature slightly higher than room temperature. It can be used as a heat-activated pressure-sensitive adhesive that can effectively increase the peel strength from the adherend. The heat activation may be performed by heating the pressure-sensitive adhesive to a temperature slightly higher than room temperature when it is attached to the adherend. The temperature slightly higher than room temperature is, for example, about 60° C. or lower, preferably about 55° C. or lower (for example, about 50° C. or lower).

(Glass-transition temperature)
The glass transition temperature (Tg) of the pressure-sensitive adhesive is not particularly limited, and can be set in consideration of flexibility in a low temperature range and cohesion (heat resistance, etc.) in a high temperature range. In some embodiments, the Tg of the pressure-sensitive adhesive is, for example, 50° C. or less, may be 40° C. or less, may be 30° C. or less, may be 15° C. or less, or may be 5° C. or less. In some preferred embodiments, the Tg of the adhesive is 0° C. or lower, more preferably -5° C. or lower, still more preferably -10° C. or lower, and -15° C. or lower (e.g., -20° C. or lower) from the viewpoint of flexibility. ° C. or less). The lower the Tg of the pressure-sensitive adhesive, the more excellent the pressure-sensitive adhesive properties such as adhesion to the adherend tend to be. The lower limit of the Tg of the adhesive is, for example, -50°C or higher, preferably -40°C or higher, and may be -30°C or higher. A pressure-sensitive adhesive having the above Tg tends to provide an appropriate cohesive force.

The storage elastic modulus G' and the glass transition temperature Tg of the adhesive at each of the above temperatures are determined by dynamic viscoelasticity measurement. Specifically, a sheet-like pressure-sensitive adhesive with a thickness of about 1.5 mm (for example, it can be prepared by appropriately laminating pressure-sensitive adhesive layers) is punched into a disk shape with a diameter of 7.9 mm. As a sample for use, dynamic viscoelasticity measurement is performed under the following conditions. From the measurement results, the storage elastic modulus G' [Pa] of the pressure-sensitive adhesive at each temperature can be determined. Further, the glass transition temperature (Tg) [° C.] of the adhesive is obtained as a temperature corresponding to the peak top temperature of the loss tangent tan δ (loss elastic modulus G″/storage elastic modulus G′) in the dynamic viscoelasticity measurement. As a measuring device, "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific or its equivalent can be used. The storage elastic modulus G′ and glass transition temperature Tg of the pressure-sensitive adhesive are determined, for example, by selecting the type and amount of the refractive index modifier, and selecting the composition of the base polymer (for example, selecting the type and content of the monomer (m1)). , the presence or absence of the use of a cross-linking agent, selection of the type and amount of use, and the like.
[Measurement condition]
Deformation mode: Torsion Measurement frequency: 1Hz
Temperature range: -50°C to 150°C
Heating rate: 5°C/min

<Adhesive sheet>
According to this specification, any pressure-sensitive adhesive disclosed herein (a pressure-sensitive adhesive formed from any pressure-sensitive adhesive composition disclosed herein, such as a cured product of the pressure-sensitive adhesive composition) , preferably in the form of an adhesive layer.
The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a substrate having the pressure-sensitive adhesive layer on one or both sides of a non-releasable substrate (supporting substrate), and the pressure-sensitive adhesive layer is held by a release liner. It may be a substrate-less pressure-sensitive adhesive sheet (that is, a pressure-sensitive adhesive sheet having no non-releasable substrate, typically a pressure-sensitive adhesive layer). The concept of the adhesive sheet as used herein can include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The pressure-sensitive adhesive sheet disclosed herein may be roll-shaped or sheet-shaped. Alternatively, it may be a pressure-sensitive adhesive sheet processed into various shapes.

　Figures 1 and 2 show configuration examples of a double-sided adhesive type baseless adhesive sheet (baseless double-sided adhesive sheet). The pressure-sensitive adhesive sheet 1 shown in FIG. 1 has a configuration in which both surfaces 21A and 21B of a substrate-less pressure-sensitive adhesive layer 21 are protected by release liners 31 and 32 whose release surfaces are at least on the pressure-sensitive adhesive layer side. The adhesive sheet 2 shown in FIG. 2 has a configuration in which one surface (adhesive surface) 21A of a substrate-less adhesive layer 21 is protected by a release liner 31 having release surfaces on both sides. When wound, the other surface (adhesive surface) 21B of the adhesive layer 21 contacts the back surface of the release liner 31, so that the other surface 21B is also protected by the release liner 31. The technology disclosed herein is preferably implemented in the form of a substrate-less pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer, from the viewpoint of flexibility to follow an adherend that is repeatedly bent. The substrate-less pressure-sensitive adhesive sheet is preferable, for example, from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet and from the viewpoint of increasing the transparency of the pressure-sensitive adhesive sheet.

The adhesive sheet disclosed here can have, for example, the cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 3 shown in FIG. Prepare. Both the first surface 10A and the second surface 10B are non-peeling surfaces (non-peeling surfaces). The adhesive sheet 3 is used by attaching the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 to an adherend. That is, the adhesive sheet 3 is configured as a double-sided adhesive sheet (double-sided adhesive adhesive sheet). The pressure-sensitive adhesive sheet 3 before use has a first pressure-sensitive adhesive surface 21A and a second pressure-sensitive adhesive surface 22A protected by release liners 31 and 32, respectively, at least on which the pressure-sensitive adhesive surface side is a surface (release surface) having releasability. have a configuration. Alternatively, the release liner 32 may be omitted and a release liner 31 having release surfaces on both sides may be used. Therefore, the second adhesive surface 22A may also be protected by the release liner 31 .

The technology disclosed herein is preferably implemented in the form of the above-described substrate-less or substrate-attached double-sided pressure-sensitive adhesive sheet for fixing or bonding members (for example, optical members). Alternatively, the PSA sheet disclosed herein may be in the form of a substrate-attached single-sided PSA sheet having an adhesive layer only on one side of a non-releasable substrate (supporting substrate), although not shown. As an example of the form of the single-sided pressure-sensitive adhesive sheet, the form shown in FIG.

(Adhesive layer)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein can be formed by applying (for example, applying) a pressure-sensitive adhesive composition to a suitable surface and then curing the composition. Application of the pressure-sensitive adhesive composition can be carried out using a conventional coater such as gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, and spray coater.

The thickness of the adhesive layer is not particularly limited, and can be, for example, 3 μm or more. In some aspects, the thickness of the pressure-sensitive adhesive layer is, for example, suitably 5 μm or more, and may be 10 μm or more, 15 μm or more, 20 μm or more, 30 μm or more, or 50 μm or more. or 70 μm or more or 85 μm or more. The adhesive strength tends to increase as the thickness of the adhesive layer increases. In some aspects, the thickness of the adhesive layer may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. In some preferred embodiments, the thickness of the adhesive layer is 100 μm or less, more preferably 75 μm or less, even more preferably 70 μm or less, and may be 50 μm or less, or 30 μm or less. It may be advantageous from the viewpoint of thinning of the adhesive sheet that the thickness of the adhesive layer is not too large. In addition, a thin pressure-sensitive adhesive layer tends to have excellent conformability to an adherend. The technique disclosed herein can be preferably carried out in a mode in which the thickness of the pressure-sensitive adhesive layer is, for example, in the range of 3 μm to 200 μm (more preferably 5 μm to 100 μm, still more preferably 5 μm to 75 μm). In the case of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first surface and the second surface of the substrate, the thickness of the pressure-sensitive adhesive layer is at least the thickness of the first pressure-sensitive adhesive layer. can be applied to The thickness of the second adhesive layer can also be selected from the same range. Moreover, in the case of a substrate-less pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive sheet matches the thickness of the pressure-sensitive adhesive layer.

(optical properties)
In some embodiments, the haze value of the adhesive layer may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less. It is more preferably 0% or less, and particularly preferably less than 1.0% (for example, 0.9% or less). Such a pressure-sensitive adhesive sheet having a highly transparent pressure-sensitive adhesive layer can be used for applications that require high light transmittance (for example, optical applications) in a structure with or without a substrate, and for applications where an adherend is passed through the pressure-sensitive adhesive sheet. It can be preferably applied to applications where good visibility performance is required. The lower limit of the haze value of the pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the better. On the other hand, in some aspects, the haze value may be, for example, 0.05% or more, or 0.10% or more, in consideration of the refractive index and adhesion properties. These haze values for the pressure-sensitive adhesive layer are the haze values of the pressure-sensitive adhesive sheet when the technology disclosed herein is implemented in the form of a substrate-less pressure-sensitive adhesive sheet (typically, a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer). can also be preferably applied.

Here, the term "haze value" refers to the ratio of diffuse transmitted light to total transmitted light when the object to be measured is irradiated with visible light. Also called cloudiness value. A haze value can be represented by the following formula.
Th (%) = Td/Tt x 100
In the above formula, Th is the haze value (%), Td is the scattered light transmittance, and Tt is the total light transmittance. The haze value can be measured according to the method described in Examples below. The haze value of the pressure-sensitive adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the pressure-sensitive adhesive layer.

In some embodiments, the haze value of the pressure-sensitive adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less, more preferably 2.0% or less, and 1.0%. % or less, and particularly preferably less than 1.0% (for example, 0.9% or less). Such a highly transparent pressure-sensitive adhesive sheet can be preferably applied to applications that require high light transmittance (for example, optical applications) and applications that require good visibility of adherends through the pressure-sensitive adhesive sheet. The lower limit of the haze value of the pressure-sensitive adhesive sheet is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the better. On the other hand, in some aspects, the haze value may be, for example, 0.05% or more, or 0.10% or more, in consideration of the refractive index and adhesion properties. The haze value of the pressure-sensitive adhesive sheet can be measured by the same method as for measuring the haze value of the pressure-sensitive adhesive layer. The haze value of the pressure-sensitive adhesive sheet can be obtained by selecting the composition of the pressure-sensitive adhesive layer described above, or by selecting the type of substrate and the thickness of the substrate in a structure having a substrate.

In some aspects, the total light transmittance of the pressure-sensitive adhesive layer is preferably 85.0% or more (eg, 88.0% or more, 90.0% or more, or more than 90.0%). Such a pressure-sensitive adhesive sheet having a highly transparent pressure-sensitive adhesive layer can be used for applications that require high light transmittance (for example, optical applications) in a structure with or without a substrate, and for applications where an adherend is passed through the pressure-sensitive adhesive sheet. It can be preferably applied to applications where good visibility performance is required. Practically, the upper limit of the total light transmittance may be, for example, approximately 98% or less, approximately 96% or less, or approximately 95% or less. In some aspects, the total light transmittance of the adhesive layer may be approximately 94% or less, approximately 93% or less, or approximately 92% or less, taking into account the refractive index and adhesive properties. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade name "Hazemeter HM-150" manufactured by Murakami Color Research Laboratory or its equivalent is used. The total light transmittance can be measured according to the method described in Examples below. The total light transmittance of the pressure-sensitive adhesive layer can be adjusted, for example, by selecting the composition, thickness, etc. of the pressure-sensitive adhesive layer.

In some aspects, the total light transmittance of the adhesive sheet is preferably 85.0% or higher (eg, 88.0% or higher, 89.0% or higher, or 90.0% or higher). Such a highly transparent pressure-sensitive adhesive sheet can be preferably applied to applications that require high light transmittance (for example, optical applications) and applications that require good visibility of adherends through the pressure-sensitive adhesive sheet. Practically, the upper limit of the total light transmittance may be, for example, approximately 98% or less, approximately 96% or less, or approximately 95% or less. In some aspects, the total light transmittance of the adhesive sheet may be approximately 94% or less, approximately 93% or less, or approximately 92% or less, in consideration of refractive index and adhesive properties. The total light transmittance of the adhesive sheet can be measured by the same method as for measuring the total light transmittance of the adhesive layer. The total light transmittance of the pressure-sensitive adhesive sheet can be obtained by selecting the composition of the pressure-sensitive adhesive layer described above, or by selecting the type of base material and the thickness of the base material in a structure having a base material.

The chromaticity b ^* defined by the L ^* a ^* b ^* color system of the pressure-sensitive adhesive layer is not particularly limited, but in some aspects (for example, aspects assumed to be applied to optical applications), ±15 , preferably ±10, more preferably ±5.0 (for example, ±1.0). In this specification, the term “±X range” is used to mean the range from −X to +X.
Here, the L ^* a ^* b ^* color system in this specification complies with the 1976 recommendation by the International Commission on Illumination or the JIS Z 8729 standard. Specifically, L ^* a ^* b ^* is measured at multiple locations (eg, 5 locations or more) on the surface of the pressure-sensitive adhesive layer using a color difference meter (trade name “CR-400” manufactured by Minolta Co., Ltd.; color difference meter). , and the average value should be adopted. The same applies to the examples described later.

(Peel strength)
The peel strength of the adhesive sheet to the glass plate is not particularly limited. In some aspects, the adhesive sheet has a peel strength to a glass plate of, for example, 0.1 N/25 mm or more, preferably 0.5 N/25 mm or more, or 1.0 N/25 mm or more, or 1.5 N /25 mm or more, 2.0 N/25 mm or more, or 3.0 N/25 mm or more. The upper limit of the peel strength is not particularly limited, and may be, for example, 30 N/25 mm or less, 25 N/25 mm or less, or 20 N/25 mm or less.
Here, the above-mentioned peel strength is measured by pressure bonding to an alkali glass plate as an adherend and leaving it for 30 minutes in an environment of 23° C. and 50% RH, and then peel strength under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm/min. is grasped by measuring In the measurement, if necessary, the adhesive sheet to be measured can be reinforced by attaching an appropriate backing material (for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm to 50 μm).

(Thickness of adhesive sheet)
The thickness of the adhesive sheet disclosed herein (substrate-less adhesive sheet or substrate-attached adhesive sheet) may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, 120 μm or less, or 75 μm or less. or less than 50 μm. The thickness of the pressure-sensitive adhesive sheet may be, for example, 5 µm or more, 10 µm or more, 25 µm or more, 80 µm or more, or 130 µm or more, from the viewpoint of handleability.
The thickness of the pressure-sensitive adhesive sheet refers to the thickness of the portion to be adhered to the adherend. For example, in the pressure-sensitive adhesive sheet 3 having the configuration shown in FIG.

<Support base material>
The pressure-sensitive adhesive sheet according to some embodiments may be in the form of a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a supporting substrate. The material of the supporting substrate is not particularly limited, and can be appropriately selected according to the intended use, mode of use, etc. of the pressure-sensitive adhesive sheet. Non-limiting examples of substrates that can be used include polyolefin films based on polyolefins such as polypropylene (PP) and ethylene-propylene copolymers, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene Plastic films such as polyester films mainly composed of polyester such as phthalate (PEN), polyvinyl chloride films mainly composed of polyvinyl chloride; foams such as polyurethane foam, polyethylene (PE) foam, polychloroprene foam, etc. Foam sheet; woven fabric and non-woven fabric made of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) alone or blended; paper such as Japanese paper, fine paper, kraft paper, and crepe paper; metal foil such as aluminum foil and copper foil; A base material having a structure in which these are combined may be used. Examples of such composite substrates include substrates having a structure in which a metal foil and the plastic film are laminated, plastic substrates reinforced with inorganic fibers such as glass cloth, and the like.

In some embodiments, various film substrates can be preferably used. The film substrate may be a porous substrate such as a foam film or a nonwoven fabric sheet, or may be a non-porous substrate. It may be a substrate having a structure in which is laminated. In some embodiments, as the film substrate, one containing a resin film that can independently maintain its shape (self-supporting or independent) as a base film can be preferably used. As used herein, "resin film" means a non-porous structure, typically a substantially voidless resin film. Therefore, the resin film is a concept distinguished from foam films and non-woven fabrics. As the resin film, a film that can maintain its shape independently (self-supporting or independent) can be preferably used. The resin film may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polyester; polyolefin; polycycloolefin derived from a monomer having an alicyclic structure such as norbornene structure; polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide. Polyimide (PI) such as transparent polyimide (CPI); Polyamideimide (PAI); Polyetheretherketone (PEEK); Polyethersulfone (PES); Polyphenylene sulfide (PPS); Polycarbonate (PC); Polyurethane (PU); Ethylene-vinyl acetate copolymer (EVA); fluorine resin such as polytetrafluoroethylene (PTFE); acrylic resin; cellulose-based polymer such as triacetyl cellulose (TAC); polyarylate; ; and other resins can be used.

The resin film may be formed using a resin material containing only one of such resins, or may be formed using a resin material in which two or more of these resins are blended. good too. The resin film may be unstretched or may be stretched (for example, uniaxially stretched or biaxially stretched). For example, PET film, PBT film, PEN film, unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, PP/PE A blend film, a cycloolefin polymer (COP) film, a CPI film, a TAC film, etc. can be preferably used. PET films, PEN films, PPS films and PEEK films are examples of preferred resin films from the viewpoint of strength and dimensional stability. PET films and PPS films are particularly preferred from the standpoint of availability, etc., and PET films are particularly preferred.

In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, coloring agents (dyes, pigments, etc.), fillers, slip agents, anti-blocking agents, etc. are added to the extent that the effects of the present invention are not significantly hindered. can be blended as needed. The blending amount of the additive is not particularly limited, and can be appropriately set according to the use of the pressure-sensitive adhesive sheet.

The method of manufacturing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

The base material may be substantially composed of such a base film. Alternatively, the substrate may contain an auxiliary layer in addition to the base film. Examples of the auxiliary layers include optical property adjusting layers (e.g., colored layers, antireflection layers), printed layers and laminate layers for imparting a desired appearance to the substrate, antistatic layers, undercoat layers, and release layers. and other surface treatment layers.

In some embodiments, a light-transmissive base (hereinafter also referred to as a light-transmissive base) can be preferably employed as the supporting base. This makes it possible to construct a pressure-sensitive adhesive sheet with a substrate having optical transparency. The total light transmittance of the light transmissive substrate may be, for example, greater than 50% and may be 70% or more. In some preferred embodiments, the total light transmittance of the supporting substrate is 80% or higher, more preferably 90% or higher, and may be 95% or higher (eg, 95-100%). The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade name "Hazemeter HM-150" manufactured by Murakami Color Research Laboratory or its equivalent is used. A suitable example of the light-transmitting substrate is a resin film having light-transmitting properties. The light transmissive substrate may be an optical film.

The thickness of the base material is not particularly limited, and can be selected according to the purpose and mode of use of the adhesive sheet. The thickness of the base material may be, for example, 500 μm or less, preferably 300 μm or less from the viewpoint of handling and workability of the adhesive sheet, may be 150 μm or less, may be 100 μm or less, may be 50 μm or less, or may be 25 μm. It may be less than or equal to 10 μm or less. As the thickness of the substrate becomes smaller, the conformability to the surface shape of the adherend tends to improve. Moreover, from the viewpoint of handleability, workability, etc., the thickness of the substrate may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

The surface of the substrate on which the pressure-sensitive adhesive layer is to be laminated may be subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer to form an undercoat layer, if necessary. Conventionally known surface treatments such as forming may be applied. Such a surface treatment may be a treatment for improving the anchoring property of the pressure-sensitive adhesive layer to the substrate. The composition of the primer used for forming the undercoat layer is not particularly limited, and can be appropriately selected from known ones. Although the thickness of the undercoat layer is not particularly limited, it is usually suitably about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. Other treatments that can be applied to the substrate as necessary include antistatic layer forming treatment, colored layer forming treatment, printing treatment, and the like. These treatments can be applied singly or in combination.

<Adhesive sheet with release liner>
The adhesive sheet disclosed herein can take the form of an adhesive product in which the surface (adhesive surface) of the adhesive layer is brought into contact with the release surface of the release liner. Accordingly, this specification provides a PSA sheet with a release liner (adhesive product) comprising any of the PSA sheets disclosed herein and a release liner having a release surface in contact with the adhesive surface of the PSA sheet. be.

The release liner is not particularly limited. For example, a release liner having a release layer on the surface of a liner substrate such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), or a fluoropolymer A release liner or the like made of a resin film formed of a low-adhesive material such as (polytetrafluoroethylene, etc.) or polyolefin resin (polyethylene, polypropylene, etc.) can be used. A release liner having a release layer on the surface of a resin film as a liner substrate or a release liner made of a resin film formed of a low-adhesive material can be preferably employed because of its excellent surface smoothness. The resin film is not particularly limited as long as it is a film capable of protecting the pressure-sensitive adhesive layer. Examples include polyethylene (PE) film, polypropylene (PP) film, polybutene film, polybutadiene film, polymethylpentene film, and polyvinyl chloride film. , vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-vinyl acetate copolymer film, and the like. For the formation of the release layer, for example, silicone-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorine-based release agents, fatty acid amide-based release agents, molybdenum sulfide, silica powder, etc. , a known release treatment agent can be used.

<Application>
The material (adherend material) to which the pressure-sensitive adhesive sheet disclosed herein is attached is not particularly limited, but examples include copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, Chromium, zinc, etc., or metal materials such as alloys containing two or more of these, for example, polyimide resin, acrylic resin, polyethernitrile resin, polyethersulfone resin, polyester resin (PET resin, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, diacetyl cellulose and triacetyl cellulose Various resin materials (typically plastic materials) such as cellulose-based polymers, vinyl butyral-based polymers, liquid crystal polymers, etc., inorganic materials such as alumina, zirconia, alkali glass, alkali-free glass, quartz glass, carbon, etc. . The pressure-sensitive adhesive sheet disclosed herein can be used by being attached to a member (for example, an optical member) made of the above materials.

The member or material (at least one adherend in the double-sided pressure-sensitive adhesive sheet) to which the pressure-sensitive adhesive sheet disclosed herein is attached is made of a material having a higher refractive index than a general acrylic pressure-sensitive adhesive. could be. The refractive index of the adherend material is, for example, 1.50 or more. .66) is also present. Such a high refractive index adherend material is typically a resin material. More specifically, it may be a polyester resin such as PET, a polyimide resin, an aramid resin, a polyphenylene sulfide resin, a polycarbonate resin, or the like. The effect of using the pressure-sensitive adhesive sheet disclosed herein (suppression of reflection of light rays caused by a difference in refractive index) can be favorably exerted on such materials. The upper limit of the refractive index of the adherend material is, for example, 1.80 or less, and may be 1.70 or less. The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode of being attached to an adherend (for example, member) having a high refractive index as described above. Suitable examples of such adherends include resin films having a refractive index of 1.50 to 1.80 (preferably 1.55 to 1.75, eg 1.60 to 1.70). The refractive index can be measured by the same method as the refractive index of the adhesive.

The member or material to which the pressure-sensitive adhesive sheet is attached (at least one adherend in the case of a double-sided pressure-sensitive adhesive sheet) may have optical transparency. With such an adherend, the advantage of the technique disclosed herein (suppression of light reflection at the interface between the adherend and the pressure-sensitive adhesive sheet) is likely to be obtained. The total light transmittance of the adherend may be, for example, greater than 50%, preferably 70% or more. In some preferred embodiments, the adherend has a total light transmittance of 80% or higher, more preferably 90% or higher, and may be 95% or higher (eg, 95-100%). The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode of being attached to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or higher. The total light transmittance is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, the trade name "Hazemeter HM-150" manufactured by Murakami Color Research Laboratory or its equivalent is used.

In some preferred embodiments, the adherend (for example, member) to which the pressure-sensitive adhesive sheet is attached may have the above-described refractive index and the above-described total light transmittance. Specifically, the refractive index is 1.50 or more (for example, 1.55 or more, 1.58 or more, 1.62 or more, about 1.66, etc.) and the total light transmittance is greater than 50% ( For example, 70% or more, preferably 80% or more, more preferably 90% or more, and further 95% or more). obtain. The effect of the technology disclosed herein is particularly preferably exhibited in the aspect of being attached to such a member.

An example of a preferred use is optical use. More specifically, for example, it is disclosed herein as an optical pressure-sensitive adhesive sheet used for laminating optical members (for laminating optical members) or for manufacturing products (optical products) using the above optical members. A pressure-sensitive adhesive sheet that is used can be preferably used.

The optical member is a member having optical properties (e.g., polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). say. The optical member is not particularly limited as long as it is a member having optical properties. For example, a member constituting a device (optical device) such as a display device (image display device) or an input device, or used for these devices. Members include, for example, polarizing plates, wave plates, retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflective films, antireflection films, hard coat (HC) films, impact absorption films, antifouling films, Photochromic films, light control films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and members in which these are laminated (these are collectively referred to as may be referred to as a "functional film".) and the like. In addition, the above-mentioned "plate" and "film" include forms such as plate-like, film-like, sheet-like, etc. For example, "polarizing film" includes "polarizing plate" and "polarizing sheet", A "light guide plate" includes a "light guide film", a "light guide sheet", and the like. Moreover, the above-mentioned "polarizing plate" shall include a circularly polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL display device, a micro LED (μLED), a mini LED (miniLED), a PDP, and electronic paper. Moreover, a touch panel etc. are mentioned as said input device.

The optical member is not particularly limited, but includes, for example, members made of glass, acrylic resin, polycarbonate, PET, metal thin films (for example, sheet-like, film-like, or plate-like members). The term "optical member" in this specification also includes members (design films, decorative films, surface protective films, etc.) that play a role of decoration and protection while maintaining the visibility of display devices and input devices.

The technology disclosed herein uses, for example, an optical film such as a film having one or more functions such as light transmission, reflection, diffusion, waveguiding, light collection, diffraction, etc., or a fluorescent film, to be used as another optical member ( It may be another optical film.). In particular, in bonding optical films having at least one function of guiding, condensing, and diffracting light, it is desirable that the entire bulk of the bonding layer has a high refractive index, and the technology disclosed herein is preferably applied. can be targeted.

The adhesive disclosed herein can be preferably used for bonding optical films such as light guide films, diffusion films, fluorescent films, toning films, prism sheets, lenticular films, and microlens array films. In these applications, there is a demand for a reduction in thickness and an improvement in light extraction efficiency from the viewpoint of miniaturization and higher performance of optical members. The adhesive disclosed herein can be preferably used as an adhesive that can meet such demands. More specifically, for example, in bonding a light guide film or a diffusion film, adjusting the refractive index (for example, increasing the refractive index) of an adhesive layer as a bonding layer can contribute to thinning. In bonding the fluorescent film, the light extraction efficiency (which can also be understood as luminous efficiency) can be improved by appropriately adjusting the refractive index difference between the fluorescent light emitter and the adhesive. In bonding the toning film, by appropriately adjusting the refractive index of the pressure-sensitive adhesive so that the refractive index difference between the toning pigment and the toning pigment is small, the scattering component can be reduced, which can contribute to the improvement of the light transmittance. In bonding prism sheets, lenticular films, microlens array films, etc., by appropriately adjusting the refractive index of the pressure-sensitive adhesive, light diffraction can be controlled, contributing to improvement in brightness and/or viewing angle.

The pressure-sensitive adhesive sheet disclosed herein is preferably used in a mode in which it is attached to a high refractive index adherend (which may be a high refractive index layer or member, etc.), and the interface reflection with the adherend is can be suppressed. The pressure-sensitive adhesive sheet used in such an embodiment preferably has a small refractive index difference with the adherend and high adhesion at the interface with the adherend as described above. In addition, from the viewpoint of improving the homogeneity of the appearance, it is preferable that the thickness of the pressure-sensitive adhesive layer is highly uniform, and for example, it is preferable that the surface smoothness of the pressure-sensitive adhesive layer is high. When the thickness of the high refractive index adherend is relatively small (for example, when it is 5 μm or less, 4 μm or less, or 2 μm or less), from the viewpoint of suppressing coloring and color unevenness due to interference of reflected light, It is particularly significant to suppress reflections. As an example of such a usage mode, in a polarizing plate with a retardation layer comprising a polarizer, a first retardation layer and a second retardation layer in this order, the bonding and / of the polarizer and the first retardation layer Alternatively, a mode in which it is used for joining the first retardation layer and the second retardation layer is exemplified.

In addition, since the adhesive sheet disclosed herein is suitable for increasing the refractive index, it is preferably attached to a light-emitting layer such as an optical semiconductor (for example, a high-refractive light-emitting layer mainly composed of an inorganic material). can be used. By reducing the refractive index difference between the light-emitting layer and the pressure-sensitive adhesive layer, reflection at their interface can be suppressed and the light extraction efficiency can be improved. The pressure-sensitive adhesive sheet used in such an embodiment preferably has a high-refractive-index pressure-sensitive adhesive layer. Moreover, from the viewpoint of improving brightness, the pressure-sensitive adhesive sheet is preferably lightly colored. This can also be advantageous from the viewpoint of suppressing unintentional coloring caused by the adhesive sheet.

The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a light-emitting device that includes a self-luminous element as a component, in a manner that it is arranged on the viewer side of the self-luminous element. Here, the self-luminous element means a light-emitting element whose luminance can be controlled by the value of the flowing current. The self-luminous element may be composed of a single body, or may be composed of an aggregate. Specific examples of self-luminous elements include, but are not limited to, light emitting diodes (LEDs) and organic ELs. Examples of the light-emitting device including the self-luminous element as a component include, but are not limited to, a light source module device (e.g., planar light-emitting module) used for illumination, and a display device in which pixels are formed. .

The adhesive disclosed herein is used in microlenses and other lens members used as constituent members of cameras, light-emitting devices, etc. (for example, microlenses constituting microlens array films and lens members such as microlenses for cameras). , a coating layer covering the lens surface, a bonding layer with a member facing the lens surface (for example, a member having a surface shape corresponding to the lens surface), a filling layer filled between the lens surface and the member, etc. can be preferably used. Since the adhesive disclosed herein is suitable for increasing the refractive index, it can be used with high refractive index lenses (for example, lenses made of a high refractive index resin or lenses having a surface layer made of a high refractive index resin). Even if there is, the refractive index difference with the lens can be reduced. This is advantageous from the viewpoint of thinning the lens and the product equipped with the lens, and can contribute to suppressing aberration and improving the Abbe number. The pressure-sensitive adhesive disclosed herein can also be used as a lens resin itself, for example, in the form of being filled in the recesses or voids of a suitable transparent member.

Modes for bonding optical members using the pressure-sensitive adhesive sheet disclosed herein are not particularly limited. ) The optical member may be attached to a member other than the optical member via the pressure-sensitive adhesive sheet disclosed herein, or (3) the pressure-sensitive adhesive sheet disclosed herein may contain the optical member. A mode in which the pressure-sensitive adhesive sheet is attached to an optical member or a member other than an optical member may be employed. In the aspect (3) above, the pressure-sensitive adhesive sheet containing an optical member may be, for example, a pressure-sensitive adhesive sheet whose support is an optical member (for example, an optical film). Such a pressure-sensitive adhesive sheet containing an optical member as a support can also be understood as a pressure-sensitive adhesive optical member (for example, pressure-sensitive adhesive optical film). Further, when the pressure-sensitive adhesive sheet disclosed herein is a type pressure-sensitive adhesive sheet having a support and the functional film is used as the support, the pressure-sensitive adhesive sheet disclosed herein is a functional film. It can also be understood as an "adhesive functional film" having the adhesive layer disclosed herein on at least one side.

As described above, according to the technology disclosed herein, a laminate including the adhesive sheet disclosed herein and a member to which the adhesive sheet is attached is provided. The member to which the pressure-sensitive adhesive sheet is attached may have the refractive index of the adherend material described above. Moreover, the difference (refractive index difference) between the refractive index of the pressure-sensitive adhesive sheet and the refractive index of the member may be the refractive index difference between the adherend and the pressure-sensitive adhesive sheet described above. The members constituting the laminate are the same as the above-described members, materials, and adherends, so redundant description will not be repeated.

As understood from the above description and the following examples, the subject matter disclosed by this specification includes the following.
[1] A refractive index modifier for adhesives,
The refractive index modifier is an organic compound having a structure having two or more substituents on the hub ring, wherein the hub ring is a ring containing a double bond, and the two or more substituents are A refractive index modifier, at least one of which is a substituent having a double bond-containing ring.
[2] The refractive index modifier according to [1] above, which has a molecular weight of less than 3,000.
[3] The refractive index modifier according to [1] or [2] above, wherein two or more of the substituents on the hub ring are substituents having a double bond-containing ring.
[4] The refractive index modifier according to any one of [1] to [3] above, wherein at least one of the substituents on the hub ring is a substituent having two or more double bond-containing rings.
[5] The refractive index modifier according to any one of [1] to [4] above, wherein the hub ring is a triazine ring.

（式（Ｉ）中、Ｘ^１，Ｘ^２およびＸ^３は、それぞれ独立に、－Ｏ－，－Ｓ－および－ＮＲ^４－からなる群から選択され、ここでＲ^４は水素原子またはアルキル基であり、
　Ｒ^１，Ｒ^２およびＲ^３のうち１つ以上は、それぞれ独立に、置換基を有していてもよいフェニル基および置換基を有していてもよいビフェニル基からなる群から選択される芳香環含有基であり、上記置換基はアルキル基、アルコキシ基またはシアノ基であり、
　Ｒ^１，Ｒ^２およびＲ^３のうち上記芳香環含有基が２つ以下である場合、残りは脂肪族炭化水素基または水素原子である。）；
で表される化合物。
　〔７〕　上記Ｘ^１，Ｘ^２およびＸ^３のうち２つ以上は、それぞれ独立に、－Ｏ－および－Ｓ－から選択される、上記〔６〕に記載の化合物。
　〔８〕　上記Ｘ^１，Ｘ^２およびＸ^３がいずれも－Ｏ－である、上記〔６〕に記載の化合物。
　〔９〕　上記Ｘ^１，Ｘ^２およびＸ^３がいずれも－Ｓ－である、上記〔６〕に記載の化合物。
　〔１０〕　上記Ｒ^１，Ｒ^２およびＲ^３が、それぞれ独立に、置換基を有するかまたは有しない２－ビフェニルである、上記〔６〕～〔９〕のいずれかに記載の化合物。
　〔１１〕　上記〔６〕～〔１０〕のいずれかに記載の化合物からなる、屈折率調整剤。 [6] the following formula (I):

(In formula (I), X ¹ , X ² and X ³ are each independently selected from the group consisting of —O—, —S— and —NR ⁴ —, where R ⁴ is a hydrogen atom or an alkyl group and
One or more of R ¹ , R ² and R ³ are each independently an aromatic selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group a ring-containing group, wherein the substituent is an alkyl group, an alkoxy group or a cyano group;
When the above aromatic ring-containing groups are two or less among R ¹ , R ² and R ³ , the rest are aliphatic hydrocarbon groups or hydrogen atoms. );
A compound represented by
[7] The compound according to [6] above, wherein two or more of X ¹ , X ² and X ³ are each independently selected from —O— and —S—.
[8] The compound according to [6] above, wherein all of X ¹ , X ² and X ³ are —O—.
[9] The compound according to [6] above, wherein all of X ¹ , X ² and X ³ are -S-.
[10] The compound according to any one of [6] to [9] above, wherein R ¹ , R ² and R ³ are each independently substituted or unsubstituted 2-biphenyl.
[11] A refractive index adjuster comprising the compound according to any one of [6] to [10] above.

[12] A pressure-sensitive adhesive comprising the refractive index modifier according to any one of [1] to [5] and [11] above.
[13] The pressure-sensitive adhesive according to [12] above, further comprising an acrylic polymer containing an aromatic ring-containing monomer (m1) as a monomer unit.
[14] The above [12] or [13], wherein the monomer component constituting the acrylic polymer contains, in addition to the aromatic ring-containing monomer (m1), a monomer (m2) having at least one of a hydroxyl group and a carboxy group. ].
[15] The pressure-sensitive adhesive according to any one of [12] to [14], wherein the content of the aromatic ring-containing monomer (m1) in the monomer component is 60% by weight or more.
[16] The pressure-sensitive adhesive according to any one of [12] to [15] above, wherein 50% by weight or more of the aromatic ring-containing monomer (m1) is a monomer whose homopolymer has a glass transition temperature of 10°C or lower. .
[17] The pressure-sensitive adhesive according to any one of [12] to [16] above, wherein the content of the refractive index modifier is 0.1 parts by weight or more and 80 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.
[18] The pressure-sensitive adhesive according to any one of [12] to [17] above, which has a refractive index of 1.550 or more.

[19] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to any one of [12] to [18] above.
[20] The pressure-sensitive adhesive sheet of [19] above, wherein the thickness of the pressure-sensitive adhesive layer is in the range of 5 to 75 μm.
[21] The pressure-sensitive adhesive sheet of [19] or [20] above, which has a total light transmittance of 85% or more.
[22] The pressure-sensitive adhesive sheet according to any one of [19] to [21] above, which has a haze value of 3% or less.
[23] The pressure-sensitive adhesive sheet according to any one of [19] to [22] above, wherein the chromaticity b ^* defined by the L ^* a ^* b ^* color system is in the range of ±5.

Although some examples of the present invention will be described below, it is not intended to limit the present invention to those shown in such specific examples. In the following description, "parts" and "%" representing amounts used and contents are based on weight unless otherwise specified.

In the synthesis examples below, the refractive index of each compound was measured as follows. That is, a 5% ethyl acetate solution or a 5% MEK solution of the compound to be measured was prepared. This solution was applied on glass so that the dry film thickness was 10 μm, and dried by heating at 130° C. for 5 minutes. The refractive index of the compound to be measured thus formed on the glass was measured using a prism coupler (manufactured by Metricon, model "2010M") under the conditions of a measurement temperature of 25°C and a measurement wavelength of 594 nm.

<Synthesis Example 1: Synthesis of Compound A1>

Under a nitrogen atmosphere, biphenyl-2-ol (5.28 g, 31 mmol), acetone (50 mL) and potassium hydroxide (1.74 g, 31 mmol) were charged into a reaction vessel and stirred at room temperature for 30 minutes. A solution of cyanuric chloride (1.84 g, 10 mmol) in acetone (20 mL) was added dropwise thereto over 15 minutes, stirred at room temperature for 2 hours, and then stirred at 55° C. for 8 hours. When the reaction solution was poured into 800 mL of distilled water, an oily sediment was produced. The supernatant liquid was removed by decantation and dried under reduced pressure at 100° C. for 4 hours to obtain a glassy solid (2.7 g). This was dissolved in acetone (20 mL), poured into hexane (100 mL), allowed to stand at room temperature for 24 hours, the supernatant was removed, and the oily precipitate was recovered and dried under reduced pressure at 80°C for 4 hours. 2.25 g (3.84 mmol) of compound A1 were obtained. Yield was 38.4%. Compound A1 exhibited a solubility capable of preparing a 50% solution in each of methyl ethyl ketone (MEK) and ethyl acetate. The refractive index was 1.645. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A1 are shown in FIGS. 4 and 5, respectively.

<Synthesis Example 2: Synthesis of compound A2>

Under a nitrogen atmosphere, biphenyl-4-ol (5.28 g, 31 mmol), acetone (50 mL), potassium hydroxide (1.74 g, 31 mmol) and water (20 mL) were charged into a reaction vessel and stirred at room temperature for 30 minutes. An acetone (20 mL) solution of cyanuric chloride (1.84 g, 10 mmol) was added dropwise thereto over 15 minutes, and the mixture was stirred at room temperature for 24 hours to precipitate a white solid. The reaction solution was poured into 800 mL of distilled water, and a white powdery precipitate was collected by filtration and dried under reduced pressure at 80° C. for 6 hours to obtain a white solid (5 g). This was recrystallized from acetone to obtain 4.85 g (7.94 mmol) of compound A2. Yield was 79.4%. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of Compound A2 are shown in FIGS. 6 and 7, respectively.

<Synthesis Example 3: Synthesis of Compound A3>

Under a nitrogen atmosphere, biphenyl-4-ol (5.28 g, 31 mmol), acetone (50 mL), potassium hydroxide (1.74 g, 31 mmol) and water (20 mL) were charged into a reaction vessel and stirred at room temperature for 30 minutes. A solution of 2,4-dichloro-6-methoxytriazine (1.80 g, 10 mmol) in acetone (30 mL) was added thereto and stirred at room temperature for 24 hours. The reaction solution was poured into 800 mL of distilled water, and the precipitated white powdery precipitate was collected by filtration, dried under reduced pressure at 80° C. for 5 hours, and recrystallized from acetone to give 1.81 g (2.96 mmol) of compound A3. got Yield was 30.2%. Compound A3 showed solubility in MEK that allowed preparation of a 7% solution. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A3 are shown in FIGS. 8 and 9, respectively.

<Synthesis Example 4: Synthesis of Compound A4>

Under a nitrogen atmosphere, biphenyl-2-thiol (19.8 g, 106.3 mmol) and acetone (100 mL) were charged into a reaction vessel, 85% aqueous solution of potassium hydroxide (7.1 g, 67.3 mmol) was added, and the mixture was stirred at room temperature. Stirred for 1 hour. The system was cooled to 10° C., and a solution of cyanuric chloride (6 g, 34.3 mmol) in acetone (60 mL) was added dropwise over 15 minutes, followed by stirring at room temperature for 6 hours. Then add water, neutralize with 0.1M hydrochloric acid, extract with ethyl acetate, dry over sodium sulfate, filter and concentrate, then use ethyl acetate:heptane=10/1 (volume ratio) as a developing solution. Purification by silica gel column chromatography gave 13 g (20.5 mmol) of compound A4. Yield was 59.8%. Compound A4 exhibited a solubility capable of preparing a 50% solution in each of methyl ethyl ketone (MEK) and ethyl acetate. The refractive index was 1.702. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A4 are shown in FIGS. 10 and 11, respectively.

<Synthesis Example 5: Synthesis of compound A5>

Under a nitrogen atmosphere, cyanuric chloride (9.28 g, 50 mmol), N-methylpyrrolidone (100 mL), p-toluenethiol (20.65 g, 166 mmol) and triethylamine (17.8 g, 176 mmol) were charged into a reaction vessel and heated to 80°C. for 24 hours. Water (1500 mL) was then added, neutralized with 0.1 M hydrochloric acid, extracted with ethyl acetate (1 L), dried over sodium sulfate (200 g), filtered and evaporated to give a pasty mixture. got The mixture was washed with acetone (100 mL) to give 7.35 g of crude product, which was recrystallized by heating in acetone to give 6.5 g (14.5 mmol) of compound A5. Yield was 29%. Compound A5 showed solubility in MEK that allowed preparation of a 5% solution. The refractive index was 1.672. ^{The 1} H-NMR (400 MHz, DMSO-d ₆ ) spectrum and ¹³ C-NMR (400 MHz, DMSO-d ₆ ) spectrum of compound A5 are shown in FIGS. 12 and 13, respectively.

<Synthesis Example 6: Synthesis of Compound A6>

Under a nitrogen atmosphere, 2-ethylhexanethiol (20 mmol), tetrahydrofuran (20 mL) and potassium hydroxide (1.24 g, 22 mmol) were charged to a reaction vessel and stirred at room temperature for 2 hours, then at 60° C. for 1 hour, Allowed to cool to room temperature. A solution of cyanuric chloride (4.06 g, 20 mmol) in tetrahydrofuran (20 mL) was added dropwise thereto over 30 minutes and stirred at room temperature for 24 hours. 2,4-dichloro-6-(2-ethylhexylthio)triazine) was obtained. To this was added N-methylpyrrolidone (50 mL), p-toluenethiol (5.47 g, 44 mmol) and triethylamine (5.06 g, 50 mmol) and stirred at 80° C. for 24 hours. Water (1500 mL) was then added, and the precipitated oil was collected and purified by silica gel column chromatography using hexane:dichloromethane=3:1 (volume ratio) as a developing solution to obtain 0.57 g (1.2 mmol). to obtain compound A6 of Yield was 6%. Compound A6 exhibited a solubility capable of preparing a 50% solution in each of MEK and ethyl acetate. The refractive index was 1.620. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A6 are shown in FIGS. 14 and 15, respectively.

<Synthesis Example 7: Synthesis of Compound A7>

Under a nitrogen atmosphere, 2-ethylhexanethiol (20 mmol), tetrahydrofuran (20 mL) and potassium hydroxide (1.24 g, 22 mmol) were charged to a reaction vessel and stirred at room temperature for 2 hours, then at 60° C. for 1 hour, Allowed to cool to room temperature. A solution of 2-(4-cyanophenyl)amino-4,6-dichloro-1,3,5-triazine (2.66 g, 10 mmol) in tetrahydrofuran (10 mL) was added dropwise thereto over 30 minutes, and the mixture was stirred at room temperature for 24 hours. Stirred. 1. Remove the sodium chloride by filtration, and purify the viscous oil obtained by distilling off the solvent by silica gel column chromatography using hexane:dichloromethane=1:1 (volume ratio) as a developing solution. 62 g (5.4 mmol) of compound A7 were obtained as a white viscous oil. Yield was 54%. Compound A7 exhibited a solubility that allowed preparation of a 50% solution in each of MEK and ethyl acetate. The refractive index was 1.594. ¹ H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A7 are shown in FIGS. 16 and 17, respectively. The refractive index of compound A7 was 1.645.

<Synthesis Example 8: Synthesis of Compound A8>

Methanol (110 mL), water (14 mL) and sodium bicarbonate (18.2 g, 217 mmol) were charged into a reaction vessel, and cyanuric chloride (20.0 g, 108 mmol) was added in 10 batches of about 2 g each, followed by stirring for about 30 minutes. add over. After stirring at 30° C. for 1 hour, water (50 mL) was added, and the precipitated white precipitate was collected by filtration, washed with water (50 mL) and then with methanol (30 mL), and then reduced pressure at room temperature for 12 hours. Drying gave 14.6 g (80 mmol) of 2,4-dichloro-6-methoxytriazine. Yield was 74.6%.
Under a nitrogen atmosphere, a reaction vessel was charged with biphenyl-4-thiol (2.00 g, 10.7 mmol), acetone (40 mL), potassium hydroxide (0.60 g, 10.7 mmol) and water (15 mL). Stir for a minute. An acetone (30 mL) solution of 2,4-dichloro-6-methoxytriazine (0.90 g, 5.0 mmol) obtained above was added thereto, stirred at room temperature for 24 hours, and the reaction solution was added to 800 mL of distilled water. . The precipitated white precipitate was collected by filtration and dried under reduced pressure at 80° C. for 5 hours, then reprecipitated from a mixed solvent of hexane:acetone=5:1 (volume ratio), and a mixed solvent of hexane:methylene chloride ( Purification by silica gel column chromatography using a gradient of 3:1 to 1:1 by volume) gave 1.42 g of compound A8. Yield was 59.2%. Compound A8 showed solubility in MEK that allowed the preparation of a 2.5% solution. ^{The 1} H-NMR (400 MHz, CDCl ₃ ) spectrum and ¹³ C-NMR (400 MHz, CDCl ₃ ) spectrum of compound A8 are shown in FIGS. 18 and 19, respectively.

<Example 1>
(Preparation of acrylic polymer solution)
A four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a cooler was charged with m-phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light acrylate POB-A", refractive index: 1) as a monomer component. .566, Tg of homopolymer: −35° C., hereinafter referred to as “POB-A”) 95 parts and 5 parts of 4-hydroxybutyl acrylate (4HBA), 2,2′-azobisiso as a polymerization initiator 0.2 parts of butyronitrile and 150 parts of ethyl acetate as a polymerization solvent were charged, nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was maintained at around 60°C to carry out a polymerization reaction for 6 hours. A solution (40%) of system polymer P1 was prepared. Mw of acrylic polymer P1 was 500,000.

(Preparation of adhesive composition)
The solution (40%) of the acrylic polymer P1 is diluted to 20% with ethyl acetate, and 500 parts of this solution (100 parts of nonvolatile matter) is added with 20 parts of 50% ethyl acetate solution of compound A1 (10 parts of nonvolatile matter). 10 parts of a 1% ethyl acetate solution (nonvolatile content 0.1 part) of an isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", trifunctional isocyanate compound) as a cross-linking agent, and a cross-linking retarder Two parts of acetylacetone and one part of a 1% ethyl acetate solution of Nasem ferric iron as a cross-linking catalyst (0.01 part of non-volatile matter) were added and mixed with stirring to prepare a pressure-sensitive adhesive composition according to this example.

(Preparation of adhesive sheet)
The acrylic pressure-sensitive adhesive composition prepared above was applied to the silicone-treated surface of a polyethylene terephthalate (PET) film R1 (thickness: 50 μm) having one surface silicone-treated, and heated at 130° C. for 2 minutes to increase the thickness. An adhesive layer having a thickness of 20 μm was formed. Next, the silicone-treated surface of PET film R2 (thickness: 25 μm) having one surface silicone-treated was attached to the surface of the pressure-sensitive adhesive layer. Thus, a substrate-less double-sided pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer was obtained. Both sides of this adhesive sheet are protected by PET films (release liners) R1 and R2.

<Examples 2 to 4>
The adhesive according to each example was prepared in the same manner as the adhesive composition in Example 1, except that Compound A4 (Example 2), Compound A5 (Example 4), or Compound A6 (Example 4) was used instead of Compound A1. A composition was prepared. PSA sheets according to Examples 2 to 4 (base-less double-sided PSA sheets consisting of PSA layers) were produced in the same manner as in the production of PSA sheets in Example 1, except that each of the obtained PSA compositions was used.

<Example 5>
A pressure-sensitive adhesive composition according to this example was prepared in the same manner as the pressure-sensitive adhesive composition in Example 1 except that compound B1 (diethylene glycol dibenzoate, refractive index 1.535) was used instead of compound A1. A pressure-sensitive adhesive sheet according to this example (a substrate-less double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer) was prepared in the same manner as the pressure-sensitive adhesive sheet in Example 1, except that each obtained pressure-sensitive adhesive composition was used.

<Example 6>
A pressure-sensitive adhesive composition according to this example was prepared in the same manner as the pressure-sensitive adhesive composition in Example 1, except that compound A1 was not used. A pressure-sensitive adhesive sheet according to this example (a substrate-less double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer) was prepared in the same manner as the pressure-sensitive adhesive sheet in Example 1, except that each obtained pressure-sensitive adhesive composition was used.

<Evaluation>
(Refractive index of adhesive)
The pressure-sensitive adhesive layer (base-less double-sided pressure-sensitive adhesive sheet) according to each example is refracted using an Abbe refractometer (manufactured by ATAGO, model "DR-M4") under the conditions of a measurement wavelength of 589 nm and a measurement temperature of 25 ° C. rate was measured.

(total light transmittance and haze)
Using a test piece in which the pressure-sensitive adhesive layer according to each example is attached to non-alkali glass (thickness 0.8 to 1.0 mm, total light transmittance 92%, haze 0.4%), a haze meter (Murakami Color Technology Research) The total light transmittance and haze of the above test piece were measured using the "HM-150" (manufactured by the company). The values obtained by subtracting the total light transmittance and haze of the alkali-free glass from the measured values were taken as the total light transmittance [%] and haze [%] of the adhesive (layer). For the substrate-less pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer, the total light transmittance [%] and haze [%] of the pressure-sensitive adhesive layer are the total light transmittance [%] and haze [%] of the pressure-sensitive adhesive sheet.

(Measurement of chromaticity b ^* )
The chromaticity b ^* of the pressure-sensitive adhesive layer according to each example was measured by the method described above. The measurement was performed at five locations on the surface of the pressure-sensitive adhesive layer, and the average value was obtained.

Table 1 shows the outline and evaluation results of the adhesive according to each example.

As shown in Table 1, the pressure-sensitive adhesive composition of Example 6 was blended with compounds A1 and A4 to A6 having a higher refractive index than the compound B1 used in Example 5. Examples 1 to 1 formed from the pressure-sensitive adhesive composition 4 showed a higher refractive index than the adhesives of Examples 5 and 6. The pressure-sensitive adhesives of Examples 1-4 had good light transmittance, haze and chromaticity b ^* at levels usable for optical applications.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1, 2, 3 adhesive sheet 10 support substrate 10A first surface 10B second surface 21 adhesive layer, first adhesive layer 21A adhesive surface, first adhesive surface 21B adhesive surface 22 second adhesive layer 22A second adhesive Faces 31, 32 release liner

Claims (10)

A refractive index modifier for an adhesive,
The refractive index adjuster is an organic compound having a structure having two or more substituents on a hub ring, wherein the hub ring is a ring containing a double bond, and the two or more substituents are A refractive index modifier, at least one of which is a substituent having a double bond-containing ring. The refractive index modifier according to claim 1, which has a molecular weight of less than 3,000. The refractive index modifier according to claim 1 or 2, wherein two or more of the substituents on the hub ring are substituents having a double bond-containing ring. The refractive index adjuster according to any one of claims 1 to 3, wherein one or more substituents on the hub ring are substituents having two or more double bond-containing rings. The refractive index modifier according to any one of claims 1 to 4, wherein the hub ring is a triazine ring. Formula (I) below:

(In formula (I), X ¹ , X ² and X ³ are each independently selected from the group consisting of —O—, —S— and —NR ⁴ —, where R ⁴ is a hydrogen atom or an alkyl group and
One or more of R ¹ , R ² and R ³ are each independently an aromatic selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group a ring-containing group, wherein said substituent is an alkyl group, an alkoxy group or a cyano group;
When the number of said aromatic ring-containing groups among R ¹ , R ² and R ³ is two or less, the rest are aliphatic hydrocarbon groups or hydrogen atoms. );
The refractive index improver according to any one of claims 1 to 5, which is a triazine compound represented by. A pressure-sensitive adhesive containing the refractive index modifier according to any one of claims 1 to 6. The pressure-sensitive adhesive according to claim 7, further comprising an acrylic polymer containing an aromatic ring-containing monomer (m1) as a monomer unit. The pressure-sensitive adhesive according to claim 7 or 8, which has a refractive index of 1.550 or more. Formula (I) below:

(In formula (I), X ¹ , X ² and X ³ are each independently selected from the group consisting of —O—, —S— and —NR ⁴ —, where R ⁴ is a hydrogen atom or an alkyl group and
One or more of R ¹ , R ² and R ³ are each independently an aromatic group selected from the group consisting of an optionally substituted phenyl group and an optionally substituted biphenyl group. an aromatic ring-containing group, wherein the substituent is an alkyl group, an alkoxy group or a cyano group;
When the number of said aromatic ring-containing groups among R ¹ , R ² and R ³ is two or less, the rest are aliphatic hydrocarbon groups or hydrogen atoms. );
A compound represented by

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