TWI890529B - Optical laminate - Google Patents

Abstract

The present invention provides an optical laminate which is capable of effectively suppressing migration of a dichroic dye contained in a polarizing film to a conductive layer and preventing deterioration of the conductive layer.

The optical laminate of the present invention includes a first cured material layer composed of a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer laminated in this order, on one surface of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin; wherein the first cured material layer has an absorbance increase rate represented by the following formula (1) of 30% or less.

Absorbance increase rate (%)=(after immersion Abs (360nm)-before immersion Abs (360nm))/before immersion Abs (360 nm) × 100 (1)

Description

Optical laminates

The present invention relates to an optical multilayer body that can be used in image display panels, etc.

Conventionally, optical multilayers are known in which a dichroic dye such as iodine is adsorbed and aligned on one side of a polarizing film of a polyvinyl alcohol-based resin film, and then a protective film is laminated via an adhesive. Patent Document 1, for example, describes a photocation-curable adhesive (curable composition) comprising an aliphatic epoxide, an alicyclic epoxide, and/or an oxycyclobutane and a photopolymerization initiator. The cured product functions as the adhesive.

In recent years, transparent conductive films such as indium tin oxide (ITO) thin films have become widely used in display devices. For example, these films are formed on the side of a liquid crystal display device (LCD) that uses an in-plane switching (IPS) method, opposite to the liquid crystal layer of the transparent substrate that constitutes the liquid crystal cell, to serve as an anti-static layer. Furthermore, these transparent conductive films, formed on a transparent resin film, are used as electrode substrates for touch panels, such as in combination LCD displays used in mobile phones and portable music players, and in video display devices and input devices for such touch panels.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2008-063397

However, when a conductive layer, such as an ITO layer, is laminated on the polarizing film side of the optical laminate described in Patent Document 1 via an adhesive layer, the dichroic dye contained in the polarizing film can easily migrate through the adhesive layer to the conductive layer, potentially causing malfunctions such as poor sensing. Such migration of the dichroic dye from the polarizing film becomes particularly significant in high-temperature, high-humidity environments. Therefore, there is a need for an optical laminate that can prevent degradation of the conductive layer caused by migration of the dichroic dye contained in the polarizing film through the adhesive layer, even in high-temperature, high-humidity environments.

Therefore, an object of the present invention is to provide an optical laminate that can effectively inhibit the migration of dichroic dyes contained in a polarizing film toward a conductive layer and prevent degradation of the conductive layer.

The present invention provides the following preferred aspects [1] to [6].

[1] An optical laminate comprising a first cured layer, an adhesive layer, and a conductive layer formed of a cured material comprising a curable composition containing a polymerizable compound, laminated in sequence on one side of a polarizing film containing a dichroic pigment in a polyvinyl alcohol resin;

Wherein, the absorbance increase rate of the first cured layer expressed by the following formula (1) is less than 30%;

Absorbance increase rate (%) = (Abs after immersion (360nm) - Abs before immersion (360nm)) / Abs before immersion (360nm) × 100 (1)

[Wherein, Abs (360 nm) after immersion represents the absorbance at 360 nm after the cured product has been immersed in a 50% potassium iodide aqueous solution for 100 hours in an atmosphere at a temperature of 23°C and a relative humidity of 60%. Abs (360 nm) before immersion represents the absorbance at 360 nm before the cured product has been immersed in the 50% potassium iodide aqueous solution].

[2] An optical laminate comprising a first cured material layer, an adhesive layer, and a conductive layer formed of a cured material comprising a curable composition containing a polymerizable compound, stacked in sequence on one side of a polarizing film containing a dichroic pigment in a polyvinyl alcohol resin;

The polymerizable compound comprises an oxycyclobutane compound having two or more oxycyclobutane groups, and the content of the oxycyclobutane compound is 40 parts by mass or more relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition.

[3] The optical laminate as described in [1] or [2], wherein the thickness of the first hardened layer is 0.1 to 15 μm.

[4] The optical laminate according to any one of [1] to [3], wherein the cured material constituting the first cured material layer is a photocurable material comprising a curable composition of the aforementioned polymerizable compound.

[5] The optical laminate according to any one of [1] to [4], wherein a second cured layer and a protective film are laminated on the surface of the polarizing film opposite to the first cured layer.

[6] The optical laminate as described in [5], wherein the moisture permeability of the protective film is less than 1200 g/24 hours at a temperature of 23°C and a relative humidity of 55%.

The optical multilayer structure of the present invention can inhibit the migration of dichroic pigments contained in the polarizing film toward the conductive layer and effectively suppress corrosion of the conductive layer.

1:Polarizing film

2: First hardened layer

3: Adhesive layer

4: Conductive layer

5: Second hardened layer

6: Second protective film

7: 1st protective film

10: Optical multilayers

X:Substrate

Figure 1 is a cross-sectional view showing the structure of one embodiment of the optical multilayer body of the present invention.

Figure 2 is a cross-sectional view showing the structure of one embodiment of the optical multilayer body of the present invention.

The following describes in detail the implementation of the present invention. Furthermore, the scope of the present invention is not limited to the implementation described herein, and various modifications are possible without detracting from the spirit of the present invention.

FIG1 illustrates the structure of one embodiment of the optical laminate of the present invention. The optical laminate 10 comprises a first cured layer 2, an adhesive layer 3, and a conductive layer 4 sequentially laminated on one side of a polarizing film 1. Optionally, a protective film 6 may be provided on the side of the polarizing film 1 opposite the first cured layer 2, via a second cured layer 5. Furthermore, in the embodiment of FIG1 , the conductive layer 4 of the optical laminate 10 is laminated on a substrate X.

Furthermore, the optical laminate of the present invention may include a first protective film 7 between the first cured layer 2 and the adhesive layer 3. This embodiment is shown in Figure 2. Optionally, the optical laminate 10 may include a protective film 6 on the surface of the polarizing film 1 opposite to the first cured layer 2, interposed between the second cured layer 5. Furthermore, in the embodiment of Figure 2, the conductive layer 4 of the optical laminate 10 is laminated on the substrate X.

The following is a detailed description of the various components of the optical multilayer structure of the present invention.

[First hardened layer]

The optical multilayer body of the present invention has a first cured material layer composed of a cured material of a curable composition containing a polymerizable compound (hereinafter sometimes referred to as a curable composition (1)) on one side of a polarizing film containing a dichroic pigment in a polyvinyl alcohol-based resin.

The absorbance increase rate of the first cured layer expressed by the following formula (1) is less than 30%.

Absorbance increase rate (%) = (Abs after immersion (360nm) - Abs before immersion (360nm)) / Abs before immersion (360nm) × 100 (1)

[Wherein, Abs (360 nm) after immersion represents the absorbance at 360 nm after the cured product has been immersed in a 50% potassium iodide aqueous solution for 100 hours in an atmosphere at a temperature of 23°C and a relative humidity of 60%. Abs (360 nm) before immersion represents the absorbance at 360 nm before the cured product has been immersed in the 50% potassium iodide aqueous solution].

Even when the first cured layer is immersed in a 50% potassium iodide aqueous solution for 100 hours, the absorbance increase rate expressed by the aforementioned formula (1) is 30% or less. This indicates that the first cured layer has a low absorption of iodine (dichroic dye). Therefore, the optical laminate of the present invention can effectively suppress the migration of iodine (dichroic dye) contained in the polarizing film toward the first cured layer and prevent corrosion of the conductive layer (e.g., ITO layer) caused by iodine (dichroic dye). Furthermore, the optical performance of the optical laminate can be maintained.

The absorbance increase rate represented by the above formula (1) is preferably 25% or less, more preferably 20% or less, even more preferably 15% or less, and particularly preferably 10% or less. When the absorbance increase rate is below the above value, as described above, the migration of iodine (dichroic dye) contained in the polarizing film to the first cured layer can be more effectively suppressed, and corrosion of the conductive layer and degradation of the optical performance of the optical laminate can be more effectively prevented.

The polymerizable compound contained in the curable composition (1) is not particularly limited as long as it can form a cured product constituting the first cured product layer. Examples of polymerizable compounds include active energy ray curable resin compositions, water-soluble resin compositions, water-dispersible resin compositions, etc. Among these, active energy ray curable resin compositions are preferred from the perspective of simplifying the process, and (meth)acrylate compounds including epoxy acrylate, amine acrylate, etc., acrylamide compounds, cyclohexane compounds, and epoxy compounds are particularly preferred.

In a preferred embodiment, the cured material constituting the first cured layer is a photocurable material comprising a curable composition comprising a polymerizable compound. Therefore, the polymerizable compound is preferably a photopolymerizable compound.

The polymerizable compound is preferably an oxycyclobutane compound (hereinafter sometimes referred to as "oxycyclobutane compound (A)") containing two or more oxycyclobutane groups (oxycyclobutane rings) in the molecule.

The cyclooxetane compound (A) is a compound having two or more cyclooxetane groups in its molecule and can be an aliphatic, alicyclic, or aromatic compound. Specific examples of the cyclooxetane compound (A) include 1,4-bis[{(3-ethylcyclooxetane-3-yl)methoxy}methyl]benzene (also known as xylylene biscyclooxetane) and bis(3-ethyl-3-cyclooxetane methyl)ether. These cyclooxetane compounds (A) can be used individually or in combination. The inclusion of the cyclooxetane compound (A) yields a highly crosslinked, dense cured product. By placing a hardened layer with a high crosslinking density on one side of the polarizing film, the migration of dichroic dye from the polarizing film can be effectively suppressed.

The content of the oxycyclobutane compound (A) is, for example, 40 parts by mass or more, preferably 45 parts by mass or more, and more preferably 50 parts by mass or more, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition (1). Furthermore, the content of the oxycyclobutane compound (A) is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 70 parts by mass or less, and particularly preferably 65 parts by mass or less, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition (1). Furthermore, the content of the aforementioned cyclohexane compound (A) may also be a combination of the lower and upper limits, preferably 40 to 65 parts by mass, and more preferably 45 to 60 parts by mass, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition (1).

Furthermore, the content of the oxycyclobutane compound (A) is, for example, 35 parts by mass or more, preferably 40 parts by mass or more, and more preferably 45 parts by mass or more, relative to 100 parts by mass of the total amount of the curable composition (1). When the content of the oxycyclobutane compound (A) is greater than or equal to the above value, migration of the dichroic dye contained in the polarizing film to the first cured layer can be more effectively suppressed, thereby more effectively preventing corrosion of the conductive layer and degradation of the optical performance of the optical laminate.

The polymerizable compound preferably further contains an epoxy compound (B). The epoxy compound (B) is preferably at least one selected from (B1) an aliphatic epoxy compound having two or more epoxy groups (hereinafter sometimes referred to as "aliphatic epoxy compound (B1)"), (B2) an alicyclic epoxy compound having two or more epoxy groups (hereinafter sometimes referred to as "alicyclic epoxy compound (B2)"), and (B3) an aromatic epoxy compound having one or more aromatic rings (hereinafter sometimes referred to as "aromatic epoxy compound (B3)").

The aforementioned aliphatic epoxy compound (B1) is a compound having at least two oxycyclobutane rings bonded to aliphatic carbon atoms in the molecule. Aliphatic epoxy compounds (B1) include bifunctional epoxy compounds such as 1,4-butanediol diglycoxypropyl ether, 1,6-hexanediol diglycoxypropyl ether, epoxiedimethanol diglycoxypropyl ether, and neopentyl glycol diglycoxypropyl ether; and trifunctional or higher epoxy compounds such as trihydroxymethylpropane triglycoxypropyl ether and neopentyltriol tetraglycoxypropyl ether.

When an aliphatic epoxy compound (B1) is included, from the perspective of adhesion between the polarizing film and the protective film or adhesive layer, an epoxy compound having two oxycyclobutane rings bonded to an aliphatic carbon atom in the molecule (also known as an aliphatic diepoxy compound) is preferred, and an aliphatic diepoxy compound represented by the following formula (I) is more preferred. By including an aliphatic diepoxy compound represented by the following formula (I) as the aliphatic epoxy compound (B1), the curable composition can be provided with a low viscosity and easy coating.

In formula (I), Z represents an alkylene group having 1 to 9 carbon atoms, an alkylene group having 3 or 4 carbon atoms, a divalent alicyclic _alkyl group, or a divalent group represented _{by -CmH2m} - ^Z1 - _CnH2n- . ^-Z1- represents -O-, -CO-O-, -O-CO-, _-SO2- , -SO-, or CO-, and m and n each independently represent an integer of 1 or greater. However, the total of m and n is 9 or less.

The divalent alicyclic alkyl group may be, for example, an alicyclic alkyl group having 4 to 8 carbon atoms, such as a divalent residual group represented by the following formula (I-1).

Specific examples of the compound represented by formula (I) include diglycidyl ethers of alkylene glycols; diglycidyl ethers of oligoalkylene glycols with a repeating number of 4 or less; and diglycidyl ethers of alicyclic glycols.

Alkane diols such as ethylene glycol, propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 2-butyl-2-ethyl-1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, and 1,9-nonanediol can be used as glycols.

Oligoalkyl glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, and dipropylene glycol;

Alicyclic diols such as cyclohexanediol and cyclohexanedimethanol, etc.

In the present invention, the aliphatic epoxy compound (B1) is preferably 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether, from the perspective of forming a curable composition with low viscosity and easy coating. From the perspective of maintaining optical properties, 1,6-hexanediol diglycidyl ether and neopentyltriol polyglycidyl ether are preferred. The aliphatic epoxy compound (B1) may be used singly or in combination of multiple types.

When the curable composition (1) contains an aliphatic epoxy compound (B1), the content of the aliphatic epoxy compound (B1) is preferably 1 to 40 parts by mass, more preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, and particularly preferably 7 to 15 parts by mass, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition. When the content of the aliphatic epoxy compound (B1) is within the above range, the curable composition (1) has a low viscosity and can be easily applied.

The aforementioned alicyclic epoxy compound (B2) is a compound having two or more epoxy groups bonded to an alicyclic ring in the molecule. The so-called "epoxy groups bonded to an alicyclic ring" refers to the following formula (a):

The bridging oxygen atom in the structure represented by -O-. In the above formula (a), m is an integer from 2 to 5.

By removing one or more hydrogen atoms from (CH ₂ ) _m in the above formula (a), two or more radicals are bonded to other chemical structures to form a compound that is an alicyclic epoxy compound (B2). One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group.

Among these, from the perspective of achieving a high glass transition temperature of the cured product and good adhesion between the polarizing film and the protective film, alicyclic epoxy compounds having an epoxycyclopentane structure [where m = 3 in the above formula (a)] or an epoxycyclohexane structure [where m = 4 in the above formula (a)] are preferred, and alicyclic diepoxy compounds represented by the following formula (II) are more preferred. By including the alicyclic diepoxy compound represented by the following formula (II) as compound (B2) in the curable composition (1), the elasticity of the cured product layer after the curable composition is cured becomes higher, and cracking due to thermal contraction of the polarizing film can be suppressed.

In formula (II), ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. If the alkyl group has 3 or more carbon atoms, it may have an alicyclic structure. The alkyl group having 1 to 6 carbon atoms may be a linear or branched alkyl group. Examples of the alkyl group having an alicyclic structure include cyclopropyl, cyclobutyl, and cyclopentyl.

In formula (II), X represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or the following formulas (IIa) to (IId):

A divalent group represented by any one of .

Examples of alkanediyl groups having 1 to 6 carbon atoms include methylene, ethylene, and propane-1,2-diyl.

When X in formula (II) is a divalent group represented by any one of formulae (IIa) to (IId), ^Y1 to ^Y4 in each formula are independently an alkanediyl group having 1 to 20 carbon atoms. When the alkanediyl group has 3 or more carbon atoms, it may have an alicyclic structure.

a and b independently represent integers from 0 to 20.

Examples of compounds represented by formula (II) include compounds A to G below. Furthermore, the chemical formulas A to G shown below correspond to compounds A to G, respectively.

A: 3,4-Epoxycyclohexylmethyl ester

B: 3,4-Epoxy-6-methylcyclohexylcarboxylic acid 3,4-Epoxy-6-methylcyclohexyl methyl ester

C: Ethylene bis(3,4-epoxycyclohexylcarboxylate)

D: Bis(3,4-epoxycyclohexylmethyl adipate)

E: Di(3,4-epoxy-6-methylcyclohexylmethyl)adipate

F: Diethylene glycol bis(3,4-epoxycyclohexyl methyl ether)

G: Ethylene glycol bis(3,4-epoxycyclohexyl methyl ether)

A:

B:

C:

D:

E:

F:

G:

In the present invention, the alicyclic epoxy compound (B2) is more preferably 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate from the perspective of easy availability. Furthermore, from the perspective of effectively suppressing corrosion of the conductive layer, the 1,2-epoxy-4-(2-oxoheterocyclobutane)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol is more preferred. In particular, the use of a combination of 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate and a 1,2-epoxy-4-(2-oxohexocyclobutane)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol as the alicyclic epoxy compound (B2) more effectively suppresses corrosion of the conductive layer. The alicyclic epoxy compound (B2) may be used singly or in combination of multiple different types.

When the curable composition (1) contains an alicyclic epoxy compound (B2), the content of the alicyclic epoxy compound (B2) is preferably 3 to 70 parts by mass, more preferably 10 to 60 parts by mass, even more preferably 20 to 55 parts by mass, and particularly preferably 25 to 50 parts by mass, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition (1). When the content of the alicyclic epoxy compound (B2) is within the above range, curing by irradiation with active energy rays such as ultraviolet rays can be accelerated, and a cured layer of sufficient hardness can be easily formed.

The aromatic epoxy compound (B3) is a compound having one or more aromatic rings in the molecule. Specifically, the following examples are exemplified.

Monovalent phenols with at least one aromatic ring, such as phenol, cresol, or butylphenol, or mono- or poly-glycidyl ether compounds of their alkylene oxide adducts, such as bisphenol A, bisphenol F, or glycidyl ether compounds of such compounds to which alkylene oxide is added, and epoxyphenolic resins;

Epoxypropyl ethers of aromatic compounds with two or more phenolic hydroxyl groups, such as resorcinol, hydroquinone, and o-catechin;

Mono- and poly-glycidyl ether compounds of aromatic compounds with two or more alcoholic hydroxyl groups, such as benzyl alcohol, benzyl alcohol, and benzyl butanol;

Epoxypropyl esters of polyprotic aromatic compounds with two or more carboxylic acids, such as phthalic acid, terephthalic acid, and trimellitic acid;

Epoxypropyl esters of benzoic acids such as benzoic acid, toluic acid, and naphthoic acid;

Styrene oxide or divinylbenzene epoxide, etc.

When an aromatic epoxy compound (B3) is included, from the perspective of reducing the viscosity of the curable composition, it is preferably at least one selected from the group consisting of phenolic glycidyl ethers, glycidyl ether compounds of aromatic compounds having two or more alcoholic hydroxyl groups, glycidyl ether compounds of polyvalent phenols, glycidyl esters of benzoic acids, glycidyl esters of polyprotic acids, and epoxides of styrene oxide or divinylbenzene.

Furthermore, since the curability of the curable composition is improved, the aromatic epoxy compound (B3) preferably has an epoxy equivalent of 80 to 500.

The aromatic epoxy compound (B3) may be used alone or in combination of two or more different types.

As the aromatic epoxy compound (B3), commercially available products can be used, for example, Denacol EX-121, Denacol EX-141, Denacol EX-142, Denacol EX-145, Denacol EX-146, Denacol EX-147, Denacol EX-201, Denacol EX-203, Denacol EX-711, Denacol EX-721, Oncoat EX-1020, Oncoat EX-1030, Oncoat EX-1040, Oncoat EX-1050, Oncoat EX-1051, Oncoat EX-1010, Oncoat EX-1011, Oncoat EX-1012 (all manufactured by Nagase Chemtex Co., Ltd.); Ogsol PG-100, Ogsol EG-200, Ogsol EG-210, Ogsol EG-250 (all manufactured by Osaka Gas Chemical Co., Ltd.); HP4032, HP4032D, HP4700 (all manufactured by DIC Corporation); ESN-475V (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.); Epicoat YX8800, jER828EL (manufactured by Mitsubishi Chemical Corporation); Marproof G-0105SA, Marproof G-0130SP (manufactured by NOF Corporation); Epiclone N-665, Epiclone HP-7200 (all manufactured by DIC Corporation); EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, XD-1000, NC-3000, EPPN-501H, EPPN-501HY, EPPN-502H, NC-7000L (all manufactured by Nippon Kayaku Co., Ltd.); Adeka Glycilol TECHMORE VG-3101L, EPOX-MKR710, EPOX-MKR151 (the above are made by Printech Corporation), etc.

The inclusion of the aromatic epoxy compound (B3) in the curable composition makes it a hydrophobic resin, and the resulting cured layer is also hydrophobic. This prevents external moisture intrusion under high temperature and high humidity conditions and effectively suppresses the migration of the dichroic dye (iodine) contained in the polarizing film.

When the curable composition (1) contains an aromatic epoxy compound (B3), the content of the aromatic epoxy compound (B3) is preferably 1 to 70 parts by mass, more preferably 5 to 60 parts by mass, even more preferably 7 to 55 parts by mass, and particularly preferably 10 to 50 parts by mass, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the curable composition (1). When the content of the aromatic epoxy compound (B3) is within the above range, the hydrophobicity of the cured layer can be improved and the permeability of the dichroic dye (iodine) to the cured layer can be reduced.

When the curable composition (1) contains an oxycyclobutane compound (A) and an alicyclic epoxy compound (B2), the mass ratio (WB2/WA) of the alicyclic epoxy compound (B2) content (WB2) to the oxycyclobutane compound (A) content (WA) is preferably 0.05 to 1.5.

When the curable composition (1) contains an oxycyclobutane compound (A) and an aliphatic epoxy compound (B1), the mass ratio (WB1/WA) of the content (WB1) of the aliphatic epoxy compound (B1) to the content (WA) of the oxycyclobutane compound (A) is preferably 0.1 to 0.5.

When the curable composition (1) contains an oxycyclobutane compound (A) and an aromatic epoxy compound (B3), the mass ratio (WB3/WA) of the content (WB3) of the aromatic epoxy compound (B3) to the content (WA) of the oxycyclobutane compound (A) is preferably 0.1 to 1.5.

The curable composition (1) may contain polymerizable compounds other than the cyclohexane compound (A) and the epoxy compound (B). Specifically, examples thereof include aliphatic monoepoxy compounds and alicyclic monoepoxy compounds.

The content of the polymerizable compound contained in the curable composition (1) is preferably 80 to 100 parts by mass, more preferably 90 to 99.5 parts by mass, and even more preferably 95 to 99 parts by mass, relative to 100 parts by mass of the total amount of the curable composition (1). When the content of the polymerizable compound is within the above range, the migration of the dichroic pigment contained in the polarizing film toward the first cured layer can be effectively suppressed.

The curable composition typically contains a polymerization initiator for initiating polymerization. The polymerization initiator can be a photopolymerization initiator (e.g., a photocationic polymerization initiator or a photoradical polymerization initiator) or a thermal polymerization initiator. For example, when the curable composition contains the aforementioned oxycyclobutane compound (A) or epoxy compound (B) as a polymerizable compound, it is preferred to use a photocationic polymerization initiator as the polymerization initiator.

Photocatalytic polymerization initiators generate cationic species or Lewis acids upon exposure to active energy rays, such as visible light, ultraviolet light, X-rays, or electron beams, initiating polymerization reactions in cationic polymerizable compounds. Because photocatalytic activity is photocatalytic, photocatalytic polymerization initiators offer excellent storage stability and handling properties even when mixed with polymerizable compounds. Examples of compounds that generate cationic species or Lewis acids upon exposure to active energy rays include aromatic iodonium salts, onium salts of aromatic sulfonium salts, aromatic diazonium salts, and iron-aromatic complexes.

Aromatic iodonium salts are compounds containing a diaryl iodonium cation, typically a diphenyl iodonium cation. Aromatic sulfonium salts are compounds containing a triaryl sulfonium cation, typically a triphenyl sulfonium cation or a 4,4'-bis(diphenylsulfonium)diphenyl sulfide cation. Aromatic diazonium salts are compounds containing a diazonium cation, typically a phenylenediazonium cation. Furthermore, the iron-arene complex is typically a cyclopentadienyl iron (II) arene complex.

The cations listed above form pairs with anions to form photocationic polymerization initiators. Examples of anions that constitute photocationic polymerization initiators include special phosphorus anions [(Rf) _{nPF6 -n} ] ^- , hexafluorophosphate anions _PF6- , hexafluoroantimonylate anions _SbF6- ^, pentafluorohydroxyantimonylate anions _SbF5 (OH ^{) -} , hexafluoroarsenate anions _AsF6- ^, tetrafluoroborate anions _BF4- ^, and tetrakis(pentafluorophenyl)boric acid anions B _{( C6F5} ) _4- ^. Among them, from the perspective of the curability of the polymerizable compound and the safety of the resulting cured layer, the photocatalytic polymerization initiator is preferably a special phosphorus anion [(Rf) _n PF _6-n ] ^- or a hexafluorophosphate anion PF ₆ ^- .

Photocatalytic polymerization initiators can be used singly or in combination. Aromatic sulfonium salts are preferred because they absorb ultraviolet light in the wavelength region around 300 nm, resulting in excellent curing properties and the ability to produce a cured product with excellent mechanical and adhesive strength.

The content of the polymerization initiator in the curable composition (1) is generally 0.5 to 10 parts by mass, preferably 6 parts by mass or less, and more preferably 3 parts by mass or less, relative to 100 parts by mass of the polymerizable compound. When the content of the polymerization initiator is within the above range, the polymerizable compound can be sufficiently cured, and the cured layer formed from the resulting cured product can be provided with high mechanical strength and adhesive strength. On the other hand, when the amount becomes too high, the product from the photo-ionized polymerization initiator reacts with the hydroxyl group of the polyvinyl alcohol constituting the polarizing film, which may reduce the optical performance of the polarizing film.

In the present invention, the curable composition (1) may contain additives commonly used in curable compositions as needed. Such additives include, for example, ion scavengers, antioxidants, chain transfer agents, polymerization promoters (polyols, etc.), sensitizers, sensitization aids, light stabilizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, defoaming agents, leveling agents, silane coupling agents, pigments, antistatic agents, ultraviolet absorbers, etc.

Examples of sensitizers include photosensitizers. Photosensitizers are compounds that exhibit maximum absorption at wavelengths longer than the maximum absorption wavelength of photocationic polymerization initiators, accelerating the polymerization reaction. Furthermore, auxiliary photosensitizers are compounds that further accelerate the action of the photosensitizers. Depending on the type of protective film, it is preferable to combine these photosensitizers with auxiliary photosensitizers. By combining these photosensitizers, it is possible to produce a cured product with the desired properties, even when using films with low UV transmittance.

The photosensitizer is preferably a compound that exhibits maximum absorption at wavelengths longer than 380 nm. Examples of such photosensitizers include the anthracene compounds described below.

9,10-dimethoxyanthracene,

9,10-diethoxyanthracene,

9,10-Dipropoxyanthracene,

9,10-Diisopropoxyanthracene,

9,10-Dibutoxyanthracene,

9,10-Dipentyloxyanthracene,

9,10-Dihexyloxyanthracene,

9,10-bis(2-methoxyethoxy)anthracene,

9,10-Bis(2-ethoxyethoxy)anthracene,

9,10-bis(2-butoxyethoxy)anthracene,

9,10-bis(3-butoxypropoxy)anthracene,

2-Methyl or 2-ethyl-9,10-dimethoxyanthracene,

2-Methyl or 2-ethyl-9,10-diethoxyanthracene,

2-Methyl or 2-ethyl-9,10-dipropoxyanthracene,

2-Methyl or 2-ethyl-9,10-diisopropoxyanthracene,

2-Methyl or 2-ethyl-9,10-dibutoxyanthracene,

2-Methyl or 2-ethyl-9,10-dipentyloxyanthracene,

2-Methyl or 2-ethyl-9,10-dihexyloxyanthracene.

The curable composition (1) can be obtained by mixing a polymerizable compound, a polymerization initiator, and additives as needed. The first curable layer can be formed by applying the curable composition (1) on a polarizing film, or on a first protective film when a first protective film is used, and curing the applied curable composition by irradiating it with active energy rays such as ultraviolet rays and electron beams.

The curable composition (1) can be coated using various coating methods such as a scraper, a wire rod, a slit coater, a notch wheel coater, and a gravure coater. The light source used to cure the curable composition (1) is, for example, a light source of active energy rays. The light source of active energy rays can be, for example, any light source that generates ultraviolet rays, electron beams, X-rays, etc. In particular, a light source having a luminescence distribution of a wavelength of 400 nm or less is preferred, and examples thereof include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

The light irradiation intensity when curing the curable composition varies depending on the composition, but the light irradiation intensity in the wavelength region effective for activating the polymerization initiator is preferably 0.1 to 1000 mW/ ^cm2 . If the light irradiation intensity when curing the curable composition (1) is too low, the time required for the reaction to proceed fully becomes longer. Conversely, if the light irradiation intensity is too high, the heat radiated from the lamp and the heat generated during the polymerization of the curable composition (1) may cause deterioration of the attached film. The light irradiation time when curing the curable composition (1) is controlled by the entire composition and is not particularly limited. However, the cumulative light amount, which is the product of the light irradiation intensity and the light irradiation time, is preferably set to 10 to 5000 mJ/ ^cm2 . If the accumulated light intensity is too low, the generation of active substances from the polymerization initiator is insufficient, and the resulting curing may be insufficient. On the other hand, if the accumulated light intensity is too high, the irradiation time becomes extremely long, which is disadvantageous in terms of improving productivity.

Furthermore, when curing the curable composition by irradiation with active energy rays, it is preferable to perform the curing without degrading the various functions of the optical laminate, such as the polarization degree, transmittance, and hue of the polarizing film, and the transparency of the various films constituting the protective film and optical layer.

In the optical laminate of the present invention, the thickness of the first cured layer is not particularly limited, but is preferably 0.1 to 15 μm, more preferably 0.5 to 10 μm, and even more preferably 0.5 to 7 μm. When the thickness of the first cured layer is above the lower limit, migration of the dichroic dye can be effectively suppressed. When the thickness is below the upper limit, the curable composition can be fully cured.

The optical laminate of the present invention has a first cured layer with an absorbance increase rate of 30%, indicating low absorption of dichroic dyes. While moisture intrusion from the outside can accelerate the migration of dichroic dyes in high-temperature, high-humidity environments, the optical laminate of the present invention effectively suppresses the migration of dichroic dyes contained in the polarizing film toward the first cured layer. Therefore, even in high-temperature, high-humidity environments, corrosion of the conductive layer is effectively suppressed while maintaining optical performance. Furthermore, when the adhesive layer constituting an optical laminate contains an ionic compound as an antistatic agent, for example, the ionic compound present in the adhesive layer can migrate through the protective film constituting the optical laminate toward the polarizing film, interacting with the dichroic dye in the polarizing film and sometimes degrading the optical performance of the optical laminate. The optical laminate of the present invention, with the first curing layer located between the polarizing film and the adhesive layer, effectively suppresses the migration of the ionic compound from the adhesive layer, thereby preventing degradation of the optical performance of the optical laminate.

Furthermore, the first cured layer also functions as an adhesive layer, bonding the polarizing film to the protective film or adhesive layer. In this case, especially for protective films that easily penetrate ionic compounds, it can prevent degradation of the optical performance of the optical laminate.

[Adhesive layer]

The adhesive constituting the adhesive layer can be any conventional adhesive, without particular limitation. Examples of adhesives include those with a base polymer composed of acrylic resins, rubber resins, urethane resins, silicone resins, and polyvinyl ether resins. Furthermore, energy-beam-curing adhesives and thermosetting adhesives are also possible. Among these, adhesives with an acrylic resin base polymer are particularly suitable due to their excellent transparency, adhesion, workability, weather resistance, and heat resistance.

In the present invention, when the adhesive layer contains an acrylic resin, the acrylic resin is not particularly limited, and conventionally known acrylic resins can be used. From the perspectives of adhesion and workability, the adhesive layer included in the optical laminate of the present invention preferably contains the following acrylic resin (P).

The acrylic resin (P) is derived from the following formula (III):

[In the formula, _Ra represents a hydrogen atom or a methyl group, and _Rb represents an alkyl group having 1 to 14 carbon atoms which may be substituted by an alkoxy group having 1 to 10 carbon atoms]

An acrylic resin containing as a main component a structural unit of the (meth)acrylate alkyl ester (P1) shown above, and further comprising a structural unit derived from an unsaturated monomer (P2) having a polar functional group (hereinafter sometimes referred to as a "polar functional group-containing monomer").

Here, in this specification, the term "(meth)acrylic acid" refers to either acrylic acid or methacrylic acid. "(Meth)" also has the same meaning when referring to (meth)acrylates, etc.

Examples of the (meth)acrylic acid alkyl ester (P1) represented by formula (III) include linear alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-octyl acrylate, and lauryl acrylate; branched alkyl acrylates such as isobutyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate; linear alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, and lauryl methacrylate; branched alkyl methacrylates such as isobutyl methacrylate, 2-ethylhexyl methacrylate, and isooctyl methacrylate; 2-methoxyethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl methacrylate, and ethoxymethyl methacrylate.

Among these, n-butyl acrylate is preferred. Specifically, n-butyl acrylate preferably accounts for 50% by mass or more of the total monomers constituting the acrylic resin (P). These alkyl (meth)acrylates (P1) may be used individually or in combination.

In the monomer (P2) containing a polar functional group, the polar functional group includes, for example, a free carboxyl group, a hydroxyl group, an amino group, a heterocyclic group headed by an epoxy group, etc. The monomer (P2) containing a polar functional group is preferably a (meth)acrylic compound having a polar functional group. Examples thereof include unsaturated monomers having a free carboxyl group such as acrylic acid, methacrylic acid, and β-carboxyethyl acrylate; unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2- or 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate; acrylamide, vinylcaprolactam, N-[4-(2-methyl-1-oxo-1-yl)-1-propene] ... - Unsaturated monomers with heterocyclic groups, such as vinyl-2-pyrrolidone, tetrahydrofuranylmethyl (meth)acrylate, caprolactone-modified tetrahydrofuranylmethyl acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran; and unsaturated monomers with heterocyclic isoamino groups, such as N,N-dimethylaminoethyl (meth)acrylate. These polar functional group-containing monomers can be used individually or in combination.

The monomer (P2) containing a polar functional group is preferably an unsaturated monomer having a hydroxyl group. Furthermore, in addition to unsaturated monomers having a hydroxyl group, it is also effective to use unsaturated monomers having other polar functional groups, such as unsaturated monomers having a free carboxyl group.

In the acrylic resin (P), the amount of the structural unit derived from the (meth)acrylate alkyl ester (P1) represented by the aforementioned formula (III) is, for example, 50 to 100 parts by mass relative to 100 parts by mass of all the structural units constituting the acrylic resin (P). The amount of the structural unit derived from the monomer (P2) containing a polar functional group is, for example, 0.1 to 20 parts by mass relative to 100 parts by mass of all the structural units constituting the acrylic resin (P).

The acrylic resin (P) may also contain structural units derived from monomers other than the (meth)acrylate alkyl ester (P1) represented by formula (III) and the polar functional group-containing monomer (P2). Examples of such structural units include structural units derived from an unsaturated monomer (P3) having one olefinic double bond and at least one aromatic ring in its molecule (hereinafter sometimes referred to as an "aromatic ring-containing monomer"), structural units derived from a (meth)acrylate having an alicyclic structure in its molecule, structural units derived from styrene-based monomers, structural units derived from vinyl-based monomers, and structural units derived from a monomer having multiple (meth)acryloyl groups in its molecule.

An unsaturated monomer (a monomer containing an aromatic ring) (P3) having one olefinic double bond and at least one aromatic ring in the molecule, preferably one having a (meth)acryloyl group as the group containing the olefinic double bond. Examples thereof include benzyl (meth)acrylate, neopentyl glycol benzoate (meth)acrylate, etc., wherein the formula (IV) is:

[In the formula, _R3 represents a hydrogen atom or a methyl group, n represents an integer from 1 to 8, and _R4 represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 11 carbon atoms, or an aromatic group having 6 to 10 carbon atoms]

The (meth)acrylic acid compounds containing an aromatic ring are preferred.

Examples of alkyl groups with 1 to 9 carbon atoms include methyl, butyl, and nonyl. Examples of aralkyl groups with 7 to 11 carbon atoms include benzyl, phenethyl, and naphthylmethyl. Examples of aromatic groups with 6 to 10 carbon atoms include phenyl, tolyl, and naphthyl.

Examples of aromatic ring-containing (meth)acrylic compounds represented by formula (IV) include 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, and 2-(o-phenylphenoxy)ethyl (meth)acrylate. These aromatic ring-containing monomers may be used individually or in combination. Among these, 2-phenoxyethyl (meth)acrylate [in the aforementioned formula (IV), R ₄ = H, n = 1 compound], 2-(o-phenylphenoxy)ethyl (meth)acrylate [in the aforementioned formula (IV), R ₄ = o-phenyl, n = 1 compound], or 2-(2-phenoxyethoxy)ethyl (meth)acrylate [in the aforementioned formula (IV), R ₄ = H, n = 2 compound] is suitable as one of the aromatic ring-containing monomers (P3) constituting the acrylic resin (P).

The alicyclic structure in the structural unit of the (meth)acrylate having an alicyclic structure in the molecule is a cycloolefin structure having generally 5 or more carbon atoms, preferably 5 to 7 carbon atoms. Specific examples of acrylic acid esters having an alicyclic structure include isoborneol acrylate, cyclohexyl acrylate, dicyclopentyl acrylate, cyclododecyl acrylate, methylcyclohexyl acrylate, trimethylcyclohexyl acrylate, 3-butylcyclohexyl acrylate, α-ethoxycyclohexyl acrylate, and cyclohexylphenyl acrylate. Specific examples of methacrylic acid esters having an alicyclic structure include isoborneol methacrylate, cyclohexyl methacrylate, dicyclopentyl methacrylate, cyclododecyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, 3-butylcyclohexyl methacrylate, and cyclohexylphenyl methacrylate.

Specific examples of styrene-based monomers include, in addition to styrene, alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; and nitrostyrene, acetylstyrene, methoxystyrene, and divinylbenzene.

Specific examples of vinyl monomers include fatty acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl laurate; vinyl halides such as vinyl chloride and vinyl bromide; vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyls such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; conjugated diene monomers such as butadiene, isoprene, and chloroprene; and acrylonitrile and methacrylonitrile.

Specific examples of monomers having multiple (meth)acryl groups in the molecule include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate, which have two (meth)acryl groups in the molecule; and trihydroxymethylpropane tri(meth)acrylate, which have three (meth)acryl groups in the molecule.

Monomers different from the (meth)acrylate (P1) and the polar functional group-containing monomer (P2) represented by formula (III) may be used alone or in combination of two or more. When included in an adhesive, the amount of structural units derived from monomers different from the (meth)acrylate (P1) and the polar functional group-containing monomer (P2) in the acrylic resin (P) is typically 0 to 30 parts by mass, based on 100 parts by mass of all structural units constituting the acrylic resin (P).

The resin component of the adhesive composition may include two or more acrylic resins, each of which comprises structural units derived from an alkyl (meth)acrylate (P1) represented by formula (III) and a monomer (P2) containing a polar functional group. Furthermore, a different acrylic resin may be mixed with the acrylic resin (P), for example, an acrylic resin having structural units derived from an alkyl (meth)acrylate (P1) represented by formula (III) but no polar functional group. The acrylic resin (P) comprising structural units derived from an alkyl (meth)acrylate (P1) represented by formula (III) and a monomer (P2) containing a polar functional group may be present in an amount of, for example, 70 parts by mass or more relative to 100 parts by mass of the total acrylic resin contained in the adhesive layer.

The acrylic resin (P), comprising a copolymer of a monomer mixture of an alkyl (meth)acrylate (P1) represented by formula (III) and a monomer containing a polar functional group (P2), preferably has a weight-average molecular weight (Mw) in the range of 1,000,000 to 2,000,000, as measured by gel permeation chromatography (GPC) in terms of polystyrene. A weight-average molecular weight in this range, as measured in terms of standard polystyrene, improves adhesion under high temperature and high humidity conditions, tends to reduce the likelihood of separation and lifting between the conductive layer and the adhesive layer, and also tends to improve reworkability. Furthermore, even if the polarizing film's dimensions change, the adhesive layer easily adjusts to that size. For example, when the optical multilayer is bonded to a liquid crystal cell, the brightness difference between the cell's periphery and center becomes uniform, tending to suppress white spots and color unevenness.

The molecular weight distribution, represented by the ratio Mw/Mn of the weight-average molecular weight Mw to the number-average molecular weight Mn, is preferably in the range of 3 to 7. When the molecular weight distribution Mw/Mn is in the range of 3 to 7, the occurrence of defects such as white spots can be suppressed even when the liquid crystal display panel or liquid crystal display device is exposed to high temperatures.

Furthermore, from the perspective of exhibiting adhesive properties, the aforementioned acrylic resin (P) preferably has a glass transition temperature in the range of -10 to -60°C. The glass transition temperature of the resin can generally be measured using a differential scanning calorimeter.

Acrylic resin (P) can be produced by various known methods, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. A polymerization initiator is generally used in the production of acrylic resin (P). The content of the polymerization initiator is preferably 0.001 to 5 parts by mass based on 100 parts by mass of all monomers used in the production of the acrylic resin.

The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator. Examples of the photopolymerization initiator include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone. Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(2-methylacrylate)dimethyl ester and 2,2'-azobis(2- Azo compounds such as hydroxymethylpropionitrile); organic peroxides such as lauryl peroxide, 3-butyl hydroperoxide, isopropyl hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, 3-butyl peroxyneodecanoate, 3-butyl peroxypivalate, and (3,5,5-trimethylhexanoyl) peroxide; and inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. Furthermore, redox initiators that combine a peroxide with a reducing agent can also be used as polymerization initiators.

The production method of the acrylic resin (P) is particularly preferably a solution polymerization method. A specific example of the solution polymerization method includes mixing the desired monomer and an organic solvent, adding a thermal polymerization initiator under a nitrogen atmosphere, and stirring at 40 to 90°C, preferably 50 to 80°C, for 3 to 10 hours. Furthermore, to control the reaction, the monomer and thermal polymerization initiator may be added continuously or intermittently during the polymerization, or may be added while dissolved in the organic solvent. Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as propanol and isopropanol; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

The adhesive layer included in the optical laminate of the present invention is preferably formed by combining an acrylic resin (P) with a crosslinking agent. The crosslinking agent is, for example, a compound that reacts with the structural units in the acrylic resin (P), particularly those derived from the monomer (P2) containing a polar functional group, to crosslink the acrylic resin. Specifically, examples include isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds. Among these, isocyanate compounds, epoxy compounds, and aziridine compounds have at least two functional groups in their molecules that react with the polar functional groups in the acrylic resin (P).

Isocyanate compounds are compounds containing at least two isocyanate groups (-NCO) within their molecules. Examples include tolyl diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolyl diisocyanate, hydrogenated tolyl diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthyl diisocyanate, and triphenylmethane triisocyanate. Furthermore, adducts formed by reacting these isocyanate compounds with polyols such as glycerol and trihydroxymethylpropane, or by converting these isocyanate compounds into dimers or trimers, can also be used as crosslinking agents in adhesives. Two or more isocyanate compounds may also be used as a mixture.

Epoxy compounds are compounds with at least two epoxy groups in the molecule. Examples include bisphenol A-type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trihydroxymethylpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane. Two or more epoxy compounds may also be used in combination.

Aziridine compounds are compounds with at least two ethyleneimines in their molecules, each containing a three-membered ring skeleton consisting of one nitrogen atom and two carbon atoms. Examples include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), trisethylene melamine, m-phenylenediamine-bis-1-(2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), tris-hydroxymethylpropane tris-β-aziridinylpropionate, and tetras-hydroxymethylmethane tris-β-aziridinylpropionate.

Examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetylacetate is coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

Among these crosslinking agents, isocyanate compounds are preferably used, particularly tolyl diisocyanate, tolyl diisocyanate, or hexamethylene diisocyanate, or adducts of these isocyanate compounds with polyols such as glycerol and trihydroxymethylpropane, dimers or trimers of these isocyanate compounds, or mixtures of these isocyanate compounds. When the polar functional group-containing monomer (P2) has a polar functional group selected from free carboxyl groups, hydroxyl groups, amino groups, and epoxy groups, it is particularly preferred to use at least one isocyanate compound as the crosslinking agent. Suitable isocyanate compounds include, for example, tolyl diisocyanate, an adduct of tolyl diisocyanate and a polyol, a dimer of tolyl diisocyanate, and a trimer of tolyl diisocyanate; or hexamethylene diisocyanate, an adduct of hexamethylene diisocyanate and a polyol, a dimer of hexamethylene diisocyanate, and a trimer of hexamethylene diisocyanate.

In the adhesive layer of the optical laminate of the present invention, the crosslinking agent is present in an amount of, for example, 0.01 to 10 parts by mass relative to 100 parts by mass of the acrylic resin (P). A crosslinking agent content within the aforementioned range is preferred because it tends to improve the durability of the adhesive layer and lessen the noticeable white spots of the liquid crystal display panel.

In the present invention, the adhesive forming the adhesive layer preferably contains a silane compound. In particular, it is preferred that the silane compound be pre-incorporated into the acrylic resin before the crosslinking agent is added. Silane compounds enhance adhesion to glass, and the inclusion of silane compounds ensures high adhesion to the display panel.

Examples of the silane compound include vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-Epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-butylenepropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, 3-glycidoxypropylethoxydimethylsilane, etc. These silane compounds can be used alone or in combination.

Silane compounds may also be polysiloxane oligomers. Examples of polysiloxane oligomers expressed as (monomer)-(monomer) copolymers include the following.

Copolymers containing butylene groups, such as 3-butylenepropyltrimethoxysilane-tetramethoxysilane copolymer, 3-butylenepropyltrimethoxysilane-tetraethoxysilane copolymer, 3-butylenepropyltriethoxysilane-tetramethoxysilane copolymer, and 3-butylenepropyltriethoxysilane-tetraethoxysilane copolymer;

Copolymers containing methyl groups, such as methyltrimethoxysilane-tetramethoxysilane copolymers, methyltrimethoxysilane-tetraethoxysilane copolymers, methyltriethoxysilane-tetramethoxysilane copolymers, and methyltriethoxysilane-tetraethoxysilane copolymers;

Copolymers containing methacryloxypropyl groups, such as 3-methacryloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-methacryloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-methacryloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-methacryloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;

Copolymers containing acryloxypropyl groups, such as 3-acryloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropyltriethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-acryloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-acryloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-acryloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;

Copolymers containing vinyl groups, such as vinyltrimethoxysilane-tetramethoxysilane copolymers, vinyltrimethoxysilane-tetraethoxysilane copolymers, vinyltriethoxysilane-tetramethoxysilane copolymers, vinyltriethoxysilane-tetraethoxysilane copolymers, vinylmethyldimethoxysilane-tetramethoxysilane copolymers, vinylmethyldimethoxysilane-tetraethoxysilane copolymers, vinylmethyldiethoxysilane-tetramethoxysilane copolymers, and vinylmethyldiethoxysilane-tetraethoxysilane copolymers;

Copolymers containing amino groups, such as 3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-aminopropylmethyldiethoxysilane-tetraethoxysilane copolymer.

These silane compounds are often liquid. The amount of the silane compound in the adhesive is, for example, 0.01 to 10 parts by mass per 100 parts by mass of the acrylic resin (P) (or their combined amount when two or more are used). The aforementioned range of silane compounds per 100 parts by mass of the acrylic resin (P) is preferred because it improves the adhesion between the adhesive layer and the substrate (or liquid crystal cell) and also tends to suppress the silane compound's leakage from the adhesive layer.

The adhesive layer may also contain an ionic compound. Ionic compounds can function as antistatic agents. In particular, when the acrylic resin (P) contains an aromatic ring-containing (meth)acrylic compound represented by formula (IV), and n in formula (IV) is 2 or greater, it is effective in suppressing white spots. By adding an ionic compound to an adhesive containing an acrylic resin copolymerized with this monomer, white spot suppression can be achieved while also providing excellent antistatic properties. The ionic compound referred to here is a compound consisting of a combination of cations and anions. The cations and anions can be either inorganic or organic. From the perspective of compatibility with the acrylic resin (P), it is preferred that at least one of the cations and anions be an ionic compound containing an organic group.

Examples of inorganic cations constituting ionic compounds include alkaline metal ions such as lithium cation [Li ⁺ ], sodium cation [Na ⁺ ], potassium cation [K ⁺ ], and cesium cation [Cs ⁺ ]; and alkaline earth metal ions such as palladium cation [Be ²⁺ ], magnesium cation [Mg ²⁺ ], and calcium cation [Ca ²⁺ ]. Among them, from the perspective of metal corrosion resistance, lithium cations [Li ⁺ ], potassium cations [K ⁺ ], or sodium cations [Na ⁺ ] are preferred, and from the perspective of durability, potassium cations [K ⁺ ] are even more preferred.

Examples of organic cations constituting ionic compounds include pyridinium cations represented by the following formula (V) and quaternary ammonium cations represented by the following formula (VI).

In formula (V), _R5 to _R9 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and _R10 represents an alkyl group having 1 to 16 carbon atoms. In formula (VI), _R11 represents an alkyl group having 1 to 12 carbon atoms, and _R12 , _R13 , and _R14 each independently represent an alkyl group having 6 to 12 carbon atoms.

The pyridinium cation represented by formula (V) has a total carbon number of 8 or more, preferably 10 or more, preferably from the perspective of compatibility with the acrylic resin (P). Furthermore, it has a total carbon number of 36 or less, preferably 30 or less. Among the pyridinium cations represented by formula (V), one preferred cation is one in which _R7 , which is bonded to the carbon atom at the 4-position of the pyridine ring, is an alkyl group, and _R5 , _R6 , _R8 , and R9 _, which are bonded to the other carbon atoms of the pyridine ring, are each a hydrogen atom.

Specific examples of the pyridinium cation represented by formula (V) include N-methyl-4-hexylpyridinium cation, N-butyl-4-methylpyridinium cation, N-butyl-2,4-diethylpyridinium cation, N-butyl-2-hexylpyridinium cation, N-hexyl-2-butylpyridinium cation, Pyridinium cation, N-hexyl-4-methylpyridinium cation, N-hexyl-4-ethylpyridinium cation, N-hexyl-4-butylpyridinium cation, N-octyl-4-methylpyridinium cation, N-octyl-4-ethylpyridinium cation, N-octylpyridinium cation, etc.

The quaternary ammonium cation represented by formula (VI) above preferably has a total carbon number of 20 or more, preferably 22 or more, from the perspective of compatibility with the acrylic resin (P). Furthermore, it preferably has a total carbon number of 36 or less, preferably 30 or less.

Specific examples of the tetraalkylammonium cation represented by formula (VI) include tetrahexylammonium cation, tetraoctylammonium cation, tributylmethylammonium cation, trihexylmethylammonium cation, trioctylmethylammonium cation, dodecylmethylammonium cation, trihexylethylammonium cation, and trioctylethylammonium cation.

On the other hand, examples of anions constituting ionic compounds include chloride anions [Cl ^- ], bromine anions [Br ^- ], iodine anions [I ^- ], tetrachloroaluminate anions [AlCl ₄ ^- ], heptachlorodialuminate anions [Al ₂ Cl ₇ ^4- ], tetrafluoroborate anions [BF ₄ ^- ], hexafluorophosphate anions [PF ₆ ^- ], perchlorate anions [ClO ₄ ^- ], nitrate anions [NO ₃ ^- ], acetate anions [CH ₃ COO ^- ], trifluoroacetate anions [CF ₃ COO ^- ], methanesulfonate anions [CH ₃ SO ₃ ^- ], trifluoromethanesulfonate anion [CF ₃ SO ₃ ^- ], bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ^- ], tris(trifluoromethanesulfonyl)methane anion [(CF ₃ SO ₂ ) ₃ C ^- ], hexafluoroarsenate anion [AsF ₆ ^- ], hexafluoroantimonate anion [SbF ₆ ^- ], hexafluoronitrogenate anion [NbF ₆ ^- ], hexafluorotibrate anion [TaF ₆ ^- ], (poly)hydrogen fluoride anion [F(HF) _n ^- ] (n is about 1 to 3), thiocyanate anion [SCN ^- ], dicyanamide anion [(CN) ₂ N ^- ], perfluorobutanesulfonate anion [C ₄ F ₉ SO ₃ ^- ], bis(pentafluoroethanesulfonyl)imide anion [(C ₂ F ₅ SO ₂ ) ₂ N ^- ], perfluorobutyrate anion [C ₃ F ₇ COO ^- ], (trifluoromethanesulfonyl)(trifluoromethanecarbonyl)imide anion [(CF ₃ SO ₂ )(CF ₃ CO)N ^- ], etc.

Specific examples of the ionic compound can be appropriately selected from the above-mentioned combination of cations and anions. Specific examples of the ionic compound of the combination of cations and anions include lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium iodide (lithium iodide), lithium bis(pentafluoroethanesulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methane, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(pentafluoroethanesulfonyl)imide, tris(trifluoromethanesulfonyl)methane, and sodium tris(trifluoromethanesulfonyl)imide. Sodium bis(trifluoromethanesulfonyl)methane, potassium bis(trifluoromethanesulfonyl)imide, potassium bis(pentafluoroethanesulfonyl)imide, potassium tris(trifluoromethanesulfonyl)methane, N-methyl-4-hexylpyridinium bis(trifluoromethanesulfonyl)imide, N-butyl-2-methylpyridinium bis(trifluoromethanesulfonyl)imide, N-hexyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide, N-octyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide , N-methyl-4-hexylpyridinium hexafluorophosphate, N-butyl-2-methylpyridinium hexafluorophosphate, N-hexyl-4-methylpyridinium hexafluorophosphate, N-octyl-4-methylpyridinium hexafluorophosphate, N-methyl-4-hexylpyridinium perchlorate, N-butyl-2-methylpyridinium perchlorate, N-hexyl-4-methylpyridinium perchlorate, N-octyl-4-methylpyridinium perchlorate, tetrahexylammonium bis(trifluoromethanesulfonyl) )imide, tributylmethylammonium bis(trifluoromethanesulfonyl)imide, trihexylmethylammonium bis(trifluoromethanesulfonyl)imide, trioctylmethylammonium bis(trifluoromethanesulfonyl)imide, tetrahexylammonium hexafluorophosphate, tributylmethylammonium hexafluorophosphate, trihexylmethylammonium hexafluorophosphate, trioctylmethylammonium hexafluorophosphate, tetrahexylammonium perchlorate, tributylmethylammonium perchlorate, trihexylmethylammonium perchlorate, trioctylmethylammonium perchlorate, etc.

These ionic compounds may be used individually or in combination. When the ionic compound is present, its amount is, for example, 0.1 to 10 parts by mass relative to 100 parts by mass of the acrylic resin (P).

In the present invention, the adhesive layer may further contain a crosslinking catalyst, weathering stabilizer, tackifier, plasticizer, softener, dye, pigment, inorganic filler, or resins other than acrylic resins. By blending a UV-curable compound such as a multifunctional acrylate and a photoinitiator into the adhesive, and then curing the adhesive layer by irradiating it with UV light, a harder adhesive layer can be achieved. This creates a secondary crosslinking structure within the adhesive, improving durability during heat tests and other tests. Furthermore, when a crosslinking agent and a crosslinking catalyst are used in conjunction with the adhesive, the adhesive layer can be cured and prepared in a short time. In the resulting optical laminate, this suppresses the occurrence of lifting and peeling between the adhesive layer and the first cured layer or the first protective film, and also suppresses the formation of bubbles within the adhesive layer, resulting in improved reworkability.

Examples of crosslinking catalysts include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamine resins, and melamine resins. When an amine compound is used as a crosslinking catalyst in an adhesive, an isocyanate compound is suitable as a crosslinking agent.

Furthermore, the adhesive layer may contain microparticles to create a light-scattering adhesive layer. Furthermore, antioxidants and UV absorbers may be blended into the adhesive layer. Examples of UV absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel cerium salt compounds.

The adhesive layer can be formed by, for example, forming the aforementioned adhesive into an organic solvent solution, applying it to the desired film or layer (e.g., a polarizing film) using a slit coater, gravure coater, or the like, and then drying it. Alternatively, the adhesive can be formed by transferring a sheet of adhesive formed on a release-treated plastic film (referred to as a separator) to the desired film or layer. The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 2 to 40 μm, more preferably in the range of 5 to 35 μm, and even more preferably in the range of 10 to 30 μm.

The adhesive layer preferably has a storage modulus of 0.10 to 5.0 MPa at 23 to 80°C, and more preferably 0.15 to 1.0 MPa. A storage modulus of 0.10 MPa or higher at 23 to 80°C is preferred because it can suppress white spots caused by shrinkage of the optical laminate when the liquid crystal display panel containing the optical laminate is exposed to high temperatures, etc. Furthermore, a storage modulus of 5 MPa or less is preferred because it is less likely to cause a decrease in durability due to a decrease in adhesion. Here, "displaying a storage modulus of 0.10 to 5.0 MPa at 23 to 80°C" means that the storage modulus is within the above range at any temperature within that range. Since the storage modulus generally decreases with increasing temperature, if either the storage modulus at 23°C or 80°C is within the above range, the adhesive layer can exhibit the above-mentioned storage modulus at temperatures within that range. The storage modulus of the adhesive layer can be measured using a commercially available viscoelasticity tester, such as the "SYNAMIC ANALYZER RDA II" manufactured by REOMETRIC.

[Conductive layer]

The conductive layer included in the optical laminate of the present invention can be, for example, a conductive transparent metal oxide layer or a metal wiring layer. Such a conductive layer can be, for example, a layer containing at least one metal element selected from aluminum, copper, silver, iron, tin, zinc, platinum, nickel, molybdenum, chromium, tungsten, lead, titanium, palladium, indium, and alloys containing two or more of these elements. Among these, a layer containing at least one metal element selected from aluminum, copper, silver, and gold is preferred from the perspective of conductivity, and a layer containing aluminum is more preferred from the perspective of conductivity and cost. Furthermore, for layers containing copper, a blackening treatment can be applied to prevent light reflection. Blackening involves oxidizing the surface of the conductive layer to precipitate _Cu2O or CuO. The conductive layer can be made of, for example, metallic silver, ITO (tin-doped indium oxide), graphite, zinc oxide, or AZO (aluminum-doped zinc oxide).

The conductive layer (conductive layer 4 in Figures 1 and 2) is, for example, disposed on a substrate (substrate X in Figures 1 and 2). The conductive layer can be formed on the substrate by, for example, sputtering. The substrate can be a transparent substrate constituting the liquid crystal cell included in the touch input element, or a glass substrate. The transparent substrate can be formed of polyethylene terephthalate, polycarbonate, polymethacrylate, polyethylene naphthalate, polyether sulfone, cyclic olefin copolymer, triacetyl cellulose, polyvinyl alcohol, polyimide, polystyrene, biaxially stretched polystyrene, etc. The glass substrate can be formed of, for example, sodium calcium glass, low-alkali glass, or alkali-free glass. The conductive layer can be formed on the entire surface of the substrate or on a portion thereof.

Conductive transparent metal oxide layers include transparent electrode layers such as ITO (tin-doped indium oxide) and AZO (aluminum-doped zinc oxide).

Examples of metal wiring layers include metal meshes, metal nanoparticles, and metal nanowires added to a binder. Furthermore, the term "metal mesh" refers to a two-dimensional mesh structure formed by metal wiring. The shape of the openings (openings or meshes between wirings) of the metal mesh is not particularly limited and can be polygonal (triangular, quadrilateral, pentagonal, hexagonal, etc.), circular, elliptical, or amorphous. Each opening can be the same or different. In a preferred embodiment, the openings of the metal mesh are all of the same shape, either square or rectangular.

When the conductive layer is a metal wiring layer (particularly a metal mesh), the metal wiring is arranged at predetermined intervals in the vertical and horizontal directions of the plane of the substrate X. In this case, the aforementioned openings can be filled with a resin (adhesive, etc.), or the metal wiring can be embedded in the resin (adhesive, etc.). Furthermore, when using a resin, the conductive layer (conductive layer 4) can be composed of both metal wiring and resin (adhesive).

The line width of metal wiring (especially metal mesh) is typically 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. It is typically 0.1 μm or greater, preferably 0.5 μm or greater, and more preferably 1 μm or greater. The line width of the metal wiring layer can be a combination of the upper and lower limits listed above, preferably 0.5 to 5 μm, and more preferably 1 to 3 μm.

The thickness of the conductive layer (conductive transparent metal oxide layer or metal wiring layer) is not particularly limited, but is typically 10 μm or less, preferably 3 μm or less, more preferably 1 μm or less, and particularly preferably 0.5 μm or less. It is typically 0.01 μm or greater, preferably 0.05 μm or greater, and more preferably 0.1 μm or greater. The thickness of the conductive layer may be a combination of the upper and lower limits, but is preferably 0.01 to 3 μm, more preferably 0.05 to 1 μm. Furthermore, when the conductive layer is a metal wiring layer composed of both a resin (adhesive, etc.) and metal wiring, the thickness of the conductive layer refers to the thickness including the resin.

The conductive layer can be formed by any method, including metal foil lamination, vacuum evaporation, sputtering, wet coating, ion plating, inkjet printing, gravure printing, electrolytic plating, or electroless plating. Preferred conductive layers are sputtering, inkjet printing, or gravure printing, and even more preferred are sputtering.

The conductive layer (e.g., a metal mesh) can also have functions such as generating a signal when the transparent substrate is touched in a touch panel, transmitting the touch coordinates to the integrated circuit.

The optical multilayer structure of the present invention is obtained by laminating (or stacking) the first cured layer and the adhesive layer sequentially on one side of the polarizing film onto a conductive layer formed on a substrate.

Optical laminates with conductive layers (such as conductive transparent metal oxide layers and metal wiring layers) are useful in applications such as touch-input liquid crystal displays with touch panel functionality. However, dichroic dye (iodine) contained in polarizing films migrates to the conductive layers, causing corrosion. This is particularly true when using metal wiring layers such as metal meshes, where narrow line widths make the conductive layers even more susceptible to corrosion. However, the optical laminate of the present invention, with its first hardened layer, effectively suppresses the migration of dichroic dye to the conductive layers, effectively preventing corrosion of the conductive layers.

[Polarizing film]

The polarizing film constituting the optical laminate of the present invention is a film capable of extracting linearly polarized light from incident natural light. In this invention, a dichroic dye, preferably iodine, is incorporated into a polyvinyl alcohol resin film and adsorbed and aligned. The polyvinyl alcohol resin constituting the polyvinyl alcohol resin film can be a saponified polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith (e.g., ethylene-vinyl acetate copolymers). Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, alkenes, vinyl ethers, unsaturated sulfonic acids, and acrylamides containing ammonium groups.

The saponification degree of polyvinyl alcohol resins is typically 85 to 100 mol%, preferably 98 mol% or higher. Polyvinyl alcohol resins can be modified, such as aldehyde-modified polyvinyl formal, polyvinyl acetaldehyde, and polyvinyl butyral. Furthermore, the degree of polymerization of polyvinyl alcohol resins is typically 1,000 to 10,000, preferably 1,500 to 5,000.

Films made from such polyvinyl alcohol-based resins can be used as polarizer films. The method for forming the polyvinyl alcohol-based resin film is not particularly limited, and conventional methods can be used. The film thickness of the polyvinyl alcohol-based resin film is not particularly limited, but considering ease of stretching, it is, for example, 10 to 150 μm, preferably 15 to 100 μm, and more preferably 20 to 80 μm.

Polarizing films are typically manufactured by: stretching a polyvinyl alcohol resin film along one axis; dyeing the polyvinyl alcohol resin film with a dichroic dye to allow the dichroic dye to adsorb; treating the polyvinyl alcohol resin film with the adsorbed dichroic dye with an aqueous boric acid solution; and finally, washing the film with water after the boric acid solution treatment.

The polyvinyl alcohol-based resin film can be uniaxially stretched before, simultaneously with, or after dyeing with a dichroic dye. When uniaxial stretching is performed after dyeing, it can be performed before or during the boric acid treatment. It can also be performed in multiple stages. Uniaxial stretching can be performed between rollers rotating at different speeds or using heated rollers. Furthermore, uniaxial stretching can be dry stretching in the open air or wet stretching in which the polyvinyl alcohol-based resin film is expanded using a solvent. To minimize deformation of the polarizing film, the stretching ratio is preferably 8 times or less, more preferably 7.5 times or less, and even more preferably 7 times or less. Furthermore, the stretching ratio is preferably 4.5 times or greater from the perspective of exhibiting its function as a polarizing film.

In the present invention, dyeing is typically performed by immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide. The iodine content of the aqueous solution is typically 0.01 to 1 part by mass per 100 parts by mass of water, and the potassium iodide content is typically 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is typically 20 to 40°C, and the immersion time (dyeing time) is typically 20 to 1800 seconds.

Boric acid treatment after iodine dyeing is performed by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. The amount of boric acid in the aqueous solution is generally 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. In the present invention, the aqueous solution containing boric acid preferably contains potassium iodide. The amount of potassium iodide in the aqueous solution containing boric acid is generally 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous solution containing boric acid is generally 60 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is generally above 50°C, preferably 50 to 85°C, and more preferably 60 to 80°C.

The polyvinyl alcohol-based resin film treated with boric acid is typically washed with water. This washing process is performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The water temperature during the washing process is typically 5 to 40°C, and the immersion time is typically 1 to 120 seconds. After washing, the film is dried to obtain a polarizing film. Drying can be performed using a hot air dryer or a far-infrared heater. The drying temperature is typically 30 to 100°C, preferably 40 to 95°C, and more preferably 50 to 90°C. The drying time is typically 60 to 600 seconds, preferably 120 to 600 seconds.

In this manner, the polyvinyl alcohol resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, preferably iodine, and boric acid treatment to obtain a polarizing film. The thickness of the polarizing film can be, for example, 5 to 40 μm.

[Second hardened layer]

The optical laminate of the present invention may also include a second cured layer composed of a cured product of a curable composition on the side of the polarizing film opposite to the first cured layer. The curable composition constituting the second cured layer can be appropriately selected based on the adhesion between the polarizing film and the second protective film. It may be a composition within the range of the curable composition constituting the first cured layer, or it may be a photocurable adhesive known in the art. When a composition within the range of the curable composition constituting the first cured layer is used, the second cured layer may have the same composition as the curable composition of the first cured layer of the optical laminate, or a curable composition with a different composition may be used.

Examples of known photocurable adhesives in this field include mixtures of photocurable epoxy resins and photo-cationic polymerization initiators, and mixtures of photocurable acrylic resins and photo-radical polymerization initiators. The curable composition that forms the cured product constituting the second cured layer may include the curable adhesive described in International Publication No. 2014/129368, which contains a photocurable component and a photo-cationic polymerization initiator.

The second cured layer can be formed, for example, by applying a curable composition constituting the second cured layer on the surface of the optical laminate opposite to the surface on which the first cured layer is deposited, by a known method, and curing the curable composition. The coating method of the curable composition constituting the second cured layer can be, for example, the same coating method as the coating method of the curable composition (1).

When the curable composition constituting the second cured layer is a photocurable composition or a known photocurable adhesive, the curable composition or curable adhesive is cured by irradiation with active energy rays. The source of the active energy rays is not particularly limited, but preferably has an active energy ray emission distribution with a wavelength of 400 nm or less. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps are preferred.

The light irradiation intensity for the curable composition constituting the second cured layer can be appropriately selected depending on the composition of the curable composition and is not particularly limited. However, the irradiation intensity in the wavelength range effective for activating the polymerization initiator is preferably 0.1 to 1000 mW/ ^cm² . The light irradiation time for the curable composition constituting the second cured layer can be appropriately selected depending on the curable composition to be cured. The accumulated light dose, expressed as the product of the aforementioned irradiation intensity and irradiation time, is preferably set to 10 to 5000 mJ/ ^cm² .

Furthermore, when curing the curable composition by irradiation with active energy rays, it is preferably performed under conditions that do not degrade the various functions of the optical laminate, such as the polarization degree, transmittance, and hue of the polarizing film, and the transparency of the various films constituting the protective film and optical layer. The thickness of the second cured layer is not particularly limited, but is typically 0.1 to 10 μm.

[Protective film]

In one embodiment, the optical laminate of the present invention comprises a first protective film (7 shown in FIG. 2) deposited on one side of the polarizing film via a first cured layer. Furthermore, in one embodiment, the optical laminate of the present invention comprises a second protective film deposited on the other side of the polarizing film (the side opposite to the first cured layer) via a second cured layer. To prevent shrinkage and expansion of the polarizing film and to prevent degradation of the polarizing film due to temperature, humidity, ultraviolet light, and the like, the optical laminate of the present invention comprises the first protective film. On the other hand, from the perspective of reducing the thickness of the optical laminate, in one embodiment, the optical laminate of the present invention does not include the aforementioned first protective film. The first cured layer of the present invention replaces the protective film and helps prevent degradation of the polarizing film. From the perspective of achieving a good balance between preventing degradation of the polarizing film and reducing the thickness of the optical laminate, it is preferred that the optical laminate of the present invention not include the first protective film.

The material forming the protective film preferably exhibits excellent transparency, mechanical strength, thermal stability, moisture shielding properties, and isotropic properties. Examples include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetylcellulose and triacetylcellulose; acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene and acrylonitrile/styrene copolymer (AS resin); and polycarbonate polymers. Examples of polymers for forming the protective film include polyethylene, polypropylene, cyclic or norbornene-structured polyolefins; polyolefin polymers such as ethylene/propylene copolymers; amide polymers such as vinyl chloride polymers, nylon, and aromatic polyamides; imide polymers, sulfonium polymers, polyethersulfonium polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers, or blends thereof. The protective film can also be formed as a cured layer obtained from a thermosetting or UV-curing resin such as an acrylic, urethane, acrylate urethane, epoxy, or silicone resin. Among them, those having a hydroxyl group reactive with an isocyanate crosslinking agent are preferred, and cellulose is particularly preferred.

In the optical laminate of the present invention, the first protective film and the second protective film may be made of the same material or different materials.

The moisture permeability of the second protective film is preferably 1200 g/(m ² · 24 hours) or less, more preferably 800 g/(m ² · 24 hours) or less, even more preferably 600 g/(m ² · 24 hours) or less, particularly preferably 400 g/(m 2 · 24 hours) or less, and most preferably 200 g/(m ² · 24 hours) or less at a temperature of 23°C and a relative humidity of 55%. A moisture permeability of the second protective film below this value prevents external ^moisture intrusion under high temperature and high humidity conditions and prevents the accelerated migration of the dichroic dye (iodine) contained in the polarizing film, thereby more effectively preventing corrosion of the conductive layer and degradation of optical properties. On the other hand, the optical laminate of the present invention has a first cured layer. Therefore, even if the second protective film does not meet the above-mentioned moisture permeability, the migration of the dichroic dye (iodine) contained in the polarizing film can be suppressed, thereby preventing degradation of the conductive layer and optical properties.

The thickness of the protective film is not particularly limited. The thickness of either the first or second protective film is typically 5 to 500 μm, preferably 1 to 300 μm, more preferably 5 to 200 μm, and even more preferably 10 to 100 μm. Furthermore, the protective film may also be formed with a protective film having an additional optical compensation function.

In the optical laminate of the present invention, the first cured layer effectively suppresses the migration of the dichroic dye from the polarizing film to the adhesive layer, and the migration of the ionic compound from the adhesive layer to the polarizing film. This broadens the selection of materials for the first protective film constituting the optical laminate. This eliminates the need for a protective film that is less permeable to ionic compounds and allows the use of a conventional, inexpensive protective film that readily permeates ionic compounds. This reduces production costs, and the optical laminate of the present invention is also advantageous from an industrial perspective.

The optical laminate of the present invention shown in Figures 1 and 2 has the first cured layer directly laminated onto the polarizing film. However, a primer layer may also be provided between the polarizing film and the first cured layer, or between the first cured layer and the adhesive layer. Materials forming the primer layer include various polymers such as urethane oligomers, metal oxide sols, and silica sols. The primer layer is thinner than the protective film, for example, 0.01 to 3 μm, preferably 0.1 to 2 μm, and even more preferably 0.5 to 1 μm.

Furthermore, the optical laminate of the present invention may include a protective film between the polarizing film and the first cured layer, interposed with an adhesive layer. This protective film may be, for example, the same as the first or second protective film described above. The thickness of the protective film is typically 5 to 500 μm, similar to the first or second protective films.

Even without a protective film between the polarizing film and the first cured layer, the optical laminate of the present invention effectively prevents the migration of the dichroic dye. Therefore, the optical laminate of the present invention preferably has the first cured layer directly laminated on the polarizing film, the first cured layer laminated on the polarizing film via a primer layer, or the first cured layer laminated via a primer layer.

The optical laminate of the present invention can be further laminated with optical layers such as phase difference films, viewing angle compensation films, and brightness enhancement films as needed. The optical layers in the optical laminate of the present invention can be formed using materials known in the art.

The optical laminate of the present invention can be manufactured by a known method. For example, a curable composition is applied to a second protective film to form a second curable composition layer, and a polarizing film is attached to the second curable composition layer to produce the laminate. In the case of an optical laminate that does not include a first protective film, a curable composition (1) is applied to a release film to form a first curable composition layer, and the polarizing film side of the laminate is attached to the coated surface. Then, the second curable composition layer and the first curable composition layer are cured by irradiating them with active energy rays such as ultraviolet rays and electron beams to form the second cured layer and the first cured layer. Then, the release film is peeled off and an adhesive layer is formed on the first cured layer. Then, for example, an adhesive layer is bonded to the conductive layer deposited on the substrate. On the other hand, in the case of an optical laminate including a first protective film, a curable composition (1) is coated on the protective film to form a first curable composition layer. After bonding the polarizing film side of the laminate to the coated surface, the first curable composition layer is irradiated with active energy rays such as ultraviolet rays and electron beams to cure the first curable composition layer to form a first cured layer. Then, an adhesive layer is formed on the first protective film. Then, for example, an adhesive layer is bonded to the conductive layer deposited on the substrate.

From the perspective of reducing thickness unevenness during application of the curable composition while also achieving thinner optical laminates, the use of a separator (peelable film) as described above allows for the formation of a laminate. For example, a laminate composed of a polarizing film and a first curable layer can be formed by depositing a separator (peelable film) on one side of the polarizing film with the first curable layer interposed therebetween. After the first curable composition layer is cured using active energy rays, for example, the separator (peelable film) is peeled off.

The present invention is an optical laminate having the above-described structure, namely, an optical laminate having a first cured layer composed of a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer sequentially laminated on one side of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin (in one embodiment, the optical laminate is shown in Figures 1 and 2);

The polymerizable compound comprises an oxycyclobutane compound having two or more oxycyclobutane groups, and the content of the oxycyclobutane compound is 40 parts by mass or more relative to 100 parts by mass of the total polymerizable compounds in the curable composition. Including the oxycyclobutane compound having two or more oxycyclobutane groups in the specified amount or more forms a first cured layer with a high crosslinking density. This effectively inhibits the migration of the dichroic dye (iodine) contained in the polarizing film into the first cured layer, effectively preventing corrosion of the conductive layer and degradation of optical performance caused by the dichroic dye (iodine). Furthermore, in such an optical laminate, the absorbance increase rate of the first cured layer may be 30% or less. In a preferred embodiment, the cyclohexane compound having two or more cyclohexane groups is the aforementioned cyclohexane compound (A). The components and contents (including preferred components and contents) of the curable composition forming the first cured layer are also the same as described above. Furthermore, the polarizing film, adhesive layer, and conductive layer included in the optical laminate are also the same as described above.

In the present invention, an optical laminate comprising a first cured layer comprising a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer is sequentially laminated on one side of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin. The first cured layer has a water contact angle of 90° or greater. The excellent hydrophobicity of the first cured layer effectively suppresses the migration of the dichroic dye (iodine) even in high-temperature and high-humidity environments, where migration of the dichroic dye is significant. This effectively prevents corrosion of the conductive layer and degradation of optical performance.

In the present invention, the water contact angle of the first cured layer is, for example, 90° or greater, preferably 95° or greater, and even more preferably 100° or greater. When the water contact angle is above this value, migration of the dichroic dye into the first cured layer is effectively suppressed, even in high-temperature and high-humidity environments, effectively preventing corrosion of the conductive layer and degradation of optical performance.

The present invention provides an optical laminate comprising a first cured layer comprising a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer, laminated in sequence on one side of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin. The first cured layer has a storage elastic modulus of at least 1500 MPa at 30°C. Due to its high crosslinking density, the laminate offers excellent barrier properties to the dichroic dye (iodine), effectively suppressing migration of the dichroic dye into the first cured layer and effectively preventing corrosion of the conductive layer and degradation of optical performance.

The storage elastic modulus of the first cured layer at 30°C is, for example, 1500 to 3500 MPa, preferably 1800 to 3500 MPa, more preferably 2000 to 3500 MPa, and even more preferably 2500 to 3500 MPa. When the elastic modulus is above the lower limit, migration of the dichroic dye into the first cured layer can be effectively suppressed, effectively preventing corrosion of the conductive layer and degradation of optical properties.

In the present invention, an optical laminate comprising a first cured layer comprising a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer is sequentially laminated on one side of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin. The first cured layer has a glass transition temperature of 90°C or higher. Due to its high crosslinking density, it exhibits high barrier properties against the dichroic dye (iodine), effectively suppressing the migration of the dichroic dye into the first cured layer and effectively preventing corrosion of the conductive layer and degradation of optical performance.

The glass transition temperature of the first cured layer is, for example, 90 to 180°C, preferably 100 to 180°C, more preferably 120 to 180°C, and even more preferably 150 to 180°C. When the glass transition temperature is above the lower limit, migration of the dichroic dye into the first cured layer can be effectively suppressed, effectively preventing corrosion of the conductive layer and degradation of optical performance.

[Example]

The present invention is described in more detail below using examples, but the present invention is not limited to these examples. Furthermore, "%" and "parts" in the examples and comparative examples represent "mass %" and "mass parts," respectively, unless otherwise specified.

[Example 1]

1. Preparation of the curable composition (I) constituting the first cured layer

According to the composition in Table 1 below, the components were mixed to prepare the curable compositions (I) of Production Examples 1 to 31.

2. Evaluation of the absorbance increase rate of the first cured layer (iodine ion absorption evaluation)

The curable composition (I) of Production Example 1 was applied to one side of a 50 μm thick cycloolefin film (trade name "ZEONOR", manufactured by ZEON Corporation, Japan) using a bar coater to a film thickness of approximately 30 μm after curing. A 50 μm thick cycloolefin film (trade name "ZEONOR", manufactured by ZEON Corporation, Japan) was then laminated to the coated surface to produce a laminate. The cycloolefin film side of the laminate was irradiated with ultraviolet light using a UV irradiation device equipped with a belt conveyor [using a "D bulb" manufactured by Fusion UV System Co., Ltd.] to achieve an accumulated light intensity of 1000 mJ/ ^cm² at 280 nm to 320 nm. The curable composition (I) was cured, resulting in a laminate having cycloolefin films laminated on both sides of the first cured layer. The cycloolefin films on both sides of the resulting laminate were peeled off, and the cured product of the curable composition (I) (the first cured layer) was isolated and used as a sample for evaluation.

The samples used for evaluation were measured for absorbance at 360 nm using a UV-visible spectrophotometer (Shimadzu Corporation, "UV2450"). This absorbance was used as the absorbance before immersion.

The evaluation samples were then immersed in a 50% aqueous potassium iodide solution for 100 hours in an atmosphere at 23°C and 60% relative humidity. The samples were removed, their surfaces wiped with pure water, and their absorbance at 360 nm was measured using a UV-visible spectrophotometer ("UV2450" manufactured by Shimadzu Corporation). This absorbance was used as the post-immersion absorbance.

The absorbance increase rate (%) was calculated using the following formula using the obtained absorbance. The results are shown in Table 1. Similarly, the absorbance increase rate of each cured layer formed from the curable composition (I) of Production Examples 2 to 31 was determined. The results are shown in Table 1.

Absorbance increase rate (%) = (absorbance after immersion (360nm) - absorbance before immersion (360nm)) / absorbance before immersion (360nm) × 100 (1)

[Table 1]

The components in Table 1 are shown below.

<Aliphatic epoxide (B2)>

B2-1: 3,4-Epoxycyclohexylmethyl 3,4-Epoxycyclohexylcarboxylate ("CELLOXIDE 2021P" (trade name), manufactured by Daicel Chemical Co., Ltd.)

B2-2: 1,2-Epoxy-4-(2-epoxyethylene)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol ("EHPE3150" (trade name), manufactured by Daicel Chemical Co., Ltd.)

<Aliphatic Epoxide (B1)>

B1-1: 1,4-Butanediol diglycidyl ether ("EX-214" (trade name), manufactured by Nagase Chemtex Co., Ltd.)

B1-2: Cyclohexanedimethanol diglycidyl ether ("EX-216" (trade name), manufactured by Nagase Chemtex Co., Ltd.)

B1-3: Cyclohexanedimethanol diglycidyl ether ("EX-411" (trade name), manufactured by Nagase Chemtex Co., Ltd.)

<Aromatic Epoxides (B3)>

B3-1: Cresol diglycidyl ether ("EX-201" (trade name), manufactured by Nagase Chemtex Co., Ltd.)

B3-2: Bisphenol A epoxy resin ("jER828EL" (trade name), manufactured by Mitsubishi Chemical Co., Ltd.)

B3-3: 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[11-bis[4-(2,3-epoxypropoxy)phenyl]ethyl]phenyl]propane ("TECHMORE VG3101L" (trade name), manufactured by Printech Co., Ltd.)

〈Oxycyclobutane compound (A)〉

A1-1: Bis(3-ethyl-3-oxocyclobutane) ether ("OXT-221" (trade name), manufactured by Toagosei Co., Ltd.)

A1-2: Xylylene dicyclobutane ("OXT-121" (trade name), manufactured by Toagosei Co., Ltd.)

〈Oxycyclobutane compound (a)〉

a1-1: 2-Ethylhexylcyclohexane ("OXT-212" (trade name), manufactured by Toagosei Co., Ltd., a compound containing one cyclohexane group)

a1-2: 3-Ethyl-3-hydroxymethylcyclohexane ("OXT-101" (trade name), manufactured by Toagosei Co., Ltd., a compound containing one cyclohexane group)

<Acrylic acid compound>

P1-1: Tricyclodecanedimethanol diacrylate ("A-DCP" (trade name), manufactured by Shin-Nakamura Chemical Co., Ltd.)

P1-2: Diacrylate of the acetal compound of hydroxypivalaldehyde and trihydroxymethylpropane ("A-DOG" (trade name), manufactured by Shin-Nakamura Chemical Co., Ltd.)

〈Polymerization initiator〉

G1-1: Photocatalytic polymerization initiator: 50% solution of triarylsulfonium hexafluorophosphate in propylene carbonate ("CPI-100P" (trade name), manufactured by SANAPRO Co., Ltd.)

G1-2: Photoradical polymerization initiator: 2-Hydroxy-2-methyl-1-phenylpropan-1-one ("DAROCURE 1173" (trade name), manufactured by BASF Japan Co., Ltd.)

Leveler

S1-1: Silicone leveling agent ("SH710" (trade name), manufactured by Toray and Dow Corning Co., Ltd.)

3. Production of polarizing film

A 20μm-thick polyvinyl alcohol film (Kuraray Co., Ltd., "Kuraray Poval KL318" (trade name), carboxyl-modified polyvinyl alcohol, average degree of polymerization approximately 2,400, saponification degree 99.9 mol% or greater) was dry-stretched to approximately 5x its original length. The film was then immersed in pure water at 60°C for 1 minute while still under tension. The film was then immersed in an aqueous solution of iodine/potassium iodide/water (mass ratio 0.05/5/100) at 28°C for 60 seconds. The film was then immersed in an aqueous solution of potassium iodide/boric acid/water (mass ratio 8.5/8.5/100) at 72°C for 300 seconds. Then, it was washed with pure water at 26°C for 20 seconds and dried at 65°C to obtain a polarizing film (1) with a thickness of 7 μm in which iodine was adsorbed and aligned on the polyvinyl alcohol film.

4. Preparation of water-based adhesives

3.0 parts by mass of polyvinyl alcohol film (Kuraray Co., Ltd., "Kuraray Poval KL318" (trade name), carboxyl-modified polyvinyl alcohol) and 1.5 parts by mass of water-soluble polyamide epoxy resin (Sumika Chemtex Co., Ltd., "SUMIREZ RESIN 650" (trade name), a working solution with a solid content concentration of 30%) were mixed with 100 parts by mass of pure water to prepare a water-based adhesive (1). The parts by mass of "SUMIREZ RESIN 650" represent the mass of the solid content.

5. Preparation of laminate (1)

A water-based adhesive (1) was applied to one side of the polarizing film (1). After saponification treatment of a triacetyl cellulose film (Toppan (Co., Ltd.) TOMOEGAWA Optical Film, "25KCHC-TC" (trade name), thickness 32μm) with a hard coating surface, the unhard coating surface was bonded to the polarizing film via the water-based adhesive (1). The film was dried at 60°C for 6 minutes to produce a laminate (1) with a protective film on one side.

6. Fabrication of laminate (2)

A curable composition (I) was applied to one side of a 50 μm thick cycloolefin film [trade name "ZEONOR", manufactured by ZEON Co., Ltd., Japan] using a rod coater so that the film thickness after curing was about 3 μm. The polarizing film side of the laminate (1) was bonded to the coated surface to produce a laminate. From the cycloolefin film side of the laminate, ultraviolet rays were irradiated using an ultraviolet irradiation device equipped with a belt conveyor [the lamp used was a "D bulb" manufactured by Fusion UV System Co., Ltd.] so that the accumulated light intensity at 280 nm to 320 nm was 200 mJ/cm ² to cure the curable composition (I), and then the cycloolefin film was peeled off. A laminate (2) is produced, which is composed of a cured product (first cured product layer) of a protective film/aqueous adhesive/polarizing film/curable composition (I).

7. Fabrication of laminate (3)

An organic solvent solution of an acrylic adhesive was prepared and applied to the release-treated surface of a 38 μm thick release-treated polyethylene terephthalate film ("SP-PLR382050" (trade name, manufactured by Lintech Co., Ltd.), referred to as a release film). The film was applied using a slit coater to a dried thickness of 20 μm and then dried to produce a sheet adhesive with a release film. Then, the first cured material layer of the laminate (2) is laminated with the peeling film of the obtained sheet adhesive on the opposite side (adhesive surface) by a laminating machine, and then aged for 7 days at a temperature of 23°C and a relative humidity of 65% to obtain a laminate (3) with an adhesive layer. The laminate has a structure in which the peeling film is laminated on the adhesive layer.

Acrylic adhesives contain the following.

Matrix polymer

Copolymer of butyl acrylate, methyl acrylate, acrylic acid and hydroxyethyl acrylate

Isocyanate crosslinking agent

Ethyl acetate solution of trihydroxymethylpropane adduct of tolyl diisocyanate (solid content concentration 75%) ("Coronate L" (trade name), manufactured by Tosoh Corporation)

〈Silane coupling agent〉

3-Glycyrrhetinol propyltrimethoxysilane, liquid ("KBM-403" (trade name), manufactured by Shin-Etsu Chemical Co., Ltd.)

Antistatic Agent

1-Hexylpyridinium hexafluorophosphate, a compound represented by the following formula (III).

8.ITO Corrosion Evaluation

An ITO film was formed on one side of an alkali-free glass by sputtering to produce a glass having an ITO film. The glass having the ITO film was cut into 25 mm × 25 mm pieces, and the center portion of the ITO film was measured using a low resistivity meter ("Loresta AX MCP-T370", manufactured by Mitsubishi Chemical Analytec) and the value was taken as the "initial resistance value". Subsequently, the laminate (3) was cut into 15 mm × 15 mm pieces and the laminate (3) was bonded so that the adhesive layer of the laminate (3) was in contact with the ITO film. The laminate was then autoclaved at a temperature of 50°C and a pressure of 5 kg/ ^cm2 (490.3 kPa) for 1 hour and then placed in an environment at a temperature of 23°C and a relative humidity of 55% for 24 hours. This was used as a sample for evaluation. Then, the evaluation sample was placed in an environment of 80°C and relative humidity of 90% for 72 hours, and then taken out and the laminate (3) was peeled off. Then, the ITO film was washed with methanol and measured using the same device as above as the "resistance after durability". From the "initial resistance value" and "resistance value after durability" measured as above, the ITO resistance value increase rate was calculated using the following formula, and the ITO corrosion resistance was evaluated using the following evaluation criteria. The results are shown in Table 2. The numbers in Table 2 represent the values of the increase rate of the following formula.

Resistance increase rate (%) = (resistance after durability - initial resistance) / initial resistance × 100

◎: Resistance value increase rate is less than 20%

○: Resistance value increase rate exceeds 20% but does not reach 30%

X: Resistance value increase rate is more than 30%

9. Durability evaluation of laminates

The laminate (3) was cut into a size of 30 mm x 30 mm, and after peeling off the peeling film, the adhesive layer side of the laminate (3) was bonded to alkali-free glass ["EAGLE XG" manufactured by Corning Incorporated]. This sample was autoclaved at a temperature of 50°C and a pressure of 5 kg/ ^cm2 (490.3 kPa) for 1 hour, and then placed in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours. Next, using a UV-visible spectrophotometer (Shimadzu Corporation, "UV2450") equipped with the optional "polarizing film holder" accessory, the transmission spectrum of the laminate in the transmission and absorption axis directions within the range of 380 to 700 nm was measured. The polarization degree Py (unit: %) was calculated based on these values. This polarization degree was defined as the initial Py. Furthermore, the polarization degree was measured after 24 hours in an environment at 80°C and a relative humidity of 90%, and this value was defined as the post-test Py. Based on these values, the change in polarization degree, ΔPy, was calculated using the following formula. The results are shown in Table 1.

△Py = Post-test Py - Initial Py

[Examples 2 to 22 and Comparative Examples 1 to 9]

Using the curable compositions (I) of Examples 2 to 31, a first cured layer and a laminate (3) were obtained in the same manner as in Example 1. Using the obtained laminate (3), the ITO resistance increase rate and polarization change ΔPy were calculated using the same method as in Example 1. These results are shown in Table 2.

[Table 2]

As shown in Table 2, Examples 1 to 22 show optical laminates having a first cured layer with an absorbance increase rate of 30% or less, effectively suppressing ITO corrosion even after prolonged exposure to high temperature and high humidity. In particular, Examples 4 to 20 and Example 22 show optical laminates having a first cured layer with an absorbance increase rate of 20% or less, which more effectively suppress ITO corrosion. Furthermore, Examples 1 to 22 show optical laminates having a first cured layer with an absorbance increase rate of 30% or less, demonstrating high durability and maintaining optical performance even under high temperature and high humidity conditions.

As shown in Table 2, Examples 1 to 22 show that optical laminates containing a first cured layer comprising 40 parts by mass or more of an oxycyclobutane compound having two or more oxycyclobutane groups, relative to 100 parts by mass of the total polymerizable compound, can more effectively suppress ITO corrosion.

1:Polarizing film

2: First hardened layer

3: Adhesive layer

4: Conductive layer

5: Second hardened layer

6: Second protective film

10: Optical multilayers

X:Substrate

Claims (6)

An optical multilayer structure is provided, wherein a first hardened layer, an adhesive layer, and a conductive layer are sequentially laminated on one side of a polarizing film containing a dichroic pigment in a polyvinyl alcohol resin; wherein the first hardened layer has an absorbance increase rate expressed by the following formula (1) of 30% or less; the adhesive layer contains an ionic compound; and the absorbance increase rate (%) = (Abs (360 nm) after immersion - Abs (360 nm) before immersion) / Abs (360 nm) before immersion × 100 (1) In the formula, Abs (360 nm) after immersion represents the absorbance at 360 nm after the cured product has been immersed in a 50% potassium iodide aqueous solution for 100 hours in an atmosphere at a temperature of 23°C and a relative humidity of 60%. Abs (360 nm) before immersion represents the absorbance at 360 nm before the cured product has been immersed in a 50% potassium iodide aqueous solution. An optical multilayer structure comprises a first cured layer, an adhesive layer, and a conductive layer, formed in sequence on one side of a polarizing film containing a dichroic dye in a polyvinyl alcohol-based resin. The first cured layer comprises a cured product of a curable composition containing a polymerizable compound, an adhesive layer, and a conductive layer. The polymerizable compound comprises an oxycyclobutane compound having two or more oxycyclobutane groups, and the content of the oxycyclobutane compound is 40 parts by mass or more relative to 100 parts by mass of the total polymerizable compound contained in the curable composition. The adhesive layer contains an ionic compound. The optical laminate as described in item 1 or 2 of the patent application, wherein the thickness of the first hardened layer is 0.1 to 15 μm. The optical laminate as described in item 1 or 2 of the patent application, wherein the cured material constituting the first cured material layer is a photocurable material comprising a curable composition of the aforementioned polymerizable compound. The optical laminate described in claim 1 or 2 comprises a second cured layer and a protective film laminated on the surface of the polarizing film opposite to the first cured layer. The optical laminate as described in claim 5, wherein the moisture permeability of the protective film is less than 1200 g/24 hours at a temperature of 23°C and a relative humidity of 55%.