TWI842162B - Light-curing adhesive sheet - Google Patents

Abstract

The present invention relates to an adhesive sheet for laminating a resin member. As an adhesive sheet having photocurability and taking into account both step absorption and anti-foaming reliability, a photocurable adhesive sheet is proposed. The photocurable adhesive sheet is characterized in that: it is a photocurable adhesive sheet for laminating a resin member (X) having a light transmittance of 10% or less at a wavelength of 365 nm and a light transmittance of 60% or more at a wavelength of 405 nm, and comprises an adhesive layer (Y) having all of the following properties (1) to (3). (1) The gel fraction is in the range of 0 to 60%. (2) The light transmittance at a wavelength of 390 nm is 89% or less, and the light transmittance at a wavelength of 410 nm is 80% or more. (3) It has photocurability to cure by irradiation with light of a wavelength of 405 nm.

Description

Light-curing adhesive sheet

The present invention relates to a photocurable adhesive sheet, which is used to adhere to a resin member having an ultraviolet cutoff property that does not transmit ultraviolet rays, and has the property of being cured by irradiation with light (referred to as "photocuring").

In recent years, in order to improve the visibility of image display devices, the following operation has been performed: by filling the gap between the image display panel such as a liquid crystal display (LCD), a plasma display (PDP), an electroluminescent display (ELD) and a protective panel or touch panel component arranged on the front side (visual side) thereof with an adhesive, the incident light or the outgoing light from the displayed image is suppressed from reflecting at the air layer interface.

As a method of filling the gaps between components of an image display device with an adhesive, there is known a method of filling the gaps with a liquid bonding resin composition containing an ultraviolet curable resin and then irradiating the gaps with ultraviolet rays to cure the composition (Patent Document 1).

In addition, there is also a method of using an adhesive sheet to fill the gaps between components of an image display device. For example, Patent Document 2 discloses the following method: after attaching an adhesive sheet that has been once cross-linked by ultraviolet rays to a component of an image display device, the adhesive sheet is irradiated with ultraviolet rays through the component of the image display device to cause secondary curing.

In patent document 3, a transparent double-sided adhesive sheet in a B-stage state is disclosed as a component of an image display device having a step portion when a transparent double-sided adhesive sheet is bonded to the bonding surface, which can follow the step portion and fill every corner, and can alleviate the strain generated in the adhesive sheet, and can maintain the foaming resistance in a high temperature or high humidity environment without compromising the handling ability. The transparent double-sided adhesive sheet contains one or more (meth)acrylate (co)polymers, an ultraviolet polymerization initiator (A) having a molar absorption coefficient of 10 or more at a wavelength of 365 nm and a molar absorption coefficient of 0.1 or less at a wavelength of 405 nm, and a wavelength of 405 nm. A visible light polymerization initiator (B) having a molar absorption coefficient of 10 or more at nm, wherein the value (E'/G') of the dynamic storage modulus at 60°C obtained by the stretching method divided by the dynamic storage modulus at 60°C obtained by the shearing method (G') is 10 or more. [Prior art literature] [Patent literature]

[Patent document 1] International Publication No. 2010/027041 [Patent document 2] Japanese Patent No. 4971529 [Patent document 3] Japanese Patent Publication No. 2014-152295

[The problem the invention is trying to solve]

When two image display device components are bonded together using a photocurable adhesive sheet as described above, the two image display device components can be bonded together once through the adhesive sheet, and then ultraviolet rays are irradiated from the outside of one image display device component to cure the adhesive sheet through the image display device component, thereby performing a second bonding. By this method, the secondary bonding can be performed while filling the unevenness of the bonded surface, and the bonded surface can be finally cured by ultraviolet rays to further improve the bonding reliability, so that both the "step absorption" when the bonded surface of the bonded component (also called "bonded component") has unevenness and the "anti-foaming reliability" after bonding can be taken into account.

For example, in a vehicle-mounted image display device, a resin front panel is used to prevent glass from scattering, and a resin member such as a conductive member or a polarizing plate is sometimes arranged on the inner side thereof. In this case, it is necessary to prevent the front panel or the resin member such as a conductive member or a polarizing plate arranged on the inner side thereof from being deteriorated by yellowing due to exposure to ultraviolet rays, so the following operation is performed: an ultraviolet absorber is mixed in the resin member on the side exposed to ultraviolet rays to make it have the ability to absorb ultraviolet rays. However, in this case, it is not possible to irradiate ultraviolet rays from the outside of the image display device component as described above, and ultraviolet rays cannot be cured by the adhesive sheet through the image display device component. Therefore, when attaching the resin front panel, a non-photocurable adhesive sheet that is sufficiently cured to have anti-foaming reliability and does not have photocurability has to be used. However, the non-photocurable adhesive sheet may not be satisfactory in terms of step absorption.

The present invention provides a novel adhesive sheet that can be bonded to a resin member having ultraviolet cutoff properties that does not transmit ultraviolet rays, and can take into account both the step absorption when the bonded surface of the bonding member has uneven surfaces and the anti-foaming reliability after bonding. [Technical means for solving the problem]

The present invention provides a photocurable adhesive sheet, which is characterized in that it is a photocurable adhesive sheet for bonding a resin member having an ultraviolet cutoff property that does not transmit ultraviolet rays, that is, a resin member (X) having a light transmittance of less than 10% at a wavelength of 365 nm and a light transmittance of more than 60% at a wavelength of 405 nm, and includes an adhesive layer (Y) having all the following properties (1) to (3). (1) The gel fraction (gel fraction X1 before light irradiation) is in the range of 0 to 60%. (2) The light transmittance at a wavelength of 390 nm is less than 89%, and the light transmittance at a wavelength of 410 nm is more than 80%. (3) It has a photocurability that can be cured by irradiating light with a wavelength of 405 nm.

The present invention further proposes a photocurable adhesive sheet laminate, which comprises the above-mentioned photocurable adhesive sheet and a resin member (X) having a light transmittance of less than 10% at a wavelength of 365 nm and a light transmittance of more than 60% at a wavelength of 405 nm. [Effect of the invention]

The gel fraction of the photocurable adhesive sheet proposed in the present invention before photocuring is 0-60%, so that the step absorption property of filling the unevenness of the adhered surface can be obtained. On the other hand, the light transmittance at a wavelength of 390 nm is less than 89%, and it has the light curing property of curing by irradiating light with a wavelength of 405 nm. Therefore, even if the light transmittance of the resin member (X) to be bonded is less than 10% at a wavelength of 365 nm and more than 60% at a wavelength of 405 nm, it can be cured by irradiating light including a wavelength of 405 nm, thereby improving the cohesion and obtaining the anti-foaming reliability after bonding. In addition, the light transmittance of the photocurable adhesive sheet proposed in the present invention at a wavelength of 410 nm is more than 80%, so the following effect can be achieved: the yellowness (YI) can be low enough to meet the requirements of optical components requiring transparency.

The photocurable adhesive sheet laminate proposed in the present invention can obtain the step absorption as described above. On the other hand, the adhesive layer (Y) of the photocurable adhesive sheet has a photocurability that increases the difference in gel fraction by more than 10% when irradiated with light of a wavelength of 405 nm from the outside of the resin member (X) through the resin member (X). Therefore, by irradiating the adhesive layer (Y) with light of a wavelength of 405 nm from the outside of the resin member (X) through the resin member (X), the adhesive layer (Y) can be cured, and the cohesion can also be improved to obtain anti-foaming reliability after bonding.

Next, an example of an implementation form of the present invention will be described. However, the present invention is not limited to this implementation form.

<<Present Adhesive Sheet>> An adhesive sheet (referred to as "present adhesive sheet") of one embodiment of the present invention is a light-curing adhesive sheet including an adhesive layer (Y) having specific characteristics.

This adhesive sheet is a photocurable adhesive sheet that cures by irradiating light. At this time, this adhesive sheet can be cured to a state where there is some light curing left (also called "temporary curing"), or it can be uncured and photocurable (called "uncured"). If this adhesive sheet is temporarily cured or uncured, after attaching this adhesive sheet to the adherend, this adhesive sheet can be photocured (also called "formal curing"), which can improve cohesion and adhesion.

As a preferred form of the present adhesive sheet which is temporarily cured or uncured and has the property of being able to be fully cured, that is, photocurable by being irradiated with light having a wavelength of 405 nm, there can be cited an adhesive sheet comprising an adhesive layer (Y) as shown in the following (1) to (3).

(1) The adhesive layer (Y) is temporarily cured until the gel fraction becomes less than 60%, and by containing the visible light initiator (c) described below, the visible light initiator (c) can be fully cured. (2) The adhesive layer (Y) is temporarily cured until the gel fraction becomes less than 60% by containing the hydrogen-scavenging visible light initiator (c-2) described below in the visible light initiator (c), and the visible light initiator (c-2) can be fully cured. (3) The adhesive layer (Y) is an adhesive layer that maintains the sheet shape in an uncured state, and by containing the visible light initiator (c) described below, the visible light initiator (c) can be fully cured.

As a method for forming the adhesive layer (Y) of (1) above, for example, the following method can be cited: a composition (an example of the present resin composition described below) comprising a visible light initiator (c), a (meth)acrylate (co)polymer (a) having a functional group (i), a compound having a functional group (ii) reactive with the functional group (i), other crosslinking agents (b) such as photopolymerizable compounds having carbon-carbon double bonds (especially multifunctional monomers) as required, and a silane coupling agent (d) as required is heated or cured to form the adhesive layer (Y). According to this method, the functional group (i) in the (meth)acrylate (co)polymer reacts with the functional group (ii) in the compound to form a chemical bond, thereby hardening (crosslinking) to form the adhesive layer (Y). By forming the adhesive layer (Y) as described above, the visible light initiator (c) can be actively present in the adhesive layer (Y).

Examples of the combination of the functional group (i) and the functional group (ii) include a carboxyl group and an epoxy group, a carboxyl group and an aziridine group, a hydroxyl group and an isocyanate group, an amino group and an isocyanate group, and a carboxyl group and an isocyanate group. Among them, a combination of a hydroxyl group and an isocyanate group, an amino group and an isocyanate group, or a carboxyl group and an isocyanate group is particularly preferred. More specifically, the case where the (meth)acrylate copolymer (a) has a hydroxyl group (using the hydroxyl group-containing monomer described below) and the compound has an isocyanate group is a particularly preferred example.

Furthermore, the compound having the functional group (ii) may further have a free radical polymerizable functional group such as a (meth)acryloyl group. This can form an adhesive layer (Y) that maintains the light curing (crosslinking) property of the (meth)acrylate (co)polymer brought by the free radical polymerizable functional group, specifically, the (meth)acrylate copolymer having the following active energy line crosslinking structural part. More specifically, the case where the (meth)acrylate (co)polymer (a) has a hydroxyl group (using the following hydroxyl group-containing monomer), and the case where the compound has a (meth)acryloyl group (2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 1,1-(diacryloyloxymethyl)ethyl isocyanate, etc.) is a particularly preferred example. As described above, by utilizing the cross-linking reaction between (meth)acrylate (co)polymers due to the free radical polymerizable functional groups, it is more preferable because it has the advantages of being able to easily and efficiently improve the cohesive force after photocuring (cross-linking) even without using a cross-linking agent (b) and having excellent reliability.

Furthermore, with regard to aspects other than those mentioned above, preferred forms of the preferred acrylate (co)polymer (a), or the preferred crosslinking agent (b), the preferred visible light initiator (c) and the preferred silane coupling agent (d) are as described below.

As a method for forming the adhesive layer (Y) of (2) above, for example, a method of using the following hydrogen-scavenging visible light initiator (c-2) as the visible light initiator (c) can be cited. Even if the hydrogen-scavenging initiator is excited once, the unreacted part of the initiator returns to the base state, so it can be reused as a visible light initiator. As described above, by using a hydrogen-scavenging visible light initiator, the visible light curing (crosslinking) property of the visible light initiator can be maintained even after temporary curing by visible light irradiation. Furthermore, aspects other than the above and the preferred form of the visible light initiator (c-2) are described below.

As a method for forming the adhesive layer (Y) of (3) above, for example, a method using the following macromonomer as a monomer component constituting the (meth)acrylate copolymer (a) can be cited. More specifically, a method using a graft copolymer having a macromonomer as a branch component can be cited. By using such a macromonomer, the branch components can be maintained at room temperature in a state where they are attracted to each other and physically crosslinked to form a composition (an example of the present resin composition described later). Therefore, an adhesive layer (Y) can be formed that can maintain the shape of a sheet in an uncured (crosslinked) state and contains a visible light initiator (c). In addition, aspects other than the above and preferred forms of graft copolymers having macromonomers as branch components are described below.

The adhesive sheet is preferably used to adhere to the resin member (X) described below.

The adhesive sheet may be a single layer of the adhesive layer (Y) or a multi-layer structure having two or more layers of the adhesive layer (Y). In the case of a multi-layer structure, at least the outermost layer may be the adhesive layer (Y), or all adhesive layers may be the adhesive layer (Y).

<Adhesive layer (Y)> It is preferred that the adhesive layer (Y) has all of the following properties (1) to (3). (1) The gel fraction in the normal state, i.e., the state before light irradiation (referred to as "gel fraction before light irradiation X1") is in the range of 0 to 60%. (2) The light transmittance at a wavelength of 390 nm is 89% or less, and the light transmittance at a wavelength of 410 nm is 80% or more. (3) It has light curing properties that can be cured by irradiation with light of a wavelength of 405 nm.

If the adhesive layer (Y) has a hot melt property that softens and even flows by heating, it is better to make the adhesive more easily fill every corner of the step when there are uneven steps on the adhered surface of the bonding component, and the step absorption can be further improved. From this point of view, it is better to set the adhesive layer (Y) as the adhesive layer (Y) mentioned above (3).

(Gel fraction) The gel fraction of the adhesive layer (Y) (gel fraction before light irradiation X1) is preferably in the range of 0 to 60%. If the gel fraction of the adhesive layer (Y) is 60% or less, it is preferred from the following viewpoints: there are enough uncrosslinked components (in a temporary hardened state or an unhardened state) with room for hardening by light irradiation, and because of this, it is soft, and when hardening, "gel fraction after light irradiation X2 - gel fraction before light irradiation X1" can be set to 10% or more. From this viewpoint, the gel fraction of the adhesive layer (Y) is preferably in the range of 0 to 60%, and more preferably 55% or less, and more preferably 50% or less.

In order to adjust the gel fraction (gel fraction before light irradiation X1) of the adhesive layer (Y) to the above range, the residual catalyst can be fully removed during the polymerization of the resin composition described below and the processing of the adhesive sheet, or a polymerization inhibitor, antioxidant, etc. can be used to prevent the undesired curing (crosslinking) reaction caused by heat, light, etc. before the actual curing. In addition, when temporary curing is performed by light irradiation, the cumulative light amount of the light irradiated for temporary curing can be sufficiently small, and the uncrosslinked components can be sufficiently increased. However, the present invention is not limited to this method.

Furthermore, it is preferred that the adhesive layer (Y) has a photocurability that can be cured by irradiation with light having a wavelength of 405 nm. As the degree of the photocurability, for example, it is preferred that when the resin member (X) is irradiated with light having a wavelength of 405 nm from the outside, the difference in gel fraction increases by 10% or more, preferably by 15% or more, more preferably by 20% or more, more preferably by 30% or more, and particularly preferably by 50% or more. Furthermore, the so-called "irradiation with light having a wavelength of 405 nm" means irradiation with light having the following photosensitivity, that is, the photosensitivity measured using an ultraviolet light meter having a wavelength of 405 nm as a photosensitivity peak and a wavelength range extending to 320 to 470 nm.

Among them, it is preferred that the adhesive layer (Y) has the following photocuring properties: when light having a cumulative light amount of 3000 (mJ/ ^cm2 ) at a wavelength of 405 nm is irradiated from the outside of the above-mentioned resin member (X) through, for example, the resin member (X), the difference (gel fraction after light irradiation X2 - gel fraction before light irradiation X1) between the gel fraction before light irradiation (gel fraction before light irradiation X1) and the gel fraction after light irradiation (referred to as "gel fraction after light irradiation X2") becomes 10% or more. Therefore, it is preferable to have the following photocurability: for example, when the gel fraction X1 before light irradiation is 40%, the gel fraction of the adhesive layer (Y) after irradiation with light having a cumulative light quantity of 3000 (mJ/ ^cm2 ) at a wavelength of 405 nm (referred to as "gel fraction X2 after light irradiation") becomes 50% or more. If the difference in gel fraction of the adhesive layer (Y) before and after light curing is 10% or more, it is preferable to have high cohesion even in a harsh high temperature and high humidity environment, and to improve the anti-foaming reliability. Therefore, it is preferred that the difference in gel fraction of the adhesive layer (Y) before and after the light irradiation is 10% or more, more preferably 15% or more, more preferably 20% or more, more preferably 30% or more, and particularly preferably 50% or more. In order to adjust the difference in gel fraction of the adhesive layer (Y) before and after the light irradiation to the above range, the absorption of the photoinitiator may exist at a wavelength of 405 nm. However, it is not limited to this method.

Furthermore, the so-called "cumulative light quantity at a wavelength of 405 nm" is the total amount of irradiation energy received per unit area, which refers to the total amount of light irradiation energy measured by using an ultraviolet cumulative light meter "UIT-250" (manufactured by Ushio Electric Co., Ltd.) and a light receiver "UVD-C405" (manufactured by Ushio Electric Co., Ltd.) in the light irradiated by a high-pressure mercury lamp, etc., and refers to the cumulative light quantity in the wavelength region corresponding to the photosensitivity characteristics of the light receiver (having a photosensitivity with a peak at 405 nm and a wavelength range extending to 320 to 470 nm). More specifically, it refers to the cumulative light quantity obtained according to the method described in the embodiment.

(Light transmittance) It is preferred that the light transmittance of the adhesive layer (Y) at a wavelength of 390 nm is 89% or less, and the light transmittance at a wavelength of 410 nm is 80% or more. Regarding the adhesive formulation containing a photoinitiator having absorption in the ultraviolet to visible light region around a wavelength of 400 nm, the greater the light absorption of the photoinitiator, the lower the light transmittance at a wavelength of 390 nm derived from the absorption, the better the photosensitivity and the easier it is to cure. On the other hand, if the light transmittance at a wavelength of 410 nm is not high enough, the adhesive layer (Y) is colored yellow and becomes difficult to use in optical components.

As the above criteria, if the light transmittance at a wavelength of 390 nm is 89% or less, the adhesive layer (Y) can ensure sufficient visible light curing, which is preferred; if the light transmittance at a wavelength of 410 nm is 80% or more, it can achieve a sufficiently low yellowness (YI) required for bonding optical components requiring transparency, which is preferred. Therefore, the light transmittance at a wavelength of 390 nm of the adhesive layer (Y) is preferably 89% or less, and more preferably 88% or less. In addition, the light transmittance at a wavelength of 410 nm is preferably 80% or more, more preferably 85% or more, and more preferably 90% or more. In order to set the light transmittance of the adhesive layer (Y) as described above, it is sufficient to use an initiator having absorption in visible light and having the following absorption peak characteristics: the periphery of the absorption peak fully reaches 390 nm, and the absorption peak at 410 nm becomes smaller. However, it is not limited to this method.

(Storage modulus) The storage modulus (G') of the adhesive layer (Y) is preferably 0.9×10 ⁵ Pa or less at a temperature of 25°C and a frequency of 1 Hz. By having such viscoelastic properties, the adhesive sheet can obtain particularly excellent step absorption required to fill the uneven steps of the adhered surface. From this point of view, the storage modulus (G') of the adhesive layer (Y) is preferably 0.9×10 ⁵ Pa or less at a temperature of 25°C and a frequency of 1 Hz, and more preferably 0.8×10 ⁵ Pa or less.

Furthermore, the storage modulus (G') of the adhesive layer (Y) after being irradiated with light having a cumulative light quantity of 3000 (mJ/cm ² ) at a wavelength of 405 nm is preferably 0.7×10 ⁴ Pa or more at a temperature of 120°C and a frequency of 1 Hz. If the storage modulus (G') of the adhesive layer (Y) after light curing is within the above range, it is preferred in that when the laminated body thereof and the resin member (X) is subjected to a high temperature test, a high temperature and high humidity test, etc., the foaming of the adhesive layer (Y) caused by outgassing components from the resin member (X) can be suppressed. From this viewpoint, the storage modulus (G') of the adhesive layer (Y) after photocuring is preferably 0.7×10 ⁴ Pa or more at a temperature of 120° C. and a frequency of 1 Hz, more preferably 1.0×10 ⁴ Pa or more, and even more preferably 2.0×10 ⁴ Pa or more.

Here, in an image display device with a touch panel function, as a touch sensor disposed on the back side of the front panel/adhesive layer, glass sensors, film sensors, polarizing plate glass (surface-embedded type or embedded type with a sensor incorporated inside), etc. are used according to the module design. Due to the structure of the sensor component, the susceptibility of defects to occur in environmental tests is different. The experimental research results of the present invention show that when the adhesive layer (Y) is bonded to the structure of resin component (X)/adhesive layer (Y)/glass sensor, the optimal range of the storage modulus (G') of the adhesive layer (Y) is as shown in the above range. On the other hand, when the structure of resin component (X)/adhesive layer (Y)/film sensor is bonded to the structure, the film sensor is usually thin-walled and less than 100 μm and has low hardness. Since the reliability improvement effect of silane coupling agent is lower than that of glass material, it is easier to generate bubbles in the wet and hot environment test than the glass sensor, and a higher level of storage modulus (G') is required.

Therefore, from this point of view, the storage modulus (G') of the adhesive layer (Y) after light curing when the adhesive layer (Y) is bonded and used in a structure of resin member (X)/adhesive layer (Y)/film sensor, that is, the storage modulus (G') of the adhesive layer (Y) when irradiated with light having a cumulative light amount of 3000 (mJ/ ^cm2 ) at a wavelength of 405 nm, is preferably in the range of 2.0× ¹⁰⁴ Pa or more, more preferably 5.0× ¹⁰⁴ Pa or more, and even more preferably 8.0× ¹⁰⁴ Pa or more.

(Composition of the adhesive layer (Y)) The adhesive layer (Y) can be formed by an adhesive composition (referred to as "the present resin composition") containing a (meth)acrylate (co)polymer (a) and a visible light initiator (c), a crosslinking agent (b) as needed, a silane coupling agent (d) as needed, and other materials as needed.

[(Meth)acrylate (co)polymer (a)] Preferably, the above-mentioned (meth)acrylate (co)polymer (a) is photocurable.

Furthermore, the term "(meth)acrylic group" means acrylic group and methacrylic group, the term "(meth)acryl group" means acryl group and methacryl group, and the term "(meth)acrylate" means both acrylate and methacrylate. The term "(co)polymer" means both polymer and copolymer. Furthermore, the term "sheet" conceptually includes sheets, films, and tapes.

Examples of the (meth)acrylate (co)polymer (a) include, in addition to a homopolymer of an alkyl (meth)acrylate, a copolymer obtained by polymerizing a monomer component copolymerizable therewith.

More specifically, the (meth)acrylate (co)polymer (a) may be a copolymer of an alkyl (meth)acrylate and a monomer component copolymerizable therewith, for example, a monomer component comprising at least one monomer selected from the following monomers: (a) a monomer containing a carboxyl group (hereinafter also referred to as "copolymerizable monomer A"), (b) a monomer containing a hydroxyl group (hereinafter also referred to as "copolymerizable monomer B"), (c) a monomer containing an amine group (hereinafter also referred to as The present invention relates to a monomer comprising a monomer having a carbonyl group (hereinafter referred to as "copolymerizable monomer C"), a monomer having a carbonyl group (hereinafter referred to as "copolymerizable monomer D"), a monomer having an amide group (hereinafter referred to as "copolymerizable monomer E"), a monomer having a vinyl group (hereinafter referred to as "copolymerizable monomer F"), a monomer having a carbonyl group (hereinafter referred to as "copolymerizable monomer G"), and a macromonomer (hereinafter referred to as "copolymerizable monomer H").

As the above-mentioned alkyl (meth)acrylate, it is preferably a straight chain or branched chain alkyl (meth)acrylate with a carbon number of 4 to 18 in the side chain. As the straight chain or branched chain alkyl (meth)acrylate with a carbon number of 4 to 18 in the side chain, for example, there can be listed: n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, Ester, tert-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isothiocyanate (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, didicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc. These can be used alone or in combination of two or more. Among the above, the linear or branched alkyl (meth)acrylate having a carbon number of 4 to 18 is preferably any one or more of butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate and isobutyl (meth)acrylate.

Examples of the copolymerizable monomer A include (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, and itaconic acid. These monomers may be used alone or in combination of two or more.

Examples of the copolymerizable monomer B include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. These monomers may be used alone or in combination of two or more.

Examples of the copolymerizable monomer C include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, and aminoisopropyl (meth)acrylate, N-alkylaminoalkyl (meth)acrylates, and N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. These monomers may be one or a combination of two or more.

Examples of the copolymerizable monomer D include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. These monomers may be used alone or in combination of two or more.

Examples of the copolymerizable monomer E include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleamide, and maleimide. These monomers may be used alone or in combination of two or more.

As the copolymerizable monomer F, compounds having a vinyl group in the molecule can be cited. As such compounds, alkyl (meth)acrylates having an alkyl group with a carbon number of 1 to 12, functional monomers having functional groups such as hydroxyl, amide and alkoxyalkyl in the molecule, polyalkylene glycol di(meth)acrylates, vinyl ester monomers such as vinyl acetate, vinyl propionate and vinyl laurate, and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes can be cited. These can be one or a combination of two or more. Furthermore, among the above, it is preferred to select the copolymerizable monomer F other than the alkyl (meth)acrylate and the alkyl (meth)acrylate.

As the copolymerizable monomer G, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, etc. can be listed. These can be one or a combination of two or more. Furthermore, among the above, it is preferred to select the copolymerizable monomer G other than the alkyl (meth)acrylate and the alkyl (meth)acrylate.

The macromonomer as the copolymerizable monomer H is a high molecular monomer having a terminal functional group and a high molecular weight skeleton component, and preferably a monomer having a side chain carbon number of 20 or more when a (meth)acrylate copolymer is formed by polymerization.

By using copolymerizable monomer H, macromonomers can be introduced as branch components of graft copolymers, so that (meth)acrylate copolymers become graft copolymers. For example, (meth)acrylate copolymers (a-1) can be prepared, which include graft copolymers having macromonomers as branch components. Therefore, the properties of the main chain and side chain of the graft copolymer can be changed by selecting or mixing the copolymerizable monomer H and other monomers.

Preferably, the skeleton component of the macromonomer comprises an acrylate polymer or a vinyl polymer. For example, the polymers exemplified in the above-mentioned linear or branched (meth)acrylic acid alkyl esters having a carbon number of 4 to 18 in the side chain, the above-mentioned copolymerizable monomer A, the above-mentioned copolymerizable monomer B, the above-mentioned copolymerizable monomer G, etc., can be used alone or in combination of two or more.

Among them, it is preferred that the dry component of the (meth)acrylate copolymer (a-1) contains hydrophobic (meth)acrylate and hydrophilic (meth)acrylate as structural units.

As the hydrophobic (meth)acrylate, an alkyl ester having no polar group (except methyl acrylate) is preferred, for example, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, 2-ethylhexyl (meth)acrylate, 2-octyl (meth) ... Isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, isothiocyanate (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, methyl methacrylate. In addition, examples of hydrophobic vinyl monomers include vinyl acetate, styrene, tert-butylstyrene, α-methylstyrene, vinyltoluene, alkyl vinyl monomers, and the like.

On the other hand, the hydrophilic (meth)acrylate monomer is preferably a methacrylate or an ester having a polar group, for example, methyl acrylate, (meth)acrylic acid, tetrahydrofurfuryl (meth)acrylate, or (meth)acrylate containing a hydroxyl group such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol (meth)acrylate, or (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, Monomers containing a carboxyl group such as 2-(meth)acryloxyethyl maleic acid, 2-(meth)acryloxypropyl maleic acid, 2-(meth)acryloxyethyl succinic acid, 2-(meth)acryloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, maleic acid monomethyl ester, itaconic acid monomethyl ester, etc.; monomers containing anhydride groups such as maleic anhydride and itaconic anhydride; monomers containing epoxy groups such as glycidyl (meth)acrylate, α-ethyl acrylate glycidyl, (meth)acrylate 3,4-epoxybutyl ester, etc.; alkoxypolyalkylene glycol (meth)acrylate such as methoxypolyethylene glycol (meth)acrylate; N,N-dimethylacrylamide, hydroxyethylacrylamide, etc.

The macromonomer as the copolymerizable monomer H is preferably one having a functional group such as a radical polymerizable group, a hydroxyl group, an isocyanate group, an epoxy group, a carboxyl group, an amine group, an amide group or a thiol group. As the macromonomer, it is preferably one having a radical polymerizable group copolymerizable with other monomers. The radical polymerizable group may contain one or more than two, and one is particularly preferred. In the case where the macromonomer has a functional group, the functional group may also contain one or more than two, and one is particularly preferred. In addition, it may contain either a radical polymerizable group or a functional group, or both. In the case of containing both a radical polymerizable group and a functional group, the functional group or the radical polymerizable group other than the functional group added to the polymer unit containing other monomers or the radical polymerizable group copolymerized with other monomers may also be two or more.

As the terminal functional group of the above-mentioned macromonomer, for example, in addition to free radical polymerizing groups such as methacryloyl, acryl, and vinyl, functional groups such as hydroxyl, isocyanate, epoxy, carboxyl, amine, amide, and thiol can also be listed. Among them, it is preferred to have a free radical polymerizing group that can be copolymerized with other monomers. The free radical polymerizing group may contain one or more than two, and one is particularly preferred. In the case where the macromonomer has a functional group, the functional group may also contain one or more than two, and one is particularly preferred. In addition, it may contain either a free radical polymerizing group or a functional group, or both. In the case of containing both a free radical polymerizable group and a functional group, the number of functional groups or free radical polymerizable groups other than the functional group added to the polymer unit containing other monomers or the free radical polymerizable group copolymerized with other monomers may be two or more.

The number average molecular weight of the macromonomer is preferably 500 to 20,000, more preferably 800 or more or 8,000 or less, and even more preferably 1,000 or more or 7,000 or less.

It is preferred that the glass transition temperature (Tg) of the above-mentioned macromonomer is higher than the glass transition temperature of the copolymer component constituting the above-mentioned (meth)acrylate (co)polymer (a-1). Specifically, the glass transition temperature (Tg) of the macromonomer has an influence on the heating melting temperature (hot melt temperature) of the adhesive sheet, and therefore it is preferably 30°C to 120°C, more preferably 40°C or more or 110°C or less, and further preferably 50°C or more or 100°C or less.

If the macromonomer has such a glass transition temperature (Tg), excellent processability or storage stability can be maintained by adjusting the molecular weight, and the heat melting can be adjusted to occur at around 50°C to 80°C. The so-called glass transition temperature of the macromonomer refers to the glass transition temperature of the macromonomer itself, which can be measured by differential scanning calorimetry (DSC).

Furthermore, in order to maintain the state of the adhesive composition in which the branch components are attracted to each other and physically cross-linked at room temperature, and to obtain fluidity by heating to an appropriate temperature to release the physical cross-links, it is preferred to adjust the molecular weight or content of the macromonomer.

From this viewpoint, it is preferred that the (meth)acrylate copolymer (a) contains macromonomers at a ratio of 5 mass % to 30 mass %, more preferably 6 mass % or more or 25 mass % or less, and more preferably 8 mass % or more or 20 mass % or less. In addition, the number average molecular weight of the macromonomer is preferably 500 to 100,000, more preferably less than 8,000, more preferably 800 or more or less than 7,500, and more preferably 1,000 or more or less than 7,000.

It is preferred that the (meth)acrylate (co)polymer (a) has an active energy ray crosslinking structure. The so-called active energy ray crosslinking structure is a structure that can react with a part of the (meth)acrylate copolymer (a) or a curing component other than the (meth)acrylate copolymer (a) in the presence of a visible light initiator (c) described later to form a crosslinking structure.

As the active energy ray crosslinking structural part, for example, a structure having a radical polymerizable functional group can be cited, and the radical polymerizable functional group is a radical polymerizable functional group having a carbon-carbon double bond, such as a (meth)acrylic acid group, a vinyl group, etc. having an unsaturated double bond. Since the polymer chain of the (meth)acrylate (co)polymer (a) has an unsaturated double bond, the polymer chains can be directly polymerized with each other even when no crosslinking agent is contained, and the storage modulus (G') can be increased to a higher level. Furthermore, when performing active energy ray irradiation, any light source including light with a wavelength of 405 nm can be used. Considering the curing speed, the availability of irradiation equipment, the price, etc., a visible light LED light source, a high-pressure mercury lamp, etc. can be used.

In order to introduce a structure containing a free radical polymerizable functional group having a carbon-carbon double bond, such as a functional group having an unsaturated double bond, for example, a monomer having a functional group is pre-copolymerized on the above-mentioned (meth)acrylate (co)polymer (a), and then a compound having a carbon-carbon double bond, such as a functional group that can react with the functional group (such as (meth)acrylate 2-isocyanatoethyl ester, etc.) and a monomer having an unsaturated double bond, is allowed to react with it while maintaining the curability of the carbon-carbon double bond.

Among them, the (meth)acrylate copolymer (a) is preferably a (meth)acrylate (co)polymer (a-2) containing a monomer component of a (meth)acrylate monomer having an active energy line crosslinking structure and a linear alkyl group with a carbon number of 10 to 24. As such (meth)acrylate (co)polymer (a-2), for example, there can be listed: decyl (meth)acrylate (alkyl group has a carbon number of 10), lauryl (meth)acrylate (carbon number 12), tridecyl (meth)acrylate (carbon number 13), hexadecyl (meth)acrylate (carbon number 16), stearyl (meth)acrylate (carbon number 18), behenyl (meth)acrylate (carbon number 22), etc. These can be used alone or in combination of two or more.

Furthermore, among the linear (meth)acrylic acid alkyl ester monomers (a) having an alkyl group with a carbon number of 10 to 24, methacrylic acid alkyl esters are preferably used, and those having an alkyl group with a carbon number of 12 to 20 are particularly preferred, and stearyl methacrylate, lauryl methacrylate, and tridecyl methacrylate are most preferred, from the viewpoint of lowering the dielectric constant and lowering the glass transition temperature of the acrylic resin.

The content of the (meth)acrylic acid alkyl ester monomer (a) having a linear alkyl group with 10 to 24 carbon atoms is 50 to 94% by weight, preferably 60 to 83% by weight, and particularly preferably 70 to 80% by weight relative to the total weight of the (co)polymer components. By setting the content within the above range, there is no concern that the dielectric constant will increase and the thermal stability of the resin will decrease.

[Crosslinking agent (b)] As the above-mentioned crosslinking agent (b), a crosslinking agent having at least double bond crosslinking is preferred. For example, a crosslinking agent having at least one crosslinking functional group selected from (meth)acryloyl, epoxy, isocyanate, carboxyl, hydroxyl, carbodiimide, oxazoline, aziridine, vinyl, amino, imine, and amide can be listed. One or more of them can be used in combination. In particular, by using two or more crosslinking agents in combination, a higher storage modulus (G') can be achieved compared to the case where each is used alone, even when the total amount of crosslinking agents is the same. Therefore, it is more preferred to use two or more crosslinking agents (b) in combination. Furthermore, it also includes a state where the crosslinking agent (b) and the (meth)acrylate (co)polymer (a) are chemically bonded.

Among them, it is preferred to use a photopolymerizable compound having a carbon-carbon double bond, especially a multifunctional (meth)acrylate. Here, multifunctional refers to a compound having two or more crosslinking functional groups. Furthermore, it may also have three or more, or four or more crosslinking functional groups as needed. Furthermore, the above crosslinking functional groups may also be protected by a protective group that can be deprotected.

Examples of the multifunctional (meth)acrylate include 1,4-butanediol di(meth)acrylate, glycerol di(meth)acrylate, neopentyl glycol di(meth)acrylate, glyceryl glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxy di(meth)acrylate, bisphenol A polypropoxy di(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trihydroxymethylpropane trioxyethyl (meth)acrylate, ε-caprolactone modified isocyanuric acid tri(2-hydroxyethyl) ester tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate Ester, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, Examples of the UV-curable multifunctional (meth)acrylic monomers include di(meth)acrylate of ε-caprolactone adduct of pentylene glycol ester, trihydroxymethylpropane tri(meth)acrylate, trihydroxymethylpropane polyethoxy tri(meth)acrylate, and di-trihydroxymethylpropane tetra(meth)acrylate. In addition, multifunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyether (meth)acrylate may be used. These may be used alone or in combination of two or more.

Among the above-mentioned multifunctional (meth)acrylates, from the viewpoint of imparting high cohesion, it is preferred to form a structure in which the distance between the crosslinking points in the formed crosslinking structure is shorter and the crosslinking density is denser, for example, it is preferred to be a multifunctional (meth)acrylate with three or more functions that has not been modified with alkylene oxide, and it is preferred to be a multifunctional (meth)acrylate (b-1) selected from the group consisting of pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, and di-trihydroxymethylpropane tetra(meth)acrylate. The multifunctional (meth)acrylate (b-1) can be used alone or in combination (as a mixture) of two or more.

Furthermore, when the multifunctional (meth)acrylate (b-1) is used as a crosslinking agent, the (meth)acrylate (a) is preferably a copolymer containing a hydrophilic monomer as a polar component from the viewpoint of self-compatibility. Since the (meth)acrylate (a) contains a polar component, its compatibility with the multifunctional (meth)acrylate (b-1) becomes good, and it becomes easy to mix when mixed. When stored for a long time in a non-crosslinked state, it becomes difficult to produce phase separation, and there is no risk of an increase in the haze value.

Specifically, the (meth)acrylate (co)polymer (a) is preferably a copolymer of the (meth)acrylate alkyl ester and the following monomer components as copolymerizable monomers therewith, wherein the monomer components are monomer components of hydrophilic monomers appropriately selected from the copolymerizable monomers A to G, wherein the hydrophilic (meth)acrylate is contained, or at least methyl (meth)acrylate selected from the copolymerizable monomers G. Furthermore, the (meth)acrylate (co)polymer (a) is preferably a copolymer of monomer components containing at least methyl (meth)acrylate, and the total amount of the hydrophilic monomers (selected from the copolymerizable monomers A to G) accounts for more than 10 parts by mass of the whole (meth)acrylate (co)polymer (a).

Furthermore, the above-mentioned (meth)acrylate (co)polymer (a-1) is preferably a copolymer comprising a monomer component of a linear or branched (meth)acrylate alkyl ester having a carbon number of 4 to 18 in the above-mentioned side chain as a backbone component (trunk component), and the above-mentioned hydrophilic monomer as a copolymerizable monomer copolymerizable therewith.

The content of the crosslinking agent (b) is preferably 0.5 to 50 parts by mass relative to 100 parts by mass of the (meth)acrylate (co)polymer (a), more preferably 1 part by mass or more or 40 parts by mass or less, and even more preferably 5 parts by mass or more or 30 parts by mass or less.

[Visible light initiator (c)] The visible light initiator (c) is preferably a visible light initiator that generates free radicals by irradiation with visible light, light having a wavelength of at least 390 nm, 405 nm and 410 nm, for example, light in the wavelength range of 380 nm to 700 nm, and becomes a reaction starting point of the (meth)acrylate (co)polymer (a). Among them, the visible light initiator (c) may be one that generates free radicals by irradiation with only visible light, and may also be one that generates free radicals by irradiation with light in a wavelength range other than the visible light range.

The visible light initiator (c) preferably has an absorbance of 10 mL/(g・/cm) or more at a wavelength of 405 nm, more preferably 15 mL/(g・/cm) or more, and more preferably 25 mL/(g・/cm) or more. By setting the absorbance at a wavelength of 405 nm to be 10 mL/(g・/cm) or more, curing (crosslinking) by irradiation with visible light can be sufficiently performed. On the other hand, the upper limit of the absorbance at a wavelength of 405 nm is preferably 1×10 ⁴ mL/(g・/cm) or less, and more preferably 1×10 ³ mL/(g・/cm) or less. Furthermore, it can be used in combination with a photoinitiator having an absorbance of less than 10 mL/(g・/cm) at a wavelength of 405 nm.

Photoinitiators are generally classified into two types according to the mechanism of free radical generation: cleavage-type photoinitiators, in which the single bonds of the photoinitiator itself can be cleaved and decomposed to generate free radicals; and hydrogen-abstracting photoinitiators, in which the photoexcited initiator and the hydrogen donor in the system can form an excited complex, thereby transferring hydrogen from the hydrogen donor.

The cleavage-type photoinitiator among these decomposes into other compounds when free radicals are generated by light irradiation, and once excited, it becomes non-functional as a reaction initiator. Therefore, it does not remain as an active species in the adhesive after the crosslinking reaction is completed, and there is no possibility of causing undesirable photodeterioration of the adhesive, so it is preferred. In addition, regarding the coloring unique to the photoinitiator, when a cleavage-type visible light initiator (c-1) that is hardened by irradiating visible light is added to the adhesive, there is a risk of coloring. Therefore, as a visible light initiator (c), it is better to select a reaction decomposition product that does not absorb the visible light region and decolorizes. On the other hand, hydrogen-scavenging photoinitiators not only maintain their function as reaction initiators even after multiple light irradiations, but also do not generate decomposition products like cleavage-type photoinitiators when free radicals are generated by irradiation with active energy rays such as ultraviolet rays. Therefore, they are unlikely to become volatile components after the reaction is completed, which is useful in reducing damage to the adherend. Therefore, hydrogen-scavenging visible light polymerization initiators (c-2) that start polymerization when excited by visible light are particularly preferred.

Examples of the above-mentioned cleavage-type visible light initiator (c-1) include: 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propane-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)-2-methyl-1-propane-1-one, ) acetone), methyl phenylglyoxylate, 2-benzyl-2-dimethylamino-1-(4-linophenyl)butane-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-linopropane-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-linophenyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, 2,4,6-trimethylbenzyldiphenylphosphine oxide, (2,4,6-trimethylbenzyl)ethoxyphenylphosphine oxide or their derivatives, etc. Among them, for the method of decolorizing by forming a decomposition product after the reaction, acylphosphine oxide-based photoinitiators such as bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, 2,4,6-trimethylbenzyldiphenylphosphine oxide, (2,4,6-trimethylbenzyl)ethoxyphenylphosphine oxide, and bis(2,6-dimethoxybenzyl)2,4,4-trimethylpentylphosphine oxide are preferred.

Examples of the hydrogen-absorptive visible light initiator (c-2) include bis(2-phenyl-2-oxoacetic acid)oxydiethyl ester, methyl phenylglyoxylate, a mixture of 2-[2-oxo-2-phenylacetyloxyethoxy]ethyl hydroxyphenylacetate and 2-[2-hydroxyethoxy]ethyl hydroxyphenylacetate, 9-thiothiophene , 2-chloro-9-oxysulfuron , 3-methyl-9-oxosulfuron , 2,4-dimethyl-9-oxosulfuron , anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, camphorquinone or their derivatives. Among them, preferably any one or two selected from the group consisting of methyl phenylglyoxylate, 2-[2-hydroxy-2-phenylacetyloxyethoxy]ethyl hydroxyphenylacetate and a mixture of 2-[2-hydroxyethoxy]ethyl hydroxyphenylacetate.

Furthermore, the visible light initiator (c) is not limited to the substances listed above. Any one of the visible light initiators (c) listed above or its derivatives may be used, or two or more may be used in combination. In addition, in addition to the visible light initiator (c), a substance that only generates free radicals by irradiating other light such as ultraviolet rays may also be mixed.

The content of the visible light initiator (c) is not particularly limited. It is preferably contained in a ratio of 0.1 to 10 parts by mass relative to 100 parts by mass of the (meth)acrylate (co)polymer (a) in the adhesive layer (Y), more preferably in a ratio of 0.5 parts by mass or more or 5 parts by mass or less, and even more preferably in a ratio of 1 part by mass or more or 3 parts by mass or less. By setting the content of the visible light initiator (c) to the above range, a moderate reaction sensitivity to visible light can be obtained.

[Silane coupling agent (d)] Silane coupling agent (d) can improve adhesion, and in particular can improve adhesion to glass materials. As silane coupling agents, for example, compounds having unsaturated groups such as vinyl, acryloxy, and methacryloxy groups, amino groups, epoxy groups, and hydrolyzable functional groups such as alkoxy groups can be listed. As specific examples of silane coupling agents, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, etc. can be listed. Among them, in the adhesive layer (Y), γ-glycidyloxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane can be preferably used from the viewpoints of good self-adhesion and less discoloration such as yellowing. The above-mentioned silane coupling agents can be used alone or in combination of two or more.

The content of the silane coupling agent (d) is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the adhesive layer (Y), and more preferably 0.2 parts by mass or more or 3.0 parts by mass or less. In addition, coupling agents such as organic titanium ester compounds can also be effectively used in the same manner as silane coupling agents.

[Other materials] Components other than the above mentioned contained in the present resin composition for forming the adhesive layer (Y) include, for example: light stabilizer, ultraviolet absorber, metal deactivator, anti-metal corrosion agent, anti-aging agent, antistatic agent, moisture absorbent, foaming agent, defoaming agent, inorganic particles, viscosity adjuster, adhesive resin, photosensitizer, fluorescent agent and other additives, reaction catalyst (tertiary amine compound, quaternary ammonium compound, tin laurate compound, etc.). In addition, known components formulated in ordinary adhesive compositions may also be appropriately contained. In addition, two or more components may be used in combination.

Among the above, it is particularly preferred that the resin composition forming the adhesive layer (Y) contains an ultraviolet absorber. As described above, the adhesive layer (Y) has a photocuring property that cures by irradiating light with a wavelength of 405 nm, so even if it contains an ultraviolet absorber, the photocuring is not hindered. Therefore, by containing an ultraviolet absorber, the excellent ultraviolet cutoff property can be achieved without damaging the properties of the adhesive sheet.

As the above-mentioned ultraviolet absorber, for example, benzotriazole ultraviolet absorber, benzophenone ultraviolet absorber, trioxane ultraviolet absorber, etc. can be listed. Furthermore, the above-mentioned ultraviolet absorber can be used alone or in combination of two or more. Among them, from the perspective of transparency, ultraviolet absorbency and compatibility, the above-mentioned ultraviolet absorber is preferably a trioxane ultraviolet absorber.

[Preferred composition of the present resin composition] As an example of a preferred present resin composition for forming an adhesive layer (Y), there can be cited a composition containing a (meth)acrylate (co)polymer (a), the above-mentioned crosslinking agent (b), a visible light initiator (c), and a silane coupling agent as required. Among them, it is preferred to use a visible light initiator (c) having an absorbance of 10 mL/(g・/cm) or more at a wavelength of 405 nm as the visible light initiator (c); and it is particularly preferred to use the above-mentioned cleavage-type visible light initiator (c-1) and/or hydrogen-absorptive visible light initiator (c-2) as the visible light initiator (c).

Among them, it is preferred that the (meth)acrylate (co)polymer (a) forms a chemical bond based on a combination of any functional group selected from carboxyl and epoxy, carboxyl and aziridine, hydroxyl and isocyanate, amino and isocyanate, and carboxyl and isocyanate. In addition, the (meth)acrylate (co)polymer (a) is preferably a copolymer comprising a linear or branched (meth)acrylate alkyl ester having a carbon number of 4 to 18 in the above-mentioned side chain and the above-mentioned hydrophilic (meth)acrylate as copolymer components. Furthermore, the crosslinking agent (b) is preferably the above-mentioned multifunctional (meth)acrylate (b-1).

As an example of a preferred resin composition for forming an adhesive layer (Y), there can be cited a composition containing the above-mentioned (meth)acrylate copolymer (a-1), the above-mentioned crosslinking agent (b), a visible light initiator (c), and a silane coupling agent as required, wherein the above-mentioned (meth)acrylate copolymer (a-1) contains a graft copolymer having a macromonomer as a branch component. Among them, it is preferred to use a visible light initiator (c) having an absorbance of 10 mL/(g・/cm) or more at a wavelength of 405 nm as the visible light initiator (c); and it is particularly preferred to use the above-mentioned cleavage-type visible light initiator (c-1) and/or hydrogen-absorptive visible light initiator (c-2) as the visible light initiator (c).

Among them, the above-mentioned (meth)acrylate (co)polymer (a-1) is preferably a copolymer comprising a straight-chain or branched (meth)acrylate alkyl ester having a carbon number of 4 to 18 in the above-mentioned side chain as a backbone component (trunk component), and the above-mentioned hydrophilic (meth)acrylate as a copolymer component. In addition, the crosslinking agent (b) is preferably the above-mentioned multifunctional (meth)acrylate (b-1).

As another example of a preferred resin composition for forming the adhesive layer (Y), there can be cited a composition containing the above-mentioned (meth)acrylate copolymer (a-1), the above-mentioned crosslinking agent (b), the above-mentioned visible light initiator (c), and a silane coupling agent as required, wherein the above-mentioned (meth)acrylate copolymer (a-1) includes a graft copolymer having a macromonomer as a branch component and having an active energy line crosslinking structure site. Among them, it is preferred to use a visible light initiator (c) having an absorbance of 10 mL/(g・/cm) or more at a wavelength of 405 nm as the visible light initiator (c); and it is particularly preferred to use the above-mentioned cleavage-type visible light initiator (c-1) and/or hydrogen-absorptive visible light initiator (c-2) as the visible light initiator (c).

Among them, the above-mentioned (meth)acrylate (co)polymer (a-1) is preferably a copolymer comprising a straight-chain or branched (meth)acrylate alkyl ester having a carbon number of 4 to 18 in the above-mentioned side chain as a backbone component (trunk component), and the above-mentioned hydrophilic (meth)acrylate as a copolymer component. In addition, the crosslinking agent (b) is preferably the above-mentioned multifunctional (meth)acrylate (b-1).

If the present resin composition of the above composition is used to form an adhesive layer (Y), the adhesive layer (Y) with (meth)acrylate copolymer (a) or (a-1) as the base resin can maintain a sheet shape at room temperature and show self-adhesiveness, and the adhesive can be filled into every corner of the step difference of the adhered surface of the bonding component. Moreover, due to the visible light initiator (c), it can be photocured by visible light irradiation, and the cohesion and anti-foaming reliability can be improved by photocuring. Furthermore, by formulating a silane coupling agent, the adhesion, especially the adhesion to glass materials, can be further improved. In addition, the adhesive layer (Y) with (meth)acrylate copolymer (a-1) as the base resin has a hot melt property that melts or flows when heated in addition to the above, and thus can have a higher step difference absorption.

As another example of a preferred resin composition for forming the adhesive layer (Y), there can be cited a composition comprising a (meth)acrylate (co)polymer (a-2) containing the following monomer components, the above-mentioned crosslinking agent (b), the above-mentioned visible light initiator (c), and a silane coupling agent as required, wherein the above-mentioned monomer component includes a (meth)acrylate monomer having an active energy line crosslinking structure and a linear alkyl group having 10 to 24 carbon atoms. Among them, it is preferred to use a visible light initiator (c) having an absorption coefficient of 10 mL/(g・/cm) or more at a wavelength of 405 nm as the visible light initiator (c); and it is particularly preferred to use the above-mentioned cleavage-type visible light initiator (c-1) and/or hydrogen-absorptive visible light initiator (c-2) as the visible light initiator (c).

If the resin composition as described above is used, a temporary cured state or an uncured adhesive layer (Y) can be formed, which can then be photocured by irradiating visible light once or twice or more. Therefore, for example, after the adhesive sheet is attached to the adherend, the adhesive sheet can be photocured by irradiating visible light ("formal curing"), and the cohesion can be improved by the formal curing to improve the anti-foaming reliability. In particular, for (meth)acrylate (co)polymers that have high fluidity at room temperature and have difficulties in storage, even if the storage is improved by temporary curing, it can be cured by the subsequent step of visible light curing after bonding. By further formulating a silane coupling agent, the adhesion can be further improved, especially the adhesion to glass materials.

(Laminated structure) As described above, when the adhesive layer (Y) is set as a laminated structure, from the viewpoint of anti-foaming, it is preferred that the adhesive layer (Y) using the resin composition is the outermost surface layer. In this case, the thickness of the adhesive layer (Y) as the surface layer is preferably 15 μm or more, and more preferably 20 μm or more. If the thickness of the adhesive layer (Y) is 15 μm or more, it is better in the following aspects: in the reliability test, the degassing pressure generated by the adherend component is pressed back, and there is less risk of abnormalities such as foaming.

In addition, from the perspective of storage stability, there is a case where it is better to have another layer with a higher viscosity than the adhesive layer (Y). That is, the adhesive layer (Y) formed by using a graft copolymer having a macromonomer is in an uncrosslinked state before photocuring. If a multifunctional (meth)acrylate monomer is used, the adhesive layer (Y) before photocuring may become a layer with a relatively low viscosity due to the effect of the multifunctional (meth)acrylate monomer component. Therefore, in this case, it is better to laminate another layer (Z) with a higher viscosity than the adhesive layer (Y) on the adhesive layer (Y). For example, if it is a multi-layer structure including three layers of adhesive layer (Y)/layer (Z)/adhesive layer (Y), it can have excellent storage stability. From the perspective of such storage stability, the viscosity of the other layer (Z) is preferably 1 to 10 kPa·s at a temperature range of 70°C to 100°C, and more preferably 1.5 to 5 kPa·s. In addition, the viscosity is a value measured according to the method described in the embodiment.

Furthermore, when the adhesive sheet is a multi-layer structure as described above, from the perspective of having both impact resistance and absorption, the glass transition temperature (Tg) of the adhesive sheet after irradiation with 405 nm light is preferably less than 20°C, and more preferably less than 10°C. By making the adhesive sheet have such a relatively low Tg, the low-temperature adhesive properties (low-temperature peel strength, etc.) can be improved, and impact resistance and absorption can be obtained. Therefore, from the perspective of impact resistance and absorption, the Tg of the other layers laminated with the above-mentioned adhesive layer (Y) after irradiation with 405 nm light is preferably less than 15°C, more preferably less than 10°C, and especially less than 5°C. Furthermore, the Tg is a value measured at the peak temperature of Tanδ of dynamic viscoelasticity, and more specifically, a value measured according to the method described in the embodiment.

<Adhesive sheet with release film> The adhesive sheet can also be an adhesive sheet with release film. For example, a single-layer or multi-layer sheet-like adhesive layer can be formed on a release film to produce an adhesive sheet with release film.

As the material of the release film, a known release film can be used appropriately. As the material of the release film, for example, a film coated with silicone resin and subjected to release treatment, such as polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic resin film, triacetyl cellulose film, fluororesin film, or release paper can be appropriately selected and used.

When release films are laminated on both sides of the adhesive sheet, one release film may have the same laminated structure or material as the other release film, or may have a different laminated structure or material. Also, they may have the same thickness or different thicknesses. Also, release films with different peeling forces or release films with different thicknesses may be laminated on both sides of the adhesive sheet.

The release film preferably has a light transmittance of 40% or less for light with a wavelength of 410 nm or less. By laminating a release film having a light transmittance of 40% or less for light with a wavelength of 410 nm or less on at least one surface of the adhesive sheet, photopolymerization due to irradiation with visible light can be effectively prevented. From this point of view, the release film laminated on one or both surfaces of the adhesive sheet preferably has a light transmittance of 40% or less for light with a wavelength of 410 nm or less, more preferably 30% or less, and more preferably 20% or less.

Here, as a release film having a light transmittance of 40% or less for light with a wavelength of less than 410 nm, that is, a film having the function of blocking the transmission of a part of visible light and ultraviolet light, for example, a multilayer film including an ultraviolet absorbing layer can be cited, wherein the ultraviolet absorbing layer is formed by coating a re-strippable micro-adhesive resin on one side of a polyester, polypropylene, or polyethylene cast film or stretched film, and coating a coating containing an ultraviolet absorber on the other side. In addition, a film can be cited in which a re-strippable micro-adhesive resin mixed with an ultraviolet absorber is coated on one side of a polypropylene or polyethylene cast film or stretched film. In addition, a film formed by coating a re-peelable slightly adhesive resin on a cast film or stretched film containing a polyester, polypropylene, or polyethylene resin mixed with an ultraviolet absorber can be cited. In addition, a film formed by coating a re-peelable slightly adhesive resin on one side of a multi-layer cast film or stretched film can be cited, and the multi-layer cast film or stretched film is formed by forming a layer containing a resin without an ultraviolet absorber on one side or both sides of a layer containing a polyester, polypropylene, or polyethylene resin mixed with an ultraviolet absorber. In addition, a coating containing a UV absorber is applied on one side of a cast film or stretched film containing a polyester, polypropylene, or polyethylene resin to provide a UV absorbing layer, and a re-peelable slightly adhesive resin is applied on the UV absorbing layer. In addition, a coating containing a UV absorber is applied on one side of a cast film or stretched film containing a polyester, polypropylene, or polyethylene resin to provide a UV absorbing layer, and a re-peelable slightly adhesive resin is applied on the other side. Furthermore, examples include a film formed by coating one side with a resin film containing a re-peelable micro-adhesive resin including polyester, polypropylene, or polyethylene resins, and laminating a separately prepared resin film, etc., with a bonding layer or adhesive layer containing an ultraviolet absorber interposed therebetween. The above film may also have other layers such as an antistatic layer, a hard coating layer, and an adhesion-enhancing layer as required.

The thickness of the release film is not particularly limited, but is preferably 25 μm to 500 μm, more preferably 38 μm or more or 250 μm or less, and even more preferably 50 μm or more or 200 μm or less from the viewpoint of processability and handling.

Furthermore, the adhesive sheet can also be formed by the following method: as described above, the resin composition is not used for extrusion molding, or it is formed by injecting it into a mold. Furthermore, the resin composition can be directly filled between the components of the image display device as the adherend, thereby forming the adhesive sheet.

<Method for producing the present adhesive sheet> An example of the method for producing the present adhesive sheet is described. First, the (meth)acrylate (co)polymer (a) and the visible light initiator (c), the crosslinking agent (b) as needed, the silane coupling agent (d) as needed, and other materials as needed are mixed in specific amounts to prepare the present resin composition. There is no particular limitation on the mixing method, and the mixing order of the components is not particularly limited. In addition, a heat treatment step may be added when producing the composition. In this case, it is ideal to mix the components of the present resin composition in advance and then heat treat them. In addition, a masterbatch obtained by concentrating the various mixed components may be used.

There is no particular limitation on the device used for mixing. For example, a universal mixer, planetary mixer, Banbury mixer, kneader, frame mixer, pressure kneader, three-roll mill, two-roll mill can be used. Solvents can also be used for mixing as needed. In addition, the resin composition can be made into a solvent-free system that does not contain a solvent. By making it into a solvent-free system, the following advantages can be achieved: no residual solvent, and improved heat resistance and light resistance. From this point of view, it is also preferred that the resin composition is in the form of a (meth)acrylate (co)polymer (a), a crosslinking agent (b) and a visible light initiator (c).

The adhesive sheet can be manufactured by applying (spreading) the resin composition prepared in the above manner on a substrate sheet or a release sheet. Furthermore, for example, the present adhesive sheet of a laminated structure can be produced by the following method: a method of repeatedly performing the following steps, i.e., coating (applying) the present resin composition on a substrate sheet or a demolding sheet to form a first layer, and coating (applying) the present resin composition on the formed first layer to form a second layer; a method of forming the first layer and the second layer in the same manner as above, and then laminating the coated (applied) surfaces to each other; or a method of forming the present resin composition into the first layer and the second layer at the same time by multi-layer coating or co-extrusion molding.

The above-mentioned coating method can be adopted without particular limitation as long as it is a general coating method, for example, roll coating, die nozzle coating, gravure coating, notch wheel coating, screen printing and the like can be listed.

Then, the adhesive layer containing the present resin composition may be irradiated with light as needed to temporarily cure the adhesive layer (Y) and the gel fraction of the adhesive layer (Y) may be set to 0-60% while the light curing is left. However, the adhesive layer (Y) may be temporarily cured without irradiating with light, for example, the adhesive layer (Y) may be temporarily cured by heat or curing, or it may be in an uncured state.

<Application of the present adhesive sheet> The present adhesive sheet can be suitably used for bonding the resin member (X) as described above. Therefore, an adhesive sheet laminate (referred to as "the present adhesive sheet laminate") comprising a resin member (X) having specific characteristics and the present adhesive sheet laminate can be provided.

The present adhesive sheet laminate can be prepared, for example, by the following steps: using a resin composition containing a (meth)acrylate (co)polymer and a visible light initiator to prepare the present adhesive sheet, and laminating the present adhesive sheet on the above-mentioned resin component (X). However, the production method of the present adhesive sheet laminate is not limited to this method.

(Resin component (X)) The resin component (X) preferably has a light transmittance of 10% or less at 365 nm and a light transmittance of 60% or more at 405 nm.

If the light transmittance of the resin component (X) at 365 nm is less than 10% and the light transmittance at 405 nm is more than 60%, the transmission of ultraviolet rays can be fully blocked (cut off), the light degradation of the resin component (X) itself and the optical components (such as polarizing films or phase difference films) located on the back side (opposite to the viewing side) thereof can be suppressed, and the yellowness (YI) can be reduced to the level required for the optical components. As such a resin component (X), there can be listed those having a resin material as the main component and adjusted to have the above light transmittance using an ultraviolet absorber.

As the above-mentioned resin material, for example, a material containing a polycarbonate resin or an acrylic resin as a main component resin can be cited. Here, the so-called "main component resin" refers to the resin with the largest mass content among the resins constituting the resin component (X).

In addition, regarding the present adhesive sheet, for example, the above-mentioned resin member (X) and the image display panel (P) can be bonded together via the present adhesive sheet to form a photocurable adhesive sheet laminate, and the present adhesive sheet is irradiated with light having a cumulative light amount of 3000 (mJ/ ^cm2 ) at 405 nm through the resin member (X) from the side of the resin member (X), thereby photocuring the adhesive layer (Y) and causing it to condense so that the difference in gel fraction before and after photocuring becomes 10% or more, thereby manufacturing an image display panel laminate.

The adhesive sheet laminate can be bonded to an image display panel (P) to produce an image display panel laminate. Specifically, the image display panel laminate comprising the adhesive sheet laminate and the image display panel (P) can be laminated to produce an image display panel laminate by, for example, irradiating a resin member (X) and an image display panel (P) with light having a wavelength of 405 nm from the outside of the resin member (X) through the resin member (X) after laminating the resin member (X) through the adhesive sheet, so that the adhesive layer (Y) of the adhesive sheet is formally cured and the resin member (X) and the image display panel (P) are bonded to produce an image display panel laminate. Furthermore, there is no particular limitation on the method of laminating the resin member (X) and the image display panel (P) via the adhesive sheet. After laminating either the resin member (X) or the image display panel (P) with the adhesive sheet, the other may be laminated with the adhesive sheet. Alternatively, the resin member (X) and the image display panel (P) may be laminated with the adhesive sheet at the same time.

(Image display panel (P)) The image display panel (P) may include, for example, a polarizing film, a phase difference film or other optical films, a liquid crystal material, and a backlight system (usually, the surface of the composition or the adhesive article to which the image display panel is adhered becomes an optical film). Depending on the control method of the liquid crystal material, there are STN method, VA method, IPS method, etc., and any method may be used. In addition, the image display panel may be an embedded type in which the touch panel function is embedded in the TFT-LCD, or may be a surface embedded type in which the touch panel function is embedded between glass substrates provided with polarizing plates and color filters.

As for the adhesive sheet, from the viewpoint of foaming resistance reliability, it is preferred that the adhesive layer (Y) in the state of being attached to the target object as described above, that is, the adhesive layer (Y) after light (photo) curing has a cross-linked structure of the resin composition. In particular, the adhesive layer (Y) is preferably formed by using a (meth)acrylate copolymer having an active energy ray curable site as described above, or having a (meth)acrylate (co)polymer (a) having a functional group (i) and a chemical bond of a compound having a functional group (ii) that reacts with the functional group (i), or using a trifunctional or more multifunctional (meth)acrylate that has not been modified with alkylene oxide, and has a cross-linked structure caused by these.

<<Explanation of terms>> In the present invention, the term "film" also includes "sheet", and the term "sheet" also includes "film". In addition, the term "panel" such as an image display panel, a protective panel, etc. includes a plate, a sheet, and a film.

In the present invention, when "X to Y" (X and Y are arbitrary numbers) is recorded, unless otherwise specified, it includes the meaning of "X or more and Y or less" and "preferably greater than X" or "preferably less than Y". In addition, when "X or more" (X is an arbitrary number) is recorded, unless otherwise specified, it includes the meaning of "preferably greater than X", and when "Y or less" (Y is an arbitrary number) is recorded, unless otherwise specified, it includes the meaning of "preferably less than Y". [Example]

The present invention is further described in detail below through examples. However, the present invention is not limited to the examples described below.

<Examples and Comparative Examples> The materials used in the examples and comparative examples are described.

[Example 1] (Photocurable adhesive sheet Y) As a (meth)acrylate (co)polymer, an acrylic graft copolymer (mass average molecular weight: 160,000) prepared by random copolymerization of 13.5 parts by mass of a macromonomer (number average molecular weight: 3000) containing isobutyl methacrylate:methyl methacrylate = 1:1 and having a methacrylic terminal functional group, 43.7 parts by mass of lauryl acrylate, 40 parts by mass of 2-ethylhexyl acrylate, and 2.8 parts by mass of acrylamide was prepared. 90 g of propoxylated pentaerythritol triacrylate (NK ESTER ATM-4PL manufactured by Shin-Nakamura Chemical Co., Ltd.) as a crosslinking agent and 15 g of a mixture of 2,4,6-trimethylbenzyldiphenylphosphine oxide, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), 2,4,6-trimethylbenzophenone, and 4-methylbenzophenone (Esacure KTO46 manufactured by Lamberti) as a visible light initiator were added to 1 kg of the acrylic graft copolymer and uniformly mixed to obtain a photocurable composition. Next, the photocurable composition was formed into a sheet with a thickness of 150 μm on a polyethylene terephthalate film (DIAFOIL MRV, manufactured by Mitsubishi Resin Corporation, with a thickness of 100 μm) with a surface subjected to a release treatment, and then coated with a polyethylene terephthalate film (DIAFOIL MRQ, manufactured by Mitsubishi Resin Corporation, with a thickness of 75 μm) with a surface subjected to a release treatment to prepare a photocurable adhesive sheet Y1 with a release film. The photocurable adhesive sheet Y1 is a photocurable adhesive sheet that is cured by irradiation with light.

(Resin member X) As the resin member (X), a polycarbonate resin sheet containing an ultraviolet absorber (manufactured by Mitsubishi Gas Chemical Co., Ltd., Iupilon sheet MR58) with a thickness of 1.0 mm (used in bonding structure P) and 1.5 mm (used in bonding structure Q and bonding structure R) was used. For any thickness, the light transmittance at 365 nm was 0% and the light transmittance at 405 nm was 83%.

(Photocurable adhesive sheet laminate) The release film on one side of the photocurable adhesive sheet Y1 with a release film is peeled off and the laminate is attached to one side of the polycarbonate plate (resin member X) using a roller to obtain a photocurable adhesive sheet laminate of resin member (X)/photocurable adhesive sheet Y1 (also referred to as "X/Y1 laminate").

[Example 2] The crosslinking agent of the photocurable adhesive sheet Y was changed to pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ESTER ATMM3) and the amount of the mixture was changed to 70 g relative to 1 kg of the acrylic graft copolymer. The same method as Example 1 was followed to obtain a photocurable adhesive sheet Y2 and an X/Y2 laminate. The photocurable adhesive sheet Y2 is a photocurable adhesive sheet that cures by irradiation with light.

[Example 3] The composition of the (meth) acrylic copolymer of the photocurable adhesive sheet Y is changed to a macromonomer (number average molecular weight: 3000) containing 12.7 parts by mass of a terminal functional group of methacrylic acid containing isobutyl methacrylate:methyl methacrylate = 1:1, 41.1 parts by mass of lauryl acrylate, 37.6 parts by mass of 2-ethylhexyl acrylate, 2.6 parts by mass of acrylamide and 6 parts by mass of 4-hydroxybutyl acrylate, to form a hydroxyl-containing acrylic graft copolymer (mass average molecular weight: 160,000) 100 parts by mass, 6.5 parts by mass of 2-isocyanatoethyl methacrylate were added to obtain a (meth)acrylic copolymer having a carbon-carbon double bond and an active energy line crosslinking structure. The same method as in Example 1 was followed to obtain a photocurable adhesive sheet Y3 and an X/Y3 laminate. The photocurable adhesive sheet Y3 is a photocurable adhesive sheet that cures by irradiation with light.

[Example 4] The following was used as a photocurable adhesive sheet, that is, methyl phenylglyoxylate (manufactured by BASF, Irgacure MBF) was used as a visible light initiator, and was previously irradiated with light so that the cumulative light amount at 405 nm was 100 (mJ/ ^cm2 ) to perform primary curing (crosslinking). The same procedures as in Example 1 were followed to obtain a photocurable adhesive sheet Y4 and an X/Y4 laminate. The photocurable adhesive sheet Y4 is a photocurable adhesive sheet that is cured by irradiation with light.

[Example 5] As the (meth)acrylate (co)polymer, 13.5 parts by mass of a macromonomer (number average molecular weight: 3000) containing a terminal functional group of methacrylic acid isocyanate:methyl methacrylate = 1:1, 73.7 parts by mass of 2-ethylhexyl acrylate, 2.8 parts by mass of acrylamide and 10 parts by mass of methacrylate were used to randomly copolymerize an acrylic graft copolymer (mass average molecular weight: 260,000), and the type of crosslinking agent was changed to pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ESTER ATMM3L), and the number of parts was changed to 70 g relative to 1 kg of the acrylic graft copolymer. The same procedures as in Example 1 were followed to obtain photocurable adhesive sheets Y5 and X/Y5 laminates. Furthermore, the photocurable adhesive sheet Y5 is a photocurable adhesive sheet that cures by irradiating light.

[Example 6] The same procedure as in Example 5 was followed except that the amount of the crosslinking agent was changed to 120 g relative to 1 kg of the acrylic graft copolymer to obtain a photocurable adhesive sheet Y6 and an X/Y6 laminate. The photocurable adhesive sheet Y6 is a photocurable adhesive sheet that cures by irradiation with light.

[Example 7] The type of crosslinking agent was set to 90 g and 30 g of pentaerythritol triacrylate (NK ESTER ATMM3L manufactured by Shin-Nakamura Chemical Co., Ltd.) and dipentaerythritol tetraacrylate (NK ESTER A9570W manufactured by Shin-Nakamura Chemical Co., Ltd.) respectively relative to 1 kg of acrylic graft copolymer, and the same method as Example 5 was followed to obtain a photocurable adhesive sheet Y7 and an X/Y7 laminate. In addition, the photocurable adhesive sheet Y7 is a photocurable adhesive sheet that is cured by irradiation with light.

[Example 8] The type of crosslinking agent was set to 1 kg of acrylic graft copolymer, and pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ESTER ATMM3L) and dipentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ESTER A9570W) were used in combination, respectively, at 120 g and 40 g, respectively. The same procedure as in Example 5 was followed to obtain a photocurable adhesive sheet Y8 and an X/Y8 laminate. In addition, the photocurable adhesive sheet Y8 is a photocurable adhesive sheet that is cured by irradiation with light.

[Example 9] With respect to 1 kg of a macromonomer (number average molecular weight 3,000) containing 13.5 parts by mass of a (meth)acrylic copolymer having a terminal functional group of methacrylic acid ester and methyl methacrylate in a ratio of 1:1, 73.7 parts by mass of 2-ethylhexyl acrylate, 2.8 parts by mass of acrylamide and 10 parts by mass of methacrylate, a random copolymerization of pentaerythritol triacrylate (produced by Shin-Nakamura Chemical Co., Ltd., NK ESTER ATMM3L) and dipentaerythritol tetraacrylate (produced by Shin-Nakamura Chemical Co., Ltd., NK ESTER A9570W) as a crosslinking agent, a mixture containing a cleavage type visible light initiator as a visible light initiator, i.e., a mixture of 2,4,6-trimethylbenzyldiphenylphosphine oxide, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), 2,4,6-trimethylbenzophenone, and 4-methylbenzophenone (Esacure KTO46 manufactured by Lamberti) 15 g, and 2 g of 3-glycidyloxypropyltrimethoxysilane (KBM403 manufactured by Shin-Etsu Silicone Co., Ltd.) as a silane coupling agent were uniformly mixed to obtain a light-curable composition. Next, the photocurable composition was formed into a sheet with a thickness of 25 μm on a polyethylene terephthalate film (DIAFOIL MRV, manufactured by Mitsubishi Chemical Corporation, with a thickness of 100 μm) with a release treatment on the surface, and then covered with a polyethylene terephthalate film (DIAFOIL MRQ, manufactured by Mitsubishi Chemical Corporation, with a thickness of 75 μm) with a release treatment on the surface to prepare an adhesive sheet Y9a for the front and back layers with a release film.

30 g of pentaerythritol triacrylate (NK ESTER ATMM3L manufactured by Shin-Nakamura Chemical Co., Ltd.) as a crosslinking agent and 15 g of a mixture of 2,4,6-trimethylbenzyldiphenylphosphine oxide, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), 2,4,6-trimethylbenzophenone, and 4-methylbenzophenone (Esacure KTO46 manufactured by Lamberti) as a visible light initiator were added to 1 kg of the same acrylic graft copolymer used in the front and back adhesive sheet Y9a as a (meth) acrylic copolymer, and the mixture was uniformly mixed to obtain a photocurable composition. Next, the photocurable composition was formed into a sheet with a thickness of 100 μm on a polyethylene terephthalate film (DIAFOIL MRV, manufactured by Mitsubishi Chemical Corporation, with a thickness of 100 μm) with a surface subjected to a release treatment, and then coated with a polyethylene terephthalate film (DIAFOIL MRQ, manufactured by Mitsubishi Chemical Corporation, with a thickness of 75 μm) with a surface subjected to a release treatment to prepare an adhesive sheet Y9b for an intermediate layer with a release film.

The PET films on both sides of the adhesive sheet Y9b for the middle layer are peeled off and removed in sequence, and the adhesive surfaces of two adhesive sheets Y9a for the front and back layers are sequentially adhered to the two surfaces of the adhesive sheet Y9b for the middle layer to obtain a photocurable adhesive sheet Y9. The photocurable adhesive sheet Y9 includes two types of three-layer laminates (with a total thickness of 150 μm) of (adhesive sheet Y9a for the front and back layers)/(adhesive sheet Y9b for the middle layer)/(adhesive sheet Y9a for the front and back layers), and the X/Y9 laminate is obtained in the same manner as in Example 1.

[Example 10] The (meth) acrylic copolymer used in the above-mentioned intermediate layer adhesive sheet Y9b is changed to a macromonomer (number average molecular weight of 3,000) having a terminal functional group of methacrylic acid and a ratio of isobutyl methacrylate to methyl methacrylate = 1:1. 13.5 parts by mass, 43.7 parts by mass of lauryl acrylate, 40 parts by mass of 2-ethylhexyl acrylate, and 2.8 parts by mass of acrylamide were randomly copolymerized to form an acrylic graft copolymer (mass average molecular weight: 160,000) to form an intermediate layer adhesive sheet Y10b. In the same manner as in Example 9, a photocurable adhesive sheet Y10 and an X/Y10 laminate were obtained. The photocurable adhesive sheet Y10 is a three-layer laminate (total thickness of 150 μm) of two types of (front and back layer adhesive sheet Y9a)/(intermediate layer adhesive sheet Y10b)/(front and back layer adhesive sheet Y9a). In addition, the photocurable adhesive sheet Y10 is a photocurable adhesive sheet that is cured by irradiation with light.

[Comparative Example 1] As a photocurable adhesive sheet, a hydrogen-absorptive initiator, i.e., a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (Esacure TZT manufactured by Lamberti) was used as a photoinitiator. The same procedure as in Example 1 was followed to obtain photocurable adhesive sheets Y11 and X/Y11 laminates.

[Comparative Example 2] As a photocurable adhesive sheet, a hydrogen-abstracting initiator, i.e., 1-[4-(4-benzoylphenylthio)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propane-1-one (produced by Lamberti, Esacure 1001M) was used as a photoinitiator. The same procedure as in Example 1 was followed to obtain photocurable adhesive sheets Y12 and X/Y12 laminates.

[Comparative Example 3] As the photocurable adhesive sheet, a commercially available non-curable optical transparent adhesive sheet that does not have photocurability was used. The same procedure as in Example 1 was followed to obtain photocurable adhesive sheets Y13 and X/Y13 laminates.

[Comparative Example 4] As the resin member X, a polycarbonate resin sheet (thickness 1.0 mm, light transmittance at 365 nm 45%, light transmittance at 405 nm 91%) without ultraviolet absorber was used. The same procedure as in Example 1 was followed to obtain a photocurable adhesive sheet Y14 and an X/Y14 laminate.

<Evaluation> This section explains the evaluation method used in this manual.

(1) Dynamic storage modulus (G') Each of the 150 μm photocurable adhesive sheets Y1 to Y14 (without release film) obtained in the examples and comparative examples was stacked 8 sheets to make a thickness of 1200 μm. The dynamic viscoelasticity measuring device, a rheometer ("MARS" manufactured by Eikon Seiki Co., Ltd.), was used to measure the adhesive jig under the conditions of Φ25 mm parallel plates, strain of 0.5%, frequency of 1 Hz, and heating rate of 3°C/min.

(2) Spectral transmittance For the resin component (X), the spectral transmittance (%T) at a wavelength of 300 nm to 800 nm was measured using a spectrophotometer (UV2000 manufactured by Shimadzu Corporation). The spectral transmittance was taken as the light transmittance.

(3) Gel fraction Each of the photocurable adhesive sheets Y1 to Y14 (without release film) obtained in the examples and comparative examples was packed into a bag with a SUS net (♯200) whose mass (X) was measured in advance, and the bag was folded and sealed. The mass (Y) of the bag was measured, and then it was immersed in 100 ml of ethyl acetate and stored in a dark place at 23°C for 24 hours. The bag was taken out and heated at 70°C for 4.5 hours to evaporate the attached ethyl acetate. The mass (Z) of the dried bag was measured, and the obtained mass was substituted into the following formula to obtain the gel fraction X1. Gel fraction (%) = [(Z-X)/(Y-X)] × 100

In addition, for each of the X/Y1 to Y14 laminates obtained in the Examples and Comparative Examples, light was irradiated from the resin member (X) side using a high-pressure mercury lamp so that the cumulative light quantity at 405 nm became 3000 (mJ/cm ² ), and then a sample was collected from the adhesive layer portion of the surface of the resin member (X) side of the photocurable adhesive sheet, and the gel fraction X2 was obtained by the same method as above. X2-X1 was also calculated.

(4) Step absorption Printing with a thickness of 22 to 24 μm was performed on the periphery of a glass measuring 58 mm × 110 mm × 0.8 mm thick (3 mm on the long side and 15 mm on the short side), and a glass plate with a printed step and a concave portion in the center measuring 52 mm × 80 mm was prepared. For each of the photocurable adhesive sheets Y1 to Y14 with release films obtained in the embodiments and comparative examples, one release film was peeled off and the sheets were rolled onto the entire surface of sodium calcium glass (54 mm×82 mm×thickness 0.5 mm). The remaining release film was then peeled off and the adhesive sheet was covered on the frame-shaped printing step of the glass plate with printing step by vacuum pressurization (temperature of 25°C, pressurization pressure of 0.13 MPa) to prepare evaluation samples. After the evaluation samples were autoclaved at 60°C, 0.2 MPa, and 20 min, the pass or fail was determined by the following evaluation criteria. ○ (good): No tiny bubbles were seen at all around the step × (poor): Tiny bubbles were seen around the step

(5) Yellowness (YI) Each of the X/Y1 to Y14 laminates obtained in the Examples and Comparative Examples was irradiated with light from the resin member (X) side using a high-pressure mercury lamp so that the cumulative light quantity at 405 nm was 3000 (mJ/cm ² ). The cumulative light quantity at 405 nm is the cumulative light quantity irradiated onto the photocurable adhesive sheets (Y1 to Y14) through the resin member (X) using an ultraviolet cumulative light meter "UIT-250" (manufactured by Ushio Electric Co., Ltd.) and a light receiver "UVD-C405" (manufactured by Ushio Electric Co., Ltd.) and is measured using a light meter installed on the side of the resin member (X) opposite to the side irradiated by the high-pressure mercury lamp. Then, the yellowness (YI) of the X/Y1 to Y14 laminates was measured using a spectrophotometer (Suga Testing Instruments Co., Ltd.) "SC-T" based on JIS K7103, and the pass or fail was determined according to the following evaluation criteria. ○ (good): YI less than 2 × (poor): YI 2 or more

(6) UV resistance reliability (ΔYI) The X/Y1 to Y14 laminates obtained in the examples and comparative examples were irradiated with light from the resin member (X) side using a high-pressure mercury lamp so that the cumulative light quantity at 405 nm was 3000 (mJ/cm ² ). The cumulative light quantity at 405 nm is the cumulative light quantity irradiated onto the photocurable adhesive sheets (Y1 to Y14) through the resin member (X) using an ultraviolet cumulative light meter "UIT-250" (manufactured by Ushio Electric Co., Ltd.) and a light receiver "UVD-C405" (manufactured by Ushio Electric Co., Ltd.) and is measured using a light meter installed on the side of the resin member (X) opposite to the side irradiated by the high-pressure mercury lamp. Afterwards, a UVB fluorescent lamp (G15T8E, manufactured by Sankyo Electric Co., Ltd., irradiance 70 μW/cm ² ) was used to conduct an irradiation test at a distance of 20 cm for 72 hours. The pass or fail test was determined based on the change in the yellowness (YI) of the X/Y1 to Y14 layered body before and after irradiation, ΔYI. ○ (Good): ΔYI less than 0.2 × (Poor): ΔYI more than 0.2

(7) Foaming resistance reliability For each of the X/Y laminates obtained in the embodiment and the comparative example, the other mold release film remaining on the Y side was peeled off, and the following three components were attached to the exposed surface by a hand roller, and the foaming resistance reliability during bonding was evaluated respectively. In addition, the X/Y laminate was cut into the size of each component for use. The specific bonding structures are X/Y laminate/component P (bonding structure P), X/Y laminate/component Q (bonding structure Q), and X/Y laminate/component R (bonding structure R). Component P: Sodium calcium glass 54 mm × 82 mm × thickness 0.55 mm Component Q: Sodium calcium glass 100 mm × 180 mm × thickness 0.55 mm Component R: PET film 100 mm × 180 mm × thickness 100 μm

In addition, for component P (bonding structure P), high pressure autoclave treatment was carried out under the conditions of temperature of 60°C, air pressure of 0.2 MPa, and 30 minutes for final bonding, and for components Q and R (bonding structures Q and R), high pressure autoclave treatment was carried out under the conditions of temperature of 80°C, air pressure of 0.2 MPa, and 30 minutes for final bonding.

After the final bonding, the resin member (X) was irradiated with light using a high-pressure mercury lamp at 405 nm at a cumulative light intensity of 3000 (mJ/cm ² ) to prepare a foaming resistance reliability evaluation sample. The evaluation sample was exposed to an environment of 85°C and 85% RH for 24 hours, and those with no appearance defects such as foaming or peeling were judged as "○ (good)", and those with foaming or peeling were judged as "× (poor)". In addition, those in which no appearance defects such as bubbling or peeling were found in the bonding structure P or Q (single-sided glass component) and the bonding structure R (double-sided resin component) were comprehensively judged as "◎ (excellent)", those in which no appearance defects such as bubbling or peeling were found in any of the bonding structures P, Q and R were comprehensively judged as "0 (good)", and those in which bubbling or peeling were found in all of the bonding structures P, Q and R were comprehensively judged as "× (poor)".

(8) Haze after long-term storage (indicator of compatibility with crosslinking agent) For each of the photocurable adhesive sheets Y obtained in the examples and comparative examples, after more than 2 months from the production of the sheets, the adhesive surfaces of both sides of the adhesive sheet Y were exposed by removing the release film and sandwiched between two sodium calcium glasses (thickness 0.55 mm), and the sheets were irradiated with light using a high-pressure mercury lamp in such a way that the accumulated light quantity at 405 nm was 3000 (mJ/cm ² ), and the haze value was measured. The haze value was measured using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries) in accordance with JIS K7136. A haze value of less than 0.5 was judged as "○ (good)", a haze value of 0.5 or more but less than 1.0 was judged as "△ (fair)", and a haze value of 1.0 or more was judged as "× (poor)".

(9) Tg after photocuring Each of the 150 μm photocurable adhesive sheets Y1 to Y14 (without release film) obtained in the examples and comparative examples was irradiated with light in advance so that the cumulative light amount at 405 nm was 3000 (mJ/cm ² ). Then, 8 sheets of the photocurable adhesive sheets Y1 to Y14 were stacked to make a thickness of 1200 μm. The sheets were measured using a dynamic viscoelasticity measuring apparatus, a rheometer ("MARS" manufactured by Eikon Seiki Co., Ltd.) with an adhesive jig of Φ25 mm parallel plates, a strain of 0.5%, a frequency of 1 Hz, and a heating rate of 3°C/min. The temperature at which the obtained Tanδ value reached a peak was determined as Tg.

(10) Viscosity For each of the 150 μm photocurable adhesive sheets Y1 to Y14 (without release film) obtained in the examples and comparative examples, 8 sheets were stacked to make a sheet of 1200 μm. The complex viscosity of the adhesive sheets before photocuring at 70°C and 100°C was measured using a dynamic viscoelasticity measuring device, a rheometer ("MARS" manufactured by Eikon Seiki Co., Ltd.), with an adhesive jig of Φ25 mm parallel plates, a strain of 0.5%, a frequency of 1 Hz, and a heating rate of 3°C/min.

(11) Storage performance The photocurable adhesive sheets Y1 to Y14 cut into 50 mm × 50 mm squares were sandwiched between two 100 mm × 100 mm square PET films with a thickness of 100 μm to prepare a laminate. After being placed in an environment of 23°C and 50% for 300 hours, the adhesive was visually observed to see if it overflowed from the laminate. The laminate was visually observed, and those with adhesive overflowing throughout the laminate were judged as "× (poor)", those with adhesive overflowing only from the corners were judged as "△ (acceptable)", and those without adhesive overflowing were judged as "○ (good)".

[Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Embodiment 6 Embodiment 7 Embodiment 8 Embodiment 9 Embodiment 10 Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 Resin ComponentsX Light transmittance (%) 365 nm 0 0 0 0 0 0 0 0 0 0 0 0 0 45 Light transmittance (%) 405 nm 83 83 83 83 83 83 83 83 83 83 83 83 83 91 Adhesive layer of light-curing adhesive sheet Y Light transmittance (%) 390 nm 77 77 77 86 76 76 76 76 76 76 91 91 90 77 Light transmittance (%) 410 nm 90 90 90 92 88 88 88 88 88 88 92 92 91 90 Gel fraction X1(%) 0 0 0 45 0 0 0 0 0 0 0 0 88 0 Dynamic storage modulus (G')(25℃)(Pa) 3.8×10 ⁴ 4.1×10 ⁴ 7.9×10 ⁴ 6.5×10 ⁴ 6.0×10 ⁴ 5.4×10 ⁴ 5.4×10 ⁴ 5.1×10 ⁴ 8.2×10 ⁴ 5.4×10 ⁴ 3.8×10 ⁴ 3.8×10 ⁴ 9.0×10 ⁴ 3.8×10 ⁴ Viscosity(Pa.s)(70℃) 1050 1120 1139 1630 1405 1178 1290 1080 1930 1570 1018 1091 13700 1018 Viscosity(Pa.s)(100℃) 154 169 168 398 334 273 291 266 436 379 149 170 14100 149 Storage △ △ △ ○ △ △ △ △ ○ ○ △ △ ○ △ X/Y Layers Step Absorption ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ × ○ Tg after 405 nm light irradiation (℃) 0 5 9 -1 twenty one 37 40 43 4 twenty one -5 -5 0 -5 Gel fraction after 405 nm light irradiation X2 (%) 78 82 88 74 78 80 82 86 69 74 0 0 90 81 X2-X1(%) 78 82 88 29 78 80 82 86 69 74 0 0 2 81 Dynamic storage modulus after 405 nm light irradiation (G') (120℃) (Pa) 0.8×10 ⁴ 3.3×10 ⁴ 9.3×10 ⁴ 0.8×10 ⁴ 4.0×10 ⁴ 1.7×10 ⁵ 2.2×10 ⁵ 2.7×10 ⁵ 2.4×10 ⁴ 3.4×10 ⁴ 5.7×10 ¹ 5.7×10 ¹ 5.4×10 ⁴ 0.8×10 ⁴ Foam resistance reliability ○ ○ ◎ ○ ○ ○ ◎ ○ ◎ ◎ × × ◎ ○ Bonding structure P: X/Y/Glass size: 54×82 mm ○ ○ ○ ○ - - - - - - × × ○ ○ Bonding structure Q: X/Y/Glass size: 100×180 mm ○ ○ ○ ○ ○ ○ ○ × ○ ○ × × ○ ○ Bonding structure R: X/Y/PET Size: 100×180 mm × × ○ × × × ○ ○ ○ ○ × × ○ × Yellowness(YI) ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.85 ０1.82 ０1.82 ０1.90 ０1.76 UV resistance reliability (ΔYI) ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 ０0.2 × 1.65 Fog after long-term storage ０0.3 △ 0.6 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3 ０0.3

<Review> When the photocurable adhesive sheet laminate (X/Y1-Y10 laminate) of the resin member (X)/photocurable adhesive sheet (Y1-Y10) of Examples 1-10 was irradiated with light from the side of the resin member (X) in such a manner that the accumulated light quantity at a wavelength of 405 nm became 3000 (mJ/cm ² ), the photocurable adhesive sheets Y1-Y10 were sufficiently cured to increase the gel fraction difference by more than 10%, and the dynamic storage modulus (G') maintained a high-temperature cohesion of more than 0.7×10 ⁴ Pa at 120°C and 1 Hz, thereby obtaining good anti-foaming reliability. In particular, the touch sensor obtained good anti-foaming reliability in the test assuming the case of a glass sensor. The dynamic storage modulus (G') of Examples 3, 7, 9, and 10 maintained a high-temperature cohesion of more than 2.0×10 ⁴ Pa at 120° C. and 1 Hz, so the touch sensor also obtained good anti-foaming reliability in the test assuming the case of a film sensor.

In addition, although the touch sensor of Example 8 obtained good anti-foaming reliability in the test assuming the case of a film sensor, the touch sensor produced glass peeling in the test assuming the case of a glass sensor. It is believed that the reason is that the dynamic storage modulus (G') becomes too high at 120°C and 1 Hz, and the viscosity and adhesion performance are reduced. Furthermore, since the content of the hydrophilic monomer constituting the (meth)acrylate (co)polymer (a) of Example 2 is less than 10 parts by mass, phase separation occurs during long-term storage, so the haze after long-term storage is "△ (acceptable)". Examples 1 to 10 have good step absorption properties, and can be durable and practical for cover components with printed steps depending on the type of touch sensor.

In addition, the viscosity (70°C) of Examples 4, 9, and 10 was as high as 1.5 kPa·s or more, so even after long-term storage, no paste overflow was found, and the storage property was excellent.

The light transmittance (%) of the photocurable adhesive sheets Y11 and Y12 of Comparative Examples 1 and 2 at a wavelength of 390 nm is as high as over 90%. When light is irradiated from the resin member (X) side in such a way that the cumulative light amount at a wavelength of 405 nm becomes 3000 (mJ/ ^cm2 ), the photoinitiator does not fully absorb the light to excite and cure (crosslink) the reaction, so the adhesive layer (Y) cannot be fully cured, and bubbles are generated during the anti-foaming reliability test.

The gel fraction of the photocurable adhesive sheet Y13 in Comparative Example 3 is 88%, and the dynamic storage modulus (G') (25°C) is as high as 1.1×10 ⁵ Pa, so the step absorption is poor and bubbles are generated. The resin component (X) in Comparative Example 4 does not contain a UV absorber, and the light transmittance at a wavelength of 365 nm is as high as 45%, so the yellowing in the UV resistance reliability test is carried out.

Claims (15)

A photocurable adhesive sheet is characterized by comprising an adhesive layer (Y) having all of the following properties (1) to (4): (1) a gel fraction (referred to as "gel fraction X1 before light irradiation") in the range of 0 to 60%; (2) a light transmittance at a wavelength of 390 nm of 89% or less and a light transmittance at a wavelength of 410 nm of 80% or more; (3) a storage modulus (G') of 0.9×10 ⁵ Pa or less at a temperature of 25° C. and a frequency of 1 Hz; and (4) having a photocurable property of curing by irradiation with light of a wavelength of 405 nm, and a storage modulus (G') of 0.7×10 ⁴ Pa or more at a temperature of 120° C. and a frequency of 1 Hz after irradiation with light of a wavelength of 405 nm with a cumulative light quantity of 3000 (mJ/cm ² ) thereof. As in claim 1, the photocurable adhesive sheet, wherein the photocurability in (4) above is the photocurability that increases the difference in gel fraction by more than 10% when irradiated with light having a wavelength of 405 nm. The photocurable adhesive sheet of claim 1, wherein the photocurability of (4) is the photocurability of a laminated body having the photocurable adhesive sheet and a resin member (X) having a light transmittance of less than 10% at a wavelength of 365nm and a light transmittance of more than 60% at a wavelength of 405nm, when irradiated with light of a wavelength of 405nm from the side of the resin member (X), the difference in gel fraction increases by more than 30%. The photocurable adhesive sheet of claim 1 has the following photocurability: when irradiated with light having a cumulative light amount of 3000 (mJ/ ^cm2 ) at a wavelength of 405nm, the difference between the gel fraction before light irradiation (gel fraction before light irradiation X1) and the gel fraction after light irradiation (referred to as "gel fraction after light irradiation X2") (gel fraction after light irradiation X2-gel fraction before light irradiation X1) becomes 10% or more. The photocurable adhesive sheet of claim 1 has the following photocurability: when a laminated body comprising the photocurable adhesive sheet and a resin member (X) having a light transmittance of 10% or less at a wavelength of 365 nm and a light transmittance of 60% or more at a wavelength of 405 nm is irradiated from the resin member (X) side with a cumulative light amount of 3000 (mJ/cm ² ) at a wavelength of 405 nm, the difference (gel fraction after light irradiation X2 - gel fraction before light irradiation X1) between the gel fraction before light irradiation (gel fraction before light irradiation X1) and the gel fraction after light irradiation (referred to as "gel fraction after light irradiation X2") becomes 30% or more. As in claim 1, the photocurable adhesive sheet has a gel fraction of 0 to 50% or less. As in claim 1, the photocurable adhesive sheet is temporarily cured by light irradiation. As in claim 1, the photocurable adhesive sheet, wherein the adhesive layer (Y) is formed by an adhesive composition containing a (meth)acrylate (co)polymer and a visible light initiator. As in claim 8, the photocurable adhesive sheet, wherein the adhesive layer (Y) contains a silane coupling agent. As in claim 8, the photocurable adhesive sheet, wherein the adhesive composition contains a crosslinking agent. As in claim 10, the photocurable adhesive sheet, wherein the crosslinking agent is chemically bonded to the (meth)acrylate (co)polymer. As in claim 10, the photocurable adhesive sheet, wherein the crosslinking agent is a multifunctional (meth)acrylate. As in claim 8, the photocurable adhesive sheet, wherein the (meth)acrylate (co)polymer has an active energy line cross-linking structural site. For example, in the photocurable adhesive sheet of claim 8, the absorbance coefficient of the visible light initiator at a wavelength of 405 nm is greater than 10 mL/(g‧/cm). As in claim 8, the photocurable adhesive sheet, wherein the visible light initiator is a hydrogen-scavenging visible light initiator.