Adhesive layer for flexible image display device constituent member, laminate, and image display device

Abstract

The present invention provides the adhesive layer described below as an adhesive layer for a flexible image display device constituent member, which has excellent bending adequacy, and good cohesive force and / or good adhesive force.　This adhesive layer for a flexible image display device constituent member satisfies the following requirements [I]-[V]. The adhesive layer is formed of a resin composition that contains a polymer (A), a crosslinking agent (B), and a polymerization initiator (C). The polymer (A) comprises a copolymer that is composed of a compound in which 50 mass% or more of the monomer component contains a (meth)acryloyl group. The crosslinking agent (B) comprises a crosslinking agent that has a functionality of 3 or more. The polymerization initiator (C) comprises a cleavage-type photopolymerization initiator. [I] The shear storage elastic modulus at -20°C is 300 kPa or less. [II] The shear storage elastic modulus at 85°C is 5.0-30 kPa. [III] The gel fraction is 45-95%. [IV] The adhesive force to a PET substrate at 23°C is 5.0 N / cm or more. [V] The recovery rate is 70% or more.

Description

Adhesive layer for flexible image display device constituent member, laminate, and image display device

[0001] The present invention relates to an adhesive layer for a component of a flexible image display device, a laminate, and an image display device.

[0002] In recent years, in order to improve the visibility of image display devices, the gap between an image display panel such as an LCD (Liquid Crystal Display), a PDP (Plasma Display Panel) or an EL (Electro-Luminescence) and a protective panel or touch panel member arranged on the front side (viewing side) of the image display panel has been filled with an adhesive layer, adhesive or the like to suppress diffused reflection that occurs when the gap is not filled, i.e., diffused reflection of incident light or emitted light from a displayed image at the interface with an air layer.

[0003] In this case, for example, if the protective panel is made of plastic, gas (called outgassing) may be generated from the protective panel. If the adhesive layer or adhesive does not have sufficient adhesive strength and cohesive strength to withstand this gas pressure, the gas will remain in the adhesive layer or adhesive, and when the temperature rises, the remaining gas will foam, reducing the visibility of the screen.

[0004] Recently, flexible displays that can be bent freely have been attracting attention as next-generation displays, and organic electroluminescence (organic EL) displays are mainly used for flexible displays.

[0005] In such an image display device, a plurality of component sheets such as a surface protection film, a cover lens, a circular polarizer, a touch film sensor, and a light-emitting element are laminated together with a transparent adhesive layer to form a laminated structure, and each laminated structure can be regarded as a laminated sheet formed by laminating a component sheet and an adhesive layer.

[0006] Bendable flexible display devices face various challenges due to interlayer stress during folding. For example, there is a need for a laminate sheet that quickly restores to a flat state when the screen is unfolded from a folded state without any residual effects from being in a bent state. Furthermore, repeated folding operations can cause the adhesive layer to peel off, and stress can be applied to the adherend, potentially causing cracks or breakage in the adherend. Therefore, there is a need for a laminate sheet that is durable against repeated folding operations, particularly under harsh conditions such as low temperatures. The adhesive layer in such flexible image display devices must have not only optical properties but also flexibility, particularly high durability against bending.

[0007] In addition to durability at low temperatures, it is also required to prevent the adhesive layer itself from protruding at high temperatures, and to prevent the adhesive layer from deforming and leaving marks when bent in a high-temperature environment.From these perspectives, it is also required to have a high elastic modulus.

[0008] For example, Patent Document 1 discloses a laminated film with an adhesive layer that is free from the risk of image distortion at the folded portion after repeated folding. Also, Patent Document 2 discloses a laminate that includes a double-sided adhesive sheet having a glass transition temperature and storage modulus within a predetermined range and a flexible member for an image display device, with the main focus being to suppress peeling and the like even in a bending test that approximates an actual usage environment.

[0009] JP 2020-196255 A International Publication No. 2018 / 173896

[0010] In Patent Documents 1 and 2, a base polymer with a low glass transition temperature is used to impart sufficient flexibility to a cured product of a resin composition at low temperatures and to obtain folding resistance at low temperatures, thereby providing the pressure-sensitive adhesive sheet with bending resistance at high and low temperatures. However, when a polymer with a low glass transition temperature is used, the adhesive strength and cohesive strength tend to be insufficient.

[0011] Therefore, under such circumstances, the present invention aims to provide an adhesive layer for a flexible image display device component, a laminate, and an image display device, which have excellent bending suitability and good cohesive strength and / or adhesive strength.

[0012] That is, the present invention has the following aspects. [1] An adhesive layer for a component of a flexible image display device, satisfying the following requirements [I] to [V]: The adhesive layer for a component of a flexible image display device is formed from a resin composition containing a polymer (A), a crosslinking agent (B), and a polymerization initiator (C), the polymer (A) contains a copolymer in which 50 mass% or more of monomer components are compounds containing a (meth)acryloyl group, the crosslinking agent (B) contains a trifunctional or higher crosslinking agent, and the polymerization initiator (C) contains a cleavage-type photopolymerization initiator. [I] The shear storage modulus at -20°C (G'(-20°C)) is 300 kPa or less. [II] The shear storage modulus at 85°C (G'(85°C)) is 5.0 kPa or more and 30 kPa or less. [III] The gel fraction is 45% or more and 95% or less. [IV] The adhesive strength to a polyethylene terephthalate substrate at 23°C is 5.0 N / cm or more. [V] The maximum strain (γ max(25) ) and the strain (γ min(25) The restoration rate calculated from the above formula using the following formula is 70% or more. max(25) -γ min(25) ) / γ max(25) ] × 100 [2] The adhesive layer for a component of a flexible image display device according to [1], wherein the adhesive strength of the adhesive layer for a component of a flexible image display device to a glass substrate at 23°C is 4.5 N / cm or more. [3] The adhesive layer for a component of a flexible image display device has a thickness of 0.5 to 1.2 mm, and a maximum strain (γ max(25)The adhesive layer for a component of a flexible image display device according to [1] or [2], wherein the glass transition temperature (Tg) of the adhesive layer for a component of a flexible image display device, defined by the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz, is -15°C or lower. [5] An adhesive layer for a component of a flexible image display device with a release film, having a laminated structure of one or more release films and the adhesive layer for a component of a flexible image display device according to any one of [1] to [4]. [6] A laminate comprising one or more components for an image display device and the adhesive layer for a component of a flexible image display device according to any one of [1] to [4]. [7] A laminate comprising two components of an image display device and the adhesive layer for a component of a flexible image display device according to any one of [1] to [4] interposed between the two components of the image display device. [8] The laminate according to [7], wherein one of the two image display device components is a surface protection panel and the other is a component consisting of one or a combination of two or more selected from the group consisting of a touch sensor film, an image display panel, a color filter, a polarizing element, and a retardation film. [9] An image display device comprising the laminate according to any one of [6] to [8].

[10] The image display device according to [9], which is a flexible image display device.

[0013] According to the present invention, it is possible to provide an adhesive layer for a component of a flexible image display device, a laminate, and an image display device, which have excellent bending suitability and good cohesive strength and / or adhesive strength.

[0014] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below. In the present invention, the term "layer" conceptually includes a sheet, a film, and a tape. Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it includes a plate, a sheet, and a film.

[0015] In this specification, when it is written as "x to y" (x and y are any numbers), unless otherwise specified, it means "x or more and y or less," and also includes the meaning of "preferably greater than x" or "preferably smaller than y." Furthermore, when it is written as "x or more" (x is any number), it also includes the meaning of "preferably greater than x" unless otherwise specified, and when it is written as "y or less" (y is any number), it also includes the meaning of "preferably smaller than y" unless otherwise specified. Furthermore, "x and / or y (x and y are any configurations)" means at least one of x and y, and can mean three possibilities: x only, y only, or x and y. Furthermore, in this specification, "(meth)acrylic" means a comprehensive definition of acrylic and methacrylic, "(meth)acrylate" means a comprehensive definition of acrylate and methacrylate, and "(meth)acryloyl" means a comprehensive definition of acryloyl and methacryloyl. For the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with a value shown in the Examples. Furthermore, in this specification, the term "major component" refers to a component that has a significant effect on the properties of the material, and the content of that component is usually 50% by mass or more, preferably 70% by mass or more, and particularly preferably 90% by mass or more, of the entire material.

[0016] <<Adhesive Layer>> In one embodiment, the present invention provides an adhesive layer for a component of a flexible image display device (hereinafter, the adhesive layer for a component of a flexible image display device according to the embodiment may be referred to as "the adhesive layer"), which satisfies the following requirements [I] to [V]: the adhesive layer is formed from a resin composition containing a polymer (A), a crosslinking agent (B), and a polymerization initiator (C), the polymer (A) comprises a copolymer in which 50% by mass or more of monomer components are compounds containing (meth)acryloyl groups, the crosslinking agent (B) comprises a trifunctional or higher crosslinking agent, and the polymerization initiator (C) comprises a cleavage-type photopolymerization initiator. [I] The shear storage modulus at -20°C (G'(-20°C)) is 300 kPa or less. [II] The shear storage modulus at 85°C (G'(85°C)) is 5.0 kPa or more and 30 kPa or less. [III] The gel fraction is 45% or more and 95% or less. [IV] The adhesive strength to a polyethylene terephthalate substrate at 23°C is 5.0 N / cm or more. [V] The maximum strain (γ max(25) ) and the strain (γ min(25) The restoration rate calculated from the above formula using the following formula is 70% or more. max(25) -γ min(25) ) / γ max(25) ] x 100 The resin composition that forms the adhesive layer will be described in detail below.

[0017] <Resin Composition> As described above, the resin composition contains the polymer (A), the crosslinking agent (B), and the polymerization initiator (C). In the present invention, the term "polymer (A)" also includes a prepolymer. The "prepolymer" is obtained by partially polymerizing the copolymerization component described below, and is a mixture of the polymer and the unpolymerized copolymerization component.

[0018] [Polymer (A)] The polymer (A) can be a copolymer in which 50% by mass or more of the monomer components are compounds having (meth)acryloyl groups, such as an acrylic copolymer obtained by polymerizing an alkyl (meth)acrylate with a monomer component copolymerizable therewith. Among them, the polymer (A) preferably contains a structural portion derived from an alkyl (meth)acrylate and a structural portion derived from a hydroxyl group-containing (meth)acrylate. In particular, from the viewpoint of adhesive properties, an acrylic copolymer containing a structural portion derived from an alkyl (meth)acrylate (a1) (hereinafter sometimes referred to as "alkyl (meth)acrylate (a1)") having an alkyl group with 3 or more carbon atoms and a structural portion derived from a hydroxyl group-containing (meth)acrylate (a2) is preferred. Such an acrylic copolymer is obtained by polymerizing a copolymerization component containing an alkyl (meth)acrylate (a1) and a hydroxyl group-containing (meth)acrylate (a2).

[0019] The copolymerization components may also contain components other than the alkyl(meth)acrylate (a1) and the hydroxyl group-containing (meth)acrylate (a2), such as at least one copolymerizable monomer (a3) ​​selected from alkyl(meth)acrylates having an alkyl group with 1 or 2 carbon atoms and vinyl ester-based monomers (hereinafter referred to as "copolymerizable monomer (a3)"), a functional group-containing ethylenically unsaturated monomer (a4), other copolymerizable monomers (a5), and the like.

[0020] The polymer (A) typically contains 50% by mass or more of an acrylic copolymer, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. The upper limit is not particularly limited and may be 100% by mass. The content range is, for example, 50 to 100% by mass.

[0021] [Alkyl (meth)acrylate (a1)] Examples of the alkyl (meth)acrylate (a1) include aliphatic (meth)acrylates such as linear alkyl (meth)acrylates and branched alkyl (meth)acrylates, and alicyclic (meth)acrylates. Examples of the aliphatic (meth)acrylates include n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl (meth)acrylate, stearyl (meth)acrylate, icosyl (meth)acrylate, heneicosyl (meth)acrylate, and behenyl (meth)acrylate. and branched-chain alkyl (meth)acrylates such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, and isoicosyl (meth)acrylate. Examples of the alicyclic (meth)acrylates include alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

[0022] Among these, linear alkyl (meth)acrylates are preferred from the viewpoint of adhesiveness and resilience. Furthermore, from the viewpoint of balancing adhesiveness and flexibility at low temperatures, linear and branched alkyl (meth)acrylates in which the alkyl group has 3 or more and 18 or less, further 16 or less, particularly 12 or less, and especially 8 or less carbon atoms are preferred, such as n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, decyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Of these, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred. From the viewpoint of reducing the refractive index, alkyl (meth)acrylates in which the alkyl group has 4 or more, particularly 6 or more, particularly 8 or more and 18 or less, particularly 16 or less, and especially 12 or less carbon atoms are preferred.

[0023] Furthermore, from the viewpoint of suppressing an increase in the shear storage modulus (G') at low temperatures and improving flexibility, it is particularly preferred that the alkyl (meth)acrylate (a1) is an acrylate.

[0024] The content of the structural moiety derived from alkyl (meth)acrylate (a1) relative to the polymer (A) is usually 50% by mass or more, preferably 60% by mass or more, particularly preferably 70% by mass or more, and usually 99% by mass or less, preferably 97% by mass or less, particularly preferably 95% by mass or less, with the range of the content being, for example, 50 to 99% by mass, in order to suppress an increase in the shear storage modulus (G') at low temperatures. When the content of the structural moiety derived from alkyl (meth)acrylate (a1) is equal to or greater than the lower limit, there is a tendency for the increase in the shear storage modulus (G') at low temperatures to be suppressed, and when it is equal to or less than the upper limit, there is a tendency for compatibility with other physical properties such as adhesion.

[0025] Furthermore, when the linear alkyl (meth)acrylate and the branched alkyl (meth)acrylate are used in combination, the mass ratio thereof [linear alkyl (meth)acrylate / branched alkyl (meth)acrylate] is usually 1 / 99 or more, preferably 50 / 50 or more, more preferably 65 / 35 or more, and usually 99 / 1 or less, preferably 95 / 5 or less, more preferably 90 / 10 or less. The mass ratio range is, for example, 1 / 99 to 99 / 1. When the mass ratio of the linear alkyl (meth)acrylate to the branched alkyl (meth)acrylate is within the above range, the adhesive strength when formed into a pressure-sensitive adhesive tends to be excellent.

[0026] [Hydroxyl Group-Containing (Meth)acrylate (a2)] Examples of the hydroxyl group-containing (meth)acrylate (a2) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified hydroxy (meth)acrylates such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; diethylene glycol (meth)acrylate; polyethylene glycol (meth)acrylate; and polypropylene glycol (meth)acrylate. Examples of such acrylates include (meth)acrylates having an oxyalkylene glycol structure, such as lamethylene glycol (meth)acrylate and polyoxyethylene polyoxypropylene glycol (meth)acrylate; primary hydroxyl group-containing (meth)acrylates, such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate; secondary hydroxyl group-containing (meth)acrylates, such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate and 3-chloro-2-hydroxypropyl (meth)acrylate; and tertiary hydroxyl group-containing (meth)acrylates, such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate. These may be used alone or in combination of two or more.

[0027] Among the hydroxyl group-containing (meth)acrylates (a2), in terms of reducing the shear storage modulus (G') at low temperatures, hydroxyl group-containing (meth)acrylates having a hydroxyalkyl group having 1 or more, preferably 2 or more, 10 or less, further 6 or less, and particularly 4 or less carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, are preferred, and primary hydroxyl group-containing (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred.

[0028] Furthermore, when 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are used as the hydroxyl group-containing (meth)acrylate (a2), the ratio [2-hydroxyethyl (meth)acrylate / 4-hydroxybutyl (meth)acrylate] by mass is usually 30 / 70 or more, preferably 40 / 60 or more, particularly preferably 45 / 55 or more, and especially preferably 50 / 50 or more, and is usually 95 / 5 or less, preferably 80 / 20 or less, more preferably 80 / 20 or less, particularly preferably 75 / 25 or less, and especially preferably 70 / 30 or less, and the ratio range is, for example, 30 / 70 to 95 / 5. When the 2-hydroxyethyl (meth)acrylate is at or above the lower limit, the adhesive strength when used as a pressure-sensitive adhesive tends to be excellent, and when it is at or below the upper limit, the bending durability when used as a pressure-sensitive adhesive tends to be excellent.

[0029] The hydroxyl group-containing (meth)acrylate (a2) preferably has a lower content of di(meth)acrylate as an impurity. Specifically, it is preferred to use one having a content of 0.5% by mass or less, particularly preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less.

[0030] The content of the structural moiety derived from the hydroxyl group-containing (meth)acrylate (a2) relative to the polymer (A) is usually 5% by mass or more, preferably 8% by mass or more, more preferably 10% by mass or more, even more preferably 11% by mass or more, particularly preferably 12% by mass or more, and is usually 60% by mass or less, preferably 45% by mass or less, more preferably 35% by mass or more, even more preferably 30% by mass or less, particularly preferably 25% by mass or less, and the content range is, for example, 5 to 45% by mass. When the content of the structural moiety derived from the hydroxyl group-containing (meth)acrylate (a2) is at least the lower limit, the adhesive layer tends to have excellent moist heat resistance, and when it is at most the upper limit, unintended self-crosslinking reactions can be suppressed and heat resistance tends to be improved.

[0031] [Copolymerizable Monomer (a3)] In the present invention, it is preferred to further contain a copolymerizable monomer (a3) ​​as a copolymerization component from the viewpoint of improving cohesive strength and further improving adhesive strength when used as a pressure-sensitive adhesive.

[0032] Examples of the copolymerizable monomer (a3) ​​include methyl (meth)acrylate, ethyl (meth)acrylate, and vinyl acetate. These copolymerizable monomers (a3) ​​may be used alone or in combination of two or more. Among them, methyl (meth)acrylate and ethyl (meth)acrylate are preferred from the viewpoint of improving cohesive strength when used as a pressure-sensitive adhesive.

[0033] When the polymer (A) contains a structural moiety derived from the copolymerizable monomer (a3), the content thereof is usually 1% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more, and is usually 70% by mass or less, preferably 60% by mass or less, and more preferably 45% by mass or less, relative to the polymer (A). The content range is, for example, 1 to 70% by mass. When the content of the copolymerizable monomer (a3) ​​is equal to or more than the lower limit, the adhesive layer tends to have excellent adhesive strength, and when it is equal to or less than the upper limit, the adhesive layer tends to have excellent durability.

[0034] Furthermore, when methyl (meth)acrylate and / or ethyl (meth)acrylate is used as the copolymerizable monomer (a3), the content of the structural moiety derived from methyl (meth)acrylate and / or ethyl (meth)acrylate, relative to the polymer (A), is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, particularly preferably 4% by mass or more, and is usually 40% by mass or less, preferably 30% by mass or less, more preferably 25% by mass or less, particularly preferably 10% by mass, and the content range is, for example, 1 to 40% by mass. When the content of the structural moiety derived from methyl (meth)acrylate and / or ethyl (meth)acrylate is equal to or greater than the lower limit, the adhesive layer tends to have excellent adhesive strength, and when it is equal to or less than the upper limit, the polymer (A) tends to have excellent handleability.

[0035] [Functional Group-Containing Ethylenically Unsaturated Monomer (a4)] In the adhesive layer, a functional group-containing ethylenically unsaturated monomer (a4) (excluding the hydroxyl group-containing (meth)acrylate (a2)) can be used as a copolymerization component of the polymer (A) as needed.

[0036] Examples of the functional group-containing ethylenically unsaturated monomer (a4) include functional group-containing monomers having a nitrogen atom, carboxy group-containing monomers, acetoacetyl group-containing monomers, isocyanate group-containing monomers, glycidyl group-containing monomers, etc. Among these, from the viewpoint of imparting cohesive strength and crosslinking promoting action, functional group-containing monomers having a nitrogen atom are preferred, amino group-containing monomers and amide group-containing monomers are more preferred, and amino group-containing monomers are particularly preferred.

[0037] Examples of the amino group-containing monomer include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; and tertiary amino group-containing (meth)acrylates such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide.

[0038] Examples of the amide group-containing monomer include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-n-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethylacrylamide, and N,N-diallyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; and alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide.

[0039] Examples of the carboxy group-containing monomer 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.

[0040] Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0041] Examples of the isocyanate group-containing monomer include 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.

[0042] Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allyl glycidyl (meth)acrylate.

[0043] These functional group-containing ethylenically unsaturated monomers (a4) may be used alone or in combination of two or more.

[0044] When the polymer (A) has a structural moiety derived from the functional group-containing ethylenically unsaturated monomer (a4), the content thereof is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the polymer (A). When the content of the structural moiety derived from the functional group-containing ethylenically unsaturated monomer (a4) is the upper limit or less, the polymer (A) tends to have excellent heat resistance.

[0045] [Other Copolymerizable Monomers (a5)] In the adhesive layer, other copolymerizable monomers (a5) may be used as copolymerization components of the polymer (A) as needed.

[0046] Examples of the other copolymerizable monomer (a5) include (meth)acrylates having an alkoxyalkylene glycol skeleton, such as methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, butoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, butoxypolypropylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, butoxypolytetramethylene glycol (meth)acrylate, methoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate, and butoxypolyoxyethylene polyoxypropylene glycol (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate; phenyl di (meth)acrylate; Examples of suitable monomers include aromatic (meth)acrylic acid ester monomers such as ethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, phenoxy polyethylene glycol-polypropylene glycol-(meth)acrylate, and nonylphenol ethylene oxide adduct (meth)acrylate, as well as monomers such as acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate ester, dialkyl fumarate ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, and dimethylallyl vinyl ketone. These may be used alone or in combination of two or more.

[0047] Furthermore, when the purpose is to increase the molecular weight of the polymer (A), a small amount of a compound having two or more ethylenically unsaturated groups, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, or divinylbenzene, can also be used in combination as the other copolymerizable monomer (a5). These compounds having two or more ethylenically unsaturated groups are highly reactive and do not usually remain unreacted when used as a polymerization component of an acrylic copolymer.

[0048] When the polymer (A) contains a structural portion derived from the other copolymerizable monomer (a5), the content thereof is usually 50% by mass or less, preferably 40% by mass or less, and more preferably 20% by mass or less, based on the polymer (A). When the content ratio of the other copolymerizable monomer (a5) is equal to or less than the upper limit, the remaining unreacted copolymerizable monomer (a5) can be suppressed, and the adhesive layer tends to have excellent heat resistance and adhesive strength.

[0049] The polymer (A) can be obtained by appropriately selecting and polymerizing the copolymerization components.

[0050] Examples of the method for polymerizing the polymer (A) include conventionally known methods such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and photopolymerization. Among these, solution polymerization is preferred in that it can safely and stably produce the polymer (A) with any monomer composition. An example of a preferred method for producing the polymer (A) is shown below.

[0051] First, the copolymerization components and polymerization initiator are mixed or dropped into an organic solvent, followed by solution polymerization to obtain a polymer (A) solution.

[0052] [Organic Solvent] Examples of organic solvents used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. These can be used alone or in combination of two or more. Among these solvents, ethyl acetate is preferred.

[0053] [Polymerization initiator] As the polymerization initiator used in the polymerization reaction, azo polymerization initiators and peroxide polymerization initiators, which are common radical polymerization initiators, can be used. Examples of azo polymerization initiators include 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, (1-phenylethyl)azodiphenylmethane, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). Examples of peroxide polymerization initiators include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-hexyl peroxyneodecanoate, diisopropyl peroxycarbonate, and diisobutyryl peroxide. These may be used alone or in combination of two or more of them, with 2,2'-azobis(2,4-dimethylvaleronitrile) being preferred.

[0054] The amount of the polymerization initiator used, relative to 100 parts by mass of the copolymerization components, is usually 0.001 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, particularly preferably 1.5 parts by mass or more, and most preferably 2 parts by mass or more, and is usually 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 6 parts by mass or less, even more preferably 4 parts by mass or less, particularly preferably 3 parts by mass or less, and most preferably 2.5 parts by mass or less, and the range of the amount used is, for example, 0.001 to 10 parts by mass. When the amount of the polymerization initiator used is equal to or greater than the lower limit, the polymerization rate of the polymer (A) tends to be high, the residual monomer content tends to be reduced, and the weight-average molecular weight of the polymer (A) tends to be within an appropriate range. When the amount is equal to or less than the upper limit, unintended gelation of the polymer (A) tends to be suppressed.

[0055] [Polymerization Conditions, etc.] The solution polymerization may be carried out under conventionally known polymerization conditions. For example, polymerization components and a polymerization initiator may be mixed or dropped into a solvent and polymerized under predetermined polymerization conditions.

[0056] The polymerization temperature in the polymerization reaction is usually 40° C. or higher, preferably 50° C. or higher, more preferably 55° C. or higher, and even more preferably 60° C. or higher in order to ensure a stable reaction, and is usually 120° C. or lower, preferably 90° C. or lower, more preferably 75° C. or lower, and even more preferably 70° C. or lower in order to ensure a stable reaction, and the polymerization temperature range is, for example, 40 to 120° C. If the polymerization temperature is equal to or higher than the lower limit, the activity of the polymerization initiator will be increased, the polymerization rate of the polymer (A) will be increased, and the amount of residual monomer will tend to be reduced, whereas if the polymerization temperature is equal to or lower than the upper limit, unintended gelation of the polymer (A) will tend to be suppressed.

[0057] The polymerization time in the polymerization reaction (when an additional heat treatment described below is performed, the time until the start of the additional heat treatment) is not particularly limited, but is preferably 0.5 hours or more from the addition of the final polymerization initiator, particularly preferably 1 hour or more, further preferably 2 hours or more, and particularly preferably 5 hours or more. The upper limit of the polymerization time is usually 72 hours, and the range of the polymerization time is, for example, 0.5 to 72 hours. The polymerization reaction is preferably carried out while refluxing the solvent, since this facilitates heat removal.

[0058] In the production of the polymer (A), in order to reduce the amount of residual polymerization initiator, it is preferable to thermally decompose the polymerization initiator by an additional heat treatment.

[0059] The temperature in the additional heating step is preferably higher than the 10-hour half-life temperature of the polymerization initiator; specifically, it is usually 40°C or higher, preferably 55°C or higher from the viewpoint of gelation prevention, particularly preferably 75°C or higher, and is usually 150°C or lower, preferably 130°C or lower from the viewpoint of gelation prevention, particularly preferably 95°C or lower; the temperature range is, for example, 40 to 150°C. If the temperature in the additional heating treatment is higher than the lower limit, unreacted copolymerization components and polymerization initiator are less likely to remain in the polymer (A), and the stability over time and thermal stability of the polymer (A) tend to be improved. If the temperature is lower than the upper limit, yellowing of the polymer (A) tends to be suppressed. Thus, the polymer (A) can be obtained.

[0060] The polymer (A) may have a photoactive moiety, such as a polymerizable carbon-carbon double bond group, introduced into its side chain, which can enhance the crosslinking efficiency of the resin composition, allowing the resin composition to be crosslinked in a shorter time, thereby increasing productivity.

[0061] Examples of a method for introducing a polymerizable carbon-carbon double bond group into the side chain of the polymer (A) include a method in which a copolymer containing the above-mentioned hydroxyl group-containing (meth)acrylate (a2) or functional group-containing ethylenically unsaturated monomer (a4) is prepared, and then a compound having a polymerizable carbon-carbon double bond group and a functional group reactive with these functional groups is subjected to a condensation or addition reaction while maintaining the activity of the polymerizable carbon-carbon double bond group.

[0062] Examples of combinations of these functional groups include an epoxy group (glycidyl group) and a carboxy group, an amino group and a carboxy group, an amino group and an isocyanate group, an epoxy group (glycidyl group) and an amino group, a hydroxyl group and an epoxy group, and a hydroxyl group and an isocyanate group. Among these combinations of functional groups, a combination of a hydroxyl group and an isocyanate group is preferred because of the ease of reaction control. Among these, a combination in which the copolymer has a hydroxyl group and the compound has an isocyanate group is preferred.

[0063] Examples of the isocyanate compound having a polymerizable carbon-carbon double bond group include the above-mentioned 2-(meth)acryloyloxyethyl isocyanate and alkylene oxide adducts thereof.

[0064] From the viewpoint of improving adhesiveness and stress relaxation properties, the content of the compound having a functional group reactive with the functional group and a polymerizable carbon-carbon double bond group is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 1 part by mass or less, and particularly preferably 0.1 parts by mass or less, per 100 parts by mass of polymer (A). The lower limit is usually 0 parts by mass. The content range is, for example, 0 to 10 parts by mass.

[0065] In addition to the above-mentioned method, the polymer (A) can also be obtained by preparing a syrup composition containing the copolymerization component or prepolymer, the crosslinking agent (B), the polymerization initiator (C), etc., and irradiating this syrup composition with active energy rays to polymerize it.

[0066] The glass transition temperature (Tg) of the polymer (A) is preferably −20° C. or lower, more preferably −23° C. or lower, even more preferably −25° C. or lower, particularly preferably −30° C. or lower, and especially preferably −40° C. or lower, from the viewpoint of preventing adhesive extrusion by maintaining the shear storage modulus at an appropriate value at high temperatures. The glass transition temperature (Tg) is usually −70° C. or higher, preferably −50° C. or higher. The range of the glass transition temperature (Tg) is, for example, −70 to −20° C.

[0067] The glass transition temperature (Tg) can be determined by reading the temperature at which the loss tangent (tanδ) reaches a maximum when dynamic viscoelasticity is measured in a shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device. For example, the polymer (A) is molded into a cylindrical body with a diameter of 8 mm (height of 0.8 mm), and the loss tangent (tanδ) can be measured using a viscoelasticity measuring device (manufactured by T.A. Instruments, "DHR 2") under the following measurement conditions.

[0068] (Measurement conditions) Measurement jig: Φ8 mm parallel plate Distortion: 0.1% Frequency: 1 Hz Measurement temperature: -60 to 100°C Heating rate: 5°C / min

[0069] The weight average molecular weight (Mw) of polymer (A) is preferably 400,000 or more, more preferably 500,000 or more, even more preferably 550,000 or more, and particularly preferably 600,000 or more, from the viewpoint of obtaining a resin composition with high cohesive strength. Furthermore, the upper limit of the weight average molecular weight (Mw) of polymer (A) is preferably 1.5 million or less, more preferably 1.2 million or less, even more preferably 1.1 million or less, and particularly preferably 1 million or less, from the viewpoint of ease of handling and uniform stirring. The range of the weight average molecular weight (Mw) is, for example, 400,000 to 1.5 million.

[0070] In the present invention, the weight-average molecular weight (Mw) can be determined, for example, as follows. (Method for measuring weight-average molecular weight) 4 mg of polymer (A) is dissolved in 12 mL of tetrahydrofuran (THF) to prepare a measurement sample, and the weight-average molecular weight (Mw) can be determined by measuring a molecular weight distribution curve under the following conditions using a gel permeation chromatography (GPC) analyzer ("HLC-8320GPC" manufactured by Tosoh Corporation). Guard column: TSKguardcolumnHXL Separation column: TSKgelGMHXL (4 columns) Temperature: 40°C Injection volume: 100 μL Polystyrene equivalent Solvent: THF Flow rate: 1.0 mL / min

[0071] The content of the polymer (A) in the resin composition is usually 25% by mass or more, preferably 35% by mass or more, more preferably 45% by mass or more, particularly preferably 55% by mass or more, and usually 99.9% by mass or less, preferably 99.5% by mass or less, more preferably 99% by mass or less, even more preferably 95% by mass or less, particularly preferably 90% by mass or less, and most preferably 85% by mass or less. The content range is, for example, 25 to 99.9% by mass.

[0072] [Crosslinking Agent (B)] The resin composition contains a crosslinking agent (B), and the crosslinking agent (B) contains a polyfunctional crosslinking agent. This allows the resin composition to efficiently form a crosslinked structure. When a crosslinked structure is formed in an adhesive layer using the resin composition, an adhesive layer with improved shape stability can be obtained, and storage and handling properties can be improved, and protrusion of the adhesive layer from the edge during lamination can be suppressed. Furthermore, the formation of a crosslinked structure in the adhesive layer allows for good adhesion and cohesion.

[0073] In the present adhesive layer, the crosslinking agent (B) includes a trifunctional or higher crosslinking agent. Here, "trifunctional or higher crosslinking agent" refers to a crosslinking agent whose molecule contains three or more functional groups active in polymerization or crosslinking. The crosslinking agent (B) preferably includes a tetrafunctional or higher crosslinking agent, more preferably a pentafunctional or higher crosslinking agent. The crosslinking agent may include a hexafunctional or higher crosslinking agent, for example, a 7- to 12-functional crosslinking agent. By including a crosslinking agent containing functional groups equal to or greater than the lower limit, an adhesive layer with good adhesive strength and / or cohesive strength after curing can be obtained. Furthermore, the trifunctional or higher crosslinking agent may include two or more different types of functional groups.

[0074] In one embodiment, the crosslinking agent (B) contains a trifunctional or higher crosslinking agent in an amount of 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total amount of crosslinking agents. The upper limit is not particularly limited and may be 100% by mass. The content of the trifunctional or higher crosslinking agent ranges, for example, from 50 to 100% by mass.

[0075] Examples of the type of crosslinking agent (B) include acrylic crosslinking agents, isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. In one embodiment, the crosslinking agent (B) includes an acrylic crosslinking agent. When the crosslinking agent (B) includes an acrylic crosslinking agent, this is preferred because the reaction is easily controlled. In this embodiment, more preferably, the crosslinking agent (B) includes a polyfunctional (meth)acrylate.

[0076] Examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylic monomers and polyfunctional (meth)acrylic oligomers having two or more (meth)acryloyl groups, which may be used alone or in combination of two or more.

[0077] Examples of the polyfunctional (meth)acrylic monomer include pentanediol di(meth)acrylate, hexadiol di(meth)acrylate, heptanediol di(meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate, undecanediol di(meth)acrylate, dodecanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether 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 tri(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone-modified tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate Pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tris(acryloxyethyl)isocyanurate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate , tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, di(meth)acrylate of hydroxypivalic acid neopentyl glycol ε-caprolactone adduct, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, etc.

[0078] Examples of the polyfunctional (meth)acrylic oligomer include polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, and polyether (meth)acrylate oligomers.

[0079] The crosslinking agent (B) preferably contains a glycol structure or a urethane bond from the viewpoint of imparting appropriate flexibility to the cured product.

[0080] The content of the crosslinking agent (B) in the resin composition is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, relative to 100 parts by mass of the polymer (A) from the viewpoint of imparting cohesive strength, adhesive strength, shape stability, and / or durability when formed into a laminate, and from the viewpoint of maintaining the flexibility of the adhesive layer, it is usually 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 5 parts by mass or less, and extremely preferably 3 parts by mass or less. The content range of the crosslinking agent (B) is, for example, 0.1 to 10% by mass.

[0081] [Polymerization Initiator (C)] In the present invention, the resin composition contains a polymerization initiator (C), and the polymerization initiator (C) includes a cleavage-type photopolymerization initiator. In this specification, the term "polymerization initiator" is a general term for compounds that are activated by stimuli such as heat or light to generate anions, cations, radicals, etc., which initiate a polymerization initiation reaction. In the present invention, it is preferable to use a compound that generates radicals (radical generator, radical polymerization initiator) because its polymerization reactivity is less affected by polar groups and the surrounding environment. Furthermore, the term "photopolymerization initiator" is a general term for polymerization initiators that are activated by exposure to active energy rays such as electromagnetic waves and radiation. Furthermore, the term "cleavage-type polymerization initiator" refers to a polymerization initiator in which intramolecular bonds are cleaved upon activation. Hereinafter, as an example of an embodiment, a case where the polymerization initiator is a cleavage-type photopolymerization initiator that generates radicals (cleavage-type photoradical polymerization initiator) will be described in detail. However, initiators other than radical polymerization initiators may be used as long as the effects of the present invention are obtained.

[0082] Radical polymerization initiators are broadly classified into two types based on the radical generation mechanism. More specifically, they are broadly divided into cleavage-type radical polymerization initiators, which can generate radicals by cleaving and decomposing the single bond of the initiator itself, and hydrogen abstraction-type radical polymerization initiators, which can generate radicals by an excited initiator abstracting hydrogen from a hydrogen donor in the system. The cleavage-type radical polymerization initiator is preferred because it does not cause unsaturation of the polymer and can suppress rigidification. Furthermore, when a cleavage-type photoradical polymerization initiator is used, it is preferred because it has high photosensitivity. On the other hand, in any embodiment, the polymerization initiator (C) may further contain a hydrogen abstraction-type radical polymerization initiator. The hydrogen abstraction-type radical polymerization initiator is preferred because it can incorporate the polymer (A) into a crosslinked structure by a hydrogen abstraction reaction. When a hydrogen abstraction-type radical polymerization initiator is used, it is preferred because it does not produce photodecomposition products.

[0083] In the present invention, from the viewpoint of suppressing rigidification of the polymer (A) due to unexpected unsaturation, the polymerization initiator (C) contains a cleavage-type photopolymerization initiator. Preferably, 50% by mass or more of the polymerization initiator (C) is a cleavage-type photopolymerization initiator, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and in a specific embodiment, 100% by mass of the polymerization initiator (C) is a cleavage-type photopolymerization initiator.

[0084] Examples of the cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)benzyl]phenyl}-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), 2-benzyl-2-dimethylamino-1-(4-morpho- Examples of suitable amines include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, and derivatives thereof.

[0085] The content of the polymerization initiator (C) in the resin composition is usually 0.1 parts by mass or more, and 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 4 parts by mass or less, particularly preferably 3 parts by mass or less, especially preferably 2.5 parts by mass or less, and most preferably 2 parts by mass or less, relative to 100 parts by mass of the polymer (A), and the range of the content of the polymerization initiator (C) is, for example, 0.1 to 10 parts by mass. When the content is equal to or more than the lower limit, poor curing tends to be prevented, and when it is equal to or less than the upper limit, it tends to be easy to suppress a decrease in solution stability such as precipitation from the pressure-sensitive adhesive composition, and it tends to be easy to suppress problems of embrittlement and coloration.

[0086] [Other Components] The resin composition may contain, as needed, various additives such as monofunctional (meth)acrylates, silane coupling agents, ultraviolet absorbers, plasticizers, tackifiers, antioxidants, light stabilizers, metal deactivators, antiaging agents, moisture absorbers, rust inhibitors, and inorganic particles as "other components" as long as the effects of the present invention are not impaired. Furthermore, the resin composition may contain, as needed, reaction catalysts such as tertiary amine compounds, quaternary ammonium compounds, and tin laurate compounds. These may be used alone or in combination of two or more.

[0087] [Monofunctional (meth)acrylate] The resin composition may further contain a monofunctional (meth)acrylate having one (meth)acryloyl group, if necessary. By containing a monofunctional (meth)acrylate having one (meth)acryloyl group, the molecular weight between crosslinking points of the cured product can be increased, which is preferable in that the degree of freedom of movement of the molecular chain is increased and it becomes easier to obtain a cured product with excellent stress relaxation properties.

[0088] Examples of the monofunctional (meth)acrylate include ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and dodecyl (meth)acrylate. (meth)acrylate, isododecyl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, cyclononyl (meth)acrylate, cyclodecyl (meth)acrylate, isobornyl (meth)acrylate acrylate, norbornyl (meth)acrylate, adamantyl (meth)acrylate, tricyclodecane dimethanol acrylate, ethoxylated-o-phenylphenol acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxydiethylene glycol benzyl (meth)acrylates such as chol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, 2-hydroxy-o-phenylphenol propyl acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxypropyl hydrophthalate, and 2-(meth)acryloyloxypropyl hexahydrophthalate;Benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, 2-naphthyl (meth)acrylate, 9-anthracenyl (meth)acrylate, 1-pyrenylmethyl (meth)acrylate, benzyl (meth)acrylate, tricyclodecane dimethanol monoacrylate monocarboxylic acid, dicyclopentanyl acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, trimethylolpropane mono(meth)acrylate, glycerin mono(meth)acrylate, pentaerythritol mono(meth)acrylate, diglycerin mono(meth)acrylate, ditrimethylolpropane mono(meth)acrylate, dipentaerythritol Examples of suitable acrylates include thritol mono(meth)acrylate, ethoxylated trimethylolpropane mono(meth)acrylate, propoxylated trimethylolpropane mono(meth)acrylate, ethoxylated glycerin mono(meth)acrylate, propoxylated glycerin mono(meth)acrylate, ethoxylated pentaerythritol mono(meth)acrylate, propoxylated pentaerythritol mono(meth)acrylate, ethoxylated ditrimethylolpropane mono(meth)acrylate, propoxylated ditrimethylolpropane mono(meth)acrylate, alkylene oxide-modified diglycerin mono(meth)acrylate, and alkylene oxide-modified dipentaerythritol mono(meth)acrylate, as well as monofunctional (meth)acrylic oligomers such as monofunctional urethane (meth)acrylate, monofunctional epoxy (meth)acrylate, and monofunctional polyester (meth)acrylate. These may be used alone or in combination of two or more. ,

[0089] Among these, as the monofunctional (meth)acrylic oligomers, monofunctional urethane (meth)acrylate, monofunctional polyester (meth)acrylate, monofunctional epoxy (meth)acrylate, etc. are preferred, and monofunctional urethane (meth)acrylate is more preferred.

[0090] The monofunctional urethane (meth)acrylate is highly polar and has a long chain length, and therefore the polymer chains are entangled to obtain high recovery, and furthermore, by having an oxypropylene structure with high molecular rotation, a low shear storage modulus is obtained, which is particularly effective.

[0091] When a monofunctional (meth)acrylate is contained, the content thereof is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or more, relative to 100 parts by mass of polymer (A), from the viewpoint of adjusting the crosslinking density and imparting appropriate flexibility to the cured product. The upper limit is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and particularly preferably 30 parts by mass or less, and the content ranges, for example, from 1 to 40 parts by mass.

[0092] [Silane coupling agent] Silane coupling agent is an organosilicon compound that contains one or more reactive functional groups and one or more alkoxy groups bonded to silicon atoms in its structure.The reactive functional groups include, for example, epoxy group, (meth)acryloyl group, mercapto group, hydroxyl group, carboxy group, amino group, amide group, and isocyanate group, and among these, epoxy group and mercapto group are preferred from the viewpoint of balance of durability.

[0093] The alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms, from the viewpoint of durability and storage stability, and is particularly preferably a methoxy group or an ethoxy group. The silane coupling agent may also contain an organic substituent other than the reactive functional group and the alkoxy group bonded to the silicon atom, such as an alkyl group or a phenyl group.

[0094] Examples of the silane coupling agent include monomeric epoxy group-containing silane coupling agents, which are silane compounds such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and silane coupling agents in which a part of the silane compound is hydrolyzed and condensed, or in which the silane compound is polymerized with methyltriethoxysilane, ethyltriethoxysilane, oligomeric epoxy group-containing silane coupling agents which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as methyltrimethoxysilane and ethyltrimethoxysilane; monomeric mercapto group-containing silane coupling agents which are silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane and 3-mercaptopropylmethyldimethoxysilane; and silane coupling agents which are obtained by hydrolysis and condensation polymerization of a part of the silane compounds or by condensation polymerization of the silane compounds with methyl groups. oligomeric mercapto group-containing silane coupling agents which are silane compounds obtained by co-condensation of alkyl group-containing silane compounds such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane; coupling agents: amino group-containing silane coupling agents such as N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane;Examples of suitable silane coupling agents include vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane. These may be used alone or in combination of two or more.

[0095] Among these, epoxy group-containing silane coupling agents and mercapto group-containing silane coupling agents are preferably used because of their excellent durability, and among these, epoxy group-containing silane coupling agents are particularly preferred.

[0096] When the resin composition contains a silane coupling agent, the content thereof is usually 0.005 parts by mass or more, preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and usually 10 parts by mass or less, preferably 5.0 parts by mass or less, particularly preferably 1.0 part by mass or less, relative to 100 parts by mass of the polymer (A). The content range is, for example, 0.05 to 10 parts by mass. When the content is within the above range, adhesive strength and durability tend to be improved.

[0097] [Ultraviolet Absorber] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, benzoxazine-based ultraviolet absorbers, etc. These ultraviolet absorbers can be used alone or in combination of two or more.

[0098] The content of the ultraviolet absorber is usually 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the polymer (A), and the content ranges from 0.01 to 20 parts by mass, etc. When the content is equal to or more than the lower limit, lightfastness reliability tends to be improved, and when the content is equal to or less than the upper limit, yellowing resistance tends to be improved.

[0099] [Plasticizer] The plasticizer may be, but is not limited to, at least one selected from the group consisting of polyisobutylene, polyisoprene, polybutadiene, amorphous polyolefins and their copolymers, silicone, polyacrylate, oligomeric polyurethane, ethylene-propylene copolymer, etc., or any combination or mixture thereof. Among these, polyisobutylene is preferred. The polyisobutylene plasticizer may be, for example, one selected from the OPPANOLB series, which is commercially available from BASF under the trade name OPPANOL.

[0100] When the resin composition contains a plasticizer, the content thereof is not particularly limited and is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, relative to 100 parts by mass of the polymer (A). The content range is, for example, 0.1 to 20 parts by mass.

[0101] [Tackifier] The resin composition may contain a tackifier to improve the adhesive strength of the adhesive layer. Examples of tackifiers include terpene resins such as polyterpenes (e.g., α-pinene resins, β-pinene resins, and limonene resins) and aromatic-modified polyterpene resins (e.g., phenol-modified polyterpene resins), coumaran-indene resins, petroleum-based resins such as C5 hydrocarbon resins, C9 hydrocarbon resins, C5 / C9 hydrocarbon resins, and dicyclopentadiene resins, and rosins such as modified rosin, hydrogenated rosin, polymerized rosin, and rosin esters.

[0102] When the resin composition contains a tackifier, the content thereof is not particularly limited and is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, and usually 20 parts by mass or less, preferably 15 parts by mass or less, relative to 100 parts by mass of the polymer (A). The content range is, for example, 0.1 to 20 parts by mass.

[0103] [Rust inhibitor] The resin composition may contain a rust inhibitor to prevent corrosion when the adherend includes a corrosive portion such as metal wiring, etc. Examples of the rust inhibitor include triazoles and benzotriazoles.

[0104] When the resin composition contains a rust inhibitor, the content thereof is usually 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and 5 parts by mass or less, preferably 3 parts by mass or less, relative to 100 parts by mass of the polymer (A). The content range is, for example, 0.01 to 5 parts by mass.

[0105] <<Method for manufacturing the present adhesive layer>> Next, a method for manufacturing the present adhesive layer will be described. However, the following description is an example of a method for manufacturing the present adhesive layer, and the present adhesive layer is not limited to layers manufactured by this manufacturing method.

[0106] This adhesive layer can be produced by preparing a resin composition containing the polymer (A), crosslinking agent (B), polymerization initiator (C), and other components as needed, molding the resin composition into a layer, crosslinking, i.e., polymerizing, to harden it, and then processing it appropriately as needed.

[0107] The resin composition may be prepared by kneading the raw materials using a temperature-controllable kneader (for example, a single-screw extruder, a twin-screw extruder, a planetary mixer, a twin-screw mixer, a pressure kneader, etc.). When kneading the various raw materials, various additives such as a silane coupling agent and an antioxidant may be blended together with the resin in advance and then supplied to the kneader, or all materials may be melt-mixed in advance and then supplied, or a masterbatch in which only the additives are concentrated in the resin may be prepared and then supplied.

[0108] The resin composition can be formed into a layer by any known method, such as wet lamination, dry lamination, extrusion casting using a T-die, extrusion lamination, calendaring, inflation, injection molding, or liquid injection curing. Among these, when producing the adhesive layer, wet lamination, extrusion casting, and extrusion lamination are preferred.

[0109] In addition, the resin composition can be cured by irradiating it with active energy rays or by heating, and when active energy rays are used, the adhesive layer can be produced by irradiating a molded product of the resin composition, for example, a layered product, with active energy rays. In addition to irradiating it with active energy rays, further curing can also be achieved by heating.

[0110] Furthermore, the irradiation energy, irradiation time, irradiation method, etc. of the active energy ray are not particularly limited as long as they can activate the polymerization initiator (C) and polymerize the photoreactive component such as the (meth)acrylic acid ester compound.

[0111] Examples of the active energy rays in the active energy ray irradiation include light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, and visible light rays, as well as ionizing radiation such as X-rays, α-rays, β-rays, γ-rays, electron beams, proton beams, and neutron beams. Among these, ultraviolet rays are preferred from the viewpoints of suppressing damage to optical device components and controlling reactions. Furthermore, ultraviolet rays are preferred from the viewpoints of curing speed, ease of availability of an irradiation device, cost, and the like.

[0112] Examples of light sources for ultraviolet irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, and LED lamps, all of which emit light in the wavelength range of 150 to 450 nm. Of these, it is preferable to use high-pressure mercury lamps, metal halide lamps, and LED lamps.

[0113] The amount of active energy ray irradiation (cumulative amount of light) is preferably 0.03 J / cm from the viewpoint of curing. ２ More preferably, 0.1 J / cm ２ More preferably, 0.3 J / cm ２ or more, and preferably 3 J / cm ２ Below, 2J / cm ２ or less, more preferably 1.5 J / cm ２ The following is the result.

[0114] The present pressure-sensitive adhesive layer can also be provided as a pressure-sensitive adhesive layer with a release film, which has a configuration in which a release film is laminated on one or both sides. In particular, from the viewpoint of preventing blocking and adhesion of foreign matter, it is preferable to coat both sides of the present pressure-sensitive adhesive layer with a release film.

[0115] When release films are provided on both sides of the adhesive layer, it is preferable to use a laminate structure in which a light release film with a relatively low release strength and a heavy release film with a relatively high release strength are laminated together. When using an adhesive layer with release films provided on both sides, first, one release film (light release film) is peeled off to expose one side of the adhesive layer, and then the adhesive layer is bonded to an image display device component (referred to as a first component), and then the other release film (heavy release film) is peeled off to expose the other side of the adhesive layer, and the image display device component (referred to as a second component) is bonded to the other side of the adhesive layer.

[0116] As such a release film, a known release film can be appropriately used. As the base material for the release film, for example, a film such as a polyester film, a polyolefin film, a polycarbonate film, a polystyrene film, an acrylic film, a triacetyl cellulose film, or a fluororesin film that has been subjected to a release treatment by coating with a release agent such as a silicone resin, or release paper, etc., can be appropriately selected and used. Among these, polyester film is preferred, polyethylene terephthalate (PET) film is more preferred, and biaxially oriented PET film is particularly preferred because of its excellent transparency, mechanical strength, heat resistance, flexibility, etc. Furthermore, a release film can be used in which a release layer formed by curing a curable silicone-based release agent containing a silicone resin as a main component is provided on the base material.

[0117] The peel strength between the adhesive layer and the release film is preferably 0.05 N / cm or more, more preferably 0.06 N / cm or more, even more preferably 0.07 N / cm or more, and is preferably 1.5 N / cm or less, more preferably 1.2 N / cm or less, even more preferably 1.0 N / cm or less. The peel strength between the adhesive layer and the release film is measured in a 180° peel test at a test speed of 300 m / min. If the peel strength between the adhesive layer and the release film is within the above range, peel marks can be prevented when the release film is peeled from the adhesive layer.

[0118] Generally, when an adhesive layer having excellent flexibility is used as an adhesive layer with a release film, if the release force of the release film is high, the adhesive layer is flexible, and when the release film is peeled off, the adhesive layer tends to deform and leave peeling marks. For this reason, the release film used for the adhesive layer having excellent flexibility, particularly the light release film, is preferably a release film that can be peeled off with even less force than the light release type release films that have been commonly used in the past.

[0119] However, if the thickness of the release agent layer is increased in order to make the release film easier to release, depending on the type of release agent used, components derived from the release agent layer may migrate to the surface of the adhesive layer, thereby impairing the reliability of the adhesive layer. For this reason, it is preferable that the release film has good releasability from the adhesive layer and little migration of the release agent into the adhesive layer.

[0120] The peak intensity of silicon atoms measured by a fluorescent X-ray analyzer on the adhesive surface exposed by peeling off the release film from this adhesive layer is preferably 100 cps or less.If the peak intensity is 100 cps or less, it is preferable that the release agent migrated to the adhesive layer surface does not impair the reliability when the adhesive layer is made into a laminate.From this point of view, the peak intensity is more preferably 90 cps or less, even more preferably 80 cps or less, and particularly preferably 70 cps or less.The lower limit is usually 0 cps.

[0121] The thickness of the release film is not particularly limited, but from the viewpoint of processability and handleability, for example, it is preferably 10 μm or more, more preferably 25 μm or more, particularly preferably 35 μm or more, and is preferably 250 μm or less, more preferably 200 μm or less, particularly preferably 190 μm or less.

[0122] The release film may be embossed or processed to have various irregularities (such as a conical, pyramidal, or hemispherical shape) as needed, and the surface may be subjected to various surface treatments such as corona treatment, plasma treatment, and primer treatment.

[0123] In another embodiment of the method for producing the adhesive layer, the resin composition can be dissolved in an appropriate solvent and various coating methods can be used. When using a coating method, the adhesive layer can be obtained by curing with heat in addition to curing with active energy rays. When using a coating method, the thickness of the adhesive layer can be adjusted by the coating thickness and the solids concentration of the coating solution.

[0124] The coating method can be a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing, or bar coating.

[0125] To produce the adhesive layer using the coating method, for example, the resin composition is dissolved in a solvent, and then coated on the release film, the component sheet, or the flexible image display component, dried, and cured by the above-mentioned active energy ray irradiation, thereby forming the adhesive layer. Furthermore, the adhesive layer obtained by the coating method may be laminated with the above-mentioned release film, if necessary. In this case, the adhesive layer may be coated on a release film, dried, cured by active energy ray irradiation, and then laminated with a release film, or the adhesive layer may be coated on a release film, dried, laminated with a release film, and then cured by active energy ray irradiation to form the adhesive layer.

[0126] The solvent is not particularly limited as long as it dissolves the resin composition, and examples thereof include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, and ethyl acetoacetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic solvents such as toluene and xylene; and alcohol solvents such as methanol, ethanol, and propyl alcohol. These can be used alone or in combination of two or more. Among these, ethyl acetate, acetone, methyl ethyl ketone, and toluene are preferred in terms of solubility, drying properties, cost, and the like, and ethyl acetate is particularly preferred.

[0127] In view of drying properties, the content of the solvent is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, relative to 100 parts by mass of the polymer (A), while it is preferably 1 part by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, and particularly preferably 150 parts by mass or more.

[0128] The solvent content in the resin composition after drying is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0% by mass.

[0129] The drying temperature is usually 40° C. or higher, preferably 45° C. or higher, more preferably 50° C. or higher, and particularly preferably 55° C. or higher, and is usually 150° C. or lower, preferably 140° C. or lower, more preferably 130° C. or lower, and particularly preferably 120° C. or lower, the temperature range being, for example, 40 to 150° C. When the temperature is within this range, the solvent can be removed efficiently and relatively safely while suppressing thermal deformation of the release film.

[0130] The drying time is usually 1 minute or more, preferably 3 minutes or more, more preferably 3 minutes or more, and usually 30 minutes or less, preferably 25 minutes or less, more preferably 20 minutes or less, for example, in the range of 1 to 30 minutes. Within this time range, the solvent can be removed efficiently and sufficiently.

[0131] Drying methods include, for example, drying with a dryer, drying with a heated roll, drying by blowing hot air onto the film, etc. Among these, using a dryer is preferred because it allows for uniform and easy drying. These methods can be used alone or in combination of two or more.

[0132] The present adhesive layer obtained by the coating method may be provided with the above-mentioned release film on at least one side thereof from the viewpoint of preventing blocking and adhesion of foreign matter. That is, the present adhesive layer obtained by the coating method may be provided as an adhesive layer with a release film (adhesive layer laminate) having a configuration in which a release film is laminated on one or both sides thereof.

[0133] Furthermore, when the resin composition is a syrup composition containing a copolymerization component and / or a prepolymer in which the copolymerization component is partially polymerized, a crosslinking agent (B), a polymerization initiator (C), etc., the adhesive layer can be obtained by the following manufacturing method (syrup method).

[0134] In the syrup method, a syrup composition is prepared, and this syrup composition is irradiated with active energy rays to polymerize. Subsequently, the syrup composition, to which additional crosslinking agent (B), polymerization initiator (C), etc. are added as needed, is coated onto a release film or the like using the coating method described above, and then the adhesive layer is obtained by curing the syrup composition by irradiating with active energy rays or heating. The crosslinking agent (C), etc. may be added to the syrup composition from the beginning, or may be added to the syrup composition after prepolymerization. Furthermore, in the syrup method, polymerization and curing may be performed in a single step.

[0135] In another embodiment of the syrup method, the adhesive layer can be produced by dissolving the syrup composition in a solvent, coating it on a release film, drying it, and then polymerizing and curing it by irradiating it with active energy rays.

[0136] In the syrup method, the release film, active energy rays, solvent, etc., the method for preparing the resin composition, the coating method, the conditions for irradiating active energy rays, the drying conditions, etc. may be the same as those described above.

[0137] The present adhesive layer obtained by the syrup method may be provided with the release film described above on at least one side thereof from the viewpoint of preventing blocking and adhesion of foreign matter. That is, the present adhesive layer obtained by the syrup method may be provided as an adhesive layer with a release film (adhesive layer laminate) having a configuration in which a release film is laminated on one or both sides thereof.

[0138] The adhesive layer thus obtained may be a single layer consisting of only the adhesive layer formed from the adhesive composition, or may be a multi-layer in which multiple adhesive layers including the adhesive layer and other adhesive layers are laminated.

[0139] <<Viscoelastic Properties of the Adhesive Layer>> <Shear Storage Modulus (G')> The shear storage modulus (G') that the adhesive layer may have will be described in detail below. In this specification, the shear storage modulus at a specific temperature (X°C) is referred to as the shear storage modulus (G'(X°C)). The shear storage modulus (G'(X°C)) is measured, for example, as follows. The adhesive layer is repeatedly laminated to a thickness of 0.7 to 1.2 mm (e.g., 0.8 mm), and then punched out to a diameter of 8 mm. The obtained sample is subjected to dynamic viscoelasticity measurement using a rheometer under the conditions of a measurement jig: 8 mm diameter parallel plates, a frequency of 1 Hz, a measurement temperature of -50 to 150°C, and a heating rate of 5°C / min, and the shear storage modulus (G') value at each temperature is read.

[0140] In one embodiment of the present invention, the shear storage modulus (G'(-30°C)) of the adhesive layer at -30°C is usually 100 kPa or more, preferably 150 kPa or more, more preferably 200 kPa or more, even more preferably 250 kPa or more, and usually 1200 kPa or less, preferably 1000 kPa or less, more preferably 700 kPa or less, even more preferably 600 kPa or less.

[0141] When the shear storage modulus (G'(-30°C)) of the adhesive layer at -30°C is equal to or greater than the lower limit, an adhesive layer with appropriate cohesive strength and shape stability can be obtained. When the shear storage modulus (G'(-30°C)) of the adhesive layer at -30°C is equal to or less than the upper limit, for example, when the adhesive layer is attached to a component sheet to form a laminate or laminate, the interlayer stress when the laminate or laminate is bent can be reduced, particularly at low to high temperatures, and peeling or damage to the component sheet or flexible image display device components due to stress can be suppressed.

[0142] In one embodiment of the present invention, the shear storage modulus (G'(-20°C)) of the pressure-sensitive adhesive layer at -20°C is 300 kPa or less, preferably 250 kPa or less, more preferably 200 kPa or less, even more preferably 180 kPa or less, and is usually 10 kPa or more, preferably 30 kPa or more, more preferably 50 kPa or more, even more preferably 100 kPa or more, and particularly preferably 120 kPa or more.

[0143] When the shear storage modulus (G'(-20°C)) of the adhesive layer at -20°C is equal to or less than the upper limit, flexibility can be maintained even at low temperatures, and an adhesive layer with good bending suitability at low temperatures can be obtained. Furthermore, when the shear storage modulus (G'(-20°C)) of the adhesive layer at -20°C is equal to or more than the lower limit, appropriate cohesion can be obtained at low temperatures.

[0144] In one embodiment of the present invention, the shear storage modulus (G'(25°C)) of the adhesive layer at 25°C is usually 5 kPa or more, preferably 10 kPa or more, more preferably 15 kPa or more, even more preferably 20 kPa or more, and particularly preferably 30 kPa or more, and is usually 100 kPa or less, preferably 80 kPa or less, and more preferably 50 kPa or less.

[0145] When the shear storage modulus (G'(25°C)) of the adhesive layer at 25°C is equal to or greater than the lower limit, an adhesive layer with good shape stability can be obtained. When the shear storage modulus (G'(25°C)) of the adhesive layer at 25°C is equal to or less than the upper limit, an adhesive layer with high adhesiveness can be obtained.

[0146] In one embodiment of the present invention, the shear storage modulus (G'(60°C)) of the adhesive layer at 60°C is usually 5 kPa or more, preferably 10 kPa or more, more preferably 15 kPa or more, and even more preferably 20 kPa or more, and is usually 40 kPa or less, preferably 35 kPa or less, and more preferably 30 kPa or less.

[0147] When the shear storage modulus (G'(60°C)) of the adhesive layer at 60°C is equal to or greater than the lower limit, an adhesive layer with good shape stability can be obtained, and when the shear storage modulus (G'(60°C)) of the adhesive layer at 60°C is equal to or less than the upper limit, an adhesive layer with high adhesiveness can be obtained.

[0148] In one embodiment of the present invention, the shear storage modulus (G'(85°C)) of the adhesive layer at 85°C is 5.0 kPa or more, more preferably 8 kPa or more, even more preferably 10 kPa or more, particularly preferably 12 kPa or more, and is 30 kPa or less, preferably 28 kPa or less, more preferably 27 kPa or less, and even more preferably 26 kPa or less.

[0149] When the shear storage modulus (G'(85°C)) of the adhesive layer at 85°C is equal to or greater than the lower limit, an adhesive layer having a sufficient degree of hardening and shape stability at high temperatures can be obtained, and when the shear storage modulus (G'(85°C)) of the adhesive layer at 85°C is equal to or less than the upper limit, an adhesive layer having a moderate degree of hardening and flexibility can be obtained.

[0150] Examples of a method for adjusting the shear storage modulus (G') at each temperature to fall within the above range include a method for adjusting the composition or molecular weight of the polymer (A) or the type or content of the crosslinking agent (B) or polymerization initiator (C), as well as a method for adjusting the amount of active energy ray irradiation, although the method is not limited to these.

[0151] <Glass Transition Temperature> In one embodiment, the adhesive layer according to the present invention preferably has a glass transition temperature (Tg) defined by the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in a shear mode at a frequency of 1 Hz of -15°C or lower, more preferably -20°C or lower, even more preferably -25°C or lower, and particularly preferably -30°C or lower, and is usually -100°C or higher, preferably -90°C or higher, more preferably -80°C or higher, and even more preferably -70°C or higher. The glass transition temperature range is, for example, -100 to -15°C. When the glass transition temperature is equal to or lower than the upper limit, an adhesive layer that exhibits good bending suitability even in low-temperature environments tends to be obtained. Furthermore, when the glass transition temperature is equal to or higher than the lower limit, an appropriate cohesive property tends to be obtained.

[0152] The glass transition temperature (Tg) can be obtained by reading the temperature at which the loss tangent (Tan δ) reaches its maximum value, i.e., the peak temperature, from the dynamic viscoelastic spectrum data in shear mode obtained by the same method as in the measurement of the shear storage modulus (G') described above. When multiple maximum values ​​exist in the viscoelastic spectrum, the "peak temperature" refers to the temperature at which the largest maximum value is reached.

[0153] Examples of a method for adjusting the glass transition temperature (Tg) within the above range include a method for adjusting the composition or molecular weight of the polymer (A) or the type or content of the crosslinking agent (B) or polymerization initiator (C), and a method for adjusting the amount of active energy ray irradiation, although the method is not limited to these.

[0154] From the viewpoint of obtaining an appropriate cohesive force, the gel fraction of the adhesive layer is 45% or more, preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. From the viewpoint of obtaining an appropriate flexibility, the gel fraction is 95% or less, preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, and particularly preferably 75% or less. The gel fraction range is, for example, 45 to 95%.

[0155] The gel fraction is measured, for example, as follows: A pre-measured mass of the adhesive layer and a 150-mesh SUS (stainless steel) wire mesh are prepared. The adhesive layer is then wrapped in the SUS wire mesh and immersed in ethyl acetate at 23°C for 24 hours. The adhesive layer is then dried at 70°C for 4.5 hours, and the mass of the SUS wire mesh is measured. The mass of the insoluble adhesive layer remaining in the wire mesh (mass after immersion) is calculated by subtracting the mass of the SUS wire mesh from the mass of the adhesive layer before immersion in ethyl acetate (mass before immersion). The gel fraction (%) is calculated as the percentage of the mass of the insoluble adhesive layer remaining in the wire mesh (mass after immersion) relative to the mass of the adhesive layer before immersion in ethyl acetate (mass before immersion).

[0156] Examples of methods for adjusting the gel fraction within the above range include, but are not limited to, a method of adjusting the composition or molecular weight of the polymer (A) or the type or content of the crosslinking agent (B) or polymerization initiator (C), and a method of adjusting the amount of active energy ray irradiation.

[0157] <Adhesive Strength> In one embodiment, the adhesive layer has an adhesive strength of 5.0 N / cm or more to a plasma-treated polyethylene terephthalate (PET) substrate at a temperature of 23°C and a peeling speed of 300 mm / min. Having an adhesive strength of 5.0 N / cm or more to a PET substrate prevents peeling of the adhesive layer edge surface, resulting in excellent bonding reliability at the peripheral edge. From this perspective, the adhesive strength to the PET substrate is more preferably 6.0 N / cm or more, even more preferably 6.5 N / cm or more, and particularly preferably 8.0 N / cm or more. While the upper limit of the adhesive strength is not particularly limited, it is typically 50 N / cm, preferably 30 N / cm, from the viewpoint of reworkability, and the adhesive strength ranges, for example, from 5.0 to 50 N / cm.

[0158] In one embodiment, the adhesive layer preferably has an adhesive strength of 4.5 N / cm or more to a plasma-treated glass substrate at a temperature of 23°C and a peeling rate of 300 mm / min. Having an adhesive strength of 4.5 N / cm or more to a glass substrate tends to prevent peeling at the edge of the adhesive layer and provide excellent bonding reliability at the peripheral edge. From this perspective, the adhesive strength to the glass substrate is more preferably 5.0 N / cm or more, and even more preferably 6.0 N / cm or more. While the upper limit of the adhesive strength is not particularly limited, it is typically 50 N / cm, preferably 30 N / cm, from the viewpoint of reworkability, and the adhesive strength ranges from 4.5 to 50 N / cm, for example.

[0159] The adhesive strength is measured, for example, as follows. A 100 μm thick polyethylene terephthalate (PET) film and this adhesive layer are laminated, and the other side is roll-pressed onto a plasma-treated polyethylene terephthalate (PET) or soda-lime glass substrate to obtain a laminate. The laminate is then autoclaved (temperature 60°C, gauge pressure 0.2 MPa, 20 minutes) to obtain a finished laminated sample for adhesive strength measurement. This sample is used to peel at a peel angle of 180° and a peel rate of 300 mm / min under an environment of 23°C and 50% RH, and the peel force (N / cm) is taken as the adhesive strength.

[0160] <Restoration Rate> The adhesive layer has a thickness of 0.5 to 1.2 mm, and the maximum strain (γ max(25) ) and the strain (γ min(25) ) using the following formula, the restoration rate is preferably 70% or more, and more preferably 75% or more. Since a higher restoration rate is preferable, the upper limit of the restoration rate is 100%, and the range of the restoration rate is, for example, 70 to 100%. Restoration rate (%) = [(γ max(25) -γ min(25) ) / γ max(25) ]×100 Also, the maximum strain (γ max(25)) is preferably 600% or less, more preferably 550% or less, even more preferably 500% or less, particularly preferably 400% or less, and particularly preferably 350% or less. In a specific embodiment, the thickness in the recovery test is 0.6 mm or more and 1.00 mm or less, and may be 0.8 mm.

[0161] If the adhesive layer has such a recovery rate, the adhesive layer can be made to be highly flexible, and even when attached to a component sheet and subjected to a folding operation at low or high temperatures, no fold marks will remain due to being placed in a bent state.

[0162] <Room Temperature Dynamic Bending Test> After a room temperature dynamic bending test, the pressure-sensitive adhesive layer preferably shows no crease or peeling at the interface with the adherend. The conditions for the room temperature dynamic bending test are not particularly limited, and a conventional method can be used. The evaluation values ​​in this specification can be measured by the method described in the Examples below.

[0163] <Static bending test under high temperature and high humidity> After a static bending test under high temperature and high humidity, the pressure-sensitive adhesive layer preferably exhibits no peeling at the interface with the adherend and has high resilience (for example, an internal angle of the bend of 30° or more). The conditions for the static bending test under high temperature and high humidity are not particularly limited, and a conventional method can be used. The evaluation values ​​in this specification can be measured by the method described in the examples below.

[0164] <Preferred use of the adhesive layer> In one embodiment, the adhesive layer is suitable for bonding optical components.Specifically, it is suitable for bonding components constituting a display, particularly components used for manufacturing a display, and is suitable for use as an adhesive layer for bonding components of an image display device such as an image display panel and a protective panel or touch panel disposed on its front side (visible side), or components constituting the image display device components.In addition, the same components as those described below can be used for the image display device components.

[0165] <<Laminate>> In one embodiment, the present invention is a laminate comprising one or more components for an image display device and the adhesive layer. (Hereinafter, the laminate according to this embodiment may be referred to as "the laminate.") In one embodiment, the laminate comprises two components of an image display device and the adhesive layer interposed between the two components of the image display device. Of the components of the laminate, the adhesive layer can adopt the configuration and characteristics of the adhesive layer described above. Elements other than the adhesive layer will be described below.

[0166] (Image Display Device Components) Examples of image display device components constituting the present laminate include flexible image display device components. Examples of the flexible image display device components include image display panels such as organic electroluminescence (EL) displays, cover lenses (cover films), surface protection panels (surface protection films), polarizing plates, color filters, polarizing elements, retardation films, barrier films, viewing angle compensation films, brightness enhancement films, contrast enhancement films, diffusion films, semi-transparent reflective films, electrode films, transparent conductive films, metal mesh films, and touch sensor films. Any one of these components or a combination of two of these components may be used. Examples include a combination of a flexible display and another flexible image display device component, or a combination of a cover lens and another flexible image display device component. Of these, it is particularly preferred that one of the two image display device components is a surface protection panel, and the other is a component consisting of one or a combination of two or more components selected from the group consisting of touch sensor films, image display panels, color filters, polarizing elements, and retardation films.

[0167] The term "flexible image display device component" refers to a bendable component, particularly a component that can be repeatedly bent. In particular, it is preferable that the component be a component that can be fixed into a curved shape with a curvature radius of 25 mm or more, and particularly a component that can withstand repeated bending at a curvature radius of less than 25 mm, more preferably less than 3 mm.

[0168] In the above-described configuration, the main component of the flexible image display device component may be a resin sheet or glass. Examples of materials for such a resin sheet include polyester resin, cycloolefin resin, triacetyl cellulose resin, polymethyl methacrylate resin, polyurethane, epoxy resin, polyimide resin, and aramid resin. These may be one type of resin or two or more types of resin. Among these, a resin sheet containing at least one resin selected from the group consisting of polyester resin, cycloolefin resin, triacetyl cellulose resin, polymethyl methacrylate resin, epoxy resin, polyimide resin, aramid resin, and polyurethane resin as its main component is preferred. Here, the term "main component" refers to the component that accounts for the largest weight percentage among the components constituting the flexible image display device component. Specifically, the main component is a component that accounts for 50% by weight or more of the resin composition (resin sheet) forming the flexible image display device component, preferably 55% by weight or more, and particularly preferably 60% by weight or more. The flexible image display device component may also be made of thin-film glass.

[0169] In the above-described configuration, the tensile strength at 25°C of one of the two flexible image display device constituent members, i.e., the first flexible image display device constituent member, measured in accordance with ASTM D882, is preferably 10 MPa or more, more preferably 15 MPa or more, and particularly preferably 20 MPa or more, and is preferably 900 MPa or less, more preferably 800 MPa or less, and particularly preferably 700 MPa or less. If the 25°C tensile strength (ASTM D882) of one of the flexible image display device constituent members is within the above-described range, it is preferable because it is less likely to crack when bent.

[0170] Furthermore, the tensile strength at 25°C of the other flexible image display device component, i.e., the second flexible image display device component, measured in accordance with ASTM D882 is preferably 10 MPa or more, more preferably 15 MPa or more, particularly preferably 20 MPa or more, and is preferably 900 MPa or less, more preferably 800 MPa or less, particularly preferably 700 MPa or less. If the 25°C tensile strength (ASTM D882) of the other flexible image display device component is within the above range, it is preferable because it is less likely to crack when bent.

[0171] Examples of flexible image display device components with high tensile strength include polyimide films, polyester films, and aramid films, which generally have a tensile strength of 900 MPa or less. On the other hand, examples of flexible image display device components with slightly lower tensile strength include triacetyl cellulose (TAC) films and cycloolefin polymer (COP) films, which generally have a tensile strength of 10 MPa or more. Even if the flexible laminate includes flexible image display device components made of such materials with slightly lower tensile strength, defects such as cracking can be suppressed by the action of the adhesive layer.

[0172] <Method for manufacturing the present laminate> The method for manufacturing the present laminate is not particularly limited, and as described above, for example, the adhesive composition may be applied onto a component of an image display device, preferably onto a component of a flexible image display device, to form an adhesive layer, or an adhesive layer may be formed in advance and then bonded to a component of an image display device, preferably a component of a flexible image display device.

[0173] <<Image Display Device>> In one embodiment, the present invention provides an image display device including the laminate. (Hereinafter, this may be referred to as the "image display device.") Examples of the image display device include an image display device having a structure in which a laminate having two image display device components bonded together via the adhesive layer is combined with other image display device components. In this case, "other image display device components" include, for example, FPC cables, reflective sheets, light guide plates and light sources, diffusion films, prism sheets, liquid crystal panels, organic EL panels, anti-reflection films, color filters, polarizing plates, retardation plates, glass substrates, surface protection films, and integrated composites of these components. Specific examples of the image display device include liquid crystal displays, organic EL displays, inorganic EL displays, electronic paper, plasma displays, and microelectromechanical system (MEMS) displays used in personal computers, mobile devices, game consoles, televisions (TVs), car navigation systems, touch panels, pen tablets, etc.

[0174] <Flexible Image Display Device> In one embodiment, the image display device is a flexible image display device. (Hereinafter, this may be referred to as "the flexible image display device.") The flexible image display device is an image display device incorporating a laminate for a flexible image display device, which has a configuration in which two flexible image display device components are bonded together via the adhesive layer. For example, the flexible image display device including the laminate can be formed by laminating a laminate for a flexible image display device, which has a configuration in which two flexible image display device components are bonded together via the adhesive layer, onto another image display device component.

[0175] The term "flexible image display device" refers to an image display device that can be repeatedly bent without leaving any traces of bending, can quickly return to its original state when released from the bending, and can display images without distortion even when bent. More specifically, an example of such a display device is an image display device made of a member that can be curved and fixed to a curvature radius of 25 mm or more, particularly a member that can withstand repeated bending with a curvature radius of less than 25 mm, more preferably less than 3 mm.

[0176] One of the features of this laminate is that it can prevent delamination and cracking of the laminate even when folded in a high-temperature environment, and has good recovery properties, making it possible to manufacture flexible image display devices with excellent flexibility.

[0177] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0178] <<Evaluation Conditions>> The pressure-sensitive adhesive layers with release films prepared in the examples and comparative examples described below were used to carry out the following various evaluations.

[0179] [Shear storage modulus (G') and glass transition temperature at -30 ° C to 85 ° C] The release film on one side of the adhesive layer with release film prepared in the examples and comparative examples was removed, and the layer was repeatedly laminated with a hand roller to a thickness of approximately 0.8 mm. A circle with a diameter of 8 mm was punched out to prepare a sample. The obtained sample was placed in a rheometer ("DHR-2" manufactured by T.A. Instruments) and subjected to dynamic viscoelasticity measurement under the conditions of measurement jig: 8 mm diameter parallel plate, frequency: 1 Hz, measurement temperature: -50 to 150 ° C, heating rate: 5 ° C / min, and the values ​​of shear storage modulus (G') and shear loss modulus (G") were read at -30 ° C, -20 ° C, 25 ° C, 60 ° C, and 85 ° C. The glass transition temperature (Tg) was determined from the maximum value of Tan δ, which is defined as the ratio of the shear storage modulus (G') to the shear loss modulus (G").

[0180] [Adhesion to Glass] (Sample Preparation) A soda-lime glass plate was prepared and treated with atmospheric pressure plasma using a nitrogen and oxygen mixed gas to achieve a water contact angle of approximately 10°. This was used as a substrate. The release film on one side of the release film-attached adhesive layer prepared in the Examples and Comparative Examples was removed, and a PET film (Mitsubishi Chemical Corporation, S100, thickness 50 μm) was attached as a backing film using a hand roller. This was cut into strips measuring 10 mm wide x 150 mm long, and the remaining release film was peeled off, resulting in the exposed adhesive sheet surface being attached to the surface of the substrate using a hand roller. The resulting laminate was autoclaved (60°C, gauge pressure 0.2 MPa, 20 minutes) for finish attachment to prepare a sample for adhesion measurement. (Measurement of Adhesion Strength) The obtained adhesion strength measurement sample was pulled at an angle of 180° at a peeling rate of 300 mm / min under conditions of 23°C and 50% RH, and the adhesive layer together with the backing film was peeled off from the substrate, and the tensile strength (N / cm) was measured with a load cell to determine the adhesion strength.

[0181] [Measurement of adhesive strength to PET] In preparing the samples, adhesive strength to PET was measured in the same manner as in the measurement of adhesive strength to glass, except that a PET film (manufactured by Mitsubishi Chemical Corporation, S100, 50 μm) treated with atmospheric pressure plasma using a mixed gas of nitrogen and oxygen so as to have a water contact angle of approximately 40° was used as the substrate.

[0182] [Restoration Rate] The release film was removed from the adhesive layer with release film prepared in the Examples and Comparative Examples, and multiple adhesive layers were laminated to obtain a laminate with a thickness of 0.8 mm. A cylindrical body with a diameter of 8 mm (height of 0.8 mm) was punched out from the obtained adhesive layer laminate, and this was used as a sample. The restoration rate of this sample was measured under the following measurement conditions using a viscoelasticity measuring device (manufactured by T.A. Instruments, "DHR 2"). That is, the strain (γ max(25) ) and the strain (γ min(25) The restoration rate was calculated from the following formula: Restoration rate (%) = [(γ max(25)x -γ min(25) ) / γ max(25)]×100

[0183] [Gel Fraction] The release film was removed from the adhesive layer with release film prepared in the Examples and Comparative Examples, and an adhesive layer piece of approximately 0.1 g was collected from the exposed adhesive layer. The collected adhesive layer piece was wrapped in a pre-formed bag of SUS mesh (#150) with a mass (X), and the bag was closed to prepare a sample, and the mass (Y) of the sample was measured. The sample was immersed in ethyl acetate and stored in a dark place at 23°C for 24 hours, and then the sample was removed and heated at 70°C for 4.5 hours to evaporate the ethyl acetate, and the mass (Z) of the dried sample was measured. The gel fraction was calculated from each measured mass using the following formula: Gel Fraction (%) = [(Z-X) / (Y-X)] x 100

[0184] [Bending test] (1) Room temperature dynamic bending test The release film was removed from the adhesive layer with release film prepared in the examples and comparative examples, and a transparent polyimide (CPI) film ("C_50" manufactured by Kolon, thickness 50 μm) and a PET film ("Diafoil S-100" manufactured by Mitsubishi Chemical Corporation, thickness 50 μm) were roll-attached to the adhesive surface of the exposed adhesive layer. A laminate consisting of a CPI film / adhesive layer / PET film was then prepared, and cut into 40 mm x 100 mm to prepare an evaluation sample for a dynamic bending test. The prepared evaluation sample was set in a bending tester ("DLDMLH-FS" manufactured by Yuasa Systems Co., Ltd.) with the CPI film on the inside, and a bending test was performed under the following test conditions in a test environment of 23 ° C. (room temperature). Test temperature: 23°C (normal temperature) Curvature radius r: 1.5 mm Test speed: 60 rpm Number of tests: 200,000 times

[0185] After the test in a test environment of 23°C (normal temperature), the evaluation samples were visually observed, and samples in which there was a crease in the adhesive layer or peeling at the interface between the adherend and the adhesive layer were judged as "× (no good)", and samples in which there was no change in the visual observation were judged as "◯ (good)".

[0186] (2) Static bending test under high temperature and high humidity The release film was removed from the adhesive layer with release film prepared in the examples and comparative examples, and a transparent polyimide (CPI) film ("C_50" manufactured by Kolon, thickness 50 μm) and a PET film ("Diafoil S-100" manufactured by Mitsubishi Chemical Corporation, thickness 50 μm) were roll-attached to the adhesive surface of the exposed adhesive layer. A laminate consisting of a CPI film / adhesive layer / PET film was then prepared, and cut into 40 mm x 100 mm to prepare an evaluation sample for a static bending test. The prepared evaluation sample was folded and fixed with a curvature radius r of 2.0 mm so that the CPI film was on the inside, and stored in an environment of 65 ° C. and 90% RH for 24 hours. The jig was opened and the restoration after 1 hour was evaluated.

[0187] The evaluation samples after the test were visually observed, and with regard to peeling prevention, samples with creases on the adhesive layer and peeling at the interface between the adherend and the adhesive layer were rated "× (no good)", and samples with no change in visual observation were rated "◯ (good)". With regard to recovery, samples with an inner angle of the bent portion of less than 30° were rated "× (no good)", and samples with an inner angle of 30° or more were rated "◯ (good)".

[0188] Prior to the examples, the following raw materials were prepared.

[0189] <Polymer (A)> A copolymer containing the monomer components shown in Table 1 in the ratios based on parts by mass shown in Table 1 was prepared. Table 1 shows the weight average molecular weight of each polymer.

[0190]

[0191] In Table 1, 2EHA means 2-ethylhexyl acrylate, BA means butyl acrylate, and HEA means 2-hydroxyethyl acrylate.

[0192] The following compounds were prepared as the crosslinking agent (B), the polymerization initiator (C), and other components.

[0193] <Crosslinking agent (B)> (B-1): Polytetramethylene glycol diacrylate (bifunctional, "A-PTMG65" manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-2): Urethane acrylate (bifunctional, "SUA-008" manufactured by Asia Kogyo Co., Ltd.) (B-3): Trimethylolpropane triacrylate (trifunctional, "TMPT" manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-4): Urethane acrylate (hexafunctional, "RUA-071" manufactured by Asia Kogyo Co., Ltd.) (B-5): Dipentaerythritol hexaacrylate (hexafunctional, "DPHA" manufactured by Nippon Kayaku Co., Ltd.) <Polymerization initiator (C)> (C-1): 2-hydroxy-2-methyl-1-phenyl-propan-1-one (cleavage-type photoradical polymerization initiator, "Omnirad 1173" manufactured by IGM) (C-2): A mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (hydrogen abstraction type radical polymerization initiator, "Esacure TZT" manufactured by IGM)

[0194] <Others (D)> (D-1): Monofunctional urethane acrylate ("LD301" manufactured by AGC) (D-2): Silane coupling agent (3-glycidyloxypropyltrimethoxysilane, "KBM403" manufactured by Shin-Etsu Silicones Co., Ltd.)

[0195] Example 1 A resin composition was prepared by uniformly mixing 100 parts by mass of polymer (A-1), 1.5 parts by mass of crosslinking agent (B-5), 2.0 parts by mass of polymerization initiator (C-1), 25 parts by mass of monofunctional urethane acrylate (D-1), and 0.5 parts by mass of silane coupling agent (D-2).

[0196] Next, the resin composition was spread in a layer having a thickness of 50 μm on a silicone release-treated release film having a thickness of 100 μm (PET film manufactured by Mitsubishi Chemical Corporation). Furthermore, a silicone release-treated release film having a thickness of 75 μm (PET film manufactured by Mitsubishi Chemical Corporation) was laminated on the layered resin composition. Then, a high-pressure mercury lamp was used to illuminate the resin composition with an integrated light intensity of 1000 mJ / cm. ２ Both surfaces of the layered resin composition were irradiated with light having a wavelength of 365 nm through a release film to obtain an adhesive layer with a release film having a structure in which a release film, an adhesive layer, and a release film were laminated in this order.

[0197] Examples 2 to 12 and Comparative Examples 1 to 4 The components and their blending ratios in parts by mass were as shown in Tables 2 and 3, and only in Example 11 the cumulative light intensity during light irradiation was 1,300 mJ / cm ２ An adhesive layer with a release film was produced in the same manner as in Example 1, except that the above-mentioned step was changed to the above.

[0198]

[0199]

[0200] [Measurement and Evaluation of Physical Properties] The adhesive layers prepared in the examples and comparative examples were subjected to the various measurements and evaluations described above. The evaluation results of the adhesive layers are summarized in Tables 4 and 5.

[0201]

[0202]

[0203] It was found that the adhesive layers of Comparative Examples 1 to 3 had a low gel fraction and an insufficient degree of curing. The adhesive layer of Comparative Example 4 had an excessively high storage shear modulus (G') at 85°C. The adhesive layers of Examples 1 to 12 all had gel fractions and storage shear moduli (G') at -20°C and 85°C that were within appropriate ranges.

[0204] Comparative Example 1 had poor shape stability and could not be subjected to a recovery rate test. Furthermore, the adhesive layers of Comparative Examples 2 and 3 had very large maximum strains in the recovery rate test, indicating that they did not satisfy the shape retention characteristics when folded. Furthermore, all of the adhesive layers of Comparative Examples 1 to 3 exhibited poor recovery in a static bending test under high temperature and high humidity, and were not suitable for applications such as foldable displays in high temperature environments. Furthermore, the adhesive layer of Comparative Example 4 lacked flexibility and had insufficient adhesion to the PET substrate. Furthermore, peeling was observed in a static bending test under high temperature and high humidity, and recovery was also insufficient.

[0205] The adhesive layers of Examples 1 to 12 all exhibited suitable adhesive strength to both glass and PET substrates. Furthermore, in the recovery test, the maximum strain was within a suitable range, and the recovery rate was good, at 70% or higher. Furthermore, good results were obtained in both the dynamic bending test at room temperature and the static bending test under high temperature and humidity. It can be seen that these adhesive layers can withstand harsh environments and repeated or prolonged bending, and have the high durability required for applications such as rollable and foldable panels.

[0206] As described above, according to the present invention, it is possible to provide an adhesive layer, an adhesive layer with a release film, a laminate, an image display device, and an adhesive layer for a component of an image display device, which have excellent bending suitability and good cohesive strength and / or adhesive strength.

[0207] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0208] The pressure-sensitive adhesive layer of the present invention has excellent flexibility and good cohesive strength and / or adhesive strength, and therefore can be suitably used as a pressure-sensitive adhesive layer for an image display device.

Claims

1. An adhesive layer for a component of a flexible image display device, satisfying the following requirements [I] to [V]: The adhesive layer for a component of a flexible image display device is formed from a resin composition containing a polymer (A), a crosslinking agent (B), and a polymerization initiator (C), the polymer (A) comprises a copolymer in which 50% by mass or more of the monomer components are compounds containing (meth)acryloyl groups, the crosslinking agent (B) comprises a trifunctional or higher crosslinking agent, and the polymerization initiator (C) comprises a cleavage-type photopolymerization initiator. [I] The shear storage modulus at -20°C (G'(-20°C)) is 300 kPa or less. [II] The shear storage modulus at 85°C (G'(85°C)) is 5.0 kPa or more and 30 kPa or less. [III] The gel fraction is 45% or more and 95% or less. [IV] The adhesive strength to a polyethylene terephthalate substrate at 23°C is 5.0 N / cm or more. [V] The maximum strain (γ) after applying a pressure of 10 kPa for 600 seconds at a temperature of 25°C with a thickness of 0.5 to 1.2 mm max(25) ) and the strain (γ min(25) The restoration rate calculated from the above formula using the following formula is 70% or more. max(25) -γ min(25) ) / γ max(25) ]×100 2. The adhesive layer for a component of a flexible image display device according to claim 1, wherein the adhesive strength of said adhesive layer for a component of a flexible image display device to a glass substrate at 23°C is 4.5 N / cm or more.

3. The adhesive layer for a flexible image display device component has a thickness of 0.5 to 1.2 mm, and the maximum strain (γ max(25) 2. The adhesive layer for a component of a flexible image display device according to claim 1, wherein the surface roughness (S) is 600% or less.

4. The adhesive layer for a component of a flexible image display device according to claim 1, wherein the glass transition temperature (Tg) of the adhesive layer for a component of a flexible image display device, defined by the maximum value of Tan δ obtained by dynamic viscoelasticity measurement in shear mode at a frequency of 1 Hz, is -15°C or lower.

5. An adhesive layer for a component of a flexible image display device with a release film, having a laminated structure of one or more release films and the adhesive layer for a component of a flexible image display device according to any one of claims 1 to 4.

6. A laminate comprising one or more members for an image display device and the adhesive layer for a flexible image display device component according to any one of claims 1 to 4.

7. A laminate comprising two components of an image display device and the adhesive layer for flexible components of an image display device according to any one of claims 1 to 4 interposed between the two components of the image display device.

8. The laminate according to claim 7, wherein one of the two image display device components is a surface protection panel and the other is a component consisting of one or a combination of two or more components selected from the group consisting of a touch sensor film, an image display panel, a color filter, a polarizing element, and a retardation film.

9. An image display device comprising the laminate according to claim 6.

10. The image display device according to claim 9, which is a flexible image display device.

Images