WO2024106519A1 - Adhesive sheet, optical laminate, method for manufacturing optical laminate, and optical device - Google Patents

Abstract

One embodiment of the present invention relates to an adhesive sheet including an adhesive layer composed of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer, wherein, in a creep test carried out using a rotary rheometer, the adhesive layer has a creep deformation rate of 10% or less when stress of 10,000 Pa is applied for one second at 50°C and has a creep deformation rate of 16% or less when stress of 10,000 Pa is applied for 30 minutes at 50°C.

Description

Adhesive sheet, optical laminate, method for producing optical laminate, and optical device

The present invention relates to an adhesive sheet, an optical laminate, a method for manufacturing an optical laminate, and an optical device.

Optical sheets such as microlens sheets, prism sheets, and brightness enhancement films are used in various optical devices such as display devices and lighting devices.

The surface of an optical sheet has an uneven structure, and when such an optical sheet is attached to a substrate or the like using an adhesive, if the adhesive penetrates into and fills the recesses in the uneven structure, this can adversely affect the function of the optical sheet.

As a solution to the above problem, Patent Document 1 discloses an optical laminate having an adhesive layer that is resistant to deformation when the creep deformation rate is below a certain level, an optical sheet having a concave-convex structure on its surface, and an adhesive layer provided on the concave-convex structure surface.

International Publication No. 2021/167090

The optical laminate described in Patent Document 1 can prevent the adhesive layer from penetrating into the recesses in the uneven structure on the surface of the optical sheet, but there is still room for improvement in terms of adhesive reliability in a humid and hot environment.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an adhesive sheet, an optical laminate, a method for manufacturing an optical laminate, and an optical device that have a small degree of penetration into recesses in the uneven structure of the optical sheet surface and have excellent adhesion reliability in a humid and hot environment.

The inventors of the present invention have conducted extensive research to solve the above problems. In order to improve the adhesive reliability in a humid and hot environment, they added a commercially available silane coupling agent to the adhesive and found that although the adhesive strength improved, significant recessed areas were filled up. As a result, they selected a compound that reacts with the base polymer as the silane coupling agent, and found that the silane coupling agent did not fill up the recessed areas and provided excellent adhesive reliability in a humid and hot environment, which led to the completion of the present invention.

The means for solving the above problems are as follows.
[1] An adhesive sheet comprising an adhesive layer made of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer,
In a creep test using a rotational rheometer, the adhesive layer has a creep deformation rate of 10% or less when a stress of 10,000 Pa is applied to it at 50° C. for 1 second, and a creep deformation rate of 16% or less when a stress of 10,000 Pa is applied to it at 50° C. for 30 minutes.
Adhesive sheet.
[2] The silane coupling agent includes a compound having a first reactive group RG1 and a second reactive group RG2,
the first reactive group RG1 is at least one selected from the group consisting of an amino group, an azide group, an azidosulfonyl group, a diazomethyl group, a diazirine group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group;
The adhesive sheet according to [1] above, wherein the second reactive group RG2 is at least one selected from a silanol group and a group that generates a silanol group by hydrolysis reaction.
[3] The adhesive sheet according to [2] above, wherein the base polymer has a functional group capable of forming a chemical bond with the first reactive group RG1.
[4] The first reactive group RG1 is an amino group,
The adhesive sheet according to [3] above, wherein the functional group of the base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.
[5] The first reactive group RG1 is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group,
The adhesive sheet according to [3] above, wherein the functional group of the base polymer is at least one selected from the group consisting of -CH ₃ , -CH ₂ -, -CH<, and -CH=CH-.
[6] The adhesive sheet according to [1] or [2], wherein the silane coupling agent contains a compound having an aromatic ring.
[7] The adhesive sheet according to [6], wherein the silane coupling agent contains a compound having a triazine ring.
[8] The adhesive sheet according to [1] or [2], wherein the content of the silane coupling agent in the adhesive composition is 0.01 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the base polymer.
[9] The adhesive sheet according to [1] or [2] above, wherein the adhesive layer has a thickness of 0.01 to 100 μm.
[10] The adhesive sheet according to [1] or [2] above, wherein the adhesive layer has a total light transmittance of 80% or more.
[11] The adhesive sheet according to [1] or [2], further comprising a substrate and having the adhesive layer on one main surface of the substrate.
[12] The adhesive sheet according to [1] or [2], further comprising a substrate and having the adhesive layer on both main surfaces of the substrate.
[13] The adhesive sheet according to [11] above, wherein one or both main surfaces of the substrate are release-treated, and the adhesive layer is provided on the release-treated main surface.
[14] An optical laminate comprising: a first optical sheet having a first main surface having a concave-convex structure and a second main surface opposite the first main surface; and an adhesive sheet according to [1] or [2] arranged on the first main surface side of the first optical sheet.
[15] The optical laminate described in [14], wherein the uneven structure includes a plurality of recesses, and the surface of the adhesive layer and the first main surface of the first optical sheet define a plurality of spaces in the plurality of recesses.
[16] The optical laminate described in [15], wherein the uneven structure includes a flat portion in contact with the adhesive layer.
[17] A method for producing the optical laminate described in [14] above, comprising a step of bonding the first optical sheet and the adhesive sheet.
[18] The manufacturing method according to [17] above, wherein the process is carried out by a roll-to-roll method.
[19] The optical laminate described in [14], further comprising a second optical sheet arranged on the opposite side of the adhesive sheet to the first optical sheet.
[20] A method for producing the optical laminate according to [19],
A manufacturing method including either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive sheet are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive sheet and the second optical sheet are laminated to the first optical sheet.
[21] The manufacturing method described in [20] above, comprising the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or comprising the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
[22] A method for producing the optical laminate according to [19],
A step A of applying the adhesive composition onto the first main surface of the first optical sheet;
and step B of reacting the base polymer and the silane coupling agent contained in the adhesive composition in a state in which the adhesive composition is applied onto the first main surface of the first optical sheet.
[23] The manufacturing method according to [22], wherein the step A includes a step of bonding the first optical sheet and the adhesive composition by a roll-to-roll method.
[24] A method for producing the optical laminate according to [19],
Either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive composition are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive composition and the second optical sheet are laminated to the first optical sheet;
A process for producing a composition comprising the steps of: (a) reacting the base polymer contained in the adhesive composition with the silane coupling agent after the step A1 or the step A2;
[25] The method includes the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or the method includes the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
The manufacturing method described in [24] above.
[26] An optical device comprising the optical laminate described in [14].

Embodiments of the present invention provide an adhesive sheet, an optical laminate, a method for manufacturing an optical laminate, and an optical device that have a small degree of penetration into recesses in the uneven structure of the optical sheet surface and have excellent adhesion reliability in a humid and hot environment.

FIG. 1 is a schematic cross-sectional view of an optical laminate 100A according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an optical laminate 101A according to another embodiment of the present invention. FIG. 3 is a schematic diagram showing a creep curve of an adhesive. FIG. 4 is a schematic cross-sectional view showing an adhesive sheet (adhesive layer) according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing an adhesive sheet according to another embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of an optical laminate 100B and an optical laminate 101B according to an embodiment of the present invention. FIG. 7 is a schematic perspective view of a first optical sheet 10b included in the optical laminate 100B. FIG. 8 is a schematic cross-sectional view of a lighting device 200 including the optical laminate 100B. FIG. 9 is a schematic plan view of the concavo-convex film used in the adhesive strength test of the examples. FIG. 10 is a schematic cross-sectional view of a concavo-convex film used in an adhesive strength test in the examples.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be modified as desired without departing from the gist of the present invention. In addition, the use of "to" to indicate a numerical range means that the numerical values before and after it are included as the lower and upper limits. In addition, in the following drawings, components and parts that perform the same function may be described using the same reference numerals, and duplicate descriptions may be omitted or simplified. In addition, the embodiments shown in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of actual devices, etc.

The adhesive sheet according to an embodiment of the present invention is an adhesive sheet including an adhesive layer made of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer, and the adhesive layer is characterized in that, in a creep test using a rotational rheometer, the adhesive layer exhibits a creep deformation rate of 10% or less when a stress of 10,000 Pa is applied for 1 second at 50°C, and a creep deformation rate of 16% or less when a stress of 10,000 Pa is applied for 30 minutes at 50°C.

The adhesive sheet according to the embodiment of the present invention includes at least the adhesive layer. The adhesive sheet according to the embodiment of the present invention may be a sheet consisting of only the adhesive layer. The adhesive sheet according to the embodiment of the present invention may also be a sheet including a substrate and having the adhesive layer on one or both main surfaces of the substrate, as described below. In this case, one or both main surfaces of the substrate may be peel-treated and bonded to the adhesive layer.

The adhesive sheet according to an embodiment of the present invention can be used to attach the optical laminate to other optical sheets or optical devices.

The adhesive layer in the adhesive sheet according to an embodiment of the present invention has a deformation rate in a specified creep test described below that is kept below a certain value, making it difficult to deform. In addition, the adhesive layer contains a silane coupling agent that reacts with the base polymer that constitutes the adhesive layer, so that the adhesive layer can be prevented from penetrating into the uneven structure of the optical sheet surface during and after application.

In addition, by using a silane coupling agent that reacts with the base polymer, the cohesive strength of the adhesive layer in the adhesive sheet is improved, the elastic modulus can be increased appropriately, and the interfacial adhesive strength with the adherend can also be improved, so deformation and peeling after application of the adhesive sheet can be suppressed, resulting in an adhesive sheet with excellent adhesive reliability in humid and hot environments.

1 and 2 are schematic cross-sectional views of optical laminates 100A and 101A according to an embodiment of the present invention described later. As shown in FIG. 1, the optical laminate 100A has an adhesive sheet 20a according to an embodiment of the present invention on the uneven structure of the first main surface 12s of the first optical sheet 10a. For example, a prism sheet or a microlens sheet may be used as the first optical sheet 10a. As shown in FIG. 2, the optical laminate 101A has the optical laminate 100A and a second optical sheet 30 arranged on the side of the adhesive sheet 20a opposite to the first optical sheet 10a side. The description of the optical laminate 100A also applies to the optical laminate 101A unless otherwise specified, so the description may be omitted to avoid duplication.

In the manufacturing process of the optical laminate 100A or the optical laminate 101A, when the adhesive sheet 20a is attached to the first optical sheet 10a, for example by a roll-to-roll method, it is required that the adhesive layer of the adhesive sheet 20a does not penetrate too far into the recesses of the uneven structure of the first optical sheet 10a. In addition, after the adhesive sheet 20a is attached to the first optical sheet 10a, it is required that the degree to which the adhesive layer of the adhesive sheet 20a penetrates into the recesses does not change easily over time.

There is a correlation between the creep deformation rate of the adhesive layer in the adhesive sheet 20a and the degree of penetration of the adhesive layer when attaching the adhesive sheet 20a to the first optical sheet 10a and the change in the degree of penetration over time, and a suitable adhesive sheet can be selected using the creep deformation rate.

Generally, when a constant stress is applied to a polymeric material with viscoelasticity, a phenomenon called creep occurs in which the strain (deformation rate) increases over time, as shown by the creep curve in Figure 3. The strain of a viscoelastic material when a constant stress is applied contains an elastic component that occurs instantaneously when the stress is applied, a viscoelastic component that is expressed as an increasing function of time and reaches a constant value after a long time, and a viscous component that increases in proportion to time. Due to the viscous component, the strain continues to increase at a constant rate even after a long time has passed. After the stress is removed, the viscous component of the strain does not recover and remains.

The degree to which the adhesive layer of the adhesive sheet 20a penetrates into the recesses when the adhesive sheet 20a is bonded is correlated with the creep strain of the adhesive layer of the adhesive sheet 20a after 1 second (referred to as the "creep deformation rate A"). In other words, the degree to which the adhesive layer of the adhesive sheet 20a penetrates into the recesses when the adhesive sheet 20a is bonded is mainly influenced by the elastic component of the adhesive layer of the adhesive sheet 20a.

On the other hand, the change over time in the degree of penetration of the adhesive layer in the adhesive sheet 20a into the recesses is correlated with the creep strain of the adhesive layer in the adhesive sheet 20a after 30 minutes (1,800 seconds) (referred to as "creep deformation rate B"). In other words, the change over time in the degree of penetration of the adhesive layer in the adhesive sheet 20a into the recesses is mainly influenced by the viscoelastic and viscous components of the adhesive layer in the adhesive sheet 20a.

The extent to which the adhesive layer in the adhesive sheet 20a penetrates into the recesses can be evaluated by the diffuse transmittance of the optical laminate 100A. The greater the extent to which the adhesive layer in the adhesive sheet 20a penetrates into the recesses of the first optical sheet 10a, the smaller the diffuse transmittance. Creep deformation includes an early stage of deformation called transition creep (primary creep) where the strain rate (slope of the creep curve) gradually decreases, and a stage called steady creep (secondary creep) where the strain rate becomes almost constant. As shown in Figure 3, 30 minutes (1800 seconds) after pressure application is a time that belongs to the steady creep region after transition creep.

As will be described in the examples below, the adhesive layer in the adhesive sheet 20a of the optical laminate 100A according to an embodiment of the present invention has a creep deformation rate A of 10% or less when a stress of 10,000 Pa is applied at 50°C for 1 second in a creep test using a rotational rheometer, and a creep deformation rate B of 16% or less when a stress of 10,000 Pa is applied at 50°C for 30 minutes in a creep test using a rotational rheometer.

In adhesive sheets 20a that include an adhesive layer with a creep deformation rate A of 10% or less, the degree to which the adhesive layer of the adhesive sheet 20a penetrates into recesses during bonding is sufficiently suppressed. In adhesive sheets 20a that include an adhesive layer with a creep deformation rate B of 16% or less, the change over time in the degree to which the adhesive layer penetrates into recesses is sufficiently suppressed.

The creep deformation rate A of the adhesive layer in the adhesive sheet 20a is, for example, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less. The creep deformation rate B of the adhesive layer in the adhesive sheet 20a is, for example, 16% or less, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less. The lower limits of the creep deformation rates A and B are not particularly limited, but are, for example, greater than 0. It is more preferable that the adhesive layer in the adhesive sheet 20a has a creep deformation rate A of 8% or less and a creep deformation rate B of 14% or less, and even more preferably a creep deformation rate A of 5% or less and a creep deformation rate B of 10% or less.

The creep deformation rate A and creep deformation rate B can be achieved by adjusting the type and amount of the silane coupling agent and crosslinking agent that react with the base polymer in the adhesive layer, which will be described later. Specifically, the greater the amount of the silane coupling agent and/or crosslinking agent that reacts with the base polymer, the smaller the creep deformation rate can be kept. On the other hand, if the amount is too large, the adhesive layer after the reaction of the silane coupling agent and/or crosslinking agent that reacts with the base polymer becomes too hard, making it difficult to approach the adherend surface, and as a result, sufficient adhesive strength may not be obtained. Based on the above viewpoint, the creep deformation rate A and creep deformation rate B can be achieved by adjusting the type and amount of the silane coupling agent and crosslinking agent that react with the base polymer.

The adhesive layer in the adhesive sheet according to an embodiment of the present invention is made of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer.

In this specification, the adhesive layer refers to a layer made of the adhesive composition after the base polymer contained in the adhesive composition reacts with the silane coupling agent.

The components contained in the adhesive composition are described in detail below.

<Adhesive composition>
<Base polymer>
The adhesive composition according to the embodiment of the present invention contains a polymer as a base polymer. In the embodiment of the present invention, the base polymer is not particularly limited as long as it is a general organic polymer compound, and is, for example, a polymer of a monomer. The monomer may be one type of monomer or a mixture of two or more types of monomers.

The base polymer in the embodiment of the present invention is not particularly limited as long as it is normally used as an adhesive and has adhesive properties, but examples include (meth)acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers. Among these, polyester polymers or (meth)acrylic polymers are preferred.

The above base polymers can be used alone or in combination of two or more.

The base polymer in the embodiment of the present invention reacts with a silane coupling agent described later. The base polymer preferably has a functional group capable of forming a chemical bond with the first reactive group RG1 in the silane coupling agent. That is, the base polymer preferably has a functional group capable of forming a chemical bond with the first reactive group RG1 contained in R ^A in the general formula (1) described later.

In particular, when the first reactive group RG1 capable of forming a chemical bond with a functional group possessed by the base polymer, or the first reactive group RG1 contained in R ^A in general formula (1) described below, is an amino group, it is preferable that the functional group possessed by the base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.

Alternatively, when the first reactive group RG1 capable of forming a chemical bond with a functional group in the base polymer, or the reactive group contained in R ^A in general formula (1) described below, is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group, it is preferable that the functional group in the base polymer is at least one selected from the group consisting of -CH ₃ , -CH ₂ -, -CH<, and -CH=CH-.

Here, chemical bonds include covalent bonds, coordinate bonds, and ionic bonds, but do not include intermolecular forces. The chemical bonds are preferably covalent bonds.

When the base polymer contains a (meth)acrylic polymer, any (meth)acrylate can be used as a monomer for use in producing the (meth)acrylic polymer, and there is no particular limitation. For example, an alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms can be used. In this case, the ratio of the alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms to the total amount of monomers used in producing the (meth)acrylic polymer is, for example, 50 mass% or more.

In this specification, "alkyl (meth)acrylate" refers to a (meth)acrylate having a straight-chain or branched-chain alkyl group. The number of carbon atoms in the alkyl group of the alkyl (meth)acrylate is preferably 4 or more, and more preferably 4 to 9. Note that (meth)acrylate refers to acrylate and/or methacrylate.

Specific examples of alkyl (meth)acrylates include n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate. Examples include acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, isomyristyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. These can be used alone or in combination.

In order to modify the cohesive strength, crosslinkability, etc., the (meth)acrylic polymer preferably contains, in addition to the monomer units derived from the alkyl (meth)acrylates described above, monomer units derived from monomers copolymerizable therewith. Examples of copolymerizable monomers include nitrogen-containing (meth)acrylic monomers, hydroxyl group-containing (meth)acrylic monomers, and carboxyl group-containing (meth)acrylic monomers.

In this specification, the term "nitrogen-containing (meth)acrylic monomer" includes, without particular limitation, monomers having a polymerizable functional group with an unsaturated double bond of a (meth)acryloyl group and having a nitrogen atom. The "nitrogen-containing (meth)acrylic monomer" has, for example, a nitrogen-containing cyclic structure. Examples of nitrogen-containing (meth)acrylic monomers having a nitrogen-containing cyclic structure include, for example, N-vinyl-2-pyrrolidone (NVP), N-vinyl-ε-caprolactam (NVC), and 4-acryloylmorpholine (ACMO). These can be used alone or in combination.

The nitrogen-containing (meth)acrylic monomer may be, for example, 5.0 parts by mass or more, 10.0 parts by mass or more, 15.0 parts by mass or more, 20.0 parts by mass or more, 25.0 parts by mass or more, 30.0 parts by mass or more, or 35.0 parts by mass or more, and 40.0 parts by mass or less, 35.0 parts by mass or less, 30.0 parts by mass or less, 25.0 parts by mass or less, 20.0 parts by mass or less, or 15.0 parts by mass or less, based on 100 parts by mass of the total amount of monomers used in the copolymerization.

In this specification, the term "hydroxyl group-containing (meth)acrylic monomer" includes, without particular limitation, monomers having a polymerizable functional group with an unsaturated double bond of a (meth)acryloyl group and having a hydroxyl group. Examples include hydroxyalkyl (meth)acrylates such as 2-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; 4-hydroxymethylcyclohexyl (meth)acrylate, and 4-hydroxybutyl vinyl ether.

The hydroxyl group-containing (meth)acrylic monomer may be used in an amount of, for example, 0.05 parts by mass or more, 0.75 parts by mass or more, 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, 5.0 parts by mass or more, 6.0 parts by mass or more, 7.0 parts by mass or more, 8.0 parts by mass or more, or 9.0 parts by mass or more, or 10.0 parts by mass or less, 9.0 parts by mass or less, 8.0 parts by mass or less, 7.0 parts by mass or less, 6.0 parts by mass or less, 5.0 parts by mass or less, 4.0 parts by mass or less, 3.0 parts by mass or less, 2.0 parts by mass or less, or 1.0 parts by mass or less, based on 100 parts by mass of the total amount of monomers used in the copolymerization.

In this specification, the term "carboxyl group-containing (meth)acrylic monomer" includes, without particular limitation, monomers that have a polymerizable functional group with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, and also have a carboxyl group. Examples of unsaturated carboxylic acid-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. These can be used alone or in combination.

The carboxyl group-containing (meth)acrylic monomer may be used in an amount of, for example, 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, 4.0 parts by mass or more, 5.0 parts by mass or more, 6.0 parts by mass or more, 7.0 parts by mass or more, 8.0 parts by mass or more, or 9.0 parts by mass or more, or 10.0 parts by mass or less, 9.0 parts by mass or less, 8.0 parts by mass or less, 7.0 parts by mass or less, 6.0 parts by mass or less, 5.0 parts by mass or less, 4.0 parts by mass or less, 3.0 parts by mass or less, or 2.0 parts by mass or less, based on 100 parts by mass of the total amount of monomers used in the copolymerization.

The base polymer may preferably contain a polyester polymer instead of or in addition to the (meth)acrylic polymer. When a polyester polymer is contained, a polyester polymer having the following characteristics is preferred.

　Type of carboxylic acid component (or skeletal characteristics, etc.): Contains at least a dicarboxylic acid containing two carboxyl groups, specifically a dicarboxylic acid. The dicarboxylic acid is not particularly limited, but examples thereof include dimer acids derived from sebacic acid, oleic acid, and erucic acid.

Other examples include aliphatic or alicyclic dicarboxylic acids such as glutaric acid, suberic acid, adipic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenylsuccinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, and citraconic acid, as well as terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid. In addition to the above dicarboxylic acids, tricarboxylic acids containing three or more carboxyl groups can also be used.

The type of diol component (or skeletal characteristics, etc.) includes those containing at least two hydroxyl groups in the molecule, specifically diols. Other examples include fatty acid esters, dimer diols derived from oleic acid, erucic acid, etc., and glycerol monostearate. Other examples include aliphatic glycols such as ethylene glycol and 1,2-propylene glycol, and, other than aliphatic glycols, ethylene oxide adducts and propylene oxide adducts of bisphenol A, and ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A.

<Silane coupling agent that reacts with base polymer>
The adhesive composition in an embodiment of the present invention contains a silane coupling agent that reacts with the above-mentioned base polymer.

The silane coupling agent in the embodiment of the present invention reacts with the base polymer, i.e., it can form a chemical bond with a functional group that the base polymer may have. This can suppress the flow and precipitation of the silane coupling agent in the adhesive layer, improve the cohesive force of the adhesive layer, and appropriately increase the elastic modulus. Therefore, it is possible to suppress the adhesive layer in the adhesive sheet from penetrating into the recesses in the uneven structure on the surface of the optical sheet.

In addition, the silane coupling agent reacts with the base polymer and forms a chemical bond with the adherend, improving the interfacial adhesion with the adherend.

The method of reacting a silane coupling agent with a base polymer, i.e., the method of forming a chemical bond between the silane coupling agent and a functional group that the base polymer may have, varies depending on the type of reactive group that the silane coupling agent has and the type of functional group that the base polymer may have, but can be carried out, for example, by heating or irradiating with ultraviolet light.

The silane coupling agent in an embodiment of the present invention includes a compound having a first reactive group RG1 and a second reactive group RG2, and the first reactive group RG1 is at least one selected from the group consisting of an amino group, an azide group, an azidosulfonyl group, a diazomethyl group, a diazirine group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group, and the second reactive group RG2 is preferably at least one selected from a silanol group and a group that generates a silanol group by hydrolysis.

Here, the first reactive group RG1 refers to a reactive group that forms a chemical bond with a functional group that the base polymer may have, and the second reactive group RG2 refers to a reactive group that forms a chemical bond with the adherend or a functional group that the adherend may have. Note that the first reactive group RG1 may be one that forms a chemical bond with the adherend or a functional group that the adherend may have, and the second reactive group RG2 may be one that forms a chemical bond with a functional group that the base polymer may have.

In addition, in the silane coupling agent according to an embodiment of the present invention, it is a preferred aspect that the first reactive group RG1 is an amino group, and the functional group possessed by the base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.

In addition, in the silane coupling agent according to an embodiment of the present invention, it is a preferred aspect that the first reactive group RG1 is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group, and the functional group possessed by the base polymer is at least one selected from the group consisting of _-CH3 , _-CH2- , -CH<, and -CH=CH-.

In addition, the silane coupling agent in the embodiment of the present invention preferably contains a compound having an aromatic ring, and more preferably contains a compound having a triazine ring. Azide groups, azidosulfonyl groups, diazomethyl groups, and diazirine groups bonded to aromatic rings, particularly triazine rings (conjugated skeletons), have high decomposition energy into carbenes or nitrenes. Therefore, they are less susceptible to near-ultraviolet light and visible light. This improves the workability of UV exposure. Carbenes or nitrenes bonded to aromatic rings, particularly triazine rings, are more stable than carbenes or nitrenes that are not bonded to aromatic rings, and therefore bonding between carbenes or nitrenes is suppressed. In addition, hydrogen abstraction activity for C-H bonds and addition activity for unsaturated bonds are enhanced. In other words, effective reactions are possible with a small amount of exposure.

In addition, even if the compound having the first reactive group RG1 and the second reactive group RG2 contained in the silane coupling agent has a highly reactive group, it is preferable that the compound does not contain a multifunctional oligomer so that the self-reaction between the reactive groups does not occur excessively compared to the reaction with the base polymer or the adherend.

More specifically, the silane coupling agent in the embodiment of the present invention can be a molecular adhesive, and the molecular adhesive preferably contains a compound represented by the following general formula (1). The molecular adhesive may contain components other than the compound represented by general formula (1) (e.g., a polymerization initiator).

(R ^A ) _x -L ¹ -[L ² -Si-(R ¹ ) _n (OR ² ) _3-n ] _y (1)
(In the general formula (1),
When a plurality of R ^{1 A} are present, each independently represents a group containing a first reactive group RG1.
^L1 represents a linking group having a valency of (x+y).
When a plurality of ^L2s are present, each independently represents a divalent linking group or a single bond.
When a plurality of R ¹ 's are present, each independently represents a chain hydrocarbon group having 1 to 4 carbon atoms.
When a plurality of ^R2s are present, each independently represents a hydrogen atom or a chain hydrocarbon group having 1 to 4 carbon atoms.
n represents an integer of 0 to 2.
x and y each represent an integer of 1 or more, provided that (x+y)≧3 is satisfied.

R ^A represents a group containing a first reactive group RG1.
The first reactive group RG1 contained in R ^A is preferably at least one selected from the group consisting of an amino group, an azide group, an azide sulfonyl group, a diazomethyl group, a diazirine group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group, more preferably at least one selected from the group consisting of an amino group, an azide group, an azide sulfonyl group, a diazomethyl group, and a diazirine group, and even more preferably at least one selected from the group consisting of an amino group and an azide group.

R ^A may be the first reactive group RG1 itself, or may be a group containing the first reactive group RG1 via a linking group.

For example, when the first reactive group RG1 is an amino group, R ^A is preferably a group represented by the following general formula (a).

 

In formula (a), * represents a bond to ^L1 in formula (1).
R ^a1 represents a divalent hydrocarbon group having 1 to 10 carbon atoms.
m represents an integer of 0 or 1.
When a plurality of R ^a1 are present in formula (a), the plurality of R ^a1 may be the same or different.

In general formula (a), the divalent hydrocarbon group having 1 to 10 carbon atoms represented by R ^a1 is preferably a divalent hydrocarbon group having 2 to 6 carbon atoms. Examples of R ^a1 include alkylene groups or arylene groups having 1 to 10 carbon atoms, and specific examples thereof include alkylene groups such as methylene, ethylene, trimethylene, and propylene groups; and arylene groups such as o-phenylene, m-phenylene, and p-phenylene groups.

In an embodiment of the present invention, the first reactive group RG1 contained in R ^A in general formula (1) is an amino group, and the functional group possessed by the above-mentioned base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.

In another preferred embodiment of the present invention, the first reactive group RG1 contained in R ^A in general formula (1) is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group, and the functional group possessed by the above-mentioned base polymer is at least one selected from the group consisting of -CH ₃ , -CH ₂ -, -CH<, and -CH=CH-.

R ^A more preferably contains at least one group selected from the group consisting of a group represented by general formula (a) above, an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group, and further preferably contains at least one group selected from the group consisting of a group represented by general formula (a) and an azide group.

When x in formula (1) represents an integer of 2 or more, a plurality of R ¹ As may be the same or different, but are preferably the same.

The (x+y)-valent linking group represented by L ¹ is preferably a group containing an aromatic ring, that is, the linking group represented by L ¹ preferably contains an aromatic ring.
The aromatic ring may be an aromatic hydrocarbon ring or an aromatic heterocycle, but is preferably an aromatic heterocycle, and more preferably a triazine ring, i.e., the linking group represented by ^L1 preferably contains a triazine ring.

Preferred examples of groups containing a triazine ring include groups represented by any of the following general formulas (T1) to (T3).

 

In formulae (T1) to (T3), * represents a bond to R ^A in formula (1), and ** represents a bond to L ² in formula (1).

R ^T represents a single bond or a divalent group represented by -N(R ^T2 )-, where R ^T2 represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.

Examples of the hydrocarbon group having 1 to 20 carbon atoms represented by R ^T2 include alkyl groups, alkenyl groups, alkynyl groups, and aryl groups having 1 to 20 carbon atoms. Specific examples include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group; alkenyl groups such as a vinyl group, a 1-propenyl group, a 2-propenyl group, an isopropenyl group, a 3-butenyl group, a 4-pentenyl group, and a 5-hexenyl group; alkynyl groups such as an ethynyl group, a propargyl group, and a butynyl group; and aryl groups such as a phenyl group, a 1-naphthyl group, and a 2-naphthyl group.
Preferably, R 1 ^T represents —NH—.

^L2 represents a divalent linking group or a single bond.
Examples of the divalent linking group represented by ^L2 include -N(R ^T2 )- (when R ^T is a single bond), a hydrocarbon group, or a divalent group combining these. Examples of the hydrocarbon group include a divalent hydrocarbon group having 1 to 20 carbon atoms, preferably a chain-like divalent hydrocarbon group having 1 to 12 carbon atoms, and more preferably a chain-like divalent hydrocarbon group having 1 to 10 carbon atoms. Of these, a linear alkylene group having 1 to 6 carbon atoms is preferred, and specific examples include a methylene group, an ethylene group, a propylene group, a butylene group, a pentamethylene group, and the like, with a propylene group being preferred.

Examples of the chain hydrocarbon group having 1 to 4 carbon atoms represented by R ¹ and R ² include a methyl group, an ethyl group, a propyl group, and a butyl group, and a methyl group and an ethyl group are preferable.

In addition, when the first reactive group RG1 contained in R ^A in the general formula (1) is at least one selected from the group consisting of an amino group, a mercapto group, an isocyanate group, and an epoxy group, R ² may represent a hydrogen atom.

n represents an integer from 0 to 2, and preferably n is 0.

x and y each represent an integer of 1 or more, provided that (x+y)≧3 is satisfied.
x is preferably 1 to 4, more preferably 1 or 2, and even more preferably 2.
y is preferably 1 or 2.

Below are examples of compounds contained in the silane coupling agent in an embodiment of the present invention, or compounds represented by general formula (1), but the present disclosure is not limited to these.

 

 

 

 

 

 

 

 

As the compound contained in the silane coupling agent in the embodiment of the present invention, or the compound represented by general formula (1), the compound N,N'-bis(2-aminoethyl)-6-(3-trihydroxysilylpropyl)amino-1,3,5-triazine-2,4-diamine or 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide is preferred.

The silane coupling agent may be used alone or in a mixture of two or more types. The above compounds contained in the silane coupling agent may be used alone or in a mixture of two or more types.

The content of the silane coupling agent in the adhesive composition or adhesive layer according to the embodiment of the present invention is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the base polymer. By making the content 0.01 parts by mass or more, it is easier to obtain the effect of improving the adhesive strength by adding the silane coupling agent to the composition. In addition, the creep deformation rate of the adhesive sheet can be kept small.

The content of the silane coupling agent is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, even more preferably 4.0 parts by mass or less, and even more preferably 1.5 parts by mass or less, per 100 parts by mass of the base polymer. By making the content 10.0 parts by mass or less, unintended reactions such as self-reactions between silane coupling agents can be suppressed, which is preferable. In addition, it is possible to prevent the adhesive layer from becoming hard, which makes it difficult to approach the surface of the adherend, and thus prevents a situation in which sufficient adhesive strength cannot be obtained.

In other words, the content of the silane coupling agent in the adhesive composition or adhesive layer is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 7.0 parts by mass or less, even more preferably 0.5 parts by mass or more and 4.0 parts by mass or less, even more preferably 1.0 parts by mass or more and 4.0 parts by mass or less, and particularly preferably 1.0 parts by mass or more and 1.5 parts by mass or less. The content of the silane coupling agent may also be 0.5 parts by mass or more and 1.5 parts by mass or less, based on 100 parts by mass of the base polymer.

<Crosslinking Agent>
The adhesive composition according to the embodiment of the present invention preferably contains a crosslinking agent from the viewpoint of suppressing the deformation rate of the adhesive layer within a predetermined range and improving the elastic modulus. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and peroxides. The crosslinking agents can be used alone or in combination of two or more.

An isocyanate-based crosslinking agent is a compound that has two or more isocyanate groups in one molecule (including isocyanate regenerating functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization, etc.).

Isocyanate-based crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate.

More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and polymethylene polyphenyl isocyanate, trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name: Coronate L), trimethylolpropane/hexamethylene diisocyanate trimer adduct ( Examples of such polyisocyanates include isocyanate adducts such as isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name: Coronate HL), trimethylolpropane adduct of xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name: D110N), trimethylolpropane adduct of hexamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc., product name: D160N); polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc.

The isocyanate-based crosslinking agent may be used alone or in a mixture of two or more. The amount of the isocyanate-based crosslinking agent is, for example, 0.01 parts by mass or more, 0.02 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more, and 15 parts by mass or less, 10 parts by mass or less, 9 parts by mass or less, 8 parts by mass or less, 7 parts by mass or less, 6 parts by mass or less, or 5 parts by mass or less, relative to 100 parts by mass of the base polymer, and preferably 0.01 parts by mass or more and 15 parts by mass or less, 0.02 parts by mass or more and 13 parts by mass or less, or 0.05 parts by mass or more and 10 parts by mass or less. The amount may be adjusted appropriately taking into account the cohesive strength, etc.

By making the content of the isocyanate-based crosslinking agent equal to or greater than the above lower limit, the creep deformation rate of the adhesive sheet can be kept small. In addition, by making the content of the isocyanate-based crosslinking agent equal to or less than the above upper limit, it is possible to prevent the adhesive layer from becoming too hard, making it difficult to approach the adherend surface, and thus preventing sufficient adhesive strength from being obtained.

Epoxy crosslinkers are multifunctional epoxy compounds that have two or more epoxy groups in one molecule. Examples of epoxy crosslinkers include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, diamine glycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol. Examples of the epoxy-based crosslinking agent include polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy-based resins having two or more epoxy groups in the molecule. Examples of the epoxy-based crosslinking agent include products manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names "Tetrad C" and "Tetrad X."

The epoxy-based crosslinking agent may be used alone or in combination of two or more. The amount of the epoxy-based crosslinking agent is, for example, 0.01 parts by mass or more, 0.02 parts by mass or more, 0.05 parts by mass or more, or 0.1 parts by mass or more, and 10 parts by mass or less, 9 parts by mass or less, 8 parts by mass or less, 7 parts by mass or less, 6 parts by mass or less, or 5 parts by mass or less, relative to 100 parts by mass of the base polymer, and preferably 0.01 parts by mass or more and 10 parts by mass or less, 0.02 parts by mass or more and 9 parts by mass or less, or 0.05 parts by mass or more and 8 parts by mass or less. The amount may be adjusted appropriately taking into account the cohesive strength, etc.

By making the content of the epoxy-based crosslinking agent equal to or greater than the lower limit, the creep deformation rate of the adhesive sheet can be kept small. In addition, by making the content of the epoxy-based crosslinking agent equal to or less than the upper limit, it is possible to prevent the adhesive layer from becoming too hard, making it difficult to approach the adherend surface, and thus preventing sufficient adhesive strength from being obtained.

As a peroxide crosslinking agent, any peroxide that generates radical active species when heated and promotes crosslinking of the base polymer can be used as appropriate, but taking into consideration workability and stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80°C or higher and 160°C or lower, and it is even more preferable to use a peroxide with a 1-minute half-life temperature of 90°C or higher and 140°C or lower.

Peroxides include, for example, di(2-ethylhexyl) peroxydicarbonate (1-minute half-life temperature: 90.6°C), di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1°C), di-sec-butyl peroxydicarbonate (1-minute half-life temperature: 92.4°C), t-butyl peroxyneodecanoate (1-minute half-life temperature: 103.5°C), t-hexyl peroxypivalate (1-minute half-life temperature: 109.1°C), t-butyl peroxypivalate (1-minute half-life temperature: 110.3°C), dilauroyl peroxide ( 1-minute half-life temperature: 116.4°C), di-n-octanoyl peroxide (1-minute half-life temperature: 117.4°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (1-minute half-life temperature: 124.3°C), di(4-methylbenzoyl)peroxide (1-minute half-life temperature: 128.2°C), dibenzoyl peroxide (1-minute half-life temperature: 130.0°C), t-butylperoxyisobutyrate (1-minute half-life temperature: 136.1°C), 1,1-di(t-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2°C), and the like. Among these, di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1°C), dilauroyl peroxide (1-minute half-life temperature: 116.4°C), dibenzoyl peroxide (1-minute half-life temperature: 130.0°C), etc. are preferably used because they have particularly excellent crosslinking reaction efficiency.

The half-life of a peroxide is an index showing the decomposition rate of the peroxide, and refers to the time it takes for the remaining amount of peroxide to be reduced to half. The decomposition temperature to obtain the half-life at any given time, and the half-life time at any given temperature are listed in manufacturer catalogs, for example NOF Corporation's "Organic Peroxide Catalog 9th Edition (May 2003)."

One type of peroxide may be used alone, or two or more types may be used in combination. The amount of peroxide is 0.02 to 2 parts by mass, and preferably 0.05 to 1 part by mass, per 100 parts by mass of base polymer. The amount is adjusted appropriately within this range to adjust processability, reworkability, crosslinking stability, peelability, etc.

The amount of decomposed peroxide remaining after the reaction process can be measured, for example, by HPLC (high performance liquid chromatography).

More specifically, for example, about 0.2 g of the adhesive after the reaction process is taken out and immersed in 10 ml of ethyl acetate, and extracted by shaking at 120 rpm at 25°C for 3 hours on a shaker, and then left to stand at room temperature for 3 days. Next, 10 ml of acetonitrile is added, and the mixture is shaken at 120 rpm at 25°C for 30 minutes, and about 10 μl of the extract obtained by filtering through a membrane filter (0.45 μm) is injected into HPLC for analysis, and the amount of peroxide after the reaction process can be determined.

Also, organic crosslinking agents and polyfunctional metal chelates may be used in combination as crosslinking agents. Polyfunctional metal chelates are those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. An example of an atom in an organic compound that forms a covalent or coordinate bond is an oxygen atom, and examples of organic compounds include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

<Other ingredients>
The adhesive composition according to the embodiment of the present invention may contain a solvent from the viewpoint of application properties. Examples of the solvent that can be used include water, alcohols (e.g., methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, cellosolve, and carbitol), ketones (e.g., acetone, methyl ethyl ketone, and cyclohexanone), aromatic hydrocarbons (e.g., benzene, toluene, and xylene), aliphatic hydrocarbons (e.g., hexane, octane, decane, dodecane, and octadecane), esters (e.g., ethyl acetate, methyl propionate, and methyl phthalate), and ethers (e.g., tetrahydrofuran, ethyl butyl ether, and anisole).

The solvent is preferably blended so that the solids concentration of the adhesive composition is 1 to 100% by mass, and more preferably 5 to 60% by mass. The solids content refers to the components other than the solvent contained in the adhesive composition.

If necessary, a surfactant is added to the adhesive composition in order to adjust the surface tension. For example, a nonionic surfactant (e.g., a nonionic surfactant consisting of a long alkyl chain and polyethylene glycol), a cationic surfactant (e.g., a quaternary ammonium salt), or an anionic surfactant (e.g., an organic carboxylate, a sulfonate) can be used.

The adhesive composition may also contain a monomer that undergoes radical polymerization by active energy rays together with the photopolymerization initiator. The monomer that undergoes radical polymerization by active energy rays is polymerized by irradiation with active energy rays to form an active energy ray curable resin. The polymerization may be carried out in a step of reacting the base polymer with a silane coupling agent, or in a step of reacting the base polymer with the first reactive group RG1 contained in R _A in the above general formula (1), or in the case where irradiation with active energy rays is not required for the reaction of the first reactive group RG1, the polymerization reaction may be carried out separately from the step of reacting with the first reactive group RG1.

<Adhesive layer>
The adhesive layer according to this embodiment is an adhesive layer made of the above-mentioned adhesive composition.
The adhesive layer can be formed, for example, by preparing a substrate having a release-treated main surface, applying the above-mentioned adhesive composition to the release-treated main surface, and then removing the solvent from the applied adhesive composition.

As described above, the adhesive layer is a layer made of the adhesive composition after the base polymer contained in the adhesive composition has reacted with the silane coupling agent, or a layer made of the adhesive composition after the first reactive group RG1 in the silane coupling agent has chemically bonded with the functional group in the base polymer.

For example, when the adhesive layer contains a compound having at least one selected from the group consisting of an azide group, an azide sulfonyl group, a diazomethyl group, and a diazirine group as the first reactive group RG1, the adhesive layer obtained is irradiated with ultraviolet light (UV: ultraviolet). The azide group, azide sulfonyl group, diazomethyl group, or diazirine group of the adhesive molecule is decomposed by ultraviolet irradiation. Carbenes or nitrenes are generated by decomposition of the azide group, azide sulfonyl group, diazomethyl group, or diazirine group. The carbene or nitrene attacks the functional groups (e.g., -CH ₃ , -CH ₂ -, -CH<, -CH=CH-) on the surface of the optical sheet. Then, a hydrogen abstraction radical addition or radical addition reaction occurs, and a chemical bond is formed between the functional groups that the base polymer may have.

For light (ultraviolet light) irradiation, for example, a UV irradiation device (for example, a high pressure mercury UV lamp, a low pressure mercury UV lamp, a fluorescent UV lamp (short ARC xenon lamp, chemical lamp), or a metal halide lamp) is used. Then, for example, ultraviolet light of 200 to 450 nm is irradiated. If the amount of irradiation light is too small, the reaction does not proceed easily. Conversely, if the amount of irradiation light is too large, there is a risk of deterioration of the base polymer and other layers. Therefore, the preferred amount of irradiation light (light source wavelength: 254 nm) is 1 mJ/cm ² to 5 J/cm ² , and more preferably 5 mJ/cm ² to 1 J/cm ² .

In addition, for example, when a compound having an amino group as the first reactive group RG1 is contained, it can be obtained by heating at a temperature of, for example, 40 to 150°C. The heating temperature is preferably 60°C or higher, and more preferably 70°C or higher. In order to suppress deactivation of reactivity, the heating temperature is preferably 150°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower.

When the formation of chemical bonds between the base polymer and the silane coupling agent (bond formation step) is carried out by heating, this may be carried out during the step of removing the solvent from the adhesive composition, or the bond formation step may be carried out after the step of removing the solvent from the adhesive composition, separately from the step of removing the solvent from the adhesive composition.

In addition, when the adhesive layer contains a crosslinking agent, the base polymer and the crosslinking agent may form a crosslinked structure. In this specification, the above crosslinked structure is to be distinguished from a structure obtained by forming a chemical bond between the base polymer and the silane coupling agent.

An adhesive layer having a crosslinked structure between the base polymer and the crosslinking agent can be obtained by heating the adhesive composition or adhesive layer at 40 to 160°C. The heating time varies depending on the heating temperature and the type and amount of the crosslinking agent used, but for example, in the case of an epoxy-based crosslinking agent, heating for about 0.5 to 10 minutes is sufficient. In the case of an isocyanate-based crosslinking agent, aging for about 12 to 120 hours is preferable.

The formation of the crosslinked structure (crosslinking step) may be carried out in the step of removing the solvent from the adhesive composition, or a crosslinking step may be carried out after the step of removing the solvent from the adhesive composition, separately from the step of removing the solvent from the adhesive composition.

The formation of the crosslinked structure (crosslinking step) may be carried out by (1) forming a crosslinked structure by the crosslinking step described above, and then laminating an adhesive sheet including the adhesive layer to an adherend, or applying an adhesive composition to a main surface of an adherend, or (2) laminating an adhesive sheet including the adhesive layer to an adherend, or applying an adhesive composition to a main surface of an adherend, and then forming a crosslinked structure by the crosslinking step described above.

From the viewpoint of improving the adhesive strength with the adherend, the above method (2) is preferred. In this case, when the adhesive composition is applied to the adherend or to the main surface of the adherend, it is in a state before the crosslinked structure is formed and is highly flexible, so it conforms well to the adherend, and the silane coupling agent in the adhesive layer or adhesive composition easily approaches the adherend. This increases the number of reaction points between the silane coupling agent and the adherend, which is thought to further improve the adhesive strength with the adherend.

The adhesive layer is obtained by carrying out the above-mentioned bond forming step and preferably a crosslinking step. That is, in the adhesive layer, the base polymer and the crosslinking agent preferably form a crosslinked structure, and the base polymer and the silane coupling agent preferably form a chemical bond. That is, the base polymer and the crosslinking agent preferably form a crosslinked structure, the base polymer preferably has a functional group capable of forming a chemical bond with the first reactive group RG1 of the silane coupling agent, and the functional group preferably forms a chemical bond with the first reactive group RG1.

The adhesive layer after bond formation according to this embodiment has an improved cohesive force due to the bond formation between the silane coupling agent dispersed in the adhesive layer and the base polymer, and therefore can have a moderately high elastic modulus, which contributes to improved adhesion reliability. The elastic modulus of the adhesive layer after bond formation is preferably 0.1 to 10 MPa, and more preferably 0.2 to 5 MPa.

The above elastic modulus was calculated from the initial slope of the stress-displacement curve measured by using a tension-compression tester (AGS-50NX, manufactured by Shimadzu Corporation) to cut the adhesive layer to a width of 30 mm and a length of 30 mm, roll it into a cylindrical shape, and stretching the cylinder in the axial direction under conditions of 23°C, 65% RH (room temperature), chuck distance of 10 mm, and a tension speed of 50 mm/min.

In this embodiment, from the viewpoint of obtaining the desired adhesive strength, the thickness of the adhesive layer is preferably 0.01 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. Furthermore, in order to suppress a decrease in productivity, the thickness is preferably 100 μm or less, more preferably 75 μm or less, and even more preferably 50 μm or less. In other words, the thickness of the adhesive layer is preferably 0.01 to 100 μm.

In this embodiment, the total light transmittance of the adhesive layer is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. By making the total light transmittance 80% or more, the adhesive layer can be preferably used, for example, in applications where high transparency is required (for example, optical applications). The total light transmittance is measured using a commercially available haze meter with D65 light. As the haze meter, a product named "HZ-1" manufactured by Suga Test Instruments Co., Ltd. or an equivalent product is used.

In the adhesive layer of this embodiment, the adhesive strength to the PMMA film measured in the examples described below is preferably 3 N/20 mm or more, more preferably 4 N/20 mm or more, and even more preferably 5 N/20 mm or more.

The haze of the adhesive layer in this embodiment is, for example, 0.01% or more and 5% or less, 4% or less, 3% or less, 2% or less, or 1.5% or less. The haze is measured using a commercially available haze meter under D65 light. The haze meter used is a product manufactured by Suga Test Instruments Co., Ltd. under the trade name "HZ-1" or an equivalent product.

<Adhesive sheet>
As described above, the adhesive sheet of the embodiment of the present invention may be a sheet consisting of only the adhesive layer, or may be a sheet including a substrate.

In other words, the adhesive sheet of the embodiment of the present invention may include a substrate and have the above-mentioned adhesive layer on one main surface of the substrate. Also, the adhesive sheet of the embodiment of the present invention may include a substrate and have the above-mentioned adhesive layer on both main surfaces of the substrate.

FIG. 5 shows an adhesive sheet 20 having an adhesive layer 22 on one main surface of a substrate 21. In the adhesive sheet 20 according to this embodiment, the main surface of the substrate 21 may be subjected to a release treatment and may be bonded to the adhesive layer 22. In other words, the substrate 21 may be a release liner.

In FIG. 5, an adhesive layer is provided on only one main surface of the substrate, but the substrate may have an adhesive layer on both main surfaces.

The above description of the adhesive layer can be used as is for the adhesive layer in the adhesive sheet according to this embodiment.

The material of the substrate is not particularly limited and can be appropriately selected depending on the purpose and manner of use of the adhesive sheet. Examples of substrates include suitable thin materials such as synthetic resin films such as polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl alcohol, rubber sheets, paper, cloth, nonwoven fabrics, nets, foam sheets, metal foils, and laminates of these.

When performing a release treatment on the main surface of the substrate, a release agent is applied (applied) to one of the main surfaces of the substrate, and then further dried as necessary. There are no particular limitations on the release agent, but examples include silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, and fatty acid amide-based release agents.

The adhesive sheet according to this embodiment may further include, for example, another substrate arranged on the opposite side of the adhesive layer to the substrate. The main surface of the other substrate may be subjected to a release treatment, and the release-treated main surface may be bonded to the adhesive layer.

The adhesive sheet 20 according to this embodiment is prepared, for example, by preparing a substrate 21 having a main surface that has been subjected to a release treatment, and applying the above-mentioned adhesive composition to this main surface that has been subjected to the release treatment. Next, the solvent of the applied adhesive composition is removed to obtain an adhesive sheet 20 having an adhesive layer 22 formed on the substrate 21. The adhesive layer 22 may further have a crosslinked structure formed between the base polymer and the crosslinking agent through a crosslinking process, or may have a chemical bond formed between the base polymer and the silane coupling agent through the bond formation process described above. Alternatively, it may form both.

Methods for forming an adhesive sheet on an adherend such as an optical sheet include: (1) a method in which an adhesive sheet including an adhesive layer is obtained by a bond-forming step between a base polymer and a silane coupling agent, and then the adhesive layer in the adhesive sheet is attached to an adherend to form an adhesive sheet on the adherend; and (2) a method in which an adhesive composition is applied to a main surface of an adherend, and then an adhesive sheet is formed on the adherend by a bond-forming step between a base polymer and a silane coupling agent.
The following are some of the reasons:

From the viewpoint of improving the adhesive strength with the adherend, the above method (2) is preferred. In this case, when the adhesive composition is applied to the main surface of the adherend, the adhesive composition is in a state before the above bond formation and is highly flexible, so it conforms well to the adherend, and the silane coupling agent in the adhesive composition easily approaches the adherend. This increases the number of reaction points between the silane coupling agent and the adherend, which is thought to further improve the adhesive strength with the adherend.

In addition, when the above method (1) is performed, the first reactive group RG1 reacts only with functional groups that the base polymer may have, but when the above method (2) is performed, the first reactive group RG1 reacts not only with the base polymer but also with functional groups that the adherend may have to form chemical bonds, which presumably results in a more complex network and stronger adhesive strength.

<Optical laminate>
An optical laminate according to another embodiment of the present invention is characterized in that it comprises a first optical sheet having a first main surface having a concave-convex structure and a second main surface opposite the first main surface, and an adhesive sheet according to the above embodiment arranged on the first main surface side of the first optical sheet.

With reference to Figures 6 to 8, optical laminates 100B and 101B according to other embodiments of the present invention will be described. Note that for components having substantially the same functions as those of the previous embodiment, the description of the previous embodiment applies unless otherwise specified. Optical laminate 100B functions as a light distribution control element described in WO 2019/087118, for example, and can be manufactured using a roll-to-roll method. The entire disclosure of WO 2019/087118 is incorporated herein by reference.

FIG. 6 is a schematic cross-sectional view of the optical laminates 100B and 101B, showing the state in which the first optical sheet 10b is adhered to the surface 38s of the second optical sheet 30 via an adhesive sheet 20b. FIG. 7 is a schematic perspective view of the optical sheet 10b of the optical laminate 100B. FIG. 8 is a schematic cross-sectional view of an illumination device 200 including the optical laminate 102B and a light source 60, and shows the trajectory of light rays.

Refer to Figures 6 and 7. The optical laminate 100B has a first optical sheet 10b having a first main surface 12s and a second main surface 18s opposite to the first main surface 12s, which have an uneven structure, and an adhesive sheet 20b arranged on the first main surface 12s side of the first optical sheet 10b. The optical laminate 101B has the optical laminate 100B and a second optical sheet 30 arranged on the side opposite to the first optical sheet 10b side of the adhesive sheet 20a. Here, the uneven structure of the first main surface 12s of the first optical sheet 10b includes a plurality of recesses 14, and the surface of the adhesive sheet 20b and the first main surface 12s of the first optical sheet 10b define a plurality of spaces 14 (indicated by the same reference numeral as the recesses) in the plurality of recesses 14. The adhesive sheet 20b is a necessary component for defining the spaces 14 of the optical laminate 100B, and is a part of the optical laminate 100B.

The uneven structure of the first optical sheet 10b includes flat portions 10s that contact the adhesive sheet 20b. The uneven structure includes, for example, a plurality of convex portions 15 each having a trapezoidal cross section. Since the uneven structure has flat portions 10s that contact the adhesive sheet 20b, the uneven structure of the first optical sheet 10b is less susceptible to the pressure-sensitive adhesive layer of the adhesive sheet 20b penetrating into the concave portions than the uneven structure of the first optical sheet 10a shown in FIG. 1. Therefore, by using the above adhesive composition, it is possible to obtain an optical laminate 100B that can suppress the pressure-sensitive adhesive layer of the adhesive sheet 20b from penetrating into the plurality of spaces 14 and does not change over time.

The first optical sheet 10b can be manufactured in a similar manner using the same materials as known prism sheets or microlens sheets. The size and shape of the uneven structure of the first optical sheet 10b can be changed as appropriate (Patent Document 2). However, as described above, the first optical sheet 10b differs from known prism sheets or microlens sheets in that it functions as an optical laminate 100B in which the space 14 is defined only after it is adhered to the adhesive sheet 20b.

As shown in FIG. 6, in the optical laminate 101B, the second optical sheet 30 may be arranged so that its surface 38s is adhered to the surface 22s of the adhesive sheet 20b. In addition, in an embodiment in which the adhesive sheet of this embodiment includes a substrate, the substrate may have the above-mentioned adhesive layer or any adhesive on the second optical sheet 30 side, and the adhesive sheet of this embodiment and the second optical sheet 30 may be adhered via the adhesive layer or any adhesive.

Any suitable material can be used as the material constituting the second optical sheet 30 depending on the purpose. Examples of materials for the second optical sheet 30 include light-transmitting thermoplastic resins, and more specifically, examples include films formed from (meth)acrylic resins such as polymethyl methacrylate (PMMA) and polycarbonate (PC) resins.

The first optical sheet 10b and the second optical sheet 30 are preferably selected so as to have a functional group capable of reacting with the second reactive group RG2 in the adhesive layer or the second reactive group RG2 represented by -Si-(R ¹ ) _n (OR ² ) _3-n contained in the compound represented by general formula (1) and to form a chemical bond with the silane coupling agent in the adhesive layer.

It is also preferable that the first optical sheet 10b and the second optical sheet 30 further have a functional group capable of reacting with the first reactive group RG1 in the adhesive layer or the first reactive group RG1 contained in R _A of the compound represented by general formula (1). When the bond formation step of the adhesive layer is performed after bonding with the first optical sheet 10b or the second optical sheet 30, the first optical sheet 10b or the second optical sheet 30 forms a chemical bond with the first reactive group RG1 as well, which makes the network more complex and results in stronger adhesive strength, which is preferable.

If necessary, the first optical sheet 10b and the second optical sheet 30 may be surface-modified to introduce functional groups capable of reacting with the second reactive group RG2 and/or functional groups capable of reacting with the first reactive group RG1. Examples of surface modification include introducing hydroxyl groups by corona treatment, sputter etching, plasma treatment, etc.

The space 14 of the optical laminate 100B is defined by surfaces 16s and 17s, which are part of the first main surface 12s of the first optical sheet 10b, and surface 28s of the adhesive sheet 20b. Here, an example is shown in which surface 16s is inclined (more than 0° and less than 90°) with respect to the sheet surface (horizontal direction in the figure) and surface 17s is approximately perpendicular to the sheet surface, but this is not limited to this and various modifications are possible (see Patent Document 2).

The optical laminate 100B is used in a lighting device 200, for example, as shown in FIG. 8. A light guide plate 50 is provided on the side of the adhesive sheet 20b of the optical laminate 100B opposite the first optical sheet 10b side. The optical laminate 100B and the light guide plate 50 are collectively referred to as the optical laminate 102B. The optical laminate 102B is adhered to the light guide plate 50 at the surface 22s of the adhesive sheet 20b of the optical laminate 100B. The light receiving surface of the light guide plate 50 is arranged so that light from a light source (e.g., an LED) 60 is incident on the light receiving surface of the light guide plate 50, and the light guided into the light guide plate 50 is totally reflected (TIR) at the interface (surface) 16s and interface (surface) 14s formed by the space 14, as shown by the arrows in FIG. 8. The light rays totally reflected at the interface (surface) 14s (surface 28s of the adhesive sheet 20b) are guided through the light guide plate 50 and the adhesive sheet 20b, and the light rays totally reflected at the inclined surface (surface) 16s are emitted to the outside from the main surface (surface) 18s of the optical laminate 100B. By adjusting the shape, size, arrangement density, etc. of the space 14, the distribution (light distribution) of the light rays emitted from the optical laminate 100B can be adjusted. Here, it is preferable that the refractive indexes of the light guide plate 50, the adhesive sheet 20b, and the first optical sheet 10b are equal to each other.

FIGS. 6 to 8 show an example in which the cross-sectional shape of the protrusions 15 is trapezoidal, but the shape of the protrusions 15 is not limited to that shown in the drawings and can be modified in various ways. By adjusting the shape, size, etc. of the protrusions 15, the shape, size, arrangement density, etc. of the spaces 14 can be adjusted. For example, WO 2011/124765 describes an example of a laminate having multiple spaces therein. The entire disclosure of WO 2011/124765 is incorporated herein by reference.

<Method for producing optical laminate>
In the case of producing an optical laminate, methods for laminating an adhesive sheet onto a first optical sheet or a second optical sheet include (1) a method of bonding an adhesive sheet including an adhesive layer obtained by reacting a silane coupling agent contained in an adhesive composition with a base polymer to the first optical sheet or the second optical sheet, and (2) a method of applying an adhesive composition onto a main surface of the first optical sheet or the second optical sheet, and then reacting a silane coupling agent contained in the adhesive composition with a base polymer to form an adhesive sheet including an adhesive layer on a main surface of the first optical sheet or the second optical sheet.

From the viewpoint of improving the adhesive strength with the first optical sheet or the second optical sheet, the above method (2) is preferred. In this case, when the adhesive composition is applied to the main surface of the first optical sheet or the second optical sheet, the adhesive composition is in a state before the silane coupling agent and the base polymer react, and is highly flexible, so it has high conformability to the first optical sheet or the second optical sheet, and the silane coupling agent in the adhesive composition easily approaches the first optical sheet or the second optical sheet. This increases the number of reaction points between the silane coupling agent and the adherend, which is thought to further improve the adhesive strength with the first optical sheet or the second optical sheet.

In addition, when the above method (1) is performed, the first reactive group RG1 reacts only with functional groups that the base polymer may have, but when the above method (2) is performed, the first reactive group RG1 reacts not only with the base polymer but also with functional groups that the first optical sheet or the second optical sheet may have to form chemical bonds, which presumably results in a more complex network and stronger adhesive strength.

　Below, we will explain the above methods (1) and (2) separately.

(1) Method of bonding an adhesive sheet including an adhesive layer to a first optical sheet or a second optical sheet To bond an adhesive sheet including an adhesive layer to a first optical sheet or a second optical sheet, a roll-to-roll method is preferably used.

In the case of producing an optical laminate further including a second optical sheet arranged on the opposite side of the adhesive sheet to the first optical sheet,
A step A1 of bonding a first laminate in which a first optical sheet and an adhesive sheet are laminated to a second optical sheet; or
It is preferable that the method includes any one of a step A2 of bonding a second laminate in which the adhesive sheet and the second optical sheet are laminated to the first optical sheet.

It is also preferable that the method includes the step A1, which includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or that the method includes the step A2, which includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.

(2) A method in which an adhesive composition is applied onto a principal surface of a first optical sheet or a second optical sheet, and then a silane coupling agent contained in the adhesive composition is reacted with a base polymer to form an adhesive sheet including an adhesive layer on the principal surface of the first optical sheet or the second optical sheet. The method for producing an optical laminate by the above-mentioned method (2) includes the following:
A step A of applying an adhesive composition onto a first main surface of a first optical sheet;
and a step B of reacting the base polymer and the silane coupling agent contained in the adhesive composition in a state in which the adhesive composition is applied onto the first main surface of the first optical sheet.
In the step A, it is preferable to apply the adhesive composition onto the first main surface of the first optical sheet by bonding the first optical sheet and the adhesive composition by a roll-to-roll method.

In the case of producing an optical laminate further including a second optical sheet arranged on the opposite side of the adhesive sheet to the first optical sheet,
Either a step A1 of bonding a first laminate in which a first optical sheet and an adhesive composition are laminated to a second optical sheet, or a step A2 of bonding a second laminate in which an adhesive composition and a second optical sheet are laminated to the first optical sheet;
It is preferable to include a step B of reacting a base polymer contained in the adhesive composition with a silane coupling agent after the step A1 or the step A2.

It is also preferable that the method includes the step A1, which includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or that the method includes the step A2, which includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.

In the method for producing the optical laminate, whether the method is (1) or (2) above, the surfaces of the first optical sheet 10b and the second optical sheet 30 that come into contact with the adhesive sheet may be pretreated, such as by cleaning or surface treatment, as necessary.

Cleaning treatments include alkaline degreasing treatments, which involve cleaning the surface with an alkaline cleaning solution, followed by rinsing with distilled water and drying.

Examples of surface treatments include corona treatment, sputter etching, and plasma treatment. As described above, the surface treatment may introduce functional groups capable of reacting with the second reactive group RG2 and/or functional groups capable of reacting with the first reactive group RG1 into the first optical sheet 10b and the second optical sheet 30.

Corona treatment can be, for example, a method in which discharge is performed in air at normal pressure using a corona treatment machine. For example, corona treatment is performed by irradiating the surface of the substrate with discharge using a corona surface treatment device with a high-frequency power source. The discharge output intensity is preferably 0.05 kW or more, more preferably 0.08 kW or more, and even more preferably 0.1 kW or more.

In sputter etching, for example, energetic particles from a gas are bombarded against the surface of a substrate, where atoms or molecules present on the substrate surface are released and reactive groups are formed at the portions of the substrate where the particles strike, thereby improving adhesion.
The sputter etching treatment can be carried out, for example, by placing the substrate in a chamber, reducing the pressure inside the chamber, and then applying a high-frequency voltage while introducing an atmospheric gas.

The atmospheric gas is at least one selected from the group consisting of rare gases such as helium, neon, argon, and krypton, nitrogen gas, and oxygen gas.

The frequency of the applied high-frequency voltage is, for example, 1 to 100 MHz, preferably 5 to 50 MHz.

The pressure in the chamber when applying the high frequency voltage is, for example, 0.05 to 200 Pa, preferably 1 to 100 Pa. The energy of the sputter etching (the product of the processing time and the applied power) is, for example, 1 to 1000 J/cm ² , preferably 2 to 200 J/cm ² .

Plasma treatment can be carried out, for example, by discharging electricity in air at normal pressure using a plasma discharger. The substrate is placed in the plasma device and exposed to plasma using a specified gas.

The conditions for the plasma treatment can be set to any appropriate conditions as long as the effects of the present invention are obtained.

The above plasma treatment may be performed under atmospheric pressure, or may be performed under reduced pressure. The pressure (degree of vacuum) during the plasma treatment is, for example, 0.05 Pa to 200 Pa, and preferably 0.5 Pa to 100 Pa.

The frequency of the high frequency power source used for plasma processing is, for example, 1 MHz to 100 MHz, and preferably 5 MHz to 50 MHz.

The amount of energy during the plasma treatment is preferably 0.1 J/cm ² to 100 J/cm ² , and more preferably 1 J/cm ² to 20 J/cm ² .

The plasma treatment time is preferably 1 second to 5 minutes, and more preferably 5 seconds to 3 minutes.

The gas supply rate during plasma processing is preferably 1 sccm to 150 sccm, and more preferably 10 sccm to 100 sccm.

The reactive gas used in the plasma treatment may be, for example, water vapor, air, oxygen, nitrogen, hydrogen, ammonia, alcohol (e.g., ethanol, methanol, isopropyl alcohol), etc. By using such a reactive gas, a substrate with excellent adhesion can be obtained. In addition, inert gases such as helium, neon, argon, etc. may be used in combination with the reactive gas.

The type of surface treatment can be selected appropriately depending on the materials that make up the support and adherend.

Optical Devices
An optical device according to another embodiment of the present invention includes the optical laminate according to the above embodiment. Examples of the optical device include an image display device, a lighting device, and a light-emitting device.

As described above, the present specification discloses the following:
[1] An adhesive sheet comprising an adhesive layer made of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer,
In a creep test using a rotational rheometer, the adhesive layer has a creep deformation rate of 10% or less when a stress of 10,000 Pa is applied to it at 50° C. for 1 second, and a creep deformation rate of 16% or less when a stress of 10,000 Pa is applied to it at 50° C. for 30 minutes.
Adhesive sheet.
[2] The silane coupling agent includes a compound having a first reactive group RG1 and a second reactive group RG2,
the first reactive group RG1 is at least one selected from the group consisting of an amino group, an azide group, an azidosulfonyl group, a diazomethyl group, a diazirine group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group;
The adhesive sheet according to [1] above, wherein the second reactive group RG2 is at least one selected from a silanol group and a group that generates a silanol group by hydrolysis reaction.
[3] The adhesive sheet according to [2] above, wherein the base polymer has a functional group capable of forming a chemical bond with the first reactive group RG1.
[4] The first reactive group RG1 is an amino group,
The adhesive sheet according to [3] above, wherein the functional group of the base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.
[5] The first reactive group RG1 is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group,
The adhesive sheet according to [3] above, wherein the functional group of the base polymer is at least one selected from the group consisting of -CH ₃ , -CH ₂ -, -CH<, and -CH=CH-.
[6] The adhesive sheet according to any one of [1] to [5] above, wherein the silane coupling agent contains a compound having an aromatic ring.
[7] The adhesive sheet according to [6], wherein the silane coupling agent contains a compound having a triazine ring.
[8] The adhesive sheet according to any one of [1] to [7], wherein the content of the silane coupling agent in the adhesive composition is 0.01 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the base polymer.
[9] The adhesive sheet according to any one of [1] to [8] above, wherein the adhesive layer has a thickness of 0.01 to 100 μm.
[10] The adhesive sheet according to any one of [1] to [9] above, wherein the adhesive layer has a total light transmittance of 80% or more.
[11] The adhesive sheet according to any one of [1] to [10] above, further comprising a substrate, the adhesive layer being provided on one main surface of the substrate.
[12] The adhesive sheet according to any one of [1] to [10] above, further comprising a substrate, the adhesive layer being provided on both main surfaces of the substrate.
[13] The adhesive sheet according to [11] or [12] above, wherein one or both main surfaces of the substrate are release-treated, and the adhesive layer is provided on the release-treated main surface.
[14] An optical laminate comprising: a first optical sheet having a first main surface having a concave-convex structure and a second main surface opposite the first main surface; and an adhesive sheet according to any one of [1] to [13] that is disposed on the first main surface side of the first optical sheet.
[15] The optical laminate described in [14], wherein the uneven structure includes a plurality of recesses, and the surface of the adhesive layer and the first main surface of the first optical sheet define a plurality of spaces in the plurality of recesses.
[16] The optical laminate described in [15], wherein the uneven structure includes a flat portion in contact with the adhesive layer.
[17] A method for producing the optical laminate according to any one of [14] to [16] above, comprising a step of bonding the first optical sheet and the adhesive sheet.
[18] The manufacturing method according to [17] above, wherein the process is carried out by a roll-to-roll method.
[19] The optical laminate according to any one of [14] to [16], further comprising a second optical sheet arranged on the opposite side of the adhesive sheet to the first optical sheet.
[20] A method for producing the optical laminate according to [19],
A manufacturing method including either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive sheet are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive sheet and the second optical sheet are laminated to the first optical sheet.
[21] The manufacturing method described in [20] above, comprising the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or comprising the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
[22] A method for producing the optical laminate according to [19],
A step A of applying the adhesive composition onto the first main surface of the first optical sheet;
and step B of reacting the base polymer and the silane coupling agent contained in the adhesive composition in a state in which the adhesive composition is applied onto the first main surface of the first optical sheet.
[23] The manufacturing method according to [22], wherein the step A includes a step of bonding the first optical sheet and the adhesive composition by a roll-to-roll method.
[24] A method for producing the optical laminate according to [19],
Either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive composition are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive composition and the second optical sheet are laminated to the first optical sheet;
A process for producing a composition comprising the steps of: (a) reacting the base polymer contained in the adhesive composition with the silane coupling agent after the step A1 or the step A2;
[25] The method includes the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or the method includes the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
The manufacturing method described in [24] above.
[26] An optical device comprising the optical laminate according to any one of [14], [15], [16] and [19].

The present invention will be explained in detail below with reference to examples, but the present invention is not limited to these examples in any way.

Example 1
<Preparation of Adhesive Composition>
(Preparation of Polyester Resin and Polymer Solutions)
A four-neck separable flask was equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a cooling tube with a trap. 47 g of terephthalic acid (molecular weight: 166) and 45 g of isophthalic acid (molecular weight: 166) as carboxylic acid components, 115 g of polytetramethylene glycol (molecular weight: 566), 4 g of ethylene glycol (molecular weight: 62), 16 g of neopentyl glycol (molecular weight: 104), and 23 g of cyclohexanedimethanol (molecular weight: 144) as alcohol components, and 0.1 g of tetrabutyl titanate as a catalyst were added to the flask. The flask was filled with nitrogen gas and the mixture was heated to 240° C. with stirring, and maintained at 240° C. for 4 hours.

Then, the nitrogen inlet tube and cooling tube with trap were removed and replaced with a vacuum pump. The mixture was heated to 240°C while stirring in a reduced pressure atmosphere (0.002 MPa) and maintained at 240°C. The reaction was continued for approximately 6 hours to obtain polyester resin A. Polyester resin A was obtained by polymerizing the above monomers without using a solvent. The mass average molecular weight (Mw) of polyester resin A measured by GPC was 59,200. The prepared polyester resin A was removed from the flask while being dissolved in ethyl acetate, and a polymer solution containing polyester resin A as a base polymer with a solids concentration of 50% by mass was prepared.

(Preparation of polyester adhesive composition)
For 100 parts by mass of the base polymer in the polymer solution prepared above, 0.197 parts by mass of zirconium tetraacetylacetonate (trade name "Orgatix ZC-162", manufactured by Matsumoto Fine Chemical Co., Ltd.) was used as a crosslinking catalyst, and 12 parts by mass of an isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) was used as a crosslinking agent. Further, 1.1 parts by mass of molecular adhesive reagent 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide (manufactured by Io Chemical Research Institute Co., Ltd.) was added to give a solids concentration of 26 μmol/g, and ethyl acetate was further added to give a solids concentration of 20% by mass to prepare a polyester adhesive composition.

<Preparation of polyester adhesive sheet>
The polyester adhesive composition was applied to one side of a silicone release-treated 38 μm polyethylene terephthalate (PET) film (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying was 3 μm, and the film was dried at 140 ° C. for 3 minutes to form an adhesive layer. Next, an acrylic resin film having a thickness of 30 μm, a transmittance of 17% at a wavelength of 250 nm, and a transmittance of 53% at a wavelength of 270 nm was subjected to corona treatment, and an adhesive layer was bonded to the treated surface. The release-treated PET film was peeled off, and the surface of the exposed adhesive layer was irradiated with ultraviolet light, and then a release-treated PET film was bonded again to prepare a polyester adhesive sheet.
The above ultraviolet irradiation was performed using an LED lamp (manufactured by Quark Technology Co., Ltd., peak illuminance: 45 mW/ ^cm2 , accumulated light quantity: 100 mJ/ ^cm2 (peak wavelength: 265 nm)), and the ultraviolet illuminance was measured using an ultraviolet integrating light meter (main device name: "UIT-250", receiver device name: "UVD-S254", manufactured by Ushio Inc.).

Example 2
<Preparation of Adhesive Composition>
(Preparation of Acrylic Polymer)
A monomer mixture containing 84 parts by mass of butyl acrylate, 12 parts by mass of N-acryloylmorpholine, 3 parts by mass of acrylic acid, and 1 part by mass of 4-hydroxybutyl acrylate was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Furthermore, 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 70 parts by mass of ethyl acetate relative to 100 parts by mass of the monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 1 hour to prepare a polymer solution ((meth)acrylic polymer solution) containing a (meth)acrylic polymer having a weight average molecular weight (Mw) of 2.9 million as a base polymer.

(Preparation of Acrylic Adhesive Composition)
An acrylic adhesive composition was prepared by blending 100 parts by mass of the base polymer in the obtained (meth)acrylic polymer solution with 0.2 parts by mass of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals, Inc. under the trade name "Takenate D-101E", tolylene diisocyanate) and 0.2 parts by mass of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc. under the trade name "Tetrad C"). Further, 1.0 part by mass of a molecular adhesive reagent 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide (manufactured by Io Chemical Laboratory Co., Ltd.) was added to give a solids concentration of 26 μmol/g, and ethyl acetate was further added to give a solids concentration of 10% by mass.

<Preparation of acrylic adhesive sheet>
An acrylic adhesive sheet was produced in the same manner as in Example 1, except that the above acrylic adhesive composition was used instead of the polyester adhesive composition, and an adhesive layer was formed so that the thickness after drying was 10 μm.

Example 3
<Preparation of Adhesive Composition>
(Preparation of Acrylic Polymer)
In the same manner as in Example 2, a solution of a (meth)acrylic polymer was prepared.

(Preparation of Acrylic Adhesive Composition)
In preparing the adhesive composition solution described in Example 3, the amount of the molecular adhesive reagent 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide was changed to 0.2 parts by mass (solids concentration: 5 μmol/g), and the rest of the procedure was the same as in Example 3 to prepare an acrylic adhesive composition.

<Preparation of acrylic adhesive sheet>
An acrylic adhesive sheet was produced in the same manner as in Example 1, except that the above acrylic adhesive composition was used instead of the polyester adhesive composition, and an adhesive layer was formed so that the thickness after drying was 10 μm.

Comparative Example 1
<Preparation of adhesive composition and polymer solution>
(Preparation of Polyester Resin)
In the same manner as in Example 1, a polymer solution containing polyester resin A as a base polymer was prepared.

(Preparation of polyester adhesive composition)
A polyester adhesive composition was prepared in the same manner as in Example 1 for preparing the adhesive composition solution, except that the molecular adhesive reagent 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide was not added.

<Preparation of polyester adhesive sheet>
The polyester adhesive composition was applied to one side of a silicone release-treated 38 μm polyethylene terephthalate (PET) film (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the adhesive layer was 3 μm thick after drying, and dried at 140 ° C for 3 minutes to form an adhesive layer. Next, an acrylic resin film with a thickness of 30 μm, a transmittance of 17% at a wavelength of 250 nm, and a transmittance of 53% at a wavelength of 270 nm was subjected to corona treatment, and an adhesive layer was attached to the treated surface. Next, the film was aged at 40 ° C for 1 day to prepare a polyester adhesive sheet.

Comparative Example 2
<Preparation of Adhesive Composition>
(Preparation of Polyester Resin)
In the same manner as in Example 1, a polyester resin and a polymer solution were prepared.

(Preparation of polyester adhesive composition)
A polyester adhesive composition was prepared in the same manner as in Example 1, except that 3-methacryloxypropyltrimethoxysilane (product name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.) was blended in place of the molecular adhesive reagent so that the solids concentration was 26 μmol/g (blended amount 0.7 parts by mass). Here, 3-methacryloxypropyltrimethoxysilane is a silane coupling agent in which the first reactive group RG1 does not react with the base polymer.

<Preparation of polyester adhesive sheet>
The polyester adhesive composition was applied to one side of a silicone release-treated 38 μm polyethylene terephthalate (PET) film (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the adhesive layer would be 3 μm thick after drying, and the adhesive layer was formed by drying for 3 minutes at 140° C. Next, an acrylic resin film having a thickness of 30 μm, a transmittance of 17% at a wavelength of 250 nm, and a transmittance of 53% at a wavelength of 270 nm was subjected to a corona treatment, and an adhesive layer was attached to the treated surface to produce a polyester adhesive sheet.

Comparative Example 3
<Preparation of Adhesive Composition>
(Preparation of Acrylic Polymer)
In the same manner as in Example 2, a solution of a (meth)acrylic polymer was prepared.

(Preparation of Acrylic Adhesive Composition)
An acrylic adhesive composition was prepared in the same manner as in Example 2, except that the molecular adhesive reagent 6-(3-triethoxysilylpropyl)amino-1,3,5-triazine-2,4-diazide was not added.

<Preparation of acrylic adhesive sheet>
An acrylic adhesive sheet was produced in the same manner as in Example 2, except that the above acrylic adhesive composition was used and the exposed surface of the adhesive layer was not irradiated with ultraviolet light.

〔evaluation〕
<5-10% elongation elastic modulus of adhesive layer>
For each of Examples 1 to 3 and Comparative Examples 2 to 3, the adhesive sheet was prepared in the same manner as above, except that the thickness of the adhesive composition was 15 μm, and further, instead of the acrylic resin film, an adhesive layer was attached to the treated surface of a 38 μm polyethylene terephthalate (PET) film (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) that had been subjected to a silicone release treatment to produce an adhesive sheet having a laminated structure of a release-treated PET film/adhesive composition layer (thickness 15 μm)/release-treated PET film. Then, the adhesive sheet was aged at 40 ° C. for 1 day, and an adhesive sheet having a laminated structure of a release-treated PET film/adhesive layer (thickness 15 μm)/release-treated PET film was produced for each of Examples 1 to 3 and Comparative Examples 2 to 3.

In addition, for Comparative Example 1, similar to the adhesive sheet described above, except that the thickness of the adhesive composition was 15 μm, and further, instead of the acrylic resin film, an adhesive layer was laminated to the treated surface of a 38 μm polyethylene terephthalate (PET) film (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) that had been subjected to a silicone release treatment, to produce an adhesive sheet having a laminated structure of release-treated PET film/adhesive layer (thickness 15 μm)/release-treated PET film.

A sample piece measuring 30 mm in width and 30 mm in length was cut from the obtained adhesive sheet, and one of the release-treated PET films was peeled off to expose the adhesive layer, which was rolled into a cylindrical shape with a cross-sectional area of approximately 0.45 ^mm2 to prepare a measurement sample.

The cylindrical measurement sample was set in a tension and compression tester (machine name "AGS-50NX", manufactured by Shimadzu Corporation) under a measurement environment of 23°C and 65% RH, and the change (mm) due to elongation in the axial direction of the cylinder was measured under conditions of a chuck distance of 10 mm and a tensile speed of 50 mm/min. In the S-S (Strain-Strength) curve obtained from this, the initial tensile modulus E ₀ of the adhesive composition was defined as E ₀ = (σ ₂ -σ ₁ )/(ε ₂ -ε ₁ ), where tensile stresses corresponding to two tensile strains (ε ₁ =5% and ε ₂ =10%) are σ1 and σ2, respectively. Here, the tensile strain ε is calculated together with the chuck distance.
ε=(L ₁ −L ₀ )/L ₀
Or ε(%)=100×(L ₁ −L ₀ )/L ₀
ε: Tensile strain (dimensionless ratio or percentage)
L ₀ : Initial chuck distance (mm)
_L1 : Distance between chucks after extension (mm)
The tensile stress σ is calculated based on the cross-sectional area of the test piece before elongation.
σ=F/A
σ: tensile stress (MPa)
F: Measurement load (N)
A: Cross-sectional area of the test piece before elongation (mm ² )

<Adhesive strength to unevenly shaped film>
(Manufacturing of textured film)
A concave-convex film was produced according to the method described in Japanese Patent Publication No. 2013-524288. Specifically, the surface of a polymethyl methacrylate (PMMA) film was coated with lacquer (Finecure RM-64, manufactured by Sanyo Chemical Industries, Ltd.), an optical pattern was embossed on the film surface containing the lacquer, and then the lacquer was cured to produce the desired concave-convex film. The total thickness of the concave-convex film was 130 μm, and the haze value was 0.8%.

FIG. 9 shows a plan view of a portion of the produced unevenly shaped film 70 as viewed from the uneven surface side. FIG. 10 shows a cross-sectional view of the unevenly shaped film of FIG. 9. A plurality of recesses 74 having a length L of 80 μm, a width W of 14 μm, and a depth H of 10 μm and a triangular cross section were arranged at intervals of width E (155 μm) in the X-axis direction. Furthermore, a pattern of such recesses 74 was arranged at intervals of width D (100 μm) in the Y-axis direction. The pitch Px of the recesses 74 in the X-axis direction was 235 μm (Px = L + E), and the pitch Py in the Y-axis direction was 114 μm (Py = W + D). The density of the recesses 74 on the unevenly shaped film surface was 3612 pieces/cm2. θa and θb in FIG. 10 were both 41°, and the occupied area ratio of the recesses 74 when the film was viewed in plan from the uneven surface side was 4.05%.

(Preparation of Adherend)
A polymethyl methacrylate (PMMA) plate (thickness 2 mm, product name "Acrylite", manufactured by Mitsubishi Chemical Corporation) and a double-sided tape (product name "NO. 5000NS", manufactured by Nitto Denko Corporation) were prepared.
One of the release-treated release films was peeled off from the double-sided tape and the exposed surface of the adhesive layer was bonded to a PMMA plate, and then the other release-treated release film was peeled off and the smooth surface of the unevenness-imparting film was bonded to the exposed surface of the adhesive layer to obtain an adherend having a laminated structure of PMMA plate/double-sided tape/unevenness-imparting film.

(Preparation of test specimens)
The adhesive sheet obtained in the examples and comparative examples was cut to a width of 20 mm. The uneven surface of the uneven surface-forming film was subjected to corona treatment, the peel-treated PET film was peeled off, and the uneven surface-forming film of the adherend (PMMA plate/double-sided tape/uneven surface-forming film) was attached to the uneven surface-forming film. The pressure bonding when attaching to the adherend was performed by rolling a 2 kg roller back and forth once to bond them together. Then, the test piece was aged at 40 ° C for 18 hours to obtain a test piece.

(measurement)
After standing for 30 minutes under the measurement temperature conditions, the 90° peel adhesive strength was measured under the following conditions using a variable angle high speed peel tester (device name "VPH-H200", manufactured by Kyowa Interface Science Co., Ltd.).
Peel speed: 150 mm/min Measurement conditions: Temperature: 23±2°C, Humidity: 65±5% RH
The evaluation results are shown in Table 1. In addition, in Examples 2 and 3 and Comparative Example 3, measurements were not performed and are indicated as "N/A."

<Peeling and peeling>
(Adherend)
As the adherend, a highly transparent glass (trade name "Optiwhite" manufactured by Nippon Sheet Glass Co., Ltd.) was used.

(Preparation of test samples)
The release-treated film of the adhesive sheet obtained in the examples and comparative examples was peeled off, and the exposed adhesive layer was attached to a light-transmitting glass to obtain a laminate having a layer structure of acrylic film/adhesive layer/highly-transmitting glass. The pressure bonding during lamination was performed in an autoclave (50°C, 0.5 MPa, 15 minutes). The obtained laminate was exposed to 40°C for 18 hours to obtain a test sample.

(measurement)
The test sample was placed in a constant temperature and humidity chamber at 85° C. and 85% RH, and the area (%) of the sample that had lifted or peeled off (lifted and peeled off) after exposure for 240 hours was measured and evaluated.
The evaluation criteria are as follows:
◎: 0%
◯: 1% or more and less than 20% △: 20% or more and less than 50% ×: 50% or more The evaluation results are shown in Table 1 below.

<Recess maintenance>
(Adherend)
As the adherend, a textured film was used.

(Preparation of test samples)
The peel-treated film of the adhesive sheet obtained in the examples and comparative examples was peeled off, and the exposed adhesive layer was subjected to corona treatment on the uneven surface of the uneven surface-forming film, and then laminated to the treated surface to obtain a laminate having a layer structure of acrylic film/adhesive layer/uneven surface-forming film. The obtained laminate was exposed to 40° C. for 18 hours to obtain a test sample.

(measurement)
First, the opening area (initial area) of the recesses of the test sample was measured by observing in a planar direction using a shape measuring microscope (VK-X1100, manufactured by Keyence Corporation). Next, the test sample was placed in a constant temperature and humidity chamber at 85°C and 85% RH, and the opening area (maintained area) of the recesses of the sample after exposure for 500 hours was measured. The recess retention rate was calculated from the following formula.
Recess retention rate (%)=(retained area)÷(initial area)×100
The evaluation criteria are as follows:
◯: Retention rate of recesses was 70% or more △: Retention rate of recesses was less than 70%, 50% or more ×: Retention rate of recesses was less than 50% Table 1 shows the evaluation results.

<Evaluation of creep deformation rate>
An adhesive layer laminate (1 mm thick) was prepared as follows.
For each of Examples 1 to 3 and Comparative Examples 1 to 3, the adhesive layer was laminated to the treated surface of a 38 μm polyethylene terephthalate (PET) film (trade name "MRE38", manufactured by Mitsubishi Chemical Corporation) that had been subjected to a silicone release treatment instead of the acrylic resin film, and the above-mentioned ultraviolet irradiation was performed. Then, the film was aged at 40 ° C. for 1 day to produce four adhesive sheets having a laminate structure of a release-treated PET film / adhesive layer (thickness 10 μm) / release-treated PET film with a width of 20 cm and a length of 30 cm. By repeating the process of laminating the adhesive layers of the obtained adhesive sheet in multiple layers and the process of dividing the adhesive layer laminate into multiple test pieces (cutting out multiple test pieces), a laminate of adhesive layers (thickness 1 mm, size 4 cm x 6 cm) in which a total of 100 adhesive layers (thickness 10 μm) were laminated was obtained.

A test specimen was prepared by punching out a cylinder with a diameter of 8 mm (height of 1 mm) from the laminate (thickness of 1 mm) of the adhesive layer obtained as described above. A stress of 10,000 Pa was applied to the test specimen for 30 minutes at a measurement temperature of 50°C using a viscoelasticity measuring device (device name "ARES G-2", manufactured by TA Instruments Japan Co., Ltd.), and the deformation rate was measured after 1 second and 30 minutes. The evaluation results are shown in Table 1 below.

In this specification, the "creep deformation rate" of the adhesive layer refers to the "creep deformation rate" obtained by the above method using a laminate (thickness 1 mm) of the adhesive layer. According to the inventor's experiments, there was no significant difference in the creep deformation rate of a 1 mm thick laminate between a laminate formed by laminating 20 adhesive layers each having a thickness of 50 μm, a laminate formed by laminating 100 adhesive layers each having a thickness of 10 μm, and a laminate formed by laminating 200 adhesive layers each having a thickness of 5 μm. In other words, the creep deformation rate of a 1 mm thick laminate does not depend on the thickness of the adhesive layers as long as the thickness of each adhesive layer constituting the laminate is at least in the range of 5 μm to 50 μm. According to the inventor's investigations, if the thickness of each adhesive layer is 0.1 μm or more, the creep deformation rate of a 1 mm thick laminate is considered to be approximately constant.

 

The adhesive layers of Examples 1 to 3 contain a silane coupling agent that reacts with the base polymer, and the creep deformation rate is suppressed below a certain level. Therefore, after application of the adhesive layer, peeling off in a humid and hot environment is suppressed, and the recesses are maintained at a high rate.
On the other hand, the adhesive layers of Comparative Examples 1 and 3 did not contain a silane coupling agent, and peeling occurred at a high rate in a humid and hot environment.
Further, although the adhesive layer of Comparative Example 2 contained a silane coupling agent, this did not react with the base polymer, and therefore the recesses could not be maintained at a high rate in a humid and hot environment.

In addition, the 5-10% elongation modulus of the adhesive layers of Examples 1 to 3 shows values equivalent to or greater than those of Comparative Examples 1 and 3, which do not contain a silane coupling agent that reacts with the base polymer.
On the other hand, the 5-10% elongation modulus of the adhesive layer of Comparative Example 2 shows a lower value compared to Comparative Example 1 which does not contain a silane coupling agent in which the first reactive group RG1 does not react with the base polymer.
From these results, it can be said that the silane coupling agent contained in the adhesive of Examples 1 to 3 reacted with the base polymer, and thus the cohesive strength of the adhesive layer was improved by the formation of a bond with the base polymer. On the other hand, the silane coupling agent contained in the adhesive layer of Comparative Example 2 did not react with the base polymer in the first reactive group RG1, and thus did not easily form a bond with the base polymer, and thus did not improve the cohesive strength of the adhesive layer.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in the different embodiments.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components in the above embodiments may be combined in any manner as long as it does not deviate from the spirit of the invention.

This application is based on a Japanese patent application (Patent Application No. 2022-185243) filed on November 18, 2022, the contents of which are incorporated by reference into this application.

10a, 10b First optical sheet 12s, 18s Main surface (front surface)
20, 20a, 20b adhesive sheet 21 substrate 22 adhesive layer 30 second optical sheet 32s, 38s principal surface (front surface)
50 Light guide plate 60 Light source 100A, 100B, 101A, 101B, 102B Optical laminate 200 Illumination device

Claims (26)

1. An adhesive sheet comprising an adhesive layer made of an adhesive composition containing a base polymer and a silane coupling agent that reacts with the base polymer,
   In a creep test using a rotational rheometer, the adhesive layer has a creep deformation rate of 10% or less when a stress of 10,000 Pa is applied to it at 50° C. for 1 second, and a creep deformation rate of 16% or less when a stress of 10,000 Pa is applied to it at 50° C. for 30 minutes.
   Adhesive sheet.
2. The silane coupling agent includes a compound having a first reactive group RG1 and a second reactive group RG2,
   the first reactive group RG1 is at least one selected from the group consisting of an amino group, an azide group, an azidosulfonyl group, a diazomethyl group, a diazirine group, a mercapto group, an isocyanate group, a ureido group, and an epoxy group;
   The adhesive sheet according to claim 1 , wherein the second reactive group RG2 is at least one selected from a silanol group and a group that generates a silanol group by hydrolysis reaction.
3. The adhesive sheet according to claim 2, wherein the base polymer has a functional group capable of forming a chemical bond with the first reactive group RG1.
4. the first reactive group RG1 is an amino group,
   The adhesive sheet according to claim 3 , wherein the functional group of the base polymer is at least one selected from the group consisting of a hydroxy group, a carboxy group, and an amino group.
5. the first reactive group RG1 is at least one selected from the group consisting of an azide group, an azidosulfonyl group, a diazomethyl group, and a diazirine group;
   4. The adhesive sheet according to claim 3, wherein the functional group of the base polymer is at least one selected from the group consisting of -CH ₃ , -CH ₂ -, -CH<, and -CH=CH-.
6. The adhesive sheet according to claim 1 or 2, wherein the silane coupling agent includes a compound having an aromatic ring.
7. The adhesive sheet according to claim 6, wherein the silane coupling agent includes a compound having a triazine ring.
8. The adhesive sheet according to claim 1 or 2, wherein the content of the silane coupling agent in the adhesive composition is 0.01 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the base polymer.
9. The adhesive sheet according to claim 1 or 2, wherein the thickness of the adhesive layer is 0.01 to 100 μm.
10. The adhesive sheet according to claim 1 or 2, wherein the adhesive layer has a total light transmittance of 80% or more.
11. The adhesive sheet according to claim 1 or 2, further comprising a substrate, the adhesive layer being provided on one main surface of the substrate.
12. The adhesive sheet according to claim 1 or 2, further comprising a substrate, the adhesive layer being provided on both major surfaces of the substrate.
13. The adhesive sheet according to claim 11, wherein one or both main surfaces of the substrate are release-treated, and the adhesive layer is provided on the release-treated main surface.
14. An optical laminate comprising a first optical sheet having a first main surface with a concave-convex structure and a second main surface opposite the first main surface, and an adhesive sheet according to claim 1 or 2 arranged on the first main surface side of the first optical sheet.
15. The optical laminate of claim 14, wherein the uneven structure includes a plurality of recesses, and the surface of the adhesive layer and the first main surface of the first optical sheet define a plurality of spaces in the plurality of recesses.
16. The optical laminate of claim 15, wherein the uneven structure includes a flat portion that contacts the adhesive layer.
17. A method for producing the optical laminate described in claim 14, comprising a step of bonding the first optical sheet and the adhesive sheet.
18. The manufacturing method according to claim 17, wherein the process is performed by a roll-to-roll method.
19. The optical laminate of claim 14, further comprising a second optical sheet disposed on the side of the adhesive sheet opposite the first optical sheet.
20. A method for producing the optical laminate according to claim 19,
    A manufacturing method including either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive sheet are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive sheet and the second optical sheet are laminated to the first optical sheet.
21. The manufacturing method according to claim 20, comprising: the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method; or the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
22. A method for producing the optical laminate according to claim 19,
    A step A of applying the adhesive composition onto the first main surface of the first optical sheet;
    and step B of reacting the base polymer and the silane coupling agent contained in the adhesive composition in a state in which the adhesive composition is applied onto the first main surface of the first optical sheet.
23. The manufacturing method according to claim 22, wherein step A includes a step of bonding the first optical sheet and the adhesive composition by a roll-to-roll method.
24. A method for producing the optical laminate according to claim 19,
    Either a step A1 of bonding a first laminate in which the first optical sheet and the adhesive composition are laminated to the second optical sheet, or a step A2 of bonding a second laminate in which the adhesive composition and the second optical sheet are laminated to the first optical sheet;
    A process for producing a composition comprising the steps of: (a) reacting the base polymer contained in the adhesive composition with the silane coupling agent after the step A1 or the step A2;
25. The method includes the step A1, in which the step A1 includes a step of bonding the first laminate and the second optical sheet by a roll-to-roll method, or the method includes the step A2, in which the step A2 includes a step of bonding the second laminate and the first optical sheet by a roll-to-roll method.
    The method of claim 24.
26. An optical device comprising the optical laminate according to claim 14.

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