Adhesive sheet and laminate

Abstract

The present invention provides: an adhesive sheet that, despite containing a silane coupling agent and a polymer having a hydroxyl group, has excellent adhesion to glass and excellent durability; and a laminate comprising said adhesive sheet.　The present invention is an adhesive sheet formed from an active energy ray curable adhesive composition that contains at least an acrylic copolymer which includes a hydroxyl group, a silane coupling agent, and an ultraviolet absorber, wherein the acrylic copolymer has a glass transition temperature of not higher than 0°C, and the silane coupling agent includes at least one silane coupling agent selected from the group consisting of silane coupling agents that have an isocyanurate skeleton and silane coupling agents that have a protected mercapto group.

Description

Pressure-sensitive adhesive sheet and laminate

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a laminate.

[0002] In recent years, pressure-sensitive adhesive sheets are materials formed with a pressure-sensitive adhesive layer containing, for example, an acrylic polymer as a main component, and are used for bonding various optical components such as touch panels and liquid crystal displays (LCDs).

[0003] Such pressure-sensitive adhesive sheets have been widely studied, and various means for improving not only adhesive strength but also various other performances have been proposed. For example, Patent Document 1 proposes a pressure-sensitive adhesive sheet containing an acrylic polymer and a triazine-based ultraviolet absorber to provide excellent ultraviolet blocking properties for touch panels, display elements, etc. Similarly, Patent Document 2 discloses a pressure-sensitive adhesive sheet containing a hydroxyphenyltriazine-based ultraviolet absorber together with an acrylic polymer.

[0004] JP 2013-075978 A JP 2019-214722 A

[0005] However, conventional pressure-sensitive adhesive sheets contain a silane coupling agent to improve adhesion between the pressure-sensitive adhesive sheet and the adherend. Such silane coupling agents are silane compounds having epoxy groups, etc., so if the base polymer contained in the pressure-sensitive adhesive sheet is, for example, an acrylic polymer having hydroxyl groups, the hydroxyl groups may react with the epoxy groups of the silane coupling agent. As a result, the silane coupling agent is incorporated into the acrylic polymer and acts as a so-called cross-linking agent, which the present inventors have discovered to harden the pressure-sensitive adhesive sheet, resulting in problems such as reduced adhesion to the adherend, such as glass, and reduced durability.

[0006] The present invention has been made in view of the above, and aims to provide an adhesive sheet that has excellent adhesion to glass and durability despite containing a polymer having a hydroxyl group and a silane coupling agent, and a laminate including the adhesive sheet.

[0007] As a result of extensive research into achieving the above object, the inventors have discovered that the above object can be achieved by using an acrylic copolymer having a hydroxyl group and a specific silane coupling agent, and have thus completed the present invention.

[0008] That is, the present invention encompasses, for example, the subject matter described in the following items. Item 1: A pressure-sensitive adhesive sheet formed from an active energy ray-curable pressure-sensitive adhesive composition containing at least a hydroxyl group-containing acrylic copolymer, a silane coupling agent, and an ultraviolet absorber, wherein the acrylic copolymer has a glass transition temperature of 0°C or lower, and the silane coupling agent contains at least one selected from the group consisting of silane coupling agents having an isocyanurate skeleton and silane coupling agents having a protected mercapto group. Item 2: The pressure-sensitive adhesive sheet according to Item 1, which has a light transmittance of less than 5% at a wavelength of 380 nm. Item 3: The pressure-sensitive adhesive sheet according to Item 1 or 2, wherein the acrylic copolymer does not contain a nitrogen atom-containing monomer unit. Item 4: The pressure-sensitive adhesive sheet according to any one of Items 1 to 3, further containing an acrylic tackifier. Item 5: The pressure-sensitive adhesive sheet according to any one of Items 1 to 4, wherein the ultraviolet absorber contains at least one selected from the group consisting of a hydroxyphenyltriazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber. Item 6. The pressure-sensitive adhesive sheet according to any one of items 1 to 5, having a thickness of 100 μm to 500 μm. Item 7. The pressure-sensitive adhesive sheet according to any one of items 1 to 6, which is used for bonding optical members. Item 8. A laminate comprising the pressure-sensitive adhesive sheet according to any one of items 1 to 6.

[0009] The pressure-sensitive adhesive sheet according to the present invention has excellent adhesion to glass and durability, despite containing a polymer having a hydroxyl group and a silane coupling agent.

[0010]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0011] The pressure-sensitive adhesive sheet of the present invention is formed from an active energy ray-curable pressure-sensitive adhesive composition (hereinafter sometimes simply referred to as "pressure-sensitive adhesive composition") containing at least a hydroxyl group-containing acrylic copolymer, a silane coupling agent, and an ultraviolet absorber. In the pressure-sensitive adhesive sheet of the present invention, the acrylic copolymer has a glass transition temperature of 0°C or lower, and the silane coupling agent contains at least one silane coupling agent selected from the group consisting of silane coupling agents having an isocyanurate skeleton and silane coupling agents having a protected mercapto group.

[0012] The pressure-sensitive adhesive sheet according to the present invention contains a silane coupling agent having a specific structure, and therefore has excellent adhesion to glass and durability despite containing a polymer having a hydroxyl group and a silane coupling agent.

[0013] The pressure-sensitive adhesive sheet of the present invention can be formed, for example, using an active energy ray-curable pressure-sensitive adhesive composition containing at least a base agent containing a hydroxyl group-containing acrylic copolymer (hereinafter abbreviated as "base agent containing an acrylic copolymer"), a silane coupling agent, and an ultraviolet absorber. That is, the pressure-sensitive adhesive sheet of the present invention contains a cured product obtained by irradiating the pressure-sensitive adhesive composition with active energy rays. Hereinafter, various components contained in the pressure-sensitive adhesive composition will be described.

[0014] (Base agent containing acrylic copolymer) The base agent containing acrylic copolymer contains at least an acrylic copolymer and is the main component of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet. The base agent containing acrylic copolymer may contain, in addition to the acrylic copolymer, a monofunctional monomer described below. When the base agent containing acrylic copolymer contains the acrylic copolymer and the monofunctional monomer, the base agent becomes a monomer solution of the acrylic copolymer, which is a so-called syrup.

[0015] The type of acrylic copolymer is not particularly limited as long as it has a hydroxyl group. For example, the acrylic copolymer may be a polymer of a (meth)acrylate having a hydroxyl group and a (meth)acrylic acid ester other than the (meth)acrylate. In this specification, "(meth)acrylic" means "acrylic" or "methacrylic", and "(meth)acrylate" means "acrylate" or "methacrylate".

[0016] Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2,2-dimethyl-2-hydroxyethyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and polyalkylene glycol mono(meth)acrylate. Of these, the (meth)acrylate having a hydroxyl group is preferably 4-hydroxybutyl (meth)acrylate.

[0017] Examples of (meth)acrylic acid esters other than (meth)acrylates having a hydroxyl group (hereinafter simply referred to as "(meth)acrylic acid esters") include (meth)acrylates having a linear or branched alkyl group, and (meth)acrylates having a ring structure in the side chain.

[0018] In a (meth)acrylate having a linear or branched alkyl group, the alkyl group may have, for example, 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 2 to 14 carbon atoms, and even more preferably 3 to 12 carbon atoms.

[0019] Specific examples of (meth)acrylates having a linear or branched alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isopropyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate.

[0020] The (meth)acrylate having a ring structure in the side chain is preferably a (meth)acrylic monomer having an alicyclic or aromatic ring in the side chain, more preferably a (meth)acrylic monomer having an alicyclic ring. Examples of the alicyclic ring include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, dicyclopentane, isobornyl, tetrahydrofuran, and tetrahydropyran. The alicyclic ring may have a spiro structure. Examples of the aromatic ring include benzene, naphthalene, anthracene, pyridine, furan, benzofuran, pyrrole, thiophene, imidazole, and oxazole. Among these, the ring structure is preferably an alicyclic ring, more preferably at least one selected from cyclohexane, dicyclopentane, isobornyl, and benzene, and particularly preferably cyclohexane or isobornyl. The above-mentioned ring structure may further have a substituent. Examples of the substituent include substitutable substituents selected from a halogen atom, a halogenated alkyl group, an alkyl group, an alkenyl group, an acyl group, a hydroxy group, a hydroxyalkyl group, an alkoxy group, an aryl group, a heteroaryl group, an alicyclic group, a cyano group, an epoxy group, an oxetanyl group, a mercapto group, an amino group, and a (meth)acryloyl group.

[0021] The (meth)acrylate having a ring structure in the side chain preferably has a structure in which a monovalent group having a ring structure is bonded to an ester oxygen of the (meth)acrylate, and in this case, the monovalent group having a ring structure preferably has 3 to 12 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0022] Specific examples of (meth)acrylates having a ring structure in the side chain include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, O-phenylphenoxyethyl (meth)acrylate, etc. Among these, the (meth)acrylate having a ring structure in the side chain is more preferably at least one selected from the group consisting of cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, with cyclohexyl (meth)acrylate being particularly preferred, in terms of particularly improving the adhesion between the pressure-sensitive adhesive sheet and the glass substrate and particularly facilitating improved durability.

[0023] The acrylic copolymer may have other functional groups in addition to hydroxyl groups, such as functional groups having active hydrogen other than hydroxyl groups. Examples of functional groups having active hydrogen include carboxyl groups, amino groups, amide groups, sulfo groups, sulfonic acid groups, sulfinic acid groups, sulfenic acid groups, and thiol groups. These functional groups having active hydrogen can be introduced into the acrylic copolymer by producing the acrylic copolymer using (meth)acrylates having the functional groups. For example, when using such carboxyl group-containing (meth)acrylates (acrylic acid, methacrylic acid, etc.), carboxyl groups can be introduced into the acrylic copolymer.

[0024] It is also preferable that the acrylic copolymer does not contain a nitrogen atom-containing monomer unit. In other words, the acrylic copolymer is preferably a polymer that does not have a structural unit containing a nitrogen atom in its structural units. When the acrylic copolymer does not contain a nitrogen atom-containing monomer unit, deterioration of the pressure-sensitive adhesive sheet is easily suppressed, and as a result, high transmittance can be achieved and weather resistance is easily improved. Examples of nitrogen atom-containing monomers include amino group-containing (meth)acrylates, (meth)acrylamides, and allylamines.

[0025] The acrylic copolymer is preferably a copolymer of a monomer containing at least a (meth)acrylate having a hydroxyl group and the (meth)acrylic acid ester, since this tends to further enhance the adhesion and durability of the pressure-sensitive adhesive sheet to an adherend such as glass, and is preferably a copolymer of a monomer containing a (meth)acrylate having a hydroxyl group and a (meth)acrylate having a linear or branched alkyl group.

[0026] The acrylic copolymer preferably contains 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more of (meth)acrylate units having a linear or branched alkyl group, and more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0027] The content of the (meth)acrylate having a ring structure in the side chain in the acrylic copolymer is not particularly limited, and for example, the acrylic copolymer preferably contains 1% by mass or more of the (meth)acrylate having a ring structure in the side chain, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and particularly preferably 10% by mass or less.

[0028] The acrylic copolymer preferably contains 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more of (meth)acrylate units having a hydroxyl group in a side chain, and preferably contains 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less.

[0029] The acrylic copolymer may contain other monomer units besides those described above, as long as the effects of the present invention are not impaired. The acrylic copolymer preferably contains structural units derived from a (meth)acrylate having a hydroxyl group, a (meth)acrylate having a linear or branched alkyl group, and a (meth)acrylate having a ring structure in a side chain in a total amount of 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. The acrylic copolymer may consist solely of structural units derived from a (meth)acrylate having a hydroxyl group, a (meth)acrylate having a linear or branched alkyl group, and a (meth)acrylate having a ring structure in a side chain.

[0030] The ratio (molar ratio) of each structural unit in the acrylic copolymer can be considered to be the same as the molar ratio of each monomer used in the production of the acrylic copolymer.

[0031] The acrylic copolymer has a glass transition temperature of 0°C or lower. This provides the pressure-sensitive adhesive sheet with high adhesion to adherends such as glass, and also with increased durability. The glass transition temperature of the acrylic copolymer is preferably -10°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower. The glass transition temperature of the acrylic copolymer is, for example, preferably -80°C or higher, more preferably -70°C or higher, even more preferably -60°C or higher, even more preferably -58°C or higher, and particularly preferably -56°C or higher.

[0032] The method for adjusting the glass transition temperature of the acrylic copolymer is not particularly limited, and it can be adjusted to a desired range, for example, by changing the type and composition ratio of the monomers constituting the acrylic copolymer. In the present invention, the glass transition temperature of the acrylic copolymer refers to Tg calculated by the following Fox formula based on the composition of the monomers used in synthesizing the copolymer. Fox formula: 1 / Tg = (W1 / Tg1) + (W2 / Tg2) + ... + (Wm / Tgm) where W1 + W2 + ... + Wm = 1. In the formula, Tg is the glass transition temperature (unit: K) of the acrylic copolymer, Tg1, Tg2, ..., Tgm are the glass transition temperatures of the respective homopolymers of m types of monomers (m is an integer) constituting the acrylic copolymer, and W1, W2, ..., Wm are the mass fractions of each structural unit in the acrylic polymer (P1). Note that Tg1 and W1 correspond to each other, i.e., the monomer that constitutes the homopolymer exhibiting the glass transition temperature of Tg1 is the same as the monomer that forms the structural unit having the mass fraction of W1. Similarly, Tg2 and W2, ... Tgm and Wm correspond to each other.

[0033] The glass transition temperature of the homopolymer can be determined, for example, from the value described in the Polymer Handbook 4th Edition (Wiley-Interscience 2003). If no such handbook is available, the glass transition temperature of the homopolymer can be measured, for example, by a differential scanning calorimeter (DSC). The DSC measurement conditions are as follows: 5 mg of sample is used in a nitrogen atmosphere; in the first measurement (1st RUN), the sample is heated from -100°C to 200°C at a heating rate of 5°C / min, and then cooled to -100°C at a cooling rate of 5°C / min; and in the second measurement (2nd RUN), the sample is heated from -100°C to 200°C at a heating rate of 5°C / min. Here, the glass transition temperature refers to the intersection of an extension of the baseline on the lower temperature side of the region where the baseline of a DSC curve measured when the temperature is raised from −100° C. to 200° C. changes to a sigmoid shape in the endothermic direction, and a tangent to an inflection point in the sigmoid.

[0034] The weight-average molecular weight of the acrylic copolymer is preferably greater than 10,000, more preferably 100,000 or more, and even more preferably 200,000 or more. The weight-average molecular weight of the acrylic copolymer is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less.

[0035] The weight-average molecular weight referred to in the present invention refers to the weight-average molecular weight measured in terms of polystyrene by gel permeation chromatography (GPC). There are no particular limitations on the GPC apparatus used in the GPC method, and commercially available GPC measuring instruments, such as the LC-2000Plus series manufactured by JASCO Corporation, and detectors such as the RI-2031Plus and UV-2075Plus, can be used. In this case, for example, a GPC column consisting of four columns connected together, namely, "Shodex KF801," "Shodex KF803L," "Shodex KF800L," and "Shodex KF800D" manufactured by Showa Denko K.K., can be used. The column temperature can be set to 40°C. Tetrahydrofuran is used as the eluent, and measurements are performed at a flow rate of 1.0 ml / min. Typically, a calibration curve is prepared using standard polystyrene, and the weight-average molecular weight (Mw) can be obtained in terms of polystyrene.

[0036] The acrylic copolymer can be produced by a known method. For example, the acrylic copolymer can be produced by polymerizing a monomer mixture for forming each structural unit in the acrylic copolymer by a known polymerization method. As the polymerization method, for example, solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc. can be used. The acrylic polymer can also be obtained from a commercial product, etc.

[0037] The base agent may contain a monofunctional monomer in addition to the acrylic copolymer described above. That is, the base agent may be a solution (also called a syrup) in which the acrylic copolymer is dissolved in the monofunctional monomer. The type of monofunctional monomer is not particularly limited, and examples thereof include the various monomers used to form the acrylic copolymer, such as the above-mentioned (meth)acrylates and (meth)acrylic acid esters having a hydroxyl group, and preferably (meth)acrylates having a hydroxyl group, (meth)acrylates having a linear or branched alkyl group, and (meth)acrylates having a ring structure in the side chain.

[0038] The content of the acrylic copolymer in the base material can be 1 to 50% by mass, preferably 5 to 30% by mass, based on the total mass of the acrylic copolymer and the monofunctional monomer. The base material may consist of only the acrylic copolymer and the monofunctional monomer.

[0039] (Silane Coupling Agent) The silane coupling agent contains at least one selected from the group consisting of silane coupling agents having an isocyanurate skeleton and silane coupling agents having a protected mercapto group. By containing such a silane coupling agent in the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet has excellent adhesion to adherends such as glass and excellent durability, despite the pressure-sensitive adhesive sheet containing an acrylic copolymer having a hydroxyl group.

[0040] Examples of silane coupling agents having an isocyanurate skeleton include silane compounds having one or more hydrolyzable silyl groups or silanol groups and one or more isocyanurate groups in the molecule.

[0041] Examples of silane coupling agents having an isocyanurate skeleton include 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-triethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-tripropoxysilylpropyl)isocyanurate, 1,3,5-tris(3-methyldimethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-methyldiethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-methyldipropoxysilylpropyl)isocyanurate, 1,3,5-tris(3-phenyldimethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-phenyldiethoxysilylpropyl)isocyanurate, 1,3,5-tris(3-phenyldipropoxysilylpropyl)isocyanurate, silylpropyl) isocyanurate, 1,3,5-tris(2-trimethoxysilylethyl) isocyanurate, 1,3,5-tris(2-triethoxysilylethyl) isocyanurate, 1,3,5-tris(2-tripropoxysilylethyl) isocyanurate, 1,3,5-tris(2-methyldimethoxysilylethyl) isocyanurate, 1,3,5-tris(2-methyldiethoxysilylethyl) isocyanurate, 1,3,5-tris(2-methyldipropoxysilylethyl) isocyanurate, 1,3,5-tris(2-phenyldimethoxysilylethyl) isocyanurate, 1,3,5-tris(2-phenyldiethoxysilylethyl) isocyanurate, 1,3,5-tris(2-phenyldipropoxysilylethyl) isocyanurate, and the like.

[0042] Among these, the silane coupling agent having an isocyanurate skeleton is preferably 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate or 1,3,5-tris(3-triethoxysilylpropyl)isocyanurate, and more preferably 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate.

[0043] The silane coupling agent having an isocyanurate skeleton can be produced by a known method, or can be obtained from a commercially available product, etc. Examples of the silane coupling agent having an isocyanurate skeleton include "KBM-9659" manufactured by Shin-Etsu Chemical Co., Ltd.

[0044] Next, in the silane coupling agent having a protected mercapto group, the term "protected mercapto group" can mean that the hydrogen atom of the mercapto group (-SH) is protected with a protecting group. Such a protecting group is, for example, -Si(OR) ３ where OR is an alkoxy group, such as a methoxy group or an ethoxy group.

[0045] Examples of the silane coupling agent having a protected mercapto group include a silane compound having one or more hydrolyzable silyl groups or silanol groups and one or more protected mercapto groups in the molecule. Examples of such an alkoxysilane include an alkoxysilane having a mercapto group protected by a protecting group, and specifically, triethoxysilylthiopropyltrimethoxysilane ((CH ３ O) ３ Si(CH ２ ) ３ S-Si(OC ２ H ５ ) ３ ) can be mentioned.

[0046] The silane coupling agent having a protected mercapto group can be produced by a known method or can be obtained from a commercially available product, etc. An example of the commercially available product is Shin-Etsu Silicone X-12-1056ES manufactured by Shin-Etsu Chemical Co., Ltd.

[0047] The silane coupling agent may contain other silane coupling agents as long as the effects of the present invention are not impaired, but it is preferable that it does not contain a silane coupling agent having a functional group such as an epoxy group that reacts with a hydroxyl group in the acrylic copolymer.More preferably, the silane coupling agent is composed of at least one selected from the group consisting of a silane coupling agent having an isocyanurate skeleton and a silane coupling agent having a protected mercapto group.

[0048] Silane coupling agents having an isocyanurate skeleton and silane coupling agents having a protected mercapto group do not function as crosslinkers for acrylic polymers having hydroxyl groups, and therefore can prevent the pressure-sensitive adhesive sheet from becoming too hard. Therefore, pressure-sensitive adhesive sheets containing these silane coupling agents have high adhesion to adherends such as glass, and are likely to have high durability.

[0049] The content ratio of the silane coupling agent in the pressure-sensitive adhesive composition is not particularly limited.In terms of easily increasing the durability of the pressure-sensitive adhesive sheet, the content ratio of the silane coupling agent is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.15 parts by mass or more, particularly preferably 0.2 parts by mass or more, and is also preferably 3 parts by mass or less, more preferably 1 part by mass or less, even more preferably 0.8 parts by mass or less, particularly preferably 0.5 parts by mass or less, relative to 100 parts by mass of the main component (i.e., 100 parts by mass of the total mass of the acrylic copolymer and the monofunctional monomer).

[0050] (Ultraviolet absorber) The ultraviolet absorber is used in the pressure-sensitive adhesive sheet to exhibit the function of absorbing ultraviolet rays. When the pressure-sensitive adhesive sheet contains an ultraviolet absorber, for example, it is possible to prevent other adherends to which the pressure-sensitive adhesive sheet is attached from being deteriorated by ultraviolet rays. For example, even when glass or the like that transmits ultraviolet rays is used as the adherend, it is possible to suppress weather deterioration of members (for example, display members) further laminated on the adherend.

[0051] The type of ultraviolet absorber contained in the pressure-sensitive adhesive sheet is not particularly limited, and a wide variety of known ultraviolet absorbers can be used. Among these, it is preferable that the ultraviolet absorber contains at least one selected from the group consisting of hydroxyphenyltriazine-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers. In this case, the pressure-sensitive adhesive sheet can particularly suppress weather resistance deterioration of the adherend.

[0052] Examples of hydroxyphenyltriazine-based ultraviolet absorbers include Tinuvin 477 (registered trademark), Tinuvin 400 (registered trademark), Tinuvin 405 (registered trademark), and Tinuvin 460 (registered trademark), all of which are manufactured by BASF Japan Co., Ltd. Examples of benzotriazole-based ultraviolet absorbers include Tinuvin 970 (registered trademark), Tinuvin PS (registered trademark), Tinuvin 99-2 (registered trademark), Tinuvin 326 (registered trademark), Tinuvin 384-2 (registered trademark), Tinuvin 900 (registered trademark), Tinuvin 928 (registered trademark), and Tinuvin 1130 (registered trademark), all of which are manufactured by BASF Japan Co., Ltd.

[0053] The ultraviolet absorber may contain an ultraviolet absorber other than a hydroxyphenyltriazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber, as long as the effects of the present invention are not impaired, or may consist of only at least one kind selected from the group consisting of a hydroxyphenyltriazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber.

[0054] The content ratio of the ultraviolet absorber in the pressure-sensitive adhesive composition is not particularly limited. In order to more easily suppress weather-resistant deterioration of the pressure-sensitive adhesive sheet, the content ratio of the ultraviolet absorber is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, particularly preferably 0.8 parts by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, particularly preferably 1.5 parts by mass or less, relative to 100 parts by mass of the main agent (i.e., 100 parts by mass of the total mass of the acrylic copolymer and the monofunctional monomer).

[0055] (Acrylic Tackifier) ​​The pressure-sensitive adhesive composition may also contain an acrylic tackifier. That is, the pressure-sensitive adhesive sheet of the present invention may further contain an acrylic tackifier. In this case, the pressure-sensitive adhesive sheet is likely to have better adhesion to the adherend.

[0056] The type of acrylic tackifier is not particularly limited, and for example, a wide range of acrylic tackifiers used in known pressure-sensitive adhesive sheets can be applied.

[0057] Examples of the acrylic tackifier include resins having a glass transition temperature of 20° C. or higher. The glass transition temperature of the acrylic tackifier is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher, and is preferably 200° C. or lower, more preferably 180° C. or lower, and even more preferably 150° C. or lower. By adjusting the glass transition temperature of the acrylic tackifier to fall within the above range, the adhesion of the pressure-sensitive adhesive sheet to the adherend can be improved.

[0058] The structural units contained in the acrylic tackifier may include a monomer unit having an alicyclic ring. When the acrylic tackifier includes a monomer unit having an alicyclic ring, the number of carbon atoms constituting the alicyclic ring is preferably 6 or more. Examples of alicyclic rings having 6 or more carbon atoms include cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, norbornene, norbornadiene, isobornyl, and dicyclopentane. Examples of preferred monomers having an alicyclic ring include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate.

[0059] The acrylic tackifier can contain alkyl(meth)acrylate units in place of or in addition to the alicyclic monomer units. Examples of alkyl(meth)acrylates include alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, lauryl(meth)acrylate, cetyl(meth)acrylate, stearyl(meth)acrylate, and behenyl(meth)acrylate. Of these, it is preferable that the acrylic tackifier contain methyl(meth)acrylate.

[0060] The acrylic tackifier is preferably a copolymer containing both an alicyclic monomer unit and an alkyl(meth)acrylate unit. In order to easily improve the adhesion between the pressure-sensitive adhesive sheet and the adherend, the content of the alkyl(meth)acrylate unit relative to the total mass of the acrylic tackifier is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less.

[0061] The acrylic tackifier may contain other monomer units as needed. The other monomers may be any monomers copolymerizable with the alkyl (meth)acrylates, such as (meth)acrylonitrile, vinyl acetate, vinyl chloride, and ethyl vinyl ether. The content of the other monomer units in the acrylic tackifier is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0062] The weight average molecular weight of the acrylic tackifier is preferably 3,000 or more, more preferably 3,200 or more, and even more preferably 3,500 or more. The weight average molecular weight of the acrylic tackifier may be 20,000 or less, more preferably 15,000 or less, and even more preferably 10,000 or less. The weight average molecular weight of the acrylic tackifier is measured by gel permeation chromatography (GPC) and converted using a calibration curve prepared using standard polystyrenes with known molecular weights. Such resins may be commercially available or may be synthesized by known methods.

[0063] The content of the acrylic tackifier in the pressure-sensitive adhesive composition is not particularly limited. In order to easily improve the adhesion of the pressure-sensitive adhesive sheet to the adherend, the content of the acrylic tackifier is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, relative to 100 parts by mass of the main agent.

[0064] The tackifier may be formed solely from an acrylic tackifier, or may contain components other than the acrylic tackifier. The tackifier contained in the pressure-sensitive adhesive composition may be one type alone or two or more types.

[0065] (Polyfunctional Monomer) The pressure-sensitive adhesive composition may contain a polyfunctional monomer. Examples of such polyfunctional monomers include compounds having two or more polymerizable double bonds in the molecule. The polyfunctional monomer has two or more polymerizable double bonds (e.g., radically polymerizable double bonds), preferably two or more but less than five, and more preferably two or more but less than four. When the pressure-sensitive adhesive composition contains a polyfunctional monomer, it can react with the monofunctional monomer in the base resin to form, for example, a crosslinked polymer. That is, when the pressure-sensitive adhesive composition contains a polyfunctional monomer, a polymer having a crosslinked structure due to the polyfunctional monomer can be contained in the pressure-sensitive adhesive sheet.

[0066] Examples of polyfunctional monomers include bifunctional monomers (monomers having two polymerizable double bonds), such as polyethylene glycol diacrylate, polypropylene diacrylate, alkyl diacrylate, polytetramethylene glycol diacrylate, polypropylene glycol diacrylate, dioxane diacrylate, tricyclodecanol diacrylate, and fluorene diacrylate. Examples of polyfunctional monomers include trifunctional or higher functional monomers, such as alkoxylated trimethylolpropane triacrylate, alkoxylated glycerin triacrylate, caprolactone-modified isocyanurate triacrylate, pentaerythritol acrylate, alkoxylated pentaerythritol acrylate, (alkoxylated) pentaerythritol acrylate, (alkoxylated) ditrimethylolpropane acrylate, (alkoxylated) dipentaerythritol acrylate, and (ethoxylated) polyglycerin acrylate.

[0067] The polyfunctional monomer may have a bisphenol skeleton in one molecule, such as a diacrylate of bisphenol A diglycidyl ether, a diacrylate of propoxylated bisphenol A, or a diacrylate of bisphenol F diglycidyl ether.

[0068] Commercially available polyfunctional monomers include, for example, "A-200" (polyethylene glycol #200 diacrylate), "A-400" (polyethylene glycol #400 diacrylate), and "A-600" (polyethylene glycol #600 diacrylate) from the NK Ester series, which are bifunctional polyethylene glycol acrylates manufactured by Shin-Nakamura Chemical Co., Ltd., the trifunctional monomer A-TMPT ((alkoxylated) trimethylolpropane acrylate), the trifunctional monomer M310 (trimethylolpropane PO-modified triacrylate) and the trifunctional monomer M321 (trimethylolpropane propylene oxide-modified triacrylate) manufactured by Toagosei Co., Ltd., the bifunctional monomer M211B (bisphenol A EO-modified diacrylate) and M240 (polyethylene glycol diacrylate), and the tetrafunctional monomer M-408 (ditrimethylolpropane tetraacrylate), all manufactured by Toagosei Co., Ltd. Other commercially available polyfunctional monomers include, for example, A-DOG, A-DCP, A-9300, and A-9200YN manufactured by Shin-Nakamura Chemical Co., Ltd., FA-731A manufactured by Hitachi Chemical Co., Ltd., and AOMA manufactured by Nippon Shokubai.

[0069] In the pressure-sensitive adhesive composition, the content of the polyfunctional monomer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.15 parts by mass or more, and particularly preferably 0.2 parts by mass or more, relative to 100 parts by mass of the main agent, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and particularly preferably 1 part by mass or less.

[0070] The polyfunctional monomer contained in the pressure-sensitive adhesive composition may be one type alone or two or more types.

[0071] (Photopolymerization initiator) The pressure-sensitive adhesive composition may further contain a photopolymerization initiator. The photopolymerization initiator initiates polymerization of the polyfunctional monomer and polymerization of the monofunctional monomer in the syrup by irradiation with active energy rays. In this specification, "active energy rays" refers to electromagnetic waves or charged particle rays that have an energy quantum, and examples thereof include ultraviolet rays, electron beams, visible light, X-rays, and ion beams. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred.

[0072] The type of photopolymerization initiator is not particularly limited, and a wide range of known photopolymerization initiators can be used. Examples of the photopolymerization initiator include acetophenone-based photopolymerization initiators such as 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxyl)-phenyl]-2-hydroxy-methylpropanone, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methyl-1-propanone; acylphosphine oxide-based photopolymerization initiators such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and 2,4,6-trimethylbenzoyl)phenylphosphine oxide; intramolecular hydrogen abstraction photopolymerization initiators such as methyl benzoylformate and 4-methylbenzophenone; and oil-soluble polymerization initiators such as oxime ester-based photopolymerization initiators and cationic photopolymerization initiators. Among these, the photopolymerization initiator is preferably at least one selected from the group consisting of acylphosphine oxide-based photopolymerization initiators and oxime ester-based photopolymerization initiators.

[0073] Commercially available acetophenone-based photopolymerization initiators include EsacureOne (oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenylpropanone], photoinitiator manufactured by IGM Resins B.V.), Omnirad 651 (2,2-dimethoxy-2-phenylacetophenone, manufactured by IGM Resins B.V.), Omnirad 184 (1-hydroxycyclohexylphenyl ketone, manufactured by IGM Resins B.V.), and Omnirad 1173 (2-hydroxy-2-methyl-1-phenylpropanone, manufactured by IGM Resins B.V.). Commercially available acylphosphine oxide-based photopolymerization initiators include Omnirad Examples of commercially available oxime ester photopolymerization initiators include 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM RESINS B.V.) and Omnirad TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide, manufactured by IGM RESINS B.V.). Examples of commercially available oxime ester photopolymerization initiators include Irgacure OXE03 (BASF Japan).

[0074] In the pressure-sensitive adhesive composition, the content ratio of the photopolymerization initiator is not particularly limited, and for example, it is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the main agent, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 1.5 parts by mass or less.

[0075] <Adhesive Sheet> The adhesive sheet of the present invention is formed by irradiating the above-mentioned adhesive composition with active energy rays such as ultraviolet rays to form a sheet. Therefore, the adhesive sheet has an adhesive layer containing a cured product of the adhesive composition. As described above, the adhesive composition contains at least the acrylic copolymer, silane coupling agent, and ultraviolet absorber, and may also contain one or more components selected from the group consisting of a tackifier, a polyfunctional monomer, and a photopolymerization initiator, as necessary. The adhesive composition may contain other components to the extent that the effects of the present invention are not impaired. Examples of other components include crosslinkers, solvents, plasticizers, antioxidants, metal corrosion inhibitors, and light stabilizers. Dyes or pigments may also be added for coloring purposes. It is also preferable that the adhesive composition be solvent-free.

[0076] The method for curing the pressure-sensitive adhesive composition is not particularly limited, and for example, a wide variety of known methods can be adopted. Specifically, the method can include a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of irradiating the coating film with active energy rays to obtain a cured product of the pressure-sensitive adhesive. This allows the pressure-sensitive adhesive to be cured to form a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet can be obtained.

[0077] The PSA composition can be applied using a known coating device, such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0078] The substrate used for coating the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition can be coated onto various substrates such as resin substrates and glass substrates. When the substrate has a release sheet as described below, the pressure-sensitive adhesive composition can also be coated onto this release sheet. The pressure-sensitive adhesive composition can also be directly coated onto the member to be adhered. The thickness of the pressure-sensitive adhesive composition after coating is not particularly limited, and can be appropriately set depending on the desired thickness of the pressure-sensitive adhesive layer (or pressure-sensitive adhesive sheet). After forming the coating film, the coating film may be subjected to a heating treatment or a drying treatment, if necessary.

[0079] The step of irradiating the coating film with active energy rays can be, for example, a step similar to a known method. In this step, the photopolymerization initiator in the pressure-sensitive adhesive composition generates radicals due to the active energy rays, and the polymerizable components in the pressure-sensitive adhesive composition (e.g., monofunctional monomers, polyfunctional monomers, etc.) initiate and progress a polymerization reaction due to the generated radicals, resulting in a polymerized and cured product. This allows the formation of a pressure-sensitive adhesive layer and improved adhesive strength.

[0080] Examples of active energy rays include ultraviolet rays, electron beams, visible light, X-rays, and ion beams, and can be appropriately selected depending on the photopolymerization initiator contained in the pressure-sensitive adhesive composition. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred. Examples of light sources that can be used for ultraviolet rays include chemical lamps, high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, carbon arcs, xenon arcs, and electrodeless ultraviolet lamps. The irradiation output of ultraviolet rays is such that the cumulative light amount is 100 to 10,000 mJ / cm. ２ It is preferable to set the value to 200 to 5000 mJ / cm ２ In the step of irradiating the coating film with active energy rays, the active energy rays may be irradiated in two stages.

[0081] The cured product formed as described above can be used as the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive layer may consist of only the cured product of the pressure-sensitive adhesive, or may contain other components in addition to the cured product of the pressure-sensitive adhesive.

[0082] The pressure-sensitive adhesive sheet of the present invention may include other layers as long as it includes the pressure-sensitive adhesive layer, or may be formed only with the pressure-sensitive adhesive layer. That is, the pressure-sensitive adhesive sheet preferably consists of only the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer has, for example, a single-layer structure.

[0083] The pressure-sensitive adhesive sheet of the present invention may also be a pressure-sensitive adhesive sheet provided with a substrate such as a release sheet on one or both sides. That is, the present invention also encompasses a pressure-sensitive adhesive sheet with a release sheet that includes a pressure-sensitive adhesive sheet and a release sheet.

[0084] Examples of the release sheet include a release laminate sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate. Paper or a polymer film is used as the release sheet substrate in the release laminate sheet. Examples of the release agent that constitutes the release agent layer include general-purpose addition-type or condensation-type silicone-based release agents and long-chain alkyl group-containing compounds. Commercially available release laminate sheets may also be used. Examples include a heavy-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films, and a light-duty separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films.

[0085] The pressure-sensitive adhesive sheet of the present invention preferably has a light transmittance of less than 5% at a wavelength of 380 nm. In this case, the pressure-sensitive adhesive sheet has a high UV blocking rate and is suitable for various optical components such as touch panels and liquid crystal displays (LCDs). The light transmittance of the pressure-sensitive adhesive sheet at a wavelength of 380 nm is more preferably 4.5% or less, even more preferably 3.5% or less, and particularly preferably 3% or less.

[0086] The thickness of the pressure-sensitive adhesive sheet of the present invention is not particularly limited and can be, for example, 75 μm to 500 μm, preferably 100 μm or more, more preferably 400 μm or less, and even more preferably 300 μm or less. The pressure-sensitive adhesive sheet of the present invention can be made relatively thick by a simple manufacturing method.

[0087] The pressure-sensitive adhesive sheet of the present invention can be used in various applications for bonding adherends together, and is particularly suitable for bonding optical members together.

[0088] Examples of optical components include various components in optical products such as touch panels and image display devices. Examples of components for touch panels include ITO films in which an ITO film is provided on a transparent resin film, ITO glass in which an ITO film is provided on the surface of a glass plate, transparent conductive films in which a transparent resin film is coated with a conductive polymer, hard coat films, and fingerprint-resistant films. Examples of components for image display devices include anti-reflection films, alignment films, polarizing films, retardation films, and brightness-enhancing films used in liquid crystal display devices. The pressure-sensitive adhesive sheet of the present invention may also be used to bond modules such as a liquid crystal module and a touch panel module. Optical components can be formed from materials such as glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

[0089] Since the pressure-sensitive adhesive sheet of the present invention contains an ultraviolet absorber, it can be applied to transparent optical members that do not contain an ultraviolet absorber as an adherend. By containing an ultraviolet absorber, the pressure-sensitive adhesive sheet of the present invention can also suppress weather deterioration of display members and the like laminated on the adherend, even when an ultraviolet-transmitting optical member (glass, etc.) is used as the adherend.

[0090] Various laminates can be formed using the pressure-sensitive adhesive sheet of the present invention. For example, various laminates can be formed by laminating the above-mentioned adherend to one or both sides of the pressure-sensitive adhesive sheet of the present invention. Since such laminates include the pressure-sensitive adhesive sheet of the present invention, they have excellent durability and are less susceptible to weather deterioration.

[0091] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification.

[0092] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0093] The following monomers (monofunctional monomers) were prepared for producing the "main agent containing an acrylic copolymer" used in each example (NVP was used for comparison): 2EHA: 2-ethylhexyl acrylate BA: butyl acrylate 4HBA: 4-hydroxybutyl acrylate IBXA: isobornyl acrylate CHMA: cyclohexyl methacrylate NVP: N-vinylpyrrolidone

[0094] In addition, the following "silane coupling agent," "ultraviolet absorber," "multifunctional monomer," and "photopolymerization initiator" were prepared for use in each example.

[0095] (Silane coupling agents) KBM-9659 ("KBM-9659" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd., 1,3,5-tris(3-trimethoxylpropyl)isocyanurate) X-12-1056ES: a silane coupling agent having a protected mercapto group manufactured by Shin-Etsu Chemical Co., Ltd. KBM-503 ("KBM-503" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropyltrimethoxysilane) KBM-403 ("KBM-403" (registered trademark) manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

[0096] (Ultraviolet absorbers) Tinuvin 477: hydroxyphenyltriazine-based ultraviolet absorber (BASF Japan) Tinuvin 970: benzotriazole-based ultraviolet absorber (BASF Japan)

[0097] (Polyfunctional Monomer) A-200: Bifunctional Monomer (Polyethylene Glycol #200 Diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., NK Ester A-200 (registered trademark))

[0098] (Photopolymerization initiator) Omnirad 819: IGM Resins B.V. Irgacure OXE03: BASF Japan

[0099] (Production Example 1: Production of Acrylic Tackifier a) 250 g of methyl methacrylate, 250 g of isobornyl methacrylate, 15 g of n-dodecyl mercaptan, 500 g of ethyl acetate, and 200 g of methyl ethyl ketone were added to a 2 L flask equipped with a stirrer, a nitrogen inlet tube, a cooling tube, and a thermometer. After 60 minutes of nitrogen substitution at a nitrogen flow rate of 300 ml / min, the nitrogen flow rate was reduced to 100 ml / min, and the temperature was raised to 70 ° C. in a water bath and heating was stopped. 2 g of AIBN was added, and the mixture was allowed to react for 3 hours while controlling the heat generation. Then, 3 g of AIBN was added, and the mixture was allowed to react for 4 hours, after which it was cooled to 30 ° C. Finally, the mixture was dried at 100 ° C. for 5 hours to remove the solvent, and an acrylic tackifier a (referred to as tackifying resin a in Table 1) having a weight average molecular weight of 8,000 and a glass transition temperature of 95 ° C. was obtained.

[0100] (Production Example 2: Production of Tackifier b) 250 g of methyl methacrylate, 250 g of dicyclopentanyl methacrylate, 20 g of n-dodecyl mercaptan, 500 g of ethyl acetate, and 200 g of methyl ethyl ketone were added to a 2 L flask equipped with a stirrer, a nitrogen inlet tube, a cooling tube, and a thermometer. After nitrogen substitution at a nitrogen flow rate of 300 ml / min for 60 minutes, the nitrogen flow rate was reduced to 100 ml / min, and the temperature was raised to 70 ° C. in a water bath and heating was stopped. 2 g of AIBN was added, and the mixture was reacted for 3 hours while controlling the heat generation, and then 3 g of AIBN was added, and the mixture was reacted for 4 hours, after which it was cooled to 30 ° C. Finally, the mixture was dried at 100 ° C. for 5 hours to remove the solvent, and an acrylic tackifier b (referred to as tackifier resin b in Table 1) having a weight average molecular weight of 6,000 and a glass transition temperature of 95 ° C. was obtained.

[0101] The tackifiers obtained in Production Examples 1 and 2 were dried at 100° C. for 5 hours to remove the solvent before use in each example.

[0102] Example 1 Production of a Main Component Containing an Acrylic Copolymer A main component (syrup) containing an acrylic copolymer was synthesized according to the main component composition shown in Table 1. Specifically, 100 parts by mass of a monomer mixture consisting of 2EHA and 4HBA (mass ratio 70:30) prepared in the amounts shown in Table 1 and 0.06 parts by mass of n-dodecyl mercaptan were charged into a 2-L flask equipped with a stirrer, a nitrogen inlet tube, a condenser, and a thermometer. The mixture was then heated to 65°C in a water bath, 0.15 g of AIBN was added, and the reaction was allowed to proceed for 30 minutes while controlling the heat generation, and then cooled to room temperature. Additional monomers (2EHA and 4HBA) were added to the flask to achieve the aforementioned monomer ratio by mass, and the solids concentration was adjusted to 20%. In this manner, a main component (syrup) containing an acrylic copolymer with a solids concentration of 20% by mass and a weight-average molecular weight of 900,000 was obtained.

[0103] <Production of Pressure-Sensitive Adhesive Composition> Next, a pressure-sensitive adhesive sheet was obtained from a pressure-sensitive adhesive composition prepared according to the blending conditions shown in Table 1. First, as shown in Table 1, 0.3 parts by mass of a polyfunctional monomer, 0.1 parts by mass of KBM-9659 as a silane coupling agent, 1 part by mass of Tinuvin 477 as an ultraviolet absorber, and 0.3 parts by mass of Omnirad 819 as a photopolymerization initiator were added relative to 100 parts by mass of the total amount of the base agent, and the mixture was stirred and degassed to obtain Pressure-Sensitive Adhesive Composition 1.

[0104] <Production of Pressure-Sensitive Adhesive Sheet> The obtained pressure-sensitive adhesive composition 1 was applied to a 100 μm thick polyester film (release sheet) coated with a silicone release agent to a thickness of 100 μm, and the coated film was then laminated with a 75 μm thick polyester film (release sheet) coated with a silicone release agent. After that, the coated film was exposed to a chemical lamp at an illuminance of 5 mW / cm. ２ , cumulative illuminance 750 mJ / cm ２ Further, a high-pressure mercury lamp was used to irradiate the sample with an illuminance of 200 mW / cm ２ , cumulative illuminance 2000 mJ / cm ２ A pressure-sensitive adhesive layer was formed by irradiating the film so as to obtain a pressure-sensitive adhesive sheet 1 having release sheets on both sides.

[0105] (Example 2) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content concentration of 20 mass% and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0106] <Preparation of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 2 was obtained in the same manner as in the preparation of the pressure-sensitive adhesive composition of Example 1, except that the preparation conditions for the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0107] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 2 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 2 was applied to a thickness of 150 μm instead of Pressure-Sensitive Adhesive Composition 1.

[0108] (Example 3) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content concentration of 20 mass% and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0109] <Production of Pressure-Sensitive Adhesive Composition> Next, a pressure-sensitive adhesive sheet was obtained from a pressure-sensitive adhesive composition prepared according to the blending conditions shown in Table 1. First, as shown in Table 1, 3 parts by mass of tackifier resin a, 0.3 parts by mass of a polyfunctional monomer, 0.2 parts by mass of KBM-9659 as a silane coupling agent, 1 part by mass of Tinuvin 477 as an ultraviolet absorber, and 0.3 parts by mass of Irgacure OXE03 as a photopolymerization initiator were added relative to 100 parts by mass of the total amount of the base agent, and the mixture was stirred and degassed to obtain Pressure-Sensitive Adhesive Composition 3.

[0110] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 3 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 3 was applied in place of Pressure-Sensitive Adhesive Composition 1 to a thickness of 175 μm.

[0111] (Example 4) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content concentration of 20 mass% and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0112] <Production of Pressure-Sensitive Adhesive Composition> Pressure-Sensitive Adhesive Composition 4 was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0113] <Production of Pressure-Sensitive Adhesive Sheet> Pressure-Sensitive Adhesive Sheet 4 was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that Pressure-Sensitive Adhesive Composition 4 was applied in place of Pressure-Sensitive Adhesive Composition 1 to a thickness of 150 μm.

[0114] (Comparative Example 1) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content of 20 mass % and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0115] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 1a was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0116] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 1a was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that pressure-sensitive adhesive composition 1a was applied in place of pressure-sensitive adhesive composition 1 so as to have a thickness of 100 μm.

[0117] (Comparative Example 2) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content of 20 mass% and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0118] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 1b was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0119] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 1b was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that pressure-sensitive adhesive composition 1b was applied in place of pressure-sensitive adhesive composition 1 so as to have a thickness of 150 μm.

[0120] (Comparative Example 3) <Production of base agent containing acrylic copolymer> A base agent (syrup) containing an acrylic copolymer with a solid content of 20 mass% and a weight-average molecular weight of 900,000 was obtained in the same manner as in the production of the base agent containing an acrylic copolymer in Example 1, except that the base agent composition was changed to the conditions shown in Table 1.

[0121] <Production of Pressure-Sensitive Adhesive Composition> A pressure-sensitive adhesive composition 1c was obtained in the same manner as in the production of the pressure-sensitive adhesive composition of Example 1, except that the conditions for preparing the pressure-sensitive adhesive composition were changed to those shown in Table 1.

[0122] <Production of Pressure-Sensitive Adhesive Sheet> A pressure-sensitive adhesive sheet 1c was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet of Example 1, except that pressure-sensitive adhesive composition 1c was applied in place of pressure-sensitive adhesive composition 1 so as to have a thickness of 100 μm.

[0123] Evaluation method (Tg of acrylic tackifier) ​​A DSC600 manufactured by Hitachi High-Tech Science was used to measure the glass transition temperature of the tackifier. 5 mg of alumina was used as a reference, and approximately 5 mg of a solvent-removed tackifier resin was placed in a 5 mm diameter aluminum sample pan, and the temperature was raised from 0°C to 150°C at a heating rate of 10°C / min in an environment with a nitrogen flow rate of 50 ml / min. The inflection point at which the specific heat changed was read as the glass transition temperature of the tackifier resin.

[0124] (Measurement of 380 nm transmittance) The 380 nm transmittance of the pressure-sensitive adhesive sheet was measured using a spectrophotometer (V-770, manufactured by JASCO Corporation). An automatic absolute reflectance measurement unit was attached to the spectrophotometer, and the spectral transmittance from 800 to 300 nm was measured using a measurement program for absolute reflectance spectrum measurement. The device settings for the measurement were as follows:

[0125] Data acquisition interval: 1 nm Bandwidth: 5.0 nm Response: 0.96 sec Scanning speed: 1000 nm / min Light source: D2 / WI Correction: Baseline / dark

[0126] (Weather Resistance Test) The pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples were cut to the same size as glass plates (manufactured by Matsunami Glass Industry) with a thickness of 1 mm, a width of 76 mm, and a length of 52 mm. One release sheet from the pressure-sensitive adhesive sheet was peeled off and the sheet was adhered to the glass surface. The other release sheet was then peeled off, and a glass plate of the same size was attached to the sheet, followed by autoclaving at 40°C and 0.5 MPa for 30 minutes to bond the sheets together. The samples thus obtained were left to stand at room temperature for 1 day, and then subjected to a 1000-hour accelerated weathering test in accordance with JASO M346 using an Atlas "Ci4400" tester. The chromaticity b* value was then measured by optical measurement (using a ColorCute i colorimeter manufactured by Ga Test Instruments). Based on the b* value measurement results, the samples were evaluated according to the following criteria. <Evaluation Criteria> ◯: The increase in b* value after light irradiation relative to the b* value before evaluation was less than 1.5, indicating excellent weather resistance. x: The increase in b* value after light irradiation relative to the b* value before evaluation was 1.5 or more, and the weather resistance was poor.

[0127] (Durability test) The adhesive sheet was placed in a thermostatic oven at 70 ° C. and left for 7 days. It was then attached to a 100 μm thick polyester film (A4300, manufactured by Toyobo) that had been treated for easy adhesion, and the attached portion was cut to a width of 25 mm and a length of 50 mm. Next, the adhesive sheet side was attached to a 1.1 mm thick float glass (manufactured by Hiraoka Glass Industry Co., Ltd.), and then pressed with a 2 kg roller twice to obtain a laminate. This laminate was treated in an autoclave at a temperature of 30 ° C. and a pressure of 0.5 MPa for 30 minutes, and then left at atmospheric pressure and room temperature for 1 day to obtain a laminate for evaluation. This evaluation laminate was then left in a thermostatic oven at a temperature of 85 ° C. and a relative humidity of 85% for 30 minutes, and then placed on a stand with the float glass side facing up. Next, a 100 g weight was hooked onto the edge of the polyester film, and the time until the pressure-sensitive adhesive sheet peeled off from the glass surface and the weight fell was measured, and weather resistance was evaluated according to the following criteria. <Evaluation criteria> A: The weight did not fall even after 30 minutes, indicating extremely high adhesion to the glass and excellent durability. B: The weight did not fall even after 15 minutes and fell before 30 minutes had passed, but showed high adhesion to the glass and good durability. C: The weight fell before 15 minutes had passed, indicating low adhesion to the glass and poor durability.

[0128] Table 1 shows the main component composition (acrylic copolymer composition, Mw and Tg of the acrylic copolymer), preparation conditions for the adhesive composition, and the thickness of the obtained adhesive sheet, as well as the measurement results of the 380 nm transmittance, weather resistance test, and durability test when producing the adhesive sheet obtained in each Example and Comparative Example. Note that in Table 1, blank cells in the preparation conditions for the adhesive composition indicate that the raw material was not used.

[0129] As can be seen from Table 1, the adhesive sheets obtained in the examples had high adhesion to glass, and the durability of the laminates including the adhesive sheets was excellent, despite containing an acrylic copolymer having a hydroxyl group and a silane coupling agent.

[0130]

Claims

1. An adhesive sheet formed from an active energy ray-curable adhesive composition containing at least an acrylic copolymer containing a hydroxyl group, a silane coupling agent, and an ultraviolet absorber, wherein the acrylic copolymer has a glass transition temperature of 0°C or lower, and the silane coupling agent contains at least one type selected from the group consisting of silane coupling agents having an isocyanurate skeleton and silane coupling agents having a protected mercapto group.

2. The pressure-sensitive adhesive sheet according to claim 1, which has a light transmittance of less than 5% at a wavelength of 380 nm.

3. The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic copolymer does not contain a nitrogen atom-containing monomer unit.

4. The pressure-sensitive adhesive sheet according to claim 1, further comprising an acrylic tackifier.

5. The pressure-sensitive adhesive sheet according to claim 1, wherein the ultraviolet absorber comprises at least one member selected from the group consisting of hydroxyphenyltriazine ultraviolet absorbers and benzotriazole ultraviolet absorbers.

6. The pressure-sensitive adhesive sheet according to claim 1, having a thickness of 100 μm to 500 μm.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, which is used for bonding optical members.

8. A laminate comprising the pressure-sensitive adhesive sheet according to any one of claims 1 to 6.

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