Adhesive sheet, laminate, and device

Abstract

To provide an adhesive sheet having an adhesive that follows surface irregularities such as steps and has excellent resistance to humid heat whitening and resistance to blistering.SOLUTION: An adhesive sheet has an adhesive for bonding a first member and a second member, the adhesive being curable by active energy rays and the adhesive containing at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive, and a laminate and a device formed using the pressure-sensitive adhesive. [Background technology]

[0002] A display member having a liquid crystal element, a light-emitting diode (LED) element, an organic electroluminescence (organic EL) element, or the like is laminated with other members (such as a protective panel for protecting the display member) to form a display (display) of a device such as an electronic device. Such a laminate of a display member and other members is generally formed by bonding the display member and other members together using an adhesive contained in an adhesive sheet.

[0003] In recent years, displays including the above-described display member have been provided in automobile instrument panels, car navigation systems, various instruments provided in consoles, and various mobile electronic devices such as smartphones and tablet terminals. Such displays are often touch panels equipped with position input means.

[0004] In such displays, a protective member (such as a protective panel) for protecting the display member from external impacts is attached to the display member via an adhesive. In this case, for example, a frame-shaped printed layer may be formed on the surface of the protective member facing the display member, resulting in unevenness on the surface. In this case, if the adhesive does not conform to the unevenness, the adhesive will float near the unevenness, resulting in light reflection loss. Therefore, the adhesive is required to have the ability to conform to unevenness. Incidentally, unevenness conformability may also be required in other parts of the display.

[0005] Glass plates, which have excellent transparency, have traditionally been used as protective members. However, in recent years, plastic plates have been used instead of glass plates in light of weight reduction and safety considerations. However, unlike glass plates, plastic plates generate outgassing and transmit water vapor under high-temperature and high-humidity (wet and hot) conditions. This can lead to the formation of blisters, such as bubbles, lifting, and peeling, between the plastic plate and the adhesive. Therefore, the adhesive is required to have blister resistance.

[0006] Patent Document 1 discloses a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an ultraviolet-curable component. By using this pressure-sensitive adhesive sheet, components are bonded together via a relatively soft pressure-sensitive adhesive layer before ultraviolet irradiation, allowing the pressure-sensitive adhesive layer to conform well to unevenness, and by irradiating the pressure-sensitive adhesive layer with ultraviolet light after bonding to harden the pressure-sensitive adhesive layer, a laminate exhibiting good blister resistance is obtained. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-10885 A Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned various instruments, various mobile electronic devices, etc., are sometimes used in high-temperature and high-humidity environments. In such high-temperature and high-humidity environments, moisture easily penetrates into the adhesive, and the absorbed moisture can cause the adhesive to turn white (whitening) (humid heat whitening). Whitening of adhesives tends to occur more easily when a polymer containing a large proportion of monomers with a low glass transition temperature (Tg) is used.

[0009] Therefore, the pressure-sensitive adhesive layer disclosed in Patent Document 1 has a problem in that it is poor in preventing whitening of the pressure-sensitive adhesive layer (resistance to whitening due to humidity and heat).

[0010] The present invention has been made in view of the above circumstances, and has an object to provide a pressure-sensitive adhesive sheet that conforms to unevenness such as steps and has a pressure-sensitive adhesive that has good resistance to wet heat whitening and blistering. [Means for solving the problem]

[0011] The aspects of the present invention are as follows.

[0012] [1] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive for bonding a first member and a second member, The adhesive is active energy ray curable, The adhesive sheet contains at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.

[0013] [2] The pressure-sensitive adhesive sheet according to [1], wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive.

[0014] [3] The pressure-sensitive adhesive sheet according to [2], wherein the acrylic pressure-sensitive adhesive has a crosslinked structure containing at least a (meth)acrylic acid ester polymer and a crosslinking agent, and an active energy ray-curable component.

[0015] [4] The pressure-sensitive adhesive sheet according to [3], wherein the (meth)acrylic acid ester polymer contains, as a monomer unit, a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.

[0016] [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the surfactant is at least one selected from a nonionic surfactant and an anionic surfactant.

[0017] [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], wherein the pressure-sensitive adhesive has a storage modulus at 23°C of 0.09 MPa or less before being irradiated with active energy rays.

[0018] [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the pressure-sensitive adhesive has a wet heat haze of 10% or less after irradiation with active energy rays.

[0019] [8] A laminate comprising a first member, a second member, and a post-curing adhesive that bonds the first member and the second member together, The cured adhesive is a laminate obtained by curing the adhesive contained in the adhesive sheet according to any one of claims 1 to 7.

[0020] [9] At least one of the first member and the second member has irregularities; The adhesive after curing is a laminate according to [8], which is bonded along the unevenness. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that conforms to unevenness such as steps and has a pressure-sensitive adhesive that has good resistance to wet heat whitening and blistering. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below based on specific embodiments.

[0024] (1. Adhesive sheet) As shown in FIG. 1, the adhesive sheet 1 according to this embodiment comprises an adhesive 10, a first release sheet 15, and a second release sheet 16. The adhesive 10 is formed in a layered form to form an adhesive layer. The adhesive 10 is also active energy ray curable. Therefore, the adhesive 10 cures after being irradiated with active energy rays, becoming an adhesive after curing. The adhesive will be described later.

[0025] Two release sheets (first release sheet 15 and second release sheet 16) support adhesive 10, and are arranged so that their release surfaces contact both main surfaces 10a, 10b of the adhesive, allowing them to be peeled off from the adhesive. In other words, adhesive 10 is sandwiched between two release sheets (first release sheet 15 and second release sheet 16) so that it can be peeled off. In this specification, the release surface of a release sheet refers to the surface of the release sheet that has releasability, and includes both a surface that has been subjected to a release treatment and a surface that exhibits releasability even without being subjected to a release treatment. Release sheets will be described later.

[0026] The pressure-sensitive adhesive sheet according to this embodiment is used to bond a first member and a second member. For example, it is preferably used to bond members (display-constituting members) that constitute a display. In particular, it is preferably used to bond members that have unevenness such as steps.

[0027] As will be described in detail later, in this embodiment, the first member and the second member are bonded together using a pressure-sensitive adhesive before being irradiated with active energy rays. Because the pressure-sensitive adhesive before being irradiated with active energy rays is relatively soft, it can adequately conform to the unevenness formed on the first member and / or the second member. After bonding the first member and the second member together, the pressure-sensitive adhesive is irradiated with a predetermined amount of active energy rays to harden the pressure-sensitive adhesive, thereby increasing the cohesive strength of the pressure-sensitive adhesive and improving the durability of the bonded members, such as blister resistance.

[0028] Furthermore, because devices equipped with displays are used in a variety of environments, they are required to be able to perform as intended even in such environments. High-temperature, high-humidity environments are particularly harsh environments, making adhesives prone to malfunction. For example, in high-temperature, high-humidity environments, moisture can penetrate the adhesive, causing it to turn white. When this type of adhesive discoloration (whitening) occurs, it is likely to cause problems such as a change in the color of the image displayed on the display.

[0029] However, there has been a problem in that it is difficult for a pressure-sensitive adhesive to simultaneously achieve the ability to conform to unevenness and the ability to suppress whitening of the pressure-sensitive adhesive (resistance to wet heat whitening).

[0030] The present inventors have found that the above problems can be addressed by controlling the components contained in the adhesive, as described below. The components of the adhesive sheet according to this embodiment will be described in detail below.

[0031] (1.1. Adhesive) As described above, in this embodiment, the pressure-sensitive adhesive is active energy ray-curable and is formed in the form of a layer in the pressure-sensitive adhesive sheet.

[0032] The layered pressure-sensitive adhesive may be composed of one layer (single layer) or two or more layers. When the pressure-sensitive adhesive has multiple layers, these multiple layers may be the same or different from each other.

[0033] The thickness of the pressure-sensitive adhesive 10 formed into a layer may be 1 to 3000 μm, 10 to 2000 μm, 50 to 1000 μm, 80 to 750 μm, 120 to 500 μm, or 160 to 250 μm, which makes it easier to obtain adhesiveness that allows the first and second members to be bonded well, and makes it easier to obtain good conformability to irregularities and blister resistance.

[0034] In this embodiment, the pressure-sensitive adhesive preferably contains at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, thereby achieving both humidity and heat whitening resistance, conformability to irregularities, and blister resistance.

[0035] (1.1.1. Surfactants) The surfactant (F) is a component having a hydrophilic group. For example, in a pressure-sensitive adhesive in a high-temperature, high-humidity environment, the hydrophilic group of the surfactant is thought to capture moisture that has penetrated into the pressure-sensitive adhesive. Therefore, even if moisture penetrates into the pressure-sensitive adhesive, it is thought that the pressure-sensitive adhesive is less likely to whiten. Furthermore, when the pressure-sensitive adhesive is transferred from a high-temperature, high-humidity environment to a normal environment, the hydrophilic group is thought to release the captured moisture, which is thought to prevent the pressure-sensitive adhesive from becoming cloudy due to excess moisture. Therefore, by including a surfactant, the pressure-sensitive adhesive can exhibit good resistance to humidity and heat whitening.

[0036] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. In this embodiment, nonionic surfactants and anionic surfactants are preferred, and from the viewpoint of adhesive strength of the adhesive, nonionic surfactants are more preferred.

[0037] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene styrenated phenyl ethers, and block copolymers of polyoxyethylene and polyoxypropylene.

[0038] Examples of anionic surfactants include polyoxyethylene alkyl ether sulfates and salts thereof, polyoxyethylene alkyl phenyl ether sulfates and salts thereof, polyoxyethylene alkyl ether phosphates and salts thereof, and polyoxyethylene alkyl phenyl ether phosphates and salts thereof.

[0039] The content of the surfactant may be 0.01 to 10 mass%, 0.1 to 5 mass%, 0.4 to 2 mass%, 0.8 to 1 mass%, or 0.85 to 0.94 mass% relative to 100 mass% of the adhesive, thereby achieving good resistance to wet heat whitening.

[0040] (1.1.2.2 Monomers having two or more hydrophilic groups and one or more (meth)acryloyl groups) A monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups is a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups in its molecule. Because the monomer has hydrophilic groups, it is believed to capture moisture that has penetrated into the adhesive, similar to a surfactant. Since it has two or more hydrophilic groups, moisture capture is efficient. Therefore, it is believed that whitening of the adhesive is unlikely to occur even if moisture penetrates into the adhesive. Furthermore, when the adhesive is transferred from a high-temperature, high-humidity environment to a normal environment, the hydroxyl groups are believed to release the captured moisture, which is believed to prevent the adhesive from becoming cloudy due to excess moisture. Therefore, by including a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, the adhesive can exhibit good resistance to humidity and heat whitening.

[0041] Furthermore, since a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups has a polymerizable (meth)acryloyl group, it is easy to form a polymer alone or with other polymerizable monomers. Therefore, it is easy to control the adhesiveness, physical properties, etc. of the pressure-sensitive adhesive. In this embodiment, the monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups is preferably a monomer unit constituting a (meth)acrylic acid ester polymer, which will be described later.

[0042] In this embodiment, examples of the hydrophilic group include a hydroxyl group, a carboxyl group, an amino group, etc., with a hydroxyl group being preferred. Examples of monomers having two or more hydroxyl groups and one or more (meth)acryloyl groups include 2-methacryloyloxyethyl acid phosphate, 2-hydroxyethyl (meth)acrylate acid phosphate, and glycerin mono(meth)acrylate. Among these, glycerin mono(meth)acrylate is preferred because it has hydroxyl groups at the end and side chain of a relatively long carbon chain. This facilitates the aforementioned capture and release of moisture, thereby fully demonstrating the above-mentioned effects. As the glycerin mono(meth)acrylate, glycerin monomethacrylate is preferred.

[0043] The content of the monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups may be 0.1 to 30 mass%, 1 to 25 mass%, 4 to 20 mass%, 6 to 16 mass%, or 8 to 12 mass% relative to 100 mass% of the adhesive, thereby achieving good resistance to wet heat whitening.

[0044] (1.2. Physical properties of adhesive) In this embodiment, the adhesive preferably has the following physical properties.

[0045] (1.2.1. Storage modulus of adhesive before irradiation with active energy rays) In this embodiment, the storage modulus (G') of the pressure-sensitive adhesive before irradiation with active energy rays at 23°C and a frequency of 1 Hz is preferably 0.09 MPa or less. The storage modulus is one indicator of the ease with which a pressure-sensitive adhesive deforms (hardness). As a result, the pressure-sensitive adhesive is relatively soft before irradiation with active energy rays, and even when attached to an adherend having irregularities, it can sufficiently conform to the irregularities and prevent lifting or peeling from the attached member.

[0046] From the above viewpoint, the storage modulus of the pressure-sensitive adhesive at 23°C may be 0.001 to 0.08 MPa, 0.01 to 0.07 MPa, 0.02 to 0.06 MPa, or 0.03 to 0.05 MPa.

[0047] In this embodiment, the storage modulus (G') of the pressure-sensitive adhesive after irradiation with active energy rays at 23°C and a frequency of 1 Hz may be 0.001 to 2 MPa, 0.01 to 1.5 MPa, 0.03 to 1 MPa, 0.04 to 0.6 MPa, or 0.05 to 0.3 MPa, thereby increasing the cohesive strength of the pressure-sensitive adhesive after curing.

[0048] The storage modulus of the adhesive can be adjusted, for example, by changing the composition of the adhesive (such as the type and amount of reactive functional groups, the molecular structure and glass transition temperature of the monomer composition used), the molecular weight of the material that constitutes the adhesive, etc., as described below.

[0049] The storage modulus (G') may be measured by a known method. For example, the pressure-sensitive adhesive is prepared into a sample of a predetermined size, and the sample is strained at a predetermined frequency within a predetermined temperature range using a dynamic viscoelasticity measuring device to measure the modulus. The storage modulus under the above conditions can be calculated from the measured modulus.

[0050] (1.2.2. Humid heat haze value of adhesive after exposure to active energy rays) In this embodiment, the pressure-sensitive adhesive preferably has a wet heat haze value of 10% or less after irradiation with active energy rays. The wet heat haze value is the haze value of the pressure-sensitive adhesive after a specified wet heat test. This suppresses wet heat whitening of the pressure-sensitive adhesive caused by a high-temperature, high-humidity environment.

[0051] From the above viewpoints, the pressure-sensitive adhesive may have a wet heat haze value of 5% or less, 2% or less, 1% or less, or 0.7% or less. The lower limit of the wet heat haze value is preferably 0%, but in practice it may be 0.01% or more, 0.05% or more, or 0.1% or more.

[0052] The wet heat test and the method for measuring the wet heat haze value will be described in detail in the Examples.

[0053] (1.3. Composition of Adhesive) In this embodiment, the adhesive is active energy ray-curable and may have any composition as long as it contains at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups. For example, the adhesive may be an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, a silicone adhesive, or the like. The adhesive may be an emulsion type, a solvent type, or a solventless type. Furthermore, the adhesive may or may not have a crosslinked structure.

[0054] In this embodiment, from the viewpoints of resistance to wet heat whitening, resistance to blistering, adhesive properties, optical properties, etc., the adhesive is preferably an acrylic adhesive, and more preferably an acrylic adhesive having a crosslinked structure.

[0055] Specifically, the crosslinked structure is preferably a crosslinked structure formed using at least a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B). In other words, the pressure-sensitive adhesive is preferably a pressure-sensitive adhesive obtained by crosslinking a pressure-sensitive adhesive composition (hereinafter sometimes referred to as "pressure-sensitive adhesive composition P") containing at least one selected from a surfactant (F) and glycerin mono(meth)acrylate, the (meth)acrylic acid ester polymer (A), and the crosslinking agent (B). Such a pressure-sensitive adhesive is likely to satisfy the above-mentioned physical properties and to obtain good adhesive strength.

[0056] When the pressure-sensitive adhesive composition P contains a surfactant (F), the content of the surfactant (F) in the pressure-sensitive adhesive composition P may be 0.01 to 10 parts by mass, 0.3 to 5 parts by mass, 0.5 to 1 part by mass, 0.7 to 1.5 parts by mass, or 0.9 to 1.2 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). This suppresses moist heat whitening of the pressure-sensitive adhesive caused by a high-temperature, high-humidity environment. Furthermore, the above-mentioned physical properties are more likely to be satisfied.

[0057] Furthermore, from the perspective of the SDGs, the adhesive may be made from a material with a high biomass content, a material that can be recycled or reused, or a recycled or reused material. In this specification, (meth)acrylic acid refers to both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer."

[0058] (1.3.1. (Meth)acrylic acid ester polymer (A)) The (meth)acrylic acid ester polymer (A) preferably contains, as monomer units constituting the polymer, a (meth)acrylic acid alkyl ester and a monomer having a reactive functional group in the molecule (a reactive functional group-containing monomer), which makes it easier to obtain a pressure-sensitive adhesive having a crosslinked structure and good adhesiveness.

[0059] Furthermore, as described above, when the pressure-sensitive adhesive composition P contains a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, the monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups is preferably contained as a monomer unit constituting the (meth)acrylic acid ester polymer (A). Note that the monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups is excluded from the reactive functional group-containing monomer.

[0060] The (meth)acrylic acid ester polymer (A) may contain, as a monomer unit constituting the polymer, a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups in an amount of 0.1 to 30 mass%, 0.6 to 24 mass%, 1.2 to 18 mass%, 3 to 15 mass%, or 6 to 12 mass%. This suppresses moist heat whitening of the pressure-sensitive adhesive caused by a high-temperature, high-humidity environment. Furthermore, the above-mentioned physical properties are more likely to be satisfied.

[0061] The (meth)acrylic acid ester polymer (A) preferably contains an aromatic ring-containing monomer as a monomer unit constituting the polymer, which makes it easier to obtain the above-mentioned physical properties.

[0062] Therefore, the (meth)acrylic acid ester polymer (A) preferably contains, as monomer units constituting the polymer, an alkyl (meth)acrylate, a reactive functional group-containing monomer, and an aromatic ring-containing monomer.

[0063] By containing a (meth)acrylic acid alkyl ester, the resulting pressure-sensitive adhesive can exhibit desirable adhesiveness. As the (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferred. The alkyl group may be linear or branched, or may have a cyclic structure.

[0064] Examples of (meth)acrylic acid alkyl esters having an alkyl group containing 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0065] Among these, from the viewpoint of improving adhesiveness, (meth)acrylic acid esters having an alkyl group with 1 to 8 carbon atoms are preferred, (meth)acrylic acid esters having an alkyl group with 4 to 8 carbon atoms are more preferred, and (meth)acrylic acid esters having an alkyl group with 4 to 8 carbon atoms and a glass transition temperature (Tg) as a homopolymer of -40°C or less are even more preferred. Specifically, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-octyl (meth)acrylate are preferred, and n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are particularly preferred. These may be used alone or in combination of two or more.

[0066] The (meth)acrylic acid ester polymer (A) preferably contains 60 to 99.9 mass %, more preferably 70 to 99 mass %, even more preferably 80 to 98.5 mass %, and particularly preferably 90 to 98 mass % of (meth)acrylic acid alkyl esters, the alkyl groups of which have 1 to 20 carbon atoms, as monomer units constituting the polymer. This allows the (meth)acrylic acid ester polymer (A) to be endowed with suitable adhesive properties. Furthermore, desired amounts of other monomer components can be incorporated into the (meth)acrylic acid ester polymer (A), making it easier to design adhesives that exhibit desired performance.

[0067] The (meth)acrylic acid ester polymer (A) contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and thus the (meth)acrylic acid ester polymer (A) reacts with the crosslinking agent (B) described below via the reactive functional group derived from the reactive functional group-containing monomer, forming a crosslinked structure as a three-dimensional network structure in the pressure-sensitive adhesive. As a result, a pressure-sensitive adhesive having the desired cohesive strength is obtained, and the pressure-sensitive adhesive is likely to satisfy the above-mentioned physical properties.

[0068] Preferred reactive functional group-containing monomers include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). These reactive functional group-containing monomers may be used alone or in combination of two or more. Among these, hydroxyl group-containing monomers or carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are particularly preferred. By including a hydroxyl group-containing monomer, desired physical properties are more easily achieved, and resistance to wet heat whitening is more easily obtained.

[0069] Examples of hydroxyl group-containing monomers include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, from the viewpoint of easily realizing physical properties related to wet heat whitening resistance, (meth)acrylic acid hydroxyalkyl esters having a hydroxyalkyl group having 1 to 4 carbon atoms are preferred. Specific examples include 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and particularly preferred are 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate. These may be used alone or in combination of two or more.

[0070] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferred from the viewpoint of the adhesive strength of the resulting (meth)acrylic acid ester polymer (A). These may be used alone or in combination of two or more.

[0071] The (meth)acrylic acid ester polymer (A) may contain, as a monomer unit constituting the polymer, 0.1 to 30 mass%, 0.3 to 20 mass%, 0.6 to 10 mass%, 0.8 to 5 mass%, or 0.9 to 2 mass% of a reactive functional group-containing monomer, which gives the pressure-sensitive adhesive obtained by the crosslinking reaction with the crosslinking agent (B) an appropriate cohesive strength, making it easier to satisfy the above-mentioned physical properties and to exhibit excellent conformability to irregularities.

[0072] It is also preferable that the (meth)acrylic acid ester polymer (A) does not contain a carboxy group-containing monomer as a monomer unit constituting the polymer. Since a carboxy group is an acid component, the absence of a carboxy group-containing monomer can suppress acid-induced defects (corrosion, resistance change, etc.) even when the target to which the pressure-sensitive adhesive is applied includes a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, or a metal mesh, which may be affected by acid.

[0073] Here, "not containing a carboxyl group-containing monomer" means that the carboxyl group-containing monomer is substantially not contained, and includes not only the case where the carboxyl group-containing monomer is not contained at all, but also the case where the carboxyl group-containing monomer is contained to an extent that the carboxyl group does not cause corrosion of the transparent conductive film, metal wiring, etc. Specifically, the (meth)acrylic acid ester polymer (A) may contain the carboxyl group-containing monomer as a monomer unit in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

[0074] Examples of aromatic ring-containing monomers include phenyl (meth)acrylate, 2-phenylethyl (meth)acrylate, benzyl (meth)acrylate, naphthyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, ethoxylated-o-phenylphenol acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, biphenyl di(meth)acrylate, pentafluorobenzyl (meth)acrylate, etc. Among these, from the viewpoint of easily satisfying the above-mentioned physical properties, phenyl (meth)acrylate, 2-phenylethyl (meth)acrylate, benzyl (meth)acrylate, naphthyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and phenoxybutyl (meth)acrylate are preferred, and from the viewpoint of easily making the above-mentioned physical properties more suitable, 2-phenoxyethyl (meth)acrylate is more preferred, and 2-phenoxyethyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0075] The (meth)acrylic acid ester copolymer (A) may contain, as a monomer unit constituting the polymer, an aromatic ring-containing monomer in an amount of 0.1 to 20 mass%, 0.5 to 10 mass%, 1 to 6 mass%, or 1.5 to 3 mass%, which makes it easier to satisfy the above-mentioned physical properties.

[0076] In this embodiment, the (meth)acrylic acid ester polymer (A) may contain other monomers as monomer units constituting the polymer, if desired. As the other monomers, monomers that do not contain reactive functional groups are preferred so as not to inhibit the above-mentioned action of the reactive functional group-containing monomer. Examples of such monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

[0077] The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

[0078] The weight-average molecular weight of the (meth)acrylic acid ester polymer (A) may be 100,000 to 3,000,000, 200,000 to 2,400,000, 300,000 to 1,800,000, 400,000 to 1,500,000, or 450,000 to 1,250,000. This makes it easier for the resulting pressure-sensitive adhesive to satisfy the above-mentioned physical properties. Note that the weight-average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0079] In the pressure-sensitive adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used singly or in combination of two or more kinds.

[0080] (1.3.2. Crosslinker (B)) The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) to form a crosslinked structure, triggered by heating the pressure-sensitive adhesive composition P containing the crosslinking agent (B), etc. As a result, the cohesive strength of the resulting pressure-sensitive adhesive is improved, and the above-mentioned physical properties tend to be satisfied.

[0081] The crosslinking agent (B) may be any agent that reacts with the reactive groups of the (meth)acrylic acid ester polymer (A). Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with reactive functional group-containing monomers. The crosslinking agent (B) may be used alone or in combination of two or more.

[0082] The isocyanate crosslinking agent contains at least a polyisocyanate compound, such as aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret and isocyanurate forms thereof, as well as adducts thereof that are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.

[0083] The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition P may be 0.01 to 10 parts by mass, 0.04 to 5 parts by mass, 0.08 to 1 part by mass, 0.1 to 0.75 parts by mass, or 0.12 to 0.5 parts by mass, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A), which makes it easier to satisfy the above-mentioned physical properties.

[0084] (1.3.3. Silane Coupling Agent (C)) The pressure-sensitive adhesive composition P according to this embodiment preferably contains a silane coupling agent (C), which improves adhesion to the adherend and provides good blister resistance and conformability to uneven surfaces.

[0085] The silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the adhesive component, particularly the (meth)acrylic acid ester polymer (A), and has optical transparency.

[0086] Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; epoxy structure-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane. Examples of such silane compounds include amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane, as well as condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These compounds may be used alone or in combination of two or more.

[0087] The content of the silane coupling agent (C) may be 0.01 to 1 part by mass, 0.04 to 0.7 parts by mass, 0.08 to 0.4 parts by mass, or 0.12 to 0.25 parts by mass relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A), which makes it easier to achieve the above-mentioned properties.

[0088] (1.3.4. Active Energy Ray-Curable Component (D)) In this embodiment, the pressure-sensitive adhesive composition P preferably contains an active energy ray-curable component (D). When the resulting pressure-sensitive adhesive is applied to an adherend and then irradiated with active energy rays, the cleavage of the photopolymerization initiator (E), which will be described later, triggers the polymerization of the active energy ray-curable component (D). The polymerized active energy ray-curable component (D) is presumed to become entangled in the crosslinked structure (three-dimensional network structure) formed by crosslinking the (meth)acrylic acid ester polymer (A) and the crosslinking agent (B). A cured pressure-sensitive adhesive having such a high-order structure exhibits excellent conformability to irregularities and blister resistance. Therefore, the active energy ray-curable component is uncured in the pressure-sensitive adhesive before it is applied to an adherend.

[0089] The active energy ray-curable component (D) is not particularly limited as long as it is a component that cures upon irradiation with active energy rays and provides the above-mentioned effects, and may be any of a monomer, oligomer, or polymer, or a mixture thereof. Among these, polyfunctional acrylate monomers, which have superior blister resistance, are preferred. Furthermore, from the viewpoint of compatibility with the (meth)acrylic acid ester polymer (A), the polyfunctional acrylate monomer preferably has a molecular weight of 3,000 or less, more preferably 2,000 or less, and particularly preferably 1,000 or less.

[0090] As the polyfunctional acrylate monomer, a bifunctional, trifunctional, tetrafunctional, pentafunctional or hexafunctional acrylate monomer is preferred.

[0091] Examples of bifunctional acrylate monomers include tricyclodecane dimethanol dimethacrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

[0092] Examples of trifunctional acrylate monomers include trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate.

[0093] Examples of tetrafunctional acrylate monomers include diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate. Examples of pentafunctional acrylate monomers include propionic acid-modified dipentaerythritol penta(meth)acrylate. Examples of hexafunctional acrylate monomers include dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0094] Among these, from the viewpoint of the blister resistance of the resulting PSA, preferred are polyfunctional acrylate monomers containing an isocyanurate structure in the molecule, such as di(acryloxyethyl)isocyanurate, tris(acryloxyethyl)isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate, or tricyclodecane dimethanol dimethacrylate, more preferred are polyfunctional acrylate monomers that are trifunctional or higher and contain an isocyanurate structure in the molecule, or tricyclodecane dimethanol dimethacrylate, and particularly preferred are ε-caprolactone-modified tris-(2-(meth)acryloxyethyl)isocyanurate and tricyclodecane dimethanol dimethacrylate. These may be used alone or in combination of two or more.

[0095] The active energy ray-curable component (D) can also be an active energy ray-curable acrylate oligomer. This acrylate oligomer preferably has a weight-average molecular weight of 50,000 or less. Examples of such acrylate oligomers include polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, and silicone acrylates.

[0096] The weight average molecular weight of the acrylate oligomer is preferably 50,000 or less, more preferably 500 to 50,000, and even more preferably 3,000 to 40,000. These acrylate oligomers may be used alone or in combination of two or more.

[0097] The active energy ray-curable component (D) may be an adduct acrylate polymer having a (meth)acryloyl group introduced into its side chain. Such an adduct acrylate polymer can be obtained by using a copolymer of a (meth)acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and reacting a compound having a group reactive with the (meth)acryloyl group and the crosslinkable functional group with a portion of the crosslinkable functional group of the copolymer.

[0098] The weight average molecular weight of the adduct acrylate polymer is preferably from 50,000 to 900,000, and more preferably from 100,000 to 500,000.

[0099] As the active energy ray-curable component (D), the above-mentioned polyfunctional acrylate monomer is preferred, but one kind may be selected from polyfunctional acrylate monomers, acrylate oligomers, and adduct acrylate polymers, or two or more kinds may be used in combination, or these components may be used in combination with other active energy ray-curable components.

[0100] The content of the active energy ray-curable component (D) in the pressure-sensitive adhesive composition P may be 1 to 50 parts by mass, 2 to 35 parts by mass, 3 to 20 parts by mass, 4 to 12 parts by mass, or 5 to 7 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). This allows the resulting pressure-sensitive adhesive to exhibit sufficient flexibility and adhesiveness before active energy ray irradiation, making it easy to conform to irregularities and to adhere well to the adherend. After active energy ray irradiation, the resulting pressure-sensitive adhesive becomes a cured pressure-sensitive adhesive with improved cohesive strength and excellent blister resistance and conformability to irregularities. When the pressure-sensitive adhesive is other than an acrylic pressure-sensitive adhesive, the content of the active energy ray-curable component (D) is preferably within the above-mentioned range per 100 parts by mass of the pressure-sensitive adhesive.

[0101] (1.3.5. Photopolymerization initiator (E)) In this embodiment, when the adhesive composition P contains an active energy ray-curable component (D) and ultraviolet rays are used as the active energy rays, the adhesive composition P preferably contains a photopolymerization initiator (E), which allows the active energy ray-curable component (D) to be cured efficiently and reduces the polymerization curing time and the ultraviolet irradiation dose.

[0102] Examples of the photopolymerization initiator (E) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4 Examples of suitable benzoxanthraquinones include '-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. These may be used alone or in combination of two or more.

[0103] Among the above, phosphine oxide-based photopolymerization initiators are preferred because they are easily cleaved and reliably cure adhesives even when UV rays are irradiated through a plastic plate containing a UV absorber or when the adhesive contains a UV absorber. Specifically, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and the like are preferred. Some display component members, which serve as adherends, contain UV absorbers and have UV-blocking properties. Even when UV rays are irradiated through such UV-blocking materials, the above-mentioned phosphine oxide-based photopolymerization initiators can promote the curing of the active energy ray-curable component (D).

[0104] The content of the photopolymerization initiator (E) in the adhesive composition P is preferably 1 to 30 parts by mass, more preferably 4 to 20 parts by mass, and even more preferably 8 to 15 parts by mass, per 100 parts by mass of the active energy ray-curable component (D).

[0105] (1.3.7. Other Additives) The pressure-sensitive adhesive composition P may contain additives commonly used in acrylic pressure-sensitive adhesives, as needed. Examples of such additives include ultraviolet absorbers, infrared absorbers, oxygen absorbers, tackifiers, plasticizers, colorants, antistatic agents, antioxidants, light stabilizers, softeners, rust inhibitors, fillers, oil absorbents, and refractive index adjusters. Note that polymerization solvents and dilution solvents, which will be described later, are not included in the additives constituting the pressure-sensitive adhesive composition P.

[0106] (1.4. Other physical properties of adhesives) In this embodiment, the adhesive may have the following physical properties.

[0107] (1.4.1. Gel fraction before and after irradiation with active energy rays) In this embodiment, the gel fraction of the pressure-sensitive adhesive before irradiation with active energy rays may be 20 to 95%, 30 to 85%, 40 to 75%, or 50 to 65%. Furthermore, the gel fraction of the pressure-sensitive adhesive after irradiation with active energy rays may be 30 to 100%, 40 to 98%, 50 to 94%, 60 to 90%, 70 to 86%, or 76 to 82%. The gel is a polymer component having a three-dimensional network structure. This facilitates the pressure-sensitive adhesive to exhibit suitable viscoelasticity, improves adhesion to the adherend, and makes it easier to adjust the adhesive strength, etc., described below, to the desired range, thereby improving conformability to uneven surfaces and blister resistance. The method for measuring the gel fraction of the pressure-sensitive adhesive will be described in detail in the Examples below.

[0108] (1.4.2. Adhesion strength before and after irradiation with active energy rays) In this embodiment, the adhesive strength of the pressure-sensitive adhesive to soda-lime glass before irradiation with active energy rays may be 0.5 to 100 N / 25 mm, 1 to 75 N / 25 mm, 5 to 55 N / 25 mm, 10 to 45 N / 25 mm, or 15 to 35 N / 25 mm. Furthermore, the adhesive strength of the pressure-sensitive adhesive to soda-lime glass after irradiation with active energy rays may be 1 to 100 N / 25 mm, 10 to 75 N / 25 mm, 20 to 55 N / 25 mm, 25 to 45 N / 25 mm, or 30 to 36 N / 25 mm. This improves the adhesiveness of the pressure-sensitive adhesive to the adherend, and also improves its conformability to irregularities and blister resistance. The adhesive strength of the pressure-sensitive adhesive may be measured using the 180-degree peeling method in accordance with JIS Z0237:2009. Specific measurement methods are described in the Examples below.

[0109] (1.4.3. Storage modulus of adhesive before and after irradiation with active energy rays) In this embodiment, the storage modulus (G') of the pressure-sensitive adhesive before irradiation with active energy rays at 70°C and a frequency of 1 Hz may be 0.001 to 0.09 MPa, 0.004 to 0.06 MPa, 0.008 to 0.04 MPa, or 0.01 to 0.03 MPa. Furthermore, the storage modulus (G') of the pressure-sensitive adhesive after irradiation with active energy rays at 70°C and a frequency of 1 Hz may be 0.001 to 2 MPa, 0.004 to 1.5 MPa, 0.008 to 1 MPa, 0.01 to 0.5 MPa, or 0.02 to 0.1 MPa. This allows the pressure-sensitive adhesive to exhibit suitable viscoelasticity before and after active energy ray irradiation, allowing it to adequately conform to irregularities when attached to an adherend, and enhancing the cohesive strength of the pressure-sensitive adhesive after curing after active energy ray irradiation. As a result, lifting or peeling from the attached member is suppressed.

[0110] (1.4.4. Total light transmittance of adhesive after irradiation with active energy rays) In this embodiment, the total light transmittance of the cured pressure-sensitive adhesive after irradiation with active energy rays may be 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more. This increases the transparency of the cured pressure-sensitive adhesive, making it suitable for optical applications. The total light transmittance is usually 100% or less. The total light transmittance of the pressure-sensitive adhesive may be measured in accordance with JIS K7361-1:1997. Specific measurement methods are as shown in the examples below.

[0111] (1.4.5. Haze value of adhesive after irradiation with active energy rays) In this embodiment, the haze value of the pressure-sensitive adhesive after curing following irradiation with active energy rays may be 10% or less, 5% or less, 1% or less, or 0.5% or less. This increases the transparency of the pressure-sensitive adhesive after curing, making it suitable for optical applications. The haze value of the pressure-sensitive adhesive may be measured in accordance with JIS K 7136:2000. Specific measurement methods are as shown in the examples below.

[0112] (1.5. Release sheet) Release sheets 15 and 16 protect adhesive 10 until adhesive sheet 1 is used, and are peeled off when adhesive sheet 1 (adhesive 10) is to be used. In adhesive sheet 1 according to this embodiment, one or both of release sheets 15 and 16 are not necessarily required.

[0113] Examples of materials that can be used as the release sheets 15, 16 include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. Crosslinked films of these materials can also be used. Furthermore, laminated films of these materials may also be used. From the perspective of the SDGs, the material constituting the release sheets may be a highly biomass material, a recyclable or reusable material, or a recycled or reused material.

[0114] The release surfaces of the release sheets 15, 16 (particularly the surfaces that come into contact with the pressure-sensitive adhesive 10) are preferably subjected to a release treatment. Examples of release agents used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. It is preferable that one of the release sheets 15, 16 is a heavy-release type release sheet with high release strength, and the other is a light-release type release sheet with low release strength.

[0115] There are no particular restrictions on the thickness of the release sheets 15 and 16, but it is preferably 10 to 250 μm, and more preferably 20 to 150 μm.

[0116] (1.6. Production of adhesive composition) The pressure-sensitive adhesive composition P containing a (meth)acrylic acid ester polymer (A), a crosslinking agent (B), an active energy ray-curable component (D), and a surfactant (F) can be produced, for example, by first producing a (meth)acrylic acid ester polymer (A), and then mixing the resulting (meth)acrylic acid ester polymer (A), the crosslinking agent (B), the active energy ray-curable component (D), and the surfactant (F). If necessary, a silane coupling agent (C), a photopolymerization initiator (E), and other additives may be added.

[0117] Furthermore, a pressure-sensitive adhesive composition P containing a (meth)acrylic acid ester polymer (A) containing, as a monomer unit, a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, a crosslinking agent (B), and an active energy ray-curable component (D) can be produced, for example, by first producing a (meth)acrylic acid ester polymer (A) containing, as a monomer unit, a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, and then mixing the resulting (meth)acrylic acid ester polymer (A) with the crosslinking agent (B) and the active energy ray-curable component (D). If necessary, a silane coupling agent (C), a photopolymerization initiator (E), a surfactant (F), and other additives may also be added.

[0118] The (meth)acrylic acid ester polymer (A) can be produced, for example, by polymerizing a mixture of polymer-constituting monomers, such as a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups, using a conventional radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (A) can be carried out by a solution polymerization method, using a polymerization initiator as needed. Polymerizing the (meth)acrylic acid ester polymer (A) using a solution polymerization method makes it easy to increase the molecular weight of the resulting polymer and adjust the molecular weight distribution, and also makes it possible to reduce the production of low-molecular-weight substances.

[0119] Examples of polymerization solvents used in solution polymerization include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone. One polymerization solvent may be used, or two or more polymerization solvents may be used in combination. Examples of polymerization initiators include azo compounds and organic peroxides, and two or more polymerization initiators may be used in combination. In the polymerization step, the weight-average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

[0120] Next, the crosslinking agent (B), the active energy ray-curable component (D), and optionally the surfactant (F) are added to the resulting solution of the (meth)acrylic acid ester polymer (A) and mixed thoroughly to obtain a solvent-diluted pressure-sensitive adhesive composition P (coating solution). Furthermore, if necessary, a dilution solvent, a silane coupling agent (C), a photopolymerization initiator (E), and other additives may be added.

[0121] In addition, if any of the above components is a solid component, or if it is a component that will precipitate when mixed with other components in an undiluted state, that component may be dissolved or diluted in advance alone in a dilution solvent and then mixed with the other components.

[0122] Examples of dilution solvents include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

[0123] The concentration and viscosity of the prepared coating solution may be within a range that allows coating, and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted to a concentration of 10 to 60 mass %. Note that the addition of a dilution solvent or the like is not a necessary condition for obtaining the coating solution, and as long as the adhesive composition P has a viscosity that allows coating, the addition of a dilution solvent is not necessary. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent for the (meth)acrylic acid ester polymer (A) itself serves as the dilution solvent.

[0124] (1.7. Manufacturing of adhesives) The pressure-sensitive adhesive is preferably obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition P. Crosslinking of the pressure-sensitive adhesive composition P can usually be carried out by heat treatment. This heat treatment can also serve as a drying treatment for volatilizing dilution solvents and the like from a coating film of the pressure-sensitive adhesive composition P applied to a desired object.

[0125] The heating temperature for the heat treatment is preferably 50 to 150° C., more preferably 70 to 120° C. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

[0126] After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (e.g., 23°C, relative humidity 50%). If curing is required, the adhesive having a crosslinked structure is obtained after the curing period has elapsed. If curing is not required, the adhesive having a crosslinked structure is obtained after the heat treatment is completed.

[0127] (1.8. Manufacturing of adhesive sheets) The method for producing the adhesive sheet 1 is not particularly limited, and it may be produced by a known method. For example, a coating solution of the adhesive composition P is applied to the release surface of one of the first release sheets 15 (or the second release sheet 16), and a heat treatment is carried out to crosslink the adhesive composition P, thereby forming a coating layer having a predetermined thickness. The release surface of the other second release sheet 16 (or the first release sheet 15) is then superimposed on the formed coating layer. If curing is required, the coating layer will become the adhesive 10 after a predetermined curing period. Alternatively, if curing is not required, the coating layer will become the adhesive 10 as is. In this way, the adhesive sheet 1 is obtained.

[0128] In another method for producing the pressure-sensitive adhesive sheet 1, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of one of the first release sheets 15, followed by a heat treatment to crosslink the pressure-sensitive adhesive composition P and form a coating layer, thereby obtaining a first release sheet 15 with a coating layer. Furthermore, a coating liquid of the above-mentioned pressure-sensitive adhesive composition P is applied to the release surface of the other of the second release sheets 16, followed by a heat treatment to crosslink the pressure-sensitive adhesive composition P and form a coating layer, thereby obtaining a second release sheet 16 with a coating layer. The first release sheet 15 with the coating layer and the second release sheet 16 with the coating layer are then bonded together so that the two coating layers are in contact with each other. If curing is required, the coating layer becomes the pressure-sensitive adhesive 10 after a predetermined curing period. If curing is not required, the coating layer becomes the pressure-sensitive adhesive 10 as is. This produces the pressure-sensitive adhesive sheet 1. This production method allows stable production of pressure-sensitive adhesive 10 even when the pressure-sensitive adhesive 10 is thick.

[0129] Examples of methods for applying the coating solution of the adhesive composition P include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0130] (2. Laminate) The laminate according to this embodiment includes a first member, a second member, and a cured adhesive layer that bonds these members together. The first and second members are preferably members used for optical applications, and in this embodiment, are preferably display component members. Examples of materials for these members include resin, glass, metal, ceramics, and semiconductors. At least one of the first and second members may have an uneven surface at the interface with the cured adhesive layer.

[0131] An example of a laminate according to this embodiment is shown in Fig. 2. In Fig. 2, laminate 2 has a first member 21 having projections and recesses, a second member 22, and a cured pressure-sensitive adhesive layer 11 located therebetween and bonding first member 21 and second member 22 to each other. Cured pressure-sensitive adhesive layer 11 is a cured product formed by curing pressure-sensitive adhesive 10 provided in pressure-sensitive adhesive sheet 1 shown in Fig. 1 by irradiation with active energy rays, and is bonded to first member 21 along the projections and recesses.

[0132] The unevenness may be the unevenness of the first member 21 itself, or may be unevenness caused by other components formed on the first member 21. An example of such a component is the printed layer 3, and the unevenness is caused by the thickness of the printed layer 3.

[0133] Another example of the laminate according to this embodiment is a laminate having a first member having irregularities, a second member, and a post-curing adhesive positioned between them to bond the first member and the second member together, with a light emitter formed on the first member. In this case, the irregularities are caused by the light emitter. There may be one or more light emitters.

[0134] (2.1.Adhesive layer after curing) The cured adhesive 11 is obtained by curing the adhesive 10 contained in the above-mentioned adhesive sheet 1 by irradiation with active energy rays. In this embodiment, the cured adhesive 11 contains a structure (polymerized structure) formed by the active energy ray-curable component (D) polymerizing and curing due to irradiation with active energy rays. The polymerized structure is presumed to be entangled with a crosslinked structure composed of the (meth)acrylic acid ester polymer (A) and the crosslinking agent (B). Due to the structure in which multiple three-dimensional structures are entangled, the cured adhesive has high cohesive strength. Therefore, the cured adhesive exhibits excellent blister resistance and unevenness-following ability.

[0135] Furthermore, the cured adhesive 11 contains a surfactant, or the (meth)acrylic acid ester polymer (A) contains a monomer unit having two or more hydrophilic groups and one or more (meth)acryloyl groups. As a result, even when the cured adhesive 11 is exposed to a high-temperature, high-humidity environment, whitening of the cured adhesive due to moisture penetration into the cured adhesive can be suppressed. Therefore, the cured adhesive 11 can simultaneously achieve humidity and heat whitening resistance, blister resistance, and unevenness conformability.

[0136] As long as the effects of the present invention can be obtained, the cured pressure-sensitive adhesive 11 may contain a photopolymerization initiator (E) that is not cleaved by irradiation with active energy rays. In this embodiment, the remaining amount of the photopolymerization initiator (E) in the cured pressure-sensitive adhesive is preferably 0.1 mass % or less, and more preferably 0.01 mass % or less.

[0137] (2.2. Other Configurations of the Laminate) When the laminate 2 is a display, examples of the display include a liquid crystal (LCD) display, a light-emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, etc., and may also be a touch panel. The display may also be a component constituting a part of any of these.

[0138] The first member 21 is preferably a protective panel made of a glass plate, a plastic plate, or a laminate containing these.

[0139] The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, etc. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, and preferably 0.2 to 2 mm.

[0140] The plastic plate is not particularly limited, but examples thereof include an acrylic plate and a polycarbonate plate. The thickness of the plastic plate is not particularly limited, but is usually 0.2 mm or more, preferably 0.4 mm or more. The thickness is usually 5 mm or less, preferably 3 mm or less.

[0141] Note that various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, etc.) may be provided on one or both sides of the glass plate or plastic plate, or other members may be laminated thereon. In addition, the transparent conductive film and metal layer may be patterned.

[0142] When the first member 21 has unevenness (steps) caused by the printed layer 3, the printed layer 3 is generally formed in a frame shape on the side of the first optical member 21 facing the pressure-sensitive adhesive 11 after curing.

[0143] There are no particular limitations on the material that constitutes the printed layer 3, and known materials for printing can be used. The thickness of the printed layer 3, i.e., the height of the step, is preferably 3 to 40 μm, more preferably 5 to 35 μm, more preferably 7 to 30 μm, and even more preferably 10 to 25 μm. This ensures sufficient concealment, such as making electrical wiring and the like invisible to the viewer.

[0144] When the first member 21 has unevenness (steps) due to a light-emitting body, examples of the light-emitting body include a light-emitting diode (LED), a laser diode (LD), an organic electroluminescence light-emitting element, an inorganic electroluminescence light-emitting element, etc. Among these, from the viewpoint of sealing properties with an adhesive, an LED is preferred, and a mini LED or a micro LED is particularly preferred.

[0145] The thickness of the light emitter is preferably 10 to 300 μm, more preferably 30 to 200 μm, even more preferably 50 to 150 μm, and particularly preferably 80 to 120 μm. When a plurality of light emitters are provided, the width of the gap between adjacent light emitters is preferably 0.01 to 100 mm, more preferably 0.1 to 10 mm, and even more preferably 0.5 to 4 mm. The shape of the light emitter is not particularly limited, but is usually a rectangular parallelepiped, hemispherical, or the like. The size of the light emitter is also not particularly limited, but from the viewpoint of light emitter sealing, the side or diameter in plan view is preferably 0.01 to 100 mm, more preferably 0.1 to 10 mm.

[0146] The second member 22 is preferably a member to be attached to the first member 21, a display module (e.g., a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (OLED) module, etc.), a member as part of a display module, or a laminate including a display module.

[0147] Examples of such members include shatterproof films, polarizing plates (polarizing films), polarizers, retardation plates (retardation films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transmitting reflective films, transparent conductive films, etc. Examples of shatterproof films include hard coat films in which a hard coat layer is formed on one side of a substrate film.

[0148] (2.3. Manufacturing of Laminate) To produce the laminate 2, for example, one release sheet 15 of the adhesive sheet 1 is peeled off, and the exposed adhesive 10 of the adhesive sheet 1 is attached to the surface of the first member 21 on which the printed layer 3 is present. Because the adhesive 10 is relatively soft before being irradiated with active energy rays, it conforms well to the unevenness caused by the printed layer 3, and the occurrence of gaps, lifting, etc. is suppressed even near the unevenness.

[0149] Thereafter, the other release sheet 16 is peeled off from the adhesive 10 of the adhesive sheet 1, and the exposed adhesive 10 is bonded to the second member 22. As another example, the bonding order of the first member 21 and the second member 22 may be reversed.

[0150] Thereafter, the pressure-sensitive adhesive 10 in the laminate is irradiated with active energy rays. In this embodiment, this causes the active energy ray-curable component (D) in the pressure-sensitive adhesive 10 to polymerize, and the pressure-sensitive adhesive 10 is cured to become a cured pressure-sensitive adhesive 11, thereby obtaining the laminate 2.

[0151] As described above, the cured pressure-sensitive adhesive 11 exhibits high cohesive strength and therefore has excellent blister resistance. Furthermore, the cured pressure-sensitive adhesive 11 also has excellent resistance to moist heat whitening because it contains at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.

[0152] The active energy ray refers to an electromagnetic wave or a charged particle beam that has an energy quantum, and specific examples thereof include ultraviolet rays, electron beams, etc. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle.

[0153] The ultraviolet irradiation can be performed using a high-pressure mercury lamp, a Heraeus H lamp, a xenon lamp, or the like, and the amount of ultraviolet irradiation is set to an illuminance of 50 to 1000 mW / cm. 2 The light intensity is preferably 50 to 10,000 mJ / cm. 2 is preferably 80 to 5000 mJ / cm 2 More preferably, it is 300 to 2000 mJ / cm2 On the other hand, the electron beam irradiation can be carried out by an electron beam accelerator or the like, and the irradiation dose of the electron beam is preferably about 10 to 1000 krad.

[0154] In this specification, when it is written "X to Y" (X and Y are any numbers), it means "X or more and Y or less" unless otherwise specified, and also includes the meaning "preferably greater than X" or "preferably smaller than Y." Furthermore, when it is written "X or more" (X is any number), it means "preferably greater than X" unless otherwise specified, and when it is written "Y or less" (Y is any number), it also means "preferably smaller than Y" unless otherwise specified.

[0155] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified in various ways within the scope of the present invention. [Example]

[0156] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0157] Example 1 1. Preparation of (meth)acrylic acid ester polymer A (meth)acrylic acid ester polymer (A) was prepared by copolymerizing 48.6 parts by mass of n-butyl acrylate, 48.6 parts by mass of 2-ethylhexyl acrylate, 1.8 parts by mass of 2-phenoxyethyl acrylate, and 1 part by mass of 4-hydroxybutyl acrylate. The molecular weight of the resulting (meth)acrylic acid ester polymer (A) was measured by the method described below, and the weight average molecular weight (Mw) was 1.2 million.

[0158] The weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). (Measurement conditions) GPC measuring device: Tosoh HLC-8020 GPC columns (passed in the following order): Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0159] 2. Preparation of adhesive composition 100 parts by mass (solid content equivalent: the same hereinafter) of the (meth)acrylic acid ester polymer (A) obtained above, 0.14 parts by mass of an isocyanate-based crosslinking agent (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75") (B1) as the crosslinking agent (B), 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane (C1) as the silane coupling agent (C), and ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester") as the active energy ray-curable component (D). A coating solution of a pressure-sensitive adhesive composition was obtained by mixing 6.4 parts by mass of a photopolymerization initiator (E) containing 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (E1) as a photopolymerization initiator (E), 0.6 parts by mass of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (E1) as a photopolymerization initiator (E), and 1 part by mass of a nonionic surfactant (manufactured by Daiichi Pharmaceutical Co., Ltd., product name "Noigen EA-87" (F1) as a surfactant (F), thoroughly stirring the mixture, and diluting it with methyl ethyl ketone.

[0160] 3. Manufacturing of adhesive sheets The obtained adhesive composition coating solution was applied to the release-treated surface of a heavy-release release sheet R1, one side of which was a polyethylene terephthalate film treated with a silicone-based release agent, using a knife coater to form a coating layer. The coating layer was then heated at 90°C for 1 minute to promote a crosslinking reaction, forming a coating layer made of an adhesive containing a crosslinked structure having at least a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B).

[0161] Next, the coating layer on the release sheet R1 obtained above was bonded to the release-treated surface of a light-release type release sheet R2, which was a polyethylene terephthalate film with one side treated with a silicone-based release agent, so that the release-treated surface contacted the coating layer. This was then cured for 7 days at 23°C and 50% relative humidity to produce a 200 μm-thick adhesive sheet. This adhesive sheet had a configuration of "release sheet R1 / adhesive (thickness: 200 μm) / release sheet R2." The adhesive thickness was measured in accordance with JIS K7130 using a constant-pressure thickness gauge (PG-02, manufactured by Teclock Corporation). It was also confirmed that the release strength from the adhesive of the resulting adhesive sheet was greater for release sheet R1 than for release sheet R2.

[0162] (Examples 2 and 3, Comparative Examples 1 to 3) Pressure-sensitive adhesive sheets were produced in the same manner as in Example 1, except that the composition and molecular weight of the (meth)acrylic acid ester polymer (A), the type and amount of the crosslinking agent (B), the amount of the silane coupling agent (C), the type and amount of the active energy ray-curable component (D), the amount of the photopolymerization initiator (E), and the amount of the surfactant (F) were changed as shown in Table 1. In Table 1, the amounts of the crosslinking agent (B), the silane coupling agent (C), the active energy ray-curable component (D), the photopolymerization initiator (E), and the surfactant (F) are expressed as amounts (in terms of solid content) relative to 100 parts by mass (in terms of solid content) of the (meth)acrylic acid ester polymer (A).

[0163] [Table 1]

[0164] Details of the abbreviations and other information listed in Table 1 are as follows: ((Meth)acrylic acid ester copolymer (A)) BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate PhEA: 2-phenoxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate GMMA: Glyceryl monomethacrylate ACMO: N-acryloylmorpholine IBXA: Isobornyl acrylate HEA: 2-hydroxyethyl acrylate (Crosslinking agent (B)) B1: Isocyanate-based crosslinking agent (manufactured by Soken Chemical & Engineering Co., Ltd., product name "TD-75") B2: Isocyanate-based crosslinking agent (Mitsui Chemicals, product name "Takenate D-110E") (Silane coupling agent (C)) C1: 3-glycidoxypropyltrimethoxysilane (Active energy ray-curable component (D)) D1: ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester A-9300-1CL") D2: Tricyclodecane dimethanol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester DCP") (Photopolymerization initiator (E)) E1: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Surfactant (F)) F1: Nonionic surfactant (manufactured by Daiichi Pharmaceutical Co., Ltd., product name "Noigen EA-87")

[0165] The resulting pressure-sensitive adhesive or pressure-sensitive adhesive sheet was subjected to the following measurements and evaluations.

[0166] (Evaluation of gel fraction of adhesive before and after irradiation with active energy rays) The adhesives prepared in the Examples and Comparative Examples were cut to a size of 80 mm x 80 mm, and the adhesive layer was wrapped in a polyester mesh (product name: Tetron Mesh #200), and the mass was weighed using a precision balance. The mass of the adhesive alone was calculated by subtracting the mass of the mesh alone from the weighed value. This mass was designated M1.

[0167] Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The mesh was then removed and air-dried for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, and then dried in an oven at 80°C for 12 hours. After drying, the mesh was weighed using a precision balance. The mass of the adhesive alone was calculated by subtracting the mass of the mesh from the weighed value. This mass was designated M2. The gel fraction of the adhesive before irradiation with active energy rays was calculated using the obtained M1 and M2 using the following formula. The results are shown in Table 2. Gel fraction (%) = (M2 / M1) × 100

[0168] In addition, before cutting the PSA sheets produced in the examples and comparative examples, ultraviolet light as active energy rays was irradiated at an illuminance of 200 mW / cm through a plastic plate (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "Iupilon Sheet MR58U", thickness: 0.7 mm, containing ultraviolet absorber) made of a polycarbonate resin (PC) plate with a polymethyl methacrylate resin (PMMA) layer laminated thereon. 2 , light intensity 1000mJ / cm 2 The gel fraction of the pressure-sensitive adhesive after being cured with active energy rays was obtained in the same manner as in the method for determining the gel fraction described above, except that the pressure-sensitive adhesive layer was cured by irradiating the active energy rays under the conditions of (a) to (c). The results are shown in Table 2.

[0169] (Measurement of adhesive strength of adhesive and cured adhesive) The release sheet R2 was peeled off from the adhesive sheets obtained in the Examples and Comparative Examples, and the exposed adhesive was attached to an easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4160", thickness: 100 μm) having an easy-adhesion layer to obtain a release sheet R1 / adhesive / PET film laminate. The resulting laminate was cut into a 25 mm wide, 100 mm long sample.

[0170] The release sheet R1 was peeled from the sample at 23°C and 50% relative humidity, and the exposed adhesive was attached to soda-lime glass (Nippon Sheet Glass Co., Ltd.). The sample was then pressurized in an autoclave (Kurihara Manufacturing Co., Ltd.) at 0.5 MPa and 50°C for 20 minutes. After 24 hours at 23°C and 50% relative humidity, the adhesive strength (N / 25 mm) of the adhesive before curing with active energy rays was measured using a tensile tester (Orientec Co., Ltd., "Tensilon") at a peel speed of 300 mm / min and a peel angle of 180°. Measurements were conducted under conditions other than those described here in accordance with JIS Z0237:2009. The results are shown in Table 2.

[0171] After the adhesive layer was pressed onto the soda lime glass, the plastic plate was placed on top of the soda lime glass. Next, ultraviolet light as active energy rays was irradiated through the plastic plate and the soda lime glass at an illuminance of 200 mW / cm. 2 , light intensity 1000mJ / cm 2 The adhesive strength (N / 25 mm) of the cured adhesive after active energy ray curing was measured in the same manner as the above-mentioned adhesive strength measurement method, except that the adhesive was cured under the conditions of irradiating the active energy ray under the conditions of irradiating the active energy ray under the conditions of irradiating the active energy ray under the conditions of irradiating the active energy ray under the conditions of

[0172] (Measurement of total light transmittance after irradiation with active energy rays) The release sheet R2 was peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed pressure-sensitive adhesive was attached to soda glass to form a measurement sample. The plastic plate was placed on the pressure-sensitive adhesive layer side of the measurement sample, and ultraviolet light as active energy rays was irradiated through the plastic plate at an illuminance of 200 mW / cm. 2 , light intensity 1000mJ / cm 2 The pressure-sensitive adhesive layer was cured under the conditions of

[0043] , and a measurement sample after active energy ray irradiation was obtained. After background measurement was performed using soda glass alone, the total light transmittance (%) of the pressure-sensitive adhesive after active energy ray irradiation was measured for the measurement sample using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7361-1:1997. The results are shown in Table 2.

[0173] (Haze value measurement) The release sheet R2 was peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed pressure-sensitive adhesive was attached to soda glass to form a measurement sample. The plastic plate was placed on the pressure-sensitive adhesive layer side of the measurement sample, and ultraviolet light as active energy rays was irradiated through the plastic plate at an illuminance of 200 mW / cm. 2 , light intensity 1000mJ / cm 2 The adhesive layer was cured under the conditions of

[0049] , and a measurement sample after active energy ray irradiation was obtained. After blank correction using only soda glass, measurement light from a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") was incident on the adhesive layer side of the measurement sample, and the haze (%) was measured in accordance with JIS K7136:2000. Each measurement was performed three times, and the average value was used as the haze value of the adhesive after active energy ray irradiation. The results are shown in Table 2.

[0174] (Haze value measurement after wet heat test) The release sheet R2 was peeled off from the resulting adhesive sheet, and an ITO layer of a polyethylene terephthalate film (manufactured by Oike Kogyo Co., Ltd., ITO-PET film, thickness: 125 μm) with a tin-doped indium oxide (ITO) layer on one side was attached to the exposed surface of the adhesive. Next, the release sheet R1 was peeled off, and the ITO layer of another ITO-PET film was attached to the exposed surface of the adhesive, resulting in a laminate having a configuration of "ITO-PET film / adhesive / ITO-PET film." Ultraviolet light as active energy rays was irradiated through the ITO-PET film at an illuminance of 200 mW / cm. 2 , light intensity 1000mJ / cm 2 The pressure-sensitive adhesive layer was cured to obtain a measurement sample after irradiation with active energy rays.

[0175] The obtained measurement sample was stored for 72 hours under humid heat conditions of 85°C and relative humidity of 85%. After storage, the measurement sample was removed and left to stand for 1 hour. After standing, the haze value (%) of the measurement sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7136:2000. The obtained haze values ​​(%) after the humid heat test are shown in Table 2.

[0176] (Storage modulus of adhesive before and after irradiation with active energy rays) The pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples were laminated in multiple layers to form a 3 mm thick laminate. From the resulting pressure-sensitive adhesive laminate, a cylindrical object with a diameter of 8 mm (height of 3 mm) was punched out to prepare a sample for measuring storage modulus.

[0177] The storage modulus of the measurement samples was measured in accordance with JIS K7244-6 using a viscoelasticity measuring device (manufactured by Anton-Paar, model "MCR302") by the torsional shear method under the conditions of a measurement temperature range of 0 to 100°C, a measurement frequency of 1 Hz, and a heating rate of 4°C / min. From the measurement results, the storage moduli at 23°C and 70°C were calculated. The results are shown in Table 2.

[0178] In addition, the pressure-sensitive adhesive sheets produced in the examples and comparative examples were irradiated with ultraviolet light as active energy rays at an illuminance of 200 mW / cm through the plastic plate. 2 , light intensity 1000mJ / cm 2 The storage modulus (MPa) of the cured adhesive after active energy ray curing at 23°C and 70°C was obtained in the same manner as in the method for determining the storage modulus described above, except that the adhesive was cured by irradiating under the conditions of (a) and (b) above to obtain a cured adhesive. The results are shown in Table 2.

[0179] (Evaluation of unevenness-following ability) On the surface of a glass plate (NSG Precision, product name "Corning Glass Eagle XG", 90 mm length x 50 mm width x 0.5 mm thickness), ultraviolet-curable ink (Teikoku Ink Co., Ltd., product name "POS-911 Sumi") was screen-printed in the shape of a picture frame (outer dimensions: 90 mm length x 50 mm width, 5 mm width). Then, ultraviolet light (80 W / cm2 The printed ultraviolet-curable ink was cured using a laser beam (two metal halide lamps, lamp height 15 cm, belt speed 10-15 m / min) to produce a stepped glass plate having steps (convexoconcave) caused by the printed layer (step height: 40 μm).

[0180] The release sheet R2 was peeled off from the adhesive sheets produced in the Examples and Comparative Examples, and the exposed adhesive was attached to the adhesive layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4160", thickness: 100 μm) having an adhesive layer. Next, the release sheet R1 was peeled off to expose the adhesive, and the adhesive was laminated to a stepped glass plate using a laminator (manufactured by Fujipla Co., Ltd., product name "LPD3214") so that the adhesive covered the entire frame-shaped print. The sheet was then autoclaved for 30 minutes under conditions of 50 ° C and 0.5 MPa, and left for 24 hours at normal pressure, 23 ° C, and relative humidity of 50%.

[0181] The interface between the adhesive and the stepped glass plate near the step was visually inspected for air bubbles or peeling, and the conformability to the unevenness before UV irradiation was evaluated according to the following criteria. The results are shown in Table 2. ○: Conforms to uneven surfaces, no bubbles or peeling is observed ×: Bubbles and peeling were observed at the interface.

[0182] Furthermore, after that, ultraviolet rays as active energy rays were applied to the adhesive at an illuminance of 200 mW / cm 2 , light intensity 1000mJ / cm 2 The adhesive was cured to obtain a cured adhesive.

[0183] The interface between the cured adhesive and the stepped glass plate near the step was visually inspected for air bubbles or peeling, and the conformability to irregularities after UV irradiation was evaluated according to the following criteria. The results are shown in Table 2. Note that for Comparative Example 3, in which the conformability to irregularities before UV irradiation was rated "x", the conformability to irregularities after UV irradiation was not evaluated. ○: Conforms to uneven surfaces, no bubbles or peeling is observed ×: Bubbles and peeling were observed at the interface.

[0184] (Evaluation of blister resistance) The release sheet R2 was peeled off from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed adhesive was attached to an ITO vapor-deposited film (manufactured by Oike Kogyo Co., Ltd., product name "Tetlite TCFKH150NMH2-125-U6 / T2"), and the release sheet R1 was peeled off from the pressure-sensitive adhesive sheet, and the exposed adhesive was attached to the plastic plate, followed by autoclaving for 20 minutes at 50°C and 0.5 MPa.

[0185] Then, ultraviolet light as active energy rays was applied to the adhesive through a plastic plate at an illuminance of 200mW / cm 2 , light intensity 1000mJ / cm 2 The adhesive was cured under these conditions to form a cured adhesive, which was used as an evaluation sample. The evaluation sample was left at normal pressure, 23°C, and 50% relative humidity for 12 hours, and then stored under high-temperature, high-humidity conditions of 85°C and 85% relative humidity for 72 hours. The condition of the interface between the adhesive and the adherend was then visually inspected, and blister resistance was evaluated according to the following criteria. The results are shown in Table 2. ○: No bubbles or peeling are observed at the interface ×: Bubbles and peeling were observed at the interface.

[0186] (Evaluation of resistance to wet heat whitening) The adhesive of the adhesive sheets produced in the examples and comparative examples was applied to a non-alkali glass plate (water vapor permeability 0.0006 g / (m 2 24h)) and a 0.7mm thick plastic plate (Mitsubishi Rayon Co., Ltd., product name "Acrylite MR-200", water vapor permeability 44g / (m 2 The adhesive was sandwiched between two sheets of plastic and then autoclaved at 50°C and 0.5 MPa for 20 minutes. Then, ultraviolet light was irradiated onto the adhesive through a plastic plate at an illuminance of 200 mW / cm. 2 , light intensity 1000mJ / cm 2The adhesive was cured to obtain a cured adhesive, which was then left at normal pressure, 23°C and 50% RH for 24 hours to obtain a sample.

[0187] The haze value (haze value before durability test; %) of each of the above samples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7136:2000.

[0188] Next, the above sample was stored under humid heat conditions of 85°C and relative humidity of 85% for 1000 hours (durability test), and then left at room temperature and humidity of 23°C and relative humidity of 50% for 24 hours. The haze value (haze value after durability test; %) of the sample was measured in the same manner as above.

[0189] Based on the difference in the haze value measured before and after the durability test, the resistance to wet heat whitening was evaluated according to the following criteria. ○: The difference in haze value is less than 1.5% ×: The difference in haze value is 1.5% or more

[0190] [Table 2]

[0191] From Table 2, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 3 were able to achieve both conformability to irregularities, blister resistance, and resistance to wet heat whitening. [Industrial Applicability]

[0192] The pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, to bond members having uneven surfaces. [Explanation of symbols]

[0193] 1...Adhesive sheet 10...Adhesive 15...First release sheet 16...Second release sheet 2...Laminate 11...Adhesive after hardening 21...First member 22...Second member

Claims

1. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive for bonding a first member and a second member, the pressure-sensitive adhesive is active energy ray-curable, The pressure-sensitive adhesive sheet comprises at least one selected from a surfactant and a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive.

3. The pressure-sensitive adhesive sheet according to claim 2 , wherein the acrylic pressure-sensitive adhesive has a crosslinked structure containing at least a (meth)acrylic acid ester polymer and a crosslinking agent, and an active energy ray-curable component.

4. The pressure-sensitive adhesive sheet according to claim 3 , wherein the (meth)acrylic acid ester polymer contains, as a monomer unit, a monomer having two or more hydrophilic groups and one or more (meth)acryloyl groups.

5. The pressure-sensitive adhesive sheet according to claim 1, wherein the surfactant is at least one selected from the group consisting of a nonionic surfactant and an anionic surfactant.

6. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive has a storage modulus at 23° C. of 0.09 MPa or less before irradiation with active energy rays.

7. The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive has a wet heat haze of 10% or less after irradiation with active energy rays.

8. A laminate comprising a first member, a second member, and a post-curing adhesive that bonds the first member and the second member together, The cured adhesive is a laminate obtained by curing the adhesive contained in the adhesive sheet according to claim 1 .

9. At least one of the first member and the second member has irregularities, The laminate according to claim 8 , wherein the post-curing adhesive is applied along the irregularities.

Images