Photocurable adhesive agent composition, adhesive agent, adhesive agent-provided member, method for producing adhesive agent, cured body, member, and method for producing cured body

Abstract

Provided is a photocurable adhesive agent composition comprising a monomer component M, a polymer of the monomer component M, a photoinitiator, and a colorant. In the photocurable adhesive agent composition, the proportion of the polymer with respect to the total of the monomer component M and the polymer is 7.5 wt% or more. The photocurable adhesive agent composition is suitable for suppressing curing failure even while containing a colorant.

Description

Photocurable adhesive composition, adhesive, adhesive-attached member, method for manufacturing adhesive, cured product, member, and method for manufacturing cured product

[0001] The present invention relates to a photocurable pressure-sensitive adhesive composition, a pressure-sensitive adhesive, a pressure-sensitive adhesive-attached member, a method for producing a pressure-sensitive adhesive, a cured product, a member, and a method for producing a cured product.

[0002] Generally, pressure-sensitive adhesives are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend under pressure. Utilizing these properties, pressure-sensitive adhesives are widely used for various applications and purposes, such as joining, fixing, and protecting components in electronic devices.

[0003] An example of an electronic device is an image display device, such as a liquid crystal display device or an electroluminescence (EL) display device. For example, a sheet (adhesive sheet) made of an adhesive is used as an optical component of the image display device. An adhesive having a light-blocking property is typically used to prevent light leakage and anti-reflection. Colored adhesives are also sometimes used to improve the design and functionality of a product. Patent Document 1 discloses an example of an adhesive sheet.

[0004] The pressure-sensitive adhesive can be formed from a pressure-sensitive adhesive composition. Patent Document 1 discloses a heat-curable pressure-sensitive adhesive composition containing a thermal initiator as a polymerization initiator. In addition to heat-curable pressure-sensitive adhesive compositions, photocurable pressure-sensitive adhesive compositions are also known. Photocurable pressure-sensitive adhesive compositions usually contain a photoinitiator as a polymerization initiator.

[0005] International Publication No. 2021 / 153500

[0006] According to the investigations of the present inventors, photocurable pressure-sensitive adhesive compositions (photocurable pressure-sensitive adhesive compositions) containing a colorant tend to be prone to poor curing.

[0007] An object of the present invention is to provide a technique suitable for suppressing poor curing of a photocurable pressure-sensitive adhesive composition containing a colorant.

[0008] [1] A photocurable pressure-sensitive adhesive composition according to an embodiment of the present invention includes a monomer component M, a polymer of the monomer component M, a photoinitiator, and a colorant, wherein the proportion of the polymer relative to the total of the monomer component M and the polymer is 7.5% by weight or more. [2] In the photocurable pressure-sensitive adhesive composition described in [1] above, the proportion of the polymer relative to the total of the monomer component M and the polymer may be 80% by weight or less. [3] In the photocurable pressure-sensitive adhesive composition described in [1] above, the proportion of the polymer relative to the total of the monomer component M and the polymer may be 40% by weight or less. [4] In the photocurable pressure-sensitive adhesive composition described in any of [1] to [3] above, the content of a (meth)acrylic monomer in the monomer component M may be 50% by weight or more. [5] In the photocurable pressure-sensitive adhesive composition described in any of [1] to [4] above, the monomer component M may include a monomer a having a double-bond-containing ring. [6] In the photocurable pressure-sensitive adhesive composition described in [5] above, the double bond-containing ring may be an aromatic ring. [7] In the photocurable pressure-sensitive adhesive composition described in [5] or [6] above, the monomer a may have two or more of the double bond-containing rings in a side chain. [8] In the photocurable pressure-sensitive adhesive composition described in [7] above, the monomer a may have a structure in a side chain in which a first double bond-containing ring and a second double bond-containing ring included in the two or more double bond-containing rings are bonded via a linking group. [9] In the photocurable pressure-sensitive adhesive composition described in any of [5] to [8] above, the monomer a may be phenoxybenzyl acrylate.

[10] The photocurable pressure-sensitive adhesive composition described in any of [1] to [9] above may contain the photoinitiator having the chemical structure shown in the following formula (1) in its molecule. In this formula (1), "*" indicates the bonding site to another atom.

[11] In the photocurable pressure-sensitive adhesive composition according to any one of [1] to

[10] above, the content of the photoinitiator in the photocurable pressure-sensitive adhesive composition may be 0.01 to 10 parts by weight per 100 parts by weight of the monomer component M.

[12] In the photocurable pressure-sensitive adhesive composition according to any one of [1] to

[11] above, the colorant may be a black colorant.

[13] The photocurable pressure-sensitive adhesive composition according to any one of [1] to

[12] above may further contain a thermal acid generator.

[14] An adhesive according to an embodiment of the present invention is an adhesive formed from the photocurable pressure-sensitive adhesive composition according to any one of [1] to

[13] above.

[15] In the pressure-sensitive adhesive according to

[14] above, the polymerization rate of the monomer component M may be 95.0% or more.

[16] The pressure-sensitive adhesive according to

[14] or

[15] above may be a pressure-sensitive adhesive having a polymerization rate of 95.0% or more according to CIE 1976 (L) as defined in JIS Z8781-4:2013. * , a * , b * ) L in color space *

[17] The adhesive according to the above

[16] may have a brightness of 60.0 or less when expressed by a * The absolute value of the chromaticity of the color space is 10.0 or less. *The adhesive may have a chromaticity of 10.0 or less, expressed as an absolute value of

[14] .

[18] The adhesive according to any one of

[14] to

[17] above may have a refractive index of 1.50 or more.

[19] The adhesive according to any one of

[14] to

[18] above may have a total light transmittance of less than 5%.

[20] The adhesive according to any one of

[14] to

[19] above may contain a thermal acid generator.

[21] A pressure-sensitive adhesive member according to an embodiment of the present invention comprises the pressure-sensitive adhesive and a member according to any one of

[14] to

[20] above.

[22] The pressure-sensitive adhesive member according to

[21] above may be a pressure-sensitive adhesive optical member.

[23] A method for producing a pressure-sensitive adhesive according to an embodiment of the present invention includes irradiating the photo-curable pressure-sensitive adhesive composition according to any one of [1] to

[13] above with light to cure the photo-curable pressure-sensitive adhesive composition.

[24] A cured product according to an embodiment of the present invention is a cured product formed from the pressure-sensitive adhesive according to any one of

[14] to

[20] above.

[25] A member according to an embodiment of the present invention comprises the cured product according to the above item

[24] .

[26] The member according to the above item

[25] may be an optical member.

[27] A method for producing a cured product according to an embodiment of the present invention includes further curing the pressure-sensitive adhesive according to any one of the above items

[14] to

[20] in a high-temperature environment.

[0009] According to an embodiment of the present invention, a technique suitable for suppressing poor curing of a photocurable pressure-sensitive adhesive composition containing a colorant can be provided.

[0010] 1 is a schematic diagram illustrating an example of a method for forming a pressure-sensitive adhesive according to an embodiment of the present invention, FIG. 2 is a schematic diagram illustrating an example of a method for forming a pressure-sensitive adhesive according to an embodiment of the present invention, FIG. 3 is a schematic diagram illustrating an example of a method for forming a pressure-sensitive adhesive according to an embodiment of the present invention,

[0011] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is commonly used as an SI unit indicating weight, and vice versa.

[0012] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic", the expression "(meth)acrylate" means "acrylate and / or methacrylate", the expression "(meth)allyl" means "allyl and / or methallyl", and the expression "(meth)acrolein" means "acrolein and / or methacrolein".

[0013] In this specification, "100 parts by weight of monomer component M" as a standard for the content of various components in a pressure-sensitive adhesive composition means 100 parts by weight of the total amount of unpolymerized monomer component M contained in the pressure-sensitive adhesive composition and monomer component M consumed in forming a polymer of monomer component M contained in the pressure-sensitive adhesive composition.

[0014] 1. Photocurable Pressure-Sensitive Adhesive Composition A photocurable pressure-sensitive adhesive composition according to an embodiment of the present invention (hereinafter referred to as "pressure-sensitive adhesive composition A") contains a monomer component M, a polymer of the monomer component M (hereinafter referred to as "polymer B"), a photoinitiator, and a colorant. The photocurable pressure-sensitive adhesive composition is a composition that can form a pressure-sensitive adhesive by photocuring through irradiation with light, typically ultraviolet light. The colorant contained in the pressure-sensitive adhesive composition can inhibit photocuring of the pressure-sensitive adhesive composition by absorbing the irradiated light. In contrast, in pressure-sensitive adhesive composition A, the proportion of polymer B relative to the total of monomer component M and polymer B is 7.5 wt % or more. This means that a predetermined amount of polymer of monomer component M is already contained in pressure-sensitive adhesive composition A before photocuring. According to the inventors' investigations, it is believed that setting the proportion to 7.5 wt % or more contributes to suppressing poor curing. The suppression of poor curing may be due to the fact that the pressure-sensitive adhesive composition contains a certain amount of polymer, which reduces the number of reaction points required for curing, thereby suppressing insufficient curing of the pressure-sensitive adhesive composition as a whole.

[0015] The ratio of polymer B to the total of monomer component M and polymer B (hereinafter, this ratio will be referred to as the "polymer fraction") may be 8 wt% or more, 8.5 wt% or more, 9 wt% or more, 9.5 wt% or more, 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, 14 wt% or more, 15 wt% or more, 16 wt% or more, or even 17 wt% or more. The upper limit of the polymer fraction is, for example, 80 wt% or less, and may be 75 wt% or less, 70 wt% or less, 65 wt% or less, 60 wt% or less, 55 wt% or less, 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 32 wt% or less, 30 wt% or less, 27 wt% or less, 25 wt% or less, 22 wt% or less, or even 20 wt% or less.

[0016] The PSA composition A can be formed, for example, by partially polymerizing a monomer component M to form a monomer syrup containing an unpolymerized monomer component M and a polymer B, which is a partial polymer of the monomer component M, and then blending the formed monomer syrup with necessary components such as a photoinitiator and a colorant. Alternatively, the PSA composition A may be formed by partially polymerizing the monomer component M in a state in which necessary components such as a photoinitiator and a colorant are contained. An additive such as a photoinitiator may be used for the partial polymerization of the monomer component M. The polymer fraction of the PSA composition A can vary depending on, for example, the polymerization conditions (e.g., light illuminance, wavelength and integrated light amount, polymerization temperature, polymerization atmosphere, stirring conditions) when partially polymerizing the monomer component M, as well as the type and amount of additives, if any, used.

[0017] <1-1. Monomer Component M> Monomer component M includes one or more monomers. The monomer included in monomer component M may be a (meth)acrylic monomer. The content of the (meth)acrylic monomer in monomer component M may be 50% by weight or more. In this case, a (meth)acrylic pressure-sensitive adhesive can be formed. The content may be 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 100% by weight or more.

[0018] In this specification, the term "(meth)acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. The (meth)acrylic monomer is preferably a monomer having one (meth)acryloyl group (in other words, a monofunctional (meth)acrylic monomer).

[0019] In this specification, the amount of monomer component M as a basis for the content of each monomer in monomer component M is the sum of the amount of unpolymerized monomer component M contained in the PSA composition and the amount of monomer component M consumed in forming polymer B contained in the PSA composition. The amount of each monomer used to calculate the content is the sum of the amount of unpolymerized monomer contained in the PSA composition and the amount of each monomer consumed in forming polymer B contained in the PSA composition.

[0020] <1-1-a. (Meth)acrylic acid alkyl ester> An example of a monomer that can be contained in the monomer component M is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, n-tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, and octadecyl(meth)acrylate. The (meth)acrylic acid alkyl ester may be at least one selected from the group consisting of 2-ethylhexyl(meth)acrylate and n-butyl(meth)acrylate.

[0021] The content of the (meth)acrylic acid alkyl ester in the monomer component M may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 0.8% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 8% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 88% by weight or more, 90% by weight or more, 93% by weight or more, 95% by weight or more, 98% by weight or more, or even 99% by weight or more. The upper limit of the content is, for example, 100% by weight or less, and may be 99% by weight or less, 98% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, 88% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 8% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. Monomer component M may be substantially free of (meth)acrylic acid alkyl ester.

[0022] In this specification, "substantially free" means that the content is less than 0.1 wt%, preferably 0.05 wt% or less, more preferably 0.01 wt% or less, even more preferably less than 0.01 wt%, and particularly preferably less than 0.001 wt%. Furthermore, with regard to a component whose content in the PSA composition A is specified by a range of parts by weight relative to 100 parts by weight of the monomer component M, "substantially free" means that the content is less than 0.1 part by weight, preferably 0.05 part by weight or less, more preferably 0.01 part by weight or less, even more preferably less than 0.01 part by weight, and particularly preferably less than 0.001 part by weight.

[0023] Monomer component M may contain one or more (meth)acrylic acid alkyl esters. Monomer component M may contain at least one (meth)acrylic acid alkyl ester selected from the group consisting of the above-exemplified ones.

[0024] <1-1-b. Monomer a> The monomer component M may contain a monomer a having a double bond-containing ring. The inclusion of monomer a is suitable for, for example, improving the refractive index of the PSA formed from the PSA composition A. In this specification, a double bond-containing ring refers to a ring in which at least one of the bonds constituting the ring is a double bond. Examples of double bonds are a carbon-carbon double bond, a carbon-heteroatom double bond, and a heteroatom-heteroatom double bond. Examples of heteroatoms are a nitrogen atom, a sulfur atom, and an oxygen atom.

[0025] The number of double bonds in the double bond-containing ring is not particularly limited and may be, for example, 1 to 10, or 2 to 5. When the double bond-containing ring contains two or more double bonds, these double bonds may be conjugated or non-conjugated. The double bond-containing ring is preferably an aromatic ring.

[0026] The double bond-containing ring may be a carbocyclic ring. Examples of the carbocyclic ring include a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure), a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, and a phenanthrene ring. The double bond-containing ring may be a heterocyclic ring (heterocyclic ring). Examples of the heterocyclic ring include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and a thiophene ring. Examples of heteroatoms that may be contained in the heterocyclic ring as ring-constituting atoms include at least one selected from the group consisting of a nitrogen atom, a sulfur atom, and an oxygen atom. The heteroatom may be one or both of a nitrogen atom and a sulfur atom. The double bond-containing ring may be a fused ring. An example of the monomer a has a structure in which one or more carbocyclic rings and one or more heterocyclic rings are fused, such as a dinaphthothiophene structure.

[0027] The double bond-containing ring may have one or more substituents (excluding ethylenically unsaturated groups, which will be described later) on the ring-constituting atoms, or may have no substituents. Examples of the substituents include alkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyalkyl groups, hydroxyalkyloxy groups, and glycidyloxy groups. However, the substituents are not limited to the above examples. The substituents may contain carbon atoms, and in such cases, the number of carbon atoms contained in the substituent may be, for example, 1 to 4, 1 to 3, or even 1 to 2. One example of the double bond-containing ring has no substituents on the ring-constituting atoms. Another example of the double bond-containing ring has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, and halogen atoms (e.g., bromine atoms) on the ring-constituting atoms.

[0028] In the monomer a, the number of double bond-containing rings contained in one molecule is, for example, 1, and may be 2 or more. The upper limit of the number of double bond-containing rings is not particularly limited and is, for example, 16 or less. The upper limit may be 12 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less.

[0029] In the monomer a, the double bond-containing ring is preferably located in a side chain. In other words, the monomer a may have the double bond-containing ring in a side chain. The monomer a preferably has at least one double bond-containing ring and at least one ethylenically unsaturated group in one molecule. As the monomer a, a compound having one ethylenically unsaturated group in one molecule (in other words, a monofunctional monomer) is preferably used.

[0030] Examples of ethylenically unsaturated groups are (meth)acryloyl groups, vinyl groups, and (meth)allyl groups. From the viewpoint of polymerization reactivity, (meth)acryloyl groups are preferred, and from the viewpoint of flexibility and adhesiveness, acryloyl groups are more preferred. In other words, monomer a preferably contains a (meth)acrylic monomer having a double bond-containing ring, and more preferably contains an acrylic monomer having a double bond-containing ring. An example of a (meth)acrylic monomer having a double bond-containing ring is an aromatic ring-containing (meth)acrylate. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0031] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. An example of the linking group includes one or more groups selected from the group consisting of alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (-O-), and thiooxy groups (-S-). In one example of Monomer A, the double bond-containing ring and the ethylenically unsaturated group are bonded directly. In another example of Monomer A, the double bond-containing ring and the ethylenically unsaturated group are bonded via a linking group selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. The number of carbon atoms in the alkylene group and oxyalkylene group that can be included in the linking group is, for example, 1 to 4, and may be 1 to 3, or even 1 to 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group that can be contained in the linking group is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, 2 to 3, or even 1 to 2, 2, or 1.

[0032] Specific examples of the monomer a include aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds may be used alone or in combination of two or more.

[0033] Monomer a may have two or more double bond-containing rings in its side chain, and may also have a structure in its side chain in which a first double bond-containing ring and a second double bond-containing ring included in the two or more double bond-containing rings are linked via a linking group.

[0034] Monomer a may contain two or more aromatic rings (preferably carbon rings) in one molecule. A monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-containing monomer) can particularly contribute to increasing the refractive index of the adhesive.

[0035] Examples of the aromatic ring-containing monomer include a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-condensed aromatic rings are directly bonded, a monomer having a condensed ring, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure. Among these, a monomer having a structure in which two or more non-condensed aromatic rings are bonded via a linking group (for example, phenoxybenzyl (meth)acrylate described below) is preferably used.

[0036] A linking group that links two or more double bond-containing rings, such as aromatic rings, may contain atoms such as P, Ge, Te, Se, N, S, and Si, and these atoms may be bonded to an oxygen atom. However, the linking group does not necessarily contain any of the above atoms. Examples of linking groups include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2)), and the like. n -; n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n -; n is 1 to 3, preferably 1), a straight chain alkylene group (-(CH2) n-; n is 1 to 6, preferably 1 to 3), and the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group in which the alkylene group is partially or completely halogenated. The linking group may contain one or more types selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. Specific examples of monomers having a structure in which two or more non-fused aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0037] Examples of the monomer having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylate, triphenyl structure-containing (meth)acrylate, and vinyl group-containing biphenyl. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0038] Examples of monomers having a condensed ring include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracenes. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0039] Examples of monomers having a fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. Note that, since monomers having a fluorene structure have a structure in which two benzene rings are directly bonded, they are included in the concept of monomers having a structure in which two or more non-fused aromatic rings are directly bonded.

[0040] Examples of the monomer having a dinaphthothiophene structure are (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), (meth)acryloyloxyethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH(CH) group or a CHCH(R)C(O)OCHCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), vinyl dinaphthothiophene (e.g., a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), and (meth)allyloxy dinaphthothiophene. Incidentally, a monomer having a dinaphthothiophene structure is included in the concept of a monomer having a fused ring because it has a naphthalene structure and also has a structure in which a thiophene ring and two naphthalene structures are fused together.

[0041] Examples of monomers having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophenes and vinyl group-containing dibenzothiophenes. Note that, since monomers having a dibenzothiophene structure have a structure in which a thiophene ring and two benzene rings are fused, they are included in the concept of monomers having fused rings. Neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly bonded.

[0042] Monomer a may be a monomer having one aromatic ring (preferably a carbon ring) and at least one ethylenically unsaturated group in one molecule (aromatic ring-single-containing monomer).

[0043] Examples of aromatic ring unit-containing monomers include carbon aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and 6-(4 bromine-substituted aromatic ring-containing (meth)acrylates such as 2,6-dibromo-4-isopropyl-2-(4,6-dibromo-2-s-butylphenoxy)hexyl (meth)acrylate, 6-(4,6-dibromo-2-isopropylphenoxy)hexyl (meth)acrylate, 2,6-dibromo-4-nonylphenyl acrylate, and 2,6-dibromo-4-dodecylphenyl acrylate; carbon-substituted aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; and compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole.

[0044] Monomer a may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the double bond-containing ring in the various monomers a described above. Monomers having this structure can be understood as ethoxylated products of the original monomers. The number of repeating oxyethylene units (—CHCHO—) in the oxyethylene chain is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, or even 1 to 2, or even 1. Examples of monomer a that is an ethoxylated product include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate.

[0045] Monomer a may contain a high refractive index monomer. In this specification, the high refractive index monomer means a monomer having a refractive index of 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, 1.65 or more, 1.66 or more, 1.67 or more, 1.68 or more, or even 1.69 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, and may be, for example, 3.00 or less, 2.50 or less, 2.00 or less, 1.90 or less, 1.80 or less, or even 1.70 or less. The high refractive index monomer may be used alone or in combination of two or more.

[0046] The refractive index of the monomer can be measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C. The Abbe refractometer may be a DR-M4 model manufactured by ATAGO or an equivalent (e.g., DR-M2 model). If the nominal value of the refractive index at 25°C is provided by the monomer manufacturer, etc., this nominal value can be used as the refractive index.

[0047] Examples of high refractive index monomers are phenoxybenzyl acrylate (refractive index 1.566), 1-naphthylmethyl acrylate (refractive index 1.595), ethoxylated o-phenylphenol acrylate (refractive index 1.578 when the number of repeating oxyethylene units is 1), benzyl acrylate (refractive index 1.519), phenoxyethyl acrylate (refractive index 1.517), phenoxydiethylene glycol acrylate (refractive index 1.510), 6-acryloyloxymethyldinaphthothiophene (refractive index 1.75), 6-methacryloyloxymethyldinaphthothiophene (refractive index 1.726), 5-acryloyloxyethyldinaphthothiophene (refractive index 1.786), 6-acryloyloxyethyldinaphthothiophene (refractive index 1.722), 6-vinyldinaphthothiophene (refractive index 1.802), and 5-vinyldinaphthothiophene (refractive index 1.793). However, the high refractive index monomer is not limited to the above examples. Monomer a preferably contains phenoxybenzyl acrylate as a high refractive index monomer.

[0048] Monomer a may be phenoxybenzyl acrylate.

[0049] The content of monomer a in monomer component M may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 0.8% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 8% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 88% by weight or more, 90% by weight or more, 93% by weight or more, 95% by weight or more, 98% by weight or more, or even 99% by weight or more. The upper limit of the content is, for example, 100% by weight or less, and may be 99% by weight or less, 98% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, 88% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 8% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less.

[0050] The monomer component M may contain one or more types of monomer a. The monomer component M may contain at least one type of monomer a selected from the group consisting of the above-mentioned examples.

[0051] <1-1-c. Other Monomers> Monomer component M may contain other monomers in addition to those described above. One example of such other monomers is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer has at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. Monomer component M may contain one or more hydroxyl group-containing monomers. Monomer component M may contain at least one hydroxyl group-containing monomer selected from the group consisting of those exemplified below.

[0052] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The hydroxyl group-containing monomer may be a (meth)acrylic monomer.

[0053] Examples of the hydroxyl group-containing monomer are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomer is preferably 4-hydroxybutyl (meth)acrylate.

[0054] The content of the hydroxyl group-containing monomer in the monomer component M may be, for example, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may be substantially free of a hydroxyl group-containing monomer.

[0055] Another example of the other monomer is an aliphatic ring-containing monomer. The aliphatic ring-containing monomer has at least one aliphatic ring and at least one ethylenically unsaturated group in one molecule. The monomer component M may contain one or more aliphatic ring-containing monomers. The monomer component M may contain at least one aliphatic ring-containing monomer selected from the group consisting of the following examples:

[0056] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The aliphatic ring-containing monomer may be a (meth)acrylic monomer.

[0057] Examples of the aliphatic ring-containing monomer are cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0058] The content of the alicyclic monomer in the monomer component M may be, for example, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may be substantially free of an alicyclic monomer.

[0059] Another example of the other monomer is a carboxyl group-containing monomer. The carboxyl group-containing monomer that can be contained in the monomer component M has at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. The monomer component M may contain one or more carboxyl group-containing monomers. The monomer component M may contain at least one carboxyl group-containing monomer selected from the group consisting of the following examples:

[0060] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The carboxyl group-containing monomer may be a (meth)acrylic monomer.

[0061] Examples of carboxyl group-containing monomers are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid.

[0062] The content of the carboxyl group-containing monomer in the monomer component M is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may be substantially free of a carboxyl group-containing monomer.

[0063] Another example of the other monomer is an ether group-containing monomer (excluding the cyclic ether group-containing monomer described below). The ether group-containing monomer that can be contained in the monomer component M has at least one ether group and at least one ethylenically unsaturated group in one molecule. The monomer component M may contain one or more ether group-containing monomers. The monomer component M may contain at least one ether group-containing monomer selected from the group consisting of the following examples:

[0064] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The ether group-containing monomer may be a (meth)acrylic monomer.

[0065] The ether group of the ether group-containing monomer is usually contained in a portion that becomes a side chain after polymerization. The side chain may be linear or branched. The ether group-containing monomer may have an oxyalkylene group, and the number of oxyalkylene groups in one molecule may be, for example, 1 to 30, 1 to 12, or even 1 to 5.

[0066] Examples of the oxyalkylene group include an oxymethylene group, an oxyethylene group, and an oxypropylene group. The ether group-containing monomer preferably has an oxyethylene group. The ether group-containing monomer having an oxyethylene group is represented, for example, by the following formula (2):

[0067] R in formula (2) 1 is a hydrogen atom or a methyl group. 2 is a hydrocarbon group. In a preferred example, the hydrocarbon group is an alkyl group. The alkyl group may be linear or branched. Examples of the alkyl group are a methyl group and an ethyl group. In another example, the hydrocarbon group contains a carbon ring. Examples of the carbon ring are the same as those mentioned above in the description of the double bond-containing ring. An example of a hydrocarbon group containing a carbon ring is a phenyl group.

[0068] In formula (2), n is an integer of 1 to 30, preferably an integer of 1 to 12, and may be an integer of 1 to 5.

[0069] Examples of ether group-containing monomers are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate.

[0070] The content of the ether group-containing monomer in the monomer component M may be, for example, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may be substantially free of an ether group-containing monomer.

[0071] Another example of the other monomer is a cyclic ether group-containing monomer. When used in combination with a crosslinking agent, the cyclic ether group-containing monomer may be suitable for accelerating the formation of a cured body, as described below. The cyclic ether group-containing monomer that the monomer component M may contain preferably has at least one cyclic ether group and at least one ethylenically unsaturated group in one molecule. As the cyclic ether group-containing monomer, a compound having one ethylenically unsaturated group in one molecule (in other words, a monofunctional monomer) is preferably used. The monomer component M may contain one or more cyclic ether group-containing monomers. The monomer component M may contain at least one cyclic ether group-containing monomer selected from the group consisting of the following examples:

[0072] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer A. The cyclic ether group-containing monomer may be a (meth)acrylic monomer.

[0073] The cyclic ether group of the cyclic ether group-containing monomer is usually contained in a portion that becomes a side chain after polymerization. The side chain may be linear or branched.

[0074] The cyclic ether group is a functional group containing a ring having an ether bond. Examples of the cyclic ether group include an epoxy group and an oxetane group. The cyclic ether group may be at least one selected from the group consisting of an epoxy group and an oxetane group, or may be an epoxy group.

[0075] The number of cyclic ether groups contained in one molecule of the cyclic ether group-containing monomer is preferably 1, and may be 2 or more. The upper limit of the number of cyclic ether groups is not particularly limited, and may be, for example, 5 or less, 4 or less, 3 or less, or even 2 or less. When two or more cyclic ether groups are contained, the types of the cyclic ether groups may all be the same, or different types of cyclic ether groups may be mixed.

[0076] The cyclic ether group and the ethylenically unsaturated group are preferably bonded via a linking group. Examples of the linking group include those described above for monomer a, and alkylene groups and oxyalkylene groups are preferred. The number of carbon atoms in the linking group (specifically, the alkylene group and oxyalkylene group) is, for example, 1 or more, and may be 2 or more, 3 or more, or even 4 or more. The upper limit of the number of carbon atoms is, for example, 10 or less, 8 or less, or even 5 or less.

[0077] Examples of cyclic ether group-containing monomers include epoxy group-containing (meth)acrylates and oxetane group-containing (meth)acrylates. Examples of epoxy group-containing (meth)acrylates include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether, with 4-hydroxybutyl acrylate glycidyl ether being preferred. Examples of oxetane group-containing (meth)acrylates include (3-oxetan-3-yl)methyl (meth)acrylate, (3-methyloxetan-3-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, (3-butyloxetan-3-yl)methyl (meth)acrylate, and (3-hexyloxetan-3-yl)methyl (meth)acrylate.

[0078] The content of the cyclic ether group-containing monomer in the monomer component M is, for example, 1% by weight or more, and may be 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, or even 30% by weight or more. The upper limit of the content may be, for example, 70% by weight or less, 60% by weight or less, 50% by weight or less, or even 40% by weight or less. The monomer component M may be substantially free of a cyclic ether group-containing monomer.

[0079] Another example of the other monomer is a nitrogen atom-containing monomer. The nitrogen atom-containing monomer refers to a monomer having at least one nitrogen atom in the molecule (per molecule). The monomer component M may contain one or more nitrogen atom-containing monomers. The monomer component M may contain at least one nitrogen atom-containing monomer selected from the group consisting of the following examples:

[0080] Examples of nitrogen atom-containing monomers are N-vinyl cyclic amides and (meth)acrylamides.

[0081] Examples of N-vinyl cyclic amides are N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, and vinylmethyloxazolidinone. Examples of (meth)acrylamides are (meth)acrylamide, N-alkyl(meth)acrylamides, and N,N-dialkyl(meth)acrylamides. (Meth)acrylamides also include various N-hydroxyalkyl(meth)acrylamides and N-alkoxyalkyl(meth)acrylamides.

[0082] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, and N-methylvinylpiperidine. heterocycle-containing monomers such as rolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers including succinimide-based monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0083] The content of the nitrogen atom-containing monomer in the monomer component M may be, for example, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may be substantially free of a nitrogen atom-containing monomer.

[0084] <1-1-d. Polymer B> At least a part of the monomer component M is contained in the pressure-sensitive adhesive composition A as polymer B. The polymer B may be either a homopolymer or a copolymer. The polymer B can also contribute to the stable formation of a coating layer, which will be described later, by appropriately increasing the viscosity of the pressure-sensitive adhesive composition A.

[0085] The weight average molecular weight (Mw) of polymer B may be, for example, greater than 30,000, 50,000 or more, 100,000 or more, 150,000 or more, 200,000 or more, 250,000 or more, 300,000 or more, 400,000 or more, 500,000 or more, 600,000 or more, 700,000 or more, 800,000 or more, 900,000 or more, 1,000,000 or more, 2,000,000 or more, 3,000,000 or more, 4,000,000 or more, 5,000,000 or more, or even 6,000,000 or more. The upper limit of Mw is not particularly limited, and may be, for example, 10,000,000 or less, 9,000,000 or less, 8,000,000 or less, 7,000,000 or less, 6,000,000 or less, 5,000,000 or less, 4,000,000 or less, 3,000,000 or less, 2,000,000 or less, 1,000,000 or less, 900,000 or less, 800,000 or less, 700,000 or less, 600,000 or less, or even 500,000 or less. The weight average molecular weight is determined from a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

[0086] In forming a pressure-sensitive adhesive from the pressure-sensitive adhesive composition A, a coating layer formed by applying the pressure-sensitive adhesive composition A to the surface of a sheet-like material such as a substrate sheet may be irradiated with light. According to the studies of the present inventors, having the Mw of polymer B be 500,000 or less may be particularly suitable for improving the coatability of the pressure-sensitive adhesive composition A for forming the coating layer. Furthermore, according to the studies of the present inventors, having the polymer fraction in the pressure-sensitive adhesive composition A be 40 wt% or less may also be particularly suitable for improving the coatability. The polymer fraction of the pressure-sensitive adhesive composition A may be 40 wt% or less, and the Mw of polymer B may be 500,000 or less. Furthermore, according to the studies of the present inventors, having the Mw of polymer B be 100,000 or more may be particularly suitable for improving the adhesive strength of a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition A.

[0087] <1-2. Photoinitiator> The pressure-sensitive adhesive composition A contains a photoinitiator, which is a type of polymerization initiator. The photoinitiator can contribute to photopolymerization of the monomer component M. The photoinitiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light having a wavelength shorter than 450 nm. The photoinitiator may be a photoradical generator that generates radicals when exposed to light having a wavelength in the range of 380 nm ± 30 nm, or may be a photoradical generator that generates radicals when exposed to light having a wavelength in the range of 380 nm ± 20 nm, light having a wavelength in the range of 380 nm ± 10 nm, light having a wavelength in the range of 380 nm ± 5 nm, or even light having a wavelength of 380 nm.

[0088] Examples of photoinitiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketol such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone-based compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine; Triazine compounds such as 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, and 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine;Examples of suitable photoinitiators include oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)phenyl]octane-1,2-dione 2-(O-benzoyloxime), and O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and titanocene compounds. However, the photoinitiator is not limited to the above examples. The pressure-sensitive adhesive composition A may contain one or more photoinitiators.

[0089] Specific examples of photoinitiators include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins), 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one (Omnirad 127, manufactured by IGM Resins), and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins).

[0090] The photoinitiator may be an oxime-based photoinitiator such as 1,2-octanedione, 1-[4-(phenylthio)phenyl]-, 2-(O-benzoyloxime); (Irgacure OXE01, manufactured by BASF), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime); (Irgacure OXE02, manufactured by BASF), Irgacure OXE03 (manufactured by BASF), or Irgacure OXE04 (manufactured by BASF).

[0091] The photoinitiator may be Omnipol TP (manufactured by IGM Resins, CAS No. 1834525-17-5), a polymeric phosphorus-based initiator, or ethyl (2,4,6-trimethylbenzoyl)-phenyl phosphenate (Omnirad TPO-L, manufactured by IGM Resins).

[0092] The photoinitiator may have the chemical structure shown in the following formula (1) within a molecule (within one molecule). Note that the "*" in formula (1) indicates the bonding site to other atoms. The above-mentioned Omnirad 819, Omnipol TP, and Omnirad TPO-L have the chemical structure shown in formula (1) within their molecules.

[0093] The pressure-sensitive adhesive composition A may contain a photoinitiator having the chemical structure shown in the above formula (1) in the molecule.

[0094] The photoinitiator may be one suitable for suppressing the curing inhibition effect of oxygen on the pressure-sensitive adhesive composition A. Examples of photoinitiators particularly suitable for suppressing the curing inhibition effect of oxygen are the above-mentioned Omnirad 127, Irgacure OXE01, Irgacure OXE02, Irgacure OXE03, and Irgacure OXE04. The pressure-sensitive adhesive composition A may contain a photoinitiator suitable for suppressing the curing inhibition effect of oxygen.

[0095] The content of the photoinitiator in the PSA composition A is, for example, 0.01 to 10 parts by weight per 100 parts by weight of the monomer component M. The lower limit of the content may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, 0.5 parts by weight or more, 0.6 parts by weight or more, 0.7 parts by weight or more, 0.8 parts by weight or more, 0.9 parts by weight or more, 1 part by weight or more, more than 1 part by weight, 1.1 parts by weight or more, 1.2 parts by weight or more, 1.3 parts by weight or more, 1.4 parts by weight or more, or even 1.5 parts by weight or more per 100 parts by weight of the monomer component M. The upper limit of the content may be 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or even 5.5 parts by weight or less per 100 parts by weight of the monomer component M.

[0096] The pressure-sensitive adhesive composition A may contain one or more photoinitiators.

[0097] <1-3. Colorant> The pressure-sensitive adhesive composition A contains a colorant. A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition A containing a colorant exhibits coloration according to the type and content of the colorant. Depending on the type and content of the colorant, a pressure-sensitive adhesive having light-blocking properties can also be formed. The pressure-sensitive adhesive composition A can contain one or more colorants.

[0098] The colorant may be a black colorant or a non-black colorant. The pressure-sensitive adhesive composition A may contain a black colorant. The use of a black colorant is suitable for forming a pressure-sensitive adhesive having light-blocking properties. Note that colorants, particularly black colorants, tend to absorb light, particularly ultraviolet light, irradiated when the pressure-sensitive adhesive composition A is cured.

[0099] The colorant may contain a metal compound, and a black colorant may contain a metal compound. An example of the metal compound is a metal nitride compound, and a more specific example is at least one selected from the group consisting of zirconium nitride and titanium nitride. In other words, the colorant may contain at least one selected from the group consisting of zirconium nitride and titanium nitride.

[0100] Another example of the metal compound is bismuth sulfide. A black colorant containing bismuth sulfide is commercially available, for example, under the trade name LUSHADE BLACK manufactured by Ishihara Sangyo Kaisha.

[0101] The colorant may include a dye. The dye may be a metal complex dye. A metal complex dye is a dye containing a complex salt of a metal atom and a dye molecule. Examples of metal atoms include chromium, copper, cobalt, nickel, iron, manganese, titanium, and aluminum. Examples of dye molecules include azo dyes and methine dyes. The dye may be a dye salt. Examples of dye salts include salts of various dyes and acids, such as onium salts of various dyes, alkylbenzene sulfonates, and alkyldiphenylether disulfonates. The dye used in the dye salt may be one designated as black in the Color Index (C.I.).

[0102] The colorant may contain carbon compounds such as carbon black, graphite, aniline black, perylene black, cyanine black, and activated carbon. Carbon blacks generally known as carbon blacks can be used without particular limitations. Examples of carbon blacks include furnace black, channel black, acetylene black, thermal black, lamp black, and pine soot. Surface-modified carbon blacks having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (e.g., alkoxysilyl groups and alkylsilyl groups) may also be used. Surface-modified carbon black particles, also known as self-dispersing carbon blacks by those skilled in the art, are suitable for reducing the amount of dispersant used.

[0103] Examples of black colorants include carbon compounds such as carbon black, graphite, aniline black, perylene black, cyanine black, and activated carbon; metal compounds such as molybdenum disulfide, chromium complexes, zirconium nitride, and titanium nitride; and organic compound-based colorants such as anthraquinone-based colorants. The black colorant may be a pigment or dye containing the above-mentioned compound. The pressure-sensitive adhesive composition A may contain carbon black. The pressure-sensitive adhesive composition may also contain at least one selected from the group consisting of zirconium nitride and titanium nitride.

[0104] The colorant may be in a particulate form. The average particle size of the particulate colorant is, for example, 10 nm or more, and may be 30 nm or more, 50 nm or more, 100 nm or more, or even 150 nm or more. The upper limit of the average particle size is not particularly limited, and may be, for example, 3000 nm or less, or 1000 nm or less. The average particle size can be determined by the median diameter d50. When the colorant has a shape with a high aspect ratio, for example, a scale-like shape, the average major axis may be within the above range.

[0105] The colorant may be non-particulate.

[0106] Particulate black colorants are suitable for imparting light-blocking properties to pressure-sensitive adhesives. Particulate black colorants having an average particle size of 500 nm or less, 300 nm or less, 250 nm or less, or even 200 nm or less, and in some cases 120 nm or less, 100 nm or less, 50 nm or less, 30 nm or less, 25 nm or less, 10 nm or less, 5 nm or less, 2 nm or less, or even 1 nm or less are particularly suitable for imparting light-blocking properties to pressure-sensitive adhesives.

[0107] Examples of non-black colorants include colorants that exhibit red, blue, yellow, green, yellow-green, orange, purple, etc. Conventionally known pigments and dyes can be used as non-black colorants. Examples of pigments include inorganic pigments and organic pigments. Examples of dyes include azo dyes, anthraquinone dyes, quinophthalone dyes, styryl dyes, diphenylmethane dyes, triphenylmethane dyes, oxazine dyes, triazine dyes, xanthan dyes, methane dyes, azomethine dyes, acridine dyes, and diazine dyes.

[0108] The content of the colorant in the PSA composition A is, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, 2 parts by weight or more, 2.2 parts by weight or more, 2.5 parts by weight or more, 3 parts by weight or more, more than 3 parts by weight, 3.5 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 9 parts by weight or more, or even 10 parts by weight or more, per 100 parts by weight of the monomer component M. The upper limit of the content is, for example, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, 20 parts by weight or less, 17 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, or even 10 parts by weight or less, per 100 parts by weight of the monomer component M. When a solid dispersion is blended as the colorant, the content of the colorant in the PSA composition A is calculated based on the weight of the solids.

[0109] The PSA composition A may be substantially free of non-black colorants.

[0110] <1-4. Other Components> The pressure-sensitive adhesive composition A may contain components other than those described above.

[0111] <1-4-a. Crosslinking Agent> The pressure-sensitive adhesive composition A may further contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may or may not have the above-mentioned ethylenically unsaturated group. The ethylenically unsaturated group may be a (meth)acryloyl group; in other words, the polyfunctional monomer may be a (meth)acrylic monomer. The polyfunctional monomer having an ethylenically unsaturated group tends to mainly contribute to the photopolymerization of the monomer component M, in other words, to the promotion of the formation of the pressure-sensitive adhesive C by photocuring of the pressure-sensitive adhesive composition A. When the polyfunctional monomer does not have an ethylenically unsaturated group, the polyfunctional monomer tends to mainly contribute to the promotion of the formation of a cured product when the pressure-sensitive adhesive C formed from the pressure-sensitive adhesive composition A is further cured in a high-temperature environment, when the polyfunctional monomer is contained in the pressure-sensitive adhesive composition A together with a thermal initiator. The pressure-sensitive adhesive composition A may contain a crosslinking agent that is a polyfunctional monomer having an ethylenically unsaturated group, or may contain a crosslinking agent that is a polyfunctional monomer that does not have an ethylenically unsaturated group, or may contain both.

[0112] Examples of polyfunctional monomers having an ethylenically unsaturated group include monomers having two or more ethylenically unsaturated groups in one molecule, and monomers having one or more ethylenically unsaturated groups and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. The polyfunctional monomer having an ethylenically unsaturated group is preferably a monomer having two or more ethylenically unsaturated groups in one molecule.

[0113] Examples of polyfunctional monomers having an ethylenically unsaturated group include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, Polyfunctional acrylates (e.g., ester compounds of polyhydric alcohols and (meth)acrylic acid) such as acrylate (NDDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer having an ethylenically unsaturated group is preferably a polyfunctional acrylate, and more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0114] The content of the polyfunctional monomer having an ethylenically unsaturated group in the pressure-sensitive adhesive composition A is, for example, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2.5 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, 0.09 parts by weight or less, 0.08 parts by weight or less, 0.07 parts by weight or less, or even 0.06 parts by weight or less, per 100 parts by weight of the monomer component M. The lower limit of the content is, for example, 0.01 parts by weight or more, 0.02 parts by weight or more, 0.03 parts by weight or more, 0.04 parts by weight or more, or even 0.05 parts by weight or more. The pressure-sensitive adhesive composition A may be substantially free of a polyfunctional monomer having an ethylenically unsaturated group.

[0115] The pressure-sensitive adhesive composition A may contain one or more polyfunctional monomers having an ethylenically unsaturated group.

[0116] The polyfunctional monomer having no ethylenically unsaturated group is preferably one that can react with a polymer (typically a (meth)acrylic polymer) of the monomer component M. In particular, the polyfunctional monomer having no ethylenically unsaturated group may contain a compound D having two or more functional groups α that can react with a polymer of the monomer component M. The pressure-sensitive adhesive composition A may contain one or more types of the compound D.

[0117] The functional group α is preferably a cyclic ether group. That is, the crosslinking agent, which is a polyfunctional monomer having no ethylenically unsaturated group, may contain a compound D having two or more cyclic ether groups. The compound D having two or more cyclic ether groups is particularly suitable for combination with a pressure-sensitive adhesive composition A containing a monomer component M including a cyclic ether group-containing monomer. The cyclic ether group is a functional group containing a ring having an ether bond. The cyclic ether group may be at least one selected from the group consisting of an epoxy group and an oxetane group, or may be an epoxy group.

[0118] In compound D, the number of functional groups α contained in one molecule is, as described above, 2 or more, and may be 3 or more, or even 4 or more. The upper limit of the number of functional groups α is not particularly limited, and may be, for example, 10 or less, 8 or less, 6 or less, or even 5 or less.

[0119] Compound D preferably contains at least one selected from the group consisting of an epoxy compound having two or more epoxy groups and an oxetane compound having two or more oxetane groups, and particularly preferably contains an epoxy compound. Examples of the epoxy compound include an alicyclic epoxy compound and an aromatic epoxy compound.

[0120] Examples of alicyclic epoxy compounds include epoxy compounds having an epoxycyclohexyl group, such as butanetetracarboxylic acid tetra(3,4-epoxycyclohexylmethyl)-modified ε-caprolactone (e.g., Epolead GT401 manufactured by Daicel Corporation) and 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (e.g., Celloxide 2021 manufactured by Daicel Corporation). Commercially available epoxy compounds having an epoxycyclohexyl group include Celloxide 2021A, Celloxide 2021P, Celloxide 2081, Celloxide 2083, and Celloxide 2085 (all manufactured by Daicel Corporation), Cyracure UVR-6105, Cyracure UVR-6107, and Cyracure UVR-6110 (all manufactured by Dow Chemical Japan).

[0121] Examples of aromatic epoxy compounds include resorcinol diglycidyl ether and phthalic acid diglycidyl ester.

[0122] The epoxy compound is not limited to those described above, and may be an epoxy resin such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, alicyclic epoxy resin, diphenyl ether type epoxy resin, hydroquinone type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, fluorene type epoxy resin, multifunctional type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, or aliphatic chain epoxy resin. These epoxy resins may be halogenated or hydrogenated. Examples of commercially available epoxy resins include jER828, 1001, 801N, 806, 807, 152, 604, 630, 871, YX8000, YX8034, and YX4000 manufactured by Mitsubishi Chemical Corporation; Epicron 830, EXA835LV, HP4032D, and HP820 manufactured by DIC Corporation; EP4100 series, EP4000 series, and EPU series manufactured by ADEKA Corporation; EHPE series manufactured by Daicel Corporation; YD series, YDF series, YDCN series, YDB series, and YP series manufactured by Nippon Steel Chemical & Material Co., Ltd.; Denacol series manufactured by Nagase ChemteX Corporation; and Epolite series manufactured by Kyoeisha Chemical Co., Ltd.

[0123] Examples of the oxetane compound include 1,4-bis[(3-ethyloxetan-3-yl)methoxymethyl]benzene, bis[(3-ethyloxetan-3-yl)methyl]ether, etc. Examples of commercially available oxetane compounds include Aron Oxetane OXT-121 and Aron Oxetane OXT-221 (both manufactured by Toagosei Co., Ltd.).

[0124] The content of the polyfunctional monomer having no ethylenically unsaturated group in the pressure-sensitive adhesive composition A is, for example, 1 part by weight or more, and may be 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, or even 30 parts by weight or more, per 100 parts by weight of the monomer component M. The upper limit of the content is not particularly limited, and may be, for example, 80 parts by weight or less, 50 parts by weight or less, or even 40 parts by weight or less. The pressure-sensitive adhesive composition A may be substantially free of a polyfunctional monomer having no ethylenically unsaturated group.

[0125] <1-4-b. Thermal initiator> The pressure-sensitive adhesive composition A may further contain a thermal initiator, which is a type of polymerization initiator. When the pressure-sensitive adhesive composition A is cured by irradiation with light, heat due to the light irradiation may be generated in the pressure-sensitive adhesive composition A. Possible examples of such heat include heat generated by photopolymerization of the monomer component M and heat generated in the pressure-sensitive adhesive composition A itself by light irradiation. Depending on the composition of the pressure-sensitive adhesive composition A, the inclusion of a thermal initiator in addition to a photoinitiator may contribute to the utilization of the heat generated by light irradiation and further promotion of curing due to such utilization.

[0126] The thermal initiator may be at least one selected from the group consisting of azo initiators, peroxide initiators, redox initiators, thermal acid generators, and persulfate initiators, or may be a thermal acid generator. According to the studies of the present inventors, using a thermal acid generator as the thermal initiator may be suitable for improving the adhesive strength of the pressure-sensitive adhesive C formed from the pressure-sensitive adhesive composition A.

[0127] The thermal initiator may be one that promotes the reaction between the polymer of the monomer component M and the crosslinking agent (more specifically, the polyfunctional monomer having no ethylenically unsaturated group) in a high-temperature environment.

[0128] Examples of azo initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(2-methylpropionamidine)disulfate, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] 2,2'-azobis[N-(2-hydroxyethyl)propionamidine] n-hydrate, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(isobutyrate) dimethyl, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate.

[0129] Examples of peroxide initiators include ketone peroxide compounds, peroxyketal compounds, hydroperoxide compounds, dialkyl peroxide compounds, diacyl peroxide compounds, peroxyester compounds, and peroxydicarbonate compounds. More specific examples include diisobutyryl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, and t-hexylperoxyneodecanoate. Noate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate peroxide, t-butylperoxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy Oxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-di-methyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,2-di-(t-butylperoxy)butane, t-butylperoxybenzoate, n-butyl-4,4-di-(t-butylperoxy)valerate, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and mixtures thereof.

[0130] An example of a redox initiator is an initiator that combines a peroxide with a reducing agent, such as a combination of persulfate and sodium bisulfite, or a combination of peroxide and sodium ascorbate.

[0131] The thermal acid generator generates an acid in a high-temperature environment, and from this viewpoint, the thermal acid generator is particularly suitable for promoting the reaction between a polymer of the monomer component M and a crosslinking agent (more specifically, a polyfunctional monomer having no ethylenically unsaturated group) in a high-temperature environment.

[0132] Examples of thermal acid generators are cationic or protonic acid catalysts such as sulfonium salts, ammonium salts, pyridinium salts, phosphonium salts, iodonium salts, triflate salts, boron trifluoride etherate, boron trifluoride, etc. The thermal acid generator may also be an onium salt that generates a cationic species by heat.

[0133] The thermal acid generator may be a sulfonium salt or a phosphonium salt, or may be a sulfonium salt.

[0134] Examples of the sulfonium ion contained in the sulfonium salt include benzyl(4-hydroxyphenyl)methylsulfonium, (4-acetoxyphenyl)dimethylsulfonium, (4-hydroxyphenyl)dimethylsulfonium, (2-methylbenzyl)(4-hydroxyphenyl)methylsulfonium, (4-acetoxyphenyl)(2-methylbenzyl)methylsulfonium, (1-naphthylmethyl)(4-hydroxyphenyl)methylsulfonium, benzyl(4-acetoxyphenyl)methylsulfonium, (4-acetoxyphenyl)benzyl(methyl)sulfonium=tetrakis(pentafluorophenyl)borate, and (4-hydroxyphenyl)methyl(4-methylbenzyl)sulfonium=tetrakis(pentafluorophenyl)borate.

[0135] Counter ions contained in the sulfonium salt include tris(pentafluoroethyl)trifluorophosphate, hexafluorophosphate, tetrakis(pentafluorophenyl)borate, hexafluoroantimonate, p-toluenesulfonate, dodecylbenzenesulfonate, trifluoromethanesulfonate, perfluorobutanesulfonate, etc. The sulfonium salt preferably contains a borate ion such as tetrakis(pentafluorophenyl)borate.

[0136] Commercially available thermal acid generators include, for example, San-Aid SI-45L, San-Aid SI-60L, San-Aid SI-80L, San-Aid SI-100L, San-Aid SI-110L, San-Aid SI-150L, ​​San-Aid SI-45, San-Aid SI-60, San-Aid SI-80, San-Aid SI-100, San-Aid SI-110, and San-Aid SI- 150, San-Aid SI-300, San-Aid SI-360, San-Aid SI-B2A, San-Aid SI-B3, San-Aid SI-B3A, San-Aid SI-B4, San-Aid SI-B5, San-Aid SI-B7, and PP-33, CP-66, and CP-77 manufactured by ADEKA Corporation, with San-Aid SI-B3, San-Aid SI-B3A, and San-Aid SI-B7 being preferred.

[0137] The thermal decomposition temperature (temperature for generating an acid) of the thermal acid generator is, for example, 60° C. or higher, and may be 70° C. or higher, 80° C. or higher, 90° C. or higher, 100° C. or higher, 110° C. or higher, or even 120° C. or higher. The upper limit of the thermal decomposition temperature may be, for example, 200° C. or lower, 180° C. or lower, or even 160° C. or lower.

[0138] Examples of persulfate initiators are potassium persulfate and ammonium persulfate.

[0139] The thermal acid generator may be an amine compound. Examples of the amine compound include aliphatic polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and diethylaminopropylamine; alicyclic polyamines such as menthenediamine, isophoronediamine, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro(5,5)undecane adduct, bis(4-amino-3-methylcyclohexyl)methane, and bis(4-aminocyclohexyl)methane; m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, 4,4-diaminodiphenylmethane, 4,4-diaminodiphenylpropane, 4,4-diaminodiphenylsulfone, 4,4-diaminodicyclohexane, bis(4-aminophenyl)phenylmethane, 1,5-diaminonaphthalene, and 1,1-bis(4-aminophenyl)silane. Aromatic polyamines such as chlorohexane, 2,2-bis[(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis(4-aminophenoxy)benzene, 4,4-methylene-bis(2-chloroaniline), and 4,4-diaminodiphenyl sulfone; carbodihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and isophthalic acid dihydrazide and guanidine derivatives such as dicyandiamide, 1-o-tolyldiguanide, α-2,5-dimethylguanide, α,ω-diphenyldiguanidide, α,α-bisguanylguanidinodiphenyl ether, p-chlorophenyldiguanide, α,α-hexamethylenebis[ω-(p-chlorophenol)]diguanide, phenyldiguanide oxalate, acetylguanidine, and diethylcyanoacetylguanidine.

[0140] The thermal initiator is not limited to the above examples.

[0141] The self-accelerating decomposition temperature (SADT) of the thermal initiator, particularly the peroxide initiator, may be 120°C or lower, 100°C or lower, 90°C or lower, 85°C or lower, 80°C or lower, 75°C or lower, 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower, 50°C or lower, 45°C or lower, 40°C or lower, 35°C or lower, 30°C or lower, 25°C or lower, 20°C or lower, 15°C or lower, 10°C or lower, or even 5°C or lower. A thermal initiator with a low SADT may allow for more effective use of the heat generated in the pressure-sensitive adhesive composition A by light irradiation. The lower limit of the SADT is, for example, 0°C or higher. SADT is well known to those skilled in the art.

[0142] The content of the thermal initiator in the pressure-sensitive adhesive composition A is, for example, 0.01 to 10 parts by weight, and may be 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, 0.1 to 1.5 parts by weight, 0.1 to 1 part by weight, 0.1 to 0.9 parts by weight, 0.1 to 0.8 parts by weight, 0.1 to 0.7 parts by weight, 0.1 to 0.6 parts by weight, 0.1 to 0.5 parts by weight, 0.1 to 0.4 parts by weight, 0.1 to 0.3 parts by weight, or even 0.1 to 0.2 parts by weight, per 100 parts by weight of the monomer component M. The pressure-sensitive adhesive composition A may be substantially free of a thermal initiator.

[0143] The pressure-sensitive adhesive composition A may contain one or more thermal initiators.

[0144] <1-4-c. Inorganic particles> The pressure-sensitive adhesive composition A may further contain inorganic particles (more specifically, inorganic particles other than colorants). The inorganic particles are suitable for improving the refractive index of the pressure-sensitive adhesive. The inorganic particles are preferably in a dispersed state in the pressure-sensitive adhesive composition A. The pressure-sensitive adhesive composition A may contain one or more types of inorganic particles.

[0145] The inorganic particles can be selected from, for example, metal compound particles and metal particles, one or more types depending on the desired purpose, such as improving the refractive index. The metal compound particles may be metal oxide particles. Examples of materials constituting the metal oxide particles include titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide. The metal oxide particles can be used alone or in combination of two or more types. The inorganic particles preferably contain zirconium oxide, and may be zirconium oxide particles composed essentially of zirconium oxide alone. The zirconium oxide particles can particularly contribute to increasing the refractive index of the pressure-sensitive adhesive.

[0146] The material constituting the metal compound particles may be a metal hydroxide such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, copper hydroxide, barium hydroxide, basic magnesium carbonate, hydrotalcite, or a hydrated metal compound. Examples of the material constituting the metal particles are iron, zinc, tungsten, and platinum.

[0147] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0148] The inorganic particles may be surface-treated, for example, by hydrophobizing treatment.

[0149] The inorganic particles may contain a high refractive index material. The refractive index of the high refractive index material is, for example, 1.60 or more, and may be 1.70 or more, 1.80 or more, or even 2.00 or more. The upper limit of the refractive index of the high refractive index material is not particularly limited, and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or even 2.20 or less. The refractive index of the material contained in the inorganic particles can be determined as the refractive index measured on a monolayer film of the material using a commercially available spectroscopic ellipsometer under conditions of 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woollam) or an equivalent.

[0150] The inorganic particles may be nanoparticles having an average particle size of less than 1 μm. The average particle size of the inorganic particles may be 100 nm or less. The average particle size may be 70 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, 7 nm or less, 5 nm or less, or even 4 nm or less. The lower limit of the average particle size may be, for example, 1 nm or more, 1.5 nm or more, 2 nm or more, or even 2.5 nm or more.

[0151] The content of inorganic particles in the pressure-sensitive adhesive composition A per 100 parts by weight of the monomer component M is, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, 50 parts by weight or more, 55 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 90 parts by weight or more, or even 100 parts by weight or more. The upper limit of the content per 100 parts by weight of the monomer component M may be, for example, 150 parts by weight or less, 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, 115 parts by weight or less, or even 110 parts by weight or less. The pressure-sensitive adhesive composition A may be substantially free of inorganic particles. The inorganic particles can be blended in the PSA composition A in the form of a dispersion, and in this case, the content of the inorganic particles is calculated based on the weight of the solid content.

[0152] <1-4-d. Dispersant> The PSA composition A may further contain a dispersant for inorganic particles. The dispersant is a component for sufficiently dispersing the inorganic particles in the PSA composition A. The dispersant is preferably in contact with the surfaces of the inorganic particles, and more preferably coats the surfaces of the inorganic particles.

[0153] An example of a dispersant is a compound having a hydrophilic portion and a hydrophobic portion in one molecule. The hydrophilic portion and the hydrophobic portion of the dispersant are presumed to exhibit relatively high affinity for the inorganic particles and the monomer component M, respectively. The dispersant may or may not have a polymerizable functional group such as an ethylenically unsaturated group.

[0154] The hydrophilic portion of the dispersant preferably has a hydrophilic group, examples of which include an ether group and an ester group.

[0155] The hydrophilic portion of the dispersant preferably has a functional group F that exhibits adsorptivity or reactivity with inorganic particles. Examples of the functional group F include at least one selected from the group consisting of alkaline groups and acidic groups. Specific examples of the functional group F include a hydroxy group, a carboxy group, a nitrogen atom-containing group, a sulfur atom-containing group, a phosphorus atom-containing group, and a silicon atom-containing group. The number of functional groups F contained in one molecule of the dispersant may be 1, or may be 2 or more (for example, about 2 to 5). The types of the two or more functional groups F present in one molecule may be the same or different from each other.

[0156] The hydrophilic portion of the dispersant may have a chain structure, or may have a composite structure of a chain structure and a cyclic structure. The dispersant may include, for example, a structure in which a functional group F and a hydrophobic portion are linked via a chain structure; a structure in which a functional group F is located on a side chain of a chain structure whose one end is linked to the hydrophobic portion; or a structure in which a functional group F is not located on the other end of a chain structure whose one end is linked to the hydrophobic portion (for example, the other end of the chain structure is open). The dispersant may have two or more of the above structures.

[0157] The dispersant may be an aromatic compound having an aromatic ring. Examples of the aromatic ring are the same as those mentioned above in the description of monomer a.

[0158] The dispersant may be selected from known surfactants. Examples of surfactants include anionic surfactants (carboxylic acid type, phosphate ester type, sulfate ester type, sulfonic acid type, etc.), nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant that can be used as the dispersant is preferably an anionic surfactant.

[0159] The amount of dispersant blended relative to 100 parts by weight of inorganic particles is, for example, 0.1 parts by weight or more, and may be 0.5 parts by weight or more, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, or even 10 parts by weight or more. The upper limit of the blending amount is, for example, 30 parts by weight or less, and may be 20 parts by weight or less. The PSA composition A may be substantially free of a dispersant.

[0160] <1-4-e. Silane Coupling Agent> The pressure-sensitive adhesive composition A may further contain a silane coupling agent. The pressure-sensitive adhesive composition A can contain one or more silane coupling agents.

[0161] Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0162] The content of the silane coupling agent in the pressure-sensitive adhesive composition A is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or even 0.1 parts by weight or less, per 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more. The pressure-sensitive adhesive composition A may be substantially free of a silane coupling agent.

[0163] <1-4-f. Antioxidant> The pressure-sensitive adhesive composition A may further contain an antioxidant. The pressure-sensitive adhesive composition A may contain one or more antioxidants.

[0164] Examples of antioxidants include phenolic antioxidants, hindered phenolic antioxidants, amine antioxidants, and phosphite antioxidants.

[0165] Examples of the phenolic antioxidants include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the bisphenol antioxidant are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of the polymeric phenolic antioxidant are 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0166] The hindered phenolic antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to the carbon atom on the aromatic ring to which the phenolic OH group is bonded. Examples of the hindered phenolic antioxidant include dibutylhydroxytoluene (BHT); Irganox 1010, Irganox 1010FF, Irganox 1035, Irganox 1035FF, Irganox 1076, Irganox 1076FD, Irganox 1076DWJ, Irganox 1098, Irganox 109 ... Irganox 1135, Irganox 1330, Irganox 1726, Irganox 1425WL, Irganox 1520L, Irganox 245, Irganox 245FF, Irganox 259, Irganox 3114, Irganox 565 and Irganox 295 (all of which are trade names manufactured by BASF).

[0167] The amine antioxidant is preferably a hindered amine antioxidant. The hindered amine antioxidant may have at least one hindered piperazine group in one molecule. Examples of hindered amine antioxidants include Adeka STAB LA-63, Adeka STAB LA-63P, Adeka STAB LA-52, and Adeka STAB LA-57 (all of which are trade names, manufactured by ADEKA Corporation).

[0168] Examples of the phosphite antioxidants are triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite; and Adeka STAB 2112, Adeka STAB 2112RG, Adeka STAB 1178, and Adeka STAB 3010 (all of which are trade names, manufactured by ADEKA Corporation).

[0169] The content of the antioxidant in the PSA composition A is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more. The PSA composition A may be substantially free of an antioxidant.

[0170] <1-4-g. Curing Accelerator> The pressure-sensitive adhesive composition A may further contain a curing accelerator. The pressure-sensitive adhesive composition A may contain one or more curing accelerators.

[0171] An example of a curing accelerator is a compound that exhibits oxygen absorption. A compound that exhibits oxygen absorption can contribute to suppressing curing inhibition due to oxygen during photocuring. Another example of a curing accelerator is a compound having an isoprenyl group and a methacryloyl group in the molecule (within one molecule). Another example of a curing accelerator is a compound having a secondary thiol group. The secondary thiol group donates hydrogen to a peroxide radical to become a thiyl radical, thereby promoting polymerization and contributing to suppressing oxygen inhibition. It is preferable that a plurality of secondary thiol groups are contained in one molecule.

[0172] Specific examples of the curing accelerator include diprenyl glycerin ether (DPNG), isoprenyl methacrylate (IPEMA), pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinane-2,4,6-trione, and trimethylolpropane-tris(3-mercaptobutyrate). DPNG exhibits oxygen absorbing properties.

[0173] The content of the curing accelerator in the pressure-sensitive adhesive composition A is, for example, 10 parts by weight or less, and may be 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or even 0.5 parts by weight or more. The pressure-sensitive adhesive composition A may be substantially free of a curing accelerator.

[0174] <1-4-h. Photosensitizer> The pressure-sensitive adhesive composition A may further contain a photosensitizer. The pressure-sensitive adhesive composition A may contain one or more photosensitizers.

[0175] Examples of the photosensitizer are benzophenone, methyl o-benzoylbenzoate, 2-isopropylthioxanthone, and 9,10-dibutoxyanthracene.

[0176] The content of the photosensitizer in the pressure-sensitive adhesive composition A is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less, relative to 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more. The pressure-sensitive adhesive composition A may be substantially free of a photosensitizer.

[0177] <1-4-i. Solvent> The content of the solvent in the PSA composition A is, for example, 5 wt % or less, and may be 4 wt % or less, 3 wt % or less, 2 wt % or less, 1 wt % or less, or even 0.5 wt % or less. The PSA composition A may be substantially free of a solvent.

[0178] <1-4-j. Additives> The PSA composition A may further contain additives (other than the above-mentioned components). Examples of the additives include chain transfer agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, surfactants, antistatic agents, leveling agents, flame retardants, and ultraviolet absorbers. The PSA composition A may be substantially free of additives.

[0179] <1-5. Viscosity> The viscosity of the PSA composition A is preferably 5 to 300 poises at 25°C. A PSA composition A having a viscosity within the above range is particularly suitable for forming a coating layer, which will be described later. Increasing the viscosity of the PSA composition A can contribute to reducing the diffusion rate of dissolved oxygen in the PSA composition A. Oxygen can be absorbed into the PSA composition A from the surface of the PSA composition A, for example, the surface of the coating layer, which will be described later. It is presumed that reducing the diffusion rate works in a favorable direction for suppressing curing inhibition due to absorbed oxygen. For this reason, increasing the viscosity of the PSA composition A may be particularly suitable for suppressing curing inhibition due to oxygen for the PSA composition A, even under curing conditions that are generally considered unfavorable for photocuring, for example.

[0180] <<2. Pressure-Sensitive Adhesive>> A pressure-sensitive adhesive according to an embodiment of the present invention (hereinafter referred to as "pressure-sensitive adhesive C") is a pressure-sensitive adhesive formed from pressure-sensitive adhesive composition A. Pressure-sensitive adhesive C is usually formed by curing pressure-sensitive adhesive composition A.

[0181] <2-1. Properties, etc.> The curing state of the adhesive C can be represented by the polymerization rate of the monomer component M in the adhesive C. The polymerization rate of the monomer component M is, for example, 90.0% or more, 91.0% or more, 92.0% or more, 93.0% or more, 94.0% or more, 95.0% or more, 95.2% or more, 95.4% or more, 95.5% or more, 95.6% or more, 95.8% or more, 96.0% or more, 96.2% or more, 96.4% or more, 96.5% or more, 96.7% or more, 96.9% or more, 97.0% or more, 97.2% or more, 97.4% or more, The polymerization rate may be 97.5% or more, 97.7% or more, 97.9% or more, 98.0% or more, 98.1% or more, 98.2% or more, 98.3% or more, 98.4% or more, 98.5% or more, 98.6% or more, 98.7% or more, 98.8% or more, 98.9% or more, 99.0% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, or even 99.7% or more. The upper limit of the polymerization rate is, for example, less than 100%, and may be 99.9% or less, or even 99.8% or less.

[0182] The adhesive C conforms to the CIE 1976 L standard specified in the Japanese Industrial Standards (JIS) Z8781-4:2013. * , a * , b * Color space L * The L of the adhesive C may be 60.0 or less. * may be 55.0 or less, 50.0 or less, 45.0 or less, 40.0 or less, 35.0 or less, 30.0 or less, 25.0 or less, 20.0 or less, 15.0 or less, 10.0 or less, 9.0 or less, 8.0 or less, 7.0 or less, 6.0 or less, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.2 or less, 3.0 or less, 2.7 or less, 2.5 or less, 2.2 or less, 2.0 or less, 1.7 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.7 or less, 0.5 or less, 0.3 or less, 0.2 or less, or even 0.1 or less. *can be 0.0. The inclusion of a colorant, especially a black colorant, * It is suitable for lowering the value of

[0183] The adhesive C is the same as the above L * , a * , b * Color space a * The absolute value of b * The color may have a chromaticity of 10.0 or less when expressed as an absolute value of a * The absolute value of and b * The absolute values ​​of may be, independently of one another, or both may be 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, 2.5 or less, 2.2 or less, 2.0 or less, 1.8 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or even 0.1 or less. * The absolute value of and b * The absolute value of L can be 0.0. * Decrease the value of a * and b * The colorant may be selected to reduce the absolute value of

[0184] Lightness L of adhesive C * and chromaticity a * , b * can be evaluated using a commercially available colorimeter capable of measurements in accordance with JIS Z8781-4:2013. However, the PSA C used for evaluation is in the form of a sheet having a thickness of 30 μm. For ease of handling, it is preferable to evaluate the PSA C in a state where it is laminated with a film or sheet serving as a supporting substrate.

[0185] The pressure-sensitive adhesive C may have a total light transmittance Tt of 91% or less. The total light transmittance Tt may be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 17% or less, 15% or less, 12% or less, 10% or less, 9% or less, 7% or less, 5% or less, less than 5%, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.8% or less, 0.6% or less, 0.5% or less, less than 0.5%, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, 0.05% or less, 0.04% or less, 0.03% or less, 0.02% or less, or even 0.01% or less. The lower limit of the total light transmittance Tt is, for example, 0.0001% or more. The total light transmittance Tt of the pressure-sensitive adhesive C can be evaluated using a commercially available spectrophotometer capable of measuring in accordance with JIS R3106, such as a spectrophotometer (for example, Hitachi High-Tech Corporation's ultraviolet-visible-near-infrared spectrophotometer UH4150 or its equivalent). However, the pressure-sensitive adhesive C used for evaluation is in the form of a sheet having a thickness of 30 μm. In addition, for ease of handling, it is preferable to evaluate the pressure-sensitive adhesive C in a state where it is laminated with a sheet or film that serves as a supporting substrate.

[0186] The pressure-sensitive adhesive C may have a haze of 40 to 100%. The haze may be 45 to 90%, 50 to 80%, or more than 50%. In this specification, haze refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the pressure-sensitive adhesive, which is the object to be measured. Haze can be calculated using the following formula. In the following formula, Th is haze (%), Td is scattered light transmittance, and Tt is total light transmittance. Th (%) = (Td / Tt) x 100

[0187] The haze of the pressure-sensitive adhesive C can be evaluated using a commercially available spectroscopic measuring device capable of measurement in accordance with JIS K7136, such as a haze meter. However, the pressure-sensitive adhesive C used for evaluation is in the form of a sheet having a thickness of 30 μm. For ease of handling, it is preferable to evaluate the haze in a state where it is laminated with a sheet or film serving as a supporting substrate.

[0188] The pressure-sensitive adhesive C may have a refractive index of 1.50 or more. The refractive index may be 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, or even 1.65 or more. The upper limit of the refractive index is, for example, 1.70 or less, and may be 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, or even 1.65 or less.

[0189] The refractive index of the adhesive C can be measured using a digital refractometer (for example, Atago's Digital Refractometer RX-9000α or an equivalent) at a measurement temperature of 25°C. However, when evaluating, the adhesive C is in the form of a sheet, and the refractive index of the sheet surface is measured. The measurement is performed by a reflection method that utilizes total reflection at the interface between the adhesive and a prism.

[0190] The gel fraction of the pressure-sensitive adhesive C is, for example, 50% or more, and may be 75% or more, 80% or more, 85% or more, or even 90% or more.

[0191] The gel fraction can be measured by the following method. First, a small piece is obtained by scraping off a part of the adhesive C. Next, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene film and tied with kite string. This gives a test piece. Next, the total weight of the adhesive C piece, the stretched porous film, and the kite string (weight W a The total weight of the stretched porous membrane and kite string used is W b Next, the test piece is immersed in a container filled with toluene and left to stand at 23°C for one week. After standing, the test piece is taken out of the container and dried in a dryer set at 130°C for two hours, and then the weight W of the test piece is measured. c The weight W is measured based on the following formula: a , W b and W c The gel fraction of the adhesive C can be determined from the following equation: Gel fraction (wt%) = (W c -W b ) / (W a -W b ) x 100

[0192] The shear storage modulus G' of the adhesive C at 25°C is 1.0 x 10 5 Pa or less, and 4 Pa or less, 8.0×10 4 Pa or less, and even 7.0 × 10 4 The lower limit of the shear storage modulus G′ of the pressure-sensitive adhesive C may be, for example, 1.0×10 3 Pa or more, and 3 Pa or more, 1.0×10 4 Pa or more, 3.0×10 4 Pa or more, and even 5.0 × 10 4 The shear storage modulus G' of the pressure-sensitive adhesive C at 25°C is not limited to the above range, but a pressure-sensitive adhesive C having G' in the above range has excellent adhesion to members and is particularly suitable for sufficiently increasing the adhesive strength between members after the members are joined together.

[0193] The shear storage modulus G' of Pressure-Sensitive Adhesive C at 25°C can be measured by the following method. First, a measurement sample made of Pressure-Sensitive Adhesive C is prepared. The measurement sample is disc-shaped. The measurement sample has a bottom diameter of 7.9 mm and a thickness of approximately 1 mm. The measurement sample may be obtained by laminating multiple pressure-sensitive adhesive sheets made of Pressure-Sensitive Adhesive C, and then tightly adhering the sheets together to form a laminate, which is then punched into a disc shape. Next, dynamic viscoelasticity measurement is performed on the measurement sample under the following measurement conditions. For dynamic viscoelasticity measurement, for example, a dynamic viscoelasticity measurement device (Advanced Rheometric Expansion System (ARES)) manufactured by TA Instruments can be used. The shear storage modulus of the measurement sample at 25°C is determined from the results of the dynamic viscoelasticity measurement, and the obtained value is considered to be the shear storage modulus G' of the pressure-sensitive adhesive. Measurement conditions: Deformation mode: Torsion Measurement frequency: 1 Hz Temperature range: -40°C to 150°C Heating rate: 5°C / min Shape: Parallel plate 7.9 mm diameter

[0194] The adhesive strength of PSA C determined by the following test may be 0.1 N / 20 mm or more, 0.2 N / 20 mm or more, 0.5 N / 20 mm or more, 1.0 N / 20 mm or more, 1.5 N / 20 mm or more, 2 N / 20 mm or more, 2.5 N / 20 mm or more, 3 N / 20 mm or more, 4 N / 20 mm or more, 5 N / 20 mm or more, 6 N / 20 mm or more, 7 N / 20 mm or more, 8 N / 20 mm or more, 9 N / 20 mm or more, 10 N / 20 mm or more, 15 N / 20 mm or more, 20 N / 20 mm or more, 25 N / 20 mm or more, or even 30 N / 20 mm or more. The upper limit of the adhesive strength is not limited, and may be, for example, 50 N / 20 mm or less, 40 N / 20 mm or less, or even 30 N / 20 mm or less.

[0195] (Adhesion Strength Test) A test piece is prepared as a laminate of the pressure-sensitive adhesive C to be evaluated and an evaluation base sheet. The pressure-sensitive adhesive C is in the form of a sheet with a thickness of 30 μm. The evaluation base sheet is not limited as long as it does not peel from the pressure-sensitive adhesive C during the peel test from the alkali-free glass surface performed in this test and allows for the peel test (180° peel test). For example, a polyethylene terephthalate (PET) sheet can be used as the evaluation base sheet. The bonding surface of the evaluation base sheet to which the pressure-sensitive adhesive C is bonded may be subjected to an adhesion-enhancing treatment such as corona treatment. As long as the above conditions are met, the base sheet or release liner used to form the sheet-like pressure-sensitive adhesive C may also be used as the evaluation base sheet. The test piece is prepared so that the portion of the evaluation base sheet to which the pressure-sensitive adhesive C is bonded is a rectangle measuring 25 mm wide x 80 mm long, and the portion consisting of only the evaluation base sheet is a rectangle measuring 25 mm wide x 170 mm long. The overall shape of the test piece was a rectangle with a width of 25 mm and a length of 250 mm.

[0196] Next, the test piece is placed on the alkali-free glass via the adhesive C, and a 2 kg hand roller is rolled back and forth once to press the pieces together. The alkali-free glass is glass that is substantially free of alkali components (alkali metal oxides). Specifically, the weight ratio of alkali components in the glass is, for example, 1000 ppm (by weight, the same applies hereinafter) or less, and even 500 ppm or less. The alkali-free glass is, for example, in the form of a plate and has a thickness of 0.5 mm or more. To perform measurements more accurately, it is recommended that the bonding surface of the alkali-free glass with the adhesive C be cleaned using isopropyl alcohol or the like.

[0197] Next, the test piece bonded to the alkali-free glass is left at room temperature (23°C ± 5°C) for 30 minutes, and then placed in a pressure degassing apparatus (autoclave) and autoclaved for 15 minutes at a temperature of 50°C and a pressure of 0.5 MPa. After autoclave treatment, the test piece is left at room temperature for 12 hours. Next, a peel test is performed at a peel angle of 180° and a peel speed of 300 mm / min to peel the test piece from the alkali-free glass. The maximum force (peel strength) measured during peeling can be identified as the adhesive strength of PSA C.

[0198] The adhesive C may have any combination of two or more of the above-mentioned properties.

[0199] The shape of the pressure-sensitive adhesive C is not limited. The pressure-sensitive adhesive C may be in a sheet form, or in a bulk form having an irregular or predetermined shape. The pressure-sensitive adhesive C may have any shape depending on the application.

[0200] The thickness of the sheet-like pressure-sensitive adhesive C is, for example, 2 mm or less, and may be 1.5 mm or less, 1 mm or less, 500 μm or less, 250 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 5 μm or less, 4 μm or less, or even 3 μm or less. The lower limit of the thickness of the sheet-like pressure-sensitive adhesive C is, for example, 2 μm or more.

[0201] There are no limitations on the use of the pressure-sensitive adhesive C. Examples of uses include optical and design applications. The pressure-sensitive adhesive C may be used in combination with an optical member to form a pressure-sensitive adhesive optical member.

[0202] The adhesive C may be used in electronic devices such as portable electronic devices. Non-limiting examples of portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as accessories, earwear devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not simply mean that the device is portable, but rather means that the device has a level of portability that allows an individual (average adult) to carry it relatively easily.

[0203] The adhesive C contains a colorant. The inclusion of the colorant can limit the optical transparency of the adhesive C. Furthermore, depending on the composition of the adhesive composition A, such as the type and content of the monomer contained in the monomer component M, the adhesive C can have a high refractive index. An adhesive C with limited optical transparency and an adhesive C with a high refractive index may be particularly suitable for use in electronic devices such as portable electronic devices. For example, some electronic devices contain light-emitting elements for purposes such as image display, and the adhesive may require limited optical transparency (e.g., light-blocking properties). Furthermore, electronic devices may use components with high refractive indexes, and a high refractive adhesive may be required for purposes such as preventing unwanted reflections. In response to such requirements, an adhesive C with the above properties is particularly suitable.

[0204] <2-2. Method for producing adhesive C> The adhesive C can be formed by irradiating the above-described adhesive composition A with light to cure the adhesive composition. The method for producing the adhesive C according to the present embodiment includes irradiating the above-described adhesive composition A with light to cure the adhesive composition.

[0205] FIG. 1 shows an example of a method for producing a pressure-sensitive adhesive C according to this embodiment. In the example shown in FIG. 1, a coated material 12 of a pressure-sensitive adhesive composition A placed on a substrate 11 is irradiated with light 13. The coated material 12 is cured by the irradiation of light 13 to form a pressure-sensitive adhesive 14. The formed pressure-sensitive adhesive 14 may be transferred to various members that are the object on which the pressure-sensitive adhesive 14 is to be placed. A member that is the object can also be used as the substrate 11, and in this case, a pressure-sensitive adhesive-attached member can be formed by curing. The substrate 11 and the member are not limited. The substrate 11 may be in a sheet form. When transferring after curing, the surface of the substrate 11 on which the pressure-sensitive adhesive 14 is formed may be subjected to a release treatment.

[0206] The substrate 11 may be formed from metal, resin, glass, or a composite material thereof. Examples of metals include aluminum and stainless steel. Examples of resins include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resin, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. With regard to the target member, at least the transfer surface and formation surface of the adhesive 14 may be formed from the materials exemplified above. However, the materials constituting the substrate 11 and the target are not limited to the above examples.

[0207] For the release treatment, various release agents can be used, such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder.

[0208] An example of a case where the substrate 11 is in sheet form is shown in Figure 2. The method of Figure 2 is suitable for forming a sheet-like pressure-sensitive adhesive C. In the method of Figure 2, light 34 is irradiated onto a coating layer 32 containing a pressure-sensitive adhesive composition A formed on a substrate sheet 31. The coating layer 32 is irradiated with light 34 and hardens to form a sheet-like pressure-sensitive adhesive C (reference numeral 1). In the formed pressure-sensitive adhesive 1, the surface opposite to the side facing the substrate sheet 31 is exposed to the outside. Another layer can be laminated on the exposed surface of the pressure-sensitive adhesive 1. The other layer may be laminated directly or via an additional layer. The pressure-sensitive adhesive 1 with its exposed surface may be attached or transferred to a target member.

[0209] The sheet-like pressure-sensitive adhesive C may be formed by the method shown in Fig. 3. In the method of Fig. 3, a first laminate 30 including, in this order, a base sheet 31, a coating layer 32 containing a pressure-sensitive adhesive composition A, and a release liner 33 is irradiated with light 34. The coating layer 32 is cured by irradiation with light 34, and becomes a sheet-like pressure-sensitive adhesive C (reference numeral 1).

[0210] The formed PSA 1 is sandwiched between the base sheet 31 and the release liner 33 until the release liner 33 is peeled off, and constitutes part of the second laminate 37. By peeling the release liner 33 from the second laminate 37, a third laminate 35 including the base sheet 31 and the PSA 1 is obtained. In the third laminate 35, the surface of the PSA 1 is exposed to the outside. Another layer can be laminated on the exposed surface of the PSA 1. The other layer may be laminated directly, or may be laminated via an additional layer. The PSA 1 with its exposed surface may be attached or transferred to a target member.

[0211] Examples of the light 13, 34 include visible light and ultraviolet light. The light 13, 34 is preferably visible light or ultraviolet light having a wavelength shorter than 450 nm, and more preferably ultraviolet light. The light 13, 34 may include light having a wavelength in the range of 380 nm ± 30 nm, light having a wavelength in the range of 380 nm ± 20 nm, light having a wavelength in the range of 380 nm ± 10 nm, light having a wavelength in the range of 380 nm ± 5 nm, or even light having a wavelength of 380 nm.

[0212] The light 13, 34 may contain light having a wavelength in the same region as the absorption wavelength of the photoinitiator contained in the pressure-sensitive adhesive composition A. The light 13, 34 may be irradiated by filtering out short-wavelength light of 300 nm or less using a filter or the like. The light source of the light 13, 34 (reference numeral 38 in FIG. 3 ) is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined. The light source of the light 13, 34 may also include a black light.

[0213] The illuminance of the light 13, 34 irradiated onto the coating material 12 and the coating layer 32 is, for example, 1.0 to 30 mW / cm 2 The illuminance is 1.5 mW / cm 2 Above, 2.0mW / cm 2 or more, and even 2.5 mW / cm 2 The upper limit of the illuminance is 25 mW / cm 2 Below, 20mW / cm 2 Below, 15mW / cm 2 Below, 10mW / cm 2 Below, 7.5mW / cm 2 Below 5mW / cm 2 It may be the following:

[0214] The time for irradiating the light 13, 34 is, for example, 10 to 2000 seconds, and may be 60 seconds or more, 100 seconds or more, 250 seconds or more, 300 seconds or more, 400 seconds or more, or even 500 seconds or more. The upper limit of the time is not limited, and may be, for example, 5 hours or less, 4 hours or less, 3 hours or less, 2 hours or less, 1 hour or less, 3000 seconds or less, 2500 seconds or less, 2000 seconds or less, 1500 seconds or less, 1250 seconds or less, 1100 seconds or less, or even 1000 seconds or less. The light irradiation may be continuous or intermittent.

[0215] The integrated light amount of the irradiated light 13, 34 is, for example, 25 mJ / cm 2 or more, and 100 mJ / cm 2Above, 500mJ / cm 2 Above, 1000mJ / cm 2 Above, 2000mJ / cm 2 Above, 2500mJ / cm 2 Above, 3000mJ / cm 2 Above, 4000mJ / cm 2 or more, and even 5000 mJ / cm 2 The upper limit of the integrated light amount is not particularly limited, and may be, for example, 30,000 mJ / cm 2 or less, and 2 Below, 20000mJ / cm 2 Below, 15000mJ / cm 2 Below, 10000mJ / cm 2 Below, 5000mJ / cm 2 Below 3000 mJ / cm 2 It may be the following:

[0216] The light may be irradiated onto the coating object 12 and the coating layer 32 in multiple stages. The illuminance and / or the integrated amount of light in each stage may be the same or different from each other. Furthermore, the light source in each stage may be the same or different from each other.

[0217] The coated material 12 or the coating layer 32 may be irradiated with light when the dissolved oxygen concentration is 0.1 vol % or less, 0.05 vol % or less, or even 0.01 vol % or less. This method is particularly suitable for suppressing curing inhibition by oxygen. In order to reduce the dissolved oxygen concentration in the coated material 12 and the coating layer 32, the PSA composition A may be bubbled with an inert gas, such as nitrogen.

[0218] A resin sheet may be used for the base sheet 31 and the release liner 33. Examples of resins that may form the resin sheet are the same as the examples of resins that may form the base 11. The surfaces of the base sheet 31 and the release liner 33 that come into contact with the coating layer 32 may be subjected to a release treatment.

[0219] At least a part of the step of forming the pressure-sensitive adhesive C may be carried out in an inert gas atmosphere, for example, a nitrogen-purged atmosphere. Alternatively, a part of the step of forming the pressure-sensitive adhesive C may be carried out in an atmosphere having an oxygen concentration reduced compared to the air, for example, an oxygen concentration of 1 vol% or less, 0.5 vol% or less, 0.1 vol% or less, 0.08 vol% or less, 0.06 vol% or less, 0.05 vol% or less, 0.04 vol% or less, 0.03 vol% or less, 0.02 vol% or less, 0.01 vol% or less, or even less than 0.01 vol%. This method is particularly suitable for suppressing curing inhibition by oxygen.

[0220] At least a part of the step of forming the pressure-sensitive adhesive C may be carried out under atmospheric pressure. Also, a part of the step of forming the pressure-sensitive adhesive C may be carried out in a reduced pressure atmosphere, for example, a vacuum atmosphere.

[0221] Steps other than those described above may be performed in the formation of the adhesive C. For example, the coated object 12, the coating layer 32, or the adhesive C may be heated after irradiation with the light 13 or 34. Furthermore, for example, the coated object 12, the coating layer 32, or the adhesive C may be microwave-dried after irradiation with the light 12 or 34.

[0222] <<3. Adhesive-Backed Member>> The adhesive-backed member according to this embodiment includes an adhesive C and a member. The adhesive C is typically in contact with the member. The adhesive C may be disposed on at least a portion of the surface of the member. The adhesive C may also be contained inside the member. The type and shape of the member are not particularly limited. The member may be an optical member, in which case the adhesive-backed member according to this embodiment is an adhesive-backed optical member.

[0223] The member may be a film or a sheet, may be made of resin, metal, glass, or a composite material thereof, or may be a release liner.

[0224] Examples of the optical member include a polarizing film, a retardation film, a protective film, and an anti-reflection film. The optical member may be any of various optical members that can be included in an image display device.

[0225] The adhesive-backed member according to this embodiment can take various forms depending on the application.

[0226] <4. Cured Body> <4-1. Cured Body> The cured body according to this embodiment is formed from the pressure-sensitive adhesive C. In particular, the cured body is formed by further curing the pressure-sensitive adhesive C in a high-temperature environment. The cured body typically contains a material derived from the pressure-sensitive adhesive composition A. The cured body also typically contains a material derived from the pressure-sensitive adhesive C.

[0227] The tensile storage modulus E' of the cured product at 25°C is, for example, 5.0 x 10 6 Pa or more, and 7 Pa or more, 5.0×10 7 Pa or more, 1.0×10 8 Pa or more, and 8 Pa or more, 5.0×10 8 Pa or more, 8.0×10 8 Pa or more, 1.0×10 9 Pa or more, 1.5×10 9 Pa or more, and even 2.0 × 10 9 The upper limit of the tensile storage modulus E′ of the cured body may be, for example, 1.0×10 11 Pa or less, and 10 The tensile storage modulus E' of the pressure-sensitive adhesive C at 25°C before curing is typically 5.0 × 10 6 It is less than Pa.

[0228] The tensile storage modulus E' of a cured body at 25°C can be measured by the following method. First, a measurement sample made of the cured body is prepared. The measurement sample measures 300 mm long x 10 mm wide x 25 μm thick. Next, dynamic viscoelasticity measurement is performed on the measurement sample under the following measurement conditions. For dynamic viscoelasticity measurement, for example, an RSA-G2 manufactured by TA Instruments can be used. From the results of the dynamic viscoelasticity measurement, the tensile storage modulus of the measurement sample at 25°C is determined, and the obtained value is regarded as the tensile storage modulus E' of the cured body. Note that, assuming a Poisson's ratio of 0.5, the tensile storage modulus E' can be converted to the shear storage modulus G' based on the relational equation E' = 3G'. Measurement conditions: Deformation mode: Tensile Measurement frequency: 1 Hz Temperature range: 20°C to 150°C Heating rate: 5°C / min

[0229] The refractive index of the cured product is, for example, 1.40 or more, 1.43 or more, 1.45 or more, 1.48 or more, 1.50 or more, 1.51 or more, 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, or even 1.65 or more. The upper limit of the refractive index is, for example, 1.70 or less, 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, or even 1.65 or less. The refractive index of the cured product can be measured by the method described above for the pressure-sensitive adhesive C.

[0230] The shape of the cured product is not limited. The cured product may be in the form of a sheet, or in the form of a bulk having an irregular or predetermined shape. The cured product may have any shape depending on the application.

[0231] <4-2. Manufacturing Method of Cured Product> The cured product according to this embodiment can be formed by further curing the pressure-sensitive adhesive C in a high-temperature environment. The pressure-sensitive adhesive C may be heated while attached to the adherend. The temperature of the high-temperature environment can be set appropriately depending on the composition of the pressure-sensitive adhesive C (particularly the type and content of the thermal initiator), and may be, for example, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, 110°C or higher, or even 120°C or higher. The upper limit of the temperature of the high-temperature environment may be, for example, 200°C or lower, 180°C or lower, or even 160°C or lower. The heating time for the pressure-sensitive adhesive C is, for example, 1 minute to 5 hours. The pressure-sensitive adhesive C may be heated while a load is applied in the direction of contact between the pressure-sensitive adhesive C and the adherend.

[0232] The adhesive C suitable for forming a cured body contains a thermal initiator and a crosslinking agent (more specifically, a polyfunctional monomer having no ethylenically unsaturated groups). When the adhesive C contains a thermal acid generator as a thermal initiator, an acid is generated from the thermal acid generator in a high-temperature environment, and the acid can cause a reaction between a polymer of the monomer component M and the crosslinking agent. As the reaction progresses, the adhesive C hardens to form a cured body.

[0233] When the thermal initiator contains a compound that reacts with the polymer of the monomer component M and the crosslinking agent in a high-temperature environment, the reaction between the polymer of the monomer component M, the crosslinking agent, and the thermal initiator proceeds when the pressure-sensitive adhesive C is heated. In other words, the polymer of the monomer component M reacts with the crosslinking agent via the thermal initiator. This causes the pressure-sensitive adhesive C to harden and form a cured product.

[0234] 4-3. Cured Sheet The cured product according to this embodiment may be a sheet-like cured product, in other words, a cured sheet.

[0235] Cured sheets tend to be able to bond components together with high adhesive strength. For example, the cured sheet may have an adhesive strength of 5.0 MPa or more as determined by the following test. Test: Two pieces of glass are bonded together via an adhesive sheet. The adhesive sheet is cured to form a cured sheet. The two pieces of glass are pulled in directions away from each other at a pulling rate of 10 mm / min in an atmosphere of 23°C and 50% RH. The adhesive strength can be determined based on the maximum stress at this time.

[0236] Specifically, the adhesive strength of the cured sheet can be measured by the following method. First, the above-mentioned pressure-sensitive adhesive sheet is cut into a size of 10 mm length x 10 mm width, and one surface of the pressure-sensitive adhesive sheet is bonded to a first glass. Next, the other surface of the pressure-sensitive adhesive sheet is bonded to a second glass. This results in a measurement sample in which the first glass and the second glass are bonded together via the pressure-sensitive adhesive sheet.

[0237] Next, the measurement sample is heated to harden the pressure-sensitive adhesive sheet and form a cured sheet. The heating conditions for the measurement sample are not particularly limited as long as a cured sheet is formed. As an example, the measurement sample may be heated for 2 hours in a dryer at 100°C with a 1 kg weight placed on it.

[0238] Next, the measurement sample is attached to an aluminum block using an adhesive (e.g., Cemedine Hi-Super 30). After the adhesive is cured, the measurement sample is placed in a commercially available tensile tester. The first and second glasses are pulled away from each other at a pulling rate of 10 mm / min in an atmosphere of 23°C and 50% RH. The adhesive strength can be determined based on the maximum stress at this time.

[0239] The adhesive strength of the cured sheet may be 3.0 MPa or more, 4.0 MPa or more, 5.0 MPa or more, 6.0 MPa or more, 7.0 MPa or more, 8.0 MPa or more, 9.0 MPa or more, 10.0 MPa or more, or even 11.0 MPa or more. The upper limit of the adhesive strength of the cured sheet may be, for example, 30.0 MPa or less, 25.0 MPa or less, 20.0 MPa or less, or even 15.0 MPa or less.

[0240] The thickness of the cured sheet may be, for example, 100 μm or less, 70 μm or less, 50 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, or even 15 μm or less. The lower limit of the thickness of the cured sheet may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 8 μm or more, or even 12 μm or more. In some cases, the thickness of the cured sheet may be 15 μm or more, 20 μm or more, 30 μm or more, 35 μm or more, or even 40 μm or more.

[0241] For the method for producing the cured sheet according to this embodiment, the explanation in the section <4-2. Method for producing the cured body> can be cited.

[0242] 5. Member Comprising the Cured Body A member comprising the cured body according to the present embodiment comprises the cured body according to the present embodiment. The cured body is typically located on the surface and / or inside the member. The type and shape of the member are not particularly limited. The member may be an optical member. Examples of optical members are as described above. Depending on the application, the member comprising the cured body according to the present embodiment may take various forms.

[0243] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0244] <<Preparation of Pressure-Sensitive Adhesive Composition>> <Preparation of Monomer Syrup> [Monomer Syrup A1] 100 parts by weight of 2-ethylhexyl acrylate (2EHA) and 1 part by weight of 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, manufactured by IGM Resins) as a photoinitiator were placed in a four-necked flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A1 in which the 2EHA was partially polymerized. Monomer Syrup A1 contained 2EHA as a monomer and a polymer of 2EHA. The ultraviolet light irradiation conditions were an illuminance of 7.6 mW / cm 2 , cumulative light intensity 2700 mJ / cm 2 The illuminance of the ultraviolet light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) at a position about 50 mm away from the liquid surface of the polymerization solution in the flask (the same was true for the preparation of monomer syrups A2 to A8).

[0245] [Monomer Syrup A2] 100 parts by weight of 2EHA, 0.05 parts by weight of Omnirad 184 as a photoinitiator, and 0.1 parts by weight of α-thioglycerol (α-TGR) as a chain transfer agent were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A2 in which the 2EHA was partially polymerized. Monomer Syrup A2 contained 2EHA as a monomer and a polymer of 2EHA. The ultraviolet light irradiation conditions were an illuminance of 7.6 mW / cm. 2 , cumulative light intensity 33,300 mJ / cm 2 It was decided.

[0246] [Monomer syrup A3] UV irradiation conditions: illuminance 7.6 mW / cm 2 , cumulative light intensity 2900 mJ / cm 2 Monomer syrup A3 was obtained by partially polymerizing 2EHA in the same manner as in the preparation of monomer syrup A1, except that the monomer syrup A3 contained 2EHA as a monomer and a polymer of 2EHA.

[0247] [Monomer Syrup A4] 100 parts by weight of 2EHA and 0.5 parts by weight of Omnirad 184 as a photoinitiator were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A4, in which the 2EHA was partially polymerized. Monomer Syrup A4 contained 2EHA as a monomer and a polymer of 2EHA. The ultraviolet light irradiation conditions were an illuminance of 7.6 mW / cm. 2 , cumulative light intensity 3100 mJ / cm 2 It was decided.

[0248] [Monomer Syrup A5] 100 parts by weight of 2EHA and 0.05 parts by weight of Omnirad 184 as a photoinitiator were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to partially polymerize the 2EHA, yielding Monomer Syrup A5. Monomer Syrup A5 contained 2EHA as a monomer and a 2EHA polymer. The ultraviolet light irradiation conditions were an illuminance of 78.6 mW / cm. 2, cumulative light intensity 8600 mJ / cm 2 It was decided.

[0249] [Monomer syrup A6] UV irradiation conditions: illuminance 78.6 mW / cm 2 , cumulative light intensity 20100 mJ / cm 2 Monomer syrup A6 was obtained by partially polymerizing 2EHA in the same manner as in the preparation of Monomer syrup A2, except that the following was used: Monomer syrup A6 contained 2EHA as a monomer and a polymer of 2EHA.

[0250] [Monomer Syrup A7] 100 parts by weight of phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") and 0.05 parts by weight of 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins) as a photoinitiator were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A7, in which POB-A was partially polymerized. Monomer Syrup A7 contained POB-A as a monomer and a polymer of POB-A. The ultraviolet light irradiation conditions were an illuminance of 7.6 mW / cm 2 , cumulative light intensity 14000 mJ / cm 2 It was decided.

[0251] [Monomer Syrup A8] 100 parts by weight of 2EHA and 0.05 parts by weight of Omnirad 184 as a photoinitiator were placed in a four-neck flask. Next, the liquid in the flask was irradiated with ultraviolet light under a nitrogen atmosphere to obtain Monomer Syrup A8, in which the 2EHA was partially polymerized. Monomer Syrup A8 contained 2EHA as a monomer and a 2EHA polymer. The ultraviolet light irradiation conditions were an illuminance of 7.6 mW / cm. 2 , cumulative light intensity 1100 mJ / cm 2 It was decided.

[0252] <Evaluation of Monomer Syrups> The following evaluations were carried out for each of the prepared monomer syrups.

[0253] [Polymer Fraction] The polymer fraction of the monomer syrup was determined by heating the prepared monomer syrup at 130°C for 2 hours to volatilize the monomer components, and using the weight W1 (g) of the monomer syrup before volatilization and the weight W2 (g) of the non-volatile content after volatilization, according to the formula: polymer fraction (wt%) = (W2 / W1) x 100. However, for Monomer Syrup A7, which contains POB-A as a monomer component, the monomer components were volatilized by heating at 130°C for 2 hours under vacuum, taking into account the high boiling point of POB-A.

[0254] [Weight-Average Molecular Weight and Molecular Weight Distribution] The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of polymer B contained in the monomer syrup were evaluated by gel permeation chromatography (GPC). The evaluation was performed on a solution obtained by preparing a 0.3 g / L tetrahydrofuran (THF) solution of the monomer syrup to be evaluated, leaving it overnight, and filtering the solution through a 0.45 μm membrane filter. The measurement equipment and measurement conditions were as follows: Analyzer: HLC-8320GPC manufactured by TOSOH; Column: TSKgel GMH-H(S) x 2 manufactured by TOSOH; Column size: 7.8 mm ID x 300 mm; Eluent: THF; Flow rate: 0.5 mL / min; Detector: Refractive index (RI); Column temperature: 40°C; Injection volume: 100 μL; Standard sample: Polystyrene (PS).

[0255] The evaluation results are shown in Table 1 below.

[0256]

[0257] <Preparation of Pressure-Sensitive Adhesive Composition> [Pressure-Sensitive Adhesive Composition B1] 100 parts by weight of the monomer syrup A1, 0.1 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 0.5 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins) as a photoinitiator, and 1 part by weight of 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one (Omnirad 127, manufactured by IGM Resins) as a colorant, and 15 parts by weight of an ethyl acetate dispersion of carbon black (solid content 22% by weight) were added to obtain a pressure-sensitive adhesive composition B1.

[0258] [Adhesive compositions B2 to B20] Adhesive compositions B2 to B20 were obtained in the same manner as adhesive composition B1, except that the types and amounts of monomer syrup, crosslinking agent, photoinitiator, thermal initiator, colorant, and curing accelerator were changed as shown in Table 2 below. The colorant column in Table 2 shows the blend amount as a carbon black solution. The polymer fraction and Mw and Mw / Mn of polymer B in each adhesive composition were the same as the polymer fraction and Mw and Mw / Mn of polymer B in the monomer syrup contained in each adhesive composition, respectively. For adhesive compositions B19 and B20, a monomer was further added in addition to the above materials.

[0259]

[0260] The abbreviations in Table 2 are as follows: (Monomer) 4HBAGE: 4-hydroxybutyl acrylate glycidyl ether (Crosslinking agent) NDDA: 1,9-nonanediol diacrylate GT401: butanetetracarboxylic acid tetra(3,4-epoxycyclohexylmethyl)-modified ε-caprolactone (manufactured by Daicel Corporation, trade name "Epolead GT401") (Photoinitiator) Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") Omnirad 127: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one (manufactured by IGM Resins, trade name "Omnirad 127") (Thermal initiator) AIBN: 2,2'-azobisisobutyronitrile (azo initiator) SI-B3: 4-hydroxyphenyl)(methyl)sulfonium tetrakis(pentafluorophenyl)borate (thermal acid generator: manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Sanaid SI-B3") (curing accelerator) IPEMA: isoprenyl methacrylate (manufactured by Kuraray Co., Ltd.) DPNG: diprenyl glycerin ether (manufactured by Kuraray Co., Ltd.) MT PE1: pentaerythritol tetrakis(3-mercaptobutyrate) (manufactured by Karenz Co., Ltd., trade name "Karenz MT PE1")

[0261] <Preparation of Pressure-Sensitive Adhesive> (Example 1) Pressure-Sensitive Adhesive Composition B1 was applied to one side of a substrate sheet (PET separator, manufactured by Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. Next, from the side of the coating layer, an illuminance of 2.5 mW / cm was applied under a nitrogen atmosphere. 2 and an integrated light intensity of 2400 mJ / cm 2 The laminate was irradiated with ultraviolet light from a black light source under the conditions of 130°C. After completion of irradiation, the laminate of the substrate sheet and the coating layer was maintained for 3 minutes in a heating furnace maintained at 130°C. The coating layer was cured as described above to obtain the pressure-sensitive adhesive of Example 1 (sheet-like, 30 μm thick). The illuminance of the ultraviolet light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) near the surface of the coating layer where the ultraviolet light was incident.

[0262] (Examples 2 to 18) PSA's of Examples 2 to 18 (each in the form of a sheet having a thickness of 30 μm) were obtained in the same manner as in Example 1, except that the PSA compositions shown in Table 3 below were used instead of PSA composition B1.

[0263] Comparative Examples 1 and 2 An attempt was made to prepare a 30 μm thick sheet-shaped adhesive in the same manner as in Example 1, except that the adhesive compositions shown in Table 3 below were used instead of adhesive composition B1. However, it was difficult to cure any of the adhesive compositions, and it was not possible to prepare an adhesive.

[0264]

[0265] <Evaluation of Pressure-Sensitive Adhesives> The following properties were evaluated for each of the pressure-sensitive adhesives prepared: Furthermore, the coating properties of each of the pressure-sensitive adhesive compositions of the Examples and Comparative Examples were evaluated.

[0266] [Polymerization rate] The polymerization rate of the monomer component in the adhesive was calculated from the change in weight of the adhesive before and after heat drying at 130°C for 2 hours. Specifically, the weight of the adhesive immediately after peeling from the substrate sheet was calculated as W A (weight before drying), and the weight of the adhesive at the time of cooling at room temperature (23°C) for about 20 minutes after the heating is W B (weight after drying) is calculated by the formula: polymerization rate (%) = W B / W A × 100. However, for the PSA of Example 13 formed from PSA composition B13 containing POB-A as a monomer component, taking into consideration the high boiling point of POB-A, the weight was calculated from the change in the weight of the PSA before and after heat drying at 130°C under vacuum for 2 hours.

[0267] [Total Light Transmittance] The total light transmittance of the pressure-sensitive adhesive was evaluated as follows. An alkali-free glass plate (thickness: 0.7 to 0.8 mm, total light transmittance: 92%, chromaticity: b * 0.10) was attached to the other surface with a cycloolefin (COP) film to obtain a test piece in which the pressure-sensitive adhesive was sandwiched between the alkali-free glass and the cycloolefin film.

[0268] Next, the test piece was placed in a pressure degassing apparatus (autoclave) and autoclave-treated for 30 minutes under conditions of a temperature of 50°C and a pressure of 0.5 MPa. Next, the treated test piece was left in an environment of a temperature of 23°C and a relative humidity of 50% for 24 hours. Next, in a measurement environment of 23°C, the total light transmittance of the test piece for light with wavelengths of 300 nm to 800 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Technologies).

[0269] [L * a * b * ] Adhesive L * Value, a * value, b * The values ​​were evaluated as follows. The same autoclaved test specimens prepared in the evaluation of total light transmittance were left for 24 hours in an environment at a temperature of 23°C and a relative humidity of 50%, and then the transmittance spectrum of the test specimens for light with wavelengths of 300 nm to 800 nm was measured using an ultraviolet-visible-near-infrared spectrophotometer (UH4150, manufactured by Hitachi High-Technologies). The measurement was carried out at 23°C. Next, the lightness L was calculated from the obtained spectral data using a color calculation program (UV Solutions, manufactured by Hitachi High-Technologies). * and chromaticity a * The absolute value of (|a * |), b * The absolute value of (|b * The chromaticity a * , b * When measuring, reference data (blank data) measured without placing a test piece in the measurement chamber of the ultraviolet-visible-near-infrared spectrophotometer was used as the standard.

[0270] [Refractive Index] The refractive index of the adhesive was evaluated as follows. The adhesive to be evaluated was attached to the prism of a digital refractometer (Atago Co., Ltd., Digital Refractometer RX-9000α) so as to uniformly cover the prism. The attachment was performed so as to avoid any exposed areas on the prism and to prevent air bubbles from forming between the adhesive and the prism. Next, the refractive index of the adhesive (measured at 25°C, in other words, nD25) was determined using a reflection method. To improve measurement accuracy, the measurement was performed 15 minutes after attachment of the adhesive in a 25°C environment. In addition, seven measurements were performed with the adhesive attached, and the refractive index was determined as the average of five measurements after removing the maximum and minimum values.

[0271] [Adhesive Strength] The adhesive strength of the pressure-sensitive adhesive was evaluated by the method described above. The substrate sheet used for forming the pressure-sensitive adhesive was used as it was for evaluation.

[0272] [Coatability] The coatability of the pressure-sensitive adhesive composition was also evaluated. The evaluation was carried out as follows. The pressure-sensitive adhesive composition to be evaluated was applied to one side of a substrate sheet (PET separator, manufactured by Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. The width of the coating layer was 300 mm, the length was 250 mm, and the thickness after curing was adjusted to 30 μm. The coating speed was 2 to 3 m / min. The surface of the formed coating layer was visually observed under a visible light illumination environment to confirm the presence and extent of coating streaks. The evaluation criteria are as follows: A: Good coatability, not corresponding to B below. B: 15 or more streaks with a width of 1 mm or more and a length of 3 cm or more were observed across the width of the coating layer in the machine direction during coating.

[0273] The evaluation results of the adhesive are shown in Table 4 below.

[0274]

[0275] As shown in Table 4, each of the pressure-sensitive adhesive compositions of the Comparative Examples was difficult to cure, but each of the pressure-sensitive adhesive compositions of the Examples was able to produce a sheet-shaped pressure-sensitive adhesive.

[0276] The photocurable pressure-sensitive adhesive composition of the present invention can be used for the same applications as conventional photocurable pressure-sensitive adhesive compositions. Examples of applications include pressure-sensitive adhesives and pressure-sensitive adhesive sheets for optical applications, optical laminates, or image display devices. However, the applications are not limited to the above examples.

Claims

1. A photocurable pressure-sensitive adhesive composition comprising a monomer component M, a polymer of said monomer component M, a photoinitiator, and a colorant, wherein the proportion of said polymer to the total of said monomer component M and said polymer is 7.5 wt % or more.

2. The photocurable adhesive composition according to claim 1, wherein the proportion of said polymer to the total of said monomer component M and said polymer is 80% by weight or less.

3. The photocurable adhesive composition according to claim 1, wherein the proportion of said polymer to the total of said monomer component M and said polymer is 40% by weight or less.

4. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the content of the (meth)acrylic monomer in the monomer component M is 50% by weight or more.

5. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the monomer component M includes a monomer a having a double bond-containing ring.

6. The photocurable pressure-sensitive adhesive composition according to claim 5, wherein the double bond-containing ring is an aromatic ring.

7. The photocurable adhesive composition according to claim 5, wherein the monomer a has two or more of the double bond-containing rings in the side chain.

8. The photocurable adhesive composition described in claim 7, wherein the monomer a has a structure in its side chain in which a first double bond-containing ring and a second double bond-containing ring contained in the two or more double bond-containing rings are bonded via a linking group.

9. The photocurable adhesive composition according to claim 5, wherein the monomer a is phenoxybenzyl acrylate.

10. The photocurable pressure-sensitive adhesive composition according to claim 1, comprising the photoinitiator having in its molecule the chemical structure shown in the following formula (1), where "*" in formula (1) indicates the bonding site to another atom.

11. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the content of the photoinitiator in the photocurable pressure-sensitive adhesive composition is 0.01 to 10 parts by weight per 100 parts by weight of the monomer component M.

12. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the colorant is a black colorant.

13. The photocurable pressure-sensitive adhesive composition according to claim 1, further comprising a thermal acid generator.

14. An adhesive formed from the photocurable adhesive composition according to any one of claims 1 to 13.

15. The pressure-sensitive adhesive according to claim 14, wherein the polymerization rate of the monomer component M is 95.0% or more.

16. CIE1976 (L) as defined in JIS Z8781-4:2013 * , a * , b * ) L in color space * The adhesive according to claim 14, having a color value of 60.0 or less, as expressed by the following formula:

17. a of the above color space * The absolute value of the chromaticity of the color space is 10.0 or less. * The adhesive according to claim 16, having a color value of 10.0 or less, expressed as an absolute value of 18. The adhesive of claim 14, having a refractive index of 1.50 or greater.

19. The adhesive of claim 14, having a total light transmittance of less than 5%.

20. The adhesive of claim 14, which contains a thermal acid generator.

21. An adhesive-backed member comprising the adhesive of claim 14 and a member.

22. The adhesive-backed member according to claim 21, which is an adhesive-backed optical member.

23. A method for producing an adhesive, comprising irradiating the photocurable adhesive composition according to any one of claims 1 to 13 with light to cure the photocurable adhesive composition.

24. A cured product formed from the adhesive of claim 14.

25. A member comprising the hardened body according to claim 24.

26. The element of claim 25, which is an optical element.

27. A method for producing a cured product, comprising further curing the adhesive according to claim 14 in a high-temperature environment.

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