Emulsion-based pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive

Abstract

To provide a pressure-sensitive adhesive composition suitable for producing a pressure-sensitive adhesive sheet having a high refractive index and improved adhesive force.SOLUTION: An emulsion-based adhesive composition according to an embodiment of the present invention contains a polymer A containing a constituent unit derived from a monomer a having a double bond-containing ring, and a colorant. The PSA sheet formed from the emulsion-based PSA composition has a refractive index of 1.50 or higher. A pressure-sensitive adhesive according to an embodiment of the present invention is formed from the above-mentioned emulsion-based pressure-sensitive adhesive composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an emulsion-based pressure-sensitive adhesive composition, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and an optical member. [Background technology]

[0002] Generally, adhesives are soft solids (viscoelastic bodies) at temperatures around room temperature and easily adhere to adherends when pressure is applied. Taking advantage of these properties, adhesives are widely used for purposes such as joining, fixing, and protecting components in electronic devices such as mobile phones.

[0003] Examples of electronic devices include image display devices such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices). As an example, a sheet made of an adhesive (adhesive sheet) is used as an optical component in the image display device. Patent Document 1 discloses an example of an adhesive sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-143639 Summary of the Invention [Problem to be solved by the invention]

[0005] In electronic devices, the object (adherend) to which the pressure-sensitive adhesive sheet is attached tends to have a high refractive index. If there is a large difference in refractive index between the adherend and the pressure-sensitive adhesive sheet, light reflection occurs at the interface between them, which can cause malfunctions and poor response of the electronic device. However, according to the studies of the present inventors, pressure-sensitive adhesive sheets with high refractive indexes have room for improvement in terms of adhesive strength.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition that has a high refractive index and is suitable for producing a pressure-sensitive adhesive sheet with improved adhesive strength. [Means for solving the problem]

[0007] [1] The emulsion-based pressure-sensitive adhesive composition according to an embodiment of the present invention comprises: a polymer A containing a structural unit derived from a monomer a having a double bond-containing ring; A colorant; An emulsion-based pressure-sensitive adhesive composition comprising: The refractive index of the pressure-sensitive adhesive sheet formed from the emulsion-based pressure-sensitive adhesive composition is 1.50 or more. [2] In the emulsion-based pressure-sensitive adhesive composition described in [1] above, the monomer a may contain the (meth)acrylic monomer having the double bond-containing ring. [3] In the emulsion-based pressure-sensitive adhesive composition according to the above [1] or [2], the double bond-containing ring may be an aromatic ring. [4] In the emulsion-based pressure-sensitive adhesive composition according to any one of the above [1] to [3], the monomer a may have two or more of the double bond-containing rings. [5] In the emulsion-based pressure-sensitive adhesive composition according to any one of [1] to [4] above, the content of the structural unit derived from the monomer a in the polymer A may be 10 wt % or more. [6] In the emulsion-based pressure-sensitive adhesive composition according to any one of [1] to [5] above, the polymer A may further comprise at least one selected from the group consisting of a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from a carboxyl group-containing monomer. [7] The emulsion-based pressure-sensitive adhesive composition according to any one of [1] to [6] above may contain particles containing the polymer A. [8] In the emulsion-based pressure-sensitive adhesive composition described in [7] above, the particles may have an average particle size of 500 nm or less. [9] In the emulsion-based pressure-sensitive adhesive composition according to the above [7] or [8], the particles may have a polydispersity index of 0.2 or less.

[10] In the emulsion-based pressure-sensitive adhesive composition according to any one of [1] to [9] above, the colorant may contain carbon black.

[11] The emulsion-based PSA composition according to any one of the above items [1] to

[10] may further contain a thickener.

[12] The emulsion-based pressure-sensitive adhesive composition according to any one of the above items [1] to

[11] may contain water as a dispersion medium.

[13] A pressure-sensitive adhesive according to an embodiment of the present invention is formed from the emulsion-based pressure-sensitive adhesive composition according to any one of [1] to

[12] above.

[14] An adhesive sheet according to an embodiment of the present invention is made from the adhesive described in

[13] above.

[15] In the pressure-sensitive adhesive sheet according to the above item

[14] , the amount of residual monomer may be 1000 wtppm or less.

[16] The pressure-sensitive adhesive sheet according to the above

[14] or

[15] may have a peel strength of 1.5 N / 10 mm or more as determined by the following test. Test: The pressure-sensitive adhesive sheet is attached to alkali-free glass and peeled from the alkali-free glass at a peeling speed of 300 mm / min and a peeling angle of 180° in an atmosphere of 23°C and 50% RH. The maximum force required at this time is determined as the peel force.

[17] The pressure-sensitive adhesive sheet according to any one of

[14] to

[16] above may have a glass transition temperature of 30°C or lower.

[18] The pressure-sensitive adhesive sheet according to any one of the above items

[14] to

[17] may have a transmittance of 50% or less for light with a wavelength of 300 nm to 800 nm.

[19] The pressure-sensitive adhesive sheet according to any one of the above items

[14] to

[18] may have a gel fraction of 80% or less.

[20] The pressure-sensitive adhesive sheet according to any one of

[14] to

[19] above may have a thickness of 100 μm or less.

[21] An optical member according to an embodiment of the present invention comprises the pressure-sensitive adhesive described in

[13] above.

[22] The adhesive according to an embodiment of the present invention comprises: a polymer including a structural unit derived from a monomer a having a double bond-containing ring; A colorant; Includes:

[23] In the pressure-sensitive adhesive according to the above

[22] , the monomer a may contain phenoxybenzyl acrylate.

[24] In the pressure-sensitive adhesive according to the above

[22] or

[23] , the refractive index of a pressure-sensitive adhesive sheet made from the pressure-sensitive adhesive may be 1.50 or more.

[25] The PSA according to any one of the above items

[22] to

[24] may be formed from an emulsion-based PSA composition.

[26] An optical member according to an embodiment of the present invention comprises the pressure-sensitive adhesive according to any one of

[22] to

[25] above. [Effects of the Invention]

[0008] According to an embodiment of the present invention, it is possible to provide a pressure-sensitive adhesive composition that has a high refractive index and is suitable for producing a pressure-sensitive adhesive sheet with improved adhesive strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing an example of a laminate including a pressure-sensitive adhesive sheet of the present invention. [Figure 3] FIG. 2 is a schematic cross-sectional view showing another example of a laminate including the pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is the commonly used SI unit for indicating weight, and vice versa.

[0011] 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".

[0012] 1. Emulsion-based pressure-sensitive adhesive composition The emulsion-based pressure-sensitive adhesive composition according to an embodiment of the present invention comprises a polymer A containing a structural unit derived from a monomer a having a double bond-containing ring, and a colorant. Furthermore, a pressure-sensitive adhesive sheet formed from the emulsion-based pressure-sensitive adhesive composition has a refractive index of 1.50 or more.

[0013] In this specification, "emulsion-based PSA composition" refers to a PSA composition containing a dispersion medium and a polymer emulsified in the dispersion medium. In this specification, an emulsion-based PSA composition containing water as the dispersion medium may be referred to as a water-dispersed PSA composition, and a polymer emulsified in water may be referred to as a water-dispersed polymer. In addition, in this specification, "emulsion-based PSA composition" may be simply referred to as "PSA composition."

[0014] The refractive index of the pressure-sensitive adhesive sheet can be measured by the following method. First, the pressure-sensitive adhesive composition is thoroughly dried to form a pressure-sensitive adhesive sheet. At this time, the thickness of the pressure-sensitive adhesive sheet is not particularly limited as long as it does not affect the refractive index measurement results, and is, for example, 25 μm. Examples of conditions for producing the pressure-sensitive adhesive sheet include those described below in Section <3-2. Method for producing pressure-sensitive adhesive sheet>. The drying conditions for the pressure-sensitive adhesive composition are set, for example, so that the content of the dispersion medium remaining in the obtained pressure-sensitive adhesive sheet is 1000 wtppm or less, preferably 500 wtppm or less.

[0015] Next, the refractive index of the surface of the adhesive sheet is measured using a prism coupler at a measurement temperature of 25°C and a measurement wavelength of 594 nm. For adhesive sheets with a thickness of less than 20 μm, measurement in optical propagation mode is generally suitable. For adhesive sheets 1 with a thickness of 20 μm or more, measurement in critical angle mode is generally suitable. A commercially available measuring device can be used as the prism coupler, such as the Model 2010 / M prism coupler manufactured by Metricon or an equivalent. The measured value obtained by the above measurement can be considered as the refractive index of the adhesive sheet.

[0016] The refractive index of the pressure-sensitive adhesive sheet is preferably 1.51 or more, and may be 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, or even 1.61 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. As mentioned above, in electronic devices, the object (adherend) to which the pressure-sensitive adhesive sheet is attached tends to have a high refractive index. Using a pressure-sensitive adhesive sheet with a high refractive index to bond the adherend is advantageous in reducing reflected light at the interface between the adherend and the pressure-sensitive adhesive sheet.

[0017] ≪1-1. Polymer A≫ As described above, the pressure-sensitive adhesive composition according to the embodiment of the present invention contains polymer A. Polymer A is typically a base polymer, and is emulsified in the pressure-sensitive adhesive composition. Examples of polymer A include (meth)acrylic polymers, urethane polymers, silicone polymers, and rubber polymers. Polymer A is preferably a (meth)acrylic polymer.

[0018] <1-1-a. Monomer a having a double bond-containing ring> As described above, polymer A contains a structural unit derived from monomer a having a double bond-containing ring. Monomer a is a component suitable for improving the refractive index of the pressure-sensitive adhesive sheet. Monomer a may be of only one type, or may be of two or more types. 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 include carbon-carbon double bonds, carbon-heteroatom double bonds, and heteroatom-heteroatom double bonds. Examples of heteroatoms include nitrogen, sulfur, and oxygen.

[0019] 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.

[0020] 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. 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 nitrogen, sulfur, and oxygen. The heteroatom may be either or both of nitrogen and sulfur. 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.

[0021] 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 is, 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.

[0022] 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. In other words, the monomer a may have two or more double bond-containing rings. 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.

[0023] In the monomer a, the double bond-containing ring is preferably located in a side chain. In other words, 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.

[0024] Examples of the ethylenically unsaturated group are a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of polymerization reactivity, a (meth)acryloyl group is preferred, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is 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. Examples of the (meth)acrylic monomer having a double bond-containing ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0025] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. Examples of the linking group include one or more 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.

[0026] 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.

[0027] 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) is particularly suitable for increasing the refractive index of the pressure-sensitive adhesive sheet.

[0028] 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 later) is preferably used.

[0029] The linking group 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 have to 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 groups 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-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth)acrylate, thiophenoxybenzyl (meth)acrylate, and benzyl benzyl (meth)acrylate.

[0030] Examples of monomers having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, and vinyl group-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0031] 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.

[0032] 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.

[0033] 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. 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.

[0034] 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.

[0035] 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).

[0036] Examples of aromatic ring-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-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; carbon-containing 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.

[0037] 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 such a 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.

[0038] Monomer a may include a high refractive index monomer. In this specification, the high refractive index monomer refers to a monomer having a refractive index of 1.51 or more, 1.53 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, 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.

[0039] 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, this nominal value can be used as the refractive index.

[0040] 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), and 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. It is preferable that monomer a contains phenoxybenzyl acrylate as a high refractive index monomer.

[0041] The content of the structural unit derived from monomer a in polymer A is, for example, 10% by weight or more, and may be 20% by weight or more, 25% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or even 95% by weight or more. The upper limit of this content is, for example, 99.5% by weight or less, and may be 99.0% by weight or less. The content is preferably 25% by weight to 99.0% by weight.

[0042] <1-1-b. (Meth)acrylic acid alkyl esters, carboxyl group-containing monomers> In addition to the structural unit derived from monomer a, polymer A preferably further contains at least one selected from the group consisting of a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from a carboxyl group-containing monomer, and particularly preferably contains a structural unit derived from a carboxyl group-containing monomer. In particular, the structural unit derived from a carboxyl group-containing monomer can contribute to stabilizing polymer A (more specifically, particles containing polymer A described below) in the pressure-sensitive adhesive composition.

[0043] The (meth)acrylic acid alkyl ester may be of one type only, or of two or more types. The (meth)acrylic acid alkyl ester preferably has 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, 2-ethylhexyl (meth)acrylate, and the like. 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 n-butyl (meth)acrylate.

[0044] The content of structural units derived from a (meth)acrylic acid alkyl ester in polymer A is, for example, 90% by weight or less, and may be 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, or even 10% by weight or less. The content may be, for example, 0.1% by weight or more, 1% by weight or more, or even 5% by weight or more. Polymer A may not contain structural units derived from a (meth)acrylic acid alkyl ester.

[0045] The carboxyl group-containing monomer has at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group are the same as those described above in the description of monomer a. The carboxyl group-containing monomer may be a (meth)acrylic monomer.

[0046] The carboxyl group-containing monomer may be of one kind or of two or more kinds. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

[0047] The content of structural units derived from carboxyl group-containing monomers in polymer A is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Polymer A may not contain structural units derived from carboxyl group-containing monomers.

[0048] <1-1-c. Reactive emulsifiers> Polymer A may further contain a structural unit derived from a reactive emulsifier. In this specification, reactive emulsifier refers to an emulsifier (surfactant) containing an ethylenically unsaturated group. Examples of the ethylenically unsaturated group are the same as those described above in the description of monomer a. The reactive emulsifier functions, for example, as an emulsifier for synthesizing polymer A by emulsion polymerization, and can also function as a monomer copolymerized with monomer a, etc. Use of a reactive emulsifier tends to prevent the emulsifier from bleeding out from the pressure-sensitive adhesive sheet, and to prevent a decrease in adhesive strength.

[0049] The reactive emulsifier may be one type only, or two or more types. Examples of the reactive emulsifier include an emulsifier (non-reactive emulsifier) ​​described later in the section <<1-4. Emulsifiers>> to which a group containing an ethylenically unsaturated group (for example, a propenyl group or an allyl ether group) has been introduced. The reactive emulsifier includes, for example, at least one selected from the group consisting of anionic reactive emulsifiers and nonionic reactive emulsifiers, and preferably includes an anionic reactive emulsifier.

[0050] Specific examples of anionic reactive emulsifiers include alkyl ether emulsifiers (commercially available products include, for example, Aqualon KH1025, KH-05, KH-10, and KH-20 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Adeka Reasoap SR-10N and SR-20N manufactured by ADEKA Co., Ltd., and Latemul PD-104 manufactured by Kao Co., Ltd.); sulfosuccinate ester emulsifiers (commercially available products include, for example, Latemul S-120, S-120A, S-180P, and S-180A manufactured by Kao Co., Ltd., and Eleminol JS-20 manufactured by Sanyo Chemical Industries, Ltd.); alkyl phenyl ether emulsifiers or alkyl phenyl ester emulsifiers (commercially available products include, for example, Aqualon H-2855A and H-3855B manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and Examples of such surfactants include H-3855C, H-3856, HS-05, HS-10, HS-20, HS-30, HS-1025, BC-05, BC-10, BC-20, and ADEKA's ADEKA REASOAP SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, and SE-20N; (meth)acrylate sulfate esters (commercially available products include Antox MS-60 and MS-2N manufactured by Nippon Nyukazai Co., Ltd., and Eleminol RS-30 manufactured by Sanyo Chemical Industry Co., Ltd.); and phosphate esters (commercially available products include H-3330PL manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and ADEKA's ADEKA REASOAP PP-70).

[0051] Specific examples of nonionic reactive surfactants include alkyl ether surfactants (commercially available products include, for example, Adeka Reasoap ER-10, ER-20, ER-30, and ER-40 manufactured by ADEKA, and Latemul PD-420, PD-430, and PD-450 manufactured by Kao); alkyl phenyl ether surfactants or alkyl phenyl ester surfactants (commercially available products include, for example, Aqualon RN-10, RN-20, RN-30, and RN-50 manufactured by Dai-ichi Kogyo Seiyaku, and Adeka Reasoap NE-10, NE-20, NE-30, and NE-40 manufactured by ADEKA); and (meth)acrylate sulfate ester surfactants (commercially available products include, for example, RMA-564, RMA-568, and RMA-1114 manufactured by Nippon Nyukazai).

[0052] The content of structural units derived from reactive surfactants in polymer A is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Polymer A may not contain structural units derived from reactive surfactants.

[0053] <1-1-d. Alkoxysilyl Group-Containing Monomers> Polymer A may further contain a structural unit derived from an alkoxysilyl group-containing monomer. The alkoxysilyl group-containing monomer has at least one alkoxysilyl group and at least one ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer a. The alkoxysilyl group-containing monomer may be a (meth)acrylic monomer.

[0054] The alkoxysilyl group-containing monomer undergoes hydrolysis during emulsification and / or emulsion polymerization in the presence of water, for example, to form a silanol group (—SiOH). That is, when polymer A is synthesized using an alkoxysilyl group-containing monomer in the presence of water, the structural unit derived from the alkoxysilyl group-containing monomer has, for example, a silanol group. In this case, when a pressure-sensitive adhesive sheet is produced from the pressure-sensitive adhesive composition, the silanol groups undergo a condensation reaction with each other, thereby crosslinking polymer A (silanol crosslinking). According to this method, a structure in which particles containing polymer A, described below, are crosslinked with each other can be formed in the pressure-sensitive adhesive sheet.

[0055] Specific examples of alkoxysilyl group-containing monomers include (meth)acryloyloxymethyl-trimethoxysilane, (meth)acryloyloxymethyl-triethoxysilane, 2-(meth)acryloyloxyethyl-trimethoxysilane, 2-(meth)acryloyloxyethyl-triethoxysilane, 3-(meth)acryloyloxypropyl-trimethoxysilane, 3-(meth)acryloyloxypropyl-triethoxysilane, 3-(meth)acryloyloxypropyl-tripropoxysilane, 3-(meth)acryloyloxypropyl-triethoxysilane, 3-(meth)acryloyloxypropyl-triprop ... -(meth)acryloyloxyalkyl-trialkoxysilanes such as (meth)acryloyloxypropyl-triisopropoxysilane and 3-(meth)acryloyloxypropyl-tributoxysilane; (meth)acryloyloxymethyl-methyldimethoxysilane, (meth)acryloyloxymethyl-methyldiethoxysilane, 2-(meth)acryloyloxyethyl-methyldimethoxysilane, 2-(meth)acryloyloxyethyl-methyldiethoxysilane, 3-(meth)acryloyloxypropyl propyl-methyldimethoxysilane, 3-(meth)acryloyloxypropyl-methyldiethoxysilane, 3-(meth)acryloyloxypropyl-methyldipropoxysilane, 3-(meth)acryloyloxypropyl-methyldiisopropoxysilane, 3-(meth)acryloyloxypropyl-methyldibutoxysilane, 3-(meth)acryloyloxypropyl-ethyldimethoxysilane, 3-(meth)acryloyloxypropyl-ethyldiethoxysilane, 3-(meth)acryloyloxypropyl (meth)acryloyloxyalkyl-alkyldialkoxysilanes such as 3-(meth)acryloyloxypropyl-ethyldiisopropoxysilane, 3-(meth)acryloyloxypropyl-ethyldibutoxysilane, 3-(meth)acryloyloxypropyl-propyldimethoxysilane, and 3-(meth)acryloyloxypropyl-propyldiethoxysilane, and the corresponding (meth)acryloyloxyalkyl-dialkyl(mono)alkoxysilanes;Examples of vinyl alkyl trialkoxysilanes include vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl triisopropoxysilane, and vinyl tributoxysilane, as well as corresponding vinyl alkyl dialkoxysilanes and vinyl dialkyl alkoxysilanes; vinyl methyl trimethoxysilane, vinyl methyl triethoxysilane, β-vinyl ethyl trimethoxysilane, β-vinyl ethyl triethoxysilane, γ-vinyl propyl trimethoxysilane, γ-vinyl propyl triethoxysilane, γ-vinyl propyl tripropoxysilane, γ-vinyl propyl triisopropoxysilane, and γ-vinyl propyl tributoxysilane; and corresponding (vinyl alkyl) alkyl dialkoxysilanes and (vinyl alkyl) dialkyl (mono) alkoxysilanes.

[0056] The content of structural units derived from alkoxysilyl group-containing monomers in polymer A is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Polymer A may not contain structural units derived from alkoxysilyl group-containing monomers.

[0057] <1-1-e. Other Monomers> Polymer A may contain structural units derived from other copolymerizable monomers. The other copolymerizable monomers may be of only one type, or may be of two or more types. Specific examples of other copolymerizable monomers include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; vinyl esters such as vinyl acetate and vinyl propionate; styrene-based monomers such as styrene; epoxy group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; nitrogen atom-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, (meth)acryloylmorpholine, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; (meth)acrylamide. Alkoxy group-containing monomers such as methoxyethyl acrylate and ethoxyethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; functional monomers such as 2-methacryloyloxyethyl isocyanate; olefin-based monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; vinyl ether-based monomers such as vinyl ether; halogen atom-containing monomers such as vinyl chloride; vinyl group-containing heterocyclic compounds and N-vinylcarboxylic acid amides such as N-vinylpyrrolidone, N-(1-methylvinyl)pyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, and N-vinylmorpholine; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide;Itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, Examples of the monomers include sulfonic acid group-containing monomers such as sulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylic ester-based monomers containing heterocycles or halogen atoms such as tetrahydrofurfuryl (meth)acrylate and fluorine (meth)acrylate.

[0058] As other copolymerizable monomers, polyfunctional monomers can also be used. Examples of polyfunctional monomers include compounds having two or more ethylenically unsaturated groups, such as (mono- or poly)ethylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetraethylene glycol di(meth)acrylate; (mono- or poly)alkylene glycol di(meth)acrylates such as propylene glycol di(meth)acrylate; ) acrylate; esters of (meth)acrylic acid and polyhydric alcohols such as neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; polyfunctional vinyl compounds such as divinylbenzene; diacetone acrylamide; and compounds having unsaturated double bonds with different reactivities such as allyl (meth)acrylate and vinyl (meth)acrylate. Polyfunctional monomers that can be used include polyester (meth)acrylates, epoxy (meth)acrylates, and urethane (meth)acrylates, which have two or more ethylenically unsaturated groups added to the backbone of polyester, epoxy, or urethane as functional groups similar to those of the monomer components.

[0059] The content of structural units derived from other copolymerizable monomers in polymer A is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, or even 3% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Polymer A may not contain structural units derived from other copolymerizable monomers.

[0060] <1-1-f. Method for producing polymer A> Polymer A can be synthesized, for example, by emulsion polymerization using an emulsion containing the raw material monomer components. In emulsion polymerization, an emulsifier, a polymerization initiator, and, if necessary, a chain transfer agent, etc. can be appropriately used. Examples of emulsion polymerization methods include a batch charge method (batch polymerization method), a monomer dropping method, and a monomer emulsion dropping method. In the monomer dropping method, a continuous dropping method or a divided dropping method can be appropriately selected. These methods can be appropriately combined. The reaction conditions for emulsion polymerization can be appropriately adjusted depending on the monomer components, etc., and, for example, the polymerization temperature is 20°C to 100°C, and the polymerization time is 10 minutes to 24 hours.

[0061] In emulsion polymerization, it is preferable to use the above-mentioned reactive emulsifier as the emulsifier. As the emulsifier, an emulsifier (non-reactive emulsifier) ​​described later in the section <1-4. Emulsifier> may also be used. The amount of emulsifier used per 100 parts by weight of the monomer components is, for example, 0.1 to 10 parts by weight.

[0062] Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] Examples of initiators include azo initiators such as methyl persulfate and methyl persulfate hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxide initiators such as benzoyl peroxide, tert-butyl hydroperoxide, and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and redox initiators such as a combination of a persulfate and sodium hydrogen sulfite or a combination of a peroxide and sodium ascorbate, with azo initiators being preferred. The amount of polymerization initiator used per 100 parts by weight of the monomer components is, for example, 0.005 to 1 part by weight.

[0063] Examples of the chain transfer agent include mercaptans such as 1-dodecanethiol, mercaptoacetic acid, 2-mercaptoethanol, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, and mercaptopropionic acid esters. The amount of the chain transfer agent used per 100 parts by weight of the monomer components is, for example, 0.001 to 0.5 parts by weight, or may be 0.01 to 0.4 parts by weight, or even 0.01 to 0.04 parts by weight.

[0064] The dispersion medium used in emulsion polymerization preferably contains water. The dispersion medium may contain an organic solvent together with water. The amount of the dispersion medium used per 100 parts by weight of the monomer components is, for example, 30 to 150 parts by weight, or may be 30 to 80 parts by weight, or even 40 to 70 parts by weight.

[0065] It is also possible to synthesize polymer A by a method other than emulsion polymerization. In this case, the PSA composition may be prepared by dispersing the synthesized polymer A in a dispersion medium using an emulsifier.

[0066] <1-1-g. Polymer A> The glass transition temperature (Tg) of polymer A is, for example, -40°C to 20°C, as a theoretically calculated value obtained by the FOX formula, and may be -10°C to 20°C, -5°C to 20°C, 0°C to 15°C, or even 5°C to 10°C.

[0067] The weight-average molecular weight of polymer A is, for example, 1,000 to 10,000,000, and may be 5,000 to 5,000,000, 10,000 to 1,000,000, or even 50,000 to 800,000. The weight-average molecular weight of polymer A can be controlled by the amounts of polymerization initiator, chain transfer agent, emulsifier, etc. used during polymerization, reaction conditions, etc.

[0068] As described above, polymer A is typically emulsified in the PSA composition. In the PSA composition, particles containing polymer A may be formed by emulsifying polymer A. In other words, the PSA composition may contain particles containing polymer A. These particles may be composed essentially of polymer A alone. The particles may not aggregate in the PSA composition and may exist as single particles (primary particles), or may aggregate in the PSA composition to form aggregates. The particles may be of a core-shell type having a core and a shell covering the core.

[0069] In the pressure-sensitive adhesive composition, the average particle size of the particles containing polymer A is, for example, 1000 nm or less, and may be 700 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or even 200 nm or less. The lower limit of the average particle size is not particularly limited and may be, for example, 50 nm or more, or 100 nm or more. The average particle size of the particles containing polymer A refers to a value measured by dynamic light scattering in accordance with the provisions of Japanese Industrial Standards (JIS) Z8828:2019. As a measuring device, for example, an "ELSZ neo" product manufactured by Otsuka Electronics Co., Ltd. or an equivalent can be used. The average particle size of the particles containing polymer A can be adjusted by, for example, the reaction conditions during the synthesis of polymer A.

[0070] The polydispersity index (PDI) of the particles containing polymer A is, for example, 0.2 or less, and may be 0.15 or less, or even 0.1 or less. The lower limit of the polydispersity index is not particularly limited, and is, for example, 0.01 or more. The polydispersity index can be measured by the dynamic light scattering method described above.

[0071] The content of polymer A in the pressure-sensitive adhesive composition is, for example, 10% by weight or more, and may be 20% by weight or more, 30% by weight or more, 40% by weight or more, or even 50% by weight or more. The upper limit of the content is not particularly limited, and is, for example, 90% by weight or less.

[0072] ≪1-2. Coloring Agent≫ As described above, the pressure-sensitive adhesive composition according to the embodiment of the present invention contains a colorant. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition containing the colorant can have light-blocking properties. A pressure-sensitive adhesive sheet having light-blocking properties can suppress light leakage from a light source used in an image display device.

[0073] The colorant may be one type only, or two or more types. The colorant may be a black colorant or a non-black colorant. The pressure-sensitive adhesive composition preferably contains a black colorant. The black colorant allows the light-blocking properties of the pressure-sensitive adhesive sheet to be efficiently adjusted with a small amount of the colorant.

[0074] Specific examples of black colorants include carbon-based colorants such as carbon black, graphite, aniline black, perylene black, cyanine black, and activated carbon; metal-based colorants such as molybdenum disulfide, chromium complexes, titanium nitride, and bismuth sulfide; and organic compound-based colorants such as anthraquinone-based colorants. The pressure-sensitive adhesive composition preferably contains carbon black.

[0075] As the carbon black, any material generally referred to as carbon black can be used without particular limitation, including furnace black, channel black, acetylene black, thermal black, lamp black, and pine soot. Surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (e.g., alkoxysilyl groups and alkylsilyl groups) can also be used as the carbon black. Such surface-modified carbon black particles are also called self-dispersing carbon black, and do not require the addition of a dispersant or can reduce the amount of dispersant added.

[0076] The black colorant is preferably particulate. Since the light-blocking properties of the PSA sheet can be efficiently adjusted by using a small amount, the average particle size of the black colorant (preferably carbon black particles) 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. From the viewpoint of improving light-blocking properties, the upper limit of the average particle size is preferably 500 nm or less, and may be 300 nm or less, 250 nm or less, or even 200 nm or less, and in some cases may be 120 nm or less, or even 100 nm or less. The average particle size of the black colorant is the particle size at 50% of the cumulative value in the particle size distribution measured using a particle size distribution measuring device based on the laser scattering / diffraction method (50% volume average particle size; hereinafter, D 50 (sometimes abbreviated as ).

[0077] The content of the black colorant (preferably carbon black particles) in the PSA composition is not particularly limited and may be, for example, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more, 2.5% by weight or more, or even 3% by weight or more. The upper limit of the content is, for example, 50% by weight or less, 30% by weight or less, 10% by weight or less, 7% by weight or less, or even 5% by weight or less.

[0078] The non-black colorant may be, for example, a red, blue, yellow, green, yellow-green, orange, purple, or other colorant. Conventionally known pigments and dyes can be used as the non-black colorant. 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.

[0079] The content of the non-black colorant in the PSA composition is, for example, less than 13 wt%, and may be less than 10 wt%, less than 5 wt%, less than 3.0 wt%, less than 2.0 wt%, or even less than 1.0 wt%. The PSA composition may be substantially free of non-black colorants.

[0080] ≪1-3. Thickener≫ The PSA composition may further contain a thickener, which tends to reduce the fluidity of the PSA composition and suppress repelling during application.

[0081] The thickener may be one type only, or two or more types may be used. The thickener preferably contains a resin that forms hydrogen bonds with the polymer A and the colorant. Examples of such thickeners include carboxylic acid copolymer thickeners, polyacrylic acid thickeners, urethane thickeners, and polyvinyl alcohol thickeners.

[0082] The carboxylic acid copolymer thickener is, for example, an emulsion-type thickener containing a carboxylic acid copolymer. The carboxylic acid copolymer is, for example, a copolymer of a monomer component containing a carboxyl group-containing acrylic monomer. Commercially available carboxylic acid copolymer thickeners include "Aron B-300K," "Aron B-500," "Aron A-7055," and "Aron A-7075" manufactured by Toa Gosei Co., Ltd., with "Aron B-500" being preferred.

[0083] Examples of polyacrylic acid thickeners include polyacrylic acid (homopolymer of acrylic acid), sodium polyacrylate, ammonium polyacrylate, etc. Commercially available polyacrylic acid thickeners include "Aron A-10H" (polyacrylic acid), "Aron A-20L" (sodium polyacrylate), "Aron A-7100" (sodium polyacrylate), "Aron A-30" (ammonium polyacrylate), and "Aron A-7195" manufactured by Toagosei Co., Ltd., with "Aron A-10H" being preferred.

[0084] The urethane thickener is, for example, a urethane compound having urethane bonds and polyether chains in the molecule, and is a urethane compound that can exhibit a thickening effect by association of the urethane bonds in water. Commercially available urethane thickeners include "ADEKA NOL UH-462," "ADEKA NOL UH-752," "ADEKA NOL UH-140S," "ADEKA NOL UH-420," "ADEKA NOL UH-438," "ADEKA NOL UH-472," "ADEKA NOL UH-450," "ADEKA NOL UH-450VF," "ADEKA NOL UH-540," "ADEKA NOL UH-550," "ADEKA NOL UH-541VF," "ADEKA NOL UH-526," and "ADEKA NOL UH-530," among which "ADEKA NOL UH-450VF" is preferred.

[0085] The thickener may be a solvent that forms hydrogen bonds with the polymer A and the colorant. Examples of such thickeners include glycols such as ethylene glycol, propylene glycol, glycerin, and 1,3-butanediol; N-methylpyrrolidone (NMP); and cellosolves such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, and cellosolve acetate.

[0086] The thickener is not limited to those mentioned above, as long as it has a thickening effect. Other thickeners include, for example, toluene.

[0087] The content of the thickener in the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, 0.1 wt% or more, 0.5 wt% or more, or even 1 wt% or more. The upper limit of the content may be, for example, 10 wt% or less, 5 wt% or less, or even 3 wt% or less. The pressure-sensitive adhesive composition may be substantially free of a thickener.

[0088] 1-4. Emulsifiers The pressure-sensitive adhesive composition may further contain an emulsifier. The emulsifier may be one type only, or two or more types. The emulsifier contained in the pressure-sensitive adhesive composition is, for example, a non-reactive emulsifier that does not contain an ethylenically unsaturated group. However, the pressure-sensitive adhesive composition may contain a reactive emulsifier that remains during the synthesis of polymer A. The emulsifier may be an anionic emulsifier or a nonionic emulsifier.

[0089] Specific examples of anionic emulsifiers include higher fatty acid salts such as sodium oleate; alkylarylsulfonates such as sodium dodecylbenzenesulfonate; alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate; polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate; polyoxyethylene alkylaryl ether sulfate salts such as sodium polyoxyethylene nonylphenyl ether sulfate; alkyl sulfosuccinate salts and derivatives thereof such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, and sodium polyoxyethylene lauryl sulfosuccinate; and polyoxyethylene distyrenated phenyl ether sulfate salts.

[0090] Specific examples of nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, and sorbitan trioleate; polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene higher fatty acid esters such as polyoxyethylene monolaurate and polyoxyethylene monostearate; glycerin higher fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride; polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene distyrenated phenyl ether, and the like.

[0091] The content of the emulsifier in the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, 0.1 wt% or more, 0.5 wt% or more, or even 1 wt% or more. The upper limit of the content may be, for example, 10 wt% or less, 5 wt% or less, or even 3 wt% or less. The pressure-sensitive adhesive composition may be substantially free of an emulsifier.

[0092] ≪1-5. Inorganic particles≫ The pressure-sensitive adhesive composition may further contain inorganic particles (specifically, inorganic particles other than colorants). The inorganic particles are a component suitable for improving the refractive index of the pressure-sensitive adhesive sheet. The inorganic particles are preferably in a dispersed state in the pressure-sensitive adhesive composition.

[0093] 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 contribute to increasing the refractive index of the pressure-sensitive adhesive sheet.

[0094] 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.

[0095] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0096] The inorganic particles may be surface-treated, for example, by hydrophobizing treatment.

[0097] 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 for a monolayer film of the material using a commercially available spectroscopic ellipsometer at 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woolam) or an equivalent.

[0098] 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.

[0099] The content of inorganic particles in the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, 0.1 wt% or more, 0.5 wt% or more, 1 wt% or more, or even 3 wt% or more. The upper limit of the content is, for example, 50 wt% or less, and may be 30 wt% or less, 10 wt% or less, 7 wt% or less, or even 5 wt% or less. The lower the content of inorganic particles, the more likely it is that the adhesive strength of the pressure-sensitive adhesive sheet will be prevented from decreasing. The pressure-sensitive adhesive composition may be substantially free of inorganic particles.

[0100] ≪1-6. Dispersion medium≫ The PSA composition may further contain a dispersion medium. The PSA composition preferably contains water as the dispersion medium. The PSA composition is typically an oil-in-water (O / W) emulsion. A PSA composition containing water as the dispersion medium can significantly reduce the amount of organic solvent emitted by heating during the production of a PSA sheet. This not only reduces the amount of fuel required to combust the organic solvent removed by heating in a deodorizing furnace or the like, but also reduces the amount of CO2 emitted by the combustion of the organic solvent. However, the PSA composition may contain an organic solvent as well as water as the dispersion medium. The content of the dispersion medium in the PSA composition is not particularly limited and is, for example, 10% by weight to 90% by weight.

[0101] 1-7. Additives The PSA composition may contain any other appropriate additives as long as the effects of the present invention are not impaired. The other additives may be one type only or two or more types. Examples of the other additives include leveling agents, dispersants, crosslinking agents, tackifiers, plasticizers, softeners, fillers, and pH adjusters.

[0102] Examples of leveling agents include "Neocol SW-C" (dialkyl sodium sulfosuccinate, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), "Neocol P" (dialkyl sodium sulfosuccinate, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), "Surfynol 420" (acetylene glycol ethylene oxide surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), "Pelex OT-P" (dialkyl sodium sulfosuccinate, manufactured by Kao Corporation), "Nopco Wet 50" (sulfonic acid-based anionic surfactant, manufactured by San Nopco Ltd.), "SN Wet 126" (modified silicone / special polyether surfactant, manufactured by San Nopco Ltd.), "SN Wet FST2" (polyoxyalkyleneamine nonionic wetting agent, manufactured by San Nopco Ltd.), "SN Wet S" (polyoxyalkyleneamine ether nonionic wetting agent, manufactured by San Nopco Ltd.), and "SN Wet 125" (modified silicone surfactant, manufactured by San Nopco Ltd.).

[0103] Examples of the crosslinking agent that can be used include commonly used crosslinking agents such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. When polymer A has a functional group, these crosslinking agents have the effect of reacting with the functional group to form a crosslink.

[0104] Examples of the tackifier include tackifying resins such as rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenol-based resins, and ketone-based resins.

[0105] The content of other additives in the pressure-sensitive adhesive composition is not particularly limited and is, for example, 0.01% by weight to 10% by weight. The pressure-sensitive adhesive composition may be substantially free of other additives.

[0106] 1-8. Physical properties of adhesive composition The pressure-sensitive adhesive composition is preferably neutral. In a neutral pressure-sensitive adhesive composition, particles containing polymer A are less likely to aggregate and tend to be highly stable. The pH of the pressure-sensitive adhesive composition is, for example, 6.0 to 8.0, and may be 6.5 to 7.5. The pH of the pressure-sensitive adhesive composition is preferably 7.0.

[0107] The viscosity of the pressure-sensitive adhesive composition is, for example, 10 mPa·s to 20,000 mPa·s under conditions of pH 7.0 and temperature 25°C.

[0108] <1-9. Method for producing adhesive composition> The pressure-sensitive adhesive composition can be prepared, for example, by the following method. First, an emulsion containing polymer A is prepared. This emulsion may be a polymerization liquid obtained by synthesizing polymer A by emulsion polymerization, or a dispersion obtained by dispersing polymer A synthesized by a method other than emulsion polymerization in a dispersion medium. Next, various additives are added to this emulsion and mixed to prepare the pressure-sensitive adhesive composition. When a colorant is added to the emulsion, a dispersion in which the colorant is dispersed may be added to the emulsion. This dispersion may further contain a dispersant in addition to the colorant.

[0109] ≪≪2. Adhesive≫≫ The adhesive according to an embodiment of the present invention is formed from the above-described adhesive composition. Specifically, the adhesive is a cured or dried product of the adhesive composition. The adhesive contains a material derived from the adhesive composition, and typically includes a polymer B containing a structural unit derived from a monomer A having a double bond-containing ring, and a colorant.

[0110] From another aspect, the present invention provides: a polymer B containing a structural unit derived from a monomer a having a double bond-containing ring; A colorant; The present invention provides a pressure-sensitive adhesive comprising:

[0111] Polymer B may be polymer A contained in the PSA composition itself, or may be a crosslinked product of polymer A. The composition of polymer B may be as described in the section <1-1. Polymer A>.

[0112] Examples of the monomer a having a double bond-containing ring include those mentioned above in the section <1-1-a. Monomer a having a double bond-containing ring>, and it is particularly preferable to include a high refractive index monomer such as phenoxybenzyl acrylate.

[0113] The physical properties, manufacturing method, uses, etc. of the adhesive can be referenced in the explanation of the section <<3. Adhesive Sheet>>.

[0114] ≪≪3. Adhesive sheet≫≫ <3-1. Adhesive sheet> An example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention is shown in Fig. 1. The pressure-sensitive adhesive sheet 1 in Fig. 1 is a sheet made from the above-mentioned pressure-sensitive adhesive. In other words, the pressure-sensitive adhesive sheet 1 is a pressure-sensitive adhesive sheet formed from the above-mentioned pressure-sensitive adhesive composition.

[0115] The amount of residual monomer in the pressure-sensitive adhesive sheet 1 is, for example, 1000 wtppm or less, and may be 500 wtppm or less, or even 100 wtppm or less. The amount of residual monomer can be evaluated, for example, by gas chromatography (GC) analysis.

[0116] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 80% or less, and may be 75% or less, 70% or less, or even 65% or less. The lower limit of the gel fraction is not particularly limited, and may be, for example, 1% or more, 10% or more, 30% or more, or even 50% or more.

[0117] The gel fraction can be measured by the following method. First, a portion is scraped off from the pressure-sensitive adhesive sheet 1 to obtain a small piece. Next, the obtained small piece is wrapped in a stretched porous polytetrafluoroethylene membrane and tied with kite string. This results in a test piece. Next, the total weight (weight A) of the small piece of pressure-sensitive adhesive sheet 1, the stretched porous membrane, and the kite string is measured. The total weight of the stretched porous membrane and kite string used is defined as weight B. Next, the test piece is immersed in a container filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test piece is removed from the container and dried for two hours in a dryer set at 130°C, and then the weight C of the test piece is measured. The gel fraction of the pressure-sensitive adhesive sheet 1 can be calculated from weight A, weight B, and weight C using the following formula. Gel fraction (wt%) = (CB) / (AB) × 100

[0118] The glass transition temperature (Tg) of the pressure-sensitive adhesive sheet 1 is, for example, 30° C. or lower, and may be 20° C. or lower, 10° C. or lower, 0° C. or lower, or even −10° C. or lower. The lower limit of Tg is, for example, −60° C. or higher, −50° C. or higher, or even −40° C. or higher.

[0119] The Tg of the adhesive sheet 1 can be measured by the following method. First, a measurement sample made of the adhesive that constitutes the adhesive sheet 1 is prepared. The measurement sample is disc-shaped. The measurement sample has a bottom diameter of 8 mm and a thickness of 1 mm. The measurement sample may also be one obtained by punching out a disc from a laminate in which multiple adhesive sheets 1 are stacked. Next, dynamic viscoelasticity measurement is performed on the measurement sample under the following measurement conditions. For example, an "ARES-G2" manufactured by TA Instruments can be used for the dynamic viscoelasticity measurement. Measurement conditions Frequency: 1Hz Deformation mode: Torsion Measurement temperature: -70℃~150℃ Heating rate: 5°C / min

[0120] Next, the storage modulus G' and loss modulus G'' of the pressure-sensitive adhesive sheet 1 are determined from the results of the dynamic viscoelasticity measurement. Based on the storage modulus G' and loss modulus G'', tanδ (loss tangent) is calculated using the following formula, and the peak value thereof can be regarded as the Tg of the pressure-sensitive adhesive sheet 1. tanδ(loss tangent)=G” / G'

[0121] As described above, the refractive index of the pressure-sensitive adhesive sheet 1 formed from the pressure-sensitive adhesive composition according to the embodiment of the present invention is 1.50 or greater. The refractive index is preferably 1.51 or greater, and may be 1.52 or greater, 1.53 or greater, 1.54 or greater, 1.55 or greater, 1.56 or greater, 1.57 or greater, 1.58 or greater, 1.59 or greater, 1.60 or greater, or even 1.61 or greater. 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. The explanation in the section <<1. Emulsion-based Pressure-sensitive Adhesive Composition>> may be used to refer to the method for measuring the refractive index of the pressure-sensitive adhesive sheet 1.

[0122] The transmittance of the pressure-sensitive adhesive sheet 1 to light with a wavelength of 300 nm to 800 nm is, for example, 50% or less, and may be 30% or less, 10% or less, 5% or less, 3% or less, 1% or less, 0.5% or less, 0.1% or less, or even 0.05% or less. The lower limit of the transmittance is not particularly limited, and is, for example, 0.01% or more.

[0123] The transmittance can be measured by the following method. First, a test piece is prepared by laminating a non-alkali glass to each surface of the pressure-sensitive adhesive sheet 1 and sandwiching the pressure-sensitive adhesive sheet 1 between the two non-alkali glass pieces. The non-alkali glass is glass that is substantially free of alkali components (alkali metal oxides), and more specifically, the weight ratio of alkali components in the glass is, for example, 1000 ppm or less, or even 500 ppm or less. The non-alkali glass is, for example, in the form of a plate, and has a thickness of 0.5 mm or more.

[0124] Next, the test piece is left in an environment of 23°C and 50% RH for 30 minutes, and then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. The test piece is then left in an atmosphere of 23°C and 50% RH for 24 hours. Next, in a measurement environment of 23°C, the transmittance of the test piece to light with a wavelength of 300 nm to 800 nm is measured using an ultraviolet-visible-near-infrared spectrophotometer. The transmittance of the pressure-sensitive adhesive sheet 1 can be determined from the measurement results.

[0125] The adhesive sheet 1 preferably has a peel strength of 1.5 N / 10 mm or more as determined by the following test. Test: Adhesive sheet 1 is attached to non-alkali glass and peeled off from the non-alkali glass at a peeling speed of 300 mm / min and a peeling angle of 180° in an atmosphere of 23°C and 50% RH. The maximum force required at this time is determined as the peel force.

[0126] The peel strength of the adhesive sheet 1 can be measured by the following method. First, a laminate including the adhesive sheet 1 and a substrate is prepared in a measurement environment of 23°C and 50% RH. The substrate is not particularly limited as long as it supports the adhesive sheet 1 and does not affect the results of the peel strength measurement. As an example, the substrate may be a polyethylene terephthalate film. Next, the laminate is cut into a strip measuring 100 mm long x 10 mm wide to prepare a test piece. Next, the test piece is placed on alkali-free glass via the adhesive sheet 1, and a 2 kg roller is rolled back and forth once to press them together. The alkali-free glass can be the same as that described above for transmittance.

[0127] Next, the test piece was left in the above environment for 30 minutes, then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, the test piece was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, using a universal tension and compression tester, the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180° in an atmosphere of 23°C and 50% RH. The maximum force (peel strength) required to peel the test piece from the alkali-free glass was determined as the peel force.

[0128] The peel force is preferably 1.8 N / 10 mm or more, and may be 2.0 N / 10 mm or more, 2.3 N / 10 mm or more, 2.5 N / 10 mm or more, 2.8 N / 10 mm or more, 3.0 N / 10 mm or more, 3.1 N / 10 mm or more, or even 3.2 N / 10 mm or more. The upper limit of the peel force is not particularly limited, and may be, for example, 10 N / 10 mm or less, or 5 N / 10 mm or less.

[0129] The adhesive sheet 1 preferably has a shear adhesive strength of 0.15 MPa or more. The shear adhesive strength is preferably 0.20 MPa or more, and may be 0.30 MPa or more, 0.50 MPa or more, 0.80 MPa or more, 1.00 MPa or more, or even 1.10 MPa or more. The upper limit of the shear adhesive strength is not particularly limited, and is, for example, 10 MPa or less.

[0130] The shear adhesive strength of the pressure-sensitive adhesive sheet 1 can be measured by the following method. First, in a measurement environment of 23°C and 50% RH, one surface of a 20mm x 20mm pressure-sensitive adhesive sheet 1 is placed on a polycarbonate plate, and a 2kg roller is moved back and forth once to press them together. Next, the other surface of the pressure-sensitive adhesive sheet 1 is placed on another polycarbonate plate, and a 2kg roller is moved back and forth once to press them together. This results in a test piece in which a polycarbonate plate, a pressure-sensitive adhesive sheet, and a polycarbonate plate are laminated in this order. The size of the polycarbonate plate is, for example, 100mm x 50mm. As the polycarbonate plate, for example, Carboglass Polish manufactured by AGC Corporation can be used.

[0131] Next, the obtained test piece was left under the above-mentioned conditions for 30 minutes, and then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, the test piece was left under an atmosphere of 23°C and 50% RH for 24 hours. Next, the test piece was placed in a universal tension-compression tester. At this time, one polycarbonate plate in the test piece was fixed with one jig of the universal tension-compression tester, and the other polycarbonate plate was fixed with the other jig of the universal tension-compression tester. Next, a tensile test was performed on the test piece under an atmosphere of 23°C and 50% RH at a tension speed of 50 mm / min so that shear stress was applied to the adhesive sheet 1. The shear adhesive strength can be determined based on the maximum force required and the area of ​​the adhesive sheet 1.

[0132] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 100 μm or less, and may be 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 pressure-sensitive adhesive sheet 1 is, for example, 1 μm or more, and may be 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 pressure-sensitive adhesive sheet 1 may be 15 μm or more, 20 μm or more, 30 μm or more, 35 μm or more, or even 40 μm or more.

[0133] 3-2. Manufacturing method of adhesive sheet The pressure-sensitive adhesive sheet 1 can be produced, for example, by the following method. First, the above-mentioned pressure-sensitive adhesive composition is applied onto a release liner to form a coating film. The method for applying the pressure-sensitive adhesive composition is not particularly limited, and examples include roll coating, kiss roll coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and extrusion coating using a die coater. The pressure-sensitive adhesive composition may be applied by a printing method such as gravure printing, offset printing, screen printing, or inkjet printing, or may be applied using a coating liquid metered application device such as a dispenser.

[0134] Examples of materials constituting the release liner include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film; porous materials such as paper, cloth, and nonwoven fabric; and appropriate thin sheets such as nets, foam sheets, metal foils, and laminates thereof. Plastic films are preferably used because of their excellent surface smoothness.

[0135] The plastic film is not particularly limited as long as it is a film that can protect the adhesive sheet 1, and examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

[0136] The thickness of the release liner is, for example, 5 to 200 μm, and preferably about 5 to 100 μm. If necessary, the release liner can be subjected to a release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agent, silica powder, or the like, or an antistatic treatment such as a coating, kneading, or vapor deposition type. In particular, by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the release liner, the releasability from the pressure-sensitive adhesive sheet 1 can be further improved.

[0137] Next, the coating film is dried to form the adhesive sheet 1. The drying of the coating film can be carried out, for example, under heating conditions. The heating temperature of the coating film is, for example, 80°C to 170°C. The heating time of the coating film is, for example, 0.5 minutes to 30 minutes. The drying conditions of the coating film are set, for example, so that the content of the dispersion medium remaining in the obtained adhesive sheet 1 is 1000 wtppm or less, preferably 500 wtppm or less.

[0138] ≪3-3. Uses of adhesive sheets≫ The pressure-sensitive adhesive sheet 1 has limited light transmittance and is suitable for use in applications where it is attached to materials with a higher refractive index than general pressure-sensitive adhesives. For example, some electronic devices, such as portable electronic devices, include light-emitting elements for purposes such as image display, and therefore the pressure-sensitive adhesive sheet 1 may be required to have limited light transmittance (e.g., light-blocking properties). The pressure-sensitive adhesive sheet 1 can be suitably used for such electronic devices.

[0139] Non-limiting examples of the 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.

[0140] ≪≪4. Laminate≫≫ A laminate according to an embodiment of the present invention includes, for example, the above-described pressure-sensitive adhesive sheet 1 and a release liner. The pressure-sensitive adhesive sheet 1 can be attached to the adherend by peeling the release liner from the laminate and placing the adherend on the exposed surface of the pressure-sensitive adhesive sheet 1.

[0141] 4-1. Overall structure of the laminate Figure 2 is a representative schematic cross-sectional view of a laminate according to an embodiment of the present invention. Laminate 10 shown in Figure 2 comprises release liner 2A, PSA sheet 1, and release liner 2B, in that order. Laminate 10 can be considered a substrate-less double-sided PSA sheet. As an example, PSA sheet 1 can be bonded to an adherend by peeling release liner 2A from laminate 10 and placing the adherend on the exposed surface of PSA sheet 1.

[0142] In laminate 10, either release liner 2A or release liner 2B may be a substrate, as described below. In this case, laminate 10 can be considered a single-sided PSA sheet with a substrate. Laminate 10 does not necessarily have to include either release liner 2A or release liner 2B. In this case, laminate 10 may be rolled up, so that the exposed surface of PSA sheet 1 abuts against the back surface of the release liner.

[0143] Figure 3 is a schematic cross-sectional view of another representative laminate according to an embodiment of the present invention. Laminate 11 shown in Figure 3 comprises, in this order, a release liner 2A, a pressure-sensitive adhesive sheet 1A, a substrate 5, a pressure-sensitive adhesive sheet 1B, and a release liner 2B. Laminate 11 can be considered a double-sided pressure-sensitive adhesive sheet with a substrate. As an example, pressure-sensitive adhesive sheet 1A can be bonded to an adherend by peeling release liner 2A from laminate 11 and placing the adherend on the exposed surface of pressure-sensitive adhesive sheet 1A.

[0144] It is noted that laminate 11 may not have either release liner 2A or release liner 2B. In this case, laminate 11 may be rolled up, so that the exposed surface of PSA sheet 1A or 1B may be in contact with the back surface of the release liner.

[0145] The laminate according to an embodiment of the present invention may have any appropriate configuration as long as it includes the adhesive sheet 1 described in section <<3. Adhesive Sheet>>, but a representative configuration is that shown in Figures 2 and 3 above.

[0146] The components of the laminate will be described below.

[0147] <4-2. Adhesive sheet> The adhesive sheet 1 in Fig. 2 and the adhesive sheets 1A and 1B in Fig. 3 are preferably the adhesive sheets described in Section <<3. Adhesive Sheet>>>. However, either one of the adhesive sheets 1A and 1B in Fig. 3 may use a known adhesive.

[0148] <4-3. Release liner> Any appropriate release liner can be used as the release liner as long as it does not impair the effects of the present invention. The release liner may be the release liner described in Section 3-2. Method for producing a pressure-sensitive adhesive sheet.

[0149] ≪4-4. Base material≫ The substrate is typically a supporting substrate that supports (backs) the PSA sheet. Examples of the substrate that can be used include resin films, paper, cloth, rubber sheets, foam sheets, metal foils, and composites of these.

[0150] Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; and the like. Examples of paper include Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, and top-coated paper. Examples of fabrics include woven and nonwoven fabrics made from various fibrous materials, either alone or in combination. Examples of the fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foam sheets include foamed polyurethane sheets and foamed polychloroprene rubber sheets. Examples of metal foils include aluminum foil and copper foil.

[0151] In this specification, the term "nonwoven fabric" is a concept that refers primarily to nonwoven fabric for adhesive sheets used in the fields of adhesive tapes and other adhesive sheets, and typically refers to nonwoven fabric (sometimes referred to as "paper") that is produced using a general papermaking machine.

[0152] The substrate preferably includes a resin film as a base film. The base film is typically an independent member that can maintain its shape independently. The substrate may essentially consist of only the base film, or may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the base film.

[0153] A resin film is a film whose main component is a resin material (e.g., a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin-based resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester-based resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride-based resin films; vinyl acetate-based resin films; polyimide-based resin films; polyamide-based resin films; fluororesin films; cellophane; and the like. The resin film may also be a rubber-based film such as a natural rubber film or a butyl rubber film. Among these, polyester films are preferred from the viewpoint of handleability and processability, and PET films are particularly preferred. In this specification, the term "resin film" typically refers to a non-porous sheet, a concept distinct from so-called nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics). The resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film.

[0154] A colorant can be contained in the substrate (e.g., a resin film). This allows the light transmittance (light blocking property) of the substrate to be adjusted. Adjusting the light transmittance (e.g., perpendicular light transmittance) of the substrate can also be useful for adjusting the light transmittance of the substrate and even the light transmittance of a laminate including the substrate.

[0155] The colorant may be any conventionally known pigment or dye, and may be, for example, a black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, or the like.

[0156] A black colorant can be preferably used as the colorant for the substrate because a small amount of the colorant can efficiently adjust the light-blocking properties (e.g., perpendicular light transmittance). Examples of black colorants include those described in the section 1-2. Colorant. As an example, a colorant having an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm (e.g., a particulate black colorant such as carbon black) can be used.

[0157] The content of the colorant in the substrate is not particularly limited and can be appropriately adjusted to impart desired optical properties. The content of the colorant is, for example, 0.1 to 30% by weight, or may be 0.1 to 25% by weight, or even 0.1 to 20% by weight.

[0158] The substrate may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc. The content of the various additives in the substrate may be, for example, less than 30% by weight, less than 20% by weight, or even less than 10% by weight.

[0159] The substrate may have a single layer structure, or a multi-layer structure of two, three or more layers. From the viewpoint of shape stability, the substrate preferably has a single layer structure. In the case of a multi-layer structure, at least one layer (preferably all layers) preferably has a continuous structure of the above resin (e.g., polyester-based resin).

[0160] The method for producing the substrate is not particularly limited and may be any conventionally known method, such as extrusion molding, inflation molding, T-die casting, or calendar roll molding.

[0161] As described above, the substrate may include a colored layer disposed on the surface of the base film. In a substrate having a configuration including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be disposed on either one surface of the base film, or may be disposed on both surfaces. In a configuration in which a colored layer is disposed on each surface of the base film, the configurations of the colored layers may be the same or different.

[0162] The colored layer can typically be formed by applying a colored layer-forming composition containing a colorant and a binder to a base film. Conventionally known pigments and dyes can be used as the colorant. Materials known in the fields of paint or printing can be used as the binder without particular limitation, including, for example, polyurethane, phenolic resin, epoxy resin, urea melamine resin, and polymethyl methacrylate. The colored layer-forming composition can be, for example, solvent-based, UV-curable, or heat-curable. The colored layer can be formed using any method conventionally used for forming colored layers without particular limitation. For example, methods of forming a colored layer (printed layer) by printing, such as gravure printing, flexographic printing, or offset printing, can be preferably used.

[0163] The colored layer may have a single layer structure consisting of a single layer, or may have a multilayer structure including two, three, or more sub-colored layers. A colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For colored layers intended to impart light-blocking properties, a multilayer structure is particularly preferred from the viewpoint of preventing pinholes and increasing the reliability of preventing light leakage.

[0164] The total thickness of the colored layer is, for example, 1 μm to 10 μm, or may be 1 μm to 7 μm, or even 1 μm to 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably 1 μm to 2 μm.

[0165] The thickness of the substrate is not particularly limited, and from the viewpoint of preventing the laminate from becoming excessively thick, it may be 200 μm or less, 100 μm or less, 70 μm or less, 30 μm or less, 15 μm or less, or even 8 μm or less. The lower limit of the thickness of the substrate is not particularly limited, and from the viewpoint of the handleability and processability of the laminate, it may be, for example, 2 μm or more, or 5 μm or more. In some cases, the thickness of the substrate may be 10 μm or more.

[0166] The surface of the substrate may be subjected to a conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, etc. Such a surface treatment may be a treatment for improving the adhesion between the substrate and the PSA sheet, in other words, the anchoring ability of the PSA sheet to the substrate.

[0167] In laminate 10, when either release liner 2A or release liner 2B is the substrate, the back surface of the substrate may be subjected to a release treatment as needed. The release treatment may be, for example, a treatment in which a typical silicone-based, long-chain alkyl-based, or fluorine-based release agent is applied in the form of a thin film having a thickness of 0.01 μm to 1 μm (preferably 0.01 μm to 0.1 μm). The release treatment has the effect of making it easier to unwind a roll of the laminate.

[0168] 5. Optical Components The pressure-sensitive adhesive according to an embodiment of the present invention can be applied to optical components. Accordingly, one embodiment of the present invention also encompasses optical components equipped with such pressure-sensitive adhesives. The optical components may include a pressure-sensitive adhesive sheet made of the pressure-sensitive adhesive. The optical components are used, for example, as components for electronic devices such as portable electronic devices. Examples of portable electronic devices include those described above in Section 3-3. Uses of Pressure-Sensitive Adhesive Sheets. [Example]

[0169] 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.

[0170] [Polymer Emulsion A1] First, 99 parts by weight of phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A"), 1 part by weight of acrylic acid (AA), 2 parts by weight of polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon KH1025"), and 34 parts by weight of ion-exchanged water were weighed and placed in a glass container. Next, the contents of the glass container were stirred with a homomixer to emulsify the monomer components. This yielded a monomer emulsion.

[0171] Next, 68 parts by weight of ion-exchanged water was weighed and added to a four-neck flask (reaction vessel) equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet pipe. Next, nitrogen substitution was performed while heating the reaction vessel so that the internal temperature reached 60°C. Next, 0.1 parts by weight of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "VA-057") as a polymerization initiator was added to the reaction vessel, and the polymerization initiator was dissolved in the ion-exchanged water.

[0172] Next, using a liquid transfer pump and a liquid transfer tube, the above monomer emulsion was added dropwise to the reaction vessel over 240 minutes. This allowed emulsion polymerization to proceed within the reaction vessel. After the dropwise addition of the monomer emulsion, the temperature within the reaction vessel (60°C) was maintained for 3 hours to allow the polymerization reaction to proceed further. After the polymerization reaction was completed, the reaction vessel was cooled in an ice bath. This yielded an emulsion of polymer A1 (polymer emulsion A1).

[0173] [Polymer emulsions A2 to A5] Except for changing the type and content of the monomer as shown in Table 1, emulsions of polymers A2 to A5 (polymer emulsions A2 to A5) were prepared in the same manner as polymer emulsion A1.

[0174] [Polymer solution A6] A four-neck flask (reaction vessel) equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 95 parts by weight of butyl acrylate (BA) and 5 parts by weight of acrylic acid (AA). Next, 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was charged into the reaction vessel along with ethyl acetate. Nitrogen gas was introduced into the reaction vessel with gentle stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at around 55°C, and a polymerization reaction was carried out for 7 hours. Ethyl acetate was then added to the resulting reaction solution to adjust the solids concentration to 30%, yielding a solution of polymer A6 (polymer solution A6).

[0175] [Table 1]

[0176] The abbreviations in Table 1 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") BA: n-butyl acrylate AA: acrylic acid KH1025: Polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt (manufactured by Daiichi Kogyo Seiyaku, trade name "Aqualon KH1025") VA-057: 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "VA-057") AIBN: Azo polymerization initiator, 2,2'-azobisisobutyronitrile (Kishida Chemical Co., Ltd.)

[0177] Example 1 To 100 parts by weight of polymer emulsion A1, 0.9 parts by weight of sodium dialkyl sulfosuccinate (manufactured by Daiichi Kogyo Seiyaku, trade name "Neocol SW-C") as a leveling agent, 1 part by weight of a carboxylic acid copolymer thickener (manufactured by Toagosei, trade name "Aron B-500") as a thickener, 0.25 parts by weight of 10% ammonia water as a pH adjuster, and 3 parts by weight of a dispersion containing carbon black (manufactured by Tokai Carbon, trade name "Aqua Black 162") as a colorant were mixed. The resulting mixture was stirred and further subjected to a centrifugal degassing treatment to obtain an emulsion-based pressure-sensitive adhesive composition of Example 1.

[0178] (Examples 2 to 4 and Comparative Example 1) Emulsion-based pressure-sensitive adhesive compositions of Examples 2 to 4 and Comparative Example 1 were prepared in the same manner as in Example 1, except that the type of polymer emulsion was changed as shown in Table 2.

[0179] (Comparative Example 2) To 100 parts by weight of polymer solution A6, 3 parts by weight of Takenate D101E (manufactured by Mitsui Chemicals) and 0.01 part by weight of TEDRAD-C (manufactured by Mitsubishi Gas Chemical) as crosslinking agents, 20 parts by weight of YS Polystar T-115 (manufactured by Yasuhara Chemical) as a tackifying resin, and 3 parts by weight of a dispersion containing carbon black (manufactured by Mikuni Shikishoku Co., Ltd., product name "PD852") as a colorant were mixed. The resulting mixture was stirred and further subjected to a centrifugal degassing treatment to obtain a solvent-based pressure-sensitive adhesive composition of Comparative Example 2.

[0180] (Comparative Example 3) A solvent-based pressure-sensitive adhesive composition of Comparative Example 3 was obtained in the same manner as in Comparative Example 2, except that 40 parts by weight of a dispersion containing zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., product name "SZR-CW") was further mixed in.

[0181] <Evaluation> Using the prepared pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet for evaluation was prepared by the following method. First, the pressure-sensitive adhesive composition was applied onto a release liner (manufactured by Mitsubishi Chemical Corporation, product name "Diafoil MRF38") to prepare a coating film. The pressure-sensitive adhesive composition was applied using an applicator. Next, the coating film was dried for 3 minutes in a dryer set at 130°C to prepare a pressure-sensitive adhesive sheet (thickness 25 μm). A release liner (manufactured by Mitsubishi Chemical Corporation, product name "Diafoil MRE38") was placed on the exposed surface of the pressure-sensitive adhesive sheet to cover the exposed surface.

[0182] [Refractive Index] The refractive index of the surface of the above pressure-sensitive adhesive sheet was measured in critical angle mode using a prism coupler (manufactured by Metricon, model "2010M") at a measurement temperature of 25°C and a measurement wavelength of 594 nm by peeling off the release liner.

[0183] [Transmittance] The release liner of the above adhesive sheet was peeled off and each surface was exposed with a non-alkali glass plate (thickness 0.7-0.8 mm, total light transmittance 92%, chromaticity b * 0.20) was bonded together to obtain a test piece in which the pressure-sensitive adhesive sheet was sandwiched between two alkali-free glass plates. This test piece was left in an environment of 23°C and 50% RH for 30 minutes, then placed in a pressure-degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, it was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, in a measurement environment of 23°C, the transmittance of the test piece to light with wavelengths of 300 nm to 800 nm was measured using a UV-Visible-Near-Infrared Spectrophotometer (Hitachi High-Tech, UH4150). From the measurement results, the transmittance of the pressure-sensitive adhesive sheet to light with wavelengths of 300 nm to 800 nm was determined.

[0184] [Peeling force] Under a measurement environment of 23°C and 50% RH, one release liner was peeled from the pressure-sensitive adhesive sheet, and a polyethylene terephthalate film (50 μm thick) was attached and backed. The resulting laminate was cut into a 100 mm long x 10 mm wide strip to prepare a test piece. The other release liner was peeled from the test piece, and the test piece was placed on alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG", thickness 0.7 mm), and the two were pressed together by moving a 2 kg roller back and forth once.

[0185] After leaving the test piece in the above environment for 30 minutes, it was placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left in an atmosphere of 23°C and 50% RH for 24 hours. Next, using a universal tension and compression tester (Shimadzu Corporation, Autograph SHIMAZU AGX-V 50N), the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180° under an atmosphere of 23°C and 50% RH. The maximum force (peel strength) required to peel the test piece from the alkali-free glass was determined as the peel force.

[0186] [Shear adhesive strength] The pressure-sensitive adhesive sheet was cut into a 20 mm x 20 mm piece under a measurement environment of 23°C and 50% RH. Next, one release liner was peeled off from the pressure-sensitive adhesive sheet, and the sheet was placed on a 100 mm x 50 mm polycarbonate plate (manufactured by AGC, Carboglass Polish), and the two were pressed together by rolling a 2 kg roller back and forth once. Furthermore, the other release liner was peeled off from the pressure-sensitive adhesive sheet, and the sheet was placed on a 100 mm x 50 mm polycarbonate plate (manufactured by AGC, Carboglass Polish), and the two were pressed together by rolling a 2 kg roller back and forth once. This resulted in a test piece in which the polycarbonate plate, pressure-sensitive adhesive sheet, and polycarbonate plate were laminated in this order.

[0187] Next, the obtained test piece was left in the above environment for 30 minutes, then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, it was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, the test piece was placed in a universal tension and compression tester (Shimadzu Corporation, Autograph SHIMAZU AGX-V 10kN). At this time, one polycarbonate plate in the test piece was fixed with one jig of the universal tension and compression tester, and the other polycarbonate plate was fixed with the other jig of the universal tension and compression tester. Next, a tensile test of the test piece was performed at a tension rate of 50 mm / min in an atmosphere of 23°C and 50% RH so that shear stress was applied to the pressure-sensitive adhesive sheet 1. The shear adhesive strength was determined based on the maximum force required and the area of ​​the pressure-sensitive adhesive sheet.

[0188] [Table 2]

[0189] The abbreviations in Table 2 are as follows: SW-C: Sodium dialkyl sulfosuccinate (manufactured by Daiichi Kogyo Seiyaku, product name "Neocol SW-C") B-500: Carboxylic acid copolymer thickener (manufactured by Toagosei Co., Ltd., product name "Aron B-500") Aqua Black 162: Dispersion liquid containing carbon black (manufactured by Tokai Carbon Co., Ltd., product name "Aqua Black 162") PD852: Dispersion liquid containing carbon black (manufactured by Mikuni Color Co., Ltd., product name "PD852") ZrO2: Dispersion liquid containing zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., product name "SZR-CW")

[0190] As can be seen from Table 2, the pressure-sensitive adhesive sheets formed from the emulsion-based pressure-sensitive adhesive compositions of the Examples had refractive indices of 1.50 or more. Compared with the Comparative Examples, the pressure-sensitive adhesive sheets of the Examples had higher peel strength and shear adhesive strength, and thus had improved adhesive strength. [Industrial Applicability]

[0191] The pressure-sensitive adhesive sheet formed from the emulsion-based pressure-sensitive adhesive composition of the present invention can be used as a component for electronic devices (for example, an optical component). [Explanation of symbols]

[0192] 1, 1A, 1B adhesive sheet 2A, 2B release liner 5 Base material

Claims

1. a polymer A including a structural unit derived from a monomer a having a double bond-containing ring; A colorant; An emulsion-based pressure-sensitive adhesive composition comprising: An emulsion-based pressure-sensitive adhesive composition, wherein a pressure-sensitive adhesive sheet formed from the emulsion-based pressure-sensitive adhesive composition has a refractive index of 1.50 or more.

2. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , wherein the monomer a comprises the (meth)acrylic monomer having the double bond-containing ring.

3. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , wherein the double bond-containing ring is an aromatic ring.

4. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , wherein the monomer a has two or more of the double bond-containing rings.

5. The emulsion-based pressure-sensitive adhesive composition according to claim 1, wherein the content of the structural unit derived from the monomer a in the polymer A is 10% by weight or more.

6. 2. The emulsion-based pressure-sensitive adhesive composition according to claim 1, wherein the polymer A further comprises at least one selected from the group consisting of a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from a carboxyl group-containing monomer.

7. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , comprising particles containing the polymer A.

8. The emulsion-based pressure-sensitive adhesive composition according to claim 7 , wherein the particles have an average particle size of 500 nm or less.

9. The emulsion-based pressure-sensitive adhesive composition according to claim 7, wherein the particles have a polydispersity index of 0.2 or less.

10. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , wherein the colorant comprises carbon black.

11. The emulsion-based pressure-sensitive adhesive composition according to claim 1, further comprising a thickener.

12. The emulsion-based pressure-sensitive adhesive composition according to claim 1 , which contains water as a dispersion medium.

13. A pressure-sensitive adhesive formed from the emulsion-based pressure-sensitive adhesive composition according to any one of claims 1 to 12.

14. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to claim 13.

15. The pressure-sensitive adhesive sheet according to claim 14, wherein the amount of residual monomer is 1000 wtppm or less.

16. The pressure-sensitive adhesive sheet according to claim 14, which has a peel strength of 1.5 N / 10 mm or more as determined by the following test. Test: The pressure-sensitive adhesive sheet is attached to alkali-free glass and peeled from the alkali-free glass at a peeling speed of 300 mm / min and a peeling angle of 180° in an atmosphere of 23°C and 50% RH. The maximum force required at this time is determined as the peel force.

17. The pressure-sensitive adhesive sheet according to claim 14, which has a glass transition temperature of 30°C or lower.

18. The pressure-sensitive adhesive sheet according to claim 14, having a transmittance of 50% or less for light with a wavelength of 300 nm to 800 nm.

19. The pressure-sensitive adhesive sheet according to claim 14, which has a gel fraction of 80% or less.

20. The pressure-sensitive adhesive sheet according to claim 14, having a thickness of 100 μm or less.

21. An optical member comprising the pressure-sensitive adhesive according to claim 13.

22. a polymer including a structural unit derived from a monomer a having a double bond-containing ring; A colorant; 1. An adhesive comprising:

23. The pressure-sensitive adhesive according to claim 22, wherein the monomer a comprises phenoxybenzyl acrylate.

24. The pressure-sensitive adhesive according to claim 22, wherein the refractive index of a pressure-sensitive adhesive sheet made from the pressure-sensitive adhesive is 1.50 or more.

25. The pressure-sensitive adhesive according to claim 22, formed from an emulsion-based pressure-sensitive adhesive composition.

26. An optical member comprising the pressure-sensitive adhesive according to any one of claims 22 to 25.

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