adhesive sheet

Abstract

To provide an adhesive sheet which has excellent adhesive force and color development property, and can maintain good color development property even after a time lapse test under high-temperature and high-humidity, a repeating test of adhesion / peeling, an abrasion resistance test, and an indentation test are performed.SOLUTION: An adhesive sheet has a laminated structure that a base material, a primer layer and a colloidal crystal layer are laminated in this order, and an adhesive layer, in which the colloidal crystal layer has a structure that core-shell type resin fine particles are aligned and a gap.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet having a colloidal crystal layer that has excellent adhesive strength and color development, and is capable of maintaining good color development even after undergoing a time-dependent test under high temperature and humidity conditions, a repeated adhesion and peeling test, a friction resistance test, and an indentation resistance test. [Background technology]

[0002] Photonic crystals are artificial crystals with a nano-periodic structure in which materials with different refractive indices are arranged at intervals similar to the wavelength of light, and have been actively studied in recent years because they have a variety of interesting optical properties, such as the reflection of light of a specific wavelength known as Bragg reflection, the light trapping effect due to the photonic band gap, and the light amplification effect. In particular, colloidal crystals, which are made up of regularly arranged monodispersed particles, have attracted attention as a relatively easy method for producing photonic crystals. In order to develop colloidal crystals as photonic crystals for a variety of applications, it is necessary to make them into adhesive sheets that can be attached to a variety of adherends. Regarding such adhesive sheets using colloidal crystals, for example, Patent Document 1 discloses an adhesive sheet in which an adhesive layer is provided on a colloidal crystal layer consisting of single-structured microparticles and a water-soluble resin, with a barrier layer interposed therebetween. Furthermore, Non-Patent Document 1 discloses a colloidal crystal sheet having an adhesive layer on the outside thereof, and the matrix portion of the colloidal crystal layer surrounding the fine particles is filled with resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-138983 [Non-patent literature]

[0004] [Non-Patent Document 1] Polymeric Particle Handbook (Supervised by Keiji Fujimoto, CMC Publishing) Summary of the Invention [Problem to be solved by the invention]

[0005] However, the adhesive sheet described in Patent Document 1 has very weak binding forces between the microparticles and the binder, and between the substrate and the binder, and the binder distribution is also non-uniform, so the binding forces between particles are not uniform, and when external force is applied, cohesive failure and interfacial peeling easily occur within the colloidal crystal layer. Furthermore, the colloidal crystal layer of the pressure-sensitive adhesive sheet described in Non-Patent Document 1 does not have air voids, so the difference in refractive index between the fine particles and the matrix is small, and excellent color development cannot be achieved. Therefore, an object of the present invention is to provide an adhesive sheet that has excellent adhesive strength and color development, and is capable of maintaining good color development even after undergoing a time-dependent test under high temperature and humidity conditions, a repeated attachment and removal test, a friction resistance test, and an indentation resistance test. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by a laminated structure in which a substrate, a primer layer, and a colloidal crystal layer having an arranged structure of core-shell resin microparticles and air voids are laminated in this order, and an adhesive sheet having an adhesive layer.

[0007] That is, the present invention relates to an adhesive sheet having a laminated structure in which a substrate, a primer layer, and a colloidal crystal layer are laminated in this order, and an adhesive layer, wherein the colloidal crystal layer has a structure in which core-shell type resin particles are arranged, and voids.

[0008] The present invention relates to the pressure-sensitive adhesive sheet, wherein the core-shell type resin fine particles contain a shell in a range of 10 to 300% by mass relative to the mass of the core.

[0009] The present invention relates to the pressure-sensitive adhesive sheet, wherein the core-shell resin microparticles contain 10 to 50% by mass of the shell relative to the mass of the core, the core has a glass transition point of 60°C or higher, and the shell has a glass transition point of -50 to 20°C.

[0010] The present invention relates to the pressure-sensitive adhesive sheet, wherein the primer layer is a layer containing at least one resin selected from the group consisting of acrylic resins and urethane resins.

[0011] The present invention relates to the pressure-sensitive adhesive sheet, wherein the glass transition point of the resin is in the range of -30 to 70°C.

[0012] The present invention relates to the above-mentioned pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive containing an acrylic resin.

[0013] The present invention relates to the pressure-sensitive adhesive sheet, wherein the acrylic resin has a glass transition point in the range of -75 to -35°C.

[0014] The present invention relates to the above pressure-sensitive adhesive sheet, wherein the acrylic resin has an acid value in the range of 4 to 30 mgKOH / g.

[0015] The present invention relates to the above-mentioned pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive further contains a crosslinking agent.

[0016] The present invention relates to the aforementioned pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is disposed on the substrate side.

[0017] The present invention relates to the aforementioned pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer is disposed on the colloidal crystal layer side.

[0018] The present invention relates to the above-mentioned pressure-sensitive adhesive sheet, wherein a resin layer is disposed between the colloidal crystal layer and the pressure-sensitive adhesive layer.

[0019] The present invention relates to the pressure-sensitive adhesive sheet, wherein the resin layer is a layer formed from a resin composition containing aqueous acrylic resin fine particles.

[0020] The present invention relates to the pressure-sensitive adhesive sheet, wherein the water-based acrylic resin fine particles have a glass transition temperature in the range of -30 to 30°C.

[0021] The present invention relates to the pressure-sensitive adhesive sheet, wherein the average particle diameter of the aqueous acrylic resin fine particles is in the range of 80 to 300 nm. [Effects of the Invention]

[0022] The present invention makes it possible to provide a pressure-sensitive adhesive sheet that has excellent adhesive strength and color development, and that can maintain good color development even after undergoing a time-dependent test under high temperature and humidity conditions, a repeated adhesion and peeling test, a friction resistance test, and an indentation resistance test. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet having a surface-printed structure according to one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet having a surface-printed structure in which a resin layer is formed on a colloidal crystal layer, according to one embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet having a reverse printing configuration according to one embodiment of the present invention. [Figure 4] FIG. 1 is a schematic cross-sectional view of an embodiment of a pressure-sensitive adhesive sheet of the present invention having a reverse-printing configuration in which a resin layer is disposed between a colloidal crystal layer and a pressure-sensitive adhesive layer. [Figure 5] FIG. 1 is a schematic cross-sectional view of an embodiment of an adhesive sheet of the present invention having a reverse-printing configuration in which a resin layer is disposed between a colloidal crystal layer and an adhesive layer, and a second substrate and an adhesive layer are further disposed via the adhesive layer. [Figure 6] FIG. 1 is a schematic cross-sectional view of an embodiment of an adhesive sheet of the present invention having a reverse-printing configuration in which a resin layer is disposed between a colloidal crystal layer and an adhesive layer, and a second substrate and an adhesive layer are further disposed via the resin layer. [Figure 7] 1 is a schematic cross-sectional view of a colloidal crystal layer in a pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] <Adhesive sheet> The pressure-sensitive adhesive sheet of the present invention has a laminated structure in which a substrate, a primer layer, and a colloidal crystal layer are laminated in this order, and an adhesive layer, wherein the colloidal crystal layer has a structure in which core-shell type resin particles are arranged and air voids are formed. The above-mentioned configuration provides excellent color development, coating resistance, and adhesive strength, does not fade over time, and maintains good color development even after repeated attachment and removal.

[0025] The adhesive sheet of the present invention may have an adhesive layer disposed on either the substrate side or the colloidal crystal layer side of the laminated structure. A configuration in which the adhesive layer is disposed on the substrate side and is visible from the colloidal crystal layer side is referred to as a "front-printed sheet," while a configuration in which the adhesive layer is disposed on the colloidal crystal layer side and is visible from the substrate side is referred to as a "reverse-printed sheet." An example of the "front-printed sheet" is a structure of "adhesive layer / substrate / primer layer / colloidal crystal layer," and an example of the "reverse-printed sheet" is a structure of "substrate / primer layer / colloidal crystal layer / adhesive layer." The pressure-sensitive adhesive sheet of the present invention may further comprise another layer as long as the effects of the present invention are not impaired. When the pressure-sensitive adhesive sheet of the present invention has a reverse-printing configuration, it is preferable that a resin layer described below be disposed between the colloidal crystal layer and the pressure-sensitive adhesive layer.

[0026] In this specification, a laminate structure in which a substrate, a primer layer, and a colloidal crystal layer are laminated in this order, or a laminate structure in which a substrate, a primer layer, a colloidal crystal layer, and a resin layer are laminated in this order, may be abbreviated as a "colloidal crystal coating film," and the pressure-sensitive adhesive sheet of the present invention has a configuration in which an adhesive layer is further disposed on the substrate side or colloidal crystal layer side of the "colloidal crystal coating film."

[0027] The pressure-sensitive adhesive sheet of the present specification is preferably a reverse-printed sheet in which the pressure-sensitive adhesive layer is disposed on the colloidal crystal layer side. A reverse-printed configuration is preferred because the substrate becomes the outermost layer, dramatically improving the coating resistance of the pressure-sensitive adhesive sheet. Furthermore, a reverse-printed configuration can improve the wettability and adhesion of the pressure-sensitive adhesive layer by using the same resin system for the pressure-sensitive adhesive layer and the colloidal crystal layer or the resin layer. Specifically, the wettability and adhesion of the pressure-sensitive adhesive layer can be improved by using, for example, an acrylic resin for the resin constituting the pressure-sensitive adhesive layer and the resin constituting the core-shell resin microparticles or the resin layer. From the above, it is possible to obtain an adhesive sheet with a colloidal crystal coating film that exhibits excellent adhesive properties (adhesive strength at room temperature and stability over time) and maintains good color development even after abrasion resistance tests and indentation resistance tests, by using a sheet with a reverse printing configuration.

[0028] In particular, the pressure-sensitive adhesive sheet of the present invention preferably has a configuration in which a resin layer formed from a resin composition containing aqueous acrylic resin microparticles (described below) is disposed between the colloidal crystal layer and the pressure-sensitive adhesive layer. With such a configuration, the resin layer seals the surface of the colloidal crystal layer, preventing excessive penetration of pressure-sensitive adhesive layer components into the voids in the colloidal crystals. The elements constituting the present invention will be described in detail below.

[0029] <Primer layer> The pressure-sensitive adhesive sheet of the present invention has a primer layer, which serves to suppress interfacial peeling between the substrate and the colloidal crystal layer. The primer layer constituting the present invention is not particularly limited and can be appropriately selected depending on the type of substrate and colloidal crystal layer, but preferably contains at least one resin selected from the group consisting of acrylic resins, urethane resins, polyolefin resins, polyester resins, and composite resins obtained by combining these resins. Among these, from the viewpoints of adhesion to the substrate and colloidal crystal layer, and the water resistance, solvent resistance, and transparency of the primer layer, it is preferable that the primer layer contains at least one resin selected from the group consisting of acrylic resins and urethane resins, more preferably an acrylic resin, and even more preferably a styrene-acrylic resin. The resin constituting the primer layer preferably has a low content of unreacted components and residual solvents in order to suppress the influence on the colloidal crystal layer, and an aqueous resin is preferably used. Here, the term "aqueous resin" refers to a resin that can be dispersed or dissolved in an aqueous medium. The term "aqueous medium" refers to an aqueous dispersion medium or aqueous solvent, and includes not only water but also dispersion media or solvents that are miscible with water.

[0030] When the resin constituting the primer layer is an aqueous resin, it can be prepared by any method, such as emulsion polymerization, which polymerizes an ethylenically unsaturated monomer in an aqueous medium, or a phase inversion emulsification method in which polymerization is performed in a non-aqueous system and then the phase is inverted to an aqueous phase while removing the solvent. Among these, emulsion polymerization is preferred because it has fewer steps, can produce a high solid content at low viscosity, and can produce a resin with a higher molecular weight.

[0031] [Acrylic resin] When the resin constituting the primer layer is an aqueous acrylic resin, the aqueous acrylic resin can be obtained by emulsion polymerization of ethylenically unsaturated monomers including a (meth)acrylic monomer.

[0032] {ethylenically unsaturated monomer} Examples of ethylenically unsaturated monomers that can be used in the production of the above-mentioned aqueous acrylic resin include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, phenoxyhexaethylene glycol (meth)acrylate, phenoxyhexaethylene glycol (meth)acrylate, and phenoxyhexaethylene glycol (meth)acrylate. Aromatic ethylenically unsaturated monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, Ethylenically unsaturated monomers containing a straight-chain or branched alkyl group, such as sil(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, stearyl(meth)acrylate, isostearyl(meth)acrylate, and behenyl(meth)acrylate; cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and 1-adamantine. ethylenically unsaturated monomers containing an alicyclic alkyl group, such as trifluoroethyl (meth)acrylate and heptadecafluorodecyl (meth)acrylate; ethylenically unsaturated monomers containing a fluorinated alkyl group, such as trifluoroethyl (meth)acrylate and heptadecafluorodecyl (meth)acrylate; ethylenically unsaturated monomers containing a carboxy group, such as maleic acid (anhydride), fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, succinic acid β-(meth)acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid;Sulfo group-containing ethylenically unsaturated monomers such as sodium 2-acrylamido 2-methylpropanesulfonate, methallylsulfonic acid, methallylsulfonic acid, sodium methallylsulfonate, allylsulfonic acid, sodium allylsulfonate, ammonium allylsulfonate, and vinylsulfonic acid; (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl) Amide group-containing ethylenically unsaturated monomers such as N-butylacrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and diacetone acrylamide; hydroxyl group-containing ethylenically unsaturated monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, and allyl alcohol; polyoxyethylene group-containing ethylenically unsaturated monomers such as methoxypolyethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate;Examples thereof include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methylethylaminoethyl (meth)acrylate, dimethylaminostyrene, and diethylaminostyrene, and amino group-containing ethylenically unsaturated monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and methylethylaminoethyl (meth)acrylate; epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth)acrylate and 3,4-epoxycyclohexyl (meth)acrylate. ketone group-containing ethylenically unsaturated monomers such as diacetone (meth)acrylamide and acetoacetoxy (meth)acrylate; allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, 1-butenyl (meth)acrylate, 2-butenyl (meth)acrylate, 3-butenyl (meth)acrylate, 1,3-methyl-3-butenyl (meth)acrylate, 2-chloroallyl (meth)acrylate, 3-chloroallyl (meth)acrylate, o-allylphenyl (meth)acrylate acrylate, 2-(allyloxy)ethyl (meth)acrylate, allyl lactyl (meth)acrylate, citronellyl (meth)acrylate, geranyl (meth)acrylate, rosinyl (meth)acrylate, cinnamyl (meth)acrylate, diallyl maleate, diaryl itaconic acid, vinyl (meth)acrylate, vinyl crotonate, vinyl oleate, vinyl linoleate, 2-(2'-vinyloxyethoxy)ethyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate ethylenically unsaturated monomers having two or more ethylenically unsaturated groups, such as tetraethylene glycol (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylpropane triacrylate, divinylbenzene, divinyl adipate, diallyl isophthalate, diallyl phthalate, and diallyl maleate;Examples of suitable ethylenically unsaturated monomers include alkoxysilyl group-containing ethylenically unsaturated monomers such as γ-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltributoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-methacryloxymethyltrimethoxysilane, 3-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, and vinylmethyldimethoxysilane; and methylol group-containing ethylenically unsaturated monomers such as N-methylol(meth)acrylamide, N,N-dimethylol(meth)acrylamide, and alkyl-etherified N-methylol(meth)acrylamide. These monomers may be used alone or in combination of two or more.

[0033] The above ethylenically unsaturated monomer may have a reactive group for the purpose of crosslinking between the primer layer and the core-shell type resin fine particles that form the colloidal crystal layer. Examples of the reactive group that may be present include an epoxy group, a carboxy group, a hydroxyl group, a ketone group, and a hydrazide group, with a ketone group being more preferred. In particular, when the reactive group is a ketone group and the crosslinking agent is a hydrazide crosslinking agent, a ketone-hydrazide crosslink can be formed. Furthermore, when the aqueous acrylic resin is in the form of resin particles dispersible in an aqueous medium, if an ethylenically unsaturated monomer having a highly hydrophilic ketone group is used in the copolymerization composition, the ketone group is introduced to the outside of the resin particles, i.e., near the interface with the aqueous medium, and is thought to be able to efficiently form crosslinks with the hydrazide crosslinking agent.

[0034] When the aqueous acrylic resin contains a ketone group, the preferred ketone group content is in the range of 0.05 to 0.3 mmol / g, based on the mass of the aqueous acrylic resin. By incorporating a ketone group in the range of 0.05 to 0.3 mmol / g, crosslinking is formed without inhibiting the fusion of the aqueous acrylic resin, resulting in a stronger bond between the primer layer and the colloidal crystal layer. This further improves the conformability of the colloidal crystal coating film, resulting in a pressure-sensitive adhesive sheet that can maintain good color development even when the pressure-sensitive adhesive sheet is repeatedly attached and detached.

[0035] {Radical polymerization initiator} As the radical polymerization initiator used in the production of the aqueous acrylic resin, known oil-soluble polymerization initiators or water-soluble polymerization initiators can be used, and these may be used alone or in combination of two or more.

[0036] The oil-soluble polymerization initiator is not particularly limited, and examples thereof include organic peroxides such as benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butylperoxy(2-ethylhexanoate), tert-butylperoxy-3,5,5-trimethylhexanoate, and di-tert-butyl peroxide; and azobis compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 1,1'-azobis-cyclohexane-1-carbonitrile.

[0037] In emulsion polymerization, it is preferable to use a water-soluble polymerization initiator, and as the water-soluble polymerization initiator, for example, conventionally known ones such as ammonium persulfate (APS), potassium persulfate (KPS), hydrogen peroxide, and 2,2'-azobis(2-methylpropionamidine) dihydrochloride can be suitably used.

[0038] {Surfactant} A surfactant is generally used in the production of aqueous acrylic resins, and the use of a surfactant can improve the stability and monodispersity of core-shell type resin microparticles. Examples of surfactants include anionic and nonionic surfactants, with anionic surfactants being preferred. These surfactants may be used alone or in combination of two or more. Examples of surfactants include anionic reactive surfactants, anionic non-reactive surfactants, nonionic reactive surfactants, and nonionic non-reactive surfactants. Here, reactive surfactant refers to a surfactant that can polymerize with the above-mentioned ethylenically unsaturated monomer. More specifically, it refers to a surfactant having a reactive group that can polymerize with an ethylenically unsaturated bond. Examples of reactive groups include alkenyl groups such as vinyl groups, allyl groups, and 1-propenyl groups, and (meth)acryloyl groups. The use of a reactive surfactant reduces the amount of free surfactant components contained in the aqueous acrylic resin, suppressing adverse effects on the particle arrangement of colloidal crystals, thereby enabling the production of a pressure-sensitive adhesive sheet with superior color development.

[0039] {Other ingredients} In the production of the aqueous acrylic resin, a reducing agent, a buffering agent, a chain transfer agent, and a neutralizing agent can be used as needed.

[0040] [Urethane resin] When the resin constituting the primer layer is an aqueous urethane resin, the aqueous urethane resin is not particularly limited, and can be obtained, for example, by a method in which any polyol and polyisocyanate are subjected to a polyaddition reaction in a non-aqueous system, and the resulting urethane resin is dispersed in water using a surfactant, or by a method in which a hydrophilic group such as a carboxy group is introduced into the urethane resin to cause self-emulsification. The aqueous urethane resin may be reacted with a diamine or a dihydrazide compound to introduce a functional group into the terminal isocyanate group, or may be polymerized by chain extension. The aqueous urethane resin may also be composited with a different resin, for example, by grafting an acrylic resin skeleton or an olefin resin skeleton via a reactive group.

[0041] Examples of polyols constituting the urethane resin include polyether polyols such as polyethylene glycol, polypropylene glycol, poly(ethylene / propylene) glycol, and polytetramethylene glycol; ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, octanediol, butylethylpentanediol, 2-ethyl-1,3-hexanediol, cyclohexanediol, and bisphenol A. Examples of the polyester polyols include polyester polyols obtained by reacting a difunctional polyol such as methyl acrylate or a trifunctional polyol such as glycerin, trimethylolpropane, or pentaerythritol with a dibasic acid such as terephthalic acid, adipic acid, azelaic acid, sebacic acid, dimer acid, hydrogenated dimer acid, phthalic anhydride, isophthalic acid, or trimellitic acid; polycarbonate polyols obtained by reacting the above-mentioned difunctional polyols with a dialkyl carbonate, alkylene carbonate, or diaryl carbonate; polyolefin polyols such as hydroxyl group-containing polybutadiene, acid group-containing hydrogenated polybutadiene, hydroxyl group-containing polyisoprene, hydroxyl group-containing hydrogenated polyisoprene, hydroxyl group-containing chlorinated polypropylene, and hydroxyl group-containing chlorinated polyethylene; and castor oil polyols made from plant-derived oils.

[0042] Polyisocyanates that make up urethane resins include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, lysine diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'- Examples of the polyisocyanate include aromatic polyisocyanates such as biphenylene diisocyanate, 1,5-naphthalene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate; aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate, 1,4-cyclohexylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0043] In the synthesis of urethane resins, a low molecular weight diol may be used in combination for the purpose of adjusting the urethane bond concentration and introducing various functional groups. The low-molecular-weight diol is preferably a diol having a molecular weight of 500 or less, and examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, hexanediol, octanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butylenediol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-butanetriol, pentaerythritol, sorbitol, N,N-bis(2-hydroxypropyl)aniline, dimethylolalkanoic acids such as dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolpentanoic acid, as well as dihydroxysuccinic acid, dihydroxypropionic acid, and dihydroxybenzoic acid.

[0044] Examples of compounds that can be used for the terminal modification or chain extension reaction include diamines such as hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylenediamine, tolylenediamine, xylenediamine, and N-(β-aminoethyl)ethanolamine, and dihydrazides such as adipic acid dihydrazide and isophthalic acid dihydrazide.

[0045] Commercially available aqueous urethane resins include, for example, the Superflex series (e.g., SF-170, SF-210, etc.) manufactured by Dai-ichi Kogyo Seiyaku, the U-Coat and Permarin series (e.g., UX-310, UX-3945, etc.) manufactured by Sanyo Chemical Industries, Ltd., the Juliano series (e.g., W-600, W-321, etc.) manufactured by Arakawa Chemical Industry Co., Ltd., the Adeka Pontitor series (e.g., HUX-420A, HUX-386, etc.) manufactured by ADEKA, the UW series (e.g., UW-5002, UW-5020, etc.) manufactured by Ube Industries, Ltd., and the Acrit series (e.g., WBR2000U, WBR2101, WEM-200U, etc.) manufactured by Taisei Fine Chemical Co., Ltd.

[0046] [Polyolefin resin] When the resin constituting the primer layer is an aqueous polyolefin resin, the aqueous polyolefin resin may be, for example, an acid-modified polyolefin obtained by modifying a base resin such as an ethylene-propylene copolymer, a propylene-1-butene copolymer, or an ethylene-propylene-1-butene copolymer with maleic acid, etc. The polyolefin resin may be composited with a different resin, for example, by grafting an acrylic resin skeleton. The aqueous polyolefin resin can be dispersed in water using a surfactant, or by introducing a hydrophilic group into the polyolefin resin to cause self-emulsification.

[0047] Commercially available aqueous polyolefin resins include, for example, the Superchron series and Auroren series (e.g., E-480T, AE-301, etc.) manufactured by Nippon Paper Industries Co., Ltd., the Arrowbase series (e.g., SB-1230N, SB-1200, etc.) manufactured by Unitika, and the Aptlock series (e.g., BW-5550, etc.) manufactured by Mitsubishi Chemical.

[0048] [Polyester resin] When the resin constituting the primer layer is an aqueous polyester resin, the aqueous polyester resin is not particularly limited, and for example, the aqueous polyester resin can be obtained by reacting a bifunctional or trifunctional polyol with a dibasic acid. The bifunctional or trifunctional polyol and the dibasic acid can be as described in the above section [Urethane Resin]. The aqueous polyester resin can be dispersed in water using a surfactant, or by introducing a hydrophilic group into the polyester resin to cause self-emulsification, to obtain an aqueous dispersion. Commercially available aqueous polyester resins include, for example, the Pluscoat series (such as Z-730 and Z-760) manufactured by GOO Chemical Co., Ltd.

[0049] The glass transition point (Tg) of the resin constituting the primer layer is preferably in the range of -30 to 70°C, more preferably in the range of -25 to 40°C. When the glass transition point is in the range of -30 to 70°C, penetration of the primer component into the voids in the colloidal crystal layer can be suppressed, allowing the pressure-sensitive adhesive sheet to maintain good color development even when left at high temperatures for long periods of time. Furthermore, because the pressure-sensitive adhesive sheet has excellent conformability while maintaining sufficient adhesion and film strength, it is possible to obtain a pressure-sensitive adhesive sheet that can maintain good color development even after various resistance tests such as repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests. The glass transition temperature in this specification is a value determined using a DSC (differential scanning calorimeter).

[0050] The resin constituting the primer layer preferably has a carboxy group and preferably has an acid value in the range of 5 to 70 mgKOH / g. When the acid value is in the above range, the coatability of the primer to the substrate is improved, and the adhesion between the primer layer and the substrate is improved. Furthermore, the coatability of the colloidal crystal layer composition to be applied onto the primer layer is not hindered, and the composition has excellent wettability to the primer layer, resulting in good bonding between the colloidal crystal layer and the primer layer. Furthermore, the possibility that the primer layer will dissolve in water and affect the ordered arrangement of the colloidal crystals can be reduced. This allows for the production of a pressure-sensitive adhesive sheet that exhibits excellent color development and maintains good color development even after various durability tests, such as aging tests under high-temperature and high-humidity conditions and repeated application and removal tests.

[0051] [Method for forming primer layer] The method for forming the primer layer is not particularly limited, but for example, the primer layer can be formed by applying a primer composition containing an aqueous resin and a hydrophilic solvent to the substrate and drying it as necessary. The thickness of the primer layer is not particularly limited, but from the viewpoints of the function expression of the primer layer and productivity, it is preferably 1 to 50 μm, more preferably 2 to 20 μm, and even more preferably 2 to 10 μm. The aqueous resin after drying and film formation is preferably a water-insoluble layer. On such a primer layer, the above-mentioned core-shell type resin fine particles are laminated in an ordered arrangement, and a colloidal crystal layer is bonded and fixed.

[0052] {hydrophilic solvent} Examples of the hydrophilic solvent include monohydric alcohol solvents such as ethanol, 1-propanol, and isopropanol; glycol solvents such as ethylene glycol, 1,3-propanediol, and propylene glycol; glycol ether solvents such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monoethyl ether; lactam solvents such as N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, and ε-caprolactam; and amide solvents such as formamide and N-methylformamide.

[0053] The primer composition may contain various additives such as achromatic black fine particles and crosslinking agents for the purpose of improving the color development of the pressure-sensitive adhesive sheet and improving the physical properties of the coating film by crosslinking, as long as they do not adversely affect the arrangement of the core-shell type resin fine particles that form colloidal crystals or the various physical properties of the pressure-sensitive adhesive sheet.

[0054] {Achromatic black particles} The achromatic black fine particles absorb scattered light within the pressure-sensitive adhesive sheet, making the color more distinct. Black dyes or pigments can be used as the achromatic black fine particles, and carbon black is preferred from the viewpoints of having little effect on the shape of the reflection spectrum in the visible region and excellent durability such as weather resistance. The carbon black may be either a dispersion type dispersed in water using a dispersant, or a self-dispersion type, but it is preferable to use self-dispersion type carbon black from the viewpoint of not affecting the particle arrangement due to the dispersant.

[0055] {Crosslinking agent} The crosslinking agent that may be contained in the primer composition is not particularly limited, and examples thereof include hydrazide compounds (polyhydrazides) having two or more hydrazino groups that react with active carbonyl groups to form keto-hydrazide crosslinks, isocyanate compounds that react with hydroxyl groups or amino groups to form urethane bonds or urea bonds, and epoxy compounds that react with carboxy groups, amino groups, etc., and can be selected appropriately depending on the application. More specifically, when the resin contained in the primer composition has a carboxy group, crosslinking can be achieved via an epoxy crosslinking agent. Furthermore, when the resin contained in the primer composition has a hydroxyl group, crosslinking can be achieved via a polyisocyanate crosslinking agent. Furthermore, when the resin contained in the primer composition has a ketone group, crosslinking can be achieved via a hydrazide crosslinking agent. As a crosslinking agent, it is preferable to use a hydrazide crosslinking agent to form a ketone-hydrazide crosslink, as described above. Examples of the hydrazide crosslinking agent include adipic acid dihydrazide and a water-soluble resin modified with a polyfunctional hydrazide group.

[0056] <Colloidal crystal layer> The pressure-sensitive adhesive sheet of the present invention has a colloidal crystal layer, which exhibits structural color derived from Bragg reflection and has a color-producing function. The colloidal crystal layer of the present invention contains core-shell resin microparticles and has a structure in which the core-shell resin microparticles are regularly arranged. The colloidal crystal layer also has air voids. The regularly arranged structure of the core-shell resin microparticles allows the shells of adjacent core-shell resin microparticles and the shells of the core-shell resin microparticles to easily bond with each other and with the layer in contact with the shells, thereby exhibiting good adhesive properties and various resistances. Furthermore, the presence of air voids in the colloidal crystal layer increases the difference in refractive index between the particles and the matrix, thereby exhibiting excellent color development properties.

[0057] The core-shell type resin microparticles have a structure in which the core and shell are water-insoluble polymers and are incompatible with each other, comprising a core (inner layer) and a shell (outer layer). The core maintains its spherical shape, while the shell has fluidity and functions as a binding site. When a composition containing core-shell type resin microparticles is applied to a substrate or the like, as the medium such as water evaporates, the particles advect and accumulate, arranging regularly to form a colloidal crystal layer. The shells of adjacent core-shell type resin microparticles, and the shells of core-shell type resin microparticles and the layer in contact with the shells, can easily be bound together. The core-shell type resin particles in the present invention are not particularly limited, but are preferably polymers of ethylenically unsaturated monomers, more preferably acrylic resins, and even more preferably styrene-acrylic resins.

[0058] The method for producing core-shell type resin microparticles is not particularly limited, and examples thereof include a method of polymerizing an ethylenically unsaturated monomer in an aqueous medium such as emulsion polymerization, and a phase inversion emulsification method in which polymerization is carried out in a non-aqueous system and then the phase is inverted to an aqueous phase while removing the solvent, but emulsion polymerization is preferred in terms of being able to produce a high molecular weight, low viscosity, and high solid content concentration.In addition, in emulsion polymerization, either two-stage polymerization in which the monomer composition is changed between the first stage and the second stage and dropped, or multi-stage polymerization in which the monomer composition is changed in three or more stages and dropped, may be used. The core-shell type resin particles can be prepared by the above-mentioned two-stage polymerization, specifically by the following procedure. (1) First, an aqueous medium and a surfactant are charged into a reaction vessel and the temperature is raised. Then, under a nitrogen atmosphere, a radical polymerization initiator is added while an emulsion of ethylenically unsaturated monomers (which will form the cores) is added dropwise. After the reaction begins, the particles gradually grow to form core particles according to the amount added. (2) Next, when the first-stage addition is completed and the heat generation has subsided, the second-stage addition of the emulsion of the ethylenically unsaturated monomer to form the shell begins. At this time, additional initiator may be added. The added second-stage ethylenically unsaturated monomer is initially distributed to the core particles, but as the polymerization proceeds, it precipitates as a polymer on the outer layer of the core particles, forming a shell layer.

[0059] {ethylenically unsaturated monomer} As for the ethylenically unsaturated monomer that can be used in producing the core-shell type resin particles, the description in the section <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited. The ethylenically unsaturated monomer forming the core particle preferably contains 70 to 100% by mass of aromatic ethylenically unsaturated monomer based on the total mass of the ethylenically unsaturated monomer forming the core particle. By including the aromatic ethylenically unsaturated monomer in the above range, the refractive index of the core increases, increasing the difference in refractive index between the particle portion and the air void portion in the colloidal crystal, thereby improving the color development of the colloidal crystal layer. Furthermore, the contrast between the core portion and the shell portion becomes clear, allowing the shell portion to be sufficiently fused. This improves film durability and allows color development to be maintained even after repeated application and removal.

[0060] The ethylenically unsaturated monomer may also have a reactive group for the purpose of forming crosslinks within the colloidal crystal layer and between the colloidal crystal layer and the layer in contact with the colloidal crystal layer. By forming crosslinks within the colloidal crystal layer and between the colloidal crystal layer and the layer in contact with the colloidal crystal layer, the coating resistance of the resulting pressure-sensitive adhesive sheet is improved. Furthermore, by forming crosslinks between the colloidal crystal layer and the pressure-sensitive adhesive layer, excessive penetration of the pressure-sensitive adhesive component into the colloidal crystal layer can be prevented. This suppresses collapse and cohesive failure of the colloidal crystal layer even after repeated application and removal, resulting in a pressure-sensitive adhesive sheet that can maintain good color development.

[0061] Crosslinking within the colloidal crystal layer and between the colloidal crystals and a layer in contact with the colloidal crystal layer can be introduced by a method of reacting reactive groups of the core-shell type resin microparticles with each other, a method of reacting reactive groups of the core-shell type resin microparticles with reactive groups in a primer layer, adhesive layer or resin layer described below, a method of crosslinking reactive groups of the core-shell type resin microparticles with each other via a polyfunctional crosslinking agent, or a method of crosslinking reactive groups of the core-shell type resin microparticles with reactive groups in a primer layer, adhesive layer or resin layer described below.

[0062] As for the reactive group that the ethylenically unsaturated monomer may have, the description in the section <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited. When the core-shell type resin particles have ketone groups, the content of the ketone groups is preferably in the range of 0.05 to 0.3 mmol / g based on the mass of the core-shell type resin particles. By incorporating the ketone groups in the range of 0.05 to 0.3 mmol / g, crosslinking is formed without inhibiting the fusion of the shells, which strengthens the bonds between particles and layers and allows the particles to maintain good color development even after various resistance tests such as repeated peeling tests and abrasion resistance tests. Furthermore, if the density is within 0.3 mmol / g, the polymerization stability of the core-shell type resin particles is improved and the uniformity of the particle diameter is improved, resulting in good color development.

[0063] When reactive groups are introduced into core-shell type resin particles, it is preferable to introduce the reactive groups into the shell portion, since this allows for more effective expression of the synergistic effect of thermal fusion and crosslinking due to entanglement of polymer chains.

[0064] {Radical polymerization initiator} As the radical polymerization initiator used in the production of the core-shell type resin microparticles, known oil-soluble polymerization initiators or water-soluble polymerization initiators can be used, and the description in the section on <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited.

[0065] {Surfactant} A surfactant is generally used in the production of core-shell type resin particles, and the use of a surfactant can improve the stability and monodispersity of the core-shell type resin particles. Examples of surfactants include anionic and nonionic surfactants, with anionic surfactants being preferred. Regarding these surfactants, the description in the section on "Surfactants" in the "Primer Layer" above can be applied.

[0066] {Other ingredients} In the production of the core-shell type resin particles, a reducing agent, a buffering agent, a chain transfer agent, and a neutralizing agent can be used as needed.

[0067] {Properties of core-shell resin particles} The average particle diameter of the core-shell type resin microparticles is preferably 180 to 330 nm. When the average particle diameter is 180 nm or more, the color development of the colloidal crystals in the visible light range becomes clear, and a pressure-sensitive adhesive sheet with even better color development can be obtained. When the average particle diameter is 330 nm or less, the color development of the colloidal crystals in the visible light range is excellent, and scattering by the particles is suppressed, resulting in even better color development. The average particle size in this specification can be measured by dynamic light scattering (measuring device manufactured by Nanotrac UPA Co., Ltd., Microtrac Bell Co., Ltd.), and the peak of the obtained volume particle size distribution data (histogram) is taken as the average particle size.

[0068] The coefficient of variation (Cv value) of the average particle diameter of the core-shell type resin particles is preferably 30% or less. The coefficient of variation is a value that indicates the uniformity of the particle diameter, and can be calculated by the following formula. Formula: Coefficient of variation Cv value (%) = standard deviation of particle size / average particle size × 100 [In the formula, the units of standard deviation and average particle size are the same] By arranging highly monodisperse fine particles with a coefficient of variation of 30% or less, the regularity of the particle arrangement is improved, and more vivid and clear structural colors can be expressed.

[0069] The glass transition temperature (Tg) of the core of the core-shell type resin microparticles is preferably 60° C. or higher, and more preferably in the range of 60° C. to 150° C. When the glass transition temperature is 60° C. or higher, the shape of the core is prevented from being deformed by the influence of external heat or force, and thus the color development can be better maintained even before and after aging tests at high temperatures.

[0070] The glass transition temperature of the shell of the core-shell resin microparticles is preferably in the range of -50 to 20°C, more preferably in the range of -30 to 10°C. Within this range, the voids in the colloidal crystal layer are prevented from being filled by fusion of the shell. Furthermore, fusion of the shell is promoted, sufficiently improving the strength of the fused portion. This allows the product to exhibit excellent color development, and the color development can be maintained even after various resistance tests, such as aging tests under high-temperature conditions, repeated attachment and removal tests, abrasion resistance tests, and indentation resistance tests.

[0071] In core-shell resin microparticles, the shell content is preferably in the range of 10 to 300% by mass, more preferably 10 to 150% by mass, based on the total mass of the core. When the shell content is 10% by mass or more, the shells are sufficiently fused together, resulting in stronger bonds between the core-shell resin microparticles and between the core-shell resin microparticles and the layer in contact with the colloidal crystal layer. This results in excellent color development, which can be maintained even after various resistance tests, such as aging tests under high-temperature conditions, repeated peeling tests, abrasion resistance tests, and indentation resistance tests. From the viewpoint of color development, the shell content is preferably 150% by mass or less, more preferably 50% by mass or less. A shell content of 150% by mass or less is preferable because it prevents the shell from being excessively fused by heat or a solvent, thereby providing sufficient voids. In colloidal crystals, the presence of air in the voids of the core-shell resin microparticles increases the difference in refractive index between the particles and the matrix, improving color development. On the other hand, from the viewpoint of indentation resistance, the shell content is preferably in the range of 50 to 300% by mass, more preferably in the range of 50 to 200% by mass. If the shell content is 50% by mass or more, fusion of the shells is further promoted when the coating film is dried, and the bonds between the core-shell type resin particles and between the core-shell type resin particles and the substrate are strengthened, resulting in colloidal crystals with excellent indentation resistance.

[0072] [Colloidal crystal layer formation] The method for forming the colloidal crystal layer is not particularly limited, but for example, it can be formed by applying a composition for a colloidal crystal layer containing core-shell resin microparticles and water onto the primer layer of a substrate that has a primer layer. The thickness of the colloidal crystal layer is not particularly limited, but from the viewpoints of color development and productivity, it is preferably 3 to 30 μm, more preferably 5 to 20 μm. The colloidal crystal layer composition may contain achromatic black fine particles, hydrophilic solvents, crosslinking agents, and the like for the purpose of improving coatability, coating film resistance, and color development, as long as such additions do not adversely affect particle arrangement or the various physical properties of the pressure-sensitive adhesive sheet.

[0073] {Achromatic black particles} The achromatic black particles absorb scattered light in the colloidal crystal layer, making the color development more vivid. The description of the achromatic black particles in the section on the primer layer above can be used for the achromatic black particles.

[0074] The average particle size of the achromatic black fine particles is preferably in the range of 30 to 300 nm, and the content of the achromatic black fine particles is preferably in the range of 0.3 to 3 mass % based on the mass of the core-shell type resin particles. When the average particle size and the content of the achromatic black fine particles are within the above ranges, the ordered arrangement of the core-shell type resin fine particles is not hindered and the particles are prevented from falling out of the colloidal crystal layer, thereby enabling the good color development to be maintained even after various durability tests such as repeated peeling tests and abrasion resistance tests.

[0075] {hydrophilic solvent} The hydrophilic solvent may be the same as that described above in the section <Hydrophilic Solvent> in <Primer Layer>.

[0076] {Crosslinking agent} There are no particular restrictions on the crosslinking agent that may be contained in the composition for the colloidal crystal layer, and the description in the section on <Crosslinking Agent> in the above <Primer Layer> can be used. As a crosslinking agent, it is preferable to use a hydrazide crosslinking agent to form a ketone-hydrazide crosslink. Examples of hydrazide crosslinking agents include adipic acid dihydrazide and a water-soluble resin modified with a polyfunctional hydrazide group.

[0077] <Resin layer> The pressure-sensitive adhesive sheet of the present invention may further have a resin layer (also referred to as a protective layer) on the colloidal crystal layer for the purpose of protecting the colloidal crystal layer. When the pressure-sensitive adhesive sheet has a front-side printing configuration, the resin layer functions as the outermost layer of the sheet, protecting the colloidal crystal layer from the outside. When the pressure-sensitive adhesive sheet has a back-side printing configuration, the resin layer functions as a layer that prevents the adhesive components in the adjacent pressure-sensitive adhesive layer from penetrating into the colloidal crystal layer. In particular, when the pressure-sensitive adhesive sheet of the present invention has a reverse-printed structure, it is preferable that a resin layer, which will be described later, be disposed between the colloidal crystal layer and the pressure-sensitive adhesive layer.

[0078] The resin constituting the resin layer is not particularly limited, but is preferably an acrylic resin, more preferably a styrene-acrylic resin, from the viewpoint of excellent adhesion to the core-shell type resin microparticles. Furthermore, from the viewpoint of suppressing penetration into the colloidal crystal layer, the resin layer is preferably a layer formed by drying aqueous resin microparticles, rather than a water-soluble resin or a solvent-based resin.

[0079] The method for producing aqueous resin microparticles is not particularly limited, and they can be produced, for example, by the following emulsion polymerization. First, an aqueous medium and a surfactant are charged into a reaction vessel and the temperature is raised to a predetermined level. Meanwhile, water, a surfactant, and an ethylenically unsaturated monomer containing a (meth)acrylic monomer are charged into a dropping vessel and stirred to prepare an emulsion of the ethylenically unsaturated monomer. Then, under a nitrogen atmosphere, a radical polymerization initiator is added while the prepared emulsion is dropped into the reaction vessel. After the reaction starts, polymer particle nuclei are generated, and the particles gradually grow to form acrylic resin microparticles.

[0080] As for the ethylenically unsaturated monomer that can be used in producing the aqueous resin particles, the description in the section <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited. Furthermore, with regard to the radical polymerization initiator, surfactant, and other components that can be used in producing the aqueous resin microparticles, the descriptions in the sections on <Radical polymerization initiator>, <Surfactant>, and <Other components> in the above-mentioned <Primer layer> can be used.

[0081] The aqueous resin particles preferably have a reactive group for forming crosslinks, and an ethylenically unsaturated monomer having a reactive group may be used as the ethylenically unsaturated monomer. The aqueous resin particles having a reactive group enable crosslinking within the resin layer and crosslinking between the resin layer and the colloidal crystal layer. The crosslinking within the resin layer further improves the coating strength of the resin layer, and the crosslinking between the resin layer and the colloidal crystal layer further strengthens the bond between the resin layer and the colloidal crystal layer, thereby making it possible to obtain a PSA sheet that can maintain its excellent color development even after various resistance tests such as repeated peeling tests, abrasion resistance tests, and indentation resistance tests.

[0082] Crosslinking within the resin layer can be introduced by a method of reacting reactive groups of the aqueous resin particles with each other, or by a method of reacting reactive groups of the aqueous resin particles via a polyfunctional crosslinking agent. Crosslinking between the resin layer and the colloidal crystal layer can be introduced by a method of reacting reactive groups of the aqueous resin microparticles with those of the core-shell type resin microparticles, or by a method of reacting reactive groups of the aqueous resin microparticles with those of the core-shell type resin microparticles via a polyfunctional crosslinking agent. Crosslinking between the resin layer and the adhesive layer can be introduced by reacting the reactive groups of the aqueous resin microparticles with the reactive groups of the resin contained in the adhesive layer, or by reacting the reactive groups of the aqueous resin microparticles with the resin contained in the adhesive layer via a polyfunctional crosslinking agent.

[0083] As for the reactive group that the ethylenically unsaturated monomer may have, the description in the section <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited. When the aqueous resin microparticles contain ketone groups, the preferred ketone group content is in the range of 0.05 to 0.3 mmol / g based on the mass of the aqueous resin microparticles. By incorporating the ketone group in the range of 0.05 to 0.3 mmol / g, crosslinking is formed without inhibiting the fusion of the aqueous resin microparticles, improving the coating strength of the resin layer and providing a stronger bond between the colloidal crystal layer and the resin layer. This improves the conformability and strength of the coating film, resulting in a PSA sheet that can better maintain its color development even after various resistance tests, such as repeated peeling tests and abrasion resistance tests.

[0084] The average particle size of the aqueous resin particles is preferably in the range of 80 to 300 nm, and the glass transition point of the aqueous resin particles is preferably in the range of -30 to 30°C. When the average particle size and glass transition point are within the above ranges, the aqueous resin particles are filled in the surface of the colloidal crystal layer, and penetration of the resin component into the voids in the colloidal crystal layer is further suppressed. Furthermore, when the average particle size is within the above range, excellent film-forming properties can be achieved, allowing the formation of a homogeneous resin layer free of coating irregularities and cracks, thereby enabling good color development and further improvement in coating durability. Furthermore, when the resin layer is disposed between the colloidal crystal layer and the adhesive layer, penetration of adhesive components from the adhesive layer can be further suppressed. This allows for the production of an adhesive sheet that exhibits excellent color development and can maintain its excellent color development even after undergoing various resistance tests such as aging tests under high temperature conditions, repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests.

[0085] [Formation of resin layer] The method for forming the resin layer is not particularly limited, but for example, the resin layer can be formed by applying a resin composition containing aqueous resin particles and water onto the colloidal crystal layer and drying it as necessary. After drying and film formation, the aqueous resin particles are preferably insoluble in water. The thickness of the resin layer is not particularly limited, but is preferably 3 to 50 μm, and more preferably 2 to 20 μm. The resin composition may contain additives such as achromatic black fine particles, hydrophilic solvents, and crosslinking agents for the purpose of improving color development, coating properties, and coating film durability, as long as the additives do not adversely affect the physical properties of the colloidal crystal layer.

[0086] {Achromatic black particles} The achromatic black particles absorb scattered light within the adhesive sheet, making the color of the colloidal crystal coating film more vivid. This is particularly effective when the colloidal crystal coating film is used for reverse printing, as it allows for clear color development. The description of the achromatic black particles in the "primer layer" section above can be used for the achromatic black particles.

[0087] {hydrophilic solvent} The hydrophilic solvent that may be contained in the resin composition can be the same as that described above in the section <Hydrophilic Solvent> in <Primer Layer>.

[0088] {Crosslinking agent} The crosslinking agent that may be contained in the resin composition is not particularly limited, and the description in the section <Crosslinking agent> in the above <Primer layer> can be used.

[0089] <Adhesive layer> The adhesive layer in the adhesive sheet of the present invention serves to adhere the colloidal crystal coating film to any adherend. The adhesive layer constituting the present invention is not particularly limited and can be appropriately selected depending on the type of substrate and colloidal crystal layer, but preferably contains at least one resin selected from the group consisting of acrylic resins and urethane resins. Of these, the adhesive layer preferably contains an acrylic resin because it has a small amount of unreactive components and excellent adhesion. In addition, the resin constituting the adhesive layer preferably has a low content of unreacted components and residual solvents in order to suppress the influence of unreacted components and residual solvents contained in the resin on the substrate, colloidal crystal layer, and resin layer, and an aqueous resin is preferably used. Here, the term "aqueous resin" refers to a resin that can be dispersed or dissolved in an aqueous medium. The term "aqueous medium" refers to an aqueous dispersion medium or aqueous solvent, and includes not only water but also dispersion media or solvents that are miscible with water.

[0090] When the resin constituting the adhesive layer is an aqueous resin, it can be prepared by any method, such as a method of polymerizing an ethylenically unsaturated monomer in an aqueous medium, such as emulsion polymerization, or a phase inversion emulsification method in which polymerization is performed in a non-aqueous system and then the phase is inverted to an aqueous phase while removing the solvent. Among these, the emulsion polymerization method is preferred because it has a small number of steps, can produce a high solid content at low viscosity, and can obtain a resin with a higher molecular weight.

[0091] [Acrylic resin] When the resin constituting the adhesive layer is an acrylic resin, the acrylic resin can be obtained by radical polymerization of an ethylenically unsaturated monomer including a (meth)acrylic monomer. When the resin constituting the adhesive layer is an aqueous acrylic resin, the aqueous acrylic resin can be obtained by emulsion polymerization of an ethylenically unsaturated monomer including a (meth)acrylic monomer.

[0092] The aqueous acrylic resin can be produced, for example, by the following emulsion polymerization. First, an aqueous medium and a surfactant are charged into a reaction vessel and the temperature is raised to a predetermined level. Meanwhile, water, a surfactant, and an ethylenically unsaturated monomer containing a (meth)acrylic monomer are charged into a dropping vessel and stirred to prepare an emulsion of the ethylenically unsaturated monomer. Then, under a nitrogen atmosphere, a radical polymerization initiator is added while the prepared emulsion is dropped into the reaction vessel. After the reaction starts, polymer particle nuclei are generated, and the particles gradually grow to form resin microparticles.

[0093] As for the ethylenically unsaturated monomer that can be used in producing the acrylic resin, the description in the section <Ethylenically unsaturated monomer> in the above <Primer layer> can be cited. Furthermore, with regard to the radical polymerization initiator, surfactant, and other components that can be used in producing the acrylic resin, the descriptions in the sections <Radical polymerization initiator>, <Surfactant>, and <Other components> in the above <Primer layer> can be used.

[0094] [Urethane resin] When the resin constituting the adhesive layer is a urethane resin, the urethane resin can be obtained by polyaddition reaction of a polyol or a low molecular weight diol with a polyisocyanate. If it is desired to further increase the molecular weight or introduce functional groups, a chain extender is appropriately used. The polyols, low molecular weight diols, polyisocyanates, and chain extenders that can be used are those described in the section on [urethane resin] in the above <Primer layer>.

[0095] The resin constituting the adhesive layer preferably has a reactive group for forming crosslinks, and an ethylenically unsaturated monomer having a reactive group may be used as the ethylenically unsaturated monomer. The reactive group in the resin constituting the adhesive layer enables crosslinking within the adhesive layer, between the adhesive layer and the colloidal crystal layer, and between the adhesive layer and the resin layer, further improving the strength of the adhesive layer and the coating resistance of the colloidal crystal film. Furthermore, in a configuration in which a resin layer is disposed between the colloidal crystal layer and the adhesive layer, crosslinking between the resin layer and the adhesive layer can suppress excessive penetration of the adhesive component into the colloidal crystal layer, even if the resin layer has cracks due to uneven coating or poor film formation. This allows for the production of an adhesive sheet that exhibits excellent adhesive properties both initially and over time and that maintains excellent color development even after various resistance tests, such as aging tests under high temperature conditions, repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests.

[0096] Crosslinking within the adhesive layer can be introduced by a method of directly reacting reactive groups between resins constituting the adhesive layer, or by a method of reacting reactive groups between resins constituting the adhesive layer via a polyfunctional crosslinking agent. Crosslinking between the adhesive layer and the colloidal crystal layer or the resin layer can be introduced by a method of reacting a reactive group of the resin constituting the adhesive layer with a reactive group of the core-shell type resin microparticles or aqueous resin microparticles constituting the resin layer, or a method of reacting a reactive group of the resin constituting the adhesive layer with a reactive group of the core-shell type resin microparticles or aqueous resin microparticles constituting the resin layer via a polyfunctional crosslinking agent.

[0097] Examples of reactive groups that may be present in the ethylenically unsaturated monomers constituting the adhesive layer include epoxy groups, carboxy groups, hydroxyl groups, ketone groups, and hydrazide groups, with ketone groups and carboxy groups being more preferred. In particular, when the reactive group is a ketone group and the crosslinking agent is a hydrazide crosslinking agent, ketone-hydrazide crosslinking can be formed. Ketone-hydrazide crosslinking is advantageous because it can form crosslinks at low temperatures and in a short time by volatilizing water, making it effective when using film substrates that are susceptible to heat damage. Furthermore, because ketone groups are highly hydrophilic, when ethylenically unsaturated monomers containing ketone groups are used in the copolymerization composition, the ketone groups are introduced to the exterior of the resin microparticles, i.e., near the interface with the aqueous medium, and are thought to effectively form crosslinks with the hydrazide crosslinking agent.

[0098] The glass transition point of the resin constituting the adhesive layer is preferably in the range of -75 to -35°C. When the glass transition point is in this range, whether the adhesive layer is disposed on a substrate, a colloidal crystal layer, or a resin layer, the adhesion between the adhesive layer and each layer is improved, and the adhesion between the adhesive layer and the adherend is also improved. Furthermore, the adhesive layer has sufficient strength, resulting in excellent coating film resistance. This allows for the production of an adhesive sheet that exhibits good adhesive strength and can further maintain excellent color development even after abrasion resistance tests and indentation resistance tests.

[0099] The acid value of the resin constituting the adhesive layer is preferably in the range of 4 to 30 mgKOH / g. When the acid value is in this range, sufficient wettability to each substrate is maintained while interaction between acidic groups such as carboxy groups occurs, improving the cohesive strength of the adhesive layer. Furthermore, interaction with carboxy groups in the colloidal crystal layer and resin layer improves adhesion to the colloidal crystal coating film. Furthermore, changes in adhesive properties in high-temperature, high-humidity environments are also reduced. This allows for the production of a pressure-sensitive adhesive sheet with excellent adhesive properties both initially and over time. The carboxyl group can also be used as a reactive group, and crosslinking can be performed within the pressure-sensitive adhesive layer, between the pressure-sensitive adhesive layer and the colloidal crystal layer, or between the pressure-sensitive adhesive layer and the resin layer using a crosslinking agent, as described below, to further improve the coating film resistance. This allows for the maintenance of good color development even after various resistance tests, such as a time test under high-temperature conditions, a repeated peel-and-remove test, and a friction resistance test, have been conducted.

[0100] [Formation of adhesive layer] The method for forming the adhesive layer is not particularly limited, but it is preferably a layer formed from a pressure-sensitive adhesive containing an acrylic resin, and can be formed, for example, by applying a resin composition containing an aqueous acrylic resin and water onto the colloidal crystal layer, the resin layer, or the substrate, and drying it. The thickness of the adhesive layer is not particularly limited, and is preferably 5 to 100 μm, more preferably 10 to 50 μm, from the viewpoint of sufficient adhesion to the adherend. The pressure-sensitive adhesive may contain various additives such as achromatic black fine particles, hydrophilic solvents, crosslinking agents, tackifiers, thickeners, etc., for the purpose of improving the color development, coating film properties, and adhesiveness of the pressure-sensitive adhesive sheet, as long as the additives do not adversely affect the physical properties of the substrate, colloidal crystal layer, and resin layer.

[0101] {Achromatic black particles} The achromatic black particles absorb scattered light within the adhesive sheet, making the color of the colloidal crystal coating film more vivid. This is particularly effective when the colloidal crystal coating film is used for reverse printing, as it allows for clear color development. The description of the achromatic black particles in the "primer layer" section above can be used for the achromatic black particles.

[0102] {hydrophilic solvent} The hydrophilic solvent that may be contained in the resin composition can be the same as that described above in the section <Hydrophilic Solvent> in <Primer Layer>.

[0103] {Crosslinking agent} The pressure-sensitive adhesive preferably contains a crosslinking agent. The inclusion of a crosslinking agent forms crosslinks within the adhesive layer, between the adhesive layer and the colloidal crystal layer, or between the adhesive layer and the resin layer. This improves the adhesive layer's adhesion and cohesive strength to the adherend or the colloidal crystal coating. It also prevents excessive penetration of the adhesive components into the colloidal crystal layer. This allows for the production of a pressure-sensitive adhesive sheet that exhibits excellent adhesive properties both initially and over time and maintains excellent color development even after various resistance tests, such as aging tests under high-temperature conditions, repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests.

[0104] The crosslinking agent that can be used in the pressure-sensitive adhesive may be any agent that reacts with a reactive group (e.g., a carboxy group, a hydroxy group, a ketone group, etc.) possessed by the resin that constitutes the pressure-sensitive adhesive, and examples thereof include titanium chelate compounds, aluminum chelate compounds, zirconium chelate compounds, zinc oxide, aziridine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and hydrazide compounds. Among these, carbodiimide compounds, aziridine compounds, epoxy compounds, and hydrazide compounds are preferred in terms of their long pot life and improved adhesion to the substrate. The crosslinking agent may be used alone or in combination of two or more.

[0105] The amount of crosslinking agent blended is preferably in the range of 0.1 to 3 mass % based on the mass of the resin constituting the pressure-sensitive adhesive. Blending within this range can improve the coating strength of the adhesive layer while maintaining good adhesive properties. This allows for the production of an adhesive sheet that exhibits excellent adhesive properties both initially and over time and that can maintain excellent color development even after various resistance tests.

[0106] {Tackifire} A tackifier can be blended into the pressure-sensitive adhesive to further improve the adhesiveness of the adhesive layer. If the tackifier is non-aqueous, it can be blended by dissolving it in a solvent in the pressure-sensitive adhesive. If the tackifier is aqueous, it can be blended by preparing an emulsion together with the ethylenically unsaturated monomer that constitutes the adhesive layer and then emulsion polymerizing the emulsion.

[0107] The tackifier that may be added is preferably at least one selected from the group consisting of rosin-based resins, terpene-based resins, aromatic petroleum resins, and aliphatic petroleum resins. Examples of rosin-based resins include natural rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, disproportionated rosin, and disproportionated rosin ester. Examples of terpene-based resins include α-pinene resin, β-pinene resin, terpene phenol resin, and hydrogenated terpene phenol resin. Examples of aromatic petroleum resins include styrene oligomer and α-methylstyrene-styrene copolymer. Among these, rosin-based resins are preferred from the viewpoint of compatibility with the resins constituting the pressure-sensitive adhesive.

[0108] The amount of tackifier blended is preferably in the range of 0.1 to 5 mass %, more preferably in the range of 0.5 to 3 mass %, based on the mass of the resin constituting the pressure-sensitive adhesive. Blending within the above range makes it possible to obtain a pressure-sensitive adhesive sheet with superior adhesive strength over time.

[0109] <Manufacturing of adhesive sheets> The pressure-sensitive adhesive sheet of the present invention may have a laminate structure in which a substrate, a primer layer, and a colloidal crystal layer having an array of core-shell resin particles and air voids are laminated in this order, and a pressure-sensitive adhesive layer, and the method for producing the pressure-sensitive adhesive sheet is not particularly limited, and the sheet can be produced using known methods. The pressure-sensitive adhesive sheet of the present invention may further have another substrate or layer. An example of a method for producing the pressure-sensitive adhesive sheet of the present invention will be given below. First, a "colloidal crystal coating film" is produced, which has a laminated structure in which a substrate, a primer layer, and a colloidal crystal layer are laminated in this order, or a laminated structure in which a substrate, a primer layer, a colloidal crystal layer, and a resin layer are laminated in this order. Next, the resulting "colloidal crystal coating film" can be used to obtain a pressure-sensitive adhesive sheet by any of the following methods (1) to (4). (1) A method in which a pressure-sensitive adhesive is applied to the release surface of a release sheet, dried to form an adhesive layer, and a colloidal crystal coating film is laminated onto the adhesive layer. (2) A method in which a pressure-sensitive adhesive is applied to the substrate of the colloidal crystal coating film, or the colloidal crystal layer or resin layer, and dried to form an adhesive layer, and the release surface of a release sheet is laminated onto the adhesive layer. (3) A method in which a pressure-sensitive adhesive is applied to one side of a substrate and dried to form an adhesive layer, and then a resin layer of a colloidal crystal coating is laminated to the side of the substrate opposite the adhesive layer. (4) A method in which a pressure-sensitive adhesive is applied to both sides of a substrate and dried to form an adhesive layer, and then a colloidal crystal coating film is laminated onto one of the adhesive layers.

[0110] [Production of colloidal crystal coatings] The colloidal crystal coating film is preferably formed on the substrate in the order of a primer layer and a colloidal crystal layer. When a resin layer is provided, the resin layer may be formed on the colloidal crystal layer.

[0111] (Formation of primer layer) The primer layer can be formed by applying a primer composition onto a substrate and drying it as needed. The application method is not particularly limited, and examples thereof include printing methods that do not use a plate, such as inkjet, spraying, dipping, and spin coating; and printing methods that use a plate, such as offset gravure coater, gravure coater, doctor coater, bar coater, blade coater, flexo coater, and roll coater. After applying the primer composition to the substrate, the composition is dried as needed to form a film, thereby forming a primer layer. The drying method is not particularly limited, and examples thereof include conventionally known methods such as heat drying, hot air drying, infrared drying, microwave drying, and drum drying. The above drying methods may be used alone or in combination of two or more, but hot air drying is preferred to reduce damage to the substrate and dry efficiently. The drying temperature is preferably in the range of 50 to 120°C.

[0112] (Formation of colloidal crystal layer) The colloidal crystal layer can be formed by applying a composition for a colloidal crystal layer containing core-shell resin particles onto the primer layer obtained above, and drying it as necessary. The application method is not particularly limited, and the application methods described in the above section (Formation of Primer Layer) can be used. After the colloidal crystal layer composition is applied onto the primer layer, it is dried as needed to form a colloidal crystal layer. There are no particular restrictions on the drying method, and any of the drying methods described in the section (Formation of Primer Layer) can be used as appropriate. The drying temperature is preferably in the range of 25 to 80°C from the viewpoint of the effect on the alignment of the colloidal resin particles and productivity.

[0113] (Formation of resin layer) The resin layer can be formed by applying a resin composition to the colloidal crystal layer obtained above and drying it as necessary. The application method is not particularly limited, and the application methods described in the above section (Formation of primer layer) can be used. After the resin composition is applied onto the colloidal crystal layer, it is dried as needed to form a film, forming a resin layer. The drying method is not particularly limited, and the drying methods described in the section (Formation of Primer Layer) can be used as appropriate. The drying temperature is preferably in the range of 50 to 120°C.

[0114] [Adhesive sheet manufacturing] The pressure-sensitive adhesive sheet of the present invention is preferably produced by any one of the above methods (1) to (4) using the "colloidal crystal coating film" obtained above and a pressure-sensitive adhesive. The method for applying the pressure-sensitive adhesive is not particularly limited, and examples thereof include known methods such as a bar coater, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, and spin coater. The drying method is not particularly limited, and hot air drying, infrared drying, and reduced pressure methods can be used. The drying temperature is usually preferably about 60 to 150°C.

[0115] [Base material] The substrate layer in the present invention is not particularly limited and can be selected from known substrates. Examples of the substrate include thermoplastic resin substrates such as polyvinyl chloride sheet, polyethylene terephthalate (PET) film, polypropylene (PP) film, polyethylene (PE) film, nylon (Ny) film, polystyrene film, and polyvinyl alcohol film; metal substrates such as aluminum foil; glass substrates; and coated paper substrates. In particular, because the pressure-sensitive adhesive sheet of the present invention has a primer layer, it is possible to use, as the substrate, non-polar film substrates such as polyethylene terephthalate film, polypropylene film, and polyethylene film, which have previously been difficult to fix because of peeling of the colloidal crystal layer, and even when such non-polar film substrates are used, the colloidal crystal coating film exhibits excellent substrate conformability, abrasion resistance, water resistance, and solvent resistance, and also has good color development. The substrate may have a smooth or uneven surface, and may be transparent, translucent, or opaque, and may be pre-colored, for example, black, or partially printed with a pigment ink or the like, to make the color of the colloidal crystals more distinct. The substrate may be subjected to a corona treatment or plasma treatment for the purpose of improving the coatability of the primer composition or the pressure-sensitive adhesive. These substrates may be used alone or in combination of two or more types. Furthermore, when the pressure-sensitive adhesive sheet of the present invention has a reverse printing configuration, the substrate is preferably transparent so that the colloidal crystal layer can be seen through the substrate.

[0116] As in the above-mentioned colloidal crystal coating film manufacturing methods (3) and (4), when a pressure-sensitive adhesive is applied to a substrate to form an adhesive layer, and then the colloidal crystal coating film is laminated to the substrate, examples of substrates that can be used include paper, cellophane, plastic sheets, rubber, foams, fabrics, rubberized fabrics, resin-impregnated fabrics, glass plates, metal plates, wood, and optical film plates or sheets such as polarizing plates.

[0117] The adhesive sheet of the present invention has excellent adhesive strength and color development, and can maintain good color development even after undergoing aging tests under high temperature and humidity, repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests, so it can be widely used on a variety of substrates such as metal, glass, plastic, rubber, wood, and painted surfaces. [Example]

[0118] The present invention will be specifically described below with reference to examples and comparative examples. In the examples and comparative examples, "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified. In the tables, the numerical values represent "parts" unless otherwise specified, and blank spaces mean that no ingredients are blended.

[0119] [Acid value] The acid value was calculated by potentiometric titration of the dried resin with a potassium hydroxide-ethanol solution in accordance with JIS K2501 using an automatic titrator COM-1600 manufactured by Hiranuma Sangyo Co., Ltd.

[0120] [Glass transition temperature (Tg)] The glass transition temperature was measured by DSC (differential scanning calorimeter, manufactured by TA Instruments Co., Ltd.) Specifically, about 2 mg of a sample obtained by drying the resin was weighed on an aluminum pan, and the aluminum pan was set in a DSC measurement holder. The glass transition temperature was determined by reading the baseline shift (inflection point) toward the endothermic side of the DSC curve obtained under the temperature rising condition of 5°C / min.

[0121] [Average particle size] The dispersion of core-shell resin particles was diluted 500 times with water, and approximately 5 ml of the diluted solution was measured using a dynamic light scattering measurement method (measuring device manufactured by Nanotrac UPA Co., Ltd., Microtrac Bell Co., Ltd.). The peak of the obtained volume particle size distribution data (histogram) was taken as the average particle size. The coefficient of variation Cv value, which represents the variation in particle size, was calculated using the following formula. Cv value % = Standard deviation of particle size / Average particle size × 100

[0122] <Production of aqueous dispersion of resin constituting primer layer> [Manufacturing Example 1] A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 68.9 parts of ion-exchanged water and 0.25 parts of a 20% aqueous solution of Aqualon KH-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (as a reactive surfactant). Separately, 7.5 parts of styrene, 10.0 parts of benzyl methacrylate, 25.0 parts of methyl methacrylate, 16.0 parts of 2-ethylhexyl acrylate, 38.0 parts of n-butyl acrylate, 3.0 parts of methacrylic acid, 0.5 parts of 3-methacryloxypropyltriethoxysilane, 4.8 parts of a 20% aqueous solution of KH-10, and 40.4 parts of ion-exchanged water were mixed and stirred to prepare an emulsion of ethylenically unsaturated monomers, and 3% of this emulsion was then added to the reaction vessel. After the internal temperature was raised to 80°C and the atmosphere was thoroughly purged with nitrogen, 2.0 parts of a 5% aqueous solution of potassium persulfate was added as an initiator to initiate emulsion polymerization. While maintaining the internal temperature at 80°C, the remaining ethylenically unsaturated monomer emulsion and 2.0 parts of a 5% aqueous solution of potassium persulfate were added dropwise over 3 hours, and the reaction was continued for an additional 4 hours to obtain an aqueous dispersion of resin microparticles. After the reaction was complete, 2.4 parts of 25% aqueous ammonia was added to neutralize the mixture, and the solids content of the aqueous dispersion of resin microparticles was adjusted to 45.0% with ion-exchanged water. The acid value of the resin was 19.5 mg KOH / g, and the Tg was -8.8°C.

[0123] [Manufacturing Examples 2 to 6] An aqueous dispersion of resin microparticles was obtained in the same manner as in Production Example 1, except that the blending composition was changed as shown in Table 1. After completion of the reaction, 25% aqueous ammonia was added to achieve an equimolar ratio with the carboxy groups in the resin, and neutralization was carried out. The solids content of the aqueous dispersion of resin microparticles was adjusted to 45.0%. The acid value and Tg of the obtained resin were measured in the same manner as in Production Example 1.

[0124] [Table 1]

[0125] [Manufacturing Example 7] A reaction vessel equipped with a stirrer, thermometer, two dropping funnels, and a reflux condenser was charged with 185.0 parts of ion-exchanged water, 42.9 parts of JONCRYL67 (styrene acrylic resin manufactured by BASF: weight average molecular weight (Mw) 12,500, acid value 213 mg KOH / g) as a polymer dispersant, and 11.1 parts of 25% aqueous ammonia. The temperature was increased with stirring to dissolve the polymer dispersant. After further increasing the temperature to 80 °C under nitrogen reflux, a mixture of 14.0 parts of styrene, 15.0 parts of n-butyl methacrylate, 30.0 parts of 2-ethylhexyl acrylate, 10.0 parts of cyclohexyl acrylate, 30.0 parts of n-butyl acrylate, and 1.0 part of glycidyl methacrylate was added dropwise from one of the dropping funnels over a period of 2 hours. 3.5 parts of a 20% aqueous solution of ammonium persulfate was added dropwise from the other funnel over a period of 2 hours. After the completion of the dropwise addition, the reaction was continued for another 5 hours to obtain an aqueous dispersion of resin particles. After the reaction was completed, the solid content of the resin particle dispersion was adjusted to 40.0% with ion-exchanged water. The acid value of the obtained resin was 63.9 mg KOH / g and the Tg was -1.3°C.

[0126] [Manufacturing Example 8] An aqueous dispersion of resin particles was obtained in the same manner as in Production Example 7, except that the amount of JONCRYL67 added was changed to 53.8 parts and 25% aqueous ammonia to 13.9 parts. After the reaction was completed, the solids content of the resin particle dispersion was adjusted to 40.0% with ion-exchanged water. The acid value of the obtained resin was 74.6 mg KOH / g, and the Tg was 3.5°C.

[0127] [Manufacturing Example 9] Into a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, 19.6 parts of PTG-2000SN (polytetramethylene glycol manufactured by Hodogaya Chemical; functionality 2, hydroxyl value 57.0 mgKOH / g, molecular weight 2,000) as polyol, 20 parts of P-2011 (3-methyl-1,5 pentanediol / adipic acid / terephthalic acid polyester polyol manufactured by Kuraray; functionality 2, hydroxyl value 55.0 mgKOH / g, molecular weight 2,000) were added. 0.3 parts, 91.6 parts of C-2090 (polycarbonate polyol manufactured by Kuraray; functionality 2, hydroxyl value 56.0 mg KOH / g, molecular weight 2,000), 19.7 parts of dimethylolbutanoic acid, 48.8 parts of isophorone diisocyanate as a polyisocyanate, 40.0 parts of methyl ethyl ketone as a solvent, and 10.0 parts of dipropylene glycol dimethyl ether were charged and heated to 78°C while stirring under a nitrogen atmosphere. 0.02 parts of titanium diisopropoxybis(ethyl acetoacetate) was added as a catalyst and allowed to react for 6 hours to obtain a urethane prepolymer with isocyanate groups at both ends. 13.5 parts of triethylamine were added as a neutralizer, followed by 400 parts of ion-exchanged water and 2.4 parts of ethylenediamine as a chain extender. The solvent was removed under reduced pressure, and the mixture was allowed to invert to an aqueous phase. The chain extension reaction of the isocyanate groups was accelerated in the aqueous medium, producing an aqueous dispersion of urethane resin with a solids content of 30.0%. The acid value of the resulting resin was 37.4 mg KOH / g and Tg was 94.0°C.

[0128] [Manufacturing Examples 10 and 11] An aqueous dispersion of a urethane resin was obtained in the same manner as in Production Example 9, except that the blending composition was changed to that shown in Table 2. The solids content of the aqueous dispersion was adjusted to 30.0%. The acid value and Tg of the obtained resin were measured in the same manner as in Production Example 1.

[0129] [Table 2]

[0130] [Manufacturing Example 12] A reactor equipped with a stirrer, thermometer, and reflux condenser was charged with 100 parts of Auroren 350S (manufactured by Nippon Paper Industries Co., Ltd.; maleic anhydride-modified polypropylene-polyethylene copolymer) as a solid olefin resin, 100 parts of toluene, and 30.0 parts of Noigen TDS-120 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; polyoxyethylene tridodecyl ether HLB14.8) as a low molecular weight surfactant. The temperature was raised to 100 °C to dissolve the resin. After confirming complete dissolution, 5.0 parts of dimethylaminoethanol and 600.0 parts of ion-exchanged water were added as a neutralizing agent. The solvent was then removed under reduced pressure, allowing for phase inversion to the aqueous phase, yielding an aqueous dispersion of olefin resin with a solids content of 30.0%. The acid value of the resulting aqueous resin was 24.0 mg KOH / g and Tg was -20 °C.

[0131] <Preparation of aqueous dispersion of core-shell type resin particles> [Manufacturing Example 13] A reactor equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 95.0 parts of ion-exchanged water and 1.5% of the first-stage ethylenically unsaturated monomer emulsion, which had been prepared separately by mixing and stirring 97.0 parts of styrene, 2.0 parts of acrylic acid, 1.0 parts of 3-methacryloxypropyltrimethoxysilane, 5.0 parts of a 20% aqueous solution of Daiichi Kogyo Seiyaku's Aqualon KH-10, and 39.1 parts of ion-exchanged water. The internal temperature of the reactor was raised to 70°C and thoroughly purged with nitrogen. Then, 5.7 parts of a 2.5% aqueous solution of potassium persulfate was added as an initiator to initiate polymerization. The internal temperature was then raised to 80°C, and while maintaining the temperature, the remaining first-stage ethylenically unsaturated monomer emulsion and 4.0 parts of a 2.5% aqueous solution of potassium persulfate were added dropwise over 2 hours to synthesize core particles. Twenty minutes after the completion of the first-stage addition, the second-stage emulsion of ethylenically unsaturated monomers was added dropwise. The emulsion was prepared by mixing and stirring 15.0 parts of methyl methacrylate, 26.1 parts of n-butyl acrylate, 0.9 parts of acrylic acid, 2.1 parts of a 20% aqueous solution of KH-10, and 16.8 parts of ion-exchanged water. The internal temperature was maintained at 80°C, and the second-stage emulsion of ethylenically unsaturated monomers and 2.1 parts of a 2.5% aqueous solution of potassium persulfate were added dropwise over two hours to further advance the reaction, yielding an aqueous dispersion of core-shell resin microparticles with a solids content of 45.0%. The core-shell type resin particles thus obtained had an average particle size of 253 nm and a Cv value of 25.7%, and the Tg of the core was 100.1°C and the Tg of the shell was -12.5°C.

[0132] [Manufacturing Examples 14-26] A water dispersion of core-shell type resin microparticles was obtained in the same manner as in Production Example 13, except for the formulation shown in Table 3. The emulsion of ethylenically unsaturated monomer was prepared by adding water so that the concentration of ethylenically unsaturated monomer in the emulsion was 69.0% and the concentration of surfactant was 0.69%. The 2.5% aqueous solution of potassium persulfate, which was added dropwise simultaneously with the emulsion, was added in an amount equivalent to 0.1% solids relative to the total amount of ethylenically unsaturated monomer added dropwise. In Production Examples 18, 19, 20, and 26, the reactive surfactant was changed to AR-10 manufactured by Daiichi Kogyo Seiyaku, and the amount of the first-stage emulsion of ethylenically unsaturated monomer added in separate batches to the reaction vessel was changed from 1.5% to 3.3%, 4.1%, 2.1%, and 3.3%, respectively. The average particle size, Cv value, Tg of the core portion, and Tg of the shell portion of the obtained core-shell type resin microparticles were measured.

[0133] [Manufacturing examples X-1, X-2] An aqueous dispersion of core-shell type resin microparticles was obtained in the same manner as in Production Example 13, except that the blending composition was changed to that shown in Table 3. The average particle size, Cv value, Tg of the core portion, and Tg of the shell portion of the obtained core-shell type resin microparticles were measured.

[0134] [Table 3]

[0135] <Preparation of non-core-shell resin microparticle aqueous dispersion> [Manufacturing Example 27] A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 68.9 parts of water. 3% of an ethylenically unsaturated monomer emulsion (prepared by mixing and stirring 85.0 parts of styrene, 5.0 parts of benzyl methacrylate, 7.0 parts of 2-ethylhexyl acrylate, 2.0 parts of acrylic acid, 1.0 parts of 3-methacryloxypropyltriethoxysilane, 5.0 parts of a 20% aqueous solution of Aqualon KH-10, and 40.4 parts of water) was then added. The internal temperature was raised to 70°C and thoroughly purged with nitrogen. Then, 2.0 parts of a 5% aqueous solution of potassium persulfate was added as an initiator to initiate emulsion polymerization. The internal temperature was then raised to 80°C, and while maintaining the temperature, the remaining ethylenically unsaturated monomer emulsion and 2.0 parts of a 5% aqueous solution of potassium persulfate were added dropwise over 3 hours. The reaction was continued for another 4 hours, yielding an aqueous dispersion of resin microparticles with a solids content of 45.0%. The resulting resin microparticles had an average particle size of 201 nm, a coefficient of variation Cv of 25.8%, and a Tg of 76.9°C.

[0136] <Preparation of aqueous dispersion of aqueous resin fine particles constituting the resin layer> [Manufacturing Example 28] A reactor equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 68.9 parts of ion-exchanged water, and 3% of an emulsion of ethylenically unsaturated monomers was added. The emulsion was previously prepared by mixing and stirring 15.0 parts of styrene, 30.0 parts of methyl methacrylate, 16.0 parts of 2-ethylhexyl acrylate, 35.0 parts of n-butyl acrylate, 2.0 parts of methacrylic acid, 1.0 parts of acrylic acid, 1.0 parts of 3-methacryloxypropyltriethoxysilane, 5.0 parts of a 20% aqueous solution of Aqualon KH-10, and 40.4 parts of ion-exchanged water. The internal temperature was raised to 70°C and the atmosphere was thoroughly purged with nitrogen. Then, 2.0 parts of a 5% aqueous solution of potassium persulfate was added as an initiator to initiate emulsion polymerization. The internal temperature was raised to 80°C, and while maintaining the temperature, the remaining ethylenically unsaturated monomer emulsion and 2.0 parts of a 5% aqueous solution of potassium persulfate were added dropwise over 3 hours, and the reaction was continued for another 4 hours to obtain an aqueous dispersion of aqueous resin microparticles with a solid content of 45.0%. The resulting aqueous resin microparticles had an average particle size of 196 nm and a Tg of -2.4°C.

[0137] [Manufacturing Examples 29-36] Aqueous dispersions of aqueous resin microparticles were prepared in the same manner as in Production Example 28, except for the formulation shown in Table 4. In Production Examples 29, 32, 33, and 34, the emulsion of ethylenically unsaturated monomers charged in separate portions to the reaction vessel was changed from 3% to 1.5%, 5%, 1.5%, and 1.3%, respectively. In Production Example 35, 1.0 part of KH-10 was added to the reaction vessel before the start of the reaction, and in Production Example 36, 1.3 parts was added. The average particle size and Tg of the obtained aqueous resin microparticles were measured.

[0138] [Table 4]

[0139] <Preparation of aqueous dispersion of acrylic resin particles constituting pressure-sensitive adhesive> [Manufacturing Example 37] A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 68.9 parts of ion-exchanged water. 1% of an ethylenically unsaturated monomer emulsion, previously prepared by mixing and stirring 97.5 parts of 2-ethylhexyl acrylate, 2.0 parts of acrylic acid, 0.5 parts of 3-methacryloxypropyltriethoxysilane, 0.04 parts of octyl thioglycolate, 7.0 parts of a 20% aqueous solution of Newcol RA9612 (manufactured by Nippon Nyukazai Co., Ltd.), and 40.4 parts of ion-exchanged water, was then added. The internal temperature was raised to 80°C and the mixture was thoroughly purged with nitrogen. Then, 2.0 parts of a 5% aqueous solution of ammonium persulfate was added as an initiator to initiate emulsion polymerization. While maintaining the internal temperature at 80°C, the remaining ethylenically unsaturated monomer emulsion and 2.0 parts of a 5% aqueous solution of ammonium persulfate were added dropwise over 3 hours, and the reaction was continued for a further 8 hours to obtain an aqueous dispersion of resin microparticles. After the reaction was completed, 1.9 parts of 25% aqueous ammonia was added to neutralize the mixture, and the solid content of the aqueous dispersion of resin particles was adjusted to 45.0% with ion-exchanged water. The acid value of the resulting resin was 15.6 mg KOH / g and Tg was -71.0°C.

[0140] [Manufacturing Examples 38-45] An aqueous dispersion of acrylic resin microparticles was obtained in the same manner as in Production Example 37, except for changing the formulation shown in Table 5. In Production Examples 43 and 44, a tackifier was added to the dropwise addition component. After completion of the reaction, 25% aqueous ammonia was added to achieve an equimolar ratio with the carboxyl groups in the resin, and neutralization was carried out. The solids content of the aqueous dispersion of resin microparticles was adjusted to 45.0%. The acid value and Tg of the obtained resin were measured.

[0141] [Table 5]

[0142] The abbreviations in Table 5 are as follows: KE364C: Rosin resin manufactured by Arakawa Chemical OTG: octyl thioglycolate

[0143] <Preparation of Primer Composition> [Manufacturing Example 46] A primer composition was prepared by adding 2.0 parts of isopropyl alcohol to 100 parts of the aqueous dispersion of the resin obtained in Production Example 1 and stirring the mixture.

[0144] [Manufacturing Examples 47-58] A primer composition was prepared in the same manner as in Production Example 46, except that the blending composition was changed to that shown in Table 6.

[0145] [Table 6]

[0146] The abbreviations used in Table 6 and Tables 7 and 8 below are as follows: CW-1: Orient Chemical Industry's BONJET BLACK CW-1 surface-modified carbon black water dispersion, average particle size 62 nm, solids content 20.0%

[0147] <Preparation of Composition for Colloidal Crystal Layer> [Manufacturing Example 59] A composition for a colloidal crystal layer was prepared by adding 2.3 parts of CW-1 (surface-modified carbon black, average particle diameter 62 nm, solid content 20.0%) manufactured by Orient Chemical Industry Co., Ltd. to 100 parts of the aqueous dispersion of the core-shell type resin microparticles of Production Example 13 and stirring the mixture.

[0148] [Manufacturing Examples 60-73] A composition for a colloidal crystal layer was prepared in the same manner as in Production Example 59, except that the blending composition was changed to that shown in Table 7.

[0149] [Manufacturing examples P-1, P-2] A composition for a colloidal crystal layer was prepared in the same manner as in Production Example 59, except that the blending composition was changed to that shown in Table 7.

[0150] [Table 7]

[0151] <Preparation of Resin Composition> [Manufacturing Example 74] To 100 parts of the aqueous dispersion of the aqueous resin particles obtained in Production Example 28, 0.2 parts of isopropyl alcohol was added and stirred to prepare a resin composition.

[0152] [Manufacturing Examples 75-83] A resin composition was prepared in the same manner as in Production Example 74, except that the blending composition was changed to that shown in Table 8.

[0153] [Table 8]

[0154] <Preparation of Pressure-Sensitive Adhesive> [Manufacturing Example 84] To 100 parts of the aqueous dispersion of acrylic resin microparticles of Production Example 37, 9.0 parts of CW-1 (surface-modified carbon black, average particle diameter 62 nm, solid content 20.0%) manufactured by Orient Chemical Industries, Ltd. and 0.5 parts of Denacol EX-313 (100% non-volatile components) manufactured by Nagase ChemteX as a crosslinking agent were added and stirred to prepare a pressure-sensitive adhesive.

[0155] [Manufacturing Examples 85-98] A pressure-sensitive adhesive was prepared in the same manner as in Production Example 84, except that the formulation was changed to that shown in Table 9.

[0156] [Table 9]

[0157] The abbreviations in Table 9 are as follows: CW-1: Orient Chemical Industry's BONJET BLACK CW-1 surface-modified carbon black water dispersion, average particle size 62 nm, solids content 20.0% EX-313: Nagase ChemteX Denacol EX-313 (multifunctional epoxy crosslinker, epoxy equivalent weight 141g / eq, 100% non-volatile content) Zinc oxide solution No.1: Zinc oxide manufactured by BASF e Solution No.1 (ammonium zinc carbonate aqueous solution, non-volatile components 15.0%)

[0158] <Preparation of colloidal crystal coating> [Example 99] The primer composition of Production Example 46 was applied to the corona-treated surface of a biaxially oriented polypropylene (OPP) film (Futamura FOR, thickness 20.0 μm) using a bar coater to a dry film thickness of 3 μm, and then dried in an oven at 50°C for 3 minutes to form a primer layer. Next, the colloidal crystal layer composition of Production Example 59 was applied to the primer layer using a bar coater to a dry film thickness of 9 μm, and then dried at 50°C for 3 minutes to obtain a colloidal crystal coating film consisting of OPP / primer layer / colloidal crystal layer.

[0159] [Manufacturing Examples 100-139] A colloidal crystal coating film was obtained in the same manner as in Production Example 99, except that the combination was changed to that shown in Table 10. In Production Example 101, the colloidal crystal layer composition was applied directly to the substrate without applying a primer composition. In Production Examples 102 to 138, the resin composition was applied to the colloidal crystal layer with a bar coater to a dry film thickness of 10 μm, and then dried in an oven at 70°C for 3 minutes to form a resin layer. In Production Example 139, the dispersion of core-shell resin particles from Production Example 13, which did not contain achromatic black particles, was used as the colloidal crystal layer composition.

[0160] [Manufacturing Examples Q-1 and Q-2] A colloidal crystal coating film was obtained in the same manner as in Production Example 99, except for changing the combination shown in Table 10. The resin composition was applied onto the colloidal crystal layer using a bar coater to a dry film thickness of 10 μm, and then dried in an oven at 70°C for 3 minutes to form a resin layer.

[0161] [Table 10]

[0162] The abbreviations in Table 10 are as follows: Treated OPP: (Futamura FOR: biaxially oriented polypropylene film, thickness 20.0 μm) Treated PET (Toyobo E5100: polyethylene terephthalate film, thickness 12.0 μm)

[0163] <Preparation of adhesive sheet> [Example 1] The pressure-sensitive adhesive of Production Example 84 was applied to a release sheet using a comma coater to a dry thickness of 18 μm, and then dried in an oven at 100° C. for 2 minutes. Next, the colloidal crystal coating film of Production Example 99 was attached to the OPP substrate surface to obtain a pressure-sensitive adhesive sheet with a surface-printed configuration.

[0164] [Examples 2 to 4, Comparative Example 1] A pressure-sensitive adhesive sheet having a surface-printed configuration was produced in the same manner as in Example 1, except that the combination was changed to that shown in Table 11.

[0165] [Example 5] The pressure-sensitive adhesive of Production Example 84 was applied to a release sheet using a comma coater to a dry thickness of 18 μm, and then dried in an oven at 100° C. for 2 minutes. It was then bonded to the colloidal crystal layer surface of the colloidal crystal coating film of Production Example 99 to produce a pressure-sensitive adhesive sheet with a reverse printing configuration.

[0166] [Examples 6 to 8, Comparative Examples 2 and 3] A pressure-sensitive adhesive sheet having a reverse printing configuration was produced in the same manner as in Example 5, except that the combination was changed to that shown in Table 11.

[0167] [Example 9] The pressure-sensitive adhesive of Production Example 85 was applied using a bar coater onto the resin layer of the colloidal crystal coating film of Production Example 103 so that the thickness after drying would be 18 μm, and then dried for 3 minutes in an oven at 90° C. Next, the release surface of a release sheet was attached to the formed adhesive layer to prepare an adhesive sheet with a reverse-printed configuration.

[0168] [Examples 10 to 52, Comparative Example 4] A pressure-sensitive adhesive sheet having a reverse printing configuration was produced in the same manner as in Example 9, except that the combinations were changed to those shown in Tables 11 and 12.

[0169] [Examples R-1 and R-2] A pressure-sensitive adhesive sheet having a reverse printing configuration was produced in the same manner as in Example 9, except that the combination was changed to that shown in Table 12.

[0170] [Example 53] The pressure-sensitive adhesive of Production Example 84 was coated onto a release sheet using a comma coater to a thickness of 18 μm after drying, dried in an oven at 100°C for 2 minutes, and then bonded to both sides of a nonwoven fabric substrate to produce a double-sided tape with adhesive layers on both sides. The release sheet on one side of the double-sided tape was peeled off, and the tape was bonded to the surface of the OPP substrate bearing the colloidal crystal coating of Production Example 99 to produce a pressure-sensitive adhesive sheet with a surface-printed configuration.

[0171] [Example 54] The pressure-sensitive adhesive of Production Example 84 was coated onto a release sheet using a comma coater to a dry thickness of 18 μm, dried in an oven at 100°C for 2 minutes, and then bonded to both sides of a nonwoven fabric substrate to produce a double-sided tape with adhesive layers on both sides. The release sheet on one side of the double-sided tape was peeled off, and the tape was bonded to the colloidal crystal layer side of the colloidal crystal coating film of Production Example 99 to produce a pressure-sensitive adhesive sheet with a reverse-printed configuration.

[0172] [Example 55] The pressure-sensitive adhesive of Production Example 85 was coated onto a release sheet using a comma coater to a thickness of 18 μm after drying, dried in an oven at 100°C for 2 minutes, and then bonded to both sides of a nonwoven fabric substrate to produce a double-sided tape with adhesive layers on both sides. The release sheet on one side of the double-sided tape was peeled off, and the tape was bonded to the surface of the OPP substrate bearing the colloidal crystal coating of Production Example 102 to produce a pressure-sensitive adhesive sheet with a surface-printed configuration.

[0173] [Example 56] The pressure-sensitive adhesive of Production Example 85 was coated onto a release sheet using a comma coater to a thickness of 18 μm after drying, dried in an oven at 100°C for 2 minutes, and then bonded to both sides of a nonwoven fabric substrate to produce a double-sided tape with adhesive layers on both sides. The release sheet on one side of the double-sided tape was peeled off, and the tape was bonded to the resin layer side of the colloidal crystal coating film of Production Example 103 to produce a reverse-printed adhesive sheet.

[0174] [Example 57] The pressure-sensitive adhesive of Production Example 85 was applied to a release sheet using a comma coater to a dry thickness of 18 μm, dried in an oven at 100°C for 2 minutes, and then bonded to one side of a nonwoven fabric substrate to produce a single-sided adhesive tape. The nonwoven fabric substrate side of the single-sided adhesive tape was bonded to the resin layer side of the colloidal crystal coating film of Production Example 103 to produce a reverse-printed adhesive sheet.

[0175] Comparative Example 5 An aqueous solution of polyvinyl alcohol (Poval 22-88, manufactured by Kuraray Co., Ltd.; solids content 20.0%) was applied onto the colloidal crystal layer of the colloidal crystal coating film of Production Example 99 using a bar coater, and then dried in an oven at 70°C for 3 minutes, completely replacing the air in the voids in the colloidal crystal layer with resin components. Separately, the pressure-sensitive adhesive of Production Example 85 was applied onto a release sheet using a comma coater so that the thickness after drying would be 18 μm, and then dried in an oven at 100° C. for 2 minutes to form an adhesive layer. The adhesive layer on the release sheet was bonded to the surface of the colloidal crystal layer in which the voids had been replaced with the resin of the colloidal crystal coating film, to prepare an adhesive sheet with a reverse printing configuration.

[0176] <Evaluation of adhesive sheets> The resulting adhesive sheets were checked for air voids in the Lloyd crystal layer. The resulting adhesive sheets were also evaluated for adhesive strength and stability over time, color development and stability over time, resistance to repeated application and removal, abrasion resistance, and indentation resistance. The results are shown in Tables 11 and 12. Blank spaces in Tables 11 and 12 indicate that no compound was added.

[0177] [Checking air voids in the colloidal crystal layer] The cross sections of the obtained pressure-sensitive adhesive sheets were observed with a scanning electron microscope (JEOL JSM-7800F) to confirm the voids in the colloidal crystal layer. As a result, it was confirmed that the voids in the colloidal crystal layer were not completely filled with the resin component and the colloidal crystal layer contained air voids in all pressure-sensitive adhesive sheets except for Comparative Example 5. In Comparative Example 5, the voids in the colloidal crystal layer were completely filled with the resin component and did not contain air voids.

[0178] [Room temperature adhesive strength] The adhesive sheet was cut into a size of 100 mm long x 25 mm wide under a 23°C, 50% RH environment to prepare a test piece. Next, in accordance with JIS Z0237, the release sheet was peeled off from the test piece, and the exposed adhesive layer was attached to a polished stainless steel plate (hereinafter referred to as SUS) and pressed back and forth with a 2 kg roll to prepare a sample. The sample was left in a 23°C, 50% RH environment for 24 hours, and the adhesive strength was measured under conditions of 23°C, 50% RH. The adhesive strength was measured using a Tensilon at a peel speed of 300 mm / min and a peel angle of 180°. The obtained adhesive strength was evaluated according to the following criteria. S: Adhesion strength is 3.0mN / 25mm or more (very good) A: Adhesion strength is 2.0mN / 25mm or more, less than 3.0mN / 25mm (good) B: Adhesive strength is 1.5mN / 25mm or more, less than 2.0mN / 25mm (usable) C: Adhesive strength less than 1.5mN / 25mm (unusable)

[0179] [Stability of adhesive strength over time] The adhesive sheet was cut into a size of 100 mm long x 25 mm wide under an environment of 23°C and 50% RH to prepare a test specimen. Next, in accordance with JIS Z0237, the release sheet was peeled off from the test specimen, and the exposed adhesive layer was attached to a polished stainless steel plate and pressed back and forth with a 2 kg roll to prepare a sample. The sample was left standing in a high-temperature, high-humidity atmosphere of 40°C and 85% RH for two weeks, after which the sample was removed and the adhesive strength was measured under conditions of 23°C and 50% RH. The adhesive strength was measured using a tensile tester at a peel speed of 300 mm / min and a peel angle of 180°. Using the above-mentioned room-temperature adhesive strength and the obtained adhesive strength after aging, the rate of change in adhesive strength was calculated using the following formula and evaluated according to the following criteria. Formula) Change in adhesive strength (%) = [(adhesive strength after aging) / (adhesive strength at room temperature)-1] x 100 S: Adhesion change rate is less than 10% (very good) A: Adhesive strength change rate is 10% or more, less than 30% (good) B: Adhesive strength change rate is 30% or more and less than 50% (usable) C: Adhesive strength change rate is 50% or more (unusable)

[0180] [Color development] The reflectance spectrum of the pressure-sensitive adhesive sheet was measured in the wavelength range of 250 to 850 nm using a UV-visible-near-infrared spectrophotometer (JASCO V-770D, integrating sphere unit ISN-923). The reflectance at each wavelength is the relative reflectance measured using a standard white board with known reflectance (Labsphere SRS-99-010) as a reference. For the obtained reflectance spectrum, the difference (ΔR) between the maximum reflectance due to the structural color and the baseline reflectance not due to the structural color was calculated. The larger the ΔR, the better the color development. The obtained ΔR and the rate of decrease in ΔR were evaluated according to the following criteria. S; △R is 30% or more (very good) A: △R is 20% or more and less than 30% (good) B: △R is 10% or more and less than 20% (usable) C: △R is less than 10% or the reflectance peak due to structural color cannot be distinguished (unusable)

[0181] [Color stability over time] The adhesive sheet was left standing for two weeks in a high-temperature, high-humidity atmosphere at 40°C and 85% RH, after which the sheet was removed and the reflectance spectrum was measured in the same manner as in the color development evaluation described above. The reflectance spectra before and after aging were compared to calculate the rate of change (decrease) in the maximum reflectance. A larger decrease indicates more discoloration of the colloidal crystals. The obtained decrease rate was evaluated according to the following criteria. S: Maximum reflectance change rate is less than 2% (very good) A: The change in maximum reflectance is 2% or more and less than 5% (good) B: The change in maximum reflectance is 5% or more and less than 10% (usable) C: The change in maximum reflectance is 10% or more (unusable)

[0182] [Repeated attachment and removal evaluation] In an environment of 23°C and 50% RH, the adhesive sheet was cut into a size of 40 mm long x 40 mm wide to prepare a test piece. The release sheet was peeled off from the test piece and attached to an aluminum can (outer diameter 66 mm, height 115.2 mm, plain) so that the long side of the test piece was parallel to the edge of the can. The adhesive sheet was then slowly peeled off from the aluminum can. After this attachment and peeling of the adhesive sheet was repeated five times, the appearance of the adhesive sheet was observed and evaluated according to the following criteria. S: No scratches or lifting on the adhesive sheet (very good) A: Scratches or lifting occurred on less than 1% of the test piece area (good) B: Scratches or lifting have occurred on 1% or more but less than 5% of the test piece area (usable) C: Scratches or lifting have occurred on more than 5% of the area of the test piece (unusable)

[0183] [Friction resistance test] In an environment of 23°C and 50% RH, the adhesive sheet was cut into a size of 40 mm long x 10 mm wide to form a test piece, the release sheet was peeled off from the test piece, and the test piece was attached to an aluminum can (outer diameter 66 mm, height 115.2 mm, plain) with the long side of the test piece parallel to the edge of the can. The attached adhesive sheet was rubbed back and forth along the curved surface of the can with the pad of a finger 100 times, and the occurrence of scratches and peeling was observed and evaluated according to the following criteria. S: No scratches or peeling (very good) A: Scratches or peeling occurred on less than 5% of the test piece area (good) B: Scratches or peeling have occurred over 5% or more but less than 10% of the test piece area (usable) C: Scratches or peeling have occurred on more than 10% of the test piece area (unusable)

[0184] [Indentation resistance test] In an environment of 23°C and 50% RH, the adhesive sheet was cut into a size of 40 mm in length and 10 mm in width to form a test piece, and the release sheet was peeled off from the test piece. The test piece was then attached to an aluminum can (outer diameter 66 mm, height 115.2 mm, plain) so that the long side of the test piece was parallel to the edge of the can. The adhesive sheet was pressed with the pad of a finger 30 times, and then the occurrence of scratches or peeling was observed and evaluated according to the following criteria. S: No scratches or peeling (very good) A: Scratches or peeling occurred on less than 5% of the test piece area (good) B: Scratches or peeling have occurred over 5% or more but less than 10% of the test piece area (usable) C: Scratches or peeling have occurred on more than 10% of the test piece area (unusable)

[0185] [Table 11]

[0186] [Table 12]

[0187] The pressure-sensitive adhesive sheets of the Examples combined excellent adhesive strength and color development, and maintained their excellent color development even after various resistance tests (aging tests under high temperature and humidity, repeated adhesion and peeling tests, abrasion resistance tests, indentation resistance tests, etc.). In particular, Examples 9 to 52, 55, 56, R-1, and R-2, which had a reverse-printed configuration with an adhesive layer on a resin layer, exhibited excellent adhesive properties and excellent coating resistance. On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 5 were significantly inferior in one of the evaluation items. From the above, the superiority of the pressure-sensitive adhesive sheets with colloidal crystal coatings of the present invention was proven. [Industrial Applicability]

[0188] The adhesive sheet of the present invention combines excellent adhesive strength and color development, and is able to maintain its excellent color development even after various coating tests such as aging tests under high temperature and humidity, repeated adhesion and peeling tests, abrasion resistance tests, and indentation resistance tests. Therefore, it can be used on adherends of various materials and shapes, and can be applied to colorants that impart high design appeal, as well as a wide range of applications such as optical filters, optical detection sensors, display elements, optical waveguides, optical resonators, and optical switches. [Explanation of symbols]

[0189] 1. Colloidal crystal layer 2 primer layer 3 Base material 3a Second substrate 4 Adhesive layer 5 Resin layer 6 Core-shell resin particles 7 void

Claims

1. A pressure-sensitive adhesive sheet having a laminated structure in which a substrate, a primer layer, and a colloidal crystal layer are laminated in this order, and an adhesive layer, the colloidal crystal layer has a structure in which core-shell type resin fine particles are arranged and voids, In the core-shell type resin microparticles, the glass transition point of the core is 58.0°C or higher, and the glass transition point of the shell is in the range of -52.8 to 23.1°C, The pressure-sensitive adhesive sheet is characterized in that the primer layer is made of a resin, and the glass transition point of the resin is in the range of -34.8 to 94.0°C.

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the core-shell type resin microparticles contain a shell in a range of 10 to 300% by mass relative to the mass of the core.

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the core-shell resin microparticles contain a shell in a range of 10 to 50% by mass relative to the mass of the core, the core has a glass transition point of 60°C or higher, and the shell has a glass transition point in the range of -50 to 20°C.

4. 4. The pressure-sensitive adhesive sheet according to claim 1, wherein the primer layer is a layer containing at least one resin selected from the group consisting of acrylic resins and urethane resins.

5. The pressure-sensitive adhesive sheet according to claim 4, wherein the glass transition temperature of the resin in the primer layer is in the range of -30 to 70°C.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive containing an acrylic resin.

7. The pressure-sensitive adhesive sheet according to claim 6, wherein the acrylic resin has a glass transition temperature in the range of -75 to -35°C.

8. The pressure-sensitive adhesive sheet according to claim 6 or 7, wherein the acrylic resin has an acid value in the range of 4 to 30 mgKOH / g.

9. The pressure-sensitive adhesive sheet according to any one of claims 6 to 8, wherein the pressure-sensitive adhesive further comprises a crosslinking agent.

10. The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive layer is disposed on the substrate side.

11. 10. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is disposed on the colloidal crystal layer side.

12. The pressure-sensitive adhesive sheet according to claim 11, further comprising a resin layer disposed between the colloidal crystal layer and the pressure-sensitive adhesive layer.

13. The pressure-sensitive adhesive sheet according to claim 12 , wherein the resin layer is a layer formed from a resin composition containing aqueous acrylic resin particles.

14. The pressure-sensitive adhesive sheet according to claim 13, wherein the water-based acrylic resin fine particles have a glass transition temperature in the range of -30 to 30°C.

15. The pressure-sensitive adhesive sheet according to claim 13 or 14, wherein the average particle diameter of the aqueous acrylic resin fine particles is in the range of 80 to 300 nm.

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