Adhesive sheet and laminate

Abstract

To provide a pressure-sensitive adhesive sheet in which, even when different adherends are laminated, defects at the interface with each adherend are suppressed.SOLUTION: The pressure sensitive adhesive sheet according to an embodiment of the present invention has a first main surface and a second main surface, the indentation hardness of the first main surface is 0. 15MPa to 1. 00MPa, and the indentation hardness of the second main surface is less than 0. 15MPa. A laminate according to an embodiment of the present invention includes a base material having a thickness of 400 μm or more and a Young's modulus of 1.0 GPa or more, and a porous layer laminated on the base material via the above-described pressure sensitive adhesive sheet, wherein the second main surface of the pressure sensitive adhesive sheet is bonded to the base material, and the first main surface of the pressure sensitive adhesive sheet is bonded to the porous layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Laminates including functional layers are widely used in various applications depending on the function of the functional layer. The layers constituting the laminate can be laminated, for example, via a pressure-sensitive adhesive sheet. However, when layers that are mechanically and / or chemically different and, as a result, have completely different adherend surface properties, are laminated via a single pressure-sensitive adhesive sheet, defects may occur at at least one interface between the layers constituting the laminate and the pressure-sensitive adhesive sheet. For example, a laminate including a substrate and a porous layer that can function as a layer with a controlled refractive index is known. However, when the substrate and the porous layer are laminated via a pressure-sensitive adhesive sheet, problems may arise, such as bubbles forming at the interface between the substrate and the pressure-sensitive adhesive sheet, impairing transparency, or the refractive index of the porous layer becoming higher than the designed value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-75999 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide an adhesive sheet in which defects at the interface with each adherend are suppressed even when different adherends are laminated. [Means for solving the problem]

[0005] [1] A pressure-sensitive adhesive sheet according to an embodiment of the present invention has a first main surface and a second main surface, the first main surface having an indentation hardness of 0.15 MPa to 1.00 MPa, and the second main surface having an indentation hardness of less than 0.15 MPa. [2] In [1] above, the difference between the indentation hardness of the first major surface and the indentation hardness of the second major surface is 0.06 MPa or more. [3] In [1] or [2] above, the peel force of the second major surface with respect to the glass is 10 N / 25 mm or more. [4] In any one of [1] to [3] above, the adhesive sheet has a first adhesive layer and a second adhesive layer, the first adhesive layer includes the first major surface, and the second adhesive layer includes the second major surface. [5] In [4] above, the thickness of the second adhesive layer is 50 μm or less. [6] In [4] or [5] above, the weight average molecular weight Mw of the base polymer of the adhesive constituting the first adhesive layer is 700,000 to 4,000,000, and the weight average molecular weight Mw of the base polymer of the adhesive constituting the second adhesive layer is 10,000 to 700,000. [7] In any one of [1] to [6] above, the adhesive sheet is laminated to form a laminate by bonding the first major surface of the adhesive sheet to a porous film having a porosity of 55% by volume, a refractive index of 1.20, and a thickness of 2.0 μm. After the laminate is placed in an environment of 65 °C and 95% RH for 100 hours, the refractive index of the porous film is n1; a laminate is formed by bonding the second major surface of the adhesive sheet to the same porous film, and after the laminate is placed in an environment of 65 °C and 95% RH for 100 hours, the refractive index of the porous film is n2; when n1 < n2 is satisfied. [8] According to another aspect of the present invention, a laminate is provided. The laminate has an adhesive sheet according to any one of [1] to [7] above and a porous layer laminated on the first major surface of the adhesive sheet. [9] Another laminate of the present invention has a base material with a thickness of 400 μm or more and a Young's modulus of 1.0 GPa or more, and a porous layer laminated on the base material through an adhesive sheet according to any one of [1] to [7] above. The second major surface of the adhesive sheet is bonded to the base material, and the first major surface of the adhesive sheet is bonded to the porous layer.

[10] In [9] above, the base material is a glass plate. [Effect of the Invention]

[0006] According to an embodiment of the present invention, a pressure-sensitive adhesive sheet can be provided in which defects at the interfaces with the respective adherends are suppressed even when different adherends are stacked together. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0009] A. Adhesive sheet A-1. Overview of adhesive sheets 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. The pressure-sensitive adhesive sheet 100 shown in the figure has a first main surface 100a and a second main surface 100b. In this embodiment of the present invention, the indentation hardness of the first main surface 100a is typically 0.15 MPa to 1.00 MPa, preferably 0.18 MPa to 0.80 MPa, more preferably 0.20 MPa to 0.70 MPa, even more preferably 0.22 MPa to 0.60 MPa, and particularly preferably 0.25 MPa to 0.50 MPa. Furthermore, the indentation hardness of the second main surface 100b is typically less than 0.15 MPa, preferably 0.008 MPa to 0.14 MPa, more preferably 0.009 MPa to 0.13 MPa, even more preferably 0.01 MPa to 0.10 MPa, and particularly preferably 0.03 MPa to 0.09 MPa. With this configuration, even when different adherends are laminated via a pressure-sensitive adhesive sheet, defects at the interface between each adherend and the pressure-sensitive adhesive sheet can be suppressed. For example, when laminating a hard substrate and a porous film (low refractive index film) via a pressure-sensitive adhesive sheet, by placing the first main surface on the porous film side and the second main surface on the substrate side, air bubbles at the interface between the substrate and the pressure-sensitive adhesive sheet are suppressed, maintaining transparency, and preventing the pressure-sensitive adhesive constituting the pressure-sensitive adhesive sheet from penetrating into the voids in the porous film, thereby maintaining the refractive index of the porous film close to its designed value. Note that the indentation hardness can be measured, for example, by a nanoindentation method using an indentation tester (typically a nanoindenter). More specifically, the indentation hardness is calculated using the following formula from the maximum load Pmax obtained from the displacement-load hysteresis curve obtained when a probe (indenter) is pressed 2000 nm into the first or second main surface of the pressure-sensitive adhesive sheet, and the contact projected area A between the indenter and the pressure-sensitive adhesive sheet. The measurement temperature can be, for example, 25°C. Indentation hardness (GPa) = Pmax / A

[0010] The difference between the indentation hardness of the first main surface 100a and the indentation hardness of the second main surface 100b is preferably 0.06 MPa or more, more preferably 0.07 MPa to 0.50 MPa, even more preferably 0.09 MPa to 0.40 MPa, and particularly preferably 0.10 MPa to 0.30 MPa. If the difference is within this range, the above-described effects of the embodiment of the present invention can be satisfactorily exhibited.

[0011] Pressure-sensitive adhesive sheets according to embodiments of the present invention may have a configuration that is visually recognized as a single layer, or may have a laminated structure including a first pressure-sensitive adhesive layer 10 and a second pressure-sensitive adhesive layer 20, as in the illustrated example. Pressure-sensitive adhesive sheets according to embodiments of the present invention (sometimes referred to as laminated pressure-sensitive adhesive sheets in Section A-1) can typically be produced by laminating multiple pressure-sensitive adhesive sheets (sometimes referred to as component pressure-sensitive adhesive sheets in Section A-1). When the laminated interface is clearly recognizable in the laminated pressure-sensitive adhesive sheet obtained in this manner, the laminated pressure-sensitive adhesive sheet can be recognized as having a laminated structure including a first pressure-sensitive adhesive layer 10 and a second pressure-sensitive adhesive layer 20, as in the illustrated example. In this case, the first pressure-sensitive adhesive layer 10 includes a first main surface 100a, and the second pressure-sensitive adhesive layer 20 includes a second main surface 100b. On the other hand, in a laminated pressure-sensitive adhesive sheet, the laminated interface between the component pressure-sensitive adhesive sheets may not be clearly recognizable. Furthermore, in many cases, the component pressure-sensitive adhesive sheets are identical in appearance, whether visually or microscopically observed. Therefore, the laminated pressure-sensitive adhesive sheet may be visually recognized as a single layer. In this case, for convenience, the adhesive sheet as a component including the first main surface may be referred to as the first adhesive layer, and the adhesive sheet as a component including the second main surface may be referred to as the second adhesive layer.

[0012] The adhesive sheet according to an embodiment of the present invention preferably has the following characteristics. That is, a porous film having a porosity of 55% by volume, a refractive index of 1.20, and a thickness of 2.0 μm is laminated with the first main surface 100a of the adhesive sheet to form a laminate, and the refractive index of the porous film after the laminate is placed in an environment of 65°C and 95% RH for 100 hours is n1; a laminate is formed by laminating the second main surface 100b of the adhesive sheet to the same porous film, and the refractive index of the porous film after the laminate is placed in an environment of 65°C and 95% RH for 100 hours is n2; when n1 < n2 is satisfied. The difference (n2 - n1) between n1 and n2 is preferably 0.03 or more, more preferably 0.03 to 0.18, and even more preferably 0.04 to 0.15. With such a configuration, the above-described effects according to the embodiment of the present invention can be more remarkable. n1 is preferably closer to the refractive index of the porous film to which the adhesive sheet is laminated. Specifically, n1 is preferably 1.20 to 1.22, and more preferably 1.20 to 1.21.

[0013] The peel force P1 of the first main surface with respect to glass is preferably smaller than the peel force P2 of the second main surface with respect to glass. The peel force P1 of the first main surface with respect to glass is preferably 2.0 N / 25 mm or more, more preferably 5.0 N / 25 mm to 10.0 N / 25 mm, and even more preferably 7.0 N / 25 mm to 9.0 N / 25 mm. The peel force P2 of the second main surface with respect to glass is preferably 10.0 N / 25 mm or more, more preferably 12.0 N / 25 mm to 20.0 N / 25 mm, and even more preferably 14.0 N / 25 mm to 18.0 N / 25 mm. The difference (P2 - P1) between the peel force P1 of the first main surface with respect to glass and the peel force P2 of the second main surface with respect to glass is preferably 1.0 N / 25 mm to 20.0 N / 25 mm, and more preferably 3.0 N / 25 mm to 10.0 N / 25 mm. With such a configuration, for example, when the second main surface of the adhesive sheet is laminated to a hard base material and the first main surface is laminated to a porous film (low refractive index film) to form a laminate, even when the laminate is placed in a high temperature and high humidity environment of 65°C and 95% RH for 100 hours, the occurrence of peeling can be suppressed.

[0014] The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are described in detail below. When the laminated pressure-sensitive adhesive sheet is recognized as a single layer from the outside, the first pressure-sensitive adhesive layer is synonymous with the pressure-sensitive adhesive sheet as a component including the first main surface, and the second pressure-sensitive adhesive layer is synonymous with the pressure-sensitive adhesive sheet as a component including the second main surface.

[0015] A-2.First adhesive layer The first pressure-sensitive adhesive layer 10 may have any suitable configuration as long as the indentation hardness of the first main surface 100a is 0.15 MPa to 1.00 MPa. The pressure-sensitive adhesive (pressure-sensitive adhesive composition) constituting the first pressure-sensitive adhesive layer typically contains a base polymer, a crosslinking agent, and, if necessary, a silane coupling agent and / or an additive. By adjusting the number, type, combination, and compounding ratio of the monomer components constituting the base polymer, as well as the number, type, combination, and compounding ratio of the crosslinking agent, silane coupling agent, and additive, a pressure-sensitive adhesive having the desired hardness can be obtained, and as a result, a first pressure-sensitive adhesive layer can be formed whose first main surface has an indentation hardness in the desired range.

[0016] The first pressure-sensitive adhesive layer is typically formed from a pressure-sensitive adhesive containing a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a rubber polymer as a base polymer. A preferred base polymer is a (meth)acrylic polymer. The (meth)acrylic polymer contains alkyl (meth)acrylate as a main monomer component. Here, (meth)acrylic refers to acrylic and / or methacrylic.

[0017] The alkyl (meth)acrylate may be contained in a proportion of preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more of all monomer components forming the (meth)acrylic polymer.

[0018] The alkyl (meth)acrylate preferably includes a linear or branched alkyl group having 1 to 18 carbon atoms. The alkyl group more preferably has 2 to 10 carbon atoms, and even more preferably has 3 to 8 carbon atoms. Examples of the alkyl (meth)acrylate include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate. Butyl acrylate is preferred. The alkyl (meth)acrylates can be used alone or in combination.

[0019] The (meth)acrylic polymer may preferably contain a carboxyl group-containing monomer and a hydroxyl group-containing monomer as monomer components. The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Acrylic acid is preferred. The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0020] The carboxyl group-containing monomer and the hydroxyl group-containing monomer may each be contained in a proportion of preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the total monomer components.

[0021] The (meth)acrylic polymer may preferably contain a heterocycle-containing acrylate or an aromatic ring-containing acrylate as a monomer component. A combination of a heterocycle-containing acrylate and an aromatic ring-containing acrylate may be used. Examples of heterocycle-containing acrylates include acryloylmorpholine. Examples of aromatic ring-containing acrylates include benzyl acrylate and phenoxybenzyl acrylate. The heterocycle-containing acrylate or aromatic ring-containing acrylate may be contained in an amount of preferably 8 wt% to 20 wt%, more preferably 10 wt% to 18 wt%, and even more preferably 12 wt% to 15 wt%, based on the total monomer components. This configuration can facilitate the realization of a first pressure-sensitive adhesive layer in which the indentation hardness of the first main surface falls within the desired range. When a combination of a heterocycle-containing acrylate and an aromatic ring-containing acrylate is used, the total content of these components may fall within the above-mentioned range.

[0022] From the viewpoint of adjusting the properties of the first pressure-sensitive adhesive layer, other monomer components (copolymerizable monomers) copolymerizable with the above-mentioned monomers may be used. Examples of copolymerizable monomers include amino group-containing monomers, amide group-containing monomers, polyfunctional monomers, cyclopolymerizable monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, (meth)acrylic acid esters having alicyclic hydrocarbon groups, vinyl esters, aromatic vinyl compounds, olefins, dienes, and vinyl ethers. The copolymerizable monomers may be used alone or in combination. The number, type, combination, and compounding ratio of the copolymerizable monomers may be appropriately set depending on the purpose.

[0023] The weight-average molecular weight Mw of the (meth)acrylic polymer (base polymer) is preferably 700,000 to 4,000,000, more preferably 1,500,000 to 3,500,000, and even more preferably 2,500,000 to 3,200,000. The molecular weight distribution Mw / Mn of the (meth)acrylic polymer (base polymer) is preferably 3.4 or less, more preferably 3.2 or less, even more preferably 3.0 or less, and particularly preferably 2.8 or less. The lower limit of the molecular weight distribution Mw / Mn can be, for example, 2.0 or, for example, 2.2.

[0024] Examples of crosslinking agents that can be used include organic crosslinking agents and polyfunctional metal chelates. Examples of organic crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, imine crosslinking agents, silicone crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, and alkyl etherified melamine crosslinking agents. Polyfunctional metal chelates are those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. The crosslinking agents may be used alone or in combination. Preferred are isocyanate crosslinking agents, epoxy crosslinking agents, or combinations thereof, and more preferred are combinations of an isocyanate crosslinking agent and an epoxy crosslinking agent.

[0025] An isocyanate crosslinking agent is a compound having two or more isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate group is temporarily protected by a blocking agent or oligomerization) per molecule. Examples of isocyanate crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate, and aliphatic isocyanates such as hexamethylene diisocyanate. More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and polymethylene polyphenyl isocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct, Examples of suitable isocyanate adducts include polyisocyanates such as hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate HL), and hexamethylene diisocyanate isocyanurate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate HX), xylylene diisocyanate trimethylolpropane adduct (manufactured by Mitsui Chemicals, Inc., trade name: D110N), and hexamethylene diisocyanate trimethylolpropane adduct (manufactured by Mitsui Chemicals, Inc., trade name: D160N); polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols; and polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, aliphatic isocyanates are preferred because of their fast reaction rate.

[0026] Epoxy crosslinkers are polyfunctional epoxy compounds having two or more epoxy groups in one molecule. Examples of epoxy crosslinkers include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, diamine glycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol, and the like. Examples of the epoxy crosslinking agent include glycerol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether, as well as epoxy resins having two or more epoxy groups in the molecule. Examples of the epoxy crosslinking agent include commercially available products manufactured by Mitsubishi Gas Chemical Company, Inc., under the trade names "Tetrad C" and "Tetrad X."

[0027] The amount of the crosslinking agent is preferably 0.01 to 5 parts by weight, more preferably 0.3 to 2 parts by weight, and even more preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer. When multiple crosslinking agents are used in combination, the total amount may fall within the above range.

[0028] The silane coupling agent is an optional component that can be contained in the PSA as needed. The silane coupling agent preferably contains a reactive functional group. The reactive functional group of the reactive functional group-containing silane coupling agent is typically a functional group other than an acid anhydride group. Examples of functional groups other than an acid anhydride group include an epoxy group, a mercapto group, an amino group, an isocyanate group, an isocyanurate group, a vinyl group, a styryl group, an acetoacetyl group, a ureido group, a thiourea group, a (meth)acrylic group, a heterocyclic group, and combinations thereof. The reactive functional group-containing silane coupling agents can be used alone or in combination.

[0029] When a reactive functional group-containing silane coupling agent is used, the amount thereof can usually be 0.001 to 2 parts by weight per 100 parts by weight of the (meth)acrylic polymer.

[0030] Specific examples of additives that can be contained in the adhesive include colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, and foil-like materials.In addition, within a controllable range, a redox system can be used by adding a reducing agent.The type, number, combination, and content of additives can be appropriately set according to the purpose.

[0031] The storage modulus of the first pressure-sensitive adhesive layer (substantially the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer) at 23°C is preferably 0.15 MPa or more, more preferably 0.18 MPa to 0.30 MPa, and even more preferably 0.20 MPa to 0.24 MPa. If the storage modulus is within this range, the desired indentation hardness can be easily achieved. The storage modulus can be determined, for example, by measuring dynamic viscoelasticity. Specifically, the storage modulus can be determined by reading the value at 23°C when measurements are made at a frequency of 1 Hz in the range of -50°C to 150°C at a heating rate of 5°C / min in accordance with the method described in JIS K 7244-1 "Plastics - Test methods for dynamic mechanical properties."

[0032] The thickness of the first pressure-sensitive adhesive layer is preferably 20 μm or less, more preferably 5 μm to 18 μm, even more preferably 7 μm to 15 μm, and particularly preferably 8 μm to 12 μm.

[0033] A-3.Second adhesive layer The second pressure-sensitive adhesive layer 20 may have any suitable configuration as long as the indentation hardness of the second main surface 100b is 0.15 MPa to 1.00 MPa. The pressure-sensitive adhesive (pressure-sensitive adhesive composition) constituting the second pressure-sensitive adhesive layer may be, for example, a photocurable pressure-sensitive adhesive or a non-curable pressure-sensitive adhesive (a conventional pressure-sensitive adhesive). A photocurable pressure-sensitive adhesive is preferred. The crosslinking structure of a photocurable pressure-sensitive adhesive can be easily controlled by appropriately adjusting the monomer component and / or prepolymer before curing, the curable component, and optional components according to the purpose. As a result, a pressure-sensitive adhesive with appropriate softness can be realized, and a second pressure-sensitive adhesive layer can be formed in which the indentation hardness of the second main surface falls within the desired range.

[0034] A photocurable pressure-sensitive adhesive typically contains a base polymer, a curing component, a polymer different from the base polymer, a photopolymerization initiator, and optional components according to the purpose.

[0035] The base polymer may typically be a (meth)acrylic polymer, as in the case of the first pressure-sensitive adhesive layer.

[0036] The alkyl(meth)acrylate, which is the main monomer component of the (meth)acrylic polymer, may be contained in an amount of preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more of all the monomer components forming the (meth)acrylic polymer.

[0037] The alkyl (meth)acrylate preferably includes a linear or branched alkyl group having 1 to 18 carbon atoms. The alkyl group more preferably has 8 to 17 carbon atoms. The alkyl (meth)acrylate preferably includes 2-ethylhexyl acrylate and isostearyl acrylate. The alkyl (meth)acrylates can be used alone or in combination.

[0038] The (meth)acrylic polymer may preferably contain a hydroxyl group-containing monomer as a monomer component. The hydroxyl group-containing monomer is as described above in section A-2 regarding the first pressure-sensitive adhesive layer. 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0039] The hydroxyl group-containing monomer may be contained in an amount of preferably 0.5 to 25% by weight, more preferably 1 to 21% by weight, based on the total monomer components.

[0040] The (meth)acrylic polymer may preferably contain a heterocycle-containing vinyl compound as a monomer component, such as N-vinyl-2-pyrrolidone.

[0041] The heterocycle-containing vinyl compound may be contained in an amount of preferably 10% by weight to 25% by weight, more preferably 15% by weight to 20% by weight, based on the total monomer components.

[0042] The (meth)acrylic polymer may preferably contain, as a monomer component, a (meth)acrylic acid ester having an alicyclic hydrocarbon group. Examples of the (meth)acrylic acid ester having an alicyclic hydrocarbon group include isobornyl acrylate.

[0043] The (meth)acrylic acid ester having an alicyclic hydrocarbon group may be contained in an amount of preferably 15 to 30% by weight, more preferably 20 to 25% by weight, based on the total monomer components.

[0044] From the viewpoint of adjusting the properties of the second pressure-sensitive adhesive layer, other monomer components (copolymerizable monomers) copolymerizable with the above-mentioned monomers may be used. Examples of copolymerizable monomers include amino group-containing monomers, amide group-containing monomers, polyfunctional monomers, cyclopolymerizable monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, vinyl esters, aromatic vinyl compounds, olefins, dienes, and vinyl ethers. The copolymerizable monomers may be used alone or in combination. The number, type, combination, and compounding ratio of the copolymerizable monomers may be appropriately set depending on the purpose.

[0045] The weight average molecular weight Mw of the (meth)acrylic polymer (base polymer) is preferably 10,000 to 700,000, more preferably 30,000 to 600,000, and even more preferably 50,000 to 450,000. The molecular weight distribution Mw / Mn of the (meth)acrylic polymer (base polymer) is preferably 4.5 or less, more preferably 4.3 or less, and even more preferably 3.5 or less. The lower limit of the molecular weight distribution Mw / Mn can be, for example, 2.0 or 2.2.

[0046] Examples of the curing component include a polyfunctional compound, a crosslinking agent, and a silane coupling agent.

[0047] The polyfunctional compound may be a compound containing two or more polymerizable functional groups (ethylenically unsaturated groups) having an unsaturated double bond in one molecule. The polyfunctional compound is typically a photopolymerizable polyfunctional compound. As the polyfunctional compound, a polyfunctional (meth)acrylate is preferred because it can be easily copolymerized with the monomer component of the (meth)acrylic polymer.

[0048] Specific examples of polyfunctional compounds include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, and urethane acrylate. The polyfunctional compounds may be used alone or in combination of two or more.

[0049] The polyfunctional compound can be used in a proportion of preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, relative to 100 parts by weight of the base polymer.

[0050] The crosslinking agent and the silane coupling agent are as explained above in section A-2 regarding the first pressure-sensitive adhesive layer.

[0051] The polymer different from the base polymer (hereinafter sometimes referred to as another polymer) may be, for example, a (meth)acrylic polymer having a weight average molecular weight Mw of 1000 to 30000. By using such another polymer, the adhesion to the adherend may be improved.

[0052] The other polymer preferably contains, as a monomer component, a (meth)acrylate having a cyclic structure in the molecule. Such a ring-containing (meth)acrylate is preferably a non-aromatic (meth)acrylate. Examples of non-aromatic ring-containing (meth)acrylates include cycloalkyl (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate; (meth)acrylates having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; and (meth)acrylates having three or more aliphatic hydrocarbon rings such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0053] The ring-containing (meth)acrylate may be contained in a proportion of preferably 10% by weight to 90% by weight, more preferably 20% by weight to 80% by weight, based on the total monomer components of the other polymer.

[0054] The monomer components other than the ring-containing (meth)acrylate in the other polymer are as described for the base polymer of the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer and the base polymer of the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer. The content of such monomer components can be specified as the remainder of the total monomer components of the other polymer.

[0055] Examples of photopolymerization initiators include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. The photopolymerization initiators may be used alone or in combination of two or more. Furthermore, a photopolymerization initiator and a thermal polymerization initiator may be used in combination.

[0056] The photopolymerization initiator can be used in a proportion of preferably 0.001 to 1 part by weight, more preferably 0.01 to 0.5 parts by weight, relative to 100 parts by weight of the base polymer.

[0057] The pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer may contain any appropriate additive depending on the purpose, as explained above in section A-2 regarding the first pressure-sensitive adhesive layer.

[0058] The second adhesive layer can be formed, for example, by partially polymerizing the monomer components of the base polymer to prepare a prepolymer composition, mixing the prepolymer composition with another polymer and a curing component, and then completing the polymerization.

[0059] The storage modulus of the second pressure-sensitive adhesive layer (substantially the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer) at 23°C is preferably 0.03 MPa or more, more preferably 0.04 MPa to 0.22 MPa, and even more preferably 0.05 MPa to 0.20 MPa. If the storage modulus is within this range, it may be easy to achieve the desired indentation hardness.

[0060] The thickness of the second pressure-sensitive adhesive layer is preferably 120 μm or less, more preferably 50 μm or less, even more preferably 10 μm to 40 μm, and particularly preferably 20 μm to 30 μm.

[0061] In one embodiment, the thickness of the second pressure-sensitive adhesive layer is greater than the thickness of the first pressure-sensitive adhesive layer. With this configuration, for example, when the second main surface of the pressure-sensitive adhesive sheet is bonded to a hard substrate and the first main surface is bonded to a porous film (low refractive index film) to form a laminate, the generation of bubbles at the interface between the substrate and the pressure-sensitive adhesive sheet can be effectively suppressed. The difference in thickness between the second pressure-sensitive adhesive layer and the first pressure-sensitive adhesive layer is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm.

[0062] B. Laminate B-1. Overview of the laminate FIG. 2 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention. The illustrated laminate 200 includes a substrate 110 and a porous layer 120 laminated on the substrate 110 via a pressure-sensitive adhesive sheet 100. The substrate 110 typically has a thickness of 400 μm or more and a Young's modulus of 1.0 GPa or more. The pressure-sensitive adhesive sheet 100 is the pressure-sensitive adhesive sheet according to the embodiment of the present invention described in Section A above. The second main surface 100b of the pressure-sensitive adhesive sheet 100 is bonded to the substrate 110, and the first main surface 100a is bonded to the porous layer 120. The substrate may be omitted from the laminate. That is, the laminate may have a configuration including the pressure-sensitive adhesive sheet 100 and the porous layer 120 laminated on the first main surface 100a of the pressure-sensitive adhesive sheet 100. The refractive index of such laminates can be controlled by the configuration of the porous layer, making them suitable for a wide range of applications, particularly optical applications.

[0063] The substrate and the porous layer will be described below.

[0064] B-2. Base material The thickness of the substrate is, as described above, 400 μm or more, preferably 700 μm to 10,000 μm, and more preferably 1,000 μm to 5,000 μm. The effects of the present invention can be particularly pronounced in laminates including substrates of such thicknesses. Specifically, by laminating the substrate 110 and the porous layer by bonding the second main surface 100b of the pressure-sensitive adhesive sheet 100 described in Section A above to the substrate 110 (and thus bonding the first main surface 100a of the pressure-sensitive adhesive sheet 100 to the porous layer 120), air bubbles at the interface between the pressure-sensitive adhesive sheet and the substrate can be suppressed, and as a result, the transparency of the laminate can be maintained. Note that when the substrate is a thin film, for example, having a thickness of 100 μm or less, such problems with air bubbles often do not occur.

[0065] As described above, the substrate has a Young's modulus of 1.0 GPa or more, preferably 10.0 GPa to 100.0 GPa, and more preferably 50.0 GPa to 80.0 GPa. The effects of the present invention can be significant in a laminate including a substrate with such a Young's modulus (hardness). Specifically, the thickness of the substrate is as described above. The Young's modulus can be measured according to JIS R1062.

[0066] The substrate may have any suitable structure as long as it satisfies the above-mentioned thickness and / or Young's modulus. Specifically, the substrate may be a glass plate or a resin sheet.

[0067] Glass constituting the glass plate can be classified by composition, for example, soda-lime glass, borate glass, aluminosilicate glass, quartz glass, etc. Also, classified by alkali component, can be alkali-free glass or low-alkali glass. The content of alkali metal components (e.g., Na2O, KO, Li2O) in the glass is preferably 15 wt% or less, more preferably 10 wt% or less. The density of the glass is preferably 2.3 g / cm 3 ~3.0g / cm 3 and more preferably 2.3 g / cm 3 ~2.7g / cm 3 If the density of the glass is within this range, the weight of the laminate can be reduced.

[0068] Examples of materials that can be used to form resin sheets include acrylic resins, styrene resins, acrylonitrile-styrene resins (AS resins), polycarbonate resins, polyester resins, and polyolefin resins. The use of resin sheets can achieve a surface hardness that is practically acceptable and can be made lighter than glass plates. Furthermore, the use of resins with higher transparency than glass can achieve low power consumption when the laminate is applied to an image display device, for example.

[0069] B-3.Porous layer As described above, the porous layer can function as a layer with a controlled refractive index, for example, as a low refractive index layer. The refractive index of the porous layer is typically 1.30 or less, with the lower limit being greater than 1.00. The refractive index of the porous layer is preferably 1.13 to 1.28, more preferably 1.14 to 1.26, even more preferably 1.15 to 1.24, and particularly preferably 1.16 to 1.22. Unless otherwise specified, the refractive index refers to a refractive index measured at a wavelength of 550 nm.

[0070] The haze of the porous layer is preferably less than 5%, more preferably less than 3%, and even more preferably less than 2%. On the other hand, the haze may be, for example, 0.1% or more, or, for example, 0.2% or more. The haze can be calculated, for example, from the value measured with a haze meter (for example, "HM-150" manufactured by Murakami Color Research Laboratory) using the following formula: Haze (%) = [Diffuse transmittance (%) / Total light transmittance (%)] x 100 (%)

[0071] The total light transmittance of the porous layer is preferably 85% to 99%, more preferably 87% to 98%, and even more preferably 89% to 97%. The total light transmittance can be measured, for example, by the above-mentioned haze meter.

[0072] The thickness of the porous layer is preferably 0.3 μm to 10 μm, more preferably 1.0 μm to 8.0 μm, still more preferably 1.5 μm to 7.0 μm, particularly preferably 2.0 μm to 6.0 μm, and especially preferably 2.5 μm to 5.0 μm.

[0073] The porosity of the porous layer may be, for example, 20% to 60% by volume, 25% to 55% by volume, 30% to 50% by volume, or 35% to 45% by volume. The porosity is a value calculated from the refractive index measured with an ellipsometer using the Lorentz-Lorenz formula.

[0074] The size of the pores that can be contained in the porous layer can be adjusted to a desired size depending on the purpose and application. The size of the pores that can be contained in the low refractive index layer is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. On the other hand, the size of the pores that can be contained in the porous layer is, for example, 500 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. Note that the size of the pores refers to the diameter of the major axis of the pores, out of the diameter of the major axis and the diameter of the minor axis.

[0075] The pore size can be quantified by the BET test method. In one embodiment, 0.1 g of a measurement sample (e.g., a formed porous layer) is placed in the capillary of a specific surface area measurement device (e.g., an ASAP2020 manufactured by Micromeritics), and then the sample is dried under reduced pressure at room temperature for 24 hours to remove gases contained in the measurement sample. Then, nitrogen gas is adsorbed onto the measurement sample, and an adsorption isotherm is drawn to determine the pore size distribution. This allows the pore size to be evaluated.

[0076] The porous layer may have any suitable structure as long as it satisfies the above-described characteristics. The porous layer may be, for example, a structure composed of one or more types of structural units that form a fine void structure, and these structural units may be bonded together (e.g., chemically bonded via catalytic action). Examples of the shape of the structural units include particles, fibers, rods, and plates. The structural units may have only one shape, or may have a combination of two or more shapes. A specific example of such a structure is a structure in which pulverized gels such as gel-like silicon compounds are chemically bonded together (chemically bonded). Examples of chemical bonds include cross-linking, covalent bonding, and hydrogen bonding. The volume average particle diameter of the pulverized material in the porous layer is, for example, 0.10 μm or more, preferably 0.20 μm or more, and more preferably 0.40 μm or more. On the other hand, the volume average particle diameter of the pulverized material in the porous layer is, for example, 2.00 μm or less, preferably 1.50 μm or less, and more preferably 1.00 μm or less. The volume average particle size is an index of the variation in particle size of the pulverized material, and can be determined by measuring the particle size distribution.

[0077] The specific structure and formation method of the porous layer (low refractive index layer) are described in detail in, for example, WO 2019 / 151073, the disclosure of which is incorporated herein by reference. [Example]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "%" and "parts" in the examples are by weight.

[0079] (1) Thickness The thickness was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000").

[0080] (2) Indentation hardness Measurement was performed by nanoindentation using a nanoindenter (manufactured by Hysitron Inc., "Triboindenter") under the following measurement conditions. Specifically, the probe (indenter) of the nanoindenter was pressed into the surface of the adhesive sheet used as a component of the laminated adhesive sheet in the examples and comparative examples, and calculation was performed from the displacement-load hysteresis curve using the following formula. Indentation hardness (GPa) = Pmax / A Here, Pmax is the maximum load obtained from the displacement-load hysteresis curve, and A is the contact projected area between the indenter and the adhesive sheet. (Measurement conditions) Measurement method: Single indentation method ·Measurement temperature: 25℃ Push-in speed: approx. 2nm / sec Indentation depth: approx. 2000 nm Indenter used: Diamond, Berkovich type (triangular pyramid type)

[0081] (3) Storage modulus A measurement sample was prepared from the adhesive constituting the adhesive sheet as a component of the laminated adhesive sheet used in the Examples and Comparative Examples. The measurement sample was disk-shaped, with a bottom diameter of 8 mm and a thickness of 2 mm. Next, using the measurement sample, dynamic viscoelasticity measurements were performed under the following conditions. For the dynamic viscoelasticity measurements, an ARES-G2 manufactured by TA Instruments was used. From the results of the dynamic viscoelasticity measurements, the storage modulus G' at 23°C of the adhesive constituting the adhesive sheet was determined. (Measurement conditions) Frequency: 1Hz Deformation mode: Torsion ·Measurement temperature: -70℃~150℃ Heating rate: 5℃ / min

[0082] (4) Peel strength The adhesive sheet used as a component of the laminated adhesive sheet in the examples and comparative examples was cut to a size of 25 mm wide and 100 mm long, and attached to a 0.7 mm thick glass plate under an environment of 23°C and 50% RH, and then pressed against the plate by rolling a 2 kg roll back and forth once. After leaving the sheet under the same environment for 30 minutes, the peel strength (N / 25 mm) was measured using a tension and compression tester (Minebea Co., Ltd., "TG-1kN") in accordance with JIS Z 0237:2000 at a peel speed of 0.3 m / min and a peel angle of 180°. The obtained peel strength was taken as the peel force.

[0083] (5) Refractive index of the porous layer The acrylic film / porous membrane laminate obtained in Production Example 7 was cut to a size of 25 mm x 50 mm. The cut laminate was attached to the surface of a glass plate (thickness: 3 mm) via an adhesive layer. The center of the back surface of the glass plate (diameter: approximately 20 mm) was filled in with black marker to create a sample that was not reflective on the back surface of the glass plate. The sample was placed in an ellipsometer (JA Woollam Japan: VASE), and the refractive index was measured at a wavelength of 550 nm and an incident angle of 50 to 80 degrees.

[0084] (6) n1 and n2 A porous film with a porosity of 55% by volume, a refractive index of 1.20, and a thickness of 2.0 μm was formed on an acrylic film in the same manner as in Production Example 7. The resulting acrylic film / porous film laminate was cut to a size of 25 mm × 50 mm. The cut laminate was attached to the surface of a glass plate (thickness: 3 mm) via the laminated adhesive sheet used in the Examples and Comparative Examples. The lamination was performed so that the first main surface of the laminated adhesive sheet faced the porous film. The center of the back surface of the glass plate (diameter: approximately 20 mm) was filled in with black marker to create a sample that was not reflective on the back surface of the glass plate. The resulting sample was left in an environment of 65°C and 95% RH for 100 hours, and the refractive index of the porous film was measured in the same manner as in (5) above, and the obtained refractive index was designated n1. A sample was prepared in the same manner as above, except that the second main surface of the laminated adhesive sheet was attached to the porous film side. The obtained sample was placed in an environment of 65 ° C and 95% RH for 100 hours, and the refractive index of the porous film was measured in the same manner as above (5), and the obtained refractive index was designated n2.

[0085] (7) Air bubbles The state of the interface between the substrate and the laminated pressure-sensitive adhesive sheet in the laminates obtained in the Examples and Comparative Examples was visually observed and evaluated according to the following criteria. ○ (Good): No bubbles were observed △ (moderate): A few bubbles were observed, but the level was acceptable for practical use. × (bad): Air bubbles were noticeable and practically unacceptable

[0086] [Production Example 1: Preparation of Adhesive Sheet A] 1. Preparation of (meth)acrylic polymer A1 A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 84 parts of butyl acrylate, 13 parts of N-acryloylmorpholine, 3 parts of acrylic acid, and 1 part of 4-hydroxybutyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 70 parts of ethyl acetate were charged to 100 parts of the monomer mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere. The temperature in the flask was maintained at around 55°C, and a polymerization reaction was carried out for 2 hours to prepare a solution of (meth)acrylic polymer A1 with a weight-average molecular weight (Mw) of 2,930,000 and Mw / Mn = 2.72.

[0087] 2. Preparation of Pressure-Sensitive Adhesive Composition A solution of an acrylic pressure-sensitive adhesive composition was prepared by blending 0.5 parts of an isocyanate crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of trimethylolpropane and tolylene diisocyanate) and 0.5 parts of an epoxy crosslinking agent (trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) with 100 parts of the solids content of the solution of (meth)acrylic polymer A1 obtained above.

[0088] 3. Preparation of adhesive sheet The solution of the acrylic pressure-sensitive adhesive composition was applied to one side of a polyethylene terephthalate film (release liner: MRF38, manufactured by Mitsubishi Chemical Polyester Film Corporation) treated with a silicone release agent, and dried at 155°C for 1 minute to form a 10µm thick pressure-sensitive adhesive sheet A on the surface of the release liner. The indentation hardness of pressure-sensitive adhesive sheet A was 0.30MPa, the storage modulus was 0.22MPa, and the peel force was 6.9N / 25mm.

[0089] [Production Example 2: Preparation of Adhesive Sheet B] A solution of (meth)acrylic polymer A1 was prepared in the same manner as in Production Example 1. 0.2 parts of an isocyanate crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd., an adduct of trimethylolpropane and tolylene diisocyanate) and 0.2 parts of an epoxy crosslinking agent (trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) were blended with 100 parts of the solids content of the resulting (meth)acrylic polymer A1 solution to prepare a solution of an acrylic pressure-sensitive adhesive composition. Subsequent procedures were the same as in Production Example 1, and an adhesive sheet B was formed on the surface of a release liner. The adhesive sheet B had an indentation hardness of 0.16 MPa, a storage modulus of 0.20 MPa, and a peel force of 9.1 N / 25 mm. Two adhesive sheets B with thicknesses of 10 μm and 20 μm were prepared.

[0090] [Production Example 3: Preparation of Adhesive Sheet C] 1. Preparation of Acrylic Polymer B1 60 parts by weight of dicyclopentanyl acrylate (DCPMA), 40 parts by weight of methyl methacrylate (MMA), 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent were placed in a four-neck flask and stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was placed in the four-neck flask and reacted at 70°C for 2 hours, followed by another 2 hours at 80°C. The reaction solution was then placed in a 130°C atmosphere, and the toluene, chain transfer agent, and unreacted monomers were dried and removed to obtain a solid acrylic polymer B1. The weight-average molecular weight Mw of the acrylic polymer B1 was 5.1 x 10 3 It was.

[0091] 2. Preparation of Pressure-Sensitive Adhesive Composition A monomer mixture consisting of 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 4 parts by weight of 2-hydroxyethyl acrylate (HEA) was mixed with 0.035 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) and 0.035 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF), and then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, yielding a prepolymer composition in which some of the above monomer components had polymerized. Next, 10 parts by weight of the acrylic polymer B1, 0.29 parts by weight of hexanediol diacrylate (HDDA), and 0.3 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition.

[0092] 3. Preparation of adhesive sheet The acrylic pressure-sensitive adhesive composition was applied to a polyethylene terephthalate (PET) release liner (trade name "MRF50", manufactured by Mitsubishi Plastics, Inc.) to form a coating layer. Next, a PET release liner (trade name "MRF38", manufactured by Mitsubishi Plastics, Inc.) was placed on the coating layer to cover the coating layer and block oxygen. In this way, a laminate of MRF50 / coating layer / MRF38 was obtained. Next, this laminate was illuminated from the top surface (MRF38 side) of the laminate with a black light (manufactured by Toshiba Corporation) at an illuminance of 5 mW / cm. 2 The adhesive sheet was then irradiated with ultraviolet light at 1000 kJ / cm² for 300 seconds. It was then dried in a 90°C dryer for 2 minutes to volatilize the remaining monomer. In this way, a pressure-sensitive adhesive sheet C was formed between the two release liners. The pressure-sensitive adhesive sheet C had an indentation hardness of 0.12 MPa, a storage modulus of 0.19 MPa, and a peel force of 11.6 N / 25 mm. Two pressure-sensitive adhesive sheets C were produced, one with a thickness of 10 μm and the other with a thickness of 25 μm.

[0093] [Production Example 4: Preparation of Adhesive Sheet D] A prepolymer composition was obtained in the same manner as in Production Example 3. Next, 10 parts by weight of the acrylic polymer B1, 0.09 parts by weight of hexanediol diacrylate (HDDA), and 0.3 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition. Subsequent procedures were the same as in Production Example 3, and a 25 μm thick pressure-sensitive adhesive sheet D was formed between two release liners. The pressure-sensitive adhesive sheet D had an indentation hardness of 0.08 MPa, a storage modulus of 0.14 MPa, and a peel force of 14.3 N / 25 mm.

[0094] [Production Example 5: Preparation of Adhesive Sheet E] A monomer mixture consisting of 28.5 parts by weight of 2-ethylhexyl acrylate (2EHA), 28.5 parts by weight of isostearyl acrylate (ISTA), 22 parts by weight of isobornyl acrylate (IBXA), and 21 parts by weight of 4-hydroxybutyl acrylate (4HBA) was mixed with 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 184" manufactured by BASF) and 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF). The mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, yielding a prepolymer composition in which some of the monomer components had polymerized. Next, 0.3 parts by weight of hexanediol diacrylate (HDDA), 0.3 parts by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF) were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition. The subsequent procedures were the same as in Production Example 3, and a 25 μm thick pressure-sensitive adhesive sheet E was formed between two release liners. The pressure-sensitive adhesive sheet E had an indentation hardness of 0.07 MPa, a storage modulus of 0.11 MPa, and a peel force of 10.5 N / 25 mm.

[0095] [Production Example 6: Preparation of Adhesive Sheet F] A monomer mixture consisting of 40.5 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), 40.5 parts by weight of isostearyl acrylate (ISTA), and 1 part by weight of 4-hydroxybutyl acrylate (4HBA) was mixed with 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) and 0.05 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF). The mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, yielding a prepolymer composition in which some of the monomer components had polymerized. Next, 1.0 part by weight of triphenyl phosphite (manufactured by Sakai Chemical Industry Co., Ltd.), 0.3 part by weight of a silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.), 0.15 part by weight of trimethylolpropane triacrylate (TMPTA), and 0.15 part by weight of 1-thioglycerol (manufactured by Asahi Chemical Industry Co., Ltd.) were added to the prepolymer composition and mixed to obtain an acrylic pressure-sensitive adhesive composition. The subsequent procedures were the same as in Production Example 3, and a 100 μm thick pressure-sensitive adhesive sheet F was formed between two release liners. The pressure-sensitive adhesive sheet F had an indentation hardness of 0.01 MPa, a storage modulus of 0.06 MPa, and a peel force of 25.7 N / 25 mm.

[0096] [Production Example 7: Preparation of porous layer] 1. Gelation of silicon compounds (preparation of gel for forming porous layer) 2.2 g of dimethyl sulfoxide (DMSO) was prepared and 0.95 g of methyltrimethoxysilane (MTMS), a precursor of a silicon compound, was dissolved in this to prepare mixed solution A. 0.5 g of a 0.01 mol / L aqueous solution of oxalic acid was added to mixed solution A and stirred at room temperature for 30 minutes to hydrolyze the MTMS, producing mixed solution B containing tris(hydroxy)methylsilane. To 5.5 g of DMSO, 0.38 g of 28 wt % ammonia water and 0.2 g of pure water were added, and then the above mixed solution B was further added and stirred at room temperature for 15 minutes to gel tris(hydroxy)methylsilane, thereby obtaining mixed solution C containing a gel-like silicon compound. In this way, a gel for forming a porous layer was obtained.

[0097] 2.Aging process The mixed solution C containing the gel-like silicon compound prepared as above was incubated as is at 40° C. for 20 hours for aging treatment.

[0098] 3. Coarse grinding and solvent substitution Next, the gel-like silicon compound aged as described above was crushed into granules of several mm to several cm in size using a spatula (coarse crushing). Next, 40 g of isopropyl alcohol (IPA) was added to the mixed solution C, and after light stirring, the mixture was left to stand at room temperature for 6 hours, and the solvent and catalyst in the gel were decanted. The same decantation process was repeated three times to replace DMSO with IPA (solvent replacement), and mixed solution D was obtained.

[0099] 4. Fine pulverization (preparation of coating liquid for forming porous layer) Next, the gel-like silicon compound in the mixed solution D was finely pulverized (high-pressure media-less pulverization). The finely pulverization (high-pressure media-less pulverization) was carried out using a homogenizer (manufactured by SMT Corporation, trade name "UH-50"), with 1.85 g of the gel-like compound in the mixed solution D and 1.15 g of IPA weighed into a 5 cc screw bottle, and the pulverization was carried out at 50 W and 20 kHz for 2 minutes. As described above, the gel-like silicon compound in the mixed solution D was pulverized, and the mixed solution D became a sol solution E of pulverized gel. The volume average particle size, which indicates the particle size variation of the pulverized gel contained in the sol solution E, was confirmed using a dynamic light scattering Nanotrac particle size analyzer (manufactured by Nikkiso Co., Ltd., UPA-EX150 model) and was found to be 0.50 μm to 0.70 μm. Furthermore, 0.015 g of a 1.5 wt % MEK (methyl ethyl ketone) solution of a photobase generator (Wako Pure Chemical Industries, Ltd., product name: WPBG266) and 0.005 g of a 5% MEK solution of a bis-crosslinking accelerator ((trimethoxysilyl)hexane) were added to 0.75 g of the sol solution E to obtain a coating solution for forming a porous layer.

[0100] 5. Formation of porous layer The porous layer-forming coating liquid obtained as described above was applied to an acrylic film, and the coating film was heated at 100°C for 1 minute to form a porous layer on the acrylic film. The resulting porous layer had a porosity of 55% by volume, a thickness of 2.0 µm, and a refractive index of 1.20.

[0101] [Example 1] A laminated adhesive sheet was produced by laminating the adhesive sheet A obtained in Production Example 1 and the adhesive sheet D obtained in Production Example 4. Specifically, the release liner on one side of the adhesive sheet D was peeled off and removed to expose the adhesive sheet D, and the exposed surface of the adhesive sheet D was laminated to the adhesive sheet A. Note that the interface between the adhesive sheet A and the adhesive sheet D was not clearly discernible in the laminated adhesive sheet, and the laminated adhesive sheet was configured to appear as a single layer. A glass plate (thickness 0.7 mm, Young's modulus 69 GPa) was prepared as the substrate, and this glass plate and the porous layer obtained in Production Example 7 were laminated via the above-mentioned laminated adhesive sheet. In the lamination, the surface (first main surface) of adhesive sheet A was attached to the porous layer, and the surface (second main surface) of adhesive sheet D was attached to the substrate. In the lamination, lamination, vacuum lamination, and autoclave treatment were performed in this order. In this way, a laminate having a structure of substrate / laminated adhesive sheet / porous layer was obtained. The obtained laminate was evaluated in the above (6) and (7). The results are shown in Table 1.

[0102] [Examples 2 to 5 and Comparative Examples 1 to 3] A laminate having a substrate / laminated adhesive sheet / porous layer configuration was obtained in the same manner as in Example 1, except that a laminated adhesive sheet obtained by combining adhesive sheets as shown in Table 1 was used. The obtained laminate was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0103] [Table 1]

[0104] As is clear from Table 1, the pressure-sensitive adhesive sheets (laminated pressure-sensitive adhesive sheets) of the examples of the present invention suppress bubbles at the interface with the substrate (glass plate), and the refractive index of the porous layer is maintained near the design value (initial value). Therefore, it can be understood that the pressure-sensitive adhesive sheets (laminated pressure-sensitive adhesive sheets) of the examples of the present invention can suppress defects at the interface with each adherend, even when different adherends are laminated together. [Industrial Applicability]

[0105] The pressure-sensitive adhesive sheet of the embodiment of the present invention can be used to laminate different adherends, and can be suitably used, for example, to laminate a hard substrate and a porous film (low refractive index film). [Explanation of symbols]

[0106] 10 First adhesive layer 20 Second adhesive layer 100 adhesive sheets 100a First principal surface 100b Second principal surface 110 Base material 120 Porous layer 200 laminate

Claims

1. having a first major surface and a second major surface; The indentation hardness of the first main surface is 0.15 MPa to 1.00 MPa, The indentation hardness of the second main surface is less than 0.15 MPa. Adhesive sheet.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the difference in indentation hardness between the first main surface and the second main surface is 0.06 MPa or more.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the peel strength of the second main surface relative to glass is 10 N / 25 mm or more.

4. It has a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, the first pressure-sensitive adhesive layer includes the first main surface, and the second pressure-sensitive adhesive layer includes the second main surface; The pressure-sensitive adhesive sheet according to claim 1 .

5. The pressure-sensitive adhesive sheet according to claim 4 , wherein the second pressure-sensitive adhesive layer has a thickness of 50 μm or less.

6. The pressure-sensitive adhesive sheet according to claim 4, wherein the weight average molecular weight Mw of the base polymer of the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer is 700,000 to 4,000,000, and the weight average molecular weight Mw of the base polymer of the pressure-sensitive adhesive constituting the second pressure-sensitive adhesive layer is 10,000 to 700,000.

7. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the refractive index of the porous film after laminating a first main surface of an adhesive sheet to a porous film having a porosity of 55 volume %, a refractive index of 1.20 and a thickness of 2.0 μm is 100 hours at 65° C. and 95% RH, and the refractive index of the porous film after laminating the first main surface of the adhesive sheet to the same porous film is 100 hours at 65° C. and 95% RH; the refractive index of the porous film after laminating the second main surface of the adhesive sheet to the same porous film is 100 hours at 65° C. and 95% RH; the relationship n1<n2 is satisfied.

8. A laminate comprising the pressure-sensitive adhesive sheet according to claim 1 and a porous layer laminated on the first main surface of the pressure-sensitive adhesive sheet.

9. A substrate having a thickness of 400 μm or more and a Young's modulus of 1.0 GPa or more, and a porous layer laminated on the substrate via the pressure-sensitive adhesive sheet according to any one of claims 1 to 7, the second main surface of the pressure-sensitive adhesive sheet is bonded to the substrate, and the first main surface of the pressure-sensitive adhesive sheet is bonded to the porous layer; Laminate.

10. The laminate according to claim 9 , wherein the substrate is a glass plate.

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