Pressure-sensitive adhesive sheet, laminate, and method for producing pressure-sensitive adhesive sheet

Abstract

Provided is an adhesive sheet 1 which is provided with at least an adhesive layer 11 and has an adhesive strength to soda-lime glass greater than 1 N / 25 mm and equal to or less than 100 N / 25 mm, wherein an adhesive constituting the adhesive layer 11 is formed of an adhesive composition including a (meth)acrylic acid ester polymer (A), and the (meth)acrylic acid ester polymer (A) includes, as a monomer unit constituting the polymer, an ethylene carbonate-containing monomer having an ethylene carbonate structure represented by formula (1). Said adhesive sheet 1 has excellent blister resistance.

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a laminate suitable for use in a display. [Background technology]

[0002] In recent years, various mobile electronic devices such as smartphones and tablet terminals are equipped with displays that use display modules having liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescence (OLED) elements, etc., and these displays are often touch panels.

[0003] In such displays, a protective panel is usually provided on the front side of the display module. As electronic devices become thinner and lighter, the protective panel is being changed from the conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate.

[0004] Here, a gap is provided between the protective panel and the display module so that even when the protective panel is deformed by an external force, the deformed protective panel will not collide with the display module.

[0005] However, when such a gap, i.e., an air layer, is present, there is a problem that the reflection loss of light caused by the refractive index difference between the protective panel and the air layer, and the refractive index difference between the air layer and the display module, is large, resulting in a deterioration in the image quality of the display.

[0006] Therefore, it has been proposed to improve the image quality of a display by filling the gap between the protective panel and the display module with an adhesive layer. For example, Patent Document 1 discloses an adhesive layer having a shear storage modulus (G') of 1.0×10 at 25° C. and 1 Hz for filling the gap between the protective panel and the display module. 5 The pressure-sensitive adhesive layer has a compressive strength of 0.1 Pa or less and a gel fraction of 40% or more. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2010-97070 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the storage modulus of the pressure-sensitive adhesive layer at room temperature is reduced as in Patent Document 1, the storage modulus at high temperatures is lowered more than necessary, causing problems under durability conditions. For example, when exposed to high temperature and high humidity conditions, outgassing may occur from the plastic plate that is the protective panel, causing blisters such as bubbles, lifting, and peeling.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a pressure-sensitive adhesive sheet and a laminate that are excellent in blister resistance. [Means for solving the problem]

[0010] In order to achieve the above object, first, the present invention provides a pressure-sensitive adhesive sheet including at least a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet having an adhesive strength to soda-lime glass of more than 1 N / 25 mm and not more than 100 N / 25 mm, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer being formed from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A), the (meth)acrylic acid ester polymer (A) being represented by the following formula (1) as a monomer unit constituting the polymer: [ka] The present invention provides a pressure-sensitive adhesive sheet comprising an ethylene carbonate-containing monomer having an ethylene carbonate structure represented by the following formula (Invention 1).

[0011] In the above invention (Invention 1), the side chain of the (meth)acrylic acid ester polymer (A) contains an ethylene carbonate structure, which strengthens the interaction between the side chains, and the glass transition temperature (Tg) of the (meth)acrylic acid ester polymer (A) becomes relatively high. This strengthens the cohesive force of the resulting adhesive, and the adhesive sheet has excellent blister resistance. In addition, the degree of polarization increases, and the dielectric constant of the resulting adhesive becomes high. Furthermore, from the viewpoint of polarity, the adhesive sheet has high adhesive strength, particularly adhesive strength to glass.

[0012] In the above invention (Invention 1), the (meth)acrylic acid ester polymer (A) preferably contains 0.5 mass % or more and 40 mass % or less of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer (Invention 2).

[0013] Secondly, the present invention provides an adhesive sheet having at least an adhesive layer, the adhesive strength to soda-lime glass being greater than 1 N / 25 mm and not greater than 100 N / 25 mm, the adhesive layer being formed from an adhesive composition containing a (meth)acrylic acid ester polymer (A), the (meth)acrylic acid ester polymer (A) containing, as a monomer unit constituting the polymer, a carbon dioxide-derived monomer obtained using carbon dioxide as a raw material (Invention 3).

[0014] According to the above invention (Invention 3), it becomes possible to consume carbon dioxide as a raw material in the production of the pressure-sensitive adhesive sheet, thereby contributing to the reduction of carbon dioxide emissions, which is an internationally important issue, and ultimately to the Sustainable Development Goals (SDGs) set forth by the United Nations.

[0015] In the above invention (Invention 3), when the carbon dioxide-derived monomer is produced, it is preferable that 0.1 mole or more of carbon dioxide is consumed per mole of the carbon dioxide-derived monomer (Invention 4).

[0016] In the above inventions (Inventions 3 and 4), it is preferable that the carbon dioxide-derived monomer is obtained by reacting an epoxy group-containing compound with carbon dioxide (Invention 5).

[0017] In the above inventions (Inventions 1 to 5), the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer preferably has a storage modulus (G') at 25° C. of 0.01 MPa or more and 2.0 MPa or less (Invention 6).

[0018] In the above inventions (Inventions 1 to 6), it is preferable that the loss tangent (tan δ) at 25° C. obtained by dynamic viscoelasticity measurement of the adhesive constituting the adhesive layer in accordance with JIS K7244-1 is 0.3 or more and 3.0 or less (Invention 7).

[0019] In the above inventions (Inventions 1 to 7), the dielectric constant ε at 40 kHz of the adhesive constituting the adhesive layer s It is preferable that the ratio is 5.80 or more and 10 or less (Invention 8).

[0020] In the above inventions (Inventions 1 to 8), it is preferable that the adhesive sheet has two release sheets, and the adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets (Invention 9).

[0021] Thirdly, the present invention provides a laminate (Invention 10) comprising two display component members and an adhesive layer sandwiched between the two display component members, the adhesive layer being formed from the adhesive layer of the adhesive sheet (Inventions 1 to 9).

[0022] In the above invention (Invention 10), it is preferable that at least one of the display body constituent members includes a plastic plate (Invention 11). Effect of the Invention

[0023] The pressure-sensitive adhesive sheet and laminate according to the present invention have excellent blister resistance. [Brief description of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a laminate according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described. [Adhesive sheet according to the first embodiment] The pressure-sensitive adhesive sheet according to the first embodiment includes at least a pressure-sensitive adhesive layer, and is preferably an adhesive sheet having a release sheet laminated on one or both sides of the pressure-sensitive adhesive layer.

[0026] FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the first embodiment. 1, an adhesive sheet 1 according to one embodiment is composed of two release sheets 12a, 12b and an adhesive layer 11 sandwiched between the two release sheets 12a, 12b so as to be in contact with the release surfaces of the two release sheets 12a, 12b. In this specification, the release surface of a release sheet refers to a surface of the release sheet that has releasability, and includes both a surface that has been subjected to a release treatment and a surface that exhibits releasability even without being subjected to a release treatment.

[0027] 1. Each component 1-1. Adhesive layer The adhesive constituting the adhesive layer 11 of the adhesive sheet 1 according to this embodiment is formed from an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylic acid ester polymer (A) and preferably a crosslinking agent (B). In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, "polymer" is also intended to include the concept of "copolymer."

[0028] (1) Components of the adhesive composition (1-1) (Meth)acrylic acid ester polymer (A) The (meth)acrylic acid ester polymer (A) has, as a monomer unit constituting the polymer, the following formula (1): [ka] The ethylene carbonate-containing monomer is not particularly limited as long as it contains an ethylene carbonate structure and can undergo a polymerization reaction with other monomers constituting the (meth)acrylic acid ester polymer (A).

[0029] Since the (meth)acrylic acid ester polymer (A) is composed of the ethylene carbonate-containing monomer, the adhesive composition P according to this embodiment contains an ethylene carbonate structure as a side chain of the (meth)acrylic acid ester polymer (A). When the (meth)acrylic acid ester polymer (A) contains an ethylene carbonate structure as a side chain, the interaction between the side chains becomes strong, and the glass transition temperature (Tg) of the (meth)acrylic acid ester polymer (A) becomes relatively high. This increases the cohesive force of the resulting adhesive, and the adhesive sheet 1 has excellent blister resistance. In addition, the degree of polarization increases, and the dielectric constant of the resulting adhesive increases. Furthermore, from the viewpoint of polarity, the adhesive sheet 1 has high adhesive strength, particularly adhesive strength to glass.

[0030] A preferred example of the ethylene carbonate-containing monomer is a (meth)acrylic acid ester having a structure in which an organic group having an ethylene carbonate structure and a (meth)acryloyloxy group are bonded. Examples of such (meth)acrylic acid esters include those represented by the following formula (2): [ka] or an acrylic acid ester represented by the following formula (3): [ka] In both formula (2) and formula (3), n represents an integer of 0 or more. Among the (meth)acrylic acid esters represented by formula (2) and formula (3), (meth)acrylic acid esters in which n is 1 or more are preferred, and (meth)acrylic acid esters in which n is 2 or more are preferred. When n is 1 or more, the ethylene carbonate group as the side chain of the (meth)acrylic acid ester polymer (A) is located at a position relatively far from the main chain, and the probability that the ethylene carbonate structures present in the obtained adhesive overlap each other increases. As a result, stacking interaction between the ethylene carbonate structures works, and the mechanical properties (viscoelasticity, tensile properties) and adhesive strength described later are easily exhibited, and the blister resistance is more excellent. The upper limit of the above n is not particularly limited, but from the viewpoint of polymerizability, it is preferably 10 or less, more preferably 6 or less, particularly preferably 4 or less, and even more preferably 3 or less. Among these, from the viewpoints of facilitating improvement in the mechanical properties (viscoelasticity, tensile properties) and adhesive strength of the resulting pressure-sensitive adhesive and of superior blister resistance, (meth)acrylic acid esters in which n = 2 are preferred, and in particular, (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate in which n = 2 in formula (3) is preferred. The ethylene carbonate-containing monomers may be used alone or in combination of two or more.

[0031] The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer, more preferably 1% by mass or more, particularly preferably 3% by mass or more, and even more preferably 5% by mass or more. This enhances the stacking interaction effect due to the ethylene carbonate group in the adhesive, improves the cohesive force of the adhesive obtained, and makes it easier to favorably exhibit the mechanical properties (viscoelasticity, tensile properties) and adhesive strength described below, and the adhesive sheet 1 has better blister resistance. In addition, the degree of polarization becomes larger, and the dielectric constant is further improved. Furthermore, from the viewpoint of polarity, the adhesive strength of the adhesive sheet 1, especially the adhesive strength to glass, becomes higher.

[0032] Moreover, the (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or less of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer, more preferably 30% by mass or less, particularly preferably 25% by mass or less, and even more preferably 20% by mass or less, which makes it easier to adjust the viscoelasticity, tensile properties, and adhesive strength of the adhesive sheet 1 to the ranges described below.

[0033] In the present embodiment, the (meth)acrylic acid ester polymer (A) preferably contains a (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer. This allows the resulting adhesive to exhibit good adhesiveness. The alkyl group may be linear or branched.

[0034] From the viewpoint of adhesion, the (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 20. Examples of the (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 20 include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0035] Among the above, from the viewpoint of imparting good adhesion, (meth)acrylic acid alkyl esters having an alkyl group with 2 to 12 carbon atoms are more preferred, and (meth)acrylic acid alkyl esters having an alkyl group with 4 to 10 carbon atoms are particularly preferred. Specifically, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These may be used alone or in combination of two or more.

[0036] From the viewpoint of imparting good adhesion, the (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or more of (meth)acrylic acid alkyl ester as a monomer unit constituting the polymer, more preferably 50% by mass or more, particularly preferably 55% by mass or more, and even more preferably 60% by mass or more. Also, from the viewpoint of ensuring the content of other monomers, it preferably contains 99.5% by mass or less of (meth)acrylic acid alkyl ester, more preferably 99% by mass or less, particularly preferably 98% by mass or less, and even more preferably 94% by mass or less.

[0037] It is also preferable that the (meth)acrylic acid ester polymer (A) contains a reactive functional group-containing monomer having a reactive functional group in the molecule as a monomer constituting the polymer. By containing the reactive functional group-containing monomer, the reactive functional group derived from the reactive functional group-containing monomer reacts with the crosslinking agent (B) described later to form a three-dimensional network structure as a crosslinked structure. As a result, the obtained pressure-sensitive adhesive has high cohesive strength, and is more likely to exhibit the mechanical properties (viscoelasticity, tensile properties) and adhesive strength described later, and has excellent blister resistance.

[0038] The reactive functional group-containing monomer is preferably a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), or a monomer having an amino group in the molecule (amino group-containing monomer). Among these, a hydroxyl group-containing monomer is preferred from the viewpoint of excellent reactivity with the crosslinking agent (B). These reactive functional group-containing monomers may be used alone or in combination of two or more.

[0039] Examples of hydroxyl group-containing monomers include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among them, from the viewpoint of reactivity with the crosslinking agent (B) and polymerizability with other monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred. These may be used alone or in combination of two or more.

[0040] Examples of the carboxy group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone or in combination of two or more.

[0041] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, and the like. These may be used alone or in combination of two or more.

[0042] The (meth)acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as a monomer constituting the polymer in an amount of 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1.0% by mass or more, based on the lower limit. Thereby, a good crosslinked structure is formed in the resulting adhesive, and mechanical properties (viscoelasticity and tensile properties) and adhesive strength described later are easily exhibited preferably, and the blister resistance is more excellent. Among them, from the viewpoint of improving the adhesive strength, it is preferable to contain a reactive functional group-containing monomer in an amount of 5% by mass or more, particularly preferably 10% by mass or more, and more preferably 15% by mass or more.

[0043] Further, the (meth)acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer in an amount of 40% by mass or less, more preferably 30% by mass or less, particularly preferably 25% by mass or less, and more preferably 20% by mass or less, based on the upper limit. When the (meth)acrylic acid ester polymer (A) contains a reactive functional group-containing monomer within the above range as a monomer unit constituting the polymer, a good crosslinked structure is formed in the resulting adhesive, and mechanical properties (viscoelasticity and tensile properties) and adhesive strength described later are easily exhibited preferably, and the blister resistance is more excellent.

[0044] The (meth)acrylic acid ester polymer (A) in this embodiment may further contain other monomers as monomers constituting the polymer. Examples of the other monomers include alicyclic structure-containing (meth)acrylic acid esters such as dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; alkoxyalkyl (meth)acrylic acid esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; non-crosslinkable acrylamides such as acrylamide and methacrylamide; non-crosslinkable (meth)acrylic acid esters having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene. These may be used alone or in combination of two or more.

[0045] The polymerization mode of the (meth)acrylic acid ester polymer (A) in this embodiment may be a random polymer or a block polymer. The (meth)acrylic acid ester polymer (A) can be obtained by polymerizing each of the above-mentioned monomers by a conventional method. For example, it can be prepared by polymerization using an emulsion polymerization method, a solution polymerization method, a suspension polymerization method, a bulk polymerization method, an aqueous solution polymerization method, or the like. Among them, from the viewpoints of stability during polymerization and ease of handling during use, it is preferable to prepare it by a solution polymerization method carried out in an organic solvent.

[0046] The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 200,000 or more, more preferably 400,000 or more, particularly preferably 500,000 or more, and even more preferably 600,000 or more. The weight average molecular weight is preferably 2,000,000 or less, more preferably 1,500,000 or less, particularly preferably 1,000,000 or less, and even more preferably 800,000 or less. When the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is within the above range, the resulting adhesive is likely to favorably exhibit mechanical properties (viscoelasticity and tensile properties) and adhesive strength described below, and the adhesive sheet 1 has better blister resistance. The weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0047] The adhesive composition P according to the present embodiment may contain one type of the (meth)acrylic acid ester polymer (A) described above, or may contain two or more types. The adhesive composition P according to the present embodiment may contain another (meth)acrylic acid ester polymer together with the (meth)acrylic acid ester polymer (A) described above.

[0048] (1-2) Crosslinking agent (B) The adhesive composition P in this embodiment preferably contains a crosslinking agent (B). When the (meth)acrylic acid ester polymer (A) contains the reactive functional group-containing monomer as a monomer constituting the polymer, the crosslinking agent (B) reacts with the reactive functional group of the reactive functional group-containing monomer to form a three-dimensional network structure. This improves the cohesive strength of the resulting adhesive, making it easier to favorably exhibit the mechanical properties (viscoelasticity and tensile properties) and adhesive strength described below, and resulting in more excellent blister resistance.

[0049] The crosslinking agent (B) may be any agent that reacts with the reactive functional group possessed by the (meth)acrylic acid ester polymer (A), and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, ammonium salt-based crosslinking agents, etc. The crosslinking agent (B) may be used alone or in combination of two or more.

[0050] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and their biuret and isocyanurate forms, as well as adducts which are reaction products with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified xylylene diisocyanate, are preferred from the viewpoint of reactivity with the reactive functional group of the (meth)acrylic acid ester polymer (A).

[0051] The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, particularly preferably 0.1 parts by mass or more, and even more preferably 0.15 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). The content of the crosslinking agent (B) is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, particularly preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). When the content of the crosslinking agent (B) is within the above range, the degree of crosslinking becomes appropriate, and the mechanical properties (viscoelasticity and tensile properties) and adhesive strength described later are easily exhibited, and the blister resistance of the adhesive sheet 1 becomes more excellent.

[0052] (1-3) Various additives If desired, various additives that are commonly used in acrylic adhesives, such as antistatic agents, silane coupling agents, rust inhibitors, UV absorbers, tackifiers, antioxidants, light stabilizers, softeners, refractive index adjusters, etc., can be added to the adhesive composition P. Note that polymerization solvents and dilution solvents described below are not included in the additives that constitute the adhesive composition P.

[0053] When the pressure-sensitive adhesive composition P contains an antistatic agent, the resulting pressure-sensitive adhesive sheet 1 can be prevented from attracting dust due to static electricity and from adverse electrical effects on the adherend.

[0054] Examples of antistatic agents include ionic compounds and nonionic compounds, among which ionic compounds are preferred. Ionic compounds may be liquid (ionic liquid) or solid (ionic solid) at room temperature. Here, the ionic compound in this specification refers to a compound in which a cation and an anion are mainly bound together by electrostatic attraction. The antistatic agent may be used alone or in combination of two or more.

[0055] As the ionic compound, nitrogen-containing onium salts, sulfur-containing onium salts, phosphorus-containing onium salts, alkali metal salts or alkaline earth metal salts are preferred, and from the viewpoint of improving adhesive strength, alkali metal salts are particularly preferred.

[0056] Specific examples of the alkali metal salt include potassium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, potassium bis(fluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, etc. Among these, lithium bis(trifluoromethanesulfonyl)imide is preferred from the viewpoint of improving adhesive strength.

[0057] When the adhesive composition P contains an antistatic agent, the content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more. The content is preferably 10% by mass or less, more preferably 5% by mass or less, particularly preferably 1% by mass or less, and even more preferably 0.6% by mass or less. By containing the antistatic agent in the above range, it becomes easier to adjust the surface resistivity described later to a desired range.

[0058] Furthermore, when the adhesive composition P contains a silane coupling agent, the adhesive obtained has improved adhesion to glass members and plastic plates, which makes the adhesive sheet 1 more excellent in blister resistance.

[0059] The silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, which has good compatibility with the (meth)acrylic acid ester polymer (A) and has optical transparency.

[0060] Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; epoxy structure-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane. , 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and other amino group-containing silicon compounds, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used alone or in combination of two or more.

[0061] When the adhesive composition P contains a silane coupling agent, the content is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic acid ester polymer (A). The content is preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less. When the content of the silane coupling agent is within the above range, the resulting adhesive exhibits good adhesion to the adherend, and the adhesive sheet 1 has better blister resistance.

[0062] (2) Preparation of adhesive composition The adhesive composition P can be prepared by preparing a (meth)acrylic acid ester polymer (A), and adding the obtained (meth)acrylic acid ester polymer (A) and, if desired, a crosslinking agent (B), a diluting solvent, additives, etc.

[0063] The (meth)acrylic acid ester polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer by a normal radical polymerization method. The polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. However, the present invention is not limited thereto, and the polymerization may be carried out without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more of them may be used in combination.

[0064] Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane 1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0065] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0066] In the above polymerization step, the weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

[0067] After the (meth)acrylic acid ester polymer (A) is obtained, the crosslinking agent (B), dilution solvent, additives, etc. are added to the solution of the (meth)acrylic acid ester polymer (A) as desired, and mixed thoroughly to obtain a solvent-diluted adhesive composition P (coating solution). When any of the above components is used in a solid state, or when precipitation occurs when mixed with other components in an undiluted state, the component may be dissolved or diluted alone in a dilution solvent before mixing with other components.

[0068] Examples of the dilution solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-based solvents such as ethyl cellosolve.

[0069] The concentration and viscosity of the coating solution thus prepared are not particularly limited as long as they are within the range that allows coating, and can be appropriately selected according to the situation. For example, the adhesive composition P is diluted so that the concentration becomes 10 to 60 mass %. In addition, when obtaining the coating solution, the addition of a dilution solvent or the like is not a necessary condition, and if the adhesive composition P has a viscosity that allows coating, it is not necessary to add a dilution solvent. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent of the (meth)acrylic acid ester polymer (A) itself serves as the dilution solvent.

[0070] (3) Formation of adhesive layer The adhesive layer 11 in this embodiment is preferably made of an adhesive obtained by crosslinking (a coating layer of) the adhesive composition P. The crosslinking of the adhesive composition P can usually be carried out by a heat treatment. This heat treatment can also serve as a drying treatment for volatilizing a diluting solvent and the like from the coating layer of the adhesive composition P applied to a desired object.

[0071] The heating temperature in the heat treatment is preferably 50 to 150° C., and more preferably 70 to 120° C. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.

[0072] After the heat treatment, a curing period of about 1 to 2 weeks may be provided at room temperature (e.g., 23°C, 50% RH) as necessary. If this curing period is required, the adhesive is formed after the curing period has elapsed, and if no curing period is required, the adhesive is formed after the heat treatment is completed.

[0073] The above heat treatment (and curing) sufficiently crosslinks the (meth)acrylic acid ester polymer (A) via the crosslinking agent (B). The pressure-sensitive adhesive thus obtained is likely to favorably exhibit mechanical properties (viscoelasticity and tensile properties) and adhesive strength described below, and has excellent blister resistance.

[0074] (4) Physical properties of adhesive (4-1) Gel fraction The gel fraction of the pressure-sensitive adhesive in this embodiment has a lower limit of preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and even more preferably 54% or more. When the gel fraction has the above lower limit, the cohesive strength of the pressure-sensitive adhesive is increased, and the mechanical properties (viscoelasticity and tensile properties) and adhesive strength described below are easily and favorably exhibited, resulting in the pressure-sensitive adhesive sheet 1 having better blister resistance.

[0075] The upper limit of the gel fraction is preferably 90% or less, more preferably 80% or less, particularly preferably 75% or less, and even more preferably 72% or less. When the upper limit of the gel fraction is as described above, the resulting pressure-sensitive adhesive has a suitable degree of crosslinking, exhibits good adhesive strength without being too hard, and has excellent adhesion to the adherend. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in the test examples described below.

[0076] (4-2) Storage modulus (G') The storage modulus (G') of the adhesive at 25°C in this embodiment is preferably 0.01 MPa or more as a lower limit, more preferably 0.02 MPa or more, particularly preferably 0.04 MPa or more, and even more preferably 0.06 MPa or more. By setting the lower limit of the storage modulus (G') as above, the adhesive sheet 1 has better blister resistance. In addition, the adhesive strength is more likely to satisfy the value described later. The method for testing the storage modulus (G') is as shown in the test example described later.

[0077] The storage modulus (G') of the pressure-sensitive adhesive in this embodiment at 25°C is preferably 2 MPa or less as an upper limit, more preferably 1 MPa or less, particularly preferably 0.5 MPa or less, and even more preferably 0.3 MPa or less. By setting the upper limit of the storage modulus (G') as above, the adhesive strength is likely to satisfy the value described below.

[0078] The storage modulus (G') of the pressure-sensitive adhesive in this embodiment at 85°C is preferably 0.001 MPa or more as a lower limit, more preferably 0.005 MPa or more, particularly preferably 0.010 MPa or more, and even more preferably 0.015 MPa or more. By setting the lower limit of the storage modulus (G') as above, the pressure-sensitive adhesive sheet 1 becomes more excellent in blister resistance.

[0079] The storage modulus (G') of the pressure-sensitive adhesive in this embodiment at 85°C is preferably 1 MPa or less as an upper limit, more preferably 0.5 MPa or less, particularly preferably 0.1 MPa or less, and even more preferably 0.05 MPa or less. By setting the upper limit of the storage modulus (G') as above, the pressure-sensitive adhesive sheet 1 becomes more excellent in blister resistance.

[0080] (4-3) Loss tangent (tanδ) The loss tangent (tan δ) of the adhesive at 25°C in this embodiment is preferably 0.3 or more as a lower limit, particularly preferably 0.34 or more, and more preferably 0.38 or more. When the lower limit of the loss tangent (tan δ) is as described above, the adhesive obtained exhibits appropriate flexibility and has good adhesion to the adherend, and the adhesive sheet 1 has better blister resistance. In addition, the adhesive strength is likely to satisfy the value described later. The test method for the loss tangent is as shown in the test example described later.

[0081] In addition, the upper limit of the loss tangent (tan δ) at 25° C. of the adhesive in this embodiment is preferably 3 or less, more preferably 2 or less, particularly preferably 1.5 or less, and even more preferably 1.2 or less. By setting the upper limit of the loss tangent (tan δ) as described above, the adhesive obtained does not become too soft and exhibits appropriate rigidity, and the adhesive sheet 1 has better blister resistance. In addition, the adhesive strength is more likely to satisfy the value described below.

[0082] The loss tangent (tan δ) of the pressure-sensitive adhesive in this embodiment at 85° C. is preferably 0.3 or more as a lower limit, more preferably 0.34 or more, particularly preferably 0.38 or more, and even more preferably 0.42 or more. When the loss tangent (tan δ) has the above lower limit, the resulting pressure-sensitive adhesive exhibits appropriate flexibility at high temperatures and has suitable adhesion to the adherend, resulting in the pressure-sensitive adhesive sheet 1 having superior blister resistance.

[0083] Furthermore, the upper limit of the loss tangent (tan δ) of the pressure-sensitive adhesive in this embodiment at 85° C. is preferably 3 or less, more preferably 2 or less, particularly preferably 1.2 or less, and even more preferably 0.8 or less. By setting the upper limit of the loss tangent (tan δ) as described above, the obtained pressure-sensitive adhesive does not become too soft at high temperatures and exhibits appropriate rigidity, and the pressure-sensitive adhesive sheet 1 has better blister resistance.

[0084] (4-4) Dielectric constant The dielectric constant ε of the adhesive in this embodiment at 40 kHz s The lower limit of the dielectric constant ε is preferably 5.8 or more, more preferably 6.0 or more, particularly preferably 6.3 or more, further preferably 6.6 or more, and most preferably 6.7 or more. s By setting the lower limit value within the above range, when the composition is applied to a member requiring a high dielectric constant, such as a component of a touch panel or the like, the sensitivity upon input can be improved.

[0085] On the other hand, the dielectric constant ε s The upper limit of the dielectric constant ε is preferably 10 or less, more preferably 9 or less, particularly preferably 8 or less, and further preferably 7 or less. s By setting the upper limit value of the dielectric constant ε , when the adhesive is applied to a component of a touch panel or the like, it is possible to suppress the generation of noise during input. s The measurement method is as shown in the test examples described later.

[0086] (5) Thickness of adhesive layer The thickness of the adhesive layer 11 in this embodiment (measured according to JIS K7130) is preferably 1 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and even more preferably 20 μm or more. This makes it easier to exert the adhesive force described below, and the blister resistance is more excellent. In addition, the thickness of the adhesive layer 11 is preferably 100 μm or less, more preferably 75 μm or less, particularly preferably 50 μm or less, and even more preferably 30 μm or less. This can suppress appearance defects such as indentations and dents on the adhesive layer 11. In addition, even with a relatively thin thickness, the desired adhesive force is easily exerted, and the blister resistance is excellent. This can contribute to making display devices such as touch panels thinner and lighter. The adhesive layer 11 may be formed as a single layer, or may be formed by laminating multiple layers.

[0087] 1-2.Release sheet Release sheets 12a and 12b protect adhesive layer 11 until adhesive sheet 1 is used, and are peeled off when adhesive sheet 1 (adhesive layer 11) is to be used. In adhesive sheet 1 according to this embodiment, one or both of release sheets 12a and 12b are not necessarily required.

[0088] Examples of the release sheets 12a and 12b include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate films, ionomer resin films, ethylene-(meth)acrylic acid polymer films, ethylene-(meth)acrylic acid ester polymer films, polystyrene films, polycarbonate films, polyimide films, and fluororesin films. Crosslinked films of these films are also used. Furthermore, laminated films of these films may be used.

[0089] The release surfaces of the release sheets 12a and 12b are preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

[0090] There is no particular limitation on the thickness of the release sheets 12a and 12b, but it is usually about 20 to 150 μm.

[0091] 2. Physical properties of adhesive sheets (1) Tensile properties (breaking elongation / coating strength / breaking energy) The lower limit of the breaking elongation in a tensile test of the pressure-sensitive adhesive layer 11 in this embodiment is preferably 200% or more, more preferably 400% or more, particularly preferably 500% or more, and even more preferably 580% or more. When the lower limit of the breaking elongation of the pressure-sensitive adhesive layer 11 is within the above range, the pressure-sensitive adhesive layer 11 has relatively high flexibility and excellent conformability (adhesion) to an adherend even if the adherend has some irregularities, resulting in good blister resistance.

[0092] On the other hand, the upper limit of the breaking elongation is preferably 3000% or less, more preferably 2000% or less, particularly preferably 1600% or less, and from the viewpoint of improving adhesion to glass and blister resistance, further preferably 1400% or less.

[0093] Specifically, the above tensile test is performed by forming only the adhesive layer into a thickness of 500 μm, a width of 10 mm, and a length in the elongation direction of 75 mm (of which the length of the measurement portion is 20 mm), and elongating it at a speed of 200 mm / min in an environment of 23°C and 50% RH.

[0094] The coating strength of the adhesive layer 11 in a tensile test was 0.45 N / mm 2 It is preferable that the resistance is 0.50N / mm or more. 2 More preferably, it is 0.60N / mm 2 More preferably, it is 0.65 N / mm 2It is preferable that the coating strength is 10 N / mm or more. This allows the resulting adhesive to exhibit suitable cohesive strength and to have better blister resistance. 2 It is preferable that the resistance is less than 8N / mm 2 More preferably, it is 6N / mm 2 It is particularly preferable that the resistance is equal to or less than 4 N / mm 2 It is preferable that the resistance is less than 2.5N / mm 2 It is most preferable that the thickness is less than 1 / 2 mm. This ensures excellent conformability (adhesion) to the adherend even if the adherend has some unevenness. The coating strength is calculated by dividing the stress at break in the tensile test by the cross-sectional area (thickness x width) of the pressure-sensitive adhesive layer.

[0095] The breaking energy of the adhesive layer 11 in the tensile test is preferably 240 J or more, more preferably 260 J or more, particularly preferably 300 J or more, and even more preferably 340 J or more. This makes the resulting adhesive less susceptible to cohesive failure, and more likely to exhibit good cohesive and adhesive strength, and particularly good blister resistance. The upper limit of the breaking energy is not particularly limited, but may be 3000 J or less, 2000 J or less, 1500 J or less, or even 1000 J or less. The breaking energy is calculated by integrating the stress-strain curve obtained by the tensile test from the initial point to the breaking point.

[0096] (2) Adhesive strength The adhesive strength of the adhesive sheet 1 according to the present embodiment to soda-lime glass is preferably more than 1 N / 25 mm as a lower limit, more preferably 6 N / 25 mm or more, particularly preferably 11 N / 25 mm or more, and even more preferably 14 N / 25 mm or more. This provides better blister resistance. On the other hand, the upper limit of the adhesive strength to soda-lime glass is not particularly limited, but taking into consideration cases where reworkability is required, it is preferably 100 N / 25 mm or less, more preferably 60 N / 25 mm or less, particularly preferably 30 N / 25 mm or less, and even more preferably 22 N / 25 mm or less.

[0097] The adhesive strength of the adhesive sheet 1 according to the present embodiment to alkali-free glass is preferably 1N / 25mm or more, more preferably 6N / 25mm or more, particularly preferably 11N / 25mm or more, and even more preferably 15N / 25mm or more, as a lower limit. This provides better blister resistance. On the other hand, the upper limit of the adhesive strength to the alkali-free glass is not particularly limited, but in consideration of cases where reworkability is required, it is preferably 100N / 25mm or less, more preferably 60N / 25mm or less, particularly preferably 30N / 25mm or less, and even more preferably 20N / 25mm or less.

[0098] In addition, the adhesive sheet 1 according to this embodiment can have an adhesive strength to glass that is about 1.2 to 2 times higher than that of an adhesive sheet using a (meth)acrylic acid ester polymer (A) having a similar monomer structure, because the (meth)acrylic acid ester polymer (A) contains the above-mentioned ethylene carbonate-containing monomer as a monomer unit constituting the polymer. Therefore, the adhesive sheet 1 according to this embodiment exhibits particularly excellent adhesive strength when the adherend is glass.

[0099] The adhesive force of the pressure-sensitive adhesive sheet 1 according to this embodiment to polycarbonate is preferably 1 N / 25 mm or more, more preferably 4 N / 25 mm or more, particularly preferably 8 N / 25 mm or more, and even more preferably 12 N / 25 mm or more as a lower limit value. Thereby, the blister resistance becomes more excellent. On the other hand, although the upper limit value of the adhesive force to the polycarbonate is not particularly limited, considering the case where reworkability is required, it is preferably 100 N / 25 mm or less, more preferably 60 N / 25 mm or less, particularly preferably 30 N / 25 mm or less, and from the viewpoint of improving the blister resistance in combination with the cohesive force of the obtained adhesive, it is preferably 22 N / 25 mm or less, and even more preferably 18 N / 25 mm or less.

[0100] Note that the above adhesive force basically refers to the adhesive force measured by the 180-degree peel method according to JIS Z0237:2009, and the specific test method is as shown in the test examples described later.

[0101] (3) Surface resistivity When the pressure-sensitive adhesive composition P contains the above-described antistatic agent, in an environment of 23°C and 50% RH, when a voltage of 100 V is applied to the pressure-sensitive adhesive sheet 1 (adhesive layer / release sheet) according to this embodiment for 10 seconds, the surface resistivity of the exposed surface of the adhesive layer is, as an upper limit value, 1.0×10 13 Ω / sq or less is preferable, 5.0×10 12 Ω / sq or less is more preferable, particularly 1.0×10 12 Ω / sq or less is preferable, and further 5.0×10 11 Ω / sq or less is preferable. When the upper limit value of the above surface resistivity is as described above, excellent antistatic properties are exhibited, and adhesion of dust due to electrostatic action and adverse electrical effects on the adherend can be suppressed. Although the lower limit value of the above surface resistivity is not particularly limited, 1.0×10 10The surface resistivity of the pressure-sensitive adhesive layer is preferably about Ω / sq or more. Measurement of the surface resistivity of the pressure-sensitive adhesive layer is carried out in accordance with JIS K6911:2006, specifically as shown in the test examples described later.

[0102] 3. Manufacturing of adhesive sheets In one example of manufacturing the adhesive sheet 1, a coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), a heat treatment is performed to thermally crosslink the adhesive composition P, and a coating layer is formed, and then the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. If a curing period is required, a curing period is left, and if no curing period is required, the coating layer becomes the adhesive layer 11 as is. In this way, the adhesive sheet 1 is obtained. The conditions for the heat treatment and curing are as described above.

[0103] In another manufacturing example of the adhesive sheet 1, the coating solution of the adhesive composition P is applied to the release surface of one release sheet 12a, and the adhesive composition P is thermally crosslinked by heat treatment to form a coating layer, thereby obtaining the release sheet 12a with the coating layer. Also, the coating solution of the adhesive composition P is applied to the release surface of the other release sheet 12b, and the adhesive composition P is thermally crosslinked by heat treatment to form a coating layer, thereby obtaining the release sheet 12b with the coating layer. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded together so that both coating layers are in contact with each other. If a curing period is required, a curing period is provided, and if no curing period is required, the laminated coating layer becomes the adhesive layer 11 as it is. This results in the adhesive sheet 1. According to this manufacturing example, even if the adhesive layer 11 is thick, it is possible to stably manufacture it.

[0104] The coating solution of the pressure-sensitive adhesive composition P can be applied by, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, or the like.

[0105] [Laminate] A laminate according to one embodiment of the present invention includes two display component members and an adhesive layer sandwiched between the two display component members, the adhesive layer being formed from the adhesive layer of the adhesive sheet described above. This laminate is a display (display panel) or a component thereof.

[0106] At least one of the display member components preferably includes a plastic plate. Unlike a glass plate, a plastic plate generates outgassing and transmits water vapor under high temperature and humidity conditions. This generally makes it easy for blisters such as air bubbles, floating, and peeling to occur between the plastic plate and the adhesive layer. However, in the laminate according to the present embodiment, by using the adhesive layer of the adhesive sheet described above, the occurrence of blisters such as air bubbles, floating, and peeling is suppressed even when the laminate is placed under high temperature and humidity conditions (e.g., 85°C, 85% RH, 96 hours).

[0107] FIG. 2 shows a specific configuration as an example of the laminate according to this embodiment. 2, the laminate 2 according to this embodiment is composed of a first display body component 21, a second display body component 22, and an adhesive layer 11 located therebetween and sandwiched between the first display body component 21 and the second display body component 22. Moreover, in the laminate 2 according to this embodiment, the first display body component 21 has a step on the surface on the adhesive layer 11 side, and specifically, has a step due to the presence or absence of a printed layer 3.

[0108] The laminate 2 may be a member constituting a part of a display such as a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, or electronic paper, or may be the display itself. The display may be a touch panel.

[0109] The pressure-sensitive adhesive layer 11 in the laminate 2 is formed from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above, and is preferably the pressure-sensitive adhesive layer 11 itself.

[0110] There are no particular limitations on the first display body component 21 and the second display body component 22 as long as they can be adhered to the adhesive layer 11. Furthermore, the first display body component 21 and the second display body component 22 may be made of the same material or different materials.

[0111] Specifically, the first display member 21 is preferably a protective panel made of a plastic plate or a laminate including a plastic plate.

[0112] The plastic plate is not particularly limited, and examples thereof include polycarbonate resin (PC) plate, acrylic resin plate such as polymethyl methacrylate resin (PMMA) plate, plastic plate in which an acrylic resin layer such as a polymethyl methacrylate resin layer is laminated on a polycarbonate resin plate, etc. The polycarbonate resin plate may contain a resin other than polycarbonate resin as a constituent material, and the acrylic resin plate may contain a resin other than acrylic resin as a constituent material.

[0113] The thickness of the plastic plate is not particularly limited, but is usually 0.2 to 5 mm, preferably 0.4 to 3 mm, particularly preferably 0.6 to 2.5 mm, and further preferably 0.8 to 2.1 mm.

[0114] In addition, various functional layers (transparent conductive film, metal layer, silica layer, hard coat layer, anti-glare layer, ultraviolet absorbing layer, etc.) may be provided on one or both sides of the plastic plate, or metal wiring may be formed. In addition, the transparent conductive film and the metal layer may be patterned.

[0115] The second display member 22 is not particularly limited, but may be a desired optical member, a display module, a part of a display module, or the like.

[0116] Examples of the optical member include a shatterproof film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retardation film), a viewing angle compensation film, a brightness improvement film, a contrast improvement film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflective film, a transparent conductive film, etc. Examples of the shatterproof film include a hard coat film having a hard coat layer formed on one side of a base film.

[0117] The optical member may be a glass plate or a laminated member including a glass plate. Examples of the glass plate include, but are not limited to, chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, and barium borosilicate glass.

[0118] The thickness of the glass plate is not particularly limited, but is usually 0.1 to 10 mm, preferably 0.2 to 8 mm, more preferably 0.8 to 4 mm, and particularly preferably 1 to 2 mm.

[0119] Examples of the display module include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (OLED) module, and electronic paper. These display modules usually have the above-mentioned glass plates, plastic plates, optical members, and the like laminated therein. For example, a polarizing plate is laminated in the LCD module, and the polarizing plate forms one surface of the LCD module.

[0120] The material constituting the printing layer 3 is not particularly limited, and known materials for printing are used. The lower limit of the thickness of the printing layer 3, i.e., the height of the step, is preferably 3 μm or more, more preferably 7.5 μm or more, and particularly preferably 10 μm or more. By setting the lower limit to the above or more, it is possible to sufficiently ensure concealment such as making the electrical wiring invisible from the viewer side. In addition, the upper limit is preferably thinner than the thickness of the adhesive layer, more preferably 80 μm or less, particularly preferably 50 μm or less, and even more preferably 25 μm or less. By setting the upper limit to the above or less, it is possible to prevent deterioration of the step-following ability of the adhesive layer 11 with respect to the printing layer 3. In addition, the printing layer 3 is generally formed in a frame shape on the adhesive layer 11 side of the display body constituent member.

[0121] To manufacture the above laminate 2, as an example, one of the release sheets 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is attached to the surface of the first display body component 21 on which the printing layer 3 is present.

[0122] Next, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display body component 22 to obtain a laminate. As another example, the bonding order of the first display body component 21 and the second display body component 22 may be reversed.

[0123] The adhesive layer 11 in the above-described laminate 2 has excellent blister resistance, so that even when the laminate 2 is placed under conditions of, for example, 85°C and 85% RH for 96 hours, the occurrence of air bubbles, floating, peeling, etc. at the interface between the adhesive layer 11 and each display component 21, 22 is suppressed.

[0124] [Adhesive sheet according to the second embodiment] The pressure-sensitive adhesive sheet according to the second embodiment includes at least a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A).

[0125] The (meth)acrylic acid ester polymer (A) in the pressure-sensitive adhesive sheet according to this embodiment contains, as a monomer unit constituting the polymer, a carbon dioxide-derived monomer obtained from carbon dioxide as a raw material. This makes it possible for the pressure-sensitive adhesive sheet according to the second embodiment to consume carbon dioxide as a raw material, thereby contributing to the reduction of carbon dioxide, which is an internationally important issue, and ultimately to the Sustainable Development Goals (SDGs) set forth by the United Nations.

[0126] When producing the carbon dioxide-derived monomer, it is preferable that 0.1 moles or more of carbon dioxide is consumed per mole of the carbon dioxide-derived monomer, more preferably 0.4 moles or more, particularly preferably 0.8 moles or more, even more preferably 0.9 moles or more, and most preferably 1 mole or more. This can effectively contribute to reducing carbon dioxide. The upper limit is not particularly limited, but it is preferable that 2 moles or less is consumed, particularly preferably 1.5 moles or less, and even more preferably 1.2 moles or less is consumed.

[0127] The carbon dioxide-derived monomer is preferably one obtained by reacting an epoxy group-containing compound with carbon dioxide. Examples of such carbon dioxide-derived monomers include ethylene carbonate-containing monomers. Among these, the ethylene carbonate-containing monomers described above are preferred from the viewpoint of excellent blister resistance, and (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate is particularly preferred.

[0128] Other than the above, the pressure-sensitive adhesive sheet according to the second embodiment is the same as the pressure-sensitive adhesive sheet according to the first embodiment. In addition, the laminate obtained by using the pressure-sensitive adhesive sheet according to the second embodiment is also the same as the laminate according to the above embodiment.

[0129] The above-described embodiments are described for the purpose of facilitating understanding of the present invention, and are not described for the purpose of limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0130] For example, either one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired display body component may be laminated in place of the release sheets 12a and / or 12b. The first display body component 21 may not have the printed layer 3 (step), or may have a step other than the printed layer 3. Furthermore, not only the first display body component 21 but also the second display body component 22 may have a step on the adhesive layer 11 side. EXAMPLES

[0131] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0132] Example 1 1. Preparation of (meth)acrylic acid ester polymer (A) 98 parts by mass of n-butyl acrylate, 1 part by mass of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate as an ethylene carbonate-containing monomer, and 1 part by mass of 4-hydroxybutyl acrylate were copolymerized by a solution polymerization method to prepare a (meth)acrylic acid ester polymer (A). The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described below, and the weight average molecular weight (Mw) was 750,000.

[0133] 2. Preparation of adhesive composition 100 parts by mass (solid content equivalent; same below) of the (meth)acrylic acid ester polymer (A) obtained in step 1 above was mixed with 0.26 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Industries, Ltd., product name "TD-75") as a crosslinking agent (B), thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition.

[0134] 3. Manufacturing of adhesive sheets The obtained adhesive composition coating solution was applied by a knife coater to the release-treated surface of a heavy-release type release sheet (manufactured by Lintec Corporation, product name "SP-PET382150"), one side of which was a polyethylene terephthalate film treated with a silicone-based release agent. The coating layer was then heat-treated at 90°C for 1 minute to form a coating layer.

[0135] Next, the coating layer on the heavy release type release sheet obtained above and a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET381130"), one side of a polyethylene terephthalate film released and treated with a silicone-based release agent, were attached so that the release-treated surface of the light release type release sheet was in contact with the coating layer, and cured for 7 days under conditions of 23°C and 50% RH to produce an adhesive sheet having an adhesive layer with a thickness of 25 μm, i.e., an adhesive sheet having a configuration of heavy release type release sheet / adhesive layer (thickness: 25 μm) / light release type release sheet.

[0136] The thickness of the adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring device (manufactured by Techclock Corporation, product name "PG-02").

[0137] Here, the formulations (solid content equivalent) of the pressure-sensitive adhesive composition when the (meth)acrylic acid ester polymer (A) is taken as 100 parts by mass (solid content equivalent) are shown in Table 1. The details of the abbreviations and the like shown in Table 1 are as follows. [(Meth)acrylic acid ester polymer (A)] BA: n-butyl acrylate CARBOM: (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate 4HBA: 4-hydroxybutyl acrylate 2EHA: 2-ethylhexyl acrylate HEA: 2-hydroxyethyl acrylate MMA: Methyl methacrylate [Crosslinking agent (B)] Trimethylolpropane modified xylylene diisocyanate (manufactured by Soken Chemical Industries, product name "TD-75") [Antistatic agent] Lithium bis(trifluoromethanesulfonyl)imide

[0138] [Examples 2 to 5, Comparative Examples 1 to 2] An adhesive sheet was produced in the same manner as in Example 1, except that the types and ratios of the monomers constituting the (meth)acrylic acid ester polymer (A), the weight average molecular weight (Mw) of the (meth)acrylic acid ester polymer (A), the amount of the crosslinking agent (B), and the amount of the antistatic agent were changed as shown in Table 1.

[0139] The weight average molecular weight (Mw) mentioned above is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> GPC measuring device: Tosoh HLC-8020 GPC columns (passed in the following order): Tosoh Corporation TSK guard column HXL-H TSK gel GMHXL (×2) TSK gel G2000HXL Measurement solvent: Tetrahydrofuran ·Measurement temperature: 40℃

[0140] [Test Example 1] (Measurement of gel fraction) The adhesive sheets prepared in the examples and comparative examples were cut to a size of 80 mm x 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was measured using a precision balance. The mass of the mesh alone was subtracted to calculate the mass of the adhesive alone. This mass was designated M1.

[0141] Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The adhesive was then removed and air-dried for 24 hours in an environment with a temperature of 23°C and a relative humidity of 50%, and then dried in an oven at 80°C for 12 hours. After drying, the mass was weighed using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. This mass was designated M2. The gel fraction (%) was expressed as (M2 / M1) x 100. The gel fraction of the adhesive was calculated from this. The results are shown in Table 2.

[0142] [Test Example 2] (Measurement of dynamic viscoelasticity) The release sheets were peeled off from the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples, and multiple pressure-sensitive adhesive layers were laminated to a thickness of 0.8 mm. A cylindrical body with a diameter of 8 mm (height of 0.8 mm) was punched out from the resulting laminate of pressure-sensitive adhesive layers, and this was used as a sample.

[0143] The dynamic viscoelasticity of the above samples was measured under the following conditions using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302") by the torsional shear method in accordance with JIS K7244-1, and the storage modulus (G') (MPa) at 25°C and 85°C, and the loss tangent (tan δ) at 25°C and 85°C were measured. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature range: 0℃~100℃ Heating rate: 3℃ / min

[0144] [Test Example 3] (Calculation of dielectric constant) The adhesive layer of the adhesive sheet produced in the Examples and Comparative Examples was laminated on one side of a 50 μm thick polyethylene terephthalate film to form an adhesive layer of 0.8 mm thickness, and a 50 μm thick polyethylene terephthalate film was attached to the adhesive layer, and then cut into a size of 50 mm×50 mm. The capacitance (C1) of the obtained laminate was measured using an impedance analyzer (manufactured by Keycom, product name "HP4194A"). In addition, two sheets of the above 50 μm thick polyethylene terephthalate film were stacked and cut into a size of 50 mm×50 mm, and the capacitance (C2) was measured in the same manner. Then, C2 was subtracted from C1 to calculate the capacitance (C3) of the adhesive. Based on this capacitance C3, the dielectric constant ε of the adhesive was calculated from the following formula: s The results are shown in Table 2.

[0145] ε s =(C3×d) / (ε 0 ×S) ε s : Dielectric constant of adhesive ε 0 : Dielectric constant of vacuum (8.854×10 -12 ) C3: Capacitance of adhesive S: Area of ​​adhesive layer d: thickness of adhesive layer

[0146] [Test Example 4] (Measurement of surface resistivity) The light release type release sheet was peeled off from the adhesive sheet produced in the examples and comparative examples, and the surface resistivity of the exposed adhesive surface of the adhesive layer was measured in accordance with JIS K6911:2006. Specifically, in an environment of 23°C and 50% RH, a resistivity meter (manufactured by Mitsubishi Analytech, product name "Hiresta UP MCP-HT450 type") was used to apply a voltage of 100V to the adhesive sheet (100mm x 100mm) from which the light release type release sheet had been peeled off for 10 seconds, and then the surface resistivity (Ω / sq) of the adhesive surface of the adhesive layer was measured. The results are shown in Table 2.

[0147] [Test Example 5] (Tensile test) The adhesive layers were laminated in multiple layers so that the total thickness of the adhesive layers in the adhesive sheets produced in the Examples and Comparative Examples was 500 μm and only the release sheet of the outermost layer remained, and the adhesive sheets were left in an atmosphere of 23° C. and 50% RH for 24 hours. Thereafter, a sample of 10 mm width×75 mm length was cut out from the adhesive sheet having multiple laminated adhesive layers, the release sheet laminated on the outermost layer was peeled off, and the sample was set so that the sample measurement site was 10 mm width×20 mm length (in the elongation direction), and the sample was elongated at a tensile speed of 200 mm / min until it broke using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon") in an environment of 23° C. and 50% RH, and the breaking elongation (%) was obtained from the obtained stress-strain curve. In addition, the stress at break (breaking stress; N) was calculated based on the cross-sectional area (5 mm 2 ) is the coating strength (N / mm 2 The breaking energy (J) was calculated by integrating the stress-strain curve from the initial point to the breaking point. The results are shown in Table 2.

[0148] [Test Example 6] (Measurement of adhesive strength) The light release type release sheet was peeled off from the adhesive sheet produced in the Examples and Comparative Examples, and the exposed adhesive layer was attached to an easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "PET TA063", thickness: 100 μm) having an easy-adhesion layer, to obtain a laminate of heavy release type release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 100 mm.

[0149] The heavy release type release sheet was peeled off from the laminate under an environment of 23°C and 50% RH, and the exposed adhesive layer was attached to the following three types of adherends, and pressurized for 20 minutes at 0.5 MPa and 50°C in an autoclave manufactured by Kurihara Seisakusho Co., Ltd. After leaving it under conditions of 23°C and 50% RH for 24 hours, the adhesive strength (N / 25mm) was measured when the laminate of the PET film and the adhesive layer was peeled off from the adherend using a tensile tester (Tensilon manufactured by Orientec Co., Ltd.) under conditions of a peel speed of 300 mm / min and a peel angle of 180 degrees. The measurement was performed under conditions other than those described here in accordance with JIS Z0237:2009. The results are shown in Table 2. <Adherend> Soda lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., product name "Soda lime glass", thickness: 1.1 mm) -Non-alkali glass plate (manufactured by Nippon Sheet Glass Co., Ltd., product name "Eagle-X", thickness: 1.1 mm) Polycarbonate sheet (manufactured by Mitsubishi Gas Chemical Company, product name "Iupilon Sheet MR58U", thickness: 0.8 mm)

[0150] [Test Example 7] (Evaluation of blister resistance) The light-release type release sheet was peeled off from the adhesive sheets prepared in the Examples and Comparative Examples, and the exposed adhesive layer was attached to the ITO side of a tin-doped indium oxide (ITO) vapor-deposited polyethylene terephthalate (PET) film (manufactured by Oike Kogyo Co., Ltd., product name "Tetlite TCF", thickness: 188 μm) to obtain an ITO-vapor-deposited PET film with an adhesive layer.

[0151] The heavy-duty release sheet was peeled off from the ITO-deposited PET film with adhesive layer obtained above, and the exposed adhesive layer was attached to the PC plate side of a plastic plate (manufactured by Mitsubishi Gas Chemical Company, product name "Iupilon Sheet MR58U", thickness: 0.8 mm) consisting of a polycarbonate (PC) plate and a polymethyl methacrylate (PMMA) layer laminated thereon. The plate was then autoclaved for 20 minutes under conditions of 50°C and 0.5 MPa, and left for 24 hours at normal pressure, 23°C, and 50% RH.

[0152] The adhesive layer was then stored for 12 and 96 hours under high temperature and humidity conditions of 85°C and 85% RH (durability test). The interface between the adhesive layer and the adherend (ITO-deposited PET film, plastic plate) was visually inspected, and the blister resistance was evaluated according to the following criteria. The results are shown in Table 2. 〇…No bubbles, lifting or peeling. △: Bubbles, lifting, or peeling occurred in some areas. ×: Lifting and peeling occurred over a wide area.

[0153] In Comparative Examples 1 and 2, since the evaluation in the 12-hour durability test was poor, the evaluation in the 96-hour durability test was not performed.

[0154] [Table 1]

[0155] [Table 2]

[0156] As can be seen from Table 2, the pressure-sensitive adhesive sheets produced in the examples had excellent blister resistance. The pressure-sensitive adhesive sheets produced in the examples also had high adhesive strength, especially adhesive strength to glass. Furthermore, the pressure-sensitive adhesive in the pressure-sensitive adhesive sheets produced in the examples had a high dielectric constant. [Industrial Applicability]

[0157] The pressure-sensitive adhesive sheet according to the present invention can be suitably used, for example, for bonding a protective panel made of a plastic plate to a desired display component. [Explanation of symbols]

[0158] 1...Adhesive sheet 11...Adhesive layer 12a, 12b...Release sheet 2...Laminate 21...First display member 22...Second display body component 3...Printing layer

Claims

1. A pressure-sensitive adhesive sheet having at least a pressure-sensitive adhesive layer, The adhesive strength to soda lime glass is more than 1 N / 25 mm and 100 N / 25 mm or less; the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B); The (meth)acrylic acid ester polymer (A) contains, as a monomer unit constituting the polymer, a monomer represented by the following formula (1): 【Chemistry 1】 The ethylene carbonate-containing monomer has an ethylene carbonate structure represented by the formula: The (meth)acrylic acid ester polymer (A) contains the ethylene carbonate-containing monomer in an amount of 0.5% by mass or more and 40% by mass or less as a monomer unit constituting the polymer. A pressure-sensitive adhesive sheet characterized by:

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer has a storage modulus (G') at 25° C. of 0.01 MPa or more and 2 MPa or less.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, characterized in that the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer has a loss tangent (tan δ) at 25°C obtained by dynamic viscoelasticity measurement in accordance with JIS K7244-1 of 0.3 or more and 3 or less.

4. The dielectric constant ε at 40 kHz of the adhesive constituting the adhesive layer ｓ The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, characterized in that:

5. The pressure-sensitive adhesive sheet has two release sheets, The pressure-sensitive adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the release sheets. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4.

6. Two display body components; An adhesive layer sandwiched between the two display body constituent members; A laminate comprising: The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 5. A laminate comprising:

7. 7. The laminate according to claim 6, wherein at least one of the display component members includes a plastic plate.

8. The adhesive strength to soda lime glass is more than 1 N / 25 mm and less than 100 N / 25 mm; The adhesive is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B), The (meth)acrylic acid ester polymer (A) contains, as a monomer unit constituting the polymer, a monomer represented by the following formula (1): 【Chemistry 2】 The ethylene carbonate-containing monomer has an ethylene carbonate structure represented by the formula: The (meth)acrylic acid ester polymer (A) contains the ethylene carbonate-containing monomer in an amount of 0.5% by mass or more and 40% by mass or less as a monomer unit constituting the polymer. A method for producing a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, comprising: The method includes a step of producing the ethylene carbonate-containing monomer using carbon dioxide as a raw material. A method for producing a pressure-sensitive adhesive sheet comprising the steps of:

9. The method for producing a pressure-sensitive adhesive sheet according to claim 8, wherein, when the ethylene carbonate-containing monomer is produced, 0.1 mole or more of carbon dioxide is consumed per mole of the ethylene carbonate-containing monomer.

10. The method for producing a pressure-sensitive adhesive sheet according to claim 8 or 9, wherein the ethylene carbonate-containing monomer is obtained by reacting an epoxy group-containing compound with carbon dioxide.

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