Adhesive sheet

Abstract

To provide an adhesive and an adhesive sheet having excellent durability when applied to an optical member such as a polarizing plate.SOLUTION: An adhesive is obtained from an adhesive composition that contains a (meth)acrylate polymer (A) containing an ethylene carbonate-containing monomer, the adhesive having a storage elastic modulus G'(80) of 0.04 MPa or more at 80°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet suitable for use in optical members such as polarizing plates. [Background technology]

[0002] In general, in liquid crystal panels, a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is often used to bond a polarizing plate or a retardation plate to a glass substrate, etc. However, optical members such as polarizing plates and retardation plates are prone to shrink due to heat, etc., and shrinkage occurs due to thermal history, and as a result, the pressure-sensitive adhesive layer laminated on the optical member cannot follow the shrinkage, causing peeling (so-called lifting or peeling) at the interface.

[0003] As a method for preventing the above-mentioned lifting and peeling and improving durability, in addition to a method using a pressure-sensitive adhesive layer that exerts a small stress when the optical component shrinks, there is a method of suppressing the shrinkage of the optical component itself by attaching a pressure-sensitive adhesive layer with high adhesive strength and excellent dimensional stability to an optical component such as a polarizing plate. As the latter method, as shown in Patent Document 1, the use of a pressure-sensitive adhesive with a high storage modulus has been proposed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-235568 A Summary of the Invention [Problem to be solved by the invention]

[0005] The adhesive disclosed in Patent Document 1 requires irradiation with active energy rays in the manufacturing process of the adhesive sheet, and therefore the productivity is not necessarily high.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that have excellent durability when applied to optical members such as polarizing plates. [Means for solving the problem]

[0007] In order to achieve the above object, first, the present invention provides a polymer comprising a monomer unit represented by the following formula (1): [ka] The present invention provides an adhesive obtained from an adhesive composition containing a (meth)acrylic acid ester polymer (A) which contains an ethylene carbonate-containing monomer having an ethylene carbonate structure represented by the following formula (1):

[0008] In the above invention (Invention 1), the (meth)acrylic acid ester polymer (A) contains an ethylene carbonate structure in the side chain. This makes the glass transition temperature (Tg) of the (meth)acrylic acid ester polymer (A) relatively high, and the cohesive strength of the adhesive is strong. By having such a strong cohesive strength and a large storage modulus G'(80) as described above, when the adhesive is applied to an optical member such as a polarizing plate or a retardation plate, the adhesive layer can suppress the shrinkage of the optical member due to heating or the like. As a result, the occurrence of lifting or peeling at the interface between the optical member and the adhesive layer is suppressed, and excellent durability is exhibited. In addition, from the viewpoint of polarity due to the ethylene carbonate structure, the adhesive has high adhesive strength, particularly adhesive strength to glass. Therefore, when an optical member such as a polarizing plate or a retardation plate is bonded to glass via the adhesive, particularly high durability is exhibited.

[0009] In the above invention (Invention 1), the storage modulus G'(23) at 23° C. is preferably 0.04 MPa or more and 50 MPa or less (Invention 2).

[0010] In the above inventions (Inventions 1 and 2), the (meth)acrylic acid ester polymer (A) preferably contains, as a monomer unit constituting the polymer, 0.1 mass % or more and 30 mass % or less of the ethylene carbonate-containing monomer (Invention 3).

[0011] In the above inventions (Inventions 1 to 3), the gel fraction is preferably 40% or more and 90% or less (Invention 4).

[0012] Secondly, the present invention provides an adhesive sheet including at least an adhesive layer, the adhesive layer comprising any one of the adhesives (Inventions 1 to 4) (Invention 5).

[0013] In the above invention (Invention 5), the pressure-sensitive adhesive sheet has a substrate, and the substrate is preferably an optical member (Invention 6).

[0014] In the above invention (Invention 6), it is preferable that the optical member is a polarizing plate (Invention 7).

[0015] In the above invention (Invention 5), it is also 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 8). Effect of the Invention

[0016] The pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention are excellent in durability when applied to optical members such as polarizing plates. [Brief description of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a cross-sectional view of a pressure-sensitive adhesive sheet according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described. [Adhesive] The pressure-sensitive adhesive according to the present embodiment has a monomer unit constituting a polymer represented by the following formula (1): [ka] It is preferable that the adhesive composition contains a (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having an ethylene carbonate structure shown in the following formula (1), and the storage modulus G'(80) at 80°C is preferably 0.04 MPa or more. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. In addition, the term "polymer" includes the concept of "copolymer". The test method for the storage modulus G' in this specification is as shown in the test example described later.

[0019] Since the (meth)acrylic acid ester polymer (A) is composed of the ethylene carbonate-containing monomer, the pressure-sensitive adhesive 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 in the 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 pressure-sensitive adhesive. Since the cohesive force is strong and the storage modulus G'(80) at 80°C is large as described above, when the pressure-sensitive adhesive is applied to an optical member such as a polarizing plate or a retardation plate, even if the optical member shrinks due to heating or the like, the shrinkage of the optical member itself can be suppressed by the pressure-sensitive adhesive layer. As a result, the occurrence of lifting or peeling at the interface between the optical member and the pressure-sensitive adhesive layer is suppressed. Thus, the pressure-sensitive adhesive according to this embodiment has excellent durability when applied to an optical member such as a polarizing plate or a retardation plate. In addition, the pressure-sensitive adhesive according to the present embodiment has high adhesive strength, particularly to glass, due to the polarity resulting from the ethylene carbonate structure, and therefore exhibits particularly high durability when an optical member such as a polarizing plate or a retardation plate is bonded to glass via the pressure-sensitive adhesive according to the present embodiment.

[0020] From the viewpoint of durability, the storage modulus G'(80) at 80°C of the pressure-sensitive adhesive according to this embodiment is preferably 0.04 MPa or more, more preferably 0.05 MPa or more, particularly preferably 0.06 MPa or more, and even more preferably 0.07 MPa or more. From the viewpoint of obtaining an appropriate adhesive strength, the storage modulus G'(80) is preferably 10 MPa or less, more preferably 5 MPa or less, particularly preferably 1 MPa or less, and even more preferably 0.10 MPa or less.

[0021] From the viewpoint of durability, the storage modulus G'(23) at 23°C of the pressure-sensitive adhesive according to this embodiment is preferably 0.04 MPa or more, more preferably 0.09 MPa or more, particularly preferably 0.11 MPa or more, and even more preferably 0.14 MPa or more. From the viewpoint of obtaining an appropriate adhesive strength, the storage modulus G'(23) is preferably 50 MPa or less, more preferably 10 MPa or less, particularly preferably 5 MPa or less, and even more preferably 1 MPa or less.

[0022] The loss tangent tan δ(80) at 80° C. of the pressure-sensitive adhesive according to this embodiment is preferably 0.15 or more, more preferably 0.18 or more, particularly preferably 0.20 or more, and even more preferably 0.22 or more, from the viewpoint of imparting fluidity at high temperatures. Moreover, the loss tangent tan δ(80) is preferably 1.00 or less, more preferably 0.80 or less, particularly preferably 0.60 or less, and even more preferably 0.40 or less, from the viewpoint of imparting rigidity at high temperatures. The test method for the loss tangent tan δ in this specification is as shown in the test examples described later.

[0023] From the viewpoint of imparting fluidity, the loss tangent tan δ(23) at 23° C. of the pressure-sensitive adhesive according to this embodiment is preferably 0.15 or more, more preferably 0.22 or more, particularly preferably 0.25 or more, and even more preferably 0.28 or more. From the viewpoint of imparting rigidity, the loss tangent tan δ(23) is preferably 1.50 or less, more preferably 1.00 or less, particularly preferably 0.80 or less, and even more preferably 0.70 or less.

[0024] The adhesive of this embodiment is preferably obtained from an adhesive composition (hereinafter sometimes referred to as "adhesive composition P") containing a (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having an ethylene carbonate structure represented by the above-mentioned formula (1) as a monomer unit constituting the polymer, and a crosslinking agent (B).

[0025] (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).

[0026] 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 the above formulas (2) and (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 resulting adhesive will overlap with each other increases. This allows stacking interaction between the ethylene carbonate structures to work, making it easier to favorably express the above-mentioned physical properties (storage modulus G', loss tangent tanδ), and making the adhesive more excellent in durability. 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. The ethylene carbonate-containing monomer may be used alone or in combination of two or more kinds.

[0027] The (meth)acrylic acid ester polymer (A) preferably contains 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and even more preferably 3% by mass or more of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer. This enhances the stacking interaction effect of the ethylene carbonate groups in the adhesive, improves the cohesive strength of the adhesive obtained, and makes it easier to favorably exhibit the above-mentioned physical properties (storage modulus G', loss tangent tanδ) and adhesive strength, resulting in an adhesive sheet 1 with superior durability.

[0028] The (meth)acrylic acid ester polymer (A) preferably contains 30% by mass or less, more preferably 25% by mass or less, particularly preferably 20% by mass or less, and even more preferably 18% by mass or less of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer, which makes it easier for the above-mentioned physical properties (storage modulus G', loss tangent tanδ) to be satisfied.

[0029] 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.

[0030] 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.

[0031] Among the above, from the viewpoint of imparting good adhesion, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 20 carbon atoms are more preferred, (meth)acrylic acid alkyl esters having an alkyl group with 1 to 14 carbon atoms are particularly preferred, and (meth)acrylic acid alkyl esters having an alkyl group with 1 to 10 carbon atoms are even more preferred. Specifically, preferred examples include methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. These may be used alone or in combination of two or more.

[0032] 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 60% by mass or more, particularly preferably 75% by mass or more, and even more preferably 80% by mass or more. Also, from the viewpoint of ensuring the content of other monomers, it preferably contains 99% by mass or less of (meth)acrylic acid alkyl ester, more preferably 98% by mass or less, particularly preferably 95% by mass or less, and even more preferably 94% by mass or less.

[0033] 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 the above-mentioned physical properties (storage modulus G', loss tangent tanδ) and adhesive strength are easily expressed, resulting in excellent durability.

[0034] 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.

[0035] 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 these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of reactivity with the crosslinking agent (B) and polymerizability with other monomers. These may be used alone or in combination of two or more.

[0036] Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, etc. These may be used alone or in combination of two or more kinds.

[0037] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, n-butylaminoethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0038] The (meth)acrylic acid ester polymer (A) preferably contains reactive functional group-containing monomer as a monomer constituting the polymer in a lower limit of 0.1% by mass or more, more preferably 0.4% by mass or more, particularly preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more. The upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and even more preferably 3% by mass or less. By the content of the reactive functional group-containing monomer being within the above range, a good crosslinked structure is formed in the obtained adhesive, and the above-mentioned physical properties (storage modulus G', loss tangent tanδ) and adhesive strength are easily exhibited, and the durability is more excellent.

[0039] It is also preferred that the (meth)acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer. Since a carboxyl group is an acid component, by not containing a carboxyl group-containing monomer, even if the target to which the pressure-sensitive adhesive is applied includes a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, a metal mesh, etc., which may be affected by acid, the absence of a carboxyl group-containing monomer can suppress such defects (corrosion, change in resistance, etc.) caused by acid.

[0040] Here, "free of carboxyl group-containing monomer" means that the carboxyl group-containing monomer is not substantially contained, and in addition to not containing any carboxyl group-containing monomer at all, the carboxyl group-containing monomer may be contained to an extent that the carboxyl group does not cause corrosion of the transparent conductive film, metal wiring, etc. Specifically, the (meth)acrylic acid ester polymer (A) may contain the carboxyl group-containing monomer as a monomer unit in an amount of 0.1% by mass or less, preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

[0041] 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.

[0042] 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.

[0043] The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 800,000 or more, more preferably 1,000,000 or more, particularly preferably 1,200,000 or more, and even more preferably 1,400,000 or more. Since the weight average molecular weight is relatively large in this way, the above-mentioned physical properties (storage modulus G', loss tangent tan δ) are easily satisfied. In addition, the weight average molecular weight is preferably 3,000,000 or less, more preferably 2,500,000 or less, particularly preferably 2,000,000 or less, and even more preferably 1,800,000 or less. This makes it easier to develop a preferable adhesive force. In this specification, the weight average molecular weight is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0044] 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.

[0045] (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, and makes it easier to favorably exhibit the above-mentioned physical properties (storage modulus G', loss tangent tanδ) and adhesive strength, resulting in more excellent durability.

[0046] 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.

[0047] 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).

[0048] 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 0.10 parts by mass or more, and even more preferably 0.12 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 above-mentioned physical properties (storage modulus G', loss tangent tanδ) and adhesive force are easily expressed, resulting in more excellent durability.

[0049] (1-3) Various additives If desired, various additives that are commonly used in acrylic adhesives, such as a silane coupling agent, an antistatic agent, an antirust agent, an ultraviolet absorber, a tackifier, an antioxidant, a light stabilizer, a softener, a refractive index adjuster, 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.

[0050] When the adhesive composition P contains a silane coupling agent, the resulting adhesive has improved adhesion to glass members or plastic plates and is more durable.

[0051] 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.

[0052] 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; 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.

[0053] 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 has excellent durability.

[0054] Furthermore, when the pressure-sensitive adhesive composition P contains an antistatic agent, the adhesion of dust due to static electricity and adverse electrical effects on the adherend can be suppressed in the resulting pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] When the adhesive composition P contains an antistatic agent, the content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 1.0% by mass or more, and even more preferably 2.0% by mass or more. The content is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 7% by mass or less, and even more preferably 4% 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.

[0059] (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.

[0060] 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.

[0061] 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].

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] (3) Formation of adhesive The adhesive of this embodiment is preferably formed from the adhesive composition described above, and specifically, is preferably formed by crosslinking the adhesive composition P described above.

[0068] The crosslinking of the pressure-sensitive 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 a coating film of the pressure-sensitive adhesive composition P applied to a desired object.

[0069] 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 5 minutes.

[0070] 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.

[0071] The above heat treatment (and curing) sufficiently crosslinks the (meth)acrylic acid ester polymer (A) via the crosslinking agent (B), and the pressure-sensitive adhesive thus obtained is likely to favorably exhibit the above-mentioned physical properties (storage modulus G', loss tangent tan δ) and adhesive strength, and has excellent durability.

[0072] (4) Physical properties of adhesive The gel fraction of the pressure-sensitive adhesive in this embodiment is preferably 40% or more as a lower limit, more preferably 50% or more, particularly preferably 60% or more, and even more preferably 65% ​​or more. By setting the lower limit of the gel fraction as above, the cohesive strength of the pressure-sensitive adhesive is increased, the above-mentioned physical properties (storage modulus G', loss tangent tan δ) and adhesive strength are easily exhibited, and durability is improved.

[0073] The upper limit of the gel fraction is preferably 90% or less, more preferably 80% or less, particularly preferably 78% or less, and even more preferably 76% 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 becoming 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.

[0074] [Adhesive sheet] The pressure-sensitive adhesive sheet according to one embodiment of the present invention includes at least a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive described above.

[0075] 1, the adhesive sheet 1A according to the first embodiment is configured to include an adhesive layer 11, a substrate 13 laminated on one surface of the adhesive layer 11, and a release sheet 12 laminated on the other surface of the adhesive layer 11. The release sheet 12 is laminated on the adhesive layer 11 such that its release surface contacts the adhesive layer 11.

[0076] 2, the adhesive sheet 1B according to the second 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. Note that the release surface of the release sheet in this specification refers to the 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.

[0077] 1. Each element 1-1. Adhesive layer The adhesive layer 11 of the adhesive sheets 1A and 1B according to this embodiment is made of the above-mentioned adhesive.

[0078] 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 9 μm or more, and even more preferably 13 μm or more. This provides superior durability when applied to optical members such as polarizing plates. The thickness of the adhesive layer 11 is preferably 1000 μm or less, more preferably 100 μm or less, particularly preferably 50 μm or less, and even more preferably 20 μm or less. This can suppress appearance defects such as indentations and dents on the adhesive layer 11. In addition, the display obtained by using the adhesive sheet 1 can be made thinner. The adhesive layer 11 may be formed as a single layer, or may be formed by laminating multiple layers.

[0079] 1-2.Release sheet The release sheets 12, 12a, 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheets 1A, 1B (adhesive layer 11) are used. In the adhesive sheets 1A, 1B according to this embodiment, one or both of the release sheets 12a, 12b are not necessarily required.

[0080] Examples of the release sheets 12, 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.

[0081] The release surfaces of the release sheets 12, 12a, and 12b are preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. It is preferable that one of the release sheets 12a and 12b is a heavy release type release sheet with a large release force, and the other is a light release type release sheet with a small release force.

[0082] There are no particular limitations on the thickness of the release sheets 12, 12a, 12b, but it is usually about 20 to 150 μm.

[0083] 1-3. Base material The substrate 13 is not particularly limited, and any substrate sheet used for a normal adhesive sheet can be used. For example, in addition to the desired optical member, woven or nonwoven fabric using fibers such as rayon, acrylic, or polyester; papers such as fine paper, glassine paper, impregnated paper, and coated paper; metal foils such as aluminum and copper; foams such as urethane foam and polyethylene foam; polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; cellulose films such as triacetyl cellulose, polyurethane films, polyethylene films, polypropylene films, polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, ethylene-vinyl acetate copolymer films, polystyrene films, polycarbonate films, acrylic resin films, norbornene resin films, and cycloolefin resin films; and laminates of two or more of these plastic films. The plastic film may be uniaxially or biaxially stretched.

[0084] Examples of optical members include 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, etc. Among them, a polarizing plate (polarizing film) is suitable as a target for forming the pressure-sensitive adhesive (the pressure-sensitive adhesive layer 11) according to the above-mentioned embodiment from the viewpoint of durability, since it is easily shrinkable and has a large dimensional change.

[0085] The thickness of the substrate 13 varies depending on the type, but in the case of an optical member, for example, it is usually 10 μm to 500 μm, preferably 30 μm to 300 μm, and more preferably 40 μm to 90 μm.

[0086] 2. Manufacturing of adhesive sheets To manufacture the pressure-sensitive adhesive sheet 1A, a solution (coating solution) containing the pressure-sensitive adhesive composition is preferably applied to the release surface of the release sheet 12, followed by heat treatment to form the pressure-sensitive adhesive layer 11, and then the substrate 13 is laminated on the pressure-sensitive adhesive layer 11. Thereafter, a curing period is provided as necessary. The conditions for the heat treatment and curing are as described above.

[0087] In addition, to manufacture the pressure-sensitive adhesive sheet 1B, a coating solution containing the pressure-sensitive adhesive composition is preferably applied to the release surface of one release sheet 12a (or 12b), followed by heat treatment to form a pressure-sensitive adhesive layer 11, and then the release surface of the other release sheet 12b (or 12a) is superimposed on the pressure-sensitive adhesive layer 11. Thereafter, a curing period is provided as necessary.

[0088] The coating solution can be applied by, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like.

[0089] 3. Physical properties of adhesive sheets (1) Adhesive strength The adhesive strength of the adhesive sheets 1A and 1B according to the present embodiment to soda lime glass is preferably more than 1N / 25mm as a lower limit, more preferably 8N / 25mm or more, particularly preferably 12N / 25mm or more, and even more preferably 15N / 25mm or more. When the lower limit of the adhesive strength is as above, the durability when applied to a polarizing plate or the like is more excellent. On the other hand, the upper limit of the adhesive strength to the soda lime glass is not particularly limited, but taking into consideration the case where reworkability is required, it is preferably 100N / 25mm or less, more preferably 60N / 25mm or less, particularly preferably 40N / 25mm or less, and even more preferably 30N / 25mm or less.

[0090] The adhesive strength of the adhesive sheets 1A and 1B according to the present embodiment to alkali-free glass is preferably more than 1N / 25mm as a lower limit, more preferably 7N / 25mm or more, particularly preferably 9N / 25mm or more, and even more preferably 14N / 25mm or more. When the lower limit of the adhesive strength is as above, the durability when applied to a polarizing plate or the like is more excellent. On the other hand, the upper limit of the adhesive strength to the alkali-free glass is not particularly limited, but considering the case where reworkability is required, it is preferably 100N / 25mm or less, more preferably 60N / 25mm or less, particularly preferably 40N / 25mm or less, and even more preferably 30N / 25mm or less.

[0091] The adhesive strength basically refers to an adhesive strength measured by a 180-degree peeling method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described later.

[0092] (2) Haze value The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheets 1A and 1B according to this embodiment is preferably 30% or less, more preferably 10% or less, particularly preferably 5% or less, and even more preferably 1% or less. The above haze value of the pressure-sensitive adhesive layer 11 provides excellent light transmittance and is suitable for optical use. The lower limit of the haze value is not particularly limited, and is preferably 0% or more, and more preferably 0.1% or more.

[0093] The haze value is a characteristic value including the thickness of the pressure-sensitive adhesive layer, and it is preferable that the haze value is satisfied regardless of the thickness of the pressure-sensitive adhesive layer. Here, the haze value in this specification is a value measured in accordance with JIS K7136:2000.

[0094] (3)Surface resistivity When the pressure-sensitive adhesive sheets 1A and 1B or the pressure-sensitive adhesive layer 11 according to this embodiment are required to have antistatic properties, the surface resistivity of the pressure-sensitive adhesive layer 11 is preferably 1.0×10 12 It is preferable that the resistance is 5.0×10 11 It is preferable that the resistance is Ω / sq or less, and more preferably 5.0×10 10 It is preferable that the surface resistivity is Ω / sq or less. When the surface resistivity is the above value or less, the display body can exhibit sufficient antistatic properties. Such a surface resistivity can be achieved by making the adhesive composition P contain an antistatic agent. The lower limit of the surface resistivity is not particularly limited, but is preferably 5.0×10 from the viewpoint of not adversely affecting durability. 8 The surface resistivity of the pressure-sensitive adhesive layer is measured in accordance with JIS K6911, specifically as shown in the test examples described later.

[0095] 4. Using adhesive sheets The pressure-sensitive adhesive sheets 1A and 1B according to the present embodiment are suitable for use in producing a display. For example, to produce a liquid crystal display device composed of a liquid crystal cell and a polarizing plate, a polarizing plate is used as the substrate 13 of the pressure-sensitive adhesive sheet 1A, and the release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off to bond the exposed pressure-sensitive adhesive layer 11 to the liquid crystal cell.

[0096] Also, for example, to manufacture a liquid crystal display device in which a retardation plate is disposed between a liquid crystal cell and a polarizing plate, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1B is bonded to the retardation plate. Next, the release sheet 12 of the adhesive sheet 1A using a polarizing plate as the substrate 13 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1A is bonded to the retardation plate. Furthermore, the other release sheet 12b (or 12a) is peeled off from the adhesive layer 11 of the adhesive sheet B, and the exposed adhesive layer 11 of the adhesive sheet B is bonded to the liquid crystal cell.

[0097] When the pressure-sensitive adhesive sheets 1A and 1B are applied to the adhesion of a polarizing plate as described above, even if the polarizing plate shrinks due to heating or the like, the shrinkage of the polarizing plate itself can be suppressed by the pressure-sensitive adhesive layer 11. As a result, lifting or peeling at the interface between the polarizing plate and the pressure-sensitive adhesive layer 11 is suppressed, and high durability is exhibited.

[0098] 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.

[0099] For example, release sheet 12 of pressure-sensitive adhesive sheet 1A may be omitted, or either release sheet 12a or 12b of pressure-sensitive adhesive sheet 1B may be omitted. In addition, another layer may be interposed between pressure-sensitive adhesive layer 11 and substrate 13. EXAMPLES

[0100] 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.

[0101] Example 1 1. Preparation of (meth)acrylic acid ester polymer (A) 78 parts by mass of n-butyl acrylate, 15 parts by mass of methyl acrylate, 5 parts by mass of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate as an ethylene carbonate-containing monomer, and 2 parts by mass of 2-hydroxyethyl acrylate were copolymerized by solution polymerization 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 1.6 million.

[0102] 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, 0.20 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Industries, Ltd., product name "TD-75") as a crosslinking agent (B), and 0.2 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of an adhesive composition.

[0103] 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 heated at 90°C for 1 minute to form an adhesive layer.

[0104] Next, the adhesive layer on the heavy release type release sheet obtained above was attached to a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET381130"), one side of a polyethylene terephthalate film released with a silicone-based release agent, so that the release-treated surface of the light release type release sheet was in contact with the adhesive 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 15 μm, i.e., an adhesive sheet having a configuration of light release type release sheet / adhesive layer (thickness: 15 μm) / heavy release type release sheet.

[0105] 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").

[0106] 4. Manufacturing of polarizing plate with adhesive layer The diluted solution of the adhesive composition obtained in the above step 2 was applied by a knife coater to the release-treated surface of a light-release type release sheet (manufactured by Lintec Corporation, product name "SP-PET381130"), one side of which was a polyethylene terephthalate film treated with a silicone-based release agent. The applied layer was then heat-treated at 90°C for 1 minute to form an adhesive layer.

[0107] Next, the adhesive layer on the above-mentioned light-release type release sheet was attached to the COP side of a polarizing plate (thickness 70 μm) consisting of a laminate of triacetyl cellulose (TAC) / polyvinyl alcohol (PVA) / cycloolefin polymer (COP), and cured at 23°C and 50% RH for 7 days to produce a polarizing plate with an adhesive layer having a thickness of 15 μm, i.e., a polarizing plate with an adhesive layer having a configuration of polarizing plate / adhesive layer (thickness: 15 μm) / light-release type release sheet.

[0108] 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 MA: Methyl acrylate ECA: (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate

[0109] [Examples 2 to 4, Comparative Examples 1 to 2] A pressure-sensitive adhesive sheet and a polarizing plate with a pressure-sensitive adhesive layer were 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), and the blending amount of the crosslinking agent (B) were changed as shown in Table 1. In Example 4, 2.0 parts by mass of lithium bis(trifluoromethanesulfonyl)imide was further blended as an antistatic agent in the pressure-sensitive adhesive composition.

[0110] 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℃

[0111] [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.

[0112] 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.

[0113] [Test Example 2] (Measurement of dynamic elastic modulus) The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples were laminated in multiple layers 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 to prepare a sample.

[0114] 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'(23) (MPa) at 23°C, the storage modulus G'(80) (MPa) at 80°C, the loss tangent tanδ(23) at 23°C, and the loss tangent tanδ(80) at 80°C were observed. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature range: -20℃~140℃ Heating rate: 3℃ / min

[0115] [Test Example 3] (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 laminate obtained as described above was cut into a width of 25 mm and a length of 100 mm.

[0116] 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 two 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 (Corning, product name "EAGLE XG", thickness: 1.1 mm)

[0117] [Test Example 4] (Haze value measurement) The adhesive layer of the adhesive sheet produced in the examples and comparative examples was attached to glass to prepare a measurement sample. After background measurement was performed on the glass, the haze value (%) of the measurement sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH-5000") in accordance with JIS K7136:2000. The results are shown in Table 2.

[0118] [Test Example 5] (Durability evaluation) The polarizing plate with the adhesive layer prepared in the examples and comparative examples was cut to prepare a sample with a size of 152 mm x 203 mm. The sample was prepared after storing the polarizing plate with the adhesive layer for 7 days under an environment of 23°C and 50% RH from the preparation (formation of the adhesive layer). The release sheet was peeled off from the sample, and the exposed adhesive layer was attached to an alkali-free glass (manufactured by Corning, product name "EAGLE XG"), and then pressurized in an autoclave manufactured by Kurihara Seisakusho at 0.5 MPa and 50°C for 20 minutes.

[0119] The specimens were then placed in the following durability conditions, and after 500 hours, the specimens were checked using a 10x magnifying glass to see if there was any lifting or peeling. The evaluation criteria were as follows. The results are shown in Table 2. ◯: No lifting or peeling was observed, or lifting or peeling of 0.5 mm or less was observed, but was at a level that did not cause any practical problems. ×: Lifting or peeling of 0.6 mm or more was observed, which was at a level that was problematic for practical use. <Durability conditions> ·80℃dry 60℃, relative humidity 90%

[0120] [Test Example 6] (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. 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.

[0121] [Table 1]

[0122] [Table 2]

[0123] As can be seen from Table 2, the polarizing plates with a pressure-sensitive adhesive layer produced in the examples were excellent in durability. [Industrial Applicability]

[0124] The pressure-sensitive adhesive of the present invention is suitable for bonding optical members such as polarizing plates and retardation plates, and the pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet for optical members such as polarizing plates and retardation plates. [Explanation of symbols]

[0125] 1A, 1B...Adhesive sheet 11...Adhesive layer 12, 12a, 12b...Release sheet 13...Base material

Claims

1. An adhesive sheet having at least an adhesive layer, The pressure-sensitive adhesive layer is As a monomer unit constituting the polymer, 【Chemistry 1】 The adhesive composition comprises a (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having an ethylene carbonate structure represented by the formula: The pressure-sensitive adhesive has a storage modulus G'(80) at 80°C of 0.05 MPa or more; Adhesive strength to non-alkali glass is 7N / 25mm or more and 100N / 25mm or less. A pressure-sensitive adhesive sheet characterized by:

2. The adhesive sheet as described in claim 1, characterized in that the storage modulus G'(23) of the adhesive at 23°C is 0.04 MPa or more and 50 MPa or less.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the (meth)acrylic acid ester polymer (A) contains, as a monomer unit constituting the polymer, 0.1 mass % or more and 30 mass % or less of the ethylene carbonate-containing monomer.

4. An adhesive sheet described in any one of claims 1 to 3, characterized in that the gel fraction of the adhesive is 40% or more and 90% or less.

5. The pressure-sensitive adhesive sheet includes a substrate, The substrate is an optical member. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4.

6. The pressure-sensitive adhesive sheet according to claim 5 , wherein the optical member is a polarizing plate.

7. 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.

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