Adhesive composition, adhesive sheet, optical member, and display device

Abstract

The present invention relates to an adhesive composition, an adhesive sheet, an optical member, and a display device, the adhesive composition comprising a (meth) acrylic polymer (A) having a reactive functional group and a weight-average molecular weight of 650,000 or more and less than 1,500,000, a (meth) acrylic polymer (B) having a reactive functional group and a weight-average molecular weight of 650,000 or more and less than 1,500,000, and a crosslinking agent. And a (meth) acrylic polymer (B) containing a constituent unit derived from tert-butyl methacrylate in a proportion of 15-87 mass% with respect to the total constituent unit, the (meth) acrylic polymer (B) having a glass transition temperature of 105-150 DEG C and a weight-average molecular weight of 100,000 or more and less than 500,000, the content of the (meth) acrylic polymer (B) being 100 parts by mass per 100 parts by mass of the (meth) acrylic polymer (A), and the content of the (meth) acrylic polymer (B) being 100 parts by mass per 100 parts by mass per 100 parts by mass per 100 parts by mass per 100 parts by mass per 100 parts by mass per 100 parts by mass of the (meth) acrylic polymer (A). The content of the (meth) acrylic polymer (B) is 1-40 parts by mass.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an adhesive composition, an adhesive sheet, an optical member, and a display device. BACKGROUND

[0002] A liquid crystal display device generally has a liquid crystal cell having a liquid crystal component oriented in a prescribed direction interposed between two support substrates, and a polarizing plate, a phase difference film, a brightness improving film, or the like optical film. When the liquid crystal cell and the optical film are layered, or the optical films are layered with each other to manufacture the liquid crystal display device, these components are attached via an adhesive layer formed using an adhesive composition. In the liquid crystal display device, from the viewpoint of ensuring visibility, an adhesive composition of a (meth)acrylic acid type is used most frequently.

[0003] For example, in Japanese Patent Application Publication No. 2023-145213, an adhesive composition for an optical film is disclosed, which contains: a (meth)acrylic acid type polymer (A) having a weight average molecular weight of 1 million or more, a (meth)acrylic acid type polymer (B) containing a constitutional unit derived from a monomer having a hydroxyl group and having a content of the hydroxyl group of 0.0007 mmol / g to 0.22 mmol / g, a glass transition temperature of 0°C or higher, and a weight average molecular weight of 30,000 to 500,000, and a crosslinking agent; and the content of the (meth)acrylic acid type polymer (B) is 1 mass part to 30 mass parts with respect to 100 mass parts of the (meth)acrylic acid type polymer (A). SUMMARY

[0004] In recent years, under the background of a rising concern for the environment, it is required to reduce the amount of use of organic solvents. If the content of the organic solvent in the adhesive composition is reduced, the viscosity of the adhesive composition increases, and thus the coatability of the adhesive composition is impaired. In order to reduce the content of the organic solvent in the adhesive composition without increasing the viscosity of the adhesive composition, it is considered to reduce the weight average molecular weight of the base resin used in the adhesive composition. If the weight average molecular weight of the base resin is low, a large amount of the organic solvent is not required to adjust the viscosity of the adhesive composition.

[0005] However, the optical film such as a polarizing plate used in a liquid crystal display device is used in a state with an adhesive layer. Such an optical film with an adhesive layer is generally produced in a wide width, and then punched into a prescribed size using a cutting knife. If the adhesive layer protrudes from the cutting surface at this time, the protruding adhesive layer can adhere to other optical films in a process of superimposing the punched optical film, and cause a problem of contamination of the optical film. Therefore, the adhesive layer is required to have excellent workability not to easily protrude from the cutting surface at the time of cutting. As a method of making the workability of the adhesive layer good, for example, a method of adding a low-molecular-weight resin having a high glass transition temperature to a base resin is considered. For example, in Japanese Patent Application Laid-Open No. 2023-145213, by adding a resin having a glass transition temperature of 0°C or higher and a weight average molecular weight of 3 to 50 million to a base resin having a weight average molecular weight of 1 million or more, an adhesive layer having excellent workability is realized. However, along with the recent large-sizing of optical displays, the area of the optical film such as a polarizing plate is increasing, and thus there is a tendency that the adhesive layer more easily protrudes from the cutting surface. Therefore, the adhesive layer is required to have more excellent workability than ever. In order to further improve the workability of the adhesive layer, it is considered to increase the glass transition temperature of the low-molecular-weight resin added to the base resin (for example, 105°C or higher). However, if the weight average molecular weight of the base resin is reduced to a certain extent (for example, less than 150 million) in consideration of reducing the amount of use of organic solvents, the compatibility of the base resin with the added resin decreases, and a problem of impairing the transparency of the adhesive layer can occur.

[0006] As described above, an adhesive composition in which the weight average molecular weight of the base resin is set to a certain extent lower in order to reduce the amount of use of organic solvents has been difficult to realize formation of an adhesive layer having workability and transparency at a high level.

[0007] In addition, when the optical film with an adhesive layer is attached to a liquid crystal cell, if foreign matter is interposed between the adhesive layer and the liquid crystal cell, or a positional shift occurs due to an error in the attachment position, the optical film with an adhesive layer is peeled from the liquid crystal cell and reattached. In order to reuse the liquid crystal cell after peeling the optical film with an adhesive layer, the adhesive layer is required to have excellent reworkability capable of being easily peeled from the liquid crystal cell without damaging the liquid crystal cell or causing a residue on the attachment surface of the liquid crystal cell.

[0008] The present disclosure is made in view of the circumstances as described above.

[0009] An object that one embodiment of the present disclosure intends to solve is to provide an adhesive composition capable of forming an adhesive layer having excellent workability, transparency, and reworkability.

[0010] Other embodiments of the present disclosure aim to provide an adhesive sheet, an optical member, and a display device each having an adhesive layer formed of the above-described adhesive composition.

[0011] Specific means for solving the problem include the following modes.

[0012] <1> An adhesive composition comprising a (meth)acrylic polymer (A), a (meth)acrylic polymer (B), and a crosslinking agent,

[0013] The above-described (meth)acrylic polymer (A) has a reactive functional group and has a weight average molecular weight of 650,000 or more and less than 1,500,000,

[0014] The above-described (meth)acrylic polymer (B) contains a constitutional unit derived from tert-butyl methacrylate at a proportion of 15 to 87 mass% with respect to the total constitutional units, the above-described (meth)acrylic polymer (B) has a glass transition temperature of 105°C to 150°C, and has a weight average molecular weight of 100,000 or more and less than 500,000,

[0015] The content of the above-described (meth)acrylic polymer (B) is 1 to 40 parts by mass with respect to 100 parts by mass of the above-described (meth)acrylic polymer (A).

[0016] <2> The adhesive composition according to <1>, wherein the above-described (meth)acrylic polymer (A) has a glass transition temperature of -60°C to -30°C.

[0017] <3> The adhesive composition according to <1> or <2>, wherein the reactive functional group in the above-described (meth)acrylic polymer (A) includes at least one of a carboxyl group and a hydroxyl group.

[0018] <4> The adhesive composition according to any one of <1> to <3>, wherein the above-described (meth)acrylic polymer (B) does not contain a constitutional unit derived from a monomer having a reactive functional group, or the content rate of the constitutional unit derived from the monomer having a reactive functional group is greater than 0 mass% and is 1.0 mass% or less with respect to the total constitutional units.

[0019] <5> The adhesive composition according to <4>, wherein the monomer having a reactive functional group in the above-described (meth)acrylic polymer (B) is a monomer having a hydroxyl group.

[0020] <6> An adhesive sheet having an adhesive layer formed of the adhesive composition according to any one of <1> to <5>.

[0021] <7> An adhesive sheet having an optical film and an adhesive layer,

[0022] The above-mentioned adhesive layer is provided on at least one side of the above-mentioned optical film and is formed from the adhesive composition described in any one of <1> to <5>.

[0023] <8> The adhesive sheet according to <7>, wherein the above-mentioned optical film is a polarizing plate.

[0024] <9> An optical member provided with a glass substrate, an adhesive layer, and an optical film in this order, wherein the above-mentioned adhesive layer is formed from the adhesive composition described in any one of <1> to <5>.

[0025] <10> A display device provided with the optical member described in <9>.

[0026] According to one embodiment of the present disclosure, it is possible to provide an adhesive composition capable of forming an adhesive layer that is excellent in processability, transparency, and reworkability.

[0027] According to other embodiments of the present disclosure, it is possible to provide an adhesive sheet, an optical member, and a display device provided with an adhesive layer formed from the above-mentioned adhesive composition. DETAILED DESCRIPTION

[0028] The adhesive composition, the adhesive sheet, the optical member, and the display device of the present disclosure are described below in detail. The description of the requirements described below is sometimes made based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be appropriately changed and implemented within the scope of the purpose of the present disclosure.

[0029] In the present disclosure, the numerical range represented by "~" means a range including the numerical values described before and after "~" as lower limit values and upper limit values, respectively.

[0030] In the present disclosure, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the upper limit value or the lower limit value of another numerically described range. In addition, in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the value shown in the examples.

[0031] In the present disclosure, a combination of two or more preferred modes is a more preferred mode.

[0032] In the present disclosure, in the case where a plurality of substances belonging to each component is present in the adhesive composition, the amount of each component in the adhesive composition means the total amount of the above-mentioned plurality of substances present in the adhesive composition, unless otherwise specified.

[0033] In the present disclosure, "solid content" means a component included in the composition other than a solvent, and "solvent" means water and an organic solvent, unless otherwise specified.

[0034] For example, in the case where the solvent contained in the composition is only water, the solid content refers to the content of the components contained in the composition other than water, in the case where the solvent contained in the composition is only an organic solvent, the solid content refers to the content of the components contained in the composition other than the organic solvent, and in the case where the solvent contained in the composition is water and an organic solvent, the solid content refers to the content of the components contained in the composition other than water and the organic solvent.

[0035] In the present disclosure, the "(meth)acrylic polymer" refers to a polymer containing constitutional units derived from a (meth)acrylic monomer, and the proportion of the constitutional units derived from the (meth)acrylic monomer is 50% by mass or more.

[0036] In the present disclosure, the "(meth)acrylic monomer" refers to a monomer having a (meth)acryloyl group.

[0037] In the present disclosure, the "(meth)acrylic acid" is a term including both "acrylic acid" and "methacrylic acid", the "(meth)acrylate" is a term including both "acrylate" and "methacrylate", and the "(meth)acryloyl group" is a term including both "acryloyl group" and "methacryloyl group".

[0038] In the present disclosure, "n-" refers to normal, "i-" refers to iso, "s-" refers to sec, and "t-" refers to tert.

[0039] In the present disclosure, the meaning of "monomer" is the same as that of "monomeric", and the meaning of "polymer" is the same as that of "polymeric".

[0040] In the present disclosure, the meaning of "mass%" is the same as that of "weight%", and the meaning of "mass part" is the same as that of "weight part".

[0041] In the present disclosure, the "constitutional unit derived from a monomer" refers to a constitutional unit formed by addition polymerization of a monomer.

[0042] In the present disclosure, the term "step" includes not only a single step, but also a step that cannot be clearly distinguished from other steps, as long as the desired purpose of the step can be achieved.

[0043] [Adhesive composition]

[0044] The adhesive composition of the present disclosure contains a (meth)acrylic polymer (A) having a reactive functional group and a weight average molecular weight of 650,000 or more and less than 1,500,000, a (meth)acrylic polymer (B) containing a constitutional unit derived from tert-butyl methacrylate at a proportion of 15 to 87 mass% with respect to the total constitutional units, the (meth)acrylic polymer (B) having a glass transition temperature of 105 to 150°C and a weight average molecular weight of 1,000,000 or more and less than 5,000,000, and a crosslinking agent, the content of the (meth)acrylic polymer (B) being 1 to 40 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A).

[0045] The adhesive composition of the present disclosure can form an adhesive layer excellent in processability, transparency, and reworkability by having the above constitution.

[0046] In the present disclosure, the "(meth)acrylic polymer (A) having a reactive functional group and a weight average molecular weight of 650,000 or more and less than 1,500,000" is also referred to as "specific (meth)acrylic polymer (A)". In addition, in the present disclosure, the "(meth)acrylic polymer (B) containing a constitutional unit derived from tert-butyl methacrylate at a proportion of 15 to 87 mass% with respect to the total constitutional units, having a glass transition temperature of 105 to 150°C, and having a weight average molecular weight of 1,000,000 or more and less than 5,000,000" is also referred to as "specific (meth)acrylic polymer (B)".

[0047] In the present disclosure, the "specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B)" are sometimes collectively referred to as "specific (meth)acrylic polymer".

[0048] 〔Specific (Meth)acrylic Polymer (A)〕

[0049] The adhesive composition of the present disclosure contains a (meth)acrylic polymer (A) having a reactive functional group and a weight average molecular weight of 650,000 or more and less than 1,500,000 (i.e., specific (meth)acrylic polymer (A)).

[0050] The adhesive composition of the present disclosure can contain one specific (meth)acrylic polymer (A) alone, or two or more.

[0051] The specific (meth)acrylic polymer (A) can be a homopolymer or a copolymer. The specific (meth)acrylic polymer (A) can be, for example, a homopolymer or a copolymer of a (meth)acrylic monomer which does not have a reactive functional group, into which a reactive functional group is introduced by substitution. Alternatively, the specific (meth)acrylic polymer (A) can be, for example, a copolymer of a (meth)acrylic monomer which does not have a reactive functional group and a monomer which does not have a reactive functional group and is other than a (meth)acrylic monomer, into which a reactive functional group is introduced by substitution. In addition, the specific (meth)acrylic polymer (A) can be, for example, a copolymer of a (meth)acrylic monomer which has a reactive functional group and a (meth)acrylic monomer which does not have a reactive functional group, a copolymer of a (meth)acrylic monomer which has a reactive functional group and a monomer which does not have a reactive functional group and is other than a (meth)acrylic monomer, or a copolymer of a (meth)acrylic monomer which does not have a reactive functional group and a monomer which has a reactive functional group and is other than a (meth)acrylic monomer.

[0052] The specific (meth)acrylic polymer (A) has a reactive functional group.

[0053] In the present disclosure, the "reactive functional group" refers to a functional group which is capable of reacting with a crosslinking agent to form a crosslinked structure.

[0054] Since the specific (meth)acrylic polymer (A) has a reactive functional group, a crosslinked structure is formed by the reaction of the reactive functional group with a crosslinking agent described later. By forming the crosslinked structure, cohesion is imparted to the adhesive layer. If the cohesion of the adhesive layer is increased, the adhesion of the adhesive layer to the substrate is increased, and thus the protrusion of the adhesive layer from the cutting surface is suppressed, and the processability of the adhesive layer becomes good. In addition, if the cohesion of the adhesive layer is increased, cohesion failure of the adhesive layer is less likely to occur, and the reworkability of the adhesive layer becomes good.

[0055] Specific examples of the reactive functional group include a hydroxyl group, a carboxyl group, and an amino group. The "amino group" in the present disclosure includes a primary amino group, a secondary amino group, and a tertiary amino group.

[0056] The reactive functional group preferably includes at least one of a hydroxyl group and a carboxyl group, and more preferably both a hydroxyl group and a carboxyl group.

[0057] The specific (meth)acrylic polymer (A) is preferably in a manner of having a reactive functional group by including a constitutional unit from a monomer having a reactive functional group described later.

[0058] < Constitutional unit from a monomer having a reactive functional group >

[0059] The kind of the monomer having a reactive functional group is not particularly limited.

[0060] As the monomer having a reactive functional group, for example, a monomer having at least one reactive functional group and an ethylenically unsaturated group in one molecule can be mentioned.

[0061] The reactive functional group is specifically exemplified above.

[0062] As the ethylenically unsaturated group, for example, a vinyl group, an allyl group, a vinylphenyl group, and a (meth)acryloyl group can be mentioned.

[0063] As the monomer having a reactive functional group, for example, a monomer having a carboxyl group, a monomer having a hydroxyl group, and a monomer having an amino group can be mentioned.

[0064] The kind of the monomer having a carboxyl group is not particularly limited.

[0065] As specific examples of the monomer having a carboxyl group, (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxylic acid-polycaprolactone mono(meth)acrylate [for example, ω-carboxy-polycaprolactone (n≈2) monoacrylate], and succinic acid derivatives (for example, succinic acid 2-acryloyloxyethyl ester) can be mentioned.

[0066] The monomer having a carboxyl group preferably contains acrylic acid, more preferably is acrylic acid.

[0067] The kind of the monomer having a hydroxyl group is not particularly limited.

[0068] As specific examples of the monomer having a hydroxyl group, (meth)acrylic acid 2-hydroxyethyl ester, (meth)acrylic acid 2-hydroxypropyl ester, (meth)acrylic acid 3-hydroxypropyl ester, (meth)acrylic acid 4-hydroxybutyl ester, (meth)acrylic acid 6-hydroxyhexyl ester, (meth)acrylic acid 8-hydroxyoctyl ester, (meth)acrylic acid 10-hydroxydecyl ester, (meth)acrylic acid 12-hydroxylauryl ester, (meth)acrylic acid 3-methyl-3-hydroxybutyl ester, (meth)acrylic acid 1,1-dimethyl-3-hydroxybutyl ester, (meth)acrylic acid 1,3-dimethyl-3-hydroxybutyl ester, (meth)acrylic acid 2,2,4-trimethyl-3-hydroxypentyl ester, (meth)acrylic acid 2-ethyl-3-hydroxyhexyl ester, glycerol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate can be mentioned.

[0069] The monomer having a hydroxyl group preferably contains a (meth)acrylic acid hydroxyalkyl ester, more preferably contains (meth)acrylic acid 2-hydroxyethyl ester, further preferably contains acrylic acid 2-hydroxyethyl ester, particularly preferably is acrylic acid 2-hydroxyethyl ester.

[0070] The kind of the monomer having an amino group is not particularly limited.

[0071] Specific examples of the monomer having an amino group include 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-diisopropylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylamide.

[0072] The monomer having a reactive functional group preferably includes at least one of a monomer having a carboxyl group and a monomer having a hydroxyl group, and more preferably includes a monomer having a carboxyl group.

[0073] When the specific (meth)acrylic polymer (A) includes a constitutional unit derived from a monomer having a reactive functional group, the specific (meth)acrylic polymer (A) can include only one kind of constitutional unit derived from a monomer having a reactive functional group, or can include two or more kinds.

[0074] When the specific (meth)acrylic polymer (A) includes a constitutional unit derived from a monomer having a reactive functional group, the content ratio of the constitutional unit derived from a monomer having a reactive functional group in the specific (meth)acrylic polymer (A) is not particularly limited, and for example, from the viewpoint of making the processability and reworkability of the adhesive layer better, it is preferably 0.5% by mass or more and 9% by mass or less, more preferably 1% by mass or more and 7% by mass or less, and further preferably 2% by mass or more and 7% by mass or less, with respect to the total constitutional units of the specific (meth)acrylic polymer (A).

[0075] < Constitutional unit derived from an alkyl (meth)acrylate monomer >

[0076] The specific (meth)acrylic polymer (A) preferably includes a constitutional unit derived from an alkyl (meth)acrylate monomer.

[0077] The kind of the alkyl (meth)acrylate monomer is not particularly limited.

[0078] The alkyl (meth)acrylate monomer can be an alkyl acrylate monomer, or can be an alkyl methacrylate monomer.

[0079] The alkyl group possessed by the alkyl (meth)acrylate monomer can be unsubstituted, or can have a substituent (wherein the reactive functional group is excluded). However, it is preferably unsubstituted.

[0080] The alkyl group possessed by the alkyl (meth)acrylate monomer can be any one of a linear shape, a branched shape, or a cyclic shape.

[0081] The number of carbon atoms of the alkyl moiety of the alkyl (meth)acrylate monomer is preferably, for example, 1 to 18, more preferably 1 to 12, further preferably 1 to 8, and particularly preferably 1 to 4.

[0082] As specific examples of the (meth)acrylic acid alkyl ester monomer, there are mentioned methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

[0083] The (meth)acrylic acid alkyl ester monomer preferably contains at least one member selected from the group consisting of n-butyl (meth)acrylate, methyl (meth)acrylate, and methyl methacrylate, more preferably contains n-butyl (meth)acrylate, and further preferably is n-butyl (meth)acrylate.

[0084] When the specific (meth)acrylic polymer (A) contains a constitutional unit derived from the (meth)acrylic acid alkyl ester monomer, it can contain only one constitutional unit derived from the (meth)acrylic acid alkyl ester monomer, or two or more constitutional units derived from the (meth)acrylic acid alkyl ester monomer.

[0085] When the specific (meth)acrylic polymer (A) contains a constitutional unit derived from the (meth)acrylic acid alkyl ester monomer, the content ratio of the constitutional unit derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic polymer (A) is not particularly limited, and for example, it is preferably 50% by mass or more, more preferably 50% by mass to 99.5% by mass, further preferably 60% by mass to 99.0% by mass, and particularly preferably 70% by mass to 98.0% by mass, relative to the total constitutional units of the specific (meth)acrylic polymer (A).

[0086] The content ratio of the constitutional unit derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic polymer (A) being 50% by mass or more relative to the total constitutional units of the specific (meth)acrylic polymer (A) means that the constitutional unit derived from the (meth)acrylic acid alkyl ester monomer is contained as a main component of the constitutional units of the specific (meth)acrylic polymer (A).

[0087] < Constitutional unit derived from other monomer >

[0088] The specific (meth)acrylic polymer (A) can contain a constitutional unit derived from a monomer other than any one of the monomer having a reactive functional group and the (meth)acrylic acid alkyl ester monomer (so-called other monomer).

[0089] As the constitutional unit from other monomers, there can be mentioned a constitutional unit from a (meth)acrylate having an aromatic ring, represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; a constitutional unit from an alkoxyalkyl (meth)acrylate, represented by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; a constitutional unit from an aromatic monovinyl, represented by styrene, a-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; a constitutional unit from a vinyl cyanide, represented by acrylonitrile and methacrylonitrile; a constitutional unit from a vinyl ester, represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; and the like.

[0090] For example, from the viewpoint of suppressing whitening, the specific (meth)acryl-based polymer (A) preferably contains a constitutional unit from a (meth)acrylate having an aromatic ring, more preferably contains a constitutional unit from at least one monomer selected from the group consisting of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, further preferably contains a constitutional unit from phenoxyethyl (meth)acrylate, particularly preferably contains a constitutional unit from phenoxyethyl acrylate, as a constitutional unit from other monomers. Here, "whitening" refers to a phenomenon in which light leakage occurs in a liquid crystal display device to cause whitening.

[0091] When the specific (meth)acryl-based polymer (A) contains a constitutional unit from other monomers, it can contain one kind of constitutional unit from other monomers alone, or two or more kinds.

[0092] When the specific (meth)acryl-based polymer (A) contains a constitutional unit from other monomers, the content ratio of the constitutional unit from other monomers in the specific (meth)acryl-based polymer (A) can be appropriately set within a range not impairing the effects of the adhesive composition of the present disclosure.

[0093] <<Glass transition temperature of specific (meth)acryl-based polymer (A)>>

[0094] The glass transition temperature of the specific (meth)acryl-based polymer (A) (also referred to as "Tg") is not particularly limited, and is preferably, for example, -60°C to -30°C, more preferably -55°C to -35°C, further preferably -50°C to -40°C.

[0095] If the glass transition temperature of the specific (meth)acryl-based polymer (A) is -60°C or higher, there is a tendency that the reworkability of the adhesive layer becomes better.

[0096] If the glass transition temperature of the specific (meth)acrylic polymer (A) is -30°C or lower, there is a tendency that the reworkability and transparency of the adhesive layer become better.

[0097] The glass transition temperature of the specific (meth)acrylic polymer (A) is a value obtained by converting the absolute temperature (unit: K) calculated from Formula 1 below into Celsius temperature (unit: °C).

[0098] 1 / Tg = m1 / Tg1 + m2 / Tg2 + ··· + m(k-1) / Tg(k-1) + mk / Tgk (Formula 1)

[0099] In Formula 1, Tg1, Tg2, ···, Tg(k-1), and Tgk each represent the glass transition temperature expressed by the absolute temperature when a homopolymer is made from each monomer constituting the specific (meth)acrylic polymer (A). m1, m2, ···, m(k-1), and mk each represent the mole fraction of each monomer constituting the specific (meth)acrylic polymer (A), and m1 + m2 + ··· + m(k-1) + mk = 1.

[0100] Note that the absolute temperature can be converted into Celsius temperature by subtracting 273 from the absolute temperature, and the Celsius temperature can be converted into the absolute temperature by adding 273 to the Celsius temperature.

[0101] The "glass transition temperature when a homopolymer is made" in the present disclosure adopts a value described in a publicly known document, or a value measured using a differential scanning calorimeter (DSC). Which value is adopted is specifically as follows.

[0102] The "glass transition temperature when a homopolymer is made" of the monomers shown below each adopts the value in parentheses.

[0103] Methyl acrylate (10°C), methyl methacrylate (105°C), ethyl acrylate (-22°C), ethyl methacrylate (65°C), n-butyl acrylate (-54°C), n-butyl methacrylate (20°C), isobutyl methacrylate (53°C), t-butyl acrylate (43°C), t-butyl methacrylate (118°C), 2-ethylhexyl acrylate (-70°C), 2-ethylhexyl methacrylate (-10°C), n-octyl acrylate (-65°C), stearyl acrylate (30°C), stearyl methacrylate (38°C), lauryl acrylate (-3°C), lauryl methacrylate (-65°C), cyclohexyl methacrylate (104°C), isobornyl acrylate (94°C), isobornyl methacrylate (180°C), benzyl acrylate (6°C), phenoxyethyl acrylate (-22°C), 2-methoxyethyl acrylate (-50°C), glycidyl methacrylate (74°C), 2-hydroxyethyl acrylate (-15°C), 2-hydroxyethyl methacrylate (85°C), 4-hydroxybutyl acrylate (-80°C), acrylic acid (106°C), methacrylic acid (228°C), dimethylaminoethyl methacrylate (18°C), ω-carboxy-poly-caprolactone (n = 2) monoacrylate (-30°C).

[0104] The "glass transition temperature of a homopolymer" of a monomer other than the above-described monomers is the value described in Polymer Handbook (Fourth Edition, Wiley-Interscience; hereinafter the same.) in the case where it is described in Polymer Handbook, and the value of the glass transition temperature of a homopolymer obtained by the following measuring method is used in the case where it is not described in Polymer Handbook.

[0105] Specifically, the glass transition temperature of a homopolymer is determined using a differential scanning calorimeter (DSC) under the conditions of a nitrogen stream, a sample (i.e., a homopolymer) of 10 mg, and a temperature increase rate of 10°C / minute, and the inflection point of the obtained DSC curve is used as the glass transition temperature of the homopolymer.

[0106] As the differential scanning calorimeter, for example, a differential scanning calorimeter (trade name: Discovery DSC 2500) manufactured by T.A. Instruments Japan, Inc. can be preferably used. However, the differential scanning calorimeter is not limited thereto.

[0107] The glass transition temperature of the specific (meth)acrylic polymer (A) can be, for example, a desired value by appropriately selecting the kind and ratio of monomers that become the polymerization components of the specific (meth)acrylic polymer (A).

[0108] <<Weight average molecular weight of the specific (meth)acrylic polymer (A)>>

[0109] The weight average molecular weight of the specific (meth)acrylic polymer (A) (also referred to as "Mw") is 650,000 or more and less than 1,500,000.

[0110] If the weight average molecular weight of the specific (meth)acrylic polymer (A) is 650,000 or more, entanglement of the polymers with each other is moderately generated, and the specific (meth)acrylic polymer (B) is inhibited from being present locally at the interface of the adhesive layer, and thus there is a tendency for the transparency of the adhesive layer to be excellent.

[0111] The weight average molecular weight of the specific (meth)acrylic polymer (A) is preferably 700,000 or more, more preferably 750,000 or more, and further preferably 850,000 or more.

[0112] If the weight average molecular weight of the specific (meth)acrylic polymer (A) is less than 1,500,000, there is a tendency for the viscosity of the adhesive composition to be excellent even if the amount of the organic solvent used is reduced to a certain extent.

[0113] The weight average molecular weight of the specific (meth)acrylic polymer (A) is preferably 1,400,000 or less, more preferably 1,300,000 or less, and further preferably 1,200,000 or less.

[0114] In one mode, the weight average molecular weight of the specific (meth)acrylic polymer (A) can be 700,000 to 1,400,000, 750,000 to 1,300,000, or 850,000 to 1,200,000.

[0115] The weight average molecular weight of the specific (meth)acrylic polymer (A) is a value determined by the following method. Specifically, the determination is performed according to (1) to (3) below.

[0116] (1) A solution of the specific (meth)acrylic polymer (A) is coated on a release paper, and then dried at 100°C for 1 minute to obtain a film-shaped specific (meth)acrylic polymer (A).

[0117] (2) The film-shaped specific (meth)acrylic polymer (A) obtained in the above (1) and tetrahydrofuran are used to obtain a sample solution having a solid content concentration of 0.2 mass%. Note that the "solid content concentration" herein refers to the mass ratio of the specific (meth)acrylic polymer (A) in the sample solution.

[0118] (3) The weight average molecular weight of the specific (meth)acrylic polymer (A) is determined as a polystyrene conversion value using a gel permeation chromatograph (GPC) under the following conditions.

[0119] ~Conditions~

[0120] Measurement device: High-speed GPC (Model: HLC-8420GPC, manufactured by Tosoh Corporation)

[0121] Detector: Differential refractometer (RI) (installed in HLC-8420, manufactured by Tosoh Corporation)

[0122] Column: 2 pieces of TSKgel GMH XL (manufactured by Tosoh Corporation)

[0123] Column temperature: 40°C

[0124] Eluent: Tetrahydrofuran

[0125] Injection amount of sample solution: 100 μL

[0126] Flow rate: 0.8 mL / minute

[0127] The weight average molecular weight of the specific (meth)acrylic polymer (A) can be made to be a desired value by adjusting the polymerization temperature, the polymerization time, the amount of use of an organic solvent, the kind of a polymerization initiator, the amount of use of a polymerization initiator, and the like at the time of polymerizing a monomer.

[0128] << Content Ratio of Specific (Meth)Acrylic Polymer (A) >>

[0129] The content ratio of the specific (meth)acrylic polymer (A) in the adhesive composition of the present disclosure is not particularly limited, and, for example, it is preferably 73.5% by mass or more and 99.0% by mass or less, more preferably 75.5% by mass or more and 98.0% by mass or less, and further preferably 76.0% by mass or more and 96.5% by mass or less, with respect to the total amount of solid components in the adhesive composition.

[0130] [Specific (Meth)Acrylic Polymer (B)]

[0131] The adhesive composition of the present disclosure contains a (meth)acrylic polymer (B) (i.e., a specific (meth)acrylic polymer (B)) that contains a constitutional unit derived from tert-butyl methacrylate at a ratio of 15% by mass or more and 87% by mass or less with respect to all constitutional units, has a glass transition temperature of 105°C or more and 150°C or less, and has a weight average molecular weight of 100,000 or more and less than 500,000.

[0132] The adhesive composition of the present disclosure can contain one specific (meth)acrylic polymer (B) alone, and can contain two or more.

[0133] < Constitutional Unit Derived from tert-Butyl Methacrylate >

[0134] The specific (meth)acrylic polymer (B) contains constitutional units derived from tert-butyl methacrylate at a proportion of 15 to 87 mass% relative to the total constitutional units.

[0135] In the adhesive composition of the present disclosure, as one of the methods of making the processability of the adhesive layer good, by combining the specific (meth)acrylic polymer (A) as a base resin with the higher specific (meth)acrylic polymer (B) having a glass transition temperature of 105°C or higher, the cohesion of the adhesive layer can be improved.

[0136] In order to make the glass transition temperature of the specific (meth)acrylic polymer (B) 105°C or higher, for example, it is considered to select an alkyl methacrylate monomer having a shorter alkyl chain (in other words, having a smaller number of carbon atoms in the alkyl site) as a monomer component of the specific (meth)acrylic polymer (B). The alkyl methacrylate monomer having a shorter alkyl chain has a tendency to have a high glass transition temperature when made into a homopolymer. However, if the proportion of the constitutional units derived from the alkyl methacrylate monomer having a short alkyl chain in the specific (meth)acrylic polymer (B) becomes larger, the specific (meth)acrylic polymer (B) is less likely to form an entangled structure with the specific (meth)acrylic polymer (A), and thus the specific (meth)acrylic polymer (B) is likely to exist locally at the interface of the adhesive layer, impairing the transparency of the adhesive layer.

[0137] In addition, in order to make the glass transition temperature of the specific (meth)acrylic polymer (B) 105°C or higher, for example, it is also considered to select an alkyl methacrylate monomer having a cyclic structure as a monomer component of the specific (meth)acrylic polymer (B). The alkyl methacrylate monomer having a cyclic structure also has a tendency to have a high glass transition temperature when made into a homopolymer. However, since the alkyl methacrylate monomer having a cyclic structure has a very large structure, if the specific (meth)acrylic polymer (B) contains a large amount of constitutional units derived from the alkyl methacrylate monomer having a cyclic structure, the compatibility of the specific (meth)acrylic polymer (A) with the specific (meth)acrylic polymer (B) decreases, and the transparency of the adhesive layer is likely to be impaired.

[0138] On the other hand, the specific (meth) acrylic polymer (B) is able to adjust the glass transition temperature to 105°C or higher even if it does not contain a large amount of a constitutional unit from an alkyl methacrylate monomer having a short alkyl chain and / or a constitutional unit from an alkyl methacrylate monomer having a cyclic structure, by containing a constitutional unit from a tert-butyl methacrylate having a tert-butyl group which is easily entangled with the specific (meth) acrylic polymer (A) at a rate of 15% by mass or more with respect to the total constitutional units. In addition, the specific (meth) acrylic polymer (B) is able to sufficiently form an entangled structure with the specific (meth) acrylic polymer (A) and thus is not easily present locally at the interface of the adhesive layer, by containing a constitutional unit from a tert-butyl methacrylate having a tert-butyl group which is easily entangled with the specific (meth) acrylic polymer (A) at a rate of 15% by mass or more with respect to the total constitutional units of the specific (meth) acrylic polymer (B). Therefore, if the content rate of the constitutional unit from the tert-butyl methacrylate in the specific (meth) acrylic polymer (B) is 15% by mass or more with respect to the total constitutional units of the specific (meth) acrylic polymer (B), the adhesive layer has a tendency to be excellent in transparency in addition to processability.

[0139] On the other hand, if the content rate of the constitutional unit from the tert-butyl methacrylate in the specific (meth) acrylic polymer (B) is 87% by mass or less with respect to the total constitutional units of the specific (meth) acrylic polymer (B), the adhesive layer has a tendency to be excellent in transparency. As a reason therefor, it is presumed that the proportion of the constitutional unit from the tert-butyl methacrylate having a large-volume tert-butyl group and a high glass transition temperature when made into a homopolymer is not excessive, and thus the specific (meth) acrylic polymer (B) is moderately compatible with the specific (meth) acrylic polymer (A) and is not easily subjected to phase separation structure formation in a size larger than the wavelength region of light, i.e., several hundred nm.

[0140] The content rate of the constitutional unit from the tert-butyl methacrylate in the specific (meth) acrylic polymer (B) with respect to the total constitutional units of the specific (meth) acrylic polymer (B) is preferably 17% by mass or more, more preferably 19% by mass or more, and further preferably 30% by mass or more. In addition, the content rate of the constitutional unit from the tert-butyl methacrylate in the specific (meth) acrylic polymer (B) with respect to the total constitutional units of the specific (meth) acrylic polymer (B) is preferably 85% by mass or less, more preferably 83% by mass or less, and further preferably 80% by mass or less.

[0141] In one embodiment, the content ratio of the constitutional unit derived from the tert-butyl methacrylate in the specific (meth)acrylic polymer (B) with respect to the total constitutional units of the specific (meth)acrylic polymer (B) can be 17 to 85% by mass, or 19 to 83% by mass, or 30 to 80% by mass.

[0142] < Constitutional unit derived from other (meth)acrylic alkyl ester monomer >

[0143] The specific (meth)acrylic polymer (B) preferably contains a constitutional unit derived from a (meth)acrylic alkyl ester monomer other than the tert-butyl methacrylate (so-called other (meth)acrylic alkyl ester monomer).

[0144] The kind of the other (meth)acrylic alkyl ester monomer is not particularly limited.

[0145] The other (meth)acrylic alkyl ester monomer can be an acrylic alkyl ester monomer or a methacrylic alkyl ester monomer, but is preferably a methacrylic alkyl ester monomer.

[0146] The alkyl group of the other (meth)acrylic alkyl ester monomer can be unsubstituted or can have a substituent (wherein a reactive functional group is excluded), but is preferably unsubstituted.

[0147] The alkyl group of the other (meth)acrylic alkyl ester monomer can be any one of linear, branched, or cyclic.

[0148] The number of carbon atoms in the alkyl moiety of the other (meth)acrylic alkyl ester monomer is preferably, for example, 1 to 18, more preferably 1 to 12, further preferably 1 to 8, and particularly preferably 1 to 4.

[0149] Specific examples of the other (meth)acrylic alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.

[0150] The other (meth)acrylic alkyl ester monomer preferably contains at least one member selected from the group consisting of methyl methacrylate, isobutyl methacrylate, and isobornyl methacrylate, more preferably contains methyl methacrylate, and further preferably is methyl methacrylate.

[0151] The specific (meth)acrylic polymer (B) can contain a constitutional unit derived from the other (meth)acrylic alkyl ester monomer.

[0152] When the specific (meth)acrylic polymer (B) contains a constitutional unit derived from the other (meth)acrylic alkyl ester monomer, the content ratio of the constitutional unit derived from the other (meth)acrylic alkyl ester monomer in the specific (meth)acrylic polymer (B) is not particularly limited, and for example, it is preferably 13% by mass or more and 85% by mass or less, more preferably 17% by mass or more and 85% by mass or less, and further preferably 19% by mass or more and 85% by mass or less, with respect to the total constitutional units of the specific (meth)acrylic polymer (B).

[0153] < Constitutional unit derived from a monomer having a reactive functional group >

[0154] The specific (meth)acrylic polymer (B) can contain a constitutional unit derived from a monomer having a reactive functional group.

[0155] The kind of the monomer having a reactive functional group is not particularly limited.

[0156] As the monomer having a reactive functional group, for example, a monomer having at least one reactive functional group and an ethylenically unsaturated group in one molecule can be mentioned.

[0157] The specific examples of the reactive functional group are as described above.

[0158] As the ethylenically unsaturated group, for example, a vinyl group, an allyl group, a vinylphenyl group, and a (meth)acryloyl group can be mentioned.

[0159] As the monomer having a reactive functional group, for example, a monomer having a carboxyl group, a monomer having a hydroxyl group, and a monomer having an amino group can be mentioned.

[0160] The specific examples of these monomers having a reactive functional group are the same as those described in the specific (meth)acrylic polymer (A).

[0161] The monomer having a reactive functional group is preferably a monomer having a hydroxyl group.

[0162] Since the crosslinking reaction proceeds slowly in comparison with other reactive functional groups such as a carboxyl group, it is preferable from the aspect of having a tendency to be less likely to hinder the reaction of the specific (meth)acrylic polymer (A) with the crosslinking agent.

[0163] The specific (meth)acrylic polymer (B) can contain a constitutional unit derived from a monomer other than the t-butyl methacrylate, the monomer having a reactive functional group, and any one of the (meth)acrylic alkyl ester monomers (so-called other monomers).

[0164] For example, from the viewpoint of making the reworkability of the adhesive layer better, the specific (meth)acrylic polymer (B) preferably contains no constitutional unit derived from a monomer having a reactive functional group, or the content rate of the constitutional unit derived from a monomer having a reactive functional group is greater than 0 mass% and 1.0 mass% or less with respect to the total constitutional units of the specific (meth)acrylic polymer (B), more preferably contains no constitutional unit derived from a monomer having a reactive functional group, or the content rate of the constitutional unit derived from a monomer having a reactive functional group is greater than 0 mass% and 0.5 mass% or less with respect to the total constitutional units of the specific (meth)acrylic polymer (B), and further preferably contains no constitutional unit derived from a monomer having a reactive functional group.

[0165] < Constitutional unit derived from other monomers >

[0166] The specific (meth)acrylic polymer (B) can contain a constitutional unit derived from a monomer other than the t-butyl methacrylate, the monomer having a reactive functional group, and any one of the (meth)acrylic alkyl ester monomers (so-called other monomers).

[0167] As the constitutional unit derived from other monomers, there can be mentioned a constitutional unit derived from a (meth)acrylic ester having an aromatic ring represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; a constitutional unit derived from an alkoxyalkyl (meth)acrylate represented by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; a constitutional unit derived from an aromatic monovinyl represented by styrene, a-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; a constitutional unit derived from a vinyl cyanide represented by acrylonitrile and methacrylonitrile; a constitutional unit derived from a vinyl ester represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; and the like.

[0168] The specific (meth)acrylic polymer (B) can contain a constitutional unit derived from a monomer other than the t-butyl methacrylate, the monomer having a reactive functional group, and any one of the (meth)acrylic alkyl ester monomers (so-called other monomers).

[0169] When the specific (meth)acrylic polymer (B) contains a constitutional unit derived from other monomers, the content rate of the constitutional unit derived from other monomers in the specific (meth)acrylic polymer (B) can be appropriately set within a range not impairing the effects of the adhesive composition of the present disclosure.

[0170] Glass transition temperature of the specific (meth)acrylic polymer (B)

[0171] The glass transition temperature (Tg) of the specific (meth)acrylic polymer (B) is 105°C to 150°C.

[0172] If the glass transition temperature of the specific (meth)acrylic polymer (B) is 105°C or higher, the formed adhesive layer can be imparted with moderate elasticity, and thus has a tendency that the processability of the adhesive layer is excellent.

[0173] The glass transition temperature of the specific (meth)acrylic polymer (B) is preferably 107°C or higher, more preferably 110°C or higher, and further preferably 113°C or higher.

[0174] In order to make the glass transition temperature of the specific (meth)acrylic polymer (B) be a temperature of more than 150°C, for example, it is considered to select an alkyl methacrylate monomer having a cyclic structure as a monomer component of the specific (meth)acrylic polymer (B). However, since the alkyl methacrylate monomer having a cyclic structure has a structure in which the volume is very large, if the specific (meth)acrylic polymer (B) contains a constitutional unit from the alkyl methacrylate monomer having a cyclic structure, the compatibility with the specific (meth)acrylic polymer (A) decreases, and the transparency of the adhesive layer is easily impaired. In contrast to this, if the glass transition temperature of the specific (meth)acrylic polymer (B) is 150°C or lower, it is not necessary to excessively contain a constitutional unit from the alkyl methacrylate monomer having a cyclic structure in the specific (meth)acrylic polymer (B) in order to adjust the glass transition temperature, and thus there is a tendency that the compatibility of the specific (meth)acrylic polymer (A) with the specific (meth)acrylic polymer (B) does not easily decrease, and the transparency of the adhesive layer is not easily impaired.

[0175] The glass transition temperature of the specific (meth)acrylic polymer (B) is preferably 140°C or lower, and more preferably 135°C or lower.

[0176] In one mode, the glass transition temperature of the specific (meth)acrylic polymer (B) can be 105°C to 140°C, can be 107°C to 140°C, can be 110°C to 135°C, and can be 113°C to 135°C.

[0177] The glass transition temperature of the specific (meth)acrylic polymer (B) is calculated by the same method as the calculation of the glass transition temperature of the specific (meth)acrylic polymer (A) described above.

[0178] The glass transition temperature of the specific (meth) acrylic polymer (B) can be made a desired value by appropriately selecting the kind and ratio of monomers that are polymerization components of the specific (meth) acrylic polymer (B), for example.

[0179] <<Specific (Meth) Acrylic Polymer (B)>>

[0180] The weight average molecular weight (Mw) of the specific (meth) acrylic polymer (B) is 100,000 or more and less than 500,000.

[0181] If the weight average molecular weight of the specific (meth) acrylic polymer (B) is 100,000 or more, the specific (meth) acrylic polymer (B) can impart appropriate cohesion to the adhesive layer formed, and thus the adhesive layer tends to have excellent processability.

[0182] The weight average molecular weight of the specific (meth) acrylic polymer (B) is preferably 130,000 or more, more preferably 200,000 or more, and further preferably 250,000 or more.

[0183] If the weight average molecular weight of the specific (meth) acrylic polymer (B) is less than 500,000, the specific (meth) acrylic polymer (A) and the specific (meth) acrylic polymer (B) having a small weight average molecular weight tend to form an entangled structure, and thus the adhesive layer tends to have excellent transparency.

[0184] The weight average molecular weight of the specific (meth) acrylic polymer (B) is preferably 470,000 or less, more preferably 440,000 or less, and further preferably 400,000 or less.

[0185] In one mode, the weight average molecular weight of the specific (meth) acrylic polymer (B) can be 130,000 to 470,000, 200,000 to 440,000, or 250,000 to 400,000.

[0186] The weight average molecular weight of the specific (meth) acrylic polymer (B) is measured by the same method as the measurement method of the weight average molecular weight of the specific (meth) acrylic polymer (A) described above.

[0187] The weight average molecular weight of the specific (meth) acrylic polymer (B) can be made a desired value by adjusting the polymerization temperature, the polymerization time, the amount of organic solvent used, the kind of polymerization initiator, the amount of polymerization initiator used, and the like when the monomers are polymerized.

[0188] <<Content of Specific (Meth) Acrylic Polymer (B)>>

[0189] The content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 1 to 40 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic polymer (A).

[0190] If the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 1 mass part or more relative to 100 mass parts of the specific (meth) acrylic polymer (A), the adhesive layer formed can be imparted with moderate elasticity, and thus there is a tendency that the processability of the adhesive layer is excellent.

[0191] The content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is preferably 2 mass parts or more, more preferably 4 mass parts or more, and further preferably 6 mass parts or more relative to 100 mass parts of the specific (meth) acrylic polymer (A).

[0192] If the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 40 mass parts or less relative to 100 mass parts of the specific (meth) acrylic polymer (A), the adhesive layer formed can not be imparted with excessively high elasticity, and thus the stress generated in the adhesive layer at the time of peeling from the adherend can be appropriately relaxed. Thus, there is a tendency that the reworkability of the adhesive layer is excellent.

[0193] The content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is preferably 35 mass parts or less, more preferably 32 mass parts or less, and further preferably 30 mass parts or less relative to 100 mass parts of the specific (meth) acrylic polymer (A).

[0194] In one mode, the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure can be 2 mass parts to 35 mass parts, can be 4 mass parts to 35 mass parts, can be 6 mass parts to 32 mass parts, and can be 6 mass parts to 30 mass parts relative to 100 mass parts of the specific (meth) acrylic polymer (A).

[0195] In the present disclosure, the "total solid content amount in the adhesive composition" means the total mass of the adhesive composition in the case where the adhesive composition does not contain a solvent, and means the mass of the residue obtained by removing the solvent from the adhesive composition in the case where the adhesive composition contains a solvent.

[0196] [Method for producing specific (meth) acrylic polymer]

[0197] The method for producing the specific (meth) acrylic polymer (A) and the specific (meth) acrylic polymer (B) (i.e., the specific (meth) acrylic polymer) is not particularly limited.

[0198] The specific (meth)acrylic polymer can be produced, for example, by a known polymerization method such as a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method, by polymerizing the above-described monomers. As the polymerization method, the solution polymerization method is preferable in view of the fact that the process is simple and can be performed in a short time when the adhesive composition of the present disclosure is prepared after production.

[0199] In the solution polymerization method, a prescribed organic solvent, a monomer, a polymerization initiator, and a chain transfer agent, if used, are generally charged into a polymerization tank, and the reaction is performed, for example, by heating while stirring at the reflux temperature of the organic solvent for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and the chain transfer agent, if used, can be added successively. The reaction can be performed in a stream of nitrogen.

[0200] As the organic solvent used in the polymerization reaction, for example, an aromatic hydrocarbon compound, an aliphatic hydrocarbon compound, an alicyclic hydrocarbon compound, an ester compound, a ketone compound, a glycol ether compound, and an alcohol compound can be mentioned.

[0201] More specifically, as the organic solvent used in the polymerization reaction, for example, an aromatic hydrocarbon compound represented by benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; an aliphatic or alicyclic hydrocarbon compound represented by n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, naphtha, and turpentine; an ester compound represented by methyl acetate, ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; a ketone compound represented by acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; a glycol ether compound represented by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and an alcohol compound represented by methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and t-butanol can be mentioned.

[0202] In the production of the specific (meth)acrylic polymer, it is preferable to use an organic solvent such as an aromatic hydrocarbon compound, an ester compound, and a ketone compound, which is less likely to cause chain transfer in the polymerization reaction, and it is particularly preferable to use methyl acetate and ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic polymer, the easiness of the polymerization reaction, and the like.

[0203] One kind of organic solvent can be used alone, or two or more kinds of organic solvents can be used in the polymerization reaction.

[0204] As the polymerization initiator, for example, organic peroxides and azo compounds used in the usual solution polymerization method can be mentioned.

[0205] As specific examples of the organic peroxides, t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxyneopentanoate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-pentylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane can be mentioned.

[0206] As specific examples of the azo compounds, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and dimethyl 2,2'-azobis(isobutyrate) can be mentioned.

[0207] At the polymerization reaction, one kind of polymerization initiator can be used alone, or two or more kinds can be used.

[0208] The amount of the polymerization initiator used is not particularly limited, and can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer targeted.

[0209] At the production of the specific (meth)acrylic polymer, a chain transfer agent can be used as needed.

[0210] As the chain transfer agent, for example, cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, aromatic compounds represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, halogenated hydrocarbon compounds represented by carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds represented by chloral and furfural, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds represented by thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds represented by pinene and terpinolene can be given.

[0211] In the production of the specific (meth)acrylic polymer, the amount of the chain transfer agent used is not particularly limited, and can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer targeted.

[0212] The polymerization temperature is not particularly limited, and can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer targeted.

[0213] 〔Crosslinking agent〕

[0214] The adhesive composition of the present disclosure contains a crosslinking agent.

[0215] The kind of the crosslinking agent is not particularly limited.

[0216] As the crosslinking agent, for example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents can be given.

[0217] In the present disclosure, the "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate-based compound). In addition, the "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called di-functional or more epoxy-based compound). In addition, the "metal chelate-based crosslinking agent" refers to a metal chelate-based compound that functions as a crosslinking agent. In addition, the "aziridine-based crosslinking agent" refers to a compound having two or more aziridine groups in one molecule (so-called polyaziridine-based compound).

[0218] The crosslinking agent preferably contains at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents, more preferably contains an isocyanate-based crosslinking agent, further preferably is an isocyanate-based crosslinking agent.

[0219] As the isocyanate-based crosslinking agent, for example, aliphatic polyisocyanate-based compounds, alicyclic polyisocyanate-based compounds, and aromatic polyisocyanate-based compounds can be given.

[0220] The "aliphatic polyisocyanate-based compound" includes, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol-based compounds, and biuret bodies of aliphatic polyisocyanate compounds. As specific examples of the aliphatic polyisocyanate compounds, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate can be given.

[0221] The "aliphatic polyisocyanate-based compound" includes, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol-based compounds, and biuret bodies of aliphatic polyisocyanate compounds. As specific examples of the aliphatic polyisocyanate compounds, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate can be given.

[0222] The "aromatic polyisocyanate-based compound" includes, for example, aromatic polyisocyanate compounds, polymers of aromatic polyisocyanate compounds, adducts of aromatic polyisocyanate compounds and polyol-based compounds, and biuret bodies of aromatic polyisocyanate compounds. As specific examples of the aromatic polyisocyanate compounds, toluene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate can be given.

[0223] The isocyanate-based crosslinking agent is preferably an aromatic polyisocyanate-based compound, more preferably at least one selected from the group consisting of toluene diisocyanate-based compounds and xylylene diisocyanate-based compounds, further preferably a toluene diisocyanate-based compound.

[0224] The "toluene diisocyanate-based compound" includes, for example, TDI, polymers of TDI, adducts of TDI and polyol-based compounds, and biuret bodies of TDI. As the toluene diisocyanate-based compound, an adduct of TDI and TMP is preferred.

[0225] The "xylylene diisocyanate-based compound" includes, for example, XDI, a polymer of XDI, an adduct of XDI with a polyol-based compound, and a bisurea of XDI. As the xylylene diisocyanate-based compound, an adduct of XDI with TMP is preferred.

[0226] As the isocyanate-based crosslinking agent, a commercially available product can be used.

[0227] Examples of the commercially available product as the isocyanate-based crosslinking agent include "COLONATE HX", "COLONATE HK", "COLONATE HL", "COLONATE HL-S", "COLONATE 2031", "COLONATE 2037", "COLONATE 2234", "COLONATE 2770", "COLONATE 2785", "COLONATE 2793", "Aquanate 200", and "Aquanate 210" (all manufactured by Nippon Shokubai Co., Ltd.), "Sumidur N75", "Sumidur N3300", "Desmodur N75 MPA / X", "Desmodur N100", "Desmodur N3200", and "Desmodur N3400" (all manufactured by Sumika Covestro Urethane Co., Ltd.), "DURANATE D201", "DURANATE E405-70B", "DURANATE E405-80T", "DURANATE AE700-100", "DURANATE 24A-100", "DURANATE TSE-100", and "DURANATE TMA-100" (all manufactured by Asahi / Kasei Corporation), and "TAKENATE D-101E", "TAKENATE D-110N", "TAKENATE D-120N", "TAKENATE D-140N", "TAKENATE D-160N", "TAKENATE D-172N", "TAKENATE M-631N", "MT-OLESTER NP1200", and "STABIO XD-340N" (all manufactured by Mitsui Chemicals, Inc.).

[0228] All of the above "COLONATE", "Aquanate", "Sumidur", "Desmodur", "DURANATE", "TAKENATE", "OLESTER", and "STABIO" are registered trademarks.

[0229] As the epoxy-based compound having a functionality of two or more, for example, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris(glycidyl)isocyanurate, tris(epoxypropoxyethyl)isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-1,3-benzenedi(methane amine), and 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate can be given.

[0230] As the epoxy-based crosslinking agent, a commercially available product can be used.

[0231] As examples of the commercially available product of the epoxy-based crosslinking agent, "TETRAD-X" and "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Company, Inc.), "DENACOL EX-201" and "DENACOL EX-931" (manufactured by Nagase Chemtex Corporation), and CELLOXIDE 2021P (manufactured by Daicel Corporation) can be given.

[0232] Each of the above "TETRAD", "DENACOL", and "CELLOXIDE" is a registered trademark.

[0233] The adhesive composition of the present disclosure can contain one crosslinking agent alone, or two or more.

[0234] The content of the crosslinking agent in the adhesive composition of the present disclosure is not particularly limited, and, for example, relative to 100 parts by mass of the specific (meth)acrylic polymer (A), it is preferably from 0.05 parts by mass to 15 parts by mass, more preferably from 0.07 parts by mass to 10 parts by mass, and further preferably from 0.1 parts by mass to 8 parts by mass.

[0235] The content of the crosslinking agent in the adhesive composition of the present disclosure is 0.05 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic polymer (A) means that the adhesive composition of the present disclosure positively contains the crosslinking agent. If the adhesive composition of the present disclosure contains the crosslinking agent, the crosslinking reaction of the specific (meth)acrylic polymer (A) proceeds, and the cohesive force can be imparted to the adhesive layer formed. Thus, there is a tendency that the processability of the adhesive layer is excellent. In addition, since the adhesive layer is imparted with the cohesive force, the cohesive failure is less likely to occur. Thus, there is a tendency that the reworkability of the adhesive layer is excellent.

[0236] If the content of the crosslinking agent in the adhesive composition of the present disclosure is 15 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic polymer (A), there is a tendency that the transparency decrease due to the excess crosslinking agent is less likely to occur.

[0237] [Organic solvent]

[0238] The adhesive composition of the present disclosure can contain an organic solvent.

[0239] If the adhesive composition of the present disclosure contains an organic solvent, the coatability can be improved.

[0240] As the organic solvent, for example, the same organic solvent as used at the time of the polymerization reaction of the above-described specific (meth)acrylic polymer can be cited.

[0241] When the adhesive composition of the present disclosure contains an organic solvent, one kind of organic solvent alone can be contained, or two or more kinds of organic solvents can be contained.

[0242] When the adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited, and can be appropriately set according to the purpose.

[0243] [Other components]

[0244] The adhesive composition of the present disclosure can contain a component other than the above-described components (so-called other component) as necessary within a range not impairing the effects thereof.

[0245] As the other component, various additives such as a polymer other than the specific (meth)acrylic polymer, a silane coupling agent, a release adjusting agent (for example, silicone oil), a crosslinking catalyst, an antioxidant, a colorant (for example, a dye and a pigment), a light stabilizer (for example, an ultraviolet absorber), and an antistatic agent can be cited.

[0246] When the adhesive composition of the present disclosure contains an other component, the content of the other component can be appropriately set within a range not impairing the effects of the adhesive composition of the present disclosure.

[0247] <<Use of the adhesive composition>>

[0248] The use of the adhesive composition of the present disclosure is not particularly limited.

[0249] The adhesive composition of the present disclosure is suitable as an adhesive composition used in an optical film (i.e., an optical film adhesive composition), particularly as an adhesive composition used for a polarizing plate in an optical film (i.e., a polarizing plate adhesive composition), since it is capable of forming an adhesive layer excellent in processability, transparency, and reworkability.

[0250] As a specific use of the adhesive composition of the present disclosure, there can be mentioned a use for bonding a polarizing plate to a glass substrate (e.g., a glass substrate of a liquid crystal cell), a use for bonding optical films to each other, and the like.

[0251] [Adhesive sheet]

[0252] The adhesive sheet of the present disclosure is provided with an adhesive layer formed of the adhesive composition of the present disclosure.

[0253] The adhesive sheet of the present disclosure also includes a sheet-shaped adhesive layer itself formed of the adhesive composition of the present disclosure.

[0254] The adhesive layer provided in the adhesive sheet of the present disclosure contains a cured product of the adhesive composition of the present disclosure.

[0255] The cured product contains, for example, a crosslinked product of the specific (meth)acrylic polymer (A) which is crosslinked and cured by a crosslinking agent.

[0256] Since the adhesive sheet of the present disclosure is provided with the adhesive layer formed of the above-described adhesive composition of the present disclosure, it tends to be excellent in processability, transparency, and reworkability.

[0257] The thickness of the adhesive layer provided in the adhesive sheet of the present disclosure is not particularly limited.

[0258] The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0259] The "thickness of the adhesive layer" in the present disclosure refers to the average thickness of the adhesive layer.

[0260] The average thickness of the adhesive layer is a value obtained by the following method.

[0261] The thickness of 10 sites randomly selected in the thickness direction of the adhesive layer is measured using a film thickness meter. The arithmetic mean of the measured values is calculated, and the obtained value is taken as the average thickness of the adhesive layer.

[0262] The adhesive sheet of the present disclosure can be an adhesive sheet of a substrate-free type that does not have a substrate, or an adhesive sheet of a substrate type that has an adhesive layer on one or both surfaces of a substrate.

[0263] When the adhesive sheet of the present disclosure is an adhesive sheet of a substrate-free type that does not have a substrate, or an adhesive sheet of a substrate type that has an adhesive layer on one surface of a substrate, the surface of the exposed adhesive layer in the adhesive sheet of the present disclosure can be protected by a release sheet.

[0264] In general, a release sheet protects the surface of the adhesive layer before the adhesive sheet is put to practical use, and is peeled off at the time of use.

[0265] The release sheet is not particularly limited as long as it can be easily peeled off from the adhesive layer.

[0266] As the release sheet, for example, a resin film, paper, synthetic paper, and a composite sheet obtained by laminating two or more of these can be cited, which have been subjected to surface treatment (so-called easy-peeling treatment) on one or both surfaces with a release treatment agent.

[0267] In the present disclosure, the release sheet of the type in which one or both surfaces of a resin film have been subjected to surface treatment (so-called easy-peeling treatment) with a release treatment agent is referred to as a "release film".

[0268] As the release treatment agent, for example, a silicone-based release treatment agent (for example, silicone), a wax-based release treatment agent (for example, paraffin wax), and a fluorine-based release treatment agent (for example, fluorine-based resin) can be cited.

[0269] As the resin film, for example, a polyester film represented by a polyethylene terephthalate (PET) film can be cited.

[0270] As the paper, for example, high-quality paper and art paper can be cited.

[0271] The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm.

[0272] When the adhesive sheet of the present disclosure has a substrate, the substrate is not particularly limited as long as it can form an adhesive layer thereon.

[0273] As the substrate, for example, a film of a resin including a polyolefin-based resin (for example, polyethylene (PE) and polypropylene (PP)), a polyester-based resin (for example, polyethylene terephthalate (PET)), an acetate-based resin (for example, triacetyl cellulose), a polyether sulfone-based resin, a polycarbonate-based resin, a polyamide-based resin, a polyimide-based resin, a polyurethane-based resin, a (meth)acrylic-based resin, a vinyl chloride-based resin, an ABS (Acrylonitrile Butadiene Styrene) resin, a fluorine-based resin, and the like can be cited.

[0274] From the viewpoint of improving the adhesion of the base material to the adhesive layer, surface treatment (so-called easy-adhesion treatment) such as corona discharge treatment or plasma discharge treatment can be performed on the surface of the side of the base material on which the adhesive layer is provided.

[0275] The base material can contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like.

[0276] A pattern can be applied to part or the entirety of the base material.

[0277] When the adhesive sheet of the present disclosure has a base material, the base material is preferably an optical film. In this case, as a mode of the adhesive sheet of the present disclosure, a mode having an optical film and an adhesive layer provided on at least one surface of the optical film and formed of the adhesive composition of the present disclosure is preferable.

[0278] The type of the optical film is not particularly limited.

[0279] As specific examples of the optical film, a polarizing plate, an AG (Anti-Glare) polarizing plate, a wavelength plate (e.g., a 1 / 2 wavelength plate and a 1 / 4 wavelength plate), a phase difference film including the above-described wavelength plate, a viewing angle compensation film, an optical compensation film, a brightness improvement film, a light guide plate, a reflective film, an antireflection film, a prism sheet, a lens sheet, a diffusion plate, and a transparent conductive film can be given.

[0280] As the optical film, a polarizing plate (so-called polarizing film) is preferable.

[0281] The polarizing plate is constituted of at least a polarizer, and can be a single polarizer or a structure in which a polarizer and a protective film are stacked. That is, the polarizing plate can be a 1-layer structure of a single polarizer, a 2-layer structure having a protective film on one surface of the polarizer, or a 3-layer structure having protective films on both surfaces of the polarizer.

[0282] As a mode of the layer constitution when the adhesive sheet of the present disclosure has a base material and the base material is a polarizing plate, for example, a mode such as an adhesive layer / polarizing plate [protective film / polarizer], an adhesive layer / polarizing plate [protective film / polarizer / protective film], an adhesive layer / polarizing plate [phase difference film / polarizer], an adhesive layer / polarizing plate [phase difference film / polarizer / protective film], an adhesive layer / polarizing plate [phase difference film / protective film / polarizer], an adhesive layer / polarizing plate [phase difference film / protective film / polarizer / protective film], an adhesive layer / polarizing plate [polarizer / brightness improvement film], an adhesive layer / polarizing plate [protective film / polarizer / brightness improvement film], an adhesive layer / polarizing plate [polarizer / protective film / brightness improvement film], an adhesive layer / polarizing plate [protective film / polarizer / protective film / brightness improvement film], and the like can be given.

[0283] The protective film can use, for example, a film containing a resin such as triacetyl cellulose (TAC), polycycloolefin (COP), polyethylene terephthalate (PET), and polymethyl methacrylate (PMMA).

[0284] The polarizer can use, for example, a stretched film of polyvinyl alcohol (PVA) impregnated with iodine.

[0285] The phase difference film can use, for example, a film containing a resin such as polycycloolefin (COP).

[0286] The thickness of the substrate (preferably, the optical film) is not particularly limited, and is preferably, for example, 10 μm to 300 μm, more preferably 10 μm to 200 μm, and further preferably 10 μm to 100 μm.

[0287] The "thickness of the substrate" in the present disclosure refers to the average thickness of the substrate.

[0288] The average thickness of the substrate is a value obtained by the following method.

[0289] The thickness of 10 sites randomly selected in the thickness direction of the substrate is measured using a film thickness gauge. The arithmetic mean of the measured values is calculated, and the obtained value is used as the average thickness of the substrate.

[0290] [Method for producing an adhesive sheet]

[0291] The method for producing the adhesive sheet of the present disclosure is not particularly limited.

[0292] The adhesive sheet of the present disclosure can be produced by a publicly known method.

[0293] As the method for producing the adhesive sheet of the present disclosure, for example, the following methods can be given.

[0294] When the adhesive sheet of the present disclosure is a substrate-free type adhesive sheet, first, a coating film is formed on a release sheet by applying the adhesive composition of the present disclosure to the easy release-treated surface of the release sheet. Next, the formed coating film is dried, thereby forming an adhesive film on the release sheet. Subsequently, the exposed surface of the formed adhesive film is laminated to the easy release-treated surface of a release sheet prepared separately, and, if necessary, aging is performed, thereby producing the adhesive sheet of the present disclosure having a layered structure of release sheet / adhesive layer / release sheet.

[0295] When the adhesive sheet of the present disclosure is an adhesive sheet having a substrate, first, a coating film is formed on the substrate by applying the adhesive composition of the present disclosure to one face of the substrate (preferably the easy-adhesion-treated face). Next, the formed coating film is dried, whereby an adhesive film is formed on the substrate. Next, after the exposed face of the formed adhesive film is laminated to the easy-peeling-treated face of the release sheet, aging is performed as necessary, whereby the adhesive sheet of the present disclosure having a layered structure of substrate / adhesive layer / release sheet can be produced.

[0296] When the adhesive sheet of the present disclosure is an adhesive sheet having a substrate, as another method, for example, the following method can be mentioned. A coating film is formed on the release sheet by applying the adhesive composition of the present disclosure to the easy-peeling-treated face of the release sheet. Next, the formed coating film is dried, whereby an adhesive film is formed on the release sheet. Next, after the exposed face of the formed adhesive film is laminated to one face of the substrate (preferably the easy-adhesion-treated face), aging is performed as necessary, whereby the adhesive sheet of the present disclosure having a layered structure of substrate / adhesive layer / release sheet can be produced.

[0297] The method of applying the adhesive composition is not particularly limited.

[0298] As the method of applying the adhesive composition, for example, the publicly known methods using a gravure coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, a bar coater, an applicator, and the like can be mentioned.

[0299] The application amount of the adhesive composition is not particularly limited, and can be appropriately set depending on the thickness of the adhesive layer to be formed.

[0300] The method of drying the coating film is not particularly limited.

[0301] As the method of drying the coating film, for example, the methods of natural drying, heating drying, hot air drying, vacuum drying, and the like can be mentioned.

[0302] The drying temperature and the drying time of the coating film are not particularly limited, and can be appropriately set depending on the thickness of the coating film, the amount of the solvent contained in the coating film, and the like.

[0303] As the drying conditions, for example, the conditions of drying using a hot air circulating type drier by blowing air at 60°C to 130°C at a wind speed of 3 m / sec to 5 m / sec for 30 seconds to 300 seconds can be mentioned.

[0304] As the method of aging, for example, the method of standing for 2 days to 7 days in an environment having an air temperature of 20°C to 35°C and a relative humidity of 45% to 65% can be mentioned.

[0305] [Optical member]

[0306] The optical member of the present disclosure has, in order, a glass substrate, an adhesive layer formed of the adhesive composition of the present disclosure, and an optical film.

[0307] The optical member of the present disclosure is less likely to cause a decrease in transparency due to the adhesive layer. In addition, in the optical member of the present disclosure, the optical film can be easily peeled from the glass substrate without causing a residue.

[0308] The thickness of the glass substrate is not particularly limited, and is generally 0.3 mm to 0.7 mm, preferably 0.3 mm to 0.5 mm.

[0309] As the glass substrate, for example, a soda glass plate, an alkali-free glass plate, and a glass plate with an ITO (Indium Tin Oxide) film can be given.

[0310] The adhesive layer and the optical film in the optical member of the present disclosure have the same meanings as the adhesive layer and the optical film in the adhesive sheet of the present disclosure, and the preferred modes are also the same, and thus the description is omitted here.

[0311] The optical member of the present disclosure can be used, for example, as a component of a display device.

[0312] As the display device, for example, a liquid crystal display and an organic EL (Electro-Luminescence) display can be given.

[0313] The method for producing the optical member of the present disclosure is not particularly limited.

[0314] The optical member of the present disclosure can be produced, for example, by using an optical film as a substrate, producing the adhesive sheet of the present disclosure by the above-described method, and then adhering the adhesive layer of the adhesive sheet to a glass substrate.

[0315] [Display device]

[0316] The display device of the present disclosure has the optical member of the present disclosure.

[0317] The display device of the present disclosure is less likely to cause a decrease in transparency due to the adhesive layer.

[0318] The display device is specifically as described above.

[0319] Examples

[0320] Hereinafter, the adhesive composition of the present disclosure will be described more specifically using examples. The present disclosure is not limited to the following examples as long as it does not exceed the gist thereof

[0321] [Production of (meth)acrylic polymer (A)]

[0322] [Production Example A-1]

[0323] In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a reflux cooler, n-butyl acrylate (n-BA) 77.7 parts by mass, phenoxyethyl acrylate (PHEA) 18.0 parts by mass, acrylic acid (AA) 1.5 parts by mass, 2-hydroxyethyl acrylate (2HEA) 2.8 parts by mass, ethyl acetate [organic solvent] 110.0 parts by mass, and methyl acetate [organic solvent] 20.0 parts by mass were put in and mixed, and after obtaining a mixture, the inside of the reactor was replaced with nitrogen. Subsequently, the mixture in the reactor was warmed to 70°C while being stirred. Subsequently, after 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] 0.01 parts by mass and ethyl acetate 30.0 parts by mass were added to the mixture in the reactor in this order, the polymerization reaction was completed in 6 hours. Subsequently, after the solution obtained by completing the polymerization reaction was diluted with ethyl acetate to a solid content concentration of 25.0% by mass, it was cooled to obtain a solution of the (meth)acrylic polymer A-1.

[0324] The "solid content concentration" referred to herein means the mass ratio of the (meth)acrylic polymer A-1 in the solution of the (meth)acrylic polymer A-1. The same applies to each of the solutions of the (meth)acrylic polymers A-2 to A-11 manufactured below.

[0325] [Manufacturing Examples A-2 to A-5]

[0326] In Manufacturing Examples A-2 to A-5, at least one of the amount of use of the organic solvent and the amount of use of the polymerization initiator was adjusted so that the weight average molecular weight of the (meth)acrylic polymer (A) would be the weight average molecular weight shown in Table 1, and the same operation as in Manufacturing Example A-1 was performed to obtain each of the solutions of the (meth)acrylic polymers A-2 to A-5 having a solid content concentration of 25.0% by mass.

[0327] [Manufacturing Examples A-6 to A-11]

[0328] In Manufacturing Examples A-6 to A-11, the monomer composition of the (meth)acrylic polymer (A) was changed to the monomer composition shown in Table 1, and at least one of the amount of use of the organic solvent and the amount of use of the polymerization initiator was adjusted so that the weight average molecular weight of the (meth)acrylic polymer (A) would be the weight average molecular weight shown in Table 1, and the same operation as in Manufacturing Example A-1 was performed to obtain each of the solutions of the (meth)acrylic polymers A-6 to A-11 having a solid content concentration of 25.0% by mass.

[0329] The monomer composition [unit: % by mass], the glass transition temperature (expressed as "Tg"), and the weight average molecular weight (expressed as "Mw") of the (meth)acrylic polymers A-1 to A-11 are shown in Table 1.

[0330] The glass transition temperature of the (meth)acrylic polymers A-1 to A-11 is obtained by the same method as that for the glass transition temperature of the specific (meth)acrylic polymer (A) described above.

[0331] The weight average molecular weight of the (meth)acrylic polymers A-1 to A-11 is measured by the same method as that for the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0332] Among the (meth)acrylic polymers A-1 to A-11, the (meth)acrylic polymers A-1 to A-4 and A-6 to A-10 belong to the specific (meth)acrylic polymer (A) in the present disclosure.

[0333] [Table 1]

[0334]

[0335] The details of each monomer described in Table 1 are shown below.

[0336] <Monomers having a reactive functional group>

[0337] "AA": Acrylic acid (reactive functional group: carboxyl group)

[0338] "2HEA": 2-Hydroxyethyl acrylate (reactive functional group: hydroxyl group)

[0339] <(Meth)acrylic acid alkyl ester monomers>

[0340] "n-BA": n-Butyl acrylate

[0341] "MA": Methyl acrylate

[0342] "MMA": Methyl methacrylate

[0343] <Other monomers>

[0344] "PHEA": Phenoxyethyl acrylate

[0345] In Table 1, "-" described in the monomer composition column means that no monomer belonging to the column is used.

[0346] [Production of (Meth)acrylic Polymer (B)]

[0347] [Production Example B-2]

[0348] A reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux cooler was charged with 16.9 parts by mass of t-butyl methacrylate (t-BMA), 3.0 parts by mass of methyl methacrylate (MMA), 0.08 parts by mass of 2-hydroxyethyl methacrylate (2HEMA), 0.01 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator], 25.0 parts by mass of ethyl acetate [organic solvent], and 2.5 parts by mass of methyl acetate [organic solvent], and mixed, and then the inside of the reaction vessel was replaced with nitrogen. Subsequently, the mixture in the reaction vessel was warmed to 70°C while being stirred. Subsequently, 67.7 parts by mass of t-butyl methacrylate (t-BMA), 12.0 parts by mass of methyl methacrylate (MMA), 0.32 parts by mass of 2-hydroxyethyl methacrylate (2HEMA), 0.1 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator], 90.0 parts by mass of ethyl acetate [organic solvent], and 10.0 parts by mass of methyl acetate [organic solvent] were added to the mixture in the reaction vessel, and after 6 hours, the polymerization was completed. Subsequently, the solution obtained by completing the polymerization was diluted with ethyl acetate to a solid content concentration of 35.0% by mass, and then cooled to obtain a solution of the (meth)acrylic polymer B-2.

[0349] The "solid content concentration" referred to herein means the mass ratio of the (meth)acrylic polymer B-2 in the solution of the (meth)acrylic polymer B-2. The same applies to the solutions of the (meth)acrylic polymers B-1 and B-3 to B-18 manufactured below.

[0350] [Manufacturing Examples B-1, B-3 to B-7, B-10, and B-12]

[0351] In the manufacturing examples B-1, B-3 to B-7, B-10, and B-12, the monomer composition of the (meth)acrylic polymer (B) was changed to the monomer composition shown in Table 2, and otherwise the same operations as in the manufacturing example B-2 were performed to obtain a solution of each of the (meth)acrylic polymers B-1, B-3 to B-7, B-10, and B-12 having a solid content concentration of 35.0% by mass.

[0352] [Manufacturing Examples B-8, B-9, B-11, B-17, and B-18]

[0353] In Production Examples B-8, B-9, B-11, B-17, and B-18, the monomer composition of the (meth)acrylic polymer (B) was changed to the monomer composition shown in Table 2, and at least one of the amount of use of the organic solvent and the amount of use of the polymerization initiator was adjusted so that the weight average molecular weight of the (meth)acrylic polymer (B) was the weight average molecular weight shown in Table 2, and otherwise the same operation as in Production Example B-2 was performed to obtain each solution of the (meth)acrylic polymers B-8, B-9, B-11, B-17, and B-18 having a solid content concentration of 35.0 mass%.

[0354] 〔Production Examples B-13 to B-16〕

[0355] In Production Examples B-13 to B-16, at least one of the amount of use of the organic solvent and the amount of use of the polymerization initiator was adjusted so that the weight average molecular weight of the (meth)acrylic polymer (B) was the weight average molecular weight shown in Table 2, and otherwise the same operation as in Production Example B-2 was performed to obtain each solution of the (meth)acrylic polymers B-13 to B-16 having a solid content concentration of 35.0 mass%.

[0356] The monomer composition (unit: mass%), the glass transition temperature (expressed as "Tg"), and the weight average molecular weight (expressed as "Mw") of the (meth)acrylic polymers B-1 to B-18 are shown in Table 2.

[0357] The glass transition temperature of the (meth)acrylic polymers B-1 to B-18 was calculated by the same method as that for calculating the glass transition temperature of the specific (meth)acrylic polymer (A) described above.

[0358] The weight average molecular weight of the (meth)acrylic polymers B-1 to B-18 was measured by the same method as that for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0359] Among the (meth)acrylic polymers B-1 to B-18, the (meth)acrylic polymers B-2 to B-6, B-8, B-12, B-14, B-15, and B-17 belong to the specific (meth)acrylic polymer (B) in the present disclosure.

[0360] [Table 2]

[0361]

[0362] The details of each monomer described in Table 2 are shown below.

[0363] "MMA": methyl methacrylate

[0364] "t-BMA": tert-butyl methacrylate

[0365] "n-BMA": n-butyl methacrylate

[0366] "i-BMA": isobutyl methacrylate

[0367] "IBXMA": isobornyl methacrylate

[0368] "2HEMA": 2-hydroxyethyl methacrylate

[0369] In Table 2, "-" described in the column of monomer composition means that no monomer belonging to the column is used.

[0370] [Preparation of adhesive composition]

[0371] [Example 1]

[0372] A solution of the (meth)acrylic polymer A-1 400.00 parts by mass (100 parts by mass as solid content), a solution of the (meth)acrylic polymer B-2 25.71 parts by mass (9 parts by mass as solid content), TAKENATE (registered trademark) D-101E [trade name, isocyanate-based crosslinking agent, solid content concentration: 45 mass%, manufactured by Mitsui Chemicals, Inc.] 0.44 parts by mass (0.20 parts by mass as solid content) as a crosslinking agent, and an appropriate amount of ethyl acetate [organic solvent] were thoroughly mixed to obtain the adhesive composition of Example 1.

[0373] [Examples 2 to 25]

[0374] In Examples 2 to 25, the composition of the adhesive composition was changed to the composition shown in Table 3, and the same operation as in Example 1 was performed, except for this, to obtain each of the adhesive compositions of Examples 2 to 25.

[0375] [Comparative Examples 1 to 13]

[0376] In Comparative Examples 1 to 13, the composition of the adhesive composition was changed to the composition shown in Table 4, and the same operation as in Example 1 was performed, except for this, to obtain each of the adhesive compositions of Comparative Examples 1 to 13.

[0377] [Production of polarizing plate with adhesive layer]

[0378] On the easy-peeling treatment surface of a peeling film (type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation) on which a silicone-based peeling treatment agent was applied (so-called easy-peeling treatment), the above-prepared adhesive composition was applied to form a coated film. Note that the amount of the adhesive composition applied was an amount that would result in a thickness of 20 μm for the adhesive film described later. Next, the coated film formed was dried using a hot air circulating dryer (product name: automatic discharge type dryer, model number: ATO-101, manufactured by Tohshi Engineering Co., Ltd.) by blowing air at 100°C at a wind speed of 3 m / sec for 60 seconds, thereby forming an adhesive film having a thickness of 20 μm on the peeling film. Next, the exposed surface of the adhesive film formed on the peeling film was overlapped and attached to one surface of a polarizing plate (thickness: 100 μm) having a triacetyl cellulose (TAC) layer / polyvinyl alcohol (PVA) layer containing iodine / TAC layer configuration. Next, the laminate obtained by the attachment was left to stand in an environment having an atmospheric temperature of 23°C and a relative humidity of 50% for 7 days (so-called aging period), thereby aging the adhesive film. Thereby, a polarizing plate with an adhesive layer having a peeling film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) configuration was produced.

[0379] [Measurement and Evaluation]

[0380] 1. Processability

[0381] The above-prepared polarizing plate with an adhesive layer was cut to prepare test pieces having a size of 25 mm (short side) x 70 mm (long side). Next, the prepared test pieces were continuously cut into 1 mm width from the short piece side in the long side direction using a super cutter (model number: NC-600, manufactured by Kani Seimitsu Kikaku Co., Ltd.), thereby obtaining 10 cut test pieces. The cut surface of the obtained cut test pieces was observed at 5 points each using a digital microscope (model number: VHX7000, magnification: 500 times, manufactured by KEYENCE Corporation), and the proportion of the cut test pieces in which the adhesive layer protruded 20 μm or more from the polarizing plate and the peeling film was calculated. Then, the evaluation was performed according to the following evaluation criteria.

[0382] The results of the evaluation are shown in Tables 3 and 4.

[0383] In the following evaluation criteria, “A”, “B”, and “C” are levels that are practically acceptable, and “A” is most preferred.

[0384] -Evaluation Criteria-

[0385] A: The proportion of the cut test pieces in which the adhesive layer protruded 20 μm or more from the polarizing plate and the peeling film was less than 15%.

[0386] B: The proportion of the cut test pieces in which the adhesive layer protruded 20 μm or more from the polarizing plate and the peeling film was 15% or more and less than 30%.

[0387] C: The ratio of the cut test pieces in which the adhesive layer protruded from the polarizing plate and the release film by 20 μm or more was 30% or more and less than 60%.

[0388] D: The ratio of the cut test pieces in which the adhesive layer protruded from the polarizing plate and the release film by 20 μm or more was 60% or more.

[0389] 2. Transparency

[0390] 2-1. Preparation of sample for evaluation of transparency

[0391] On the easy-peeling treatment surface of the release film (type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation) which was surface-treated with an organic silicon-based release treatment agent (so-called easy-peeling treatment), the above-prepared adhesive composition was applied to form a coated film. Note that the amount of application of the adhesive composition was such that the thickness of the adhesive film described later would be 40 μm. Next, the coated film thus formed was dried using a hot air circulating type drier (product name: automatic discharge type drier, model number: ATO-101, manufactured by Tohshin Heat Technology Co., Ltd.) by blowing air at 100°C at a wind speed of 3 m / sec for 60 seconds, thereby forming an adhesive film having a thickness of 40 μm on the release film. Next, the exposed surface of the adhesive film thus formed on the release film was overlapped and attached to one surface of a PET film (trade name: COSMOSHINE (registered trademark) A4100, thickness: 100 μm, manufactured by Toyo Spinning Co., Ltd.). Next, the laminate thus obtained by the attachment was left to stand in an environment at an atmospheric temperature of 23°C and a relative humidity of 50% for 7 days (so-called curing period), to cure the adhesive film.

[0392] Thereby, a sample for evaluation of transparency having a constitution of release film / adhesive layer / PET film was prepared.

[0393] 2-2. Evaluation test

[0394] (1) Evaluation 1 (transparency)

[0395] The sample for evaluation of transparency thus prepared was cut to prepare an evaluation adhesive sheet having a size of 100 mm (short side) x 150 mm (long side). The adhesive sheet obtained by peeling the release film from the prepared evaluation adhesive sheet was used as a test piece. The haze of 5 sites randomly selected in the test piece was measured using a haze meter (model number: NDH 5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.). The obtained values were arithmetically averaged to be the haze value. Then, the evaluation was performed according to the following evaluation criteria.

[0396] The haze value and the result of the evaluation are shown in Tables 3 and 4.

[0397] In the following evaluation criteria, "A", "B", and "C" are levels that are practically allowable, and "A" is most preferred.

[0398] Evaluation Criteria

[0399] A: Haze value is less than 1.0%.

[0400] B: Haze value is 1.0% or more and less than 3.0%.

[0401] C: Haze value is 3.0% or more and less than 6.0%.

[0402] D: Haze value is 6.0% or more.

[0403] (2) Evaluation 2

[0404] The transparent evaluation sample prepared above was cut to prepare an evaluation adhesive sheet of 100 mm (short side) x 150 mm (long side) in size. The adhesive sheet obtained by peeling the release film from the prepared evaluation adhesive sheet was used as a test piece. The haze of 10 parts randomly selected in the test piece was measured using a haze meter (Model: NDH 5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.). The obtained values were divided into two groups, Group X of the 5th value from the larger value side and Group Y of the 5th value from the smaller value side. Next, the 5 values of Group X and the 5 values of Group Y were each arithmetically averaged to obtain the haze value (X) and the haze value (Y). The difference (Z) in the haze value was calculated from the haze value (X) and the haze value (Y) based on the following calculation formula. Then, the evaluation was performed according to the following evaluation criteria.

[0405] The difference (Z) in the haze value and the results of the evaluation are shown in Tables 3 and 4.

[0406] In the following evaluation criteria, "A", "B", and "C" are levels that are practically allowable, and "A" is most preferred.

[0407] Difference (Z) in the haze value = [haze value (X) - haze value (Y)]

[0408] Evaluation Criteria

[0409] A: Difference (Z) in the haze value is less than 1.0%.

[0410] B: Difference (Z) in the haze value is 1.0% or more and less than 3.0%.

[0411] C: Difference (Z) in the haze value is 3.0% or more and less than 6.0%.

[0412] D: Difference (Z) in the haze value is 6.0% or more.

[0413] In the evaluation test of transparency, in the case where the evaluation results of the above Evaluation 1 and Evaluation 2 are "A", "B" or "C", it is judged that the transparency of the adhesive layer is excellent.

[0414] 3. Processability

[0415] 3-1. Preparation of sample for processability evaluation

[0416] The above prepared polarizing plate with adhesive layer was cut to prepare a test piece Xl of 25 mm (short side) x 75 mm (long side) in size. Next, the release film was peeled from the cut test piece Xl (composition: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)) to obtain a test piece X2 (composition: adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)). Next, the exposed adhesive layer face of the test piece X2 was overlapped on one face of a soda glass plate (manufactured by Matsunami Glass Ind. Ltd.) as an adherend, and pressure bonding was performed using a laminator.

[0417] Thus, a sample for processability evaluation having a composition of adherend (soda glass plate) / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) was prepared.

[0418] 3-2. Evaluation test

[0419] The above prepared sample for processability evaluation was subjected to autoclave treatment for 20 minutes under conditions of a treatment temperature of 50°C and a treatment pressure of 5 kg / cm 2 Next, the sample for processability evaluation after autoclave treatment was left to stand for 5 hours in an atmosphere of an atmospheric temperature of 80°C, and then left to stand for 30 minutes in an atmosphere of an atmospheric temperature of 23°C and 50% RH to prepare a test piece. For this test piece, the adhesive force (unit: N / 25 mm) when the test piece X2 was peeled 90° from the adherend (soda glass plate) in the long side (75 mm) direction was measured using a single column type material tester (model: STA-1225, manufactured by A&D Co.) as a measuring device under conditions of an atmospheric temperature of 23°C and 50% RH and a peeling speed of 0.3 m / minute. Then, evaluation was performed according to the following evaluation criteria.

[0420] The measured values of the adhesive force and the results of evaluation are shown in Tables 3 and 4.

[0421] In the following evaluation criteria, "A", "B" and "C" are levels that are practically allowable, and "A" is most preferred.

[0422] - Evaluation Criteria -

[0423] A: Adhesive force is less than 14 N / 25 mm.

[0424] B: adhesive strength of 14 N / 25 mm or more and less than 16 N / 25 mm.

[0425] C: adhesive strength of 16 N / 25 mm or more and less than 18 N / 25 mm.

[0426] D: adhesive strength of 18 N / 25 mm or more, or confirmed to have a residue on the adherend.

[0427] 4. Coatability

[0428] A sample for coatability evaluation was prepared by adjusting the solid content concentration of the above-prepared adhesive composition to 25 mass% using ethyl acetate. The viscosity of the sample for coatability evaluation was measured using a BH-type rotational viscometer (Model: BHII, manufactured by Tokimec, Inc.) at a liquid temperature of 25°C and a rotational speed of 10 rpm (revolution per minute).

[0429] The measured values of the viscosity are shown in Tables 3 and 4.

[0430] The higher the measured value of the viscosity, the more likely the adhesive composition is judged to be poor in coatability.

[0431] [Table 3]

[0432]

[0433] [Table 4]

[0434]

[0435] The details of the components described in Tables 3 and 4 are shown below.

[0436] < Cross-linking agent >

[0437] "D-101E" (trade name: TAKENATE (registered trademark) D-101E, isocyanate-based cross-linking agent, trimethylolpropane (TMP) adduct of toluene diisocyanate (TDI), solid content concentration: 45 mass%, manufactured by Mitsui Chemicals, Inc.)

[0438] "D-110N" (trade name: TAKENATE (registered trademark) D-110N, isocyanate-based cross-linking agent, adduct of xylylenediisocyanate (XDI) and trimethylolpropane (TMP), solid content concentration: 75 mass%, manufactured by Mitsui Chemicals, Inc.)

[0439] "2021P" (trade name: CELLOXIDE (registered trademark) 2021P, epoxy-based cross-linking agent, 3', 4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, solid content concentration: 100 mass%, manufactured by Daicel Corporation)

[0440] <Other components>

[0441] "X-41-1810" (trade name, silane coupling agent, thiol group-containing silane compound, solid content concentration: 100 mass%, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0442] "KF-859" (trade name, release adjusting agent, silicone oil, amino group-containing silane compound, solid content concentration: 100 mass%, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0443] In Tables 3 and 4, the values described in the "blending amount" column are solid content conversion values.

[0444] In Tables 3 and 4, "-" described in the "composition of the adhesive composition" column means that no component belonging to the column is blended.

[0445] In Table 4, "residual adhesive" described in the "adhesive force of reworkability" column means that residual adhesive is confirmed on the adherend after the measurement of the adhesive force. In addition, "evaluation impossible" described in the "reworkability" column means that the adhesive layer is damaged when the adhesive layer is peeled from the adherend, and thus the evaluation is impossible.

[0446] As shown in Table 3, it was confirmed that the adhesive layer formed from the adhesive composition of the examples was excellent in processability, transparency, and reworkability. In addition, it was presumed that the viscosity of the adhesive composition of the present disclosure would not be excessively high, and the coatability would be excellent.

[0447] On the other hand, as shown in Table 4, it was confirmed that the adhesive layer formed from the adhesive composition of the comparative examples was inferior to the adhesive layer formed from the adhesive composition of the examples in at least one or more evaluation items among processability, transparency, and reworkability.

Claims

1. An adhesive composition comprising a (meth)acrylic polymer A, a (meth)acrylic polymer B, and a crosslinking agent, the (meth)acrylic polymer A has a reactive functional group, and has a weight average molecular weight of 650,000 or more and less than 1,500,000, the (meth)acrylic polymer B contains a constitutional unit derived from tert-butyl methacrylate at a proportion of 15 to 87 mass% with respect to the total constitutional units, has a glass transition temperature of 105°C to 150°C, and has a weight average molecular weight of 1,000,000 or more and less than 5,000,000, the content of the (meth)acrylic polymer B is 1 to 40 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer A.

2. The adhesive composition of claim 1, wherein, the (meth)acrylic polymer A has a glass transition temperature of -60°C to -30°C.

3. The adhesive composition of claim 1, wherein, the reactive functional group in the (meth)acrylic polymer A includes at least one of a carboxyl group and a hydroxyl group.

4. The adhesive composition of claim 1, wherein, the (meth)acrylic polymer B does not contain a constitutional unit derived from a monomer having a reactive functional group, or the content of the constitutional unit derived from a monomer having a reactive functional group is more than 0 mass% and 1.0 mass% or less with respect to the total constitutional units.

5. The adhesive composition of claim 4, wherein, the monomer having a reactive functional group in the (meth)acrylic polymer B is a monomer having a hydroxyl group.

6. An adhesive sheet provided with an adhesive layer formed of the adhesive composition according to any one of claims 1 to 5.

7. An adhesive sheet provided with an optical film and an adhesive layer, the adhesive layer is provided on at least one side of the optical film, and is formed of the adhesive composition according to any one of claims 1 to 5.

8. The adhesive sheet according to claim 7, wherein the optical film is a polarizing plate.

9. An optical member provided with a glass substrate, an adhesive layer, and an optical film in this order, the adhesive layer is formed of the adhesive composition according to any one of claims 1 to 5.

10. A display device provided with the optical member according to claim 9.

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