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

Abstract

This invention relates to an adhesive composition for optical thin films, comprising a (meth)acrylic polymer (A), a (meth)acrylic polymer (B), and a crosslinking agent. The (meth)acrylic polymer (A) has a weight-average molecular weight of 1 million or more. The (meth)acrylic polymer (B) contains constituent units derived from monomers having hydroxyl groups, with a hydroxyl content of 0.0007 mmol / g to 0.22 mmol / g, a glass transfer temperature of 0°C or higher, and a weight-average molecular weight of 30,000 to 500,000. The content of the (meth)acrylic polymer (B) is 1 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). The invention also relates to adhesive sheets, optical components, and display devices.

Description

[Technical Field]

[0001] This disclosure relates to adhesive compositions for optical thin films, adhesive sheets, optical components, and display devices. [Previous Technology]

[0002] A liquid crystal display device generally comprises a liquid crystal cell with a liquid crystal layer sandwiched between two support substrates, and optical films such as a polarizing plate, a phase retardation film, and a brightness improvement film. When manufacturing a liquid crystal display device by laminating the liquid crystal cell and the optical films, these components are bonded together with an adhesive layer formed by an adhesive composition. For the purpose of ensuring visibility, liquid crystal display devices often use (meth)acrylic acid-based adhesive compositions.

[0003] For example, Japanese Patent Application Publication No. 2002-121521 discloses an adhesive composition for polarizing films, comprising 100 parts by weight of a high molecular weight acrylic polymer with a weight average molecular weight of 1 million to 2.5 million containing reactive functional groups, 10 to 100 parts by weight of a low molecular weight acrylic polymer with a weight average molecular weight of 30,000 to 100,000 and a glass transition point of 0°C to -80°C, and 0.001 to 10 parts by weight of a multifunctional compound containing two or more functional groups that can react with the above-mentioned reactive functional groups to form a cross-linked structure. Furthermore, Japanese Patent Application Publication No. 2007-326910 discloses an adhesive composition comprising: a first polymer and a second polymer, wherein the first polymer comprises 40% to 98% by weight of a (meth)acrylate monomer (a) having a specific structural formula, and 1% to 59.9% by weight of a (meth)acrylate monomer (b) having an aromatic ring and capable of copolymerizing with the (meth)acrylate monomer (a), and having a reactive... The second polymer contains 0.1% to 5% by weight of a polymerizable monomer (c) with a functional group, and 0% to 59.9% by weight of a polymerizable monomer (d) that can copolymerize with (meth)acrylic monomer (a), (meth)acrylic monomer (b), and polymerizable monomer (c) as monomer units, and has a weight average molecular weight of 300,000 or more. The second polymer contains alkyl methacrylate as monomer units and has a weight average molecular weight of 100,000 or less. The content of the second polymer is 1 to 40 parts by weight relative to 100 parts by weight of the first polymer. Furthermore, International Publication No. 2019 / 150729 discloses an adhesive composition containing a vinyl polymer (A) and an acrylic adhesive polymer (B). The first glass transition temperature (Tg) of the entire adhesive layer formed from the adhesive composition is -80°C to 10°C. The second glass transition temperature (Tg) of the adhesive layer, calculated from its surface portion by X-ray photoelectron spectroscopy analysis, is at least 30°C higher than the first Tg. The peel strength of an adhesive sheet with a 50μm thick adhesive layer formed from the adhesive composition on a 100μm thick polyethylene terephthalate film substrate to glass at 100°C is 4.0 N / 25mm or higher. [Summary of the Invention]

[0004] [The problem that the invention aims to solve]

[0005] Optical films such as polarizing plates are typically constructed by laminating multiple components with different shrinkage rates, making them prone to dimensional changes due to variations in temperature and / or humidity. Therefore, optical films bonded together with adhesive layers can experience shrinkage, wrinkling of the adhesive layer and / or the optical film, and peeling of the adhesive layer from the substrate if placed in harsh environments such as high temperatures or repeated cycles of low and high temperatures. Furthermore, in recent years, with increasing demands for lightweight and miniaturized displays, optical films used in displays require further thinning. Because thinning reduces rigidity, optical films tend to shrink more easily than before.

[0006] However, due to the rise of bezel-less smartphones, optical films such as polarizing plates have become subject to complex cutting and processing (hereinafter referred to as "processing") in shapes other than rectangles. When processing optical films with laminated adhesive layers, adhesive layers sometimes overflow from the processing end, polluting the surrounding environment. To improve the processability of the adhesive layer, increasing its cohesive strength has been considered. However, increasing the cohesive strength of the adhesive layer hardens it, making it difficult to mitigate the stress generated by the shrinkage of the optical film. Therefore, if the shrinkage of the optical film increases, the adhesive layer cannot completely mitigate the generated stress, leading to problems such as wrinkles in the adhesive layer and / or the optical film, and peeling of the adhesive layer from the substrate. Considering the above, adhesive compositions used in optical films are required to form adhesive layers that are not prone to wrinkling and peeling even under harsh environments, and have excellent processability.

[0007] In addition, generally speaking, adhesive compositions used in optical films are required to form adhesive layers with excellent transparency. However, adhesive layers exposed to high temperatures for extended periods may sometimes experience separation of components within the adhesive layer, impairing transparency.

[0008] This disclosure arises from the consideration of the above-described situation. One embodiment of this disclosure aims to solve the problem of providing an adhesive composition for optical thin films that can form an adhesive layer that is not prone to wrinkling and peeling even when subjected to repeated low and high temperature environments, maintains excellent transparency even after prolonged exposure to high temperatures, and has excellent processability. Another embodiment of this disclosure aims to solve the problem of providing adhesive sheets, optical components, and display devices that are not prone to wrinkling and peeling even when subjected to repeated low and high temperature environments, maintain excellent transparency even after prolonged exposure to high temperatures, and have excellent processability. [Means for Solving the Problem]

[0009] Specific means to solve the problem include the following: <1> An adhesive composition for optical thin films, comprising a (meth)acrylic polymer (A), a (meth)acrylic polymer (B), and a crosslinking agent, wherein the (meth)acrylic polymer (A) has a weight average molecular weight of 1 million or more, the (meth)acrylic polymer (B) comprises a constituent unit from a monomer having a hydroxyl group, the content of the hydroxyl group is 0.0007 mmol / g to 0.22 mmol / g, the glass transfer temperature is 0°C or higher, and the weight average molecular weight is 30,000 to 500,000, and the content of the (meth)acrylic polymer (B) is 1 part by mass to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). <2> The adhesive composition for optical thin films as described in <1>, wherein the (meth)acrylic polymer (A) comprises at least one of a constituent unit from a monomer having a hydroxyl group and a constituent unit from a monomer having a carboxyl group. <3> An adhesive composition for optical films as described in <1> or <2>, wherein the content of the crosslinking agent is 0.05 to 15 parts by weight relative to 100 parts by weight of the (meth)acrylic acid polymer (A). <4> An adhesive composition for optical films as described in any one of <1> to <3>, wherein the crosslinking agent is an isocyanate-based crosslinking agent. <5> An adhesive composition for optical films as described in any one of <1> to <4> further comprises a silane coupling agent. <6> An adhesive sheet having an adhesive layer formed by an adhesive composition for optical films as described in any one of <1> to <5>. <7> An adhesive sheet as described in <6> has an optical film and an adhesive layer disposed on at least one side of the optical film, formed by an adhesive composition for optical films as described in any one of <1> to <5>. <8> As in <7>, the optical thin film is a polarizing plate. <9> An optical component comprising, in sequence: a glass substrate, an adhesive layer formed by an adhesive composition for optical thin films as described in any one of <1> to <5>, and an optical thin film. <10> A display device having the optical component as described in <9>. [Effects of the Invention]

[0010] According to one embodiment of this disclosure, an adhesive composition for optical thin films is provided, which can form an adhesive layer that is not prone to wrinkling and peeling even when subjected to repeated low and high temperature environments, and maintains excellent transparency and processability even after prolonged exposure to high temperature environments. According to other embodiments of this disclosure, an adhesive sheet, optical component, and display device are provided, which are provided with an adhesive layer that is not prone to wrinkling and peeling even when subjected to repeated low and high temperature environments, and maintains excellent transparency and processability even after prolonged exposure to high temperature environments.

Implementation Method

[0012] Hereinafter, the adhesive composition for optical thin films, adhesive sheets, optical components, and display devices disclosed herein will be described in detail. The following description of the requirements is based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. Within the scope of the purpose of the present disclosure, appropriate changes and implementations may be made.

[0013] In this disclosure, the numerical range indicated by "~" refers to the range in which the values ​​recorded before and after "~" are respectively used as lower and upper limits. In the numerical ranges recorded in stages in this disclosure, the upper or lower limit recorded in a certain numerical range can also be replaced by the upper or lower limit of the numerical range recorded in other stages. Furthermore, in the numerical ranges recorded in this disclosure, the upper or lower limit recorded in a certain numerical range can also be replaced by the values ​​represented in the embodiments.

[0014] In this disclosure, a combination of two or more preferred states is a better state.

[0015] In this disclosure, the amount of each component in the adhesive composition, when there are multiple substances in the adhesive composition corresponding to each component, refers to the total amount of the aforementioned multiple substances present in the adhesive composition, unless otherwise specified.

[0016] In this disclosure, "(meth)acrylic monomer" refers to a monomer having a (meth)acrylic group. In this disclosure, "(meth)acrylic polymer" refers to a polymer containing constituent units derived from (meth)acrylic monomers, wherein the proportion of constituent units derived from (meth)acrylic monomers is 50% by mass or more.

[0017] In this disclosure, "(meth)acrylic acid" is a term that includes both "acrylic acid" and "methacrylic acid", "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate", "(meth)acrylyl" is a term that includes both "acrylyl" and "methacrylyl", and "(meth)acrylamine" is a term that includes both "acrylamine" and "methacrylamine".

[0018] In this disclosure, "n-" refers to "positive", "i-" refers to "different", "s-" refers to "second", and "t-" refers to "third".

[0019] In this disclosure, "polymer" and "polymer" have the same meaning.

[0020] In this disclosure, the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B) are collectively referred to as "specific (meth)acrylic polymer".

[0021] [Adhesive composition for optical thin films] The adhesive composition for optical thin films disclosed herein (hereinafter also referred to as "adhesive composition") contains a (meth)acrylic polymer (A), a (meth)acrylic polymer (B), and a crosslinking agent. The (meth)acrylic polymer (A) has a weight average molecular weight of 1 million or more. The (meth)acrylic polymer (B) contains constituent units derived from monomers having hydroxyl groups. The content of hydroxyl groups is 0.0007 mmol / g to 0.22 mmol / g. The glass transfer temperature is 0°C or higher, and the weight average molecular weight is 30,000 to 500,000. The content of the (meth)acrylic polymer (B) is 1 part to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). The adhesive composition disclosed herein can form an adhesive layer that is resistant to wrinkling and peeling even under repeated exposure to low and high temperatures, maintains excellent transparency even after prolonged exposure to high temperatures, and exhibits excellent processability. While the reasons for the effectiveness of the adhesive composition disclosed herein are not yet clear, the inventors speculate as follows. However, the following speculation is not a limiting interpretation of the adhesive composition disclosed herein, but is provided as an example.

[0022] The adhesive composition disclosed herein contains a high molecular weight (meth)acrylic polymer (A) as the base polymer. By increasing the molecular weight of the base polymer, the cohesiveness of the formed adhesive layer is improved. On the other hand, while improved cohesiveness enhances processability, the adhesive layer becomes harder, making it difficult to mitigate the stress generated by the shrinkage of the optical film. Therefore, if the shrinkage of the optical film increases, the stress may become unmanageable by the adhesive layer, leading to problems such as wrinkles in the adhesive layer and / or the optical film, and peeling of the adhesive layer from the adherend. In contrast, the adhesive composition disclosed herein, in addition to the high molecular weight (meth)acrylic polymer (A) and crosslinking agent, moderately contains a (meth)acrylic polymer (B) with a higher glass transition temperature and moderate hydroxyl groups, thereby controlling the cohesiveness, viscosity, and elasticity of the formed adhesive layer and solving the aforementioned problems. It is believed that the adhesive layer formed by the adhesive composition disclosed herein constitutes an island structure of (meth)acrylic acid polymer (A) and (meth)acrylic acid polymer (B). It is believed that through the formation of this island structure, the adhesive layer exhibits a good balance of viscosity and cohesion, thus effectively mitigating the stress caused by the shrinkage of the optical film. The overall elasticity of the adhesive layer is improved, thereby suppressing overflow from the processing end face during processing. The molecular weight of the (meth)acrylic acid polymer (B) in the adhesive composition disclosed herein is lower than that of the (meth)acrylic acid polymer (A), but not excessively low, resulting in moderately strong entanglement of the polymer chains and low degree of freedom within the adhesive layer. Furthermore, the (meth)acrylic acid polymer (B) contains a moderate amount of hydroxyl groups, thus facilitating its integration into the cross-linking structure. Therefore, it is believed that even when the adhesive layer is subjected to a high-temperature environment for a long period of time, the (meth)acrylate polymer (B) in the adhesive layer is unlikely to migrate to the interface of the adhesive layer, and the decrease in transparency caused by the separation of (meth)acrylate polymer (B) and (meth)acrylate polymer (A) is unlikely to occur. Furthermore, the molecular weight of (meth)acrylate polymer (B) is moderately lower than that of (meth)acrylate polymer (A), and the content of (meth)acrylate polymer (B) is not excessive relative to the content of (meth)acrylate polymer (A), thus the compatibility between (meth)acrylate polymer (A) and (meth)acrylate polymer (B) becomes good. Therefore, it is believed that the adhesive layer formed by the adhesive composition disclosed herein is unlikely to experience a decrease in transparency caused by poor compatibility.Considering the above, it is speculated that the adhesive layer system formed by the adhesive composition disclosed herein is not prone to wrinkling and peeling even when subjected to repeated low and high temperature environments, and still has excellent transparency and good processability even after being subjected to high temperature environments for a long time.

[0023] On the other hand, Japanese Patent Application Publication No. 2002-121521, Japanese Patent Application Publication No. 2007-326910, and International Publication No. 2019 / 150729 did not focus on forming an adhesive layer that has all the properties of wrinkle and peel suppression, processability, and transparency as described above.

[0024] In addition, the adhesive layer formed by the adhesive composition disclosed herein, besides the above-mentioned effects, can also prevent wrinkles and peeling even when placed in a high-temperature environment, and can effectively suppress the shrinkage of the substrate that will occur when placed in a high-temperature environment.

[0025] In this disclosure, "(meth)acrylic polymer (A) with a weight average molecular weight of 1 million or more" is also referred to as "specific (meth)acrylic polymer (A)". In addition, in this disclosure, "(meth)acrylic polymer (B) containing constituent units derived from monomers having hydroxyl groups, with a hydroxyl content of 0.0007 mmol / g to 0.22 mmol / g, a glass transfer temperature of 0°C or more, and a weight average molecular weight of 30,000 to 500,000" is also referred to as "specific (meth)acrylic polymer (B)".

[0026] [Specific (meth)acrylic polymer (A)] The adhesive composition disclosed herein contains a (meth)acrylic polymer (A) with a weight average molecular weight of 1 million or more [that is, a specific (meth)acrylic polymer (A)]. The adhesive composition disclosed herein may contain only one specific (meth)acrylic polymer (A), or it may contain two or more.

[0027] A specific (meth)acrylic polymer (A) may be a homopolymer or a copolymer, provided that its weight average molecular weight is 1 million or more. The following will describe the constituent units that a specific (meth)acrylic polymer (A) may contain, followed by an explanation of its physical properties, such as its weight average molecular weight.

[0028] <Building Units from (Meth)acrylate Monomers> A particular (meth)acrylate polymer (A) preferably contains building units from (meth)acrylate monomers. In this disclosure, "building units from (meth)acrylate monomers" means building units formed by the addition polymerization of (meth)acrylate monomers. Furthermore, "(meth)acrylate monomers" in this disclosure does not include monomers equivalent to monomers having hydroxyl groups or monomers equivalent to monomers having carboxyl groups.

[0029] There is no particular limitation on the type of (meth)acrylate alkyl monomer. The (meth)acrylate alkyl monomer may be an acrylate monomer or a methacrylate alkyl monomer. The alkyl group in the (meth)acrylate alkyl monomer may be unsubstituted or substituent (but excluding carboxyl and hydroxyl groups), and preferably unsubstituted. The alkyl group in the (meth)acrylate alkyl monomer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the (meth)acrylate alkyl monomer is preferably 1 to 18, more preferably 1 to 12, and even more preferably 1 to 8.

[0030] Specific examples of alkyl methacrylate monomers include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, tributyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, stearyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, and isocamphenyl methacrylate. Preferably, the alkyl methacrylate monomer is selected from at least one monomer from the group consisting of n-butyl acrylate, tributyl acrylate, methyl acrylate, methyl methacrylate, and 2-ethylhexyl methacrylate.

[0031] When a certain (meth)acrylic polymer (A) contains a constituent unit derived from an alkyl methacrylate monomer, the constituent unit derived from the alkyl methacrylate monomer may contain only one type or may contain two or more types.

[0032] When a specific (meth)acrylate polymer (A) contains constituent units derived from alkyl methacrylate monomers, the content of constituent units derived from alkyl methacrylate monomers in the specific (meth)acrylate polymer (A) is not particularly limited. For example, relative to all constituent units of the specific (meth)acrylate polymer (A), 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 especially preferably 70% by mass to 98.5% by mass. Here, the content of constituent units derived from alkyl methacrylate monomers in the specific (meth)acrylate polymer (A) being 50% by mass or more relative to all constituent units of the specific (meth)acrylate polymer (A) means that the constituent units derived from alkyl methacrylate monomers are included as the main components constituting the constituent units of the specific (meth)acrylate polymer (A).

[0033] <Constructing units from monomers having hydroxyl groups> Certain (meth)acrylic polymers (A) may also contain constructing units from monomers having hydroxyl groups. In this disclosure, "constructing units from monomers having hydroxyl groups" means constructing units formed by the addition polymerization of monomers having hydroxyl groups.

[0034] There is no particular limitation on the type of monomer having a hydroxyl group. Examples of monomers having a hydroxyl group include monomers having at least one hydroxyl group and an vinyl unsaturated group in one molecule. There is no particular limitation on the vinyl unsaturated group; examples include vinyl, allyl, vinylphenyl, (meth)acrylamide, and (meth)acrylyl. (meth)acrylyl is preferred as the vinyl unsaturated group.

[0035] Specific examples of monomers having hydroxyl groups include, for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylaurate methacrylate, 3-methyl-3-hydroxybutyl methacrylate, 1,1-dimethyl-3-hydroxybutyl methacrylate, 1,3-dimethyl-3-hydroxybutyl methacrylate, 2,2,4-trimethyl-3-hydroxypentyl methacrylate, 2-ethyl-3-hydroxyhexyl methacrylate, N-hydroxyethyl(meth)acrylamide, glycerol-(meth)acrylate, polypropylene glycol-(meth)acrylate, polyethylene glycol-(meth)acrylate, and poly(ethylene glycol-propylene glycol)-(meth)acrylate. Regarding monomers containing hydroxyl groups, from the viewpoint of good copolymerization with other monomers, hydroxyalkyl (meth)acrylates are preferable. Of particular, hydroxyalkyl (meth)acrylates with 2 to 4 carbon hydroxyalkyl groups are preferable, and 2-hydroxyethyl acrylate is even more preferable.

[0036] When a specific (meth)acrylic polymer (A) contains a constituent unit derived from a monomer having a hydroxyl group, the constituent unit derived from the monomer having a hydroxyl group may contain only one type or may contain two or more types.

[0037] <Building units from monomers having carboxyl groups> Certain (meth)acrylic polymers (A) may also contain building units from monomers having carboxyl groups. In this disclosure, "building units from monomers having carboxyl groups" means building units formed by the addition polymerization of monomers having carboxyl groups.

[0038] There is no particular limitation on the type of monomer having a carboxyl group. Examples of monomers having a carboxyl group include monomers having at least one carboxyl group and an vinyl unsaturated group per molecule. There is no particular limitation on the vinyl unsaturated group; examples include vinyl, allyl, vinylphenyl, (meth)acrylamide, and (meth)acrylyl. (meth)acrylyl is preferred as the vinyl unsaturated group.

[0039] Specific examples of monomers having a carboxyl group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, iconic acid, penteneic acid, citrate, ω-carboxy-polycaprolactone-(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2)-acrylate], and succinic acid derivatives (e.g., 2-acrylic acid oxyethyl succinic acid). Among monomers having a carboxyl group, (meth)acrylic acid monomers having a carboxyl group are preferred, and acrylic acid is more preferred.

[0040] A specific (meth)acrylic polymer (A) may contain only one type of constituent unit derived from a monomer having a carboxyl group, or may contain two or more types of constituent units derived from a monomer having a carboxyl group.

[0041] - Total content of hydroxyl and carboxyl groups - When a specific (meth)acrylic polymer (A) contains at least one of a monomer having hydroxyl groups and a monomer having carboxyl groups, the total content of hydroxyl and carboxyl groups in the specific (meth)acrylic polymer (A) is preferably 0.01 mmol / g or more, more preferably 0.01 mmol / g to 0.7 mmol / g, further preferably 0.05 mmol / g to 0.7 mmol / g, and particularly preferably 0.30 mmol / g to 0.5 mmol / g. If the total content of hydroxyl and carboxyl groups in the specific (meth)acrylic polymer (A) is 0.01 mmol / g or more, there is a tendency to further improve the processability of the formed adhesive layer. In addition, the formed adhesive layer system tends to better suppress the shrinkage of the substrate that occurs when exposed to a high-temperature environment for a long period of time.

[0042] The total content (unit: mmol / g) of hydroxyl and carboxyl groups in a specific (meth)acrylic polymer (A) can be obtained by the following calculation formulas (A1) to (A3). In addition, if there are multiple monomers having hydroxyl groups and / or monomers having carboxyl groups that form a specific (meth)acrylic polymer (A), the total value is obtained by calculating for each monomer.

[0043] Hydroxy content (unit: mmol / g) = [Percentage of constituent units of monomers containing hydroxyl groups in a specific (meth)acrylic polymer (A) (unit: mass%) / [Moles of constituent units of monomers containing hydroxyl groups (unit: g / mol) × 100]] × Number (valence) of hydroxyl groups in constituent units of monomers containing hydroxyl groups × 1000･･･(A1)

[0044] Carboxyl group content (unit: mmol / g) = [Content percentage of constituent units of monomers with carboxyl groups in a specific (meth)acrylic polymer (A) (unit: mass%) / [Moles of constituent units of monomers with carboxyl groups (unit: g / mol) × 100]] × Number (valence) of carboxyl groups in constituent units of monomers with carboxyl groups × 1000･･･(A2)

[0045] Total content of hydroxyl and carboxyl groups (unit: mmol / g) = Content of hydroxyl groups (unit: mmol / g) + Content of carboxyl groups (unit: mmol / g) ･･･(A3)

[0046] <Other Constituent Units> Other constituent units that may be contained in a particular (meth)acrylic polymer (A) include constituent units from (meth)acrylates having aromatic rings, represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units from (meth)acrylate alkoxyalkyl esters, represented by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units from aromatic vinyl groups, represented by styrene, α-methylstyrene, tert-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; constituent units from vinyl cyanides, represented by acrylonitrile and methacrylonitrile; constituent units from vinyl esters, represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; etc. In this disclosure, monomers forming other constituent units are also referred to as "other monomers".

[0047] When a specific (meth)acrylic polymer (A) contains other constituent units, the other constituent units may contain only one type or more types.

[0048] In the case where a particular (meth)acrylic polymer (A) contains other constituent units, the content of the other constituent units in the particular (meth)acrylic polymer (A) may be appropriately set within the range that does not impair the effect of the adhesive composition disclosed herein.

[0049] <<Weight Average Molecular Weight of a Specific (Meth)acrylate Polymer (A)>> The weight average molecular weight (hereinafter also referred to as "Mw") of the specific (meth)acrylate polymer (A) is 1 million or more, preferably 1 million to 2.5 million, more preferably 1.2 million to 2.5 million, further preferably 1.4 million to 2.5 million, and particularly preferably 1.6 million to 2.5 million. If the weight average molecular weight of the specific (meth)acrylate polymer (A) is 1 million or more, an adhesive layer with excellent processability can be formed. In addition, an adhesive layer that can effectively suppress the shrinkage of the substrate that occurs when exposed to a high-temperature environment for a long period of time can be formed.

[0050] The weight-average molecular weight of the specific (meth)acrylic polymer (A) was determined by the following method. Specifically, it was determined according to (1) to (3) below. (1) A solution of the specific (meth)acrylic polymer (A) was coated onto release paper and dried at 100°C for 1 minute to obtain a thin film of the specific (meth)acrylic polymer (A). (2) Using the thin film of the specific (meth)acrylic polymer (A) obtained in (1) above and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass was obtained. In addition, the "solid content concentration" here refers to the mass ratio of the specific (meth)acrylic polymer (A) in the sample solution. (3) The weight-average molecular weight of the specific (meth)acrylic polymer (A) was obtained by gel permeation chromatography (GPC) under the following conditions as a standard polystyrene conversion value.

[0051] ~Conditions~ Measurement Apparatus: High-speed GPC [Model: HLC-8220 GPC, Tosoh Corporation] Detector: Differential Refractive Index Meter (RI) [Installed in HLC-8220, Tosoh Corporation] Column: 4 TSKgel GMH XL [Tosoh Corporation] Column Temperature: 40℃ Dissociation Solution: Tetrahydrofuran sample solution Injection Volume: 100 μL Flow Rate: 0.8 mL / min

[0052] The weight average molecular weight of a specific (meth)acrylic polymer (A) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, and amount of polymerization initiator during monomer polymerization.

[0053] <<Glass Transition Temperature of a Specific (Meth)acrylate Polymer (A)>> The glass transition temperature (also known as "Tg") of the specific (meth)acrylate polymer (A) is not particularly limited, but is preferably below -10°C, more preferably -70°C to -10°C, further preferably -70°C to -20°C, and especially preferably -70°C to -30°C. If the glass transition temperature of the specific (meth)acrylate polymer (A) is within the above range, even if the weight average molecular weight of the specific (meth)acrylate polymer (A) is 1 million or more, the formed adhesive layer can sufficiently impart wettability to the substrate and the adherend, and a more suitable adhesive force can be obtained.

[0054] The glass transition temperature of a specific (meth)acrylic polymer (A) is calculated using Equation 1, which is then converted to Celsius (°C). 1 / Tg = m1 / Tg1 + m2 / Tg2 + ... + m(k-1) / Tg(k-1) + mk / Tgk (Equation 1)

[0055] In Formula 1, Tg1, Tg2, ..., Tg(k-1), and Tgk each represent the glass transition temperature, expressed as absolute temperature, when the monomers constituting a specific (meth)acrylic polymer (A) are made into homopolymers. m1, m2, ..., m(k-1), and mk each represent the molar fraction of the monomers constituting the specific (meth)acrylic polymer (A), where m1 + m2 + ... + m(k-1) + mk = 1. Furthermore, absolute temperature can be converted to Celsius temperature by subtracting 273 from absolute temperature, and Celsius temperature can be converted to absolute temperature by adding 273 to Celsius temperature.

[0056] The "glass transition temperature during the preparation of homopolymer" in this disclosure is a value recorded in known sources or a value measured using a differential scanning calorimeter (DSC). Specifically, the value used is as follows.

[0057] Regarding the "glass transition temperature when preparing homopolymers" of the monomers shown below, the values ​​described individually are used. 2-Ethylhexyl acrylate: -70℃, 2-Ethylhexyl methacrylate: -10℃, n-Butyl acrylate: -54℃, n-Butyl methacrylate: 20℃, Tertiary butyl acrylate: 43℃, Tertiary butyl methacrylate: 118℃, Isobutyl methacrylate: 53℃, Methyl acrylate: 10℃, Methyl methacrylate: 105℃, Ethyl acrylate: -22℃, Ethyl methacrylate: 65℃, Methacrylic acid: 228℃, 4-Hydroxybutyl acrylate: -80℃, ...70℃, 2-Ethylhexyl methacrylate: -70℃, 2-Ethylhexyl methacrylate: -70℃, 2-Ethylhexyl methacrylate: -70℃, 2-Ethylhexyl methacrylate: -70℃, 2-Ethylhexyl methacrylate: -70℃, 2- -Hydroxyethyl acrylate: -15℃, 2-hydroxyethyl methacrylate: 85℃, Acrylic acid: 106℃, n-octyl acrylate: -65℃, Stearyl acrylate: 30℃, Stearyl methacrylate: 38℃, Lauryl acrylate: -3℃, Lauryl methacrylate: -65℃, Dimethylaminoethyl methacrylate: 18℃, ω-carboxy-polycaprolactone (n≒2) monoacrylate: -30℃, Phenoxyethyl acrylate: -22℃, Benzyl acrylate: 6℃, Isoborneol methacrylate: 180℃.

[0058] Regarding the "glass transition temperature when forming homopolymers" of monomers other than those mentioned above, the values ​​recorded in the Polymer Handbook (4th edition, Wiley-Interscience; hereinafter the same) shall be used. If not recorded in the Polymer Handbook, the glass transition temperature of the homopolymer obtained by the following determination method shall be used.

[0059] - Determination of Glass Transition Temperature of Homopolymer - Using a differential scanning calorimeter (DSC), the glass transition temperature of the homopolymer is determined under nitrogen gas flow conditions, with 10 mg of sample (i.e., homopolymer) and a heating rate of 10°C / min. The inflection point of the obtained DSC curve is taken as the glass transition temperature of the homopolymer. For example, a differential scanning calorimeter (trade name: Discovery DSC 2500) manufactured by TA Instruments Japan Inc. can be used as a differential scanning calorimeter. However, the differential scanning calorimeter is not limited to this.

[0060] The glass transition temperature of a specific (meth)acrylic polymer (A) can be appropriately adjusted, for example, by using two or more monomers with different glass transition temperatures when forming homopolymers.

[0061] <<Content of a specific (meth)acrylic polymer (A)>> The content of a specific (meth)acrylic polymer (A) in the adhesive composition disclosed herein is not particularly limited, but is preferably 70% to 99.5% by mass relative to the total amount of solid components in the adhesive composition, more preferably 75% to 99.0% by mass, and even more preferably 80% to 98.5% by mass.

[0062] In this disclosure, "total solid content in the adhesive composition" refers to the total mass of the adhesive composition when the adhesive composition does not contain solvent, and refers to the mass of the residue after removing the solvent from the adhesive composition when the adhesive composition contains solvent. In this disclosure, "solvent" refers to water and organic solvents.

[0063] [Specific (meth)acrylic polymer (B)] The adhesive composition disclosed herein contains a (meth)acrylic polymer (B) [i.e., specific (meth)acrylic polymer (B)] comprising a monomer having hydroxyl groups, wherein the hydroxyl content is 0.0007 mmol / g to 0.22 mmol / g, the glass transfer temperature is above 0°C, and the weight average molecular weight is 30,000 to 500,000. This is 1 to 30 parts by weight relative to 100 parts by weight of the previously described specific (meth)acrylic polymer (A). The adhesive composition disclosed herein may contain only one specific (meth)acrylic polymer (B), or it may contain two or more.

[0064] <Busty unit from a monomer having a hydroxyl group> A particular (meth)acrylic polymer (B) comprises a bulk unit from a monomer having a hydroxyl group. The type of monomer having a hydroxyl group is not particularly limited. Examples of monomers having a hydroxyl group include monomers having at least one hydroxyl group and an vinyl unsaturated group in one molecule. Examples of vinyl unsaturated groups are not particularly limited, including vinyl, allyl, vinylphenyl, (meth)acrylamide, and (meth)acrylyl. Preferably, the vinyl unsaturated group is (meth)acrylyl.

[0065] Specific examples of monomers containing hydroxyl groups in a particular (meth)acrylic polymer (B) are the same as specific examples of monomers containing hydroxyl groups in a particular (meth)acrylic polymer (A). Regarding monomers containing hydroxyl groups, for example, from the viewpoint of good copolymerization with other monomers, hydroxyalkyl (meth)acrylic acid esters are preferable. Regarding hydroxyalkyl (meth)acrylic acid esters, hydroxyalkyl (meth)acrylic acid esters containing 2 to 4 carbon atoms are preferable, more preferably 2-hydroxyethyl (meth)acrylic acid ester, and even more preferably 2-hydroxyethyl methacrylic acid ester.

[0066] A specific (meth)acrylic polymer (B) may contain only one type of constituent unit derived from a monomer having a hydroxyl group, or it may contain two or more types.

[0067] -Hydroxyl Content- The hydroxyl content in the specific (meth)acrylic polymer (B) is 0.0007 mmol / g to 0.22 mmol / g. If the hydroxyl content in the specific (meth)acrylic polymer (B) is 0.0007 mmol / g or more, an adhesive layer with excellent transparency can be formed even after prolonged exposure to high temperature environments. Considering this viewpoint, the hydroxyl content in the specific (meth)acrylic polymer (B) is preferably 0.005 mmol / g or more, more preferably 0.01 mmol / g or more, and even more preferably 0.02 mmol / g or more. If the hydroxyl content in the specific (meth)acrylic polymer (B) is 0.22 mmol / g or less, an adhesive layer that is not prone to wrinkling or peeling can be formed not only when exposed to high temperature and low humidity environments, but also when exposed to environments with repeated low and high temperatures. Considering this viewpoint, the hydroxyl content in a specific (meth)acrylic acid polymer (B) should preferably be below 0.2 mmol / g, more preferably below 0.1 mmol / g, and even more preferably below 0.06 mmol / g. The hydroxyl content in the specific (meth)acrylic acid polymer (B) can be 0.005 mmol / g to 0.2 mmol / g, 0.01 mmol / g to 0.1 mmol / g, or 0.02 mmol / g to 0.06 mmol / g in a single-state sample.

[0068] The content of hydroxyl groups in a specific (meth)acrylic polymer (B) (unit: mmol / g) can be obtained by the following calculation formula (B1). In addition, if there are multiple monomers with hydroxyl groups that form a specific (meth)acrylic polymer (B), the value is obtained by summing the calculations for each monomer.

[0069] Hydroxy content (unit: mmol / g) = [Content of hydroxyl-containing monomer units in a specific (meth)acrylic polymer (B) (unit: mass%) / [Moles of hydroxyl-containing monomer units (unit: g / mol) × 100] × Number (valence) of hydroxyl groups in hydroxyl-containing monomer units × 1000 ･･･(B1)

[0070] <Constructing Units from (Meth)acrylate Alkyl Ester Monomers> A particular (meth)acrylate polymer (B) preferably contains constructing units derived from (meth)acrylate monomers. There is no particular limitation on the type of (meth)acrylate monomer. The (meth)acrylate monomer may be an alkyl acrylate monomer or a alkyl methacrylate monomer. The alkyl group in the (meth)acrylate monomer may be unsubstituted or substituent (excluding carboxyl and hydroxyl groups), but preferably unsubstituted. The alkyl group in the (meth)acrylate monomer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the (meth)acrylate monomer is preferably 1 to 18, more preferably 1 to 12, and even more preferably 1 to 8.

[0071] Specific examples of the alkyl methacrylate monomer in the specific (meth)acrylate polymer (B) are the same as specific examples of the alkyl methacrylate monomer in the specific (meth)acrylate polymer (A). The alkyl methacrylate monomer is preferably selected from at least one of the group consisting of n-butyl acrylate, n-butyl methacrylate, isobutyl methacrylate, tributyl methacrylate, methyl acrylate, methyl methacrylate, and 2-ethylhexyl methacrylate, and more preferably from at least one of isobutyl methacrylate and methyl methacrylate.

[0072] A specific (meth)acrylic polymer (B) may contain only one type of (meth)acrylic alkyl ester monomer or more, when it contains a constituent unit derived from a (meth)acrylic alkyl ester monomer.

[0073] When a specific (meth)acrylate polymer (B) contains constituent units derived from alkyl methacrylate monomers, the content percentage of constituent units derived from alkyl methacrylate monomers in the specific (meth)acrylate polymer (B) is not particularly limited. For example, relative to all constituent units of the specific (meth)acrylate polymer (B), it is preferably 50% by mass or more, more preferably 50% by mass to 99.99% by mass, further preferably 60% by mass to 99.90% by mass, and especially preferably 70% by mass to 99.60% by mass. Here, the content percentage of constituent units derived from alkyl methacrylate monomers in the specific (meth)acrylate polymer (B) relative to all constituent units of the specific (meth)acrylate polymer (B) being 50% by mass or more means that the constituent units derived from alkyl methacrylate monomers are contained as the main component constituting the constituent units of the specific (meth)acrylate polymer (B).

[0074] <Other Constituent Units> Other constituent units that may be included in a particular (meth)acrylic polymer (B) may include constituent units from monomers having carboxyl groups, represented by (meth)acrylic acid; constituent units from (meth)acrylic esters having aromatic rings, represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units from (meth)acrylic alkoxyalkyl esters, represented by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units from aromatic monovinyl groups, represented by styrene, α-methylstyrene, tert-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; constituent units from cyanide vinyl groups, represented by acrylonitrile and methacrylonitrile; constituent units from vinyl esters, represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; etc.

[0075] When a specific (meth)acrylic polymer (B) contains other constituent units, the other constituent units may contain only one type or more types.

[0076] In the case where a particular (meth)acrylic polymer (B) contains other constituent units, the content of the other constituent units in the particular (meth)acrylic polymer (B) may be appropriately set within the range that does not impair the effect of the adhesive composition disclosed herein.

[0077] <<Weight Average Molecular Weight of a Specific (Meth)acrylate Polymer (B)>> The weight average molecular weight of the specific (meth)acrylate polymer (B) is 30,000 to 500,000. If the weight average molecular weight of the specific (meth)acrylate polymer (B) is 30,000 or more, an adhesive layer with excellent transparency can still be formed even after prolonged exposure to high temperatures. Considering this viewpoint, the weight average molecular weight of the specific (meth)acrylate polymer (B) is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 150,000 or more. If the weight average molecular weight of the specific (meth)acrylate polymer (B) is 500,000 or less, an adhesive layer with excellent transparency can be formed. Considering this viewpoint, the weight average molecular weight of the specific (meth)acrylate polymer (B) is preferably 400,000 or less, more preferably 350,000 or less, and even more preferably 250,000 or less. The weight average molecular weight of a specific (meth)acrylic polymer (B) can be 50,000 to 400,000, 100,000 to 350,000, or 150,000 to 250,000.

[0078] The weight-average molecular weight of the specific (meth)acrylic polymer (B) is a value obtained by means of the same method as the method for determining the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0079] The weight average molecular weight of a specific (meth)acrylic polymer (B) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, and amount of polymerization initiator used during monomer polymerization.

[0080] <<Glass Transition Temperature of a Specific (Meth)acrylate Polymer (B)>> The glass transition temperature of the specific (meth)acrylate polymer (B) is 0°C or higher. If the glass transition temperature of the specific (meth)acrylate polymer (B) is 0°C or higher, an adhesive layer can be formed that is not prone to wrinkling or peeling not only when placed in a high-temperature, low-humidity environment, but also when placed in repeated low-temperature and high-temperature environments. Furthermore, an adhesive layer with excellent processability can be formed. In addition, an adhesive layer can be formed that effectively suppresses the shrinkage of the substrate that occurs when placed in a high-temperature environment for a long period. The glass transition temperature of the specific (meth)acrylate polymer (B) is preferably 0°C to 200°C, more preferably 25°C to 180°C, further preferably 55°C to 150°C, further preferably 70°C to 130°C, and particularly preferably 75°C to 130°C.

[0081] The glass transition temperature of a specific (meth)acrylic polymer (B) is obtained by means of the same method as that used to determine the glass transition temperature of the specific (meth)acrylic polymer (A) described above.

[0082] The glass transition temperature of a specific (meth)acrylic polymer (B) can be appropriately adjusted, for example, by using two or more monomers with different glass transition temperatures when forming homopolymers.

[0083] <Content of Specific (Meth)acrylate Polymer (B)> The content of the specific (meth)acrylate polymer (B) in the adhesive composition disclosed herein is 1 to 30 parts by mass relative to 100 parts by mass of the specific (meth)acrylate polymer (A). If the content of the specific (meth)acrylate polymer (B) in the adhesive composition disclosed herein is 1 part by mass or more relative to 100 parts by mass of the specific (meth)acrylate polymer (A), an adhesive layer with excellent processability can be formed. Considering this viewpoint, the content of the specific (meth)acrylate polymer (B) in the adhesive composition disclosed herein is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 7 parts by mass or more, relative to 100 parts by mass of the specific (meth)acrylate polymer (A). If the content of the specific (meth)acrylic polymer (B) in the adhesive composition disclosed herein is 30 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic polymer (A), an adhesive layer with excellent transparency can be formed. Considering this viewpoint, the content of the specific (meth)acrylic polymer (B) in the adhesive composition disclosed herein is preferably 25 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic polymer (A), more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. The content of the specific (meth)acrylic polymer (B) in the adhesive composition disclosed herein, in one state, relative to 100 parts by mass of the specific (meth)acrylic polymer (A), can be 3 parts by mass to 25 parts by mass, or 5 parts by mass to 20 parts by mass, or 7 parts by mass to 15 parts by mass.

[0084] [Manufacturing Method of Specific (Meth)acrylate Polymers] There are no particular limitations on the manufacturing method of specific (meth)acrylate polymers (A) and (B) [i.e., specific (meth)acrylate polymers]. Specific (meth)acrylate polymers can be manufactured, for example, by polymerizing the monomers described herein using known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. From the viewpoint that the processing steps are simpler and can be carried out in a shorter time when preparing the adhesive composition disclosed herein after manufacturing, solution polymerization is preferable.

[0085] Solution polymerization generally involves adding a predetermined organic solvent, monomer, polymerization initiator, and chain transfer agent as needed to a polymerization tank, for example, heating and reacting the mixture for several hours while stirring at the reflux temperature of the organic solvent. Alternatively, at least a portion of the organic solvent, monomer, polymerization initiator, and chain transfer agent as needed can be added sequentially. Furthermore, the reaction can be carried out in a nitrogen gas stream.

[0086] Examples of organic solvents used in polymerization reactions include aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, esters, ketones, glycol ethers, and alcohols. More specifically, examples of organic solvents used in polymerization reactions include aromatic hydrocarbons such as benzene, toluene, ethylbenzene, n-propylbenzene, tert-butylbenzene, o-xylene, m-xylene, p-xylene, tetrahydronaphthalene, decahydronaphthalene, and aromatic naphtha; and aromatic hydrocarbons such as n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, mineral oil, and petroleum naphtha. Hydrocarbons represented by naphtha and turpentine, including aliphatic or alicyclic hydrocarbons; esters represented by methyl acetate, ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; ketones represented by acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ethers 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 alcohols represented by methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, dibutanol, and tert-butanol.

[0087] In the manufacture of a specific (meth)acrylic polymer, it is advisable to use an organic solvent that is not prone to chain transfer in the polymerization reaction of aromatic hydrocarbon compounds, ester compounds, ketone compounds, etc. In particular, considering the solubility of the specific (meth)acrylic polymer and the ease of polymerization reaction, ethyl acetate is preferred.

[0088] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0089] Examples of polymerization initiators include organic peroxides and azo compounds commonly used in solution polymerization. Specific examples of organic peroxides include tert-butylperoxy-2-ethylhexanoate, tert-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene peroxide, benzoyl peroxide, lauryl peroxide, hexyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, tert-butyl peroxyneopentate, 2,2-bis(4,4-ditert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-ditert-pentylperoxycyclohexyl)propane, 2,2-bis(4,4-ditert-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-isopropylphenylperoxycyclohexyl)propane, 2,2-bis(4,4-ditert-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-ditert-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylpentanitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylpentanitrile), 1,1'-azobis(cyclohexane-1-carboxynitrile), and dimethyl 2,2'-azobis(isobutyric acid) ester.

[0090] During the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0091] The amount of polymerization initiator used is not particularly limited, but can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer for the purpose.

[0092] In the manufacture of certain (meth)acrylic acid polymers, chain transfer agents may also be used as required. Examples of chain transfer agents include cyanoacetic acid, alkyl esters of cyanoacetic acid having 1 to 8 carbon atoms, alkyl esters of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, aromatic compounds represented by anthracene, phenanthrene, fentanyl, and 9-phenylfentanyl, 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, and carbon tetrabromide. Halogenated hydrocarbons represented by carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromochloromethane, tribromomethane, and 3-chloro-1-propene; aldehydes represented by trichloroacetaldehyde and furfural; alkyl thiols with 1 to 18 carbon atoms; aromatic thiols represented by thiophenol and toluene thiols; mercaptoacetic acid; alkyl esters of mercaptoacetic acid with 1 to 10 carbon atoms; hydroxyalkyl thiols with 1 to 12 carbon atoms; and terpenes represented by pinene and terpinene.

[0093] When a chain transfer agent is used in the manufacture of a specific (meth)acrylic polymer, there is no particular limitation on the amount of chain transfer agent used, for example, it can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer for the purpose.

[0094] There is no particular limitation on the polymerization temperature system, for example, it can be appropriately set according to the molecular weight of the specific (meth)acrylic polymer for the purpose.

[0095] [Crosslinking Agent] The adhesive composition disclosed herein contains a crosslinking agent. There is no particular limitation on the type of crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal-chelate crosslinking agents. The crosslinking agent is preferably selected from at least one of the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents, and is preferably an isocyanate-based crosslinking agent.

[0096] In this disclosure, "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate compound). Furthermore, "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called epoxy compound with two or more functions). Additionally, "metal chelate-based crosslinking agent" refers to a metal chelate compound that functions as a crosslinking agent.

[0097] Examples of polyisocyanate compounds include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds.

[0098] Aliphatic polyisocyanate compounds, including, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol compounds [e.g., trimethylolpropane (TMP); hereinafter the same]., and biuret forms of aliphatic polyisocyanate compounds. Specific examples of aliphatic polyisocyanate compounds include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0099] Alicyclic polyisocyanate compounds, including, for example, alicyclic polyisocyanate compounds, polymers of alicyclic polyisocyanate compounds, adducts of alicyclic polyisocyanate compounds and polyol compounds, and biuret forms of alicyclic polyisocyanate compounds. Specific examples of alicyclic polyisocyanate compounds include isophorone diisocyanate (IPDI), hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0100] Aromatic polyisocyanate compounds, including, for example, aromatic polyisocyanate compounds, polymers of aromatic polyisocyanate compounds, adducts of aromatic polyisocyanate compounds and polyol compounds, and biuret forms of aromatic polyisocyanate compounds. Specific examples of aromatic polyisocyanate compounds include toluene diisocyanate (TDI), xylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate.

[0101] The polyisocyanate compound is preferably selected from at least one compound from the group consisting of aliphatic polyisocyanate compounds and aromatic polyisocyanate compounds, and more preferably an aromatic polyisocyanate compound. The aromatic polyisocyanate compound is preferably selected from at least one compound from the group consisting of toluene diisocyanate compounds and xylene diisocyanate compounds. Toluene diisocyanate compounds include, for example, TDI, polymers of TDI, adducts of TDI and polyol compounds, and biuret forms of TDI. The toluene diisocyanate compound is preferably an adduct of TDI and TMP. Xylene diisocyanate compounds include, for example, XDI, polymers of XDI, adducts of XDI and polyol compounds, and biuret forms of XDI. The xylene diisocyanate compound is preferably an adduct of XDI and TMP.

[0102] Commercially available products can be used as isocyanate-based crosslinking agents. Examples of commercially available isocyanate-based crosslinking agents include "Coronate HX", "Coronate HL-S", "Coronate L", "Coronate L-45E", "Coronate 2031", "Coronate 2037", "Coronate 2234", "Coronate 2785", "Aquanate 200", and "Aquanate 210" [all manufactured by Tosoh Corporation], "Sumidur N3300", "Desmodur N3400", and "Sumidur N75" [all manufactured by Sumika Covestro Urethane Co., Ltd.], and "DURANATE". "D201", "DURANATE (registered trademark) E405-70B", "DURANATE (registered trademark) E405-80T", "DURANATE (registered trademark) AE700-100", "DURANATE (registered trademark) 24A-100", and "DURANATE (registered trademark) TSE-100" [all manufactured by Asahi Kasei Corporation], and "TAKENATE (registered trademark) D-110N", "TAKENATE (registered trademark) D-101E(45EA)", "TAKENATE (registered trademark) D-120N", "TAKENATE (registered trademark) D-140N", "TAKENATE (registered trademark) M-631N", "MT-OLESTER (registered trademark) NP1200", and "STABiO (registered trademark) XD-340N" [all manufactured by Mitsui Chemicals Corporation].

[0103] Examples of epoxy compounds with two or more functions include 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, and polyglycerol polyglycidyl ether. Resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, neopentyl tetraethanolamine polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, serotonin (glycidyl) isocyanurate, serotonin (glycidyl) isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-1,3-phenylenediamine.

[0104] Commercially available products can be used as epoxy crosslinking agents. Examples of commercially available epoxy crosslinking agents include "TETRAD (registered trademark)-X" and "TETRAD (registered trademark)-C" [manufactured by Mitsubishi Gas Chemical Co., Ltd.], as well as "DENACOL (registered trademark) EX-201" and "DENACOL (registered trademark) EX-931" [manufactured by Nagase ChemteX Corporation.].

[0105] The adhesive composition disclosed herein may contain only one crosslinking agent or may contain two or more crosslinking agents.

[0106] The content of the crosslinking agent in the adhesive composition disclosed herein is not particularly limited. For example, relative to 100 parts by weight of a specific (meth)acrylic polymer (A), it is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.07 parts by weight to 13 parts by weight, further preferably 0.10 parts by weight to 10 parts by weight, and particularly preferably 0.15 parts by weight to 8 parts by weight. If the content of the crosslinking agent in the adhesive composition disclosed herein is 0.05 parts by weight or more relative to 100 parts by weight of a specific (meth)acrylic polymer (A), there is a tendency to form an adhesive layer with better processability. In addition, there is a tendency to form an adhesive layer that can better suppress the shrinkage of the substrate that occurs when exposed to a high temperature environment for a long period of time. The crosslinking agent content in the adhesive composition disclosed herein, if less than 15 parts by mass relative to 100 parts by mass of a specific (meth)acrylic polymer (A), tends to form an adhesive layer that better suppresses wrinkling and peeling that occurs under conditions of high temperature and low humidity, and under conditions of repeated low temperature and high temperature. Furthermore, it tends to form an adhesive layer with superior transparency, maintaining excellent transparency even under prolonged exposure to high temperatures. The crosslinking agent content in the adhesive composition disclosed herein, in a single state, can be 0.10 parts by mass to 5 parts by mass, 0.10 parts by mass to 3 parts by mass, 0.15 parts by mass to 3 parts by mass, or 0.3 parts by mass to 1 part by mass relative to 100 parts by mass of the specific (meth)acrylic polymer (A).

[0107] [Silane Coupling Agent] The adhesive composition disclosed herein may also contain a silane coupling agent. There is no particular limitation on the type of silane coupling agent. Examples of silane coupling agents include, for instance, polymerizable unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane; thiol-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; and silane compounds containing thiol groups such as 3-epoxypropoxypropyltrimethoxysilane. Epoxy-containing silane compounds, represented by 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino-containing silane compounds, represented by 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; and tris-(3-trimethoxysilylpropyl)isocyanurate. Furthermore, silane coupling agents can be exemplified by silane compounds having multiple polymerizable unsaturated groups, thiols, epoxy groups, amino groups, and other reactive functional groups (so-called polyfunctional silane compounds).

[0108] Commercially available products can be used as silane coupling agents. Examples of commercially available silane coupling agents include "KBM-803", "KBM-802", "X-41-1810", "X-41-1811", "X-41-1805", "X-41-1818", "KBM-403", "KBM-303", "KBM-402", "KBE-402", "KBE-403", "X-41-1053", "X-41-1056", "KBM-9659", "KBE-9007N", and "KBM-573" (all trade names) manufactured by Shin-Etsu Chemical Co., Ltd.

[0109] The adhesive composition disclosed herein may contain only one type of silane coupling agent or more than two types when it contains silane coupling agents.

[0110] In the case where the adhesive composition disclosed herein contains a silane coupling agent, the content of the silane coupling agent is not particularly limited. For example, it is preferably 0.1 to 1 part by mass relative to 100 parts by mass of a specific (meth)acrylic polymer (A), more preferably 0.1 to 0.8 parts by mass, and even more preferably 0.1 to 0.5 parts by mass.

[0111] [Organic Solvents] The adhesive composition disclosed herein may also contain organic solvents. If the adhesive composition disclosed herein contains organic solvents, it will improve coatability. Examples of organic solvents include those used in the polymerization reaction of the specific (meth)acrylic polymers described herein.

[0112] The adhesive composition disclosed herein may contain only one organic solvent or two or more organic solvents.

[0113] In the case where the adhesive composition disclosed herein contains organic solvents, the content of organic solvents is not particularly limited and can be appropriately set according to the purpose.

[0114] [Other Ingredients] The adhesive composition disclosed herein may contain ingredients other than those described (so-called other ingredients) as needed, without impairing its effectiveness. Examples of other ingredients include polymers other than specific (meth)acrylic polymers, crosslinking catalysts, antioxidants, light stabilizers (e.g., UV absorbers), antistatic agents, and various other additives.

[0115] In cases where the adhesive composition disclosed herein contains other components, the content of the other components may be appropriately set within the range that does not impair the effect of the adhesive composition disclosed herein.

[0116] <<Applications of the Adhesive Composition>> The adhesive composition disclosed herein is used in optical thin films (i.e., adhesive compositions for optical thin films). The adhesive layer formed by the adhesive composition disclosed herein possesses the following characteristics: it is not prone to wrinkling or peeling not only when exposed to high temperatures, but also when subjected to repeated low and high temperature environments; it maintains excellent transparency even after prolonged exposure to high temperatures; and it has excellent processability. These characteristics make it suitable for optical thin film applications. Furthermore, the adhesive layer formed by the adhesive composition disclosed herein also effectively suppresses substrate shrinkage that occurs when exposed to high temperatures. Therefore, it is particularly suitable as an adhesive composition for polarizing plates (so-called adhesive compositions for polarizing plates) in optical thin films. Specific applications of the adhesive composition disclosed herein include bonding polarizing plates to the glass substrate of liquid crystal cells and bonding optical thin films together.

[0117] [Adhesive Sheet] The adhesive sheet disclosed herein comprises an adhesive layer formed by the adhesive composition disclosed herein. Therefore, the adhesive sheet disclosed herein is not prone to wrinkling in the adhesive layer (which is the substrate and adhesive layer in the case of an adhesive sheet having a substrate) and is not prone to peeling of the adhesive layer from the adhered object, even when subjected to high temperature environments or repeated low temperature and high temperature environments. In addition, the adhesive sheet disclosed herein has excellent transparency and maintains excellent transparency even when subjected to high temperature environments for a long period of time. Furthermore, the adhesive sheet disclosed herein has excellent processability. Furthermore, the adhesive sheet disclosed herein is not prone to substrate shrinkage even when subjected to high temperature environments. The adhesive layer of the adhesive sheet disclosed herein contains a cured product of the adhesive composition disclosed herein. The cured product may, for example, contain a cross-linked product of a specific (meth)acrylic polymer (A) and a specific (meth)acrylic polymer (B) formed by cross-linking curing caused by a cross-linking agent.

[0118] The thickness of the adhesive layer in the adhesive sheet disclosed herein is not particularly limited. The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 3 μm to 50 μm, and more preferably 5 μm to 30 μm.

[0119] The "thickness of the adhesive layer" in this disclosure refers to the average thickness of the adhesive layer. The average thickness of the adhesive layer is obtained by the following method: Ten points are randomly selected along the thickness direction of the adhesive layer, and the thickness is measured using a film thickness gauge. The arithmetic mean of the measured values ​​is calculated, and the obtained value is taken as the average thickness of the adhesive layer.

[0120] The adhesive sheet disclosed herein can be a substrate-free type without a substrate, or a substrate-based type with an adhesive layer on one or both sides of a substrate. In the case of a substrate-free type adhesive sheet without a substrate, or a substrate-based type adhesive sheet with an adhesive layer on one side of a substrate, the exposed adhesive layer surface of the adhesive sheet disclosed herein can also be protected by a peelable sheet. Generally, the peelable sheet protects the surface of the adhesive layer until the adhesive sheet is supplied for actual use, and is peeled off during use.

[0121] There is no particular limitation on the type of release sheet as long as it can be easily peeled off from the adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets obtained by laminating two or more of these, which have undergone a surface treatment (so-called easy-peel treatment) on one or both sides with a release agent. In this disclosure, release sheets in which a resin film has undergone a surface treatment (so-called easy-peel treatment) on one or both sides with a release agent are also referred to as "release films". Examples of release agents include polysiloxane-based release agents (e.g., polysiloxane), wax-based release agents (e.g., paraffin wax), and fluorine-based release agents (e.g., fluorine resins). Examples of resin films include polyester films, such as polyethylene terephthalate (PET) films. Examples of paper include high-quality paper and coated paper. There is no particular limitation on the film thickness of the release sheet; generally, it ranges from 20 μm to 180 μm.

[0122] When the adhesive sheet disclosed herein has a substrate, there is no particular limitation as long as the substrate can form an adhesive layer thereon. Examples of substrates include films containing resins such as polyolefin resins [e.g., polyethylene (PE) and polypropylene (PP)], polyester resins [e.g., polyethylene terephthalate (PET)], acetate resins (e.g., triacetyl cellulose), polyether resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, acrylic resins, vinyl chloride resins, ABS (acrylonitrile butadiene styrene) resin, and fluorine resins.

[0123] On the side where the adhesive layer of the substrate is provided, from the viewpoint of improving the adhesion between the substrate and the adhesive layer, surface treatments such as corona discharge treatment and plasma discharge treatment (so-called easy-adhesion treatment) can also be performed.

[0124] The substrate may also contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers. The substrate may also be partially or entirely patterned.

[0125] In the case where the adhesive sheet disclosed herein has a substrate, the substrate is preferably an optical thin film. In this case, the adhesive sheet disclosed herein is preferably in the form of having an optical thin film and an adhesive layer disposed on at least one side of the optical thin film and formed by the adhesive composition disclosed herein.

[0126] There is no particular limitation on the types of optical thin films. Specific examples of optical thin films include polarizing plates, AG (Anti-Glare) polarizing plates, wavelength plates, phase difference films of 1 / 2 and 1 / 4 wavelength plates, viewing angle compensation films, optical compensation films, brightness improvement films, light guide plates, reflective films, anti-reflective films, prisms, lenses, diffusers, transparent conductive films, etc.

[0127] As an optical thin film, it is preferably a polarizing plate. A polarizing plate is a component that includes at least a polarizer, which can be a single polarizer or a composite of a polarizer and a protective film. That is, a polarizing plate can be a single-layer structure of a polarizer, a two-layer structure with a protective film on one side of the polarizer, or a three-layer structure with protective films on both sides of the polarizer.

[0128] Regarding the layer structure of the adhesive sheet disclosed herein, where the substrate is a polarizing plate, examples include adhesive layer / polarizing plate [protective film / polarizer / protective film], adhesive layer / polarizing plate [phase retardation film / polarizer / protective film], and adhesive layer / polarizing plate [phase retardation film / protective film / polarizer / protective film]. For polarizers, examples include polyvinyl alcohol (PVA) film. For protective films, examples include triacetyl cellulose (TAC) film, polycyclic olefin (COP) film, polyethylene terephthalate (PET) film, and polymethyl methacrylate (PMMA) film. For phase retardation films, examples include polycyclic olefin (COP) film.

[0129] There is no particular limitation on the thickness of the substrate. For example, it is preferable to be less than 100μm, more preferably 10μm to 100μm, and even more preferably 30μm to 100μm.

[0130] In this disclosure, "substrate thickness" refers to the meaning of the average thickness of the substrate. The average thickness of the substrate is a value obtained by the same method as the average thickness of the adhesive layer described above.

[0131] [Method for Manufacturing the Adhesive Sheet] There are no particular limitations on the method for manufacturing the adhesive sheet disclosed herein. The adhesive sheet disclosed herein can be manufactured by known methods. For example, the following methods can be used to manufacture the adhesive sheet disclosed herein.

[0132] In the case of a substrate-free adhesive sheet disclosed herein, firstly, a coating film is formed on the release sheet by applying the adhesive composition disclosed herein to the easily peelable surface of the release sheet. Then, an adhesive film is formed on the release sheet by drying the formed coating film. Then, the exposed surface of the formed adhesive film is overlapped and bonded to the easily peelable surface of another prepared release sheet, and cured as needed, thereby producing the adhesive sheet disclosed herein with a laminated structure of release sheet / adhesive layer / release sheet.

[0133] In the case of a substrate-type adhesive sheet disclosed herein, firstly, the adhesive composition disclosed herein is applied to an easily bondable surface of the substrate to form a coating film on the substrate. Then, by drying the formed coating film, an adhesive film is formed on the substrate. Then, the exposed surface of the formed adhesive film is overlapped and bonded to the easily peelable surface of the release sheet, and cured as needed, thereby producing the adhesive sheet disclosed herein with a laminated structure of substrate / adhesive layer / release sheet.

[0134] In the case where the adhesive sheet disclosed herein is a substrate-type adhesive sheet, other methods may also be listed below, for example. A coating film is formed on the release sheet by applying the adhesive composition disclosed herein to the easily peelable surface of the release sheet. Then, by drying the formed coating film, an adhesive film is formed on the release sheet. Then, the exposed surfaces of the formed adhesive film are overlapped and bonded to the easily adhesive surface of the substrate, and cured as needed, thereby producing the adhesive sheet disclosed herein with a laminated structure of substrate / adhesive layer / release sheet.

[0135] There are no particular limitations on the coating method of the adhesive composition. For example, known methods such as using a gravure roller coater, a reverse roller coater, a kiss-roll coater, a dip roller coater, a doctor blade coater, a sprayer, a coater bar, or an applicator can be used. There are no particular limitations on the coating amount of the adhesive composition; it can be appropriately set according to the thickness of the adhesive layer to be formed.

[0136] There are no particular limitations on the drying method for the coated film. Examples of drying methods include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time are not particularly limited and can be appropriately set according to the thickness of the coated film and the amount of organic solvent in the coated film. As an example of drying conditions, a hot air circulating dryer can be used to dry the film at 60°C to 120°C for 30 to 180 seconds.

[0137] When carrying out maintenance, in terms of maintenance methods, one can take, for example, the method of leaving it in an environment with an ambient temperature of 20℃~35℃ and a relative humidity of 45%~55% (that is, 45%RH~55%RH) for 2 to 7 days.

[0138] [Optical Components] The optical component disclosed herein comprises, in sequence, a glass substrate, an adhesive layer formed by the adhesive composition described herein, and an optical thin film. Therefore, the optical component disclosed herein is not prone to wrinkling of the optical thin film and adhesive layer, nor is it prone to peeling of the adhesive layer from the glass substrate, even when subjected to high temperature and low humidity environments or repeated exposure to low and high temperatures. Furthermore, the optical component disclosed herein exhibits excellent transparency, maintaining excellent transparency even when subjected to high temperatures for extended periods. Additionally, the optical component disclosed herein is not prone to shrinkage of the optical thin film, even when subjected to high temperatures.

[0139] There is no particular limitation on the thickness of the glass substrate. Generally speaking, it is 0.3mm to 0.7mm, and preferably 0.3mm to 0.5mm.

[0140] In terms of glass substrates, examples include soda-lime glass, alkali-free glass, and glass with an ITO (Indium Tin Oxide) film.

[0141] The adhesive layer and optical film in the optical component disclosed herein have the same meaning as the adhesive layer and optical film in the adhesive sheet disclosed herein, and their ideal state is also the same, so the description is omitted here.

[0142] The optical components disclosed herein can be used, for example, as components of a display device. Examples of display devices include liquid crystal displays and organic EL (Electro-Luminescence) displays.

[0143] There are no particular limitations on the manufacturing method of the optical component disclosed herein. The optical component disclosed herein is manufactured by, for example, using an optical thin film as a substrate, fabricating the adhesive sheet disclosed herein using the method described above, and then bonding the adhesive layer of the adhesive sheet to a glass substrate.

[0144] [Display Device] The display device disclosed herein incorporates the optical components described herein. Therefore, the display device disclosed herein is not prone to wrinkling of the optical film and adhesive layer, nor is it prone to peeling of the adhesive layer from the glass substrate, even when subjected to high temperature and low humidity environments or repeated low temperature and high temperature environments. Furthermore, the display device disclosed herein exhibits excellent transparency, maintaining its excellent transparency even after prolonged exposure to high temperature environments. Moreover, the display device disclosed herein is not prone to shrinkage of the optical film, even when subjected to high temperature environments.

[0145] Specific examples of the display device are the same as those already described. [Example]

[0146] Hereinafter, the adhesive composition disclosed herein will be described in more detail by way of examples. This disclosure is not limited to the following examples without departing from its spirit.

[0147] [Manufacturing of (meth)acrylic polymer (A)] [Manufacturing Example A-1] In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe, and a reflux condenser, 210.9 parts by mass of n-butyl acrylate [n-BA; alkyl acrylate monomer], 30.0 parts by mass of methyl acrylate [MA; alkyl acrylate monomer], 54.0 parts by mass of phenoxyethyl acrylate [PHEA; other monomers], 4.5 parts by mass of acrylic acid [AA; monomers with carboxyl groups], 0.6 parts by mass of 2-hydroxyethyl acrylate [2HEA; monomers with hydroxyl groups], and 155.0 parts by mass of ethyl acetate [organic solvent] were added and mixed. After obtaining the mixture, the reactor was replaced with nitrogen. Then, while stirring the mixture in the reactor, the temperature was raised to 70°C. 0.003 parts by mass of 2,2'-azobis(2,4-dimethylpentanonitrile) [ABVN; polymerization initiator] and 15.0 parts by mass of ethyl acetate were added sequentially, and the mixture was maintained for 1 hour. Then, 0.08 parts by mass of ABVN and 340.0 parts by mass of ethyl acetate were added sequentially, and the mixture was maintained for 5 hours to complete the polymerization reaction. The resulting solution was then diluted with ethyl acetate to a solids concentration of 15.0% by mass, and cooled to obtain a solution of (meth)acrylic acid polymer A-1.

[0148] The term "solid component concentration" as used herein refers to the mass ratio of (meth)acrylic polymer A-1 in the solution of (meth)acrylic polymer A-1. The same meaning applies to the solutions of (meth)acrylic polymers A-2 to A-12 manufactured below.

[0149] [Manufacturing Examples A-2, A-3 and A-12] Manufacturing Examples A-2, A-3 and A-12 are obtained by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used to adjust the weight average molecular weight of the (meth)acrylic polymer to the weight average molecular weight shown in Table 1. Otherwise, the same operation as in Manufacturing Example A-1 is performed to obtain solutions of (meth)acrylic polymers A-2, A-3 and A-12 with a solid content concentration of 15.0% by mass.

[0150] [Manufacturing Examples A-4 to A-11] Manufacturing Examples A-4 to A-11 are those in which the monomer composition of the (meth)acrylic polymer is changed to the monomer composition shown in Table 1. Otherwise, the same operation as in Manufacturing Example A-1 is performed to obtain solutions of (meth)acrylic polymers A-4 to A-11 with a solid content concentration of 15.0% by mass.

[0151] The monomer composition [unit: mass%], total content of hydroxyl and carboxyl groups (expressed as "functionality") [unit: mmol / g], glass transition temperature (expressed as "Tg") [unit: °C], and weight average molecular weight (expressed as "Mw") of (meth)acrylic polymers A-1 to A-12 are shown in Table 1.

[0152] The total content (functionality) of hydroxyl and carboxyl groups in (meth)acrylic polymers A-1 to A-12 was obtained by the same method as that used to determine the total content (functionality) of hydroxyl and carboxyl groups in the specific (meth)acrylic polymer (A) described above. The glass transition temperature (Tg) of (meth)acrylic polymers A-1 to A-12 was obtained by the same method as that used to determine the glass transition temperature of the specific (meth)acrylic polymer (A) described above. The weight-average molecular weight (Mw) of (meth)acrylic polymers A-1 to A-12 was determined by the same method as that used to determine the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0153] Among the (meth)acrylic polymers A-1 to A-12, (meth)acrylic polymers A-1 to A-11 are equivalent to the specific (meth)acrylic polymer (A) in this disclosure.

[0154] [Table 1]

[0155] The details of each monomer listed in Table 1 are as follows. <(Meth)acrylate alkyl ester monomers> "n-BA": n-butyl acrylate [Tg when forming homopolymer: -54℃] "2EHA": 2-ethylhexyl acrylate [Tg when forming homopolymer: -70℃] "MA": methyl acrylate [Tg when forming homopolymer: 10℃] "MMA": methyl methacrylate [Tg when forming homopolymer: 105℃] <Monomers with carboxyl groups> "AA": acrylic acid [Tg when forming homopolymer: 106℃, molar mass: 72.06 g / mol] <Monomers with hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate [Tg when forming homopolymer: -15℃, molar mass: 116.12 g / mol] <Other monomers> "PHEA": phenoxyethyl acrylate [Tg when forming homopolymer: -22℃]

[0156] [Manufacturing of (Meth)acrylic Polymer (B)] [Manufacturing Example B-1] In a reactor equipped with a thermometer, stirrer, nitrogen inlet pipe, and reflux condenser, 280.0 parts by mass of methyl methacrylate [MMA; alkyl methacrylate monomer], 118.0 parts by mass of isobutyl methacrylate [i-BMA; alkyl methacrylate monomer], 2.0 parts by mass of 2-hydroxyethyl methacrylate [2HEMA; hydroxyl monomer], and 50.0 parts by mass of ethyl acetate [organic solvent] were added and mixed. After obtaining the mixture, the reactor was replaced with nitrogen gas. Then, while stirring the mixture in the reactor, the temperature was raised to 70°C, and 0.50 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] and 120.0 parts by mass of ethyl acetate were added to the mixture in the reactor in sequence. The polymerization reaction was maintained for 6 hours to complete. Then, the solution obtained after the polymerization reaction was completed was diluted with ethyl acetate to a solid content concentration of 30.0% by mass, and then cooled to obtain a solution of (meth)acrylic polymer B-1.

[0157] The term “solid component concentration” here refers to the mass ratio of (meth)acrylic polymer B-1 in the solution. The same meaning applies to the solutions of (meth)acrylic polymers B-2 to B-23 manufactured below.

[0158] [Manufacturing Examples B-14 to B-19] In Manufacturing Examples B-14 to B-19, the weight average molecular weight of the (meth)acrylic polymer was adjusted to the weight average molecular weight shown in Table 2 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. Otherwise, the same operation as in Manufacturing Example B-1 was performed to obtain solutions of (meth)acrylic polymers B-14 to B-19 with a solid content concentration of 30.0% by mass.

[0159] [Manufacturing Examples B-2 to B-13 and B-20 to B-23] Manufacturing Examples B-2 to B-13 and B-20 to B-23 are obtained by changing the monomer composition of the (meth)acrylic polymer to the monomer composition shown in Table 2. Otherwise, the same operation as in Manufacturing Example B-1 is performed to obtain solutions of (meth)acrylic polymers B-2 to B-13 and B-20 to B-23 with a solid content concentration of 30.0% by mass.

[0160] The monomer composition [unit: mass%], hydroxyl content (expressed as "hydroxyl content") [unit: mmol / g], glass transfer temperature (expressed as "Tg") [unit: °C], and weight average molecular weight (expressed as "Mw") of (meth)acrylic polymers B-1 to B-23 are shown in Table 2.

[0161] The hydroxyl content (hydroxyl content) of (meth)acrylic polymers B-1 to B-23 was obtained by the same method as that used to determine the hydroxyl content (hydroxyl content) of the specific (meth)acrylic polymer (B). The glass transition temperature (Tg) of (meth)acrylic polymers B-1 to B-23 was obtained by the same method as that used to determine the glass transition temperature of the specific (meth)acrylic polymer (A). The weight-average molecular weight (Mw) of (meth)acrylic polymers B-1 to B-23 was determined by the same method as that used to determine the weight-average molecular weight of the specific (meth)acrylic polymer (A).

[0162] Among (meth)acrylic polymers B-1 to B-23, (meth)acrylic polymers B-1 to B-17 are equivalent to specific (meth)acrylic polymers (B) in this disclosure.

[0163] [Table 2]

[0164] The details of each individual entity recorded in Table 2 are as follows. <(Meth)acrylate alkyl ester monomers> "MA": Methyl acrylate [Tg when forming homopolymer: 10℃] "MMA": Methyl methacrylate [Tg when forming homopolymer: 105℃] "2EHMA": 2-Ethylhexyl methacrylate [Tg when forming homopolymer: -10℃] "n-BA": n-Butyl acrylate [Tg when forming homopolymer: -54℃] "n-BMA": n-Butyl methacrylate [Tg when forming homopolymer: 20℃] "i-BMA": Isobutyl methacrylate [Tg when forming homopolymer: 53℃] "t-BMA": Tertiary butyl methacrylate [Tg when forming homopolymer: 118℃] <Molecules with hydroxyl groups> "2HEA": 2-Hydroxyethyl acrylate [Tg when forming homopolymer: -15℃, molar mass: 116.12 g / mol] "2HEMA": 2-Hydroxyethyl methacrylate [Tg when forming homopolymer: 85℃, molar mass: 130.14 g / mol] <Monomer with carboxyl group> "MAA": Methacrylic acid [Tg when forming homopolymer: 228℃]

[0165] [Preparation of Adhesive Composition] [Example 1] 666.7 parts by weight of a solution of (meth)acrylic polymer A-1 (100 parts by weight of solids), 33.3 parts by weight of a solution of (meth)acrylic polymer B-1 (10 parts by weight of solids), 0.67 parts by weight of Coronate (registered trademark) L-45E [trade name, adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid concentration: 45% by weight, manufactured by Tosoh Co., Ltd.] as an isocyanate crosslinking agent (0.30 parts by weight of solids), and an appropriate amount of ethyl acetate [organic solvent] were thoroughly mixed to obtain the adhesive composition of Example 1.

[0166] [Examples 2-21] In Example 1, the composition of the adhesive composition was changed to the composition shown in Table 3. Otherwise, the same operation as in Example 1 was performed to obtain the adhesive compositions of Examples 2-21.

[0167] [Examples 22-44] In Example 1, the composition of the adhesive composition was changed to the composition shown in Table 4. Otherwise, the same operation as in Example 1 was performed to obtain the adhesive compositions of Examples 22-44.

[0168] [Comparative Examples 1-11] In Example 1, the composition of the adhesive composition was changed to the composition shown in Table 5. Otherwise, the same operation as in Example 1 was performed to obtain each adhesive composition of Comparative Examples 1-11.

[0169] [Fabrication of a Polarizing Plate with an Adhesive Layer] The adhesive composition prepared above is coated onto the easily peelable surface of a release film [Type: MRF, Thickness: 38 μm, manufactured by Mitsubishi Chemical Co., Ltd.] that has undergone surface treatment (so-called easy peel treatment) using a polysiloxane-based release agent, forming a coated film. Furthermore, the amount of adhesive composition coated is such that the thickness of the adhesive film, as described later, is 10 μm. Then, the formed coated film is dried by blowing air at 100°C at a wind speed of 3 m / s onto the release film using a hot air circulating dryer, forming an adhesive film with a thickness of 10 μm on the release film. Then, the exposed surface of the formed adhesive film is overlapped and bonded to the surface of the TAC layer on one side of the polarizing plate, which is composed of a triacetyl cellulose (TAC) layer / polarizing film / polyvinyl alcohol (PVA) layer / TAC layer. The adhesive film is then left to stand for 7 days at an ambient temperature of 23°C and 50%RH to cure it, thereby producing a polarizing plate (thickness: 131μm) with an adhesive layer attached, which is composed of a release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0170] [Measurement and Evaluation] 1. Durability (1) High temperature and low humidity environment The above-prepared polarizing plate with an adhesive layer was cut into 60mm × 136mm (long side) sizes with the long side at 0° relative to the absorption axis of the polarizing plate. Then, the release film of the cut polarizing plate with an adhesive layer was peeled off, and the adhesive layer exposed by peeling was overlapped with one side of the glass plate [Type: soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.], and then pressed together using a press to bond the cut polarizing plate with an adhesive layer to the glass plate, thereby making a test sample. The test sample is composed of a glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). Then, the prepared test samples were autoclaved for 20 minutes at a processing temperature of 50°C and a processing pressure of 5 kg / cm², and then left to stand for 24 hours at an ambient temperature of 23°C and 50% RH. After standing, the test samples were then subjected to a 150-hour stand-up test at an ambient temperature of 85°C and below 10% RH (a so-called high-temperature, low-humidity environment). This test was designed to be a long-term exposure to a high-temperature environment, also known as an accelerated test. After the test, the condition of the test samples was visually observed and evaluated according to the following evaluation criteria. The results are shown in Tables 3-5. In the following evaluation criteria, "A", "B", and "C" are within the practically permissible range, with "A" being the most ideal.

[0171] -Evaluation Criteria- A: No wrinkles or peeling were found in the test sample. B: Minor wrinkles and / or peeling were found in the test sample, but at a level that is not practically problematic. C: Wrinkles and / or peeling were found in the test sample, but at a level that is practically acceptable. D: Significant wrinkles and / or peeling were found in the test sample, and at a level that is practically unacceptable.

[0172] (2) Thermal shock environment The polarizing plate with adhesive layer prepared above was cut into a size of 60mm×136mm (long side) with the long side at 0° relative to the absorption axis of the polarizing plate. Then, the release film of the cut polarizing plate with adhesive layer was peeled off, and the adhesive layer exposed by peeling was overlapped with one side of the glass plate [type: soda-lime glass, manufactured by Matsunaga Glass Industry Co., Ltd.] and pressed together using a press to bond the cut polarizing plate with adhesive layer to the glass plate, thereby making a test sample. The test sample is composed of a glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). Then, the test sample was treated in an autoclave at a treatment temperature of 50°C and a treatment pressure of 5kg / cm2 for 20 minutes, and then placed in an environment with an ambient temperature of 23°C and 50%RH for 24 hours. For the test samples after settling, a thermal shock device [model: TSA-301L-W, manufactured by ESPEC CORP.] was used to conduct a test that repeated 300 times, with the samples settling at an ambient temperature of -40°C for 0.5 hours and then at an ambient temperature of 85°C for 0.5 hours. After the test, the condition of the test samples was visually observed and evaluated according to the following evaluation criteria. The results are shown in Tables 3 to 5. In the following evaluation criteria, "A", "B" and "C" are within the practically permissible range, with "A" being the most ideal.

[0173] -Evaluation Criteria- A: No wrinkles or peeling were found in the test sample. B: Minor wrinkles and / or peeling were found in the test sample, but at a level that is not practically problematic. C: Wrinkles and / or peeling were found in the test sample, but at a level that is practically acceptable. D: Significant wrinkles and / or peeling were found in the test sample, and at a level that is practically unacceptable.

[0174] 2. Machinability The polarizing plate with adhesive layer (thickness: 131 μm) prepared above was cut into 100 mm × 100 mm sizes to make test samples. For the prepared test samples, end face processing was performed using an end face processing machine [model: MCPB-600A-SP, manufactured by MEGAROTECHNICA CO.,LTD.] with a blade speed of 3000 rpm and a cutting distance of 200 μm. The machined end face of the test sample after end face processing was observed using a digital microscope [model: VHX7000, magnification: 500x, KEYENCE CORPORATION.] to measure the width of the adhesive layer overflow, and the proportion was calculated using the following formula. The specific measurement method will be explained with reference to Figure 1. Figure 1 shows an example of the state of the machined end face of the test piece 100 after end face processing. In the processed end face of the test sample 100, which consists of a release film 10, an adhesive layer 20, and a polarizing plate 30, the total widths (X1, X2, X3, and X4) of the adhesive layer 20 overflow points are measured. The ratio (hereinafter also referred to as the "overflow ratio") relative to the width (Y; 100 cm) of the test sample 100 is calculated using the following formula. Here, the adhesive layer 20 overflow point refers to the area where the adhesive layer 20 overflows into the polarizing plate 30. Adhesive layer overflow ratio (unit: %) = [Total widths of adhesive layer overflow points (unit: mm) / Width of the test sample (100 mm)] × 100

[0175] Furthermore, the calculated values ​​are rounded to the first decimal place. Based on the calculated adhesive layer overflow ratio, the following evaluation criteria are applied. The results are shown in Tables 3-5. In the following evaluation criteria, "A", "B" and "C" are within the practical tolerance range, and "A" is preferred.

[0176] -Evaluation Criteria- A: Adhesive layer overflow rate is less than 10%. B: Adhesive layer overflow rate is between 10% and 25%. C: Adhesive layer overflow rate is between 25% and 40%. D: Adhesive layer overflow rate is 40% or more.

[0177] 3. Transparency: The adhesive composition prepared above is coated onto the easily peelable surface of a release film [Type: MRF, Thickness: 38 μm, manufactured by Mitsubishi Chemical Co., Ltd.] that has undergone surface treatment (so-called easy peel treatment) using a polysiloxane-based release agent to form a coated film. Furthermore, the amount of adhesive composition coated is such that the thickness of the adhesive film described later is 100 μm. The formed coated film is then placed at 23°C for 2 minutes. After placement, the coated film is dried by blowing air at 100°C at a wind speed of 3 m / s for 60 seconds using a hot air circulating dryer, forming an adhesive film with a thickness of 100 μm on the release film. Then, the exposed surface of the formed adhesive film is overlapped and bonded with one side of a polyethylene terephthalate (PET) film [trade name: COSMOSHINE (registered trademark) A4100, thickness: 100μm, manufactured by Toyobo Co., Ltd.], and left to stand for 7 days at an ambient temperature of 23°C and 50%RH to cure the adhesive film, thereby creating a laminate consisting of a release film / adhesive layer / PET film. The resulting laminate is cut to prepare two 50mm × 50mm test samples. For one of the prepared test samples, the release film is peeled off, and the haze (so-called initial haze) is measured. For the other prepared test sample, a test is conducted at an ambient temperature of 85°C and below 10%RH (so-called high temperature and low humidity environment) for 150 hours. This test is intended to be a long-term exposure to a high temperature environment, also known as an accelerated test. After the test, the release film of the test sample was peeled off, and the haze of the laminate consisting of an adhesive layer and a PET film was measured. The haze was measured using a haze meter (model: NDH 5000SP) manufactured by Nippon Denshoku Kogyo Co., Ltd. The haze value of the adhesive layer was obtained by subtracting the haze value of the PET film from the haze value of the laminate consisting of the adhesive layer and the PET film. Based on the haze value of the adhesive layer (unit: %), the following evaluation criteria were used for evaluation. The results are shown in Tables 3-5. In the following evaluation criteria, "A", "B", and "C" are within the practically permissible range, with "A" being the most ideal.

[0178] -Evaluation Criteria- A: Haze value less than 1.0%. B: Haze value between 1.0% and 2.0%. C: Haze value between 2.0% and 3.0%. D: Haze value 3.0% or higher.

[0179] 4. Shrinkage Inhibition The polarizing plate with adhesive layer prepared above is cut into 60mm × 136mm (long side) sizes with the long side at 0° relative to the absorption axis of the polarizing plate. Then, the release film of the cut polarizing plate with adhesive layer is peeled off, and the adhesive layer exposed by peeling is overlapped with one side of the glass plate [type: soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.], and then pressed together using a press to bond the cut polarizing plate with adhesive layer to the glass plate, thereby producing a test sample. The test sample has a layer structure of glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). Then, the prepared test sample is treated in an autoclave at a processing temperature of 50°C and a processing pressure of 5kg / cm2 for 20 minutes, and then left to stand for 24 hours at an ambient temperature of 23°C and 50%RH. The test sample, after being left to stand, was subjected to a 150-hour test in an environment with an ambient temperature of 85°C and RH below 10% (a so-called high-temperature, low-humidity environment). This test was designed to be a long-term exposure to a high-temperature environment, also known as an accelerated test. After the test, the length of the long side of the test sample (i.e., the side that is 0° relative to the absorption axis) was measured using a digital microscope [model: VHX-100F, manufactured by KEYENCE CORPORATION]. The shrinkage rate was calculated using the following formula. Furthermore, the calculated value was rounded to the third decimal place.

[0180] Shrinkage rate (unit: %) = [[Length of the long side of the test sample before standing (unit: mm)] - [Length of the long side of the test sample after standing (unit: mm)]] / Length of the long side of the test sample before standing (unit: mm) × 100

[0181] Based on the shrinkage rate obtained above, the following evaluation criteria were used for evaluation. The results are shown in Tables 3 to 5. In the following evaluation criteria, "A", "B" and "C" are within the practical tolerance range, with "A" being the best.

[0182] -Evaluation Criteria- A: The shrinkage rate of the test sample is less than 0.20%. B: The shrinkage rate of the test sample is between 0.20% and 0.35%. C: The shrinkage rate of the test sample is between 0.35% and 0.50%. D: The shrinkage rate of the test sample is 0.50% or more.

[0183] [Table 3]

[0184] [Table 4]

[0185] [Table 5]

[0186] The details of the components listed in Tables 3 to 5 are as follows. <Crosslinking Agents> -Isocyanate Crosslinking Agents- "Coronate L-45E" [Trade name, adduct of TDI and TMP, manufactured by Tosoh Corporation] "TAKENATE D-110N" [Trade name, adduct of XDI and TMP, manufactured by Mitsui Chemicals Corporation] "Sumidur N3300" [Trade name, trimer of HMDI, manufactured by Sumika Covestro Urethane Co., Ltd.] -Epoxy Crosslinking Agents- "TETRAD-X" [Trade name, manufactured by Mitsubishi Gas Chemical Corporation] "Coronate", "TAKENATE", "Sumidur" and "TETRAD" are all registered trademarks.

[0187] <Other Ingredients> -Silane Coupling Agent- "KBE-403" [Trade name, epoxy-containing silane compound, Shin-Etsu Chemical Co., Ltd.] "X-41-1810" [Trade name, thiol-containing silane compound (polyfunctional silane compound), Shin-Etsu Chemical Co., Ltd.] -Antistatic Agent- "MP-402A" [Trade name, Daiichi Kogyo Pharmaceutical Co., Ltd.]

[0188] The values ​​recorded in the "Admixture Amount" column of Tables 3-5 are all converted values ​​of solid components. In Tables 3-5, "-" indicates that the component corresponding to that column has not been admixed.

[0189] As shown in Tables 3 and 4, it was confirmed that the adhesive layers formed by the adhesive compositions of Examples 1 to 44 are not prone to wrinkling and peeling, not only when placed in a high-temperature and low-humidity environment, but also when placed in repeated low-temperature and high-temperature environments. Furthermore, it was confirmed that the adhesive layers formed by the adhesive compositions of Examples 1 to 44 have excellent transparency. Furthermore, it was confirmed that the adhesive layers formed by the adhesive compositions of Examples 1 to 44 maintain excellent transparency even after prolonged exposure to high-temperature environments. Furthermore, it was confirmed that the adhesive layers formed by the adhesive compositions of Examples 1 to 44 have excellent processability. Furthermore, it was confirmed that the adhesive layers formed by the adhesive compositions of Examples 1 to 44 can effectively suppress substrate shrinkage that occurs under prolonged exposure to high-temperature environments.

[0190] On the other hand, as shown in Table 5, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 1, which has a weight average molecular weight of less than 1 million for (meth)acrylic polymer (A), has poorer processability than the adhesive layer system formed by the adhesive composition of the Examples. Furthermore, it was confirmed that the adhesive layer system formed by the adhesive composition of Comparative Example 1 could not effectively suppress substrate shrinkage caused by prolonged exposure to high temperatures. In addition, while no wrinkles or peeling were observed in the adhesive layer formed by the adhesive composition of Comparative Example 1 under conditions of high temperature and low humidity, and under conditions of repeated low and high temperature, foaming was observed. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 2, which has a weight average molecular weight of less than 30,000 for (meth)acrylic polymer (B), is prone to damage to transparency if exposed to high temperatures for prolonged periods. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 3, which has a weight average molecular weight of (meth)acrylic polymer (B) exceeding 500,000, has poorer transparency compared to the adhesive layer formed by the adhesive composition of the examples. It was also confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4, which has a glass transition temperature of less than 0°C for (meth)acrylic polymer (B), is prone to wrinkling and peeling under high temperature and low humidity conditions and under repeated low temperature and high temperature conditions. Furthermore, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4 has poorer processability compared to the adhesive layer formed by the adhesive composition of the examples. Additionally, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4 cannot effectively suppress substrate shrinkage that occurs under prolonged exposure to high temperatures.

[0191] It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 5, which does not contain constituent units derived from monomers having hydroxyl groups in the (meth)acrylate polymer (B), is prone to damage in transparency when exposed to high temperatures for extended periods. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 6, which has a hydroxyl content exceeding 0.22 mmol / g in the (meth)acrylate polymer (B), is prone to wrinkling and peeling when exposed to high temperature and low humidity environments and repeated low temperature and high temperature environments. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 7, which contains only the specific (meth)acrylate polymer (A) among specific (meth)acrylate polymers (A) and specific (meth)acrylate polymers (B), has poorer processability compared to the adhesive layer formed by the adhesive composition of the examples. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 8, which contains a specific (meth)acrylic polymer (B) but whose content is less than 1 part by weight relative to 100 parts by weight of the specific (meth)acrylic polymer (A), has poorer processability than the adhesive layer formed by the adhesive composition of the examples. It was also confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 9, where the content of the specific (meth)acrylic polymer (B) is more than 30 parts by weight relative to 100 parts by weight of the specific (meth)acrylic polymer (A), has poorer transparency than the adhesive layer formed by the adhesive composition of the examples. Finally, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 10, which does not contain a crosslinking agent, has poorer processability than the adhesive layer formed by the adhesive composition of the examples. Furthermore, it was confirmed that the adhesive layer system formed by the adhesive composition of Comparative Example 10 could not effectively suppress substrate shrinkage caused by prolonged exposure to high temperatures. It was also confirmed that the adhesive layer system formed by the adhesive composition of Comparative Example 11, which uses a (meth)acrylic polymer (B) comprising units derived from monomers having carboxyl groups but not from monomers having hydroxyl groups, was prone to impaired transparency when exposed to high temperatures for extended periods. [Figure 1] A diagram illustrating the processability evaluation method in the examples.

Claims

1. An adhesive composition for optical thin films, comprising a (meth)acrylic polymer (A), a (meth)acrylic polymer (B), and a crosslinking agent, wherein the (meth)acrylic polymer (A) has a weight average molecular weight of 1,000,000 to 2,500,000, the (meth)acrylic polymer (B) comprises constituent units derived from monomers having hydroxyl groups, the hydroxyl group content is 0.0007 mmol / g to 0.22 mmol / g, the glass transfer temperature is 53.2°C to 200°C, and the weight average molecular weight is 30,000 to 500,000, and the content of the (meth)acrylic polymer (B) is 1 to 30 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A).

2. The adhesive composition for optical thin films as claimed in claim 1, wherein, The (meth)acrylic polymer (A) comprises at least one of a monomer having a hydroxyl group and a monomer having a carboxyl group.

3. The adhesive composition for optical thin films as claimed in claim 1, wherein, The content of the crosslinking agent is 0.05 to 15 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A).

4. The adhesive composition for optical thin films as claimed in claim 1, wherein, The crosslinking agent is an isocyanate-based crosslinking agent.

5. The adhesive composition for optical thin films as claimed in claim 1 further includes a silane coupling agent.

6. An adhesive sheet having an adhesive layer formed by an adhesive composition for optical films as claimed in any one of claims 1 to 5.

7. The adhesive sheet of claim 6 has an optical film and an adhesive layer formed by an adhesive composition of the optical film of any one of claims 1 to 5, and is disposed on at least one side of the optical film.

8. As in claim 7, the adhesive sheet, the optical thin film is a polarizing plate.

9. An optical component comprising, in sequence: a glass substrate, an adhesive layer formed by an adhesive composition for an optical film as claimed in any one of claims 1 to 5, and an optical film.

10. A display device comprising the optical components of claim 9.

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