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

Abstract

To provide an adhesive composition for optical film, which can form an adhesive layer which is excellent in durability under a high temperature and low humidity environment, inhibition of shrinkage of the optical film, and processability.SOLUTION: An adhesive composition for optical film comprises: a (meth)acrylic copolymer which comprises a monomer unit with a hydroxyl group in a ratio of more than 0 mass% and 1.0 mass% or less relative to all constituent units and does not contain a monomer unit with a carboxylic acid group; and an aromatic polyisocyanate compound in an amount of 0.25 to 5 pts.mass relative to 100 pts.mass of the copolymer, and an aliphatic polyisocyanate compound, where the functional group ratio determined by Formula (A) is 0.050 to 3.5. Functional group ratio=[NCOY1]×[OHX] / [NCOY2] (A), where OHX is the number of moles of hydroxy groups in the copolymer, NCOY1 is the number of moles of isocyanate groups in the aromatic isocyanate compound, and NCOY2 is the number of moles of isocyanate groups in the aliphatic isocyanate compound.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition for optical films, a pressure-sensitive adhesive sheet, an optical member, and a display device. [Background technology]

[0002] A liquid crystal display device generally includes a liquid crystal cell having a liquid crystal layer sandwiched between two supporting substrates, and optical films such as a polarizing plate, a retardation film, and a brightness enhancing film. When manufacturing a liquid crystal display device by laminating a liquid crystal cell and an optical film, or laminating optical films together, these members are bonded together via an adhesive layer formed from an adhesive composition. In liquid crystal display devices, (meth)acrylic adhesive compositions are often used from the viewpoint of ensuring visibility.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition comprising an acrylic polymer which is a copolymer having an acid value of 0.1 or less and a weight-average molecular weight of 1,000,000 or more, obtained by copolymerizing 0.1 to 3.5 parts by weight of a hydroxyl group-containing copolymerizable vinyl monomer without containing a carboxyl group-containing copolymerizable vinyl monomer and an amino group-containing (meth)acrylate, relative to a total of 100 parts by weight of at least two or more main component monomers, 0.01 to 0.8 parts by weight of an isocyanate compound as a crosslinking agent, and 0.01 to 0.5 parts by weight of a silane coupling agent, wherein the isocyanate compound is a trimethylolpropane adduct of tolylene diisocyanate, and the gel fraction after crosslinking is more than 40% and less than 75%. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-073721 A Summary of the Invention [Problem to be solved by the invention]

[0005] Optical films such as polarizing plates are usually constructed by laminating a plurality of members with different shrinkage rates, and therefore, dimensional changes are likely to occur due to changes in temperature and / or humidity. For this reason, when an adherend to which an optical film is bonded via a pressure-sensitive adhesive layer is placed in a high-temperature environment (for example, a high-temperature, low-humidity environment or a high-temperature, high-humidity environment), the optical film shrinks, and problems such as wrinkles in the pressure-sensitive adhesive layer and / or the optical film, peeling of the pressure-sensitive adhesive layer from the adherend, etc. may occur. Particularly in recent years, with the increase in size of optical displays, the area of ​​the optical film required is increased, and the total shrinkage of the optical film is also larger than ever before, so that the above-mentioned problems tend to occur easily. In addition, when an adherend to which an optical film is bonded via a pressure-sensitive adhesive layer is placed in a high-temperature environment, moisture in the pressure-sensitive adhesive layer evaporates, and foaming may occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or the adherend. For this reason, the pressure-sensitive adhesive composition used in the optical film is required to be able to form a pressure-sensitive adhesive layer (so-called a pressure-sensitive adhesive layer with excellent durability) that can suppress the above-mentioned foaming, wrinkles, and peeling that may occur in a high-temperature environment.

[0006] In general, in order to suppress wrinkles and peeling caused by the shrinkage of the optical film, it is considered that the stress caused by the shrinkage of the optical film is relaxed by the adhesive layer. However, if the adhesive layer is softened to increase the stress relaxation property of the adhesive layer, foaming is likely to occur. In addition, if the adhesive layer is softened, the adhesive layer will protrude from the cut surface when cutting the optical film with the adhesive layer, and will easily adhere to the cutting blade, which will easily cause contamination of the optical film. Furthermore, if the adhesive layer is softened, the shrinkage amount of the optical film will increase, which may cause a problem such as a reduction in the image displayable area of ​​the image display device.

[0007] In order to improve the durability of the adhesive layer in a high-temperature environment, it is also possible to increase the cohesive strength of the adhesive layer. One method for increasing the cohesive strength of the adhesive layer is to use a resin having a carboxy group as a component of the adhesive composition. However, metals such as copper and metal oxides such as indium tin oxide (ITO) are often used in image display devices. Components having a carboxy group have a relatively high acidity and can cause corrosion of metals and metal oxides. For this reason, adhesive compositions used in optical films are required to be designed to not contain components having a carboxy group.

[0008] For the reasons described above, it has conventionally been difficult to realize the formation of a pressure-sensitive adhesive layer that combines high levels of durability in high-temperature environments, suppression of shrinkage of optical films, and processability.

[0009] Regarding the above-mentioned points, Patent Document 1 does not focus on the formation of a pressure-sensitive adhesive layer that has both durability in a high-temperature environment and adhesiveness in a low-temperature environment.

[0010] The present disclosure has been made in consideration of the above-mentioned circumstances. An object of one embodiment of the present disclosure is to provide a pressure-sensitive adhesive composition for optical films that can form a pressure-sensitive adhesive layer that is excellent in durability and suppression of shrinkage of an optical film in a high-temperature, low-humidity environment, as well as excellent in processability. According to another embodiment of the present disclosure, there is provided an adhesive sheet, an optical member, and a display device that include an adhesive layer that is durable in a high-temperature, low-humidity environment, suppresses shrinkage of the optical film, and has excellent processability. [Means for solving the problem]

[0011] Specific means for solving the problems include the following aspects. <1> a (meth)acrylic copolymer containing structural units derived from a monomer having a hydroxyl group in a proportion of more than 0 mass% and not more than 1.0 mass% based on all structural units, and not containing any structural units derived from a monomer having a carboxy group; An aromatic polyisocyanate compound, An aliphatic polyisocyanate compound, Including, the content of the aromatic polyisocyanate compound is 0.25 parts by mass to 5 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer, A pressure-sensitive adhesive composition for use on an optical film, having a functional group ratio calculated by the following formula (A) of from 0.050 to 3.5: Functional group ratio=[NCO Y1 ]×[OH X ] / [NCO Y2 ]···(A) OH X : Number of moles of hydroxyl groups in the (meth)acrylic copolymer (mmol) NCO Y1 : The number of moles (mmol) of isocyanate groups in the aromatic polyisocyanate compound NCO Y2 : The number of moles (mmol) of isocyanate groups in the aliphatic polyisocyanate compound <2> The weight average molecular weight of the (meth)acrylic copolymer is 400,000 to 2,500,000. <1> The pressure-sensitive adhesive composition for optical films according to claim 1 . <3> Furthermore, a silane coupling agent is included. <1> or <2> The pressure-sensitive adhesive composition for optical films according to claim 1 . <4> Further, a crosslinking catalyst is included. <1> ~ <3> 13. The pressure-sensitive adhesive composition for use on an optical film according to claim 12. <5> <1> ~ <4> 2. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for use on an optical film according to claim 1. <6> An optical film; provided on at least one surface of the optical film, <1> ~ <4> A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for optical films according to any one of the above items. An adhesive sheet comprising: <7> The optical film is a polarizing plate. <6> The adhesive sheet according to claim 1. <8> A glass substrate; <1> ~ <4> A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for optical films according to any one of the above items. An optical film; An optical member comprising the above in this order. <9> <8> A display device comprising the optical member according to claim 1. Effect of the Invention

[0012] According to one embodiment of the present disclosure, there is provided a pressure-sensitive adhesive composition for an optical film, which is capable of forming a pressure-sensitive adhesive layer that is excellent in durability in a high-temperature, low-humidity environment, suppresses shrinkage of the optical film, and has excellent processability. According to another embodiment of the present disclosure, there are provided a pressure-sensitive adhesive sheet, an optical member, and a display device, each of which includes a pressure-sensitive adhesive layer that is excellent in durability in a high-temperature, low-humidity environment, suppresses shrinkage of the optical film, and has excellent processability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The pressure-sensitive adhesive composition for optical films, the pressure-sensitive adhesive sheet, the optical member, and the display device of the present disclosure will be described in detail below. The following description of the requirements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment, and can be modified as appropriate within the scope of the purpose of the present disclosure.

[0014] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower limit and upper limit, respectively. In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0015] In the present disclosure, combinations of two or more preferred embodiments are more preferred embodiments.

[0016] In the present disclosure, the amount of each component in the pressure-sensitive adhesive composition for optical films means the total amount of the above-mentioned multiple substances present in the pressure-sensitive adhesive composition for optical films, unless otherwise specified, when multiple substances corresponding to each component are present in the pressure-sensitive adhesive composition for optical films.

[0017] In the present disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In the present disclosure, "(meth)acrylic copolymer" means a copolymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of structural units derived from (meth)acrylic monomers is 50 mass% or more.

[0018] In this disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl," and "(meth)acrylamide" is a term that encompasses both "acrylamide" and "methacrylamide."

[0019] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0020] In the present disclosure, "mass %" and "weight %" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0021] In the present disclosure, the terms "polymer" and "polymeric" are synonymous.

[0022] In this disclosure, "room temperature" means 20°C to 35°C.

[0023] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0024] In the present disclosure, "a (meth)acrylic copolymer containing structural units derived from a monomer having a hydroxyl group in a ratio of more than 0 mass% to 1.0 mass% or less relative to all structural units, and containing no structural units derived from a monomer having a carboxy group" is also referred to as "specific (meth)acrylic copolymer." In addition, in the present disclosure, "the functional group ratio calculated by formula (A)" is also referred to as "functional group ratio (A)."

[0025] [Adhesive composition for optical films] The pressure-sensitive adhesive composition for optical films of the present disclosure (hereinafter also simply referred to as "pressure-sensitive adhesive composition") contains a (meth)acrylic copolymer containing structural units derived from a monomer having a hydroxyl group in a ratio of more than 0 mass% to 1.0 mass% or less with respect to all structural units and containing no structural units derived from a monomer having a carboxy group, an aromatic polyisocyanate compound, and an aliphatic polyisocyanate compound, in which the content of the aromatic polyisocyanate compound is 0.25 parts by mass to 5 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic copolymer, and the functional group ratio calculated by formula (A) [i.e., functional group ratio (A)] is 0.050 to 3.5. The pressure-sensitive adhesive composition of the present disclosure has the above-mentioned configuration, and thus can form a pressure-sensitive adhesive layer that is excellent in durability in high-temperature, low-humidity environments, inhibits shrinkage of an optical film, and has excellent processability. The reason why the pressure-sensitive adhesive composition of the present disclosure can exhibit such an effect is unclear, but the present inventors speculate as follows, however, the following speculation is not intended to limit the pressure-sensitive adhesive composition of the present disclosure, but is merely an example.

[0026] The present inventors have focused on the reaction of a (meth)acrylic copolymer containing a structural unit derived from a monomer having a hydroxyl group and not containing a structural unit derived from a monomer having a carboxyl group, an aromatic polyisocyanate compound, and an aliphatic polyisocyanate compound. In particular, the present inventors have focused on the reaction of a (meth)acrylic copolymer containing a structural unit derived from a monomer having a hydroxyl group and not containing a structural unit derived from a monomer having a carboxyl group with an aromatic polyisocyanate compound, and the reaction of an aromatic polyisocyanate compound with an aliphatic polyisocyanate compound, and have realized the formation of a pressure-sensitive adhesive layer that exhibits appropriate cohesive strength and stress relaxation properties by controlling this reaction, and has achieved durability in a high-temperature, low-humidity environment, suppression of shrinkage of an optical film, and processability at a high level. The adhesive composition of the present disclosure includes a (meth)acrylic copolymer and two types of compounds that function as crosslinkers, that is, an aromatic polyisocyanate compound and an aliphatic polyisocyanate compound, and the (meth)acrylic copolymer includes a relatively small amount of structural units derived from a monomer having a hydroxyl group and does not include structural units derived from a monomer having a carboxyl group. Therefore, in the adhesive composition of the present disclosure, the crosslinking reaction between the (meth)acrylic copolymer and the aromatic polyisocyanate compound proceeds quickly even under general curing temperature conditions (so-called room temperature), whereas the crosslinking reaction between the (meth)acrylic copolymer and the aliphatic polyisocyanate compound proceeds slower than the crosslinking reaction between the (meth)acrylic copolymer and the aromatic polyisocyanate compound. On the other hand, the reaction between the aromatic polyisocyanate compound and the aliphatic polyisocyanate compound proceeds quickly even at room temperature. This reaction produces a condensate of the aromatic polyisocyanate compound and the aliphatic polyisocyanate compound. In the pressure-sensitive adhesive composition of the present disclosure, the (meth)acrylic copolymer reacts with the aromatic polyisocyanate compound to form a crosslinked structure, and the cohesive strength of the pressure-sensitive adhesive layer is believed to contribute to suppression of foaming that may occur in a high-temperature, low-humidity environment, suppression of shrinkage of the optical film in a high-temperature, low-humidity environment, and improvement of processability. In addition, in the pressure-sensitive adhesive composition of the present disclosure, the stress relaxation property of the pressure-sensitive adhesive layer is believed to contribute to suppression of wrinkles and peeling that may occur in a high-temperature, low-humidity environment by the formation of a condensate of the aromatic polyisocyanate compound and the aliphatic polyisocyanate compound. The pressure-sensitive adhesive composition of the present disclosure can cause the pressure-sensitive adhesive layer to exhibit appropriate cohesive strength and stress relaxation properties. It is therefore presumed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure will have excellent durability in high-temperature, low-humidity environments, excellent suppression of shrinkage of the optical film, and excellent processability.

[0027] In addition, since the pressure-sensitive adhesive composition of the present disclosure does not contain a constituent unit derived from a monomer having a carboxy group in the (meth)acrylic copolymer, even when used to bond a glass substrate of a liquid crystal cell having a transparent conductive film (e.g., an ITO film) on its surface to a polarizing plate, it is possible to form a pressure-sensitive adhesive layer that is less likely to corrode the transparent conductive film.

[0028] [Specific (meth)acrylic copolymer] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic copolymer (i.e., a specific (meth)acrylic copolymer) that contains structural units derived from a monomer having a hydroxyl group in a proportion of more than 0 mass% to 1.0 mass% relative to all structural units, and does not contain any structural units derived from a monomer having a carboxy group. The pressure-sensitive adhesive composition of the present disclosure may contain only one type of specific (meth)acrylic copolymer, or may contain two or more types.

[0029] <Structural Unit Derived from Monomer Having a Hydroxyl Group> The specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group in a proportion of more than 0 mass% to 1.0 mass% or less of all structural units. In the present disclosure, "structural unit derived from a monomer having a hydroxyl group" means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

[0030] The type of the monomer having a hydroxyl group is not particularly limited. An example of a monomer having a hydroxyl group is a monomer having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The ethylenically unsaturated group is preferably a (meth)acryloyl group.

[0031] Specific examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate. As the monomer having a hydroxyl group, a hydroxyalkyl(meth)acrylate is preferable, a hydroxyalkyl(meth)acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable, 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is further preferable, and 2-hydroxyethyl acrylate is particularly preferable.

[0032] The specific (meth)acrylic copolymer may contain only one type of structural unit derived from a monomer having a hydroxyl group, or may contain two or more types.

[0033] The content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer is more than 0 mass % and 1.0 mass % or less with respect to all structural units of the specific (meth)acrylic copolymer. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer exceeds 0% by mass relative to the total structural units of the specific (meth)acrylic copolymer means that the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group. When the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group, a crosslinking reaction can proceed. In the pressure-sensitive adhesive composition of the present disclosure, the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer contributes to durability in a high-temperature, low-humidity environment, suppression of shrinkage of the optical film, and formation of a pressure-sensitive adhesive layer having excellent processability. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is, for example, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer. When the content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 1.0% by mass or less based on the total structural units of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed tends to exhibit excellent durability in a high-temperature, low-humidity environment. The reason for this is considered to be as follows. The crosslinking reaction between the specific (meth)acrylic copolymer and the aliphatic polyisocyanate compound becomes difficult to occur, and a condensate of the aromatic polyisocyanate compound and the aliphatic polyisocyanate compound is generated. It is considered that the stress relaxation property of the pressure-sensitive adhesive layer expressed by the generated condensate contributes to suppression of wrinkles and peeling that may occur in a high-temperature, low-humidity environment. The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is preferably 0.8% by mass or less, more preferably 0.6% by mass or less, and even more preferably 0.4% by mass or less based on the total structural units of the specific (meth)acrylic copolymer. In one embodiment, the content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer may be 0.01% by mass to 1.0% by mass, 0.02% by mass to 1.0% by mass, 0.05% by mass to 1.0% by mass, 0.05% by mass to 0.8% by mass, 0.1% by mass to 0.6% by mass, or 0.1% by mass to 0.4% by mass.

[0034] <Structural Unit Derived from Monomer Having a Carboxy Group> The specific (meth)acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group. In the present disclosure, the term "structural unit derived from a monomer having a carboxy group" refers to a structural unit formed by addition polymerization of a monomer having a carboxy group.

[0035] The component having a carboxyl group has a relatively high acidity and may cause metal corrosion. Since the specific (meth)acrylic copolymer of the pressure-sensitive adhesive composition of the present disclosure does not contain a structural unit derived from a monomer having a carboxyl group, even if the pressure-sensitive adhesive layer formed is used to bond a glass substrate of a liquid crystal cell having a transparent conductive film (e.g., an ITO film) on its surface to a polarizing plate, the transparent conductive film is unlikely to corrode.

[0036] The type of the monomer having a carboxy group is not particularly limited. An example of a monomer having a carboxy group is a monomer having at least one carboxy group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group.

[0037] Specific examples of monomers having a carboxy group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl-succinic acid).

[0038] <Structural Unit Derived from (Meth)acrylic Acid Alkyl Ester Monomer> The specific (meth)acrylic copolymer preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer. In the present disclosure, the term "structural unit derived from a (meth)acrylic acid alkyl ester monomer" refers to a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer. In addition, the "(meth)acrylic acid alkyl ester monomer" in this disclosure does not include a monomer corresponding to a monomer having a hydroxyl group and a monomer corresponding to a monomer having a carboxyl group. In other words, when a monomer having a hydroxyl group also corresponds to a (meth)acrylic acid alkyl ester monomer, it is classified as a monomer having a hydroxyl group. In addition, when a monomer having a carboxyl group also corresponds to a (meth)acrylic acid alkyl ester monomer, it is classified as a monomer having a carboxyl group.

[0039] The type of the (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The alkyl group in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent (excluding a hydroxyl group and a carboxy group), but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl group of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0040] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic acid alkyl ester monomer is preferably at least one selected from n-butyl acrylate and methyl acrylate.

[0041] When the specific (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it may contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer, or it may contain two or more types of structural units derived from the (meth)acrylic acid alkyl ester monomer.

[0042] When the specific (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, the content of the structural unit derived from the (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably 50 mass% or more, more preferably 50 mass% to 99.99 mass%, further preferably 60 mass% to 99.95 mass%, and preferably 70 mass% to 99.9 mass%, relative to all structural units of the specific (meth)acrylic copolymer. Here, the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic copolymer being 50 mass% or more relative to the total structural units of the specific (meth)acrylic copolymer means that the structural units derived from the (meth)acrylic acid alkyl ester monomer are contained as the main component of the structural units of the specific (meth)acrylic copolymer.

[0043] <Constituent units derived from other monomers> The specific (meth)acrylic copolymer may contain a constituent unit derived from a monomer (so-called other monomer) that does not fall under either a monomer having a hydroxyl group or a (meth)acrylic acid alkyl ester monomer. In the present disclosure, the "constituent unit derived from other monomer" means a constituent unit formed by addition polymerization of other monomer.

[0044] Examples of structural units derived from other monomers include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0045] From the viewpoint of suppressing white spots, the specific (meth)acrylic copolymer preferably contains a structural unit derived from an aromatic ring-containing (meth)acrylate as a structural unit derived from another monomer, more preferably contains a structural unit derived from phenoxyethyl (meth)acrylate, and even more preferably contains a structural unit derived from phenoxyethyl acrylate. Here, the "white spots" refers to a phenomenon in which light leakage occurs in a liquid crystal display device, resulting in white spots.

[0046] When the specific (meth)acrylic copolymer contains a structural unit derived from another monomer, it may contain only one type of structural unit derived from the other monomer, or may contain two or more types of structural units derived from the other monomer.

[0047] When the specific (meth)acrylic copolymer contains a structural unit derived from another monomer, the content of the structural unit derived from the other monomer can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0048] <<Weight average molecular weight of specific (meth)acrylic copolymer>> The weight average molecular weight (also referred to as "Mw") of the specific (meth)acrylic copolymer is not particularly limited, but is, for example, preferably 400,000 to 2.5 million, more preferably 600,000 to 2.5 million, even more preferably 800,000 to 2.5 million, and particularly preferably 1 million to 2.5 million. When the weight average molecular weight of the specific (meth)acrylic copolymer is 400,000 or more, the cohesive strength of the pressure-sensitive adhesive layer is improved, and the durability of the pressure-sensitive adhesive layer formed tends to improve. The specific (meth)acrylic copolymer tends to be easier to produce when the weight average molecular weight is 2.5 million or less.

[0049] The weight average molecular weight of the specific (meth)acrylic copolymer is a value measured by the following method, specifically, according to the following (1) to (3). (1) A solution of the specific (meth)acrylic copolymer is applied to a release paper and dried at 100° C. for 1 minute to obtain a film of the specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. Note that the "solid content concentration" here means the mass ratio of the specific (meth)acrylic copolymer in the sample solution. (3) The weight average molecular weight of the specific (meth)acrylic copolymer is determined by gel permeation chromatography (GPC) under the following conditions, expressed as a standard polystyrene equivalent value.

[0050] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [installed in HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two Tosoh products are used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0051] The weight average molecular weight of the specific (meth)acrylic copolymer can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomer.

[0052] <<Content of specific (meth)acrylic copolymer>> The content of the specific (meth)acrylic copolymer in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but for example, it is preferably 50.0 mass% to 98.0 mass%, more preferably 55.0 mass% to 98.0 mass%, and even more preferably 60.0 mass% to 98.0 mass%, relative to the total solid content in the pressure-sensitive adhesive composition.

[0053] In the present disclosure, the "total solid content in the PSA composition" means the total mass of the PSA composition when the PSA composition does not contain a solvent, and means the mass of the residue remaining after removing the solvent from the PSA composition when the PSA composition contains a solvent. In this disclosure, "solvent" means water and organic solvents.

[0054] [Method for producing specific (meth)acrylic copolymer] The method for producing the specific (meth)acrylic copolymer is not particularly limited. The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, or a bulk polymerization method. As a polymerization method, a solution polymerization method is preferred in that the processing steps are relatively simple and can be carried out in a short time when preparing the pressure-sensitive adhesive composition of the present disclosure after production.

[0055] In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as required are generally charged into a polymerization tank, and the mixture is heated and reacted for several hours with stirring at the reflux temperature of the organic solvent. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and the chain transfer agent used as required may be added successively. The reaction may also be carried out in a nitrogen gas flow.

[0056] Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone, methyl Examples of the alcohol compounds include ketone compounds represented by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds 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 alcohol compounds represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0057] In producing the specific (meth)acrylic copolymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, it is preferable to use methyl acetate and / or ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic copolymer, ease of polymerization reaction, etc.

[0058] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0059] Examples of the polymerization initiator include organic peroxides and azo compounds that are used in ordinary solution polymerization methods. Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butyl peroxysilane), peroxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl.

[0060] In the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0061] The amount of the polymerization initiator used is not particularly limited, and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0062] In producing the specific (meth)acrylic copolymer, a chain transfer agent may be used, if necessary. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, aromatic compounds such as α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives such as tributylborane, carbon tetrabromide, ... Examples of the halogenated hydrocarbon compounds include carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds such as chloral and furaldehyde, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds such as thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds such as pinene and terpinolene.

[0063] When a chain transfer agent is used in producing the specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0064] The polymerization temperature is not particularly limited, and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0065] [Aromatic polyisocyanate compounds] The pressure-sensitive adhesive composition of the present disclosure contains an aromatic polyisocyanate compound, and the content of the aromatic isocyanate compound is 0.25 parts by mass to 5 parts by mass per 100 parts by mass of the specific (meth)acrylic copolymer. In the present disclosure, the aromatic polyisocyanate compound functions as a crosslinking agent.

[0066] The "aromatic polyisocyanate compound" includes, for example, an aromatic polyisocyanate compound, a polymer of an aromatic polyisocyanate compound, an adduct of an aromatic polyisocyanate compound and a polyol compound (e.g., trimethylolpropane (TMP); the same applies below), and a biuret of an aromatic polyisocyanate compound. Specific examples of aromatic polyisocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate.

[0067] The aromatic polyisocyanate compound is preferably at least one selected from the group consisting of tolylene diisocyanate compounds and xylylene diisocyanate compounds. The "tolylene diisocyanate-based compound" includes, for example, TDI, TDI polymers, adducts of TDI and polyol-based compounds, and biuret forms of TDI. As the tolylene diisocyanate compound, an adduct of TDI and TMP is preferable. The "xylylene diisocyanate-based compound" includes, for example, XDI, XDI polymers, adducts of XDI and polyol-based compounds, and biuret forms of XDI. As the xylylene diisocyanate compound, an adduct of XDI and TMP is preferable.

[0068] As the aromatic polyisocyanate compound, commercially available products can be used. Examples of commercially available aromatic polyisocyanate compounds include "Coronate (registered trademark) L", "Coronate (registered trademark) L-45E", "Coronate (registered trademark) 2031", "Coronate (registered trademark) 4370", "Coronate (registered trademark) 2031", "Coronate (registered trademark) 2037" and "Millionate (registered trademark) MR-100" (all manufactured by Tosoh Corporation), as well as "Takenate (registered trademark) D-110N", "Takenate (registered trademark) D101-E" and "Takenate (registered trademark) D-262" (all manufactured by Mitsui Chemicals, Inc.).

[0069] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of aromatic polyisocyanate compound, or may contain two or more types.

[0070] The content of the aromatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is 0.25 parts by mass to 5 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the aromatic polyisocyanate-based compound in the pressure-sensitive adhesive composition of the present disclosure is 0.25 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed tends to be excellent in suppressing the shrinkage of the optical film in a high-temperature, low-humidity environment. In addition, the pressure-sensitive adhesive layer tends to exhibit excellent processability. This is believed to be because the cohesive force of the pressure-sensitive adhesive layer formed is sufficiently increased. The content of the aromatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is preferably 0.4 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, and particularly preferably 1 part by mass or more, relative to 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the aromatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is 5 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed tends to exhibit excellent durability in a high-temperature, low-humidity environment. This is believed to be because the pressure-sensitive adhesive layer formed exhibits appropriate stress relaxation properties. The content of the aromatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and particularly preferably 1.5 parts by mass or less, relative to 100 parts by mass of the specific (meth)acrylic copolymer. In one embodiment, the content of the aromatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure may be 0.4 parts by mass to 4 parts by mass, 0.6 parts by mass to 3 parts by mass, 0.8 parts by mass to 2 parts by mass, or 1 part by mass to 1.5 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer.

[0071] [Aliphatic polyisocyanate compounds] The pressure-sensitive adhesive composition of the present disclosure contains an aliphatic polyisocyanate compound. In the present disclosure, the aliphatic polyisocyanate-based compound functions as a crosslinking agent.

[0072] The "aliphatic polyisocyanate compound" includes, for example, an aliphatic polyisocyanate compound, a polymer of an aliphatic polyisocyanate compound, an adduct of an aliphatic polyisocyanate compound and a polyol compound, and a biuret of an aliphatic polyisocyanate compound. Specific examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0073] The "aliphatic polyisocyanate compound" also includes, for example, an alicyclic polyisocyanate compound, a polymer of an alicyclic polyisocyanate compound, an adduct of an alicyclic polyisocyanate compound and a polyol compound, and a biuret of an alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0074] The aliphatic polyisocyanate compound is preferably at least one selected from the group consisting of hexamethylene diisocyanate compounds and isophorone diisocyanate compounds. The "hexamethylene diisocyanate-based compound" includes, for example, HMDI, HMDI polymers, adducts of HMDI and polyol-based compounds, and biuret forms of HMDI. As the hexamethylene diisocyanate compound, a polymer of HMDI or an adduct of HMDI and TMP is preferred. The "isophorone diisocyanate-based compound" includes, for example, IPDI, IPDI polymers, adducts of IPDI and polyol-based compounds, and biuret forms of IPDI. As the isophorone diisocyanate compound, an adduct of IPDI and TMP is preferred.

[0075] As the aliphatic polyisocyanate compound, commercially available products can be used. Examples of commercially available aliphatic polyisocyanate compounds include "Coronate (registered trademark) HK", "Coronate (registered trademark) HX", "Coronate (registered trademark) 2096", and "Aquanate (registered trademark) 210" (all manufactured by Tosoh Corporation), "Duranate (registered trademark) P301-75E", "Duranate (registered trademark) D-201", "Duranate (registered trademark) E405-70B", "Duranate (registered trademark) E405-80T", and "Duranate (registered trademark) 24A-100" (all manufactured by Asahi Kasei Corporation), "Takenate (registered trademark) D-140N" and "Takenate (registered trademark) D-160N" (all manufactured by Mitsui Chemicals, Inc.), as well as "Sumidur (registered trademark) N3300", "Desmodur (registered trademark) N3400", and "Sumidur (registered trademark) "N75" (all manufactured by Sumika Covestro Urethane Co., Ltd.)

[0076] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of aliphatic polyisocyanate compound, or may contain two or more types.

[0077] The content of the aliphatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, so long as the content is such that the functional group ratio (A) is 0.050 to 3.5. The functional group ratio (A) will be described in detail later. In one embodiment, the content of the aliphatic polyisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure may be 2.5 parts by mass to 30 parts by mass, 2.5 parts by mass to 10 parts by mass, 5 parts by mass to 30 parts by mass, 10 parts by mass to 30 parts by mass, or 5 parts by mass to 10 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer.

[0078] <<Functional group ratio (A)>> The pressure-sensitive adhesive composition of the present disclosure has a functional group ratio calculated by the following formula (A) [that is, functional group ratio (A)] of 0.050 to 3.5. When the pressure-sensitive adhesive composition of the present disclosure has a functional group ratio (A) of 0.050 or more, the pressure-sensitive adhesive layer formed tends to have excellent processability, presumably because the pressure-sensitive adhesive layer formed has increased cohesive strength. The functional group ratio (A) in the pressure-sensitive adhesive composition of the present disclosure is preferably 0.065 or more, more preferably 0.10 or more, and even more preferably 0.20 or more. When the functional group ratio (A) in the pressure-sensitive adhesive composition of the present disclosure is 3.5 or less, the pressure-sensitive adhesive layer formed therefrom tends to exhibit excellent durability in a high-temperature, low-humidity environment, presumably because the pressure-sensitive adhesive layer formed therefrom exhibits sufficient stress relaxation properties. The functional group ratio (A) in the pressure-sensitive adhesive composition of the present disclosure is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.0 or less. In an embodiment, the functional group ratio (A) in the pressure-sensitive adhesive composition of the present disclosure may be 0.065 to 2.5, 0.10 to 2.0, or 0.20 to 1.0.

[0079] Functional group ratio=[NCO Y1 ]×[OH X ] / [NCO Y2 ]···(A)

[0080] In formula (A), OH X represents the number of moles (unit: mmol) of hydroxyl groups in the specific (meth)acrylic copolymer contained in the pressure-sensitive adhesive composition of the present disclosure. OH X can be calculated using the following formula (a1).

[0081] OH X (Unit: mmol) = Content of structural units derived from monomers having hydroxyl groups in specific (meth)acrylic copolymer [unit: mass %] / 100 × blend amount of specific (meth)acrylic copolymer [unit: g] / molecular weight of structural units derived from monomers having hydroxyl groups [unit: g / mol] × number of hydroxyl groups in structural units derived from monomers having hydroxyl groups (so-called valence) × 1000 (a1) The molecular weight of the constituent unit derived from 2-hydroxyethyl acrylate, which is a monomer having a hydroxyl group, is 116 g / mol, and the molecular weight of the constituent unit derived from 4-hydroxybutyl acrylate is 144 g / mol.

[0082] In formula (A), NCO Y1 represents the number of moles (unit: mmol) of isocyanate groups in the aromatic polyisocyanate compound contained in the pressure-sensitive adhesive composition of the present disclosure. NCO Y1 can be calculated using the following formula (a2). The molar mass of the isocyanate group is 42 g / mol.

[0083] NCO Y1 (Unit: mmol) = [Isocyanate group content in aromatic polyisocyanate compound (unit: mass%) / Solid content concentration of aromatic polyisocyanate compound (unit: mass%) × Amount of aromatic polyisocyanate compound (amount as solid content) (unit: g)] / Molar mass of isocyanate group (unit: g / mol) × 1000 (a2)

[0084] In formula (A), NCO Y2 represents the number of moles (unit: mmol) of isocyanate groups in the aliphatic polyisocyanate compound contained in the pressure-sensitive adhesive composition of the present disclosure. NCO Y2 can be calculated using the following formula (a3).

[0085] NCO Y2 (Unit: mmol) = [Isocyanate group content in aliphatic polyisocyanate compound (unit: mass%) / Solid content concentration of aliphatic polyisocyanate compound (unit: mass%) × Amount of aliphatic polyisocyanate compound (amount as solid content) (unit: g)] / Molar mass of isocyanate group (unit: g / mol) × 1000 (a3)

[0086] [Silane coupling agent] The pressure-sensitive adhesive composition of the present disclosure preferably further contains a silane coupling agent. In the pressure-sensitive adhesive composition of the present disclosure, the silane coupling agent can contribute to improving the durability of the pressure-sensitive adhesive layer formed in a high-temperature, low-humidity environment. This is thought to be because the alkoxy groups of the silane coupling agent are hydrolyzed to silanol groups, which react with hydroxyl groups on the glass surface, thereby enhancing the adhesion of the pressure-sensitive adhesive layer to glass.

[0087] The type of silane coupling agent is not particularly limited. Examples of the silane coupling agent include polymerizable unsaturated group-containing silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane; thiol group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; epoxy group-containing silane compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; and tris-(3-trimethoxysilylpropyl)isocyanurate. Examples of the silane coupling agent include silane compounds having a plurality of reactive functional groups such as polymerizable unsaturated groups, thiol groups, epoxy groups, and amino groups (so-called polyfunctional silane compounds).

[0088] As the silane coupling agent, a commercially available product can be used. Examples of commercially available silane coupling agents include "KBM-803", "KBM-802", "X-41-1810", "X-41-1805", "X-41-1818", "KBM-403", "KBM-303", "KBM-402", "KBE-402", "KBE-403", "KBE-9007N", "X-41-1053", "X-41-1056", "KBM-903", "KBM-9659", and "KBM-573" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0089] When the pressure-sensitive adhesive composition of the present disclosure contains a silane coupling agent, it may contain only one type of silane coupling agent, or may contain two or more types of silane coupling agents.

[0090] When the pressure-sensitive adhesive composition of the present disclosure contains a silane coupling agent, the content of the silane coupling agent is not particularly limited, but is, for example, preferably 0.1 parts by mass to 1 part by mass, more preferably 0.2 parts by mass to 0.9 parts by mass, and even more preferably 0.3 parts by mass to 0.8 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer.

[0091] [Crosslinking catalyst] The pressure-sensitive adhesive composition of the present disclosure may further contain a crosslinking catalyst. The type of the crosslinking catalyst is not particularly limited. Examples of crosslinking catalysts include imidazole compounds such as 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, organometallic compounds such as dioctyltin dilaurate and 1,3-diacetoxytetrabutylstannoxane, and tertiary amine compounds such as triethylenediamine and N-methylmorpholine.

[0092] As the crosslinking catalyst, a commercially available product can be used. Examples of commercially available crosslinking catalysts include "Curezol (registered trademark) 1B2MZ", "Curezol (registered trademark) 1B2PZ", "Curezol (registered trademark) TBZ", and "Curezol (registered trademark) 1,2DMZ" (all manufactured by Shikoku Chemical Industry Co., Ltd.).

[0093] When the pressure-sensitive adhesive composition of the present disclosure contains a crosslinking catalyst, it may contain only one type of crosslinking catalyst, or may contain two or more types of crosslinking catalyst.

[0094] When the pressure-sensitive adhesive composition of the present disclosure contains a crosslinking catalyst, the content of the crosslinking catalyst is, for example, preferably 0.01 parts by mass to 1.5 parts by mass, more preferably 0.05 parts by mass to 1.0 parts by mass, and even more preferably 0.1 parts by mass to 0.5 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the crosslinking catalyst in the pressure-sensitive adhesive composition of the present disclosure is within the above range, the curing time tends to be further shortened.

[0095] [Organic Solvent] The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coatability and pot life can be improved. As the organic solvent, for example, the same organic solvents as those used in the polymerization reaction of the above-mentioned specific (meth)acrylic copolymer can be mentioned.

[0096] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvent.

[0097] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be appropriately set depending on the purpose.

[0098] [Other ingredients] The pressure-sensitive adhesive composition of the present disclosure may contain components other than the components described above (so-called other components) as necessary, provided that the effects of the composition are not impaired. Examples of other components include various additives such as antioxidants, light stabilizers (for example, ultraviolet absorbers), and antistatic agents.

[0099] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the contents of the other components can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0100] <<Applications of adhesive composition>> The pressure-sensitive adhesive composition of the present disclosure is a pressure-sensitive adhesive composition used for optical films (i.e., a pressure-sensitive adhesive composition for optical films). The pressure-sensitive adhesive composition of the present disclosure is suitable for optical film applications because it can form a pressure-sensitive adhesive layer that is excellent in durability and suppression of shrinkage of optical films in high-temperature and low-humidity environments, as well as excellent processability. The pressure-sensitive adhesive composition of the present disclosure is also suitable for optical film applications because it can form a pressure-sensitive adhesive layer that is unlikely to corrode an adherend containing a metal and / or metal oxide, for example, a transparent conductive film represented by an ITO (indium-tin oxide) film. The pressure-sensitive adhesive composition of the present disclosure is particularly suitable as a pressure-sensitive adhesive composition used for polarizing plates among optical films (i.e., a pressure-sensitive adhesive composition for polarizing plates). Specific applications of the pressure-sensitive adhesive composition of the present disclosure include applications for bonding a polarizing plate to a glass substrate of a liquid crystal cell (preferably a glass substrate having a transparent conductive film on its surface), and applications for bonding optical films together.

[0101] [Adhesive sheet] The pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure. The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present disclosure includes a cured product of the pressure-sensitive adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic copolymer obtained by crosslinking and curing with an aromatic polyisocyanate compound and an aliphatic polyisocyanate compound. The pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure described above, and therefore, in a high-temperature, low-humidity environment, defects due to shrinkage of the optical film, specifically, wrinkles of the pressure-sensitive adhesive layer and the optical film, peeling of the pressure-sensitive adhesive layer from the adherend, and the like, are unlikely to occur. In addition, the pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure described above, and therefore, in a high-temperature, low-humidity environment, foaming is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or the adherend. In addition, the pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure described above, and therefore, in a high-temperature, low-humidity environment, the optical film is unlikely to shrink. In addition, the pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure described above, and therefore, has excellent processability, and when an optical film including a pressure-sensitive adhesive layer is cut, the pressure-sensitive adhesive layer is unlikely to protrude. Furthermore, since the pressure-sensitive adhesive sheet of the present disclosure comprises a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure described above, even when the sheet is used to bond an adherend containing a metal and / or metal oxide, specifically a liquid crystal cell having a transparent conductive film (e.g., an ITO film) on its surface, to a polarizing plate, corrosion of the transparent conductive film is unlikely to occur. An example of an adherend to which the pressure-sensitive adhesive sheet of the present disclosure can be applied is a glass substrate (so-called optical glass) of a liquid crystal cell, and a glass substrate having a transparent conductive film on its surface is preferred.

[0102] The thickness of the pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The thickness of the pressure-sensitive adhesive layer is generally from 1 μm to 100 μm, preferably from 5 μm to 50 μm, and more preferably from 10 μm to 30 μm.

[0103] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" means the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value determined by the following method. The thickness of the adhesive layer is measured at 10 randomly selected locations in the thickness direction using a thickness gauge. The arithmetic mean of the measured values ​​is calculated and this value is regarded as the average thickness of the adhesive layer.

[0104] The pressure-sensitive adhesive sheet of the present disclosure may be a substrate-free pressure-sensitive adhesive sheet that does not have a substrate, or a substrate-containing pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one or both sides of a substrate. When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-free type pressure-sensitive adhesive sheet that does not have a substrate, or when it is a substrate-containing type pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one side of a substrate, the exposed surface of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present disclosure may be protected by a release sheet. In general, the release sheet protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put to practical use, and is peeled off at the time of use.

[0105] The release sheet is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets obtained by laminating two or more of these, each of which has been surface-treated with a release agent on one or both sides (so-called easy-release treatment). In the present disclosure, a release sheet in an embodiment in which one or both sides of a resin film have been subjected to a surface treatment with a release treating agent (so-called easy-release treatment) is also referred to as a "release film". Examples of the release agent include silicone-based release agents (eg, silicone), wax-based release agents (eg, paraffin wax), and fluorine-based release agents (eg, fluorine-based resins). An example of the resin film is a polyester film, typically a polyethylene terephthalate (PET) film. Examples of the paper include fine paper and coated paper. The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm.

[0106] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is not particularly limited as long as a pressure-sensitive adhesive layer can be formed thereon. Examples of the substrate 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), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins.

[0107] The surface of the substrate on which the adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or plasma discharge treatment (so-called adhesion enhancing treatment) in order to improve adhesion between the substrate and the adhesive layer.

[0108] The substrate may contain various additives, such as plasticizers, colorants (eg, dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like. The substrate may be partially or entirely patterned.

[0109] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is preferably an optical film. In this case, the pressure-sensitive adhesive sheet of the present disclosure preferably includes an optical film and a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition of the present disclosure.

[0110] The type of the optical film is not particularly limited. Specific examples of optical films include polarizing plates, AG (Anti-Glare) polarizing plates, wave plates (e.g., ½ wave plates and ¼ wave plates), retardation films including the wave plates, viewing angle compensation films, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, prism sheets, lens sheets, diffusion plates, and transparent conductive films.

[0111] The optical film is preferably a polarizing plate (so-called polarizing film). The polarizing plate includes at least a polarizer, and may be a single polarizer or a laminate of a polarizer and a protective film. That is, the polarizing plate may have a single-layer structure including a polarizer, a two-layer structure including a protective film on one side of the polarizer, or a three-layer structure including protective films on both sides of the polarizer.

[0112] When the pressure-sensitive adhesive sheet of the present disclosure has a substrate and the substrate is a polarizing plate, examples of the layer configuration include pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / protective film / polarizer / protective film], and the like.

[0113] The protective film may be a film containing a resin such as triacetyl cellulose (TAC), polycycloolefin (COP), polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA). The polarizer may be, for example, a stretched film of polyvinyl alcohol (PVA) impregnated with iodine. For the retardation film, for example, a film containing a resin such as polycycloolefin (COP) is used.

[0114] The thickness of the substrate is not particularly limited, but is generally from 10 μm to 500 μm, preferably from 10 μm to 300 μm, more preferably from 10 μm to 200 μm, and further preferably from 10 μm to 130 μm.

[0115] "Substrate thickness" in this disclosure means the average thickness of the substrate. The average thickness of the substrate is a value determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is regarded as the average thickness of the substrate.

[0116] [How to make adhesive sheets] The method for producing the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The pressure-sensitive adhesive sheet of the present disclosure can be produced by known methods. The pressure-sensitive adhesive sheet of the present disclosure can be produced, for example, by the following method.

[0117] When the adhesive sheet of the present disclosure is a substrate-free type adhesive sheet, first, the adhesive composition of the present disclosure is applied to the easy-release treated surface of the release sheet to form a coating film on the release sheet.Then, the formed coating film is dried to form an adhesive film on the release sheet.Then, the exposed surface of the formed adhesive film is laminated and attached to the easy-release treated surface of a separately prepared release sheet, and then cured to produce the adhesive sheet of the present disclosure having a laminated structure of release sheet / adhesive layer / release sheet.

[0118] When the adhesive sheet of the present disclosure is a substrate-type adhesive sheet, first, the adhesive composition of the present disclosure is applied to the easy-adhesion-treated surface of the substrate to form a coating film on the substrate. Then, the formed coating film is dried to form an adhesive film on the substrate. Then, the exposed surface of the formed adhesive film is laminated on the easy-release-treated surface of the release sheet, and the laminate is cured to produce the adhesive sheet of the present disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0119] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-type pressure-sensitive adhesive sheet, another method may be, for example, the following method. The pressure-sensitive adhesive composition of the present disclosure is applied to the easy-release treated surface of a release sheet to form a coating film on the release sheet. The formed coating film is then dried to form an adhesive film on the release sheet. The exposed surface of the formed adhesive film is then laminated onto the easy-adhesion treated surface of the substrate, and cured to produce the pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0120] The method for applying the pressure-sensitive adhesive composition is not particularly limited. Examples of methods for applying the pressure-sensitive adhesive composition include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, and the like. The amount of the adhesive composition to be applied is not particularly limited, and is appropriately set depending on, for example, the thickness of the adhesive layer to be formed.

[0121] The method for drying the coating film is not particularly limited. Examples of methods for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set depending on the thickness of the coating film, the amount of the organic solvent in the coating film, and the like. An example of the drying conditions is a condition in which air at 60° C. to 130° C. is blown at a speed of 3 m / sec to 5 m / sec for 30 seconds to 300 seconds using a hot air circulation dryer.

[0122] The curing method may be, for example, a method in which the product is left to stand for 2 to 7 days in an environment with an atmospheric temperature of 20° C. to 35° C. and a relative humidity of 45% to 55%.

[0123] [Optical components] The optical member of the present disclosure includes, in this order, a glass substrate, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure described above, and an optical film. Since the optical member of the present disclosure has a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure, defects due to shrinkage of the optical film, specifically wrinkles of the pressure-sensitive adhesive layer and the optical film, peeling of the pressure-sensitive adhesive layer from the glass substrate, etc., are unlikely to occur in a high-temperature, low-humidity environment. In addition, since the optical member of the present disclosure has a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure, foaming is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or the glass substrate in a high-temperature, low-humidity environment. In addition, since the optical member of the present disclosure has a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure, the optical film is unlikely to shrink in a high-temperature, low-humidity environment. In addition, since the optical member of the present disclosure has a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure, even when the optical member of the present disclosure is used to bond a glass substrate having a transparent conductive film (e.g., an ITO film) on its surface to a polarizing plate, corrosion of the transparent conductive film is unlikely to occur.

[0124] The thickness of the glass substrate is not particularly limited, and is generally 0.3 mm to 0.7 mm, and preferably 0.3 mm to 0.5 mm.

[0125] Examples of glass substrates include soda glass, non-alkali glass, and ITO (Indium Tin Oxide) coated glass.

[0126] The pressure-sensitive adhesive layer and the optical film in the optical member of the present disclosure are synonymous with the pressure-sensitive adhesive layer and the optical film in the pressure-sensitive adhesive sheet of the present disclosure, and preferred embodiments are also the same, so description thereof will be omitted here.

[0127] The optical member of the present disclosure can be suitably used, for example, as a member of a display device. Examples of display devices include liquid crystal displays and organic EL (Electro-Luminescence) displays.

[0128] The method for producing the optical member of the present disclosure is not particularly limited. The optical member of the present disclosure can be produced, for example, by using an optical film as a substrate, producing a pressure-sensitive adhesive sheet of the present disclosure by the method described above, and then bonding the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to a glass substrate.

[0129] [Display device] The display device of the present disclosure includes the optical member of the present disclosure described above. Since the display device of the present disclosure includes the optical member of the present disclosure, even when placed in a high-temperature, low-humidity environment, foaming is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or the glass substrate, peeling is unlikely to occur between the pressure-sensitive adhesive layer and the glass substrate, and wrinkles are unlikely to occur in the pressure-sensitive adhesive layer and / or the optical film. In addition, since the display device of the present disclosure includes the optical member of the present disclosure, corrosion of the transparent conductive film is unlikely to occur.

[0130] Specific examples of the display device are as described above. EXAMPLES

[0131] The pressure-sensitive adhesive composition of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0132] [Production of (meth)acrylic copolymer] [Manufacturing example A-1] In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 75.3 parts by mass of n-butyl acrylate [n-BA], 24.5 parts by mass of methyl acrylate [MA], 0.2 parts by mass of 2-hydroxyethyl acrylate [2HEA], 25.0 parts by mass of ethyl acetate [organic solvent], and 50.0 parts by mass of methyl acetate [organic solvent] were mixed to obtain a mixture, and then the inside of the reactor was replaced with nitrogen. Next, the mixture in the reactor was heated to 70°C while stirring, and then 0.01 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] and 140.0 parts by mass of ethyl acetate were successively added to the mixture in the reactor. After the addition was completed, the mixture was held for 6 hours to polymerize, and a polymerization reaction product was obtained. The obtained polymerization reaction product was diluted with ethyl acetate to a solid concentration of 15.5% by mass, and then cooled to obtain a solution of (meth)acrylic copolymer A-1.

[0133] The term "solid content" used herein means the mass ratio of the (meth)acrylic copolymer A-1 in the solution of the (meth)acrylic copolymer A-1. The same applies to each of the solutions of the (meth)acrylic copolymers A-2 to A-11 produced below.

[0134] [Production Examples A-2 to A-4 and A-6 to A-11] In Production Examples A-2 to A-4 and A-6 to A-11, the same operation as in Production Example A-1 was carried out except that the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and solutions of (meth)acrylic copolymers A-2 to A-4 and A-6 to A-11 each having a solid content concentration of 15.5 mass% were obtained.

[0135] [Manufacturing example A-5] In Production Example A-5, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and at least one of the amount of the organic solvent and the amount of the polymerization initiator was adjusted to adjust the weight average molecular weight of the (meth)acrylic copolymer to the weight average molecular weight shown in Table 1. Except for this, the same operation as in Production Example A-1 was performed to obtain a solution of (meth)acrylic copolymer A-5 having a solid content concentration of 15.5 mass%.

[0136] Table 1 shows the monomer compositions (unit: mass %) and weight average molecular weights (represented as "Mw") of the (meth)acrylic copolymers A-1 to A-11.

[0137] The weight average molecular weights of the (meth)acrylic copolymers A-1 to A-11 were measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the specific (meth)acrylic copolymer.

[0138] Among the (meth)acrylic copolymers A-1 to A-11, the (meth)acrylic copolymers A-1 to A-7 correspond to the specific (meth)acrylic copolymer in the present disclosure.

[0139] [Table 1]

[0140] Details of each monomer listed in Table 1 are as follows. <(Meth)acrylic acid alkyl ester monomer> "n-BA": n-butyl acrylate "MA": Methyl acrylate <Monomers having a carboxy group> "AA": acrylic acid <Monomers having hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate "4HBA": 4-hydroxybutyl acrylate <Other monomers> "PHEA": Phenoxyethyl acrylate

[0141] In Table 1, "-" in the monomer composition column means that the monomer in that column was not used.

[0142] [Preparation of Adhesive Composition] Example 1 645.16 parts by mass (100 parts by mass as solid content) of the (meth)acrylic copolymer A-1 solution, 11.11 parts by mass (5 parts by mass as solid content) of Coronate (registered trademark) L-45E (trade name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, manufactured by Tosoh Corporation) as an aromatic polyisocyanate compound, and Takenate (registered trademark) as an aliphatic polyisocyanate compound. D-140N [trade name, adduct of isophorone diisocyanate (IPDI) and trimethylolpropane (TMP), solid content concentration: 100% by mass, manufactured by Mitsui Chemicals, Inc.] 30.00 parts by mass (30 parts by mass as solid content), X-41-1810 [trade name, thiol group-containing silane compound, solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.] 0.55 parts by mass (0.55 parts by mass as solid content) as a silane coupling agent, Curesol (registered trademark) 1B2PZ [trade name, 1-benzyl-2-phenylimidazole, solid content concentration: 100% by mass, manufactured by Shikoku Chemical Industry Co., Ltd.] 0.20 parts by mass (0.20 parts by mass as solid content) as a crosslinking catalyst, and an appropriate amount of ethyl acetate [organic solvent] were thoroughly mixed to obtain a pressure-sensitive adhesive composition of Example 1.

[0143] [Examples 2 to 18] In Examples 2 to 18, the pressure-sensitive adhesive compositions of Examples 2 to 18 were obtained in the same manner as in Example 1, except that the types and amounts of the (meth)acrylic copolymer, aromatic polyisocyanate compound, aliphatic polyisocyanate compound, and silane coupling agent were as shown in Table 2.

[0144] [Comparative Examples 1 to 11] In Comparative Examples 1 to 11, the same operation as in Example 1 was carried out, except that the types and amounts of the (meth)acrylic copolymer, aromatic polyisocyanate compound, aliphatic polyisocyanate compound, and silane coupling agent were as shown in Table 3, to obtain each of the pressure-sensitive adhesive compositions of Comparative Examples 1 to 11.

[0145] Tables 2 and 3 show the type and amount of the (meth)acrylic copolymer, the type and amount of the aromatic polyisocyanate compound, the type and amount of the aliphatic polyisocyanate compound, and the type and amount of the silane coupling agent in each of the pressure-sensitive adhesive compositions of Examples 1 to 18 and Comparative Examples 1 to 11.

[0146] The number of moles of hydroxyl groups in the (meth)acrylic copolymer contained in each of the pressure-sensitive adhesive compositions of Examples 1 to 18 and Comparative Examples 1 to 11 [OH X , unit: mmol), the number of moles of isocyanate groups in the aromatic polyisocyanate compound [NCO Y1 , unit: mmol)], and the number of moles of isocyanate groups in the aliphatic polyisocyanate compound [NCO Y2 , unit: mmol) are shown in Tables 2 and 3. Furthermore, Tables 2 and 3 show the functional group ratios in the pressure-sensitive adhesive compositions of Examples 1 to 18 and Comparative Examples 1 to 11. OH X , N.C.O. Y1 , N.C.O. Y2 and the functional group ratio were calculated by the above-mentioned formula.

[0147] [Table 2]

[0148] [Table 3]

[0149] Details of the components listed in Tables 2 and 3 are as follows. <Aromatic polyisocyanate compounds> "Coronate L-45E" [Product name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45% by mass, isocyanate group content (catalog value): 7.9% by mass, manufactured by Tosoh Corporation] "Takenate D-110N" [Product name, adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content: 75% by mass, isocyanate group content (catalog value): 11.5% by mass, manufactured by Mitsui Chemicals, Inc.]

[0150] <Aliphatic polyisocyanate compounds> "Takenate D-140N" [product name, adduct of isophorone diisocyanate (IPDI) and trimethylolpropane (TMP), solid content: 75% by mass, isocyanate group content (catalog value): 10.5% by mass, manufactured by Mitsui Chemicals, Inc.] "Duranate P301-75E" [Product name, adduct of hexamethylene diisocyanate (HMDI) and trimethylolpropane (TMP), solids concentration: 75% by mass, isocyanate group content (catalog value): 12.5% ​​by mass, manufactured by Asahi Kasei Corporation] "Coronate HK" [Product name, trimer of hexamethylene diisocyanate (HMDI), solid content: 100% by mass, isocyanate group content (catalog value): 20.0% by mass, manufactured by Tosoh Corporation] The above-mentioned "Coronate," "Takenate," and "Duranate" are all registered trademarks.

[0151] <Silane coupling agent> "X-41-1810" [product name, thiol group-containing silane compound, solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.]

[0152] In Tables 2 and 3, the values ​​shown in the "blended amount" column are all values ​​calculated as solid content. In Tables 2 and 3, "-" means that the ingredient in that column was not included.

[0153] [Preparation of polarizing plate with adhesive layer] The adhesive composition prepared above was applied to the easy-release treated surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] that had been surface-treated (so-called easy-release treatment) with a silicone-based release treatment agent, to form a coating film. The amount of the adhesive composition applied was set to an amount that would result in a thickness of 20 μm, as described below. Next, the formed coating film was dried by blowing air at 100° C. at a wind speed of 3 m / sec for 60 seconds using a hot air circulation dryer, thereby forming an adhesive film with a thickness of 20 μm on the release film. Next, the exposed surface of the formed adhesive film was laminated to one of the TAC layer surfaces of a polarizing plate (thickness: 100 μm) having a configuration of a triacetyl cellulose (TAC) layer / polyvinyl alcohol (PVA) layer containing a polarizer / TAC layer. Next, the laminate obtained by lamination was left to stand for 7 days (so-called curing period) in an environment of an atmospheric temperature of 23°C and 50% RH to cure the adhesive film. In this manner, a polarizing plate with an adhesive layer having a structure of release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) was produced.

[0154] [evaluation] 1. Durability in high temperature and low humidity environments (1) Preparation of samples for durability evaluation The polarizing plate with the adhesive layer prepared above was cut so that the long side was 0° with respect to the absorption axis of the polarizing plate, and a test piece with a size of 60 mm (short side) × 130 mm (long side) was prepared. Next, the release film of the test piece was peeled off. The surface of the adhesive layer exposed by peeling was placed on one side of a glass plate [type: soda glass, manufactured by Matsunami Glass Industry Co., Ltd.] so that the surface was in contact with one side of the glass plate, and then the test piece was laminated with pressure using a laminator to bond the test piece and the glass plate. In this manner, a sample for evaluating durability was prepared having a structure of glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0155] (2) Durability evaluation test The durability evaluation sample prepared above was subjected to a treatment at a temperature of 50°C and a treatment pressure of 5 kg / cm. 2After autoclaving for 20 minutes under the above conditions, the samples were left to stand for 24 hours in an environment with an atmospheric temperature of 23°C and 50% RH. After standing for 24 hours, the durability evaluation samples were left to stand for 500 hours in an environment with an atmospheric temperature of 115°C and 10% RH (so-called high temperature, low humidity environment). The condition of the durability evaluation samples after standing for 500 hours was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 4 and 5. In the following evaluation criteria, "A", "B" and "C" are practically acceptable levels, with "A" being the most preferable.

[0156] -Evaluation criteria- A: No bubbling, wrinkling or peeling was observed in the durability evaluation sample. B: At least one of bubbling, wrinkling, and peeling was slightly observed in the durability evaluation sample, but was at a level that did not pose any practical problems. C: At least one of bubbling, wrinkling, and peeling was observed in the durability evaluation sample, but was at a level acceptable for practical use. D: At least one of bubbling, wrinkling, and peeling was significantly observed in the durability evaluation sample, and was at a level that was not acceptable for practical use.

[0157] 2. Suppression of shrinkage of optical films in high temperature and low humidity environments (1) Preparation of samples for evaluating shrinkage suppression The polarizing plate with the adhesive layer prepared above was cut so that the long side was 0° with respect to the absorption axis of the polarizing plate, and a test piece with a size of 60 mm (short side) × 130 mm (long side) was prepared. Next, the release film of the test piece was peeled off. The surface of the adhesive layer exposed by peeling was placed on one side of a glass plate [type: soda glass, manufactured by Matsunami Glass Industry Co., Ltd.] so that the surface was in contact with one side of the glass plate, and then the test piece was laminated with pressure using a laminator to bond the test piece and the glass plate. In this manner, a sample for evaluating shrinkage suppression was prepared, having a structure of glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0158] (2) Shrinkage inhibition evaluation test The sample for evaluating shrinkage suppression prepared above was treated at a temperature of 50°C and a pressure of 5 kg / cm 2 After autoclaving for 20 minutes under the conditions, the sample was left to stand for 24 hours under an environment with an atmospheric temperature of 23°C and 50% RH. The sample for evaluating shrinkage inhibition after standing for 24 hours was left to stand for 200 hours under an environment with an atmospheric temperature of 115°C and 10% RH (so-called high temperature and low humidity environment). The length of the long side (i.e., the side at 0° to the absorption axis) of the sample for evaluating shrinkage inhibition after standing for 200 hours was measured using a digital microscope (model: VHX-100F, manufactured by Keyence Corporation), and the shrinkage rate was calculated by the following formula. The calculated value was rounded off to one decimal place.

[0159] Shrinkage rate (unit: %) = [[Length of the long side of the sample for evaluating shrinkage suppression before evaluation test (unit: mm)] - [Length of the long side of the sample for evaluating shrinkage suppression after evaluation test (unit: mm)]] / Length of the long side of the sample for evaluating shrinkage suppression before evaluation test (unit: mm) × 100

[0160] Based on the shrinkage rate obtained above, evaluation was performed according to the following evaluation criteria. The results are shown in Tables 4 and 5. In the following evaluation criteria, "A", "B" and "C" are practically acceptable levels, with "A" being the most preferable.

[0161] -Evaluation criteria- A: The shrinkage rate was less than 0.4%. B: The shrinkage rate was in the range of 0.4% or more and less than 0.8%. C: The shrinkage rate was in the range of 0.8% or more and less than 1.1%. D: The shrinkage rate was 1.1% or more.

[0162] 3. Processability The polarizing plate with the adhesive layer prepared above was cut to prepare a test piece measuring 1 cm x 1 cm. A feather blade was applied to the prepared test piece from the release film side in a direction parallel to the stretching direction of the polarizing plate, and the test piece was cut. The cut surface was observed using a digital microscope (model number: VHX7000, magnification: 500 times, manufactured by Keyence Corporation) to confirm the presence or absence and the degree of protrusion of the adhesive layer. Evaluation was then performed according to the following evaluation criteria. The results are shown in Tables 4 and 5. In the following evaluation criteria, "A" and "B" are practically acceptable levels, with "A" being the most preferable.

[0163] -Evaluation criteria- A: No protrusion of the adhesive layer was observed. B: Protrusion of the adhesive layer was observed, but was at a level that did not cause any practical problems. C: The pressure-sensitive adhesive layer protruded significantly, to a level that was not acceptable for practical use.

[0164] 4. Corrosivity of the substrate A glass plate with a conductive film (ITO film; the same applies below) measuring 20 mm x 25 mm was prepared. The lead rod of a tester was placed on the conductive film of the prepared glass plate with a conductive film, and the resistance value was measured. The resistance value obtained by this measurement was defined as the "resistance value before the test." Next, the polarizing plate with the adhesive layer prepared above was cut into a size of 25 mm x 30 mm. Then, the release film of the cut polarizing plate with the adhesive layer was peeled off. The conductive film surface of the glass with the conductive film, whose resistance value was measured above, was placed on the surface of the adhesive layer exposed by peeling, and then pressed with a 2 kg roller. The polarizing plate with the adhesive layer protruding from the glass with the conductive film was cut off to prepare a sample for corrosiveness evaluation. Next, the prepared sample for corrosiveness evaluation was left for one week in an environment with an atmospheric temperature of 60°C and 90% RH. The lead rod of a tester was applied to the conductive film part of the sample for corrosiveness evaluation that had been left for one week, and the resistance value was measured. The resistance value obtained by this measurement was designated as the "resistance value after test". The rate of change in resistance value was calculated from the resistance value before the test and the resistance value after the test according to the following formula. Resistance change rate (%) = [(resistance value after test - resistance value before test) ÷ resistance value before test] x 100

[0165] Based on the calculated rate of change in resistance (%), an evaluation was performed according to the following evaluation criteria. The results are shown in Tables 4 and 5. When the adhesive layer corrodes the conductive film, the rate of change in resistance increases. In the evaluation criteria below, "A" is a practical level.

[0166] -Evaluation criteria- A: The rate of change in resistance value was 3% or less. B: The rate of change in resistance value exceeded 3%.

[0167] [Table 4]

[0168] [Table 5]

[0169] From the results shown in Table 4, it was revealed that the pressure-sensitive adhesive compositions of Examples 1 to 18 could form pressure-sensitive adhesive layers that were excellent in durability and suppression of shrinkage of optical films in high-temperature, low-humidity environments, as well as in processability. It was also confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 18 were less likely to corrode conductive films. On the other hand, as shown in Table 5, the pressure-sensitive adhesive layers formed with the pressure-sensitive adhesive compositions of Comparative Examples 1 to 11 showed inferior results to the pressure-sensitive adhesive layers formed with the pressure-sensitive adhesive compositions of the Examples in at least one of the evaluations of durability in a high-temperature, low-humidity environment, shrinkage suppression of the optical film in a high-temperature, low-humidity environment, and processability.

Claims

1. a (meth)acrylic copolymer containing structural units derived from a monomer having a hydroxyl group in a proportion of more than 0 mass% and not more than 1.0 mass% based on all structural units, and not containing structural units derived from a monomer having a carboxy group; an aromatic polyisocyanate compound; an aliphatic polyisocyanate compound; Including, the content of the aromatic polyisocyanate compound is 0.25 parts by mass to 5 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer, A pressure-sensitive adhesive composition for use on an optical film, wherein the functional group ratio calculated by the following formula (A) is 0.050 to 3.5: Functional group ratio = [NCO] Ｙ１ ]×[OH] Ｘ ] / [NCO Ｙ２ ]・・・(A) OH Ｘ : the number of moles (mmol) of hydroxyl groups in the (meth)acrylic copolymer NCO Ｙ１ : the number of moles (mmol) of isocyanate groups in the aromatic polyisocyanate compound NCO Ｙ２ : the number of moles (mmol) of isocyanate groups in the aliphatic polyisocyanate compound

2. 2. The pressure-sensitive adhesive composition for optical films according to claim 1, wherein the (meth)acrylic copolymer has a weight average molecular weight of 400,000 to 2,500,000.

3. The pressure-sensitive adhesive composition for an optical film according to claim 1 , further comprising a silane coupling agent.

4. The pressure-sensitive adhesive composition for an optical film according to claim 1 , further comprising a crosslinking catalyst.

5. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for use on an optical film according to any one of claims 1 to 4.

6. An optical film; a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 4; An adhesive sheet comprising:

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

8. A glass substrate; A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for an optical film according to any one of claims 1 to 4; An optical film; An optical element comprising the above in this order.

9. A display device comprising the optical member according to claim 8 .