CN116814198A

CN116814198A - Adhesive composition for optical film, adhesive sheet, optical member, and display device

Info

Publication number: CN116814198A
Application number: CN202310304444.3A
Authority: CN
Inventors: 藤川春奈; 广田智也; 长谷川良; 守山史朗
Original assignee: Nippon Carbide Industries Co Inc
Current assignee: Nippon Carbide Industries Co Inc
Priority date: 2022-03-28
Filing date: 2023-03-24
Publication date: 2023-09-29
Also published as: TW202400748A; JP2023145214A

Abstract

The present invention is an adhesive composition for an optical film, an adhesive sheet, an optical member, and a display device, the adhesive composition for an optical film comprising: a (meth) acrylic polymer (A) having a Mw of 100 ten thousand or more and containing a structural unit derived from an n-butyl acrylate, a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety, a (meth) acrylic polymer (B) having a hydroxyl group content of 0.0007 to 0.22mmol/g and a Tg of 0 ℃ or more and a Mw of 70 ten thousand or less, and a crosslinking agent; the content of the (meth) acrylic polymer (B) is 3 to 50 parts by mass per 100 parts by mass of the (meth) acrylic polymer (a).

Description

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

Technical Field

The present disclosure relates to an adhesive composition for an optical film, an adhesive sheet, an optical member, and a display device.

Background

A liquid crystal display device generally includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two support substrates, and an optical film such as a polarizing plate, a retardation film, and a brightness enhancement film. When a liquid crystal cell, an optical film, and an optical film are laminated to each other to manufacture a liquid crystal display device, these members are bonded via an adhesive layer formed of an adhesive composition. In a liquid crystal display device, a (meth) acrylic adhesive composition is often used from the viewpoint of ensuring visibility.

For example, JP-A2002-121521 discloses an adhesive composition for a polarizing film, which comprises: 100 parts by weight of a high molecular weight acrylic polymer component having a weight average molecular weight of 100 to 250 tens of thousands containing a reactive functional group, 10 to 100 parts by weight of a low molecular weight acrylic polymer component having a weight average molecular weight of 3 to 10 tens of thousands having a glass transition temperature of 0 to-80 ℃, and 0.001 to 10 parts by weight of a polyfunctional compound component containing 2 or more functional groups capable of reacting with the reactive functional groups to form a crosslinked structure.

In addition, japanese patent application laid-open No. 2007-326910 discloses an adhesive composition comprising a first polymer and a second polymer, wherein the first polymer comprises, as monomer units, from 40 to 98% by weight of a (meth) acrylic monomer (a) having a specific structural formula, from 1 to 59.9% by weight of a (meth) acrylic monomer (b) copolymerizable with the (meth) acrylic monomer (a) and having an aromatic ring, from 0.1 to 5% by weight of a polymerizable monomer (c) copolymerizable with the (meth) acrylic monomer (a) and the (meth) acrylic monomer (b) and having a reactive functional group, and from 0 to 59.9% by weight of a polymerizable monomer (d) copolymerizable with the (meth) acrylic monomer (b) and the polymerizable monomer (c), and the second polymer comprises, as monomer units, from 0 to 59.9% by weight of an alkyl methacrylate, and has a weight average molecular weight of 10 ten thousand or less; the content of the second polymer is 1 to 40 parts by weight relative to 100 parts by weight of the first polymer.

In addition, international publication No. 2019/150729 discloses an adhesive composition comprising a vinyl polymer (a) and an acrylic adhesive polymer (B), wherein the adhesive composition has a first Tg which is the glass transition temperature of the entire adhesive layer formed from the adhesive composition of-80 to 10 ℃, and a second Tg which is the glass transition temperature calculated from the surface layer portion of the adhesive layer obtained by X-ray photoelectron spectroscopy of the adhesive layer, which is 30 ℃ or higher than the first Tg, and wherein the adhesive sheet comprising an adhesive layer having a film thickness of 50 μm formed from the adhesive composition on a 100 μm thick polyethylene terephthalate film substrate has a peel strength to glass of 4.0N/25mm or higher at 100 ℃.

Disclosure of Invention

Since an optical film such as a polarizing plate is generally formed by laminating a plurality of members having different shrinkage rates, dimensional changes are likely to occur due to changes in temperature and/or humidity. Therefore, when the optical film bonded via the adhesive layer is subjected to severe environments such as a high-temperature environment and an environment in which the temperature is repeated at a low temperature, there are cases where the optical film shrinks and the adhesive layer and/or the optical film is wrinkled, or the adhesive layer is peeled off from the adherend. In addition, in recent years, with the increasing demand for weight reduction and miniaturization of displays, there is a demand for further thinning of an optical film used in a display, and the optical film tends to shrink more easily than before due to a reduction in rigidity accompanying thinning.

However, due to the rise of borderless smartphones, optical films such as polarizers are cut (hereinafter simply referred to as "processed") into complex shapes other than rectangles. When an optical film in which an adhesive layer is laminated is processed, there is a problem that the adhesive layer protrudes from a processed end surface and pollutes the surrounding environment. In order to improve the workability of the adhesive layer, it is considered to increase the cohesive force of the adhesive layer. However, if the cohesive force of the adhesive layer is increased, the adhesive layer becomes hard, and thus, conversely, the stress due to shrinkage of the optical film is hardly relaxed by the adhesive layer. Therefore, when the shrinkage of the optical film increases, the stress generated cannot be completely relaxed by the adhesive layer, and defects such as wrinkles in the adhesive layer and/or the optical film, and peeling of the adhesive layer from the adherend occur.

In view of the above, an adhesive composition used for an optical film is required to be capable of forming an adhesive layer which is less likely to cause wrinkles and peeling even when placed under severe environments and is excellent in workability.

In addition, it is generally required that an adhesive composition used in an optical film can form an adhesive layer excellent in transparency. However, in the adhesive layer which is left under a high temperature environment for a long period of time, components contained in the adhesive layer may be separated from each other, and transparency may be impaired.

The present disclosure has been made in view of the above circumstances.

An embodiment of the present disclosure has an object to provide an adhesive composition for an optical film, which is capable of forming an adhesive layer that is less likely to cause wrinkles and peeling even when placed under repeated low-temperature and high-temperature environments and has excellent transparency and excellent processability even after being placed under high-temperature environments for a long period of time.

Another embodiment of the present disclosure is directed to providing an adhesive sheet, an optical member, and a display device, each of which has an adhesive layer that is less likely to cause wrinkles and peeling even when exposed to repeated low-temperature and high-temperature environments, and that has excellent transparency and excellent processability even after being exposed to high-temperature environments for a long period of time.

Specific methods for solving the problems include the following.

1 > an adhesive composition for optical films comprising: a (meth) acrylic polymer (A) comprising a structural unit derived from n-butyl acrylate and having a weight average molecular weight of 100 ten thousand or more, a (meth) acrylic polymer (B) comprising a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety and a structural unit derived from a monomer having a hydroxyl group and having a hydroxyl group content of 0.0007 to 0.22mmol/g, a glass transition temperature of 0 ℃ or more and a weight average molecular weight of 70 ten thousand or less, and a crosslinking agent; the content of the (meth) acrylic polymer (B) is 3 to 50 parts by mass per 100 parts by mass of the (meth) acrylic polymer (a).

The adhesive composition for an optical film according to < 2 > to < 1 >, wherein the (meth) acrylic polymer (A) contains at least one of a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxyl group.

The adhesive composition for an optical film according to < 1 > or < 2 > wherein the content of the n-butyl acrylate-derived structural unit in the (meth) acrylic polymer (A) is 50% by mass or more.

The pressure-sensitive adhesive composition for optical films of any one of < 1 > - < 3 >, wherein the content of the crosslinking agent is 0.05 to 15 parts by mass per 100 parts by mass of the (meth) acrylic polymer (A).

The adhesive composition for an optical film according to any one of < 1 > < 4 >, wherein the crosslinking agent is an isocyanate-based crosslinking agent.

The adhesive composition for an optical film according to any one of < 1 > - < 5 >, wherein the adhesive composition further comprises a silane coupling agent.

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition for optical films described in any one of < 1 > < 6 >.

The pressure-sensitive adhesive sheet according to claim 8 to 7, wherein the pressure-sensitive adhesive sheet comprises an optical film and a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition for an optical film according to any one of 1 to 6.

The pressure-sensitive adhesive sheet according to < 9 > to < 8 >, wherein the optical film is a polarizing plate.

An optical member comprising, in order, a glass substrate, an adhesive layer formed of the adhesive composition for an optical film of any one of < 1 > - < 6 >, and an optical film.

< 11 > a display device comprising the optical member described as < 10 >.

According to one embodiment of the present disclosure, an adhesive composition for an optical film capable of forming an adhesive layer which is less likely to cause wrinkles and peeling even when placed under repeated low-temperature and high-temperature environments and which has excellent transparency and excellent processability even after being placed under high-temperature environments for a long period of time is provided.

According to other embodiments of the present disclosure, there are provided an adhesive sheet, an optical member, and a display device having an adhesive layer which is less likely to cause wrinkles and peeling even when placed under a repeated low-temperature and high-temperature environment, and which has excellent transparency and excellent processability even after being placed under a high-temperature environment for a long period of time.

Drawings

Fig. 1 is a diagram for explaining a method of evaluating workability in examples.

[ description of the symbols ]

10: release film, 20: adhesive layer, 30: polarizing plate, 100: test samples (adhesive layer-carrying polarizers), X1, X2, X3 and X4: protrusion width of adhesive layer, Y: width of test sample (adhesive layer-carrying polarizing plate)

Detailed Description

Hereinafter, the adhesive composition for an optical film, the adhesive sheet, the optical member, and the display device of the present disclosure will be described in detail. The following description of the elements is made based on the representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments, and may be implemented with appropriate modifications within the scope of the object of the present disclosure.

In the present disclosure, a numerical range indicated by "to" means a range including numerical values described before and after "to" as a lower limit value and an upper limit value, respectively.

In the numerical ranges described in stages in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stages. In addition, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present disclosure, in the case where a plurality of substances corresponding to the respective components are present in the adhesive composition, unless otherwise specified, the amount of the respective components in the adhesive composition represents the total amount of the plurality of substances present in the adhesive composition.

In the present disclosure, "(meth) acrylic monomer" means a monomer having a (meth) acryloyl group.

In the present disclosure, "a (meth) acrylic polymer" refers to a polymer that contains structural units derived from a (meth) acrylic monomer and that has a proportion of structural units derived from a (meth) acrylic monomer of 50 mass% or more.

In the present disclosure, "(meth) acrylic acid" is a term containing both "acrylic acid" and "methacrylic acid", "(meth) acrylate" is a term containing both "acrylate" and "methacrylate", "(meth) acryl" is a term containing both "acryl" and "methacryl", and "(meth) acrylamide" is a term containing both "acrylamide" and "methacrylamide".

In the present disclosure, "n-" means positive, "i-" means different, "s-" means secondary, and "t-" means tertiary.

In this disclosure, "polymer" and "polymer" are synonymous.

In the present disclosure, the specific (meth) acrylic polymer (a) and the specific (meth) acrylic polymer (B) are collectively referred to as "specific (meth) acrylic polymer".

[ adhesive composition for optical film ]

The adhesive composition for an optical film of the present disclosure (hereinafter also simply referred to as "adhesive composition") includes: a (meth) acrylic polymer (A) comprising a structural unit derived from n-butyl acrylate and having a weight average molecular weight of 100 ten thousand or more, a (meth) acrylic polymer (B) comprising a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety and a structural unit derived from a monomer having a hydroxyl group, the content of the hydroxyl group being 0.0007 to 0.22mmol/g, the glass transition temperature being 0 ℃ or more and the weight average molecular weight being 70 ten thousand or less, and a crosslinking agent; the content of the (meth) acrylic polymer (B) is 3 to 50 parts by mass per 100 parts by mass of the (meth) acrylic polymer (a).

The adhesive composition of the present disclosure is capable of forming an adhesive layer which is less likely to cause wrinkles and peeling even when placed under repeated low-temperature and high-temperature environments and which is excellent in transparency and workability even after being placed under high-temperature environments for a long period of time.

The reason why such effects can be exerted on the adhesive composition of the present disclosure is not clear, but the present inventors speculate as follows. However, the following presumption is not intended to limit the explanation of the adhesive composition of the present disclosure, but is instead given as an example.

The adhesive composition of the present disclosure comprises a higher molecular weight (meth) acrylic polymer (a) as a base polymer. By increasing the molecular weight of the base polymer, the cohesive force of the adhesive layer formed is improved. On the other hand, if the cohesive force of the adhesive layer is increased, the workability is improved, but the adhesive layer is hardened, and thus conversely, the stress due to shrinkage of the optical film is hardly relaxed by the adhesive layer. Therefore, when the shrinkage of the optical film increases, the stress generated cannot be completely relaxed by the adhesive layer, and defects such as wrinkles in the adhesive layer and/or the optical film, and peeling of the adhesive layer from the adherend occur. In contrast, the adhesive composition of the present disclosure, in addition to the (meth) acrylic polymer (a) having a relatively high molecular weight and the crosslinking agent, properly contains the (meth) acrylic polymer (B) having a relatively high glass transition temperature and properly having hydroxyl groups, thereby controlling the cohesive force, tackiness, and elasticity of the adhesive layer formed, and solving the above-mentioned problems.

In the adhesive layer formed from the adhesive composition of the present disclosure, the sea-island structure of the (meth) acrylic polymer (a) and the (meth) acrylic polymer (B) is formed. By forming the island structure, since the tackiness and the cohesive force are uniformly exhibited in the adhesive layer, the stress due to shrinkage of the optical film can be satisfactorily relaxed, and the elasticity of the entire adhesive layer can be improved, so that the protrusion from the processed end face during processing can be suppressed.

Since the (meth) acrylic polymer (B) contained in the adhesive composition of the present disclosure moderately contains hydroxyl groups, it is easy to enter into a crosslinked structure. Therefore, in the formed adhesive layer, even when left under a high-temperature environment for a long period of time, the (meth) acrylic polymer (B) in the adhesive layer is less likely to move to the interface of the adhesive layer, and a decrease in transparency due to separation of the (meth) acrylic polymer (B) and the (meth) acrylic polymer (a) is less likely to occur. In addition, the molecular weight of the (meth) acrylic polymer (B) is moderately lower than that of the (meth) acrylic polymer (a), and the content of the (meth) acrylic polymer (B) is not excessive with respect to the content of the (meth) acrylic polymer (a), so that the compatibility of the (meth) acrylic polymer (a) with the (meth) acrylic polymer (B) is good. In addition, since the alkyl acrylate monomer and the alkyl methacrylate monomer are generally poor in compatibility, the low molecular weight (meth) acrylic polymer containing one of them tends to move to the interface in the adhesive layer placed under a high temperature environment for a long period of time. In the adhesive composition of the present disclosure, the structural unit contained in the (meth) acrylic polymer (a) is a structural unit derived from n-butyl acrylate, and the structural unit contained in the (meth) acrylic polymer (B) is a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety, so that the compatibility is good. Therefore, in the adhesive layer formed of the adhesive composition of the present disclosure, a decrease in transparency due to poor compatibility is less likely to occur.

To sum up, it is assumed that: an adhesive layer formed from the adhesive composition of the present disclosure is less likely to generate wrinkles and peeling even when placed under repeated low-temperature and high-temperature environments and has excellent transparency even after being placed under high-temperature environments for a long period of time, and is excellent in workability.

On the other hand, in Japanese patent application laid-open No. 2002-121521, japanese patent application laid-open No. 2007-326910 and International publication No. 2019/150729, there is no focus on forming an adhesive layer having both of wrinkle and peeling inhibition, processability and transparency as described above.

In addition, the adhesive layer formed of the adhesive composition of the present disclosure can exert the following effects in addition to the above effects: wrinkles and peeling are less likely to occur even when exposed to a high temperature environment, and shrinkage of the substrate that may occur when exposed to a high temperature environment can be well suppressed.

In the present disclosure, "a (meth) acrylic polymer (a) having a weight average molecular weight of 100 ten thousand or more, which contains a structural unit derived from n-butyl acrylate", is also referred to as "a specific (meth) acrylic polymer (a)". In the present disclosure, the term "a (meth) acrylic polymer (B) having a content of hydroxyl groups of 0.0007mmol/g to 0.22mmol/g, a glass transition temperature of 0 ℃ or higher and a weight average molecular weight of 70 ten thousand or less" is also referred to as "a specific (meth) acrylic polymer (B)", which includes a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety and a structural unit derived from a monomer having hydroxyl groups.

[ specific (meth) acrylic Polymer (A) ]

The adhesive composition of the present disclosure comprises a (meth) acrylic polymer (A) [ i.e., a specific (meth) acrylic polymer (A) ] having a structural unit derived from n-butyl acrylate and a weight average molecular weight of 100 ten thousand or more.

The adhesive composition of the present disclosure may contain only 1 specific (meth) acrylic polymer (a) or may contain 2 or more.

The specific (meth) acrylic polymer (a) may be a homopolymer or a copolymer as long as it contains a structural unit derived from n-butyl acrylate and has a weight average molecular weight of 100 ten thousand or more.

< structural Unit derived from n-butyl acrylate >)

The specific (meth) acrylic polymer (a) contains a structural unit derived from n-butyl acrylate. In the present disclosure, "structural unit derived from n-butyl acrylate" refers to a structural unit formed by addition polymerization of n-butyl acrylate.

The structural unit derived from n-butyl acrylate in the specific (meth) acrylic polymer (a) contributes to suppression of reduction in transparency of the adhesive layer placed under a high-temperature environment.

The content of the n-butyl acrylate-derived structural unit in the specific (meth) acrylic polymer (a) is not particularly limited, but is, for example, preferably 50% by mass or more, more preferably 50% by mass to 95% by mass, still more preferably 55% by mass to 95% by mass, and particularly preferably 60% by mass to 90% by mass, relative to the total structural units of the specific (meth) acrylic polymer (a).

Here, the content of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic polymer (a) is 50 mass% or more with respect to the entire structural units of the specific (meth) acrylic polymer (a), which means that: comprises a structural unit derived from n-butyl acrylate as a main component constituting a structural unit of the specific (meth) acrylic polymer (A).

Structural units derived from other alkyl (meth) acrylate monomers A >)

The specific (meth) acrylic polymer (a) preferably contains structural units derived from an alkyl (meth) acrylate monomer other than n-butyl acrylate.

In the present disclosure, "alkyl (meth) acrylate monomers other than n-butyl acrylate in the specific (meth) acrylic polymer (a)" will also be referred to as "other alkyl (meth) acrylate monomers a".

In the present disclosure, "structural unit derived from other alkyl (meth) acrylate monomer a" refers to a structural unit formed by addition polymerization of other alkyl (meth) acrylate monomer a. The "other alkyl (meth) acrylate monomer a" in the present 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.

The kind of the other alkyl (meth) acrylate monomer a is not particularly limited.

The other alkyl (meth) acrylate monomer a may be an alkyl acrylate monomer or an alkyl methacrylate monomer.

The alkyl group of the other alkyl (meth) acrylate monomer a may be unsubstituted or substituted (excluding carboxyl and hydroxyl groups), but is preferably unsubstituted.

The alkyl group of the other alkyl (meth) acrylate monomer a may be any of linear, branched, or cyclic.

The number of carbon atoms of the alkyl group of the other alkyl (meth) acrylate monomer a is, for example, preferably 1 to 18, more preferably 1 to 12, and still more preferably 1 to 8.

Specific examples of the other alkyl (meth) acrylate monomer a include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl methacrylate, 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.

As the other alkyl (meth) acrylate monomer a, at least 1 selected from t-butyl acrylate, methyl methacrylate and 2-ethylhexyl acrylate is preferable.

When the specific (meth) acrylic polymer (a) contains structural units derived from other alkyl (meth) acrylate monomers a, the specific (meth) acrylic polymer (a) may contain only 1 structural unit derived from other alkyl (meth) acrylate monomers a or may contain 2 or more structural units.

When the specific (meth) acrylic polymer (a) contains a structural unit derived from another (meth) acrylic acid alkyl ester monomer a, the content of the structural unit derived from another (meth) acrylic acid alkyl ester monomer a in the specific (meth) acrylic polymer (a) is not particularly limited, but is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, still more preferably 5 to 30% by mass, and particularly preferably 7 to 20% by mass, with respect to the total structural units of the specific (meth) acrylic polymer (a).

Structural unit derived from monomer having hydroxyl group

The specific (meth) acrylic polymer (a) may contain a structural unit derived from a monomer having a hydroxyl group.

In the present disclosure, "structural unit derived from a monomer having a hydroxyl group" refers to a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

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

Examples of the monomer having a hydroxyl group include monomers 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) acryl group.

As the ethylenically unsaturated group, (meth) acryl is preferable.

Specific examples of the monomer 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-dimethyl-3-hydroxybutyl (meth) acrylate, 1, 3-dimethyl-3-hydroxybutyl (meth) acrylate, 2, 4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, N-hydroxyethyl (meth) acrylamide, glycerol 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, for example, a hydroxyalkyl (meth) acrylate is preferable from the viewpoint of good copolymerizability with other monomers. As the hydroxyalkyl (meth) acrylate, a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is preferable, and 2-hydroxyethyl acrylate is more preferable.

When the specific (meth) acrylic polymer (a) contains structural units derived from a monomer having a hydroxyl group, the specific (meth) acrylic polymer (a) may contain only 1 structural unit derived from a monomer having a hydroxyl group, or may contain 2 or more structural units.

Structural unit derived from monomer having carboxyl group

The specific (meth) acrylic polymer (a) may contain a structural unit derived from a monomer having a carboxyl group.

In the present disclosure, "structural unit derived from a monomer having a carboxyl group" refers to a structural unit formed by addition polymerization of a monomer having a carboxyl group.

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

Examples of the monomer having a carboxyl group include monomers having at least one carboxyl group and an ethylenically unsaturated group in one molecule.

As the ethylenically unsaturated group, (meth) acryl is preferable.

Specific examples of the monomer having a carboxyl group include (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, pentadienoic acid, citraconic acid, ω -carboxyl-polycaprolactone mono (meth) acrylate [ e.g., ω -carboxyl-polycaprolactone (n.apprxeq.2) monoacrylate ], and succinic acid derivatives (e.g., 2-acryloyloxyethyl succinate).

As the monomer having a carboxyl group, (meth) acrylic monomer having a carboxyl group is preferable, and acrylic acid is more preferable.

When the specific (meth) acrylic polymer (a) contains structural units derived from a monomer having a carboxyl group, the specific (meth) acrylic polymer (a) may contain only 1 structural unit derived from a monomer having a carboxyl group, or may contain 2 or more structural units.

Total content of hydroxyl and carboxyl groups

When the specific (meth) acrylic polymer (a) contains at least one of a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxyl group, the total content of the hydroxyl group and the carboxyl group in the specific (meth) acrylic polymer (a) is, for example, preferably 0.01mmol/g or more, more preferably 0.01mmol/g to 0.7mmol/g, still more preferably 0.05mmol/g to 0.7mmol/g, and particularly preferably 0.30mmol/g to 0.5mmol/g.

If the total content of hydroxyl groups and carboxyl groups in the specific (meth) acrylic polymer (A) is 0.01mmol/g or more, the workability of the formed adhesive layer tends to be further improved. In addition, the formed adhesive layer is more likely to suppress shrinkage of the substrate that may occur when exposed to a high temperature environment for a long period of time.

The total content (unit: mmol/g) of hydroxyl groups and carboxyl groups in the specific (meth) acrylic polymer (A) is determined by the following formulas (A1) to (A3). When a plurality of monomers having a hydroxyl group and/or monomers having a carboxyl group forming the specific (meth) acrylic polymer (a) are present, the numerical values obtained by calculating the respective monomers are summed up.

Hydroxyl group content (Unit: mmol/g)

= [ content (unit: mass%) of structural unit derived from monomer having hydroxyl group in specific (meth) acrylic polymer (a)/(molar mass (unit: g/mol) ×100 ] of structural unit derived from monomer having hydroxyl group×number (valence) ×1000·· (A1) of hydroxyl group in structural unit derived from monomer having hydroxyl group

Carboxyl group content (Unit: mmol/g)

= [ content (unit: mass%) of structural unit derived from monomer having carboxyl group in specific (meth) acrylic polymer (a)/(molar mass (unit: g/mol) ×100 ] of structural unit derived from monomer having carboxyl group×number (valence) ×1000· (A2) of carboxyl group in structural unit derived from monomer having carboxyl group

Total content of hydroxyl groups and carboxyl groups (unit: mmol/g)

Content of hydroxyl group (unit: mmol/g) +content of carboxyl group (unit: mmol/g) · (A3)

< other structural units >)

Examples of other structural units that may be contained in the specific (meth) acrylic polymer (a) include structural units derived from (meth) acrylic esters having an aromatic ring represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; structural units derived from alkoxyalkyl (meth) acrylates represented by methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; structural units derived from monovinylaromatic groups represented by styrene, α -methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene and vinyltoluene; structural units derived from vinyl cyanide typified by acrylonitrile and methacrylonitrile; structural units derived from vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate; etc.

In the present disclosure, monomers forming other structural units are also referred to as "other monomers".

When the specific (meth) acrylic polymer (a) contains other structural units, it may contain only 1 or 2 or more other structural units.

In the case where the specific (meth) acrylic polymer (a) contains other structural units, the content of the other structural units in the specific (meth) acrylic polymer (a) may be appropriately set within a range that does not impair the effects of the adhesive composition of the present disclosure.

Specific weight average molecular weight of (meth) acrylic Polymer (A)

The weight average molecular weight (hereinafter also referred to as "Mw") of the specific (meth) acrylic polymer (A) is 100 ten thousand or more, preferably 100 ten thousand to 250 ten thousand, more preferably 120 ten thousand to 250 ten thousand, still more preferably 140 ten thousand to 250 ten thousand, and particularly preferably 160 ten thousand to 250 ten thousand.

When the weight average molecular weight of the specific (meth) acrylic polymer (a) is 100 ten thousand or more, an adhesive layer excellent in processability can be formed. In addition, an adhesive layer capable of favorably suppressing shrinkage of a substrate that may occur when left in a high-temperature environment for a long period of time can be formed.

The weight average molecular weight of the specific (meth) acrylic polymer (a) is a value measured by the following method. Specifically, the measurement was performed according to the following (1) to (3).

(1) The solution of the specific (meth) acrylic polymer (a) was applied to a release paper and dried at 100 ℃ for 1 minute to obtain a specific (meth) acrylic polymer (a) in the form of a film.

(2) A sample solution having a solid content concentration of 0.2% by mass was obtained by using the specific (meth) acrylic polymer (A) in the form of a film obtained in the above (1) and tetrahydrofuran. The "solid content concentration" as used herein refers to the mass ratio of the specific (meth) acrylic polymer (a) in the sample solution.

(3) The weight average molecular weight of the specific (meth) acrylic polymer (a) was determined as a standard polystyrene equivalent by Gel Permeation Chromatography (GPC) under the following conditions.

Conditions to the extent

Measurement device: high speed GPC [ model: HLC-8220GPC, manufactured by Tosoh Co., ltd

A detector: differential Refractometer (RI) [ incorporated HLC-8220, manufactured by Tosoh Co., ltd.)

Column: using 4 TSKgel GMH _XL [ manufactured by Tosoh Co., ltd.)

Column temperature: 40 DEG C

Eluent: tetrahydrofuran (THF)

Injection amount of sample solution: 100 mu L

Flow rate: 0.8 mL/min

The weight average molecular weight of the specific (meth) acrylic polymer (a) can be adjusted to a desired value by adjusting the polymerization temperature, the polymerization time, the amount of the organic solvent used, the kind of the polymerization initiator, the amount of the polymerization initiator used, and the like when polymerizing the monomer.

Specific glass transition temperature of (meth) acrylic Polymer (A)

The glass transition temperature (also referred to as "Tg") of the specific (meth) acrylic polymer (A) is not particularly limited, but is, for example, preferably not more than-10 ℃, more preferably from-70℃to-10 ℃, still more preferably from-70℃to-20 ℃, and particularly preferably from-70℃to-30 ℃.

When the glass transition temperature of the specific (meth) acrylic polymer (a) is within the above range, even if the weight average molecular weight of the specific (meth) acrylic polymer (a) is 100 ten thousand or more, wettability to the substrate and the adherend can be sufficiently imparted to the formed adhesive layer, and more appropriate adhesive force can be obtained.

The glass transition temperature of the specific (meth) acrylic polymer (A) is a value obtained by converting the absolute temperature (unit: K) calculated from the following formula 1 into the temperature (unit:. Degree. C.).

1/Tg=m1/Tg1+m2/Tg2+. Cndot. +m (k-1)/Tg (k-1) +mk/Tgk (formula 1)

In formula 1, tg2, & gtTg (k-1) and Tgk each represent the glass transition temperature represented by the absolute temperature at the time of preparing each monomer constituting the specific (meth) acrylic polymer (A) into a homopolymer. m1, m2, & gtm (k-1) and mk represent the molar fraction of each monomer constituting the specific (meth) acrylic polymer (a), m1+m2+ & gtm (k-1) +mk=1, respectively.

The absolute temperature may be converted into a celsius temperature by subtracting 273 from the absolute temperature, and the celsius temperature may be converted into the absolute temperature by adding 273 to the celsius temperature.

The "glass transition temperature at the time of producing a homopolymer" in the present disclosure is a value described in known data or a value measured using a Differential Scanning Calorimeter (DSC). Which value is adopted is specified as follows.

The values described below are used for the "glass transition temperature at the time of producing a homopolymer" of the monomer shown below.

2-ethylhexyl acrylate: -2-ethylhexyl methacrylate at 70 ℃): -10 ℃, n-butyl acrylate: -n-butyl methacrylate at-54 ℃): 20 ℃, t-butyl acrylate: 43 ℃ and t-butyl methacrylate: 118 ℃ and i-butyl methacrylate: 53 ℃, methyl acrylate: 10 ℃, methyl methacrylate: 105 ℃, ethyl acrylate: -22 ℃, ethyl methacrylate: 65 ℃, methacrylic acid: 228 ℃, 4-hydroxybutyl acrylate: -2-hydroxyethyl acrylate at-80 ℃): -2-hydroxyethyl methacrylate at 15 ℃): 85 ℃, acrylic acid: 106 ℃, n-octyl acrylate: -65 ℃, stearyl acrylate: stearyl methacrylate at 30 ℃): 38 ℃, lauryl acrylate: -3 ℃, lauryl methacrylate: -dimethylaminoethyl methacrylate at-65 ℃): omega-carboxy-polycaprolactone (n.apprxeq.2) monoacrylate at 18 ℃): -phenoxy ethyl acrylate at-30 ℃): -22 ℃, benzyl acrylate: isobornyl methacrylate at 6 ℃): 180 ℃.

The "glass transition temperature at the time of producing a homopolymer" of a monomer other than the above-mentioned monomers is a value described in a polymer manual (4 th edition; the same applies hereinafter), and when not described in the polymer manual, a value of the glass transition temperature of a homopolymer obtained by the following measurement method is used.

Determination of the glass transition temperature of the homopolymer

The glass transition temperature of the homopolymer was determined by using a Differential Scanning Calorimeter (DSC) under a nitrogen flow at a temperature rise rate of 10mg and a temperature sample (i.e., homopolymer) of 10 ℃/min.

As a differential scanning calorimeter, for example, a differential scanning calorimeter (trade name: discovery DSC 2500) manufactured by TAInstruments Japan Inc. can be suitably used. However, the differential scanning calorimeter is not limited to this.

The glass transition temperature of the specific (meth) acrylic polymer (a) can be suitably adjusted by using, for example, 2 or more monomers having different glass transition temperatures when a homopolymer is produced.

Specific (meth) acrylic Polymer (A) content-

The content of the specific (meth) acrylic polymer (a) in the adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 60 to 99% by mass, more preferably 70 to 98% by mass, and even more preferably 80 to 97% by mass, relative to the total solid content in the adhesive composition.

In the present disclosure, the "total solid component amount in the adhesive composition" refers to the total mass of the adhesive composition in the case where the adhesive composition does not contain a solvent, and refers to the mass of the residue from which the solvent is removed from the adhesive composition in the case where the adhesive composition contains a solvent.

In the present disclosure, "solvent" refers to water and organic solvents.

[ specific (meth) acrylic Polymer (B) ]

The pressure-sensitive adhesive composition of the present disclosure comprises 3 to 50 parts by mass of a structural unit containing an alkyl methacrylate monomer having 4 carbon atoms derived from an alkyl moiety and a structural unit derived from a monomer having a hydroxyl group, the content of the hydroxyl group being 0.0007 to 0.22mmol/g, and the glass transition temperature being 0 ℃ or higher and the weight average molecular weight being 70 ten thousand or less, relative to 100 parts by mass of the specific (meth) acrylic polymer (A).

The adhesive composition of the present disclosure may contain only 1 specific (meth) acrylic polymer (B) or may contain 2 or more.

Structural unit of alkyl methacrylate monomer having 4 carbon atoms derived from alkyl moiety

The specific (meth) acrylic polymer (B) contains a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety.

In the present disclosure, "structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety" refers to a structural unit formed by addition polymerization of an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety.

Specific examples of the alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety include n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate and s-butyl methacrylate.

The alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety is preferably at least 1 selected from n-butyl methacrylate, i-butyl methacrylate and t-butyl methacrylate, more preferably at least 1 selected from i-butyl methacrylate and t-butyl methacrylate, and even more preferably t-butyl methacrylate, from the viewpoints of, for example, inhibition of wrinkles and peeling which may occur when exposed to a high temperature environment or an environment in which a low temperature and a high temperature are repeated, and processability.

Since the (meth) acrylic polymer (B) containing t-butyl methacrylate has a higher glass transition temperature than the (meth) acrylic polymer (B) containing n-butyl methacrylate or i-butyl methacrylate, an adhesive layer which is less likely to cause wrinkles and peeling and is more excellent in workability even when placed under a high-temperature environment or an environment where low temperature and high temperature are repeated can be formed.

The specific (meth) acrylic polymer (B) may contain only 1 structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety, or may contain 2 or more types.

The content of the structural unit derived from the alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety in the specific (meth) acrylic polymer (B) is not particularly limited, but is, for example, preferably 10 to 99.9 mass%, more preferably 20 to 99.9 mass%, and even more preferably 30 to 99.9 mass% relative to the total structural units in the specific (meth) acrylic polymer (B).

Structural unit derived from monomer having hydroxyl group

The specific (meth) acrylic polymer (B) contains a structural unit derived from a monomer having a hydroxyl group.

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

As the ethylenically unsaturated group, (meth) acryl is preferable.

Specific examples of the monomer having a hydroxyl group in the specific (meth) acrylic polymer (B) are the same as specific examples of the monomer having a hydroxyl group in the specific (meth) acrylic polymer (a).

As the monomer having a hydroxyl group, for example, a hydroxyalkyl (meth) acrylate is preferable from the viewpoint of good copolymerizability with other monomers. The hydroxyalkyl (meth) acrylate is preferably a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms, more preferably 2-hydroxyethyl (meth) acrylate, and still more preferably 2-hydroxyethyl methacrylate.

The specific (meth) acrylic polymer (B) may contain only 1 structural unit derived from a monomer having a hydroxyl group, or may contain 2 or more types.

Content of hydroxyl groups-

The content of hydroxyl groups in the specific (meth) acrylic polymer (B) is 0.0007 to 0.22mmol/g.

If the content of hydroxyl groups in the specific (meth) acrylic polymer (B) is 0.0007mmol/g or more, an adhesive layer having excellent transparency even after being left under a high-temperature environment for a long period of time can be formed. From such a viewpoint, the content of hydroxyl groups in the specific (meth) acrylic polymer (B) is preferably 0.005mmol/g or more, more preferably 0.01mmol/g or more, and still more preferably 0.02mmol/g or more.

If the content of hydroxyl groups in the specific (meth) acrylic polymer (B) is 0.22mmol/g or less, an adhesive layer which is less likely to cause wrinkles and peeling not only in the case of being placed under a high-temperature low-humidity environment but also in the case of being placed under an environment where low temperature and high temperature are repeated can be formed. From such a viewpoint, the content of hydroxyl groups in the specific (meth) acrylic polymer (B) is preferably 0.2mmol/g or less, more preferably 0.1mmol/g or less, and still more preferably 0.06mmol/g or less.

The hydroxyl group content in the specific (meth) acrylic polymer (B) may be 0.005mmol/g to 0.2mmol/g, may be 0.01mmol/g to 0.1mmol/g, or may be 0.02mmol/g to 0.06mmol/g in some cases.

The hydroxyl group content (unit: mmol/g) of the specific (meth) acrylic polymer (B) was determined by the following formula (B1). When a plurality of monomers having hydroxyl groups forming the specific (meth) acrylic polymer (B) are present, the values obtained by calculating the respective monomers are summed up.

Hydroxyl group content (Unit: mmol/g)

= [ content (unit: mass%) of structural unit derived from monomer having hydroxyl group in specific (meth) acrylic polymer (B)/(molar mass (unit: g/mol) ×100 ] of structural unit derived from monomer having hydroxyl group×number (valence) ×1000·· (B1) of hydroxyl group in structural unit derived from monomer having hydroxyl group

Structural units derived from other alkyl (meth) acrylate monomers B

The specific (meth) acrylic polymer (B) may contain structural units derived from an alkyl (meth) acrylate monomer other than the alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety.

In the present disclosure, "alkyl (meth) acrylate monomers other than alkyl (meth) acrylate monomers having 4 carbon atoms in the alkyl moiety" in the specific (meth) acrylic polymer (B) are also referred to as "other alkyl (meth) acrylate monomers B".

In the present disclosure, "structural unit derived from other alkyl (meth) acrylate monomer B" refers to a structural unit formed by addition polymerization of other alkyl (meth) acrylate monomer B. The "other alkyl (meth) acrylate monomer B" in the present 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.

The kind of the other alkyl (meth) acrylate monomer B is not particularly limited.

The other alkyl (meth) acrylate monomer B may be an alkyl acrylate monomer or an alkyl methacrylate monomer.

The alkyl group of the other alkyl (meth) acrylate monomer B may be unsubstituted or substituted (excluding carboxyl and hydroxyl groups), but is preferably unsubstituted.

The alkyl group of the other alkyl (meth) acrylate monomer B may be any of linear, branched, or cyclic.

The number of carbon atoms of the alkyl group of the other alkyl (meth) acrylate monomer B is, for example, preferably 1 to 18, more preferably 1 to 12, and still more preferably 1 to 8.

Specific examples of the other alkyl (meth) acrylate monomer B include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl acrylate, i-butyl acrylate, s-butyl acrylate, t-butyl 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.

As the other alkyl (meth) acrylate monomer B, at least 1 selected from the group consisting of methyl methacrylate and 2-ethylhexyl methacrylate is preferable.

When the specific (meth) acrylic polymer (B) contains structural units derived from other alkyl (meth) acrylate monomers B, the specific (meth) acrylic polymer (B) may contain only 1 structural unit derived from other alkyl (meth) acrylate monomers B or may contain 2 or more structural units.

In the case where the specific (meth) acrylic polymer (B) contains a structural unit derived from another (meth) acrylic acid alkyl ester monomer B, the content of the structural unit derived from another (meth) acrylic acid alkyl ester monomer B in the specific (meth) acrylic polymer (B) may be appropriately set within a range that does not impair the effects of the adhesive composition of the present disclosure.

< other structural units >)

Examples of the other structural unit that the specific (meth) acrylic polymer (B) may contain include structural units derived from a monomer having a carboxyl group represented by (meth) acrylic acid; structural units derived from (meth) acrylic esters having an aromatic ring represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; structural units derived from alkoxyalkyl (meth) acrylates represented by methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; structural units derived from monovinylaromatic groups represented by styrene, α -methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene and vinyltoluene; structural units derived from vinyl cyanide typified by acrylonitrile and methacrylonitrile; structural units derived from vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate; etc.

When the specific (meth) acrylic polymer (B) contains other structural units, it may contain only 1 or 2 or more other structural units.

In the case where the specific (meth) acrylic polymer (B) contains other structural units, the content of the other structural units in the specific (meth) acrylic polymer (B) may be appropriately set within a range that does not impair the effects of the adhesive composition of the present disclosure.

Weight average molecular weight of specific (meth) acrylic Polymer (B)

The weight average molecular weight of the specific (meth) acrylic polymer (B) is 70 ten thousand or less.

If the weight average molecular weight of the specific (meth) acrylic polymer (B) is 70 ten thousand or less, an adhesive layer which is excellent in transparency and maintains excellent transparency even when left under a high-temperature environment for a long period of time can be formed.

The weight average molecular weight of the specific (meth) acrylic polymer (B) is preferably 1 to 70 tens of thousands, more preferably 1 to 50 tens of thousands, still more preferably 3 to 30 tens of thousands, particularly preferably 3 to 20 tens of thousands.

The weight average molecular weight of the specific (meth) acrylic polymer (B) is a value measured by the same method as the method for measuring the weight average molecular weight of the specific (meth) acrylic polymer (a).

The weight average molecular weight of the specific (meth) acrylic polymer (B) can be adjusted to a desired value by adjusting the polymerization temperature, the polymerization time, the amount of the organic solvent used, the kind of the polymerization initiator, the amount of the polymerization initiator used, and the like when polymerizing the monomer.

Specific glass transition temperature of (meth) acrylic Polymer (B)

The glass transition temperature of the specific (meth) acrylic polymer (B) is 0 ℃ or higher.

If the glass transition temperature of the specific (meth) acrylic polymer (B) is 0 ℃ or higher, an adhesive layer which is less likely to cause wrinkles and peeling not only in the case of being placed under a high-temperature low-humidity environment but also in the case of being placed under an environment where a low temperature and a high temperature are repeated can be formed. In addition, an adhesive layer excellent in workability can be formed. In addition, an adhesive layer capable of favorably suppressing shrinkage of a substrate that may occur when left in a high-temperature environment for a long period of time can be formed.

The glass transition temperature of the specific (meth) acrylic polymer (B) is preferably 0 to 150 ℃, more preferably 25 to 150 ℃, still more preferably 55 to 150 ℃, still more preferably 70 to 150 ℃, particularly preferably 75 to 150 ℃.

The glass transition temperature of the specific (meth) acrylic polymer (B) is a value obtained by the same method as the method for obtaining the glass transition temperature of the specific (meth) acrylic polymer (a).

The glass transition temperature of the specific (meth) acrylic polymer (B) can be suitably adjusted by using, for example, 2 or more monomers having different glass transition temperatures when a homopolymer is produced.

< content of specific (meth) acrylic Polymer (B) >)

The content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 3 to 50 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic polymer (a).

If the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 3 parts by mass or more per 100 parts by mass of the specific (meth) acrylic polymer (a), an adhesive layer excellent in processability can be formed. From such a viewpoint, the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and still more preferably 10 parts by mass or more, per 100 parts by mass of the specific (meth) acrylic polymer (a).

If the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is 50 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic polymer (a), an adhesive layer that is excellent in transparency and that maintains excellent transparency even when left under a high-temperature environment for a long period of time can be formed. From such a viewpoint, the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less, per 100 parts by mass of the specific (meth) acrylic polymer (a).

In some embodiments, the content of the specific (meth) acrylic polymer (B) in the adhesive composition of the present disclosure may be 5 to 40 parts by mass, may be 7 to 30 parts by mass, or may be 10 to 20 parts by mass, with respect to 100 parts by mass of the specific (meth) acrylic polymer (a).

[ method for producing specific (meth) acrylic Polymer ]

The method for producing the specific (meth) acrylic polymer (a) and the specific (meth) acrylic polymer (B) [ specific (meth) acrylic polymer ] is not particularly limited.

The specific (meth) acrylic polymer can be produced by polymerizing the above monomers by a known polymerization method typified by a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method.

The polymerization method is preferably a solution polymerization method from the viewpoint that the treatment process is relatively simple and can be performed in a short time when the adhesive composition of the present disclosure is prepared after production.

In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent, which are used as needed, are generally placed in a polymerization tank, and the reaction is heated for several hours while stirring at the reflux temperature of the organic solvent, for example. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and the chain transfer agent used as needed may be gradually added. Alternatively, the reaction may be carried out in a nitrogen stream.

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 represented by benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetrahydronaphthalene, decalin and aromatic naphtha, aliphatic or alicyclic hydrocarbon compounds represented by n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, naphtha and turpentine, ester compounds represented by methyl acetate, ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate and methyl benzoate, ketone compounds represented by acetone, methyl ethyl ketone, methyl-i-butylketone, isophorone, cyclohexanone and methylcyclohexanone, glycol ether compounds represented by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether, and glycol ether compounds represented by methanol, ethanol, n-propanol, n-butanol, t-butanol and butanol.

In the production of a specific (meth) acrylic polymer, an organic solvent such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound, which is less likely to cause chain transfer during polymerization, is preferably used, and in particular, ethyl acetate is preferably used from the viewpoints of the solubility of the specific (meth) acrylic polymer, the ease of polymerization, and the like.

In the polymerization reaction, only 1 kind of organic solvent may be used, or 2 or more kinds may be used.

Examples of the polymerization initiator include organic peroxides and azo compounds used in a general solution polymerization method.

Specific examples of the organic peroxide include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, hexanoyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2-bis (4, 4-di-t-butylperoxycyclohexyl) propane, 2-bis (4, 4-di-t-pentylperoxycyclohexyl) propane, 2-bis (4, 4-di-t-octylperoxycyclohexyl) propane, 2-bis (4, 4-di- α -cumylperoxycyclohexyl) propane, 2-bis (4, 4-di-t-butylperoxycyclohexyl) butane and 2, 2-bis (4, 4-di-t-octylperoxycyclohexyl) butane.

Specific examples of the azo compound include 2,2 '-azobisisobutyronitrile [ AIBN ], 2' -azobis (2, 4-dimethylvaleronitrile) [ ABVN ], 2 '-azobis (4-methoxy-2, 4-dimethylvaleronitrile), 1' -azobis (cyclohexane-1-carbonitrile), dimethyl 2,2 '-azobis (2-methylpropionate) and dimethyl 2,2' -azobis (isobutyric acid).

In the polymerization reaction, only 1 kind of polymerization initiator may be used, or 2 or more kinds may be used.

The amount of the polymerization initiator to be used is not particularly limited, and may be appropriately set according to the molecular weight of the specific (meth) acrylic polymer to be used, for example.

In the production of the specific (meth) acrylic polymer, a chain transfer agent may be used as needed.

Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds having 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, alkyl ester compounds having 1 to 8 carbon atoms of bromoacetic acid, aromatic compounds represented by α -methylstyrene, anthracene, phenanthrene, fluorene and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5, 6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1, 2-tetrabromoethane, tribromoethylene, trichlorobromotrichloromethane, tribromomethane and 3-chloro-1-propene, aldehyde compounds represented by chloral and furfural, alkyl thiol compounds represented by thiophenol and toluene, aromatic thiol compounds represented by mercaptoacetic acid, alkyl ester derivatives having 1 to 10 carbon atoms of mercaptoacetic acid, and terpene compounds represented by terpene having 1 to 12 carbon atoms of hydrocarbon thiol.

In the case of using a chain transfer agent in the production of a specific (meth) acrylic polymer, the amount of the chain transfer agent used is not particularly limited, and may be appropriately set according to the molecular weight of the specific (meth) acrylic polymer to be used, for example.

The polymerization temperature is not particularly limited, and may be appropriately set according to the molecular weight of the specific (meth) acrylic polymer to be used.

[ Cross-linking agent ]

The adhesive compositions of the present disclosure comprise a crosslinker.

The kind of the crosslinking agent is not particularly limited.

Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents.

The crosslinking agent is preferably at least 1 selected from isocyanate-based crosslinking agents and epoxy-based crosslinking agents, and more preferably isocyanate-based crosslinking agents.

In the present disclosure, the "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate compound). The "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called 2-functional or more epoxy compound). The term "metal chelate-based crosslinking agent" means a metal chelate compound that functions as a crosslinking agent.

Examples of the polyisocyanate compound include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds.

Examples of the aliphatic polyisocyanate compound include aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, aliphatic polyisocyanate compounds and polyhydric alcohol compounds [ e.g., trimethylol propane (TMP) ]; the same applies hereinafter to adducts of aliphatic polyisocyanate compounds and biuret forms of aliphatic polyisocyanate compounds. Specific examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HMDI), pentamethylene Diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

Examples of the alicyclic polyisocyanate compound include an alicyclic polyisocyanate compound, a polymer of the alicyclic polyisocyanate compound, an adduct of the alicyclic polyisocyanate compound and a polyol compound, and a biuret of the alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4 '-diphenylmethane diisocyanate, and 4,4' -dicyclohexylmethane diisocyanate.

Examples of the aromatic polyisocyanate compound include an aromatic polyisocyanate compound, a polymer of an aromatic polyisocyanate compound, an adduct of an aromatic polyisocyanate compound and a polyol compound, and a biuret of an aromatic polyisocyanate compound. Specific examples of the aromatic polyisocyanate compound include Toluene Diisocyanate (TDI), xylene Diisocyanate (XDI), and 4,4' -diphenylmethane diisocyanate.

The polyisocyanate compound is preferably at least 1 selected from aliphatic polyisocyanate compounds and aromatic polyisocyanate compounds, and more preferably aromatic polyisocyanate compounds. The aromatic polyisocyanate compound is preferably at least 1 selected from the group consisting of toluene diisocyanate compounds and xylene diisocyanate compounds.

Toluene diisocyanate-based compounds include, for example, TDI, a polymer of TDI, an adduct of TDI and a polyol-based compound, and a biuret of TDI. As the toluene diisocyanate compound, an adduct of TDI and TMP is preferable.

Examples of the xylylene diisocyanate compound include XDI, a polymer of XDI, an adduct of XDI and a polyol compound, and a biuret of XDI. As the xylene diisocyanate-based compound, an adduct of XDI and TMP is preferable.

As the isocyanate-based crosslinking agent, commercially available ones can be used.

Examples of the commercially available isocyanate-based crosslinking agents include "CORONATE (registered trademark) HX", "CORONATE (registered trademark) HL-S", "CORONATE (registered trademark) L-45E", "CORONATE (registered trademark) 2031", "CORONATE (registered trademark) 2037", "CORONATE (registered trademark) 2234", "CORONATE (registered trademark) 2785", "AQUANATE (registered trademark) 200", and "AQUANATE (registered trademark) 210" [ manufactured by Tosoh corporation "," SUMIDUR (registered trademark) N3300"," DESMODUR (registered trademark) N3400", and" SUMIDUUR (registered trademark) N75 "[ above Sumika Covestro Urethane Co., ltd.," DURATE (registered trademark) D201"," DUATE (registered trademark) 405-70B "," DURANE (registered trademark) 405-80T "," DURATE (registered trademark) ]

(registered trademark) AE700-100"," DURANATE 24A-100 "and" DURANATE TSE-100 "[ more than" manufactured by Kabushiki Kaisha ", TAKENATE D-110N", "TAKENATE D-101E (45 EA)", "TAKENATE D-120N", "TAKENATE ]

(registered trademark) D-140N "," TAKENATE (registered trademark) M-631N "," MT-OLESTER (registered trademark) NP1200 "and" STABIO (registered trademark) XD-340N "

The above are manufactured by Mitsui chemical Co., ltd.).

Examples of the epoxy compound having a function of 2 or more include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol triglycidyl ether, diglycidyl polyglycidyl ether, resorcinol diglycidyl ether, 2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanate, tris (glycidoxylethyl) isocyanate, 1, 3-bis (N, N-glycidylaminomethyl) cyclohexane and N, N' -tetraglycidyl-1, 3-benzene bis (methane amine).

As the epoxy-based crosslinking agent, commercially available ones can be used.

Examples of the commercial products of the epoxy-based crosslinking agent include "TETRAD (registered trademark) -X" and "TETRAD (registered trademark) -C" [ available from Mitsubishi gas chemical Co., ltd. ] "DENACOL (registered trademark) EX-201" and "DENACOL (registered trademark) EX-931" [ available from Mitsubishi gas chemical Co., ltd. ] and "DENACOL (registered trademark) EX-931" [ available from Nagase Chemtex Corporation).

The adhesive composition of the present disclosure may contain only 1 kind of crosslinking agent, or may contain 2 or more kinds.

The content of the crosslinking agent in the adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.05 to 15 parts by mass, more preferably 0.07 to 13 parts by mass, still more preferably 0.10 to 10 parts by mass, and particularly preferably 0.15 to 8 parts by mass per 100 parts by mass of the specific (meth) acrylic polymer (a).

If the content of the crosslinking agent in the adhesive composition of the present disclosure is 0.05 parts by mass or more per 100 parts by mass of the specific (meth) acrylic polymer (a), an adhesive layer having more excellent processability tends to be formed. In addition, there is a tendency that an adhesive layer capable of better suppressing shrinkage of a substrate which may occur when the substrate is left under a high-temperature environment for a long period of time can be formed.

If the content of the crosslinking agent in the adhesive composition of the present disclosure is 15 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic polymer (a), there is a tendency that an adhesive layer capable of better suppressing wrinkles and peeling that may occur in the case of being placed under a high-temperature low-humidity environment and in the case of being placed under a repeated low-temperature and high-temperature environment can be formed. In addition, an adhesive layer which is more excellent in transparency and which maintains excellent transparency even when left under a high-temperature environment for a long period of time tends to be formed.

In some embodiments, the content of the crosslinking agent in the adhesive composition of the present disclosure may be 0.10 to 5 parts by mass, may be 0.10 to 3 parts by mass, may be 0.15 to 3 parts by mass, and may be 0.2 to 1 part by mass, relative to 100 parts by mass of the specific (meth) acrylic polymer (a).

[ silane coupling agent ]

The adhesive composition of the present disclosure may include a silane coupling agent.

The kind of the silane coupling agent is not particularly limited.

Examples of the silane coupling agent include silane compounds having a polymerizable unsaturated group represented by vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyl trimethoxysilane, silanol-containing silane compounds represented by 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, and 3-mercaptopropyl dimethoxymethylsilane, epoxy-containing silane compounds represented by 3-glycidoxypropyl trimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, amino-containing silane compounds represented by 3-aminopropyl trimethoxysilane, N- (2-aminoethyl) -3-aminopropyl trimethoxysilane, and N- (2-aminoethyl) -3-aminopropyl methyldimethoxysilane, and tris- (3-trimethoxysilylpropyl) isocyanate. 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 multifunctional silane compounds).

As the silane coupling agent, commercially available ones can be used.

Examples of the commercially available silane coupling agents include "KBM-803", "KBM-802", "X-41-1810", "X-41-1811", "X-41-1805", "X-41-1818", "KBM-403", "KBM-303", "KBM-402", "KBE-403", "X-41-1053", "X-41-1056", "KBM-9659", "KBE-9007N" and "KBM-573" manufactured by the trade name.

When the adhesive composition of the present disclosure contains a silane coupling agent, the adhesive composition may contain only 1 kind of silane coupling agent, or may contain 2 or more kinds of silane coupling agents.

In the case where the 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 to 1 part by mass, more preferably 0.1 to 0.8 part by mass, and even more preferably 0.1 to 0.5 part by mass per 100 parts by mass of the specific (meth) acrylic polymer (a).

[ organic solvent ]

The adhesive composition of the present disclosure may comprise an organic solvent.

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

Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the specific (meth) acrylic polymer.

When the adhesive composition of the present disclosure contains an organic solvent, the adhesive composition may contain only 1 organic solvent or may contain 2 or more organic solvents.

In the case where the adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited, and may be appropriately set according to the purpose.

[ other Components ]

The adhesive composition of the present disclosure may contain components other than the above components (so-called other components) as necessary within a range that does not impair the effects thereof.

Examples of the other components include various additives such as polymers other than the specific (meth) acrylic polymer, crosslinking catalysts, antioxidants, light stabilizers (for example, ultraviolet absorbers), and antistatic agents.

In the case where the adhesive composition of the present disclosure contains other components, the content of the other components may be appropriately set within a range that does not impair the effects of the adhesive composition of the present disclosure.

Use of adhesive composition

The adhesive composition of the present disclosure is an adhesive composition used in an optical film (i.e., an adhesive composition for an optical film). The adhesive layer formed from the adhesive composition of the present disclosure has the following characteristics suitable for optical film applications: not only in the case of being placed under a high-temperature environment, wrinkles and peeling are not easily generated even in the case of being placed under an environment of repeated low and high temperatures, but also excellent transparency is obtained even after being placed under a high-temperature environment for a long period of time, and workability is excellent. In addition, the adhesive layer formed from the adhesive composition of the present disclosure has a characteristic of being able to satisfactorily suppress shrinkage of the substrate that may occur when placed under a high-temperature environment, and is therefore particularly suitable as an adhesive composition for use in a polarizing plate (so-called adhesive composition for a polarizing plate) in an optical film.

Specific applications of the adhesive composition of the present disclosure include an application of bonding a polarizing plate to a glass substrate of a liquid crystal cell, an application of bonding optical films to each other, and the like.

[ adhesive sheet ]

The adhesive sheet of the present disclosure is provided with an adhesive layer formed from the adhesive composition of the present disclosure. Therefore, in the adhesive sheet of the present disclosure, not only in the case of being placed under a high-temperature environment, but also in the case of being placed under an environment where low temperature and high temperature are repeated, the adhesive layer (the substrate and the adhesive layer in the case of the adhesive sheet having the substrate) is less likely to be wrinkled, and the adhesive layer is less likely to be peeled off from the adherend. In addition, the adhesive sheet of the present disclosure is excellent in transparency and maintains excellent transparency even in the case of being left under a high-temperature environment for a long period of time. In addition, the adhesive sheet of the present disclosure is also excellent in processability. In addition, the adhesive sheet of the present disclosure is less likely to cause shrinkage of the substrate even when placed in a high-temperature environment.

The pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure contains 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 polymer (a) and a specific (meth) acrylic polymer (B) which are crosslinked and cured by a crosslinking agent.

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 1 μm to 100. Mu.m, preferably 3 μm to 50. Mu.m, more preferably 5 μm to 30. Mu.m.

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

The average thickness of the adhesive layer was determined by the following method.

The thickness of 10 portions randomly selected in the thickness direction of the adhesive layer was measured using a film thickness meter. An arithmetic average of the measured values was obtained, and the obtained value was used as an average thickness of the adhesive layer.

The pressure-sensitive adhesive sheet of the present disclosure may be a base-free pressure-sensitive adhesive sheet having no base material, or may be a base-based pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a base material.

In the case where the adhesive sheet of the present disclosure is a substrate-free adhesive sheet having no substrate, or a substrate-provided adhesive sheet having an adhesive layer on one side of a substrate, the exposed surface of the adhesive layer may be protected by a release sheet in the adhesive sheet of the present disclosure.

In general, the release sheet protects the surface of the adhesive layer before the adhesive sheet is supplied to practical use, and is released at the time of use.

The release sheet is not particularly limited as long as it can be easily released from the pressure-sensitive adhesive layer.

Examples of the release sheet include a resin film, paper, synthetic paper, and a composite sheet obtained by laminating 2 or more of them, each of which has been subjected to a surface treatment (so-called easy-release treatment) with a release agent on one or both surfaces.

In the present disclosure, a release sheet obtained by applying a surface treatment (so-called easy-release treatment) with a release treatment agent to one or both surfaces of a resin film is also referred to as a "release film".

Examples of the release agent include silicone release agents (for example, silicone), wax release agents (for example, paraffin wax), and fluorine release agents (for example, fluorine resin).

Examples of the resin film include polyester films typified by polyethylene terephthalate (PET) films.

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. Mu.m.

In the case where the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is not particularly limited as long as the substrate can form a pressure-sensitive adhesive layer thereon.

Examples of the substrate include films containing a polyolefin resin [ for example, polyethylene (PE) and polypropylene (PP) ] and a polyester resin [ for example, polyethylene terephthalate (PET) ] and an acetate resin (for example, cellulose triacetate), a polyethersulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyurethane resin, an acrylic resin, a vinyl chloride resin, an ABS (Acrylonitrile Butadiene Styrene, acrylonitrile-butadiene-styrene) resin, a fluorine resin, and the like.

From the viewpoint of improving the adhesion between the substrate and the adhesive layer, a surface treatment (so-called easy-to-adhere treatment) such as corona discharge treatment or plasma discharge treatment may be performed on the surface of the substrate on the side where the adhesive layer is provided.

The substrate may contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like.

The substrate may be patterned in part or in whole.

In the case where the adhesive sheet of the present disclosure is provided with a substrate, the substrate is preferably an optical film. In this case, as an embodiment of the pressure-sensitive adhesive sheet of the present disclosure, an embodiment including an optical film and a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed of the pressure-sensitive adhesive composition of the present disclosure is preferable.

The kind of the optical film is not particularly limited.

Specific examples of the optical film include a polarizing plate, an AG (Anti-Glare) polarizing plate, a wavelength plate, a retardation film including a 1/2 or 1/4 wavelength plate, a viewing angle compensation film, an optical compensation film, a brightness enhancement film, a light guide plate, a reflection film, an Anti-reflection film, a prism sheet, a lens sheet, a diffusion plate, a transparent conductive film, and the like.

As the optical film, a polarizing plate is preferable.

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 of the polarizer, a double layer structure having a protective film on one side of the polarizer, or a triple layer structure having protective films on both sides of the polarizer.

Examples of the layer configuration of the pressure-sensitive adhesive sheet of the present disclosure, which includes a base material and the base material is a polarizing plate, include pressure-sensitive adhesive layers/polarizing plates [ protective films/polarizers/protective films ], pressure-sensitive adhesive layers/polarizing plates [ retardation films/protective films/polarizers/protective films ], and the like.

Examples of the polarizer include a polyvinyl alcohol (PVA) film.

Examples of the protective film include a cellulose Triacetate (TAC) film, a polycycloolefin (COP) film, a polyethylene terephthalate (PET) film, and a polymethyl methacrylate (PMMA) film.

As the retardation film, for example, a polycycloolefin (COP) film is cited.

The thickness of the base material is not particularly limited, but is, for example, preferably 100 μm or less, more preferably 10 μm to 100 μm, and still more preferably 30 μm to 100 μm.

The "thickness of the substrate" in the present disclosure refers to the average thickness of the substrate. The average thickness of the base material is a value obtained by the same method as the average thickness of the adhesive layer.

[ method for producing adhesive sheet ]

The method of producing the adhesive sheet of the present disclosure is not particularly limited.

The adhesive sheet of the present disclosure may be manufactured by a known method.

As a method for producing the pressure-sensitive adhesive sheet of the present disclosure, the following method can be exemplified.

In the case where the adhesive sheet of the present disclosure is a substrate-less adhesive sheet, a coating film is first formed on the release sheet by coating the adhesive composition of the present disclosure on the release-treated surface of the release sheet. Then, by drying the formed coating film, an adhesive film is formed on the release sheet. Then, the exposed surface of the formed adhesive film is laminated on the release-treated surface of the release sheet prepared separately and cured as necessary, whereby the adhesive sheet of the present disclosure having a laminated structure of release sheet/adhesive layer/release sheet can be produced.

In the case where the adhesive sheet of the present disclosure is a substrate-provided adhesive sheet, a coating film is first formed on a substrate by applying the adhesive composition of the present disclosure to the easy-adhesion treated surface of the substrate. Then, by drying the formed coating film, an adhesive film is formed on the substrate. Then, the exposed surface of the formed adhesive film is laminated on the release-treated surface of the release sheet and cured as necessary, whereby the adhesive sheet of the present disclosure having a laminated structure of a base material, an adhesive layer and a release sheet can be produced.

In the case where the pressure-sensitive adhesive sheet of the present disclosure is a pressure-sensitive adhesive sheet having a base material, the following methods are also exemplified as other methods. The adhesive composition of the present disclosure is applied to the release-treated surface of the release sheet to form a coating film on the release sheet. Then, by drying the formed coating film, an adhesive film is formed on the release sheet. Then, the exposed surface of the formed adhesive film is laminated on the adhesion-facilitating treated surface of the base material and cured as necessary, whereby a laminate having a base material/adhesive layer can be produced

Adhesive sheet of the present disclosure in a laminated structure of release sheets.

The method of coating the adhesive composition is not particularly limited.

Examples of the method for applying the adhesive composition include known methods using a gravure roll coater, a reverse roll coater, a roll lick (kiss roll) coater, a dip roll coater, a knife coater, a spray coater, a bar coater, and an applicator.

The coating amount of the adhesive composition is not particularly limited, and is appropriately set according to the thickness of the formed adhesive layer, for example.

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

Examples of the method 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 according to the thickness of the coating film, the amount of the organic solvent in the coating film, and the like.

As an example of the drying conditions, a condition of drying at 60 to 120℃for 30 to 180 seconds using a hot air circulation dryer is given.

In the case of curing, for example, a method of standing for 2 to 7 days in an atmosphere having an atmospheric temperature of 20 to 35℃and a relative humidity of 45 to 55% (i.e., 45 to 55% RH) is mentioned as a method of curing.

[ optical Member ]

The optical member of the present disclosure includes, in order, a glass substrate, an adhesive layer formed from the adhesive composition of the present disclosure described above, and an optical film. Therefore, in the optical member of the present disclosure, not only in the case of being placed under a high-temperature low-humidity environment, but also in the case of being placed under a repeated low-temperature and high-temperature environment, the optical film and the adhesive layer are less likely to generate wrinkles, and the adhesive layer is less likely to be peeled from the glass substrate. In addition, the optical member of the present disclosure is excellent in transparency, and maintains excellent transparency even in the case of being left under a high-temperature environment for a long period of time. In addition, in the optical member of the present disclosure, shrinkage of the optical film is less likely to occur even when placed under a high-temperature environment.

The thickness of the glass substrate is not particularly limited, but is generally 0.3mm to 0.7mm, preferably 0.3mm to 0.5mm.

Examples of the glass substrate include sodium glass, alkali-free glass, and glass with an ITO (indium tin Oxide) film.

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 the preferable embodiments are the same, and therefore, the description thereof is omitted here.

The optical member of the present disclosure may be suitably used as a member of a display device, for example.

Examples of the display device include a liquid crystal display and an organic EL device

(Electro-Luminescence) display.

The method of manufacturing the optical member of the present disclosure is not particularly limited.

The optical member of the present disclosure can be manufactured, for example, by using an optical film as a base material, manufacturing the adhesive sheet of the present disclosure by the above-described method, and then bonding the adhesive layer of the adhesive sheet to a glass substrate.

[ display device ]

The display device of the present disclosure includes the optical member of the present disclosure described above. Therefore, in the display device of the present disclosure, not only in the case of being placed under a high-temperature low-humidity environment, but also in the case of being placed under a repeated low-temperature and high-temperature environment, the optical film and the adhesive layer are less likely to generate wrinkles, and the adhesive layer is less likely to be peeled from the glass substrate. In addition, the display device of the present disclosure is excellent in transparency, and maintains excellent transparency even in a case of being left under a high-temperature environment for a long period of time. In addition, in the display device of the present disclosure, shrinkage of the optical film is less likely to occur even when placed in a high-temperature environment.

The display device is specifically described above, for example.

Examples

Hereinafter, the adhesive composition of the present disclosure will be described more specifically by way of examples. The present disclosure is not limited to the following examples as long as the gist thereof is not exceeded.

[ (meth) acrylic Polymer (A) production ]

[ production example A-1 ]

264.9 parts by mass of n-butyl acrylate [ n-BA ] and methyl acrylate [ MA ] were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe and a reflux condenser; 30.0 parts by mass of other alkyl acrylate monomer A and acrylic acid [ AA; 4.5 parts by mass of a monomer having a carboxyl group, 2-hydroxyethyl acrylate [ 2HEA; 0.6 part by mass of a monomer having a hydroxyl group and 155.0 parts by mass of ethyl acetate (organic solvent) were mixed to obtain a mixture, and then nitrogen substitution was performed in the reactor. Then, after the mixture in the reactor was heated to 70 ℃ with stirring, 2' -azobis (2, 4-dimethylvaleronitrile) [ ABVN ] was gradually added to the mixture in the reactor; polymerization initiator ] 0.003 mass part and ethyl acetate 15.0 mass part, and was kept for 1 hour. Then, 0.08 parts by mass of ABVN and 340.0 parts by mass of ethyl acetate were gradually added, and the polymerization was ended after holding for 5 hours. Then, the solution obtained by ending the polymerization reaction was diluted with ethyl acetate to a solid content concentration of 15.0 mass%, and then cooled to obtain a solution of (meth) acrylic polymer a-1.

The "solid content concentration" as used herein means the mass ratio of the (meth) acrylic polymer A-1 in the solution of the (meth) acrylic polymer A-1. The same applies to each of the solutions of the (meth) acrylic polymers A-2 to A-14 produced below.

[ PREPARATION EXAMPLES A-2, A-3 and A-13 ]

In production examples A-2, A-3 and A-13, the same operations as in production example A-1 were carried out except that the weight average molecular weight of the (meth) acrylic polymer was adjusted to the weight average molecular weight shown in Table 1 by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used, to obtain solutions of the (meth) acrylic polymers A-2, A-3 and A-13 having a solid content of 15.0% by mass.

[ PREPARATION EXAMPLES A-4 to A-12 AND A-14 ]

In production examples A-4 to A-12 and A-14, the same operations as in production example A-1 were carried out except that the monomer composition of the (meth) acrylic polymer was changed to the monomer composition shown in Table 1, to obtain solutions of the (meth) acrylic polymers A-4 to A-12 and A-14 having a solid content concentration of 15.0% by mass.

Monomer compositions [ unit ] of (meth) acrylic polymers A-1 to A-14: the total content of hydroxyl groups and carboxyl groups (labeled "functional group amount") [ unit: mmol/g), glass transition temperature (labeled "Tg") [ units: DEG C) and weight average molecular weight (labeled "Mw") are shown in Table 1.

The total content (functional group amount) of hydroxyl groups and carboxyl groups in the (meth) acrylic polymers A-1 to A-14 is obtained by the same method as the method for obtaining the total content (functional group amount) of hydroxyl groups and carboxyl groups in the specific (meth) acrylic polymer (A).

The glass transition temperatures (Tg) of the (meth) acrylic polymers A-1 to A-14 were obtained by the same method as the method for obtaining the glass transition temperature of the above-mentioned specific (meth) acrylic polymer (A).

The weight average molecular weights (Mw) of the (meth) acrylic polymers A-1 to A-14 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth) acrylic polymer (A).

Among the (meth) acrylic polymers A-1 to A-14, the (meth) acrylic polymers A-1 to A-12 correspond to the specific (meth) acrylic polymer (A) in the present disclosure.

TABLE 1

Details of the respective monomers described in table 1 are as follows.

"n-BA": n-butyl acrylate [ Tg at the time of homopolymer: -54 DEG C

< other alkyl (meth) acrylate monomer A >

"MA": methyl acrylate [ Tg when made into a homopolymer: 10 ℃ C

"MMA": methyl methacrylate [ Tg when made into a homopolymer: 105 ℃ C

"2EHA": 2-ethylhexyl acrylate [ Tg at the time of homopolymer: -70 DEG C

< monomer having carboxyl group >

"AA": acrylic acid

[ Tg when made into a homopolymer: 106 ℃, molar mass: 72.06g/mol ]

< monomer having hydroxyl group >

"2HEA": acrylic acid 2-hydroxy ethyl ester

[ Tg when made into a homopolymer: -15 ℃, molar mass: 116.12g/mol ]

< other monomer >)

"PHEA": phenoxy ethyl acrylate

[ Tg when made into a homopolymer: -22 DEG C

"BZA": benzyl acrylate [ Tg when made into a homopolymer: 6 ℃ C

[ (meth) acrylic Polymer (B) production ]

[ production example B-1 ]

Methyl methacrylate [ MMA ] was charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe and a reflux cooler; 291.0 parts by mass of other alkyl methacrylate monomer B, i-butyl methacrylate [ i-BMA; 306.0 parts by mass of an alkyl methacrylate monomer having 4 carbon atoms in the alkyl portion, 2-hydroxyethyl methacrylate [ 2HEMA; 3.0 parts by mass of a monomer having a hydroxyl group and 300.0 parts by mass of ethyl acetate (organic solvent) were mixed to obtain a mixture, and then nitrogen substitution was performed in the reactor. Then, after the mixture in the reactor was heated to 70℃with stirring, 3.0 parts by mass of dimethyl 2,2' -azobis (2-methylpropionate) and 120.0 parts by mass of ethyl acetate were gradually added to the mixture in the reactor, and the polymerization was terminated after 6 hours. Then, the solution obtained by ending the polymerization reaction was diluted with ethyl acetate to a solid content concentration of 60.0 mass%, and then cooled to obtain a solution of (meth) acrylic polymer B-1.

The "solid content concentration" as used herein means the mass ratio of the (meth) acrylic polymer B-1 in the solution of the (meth) acrylic polymer B-1. The same applies to each of the solutions of the (meth) acrylic polymers B-2 to B-22 produced below.

[ production examples B-14 to B-17 ]

In production examples B-14 to B-17, the same operations as in production example B-1 were carried out except that at least one of the amount of the organic solvent used and the amount of the polymerization initiator used was adjusted so that the weight average molecular weight of the (meth) acrylic polymer was adjusted to the weight average molecular weight shown in Table 2, whereby solutions of the (meth) acrylic polymers B-14 to B-17 having a solid content concentration of 60.0 mass% were obtained.

[ production examples B-2 to B-13 and B-18 to B-22 ]

In production examples B-2 to B-13 and B-18 to B-22, the same operations as in production example B-1 were carried out except that the monomer composition of the (meth) acrylic polymer was changed to the monomer composition shown in Table 2, and solutions of the (meth) acrylic polymers B-2 to B-13 and B-18 to B-22 having a solid content concentration of 60.0% by mass were obtained.

Monomer composition [ unit ] of (meth) acrylic polymers B-1 to B-22: content of hydroxyl group (labeled "hydroxyl group amount") [ unit: mmol/g), glass transition temperature (labeled "Tg") [ units: DEG C) and weight average molecular weight (labeled "Mw") are shown in Table 2.

The hydroxyl group content (hydroxyl group amount) in the (meth) acrylic polymers B-1 to B-22 was obtained by the same method as the method for obtaining the hydroxyl group content (hydroxyl group amount) in the specific (meth) acrylic polymer (B).

The glass transition temperatures (Tg) of the (meth) acrylic polymers B-1 to B-22 were obtained by the same method as the method for obtaining the glass transition temperature of the specific (meth) acrylic polymer (A).

The weight average molecular weights (Mw) of the (meth) acrylic polymers B-1 to B-22 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth) acrylic polymer (A).

Among the (meth) acrylic polymers B-1 to B-22, the (meth) acrylic polymers B-1 to B-16 correspond to the specific (meth) acrylic polymer (B) in the present disclosure.

TABLE 2

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Details of the respective monomers described in table 2 are as follows.

Alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety

"n-BMA": n-butyl methacrylate [ Tg at the time of homopolymer: 20 ℃ C

"i-BMA": i-butyl methacrylate [ Tg at the time of homopolymer: 53 ℃ C

"t-BMA": methacrylic acid t-butyl ester

[ Tg when made into a homopolymer: 118 ℃ C

< other alkyl (meth) acrylate monomer B >

"MA": methyl acrylate [ Tg when made into a homopolymer: 10 ℃ C

"MMA": methyl methacrylate [ Tg when made into a homopolymer: 105 ℃ C

"n-BA": n-butyl acrylate [ Tg at the time of homopolymer: -54 DEG C

"2EHMA": 2-ethylhexyl methacrylate

[ Tg when made into a homopolymer: -10 DEG C

< monomer having hydroxyl group >

"2HEA": acrylic acid 2-hydroxy ethyl ester

[ Tg when made into a homopolymer: -15 ℃, molar mass: 116.12g/mol ]

"2HEMA": methacrylic acid 2-hydroxy ethyl ester

[ Tg when made into a homopolymer: 85 ℃, molar mass: 130.14g/mol ]

< monomer having carboxyl group >

"MAA": methacrylic acid [ Tg when made into homopolymer: 228 ℃ of

[ preparation of adhesive composition ]

[ example 1 ]

666.7 parts by mass (100 parts by mass in terms of solid content) of a solution of a (meth) acrylic polymer A-1, 25.0 parts by mass (15 parts by mass in terms of solid content) of a solution of a (meth) acrylic polymer B-1, CORONATE (registered trademark) L-45E as an isocyanate-based crosslinking agent (trade name, adduct of Toluene Diisocyanate (TDI) and Trimethylolpropane (TMP), solid content concentration: 45% by mass, 0.44 parts by mass (0.20 parts by mass as a solid component) of Tosoh corporation and an appropriate amount of ethyl acetate (organic solvent) were thoroughly mixed to obtain an adhesive composition of example 1.

Examples 2 to 21

In example 1, the same operations as in example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in table 3, to obtain each of the adhesive compositions of examples 2 to 21.

[ examples 22 to 44 ]

In example 1, the same operations as in example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in table 4, to obtain each of the adhesive compositions of examples 22 to 44.

Comparative examples 1 to 12

In example 1, the same operations as in example 1 were performed except that the composition of the adhesive composition was changed to the composition shown in table 5, and each adhesive composition of comparative examples 1 to 12 was obtained.

[ production of adhesive layer-attached polarizing plate ]

In a release film surface-treated with a silicone release treating agent (so-called easy release treatment) [ type: MRF, thickness: the adhesive composition prepared above was coated on a release-treated surface of 38 μm, mitsubishi chemical corporation, to form a coating film. The coating amount of the adhesive composition was such that the thickness of an adhesive film to be described later was 10. Mu.m. Then, for the formed coating film, air of 100℃was blown at a wind speed of 3 m/sec for 60 seconds using a heated air circulation dryer, thereby drying the coating film and forming an adhesive film having a thickness of 10 μm on the release film. Then, the exposed surface of the adhesive film formed was laminated on the surface of one TAC layer of the polarizer composed of a cellulose Triacetate (TAC) layer/a polyvinyl alcohol (PVA) layer containing a polarizer/TAC layer, and then, the adhesive film was allowed to stand still for 7 days at an atmospheric temperature of 23 ℃ and 50% rh, whereby the adhesive layer-attached polarizer composed of a layer of a release film/adhesive layer/polarizer (TAC layer/PVA layer/TAC layer) (thickness: 131 μm) was produced.

[ measurement and evaluation ]

1. Durability of

(1) High temperature and low humidity environment

The polarizing plate with the adhesive layer produced above was cut into a size of 60mm×136mm (long side) so that the long side was 0 ° with respect to the absorption axis of the polarizing plate. Then, the release film of the cut adhesive layer-attached polarizing plate is peeled off, and the surface of the adhesive layer exposed by the peeling off is bonded to a glass plate

[ category: sodium glass, manufactured by Song Nitro Co., ltd.) was superimposed on one surface thereof, and then pressure-bonded using a laminator, and the cut polarizing plate with an adhesive layer was bonded to a glass plate, thereby producing a test sample. The test specimen had a layer composition of glass plate/adhesive layer/polarizer (TAC layer/PVA layer/TAC layer). Then, the test sample was prepared at a treatment temperature of 50℃and a treatment pressure of 5kg/cm ² After autoclave treatment for 20 minutes under the conditions of (2) and standing for 24 hours at an atmosphere temperature of 23 ℃ and 50% rh. The test sample after standing was subjected to a test of standing at an atmosphere temperature of 85℃and 10% RH or less (so-called high-temperature low-humidity environment) for 150 hours. The test is a so-called acceleration test in which it is assumed that the test is placed in a high-temperature environment for a long period of time. After the completion of the test, the state of the test sample was visually observed, and the evaluation was performed based on the following evaluation criteria. The results are shown in tables 3 to 5.

The "a", "B" and "C" in the evaluation criteria described below are within the practically allowable range, and are most preferably "a".

Evaluation criterion-

A: no wrinkles and peeling were confirmed at all in the test samples.

B: wrinkles and/or peeling were slightly observed in the test sample, but the level was practically no problem.

C: wrinkles and/or peeling were confirmed in the test sample, but at a practically allowable level.

D: wrinkles and/or peeling were significantly confirmed in the test sample, which was a practically unacceptable level.

(2) Thermal shock environment

[ category: sodium glass, manufactured by Song Nitro Co., ltd.) was superimposed on one surface thereof, and then pressure-bonded using a laminator, and the cut polarizing plate with an adhesive layer was bonded to a glass plate, thereby producing a test sample. The test specimen had a layer composition of glass plate/adhesive layer/polarizer (TAC layer/PVA layer/TAC layer). Then, the test sample was prepared at a treatment temperature of 50℃and a treatment pressure of 5kg/cm ² After autoclave treatment for 20 minutes under the conditions of (2) and standing for 24 hours at an atmosphere temperature of 23 ℃ and 50% rh. For this test sample after standing, a cold thermal shock device [ model: TSA-301L-W, ESPEC CORP. Manufactured), and repeated 300 times were allowed to stand at an atmosphere temperature of-40℃for 0.5 hours and then at an atmosphere temperature of 85℃for 0.5 hours. After the completion of the test, the state of the test sample was visually observed, and the evaluation was performed based on the following evaluation criteria. The results are shown in tables 3 to 5.

Evaluation criterion-

A: no wrinkles and peeling were confirmed at all in the test samples.

C: wrinkles and/or peeling were confirmed in the test sample, but at practically allowable levels.

2. Workability and workability of the product

The adhesive layer-equipped polarizing plate (thickness: 131 μm) prepared above was cut into a size of 100 mm. Times.100 mm, and a test sample was prepared. For the test specimens produced, an end face processor [ model: MCPB-600A-SP, MEGAROTECHNICACO., LTD.), and end face machining was performed under the conditions of a blade rotation speed of 3000rpm and a cutting pitch of 200. Mu.m. Digital microscope [ model: VHX7000, magnification: 500 times, keyence Corporation ] the processed end face of the test sample after the end face processing was observed, and the width of the protruding portion of the adhesive layer was measured, and the ratio was determined by the following calculation formula. A specific measurement method will be described with reference to fig. 1. Fig. 1 shows an example of a state of a processed end surface of a test piece 100 after the end surface processing. The sum of the widths (X1, X2, X3, and X4) of the portions where the adhesive layer 20 protrudes was measured on the processed end face of the test sample 100 composed of the layers of the release film 10/the adhesive layer 20/the polarizing plate 30, and the ratio (hereinafter also referred to as "protruding ratio") to the width (Y; 100 cm) of the test sample 100 was determined by the following calculation formula. Here, the portion where the adhesive layer 20 protrudes refers to the portion where the adhesive layer 20 protrudes to the polarizing plate 30.

Stretching ratio of adhesive layer (unit:%)

= [ adhesive layer protruding beyond the width of the portion (unit: mm)/width of test sample (100 mm) ], 100

The calculated value was rounded off at the 1 st position after the decimal point. Based on the calculated protrusion ratio of the adhesive layer, evaluation was performed according to the following evaluation criteria. The results are shown in tables 3 to 5.

Evaluation criterion-

A: the adhesive layer has a protrusion ratio of less than 10%.

B: the adhesive layer has a protrusion ratio in a range of 10% or more and less than 25%.

C: the adhesive layer has a protrusion ratio in a range of 25% or more and less than 40%.

D: the adhesive layer has a protrusion ratio of 40% or more.

3. Transparency of

In a release film surface-treated with a silicone release treating agent (so-called easy release treatment) [ type: MRF, thickness: the adhesive composition prepared above was coated on a release-treated surface of 38 μm, mitsubishi chemical corporation, to form a coating film. The coating amount of the adhesive composition was such that the thickness of an adhesive film to be described later was 50. Mu.m. Then, the formed coating film was left to stand at 23℃for 2 minutes. Then, for the coating film after the placement, air of 100℃was blown at a wind speed of 3 m/sec for 60 seconds using a heated air circulation dryer, thereby drying the coating film and forming an adhesive film of 100 μm in thickness on the release film. Then, the exposed face of the formed adhesive film was laminated with a polyethylene terephthalate (PET) film (trade name: cosmosfine (registered trademark) a4100, thickness: after one surface of 100 μm was laminated, the laminate was left standing at an atmospheric temperature of 23℃and 50% RH for 7 days, and the adhesive film was cured to prepare a laminate having layers of a release film, an adhesive layer and a PET film.

The laminate thus produced was cut, and two test specimens having a size of 50mm×50mm were prepared. One of the prepared test samples was measured for haze (so-called initial haze) after peeling the release film. For another test sample to be prepared, a test was performed by standing for 150 hours in an atmosphere at an atmospheric temperature of 85℃and 10% RH or less (so-called high-temperature low-humidity atmosphere). The test is a so-called acceleration test in which it is assumed that the test is placed in a high-temperature environment for a long period of time. After the test, the release film of the test sample was peeled off, and the haze of the laminate composed of the layers having the adhesive layer/PET film was measured. For measuring haze, a haze meter (model: NDH 5000 SP) manufactured by Nippon Denshoku industries Co., ltd was used. The haze value of the adhesive layer was obtained by subtracting the haze value of the PET film from the haze value of the laminate composed of the layers having the adhesive layer/the PET film. Based on the haze value (unit:%) of the adhesive layer, evaluation was performed according to the following evaluation criteria. The results are shown in tables 3 to 5.

Evaluation criterion-

A: haze value is less than 0.5%.

B: the haze value is in the range of 0.5% or more and less than 1.0%.

C: the haze value is in a range of 1.0% or more and less than 1.5%.

D: the haze value is 1.5% or more.

4. Shrinkage inhibition

[ category: sodium glass, manufactured by Song Nitro Co., ltd.) was superimposed on one surface thereof, and then pressure-bonded using a laminator, and the cut polarizing plate with an adhesive layer was bonded to a glass plate, thereby producing a test sample. The test specimen had a layer composition of glass plate/adhesive layer/polarizer (TAC layer/PVA layer/TAC layer). Then, the test sample was prepared at a treatment temperature of 50℃and a treatment pressure of 5kg/cm ² After autoclave treatment for 20 minutes under the conditions of (2) and standing for 24 hours at an atmosphere temperature of 23 ℃ and 50% rh. The test sample after the standing was allowed to stand in an atmosphere at an atmospheric temperature of 85℃and 10% RH or less (so-called high-temperature low-humidity atmosphere) for 150 hours. The test is a so-called acceleration test in which it is assumed that the test is placed in a high-temperature environment for a long period of time. After the end of the test, a digital microscope [ model: the shrinkage was calculated by measuring the length of the long side (i.e., 0℃with respect to the absorption axis) of the test sample by the following formula. The calculated value was rounded off at the 3 rd position after the decimal point.

Shrinkage (unit:%)

= [ [ length of long side of test sample before standing (unit: mm) ] length of long side of test sample after standing (unit: mm) ]/-length of long side of test sample before standing (unit: mm) ×100)

Based on the shrinkage obtained above, evaluation was performed according to the following evaluation criteria. The results are shown in tables 3 to 5. The "a", "B" and "C" in the evaluation criteria described below are within the practically allowable range, and are most preferably "a".

Evaluation criterion-

A: the shrinkage of the test sample was less than 0.20%.

B: the shrinkage of the test sample was in the range of 0.20% or more and less than 0.35%.

C: the shrinkage of the test sample was in the range of 0.35% or more and less than 0.50%.

D: the shrinkage of the test sample was 0.50% or more.

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The details of the components shown in tables 3 to 5 are as follows.

< crosslinker >

Isocyanate-based crosslinking agent

“CORONATE L－45E”

[ trade name, adduct of TDI and TMP, manufactured by Tosoh Co., ltd.)

“TAKENATE D－110N”

[ trade name, adduct of XDI and TMP, manufactured by Mitsui chemical Co., ltd.)

“SUMIDUR N3300”

[ trade name, HMDI 3 Polymer, sumika Covestro Urethane Co., ltd.)

Epoxy-based crosslinking agent

"TETRAD-X" [ trade name, mitsubishi gas Chemicals Co., ltd. ]

The above "CORONATE", "TAKENATE", "SUMIDUR" and "TETRAD" are registered trademarks.

< other Components >)

Silane coupling agent

"KBE-403" [ trade name, silane compound containing epoxy group, xinyue chemical Co., ltd ]

“X－41－1810”

[ trade name, thiol group-containing silane compound (multifunctional silane compound), xinyue chemical industry Co., ltd ]

Antistatic agent-

"MP-402A" [ trade name, first Industrial pharmaceutical Co., ltd ]

In tables 3 to 5, the numerical values described in the column "amount of addition" are all solid content converted values.

In tables 3 to 5, "-" indicates that the components corresponding to this column are not blended.

As shown in tables 3 and 4, it was confirmed that the adhesive layers formed from the adhesive compositions of examples 1 to 44 were less likely to cause wrinkles and peeling not only when they were placed under a high-temperature low-humidity environment, but also when they were placed under a repeated low-temperature and high-temperature environment. In addition, it was confirmed that the adhesive layers formed from the adhesive compositions of examples 1 to 44 were excellent in transparency. In addition, it was confirmed that the adhesive layers formed from the adhesive compositions of examples 1 to 44 have excellent transparency even after being left under a high-temperature environment for a long period of time. In addition, it was confirmed that the adhesive layers formed from the adhesive compositions of examples 1 to 44 were excellent in workability. In addition, it was confirmed that the adhesive layers formed from the adhesive compositions of examples 1 to 44 can favorably suppress shrinkage of the substrate that may occur when left under a high-temperature environment for a long period of time.

On the other hand, as shown in table 5, it was confirmed that the adhesive layer formed of the adhesive composition of comparative example 1 in which the weight average molecular weight of the (meth) acrylic polymer (a) was less than 100 ten thousand was inferior in processability to the adhesive layer formed of the adhesive composition of example. In addition, it was confirmed that the adhesive layer formed from the adhesive composition of comparative example 1 could not well suppress shrinkage of the substrate that may occur when left under a high temperature environment for a long period of time. In the adhesive layer formed from the adhesive composition of comparative example 1, wrinkles and peeling were not confirmed, but foaming was confirmed in the case of being placed under a high-temperature low-humidity environment and in the case of being placed under an environment where the temperature was repeated at a low temperature and a high temperature.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 2 in which the (meth) acrylic polymer (a) did not contain a structural unit derived from n-butyl acrylate was liable to be impaired in transparency when left under a high temperature environment for a long period of time.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 3, in which the weight average molecular weight of the (meth) acrylic polymer (B) exceeded 70 ten thousand, was inferior in transparency to the adhesive layer formed of the adhesive composition of example.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 4, in which the glass transition temperature of the (meth) acrylic polymer (B) was less than 0 c, was liable to generate wrinkles and peeling in the case of being placed under a high-temperature low-humidity environment and in the case of being placed under an environment where repeated low-temperature and high-temperature are present. In addition, it was confirmed that the adhesive layer formed of the adhesive composition of comparative example 4 was inferior in processability to the adhesive layer formed of the adhesive composition of example. In addition, it was confirmed that the adhesive layer formed from the adhesive composition of comparative example 4 could not well suppress shrinkage of the substrate that may occur when left under a high temperature environment for a long period of time.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 5, in which the (meth) acrylic polymer (B) did not contain a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety, was inferior in transparency to the adhesive layer formed of the adhesive composition of example.

It was confirmed that the content of hydroxyl groups in the (meth) acrylic polymer (B) exceeded 0.22mmol

The adhesive layer formed of the adhesive composition of comparative example 6 per gram was liable to generate wrinkles and peeling in the case of being placed under a high-temperature and low-humidity environment and in the case of being placed under a repeated low-temperature and high-temperature environment.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 7, which contained only the specific (meth) acrylic polymer (a) among the specific (meth) acrylic polymer (a) and the specific (meth) acrylic polymer (B), was inferior in processability to the adhesive layer formed of the adhesive composition of examples.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 8, which contained the specific (meth) acrylic polymer (B) but whose content was less than 3 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic polymer (a), was inferior in processability to the adhesive layer formed of the adhesive composition of example.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 9, in which the content of the specific (meth) acrylic polymer (B) was more than 50 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic polymer (a), was inferior in transparency to the adhesive layer formed of the adhesive composition of example.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 10 containing no crosslinking agent was inferior in processability to the adhesive layer formed of the adhesive composition of example. In addition, it was confirmed that the adhesive layer formed from the adhesive composition of comparative example 10 could not well suppress shrinkage of the substrate that may occur when left under a high temperature environment for a long period of time.

It was confirmed that the adhesive layer formed of the adhesive composition of comparative example 11 in which the (meth) acrylic polymer (B) did not contain a structural unit derived from a monomer having a hydroxyl group was liable to be impaired in transparency when left under a high-temperature environment for a long period of time.

It was confirmed that the transparency of the adhesive layer formed from the adhesive composition of comparative example 12 in which the (meth) acrylic polymer (B) contained the structural unit derived from the monomer having a carboxyl group and did not contain the structural unit derived from the monomer having a hydroxyl group was easily impaired when left under a high temperature environment for a long period of time.

Claims

1. An adhesive composition for an optical film, comprising:

a (meth) acrylic polymer (A) comprising a structural unit derived from n-butyl acrylate and having a weight average molecular weight of 100 ten thousand or more,

a (meth) acrylic polymer (B) comprising a structural unit derived from an alkyl methacrylate monomer having 4 carbon atoms in the alkyl moiety and a structural unit derived from a monomer having a hydroxyl group, and having a hydroxyl group content of 0.0007 to 0.22mmol/g, a glass transition temperature of 0 ℃ or higher and a weight average molecular weight of 70 ten thousand or less, and

a cross-linking agent;

wherein the content of the (meth) acrylic polymer (B) is 3 to 50 parts by mass per 100 parts by mass of the (meth) acrylic polymer (a).

2. The adhesive composition for an optical film according to claim 1, wherein the (meth) acrylic polymer (a) contains at least one of a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxyl group.

3. The adhesive composition for an optical film according to claim 1, wherein the content of the n-butyl acrylate-derived structural unit in the (meth) acrylic polymer (a) is 50 mass% or more.

4. The adhesive composition for an optical film according to claim 1, wherein the content of the crosslinking agent is 0.05 to 15 parts by mass per 100 parts by mass of the (meth) acrylic polymer (a).

5. The adhesive composition for an optical film according to claim 1, wherein the crosslinking agent is an isocyanate-based crosslinking agent.

6. The adhesive composition for an optical film according to claim 1, further comprising a silane coupling agent.

7. An adhesive sheet comprising an adhesive layer formed from the adhesive composition for an optical film according to any one of claims 1 to 6.

8. The adhesive sheet according to claim 7, comprising:

optical film, and

An adhesive layer provided on at least one surface of the optical film and formed of the adhesive composition for an optical film according to any one of claims 1 to 6.

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

10. An optical member comprising, in order:

a glass substrate having a glass substrate surface and a glass layer,

an adhesive layer formed of the adhesive composition for an optical film according to any one of claims 1 to 6, and

an optical film.

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