JP2021155594A - Adhesive composition and optical member with adhesive layer - Google Patents

Abstract

To provide: an adhesive composition which has excellent sticking suitability after long-term storage and can form an adhesive layer having appropriate viscoelasticity immediately after curing and after long term storage; and an optical member with an adhesive layer.SOLUTION: An adhesive composition comprises: a (meth)acrylic copolymer (A) containing a structural unit derived from an alkyl (meth)acrylate monomer and a structural unit derived from a monomer having a carboxylic group, and having a Mw of 400,000 to 2,500,000; a (meth)acrylic copolymer (B) containing a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate, and having a Mw of 3,000 to 50,000; and a polyisocyanate compound. A content of the copolymer (B) is 5 to 25 pts.mass relative to 100 pts.mass of the copolymer (A) and a content of the polyisocyanate compound is 6 to 30 pts.mass relative to 100 pts.mass of the copolymer (A). Also provided is a use thereof.SELECTED DRAWING: None

Description

The present invention relates to a pressure-sensitive adhesive composition and an optical member with a pressure-sensitive adhesive layer.

Many mobile electronic devices such as mobile phones and mobile terminals have a built-in liquid crystal display device. Generally, a liquid crystal display device includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. The liquid crystal cell and the polarizing plate are generally bonded to each other via a pressure-sensitive adhesive layer formed of an acrylic pressure-sensitive adhesive from the viewpoint of ensuring the visibility of the liquid crystal display device.
For example, Patent Document 1 discloses an optical pressure-sensitive adhesive containing 100 parts by weight of an acrylic polymer and 5 to 50 parts by weight of an isocyanate-based curing agent.

Japanese Unexamined Patent Publication No. 2011-37927

A polarizing plate having a pressure-sensitive adhesive layer (so-called polarizing plate with a pressure-sensitive adhesive layer) may be attached to a liquid crystal cell after being stored for a long period of time (for example, 6 months; hereinafter the same). Therefore, the pressure-sensitive adhesive layer in the polarizing plate with the pressure-sensitive adhesive layer is required to have excellent bonding suitability even after long-term storage. However, in a pressure-sensitive adhesive layer formed of a so-called hard-type pressure-sensitive adhesive composition, which uses a large amount of a polyisocyanate compound as a cross-linking agent, for example, due to the action of a small amount of water in the pressure-sensitive adhesive layer or in the air, over time A condensate of water and a polyisocyanate compound may be formed. When this condensate is formed, the pressure-sensitive adhesive layer becomes hard, which may cause problems such as a decrease in foam removal property when the polarizing plate with the pressure-sensitive adhesive layer is attached to a glass substrate or the like.
Further, in general, when the temperature of a polarizing plate changes, stress may be generated in an attempt to shrink or expand. If the generated stress is not relieved, the stress remains in the pressure-sensitive adhesive layer. When the stress remaining in the pressure-sensitive adhesive layer becomes non-uniform, for example, a phenomenon in which light leaks and whitening occurs in a liquid crystal display device, so-called white spots may occur.

In order to realize a pressure-sensitive adhesive layer having excellent bonding suitability even after long-term storage, for example, it is conceivable to prevent the storage elastic modulus (G') of the pressure-sensitive adhesive layer from increasing excessively over time. On the other hand, as described above, the pressure-sensitive adhesive layer in the polarizing plate with a pressure-sensitive adhesive layer is required to have a property that white spots are unlikely to occur even when exposed to a high temperature environment (for example, 105 ° C.; the same applies hereinafter). However, from the viewpoint of suppressing the occurrence of white spots, it is desirable that the pressure-sensitive adhesive layer has a high storage elastic modulus (G') that does not shrink with respect to the generated stress.

The problem to be solved by the present invention is an adhesive composition capable of forming an adhesive layer having excellent bonding suitability after long-term storage and having appropriate viscoelasticity immediately after curing and after long-term storage, and a long-term adhesive composition. It is an object of the present invention to provide an optical member with an adhesive layer having an adhesive layer having excellent bonding suitability after storage and having appropriate viscoelasticity immediately after curing and after long-term storage.

Specific means for solving the problem include the following aspects.
<1> (Meta) Containing a structural unit derived from an acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group, and having a weight average molecular weight of 400,000 to 2.5 million (meth). Acrylic copolymer (A) and
A (meth) acrylic copolymer (B) containing a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate and having a weight average molecular weight of 30,000 to 50,000.
Containing with polyisocyanate compounds,
The content of the (meth) acrylic copolymer (B) is 5 parts by mass to 25 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A).
A pressure-sensitive adhesive composition in which the content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A).
<2> The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (B) becomes the total structural unit of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition according to <1>, which is 5% by mass to 25% by mass.
<3> The content of the structural unit derived from the methyl methacrylate in the (meth) acrylic copolymer (B) is 40% by mass with respect to all the structural units of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition according to <1> or <2>, which is% to 95% by mass.
<4> The content of the structural unit derived from the monomer having a carboxy group in the (meth) acrylic copolymer (A) is the total structural unit of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition according to any one of <1> to <3>, which is 1% by mass to 5% by mass.
<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group.
<6> The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (A) becomes the total structural unit of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition according to <5>, which is 0.1% by mass to 3% by mass.
<7> The pressure-sensitive adhesive composition according to any one of <1> to <6>, wherein the (meth) acrylic copolymer (B) has a glass transition temperature of 60 ° C. to 105 ° C.
<8> Optical members and
A pressure-sensitive adhesive layer provided on the optical member and formed by the pressure-sensitive adhesive composition according to any one of <1> to <7>.
An optical member with an adhesive layer comprising.

According to the present invention, a pressure-sensitive adhesive composition having excellent bonding suitability after long-term storage and capable of forming a pressure-sensitive adhesive layer having appropriate viscoelasticity immediately after curing and after long-term storage, and excellent after long-term storage. Provided is an optical member with an adhesive layer having an adhesive layer having adhesive suitability and having appropriate viscoelasticity immediately after curing and after long-term storage.

Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

The numerical range indicated by using "~" in the present specification means a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present specification, 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 specification, a combination of two or more preferred embodiments is a more preferred embodiment.
In the present specification, the amount of each component means the total amount of a plurality of kinds of substances when a plurality of kinds of substances corresponding to each component are present, unless otherwise specified.

In the present specification, the "(meth) acrylic copolymer" means that the content of the structural unit derived from the monomer having a (meth) acryloyl group is the total structural unit [that is, the (meth) acrylic copolymer. It means a copolymer which is 50% by mass or more of [the total constituent unit of the polymer].

In the present specification, "(meth) acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth) acrylate" is a term that includes both "acrylate" and "methacrylate". , "(Meta) acryloyl" is a term that includes both "acryloyl" and "methacrylic".

In the present specification, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group, and has a weight average molecular weight of 400,000 to 250. Ten thousand (meth) acrylic copolymer (A) [hereinafter, also referred to as "specific (meth) acrylic copolymer (A)". ], And a (meth) acrylic copolymer (B) containing a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate, and having a weight average molecular weight of 30,000 to 50,000. ) [Hereinafter, it is also referred to as "specific (meth) acrylic copolymer (B)". ] And the polyisocyanate compound, and the content of the specific (meth) acrylic copolymer (B) is 5 parts by mass to 100 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It is 25 parts by mass, and the content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A).
According to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer having excellent bonding suitability after long-term storage and having appropriate viscoelasticity immediately after curing and after long-term storage can be formed.
Although it is not clear why the pressure-sensitive adhesive composition of the present invention can exert such an effect, the present inventors speculate as follows. However, the following speculation does not limit the interpretation of the pressure-sensitive adhesive composition of the present invention, but is described as an example.

The pressure-sensitive adhesive composition of the present invention contains a relatively large amount of a polyisocyanate compound. When the pressure-sensitive adhesive layer is formed by the pressure-sensitive adhesive composition containing a large amount of the polyisocyanate compound, a small amount of water in the pressure-sensitive adhesive layer or in the air and the polyisocyanate compound are formed in the formed pressure-sensitive adhesive layer during long-term storage. It may react over time to form a hard condensate. When the pressure-sensitive adhesive layer becomes hard due to the formation of the condensate, the adhesive strength decreases, and for example, there may be a problem that the foam removal property when the polarizing plate with the pressure-sensitive adhesive layer is attached to a glass substrate or the like is reduced. On the other hand, the pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate, and has a weight average molecular weight of 30,000 to 50,000. Since the (meth) acrylic copolymer (B) [that is, the specific (meth) acrylic copolymer (B)] is contained, the formation of the condensate over time in the formed pressure-sensitive adhesive layer is suppressed. .. Since the specific (meth) acrylic copolymer (B) contains a structural unit derived from methyl methacrylate, the glass transition temperature is relatively high. Further, the specific (meth) acrylic copolymer (B) has a hydroxyl group capable of reacting with the isocyanate group of the polyisocyanate compound. Further, the specific (meth) acrylic copolymer (B) has a relatively low weight average molecular weight. That is, the pressure-sensitive adhesive composition of the present invention has a specific (meth) acrylic copolymer having a hydroxyl group in addition to a large amount of polyisocyanate compound, a relatively high glass transition temperature, and a relatively low weight average molecular weight. Since the coalescence (B) is contained in a specific ratio, in the formed pressure-sensitive adhesive layer, the specific (meth) acrylic copolymer (B) reacts with the polyisocyanate compound to proceed during long-term storage. It is considered that the formation of the condensate is appropriately suppressed. The specific (meth) acrylic copolymer (A) has a carboxy group that cross-reacts with the isocyanate group of the polyisocyanate compound, but since the carboxy group has a higher reactivity with the isocyanate group than the hydroxyl group, the pressure-sensitive adhesive layer is formed. At the time of formation, it is considered that the cross-linking reaction between the carboxy group in the specific (meth) acrylic copolymer (A) and the isocyanate group of the polyisocyanate compound is not impaired. Therefore, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention has excellent bonding suitability after long-term storage and has appropriate viscoelasticity immediately after curing and after long-term storage.

With respect to the pressure-sensitive adhesive composition of the present invention, the optical pressure-sensitive adhesive described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-37927) contains a large amount of polyisocyanate compound, but is derived from a monomer having a hydroxyl group. A (meth) acrylic copolymer containing a unit and a structural unit derived from methyl methacrylate and having a weight average molecular weight of 30,000 to 50,000 [that is, a specific (meth) acrylic copolymer (B). ] Is not included. Therefore, when the formed pressure-sensitive adhesive layer is stored for a long period of time, it is considered that the adhesive strength is lowered, the foam removal property is lowered, and the bonding suitability is deteriorated.

Hereinafter, in the present specification, the specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B) are collectively referred to as “specific (meth) acrylic copolymer”.

[Specific (meth) acrylic copolymer (A)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group, and has a weight average molecular weight of 400,000 to 250. It includes the (meth) acrylic copolymer (A) [that is, the specific (meth) acrylic copolymer (A)].
The pressure-sensitive adhesive composition of the present invention may contain only one type of the specific (meth) acrylic copolymer (A), or may contain two or more types.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer>
The specific (meth) acrylic copolymer (A) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer.
The structural unit derived from the (meth) acrylic acid alkyl ester monomer contributes to the adjustment of the adhesive strength of the pressure-sensitive adhesive layer.

In the present specification, the “constituent unit derived from the (meth) acrylic acid alkyl ester monomer” means a structural unit formed by addition polymerization of the (meth) acrylic acid alkyl ester monomer.
The "(meth) acrylic acid alkyl ester monomer" does not include a (meth) acrylic acid alkyl ester monomer having at least one of a hydroxyl group and a carboxy group.

The type of the (meth) acrylic acid alkyl ester monomer is not particularly limited.
As the (meth) acrylic acid alkyl ester monomer, an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic.
The number of carbon atoms of the alkyl group is, for example, preferably 1 to 18, more preferably 1 to 8, and even more preferably 1 to 4.

Specific examples of the (meth) acrylic acid alkyl ester monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and 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, Examples thereof include n-decyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
As the (meth) acrylic acid alkyl ester monomer, at least one selected from n-butyl acrylate and methyl acrylate is preferable, and n-butyl acrylate is more preferable.

The specific (meth) acrylic copolymer (A) may contain only one type of structural unit derived from the (meth) acrylic acid alkyl ester monomer, or may contain two or more types.

The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (A) is not particularly limited, but for example, the specific (meth) acrylic copolymer ( It is preferably 50% by mass or more, more preferably 50% by mass to 99% by mass, further preferably 60% by mass to 99% by mass, and 70% by mass with respect to all the constituent units of A). It is particularly preferably% to 99% by mass.
Here, the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (A) is the total content of the specific (meth) acrylic copolymer (A). The fact that the content is 50% by mass or more with respect to the constituent unit means that the constituent unit derived from the (meth) acrylic acid alkyl ester monomer is the main constituent unit constituting the specific (meth) acrylic copolymer (A). It means that it is contained as an ingredient.

<Constituent unit derived from a monomer having a carboxy group>
The specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group.
As used herein, the "constituent unit derived from a monomer having a carboxy group" means a structural unit formed by addition polymerization of a monomer having a carboxy group.
When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group, cross-linking proceeds sufficiently immediately after curing, and the pressure-sensitive adhesive layer has an appropriate elastic modulus. Tend. Therefore, even if the pressure-sensitive adhesive layer immediately after curing is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.

The type of monomer having a carboxy group is not particularly limited.
Specific examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, and ω-carboxy-polycaprolactone mono (meth) acrylate [ For example, ω-carboxy-polycaprolactone (n≈2) monoacrylate] and succinic acid ester [for example, 2-acryloyloxyethyl-succinic acid].
As the monomer having a carboxy group, at least one selected from acrylic acid and ω-carboxy-polycaprolactone monoacrylate is preferable, and acrylic acid is more preferable.

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

The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is not particularly limited, but for example, the specific (meth) acrylic copolymer (A) It is preferably 0.5% by mass to 7% by mass, more preferably 1% by mass to 5% by mass, and further preferably 2% by mass to 4% by mass with respect to all the constituent units.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is 0 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is 5.5% by mass or more, the cross-linking proceeds sufficiently immediately after curing, and the pressure-sensitive adhesive layer tends to have a more appropriate elastic coefficient. Therefore, even if the pressure-sensitive adhesive layer immediately after curing is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is 7 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is less than mass%, the pressure-sensitive adhesive layer after long-term storage tends to have better bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show higher adhesive strength and to be more excellent in foam removal property when it is attached to an adherend.

<Constituent unit derived from a monomer having a hydroxyl group>
The specific (meth) acrylic copolymer (A) preferably contains a structural unit derived from a monomer having a hydroxyl group.
When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. .. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.

In the present specification, the “constituent unit derived from a monomer having a hydroxyl group” means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The type of monomer having a hydroxyl group is not particularly limited.
Specific examples of the monomer having a hydroxyl group include hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl. (Meta) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl -3-Hydroxybutyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (Meta) acrylate, N-hydroxyethyl (meth) acrylamide, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, and poly (ethylene glycol-propylene glycol) mono (meth) Acrylate can be mentioned.
As the monomer having a hydroxyl group, a hydroxyalkyl (meth) acrylate is preferable, a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 5 carbon atoms is more preferable, and a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable. Hydroxyalkyl (meth) acrylates having the above are more preferable, and at least one selected from 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is particularly preferable.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, it may contain only one structural unit derived from the monomer having a hydroxyl group. Two or more types may be included.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group, it is derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A). The content of the constituent units is not particularly limited, but is preferably 0.05% by mass to 5% by mass, and is 0, for example, with respect to all the constituent units of the specific (meth) acrylic copolymer (A). .1% by mass to 3% by mass is more preferable, and 0.3% by mass to 2% by mass is further preferable.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is 0. When it is 05% by mass or more, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is 5% by mass with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is less than%, the pressure-sensitive adhesive layer after long-term storage tends to have better bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show higher adhesive strength and to be more excellent in foam removal property when it is attached to an adherend.

<Other building blocks>
The specific (meth) acrylic copolymer (A) may contain a structural unit (so-called other structural unit) other than the above-mentioned structural unit as long as the effect of the present invention is not impaired.

The monomer constituting the other structural unit (hereinafter, also referred to as “other monomer”) has, for example, an aromatic ring typified by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate. Alkoxyalkyl (meth) acrylate represented by (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, Examples thereof include aromatic monovinyl represented by vinyl toluene, vinyl cyanide represented by acrylonitrile and methacrylonitrile, and vinyl esters represented by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versatic acid. In addition, various derivatives of these monomers can be mentioned.

When the specific (meth) acrylic copolymer (A) contains other structural units, it may contain only one type of other structural units, or may contain two or more types of other structural units.

When the specific (meth) acrylic copolymer (A) contains other structural units, the content of the other structural units in the specific (meth) acrylic copolymer (A) is not particularly limited and is intended for the purpose. It can be set as appropriate.

<< Weight average molecular weight of specific (meth) acrylic copolymer (A) >>
The weight average molecular weight (Mw; hereinafter the same) of the specific (meth) acrylic copolymer (A) is 400,000 to 2.5 million, preferably 500,000 to 2 million, and preferably 1 million to 2 million. Is more preferable, and 1.2 million to 1.8 million is even more preferable.
A weight average molecular weight of the specific (meth) acrylic copolymer (A) of 400,000 or more indicates that it is a polymer, and is to distinguish it from the specific (meth) acrylic copolymer (B) described later. It is a regulation of.
When the weight average molecular weight of the specific (meth) acrylic copolymer (A) is 2.5 million or less, the viscosity of the pressure-sensitive adhesive composition does not become too high, and the pressure-sensitive adhesive composition tends to be applied satisfactorily.

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

~conditions~
Measuring device: High-speed GPC [Model number: HLC-8220 GPC, Tosoh Corporation]
Detector: Differential Refractometer (RI) [Built-in to HLC-8220, Tosoh Corporation]
Column: TSK-GEL GMHXL [Tosoh Co., Ltd.] connected in series 4 Column temperature: 40 ° C
Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL
Flow rate: 0.8 mL / min

The weight average molecular weight of the specific (meth) acrylic copolymer (A) is desired by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, and the like. Can be the value of.

<< Content of specific (meth) acrylic copolymer (A) >>
The content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is, for example, 64% by mass to 91% by mass with respect to the total solid content in the pressure-sensitive adhesive composition. It is preferably mass%, more preferably 68% by mass to 88% by mass, and even more preferably 73% by mass to 85% by mass.

[Specific (meth) acrylic copolymer (B)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate, and has a weight average molecular weight of 30,000 to 50,000 (meth) acrylic. The system copolymer (B) [that is, the specific (meth) acrylic copolymer (B)] is included. The content of the specific (meth) acrylic copolymer (B) is 5 parts by mass to 25 parts by mass with respect to 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer (A).
The pressure-sensitive adhesive composition of the present invention may contain only one type of the specific (meth) acrylic copolymer (B), or may contain two or more types.

<Constituent unit derived from a monomer having a hydroxyl group>
The specific (meth) acrylic copolymer (B) contains a structural unit derived from a monomer having a hydroxyl group.
The type of monomer having a hydroxyl group is not particularly limited.
The specific example of the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is the same as the specific example of the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A). Therefore, the description thereof is omitted here.
As the monomer having a hydroxyl group, a hydroxyalkyl (meth) acrylate is preferable, a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 5 carbon atoms is more preferable, and a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable. Hydroxyalkyl (meth) acrylates having are further preferred, and 2-hydroxyethyl methacrylate is particularly preferred.

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

The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is not particularly limited, but for example, all of the specific (meth) acrylic copolymer (B). It is preferably 3% by mass to 28% by mass, more preferably 5% by mass to 25% by mass, and further preferably 10% by mass to 25% by mass with respect to the structural unit.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is as described above with respect to all the structural units of the specific (meth) acrylic copolymer (B). Within the range, the pressure-sensitive adhesive layer after long-term storage tends to have better bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show higher adhesive strength and to be more excellent in foam removal property when it is attached to an adherend. Further, the content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is higher than that of all the structural units of the specific (meth) acrylic copolymer (B). Within the above range, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.

<Constituent unit derived from methyl methacrylate>
The specific (meth) acrylic copolymer (B) contains a structural unit derived from methyl methacrylate.
When the specific (meth) acrylic copolymer (B) contains a structural unit derived from methyl methacrylate, the pressure-sensitive adhesive layer after long-term storage tends to have excellent bonding suitability. Specifically, the pressure-sensitive adhesive layer after long-term storage tends to have excellent foam removal property when it is attached to an adherend.

The content of the structural unit derived from methyl methacrylate in the specific (meth) acrylic copolymer (B) is not particularly limited, but for example, with respect to all the structural units of the specific (meth) acrylic copolymer (B). It is preferably 30% by mass to 95% by mass, more preferably 40% by mass to 95% by mass, further preferably 55% by mass to 95% by mass, and 70% by mass to 90% by mass. Is particularly preferable.
The content of the structural unit derived from methyl methacrylate in the specific (meth) acrylic copolymer (B) is within the above range with respect to all the structural units of the specific (meth) acrylic copolymer (B). And, the pressure-sensitive adhesive layer after long-term storage tends to have better bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show higher adhesive strength and to be more excellent in foam removal property when it is attached to an adherend. Further, the content of the structural unit derived from methyl methacrylate in the specific (meth) acrylic copolymer (B) is within the above range with respect to all the structural units of the specific (meth) acrylic copolymer (B). If this is the case, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer>
The specific (meth) acrylic copolymer (B) may contain a structural unit derived from the (meth) acrylic acid alkyl ester monomer.

The "(meth) acrylic acid alkyl ester monomer" in the specific (meth) acrylic copolymer (B) includes methyl methacrylate and the (meth) acrylic acid alkyl ester monomer having a hydroxyl group. Not included.

The type of the (meth) acrylic acid alkyl ester monomer is not particularly limited.
As the (meth) acrylic acid alkyl ester monomer, an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic.
The number of carbon atoms of the alkyl group is, for example, preferably 1 to 18, more preferably 1 to 8, and even more preferably 1 to 4.

Specific examples of the (meth) acrylic acid alkyl ester monomer include methyl acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, and 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 Examples thereof include (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
As the (meth) acrylic acid alkyl ester monomer, n-butyl acrylate is preferable.

When the specific (meth) acrylic copolymer (B) contains a (meth) acrylic acid alkyl ester monomer, the specific (meth) acrylic copolymer (B) contains only one structural unit derived from the (meth) acrylic acid alkyl ester monomer. It may contain two or more kinds.

When the specific (meth) acrylic copolymer (B) contains a (meth) acrylic acid alkyl ester monomer, the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (B) The content of the structural unit derived from is not particularly limited.
The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (B) is, for example, the total composition of the specific (meth) acrylic copolymer (B). With respect to the unit, it is preferably 55% by mass or less, more preferably 50% by mass or less, further preferably 40% by mass or less, and particularly preferably 30% by mass or less.
The lower limit of the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (B) is, for example, the specific (meth) acrylic copolymer (B). It may be 1% by mass or more, 3% by mass or more, or 5% by mass or more with respect to all the constituent units.

<Other building blocks>
The specific (meth) acrylic copolymer (B) may contain a structural unit (so-called other structural unit) other than the above-mentioned structural unit as long as the effect of the present invention is not impaired.

The monomer constituting the other structural unit (hereinafter, also referred to as “other monomer”) has, for example, an aromatic ring typified by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate. Alkoxyalkyl (meth) acrylate represented by (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, Examples thereof include aromatic monovinyl represented by vinyl toluene, vinyl cyanide represented by acrylonitrile and methacrylonitrile, and vinyl esters represented by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versatic acid. In addition, various derivatives of these monomers can be mentioned.

When the specific (meth) acrylic copolymer (B) contains other structural units, it may contain only one type of other structural units, or may contain two or more types of other structural units.

When the specific (meth) acrylic copolymer (B) contains other structural units, the content of the other structural units in the specific (meth) acrylic copolymer (B) is not particularly limited and is intended for the purpose. It can be set as appropriate.

<< Weight average molecular weight of specific (meth) acrylic copolymer (B) >>
The weight average molecular weight of the specific (meth) acrylic copolymer (B) is 3,000 to 50,000, preferably 3,000 to 45,000, and 30,000 to 40,000. It is more preferably 05,000 to 30,000, and particularly preferably 40,000 to 20,000.
The weight average molecular weight of the specific (meth) acrylic copolymer (B) is 3,000 to 50,000, indicating that the specific (meth) acrylic copolymer (B) is an oligomer.
When the weight average molecular weight of the specific (meth) acrylic copolymer (B) is 3,000 or more, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.
When the weight average molecular weight of the specific (meth) acrylic copolymer (B) is 50,000 or less, the pressure-sensitive adhesive layer after long-term storage tends to have excellent bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show high adhesive strength and excellent foam removal property when bonded to an adherend.

The weight average molecular weight of the specific (meth) acrylic copolymer (B) is a value measured by the same method as the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A).

The weight average molecular weight of the specific (meth) acrylic copolymer (B) is desired by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, and the like. Can be the value of.

<< Glass transition temperature of specific (meth) acrylic copolymer (B) >>
The glass transition temperature (Tg; hereinafter the same) of the specific (meth) acrylic copolymer (B) is not particularly limited, but is preferably, for example, 0 ° C to 105 ° C, and 20 ° C to 105 ° C. It is more preferably 40 ° C to 105 ° C, and particularly preferably 60 ° C to 105 ° C.
When the glass transition temperature of the specific (meth) acrylic copolymer (B) is 0 ° C. or higher, the pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.
When the glass transition temperature of the specific (meth) acrylic copolymer (B) is 105 ° C. or lower, the pressure-sensitive adhesive layer after long-term storage tends to have better bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show higher adhesive strength and to be more excellent in foam removal property when it is attached to an adherend.

The glass transition temperature of the specific (meth) acrylic copolymer (B) is the absolute temperature (unit: K; hereinafter the same) calculated from the following formula 1 as the Celsius temperature (unit: ° C; hereinafter the same). .) Is the value converted.
1 / Tg = m1 / Tg1 + m2 / Tg2 + ... + m (k-1) / Tg (k-1) + mk / Tgk (Equation 1)

In Formula 1, Tg1, Tg2, ..., Tg (k-1), and Tgk are when each monomer constituting the specific (meth) acrylic copolymer (B) is used as a homopolymer. Each represents the glass transition temperature expressed in absolute temperature. m1, m2, ..., m (k-1), and mk represent the mole fractions of each monomer constituting the specific (meth) acrylic copolymer (B), and m1 + m2 + ... + M (k-1) + mk = 1.
The absolute temperature can be converted to the Celsius temperature by subtracting 273 from the absolute temperature, and the Celsius temperature can be converted to the absolute temperature by adding 273 to the Celsius temperature.

In the present specification, the "glass transition temperature represented by the absolute temperature when made into a homopolymer" is the glass transition represented by the absolute temperature of the homopolymer produced by polymerizing the monomer alone. Refers to temperature.
The glass transition temperature of the homopolymer was measured using a differential scanning calorimetry device (DSC) [model number: EXSTAR6000, Seiko Instruments Co., Ltd.] under the conditions of a measurement sample of 10 mg and a temperature rise rate of 10 ° C./min in a nitrogen stream. The measured and obtained bending point of the DSC curve is taken as the glass transition temperature of the homopolymer.

The "glass transition temperature represented by the Celsius temperature when made into a homopolymer" of a typical monomer is -76 ° C for 2-ethylhexyl acrylate (2EHA) and -10 ° C for 2-ethylhexyl methacrylate (2EHMA). , N-butyl acrylate (n-BA) at −57 ° C., n-butyl methacrylate (n-BMA) at 21 ° C., t-butyl acrylate (t-BA) at 41 ° C., t-butyl methacrylate (t-BMA). Is 107 ° C, i-butyl methacrylate (i-BMA) is 48 ° C, methyl acrylate (MA) is 5 ° C, methyl methacrylate (MMA) is 103 ° C, isobonyl methacrylate (IBXMA) is 155 ° C, and isobonyl acrylate (IBXA). ) Is 96 ° C, ethyl acrylate (EA) is -27 ° C, methacrylic acid is 185 ° C, 4-hydroxybutyl acrylate (4HBA) is -39 ° C, 2-hydroxyethyl acrylate (2HEA) is -15 ° C, 2-hydroxy. Ethyl methacrylate (2HEMA) at 55 ° C, 2-hydroxypropyl acrylate (2HPA) at -7 ° C, acrylic acid (AA) at 163 ° C, i-octyl acrylate (i-OA) at -75 ° C, dimethylaminoethyl methacrylate ( DM) is 18 ° C., ω-carboxy-polycaprolactone (n≈2) monoacrylate is −30 ° C., and 2-acryloyloxyethyl-succinic acid is −40 ° C.

The glass transition temperature of the specific (meth) acrylic copolymer (B) can be appropriately adjusted by using, for example, two or more types of monomers having different glass transition temperatures when they are homopolymers.

<< Content of specific (meth) acrylic copolymer (B) >>
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 5 parts by mass to 25 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It is preferably 6 parts by mass to 23 parts by mass, more preferably 7 parts by mass to 20 parts by mass, and further preferably 8 parts by mass to 18 parts by mass.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 5 parts by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The pressure-sensitive adhesive layer after long-term storage tends to have excellent bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to show high adhesive strength and excellent foam removal property when bonded to an adherend.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 25 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The pressure-sensitive adhesive layer immediately after curing and after long-term storage tends to have appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.

[Method for producing specific (meth) acrylic copolymer]
The method for producing the specific (meth) acrylic copolymer [that is, the specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B)] is not particularly limited.
The specific (meth) acrylic copolymer is obtained by polymerizing the above-mentioned monomers by a known polymerization method represented by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a massive polymerization method. Can be manufactured by
As the polymerization method, the solution polymerization method is preferable because the treatment step is relatively simple and can be performed in a short time in preparing the pressure-sensitive adhesive composition of the present invention after production.

In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, for example, in a nitrogen stream at the reflux temperature of the organic solvent. , Heat reaction for several hours with stirring. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be added sequentially.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, alcohol compounds and the like.
More specifically, examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetraline, and decalin. And aromatic hydrocarbon compounds typified by aromatic naphtha, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and fat typified by terepine oil. Represented by group or alicyclic hydrocarbon compounds, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate. Estel compounds, acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and ketone compounds typified by methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Glycol ether compounds typified by ether and diethylene glycol monobutyl ether, as well as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t- Examples thereof include alcohol compounds typified by butyl alcohol.

In the production of the specific (meth) acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of the aromatic hydrocarbon compound, ester compound, ketone compound and the like, and in particular, the specific (meth) acrylic. From the viewpoint of solubility of the system copolymer, ease of polymerization reaction and the like, it is preferable to use ethyl acetate, n-butyl acetate or the like.

At the time of the polymerization reaction, only one kind of organic solvent may be used, or two or more kinds may be used.

Examples of the polymerization initiator include organic peroxides and azo compounds used in ordinary solution polymerization methods.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, and di-2-ethylhexylperoxydi. Carbonate, t-butylperoxypivalate, 2,2-bis (4,5-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,54-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4) Examples include -di-t-butylperoxycyclohexyl) butane and 2,2-bis (4,5-di-t-octylperoxycyclohexyl) butane.
Examples of the azo compound include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis (2,4-dimethylvaleronitrile) [ABVN], and 2,2'-azobis (4-). Methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), and 2,2'-azobis (isobutyric acid) dimethyl.
In the production of the specific (meth) acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and in particular, the use of an azo compound is preferable.

At the time of the polymerization reaction, only one kind of polymerization initiator may be used, or two or more kinds of polymerization initiators may be used.

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

A chain transfer agent may be used in the production of the specific (meth) acrylic copolymer, if necessary.
Examples of the chain transfer agent include cyanoacetic acid, an alkyl ester compound having 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, an alkyl ester compound having 1 to 8 carbon atoms of bromoacetic acid, α-methylstyrene, anthracene, phenanthrene, and fluorene. , And aromatic compounds such as 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds such as p-nitrotoluene, benzoquinone and A benzoquinone derivative typified by 2,3,5,6-tetramethyl-p-benzoquinone, a borane derivative typified by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane. , Tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and halogenated hydrocarbon compounds typified by 3-chloro-1-propene, aldehyde compounds typified by chloral and furaldehyde, alkyl having 1 to 18 carbon atoms. For mercaptan compounds, aromatic mercaptan compounds typified by thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds having 1 to 10 carbon atoms of mercaptoacetic acid, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and pinen and turpinolene. A typical terpen compound can be mentioned.

When a chain transfer agent is used in the production of the specific (meth) acrylic copolymer, the amount of the chain transfer agent used is not particularly limited, and is, for example, the molecular weight of the target specific (meth) acrylic copolymer. It can be set as appropriate.

The polymerization temperature is not particularly limited, and can be appropriately set, for example, according to the molecular weight of the target specific (meth) acrylic copolymer.

[Polyisocyanate compound]
The pressure-sensitive adhesive composition of the present invention contains a polyisocyanate compound. The content of the polyisocyanate compound in the pressure-sensitive adhesive composition of the present invention is 6 parts by mass to 30 parts by mass with respect to 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer (A).
The polyisocyanate compound is a compound having two or more isocyanate groups in the molecule, and functions as a cross-linking agent in the pressure-sensitive adhesive composition of the present invention.

The polyisocyanate compound is not particularly limited.
Examples of the polyisocyanate compound include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), and pentamethylene diisocyanate (PDI). , Isophorone diisocyanate, aliphatic or alicyclic polyisocyanate compounds such as hydrogenated additives of aromatic polyisocyanate compounds, and the like.
The polyisocyanate compound includes a dimer, trimeric or pentameric of the polyisocyanate compound, an adduct of the polyisocyanate compound and a polyol compound such as trimethylolpropane, and a biuret of the polyisocyanate compound. And so on.
As the polyisocyanate compound, for example, a tolylene diisocyanate compound is preferable from the viewpoint of coatability.
In the present specification, the "toluene diisocyanate compound" includes not only tolylene diisocyanate (TDI) but also multimers of tolylene diisocyanate (for example, dimers, trimers, or pentamers) and tolylene diisocyanates. Includes an adduct form with a polyol compound, a biuret form of tolylene diisocyanate, and the like.

As the polyisocyanate compound, a commercially available product can be used.
Examples of commercially available polyisocyanate compounds are "Coronate (registered trademark) HX", "Coronate (registered trademark) HL-S", "Coronate (registered trademark) L", and "Coronate (registered trademark) L-45E". , "Coronate® 2031", "Coronate® 2030", "Coronate® 2234", "Coronate® 2785", "Aquanate® 200", and "Aqua". Nate (registered trademark) 210 "[above, Toso Co., Ltd.]," Sumijuru (registered trademark) N3300 "," Death Module (registered trademark) N3400 ", and" Sumijuru (registered trademark) N75 "[above, Sumi Cobestrolethane Co., Ltd.], "Duranate (registered trademark) E-405-80T", "Duranate (registered trademark) AE700-100", "Duranate (registered trademark) 24A-100", and "Duranate (registered trademark)" ) TSE-100 "[above, Asahi Kasei Co., Ltd.], and" Takenate (registered trademark) D-110N "," Takenate (registered trademark) D-120N "," Takenate (registered trademark) M-631N "," Examples include "MT-Orestar (registered trademark) NP1200" and "Stavio (registered trademark) XD-340N" [above, Mitsui Kagaku Co., Ltd.].

The pressure-sensitive adhesive composition of the present invention may contain only one type of polyisocyanate compound, or may contain two or more types.

The content of the polyisocyanate compound in the pressure-sensitive adhesive composition of the present invention is 6 parts by mass to 30 parts by mass and 7 parts by mass to 28 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The amount is preferably 8 parts by mass to 25 parts by mass, more preferably 10 parts by mass to 20 parts by mass.
When the content of the polyisocyanate compound in the pressure-sensitive adhesive composition of the present invention is 6 parts by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A), the pressure-sensitive adhesive immediately after curing and after long-term storage The agent layer tends to have moderate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer immediately after curing and after long-term storage is used for polarizing plates, white spots tend to be less likely to occur when exposed to a high temperature environment.
When the content of the polyisocyanate compound in the pressure-sensitive adhesive composition of the present invention is 30 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A), the pressure-sensitive adhesive layer after long-term storage is formed. , Tends to have excellent bonding suitability. For example, the pressure-sensitive adhesive layer after long-term storage tends to exhibit high adhesive strength and to have excellent foam removal property when bonded to an adherend.

〔Silane coupling agent〕
The pressure-sensitive adhesive composition of the present invention may contain a silane coupling agent.
When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the adhesiveness of the pressure-sensitive adhesive layer formed to the glass is improved. Therefore, when the adherend is glass, the pressure-sensitive adhesive layer after long-term storage tends to show better bonding suitability.

The silane coupling agent is not particularly limited.
Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, and a polymerizable unsaturated group-containing silane compound typified by 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3 -Mercaptopropyltriethoxysilane and thiol group-containing silane compounds typified by 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Epoxy group-containing silane compounds represented by, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and N- (2-aminoethyl) -3-aminopropylmethyl. Examples thereof include amino group-containing silane compounds typified by dimethoxysilane, and tris- (3-trimethoxysilylpropyl) isocyanurate.

As the silane coupling agent, a commercially available product can be used.
Examples of commercially available silane coupling agents include "KBM-403", "X-41-1053", and "KBM-402" [above, Shin-Etsu Chemical Co., Ltd.].

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

When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent is not particularly limited, but for example, with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). , 0.1 part by mass to 1 part by mass, more preferably 0.1 part by mass to 0.8 part by mass, and further preferably 0.1 part by mass to 0.5 part by mass. preferable.
When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent is within the above range with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). When the adherend is glass, the pressure-sensitive adhesive layer after long-term storage tends to show better bonding suitability.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent.
When the pressure-sensitive adhesive composition of the present invention contains an organic solvent, the coatability can be improved.
Examples of the organic solvent include the same organic solvents as those described above, which are used in the polymerization reaction of the specific (meth) acrylic copolymer.

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

When the pressure-sensitive adhesive composition of the present invention contains an organic solvent, the content of the organic solvent is not particularly limited and can be appropriately set according to the intended purpose.

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the above-mentioned components (so-called other components), if necessary, as long as the effects of the present invention are not impaired.
Other components include polymers other than specific (meth) acrylic copolymers, cross-linking catalysts, tackifier resins (so-called tack fires), colorants (eg dyes and pigments), and light stabilizers (eg UV rays). Absorbent) and the like.

[Use]
The use of the pressure-sensitive adhesive composition of the present invention is not particularly limited.
The pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer having excellent bonding suitability after long-term storage. That is, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention exhibits high adhesive strength and excellent foam removal property even when stored for a long period of time. Further, the pressure-sensitive adhesive composition of the present invention is immediately after curing. And after long-term storage, a pressure-sensitive adhesive layer having appropriate viscoelasticity can be formed. Therefore, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention causes white spots not only when exposed to a high-temperature environment immediately after curing but also when exposed to a high-temperature environment after long-term storage. It's hard to let.
Since the pressure-sensitive adhesive composition of the present invention has the above-mentioned characteristics, it is suitable for, for example, an application for attaching an optical member to an adherend (for a so-called optical member). Specific applications include, for example, an application in which a polarizing plate is attached to a liquid crystal cell (specifically, a glass substrate of a liquid crystal cell), an application in which a polarizing plate is attached to an optical film such as a retardation film, and the like. Be done.

[Optical member with adhesive layer]
The optical member with a pressure-sensitive adhesive layer of the present invention includes an optical member and a pressure-sensitive adhesive layer provided on the optical member and formed by the above-mentioned pressure-sensitive adhesive composition of the present invention. That is, in the optical member with the pressure-sensitive adhesive layer of the present invention, the optical member and the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention are laminated.
Since the optical member with the pressure-sensitive adhesive layer of the present invention includes the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, it has excellent bonding suitability after long-term storage. Further, since the optical member with the pressure-sensitive adhesive layer of the present invention includes the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, it is not only when exposed to a high temperature environment immediately after curing but also at a high temperature after long-term storage. It is unlikely to cause white spots even when exposed to the environment.

The optical member in the optical member with an adhesive layer of the present invention is not particularly limited.
Examples of the optical member include a member constituting a device (so-called optical device) such as an image display device and an input device, or a member used for these devices.
Specific examples of the optical member include a polarizing plate, an AG (Anti-Glare) polarizing plate, a wave plate, a retardation plate including a wave plate such as 1/2 and 1/4, a viewing angle compensation film, an optical compensation film, and brightness improvement. Examples thereof include a film, a light guide plate, a reflective film, an antireflection film, a transparent conductive film such as an ITO (Indium-Tin Oxide) film, a prism sheet, a lens sheet, and a diffusing plate.
As the material of the optical member, polyester resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, vinyl chloride resin, ABS (Acrylonitrile) Butadiene Styrene) Resins, fluororesins and other resins can be mentioned.

A polarizing plate is preferable as the optical member in the optical member with the pressure-sensitive adhesive layer of the present invention.
The polarizing plate is configured to include at least a polarizing element, and may be a single polarizer or a laminate of a polarizing element and a protective film. That is, the polarizing plate may have a one-layer structure of a single polarizer, a two-layer structure having a protective film on one side of the polarizer, or a three-layer structure having protective films on both sides of the polarizer. There may be.
When the optical member of the optical member with the pressure-sensitive adhesive layer of the present invention is a polarizing plate, the layer structure includes, for example, a pressure-sensitive adhesive layer / polarizing element, a pressure-sensitive adhesive layer / polarizing element / protective film, and a pressure-sensitive adhesive layer / protective film /. Polarizers / protective films and pressure-sensitive adhesive layers / protective films / polarizers can be mentioned. Further, between the polarizer and the protective film, between the protective film and the pressure-sensitive adhesive layer, and between the polarizer and the pressure-sensitive adhesive layer, there is an optical functional layer represented by a retardation film (for example, an EWV layer). , Adhesive layer, and easy-adhesive layer).
Examples of the polarizer include a polyvinyl alcohol (PVA) film.
Examples of the protective film include a triacetyl cellulose (TAC) film, a polycycloolefin (COP) film, a polyethylene terephthalate (PET) film, and an acrylic film.

The exposed pressure-sensitive adhesive layer in the optical member with the pressure-sensitive adhesive layer of the present invention may be protected by a release film.
The release film is not particularly limited as long as it can be easily peeled from the pressure-sensitive adhesive layer. For example, a resin film having one or both sides surface-treated with a release treatment agent (so-called easy peeling treatment). Can be mentioned.
Examples of the resin film include a polyester film typified by a polyethylene terephthalate (PET) film. Examples of the stripping agent include fluororesins, paraffin waxes, silicones, long-chain alkyl group compounds and the like.
The release film protects the surface of the pressure-sensitive adhesive layer and is peeled off during use until the optical member with the pressure-sensitive adhesive layer is put into practical use.

The thickness of the pressure-sensitive adhesive layer in the optical member with the pressure-sensitive adhesive layer of the present invention is not particularly limited, and can be appropriately set according to the material, shape, and the like of the adherend.
The thickness of the pressure-sensitive adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

The optical member with an adhesive layer of the present invention can be produced by a known method.
Examples of the method for producing the optical member with the pressure-sensitive adhesive layer of the present invention include the following methods. By applying the pressure-sensitive adhesive composition of the present invention to the easily peelable surface of the release film, a coating film is formed on the release film. Next, the formed coating film is dried to form an adhesive film on the release film. Next, the exposed surface of the formed adhesive film is brought into contact with the optical member and pressurized, and the adhesive film is transferred to the optical member to form the adhesive film on the optical member. Next, the formed adhesive film is cured to form an adhesive layer. As described above, the optical member with the pressure-sensitive adhesive layer of the present invention is obtained.

As another method for producing the optical member with the pressure-sensitive adhesive layer of the present invention, for example, the following method can be mentioned. By applying the pressure-sensitive adhesive composition of the present invention to the easily peelable surface of the release film, a coating film is formed on the release film. Next, the formed coating film is dried to form an adhesive film on the release film. Next, an easily peelable surface of the separately prepared release film is placed on the exposed surface of the formed pressure-sensitive adhesive film, and then pressure-bonded to prepare a double-sided pressure-sensitive adhesive sheet having no base material. Next, the adhesive film of the produced double-sided adhesive sheet is cured to form an adhesive layer. Next, one of the release films is peeled off, and the exposed pressure-sensitive adhesive layer is brought into contact with the optical member and pressed to transfer the pressure-sensitive adhesive layer to the optical member. As described above, the optical member with the pressure-sensitive adhesive layer of the present invention is obtained.

Further, as another method for producing the optical member with the pressure-sensitive adhesive layer of the present invention, for example, the following method can be mentioned. A coating film is formed on the optical member by applying the pressure-sensitive adhesive composition of the present invention to one surface of the optical member. Next, the formed coating film is dried to form an adhesive film on the optical member. Next, the formed adhesive film is cured to form an adhesive layer. As described above, the optical member with the pressure-sensitive adhesive layer of the present invention is obtained.

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

The method for drying the coating film is not particularly limited.
Examples of the method for drying the coating film include methods such as 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.
An example of the drying condition is a condition of drying at 70 ° C. to 120 ° C. for 30 seconds to 180 seconds using a hot air dryer.

Curing is performed, for example, in an environment with an atmospheric temperature of 23 ° C. to 35 ° C. and 50% RH for 3 to 7 days. By curing, the cross-linking reaction of the pressure-sensitive adhesive composition is completed, and a pressure-sensitive adhesive layer is formed.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Manufacture of (meth) acrylic copolymer (A)]
[Manufacturing Example A-1]
In a reactor equipped with a thermometer, stirrer, nitrogen introduction tube, and reflux cooling tube, n-butyl acrylate [n-BA; (meth) acrylic acid alkyl ester monomer] 95.5 parts by mass, 2- Hydroxyethyl acrylate [2HEA; monomer having a hydroxyl group] 1.5 parts by mass, acrylic acid [AA; monomer having a carboxy group] 3.0 parts by mass, and ethyl acetate [organic solvent] 70.0 parts by mass. Was added and mixed to obtain a mixture, and then the inside of the reactor was replaced with nitrogen.
Then, the mixture in the reactor was heated to 70 ° C. with stirring, and then 2,2'-azobis (2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] was added to the mixture in the reactor. 02 parts by mass and 120.0 parts by mass of ethyl acetate were sequentially added and held for 6 hours to carry out a polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 18.5% by mass and then cooled to obtain a solution of the (meth) acrylic copolymer (A).

The "solid content concentration" here means the mass ratio of the (meth) acrylic copolymer (A) to the solution of the (meth) acrylic copolymer (A). The same applies to each solution of the (meth) acrylic copolymer (A) produced according to Production Examples A-2 to A-13 shown below.

[Manufacturing Examples A-2 to A-6 and A-8 to A-13]
In Production Examples A-2 to A-6 and A-8 to A-13, the monomer composition of the (meth) acrylic copolymer (A) was changed to the monomer composition shown in Table 1, and that the monomer composition was changed to the monomer composition shown in Table 1. , Except that the weight average molecular weight of the (meth) acrylic copolymer (A) 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. In the same operation as in Production Example A-1, each solution of the (meth) acrylic copolymer (A) having a solid content concentration of 18.5% by mass was obtained.

[Manufacturing Example A-7]
In Production Example A-7, by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used, the weight average molecular weight of the (meth) acrylic copolymer (A) is the weight average shown in Table 1. The same operation as in Production Example A-1 was carried out except that the molecular weight was adjusted, to obtain a solution of the (meth) acrylic copolymer (A) having a solid content concentration of 18.5% by mass.

Monomer composition (unit: mass%) and weight average molecular weight [Mw, unit: 10,000 (in the table, in the table,) of the (meth) acrylic copolymer (A) produced according to Production Examples A-1 to A-13. “× 10 ⁴ )] is shown in Table 1.
The weight average molecular weight of the (meth) acrylic copolymer (A) produced according to Production Examples A-1 to A-13 is the measurement of the weight average molecular weight of the specific (meth) acrylic copolymer (A) described above. It was measured by the same method as the method.

Among the (meth) acrylic copolymers (A) produced by Production Examples A-1 to A-13, the (meth) acrylic copolymers produced by Production Examples A-1 to A-11 and A-13. (A) corresponds to the specific (meth) acrylic copolymer (A) in the present invention.

Details of each monomer shown in Table 1 are as shown below.
<(Meta) acrylic acid alkyl ester monomer>
"N-BA": n-butyl acrylate "MA": methyl acrylate <monomer having a hydroxyl group>
"2HEA": 2-hydroxyethyl acrylate "4HBA": 4-hydroxybutyl acrylate <monomer having a carboxy group>
"AA": Acrylic acid "M-5300" [Product name: Aronix (registered trademark) M-5300, Toagosei Co., Ltd.]: ω-carboxy-polycaprolactone (n≈2) monoacrylate <other monomers ＞
"PHEA": Phenoxyethyl acrylate

In Table 1, "-" described in the column of monomer composition means that the monomer corresponding to the column is not contained.
In Table 1, "weight average molecular weight" is expressed as "Mw".

[Manufacture of (meth) acrylic copolymer (B)]
[Manufacturing Example B-1]
In a reactor equipped with a thermometer, a stirrer, and a reflux cooling tube, 5.0 parts by mass of n-butyl acrylate [n-BA; (meth) acrylic acid alkyl ester monomer other than MMA], methyl methacrylate [ MMA] 75.0 parts by mass, 2-hydroxyethyl methacrylate [2HEMA; monomer having a hydroxyl group] 20.0 parts by mass, ethyl acetate [organic solvent] 66.7 parts by mass, n-butyl acetate [organic solvent] 36 .7 parts by mass and 11.7 parts by mass of 2,2'-azobis (isobutyric acid) dimethyl [V-601; polymerization initiator] were added and mixed to obtain a mixture.
Next, the mixture in the reactor was heated to 95 ° C. with stirring, and then held for 6 hours for a polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 50.0% by mass and then cooled to obtain a solution of the (meth) acrylic copolymer (B).

[Production Examples B-2, B-3, B-10, and B-11]
In Production Examples B-2, B-3, B-10, and B-11, the (meth) acrylic copolymer (meth) is obtained by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used. Except that the weight average molecular weight of B) was adjusted to the weight average molecular weight shown in Table 2, the same operation as in Production Example B-1 was carried out, and the (meth) acrylic copolymer having a solid content concentration of 50.0% by mass was used. A solution of the polymer (B) was obtained.

[Production Examples B-4 to B-9, B-12, and B-13]
In Production Examples B-4 to B-9, B-12, and B-13, the monomer composition of the (meth) acrylic copolymer (B) was changed to the monomer composition shown in Table 2. In addition, the weight average molecular weight of the (meth) acrylic copolymer (B) was adjusted to the weight average molecular weight shown in Table 2 by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used. Except for the above, the same operation as in Production Example B-1 was carried out to obtain a solution of the (meth) acrylic copolymer (B) having a solid content concentration of 50.0% by mass.

Monomer composition (unit: mass%), weight average molecular weight [Mw, unit: 10,000 (in the table, " × 10 ⁴ hereinafter)], and the glass transition temperature (Tg, unit: ° C.) are shown in Table 2.

The weight average molecular weight of the (meth) acrylic copolymer (B) produced according to Production Examples B-1 to B-13 is the measurement of the weight average molecular weight of the specific (meth) acrylic copolymer (A) described above. It was measured by the same method as the method.
The glass transition temperature of the (meth) acrylic copolymer (B) produced according to Production Examples B-1 to B-13 is the calculation of the glass transition temperature of the specific (meth) acrylic copolymer (A) described above. It was calculated by the same method as the method.

Among the (meth) acrylic copolymers (B) produced by Production Examples B-1 to B-13, the (meth) acrylic copolymers (B) produced by Production Examples B-1 to B-9 are , Corresponds to the specific (meth) acrylic copolymer (B) in the present invention.

Details of each monomer shown in Table 2 are as shown below.
"N-BA": n-butyl acrylate [(meth) acrylic acid alkyl ester monomer other than MMA, glass transition temperature when used as a homopolymer: -57 ° C]
"MMA": Methyl methacrylate [Glass transition temperature when made into a homopolymer: 103 ° C]
"2HEMA": 2-Hydroxyethyl methacrylate [monomer having a hydroxyl group, glass transition temperature when made into a homopolymer: 55 ° C.]
"T-BMA": t-butyl methacrylate [(meth) acrylic acid alkyl ester monomer other than MMA, glass transition temperature when used as a homopolymer: 107 ° C.]

In Table 2, "-" described in the column of monomer composition means that the monomer corresponding to the column is not contained.
In Table 2, "weight average molecular weight" is expressed as "Mw", and "glass transition temperature" is expressed as "Tg".

[Preparation of adhesive composition]
[Example 1]
Both the 540.5 parts by mass (100 parts by mass as solid content) of the solution of the (meth) acrylic copolymer (A) produced by Production Example A-1 and the (meth) acrylic-based compound produced by Production Example B-1. 20.0 parts by mass of the solution of the polymer (B) (10.0 parts by mass as the solid content) and Coronate® L-45E [trade name, tolylene diisocyanate (TDI) and trimethylol propane as the polyisocyanate compound] Adduct compound with (TMP), solid content concentration: 45% by mass, Toso Co., Ltd.] 31.1 parts by mass (14.0 parts by mass as solid content) and KBM-403 as a silane coupling agent [trade name, 3-glycidoxypropyltriethoxysilane, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Industry Co., Ltd.] 0.3 parts by mass and an appropriate amount of ethyl acetate are sufficiently mixed. , The pressure-sensitive adhesive composition of Example 1 was obtained.

[Examples 2 to 30]
In Example 1, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 3, to obtain each pressure-sensitive adhesive composition of Examples 2 to 30.

[Comparative Examples 1 to 11]
In Example 1, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 4, and each pressure-sensitive adhesive composition of Comparative Examples 1 to 11 was obtained.

In Tables 3 and 4, "-" in the composition column means that the corresponding component is not blended in the column.
In Table 3, "parts by mass" in the columns of the specific (meth) acrylic copolymer (A), the specific (meth) acrylic copolymer (B), the polyisocyanate compound, the tackifier resin, and the silane coupling agent. The numerical values shown in the column of are all solid content conversion values. Further, in Table 4, (meth) acrylic copolymer (A) [specific (meth) acrylic copolymer (A) and comparative polymer], (meth) acrylic copolymer (B) [specific (meth) acrylic copolymer (B) Meta) Acrylic copolymer (B) and comparative polymer], polyisocyanate compound (X), and the numerical values described in the column of "parts by mass" in the column of the silane coupling agent are all solid content conversion values. ..

Details of the components shown in Tables 3 and 4 are as shown below.
<Polyisocyanate compound>
"Coronate L-45E" [Product name, adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, Tosoh Corporation]
"Coronate 2030" [Product name, isocyanate nurate of toluene diisocyanate (TDI), solid content concentration: 50% by mass, Tosoh Corporation]
"Takenate D-110N" [Product name, adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content concentration: 75% by mass, Mitsui Chemicals, Inc.]
"Sumijour N75" [Burette of hexamethylene diisocyanate HMDI, solid content concentration: 75% by mass, Sumika Cobestrourethane Co., Ltd.]
The above-mentioned "Coronate", "Takenate", and "Sumijour" are all registered trademarks.

<Adhesive-imparting resin>
"TH130": YS Polystar TH130 [Product name, Yasuhara Chemical Co., Ltd.]
<Silane coupling agent>
"KBM-403" [Product name, 3-glycidoxypropyltriethoxysilane, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.]
"X-41-1053" [Product name, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.]
"KBM-402" [Product name, 3-glycidoxypropylmethyldiethoxysilane, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.]

<Preparation of polarizing plate with adhesive layer>
The pressure-sensitive adhesive composition was applied onto the surface-treated surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] surface-treated with a silicone-based release agent to form a coating film. The amount of the pressure-sensitive adhesive composition applied was such that the thickness of the pressure-sensitive adhesive film described later was 20 μm. Next, air at 100 ° C. was blown onto the formed coating film at a wind speed of 3 m / sec for 60 seconds using a hot air circulation dryer to form an adhesive film having a thickness of 20 μm on the release film. Next, the exposed surface of the formed adhesive film and the surface of one TAC layer of the polarizing plate having the constitution of the triacetyl cellulose (TAC) layer / the polyvinyl alcohol (PVA) layer containing the polarizer / the TAC layer are overlapped. After bonding, the adhesive film is cured by leaving it in an environment of an atmospheric temperature of 23 ° C. and 50% RH for 7 days to cure a release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). A polarizing plate with an adhesive layer having the above-mentioned structure was produced.

<Making a film with an adhesive layer>
The pressure-sensitive adhesive composition was applied onto the surface-treated surface of a release film [type: MRF, thickness: 38 μm, Mitsubishi Chemical Corporation] surface-treated with a silicone-based release agent to form a coating film. The amount of the pressure-sensitive adhesive composition applied was such that the thickness of the pressure-sensitive adhesive film described later was 20 μm.
Next, air at 100 ° C. was blown onto the formed coating film at a wind speed of 3 m / sec for 60 seconds using a hot air circulation dryer to form an adhesive film having a thickness of 20 μm.
Next, the exposed surface of the adhesive film and the surface-treated surface of a separately prepared release film [type: MRF, thickness: 38 μm, Mitsubishi Chemical Co., Ltd.] were laminated and bonded, and then the atmosphere temperature was 23 ° C. The adhesive film was cured by leaving it in an environment of 50% RH for 7 days to prepare a film with an adhesive layer having a composition of a release film / an adhesive layer / a release film.

[evaluation]
1. 1. Adhesiveness (1) Adhesive strength Adhesive strength was measured as one of the indicators of adhesiveness.
The polarizing plate with the pressure-sensitive adhesive layer prepared above was left to stand in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 6 months. Next, the polarizing plate with the adhesive layer after being left to stand was cut to obtain a test piece A-1 having a size of 25 mm × 75 mm (long side). Next, the release film of the obtained test piece A-1 [Structure: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)] was peeled off, and the surface of the pressure-sensitive adhesive layer exposed by the peeling was formed. , The surface of the adherend shown in Table 5 or Table 6, and then pressure-bonded with a laminator to obtain an adherend / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). A laminate having the above constitution was obtained. Next, the obtained laminate was subjected to an autoclave treatment (treatment temperature: 50 ° C., treatment pressure: 5 kg / cm ² , treatment time: 20 minutes), and then placed in an environment with an atmospheric temperature of 23 ° C. and 50% RH. The mixture was left for 0.5 hour to obtain a test piece A-2. With respect to this test piece A-2, when a polarizing plate with an adhesive layer having a structure of an adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) is peeled off from the adherend by 180 ° in the long side direction. Using a single column type material testing machine [model number: STA-1225, A & D Co., Ltd.] as a measuring device for adhesive strength (unit: N / 25 mm), an environment with an ambient temperature of 23 ° C and 50% RH. Below, the measurement was performed under the condition of a peeling speed of 300 mm / min.
The results are shown in Tables 5 and 6.
When the adhesive strength was 0.7 N / 25 mm or more, it was judged that the adhesive layer showed high adhesive strength to the adherend even when stored for a long period of time, and the adhesive layer was excellent in bonding suitability.
The adhesive strength is preferably 0.7 N / 25 mm or more, more preferably 1.0 N / 25 mm or more, and further preferably 1.3 N / 25 mm or more.

(2) Foam loss after autoclave treatment Foam loss after autoclave treatment was evaluated as one of the indexes of bonding suitability.
The polarizing plate with the pressure-sensitive adhesive layer prepared above was left to stand in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 6 months. Next, the polarizing plate with the pressure-sensitive adhesive layer after being left to stand was cut to obtain a test piece B-1 having a size of 62 mm × 110 mm. Next, the release film of the obtained test piece B-1 [Structure: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)] was peeled off, and the surface of the pressure-sensitive adhesive layer exposed by the peeling was formed. , The surface of the adherend shown in Table 5 or Table 6, and then pressure-bonded with a laminator to obtain an adherend / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer). A laminate having the above constitution was obtained. Next, the obtained laminate was subjected to an autoclave treatment (treatment temperature: 50 ° C., treatment pressure: 5 kg / cm ² , treatment time: 20 minutes), and then placed in an environment with an atmospheric temperature of 23 ° C. and 50% RH. The mixture was left for 0.5 hour to obtain a test piece B-2. With respect to this test piece B-2, the end portion of the polarizing plate was visually observed to observe whether or not air bubbles were removed, specifically, the presence or absence and degree of air bubbles. Then, based on the observation results, the foam loss after the autoclave treatment (hereinafter, also referred to as “after A / C”) was evaluated according to the following evaluation criteria.
The results are shown in Tables 5 and 6.
If the evaluation result is "A", "B", or "C", it is an adhesive layer having excellent foam removal property when bonded to the adherend even when stored for a long period of time, and the adhesive has excellent bonding suitability. It was judged to be a drug layer.

-Evaluation criteria-
A: No bubbles were observed at the end of the polarizing plate.
B: Almost no bubbles were observed at the end of the polarizing plate.
C: A few bubbles were observed at the end of the polarizing plate, but it was within the permissible range.
D: Bubbles were noticeably observed at the end of the polarizing plate, which was out of the permissible range.

2. A polarizing plate with an adhesive layer immediately after curing was cut to obtain a test piece C-1 having a size of 62 mm × 110 mm (long side).
Further, the polarizing plate with the pressure-sensitive adhesive layer prepared above was left to stand in an environment of an atmospheric temperature of 23 ° C. and 50% RH for 6 months. Next, the polarizing plate with the pressure-sensitive adhesive layer after being left to stand was cut to obtain a test piece D-1 having a size of 62 mm × 110 mm.
With respect to the test piece C-1 and the test piece D-1, the release film of the test piece [structure: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)] was peeled off, and the adhesive exposed by the peeling was peeled off. The surfaces of the agent layer are laminated on both sides of the Twisted Nematic (TN) type liquid crystal panel so that the absorption axes of the respective test pieces are orthogonal to each other, and then crimped using a laminator to form the laminate C-1 and the laminate. D-1 was obtained.
Next, the obtained laminate C-1 and laminate D-1 were subjected to an autoclave treatment (treatment temperature: 50 ° C., treatment pressure: 5 kg / cm ² , treatment time: 20 minutes). Next, the laminated body after the autoclave treatment was left to stand in an environment of an atmospheric temperature of 23 ° C. and 50% RH for 24 hours to obtain a laminated body C-2 and a laminated body D-2.
Next, the obtained laminate C-2 and the laminate D-2 were left to stand in an environment with an atmospheric temperature of 105 ° C. for 500 hours to obtain a test piece C-2 and a test piece D-2. The test piece C-2 and the test piece D-2 were placed on the backlight of the liquid crystal monitor in an environment of an atmospheric temperature of 23 ° C. and 50% RH, and the presence or absence and degree of white spots were visually observed. Then, based on the observation results, white spots were evaluated according to the following evaluation criteria.
The results are shown in Tables 5 and 6.
If the evaluation result is "A", "B", or "C", it is determined that the adhesive layer is unlikely to cause white spots even when exposed to a high temperature environment.

-Evaluation criteria-
A: No white spots were observed.
B: Almost no white spots were observed.
C: A slight white spot was observed, but it was within the permissible range.
D: White spots were noticeably observed, which was out of the permissible range.

3. 3. Viscoelasticity The storage elastic modulus (G') was measured as one of the indexes of viscoelasticity.
The release film of the film with the pressure-sensitive adhesive layer immediately after curing is peeled off to expose the pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layers are bonded to each other by folding in two, and the release film / pressure-sensitive adhesive layer (thickness: 40 μm). ) / A laminated body having a laminated structure of a release film was obtained. Next, one of the release films of the obtained laminate was peeled off to expose the pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layers were bonded to each other by folding in two, and the release film / pressure-sensitive adhesive layer (thickness:: A laminated body having a laminated structure of 80 μm) / release film was obtained. The above operation (peeling the release film and laminating the pressure-sensitive adhesive layers) was repeated until the thickness of the pressure-sensitive adhesive layer reached 500 μm, and the obtained laminate was used as a sample E for measuring the storage elastic modulus. It was set to -1.
Further, the film with the pressure-sensitive adhesive layer prepared above was left to stand in an environment of an atmospheric temperature of 23 ° C. and 50% RH for 6 months. Next, the same operation as described above was performed on the film with the pressure-sensitive adhesive layer after being left to stand, and the obtained laminate was used as a sample E-2 for measuring the storage elastic modulus.
Using a dynamic viscoelasticity measuring device (product name: Physica MCR301, Antonio Par) as a measuring device, the storage elastic modulus measurement sample E is used at an evaluation temperature of 25 ° C., a cone used: 8 mmφ, and a measurement gap of 0.6 mm. The storage elastic modulus (G') (unit: Pa) was measured while applying shear stress to -1 and E-2 at a frequency of 1 Hz.
The results are shown in Tables 5 and 6.
When the storage elastic modulus (G') was 1.1 × 10 ⁵ Pa to 12.0 × 10 ⁵ Pa, it was judged that the pressure-sensitive adhesive layer had appropriate viscoelasticity. Storage modulus (G ') is more to be preferably from ^{1.1 × 10 5 Pa~12.0 × 10 5} Pa, 4.0 × 10 5 Pa~12.0 × 10 5 Pa It is preferably 7.0 × 10 ⁵ Pa to 12.0 × 10 ⁵ Pa, and more preferably.

In Tables 5 and 6, "-" in the white column means that the evaluation has not been performed.

The details of the adherends shown in Tables 5 and 6 are as follows.
"Glass" [Soda glass, Matsunami Glass Industry Co., Ltd.]
"BASUS" [Stainless steel sheet, product name: SUS304, Paltek Corporation]
"PET": Polyethylene terephthalate film, trade name: Teijin (registered trademark) Tetron (registered trademark) film HPE, thickness: 50 μm, Teijin Film Solutions Co., Ltd.

As shown in Table 5, it contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group, and has a weight average molecular weight of 400,000 to 2.5 million. A certain (meth) acrylic copolymer (A) [that is, a specific (meth) acrylic copolymer (A)], a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from methyl methacrylate. A (meth) acrylic copolymer (B) [that is, a specific (meth) acrylic copolymer (B)] containing 3,000 to 50,000 in weight average molecular weight, and a polyisocyanate compound. , And the content of the specific (meth) acrylic copolymer (B) is 5 parts by mass to 25 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). Adhesion formed by the pressure-sensitive adhesive compositions of Examples 1 to 30, wherein the content of the isocyanate compound is 6 parts by mass to 30 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the polymer layer has high adhesive strength after long-term storage and excellent foam removal property after autoclave treatment, and has excellent bonding suitability even after long-term storage. Further, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 30 has appropriate viscoelasticity both immediately after curing and after long-term storage, and when exposed to a high temperature environment. However, it became clear that it was difficult to cause white spots.

On the other hand, as shown in Table 6, according to the pressure-sensitive adhesive composition of Comparative Example 1, the content of the polyisocyanate compound is less than 6 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the formed adhesive layer has an excessively low storage elastic modulus (G') both immediately after curing and after long-term storage, and tends to cause white spots when exposed to a high temperature environment. Was done.
Formed by the pressure-sensitive adhesive compositions of Comparative Example 2, Comparative Example 9, and Comparative Example 10 in which the content of the polyisocyanate compound exceeds 30 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that when the pressure-sensitive adhesive layer was used after long-term storage, the adhesive strength was excessively low, the foam was poorly removed after the autoclave treatment, and the bonding suitability was poor.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 3 in which the weight average molecular weight of the (meth) acrylic copolymer (B) is less than 3,000 can be obtained either immediately after curing or after long-term storage. However, it was confirmed that the storage elastic modulus (G') was excessively low, and that white spots were likely to occur when exposed to a high temperature environment.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 4, in which the weight average molecular weight of the (meth) acrylic copolymer (B) exceeds 50,000, has an excessively low adhesive strength when used after long-term storage. In addition, it was confirmed that the foam removal after the autoclave treatment was poor and the bonding suitability was inferior.
The pressure-sensitive adhesive composition of Comparative Example 5 in which the content of the specific (meth) acrylic copolymer (B) is less than 5 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the pressure-sensitive adhesive layer formed by the above method had an excessively low adhesive strength when used after long-term storage, and had poor foam removal after the autoclave treatment, resulting in poor bonding suitability.
According to the pressure-sensitive adhesive composition of Comparative Example 6, the content of the specific (meth) acrylic copolymer (B) exceeds 25 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the formed adhesive layer had an excessively low storage elasticity (G') both immediately after curing and after long-term storage, and was prone to white spots when exposed to a high temperature environment. Was done.
Adhesive of Comparative Example 7 in which the (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group and does not contain a structural unit derived from a monomer having a carboxy group. It was confirmed that the pressure-sensitive adhesive layer formed by the agent composition had poor foam removal after the autoclave treatment and was inferior in bonding suitability when used after long-term storage.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 8 in which the (meth) acrylic copolymer (B) does not contain a structural unit derived from methyl methacrylate has excessive adhesive strength when used after long-term storage. It was confirmed that the value was low and the foam removal after the autoclave treatment was poor, resulting in poor bonding suitability.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 11 in which the (meth) acrylic copolymer (B) does not contain a structural unit derived from a monomer having a hydroxyl group can be used after long-term storage. It was confirmed that the adhesive strength was excessively low, the foam was poorly removed after the autoclave treatment, and the bonding suitability was inferior.

Claims (8)

A (meth) acrylic copolymer containing a structural unit derived from a (meth) acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group, and having a weight average molecular weight of 400,000 to 2.5 million. Polymer (A) and
A (meth) acrylic copolymer (B) containing a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from methyl methacrylate and having a weight average molecular weight of 30,000 to 50,000.
Containing with polyisocyanate compounds,
The content of the (meth) acrylic copolymer (B) is 5 parts by mass to 25 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A).
A pressure-sensitive adhesive composition in which the content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (B) is 5 with respect to all the structural units of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition according to claim 1, which is from mass% to 25% by mass. The content of the structural unit derived from the methyl methacrylate in the (meth) acrylic copolymer (B) is 40% by mass to 95% by mass with respect to all the structural units of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition according to claim 1 or 2, which is by mass%. The content of the structural unit derived from the monomer having a carboxy group in the (meth) acrylic copolymer (A) is higher than that of all the structural units of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition according to any one of claims 1 to 3, which is 1% by mass to 5% by mass. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group. The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (A) is 0 with respect to all the structural units of the (meth) acrylic copolymer (A). .. The pressure-sensitive adhesive composition according to claim 5, which is 1% by mass to 3% by mass. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the glass transition temperature of the (meth) acrylic copolymer (B) is 60 ° C to 105 ° C. Optical members and
A pressure-sensitive adhesive layer provided on the optical member and formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 7.
An optical member with an adhesive layer comprising.