JP2021088648A - Adhesive composition, adhesive sheet and optical member - Google Patents

Abstract

To provide an adhesive composition from which an adhesive layer can be formed that shows light releasability in the initial state of sticking to an adherend and shows high adhesive force after heated and that has excellent high-temperature durability, and an adhesive sheet and an optical member.SOLUTION: The adhesive composition comprises: a (meth)acrylic copolymer (A) that contains a structural unit derived from a monomer having a hydroxyl group of 1 mass% to 40 mass% with respect to the whole structural units and has a glass transition temperature of lower than 0°C; a (meth)acrylic copolymer (B) that contains a structural unit derived from a monomer having an organosiloxane skeleton of 2 mass% to 9 mass% with respect to the whole structural units, in which the monomer having an organosiloxane skeleton has a number average molecular weight of 400 to 1500, and that has a weight average molecular weight of 10000 to 100000; and a xylylene diisocyanate compound. The content of the (meth)acrylic copolymer (B) is 0.1 pts.mass to 20 pts.mass with respect to 100 pts.mass of the (meth)acrylic copolymer (A). An application of the composition is also disclosed.SELECTED DRAWING: None

Description

The present invention relates to pressure-sensitive adhesive compositions, pressure-sensitive adhesive sheets, and optical members.

The pressure-sensitive adhesive composition used in various display devices is required to be able to form a pressure-sensitive adhesive layer that exhibits light peelability at the initial stage of bonding and high adhesive strength after heating. Various pressure-sensitive adhesive compositions have been developed to meet such demands.

For example, Patent Document 1 describes a monomer having 100 parts by mass of a polymer (A) having a glass transition temperature of less than 0 ° C., a monomer having an organosiloxane skeleton having a functional group equivalent of 1000 g / mol or more and less than 15000 g / mol, and a monomer having an organosiloxane skeleton. Adhesion containing a monomer having a glass transition temperature of 40 ° C. or higher as a monomer unit of a homopolymer and 0.1 parts by mass to 20 parts by mass of a copolymer (B) having a weight average molecular weight in the range of 10,000 or more and less than 100,000. The agent composition is disclosed.
Further, for example, Patent Document 2 describes a monomer having 100 parts by mass of a polymer (A) having a glass transition temperature of less than 0 ° C. and an organosiloxane skeleton having a functional group equivalent in the range of 1000 g / mol or more and 4600 g / mol or less. B1) and 0.1 part by mass of the copolymer (B) containing a monomer (B2) having a glass transition temperature of 40 ° C. or higher as a monomer unit and having a weight average molecular weight in the range of 10,000 or more and less than 100,000. Adhesive that contains 20 parts by mass, and the copolymer (B) is a copolymer containing 10% by mass to 20% by mass of the monomer (B1) and 30% by mass to 50% by mass of the monomer (B2). The agent composition is disclosed.

International Publication No. 2015/163115 JP-A-2017-203164

By the way, the pressure-sensitive adhesive composition used in an electronic device is required to have a property of being able to withstand the heat generated from the electronic device for a long time (so-called high temperature durability). In general, the pressure-sensitive adhesive layer exposed to a high temperature environment tends to have defects such as foaming. Therefore, it is desirable that the pressure-sensitive adhesive composition used in electronic devices can form a pressure-sensitive adhesive layer in which foaming is unlikely to occur even when exposed to an environment of 85 ° C. for 7 days. In order to suppress possible foaming in the pressure-sensitive adhesive layer, it is conceivable to increase the cohesive force of the pressure-sensitive adhesive layer. However, if the cohesive force of the pressure-sensitive adhesive layer is increased, foaming can be suppressed, but the adhesive force tends to decrease. That is, the suppression of foaming in the pressure-sensitive adhesive layer and the improvement of the adhesive strength are in a trade-off relationship, and it has been difficult to improve both of them.

The problem to be solved by the present invention is a pressure-sensitive adhesive layer that exhibits light peelability at the initial stage of bonding and high adhesive strength after heating, and has excellent high-temperature durability. It is an object of the present invention to provide a pressure-sensitive adhesive composition capable of forming a layer, and a pressure-sensitive adhesive sheet and an optical member including the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition.

Specific means for solving the problem include the following aspects.
<1> (Meta) acrylic containing a structural unit derived from a monomer having a hydroxyl group in a range of 1% by mass or more and 40% by mass or less with respect to all the structural units, and having a glass transition temperature of less than 0 ° C. With the system copolymer (A),
Constituent units derived from a monomer having an organosiloxane skeleton are contained in a range of 2% by mass or more and 9% by mass or less with respect to all the structural units, and the number average molecular weight of the monomer having an organosiloxane skeleton is 400 or more. With the (meth) acrylic copolymer (B) having a weight average molecular weight in the range of 10,000 or more and 100,000 or less, which is in the range of 1500 or less.
Xylylene diisocyanate compound and
Including
The content of the (meth) acrylic copolymer (B) is in the range of 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). Adhesive composition.

<2> The monomer having an organosiloxane skeleton is at least one compound selected from the group consisting of the compound represented by the following formula (1) and the compound represented by the formula (2) <1. > The pressure-sensitive adhesive composition.

In formulas (1) and (2), R ¹ represents a hydrogen atom or a methyl group, R ² represents a monovalent organic group, and m and n each independently represent an integer of 0 or more. ..

<3> The (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group in a range of 10% by mass or more and 30% by mass or less with respect to all the structural units <1. > Or the pressure-sensitive adhesive composition according to <2>.
<4> A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition according to any one of <1> to <3>.
<5> An optical member including a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition according to any one of <1> to <3>.

According to the present invention, it is possible to form an adhesive layer that exhibits light peelability at the initial stage of bonding and high adhesive strength after heating, and has excellent high temperature durability. Provided are a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive sheet and an optical member including a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition.

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 a certain 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 "methacryloyl".

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

In the present invention, "after heating" means, for example, after applying a temperature of 50 ° C. or higher. The upper limit of the temperature is, for example, 300 ° C.

In the present invention, "high temperature durability" means a property that can suppress foaming even when exposed to a high temperature (for example, 85 ° C. or higher) environment for a long time (for example, 168 hours or longer).

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".

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group in a range of 1% by mass or more and 40% by mass or less with respect to all the structural units, and has a glass transition temperature (“Tg””. (Also also referred to as) is less than 0 ° C. (meth) acrylic copolymer (A) [hereinafter, also referred to as “specific (meth) acrylic copolymer (A)”. ] And the structural units derived from the monomer having an organosiloxane skeleton in the range of 2% by mass or more and 9% by mass or less with respect to all the structural units, and the number average molecular weight of the monomer having the organosiloxane skeleton. (Also referred to as "Mn") is in the range of 400 or more and 1500 or less, and the weight average molecular weight (also referred to as "Mw") is in the range of 10,000 or more and 100,000 or less (meth) acrylic copolymer. (B) [Hereinafter, it is also referred to as "specific (meth) acrylic copolymer (B)". ] And the xylylene diisocyanate compound, and the content of the (meth) acrylic copolymer (B) is 0. The range is 1 part by mass or more and 20 parts by mass or less.
According to the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer exhibits light peelability at the initial stage of bonding and high adhesive strength after heating, and is exposed to a high temperature environment. It is possible to form an adhesive layer in which foaming is unlikely to occur (that is, excellent in high temperature durability).
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.

Monomers having an organosiloxane skeleton tend to have the specific (meth) acrylic copolymer (B) unevenly distributed on the adhesive surface of the pressure-sensitive adhesive layer due to the low polarity derived from the structure. The "adhesive surface of the pressure-sensitive adhesive layer" includes, for example, the interface between the pressure-sensitive adhesive layer and the adherend. In the pressure-sensitive adhesive composition of the present invention, the content of structural units derived from the monomer having an organosiloxane skeleton in the specific (meth) acrylic copolymer (B) and the number average of the monomers having an organosiloxane skeleton. By adjusting the molecular weight and the content of the specific (meth) acrylic copolymer (B), the specific (meth) acrylic copolymer (B) is appropriately unevenly distributed on the adhesive surface of the pressure-sensitive adhesive layer. There is. The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention is light at the initial stage of bonding with respect to the adherend because the specific (meth) acrylic copolymer (B) is appropriately unevenly distributed on the bonding surface. It is presumed to show peelability.

By the way, when the adherend is glass, the hydrophilic group on the glass surface easily interacts with the water in the air and the cleaning solvent such as alcohol, so that a small amount of water, solvent and the like remain on the glass surface. There is. Moisture, solvent, etc. remaining on the glass surface can cause foaming in the pressure-sensitive adhesive layer by vaporizing in a high temperature environment. Further, when the polymer contained in the pressure-sensitive adhesive composition contains a structural unit derived from a monomer having an organosiloxane skeleton, when the pressure-sensitive adhesive layer is formed, the organosiloxane skeleton portion is the adhesive surface of the pressure-sensitive adhesive layer. Since it is unevenly distributed in the area, the adhesive layer and the glass have low adhesion, and foaming tends to occur in a high temperature environment. In the pressure-sensitive adhesive composition of the present invention, since the specific (meth) acrylic copolymer (A) contains a specific amount of a structural unit derived from a monomer having a hydroxyl group, the hydroxyl group is oriented toward the glass interface under a high temperature environment. However, by capturing the water, solvent, etc. by hydrogen bonds, it is possible to prevent the water, solvent, etc. from migrating into the pressure-sensitive adhesive layer. Further, since the pressure-sensitive adhesive composition of the present invention contains a xylylene diisocyanate compound as a cross-linking agent, the pressure-sensitive adhesive layer formed has an appropriate cohesive force, and foaming is unlikely to occur even when exposed to a high temperature environment. It is presumed. On the other hand, when the cohesive force of the pressure-sensitive adhesive layer is increased, foaming is less likely to occur, but the adhesive strength tends to decrease. On the other hand, the pressure-sensitive adhesive composition of the present invention contains the specific (meth) acrylic copolymer (A) having a low glass transition temperature (Tg), and the specific (meth) acrylic copolymer (B). Since the number average molecular weight and the copolymerization amount of the monomers having an organosiloxane skeleton in the above are relatively low, the formed pressure-sensitive adhesive layer exhibits appropriate wettability to the adherend. Therefore, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention is unlikely to foam even when exposed to a high temperature environment and exhibits high adhesive strength after heating.

For the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive composition described in Patent Document 1 (International Publication No. 2015/163115) and the pressure-sensitive adhesive composition described in Patent Document 2 (Japanese Patent Laid-Open No. 2017-203164). The product contains a structural unit in which the polymer (A) is derived from a monomer having a carboxy group, not a structural unit derived from a monomer having a hydroxyl group. Therefore, it is considered that the formed pressure-sensitive adhesive layer has a relatively low cohesive force and is likely to foam when exposed to a high temperature environment.

[Specific (meth) acrylic copolymer (A)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group in a range of 1% by mass or more and 40% by mass or less with respect to all the structural units, and the glass transition temperature is less than 0 ° C. The (meth) acrylic copolymer (A) [that is, the specific (meth) acrylic copolymer (A)] is included.

<Constituent unit derived from a monomer having a hydroxyl group>
The specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group in a range of 1% by mass or more and 40% by mass or less with respect to all the structural units.
The hydroxyl group of the structural unit derived from the monomer having a hydroxyl group is crosslinked with the isocyanate group of the xylylene diisocyanate compound.

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 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-. Hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1 -Dimethyl-3-hydroxybutyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-3 Examples thereof include hydroxyhexyl (meth) acrylate and N-hydroxyethyl (meth) acrylamide.
As the monomer having a hydroxyl group, for example, when the specific (meth) acrylic copolymer (A) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer described later, (meth) acrylic. From the viewpoint of good copolymerizability with the acid alkyl ester monomer, hydroxyalkyl (meth) acrylate is preferable, and from the viewpoint of good compatibility with the (meth) acrylic acid alkyl ester monomer. From the viewpoint of good reactivity with the xylylene diisocyanate compound, hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 5 carbon atoms is more preferable, and hydroxy having 2 to 4 carbon atoms. A hydroxyalkyl (meth) acrylate having an alkyl group is more preferable, a 2-hydroxyethyl (meth) acrylate is further preferable, and a 2-hydroxyethyl acrylate is particularly preferable.

The specific (meth) acrylic copolymer (A) may contain only one type of structural unit derived from a 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 (A) is 1 with respect to all the structural units of the specific (meth) acrylic copolymer (A). It is in the range of mass% or more and 40% by mass or less, preferably in the range of 5% by mass or more and 40% by mass or less, more preferably in the range of 10% by mass or more and 40% by mass or less, and 10% by mass or more and 30%. It is more preferably in the range of mass% or less, and particularly preferably in the range of 15% by mass or more and 30% by mass or less.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is 1 mass with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is more than%, the light peelability of the pressure-sensitive adhesive layer with respect to the adherend at the initial stage of bonding tends to be difficult to be impaired. In addition, there is a tendency that an adhesive layer that is less likely to foam (that is, has excellent high temperature durability) can be formed even 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 40% by mass with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is less than%, the adhesive force of the pressure-sensitive adhesive layer to the adherend after heating tends to be high.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer>
The specific (meth) acrylic copolymer (A) preferably 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 adhesive strength.

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" in the present specification does not include the (meth) acrylic acid alkyl ester monomer having a hydroxyl group.

The type of (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 and more preferably 1 to 12 from the viewpoint of adhesive strength.

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, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
Examples of the (meth) acrylic acid alkyl ester monomer include n-butyl acrylate (n-BA), from the viewpoint that a (meth) acrylic copolymer having a glass transition temperature of less than 0 ° C. can be easily produced. At least one selected from the group consisting of methyl acrylate (MA) and 2-ethylhexyl acrylate (2EHA) is preferable.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the specific (meth) acrylic copolymer (A) contains 1 structural unit derived from the (meth) acrylic acid alkyl ester monomer. Only seeds may be contained, or two or more kinds may be contained.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the (meth) acrylic acid in the specific (meth) acrylic copolymer (A) The content of the structural unit derived from the alkyl ester monomer is not particularly limited, but is, for example, 50% by mass or more with respect to all the structural units of the specific (meth) acrylic copolymer (A). It is more preferably in the range of 50% by mass or more and 99% by mass or less, further preferably in the range of 60% by mass or more and 99% by mass or less, and more preferably in the range of 60% by mass or more and 95% by mass or less. It is more preferably 60% by mass or more and 90% by mass or less, further preferably 65% by mass or more and 85% by mass or less, and 70% by mass or more and 85% by mass or less. Is particularly preferable.
Here, the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer is 50% by mass or more with respect to all the structural units of the specific (meth) acrylic copolymer (A). , It means that the structural unit derived from the (meth) acrylic acid alkyl ester monomer is contained as the main component of the structural unit constituting the specific (meth) acrylic copolymer (A).
When the specific (meth) acrylic copolymer (A) contains a structural unit derived from methyl acrylate, the content of the structural unit derived from methyl acrylate in the specific (meth) acrylic copolymer (A). Is not particularly limited, but for example, 10 mass with respect to all the constituent units of the specific (meth) acrylic copolymer (A) in that zipping is unlikely to occur when peeling at a peeling speed of 1000 mm / min or more. It is preferably less than%.

<Other building blocks>
The specific (meth) acrylic copolymer (A) has a configuration derived from the above-mentioned structural unit, that is, a monomer having a hydroxyl group, which is an essential structural unit, within the range in which the effect of the present invention is exhibited. It may contain a unit and a structural unit (so-called other structural unit) other than the structural unit derived from the (meth) acrylic acid alkyl ester monomer which is an arbitrary structural unit.

Examples of the monomer constituting the other structural unit include (meth) acrylate having an aromatic ring represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl. Alkoxyalkyl (meth) acrylate represented by (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, acrylonitrile and methacryl. Examples thereof include vinyl cyanide typified by acrylonitrile, and vinyl esters typified by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versatic acid. In addition, various derivatives of these monomers can be mentioned.

<< Glass transition temperature of specific (meth) acrylic copolymer (A) >>
The glass transition temperature of the specific (meth) acrylic copolymer (A) is less than 0 ° C., preferably -10 ° C. or lower, more preferably -20 ° C. or lower, and more preferably -30 ° C. or lower. It is more preferable to have.
When the glass transition temperature of the specific (meth) acrylic copolymer (A) is less than 0 ° C., the formed pressure-sensitive adhesive layer has an appropriate wettability to the adherend and has a high adhesive strength after heating. Tend.
The lower limit of the glass transition temperature of the specific (meth) acrylic copolymer (A) is not particularly limited, and is preferably −70 ° C. or higher from the viewpoint of adhesive strength, for example.
The glass transition temperature of the specific (meth) acrylic copolymer (A) may be, for example, in the range of −70 ° C. or higher and lower than 0 ° C., or in the range of −70 ° C. or higher and lower than -10 ° C. , −70 ° C. or higher and −20 ° C. or lower, or −70 ° C. or higher and −30 ° C. or lower.

The glass transition temperature of the specific (meth) acrylic copolymer (A) is the absolute temperature (unit: K; hereinafter the same) calculated from the following formula 1 as the Celsius temperature (unit: ° C; hereinafter the same). It is a value converted to.).
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 (A) 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 (A), 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 turning point of the measured 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, acrylic acid (AA) at 163 ° C, isooctyl acrylate (i-OA) at -75 ° C, dimethylaminoethyl methacrylate (DM) at 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 (A) can be appropriately adjusted by using, for example, two or more types of monomers having different glass transition temperatures when used as a homopolymer.

<< Weight average molecular weight of specific (meth) acrylic copolymer (A) >>
The weight average molecular weight of the specific (meth) acrylic copolymer (A) is not particularly limited, and is preferably in the range of 400,000 or more and 2 million or less, and preferably in the range of 400,000 or more and 1.5 million or less. Is more preferable, and the range is more preferably 400,000 or more and 1 million or less, and particularly preferably 400,000 or more and 800,000 or less.
When the weight average molecular weight of the specific (meth) acrylic copolymer (A) is 400,000 or more, the light peelability of the pressure-sensitive adhesive layer to the adherend at the initial stage of bonding tends to be less likely to be impaired.
When the weight average molecular weight of the specific (meth) acrylic copolymer (A) is 2 million or less, the adhesive strength of the pressure-sensitive adhesive layer to the adherend after heating tends to be higher.

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

For the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A), adjust the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, and the like. Therefore, the desired value can be obtained.

<< 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, 80% by mass or more and 99 with respect to the total solid content in the pressure-sensitive adhesive composition. It is preferably in the range of mass% or less, more preferably in the range of 80% by mass or more and 95% by mass or less, and further preferably in the range of 85% by mass or more and 93% by mass or less.
When the content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is 80% by mass or more with respect to the total solid content in the pressure-sensitive adhesive composition, it is exposed to a high temperature environment. Even when this is done, there is a tendency to form an adhesive layer in which foaming is less likely to occur (that is, it is superior in high temperature durability).
When the content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is 99% by mass or less with respect to the total solid content in the pressure-sensitive adhesive composition, the coating material at the initial stage of bonding is applied. The light peelability of the pressure-sensitive adhesive layer on the body tends to be less likely to be impaired.
In the present specification, the "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a solvent, and the pressure-sensitive adhesive composition contains a solvent. When included, it means the mass of the residue obtained by removing the solvent from the pressure-sensitive adhesive composition.

[Specific (meth) acrylic copolymer (B)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having an organosiloxane skeleton in a range of 2% by mass or more and 9% by mass or less with respect to all the structural units, and has the above-mentioned organosiloxane skeleton. The (meth) acrylic copolymer (B) [that is, the specific (meth)) having a number average molecular weight of 400 or more and 1500 or less and a weight average molecular weight of 10,000 or more and 100,000 or less. Acrylic copolymer (B)] is included.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 0.1% by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The range is from 10 parts to 20 parts by mass.

<Constituent unit derived from a monomer having an organosiloxane skeleton>
The specific (meth) acrylic copolymer (B) contains a structural unit derived from a monomer having an organosiloxane skeleton.
As used herein, the "constituent unit derived from a monomer having an organosiloxane skeleton" means a structural unit formed by addition polymerization of a monomer having an organosiloxane skeleton.

The number average molecular weight of the monomer having an organosiloxane skeleton is in the range of 400 or more and 1500 or less, preferably in the range of 600 or more and 1400 or less, and more preferably in the range of 800 or more and 1300 or less.
The number average molecular weight of the monomer having an organosiloxane skeleton is, for example, 400 or more from the viewpoint of availability.
When the number average molecular weight of the monomer having an organosiloxane skeleton is 1500 or less, the adhesive strength of the pressure-sensitive adhesive layer to the adherend after heating tends to be high.

The number average molecular weight of the monomer having an organosiloxane skeleton is a value measured by the following method. Specifically, the measurement is performed according to the following (1) and (2).
(1) A sample solution having a solid content concentration of 0.2% by mass is obtained by using a monomer having an organosiloxane skeleton and tetrahydrofuran. The "solid content concentration" here means the mass ratio of the monomer having an organosiloxane skeleton to the sample solution.
(2) Using gel permeation chromatography (GPC), the number average molecular weight of the monomer having an organosiloxane skeleton 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

When the specific (meth) acrylic copolymer (B) contains a monomer having two or more kinds of organosiloxane skeletons having different number average molecular weights, the number average molecular weight means an arithmetic mean value. ..
In the present specification, when the (meth) acrylic copolymer contains a monomer having two or more kinds of organosiloxane skeletons having different number average molecular weights, "the number average molecular weight of the monomer having an organosiloxane skeleton". Is calculated by the following formula.
Number average molecular weight of monomer having an organosiloxane skeleton = [Number average molecular weight of monomer 1 x amount of monomer 1 + number average molecular weight of monomer 2 x amount of monomer 2 + ... -+ Number average molecular weight of monomer n x amount of monomer n] / [amount of monomer 1 + amount of monomer 2 + ... + amount of monomer n]

The type of the monomer having an organosiloxane skeleton is not particularly limited as long as it has an organosiloxane skeleton and has a number average molecular weight in the range of 400 or more and 1500 or less.
Specific examples of the monomer having an organosiloxane skeleton include at least one compound selected from the group consisting of the compound represented by the following formula (1) and the compound represented by the formula (2).

In the formulas (1) and (2), R ¹ represents a hydrogen atom or a methyl group, and is preferably a methyl group.
In formulas (1) and (2), R ² represents a monovalent organic group.
The ^{monovalent organic group represented by R 2} may be linear, may have a branch, or may be cyclic. Examples of the monovalent organic group include an alkyl group, an alkenyl group, an alkynyl group, an aryl group and the like, and an alkyl group is preferable.
When R ² represents an alkyl group, an alkyl group having 1 to 12 carbon atoms is preferable, an alkyl group having 1 to 6 carbon atoms is more preferable, and an alkyl group having 1 to 4 carbon atoms is further preferable.
Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group and the like. , Methyl group is preferred.
Examples ^{of the alkenyl group in which R 2} represents an alkenyl group include a vinyl group, an allyl group, a 2-propenyl group and the like, and a vinyl group is preferable.
Examples of the alkynyl group when R ² represents an alkynyl group include an ethynyl group, a propargyl group, a propa-2-in-1-yl group and the like, and an ethynyl group is preferable.
Examples ^{of the aryl group when R 2} represents an aryl group include a phenyl group, a tolyl group, a pyridyl group and the like, and a phenyl group is preferable.
m and n each independently represent an integer of 0 or more. m is preferably an integer of 1 to 10, and more preferably an integer of 1 to 6. n is preferably an integer of 1 to 250, more preferably an integer of 5 to 200.

As the monomer having an organosiloxane skeleton, a commercially available product can be used.
Examples of commercially available products of monomers having an organosiloxane skeleton include X-22-2404 [trade name, number average molecular weight: 420, Shin-Etsu Chemical Industry Co., Ltd.], Silaplane TM-0701T [trade name, number average. Molecular weight: 423, JNC Co., Ltd.], X-22-174ASX [Product name, number average molecular weight: 1100, Shin-Etsu Chemical Industry Co., Ltd.], Silaplane FM-0711 [Product name, number average molecular weight: 1200, JNC ( Co., Ltd.] and the like.
All of the above commercially available products correspond to the compounds represented by the formula (2).

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

The specific (meth) acrylic copolymer (B) preferably does not contain a structural unit derived from a monomer having an organosiloxane skeleton having a number average molecular weight of 2000 or more.

The content of the structural units derived from the monomer having an organosiloxane skeleton in the specific (meth) acrylic copolymer (B) is based on all the structural units of the specific (meth) acrylic copolymer (B). , 2% by mass or more and 9% by mass or less, preferably 3% by mass or more and 9% by mass or less, and more preferably 4% by mass or more and 9% by mass or less. It is more preferably in the range of 9% by mass or less.
The content of the structural units derived from the monomer having an organosiloxane skeleton in the specific (meth) acrylic copolymer (B) is higher than that of all the structural units of the specific (meth) acrylic copolymer (B). When it is 2% by mass or more, the light peelability of the pressure-sensitive adhesive layer with respect to the adherend at the initial stage of bonding tends to be difficult to be impaired.
The content of the structural units derived from the monomer having an organosiloxane skeleton in the specific (meth) acrylic copolymer (B) is higher than that of all the structural units of the specific (meth) acrylic copolymer (B). When it is 9% by mass or less, the adhesive force of the pressure-sensitive adhesive layer on the adherend after heating tends to be high.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer>
The specific (meth) acrylic copolymer (B) preferably 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 adhesive strength.

The type of (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 and more preferably 1 to 12 from the viewpoint of adhesive strength.

Specific examples of the (meth) acrylic acid alkyl ester monomer are the same as specific examples of the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer (A), and thus will be described here. Is omitted.
Examples of the (meth) acrylic acid alkyl ester monomer include methyl methacrylate (MMA) and n-butyl methacrylate (n-BMA) from the viewpoint of compatibility with the specific (meth) acrylic copolymer (A). , And at least one selected from the group consisting of 2-ethylhexyl methacrylate (2EHMA) is preferred.

When the specific (meth) acrylic copolymer (B) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the specific (meth) acrylic copolymer (B) has 1 structural unit derived from the (meth) acrylic acid alkyl ester monomer. Only seeds may be contained, or two or more kinds may be contained.

When the specific (meth) acrylic copolymer (B) contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the (meth) acrylic acid in the specific (meth) acrylic copolymer (B) The content of the structural unit derived from the alkyl ester monomer is not particularly limited, but may be, for example, 50% by mass or more with respect to all the structural units of the specific (meth) acrylic copolymer (B). It is more preferably in the range of 50% by mass or more and 98% by mass or less, further preferably in the range of 60% by mass or more and 97% by mass or less, and preferably in the range of 70% by mass or more and 96% by mass or less. It is more preferably in the range of 75% by mass or more and 97% by mass or less, and particularly preferably in the range of 80% by mass or more and 95% by mass or less.
The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer is 50% by mass or more with respect to all the structural units of the specific (meth) acrylic copolymer (B). ) It means that the structural unit derived from the acrylic acid alkyl ester monomer is contained as the main component of the structural unit constituting the specific (meth) acrylic copolymer (B).

<Other building blocks>
The specific (meth) acrylic copolymer (B) is derived from the above-mentioned structural unit, that is, a monomer having an organosiloxane skeleton, which is an essential structural unit, within the range in which the effect of the present invention is exhibited. It may contain a structural unit to be used and a structural unit (so-called other structural unit) other than the structural unit derived from the (meth) acrylic acid alkyl ester monomer which is an arbitrary structural unit.

Examples of the monomer constituting the other structural unit include (meth) acrylate having an aromatic ring represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl. Alkoxyalkyl (meth) acrylate represented by (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, acrylonitrile and methacryl. Examples thereof include vinyl cyanide typified by acrylonitrile, and vinyl esters typified by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versatic acid. In addition, various derivatives of these monomers can be mentioned.
Further, as a specific example of the monomer constituting another structural unit, a monomer having a hydroxyl group can be mentioned. Since the specific example of the monomer having a hydroxyl group is the same as the specific example of the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A), the description thereof is omitted here.
However, the specific (meth) acrylic copolymer (B) preferably does not contain a structural unit derived from a monomer having a hydroxyl group, for example, from the viewpoint of easiness of uneven distribution at the interface.

<< Glass transition temperature of specific (meth) acrylic copolymer (B) >>
The glass transition temperature of the specific (meth) acrylic copolymer (B) is not particularly limited, but is preferably in the range of 40 ° C. or higher and 65 ° C. or lower, and is preferably in the range of 40 ° C. or higher and 60 ° C. or lower. Is more preferable, and the range is more preferably 40 ° C. or higher and 55 ° C. or lower.
When the glass transition temperature of the specific (meth) acrylic copolymer (B) is within the above range, the initial and post-heating adhesive strength of the pressure-sensitive adhesive layer to the adherend tends to be more appropriate. In addition, the adhesive layer does not become too hard at room temperature, and tends to exhibit more appropriate wettability with respect to the adherend.

The glass transition temperature of the specific (meth) acrylic copolymer (B) was set to 8 mg in a nitrogen stream using a differential scanning calorimetry device (DSC), the measurement start temperature was -70 ° C, and the measurement end temperature was 150. The measurement was performed under the conditions of ° C. and a heating rate of 10 ° C./min, and the bending point of the obtained DSC curve was defined as the glass transition temperature of the specified (meth) acrylic copolymer (B).
As the differential scanning calorimetry apparatus, for example, DSC2500 (model number) of TA Instruments Co., Ltd. can be preferably used. However, the differential scanning calorimetry device is not limited to this.

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 used as a homopolymer.

<< Weight average molecular weight of specific (meth) acrylic copolymer (B) >>
The weight average molecular weight of the specific (meth) acrylic copolymer (B) is in the range of 10,000 or more and 100,000 or less, preferably in the range of 12,000 or more and 80,000 or less, and preferably 15,000 or more. It is more preferably in the range of 60,000 or less, further preferably in the range of 18,000 or more and 40,000 or less, and particularly preferably in the range of 20,000 or more and 30,000 or less.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B) is 10,000 or more, the light peelability of the pressure-sensitive adhesive layer to the adherend at the initial stage of bonding tends not to be impaired. In addition, there is a tendency that an adhesive layer that is less likely to foam (that is, has excellent high temperature durability) can be formed even when exposed to a high temperature environment.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B) is 100,000 or less, the light peelability of the pressure-sensitive adhesive layer to the adherend at the initial stage of bonding tends not to be impaired.

The weight average molecular weight of the specific (meth) acrylic copolymer (B) is a value measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the specific (meth) acrylic copolymer (A). is there.

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.

<< 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 0.1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The range is 20 parts by mass or less, preferably 3 parts by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 20 parts by mass or less, and 7 parts by mass or more and 20 parts by mass or less. The range is more preferably 7 parts by mass or more and 15 parts by mass or less.
When the content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 0.1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). If there is, there is a tendency that the light peelability of the pressure-sensitive adhesive layer with respect to the adherend at the initial stage of bonding is not impaired.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 20 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). There is a tendency to form an adhesive layer that is less likely to foam (that is, has excellent high temperature durability) even when exposed to a high temperature environment.

[Method for producing specific (meth) acrylic copolymer]
The method for producing the specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B) [that is, the specific (meth) acrylic copolymer] is not particularly limited.
The specific (meth) acrylic copolymer is obtained by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, 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, generally, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are charged in a polymerization tank, and the mixture is stirred in a nitrogen stream at the reflux temperature of the organic solvent. While heating for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and the chain transfer agent used as needed may be sequentially added.

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, 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. Representative terpene compounds 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.

[Xylylene diisocyanate compound]
The pressure-sensitive adhesive composition of the present invention contains a xylylene diisocyanate compound.
In the pressure-sensitive adhesive composition of the present invention, the xylylene diisocyanate compound functions as a cross-linking agent.
When the pressure-sensitive adhesive composition of the present invention contains a xylylene diisocyanate compound, the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer on the adherend after heating tends to be high. In addition, there is a tendency that an adhesive layer that is less likely to foam (that is, has excellent high temperature durability) can be formed even when exposed to a high temperature environment.

The xylylene diisocyanate compound is not particularly limited.
Examples of the xylylene diisocyanate compound include xylylene diisocyanate (XDI), hydride xylylene diisocyanate, multimers of xylylene diisocyanate (for example, dimer, trimer, or pentamer), hydride xylylene diisocyanate and tri. Examples thereof include an adduct form with a polyol compound such as methylolpropane, and a biuret form of xylylene diisocyanate.

As the xylylene diisocyanate compound, a commercially available product can be used.
Examples of commercially available xylylene diisocyanate compounds include "Takenate (registered trademark) D-110N" and "Takenate (registered trademark) D-120N" of Mitsui Chemicals, Inc.

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

The content of the xylylene diisocyanate compound in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is, for example, 0.05 parts by mass or more and 10 parts by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The range is preferably 0.1 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less, and further preferably 0.1 parts by mass or more and 1 part by mass or less.
When the content of the xylylene diisocyanate compound in the pressure-sensitive adhesive composition of the present invention is within the above range with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A), the pressure-sensitive adhesive layer on the adherend. The adhesive strength after heating tends to be higher. In addition, there is a tendency to form an adhesive layer in which foaming is less likely to occur (that is, more excellent in high temperature durability) even when exposed to a high temperature environment.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent, for example, from the viewpoint of improving coatability.
Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the specific (meth) acrylic copolymer described above.

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, tackifiers, antioxidants, colorants (eg dyes and pigments), release modifiers, light stabilizers (eg). , Ultraviolet absorber), various additives such as antistatic agents.

In the pressure-sensitive adhesive composition of the present invention, the above-mentioned release adjusting agent can be used from the viewpoint of adjusting the adhesive strength.
A commercially available product can be used as the peeling adjuster.
Examples of commercially available release modifiers include SF-8411, SF-8413, SZ-3720, SF-8421, FZ-3736, BY16-876, BY16-760, SF8417, BY16 of Toray Dow Corning Co., Ltd. -849, FZ-3789, BY16-205, FS-1265-300CS, FS-1265-1000CS, FS-1265-10000CS, BY16-201, SF8427, SF8428, FZ-2162, FZ-2110, SH8400, SH3773M, FZ -2203, BY16-750, BY16-880, Shin-Etsu Chemical Co., Ltd. X-22-343, KF-101, KF-1001, X-22-2046, KF-102, X-22-4741, KF- 1002, KF-868, KF-865, KF-859, KF-393, KF-860, KF-880, KF-8004, KF-867, KF-861, X-22-3939A, PAM-E, X- 22-161B, KF-8008, X-22-4952, X-22-3701E and the like can be mentioned.

When the pressure-sensitive adhesive composition of the present invention contains these other components, the content of the other components can be appropriately set within the range in which the effects of the present invention are exhibited.

<Gel fraction after cross-linking>
The gel fraction after cross-linking of the pressure-sensitive adhesive composition of the present invention (so-called gel fraction of the pressure-sensitive adhesive layer) is preferably 50% by mass or more, and is in the range of 50% by mass or more and 90% by mass or less. Is more preferable, and the range is more preferably 50% by mass or more and 85% by mass or less.
When the gel fraction of the pressure-sensitive adhesive composition after cross-linking is 50% by mass or more, foaming is less likely to occur even when exposed to a high-temperature environment (that is, the pressure-sensitive adhesive layer is more excellent in high-temperature durability). There is.

In the present specification, the "gel fraction after cross-linking of the pressure-sensitive adhesive composition" is the percentage of the solvent-insoluble component measured using ethyl acetate as the extraction solvent. The gel fraction after cross-linking of the pressure-sensitive adhesive composition is specifically measured according to the following (1) to (4).
(1) Approximately 0.15 g of the crosslinked pressure-sensitive adhesive composition (that is, the pressure-sensitive adhesive layer) was attached to a 250-mesh wire mesh (100 mm × 100 mm) whose mass was accurately measured with a precision balance, and the gel content leaked. Fold the wire mesh 5 times with the attached adhesive layer inside so that it does not exist, and use it as a sample. After that, the mass is accurately measured with a precision balance.
(2) The obtained sample is immersed in 80 mL of ethyl acetate for 3 days.
(3) The sample is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. After that, the mass is accurately measured with a precision balance.
(4) Calculate the gel fraction by the following formula.
Gel fraction (unit: mass%) = (ZX) / (YX) x 100
However, X is the mass of the wire mesh (unit: g), Y is the mass of the wire mesh to which the adhesive layer is attached before immersion (unit: g), and Z is the mass of the wire mesh to which the adhesive layer is attached and dried after immersion. (Unit: g).

<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 is a pressure-sensitive adhesive layer that exhibits light peelability at the initial stage of bonding and high adhesive strength after heating, and is exposed to a high temperature environment. However, since it is possible to form an adhesive layer in which foaming is unlikely to occur (that is, excellent in high temperature durability), it is suitable for, for example, an application in which a display and an optical member are bonded together.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition containing a polymer containing a structural unit derived from a monomer having an organosiloxane skeleton, when the adherend is glass, is exposed to a high temperature environment. In addition, foaming tends to occur more easily. On the other hand, although the pressure-sensitive adhesive composition of the present invention contains a polymer containing a structural unit derived from a monomer having an organosiloxane skeleton, the pressure-sensitive adhesive layer formed is exposed to a high temperature environment. In that case, foaming is unlikely to occur. Therefore, the pressure-sensitive adhesive composition of the present invention can also be preferably applied to an adherend made of glass (for example, a glass substrate of a liquid crystal cell). The pressure-sensitive adhesive composition of the present invention can also be preferably applied to other adherends (for example, polyimide film, polyethylene terephthalate film, stainless steel plate, copper plate, etc.).

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention.
Since the pressure-sensitive adhesive sheet of the present invention includes the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention described above, it exhibits light peelability to the adherend at the initial stage of bonding and is high after heating. Shows adhesive strength. In particular, since the pressure-sensitive adhesive sheet of the present invention has an adhesive layer that exhibits light peelability at the initial stage of bonding to the adherend, for example, when the pressure-sensitive adhesive sheet is attached to a thin adherend having a thickness of about 10 μm. Even if there is, it has the advantage that it can be peeled off without problems.
Further, since the pressure-sensitive adhesive sheet of the present invention includes the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention described above, foaming is unlikely to occur even when exposed to a high-temperature environment (that is, high-temperature durability). Excellent).

The pressure-sensitive adhesive sheet of the present invention may be a non-base material type pressure-sensitive adhesive sheet having no base material, or a base material-type pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one side of the base material.
In the pressure-sensitive adhesive sheet of the present invention, the surface of the exposed pressure-sensitive adhesive layer 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, and examples thereof include a resin film in which at least one surface is easily peeled with a release treatment agent.
Examples of the resin film include a polyester film typified by a polyethylene terephthalate film.
Examples of the peeling treatment agent include a silicone-based peeling treatment agent (for example, silicone), a wax-based peeling treatment agent (for example, paraffin wax), and a fluorine-based peeling treatment agent (for example, a fluorine-based resin).
The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put into practical use, and is peeled off during use.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is generally in the range of 1 μm or more and 100 μm or less, preferably in the range of 3 μm or more and 50 μm or less, and more preferably in the range of 5 μm or more and 30 μm or less.

When the pressure-sensitive adhesive sheet of the present invention includes a base material, the base material is not particularly limited.
Examples of the base material include polyethylene-based resin, polyester-based resin, acetate-based resin (for example, triacetyl cellulose resin), polyether sulfone-based resin, polycarbonate-based resin, polyamide-based resin, polyimide-based resin, and polyolefin-based resin. Examples thereof include films containing resins such as acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluororesins.

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

The thickness of the base material is not particularly limited, but is generally 500 μm or less, preferably in the range of 30 μm or more and 300 μm or less, and more preferably in the range of 50 μm or more and 200 μm or less.

[Manufacturing method of adhesive sheet]
The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited.
The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by the following method.
In the case of a base-free type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present invention is applied onto the surface of the release film to form a coating film. Then, the formed coating film is dried. It has a laminated structure of release film / adhesive layer / release film by stacking the dried coating film on the exposed surface that does not come into contact with the release film so that the surface of another release film is in contact with the coating film and then curing it. , A base-free type adhesive sheet can be manufactured.

In the case of a base material type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present invention is applied onto the surface of the base material to form a coating film. Then, the formed coating film is dried. It has a laminated structure of base material / adhesive layer / release film by stacking the dried coating film on the exposed surface that does not come into contact with the base material so that the surface of the release film is in contact with the base material and then curing the coating film. A base material type adhesive sheet can be manufactured.

As another method, for example, the following method can be mentioned.
The pressure-sensitive adhesive composition of the present invention is applied onto the surface of the release film to form a coating film. Next, the formed coating film is dried to prepare a film with an adhesive. Next, by adhering the base material to the adhesive surface of the film with the pressure-sensitive adhesive and curing it, a base material-type pressure-sensitive adhesive sheet having a laminated structure of a base material / pressure-sensitive adhesive layer / release film can be produced.

The method of applying the pressure-sensitive adhesive composition on the surface of the base material or the release film is not particularly limited, and for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, etc. A known method using a bar coater, an applicator, or the like can be mentioned.
The amount of the pressure-sensitive adhesive composition applied onto the surface of the base material or the release film can be appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed.

The method for drying the coating film formed on the surface of the base material or the release film is not particularly limited, and examples thereof include natural drying, heat drying, hot air drying, and vacuum drying.
The drying temperature and drying time of the coating film formed on the surface of the base material or the release 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.

Curing is performed, for example, in an environment of 20 ° C. to 35 ° C. for 4 to 7 days.
Curing completes the cross-linking reaction of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.

[Optical member]
The optical member of the present invention comprises a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention.
The optical member is not particularly limited, and examples thereof 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, polyethylene resin, polyester resin, acetate resin (for example, triacetyl cellulose resin), polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, etc. Examples thereof include acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluororesins.

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]
70.0 parts by mass of ethyl acetate (organic solvent for polymerization) was charged into a reaction device equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer. Then, in another container, 100.0 parts by mass of a monomer mixture consisting of 90.0 parts by mass of n-butyl acrylate (n-BA) and 10.0 parts by mass of methyl acrylate (MA) was prepared. 20% by mass of the prepared monomer mixture was charged into a reactor, heated, and refluxed at the reflux temperature for 10 minutes. Then, under reflux temperature conditions, the remaining 80% by mass of the monomer mixture, 50.0 parts by mass of ethyl acetate (organic solvent for polymerization), and 2,2'-azobis (2,4-dimethylvaleronitrile) ) [ABVN; polymerization initiator] 0.026 parts by mass was sequentially added dropwise over 120 minutes and reacted for 30 minutes after the completion of the addition to complete the reaction. The solution after completion of the reaction was diluted with ethyl acetate so that the solid content concentration became 32% by mass to obtain a solution of the (meth) acrylic copolymer A-1.

The "solid content concentration" here means the mass ratio of the (meth) acrylic copolymer A-1 in the solution of the (meth) acrylic copolymer A-1.
The same applies to the following solutions of the (meth) acrylic copolymers A-2 to A-11.

[Manufacturing Examples A-2 to A-11]
In Production Examples A-2 to A-11, the monomer composition of the (meth) acrylic copolymer was changed to the monomer composition shown in Table 1, the amount of the organic solvent used, and the polymerization initiator. The same operation as in Production Example A-1 was performed except that the weight average molecular weight of the (meth) acrylic copolymer was changed to the weight average molecular weight shown in Table 1 by adjusting at least one of the amounts used. This was carried out to obtain solutions of (meth) acrylic copolymers A-2 to A-11 having a solid content concentration of 32% by mass.

Among the (meth) acrylic copolymers A obtained above, the (meth) acrylic copolymers A-2 to A-6 and A-8 are the specific (meth) acrylic copolymers in the present invention. Corresponds to the polymer (A).

Monomer composition (unit: mass%) of (meth) acrylic copolymers A-1 to A-11, glass transition temperature (Tg, unit) of (meth) acrylic copolymers A-1 to A-11. : ° C.) and the weight average molecular weights (Mw) of the (meth) acrylic copolymers A-1 to A-11 are shown in Table 1.
The glass transition temperature of the (meth) acrylic copolymers A-1 to A-11 was calculated by the same method as the method for calculating the glass transition temperature of the specific (meth) acrylic copolymer (A) described above. ..
The weight average molecular weights of the (meth) acrylic copolymers A-1 to A-11 were measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the specific (meth) acrylic copolymer (A). ..

Details of each monomer shown in Table 1 are as shown below.
"N-BA": n-butyl acrylate (acrylic acid alkyl ester monomer, glass transition temperature when made into a homopolymer: -57 ° C.)
"MA": Methyl acrylate (acrylic acid alkyl ester monomer, glass transition temperature when made into a homopolymer: 5 ° C.)
"2EHA": 2-ethylhexyl acrylate (acrylic acid alkyl ester monomer, glass transition temperature when homopolymer: -76 ° C)
"2HEA": 2-hydroxyethyl acrylate (monomer having a hydroxyl group, glass transition temperature when made into a homopolymer: -15 ° C)
"AA": Acrylic acid (monomer having a carboxy group, glass transition temperature when made into a homopolymer: 163 ° C)

In Table 1, "-" means that the monomer in the corresponding column is not used.
In Table 1, the "glass transition temperature" is simply referred to as "Tg", and the "weight average molecular weight" is simply referred to as "Mw".

[Manufacture of (meth) acrylic copolymer B]
[Manufacturing Example B-1]
60 parts by mass of ethyl acetate (organic solvent for polymerization) was charged into a reactor equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer. Then, in another container, 45.0 parts by mass of methyl methacrylate (MMA), 27.0 parts by mass of n-butyl methacrylate (n-BMA), 27.0 parts by mass of 2-ethylhexyl methacrylate (2-EHMA), Monomer having an organosiloxane skeleton [trade name: X-22-174ASX, number average molecular weight: 1100, Shin-Etsu Chemical Industry Co., Ltd.] 1.0 part by mass, 2,2'-azobis (isobutyric acid) dimethyl [polymerization] Initiator] 1.7 parts by mass and 40.0 parts by mass of ethyl acetate (organic solvent for polymerization) were added and mixed to prepare a solution. The prepared solution was sequentially added dropwise over 180 minutes under reflux temperature conditions, and after completion of the addition, the reaction was carried out for 180 minutes to complete the reaction. The solution after completion of the reaction was diluted with ethyl acetate so that the solid content was 48% by mass to obtain a solution of the (meth) acrylic copolymer B-1.

The "solid content concentration" here means the mass ratio of the (meth) acrylic copolymer B-1 to the solution of the (meth) acrylic copolymer B-1.
The same applies to the following (meth) acrylic copolymers B-2 to B-13 solutions.

[Manufacturing Examples B-2 to B-13]
In Production Examples B-2 to B-13, the monomer composition of the (meth) acrylic copolymer was changed to the monomer composition shown in Table 2, and the amount of the organic solvent used and the polymerization initiator were changed. The same operation as in Production Example B-1 was performed except that the weight average molecular weight of the (meth) acrylic copolymer was changed to the weight average molecular weight shown in Table 2 by adjusting at least one of the amounts used. This was carried out to obtain solutions of (meth) acrylic copolymers B-2 to B-13 having a solid content concentration of 48% by mass.

Among the (meth) acrylic copolymers B-1 to B-13 obtained above, the (meth) acrylic copolymers B-2 to B-4, B-7, B-10, and B -11 corresponds to the specific (meth) acrylic copolymer (B) in the present invention.

Monomer composition (unit: mass%) of (meth) acrylic copolymers B-1 to B-13, and a single amount having an organosiloxane skeleton in (meth) acrylic copolymers B-1 to B-13. Number average molecular weight (Mn) of the body, glass transition temperature (Tg, unit: ° C.) of (meth) acrylic copolymers B-1 to B-13, and (meth) acrylic copolymers B-1 to B. The weight average molecular weight (Mw) of -13 is shown in Table 2.
The number average molecular weight of the monomers having an organosiloxane skeleton in the (meth) acrylic copolymers B-1 to B-13 is the same as that of the organosiloxane skeleton in the specific (meth) acrylic copolymer (B) described above. It was measured by the same method as the method for measuring the number average molecular weight of the monomers having.
The glass transition temperature of the (meth) acrylic copolymers B-1 to B-13 was measured by the same method as the method for measuring the glass transition temperature of the specific (meth) acrylic copolymer (B) described above. ..
The weight average molecular weights of the (meth) acrylic copolymers B-1 to B-13 were measured by the same method as the above-mentioned method for measuring the weight average molecular weight of the specific (meth) acrylic copolymer (A). ..

Details of each monomer shown in Table 2 are as shown below.
"MMA": Methyl methacrylate (methacrylic acid alkyl ester monomer)
"N-BMA": n-butyl methacrylate (methacrylic acid alkyl ester monomer)
"2EHMA": 2-ethylhexyl methacrylate (methacrylic acid alkyl ester monomer)

"X-22-174ASX" [trade name, number average molecular weight: 1100, Shin-Etsu Chemical Industry Co., Ltd.]: Monomer having an organosiloxane skeleton, compound represented by the formula (2) "X-22-2404" [Product name, number average molecular weight: 420, Shin-Etsu Chemical Industry Co., Ltd.]: Monomer having an organosiloxane skeleton, compound represented by the formula (2) "X-22-174DX" [Product name, number average molecular weight : 5400, Shin-Etsu Chemical Industry Co., Ltd.]: Monomer having an organosiloxane skeleton, compound "FM-0711" represented by the formula (2) [Product name: Silaplane FM-0711, number average molecular weight: 1200, JNC Co., Ltd.]: Monomer having an organosiloxane skeleton, a compound represented by the formula (2)

In Table 2, "-" means that the monomer in the corresponding column is not used.
In Table 2, "the number average molecular weight of the monomer having an organosiloxane skeleton" is simply expressed as "Mn". Further, in Table 2, the "glass transition temperature" is simply expressed as "Tg", and the "weight average molecular weight" is simply expressed as "Mw".

[Preparation of adhesive composition]
[Example 1]
100 parts by mass of the solution of the (meth) acrylic copolymer A-2 (solid content conversion value), 13 parts by mass of the solution of the (meth) acrylic copolymer B-3 (solid content conversion value), and a cross-linking agent. [Product name: Takenate (registered trademark) D-110N, xylylene diisocyanate compound, solid content: 75% by mass, Mitsui Kagaku Co., Ltd.] 0.5 parts by mass (solid content conversion value) is sufficiently mixed. , The pressure-sensitive adhesive composition of Example 1 was obtained.

[Examples 2 to 14]
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, and each pressure-sensitive adhesive composition of Examples 2 to 14 was obtained.

[Comparative Examples 1 to 16]
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 16 was obtained.

[Measurement and evaluation]
1. 1. Gel Fraction The gel fraction after cross-linking (that is, the gel fraction of the pressure-sensitive adhesive layer) was measured using each of the pressure-sensitive adhesive compositions of Examples 1 to 14 and Comparative Examples 1 to 16. Specifically, it was measured by the following method.
Adhesive on the surface-treated surface of a release film [trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent so that the thickness after drying is 20 μm. The composition was applied to form a coating film.
Next, the formed coating film was dried using a hot air circulation type dryer under drying conditions of a drying temperature of 100 ° C. and a drying time of 1 minute to form an adhesive film on the release film.
Next, the exposed surface of the adhesive film was laminated on the surface-treated surface of a separately prepared release film [trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd.], and then the atmosphere temperature was 25. By allowing it to stand in an environment of ℃ and 50% RH for 168 hours and curing it, the cross-linking reaction was allowed to proceed, and a base-free type pressure-sensitive adhesive sheet having a structure of a release film / adhesive layer / release film was prepared. ..

Using the pressure-sensitive adhesive layer peeled off from the obtained pressure-sensitive adhesive sheet, the gel fraction was measured according to the following (1) to (4). The results are shown in Tables 3 and 4.
(1) Approximately 0.15 g of an adhesive layer is attached to a 250 mesh wire mesh (100 mm x 100 mm) whose mass is accurately measured with a precision balance, and the attached adhesive layer is placed inside so that the gel does not leak. Then, the wire mesh is folded 5 times and used as a sample. After that, the mass is accurately measured with a precision balance.
(2) The obtained sample is immersed in 80 mL of ethyl acetate for 3 days.
(3) The sample is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. After that, the mass is accurately measured with a precision balance.
(4) Calculate the gel fraction by the following formula.
Gel fraction (unit: mass%) = (ZX) / (YX) x 100
However, X is the mass of the wire mesh (unit: g), Y is the mass of the wire mesh to which the adhesive layer is attached before immersion (unit: g), and Z is the mass of the wire mesh to which the adhesive layer is attached and dried after immersion. (Unit: g).

2. Adhesive strength (preparation of adhesive sheet for evaluation)
Polyethylene terephthalate (PET) film [trade name: Teijin (registered trademark) Tetron (registered trademark) film, model number: G2P2, thickness: 50 μm, Teijin Film Solution (Teijin Film Solution) Co., Ltd.] was applied to the easy-adhesion-treated surface so that the thickness after drying was 20 μm to form a coating film. Next, the formed coating film was dried at 100 ° C. for 1 minute using a hot air circulation type dryer to form an adhesive film on the PET film.
Next, the peeled surface of the peeling film [trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd.] in which the exposed surface of the adhesive film was easily peeled with a separately prepared silicone-based peeling agent. An evaluation adhesive sheet having a laminated structure of a release film / adhesive layer / PET film, which is allowed to stand for 4 days in an environment of an atmospheric temperature of 23 ° C. and 50% RH to allow the cross-linking reaction to proceed. Got

(1) Initial Adhesive Strength The evaluation adhesive sheet prepared above was cut into a size of 25 mm × 150 mm to prepare a piece of the evaluation adhesive sheet.
The release film is peeled off from the prepared adhesive sheet piece for evaluation (composition: release film / adhesive layer / PET film), and the surface of the adhesive layer exposed by the release is made of non-alkali glass [trade name: Eagle XG, Corning Inc.] ] (Hereinafter, simply referred to as "glass"), the test piece X-1 was prepared by laminating and adhering the test piece X-1 by reciprocating a 2 kg roller once and crimping the film.

The test piece X-1 was allowed to stand in an environment with an ambient temperature of 23 ° C. and 50% RH for 30 minutes.
Regarding the test piece X-1 after standing, the adhesive force (unit: N / 25 mm) when the evaluation adhesive sheet piece (structure: adhesive layer / PET film) is peeled 180 ° in the long side (150 mm) direction from the glass. ) As a measuring device using a single column type material testing machine (model number: STA-1225) of A & D Co., Ltd. under the condition of an ambient temperature of 23 ° C. and a peeling speed of 300 mm / min in an environment of 50% RH. Measured at. Then, the initial adhesive strength was evaluated according to the following evaluation criteria.
The results are shown in Tables 3 and 4.
If the evaluation result is "A" or "B", it is judged that there is no practical problem.

-Evaluation criteria-
A: The adhesive strength is 0.01 N / 25 mm or more and less than 0.2 N / 25 mm.
B: The adhesive strength is 0.2 N / 25 mm or more and less than 1 N / 25 mm.
C: Adhesive strength is 1N / 25mm or more.

(2) Adhesive Strength after Heating The evaluation adhesive sheet prepared above was cut into a size of 25 mm × 150 mm to prepare a piece of the evaluation adhesive sheet.
The release film is peeled off from the prepared adhesive sheet piece for evaluation (composition: release film / adhesive layer / PET film), and the surface of the adhesive layer exposed by the release is overlapped with the glass surface and then bonded to each other, and then 2 kg. The roller of No. 1 was reciprocated twice and crimped to prepare a test piece X-2.

The test piece X-2 was allowed to stand in a dryer set at a temperature of 50 ° C. for 20 minutes, then taken out from the dryer and allowed to stand in an environment with an ambient temperature of 23 ° C. and 50% RH for 30 minutes.
Regarding the test piece X-2 after standing, the adhesive force (unit: N / 25 mm) when the evaluation adhesive sheet piece (structure: adhesive layer / PET film) is peeled 180 ° in the long side (150 mm) direction from the glass. ) As a measuring device using a single column type material testing machine (model number: STA-1225) of A & D Co., Ltd. under the condition of an ambient temperature of 23 ° C. and a peeling speed of 300 mm / min in an environment of 50% RH. Measured at. Then, the adhesive strength after heating was evaluated according to the following evaluation criteria.
The results are shown in Tables 3 and 4.
If the evaluation result is "A" or "B", it is judged that there is no practical problem.

-Evaluation criteria-
A: The adhesive strength is 10 N / 25 mm or more.
B: The adhesive strength is 5 N / 25 mm or more and less than 10 N / 25 mm.
C: Adhesive strength is less than 5N / 25mm.

3. 3. High temperature durability The evaluation adhesive sheet prepared above was cut into a size of 25 mm × 150 mm to prepare a piece of the evaluation adhesive sheet.
The release film is peeled off from the prepared adhesive sheet piece for evaluation (composition: release film / adhesive layer / PET film), and the surface of the adhesive layer exposed by the release is overlapped with the glass surface and then bonded to each other, and then 2 kg. The roller of No. 1 was reciprocated twice and crimped to prepare a test piece X-3.

The test piece X-3 was allowed to stand in a dryer set at a temperature of 50 ° C. for 20 minutes. Next, the set temperature of the dryer was changed to 85 ° C., and the test piece X-3 was allowed to stand for another 168 hours. Next, the test piece X-3 was taken out from the dryer and allowed to stand in an environment with an ambient temperature of 23 ° C. and 50% RH for 30 minutes. Next, the test piece X-3 was visually observed, and the high temperature durability was evaluated according to the following evaluation criteria.
The results are shown in Tables 3 and 4.
If the evaluation result is "A" or "B", it is judged that there is no practical problem.

-Evaluation criteria-
A: No foaming was confirmed on the test piece.
B: Slight foaming was confirmed at the end of the test piece, which is within the permissible range.
C: Foaming was confirmed on the entire surface of the test piece.

Details of the cross-linking agents shown in Tables 3 and 4 are as shown below.
"XDI" [Product name: Takenate (registered trademark) D-110N, xylylene diisocyanate compound, solid content: 75% by mass, Mitsui Chemicals, Inc.]
"TDI" [Product name: Coronate (registered trademark) L-45E, Tolylene diisocyanate compound, Solid content: 45% by mass, Tosoh Corporation]
"HMDI" [Product name: Sumijule (registered trademark) N-75, hexamethylene diisocyanate compound, solid content: 75% by mass, Sumitomo Bayer Urethane Co., Ltd.]

In Tables 3 and 4, the numerical values described in the column of "blending amount" are all solid content conversion values.
In Table 4, "-" means that the corresponding component is not blended in the column.

As shown in Table 3, the pressure-sensitive adhesive layers formed by the pressure-sensitive adhesive compositions of Examples 1 to 14 all showed light peelability to the adherend at the initial stage of bonding and were high after heating. It was confirmed that it showed adhesive strength. Further, it was confirmed that the pressure-sensitive adhesive layers formed by the pressure-sensitive adhesive compositions of Examples 1 to 14 were all excellent in durability.

On the other hand, as shown in Table 4, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 in which the (meth) acrylic copolymer A does not contain a structural unit derived from a monomer having a hydroxyl group It was confirmed that the adhesive strength at the initial stage of bonding to the adherend was high and that the adherend did not show light peelability. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 was significantly foamed when exposed to a high-temperature environment and was inferior in high-temperature durability.
The pressure-sensitive adhesive composition of Comparative Example 2 and Comparative Example 3 in which the (meth) acrylic copolymer A contains a structural unit derived from a monomer having a carboxy group instead of a structural unit derived from a monomer having a hydroxyl group. It was confirmed that the pressure-sensitive adhesive layer formed of the material was inferior in high-temperature durability due to remarkable foaming when exposed to a high-temperature environment.
Adhesive formed by the pressure-sensitive adhesive composition of Comparative Example 14 in which the content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer A exceeds 40% by mass with respect to all the structural units. It was confirmed that the agent layer did not exhibit high adhesive strength to the adherend after heating due to the excessively high cohesive force.

Formed by the pressure-sensitive adhesive composition of Comparative Example 4 in which the content of the structural unit derived from the monomer having an organosiloxane skeleton in the (meth) acrylic copolymer B is less than 2% by mass with respect to all the structural units. It was confirmed that the adhesive layer was highly adhesive at the initial stage of bonding to the adherend and did not show light peelability to the adherend.
Adhesive composition of Comparative Example 5 and Comparative Example 15 in which the content of the structural unit derived from the monomer having an organosiloxane skeleton in the (meth) acrylic copolymer B exceeds 9% by mass with respect to all the structural units. It was confirmed that the pressure-sensitive adhesive layer formed of the material did not show high adhesive strength to the adherend after heating.

The content of the structural unit derived from the monomer having an organosiloxane skeleton in the (meth) acrylic copolymer B exceeds 9% by mass with respect to all the structural units, and the monomer has an organosiloxane skeleton. It was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 6 having a number average molecular weight of more than 1500 did not exhibit high adhesive strength to the adherend after heating.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 7 in which the number average molecular weight of the monomers having an organosiloxane skeleton in the (meth) acrylic copolymer B exceeds 1500 is relative to the adherend. It was confirmed that it did not show high adhesive strength after heating.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 8 in which the weight average molecular weight of the (meth) acrylic copolymer B exceeds 100,000 has high adhesive strength at the initial stage of bonding to the adherend, and is coated. It was confirmed that it did not show light peelability with respect to the adherend.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 9 in which the weight average molecular weight of the (meth) acrylic copolymer B is less than 10,000 has a high adhesive strength at the initial stage of bonding to an adherend. It was confirmed that the adherend did not show light peelability. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 9 was significantly foamed when exposed to a high-temperature environment and was inferior in high-temperature durability.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 10 containing no specific (meth) acrylic copolymer (B) has high adhesive strength at the initial stage of bonding to the adherend, and has a high adhesive strength to the adherend. It was confirmed that it did not show light peelability.
The content of the specific (meth) acrylic copolymer (B) is formed by the pressure-sensitive adhesive composition of Comparative Example 11 in which the content of the specific (meth) acrylic copolymer (B) exceeds 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). It was confirmed that the adhesive layer was significantly foamed when exposed to a high temperature environment and was inferior in high temperature durability.

It was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 12 containing the tolylene diisocyanate compound instead of the xylylene diisocyanate compound did not exhibit high adhesive strength to the adherend after heating. ..
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 13 containing a hexamethylene diisocyanate compound instead of the xylylene diisocyanate compound causes remarkable foaming when exposed to a high-temperature environment, and is inferior in high-temperature durability. It was confirmed that.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 16 in which the glass transition temperature of the (meth) acrylic copolymer A is 0 ° C. or higher exhibits high adhesive strength to the adherend after heating. It was confirmed that there was no such thing.

Claims (5)

A (meth) acrylic copolymer containing a structural unit derived from a monomer having a hydroxyl group in a range of 1% by mass or more and 40% by mass or less with respect to all the structural units, and having a glass transition temperature of less than 0 ° C. Coalescence (A) and
Constituent units derived from a monomer having an organosiloxane skeleton are contained in a range of 2% by mass or more and 9% by mass or less with respect to all the structural units, and the number average molecular weight of the monomer having an organosiloxane skeleton is 400 or more. With the (meth) acrylic copolymer (B) having a weight average molecular weight in the range of 10,000 or more and 100,000 or less, which is in the range of 1500 or less.
Xylylene diisocyanate compound and
Including
The content of the (meth) acrylic copolymer (B) is in the range of 0.1 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). Adhesive composition. The first aspect of the present invention, wherein the monomer having an organosiloxane skeleton is at least one compound selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the formula (2). Adhesive composition.

In formulas (1) and (2), R ¹ represents a hydrogen atom or a methyl group, R ² represents a monovalent organic group, and m and n each independently represent an integer of 0 or more. .. Claim 1 or claim that the (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a hydroxyl group in a range of 10% by mass or more and 30% by mass or less with respect to all the structural units. Item 2. The pressure-sensitive adhesive composition according to Item 2. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 3. An optical member including a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 3.