JP7334601B2 - Adhesive composition, adhesive sheet, and optical member - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, an adhesive sheet, and an optical member.

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

For example, in Patent Document 1, 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 weight in the range of 1000 g / mol or more and less than 15000 g / mol, and Adhesive containing 0.1 parts by mass to 20 parts by mass of a copolymer (B) having a homopolymer 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 10000 or more and less than 100000 Agent compositions are disclosed.
Further, for example, in Patent Document 2, 100 parts by mass of a polymer (A) having a glass transition temperature of less than 0 ° C. and a monomer having an organosiloxane skeleton having a functional group equivalent weight of 1000 g / mol or more and 4600 g / mol or less ( B1), and a copolymer (B) containing, as monomer units, a monomer (B2) having a homopolymer glass transition temperature of 40° C. or higher, and having a weight average molecular weight in the range of 10,000 or more and less than 100,000 (B) 0.1 parts by mass to 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). An agent composition is disclosed.

WO2015/163115 JP 2017-203164 A

By the way, a pressure-sensitive adhesive composition used in electronic devices is required to have a property (so-called high-temperature durability) to withstand heat generated from electronic devices for a long period of time. In general, a 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 for electronic devices can form a pressure-sensitive adhesive layer that hardly foams even when exposed to an environment of 85° C. for 7 days. In order to suppress foaming that may occur in the pressure-sensitive adhesive layer, it is conceivable to increase the cohesive strength 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, suppression of foaming and improvement of adhesive strength in the adhesive layer are in a trade-off relationship, and it has been difficult to improve both.

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

Specific means for solving the problems include the following aspects.
<1> A (meth)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 structural units and having a glass transition temperature of less than 0°C System copolymer (A),
Containing structural units derived from a monomer having an organosiloxane skeleton in a range of 2% by mass or more and 9% by weight or less with respect to all structural units, and the monomer having an organosiloxane skeleton has a number average molecular weight of 400 or more. a (meth)acrylic copolymer (B) in the range of 1500 or less and having a weight average molecular weight in the range of 10,000 or more and 100,000 or less;
A xylylene diisocyanate compound,
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 compounds represented by the following formula (1) and compounds represented by formula (2) <1 > The pressure-sensitive adhesive composition according to .

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 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 from the pressure-sensitive adhesive composition according to any one of <1> to <3>.
<5> An optical member comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of <1> to <3>.

According to the present invention, it is possible to form a pressure-sensitive adhesive layer that exhibits light releasability from an adherend at the initial stage of bonding, exhibits 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 comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

Specific embodiments of the present invention will be described in detail below. However, the present invention is by no means limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

In this specification, the numerical range indicated using "to" means a range including the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. . Moreover, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the values shown in the examples.
In the present specification, a combination of two or more preferred aspects is a more preferred aspect.
In the present specification, the amount of each component means the total amount of the multiple types of substances unless otherwise specified when there are multiple types of substances corresponding to each component.

As used herein, the term "(meth)acrylic copolymer" means that the content of structural units derived from a monomer having a (meth)acryloyl group is the total structural units [i.e., (meth)acrylic copolymer total structural units of the polymer] is 50% by mass or more.

As used herein, "(meth)acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate". , "(meth)acryloyl" is a term encompassing both "acryloyl" and "methacryloyl".

As used herein, "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. In addition, as an upper limit of temperature, 300 degreeC is mentioned, for example.

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

In this 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 structural units, and has a glass transition temperature ("Tg" is less than 0° C. (hereinafter also referred to as “specific (meth)acrylic copolymer (A)”). ] and a structural unit derived from a monomer having an organosiloxane skeleton in the range of 2% by mass or more and 9% by mass or less with respect to all 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. (B) [hereinafter also referred to as “specific (meth)acrylic copolymer (B)”. ] and a xylylene diisocyanate compound, and the content of the (meth)acrylic copolymer (B) is 0.5 parts per 100 parts by mass of the (meth)acrylic copolymer (A). It is in the range of 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 releasability from the adherend at the initial stage of lamination and exhibits high adhesive strength after heating, and is exposed to a high-temperature environment. It is possible to form a pressure-sensitive adhesive layer that is resistant to foaming (that is, has excellent high-temperature durability) even when it is heated.
Although the reason why the pressure-sensitive adhesive composition of the present invention can exhibit such effects is not clear, the present inventors speculate as follows. However, the following assumptions are not intended to limit the interpretation of the pressure-sensitive adhesive composition of the present invention, but are explained as an example.

The monomer having an organosiloxane skeleton tends to cause the specific (meth)acrylic copolymer (B) to be unevenly distributed on the adhesive surface of the pressure-sensitive adhesive layer due to its structure-derived low polarity. 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 monomer 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 moderately unevenly distributed on the adhesive surface of the pressure-sensitive adhesive layer. there is The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a specific (meth)acrylic copolymer (B) that is moderately unevenly distributed on the adhesive surface, so that it is light against the adherend at the initial stage of lamination. It is presumed to exhibit releasability.

By the way, when the adherend is glass, the hydrophilic groups on the glass surface tend to interact with moisture in the air and cleaning solvents such as alcohol. There is Moisture, solvent, etc. remaining on the glass surface can cause foaming in the pressure-sensitive adhesive layer by evaporating 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. Therefore, the adhesion between the pressure-sensitive adhesive layer and the glass tends to be low, and foaming tends to occur in a high-temperature environment. In the pressure-sensitive adhesive composition of the present invention, the specific (meth)acrylic copolymer (A) contains a specific amount of structural units derived from a monomer having a hydroxyl group. However, by trapping moisture, solvent, etc. by hydrogen bonding, migration of moisture, solvent, etc. into the pressure-sensitive adhesive layer can be prevented. In addition, since the pressure-sensitive adhesive composition of the present invention contains a xylylene diisocyanate compound as a cross-linking agent, the formed pressure-sensitive adhesive layer has an appropriately increased cohesive force, and foaming hardly occurs even when exposed to a high-temperature environment. It is speculated that On the other hand, when the cohesive strength of the adhesive layer increases, foaming is less likely to occur, but the adhesive strength tends to decrease. In contrast, the pressure-sensitive adhesive composition of the present invention contains a specific (meth)acrylic copolymer (A) having a low glass transition temperature (Tg), and a specific (meth)acrylic copolymer (B) Since the number average molecular weight and copolymerization amount of the monomer having an organosiloxane skeleton in are relatively low, the pressure-sensitive adhesive layer formed exhibits appropriate wettability to the adherend. Therefore, it is presumed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention hardly foams even when exposed to a high-temperature environment, and exhibits high adhesive strength after heating.

For the adhesive composition of the present invention, the adhesive composition described in Patent Document 1 (International Publication No. 2015/163115) and the adhesive composition described in Patent Document 2 (JP 2017-203164) In the product, the polymer (A) contains structural units derived from a monomer having a carboxy group rather than structural units derived from a monomer having a hydroxyl group. Therefore, it is considered that the pressure-sensitive adhesive layer to be formed has a relatively low cohesive strength and foams easily when exposed to a high-temperature environment.

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

<Structural Unit Derived from Monomer Having Hydroxyl Group>
The specific (meth)acrylic copolymer (A) contains structural units derived from hydroxyl group-containing monomers in an amount of 1% by mass or more and 40% by mass or less based on all structural units.
The hydroxyl group of the constituent unit derived from the hydroxyl group-containing monomer crosslinks with the isocyanate group of the xylylene diisocyanate compound.

As used herein, the term “structural unit derived from a monomer having a hydroxyl group” means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The type of hydroxyl group-containing monomer is not particularly limited.
Specific examples of monomers having a hydroxyl group include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4- Hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1 -dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3- Hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide and the like.
As the monomer having a hydroxyl group, for example, when the specific (meth)acrylic copolymer (A) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer described later, (meth)acrylic Hydroxyalkyl (meth)acrylates are preferred from the viewpoint of good copolymerizability with acid alkyl ester monomers, and from the viewpoint of good compatibility with (meth)acrylic acid alkyl ester monomers. , And, from the viewpoint of good reactivity with xylylene diisocyanate compounds, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 1 to 5 carbon atoms are more preferable, and hydroxy having 2 to 4 carbon atoms Hydroxyalkyl (meth)acrylates having an alkyl group are more preferred, 2-hydroxyethyl (meth)acrylate is more preferred, and 2-hydroxyethyl acrylate is particularly preferred.

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 thereof.

The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A) is 1 per all structural units of the specific (meth)acrylic copolymer (A). It is in the range of 40% by mass or more, preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and 10% by mass or more and 30% by mass. It is more preferably in the range of 15% by mass or more and 30% by mass or less, and particularly preferably in the range of 15% by mass or more and 30% by mass or less.
The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A) is 1 mass with respect to all structural units of the specific (meth)acrylic copolymer (A) % or more, there is a tendency that the easy releasability of the pressure-sensitive adhesive layer from the adherend at the initial stage of lamination is difficult to be impaired. In addition, there is a tendency that a pressure-sensitive adhesive layer that is resistant to foaming even when exposed to a high-temperature environment (that is, has excellent high-temperature durability) can be formed.
The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer (A) is 40 mass with respect to all structural units of the specific (meth)acrylic copolymer (A) % or less, the adhesive strength of the adhesive layer to the adherend after heating tends to increase.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>
The specific (meth)acrylic copolymer (A) preferably contains structural units derived from (meth)acrylic acid alkyl ester monomers.
The structural unit derived from the (meth)acrylic acid alkyl ester monomer contributes to the adjustment of adhesive strength.

In the present specification, "a structural unit derived from a (meth)acrylic acid alkyl ester monomer" means a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer.
In addition, the "(meth)acrylic acid alkyl ester monomer" in the present specification does not include a (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 in the alkyl group is preferably 1 to 18, more preferably 1 to 12, for example, from the viewpoint of adhesive strength.

Specific examples of (meth) acrylic acid alkyl ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylates, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and the like.
(Meth)acrylic acid alkyl ester monomers include, for example, n-butyl acrylate (n-BA), from the viewpoint of easy production of a (meth)acrylic copolymer having a glass transition temperature of less than 0°C, At least one selected from the group consisting of methyl acrylate (MA) and 2-ethylhexyl acrylate (2EHA) is preferred.

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

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

Examples of monomers constituting other structural units include (meth)acrylates having an aromatic ring represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate and ethoxyethyl Alkoxyalkyl (meth)acrylates typified by (meth)acrylates, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyls typified by vinyltoluene, acrylonitrile and methacrylates. vinyl cyanides typified by lonitrile; and vinyl esters typified by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. Various derivatives of these monomers are also included.

<<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 less, more preferably −20° C. or less, and −30° C. or less. It is even more preferable to have
When the glass transition temperature of the specific (meth)acrylic copolymer (A) is less than 0°C, the pressure-sensitive adhesive layer formed has moderate wettability to the adherend and 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, a range of -70°C or higher and lower than 0°C, or a range of -70°C or higher and -10°C or lower. , -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) obtained by calculation from the following formula 1 is the Celsius temperature (unit: ° C.; hereinafter the same ).
1/Tg=m1/Tg1+m2/Tg2+...+m(k-1)/Tg(k-1)+mk/Tgk (Formula 1)

In Formula 1, Tg1, Tg2, . Each represents the glass transition temperature expressed in absolute temperature. m1, m2, . +m(k−1)+mk=1.
The absolute temperature can be converted to a Celsius temperature by subtracting 273 from the absolute temperature, and the Celsius temperature can be converted to an absolute temperature by adding 273 to the Celsius temperature.

As used herein, the term "glass transition temperature expressed as an absolute temperature when a homopolymer is used" refers to a glass transition temperature expressed as an absolute temperature of a homopolymer produced by polymerizing the monomer alone. means temperature.
The glass transition temperature of the homopolymer was measured using a differential scanning calorimeter (DSC) [model number: EXSTAR6000, Seiko Instruments Inc.] under the conditions of a measurement sample of 10 mg and a heating rate of 10°C/min in a nitrogen stream. The inflection 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 converted to a homopolymer" of representative monomers is -76 ° C. for 2-ethylhexyl acrylate (2EHA) and -10 ° C. for 2-ethylhexyl methacrylate (2EHMA). , n-butyl acrylate (n-BA) is −57° C., n-butyl methacrylate (n-BMA) is 21° C., t-butyl acrylate (t-BA) is 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, isobornyl methacrylate (IBXMA) is 155°C, isobornyl 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) -30°C for monoacrylate and -40°C for 2-acryloyloxyethyl-succinic acid.

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

<<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. is more preferably in the range of 400,000 to 1,000,000, and particularly preferably in the range of 400,000 to 800,000.
When the weight-average molecular weight of the specific (meth)acrylic copolymer (A) is 400,000 or more, the easy release property of the adhesive layer from the adherend in the initial stage of lamination tends to be less impaired.
When the weight average molecular weight of the specific (meth)acrylic copolymer (A) is 2,000,000 or less, the adhesive strength of the 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, it is measured according to the following (1) to (3).
(1) A solution of the specific (meth)acrylic copolymer (A) is applied to release paper and dried at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic copolymer (A).
(2) Using the film-like specific (meth)acrylic copolymer (A) obtained in (1) above and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained. The term "solid content concentration" as used herein means the mass ratio of the specific (meth)acrylic copolymer (A) in 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 into HLC-8220, Tosoh Corporation]
Column: Four TSK-GEL GMHXL [Tosoh Corporation] connected in series Column temperature: 40°C
Eluent: Tetrahydrofuran Injection volume of sample solution: 100 μL
Flow rate: 0.8 mL/min

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer (A) can be adjusted by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. can be set to the desired value.

<<Specific (meth)acrylic copolymer (A) content>>
The content of the specific (meth)acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is not particularly limited. It is preferably in the range of 80% by mass or more and 95% by mass or less, and even more 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, exposure to a high temperature environment There is a tendency that a pressure-sensitive adhesive layer that is less prone to foaming (that is, has better high-temperature durability) can be formed.
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, There is a tendency that the easy releasability of the pressure-sensitive adhesive layer from the adherend is less likely to be impaired.
As used herein, "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. When included, it means the mass of the residue after 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 structural units, and the above-mentioned monomer having an organosiloxane skeleton. A (meth)acrylic copolymer (B) having a number average molecular weight in the range of 400 or more and 1500 or less and a weight average molecular weight in the range of 10,000 or more and 100,000 or less [that is, a specific (meth) acrylic copolymer (B)].
In addition, the content of the specific (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 0.1 mass with respect to 100 parts by mass of the specific (meth)acrylic copolymer (A). part or more and 20 parts by mass or less.

<Structural Unit Derived from Monomer Having Organosiloxane Skeleton>
The specific (meth)acrylic copolymer (B) contains structural units derived from a monomer having an organosiloxane skeleton.
As used herein, the term "structural 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 to 1500, preferably in the range of 600 to 1400, and more preferably in the range of 800 to 1300.
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 adhesive layer to the adherend after heating tends to increase.

The number average molecular weight of the monomer having an organosiloxane skeleton is a value measured by the following method. Specifically, it is measured according to the following (1) and (2).
(1) Using a monomer having an organosiloxane skeleton and tetrahydrofuran, a sample solution having a solid concentration of 0.2% by mass is obtained. The term "solid content concentration" as used herein means the mass ratio of the monomer having an organosiloxane skeleton in 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 into HLC-8220, Tosoh Corporation]
Column: Four TSK-GEL GMHXL [Tosoh Corporation] connected in series Column temperature: 40°C
Eluent: Tetrahydrofuran Injection volume of sample solution: 100 μL
Flow rate: 0.8 mL/min

When the specific (meth)acrylic copolymer (B) contains monomers having two or more organosiloxane skeletons with different number average molecular weights, the number average molecular weight is an arithmetic average value. .
In the present specification, when the (meth)acrylic copolymer contains monomers having two or more organosiloxane skeletons with 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 the monomer having an organosiloxane skeleton = [number average molecular weight of monomer 1 x blending amount of monomer 1 + number average molecular weight of monomer 2 x blending amount of monomer 2 + ... + number average molecular weight of monomer n × compounding amount of monomer n]/[compounding amount of monomer 1 + compounding amount of monomer 2 + ... + compounding amount of monomer n]

The type of the monomer having an organosiloxane skeleton is not particularly limited as long as it is a monomer having an organosiloxane skeleton and 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 compounds represented by the following formula (1) and compounds represented by the formula (2).

In formulas (1) and (2), R ¹ represents a hydrogen atom or a methyl group, 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, branched, or cyclic. The monovalent organic group includes an alkyl group, an alkenyl group, an alkynyl group, an aryl group and the like, and an alkyl group is preferred.
When R ² represents an alkyl group, the alkyl group is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and still more preferably an alkyl group having 1 to 4 carbon atoms.
Examples of alkyl groups having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group and t-butyl group. , is preferably a methyl group.
When R ² represents an alkenyl group, the alkenyl group includes a vinyl group, an allyl group, a 2-propenyl group and the like, and a vinyl group is preferred.
When R ² represents an alkynyl group, the alkynyl group includes an ethynyl group, a propargyl group, a prop-2-yn-1-yl group and the like, with an ethynyl group being preferred.
When R ² represents an aryl group, the aryl group includes a phenyl group, a tolyl group, a pyridyl group and the like, and is preferably a phenyl group.
m and n each independently represent an integer of 0 or more. m is preferably an integer of 1-10, more preferably an integer of 1-6. n is preferably an integer of 1-250, more preferably an integer of 5-200.

Commercially available products can be used as the monomer having an organosiloxane skeleton.
Examples of commercially available monomers having an organosiloxane skeleton include X-22-2404 [trade name, number average molecular weight: 420, Shin-Etsu Chemical Co., Ltd.], Silaplane TM-0701T [trade name, number average Molecular weight: 423, JNC Corporation], X-22-174ASX [trade name, number average molecular weight: 1100, Shin-Etsu Chemical Co., Ltd.], Silaplane FM-0711 [trade name, number average molecular weight: 1200, JNC ( stock)] and the like.
All of the above commercial products correspond to 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 thereof.

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

The content of structural units derived from a monomer having an organosiloxane skeleton in the specific (meth)acrylic copolymer (B) is based on the total 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, more preferably 4% by mass or more and 9% by mass or less, 5% by mass More preferably, it is in the range of 9 mass % or less.
The content of structural units derived from a monomer having an organosiloxane skeleton in the specific (meth)acrylic copolymer (B) is based on the total structural units of the specific (meth)acrylic copolymer (B) When the amount is 2% by mass or more, there is a tendency that the easy releasability of the pressure-sensitive adhesive layer from the adherend at the initial stage of lamination is less likely to be impaired.
The content of structural units derived from a monomer having an organosiloxane skeleton in the specific (meth)acrylic copolymer (B) is based on the total structural units of the specific (meth)acrylic copolymer (B) When the amount is 9% by mass or less, the adhesive strength of the adhesive layer to the adherend after heating tends to increase.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>
The specific (meth)acrylic copolymer (B) preferably contains structural units derived from (meth)acrylic acid alkyl ester monomers.
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 in the alkyl group is preferably 1 to 18, more preferably 1 to 12, for example, from the viewpoint of adhesive strength.

Specific examples of the (meth)acrylic acid alkyl ester monomer are the same as the specific examples of the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic copolymer (A), so they are described here. omitted.
Examples of (meth)acrylic acid alkyl ester monomers include, from the viewpoint of compatibility with the specific (meth)acrylic copolymer (A), methyl methacrylate (MMA) and n-butyl methacrylate (n-BMA). , and 2-ethylhexyl methacrylate (2EHMA).

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

<Other structural units>
The specific (meth)acrylic copolymer (B) is derived from a monomer having an organosiloxane skeleton, which is an essential structural unit, as long as the effect of the present invention is exhibited. 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 monomers constituting other structural units include (meth)acrylates having an aromatic ring represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate and ethoxyethyl Alkoxyalkyl (meth)acrylates typified by (meth)acrylates, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyls typified by vinyltoluene, acrylonitrile and methacrylates. vinyl cyanides typified by lonitrile; and vinyl esters typified by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. Various derivatives of these monomers are also included.
Further, specific examples of monomers constituting other structural units include monomers having a hydroxyl group. Since specific examples of the hydroxyl group-containing monomer are the same as those of the hydroxyl group-containing monomer in the specific (meth)acrylic copolymer (A), 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 to 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 for example, it is preferably in the range of 40° C. or higher and 65° C. or lower, and is in the range of 40° C. or higher and 60° C. or lower. is more preferable, and a range of 40° C. or higher and 55° C. or lower is even more preferable.
When the glass transition temperature of the specific (meth)acrylic copolymer (B) is within the above range, the adhesive strength of the pressure-sensitive adhesive layer to the adherend tends to be more moderate at the initial stage and after heating. In addition, the pressure-sensitive adhesive layer does not become too hard at room temperature, and tends to exhibit more moderate wettability with respect to the adherend.

The glass transition temperature of the specific (meth)acrylic copolymer (B) was measured using a differential scanning calorimeter (DSC) in a nitrogen stream with a measurement sample of 8 mg, a measurement start temperature of −70° C., and a measurement end temperature of 150. ° C. and a heating rate of 10 ° C./min, and the inflection point of the obtained DSC curve is taken as the glass transition temperature of the specific (meth)acrylic copolymer (B).
As a differential scanning calorimeter, for example, DSC2500 (model number) manufactured by TA Instruments Co., Ltd. can be suitably used. However, the differential scanning calorimeter is not limited to this.

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

<<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 15,000 or more. It is more preferably in the range of 60,000 or less, further preferably in the range of 18,000 to 40,000, and particularly preferably in the range of 20,000 to 30,000.
When the weight-average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) is 10,000 or more, the easy release property of the adhesive layer from the adherend at the initial stage of lamination tends to be less likely to be impaired. In addition, there is a tendency that a pressure-sensitive adhesive layer that is resistant to foaming even when exposed to a high-temperature environment (that is, has excellent high-temperature durability) can be formed.
When the weight-average molecular weight (Mw) of the specific (meth)acrylic copolymer (B) is 100,000 or less, it tends to be difficult for the pressure-sensitive adhesive layer to easily release from the adherend at the initial stage of lamination.

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

The weight average molecular weight of the specific (meth)acrylic copolymer (B) can be adjusted to the desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. 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 parts 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. More preferably, it is in the range of 7 parts by mass or more and 15 parts by mass or less.
The content of the specific (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 0.1 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer (A). If there is, there is a tendency that the easy releasability of the pressure-sensitive adhesive layer from the adherend at the initial stage of lamination is less likely to be impaired.
If 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 that it is possible to form a pressure-sensitive adhesive layer that hardly foams even when exposed to a high-temperature environment (that is, has excellent high-temperature durability).

[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-described monomers by a known polymerization method represented by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method. can be manufactured by
As the polymerization method, the solution polymerization method is preferable because the processing steps are relatively simple and can be performed in a short period of time when preparing the pressure-sensitive adhesive composition of the present invention after production.

In the solution polymerization method, generally, a predetermined organic solvent, monomers, a polymerization initiator, and optionally a chain transfer agent are charged in a polymerization tank, and stirred at the reflux temperature of the organic solvent in a nitrogen stream. Heat and react for several hours while stirring. In this case, the organic solvent, the monomer, the polymerization initiator, and at least part of the optionally used chain transfer agent may be added successively.

Organic solvents 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 specific examples of the organic solvent used during the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic hydrocarbon compounds typified by aromatic naphtha, fats typified by n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine. or alicyclic hydrocarbon compounds, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate. Ester compounds, acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and ketone compounds represented by methyl cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ethers and glycol ether compounds typified by diethylene glycol monobutyl ether, and methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t- Alcohol compounds represented by butyl alcohol are mentioned.

In the production of the specific (meth)acrylic copolymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction of aromatic hydrocarbon compounds, ester compounds, ketone compounds, etc. In particular, the specific (meth)acrylic Ethyl acetate, butyl acetate and the like are preferably used from the viewpoint of the solubility of the system copolymer and the ease of the polymerization reaction.

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

Examples of the polymerization initiator include organic peroxides, azo compounds, and the like, which are used in ordinary solution polymerization methods.
Examples of organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, carbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4 -di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.
Examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4- methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), and 2,2′-azobis(isobutyrate)dimethyl.
In producing 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 particularly preferably an azo compound.

At the time of the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

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

If necessary, a chain transfer agent may be used in the production of the specific (meth)acrylic copolymer.
Examples of chain transfer agents include cyanoacetic acid, cyanoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, bromoacetic acid, bromoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, and fluorene. , and aromatic compounds represented by 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone and Benzoquinone derivatives typified by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives typified by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane Halogenated hydrocarbon compounds typified by , tribromoethylene, trichlorethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds typified by chloral and furaldehyde; alkyls having 1 to 18 carbon atoms; Mercaptan compounds, aromatic mercaptan compounds represented by thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and pinene and terpinolene Representative terpene compounds are 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. It can be set as appropriate.

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

[Xylylene diisocyanate compound]
The 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 layer tends to have a higher adhesive strength to an adherend after heating. In addition, there is a tendency that a pressure-sensitive adhesive layer that is resistant to foaming even when exposed to a high-temperature environment (that is, has excellent high-temperature durability) can be formed.

The xylylene diisocyanate compound is not particularly limited.
Xylylene diisocyanate compounds include xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate, polymers of xylylene diisocyanate (for example, dimers, trimers, or pentamers), hydrogenated xylylene diisocyanate and tri Examples thereof include adducts with polyol compounds such as methylolpropane and biuret forms of xylylene diisocyanate.

A commercial item can be used as a xylylene diisocyanate compound.
Examples of commercially available xylylene diisocyanate compounds include “Takenate (registered trademark) D-110N” and “Takenate (registered trademark) D-120N” manufactured by 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. It is preferably in the range of 0.1 to 5 parts by mass, and even more preferably in the range of 0.1 to 1 part by mass.
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 for the adherend , the adhesive strength after heating tends to be higher. In addition, there is a tendency to form a pressure-sensitive adhesive layer that is less likely to foam even when exposed to a high-temperature environment (that is, more excellent in high-temperature durability).

[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 those similar to 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.

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 purpose.

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the components described above (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, crosslinking catalysts, tackifiers, antioxidants, colorants (e.g. dyes and pigments), release modifiers, light stabilizers (e.g. , ultraviolet absorbers), and various additives such as antistatic agents.

In the pressure-sensitive adhesive composition of the present invention, the release modifier can be used from the viewpoint of adjusting the pressure-sensitive adhesive strength.
Commercially available products can be used as the release modifier.
Examples of commercially available release modifiers include SF-8411, SF-8413, SZ-3720, SF-8421, FZ-3736, BY16-876, BY16-760, SF8417 and BY16 manufactured by Dow Corning Toray 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.

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 mass % or more, and is in the range of 50 mass % or more and 90 mass % or less. is more preferable, and a range of 50% by mass or more and 85% by mass or less is even more preferable.
When the gel fraction of the pressure-sensitive adhesive composition after cross-linking is 50% by mass or more, it tends to form a pressure-sensitive adhesive layer that is more resistant to foaming even when exposed to high-temperature environments (i.e., more excellent in high-temperature durability). There is

As used herein, the "gel fraction after cross-linking of the pressure-sensitive adhesive composition" is the solvent-insoluble fraction measured using ethyl acetate as an extraction solvent. Specifically, the gel fraction after cross-linking of the pressure-sensitive adhesive composition is measured according to the following (1) to (4).
(1) About 0.15 g of the adhesive composition after cross-linking (i.e., the adhesive layer) is attached to a 250-mesh wire mesh (100 mm × 100 mm) whose mass is accurately measured with a precision balance, and the gel leaks. The wire mesh is folded 5 times with the attached adhesive layer facing inward so that it is not exposed, and this is 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) A 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 weight of the wire mesh (unit: g), Y is the weight of the wire mesh with the adhesive layer attached before immersion (unit: g), and Z is the weight of the wire mesh with the adhesive layer attached, dried after immersion. (unit: g).

<Application>
Applications of the pressure-sensitive adhesive composition of the present invention are not particularly limited.
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive layer that exhibits light releasability to an adherend at the initial stage of lamination and exhibits high adhesive strength after heating, and when exposed to a high-temperature environment. However, since it is possible to form a pressure-sensitive adhesive layer that is resistant to foaming (that is, it is excellent in high-temperature durability), it is suitable for use in bonding a display and an optical member together, for example.
A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a polymer containing a structural unit derived from a monomer having an organosiloxane skeleton is exposed to a high-temperature environment when the adherend is glass. At the same time, foaming tends to occur more easily. In contrast, the pressure-sensitive adhesive composition of the present invention contains a polymer containing a structural unit derived from a monomer having an organosiloxane skeleton, but the pressure-sensitive adhesive layer formed is exposed to a high-temperature environment. Foaming is less likely to occur when Therefore, the pressure-sensitive adhesive composition of the present invention can be preferably applied to adherends made of glass (for example, glass substrates of liquid crystal cells). The pressure-sensitive adhesive composition of the present invention can also be preferably applied to other adherends (eg, polyimide film, polyethylene terephthalate film, stainless plate, copper plate, etc.).

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention comprises a pressure-sensitive adhesive layer formed from 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 from the pressure-sensitive adhesive composition of the present invention, it exhibits light releasability from the adherend at the initial stage of lamination, and high releasability after heating. Shows stickiness. In particular, since the pressure-sensitive adhesive sheet of the present invention is provided with a pressure-sensitive adhesive layer that exhibits light releasability at the initial stage of bonding to the adherend, it can be applied to a thin adherend having a thickness of, for example, about 10 μm. Even if there is, it has the advantage that it can be peeled off without any problem.
In addition, since the pressure-sensitive adhesive sheet of the present invention includes the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, 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 substrate-free pressure-sensitive adhesive sheet having no substrate, or a substrate-containing pressure-sensitive adhesive sheet having an adhesive layer on at least one side of a substrate.
In the pressure-sensitive adhesive sheet of the present invention, the exposed surface of the pressure-sensitive adhesive layer may be protected with a release film.

The release film is not particularly limited as long as it can be easily separated from the pressure-sensitive adhesive layer.
Examples of resin films include polyester films typified by polyethylene terephthalate films.
Examples of release agents include silicone-based release agents (eg, silicone), wax-based release agents (eg, paraffin wax), fluorine-based release agents (eg, fluorine-based resins), and the like.
The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put to practical use, and is peeled off during use.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but generally ranges from 1 μm to 100 μm, preferably from 3 μm to 50 μm, and more preferably from 5 μm to 30 μm.

When the pressure-sensitive adhesive sheet of the present invention has a base material, the base material is not particularly limited.
Examples of base materials include polyethylene-based resins, polyester-based resins, acetate-based resins (e.g., triacetylcellulose resin), polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, Films containing resins such as acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, fluorine resins, and the like can be mentioned.

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 substrate may be partially or wholly patterned.

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

[Method for producing 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 invention can be produced, for example, by the following method.
In the case of a substrate-free pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present invention is applied onto the surface of a release film to form a coating film. Next, the formed coating film is dried. After drying, the exposed surface of the coating film that does not contact the release film is overlapped so that the surface of another release film is in contact, and then cured to form a laminate structure of release film / adhesive layer / release film. , it is possible to manufacture a substrate-free pressure-sensitive adhesive sheet.

In the case of a substrate type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present invention is applied onto the surface of a substrate to form a coating film. Next, the formed coating film is dried. After drying, the exposed surface of the coating film that does not contact the substrate is laminated so that the surface of the release film is in contact, and then cured to form a laminated structure of substrate / adhesive layer / release film. A substrate type PSA sheet can be manufactured.

Another method includes, for example, the following method.
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 produce a film with an adhesive. Next, a base material is attached to the adhesive surface of the adhesive-attached film and cured to produce a base-material type pressure-sensitive adhesive sheet having a laminated structure of base material/adhesive layer/release film.

The method of applying the pressure-sensitive adhesive composition onto the surface of the base material or release film is not particularly limited. A known method using a bar coater, an applicator, or the like can be mentioned.
The amount of the pressure-sensitive adhesive composition to be applied onto the surface of the substrate or 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 substrate or release film is not particularly limited, and includes natural drying, heat drying, hot air drying, vacuum drying and the like.
The drying temperature and drying time of the coating film formed on the surface of the substrate or 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 adhesive composition to form an adhesive layer.

[Optical member]
The optical member of the invention comprises a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the invention.
The optical member is not particularly limited, and includes, for example, members constituting devices (so-called optical devices) such as image display devices and input devices, and members used in these devices.
Specific examples of optical members include polarizing plates, AG (Anti-Glare) polarizing plates, wave plates, retardation plates including wave plates such as 1/2 and 1/4 wave plates, viewing angle compensation films, optical compensation films, and luminance enhancement. Films, light guide plates, reflective films, antireflection films, transparent conductive films such as ITO (Indium-Tin Oxide) films, prism sheets, lens sheets, diffusion plates, and the like.
Materials for optical members include polyethylene-based resin, polyester-based resin, acetate-based resin (for example, triacetyl cellulose resin), polyethersulfone-based resin, polycarbonate-based resin, polyamide-based resin, polyimide-based resin, polyolefin-based resin, Resins such as acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine resins can be used.

EXAMPLES Hereinafter, the present invention will be described more specifically 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.

[Production of (meth)acrylic copolymer A]
[Production Example A-1]
A reactor equipped with a stirrer, a reflux condenser, a sequential dropping device and a thermometer was charged with 70.0 parts by mass of ethyl acetate (organic solvent for polymerization). Next, 100.0 parts by mass of a monomer mixture composed of 90.0 parts by mass of n-butyl acrylate (n-BA) and 10.0 parts by mass of methyl acrylate (MA) was prepared in another container. 20% by mass of the prepared monomer mixture was charged into the 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 successively added dropwise over 120 minutes, and after completion of the dropwise addition, the reaction was allowed to proceed for 30 minutes to complete the reaction. After completion of the reaction, the solution was diluted with ethyl acetate so that the solid content concentration was 32% by mass to obtain a solution of (meth)acrylic copolymer A-1.

The term "solid content concentration" as used herein means the mass proportion of the (meth)acrylic copolymer A-1 in the solution of the (meth)acrylic copolymer A-1.
The same applies to each solution of (meth)acrylic copolymers A-2 to A-11 below.

[Production 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, and the amount of organic solvent used and the polymerization initiator By adjusting at least one of the amounts used, the weight average molecular weight of the (meth)acrylic copolymer was changed to the weight average molecular weight shown in Table 1. The same operation as in Production Example A-1 was performed. Each solution of (meth)acrylic copolymers A-2 to A-11 having a solid content concentration of 32% by mass was obtained.

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. It corresponds to polymer (A).

(Meth) acrylic copolymers A-1 to A-11 monomer composition (unit: mass%), (meth) acrylic copolymers A-1 to A-11 glass transition temperature (Tg, unit : °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 temperatures of the (meth)acrylic copolymers A-1 to A-11 were 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 method for measuring the weight average molecular weight of the specific (meth)acrylic copolymer (A) described above. .

Details of each monomer listed in Table 1 are as shown below.
"n-BA": n-butyl acrylate (acrylic acid alkyl ester monomer, glass transition temperature when homopolymer: -57 ° C.)
"MA": methyl acrylate (acrylic acid alkyl ester monomer, glass transition temperature when 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 homopolymer: -15 ° C.)
"AA": acrylic acid (monomer having a carboxy group, glass transition temperature when homopolymer: 163 ° C.)

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

[Production of (meth)acrylic copolymer B]
[Production Example B-1]
A reactor equipped with a stirrer, a reflux condenser, a sequential dropping device and a thermometer was charged with 60 parts by mass of ethyl acetate (organic solvent for polymerization). Next, 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 Co., Ltd.] 1.0 parts by mass, 2,2'-azobis(isobutyrate) dimethyl [polymerization Initiator] 1.7 parts by mass and 40.0 parts by mass of ethyl acetate (organic solvent for polymerization) were mixed to prepare a solution. The prepared solution was added dropwise over 180 minutes under reflux temperature conditions, and after the completion of dropwise addition, the reaction was allowed to proceed for 180 minutes to complete the reaction. After completion of the reaction, the solution was diluted with ethyl acetate to a solid content of 48 mass % to obtain a solution of (meth)acrylic copolymer B-1.

The term "solid content concentration" as used herein means the mass proportion of the (meth)acrylic copolymer B-1 in the solution of the (meth)acrylic copolymer B-1.
The same applies to each solution of (meth)acrylic copolymers B-2 to B-13 below.

[Production 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 organic solvent used and the polymerization initiator By adjusting at least one of the amounts used, the weight average molecular weight of the (meth)acrylic copolymer was changed to the weight average molecular weight shown in Table 2. The same operation as in Production Example B-1 was performed. Each solution of (meth)acrylic copolymers B-2 to B-13 having a solid content concentration of 48% by mass was obtained.

Among the (meth)acrylic copolymers B-1 to B-13 obtained above, (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 of (meth)acrylic copolymers B-1 to B-13 (unit: % by mass), monomer having an organosiloxane skeleton in (meth)acrylic copolymers B-1 to B-13 The number average molecular weight (Mn) of the body, the glass transition temperature (Tg, unit: ° C.) of the (meth)acrylic copolymers B-1 to B-13, and the (meth)acrylic copolymers B-1 to B Table 2 shows the weight average molecular weight (Mw) of -13.
The number average molecular weight of the monomer having an organosiloxane skeleton in the (meth)acrylic copolymers B-1 to B-13 is 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 monomer having.
The glass transition temperatures of the (meth)acrylic copolymers B-1 to B-13 were 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 method for measuring the weight average molecular weight of the specific (meth)acrylic copolymer (A) described above. .

Details of each monomer listed 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 Co., Ltd.]: a monomer having an organosiloxane skeleton, a compound represented by formula (2) "X-22-2404" [trade name, number average molecular weight: 420, Shin-Etsu Chemical Co., Ltd.]: monomer having an organosiloxane skeleton, compound represented by formula (2) "X-22-174DX" [trade name, number average molecular weight : 5400, Shin-Etsu Chemical Co., Ltd.]: monomer having an organosiloxane skeleton, compound represented by formula (2) "FM-0711" [trade name: Silaplane FM-0711, number average molecular weight: 1200, JNC Co., Ltd.]: a monomer having an organosiloxane skeleton, a compound represented by formula (2)

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

[Preparation of adhesive composition]
[Example 1]
100 parts by mass of a solution of (meth)acrylic copolymer A-2 (solid content conversion value), 13 parts by mass of a solution of (meth)acrylic copolymer B-3 (solid content conversion value), and a cross-linking agent [Trade name: Takenate (registered trademark) D-110N, xylylene diisocyanate compound, solid content: 75% by mass, Mitsui Chemicals, Inc.] 0.5 parts by mass (solid content conversion value), and , to obtain the adhesive composition of Example 1.

[Examples 2 to 14]
In Example 1, except that the composition of the adhesive composition was changed to the composition shown in Table 3, the same operation as in Example 1 was performed to obtain each adhesive composition of Examples 2 to 14.

[Comparative Examples 1 to 16]
In Example 1, except that the composition of the adhesive composition was changed to the composition shown in Table 4, the same operation as in Example 1 was performed to obtain each adhesive composition of Comparative Examples 1 to 16.

[Measurement and evaluation]
1. Gel Fraction Using the adhesive compositions of Examples 1 to 14 and Comparative Examples 1 to 16, the gel fraction after cross-linking (that is, the gel fraction of the adhesive layer) was measured. Specifically, it was measured by the following method.
A pressure-sensitive adhesive is applied to the surface-treated surface of a release film [trade name: Film Bina (registered trademark) 100E-0010N023, Fujimori Industry Co., Ltd.] that has been surface-treated with a silicone-based release agent so that the thickness after drying is 20 μm. The composition was applied to form a coating film.
Then, the formed coating film was dried using a hot air circulating 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 superimposed on the surface-treated surface of a separately prepared release film [trade name: Film Binner (registered trademark) 100E-0010N023, Fujimori Industry Co., Ltd.], and then the atmosphere temperature was 25. C. and 50% RH for 168 hours and allowed to cure to promote the cross-linking reaction to produce a substrate-free pressure-sensitive adhesive sheet having a configuration of release film/adhesive layer/release film. .

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). Tables 3 and 4 show the results.
(1) About 0.15 g of the 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 content 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) A 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 weight of the wire mesh (unit: g), Y is the weight of the wire mesh with the adhesive layer attached before immersion (unit: g), and Z is the weight of the wire mesh with the adhesive layer attached, dried after immersion. (unit: g).

2. Adhesive strength (preparation of adhesive sheet for evaluation)
The adhesive composition prepared above was applied to a polyethylene terephthalate (PET) film [trade name: Teijin (registered trademark) Tetoron (registered trademark) film, model number: G2P2, thickness: 50 µm, Teijin Film Solution (PET) film treated for easy adhesion. Co., Ltd.] was applied to the easy-adhesion-treated surface of the product so that the thickness after drying was 20 μm to form a coating film. Then, the formed coating film was dried using a hot air circulating dryer under drying conditions of 100° C. for 1 minute to form an adhesive film on the PET film.
Next, the surface where the adhesive film is exposed is the release-treated surface of a release film [trade name: Film Binah (registered trademark) 100E-0010N023, Fujimori Industry Co., Ltd.] that has been subjected to an easy-release treatment with a separately prepared silicone-based release agent. After lamination, the pressure-sensitive adhesive sheet for evaluation having a laminated structure of release film/adhesive layer/PET film is allowed to stand still for 4 days in an environment at an atmospheric temperature of 23° C. and 50% RH to allow the cross-linking reaction to proceed. got

(1) Initial adhesive strength The pressure-sensitive adhesive sheet for evaluation prepared above was cut into a size of 25 mm x 150 mm to prepare a piece of pressure-sensitive adhesive sheet for evaluation.
The release film was peeled off from the prepared adhesive sheet piece for evaluation (constitution: release film/adhesive layer/PET film), and the surface of the adhesive layer exposed by peeling was covered with non-alkali glass [trade name: Eagle XG, Corning Incorporated]. ] (hereinafter simply referred to as “glass”), and then crimped by reciprocating a 2 kg roller once to prepare a test piece X-1.

The test piece X-1 was allowed to stand for 30 minutes in an atmosphere of 23° C. and 50% RH.
Regarding the test piece X-1 after standing, the adhesive force (unit: N / 25 mm ), using a single column type material testing machine (model number: STA-1225) of A&D Co., Ltd. as a measuring device, under the conditions of an atmosphere temperature of 23 ° C., 50% RH, and a peeling speed of 300 mm / min. measured in Then, the initial adhesive strength was evaluated according to the following evaluation criteria.
Tables 3 and 4 show the results.
If the evaluation result was "A" or "B", it was judged that there was 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: The adhesive strength is 1 N/25 mm or more.

(2) Adhesive strength after heating The pressure-sensitive adhesive sheet for evaluation prepared above was cut into a size of 25 mm x 150 mm to prepare a piece of pressure-sensitive adhesive sheet for evaluation.
After peeling off the release film from the prepared adhesive sheet piece for evaluation (constitution: release film/adhesive layer/PET film) and pasting the surface of the adhesive layer exposed by peeling onto the surface of the glass, 2 kg The roller was reciprocated twice to produce a test piece X-2.

After leaving the test piece X-2 in a dryer set at a temperature of 50° C. for 20 minutes, it was taken out of the dryer and allowed to stand in an atmosphere of 23° C. and 50% RH for 30 minutes.
Regarding the test piece X-2 after standing, the adhesive force (unit: N / 25 mm ), using a single column type material testing machine (model number: STA-1225) of A&D Co., Ltd. as a measuring device, under the conditions of an atmosphere temperature of 23 ° C., 50% RH, and a peeling speed of 300 mm / min. measured in Then, the adhesive strength after heating was evaluated according to the following evaluation criteria.
Tables 3 and 4 show the results.
If the evaluation result was "A" or "B", it was judged that there was 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: The adhesive strength is less than 5 N/25 mm.

3. High Temperature Durability The pressure-sensitive adhesive sheet for evaluation prepared above was cut into a size of 25 mm×150 mm to prepare a piece of pressure-sensitive adhesive sheet for evaluation.
After peeling off the release film from the prepared adhesive sheet piece for evaluation (constitution: release film/adhesive layer/PET film) and pasting the surface of the adhesive layer exposed by peeling onto the surface of the glass, 2 kg The roller was reciprocated twice to produce a test piece X-3.

The test piece X-3 was placed 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 an additional 168 hours. Next, the test piece X-3 was taken out from the dryer and left to stand for 30 minutes in an atmosphere of 23° C. and 50% RH. Next, the test piece X-3 was visually observed and evaluated for high temperature durability according to the following evaluation criteria.
Tables 3 and 4 show the results.
If the evaluation result was "A" or "B", it was judged that there was no practical problem.

-Evaluation criteria-
A: No foaming was observed in the test piece.
B: Slight foaming was confirmed at the edge of the test piece, but within an acceptable range.
C: Foaming was confirmed on the entire surface of the test piece.

Details of the cross-linking agents listed in Tables 3 and 4 are as follows.
“XDI” [trade name: Takenate (registered trademark) D-110N, xylylene diisocyanate compound, solid content: 75% by mass, Mitsui Chemicals, Inc.]
"TDI" [trade name: Coronate (registered trademark) L-45E, tolylene diisocyanate compound, solid content: 45% by mass, Tosoh Corporation]
“HMDI” [trade name: Sumidule (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 "compounding amount" are all solid content conversion values.
In Table 4, "-" means that the component corresponding to that column was not blended.

As shown in Table 3, the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 14 all exhibited light release properties from the adherends at the initial stage of lamination, and high releasability after heating. It was confirmed that the adhesive force was exhibited. Moreover, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 14 are all excellent in durability.

On the other hand, as shown in Table 4, the pressure-sensitive adhesive layer formed from 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 to the adherend in the initial stage of lamination is high, and that the adherend does not show easy releasability. In addition, it was confirmed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 1 significantly foamed when exposed to a high-temperature environment, and was inferior in high-temperature durability.
(Meth)acrylic copolymer A contains structural units derived from a monomer having a carboxyl group instead of structural units derived from a monomer having a hydroxyl group Pressure-sensitive adhesive compositions of Comparative Examples 2 and 3 It was confirmed that the pressure-sensitive adhesive layer formed by the material significantly foamed when exposed to a high-temperature environment, and was inferior in high-temperature durability.
The content of structural units derived from a monomer having a hydroxyl group in the (meth)acrylic copolymer A is greater than 40% by mass based on the total structural units The adhesive formed by the adhesive composition of Comparative Example 14 It was confirmed that the agent layer did not exhibit high adhesive strength to the adherend after heating due to excessively high cohesive strength.

Formed from the pressure-sensitive adhesive composition of Comparative Example 4 in which the content of structural units derived from a monomer having an organosiloxane skeleton in the (meth)acrylic copolymer B is less than 2% by mass relative to the total structural units It was confirmed that the pressure-sensitive adhesive layer thus formed has a high adhesive strength to the adherend in the initial stage of lamination and does not exhibit easy peelability from the adherend.
The pressure-sensitive adhesive compositions of Comparative Examples 5 and 15 in which the content of structural units derived from the monomer having an organosiloxane skeleton in the (meth)acrylic copolymer B exceeds 9% by mass with respect to the total structural units It was confirmed that the pressure-sensitive adhesive layer formed from the material did not exhibit high adhesive strength to the adherend after heating.

(Meth) content of structural units derived from a monomer having an organosiloxane skeleton in the acrylic copolymer B exceeds 9% by mass with respect to all structural units, and a monomer having an organosiloxane skeleton It was confirmed that the pressure-sensitive adhesive layer formed from 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.
(Meth) 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 monomer having an organosiloxane skeleton in the acrylic copolymer B exceeds 1500 is , it was confirmed that it does not show high adhesion after heating.

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

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 10, which does not contain the specific (meth)acrylic copolymer (B), has high adhesive strength to the adherend at the initial stage of lamination, and It was confirmed that it does not show easy peelability.
The content of the specific (meth)acrylic copolymer (B) is formed by the adhesive composition of Comparative Example 11 exceeding 20 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer (A). It was confirmed that the pressure-sensitive adhesive layer thus prepared causes significant 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 from the pressure-sensitive adhesive composition of Comparative Example 12 containing the tolylene diisocyanate compound instead of the xylylene diisocyanate compound does not exhibit high adhesive strength to the adherend after heating. .
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 13 containing a hexamethylene diisocyanate compound instead of a xylylene diisocyanate compound causes significant foaming when exposed to a high-temperature environment, resulting in poor high-temperature durability. was confirmed.

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 16, in which the (meth)acrylic copolymer A has a glass transition temperature of 0° C. or higher, exhibits high adhesive strength to the adherend after heating. Confirmed not.

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 structural units, and having a glass transition temperature of less than 0 ° C. Union (A);
Containing structural units derived from a monomer having an organosiloxane skeleton in a range of 2% by mass or more and 9% by weight or less with respect to all structural units, and the monomer having an organosiloxane skeleton has a number average molecular weight of 400 or more. a (meth)acrylic copolymer (B) in the range of 1500 or less and having a weight average molecular weight in the range of 10,000 or more and 100,000 or less;
A xylylene diisocyanate compound,
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). the law of nature,
A pressure-sensitive adhesive composition in which the content of the xylylene diisocyanate compound is in the range of 0.1 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the (meth)acrylic copolymer (A). 2. The monomer according to claim 1, wherein the monomer having an organosiloxane skeleton is at least one compound selected from the group consisting of compounds represented by the following formula (1) and compounds represented by the following 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. . 1 or claim 1, wherein 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 based on all structural units. Item 3. The pressure-sensitive adhesive composition according to item 2. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 3. An optical member comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 3.