JP6811631B2 - Adhesive composition for film and adhesive sheet - Google Patents

Description

The present invention relates to a film pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

A film containing a vinyl chloride resin is often used as a base material for marking films used for advertising signs, stickers, and the like. The marking film is provided with an adhesive layer for sticking to an adherend, and an acrylic adhesive is often used as the adhesive.
In addition, printed matter is often used for advertising signs, and an overlaminated film is used as a film for protecting the surface of the printed matter. A film containing a vinyl chloride resin is often used as an overlaminate film, and an acrylic adhesive is often used to attach it to the surface of printed matter.

Generally, a film containing a vinyl chloride resin is softened by a plasticizer. The plasticizer may migrate from the film to the pressure-sensitive adhesive layer applied to the film over time, causing a decrease in the adhesive strength and cohesive power of the pressure-sensitive adhesive layer, and as a result, the film may peel off from the adherend. Can occur. The transfer of plasticizer from the film to the pressure-sensitive adhesive layer is particularly likely to occur in high temperature environments.
Further, since films such as marking films and overlaminated films are used not only in a high temperature environment but also in a low temperature (for example, 5 ° C) environment, the adhesive for a film is used in either a high temperature environment or a low temperature environment. Even so, it is required that the adhesive strength of the pressure-sensitive adhesive layer is hard to decrease and it is hard to be peeled off from the adherend.

Even if a vinyl chloride resin containing a plasticizer is used as the base material, there are some acrylic adhesives and adhesive sheets using the acrylic adhesive, which do not easily reduce the adhesive strength of the adhesive layer due to the migration of the plasticizer. Are known.
For example, Patent Document 1 describes a weight average molecular weight obtained by copolymerizing 100 parts by weight of n-butyl acrylate, 3 to 10 parts by weight of acrylic acid, and 0.03 to 0.2 parts by weight of 2-hydroxyethyl (meth) acrylate. Acrylic adhesive having a gel content of 35 to 50% in which 700,000 to 950,000 acrylic copolymers are crosslinked with a cross-linking agent contains a plastic agent having a molecular weight of 180 to 500 and epoxidized soybean oil. A vinyl chloride resin adhesive sheet is disclosed, which is characterized in that it is laminated on one surface of the vinyl chloride resin sheet.
Patent Document 2 describes a structural unit A derived from a (meth) acrylic monomer having a carboxy group and a (meth) acrylic acid alkyl ester having a glass transition temperature of 0 ° C. to 45 ° C. when used as a homopolymer. The structural unit B is 44% by mass to 70% by mass, and the structural unit C derived from the (meth) acrylic acid alkyl ester having a glass transition temperature of -80 ° C to -60 ° C when used as a copolymer is 29% by mass. A film pressure-sensitive adhesive composition containing a (meth) acrylic copolymer containing ~ 55% by mass and a cross-linking agent is disclosed.

Japanese Unexamined Patent Publication No. 9-21740 Japanese Unexamined Patent Publication No. 2015-174969

In recent years, films such as marking films and overlaminated films tend to be required to have durability for use in a higher temperature environment than before, for example, use in a high temperature environment of 90 ° C. or higher.
On the other hand, in the acrylic pressure-sensitive adhesives described in Patent Documents 1 and 2, when used in a high temperature environment of 90 ° C. or higher, the plasticizer is transferred from the base material containing the plasticizer to the pressure-sensitive adhesive layer. It cannot be suppressed sufficiently. Further, in the pressure-sensitive adhesive sheet using the acrylic pressure-sensitive adhesive described in Patent Document 1 and Patent Document 2, when the pressure-sensitive adhesive sheet is attached to an adherend containing a plasticizer, the plasticizer is transferred from the adherend to the pressure-sensitive adhesive layer. There is room for improvement because it cannot be sufficiently suppressed.

The problem to be solved by the present invention is that the decrease in adhesive strength due to the transfer of the plasticizer from the adherend containing the plasticizer to the pressure-sensitive adhesive layer in a high-temperature environment is suppressed, and the adhesive strength in a low-temperature environment is excellent. The present invention provides a pressure-sensitive adhesive composition for a film capable of forming a pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet.

Specific means for solving the problem include the following aspects.
<1> A (meth) acrylic copolymer A containing a structural unit derived from a (meth) acrylic monomer having a carboxy group and having a weight average molecular weight of 200,000 to 2 million.
Crosslinked with a (meth) acrylic copolymer B containing a structural unit derived from a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group and having a weight average molecular weight of 40,000 to 20,000. Derived from a (meth) acrylic monomer having a carboxy group and a structural unit derived from a (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer B containing an agent. The total content b (unit: mol%) of the structural unit has a structural unit derived from the (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer A and a (meth) group. A pressure-sensitive adhesive composition for a film having a total content a (unit: mol%) of constituent units derived from an acrylic monomer.
<2> Total of the structural units derived from the (meth) acrylic monomer having a hydroxyl group and the structural units derived from the (meth) acrylic monomer having a carboxy group in the (meth) acrylic copolymer A. A structural unit derived from a (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer B and a (meth) acrylic single amount having a carboxy group with respect to the content a (unit: mol%). The pressure-sensitive acrylic composition for a film according to <1>, wherein the ratio of the total content rate b (unit: mol%) of the constituent units derived from the body is more than 1 and 3 or less.
<3> The pressure-sensitive adhesive composition for a film according to <1> or <2>, wherein the (meth) acrylic copolymer B contains a structural unit derived from a (meth) acrylic monomer having a hydroxyl group.
<4> The glass transition temperature of the (meth) acrylic copolymer A is -80 ° C to -60 ° C, and the glass transition temperature of the (meth) acrylic copolymer B is 90 ° C to 90 ° C. The adhesive composition for a film according to any one of <1> to <3> at 120 ° C.
<5> The ratio of the content of the (meth) acrylic copolymer A to the total content of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B is based on the mass. , 0.5 to 0.8. The film pressure-sensitive adhesive composition according to any one of <1> to <4>.
<6> The pressure-sensitive film pressure-sensitive adhesive composition according to any one of <1> to <5>, wherein the (meth) acrylic copolymer A contains a structural unit derived from 2-ethylhexyl acrylate.
<7> An adhesive sheet having an adhesive layer containing the adhesive composition for a film according to any one of <1> to <6>.

According to the present invention, a pressure-sensitive adhesive layer in which a decrease in adhesive strength due to transfer of a plasticizer from an adherend containing a plasticizer to a pressure-sensitive adhesive layer in a high-temperature environment is suppressed and the adhesive strength is excellent in a low-temperature environment is provided. A film pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet that can be formed are provided.

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

The numerical range indicated by using "~" in the present specification means a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
In the present specification, the content rate of each component means the total content rate of a plurality of types of substances when a plurality of substances corresponding to each component are present, unless otherwise specified.

In the present invention, "under a high temperature environment" means a temperature environment of 90 ° C. or higher.
In the present invention, "under a low temperature environment" means a temperature environment of 5 ° C. or lower.

As used herein, the term "adhesive composition" means a liquid or paste-like substance after the (meth) acrylic copolymer and the cross-linking agent are mixed and before the cross-linking reaction is completed.
As used herein, the term "adhesive layer" means a substance after the cross-linking reaction of the pressure-sensitive adhesive composition is completed.
In the present specification, the “adhesive material” means a material in contact with the pressure-sensitive adhesive layer, and for example, in the pressure-sensitive adhesive sheet, means a base material constituting the pressure-sensitive adhesive sheet and an adherend of the pressure-sensitive adhesive sheet.
In the present specification, the "(meth) acrylic copolymer" is a monomer in which at least the main component of the monomers constituting the copolymer has a (meth) acryloyl group. It means a copolymer. The monomer which is the main component here means the monomer having the largest content (mass%) among the monomers constituting the copolymer. In some embodiments of the (meth) acrylic copolymer in the present invention, the content of the structural units derived from the monomer having the (meth) acryloyl group as the main component is 50% by mass or more of the total structural units. ..
In the present specification, "(meth) acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth) acrylate" is a term that includes both "acrylate" and "methacrylate". "(Meta) acryloyl" is a term that includes both "acryloyl" and "methacryloyl".

[Adhesive composition for film]
The film pressure-sensitive adhesive composition of the present invention (hereinafter, also simply referred to as “pressure-sensitive adhesive composition”) contains a structural unit derived from a (meth) acrylic monomer having a carboxy group, and has a weight average molecular weight of 20. A (meth) acrylic copolymer A (hereinafter, also referred to as “specific (meth) acrylic copolymer A”) which is 10,000 to 2 million, and a (meth) acrylic copolymer having at least one of a hydroxyl group and a carboxy group. A (meth) acrylic copolymer B containing a structural unit derived from a monomer and having a weight average molecular weight of 40,000 to 20,000 (hereinafter, also referred to as “specific (meth) acrylic copolymer B”). ) And a cross-linking agent.
Further, the pressure-sensitive adhesive composition for a film of the present invention is a (meth) acrylic type having a structural unit derived from a (meth) acrylic monomer having a hydroxyl group and a carboxy group in the above (meth) acrylic copolymer B. The total content b (unit: mol%) of the structural unit derived from the monomer is the structural unit and carboxy derived from the (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer A. The pressure-sensitive adhesive composition is larger than the total content a (unit: mol%) of the constituent units derived from the (meth) acrylic monomer having a group.

The pressure-sensitive adhesive composition of the present invention is produced by transferring a plasticizer from an adherend material containing a plasticizer such as a base material and an adherend to a pressure-sensitive adhesive layer in a high temperature environment (that is, in a temperature environment of 90 ° C. or higher). It is a pressure-sensitive adhesive composition for a film that can suppress a decrease in adhesive strength and can form a pressure-sensitive adhesive layer having excellent adhesive strength in a low temperature environment (that is, in a temperature environment of 5 ° C. or lower).
In the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of the present invention, the plasticizer is transferred from the base material to the pressure-sensitive adhesive layer when it comes into contact with a base material containing a plasticizer, for example, a film containing soft vinyl chloride. The decrease in adhesive strength due to the above is suppressed. Further, even when the adherend to which the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of the present invention contains a plasticizer, the plasticizer is transferred from the adherend to the pressure-sensitive adhesive layer. The decrease in adhesive strength is suppressed. Further, the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of the present invention does not easily lose its adhesive strength even in a low temperature environment, and its excellent adhesive strength is maintained.
The reason why the pressure-sensitive adhesive composition of the present invention can exert such an effect is not clear, but the present inventors speculate as follows.

The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a (meth) acrylic monomer having a carboxy group, and has a weight average molecular weight of 200,000 to 2 million (meth) acrylic copolymer A (meth). That is, it is considered that a pressure-sensitive adhesive layer having excellent adhesive strength in a low temperature environment can be formed by containing the specific (meth) acrylic copolymer A).
Further, the pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group, and has a weight average molecular weight of 40,000 to 20,000 (). A (meth) acrylic monomer containing a specific (meth) acrylic copolymer B (that is, a specific (meth) acrylic copolymer B) and having a hydroxyl group in the specific (meth) acrylic copolymer B. The total content b (unit: mol%) of the structural unit derived from and the structural unit derived from the (meth) acrylic monomer having a carboxy group has a hydroxyl group in the specific (meth) acrylic copolymer A. The molecular weight is greater than the total content a (unit: mol%) of the structural unit derived from the (meth) acrylic monomer and the structural unit derived from the (meth) acrylic monomer having a carboxy group. A small specific (meth) acrylic copolymer B is unevenly distributed at the interface between the pressure-sensitive adhesive composition and the base material and the adherend, and then forms a cross-linked structure with the cross-linking agent near the interface to form an appropriate hardness. Since the pressure-sensitive adhesive layer is formed, the transfer of the adherend material containing the plasticizer such as the substrate and the adherend to the pressure-sensitive adhesive layer is suppressed in a high-temperature environment, and as a result, the pressure-sensitive adhesive is suppressed even in a high-temperature environment. It is considered that the decrease in the adhesive strength of the layer is suppressed.

The pressure-sensitive adhesive composition of the present invention can be suitably used for bonding a base material and an adherend.
The base material is not particularly limited, but a film containing a plasticizer is preferable, and a film containing soft vinyl chloride is more preferable. According to the pressure-sensitive adhesive composition of the present invention, even when a film containing a plasticizer is used as the base material, the pressure-sensitive adhesive layer is formed by the transfer of the plasticizer from the base material to the pressure-sensitive adhesive layer in a high temperature environment. The decrease in adhesive strength is suppressed.
In addition, in this specification, "soft vinyl chloride" means a thing containing 10 parts by mass or more of a plasticizer with respect to 100 parts by mass of a vinyl chloride resin.

The above speculation does not limitly interpret the effect of the present invention, but is described as an example.

[Specific (meth) acrylic copolymer A]
The (meth) acrylic copolymer A (that is, the specific (meth) acrylic copolymer A) contained in the pressure-sensitive adhesive composition of the present invention is derived from a (meth) acrylic monomer having a carboxy group. It contains a structural unit and has a weight average molecular weight (Mw) of 200,000 to 2 million.
In the pressure-sensitive adhesive composition of the present invention, the specific (meth) acrylic copolymer A contributes to suppressing a decrease in the adhesive strength of the pressure-sensitive adhesive layer in a low-temperature environment.
The specific (meth) acrylic copolymer A contained in the pressure-sensitive adhesive composition of the present invention may be only one type, or may be two or more types having different monomer compositions, weight average molecular weights, and the like. Good.

In the present specification, the "constituent unit derived from a (meth) acrylic monomer having a carboxy group" means a structural unit formed by addition polymerization of a (meth) acrylic monomer having a carboxy group. To do.

The type of (meth) acrylic monomer having a carboxy group is not particularly limited.
Specific examples of the (meth) acrylic monomer having a carboxy group include (meth) acrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, and citraconic acid ω-carboxy-polycaprolactone (n). ≈ 2) Monoacrylate and the like can be mentioned.
Among these, as the (meth) acrylic monomer having a carboxy group, acrylic acid is used from the viewpoint that the adhesive strength can be easily improved and the decrease in the adhesive strength of the pressure-sensitive adhesive layer in a low temperature environment can be further suppressed. preferable.

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

The proportion of the structural unit derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer A, for example, further suppresses the decrease in the adhesive strength of the pressure-sensitive adhesive layer in a low temperature environment. From the viewpoint of being able to maintain excellent adhesive strength satisfactorily, 0.5% by mass or more is preferable with respect to the total mass of all the constituent units constituting the specific (meth) acrylic copolymer A, and 1.0. It is more preferably mass% or more, and further preferably 1.5 mass% or more.
Further, the proportion of the structural unit derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer A is specified (meth) from the viewpoint that the occurrence of zipping can be suppressed, for example. ) 10% by mass or less is preferable, 5% by mass or less is more preferable, and 3% by mass or less is further preferable with respect to the total mass of all the structural units constituting the acrylic copolymer A.

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

In the present specification, the “constituent unit derived from the (meth) acrylic acid alkyl ester monomer” means a structural unit formed by addition polymerization of the (meth) acrylic acid alkyl ester monomer.

When the specific (meth) acrylic copolymer A contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the (meth) acrylic acid alkyl ester monomer is an unsubstituted (meth) acrylic. The acid alkyl ester monomer is preferable, and the type thereof is not particularly limited.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably in the range of 1 to 18, and more preferably in the range of 1 to 12. When the number of carbon atoms of the alkyl group is within the above range, a pressure-sensitive adhesive layer having better adhesive strength to the adherend and adhesion to the base material when used as a pressure-sensitive adhesive sheet can be formed.

Examples of the (meth) acrylic acid alkyl ester monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, and t. -Butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl Examples thereof include (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
Among these, as the (meth) acrylic acid alkyl ester monomer, at least one selected from 2-ethylhexyl acrylate and n-butyl acrylate is preferable, the glass transition temperature is relatively low, and the pressure-sensitive adhesive layer in a low temperature environment. 2-Ethylhexyl acrylate is more preferable from the viewpoint that the decrease in the adhesive strength of the resin can be further suppressed and the excellent adhesive strength can be well maintained.

When the specific (meth) acrylic copolymer A contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the specific (meth) acrylic copolymer A is a (meth) acrylic acid alkyl ester simple. It may have only one type of structural unit derived from the polymer, or may have two or more types.

When the specific (meth) acrylic copolymer A contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the amount of the (meth) acrylic acid alkyl ester in the specific (meth) acrylic copolymer A The ratio of the constituent units derived from the body is, for example, relative to the total mass of all the constituent units constituting the specific (meth) acrylic copolymer A from the viewpoint that the adhesive strength of the pressure-sensitive adhesive layer can be easily adjusted. 80% by mass or more is preferable, 90% by mass or more is more preferable, and 95% by mass or more is further preferable.
Further, the proportion of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer A is not particularly limited, and for example, the specific (meth) acrylic copolymer A can be used. It is preferably 97% by mass or less with respect to the total mass of all the constituent units.

The specific (meth) acrylic copolymer A is a structural unit derived from a (meth) acrylic monomer having a carboxy group and an arbitrary structural unit within the range in which the effect of the present invention is exhibited (. Meta) A structural unit other than the structural unit derived from the acrylic acid alkyl ester monomer (hereinafter, also referred to as “other structural unit”) may be contained. In this case, the structural unit derived from the (meth) acrylic monomer having a carboxy group and the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer A. The total ratio of the above is preferably 95% by mass or more, more preferably 98% by mass or more, still more preferably 99% by mass or more, based on the total mass of all the constituent units constituting the specific (meth) acrylic copolymer A. preferable.

The type of monomer constituting the other structural unit is not particularly limited.
Examples of the monomer constituting the other structural unit include (meth) acrylic monomers having a hydroxyl group.

Examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. 6-Hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-hydroxybutyl (Meta) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, Examples thereof include glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, and poly (ethylene glycol-propylene glycol) mono (meth) acrylate.
Among these, as the (meth) acrylic monomer having a hydroxyl group, an adhesive layer having an excellent ability to suppress a decrease in adhesive force to an adherend containing a plasticizer in a high temperature environment, that is, an ability to retain adhesive force is formed. 2-Hydroxyethyl methacrylate is preferable from the viewpoint of being able to do so.

When the specific (meth) acrylic copolymer A contains a structural unit derived from a (meth) acrylic monomer having a hydroxyl group, the specific (meth) acrylic copolymer A has a (meth) acrylic having a hydroxyl group. It may have only one kind of structural unit derived from a system monomer, or may have two or more kinds.

The total content of the structural units derived from the (meth) acrylic monomer having a hydroxyl group and the structural unit derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer A a (Unit: mol%) is from the viewpoint that an adhesive layer having excellent adhesive strength retention ability to an adherend containing a plasticizer in a high temperature environment and also excellent adhesive strength in a low temperature environment can be obtained. It is preferably 5.0 mol% or more and 9.0 mol% or less, more preferably 6.0 mol% or more and 8.5 mol% or less, and further preferably 6.8 mol% or more and 7.8 mol% or less.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer A is 200,000 to 2,000,000, preferably 400,000 to 1.3 million, and more preferably 550,000 to 800,000.
A weight average molecular weight (Mw) of the specific (meth) acrylic copolymer A of 200,000 to 2 million indicates that the specific (meth) acrylic copolymer A is a polymer, and is distinguished from the specific (meth) acrylic copolymer B described later. It is a thing.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer A is 2 million or less, the viscosity of the pressure-sensitive adhesive composition is appropriately lowered, and the coatability is improved.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer A is a value measured by the following method. Specifically, the measurement is performed according to the following (1) to (3).
(1) A solution of the specific (meth) acrylic copolymer A is applied to a release paper and dried at 100 ° C. for 2 minutes to obtain a film-like specific (meth) acrylic copolymer A.
(2) A sample solution having a solid content concentration of 0.2% by mass is obtained by using the film-shaped specific (meth) acrylic copolymer A obtained in (1) above and tetrahydrofuran.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) 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, manufactured by Tosoh Corporation)
Detector: Differential refractometer (RI) (built into HLC-8220, manufactured by Tosoh Corporation)
Column: 4 TSK-GEL GMHXL (manufactured by Tosoh Corporation) are connected in series Column temperature: 40 ° C
Eluent: tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL / min

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer A is not particularly limited, and is, for example, preferably −100 ° C. to −40 ° C., more preferably −90 ° C. to −50 ° C., and −80 ° C. ~ -60 ° C. is more preferable.
When the Tg of the specific (meth) acrylic copolymer A is −100 ° C. or higher, a pressure-sensitive adhesive layer having an excellent adhesive strength-retaining ability to an adherend containing a plasticizer in a high-temperature environment can be formed.
Further, when the Tg of the specific (meth) acrylic copolymer A is −40 ° C. or lower, a pressure-sensitive adhesive layer having excellent adhesive strength in a low temperature environment can be formed.

The Tg of the specific (meth) acrylic copolymer A is a value obtained by converting the absolute temperature (K) calculated from the following formula into the Celsius temperature (° C.).

In the formula, Tg1, Tg2, ..., Tg (k-1), and Tgk are the absolute temperatures (K) when each monomer constituting the specific (meth) acrylic copolymer A is used as a homopolymer. ) Represents the glass transition temperature. w1, w2, ..., W (k-1), wk represent the mass fractions of each monomer constituting the specific (meth) acrylic copolymer A, and w1 + w2 + ... + w (k). -1) + wk = 1.
The absolute temperature (K) can be converted to the Celsius temperature (° C) by subtracting 273 from the absolute temperature (K), and the Celsius temperature (° C) can be converted to the absolute temperature (K) by adding 273 to the Celsius temperature (° C). Can be converted to.

The "glass transition temperature when made into a homopolymer" refers to the glass transition temperature of a homopolymer produced by polymerizing the monomer alone. The glass transition temperature of the homopolymer referred to here is measured using a differential scanning calorimetry device (DSC) (model number: EXSTAR6000, Seiko Instruments Co., Ltd.) in a nitrogen stream, with a measurement sample of 10 mg and a heating rate of 10 ° C./min. The curve point of the obtained DSC curve was taken as the Tg of the homopolymer.
The glass transition temperature (Tg) of a homopolymer using a typical monomer is -76 ° C for 2-ethylhexyl acrylate, -10 ° C for 2-ethylhexyl methacrylate, -57 ° C for n-butyl acrylate, and n-. Butyl methacrylate 21 ° C, t-butyl acrylate 41 ° C, t-butyl methacrylate 107 ° C, methyl acrylate 5 ° C, ethyl acrylate -27 ° C, methacrylic acid 185 ° C, 4-hydroxybutyl acrylate -39 ° C., 2-hydroxyethyl acrylate at -15 ° C, 2-hydroxyethyl methacrylate at 55 ° C, acrylic acid at 163 ° C.

The content of the specific (meth) acrylic copolymer A in the pressure-sensitive adhesive composition of the present invention is excellent in the ability to retain the adhesive force to the adherend containing the plasticizer in a high-temperature environment, and in a low-temperature environment. From the viewpoint that a pressure-sensitive adhesive layer having excellent adhesive strength can be formed, 50% by mass to 80% by mass is preferable with respect to the total solid content of the pressure-sensitive adhesive composition.

Ratio of the content of the specific (meth) acrylic copolymer A to the total content of the specific (meth) acrylic copolymer A and the (meth) acrylic copolymer B described later (specific (meth) acrylic) The content of the copolymer A / the total content of the specific (meth) acrylic copolymer A and the specific (meth) acrylic copolymer B) is preferably 0.5 to 0.8 on a mass basis. 0.65 to 0.8 is more preferable, and 0.7 to 0.8 is even more preferable.
Content of Specified (Meta) Acrylic Copolymer A / When the total content of Specified (Meta) Acrylic Copolymer A and Specified (Meta) Acrylic Copolymer B is within the above range, the temperature is low. The decrease in the adhesive strength of the pressure-sensitive adhesive layer in the environment is further suppressed, and the excellent adhesive strength can be well maintained.

[Specific (meth) acrylic copolymer B]
The (meth) acrylic copolymer B (that is, the specific (meth) acrylic copolymer B) contained in the pressure-sensitive adhesive composition of the present invention is a (meth) acrylic single having at least one of a hydroxyl group and a carboxy group. It contains a structural unit derived from a polymer and has a weight average molecular weight of 40,000 to 20,000.
In the pressure-sensitive adhesive composition of the present invention, the specific (meth) acrylic copolymer B suppresses the transfer of the plasticizer from the adherend containing the plasticizer to the pressure-sensitive adhesive layer in a high-temperature environment, and the pressure-sensitive adhesive layer. Contributes to suppressing the decrease in adhesive strength.
The specific (meth) acrylic copolymer B contained in the pressure-sensitive adhesive composition of the present invention may be only one type, or may be two or more types having different monomer compositions, weight average molecular weights, and the like. Good.

In the present specification, "a structural unit derived from a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group" is added to a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group. It means a structural unit formed by polymerization.

The type of (meth) acrylic monomer having a hydroxyl group is not particularly limited.
Examples of the (meth) acrylic monomer having a hydroxyl group include the same ones as the (meth) acrylic monomer having a hydroxyl group in the above-mentioned specific (meth) acrylic copolymer A.
As the (meth) acrylic monomer having a hydroxyl group in the specific (meth) acrylic copolymer B, a pressure-sensitive adhesive layer having an excellent adhesive force-retaining ability to an adherend containing a plasticizer in a high temperature environment can be formed. 2-Hydroxyethyl methacrylate is more preferable from the viewpoint of.

The type of (meth) acrylic monomer having a carboxy group is not particularly limited.
Examples of the (meth) acrylic monomer having a carboxy group include those similar to the (meth) acrylic monomer having a carboxy group in the above-mentioned specific (meth) acrylic copolymer A.
The (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer B forms a pressure-sensitive adhesive layer having an excellent adhesive strength-retaining ability to an adherend containing a plasticizer in a high-temperature environment. Acrylic acid is preferable from the viewpoint of being able to do so.

The specific (meth) acrylic copolymer B is a structural unit derived from a (meth) acrylic monomer having only a hydroxyl group among hydroxyl groups and carboxy groups, and a (meth) acrylic monomer having only a carboxy group. It may contain any of the structural units derived from, and the structural units derived from the (meth) acrylic monomer having both a hydroxyl group and a carboxy group, but the (meth) acrylic single amount having only a hydroxyl group. It preferably contains structural units derived from the body.
The specific (meth) acrylic copolymer B containing a structural unit derived from a (meth) acrylic monomer having a hydroxyl group is a structural unit (or a hydroxyl group) derived from a (meth) acrylic monomer having a carboxy group. And from the adherend containing a plasticizer in a high temperature environment as compared to the specific (meth) acrylic copolymer B containing (a structural unit derived from a (meth) acrylic monomer having both a carboxy group). Since the transfer of the plasticizer to the pressure-sensitive adhesive layer can be further suppressed, it is preferable from the viewpoint that the adhesive strength of the pressure-sensitive adhesive layer is less likely to decrease in a high temperature environment.

The specific (meth) acrylic copolymer B may have only one structural unit derived from the (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group, and may have two or more of them. May be.

The proportion of the structural unit derived from the (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group in the specific (meth) acrylic copolymer B is, for example, an adherend containing a plasticizer in a high temperature environment. From the viewpoint of effectively suppressing the transfer of the plasticizer from the to the pressure-sensitive adhesive layer, 3% by mass or more is preferable with respect to the total mass of all the constituent units constituting the specific (meth) acrylic copolymer B. 5% by mass or more is more preferable, and 8% by mass or more is further preferable.
Further, the proportion of the structural unit derived from the (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group in the specific (meth) acrylic copolymer B is, for example, the adhesion of the pressure-sensitive adhesive layer in a low temperature environment. From the viewpoint that the decrease in force is further suppressed and the excellent adhesive force can be well maintained, 30% by mass or less is based on the total mass of all the constituent units constituting the specific (meth) acrylic copolymer B. It is preferable, 20% by mass or less is more preferable, and 15% by mass or less is further preferable.

The total content of the structural units derived from the (meth) acrylic monomer having a hydroxyl group and the structural units derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer B b (Unit: mol%) is excellent in the ability to retain the adhesive force to the adherend containing the plasticizer in a high temperature environment, and can form an adhesive layer having an excellent adhesive force in a low temperature environment. It is preferably 3 mol% or more and 30 mol% or less, more preferably 5 mol% or more and 20 mol% or less, and further preferably 8 mol% or more and 13 mol% or less.

In the pressure-sensitive adhesive composition of the present invention, the constituent unit derived from the (meth) acrylic monomer having a hydroxyl group and the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer B are used. The total content b (unit: mol%) of the derived structural units is the structural unit and the carboxy group derived from the (meth) acrylic monomer having a hydroxyl group in the above-mentioned specific (meth) acrylic copolymer A. It is more than the total content a (unit: mol%) of the constituent units derived from the (meth) acrylic monomer having.
The total content of the structural unit derived from the (meth) acrylic monomer having a hydroxyl group and the structural unit derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer B b (Unit: mol%) is derived from a structural unit derived from a (meth) acrylic monomer having a hydroxyl group in the specific (meth) acrylic copolymer A and a (meth) acrylic monomer having a carboxy group. If the total content of the constituent units is greater than a (unit: molar%), the specific (meth) acrylic copolymer B is unevenly distributed at the interface between the pressure-sensitive adhesive composition and the substrate and the adherend. , A cross-linked structure is formed with the cross-linking agent near the interface, and the adhesive layer exhibits appropriate hardness. Therefore, from the adherend material containing the plasticizer such as the substrate and the adherend in a high temperature environment. The transfer of plasticizer is suppressed. As a result, the decrease in the adhesive strength of the adhesive layer in a high temperature environment is suppressed.
The total content of the structural unit derived from the (meth) acrylic monomer having a hydroxyl group and the structural unit derived from the (meth) acrylic monomer having a carboxy group in the specific (meth) acrylic copolymer A a Derived from the structural unit derived from the (meth) acrylic monomer having a hydroxyl group in the specific (meth) acrylic copolymer B and the (meth) acrylic monomer having a carboxy group with respect to (unit: mol%). The ratio of the total content rate b (unit: mol%) of the constituent units (that is, (total content rate b / total content rate a) is preferably more than 1 and 3 or less, more preferably 1.2 or more and 2.0 or less. preferable.
When the total content rate b / total content rate a is within the above range, the transfer of the plasticizer from the adherend containing the plasticizer to the pressure-sensitive adhesive layer in a high-temperature environment is more effectively suppressed, and thus the adhesiveness is adhered. The decrease in the adhesive strength of the agent layer is less likely to occur.

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

When the specific (meth) acrylic copolymer B contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the type of the (meth) acrylic acid alkyl ester monomer is not particularly limited.
Examples of the (meth) acrylic acid alkyl ester monomer include those similar to the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer A described above.
As the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer B, at least one selected from t-butyl methacrylate (t-BMA) and t-butyl acrylate (t-BA) is used. Preferably, t-butyl methacrylate (t-BMA) is more preferable from the viewpoint that the glass transition temperature is relatively high.
When the specific (meth) acrylic copolymer B contains a (meth) acrylic acid alkyl ester monomer having a high glass transition temperature, it is a plasticizer from an adherend material containing a plasticizer to the pressure-sensitive adhesive layer in a high temperature environment. Since the migration of the adhesive layer is effectively suppressed, the decrease in the adhesive strength of the adhesive layer is less likely to occur.

When the specific (meth) acrylic copolymer B contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the specific (meth) acrylic copolymer B is a (meth) acrylic acid alkyl ester simple. It may have only one type of structural unit derived from the polymer, or may have two or more types.

When the specific (meth) acrylic copolymer B contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer, the amount of the (meth) acrylic acid alkyl ester in the specific (meth) acrylic copolymer B The ratio of the constituent units derived from the body is, for example, the total mass of all the constituent units constituting the specific (meth) acrylic copolymer B from the viewpoint that an adhesive layer having excellent adhesive strength in a low temperature environment can be formed. On the other hand, 70% by mass or more is preferable, 80% by mass or more is more preferable, and 85% by mass or more is further preferable.
Further, the proportion of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer B is, for example, the adhesive strength retention to the adherend material containing the plasticizer in a high temperature environment. From the viewpoint of forming a pressure-sensitive adhesive layer having excellent performance, 99% by mass or less is preferable, and 97% by mass or less is more preferable with respect to the total mass of all the constituent units constituting the specific (meth) acrylic copolymer B. It is preferable, and more preferably 95% by mass or less.

The specific (meth) acrylic copolymer B is a structural unit derived from a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group within the range in which the effect of the present invention is exhibited, and any arbitrary. It may contain a structural unit other than the structural unit derived from the (meth) acrylic acid alkyl ester monomer, which is a structural unit (hereinafter, also referred to as “other structural unit”). In this case, the constituent unit derived from the (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group in the specific (meth) acrylic copolymer B and the (meth) acrylic acid alkyl ester monomer are used. The total ratio with the derived constituent unit is not particularly limited.
The type of monomer constituting the other structural unit is not particularly limited.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer B is 04,000 to 20,000, preferably 405,000 to 15,000, and more preferably 5,000 to 10,000. preferable.
A weight average molecular weight (Mw) of the specific (meth) acrylic copolymer B of 40,000 to 20,000 indicates that it is an oligomer, and the above-mentioned specific (meth) acrylic copolymer A It distinguishes from.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer B is 40,000 or more, the compatibility with the specific (meth) acrylic copolymer A is improved, and the durability of the pressure-sensitive adhesive layer is improved. It is preferable because the property is improved.

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

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer B is not particularly limited, and is, for example, preferably 50 ° C. to 150 ° C., more preferably 75 ° C. to 130 ° C., and further preferably 90 ° C. to 120 ° C. preferable.
When the Tg of the specific (meth) acrylic copolymer B is 50 ° C. or higher, a pressure-sensitive adhesive layer having an excellent adhesive strength-retaining ability to an adherend containing a plasticizer in a high-temperature environment can be formed.
Further, when the Tg of the specific (meth) acrylic copolymer B is 150 ° C. or lower, a pressure-sensitive adhesive layer having excellent adhesive strength in a low temperature environment can be formed.

In the pressure-sensitive adhesive composition of the present invention, the glass transition temperature of the specific (meth) acrylic copolymer A is -80 ° C to -60 ° C, and the glass transition of the specific (meth) acrylic copolymer B is The temperature is preferably 90 ° C to 120 ° C.
According to such an aspect, the decrease in adhesive strength due to the transfer of the plasticizer from the adherend containing the plasticizer to the pressure-sensitive adhesive layer in a high-temperature environment and the decrease in the adhesive strength of the pressure-sensitive adhesive layer in a low-temperature environment are further improved. It is remarkably suppressed, and even when the adherend contains a plasticizer, a pressure-sensitive adhesive layer having good adhesive strength can be formed in both a high temperature environment and a low temperature environment.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer B is calculated by the same method as the above-mentioned method for calculating the glass transition temperature (Tg) of the specific (meth) acrylic copolymer A. ..

The content of the specific (meth) acrylic copolymer B in the pressure-sensitive adhesive composition of the present invention is excellent in the ability to retain the adhesive force to the adherend containing the plasticizer in a high-temperature environment, and in a low-temperature environment. From the viewpoint that a pressure-sensitive adhesive layer having excellent adhesive strength can be formed, 15% by mass to 30% by mass is preferable with respect to the total solid content of the pressure-sensitive adhesive composition.

[Method for Producing (Meta) Acrylic Copolymer A and (Meta) Acrylic Copolymer B]
The (meth) acrylic copolymer A (that is, the specific (meth) acrylic copolymer A) and the (meth) acrylic copolymer B (that is, the specific (meth) acrylic copolymer) in the pressure-sensitive adhesive composition of the present invention. The method for producing the copolymer B) is not particularly limited. For example, the monomer can be produced by polymerizing by a known polymerization method typified by solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, as a polymerization method, solution polymerization is preferable because the treatment step is relatively simple and can be performed in a short time.

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

Examples of the organic solvent used in the polymerization reaction are benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetraline, decalin, and aromatic naphtha. Aromatic hydrocarbons, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and fatty or alicyclic group typified by terepine oil. Hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and esters typified by methyl benzoate, acetone, methyl ethyl ketone, For methyl-i-butyl ketone, isophorone, cyclohexanone, and ketones typified by methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Representative glycol ethers, as well as alcohols represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol. Kind. At the time of the polymerization reaction, these organic solvents may be used alone or in combination of two or more.

In the production of the specific (meth) acrylic copolymer A, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of esters, ketones, etc., and in particular, the specific (meth) acrylic copolymer A From the viewpoint of solubility and easiness of polymerization reaction, it is preferable to use ethyl acetate, toluene or the like.
Further, in the production of the specific (meth) acrylic copolymer B, it is preferable to use an organic solvent such as ketones and aromatic hydrocarbons. For example, from the viewpoint of easiness of polymerization reaction, methyl ethyl ketone, toluene and the like can be used. Preferable to use.

As the polymerization initiator, organic peroxides, azo compounds and the like used in ordinary solution polymerization can be used.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonato, and di-2-ethylhexylperoxydi. Carbonato, t-butylperoxyvibalato, 2,2-bis (4,5-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,54-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4) Examples include -di-t-butylperoxycyclohexyl) butane and 2,2-bis (4,5-di-t-octylperoxycyclohexyl) butane.
Examples of the azo compound include 2,2'-azobisisobutynitrile (AIBN), 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-4-methoxy-2,4-. Included are dimethylvaleronitrile, 1,1'-azobis-cyclohexane-1-carbonitrile, and 2,2'-azobis (methyl isobutyrate).

In the production of the specific (meth) acrylic copolymer A and the specific (meth) acrylic copolymer B, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and in particular, an azobis-based polymerization initiator. Is preferable.

In the production of the specific (meth) acrylic copolymer A, the amount of the polymerization initiator used is 0 with respect to 100 parts by mass of the total amount of the monomers constituting the specific (meth) acrylic copolymer A. .2 parts by mass or more and 0.4 parts by mass or less is preferable, and 0.25 parts by mass or more and 0.35 parts by mass or less is more preferable.
In addition, the amount of the polymerization initiator used is 100 parts by mass based on the total amount of the monomers constituting the specific (meth) acrylic copolymer B in the production of the specific (meth) acrylic copolymer B. It is preferably 10 parts by mass or more and 16 parts by mass or less, and more preferably 12 parts by mass or more and 14 parts by mass or less.

In the production of the specific (meth) acrylic copolymer A and the specific (meth) acrylic copolymer B, a chain transfer agent can be used as necessary as long as the object and effect of the present invention are not impaired. ..
Examples of the chain transfer agent include cyanoacetic acid, alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, alkyl esters having 1 to 8 carbon atoms of bromoacetic acid, α-methylstyrene, anthracene, phenanthrene, and fluorene. , And aromatic compounds such as 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds such as p-nitrotoluene, Benzoquinone and 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, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, halogenated hydrocarbons typified by 3-chloro-1-propene, aldehydes typified by chloral and furaldehyde, carbon number 1 to 1 18 alkyl mercaptans, aromatic mercaptans typified by thiophenols and toluene mercaptans, mercaptoacetic acid, alkyl esters of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptans having 1 to 12 carbon atoms, and binen. And terpenes represented by turpinolene.

The amount of the chain transfer agent used is, for example, 100 parts by mass in total of the monomers constituting the specific (meth) acrylic copolymer A and the monomers constituting the specific (meth) acrylic copolymer B. On the other hand, the range can be 0.005 parts by mass or more and 10.0 parts by mass or less.

The polymerization temperature is preferably 70 ° C. or higher and 90 ° C. or lower, more preferably 75 ° C. or higher and 88 ° C. or lower, and further preferably 80 ° C. or higher and 85 ° C. or lower in the production of the specific (meth) acrylic copolymer A.
Further, the polymerization temperature is preferably 75 ° C. or higher and 99 ° C. or lower, more preferably 80 ° C. or higher and 98 ° C. or lower, and further preferably 85 ° C. or higher and 97 ° C. or lower in the production of the specific (meth) acrylic copolymer B.

<Crosslinking agent>
The pressure-sensitive adhesive composition of the present invention contains a cross-linking agent.
The type of the cross-linking agent is not particularly limited as long as it can cross-link the (meth) acrylic copolymer A and the (meth) acrylic copolymer B contained in the pressure-sensitive adhesive composition of the present invention.
Examples of the cross-linking agent include cross-linking agents such as an isocyanate compound having an isocyanate group and an epoxy compound having an epoxy group.

Examples of the isocyanate compound include xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, aromatic polyisocyanate compounds typified by tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated compounds of the above-mentioned aromatic polyisocyanate compounds. Chained or cyclic aliphatic polyisocyanate compounds typified by, biuret, dimer, trimeric or pentameric of these polyisocyanate compounds, these polyisocyanate compounds and polyol compounds such as trimethylolpropane. Adduct body and the like.

Examples of the epoxy compound include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-Hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl Glycoldiglycidyl ether, trimethylpropan triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocia Examples thereof include nurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylene diamine and the like.

Among these, as the cross-linking agent, an isocyanate compound is preferable from the viewpoint of being able to form an adhesive layer having excellent adhesive strength in a low temperature environment and less likely to cause zipping.

As the cross-linking agent, a commercially available product can be used.
Commercially available products of the isocyanate compound as a cross-linking agent include, for example, "Coronate HX", "Coronate HL-S", "Coronate L", "Coronate 2031", "Coronate 2030", and "Coronate 2234" manufactured by Tosoh Corporation. , "Coronate 2785", "Aquanate 200", and "Aquanate 210", "Sumijuru N3300", "Death Module N3400", and "Sumijuru N-75" manufactured by Sumika Cobestro Urethane Co., Ltd. , "Duranate E-405-80T", "Duranate 24A-100" and "Duranate TSE-100" manufactured by Asahi Kasei Corporation, and "Takenate D-110N" and "Takenate" manufactured by Mitsui Takeda Chemical Co., Ltd. Those commercially available under the trade names of "D-120N", "Takenate M-631N" and "MT-Orestar NP1200" can be preferably used.
As a commercially available epoxy compound as a cross-linking agent, for example, those commercially available under the trade names of "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc. can be preferably used.

The pressure-sensitive adhesive composition of the present invention may contain only one type of cross-linking agent, or may contain two or more types of cross-linking agents.

The content of the cross-linking agent in the pressure-sensitive adhesive composition of the present invention is not particularly limited.
For example, when the cross-linking agent is an isocyanate compound having an isocyanate group, the content of the cross-linking agent in the pressure-sensitive adhesive composition is excellent in the ability to retain the adhesive force to the adherend material containing the plasticizer in a high temperature environment, and From the viewpoint that an adhesive layer having excellent adhesive strength in a low temperature environment can be formed, the total amount of the above-mentioned specific (meth) acrylic copolymer A and specific (meth) acrylic copolymer B is 100 parts by mass. On the other hand, 1 part by mass to 8 parts by mass is preferable, and 2 parts by mass to 5 parts by mass is more preferable.
For example, when the cross-linking agent is an epoxy compound having an epoxy group, the content of the cross-linking agent in the pressure-sensitive adhesive composition is the above-mentioned specified (meth) acrylic copolymer A and specified from the same viewpoint as above. With respect to 100 parts by mass of the total amount of the (meth) acrylic copolymer B, 0.005 parts by mass to 0.08 parts by mass is preferable, and 0.01 parts by mass to 0.05 parts by mass is more preferable.

<Other ingredients>
The pressure-sensitive adhesive composition of the present invention may contain components (so-called other components) other than the components described above, if necessary, as long as the effects of the present invention are not impaired.
Other components include various additives such as cross-linking catalysts, solvents, antioxidants, colorants (eg dyes and pigments).
In the pressure-sensitive adhesive composition of the present invention, since the (meth) acrylic copolymer A described above has a carboxy group as a functional group serving as a cross-linking point, the cross-linking reaction is completed even if the cross-linking catalyst is not contained. Be made to.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is configured to have a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present invention described above.
Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present invention, the adhesive strength of the pressure-sensitive adhesive layer is reduced due to the transfer of the plasticizer from the base material to the pressure-sensitive adhesive layer in a high-temperature environment. It is an adhesive sheet that is suppressed and has excellent adhesive strength of the adhesive layer in a low temperature environment.
Further, since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition of the present invention, even if the adherend to which the pressure-sensitive adhesive sheet is attached contains a plasticizer, the pressure-sensitive adhesive sheet adheres to the adherend. The decrease in adhesive strength due to the transfer of the plasticizer to the agent layer is suppressed.

Specific examples of the pressure-sensitive adhesive sheet of the present invention include a marking film having a pressure-sensitive adhesive layer formed by applying a pressure-sensitive adhesive composition, an over-laminated film, and the like. These films are formed by applying the pressure-sensitive adhesive composition of the present invention as a pressure-sensitive adhesive solution onto a release paper (or release film) and drying to form a pressure-sensitive adhesive layer on the release paper (or release film). It can be produced by laminating the formed pressure-sensitive adhesive layer and a film as a base material.

The base material in the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but the effect of the present invention is remarkably exhibited by using a film containing a plasticizer as the base material. Further, among these, the effect of the present invention is more remarkablely exhibited by using a film containing soft vinyl chloride as a base material.
Examples of the plasticizer that can be contained in the base material in the pressure-sensitive adhesive sheet of the present invention include phthalic acid-based plasticizer, maleic acid-based plasticizer, adipic acid-based plasticizer, trimellitic acid-based plasticizer, phosphoric acid ester-based plasticizer, and polyester-based plasticizer. Examples thereof include plasticizers and epoxy-based plasticizers.

The base material in the pressure-sensitive adhesive sheet of the present invention may contain various additives such as colorants (for example, dyes and pigments), heat stabilizers, light stabilizers, fillers, antistatic agents, and flame retardants.

The thickness of the base material in the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and is preferably about 25 μm to 200 μm from the viewpoint of the strength of the pressure-sensitive adhesive sheet, for example.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably about 20 μm to 175 μm from the viewpoint of followability to irregularities, steps, etc. on the base material.

The method of applying the pressure-sensitive adhesive composition to the base material or the release film is not particularly limited, and for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, or the like is used. The method that was used is mentioned.

The use of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and for example, it can be suitably used in a mode in which at least one of the adherend material, that is, the base material and the adherend contains a plasticizer.

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

The weight average molecular weight (Mw) of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B produced in this example was measured by the method described above.
The glass transition temperature (Tg) of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B produced in this example was calculated by the method described above.

[Production of (meth) acrylic copolymer A]
[Manufacturing Example A1]
100 parts by mass of ethyl acetate was charged into a reactor equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer.
On the other hand, in another container, as a (meth) acrylic monomer having a carboxy group, 12 parts by mass of acrylic acid (AA) [equivalent to 3.0% by mass based on the total mass of the (meth) acrylic copolymer A1. , Equivalent to 7.3 mol% with respect to the (meth) acrylic copolymer A1] and 388 parts by mass of 2-ethylhexyl acrylate (2EHA) as the other monomer [total mass of the (meth) acrylic copolymer A1 Equivalent to 97.0% by mass and 92.7 mol% with respect to the (meth) acrylic copolymer A1], 400 parts by mass of a mixture was prepared. After charging 100 parts by mass of this prepared mixture into the above reactor, 0.05 part by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator. After the addition, it was heated and kept at reflux temperature (82 ° C.) for 20 minutes. Next, 300 parts by mass of the remaining mixture, 10 parts by mass of ethyl acetate, and 0.3 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) of the mixture were placed in the reactor after this retention for 60 minutes. It was dropped sequentially over. After the dropwise addition, the mixture was kept at 83 ° C. for 90 minutes, and then a mixture of 50 parts by mass of ethyl acetate and 1.0 part by mass of 2,2'-azobisisobutyronitrile (AIBN) was sequentially placed in a reactor over 60 minutes. Dropped. After the dropping, the temperature was maintained at 83 ° C. for 60 minutes, diluted with toluene so that the solid content was 40% by mass, and then cooled to obtain a solution of the (meth) acrylic copolymer A1.

[Manufacturing Example A2]
In Production Example A1, 400 parts by mass of the mixture prepared in another container was used as a (meth) acrylic monomer having a carboxy group, and 6 parts by mass of acrylic acid (AA) [(meth) acrylic copolymer A2 was completely added. Equivalent to 1.5% by mass with respect to mass, equivalent to 3.7 mol% with respect to the (meth) acrylic copolymer A2], and 2-hydroxyethyl methacrylate (2HEMA) as a (meth) acrylic monomer having a hydroxyl group. ) 6 parts by mass [equivalent to 1.5% by mass with respect to the total mass of the (meth) acrylic copolymer A2, equivalent to 2.1 mol% with respect to the (meth) acrylic copolymer A2] and other simple substances. As a weight, 388 parts by mass of 2-ethylhexyl acrylate (2EHA) [corresponding to 97.0% by mass based on the total mass of the (meth) acrylic copolymer A2, 94. A solution of the (meth) acrylic copolymer A2 was obtained in the same manner as in Production Example A1 except that the mixture was changed to 400 parts by mass of [2 mol% equivalent].

[Manufacturing Example A3]
In Production Example A1, 400 parts by mass of the mixture prepared in another container was used as a (meth) acrylic monomer having a carboxy group, and 12 parts by mass of acrylic acid (AA) [(meth) acrylic copolymer A3). Equivalent to 3.0% by mass with respect to mass, equivalent to 5.2 mol% with respect to (meth) acrylic copolymer A3] and 388 parts by mass of n-butyl acrylate (n-BA) as other monomers [ 97.0% by mass with respect to the total mass of the (meth) acrylic copolymer A3, 94.8 mol% with respect to the (meth) acrylic copolymer A3], changed to 400 parts by mass of the mixture. Except for the above, the same operation as in Production Example A1 was carried out to obtain a solution of the (meth) acrylic copolymer A3.

[Manufacturing Example A4]
In Production Example A1, 400 parts by mass of the mixture prepared in another container was used as a (meth) acrylic monomer having a carboxy group, and 12 parts by mass of acrylic acid (AA) [(meth) acrylic copolymer A4). Equivalent to 3.0% by mass with respect to mass, equivalent to 7.3 mol% with respect to (meth) acrylic copolymer A4], 2-hydroxyethyl methacrylate (2HEMA) as a (meth) acrylic monomer having a hydroxyl group. ) 6 parts by mass [equivalent to 1.5% by mass with respect to the total mass of the (meth) acrylic copolymer A4, equivalent to 2.0 mol% with respect to the (meth) acrylic copolymer A4] and other simple substances. As a weight, 382 parts by mass of 2-ethylhexyl acrylate (2EHA) [corresponding to 95.5% by mass with respect to the total mass of the (meth) acrylic copolymer A4, 90. With respect to the (meth) acrylic copolymer A4. 7 mol% equivalent] was changed to 400 parts by mass of the mixture, and the same operation as in Production Example A1 was carried out to obtain a solution of the (meth) acrylic copolymer A4.

[Manufacturing Example A5]
In Production Example A1, 400 parts by mass of the mixture prepared in another container was added to 12 parts by mass of 2-hydroxyethyl methacrylate (2HEMA) as a (meth) acrylic monomer having a hydroxyl group [(meth) acrylic copolymer A5. Equivalent to 3.0% by mass with respect to the total mass of the (meth) acrylic copolymer [equivalent to 4.2 mol% with respect to the (meth) acrylic copolymer A5] and 388 parts by mass of 2-ethylhexyl acrylate (2EHA) as other monomers [ 97.0% by mass with respect to the total mass of the (meth) acrylic copolymer A5, 95.8 mol% with respect to the (meth) acrylic copolymer A5], changed to 400 parts by mass of the mixture. Except for the above, the same operation as in Production Example A1 was carried out to obtain a solution of the (meth) acrylic copolymer A5.

Among the (meth) acrylic copolymers A1 to A5 obtained above, the (meth) acrylic copolymers A1 to A4 are configured to be derived from a (meth) acrylic monomer having at least a carboxy group. Since it contains a unit and has a weight average molecular weight of 200,000 to 2,000,000, it is included in the specific (meth) acrylic copolymer A in the present invention.

Monomer composition (unit: mass%) of (meth) acrylic copolymers A1 to A5, structural units derived from (meth) acrylic monomers having a hydroxyl group in (meth) acrylic copolymer A, and Total content a (unit: mol%) of constituent units derived from (meth) acrylic monomer having a carboxy group, weight average molecular weight (Mw, unit: 10,000), and glass transition temperature (Tg, unit: ° C.) ) Is shown in Table 1.
In Table 1, "2EHA" is "2-ethylhexyl acrylate", "n-BA" is "n-butyl acrylate", "AA" is "acrylic acid", and "2HEMA" is "2-hydroxyethyl methacrylate". Represent.

[Manufacture of (meth) acrylic copolymer B]
[Manufacturing Example B1]
A reactor equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer was charged with 237.3 parts by mass of toluene and 237.3 parts by mass of methyl ethyl ketone, and kept at the reflux temperature (90 ° C.) for 10 minutes. .. Next, in this reactor, 180 parts by mass of 2-hydroxyethyl methacrylate (2HEMA) as a (meth) acrylic monomer having a hydroxyl group [10.0 with respect to the total mass of the (meth) acrylic copolymer B1. Equivalent to mass%, equivalent to 10.8 mol% with respect to (meth) acrylic copolymer B1], and 1620 parts by mass of t-butyl methacrylate (t-BMA) as other monomers [(meth) acrylic copolymer 90.0% by mass with respect to the total mass of B1, 89.2 mol% with respect to the (meth) acrylic copolymer B1], 180.6 parts by mass of toluene, 180.6 parts by mass of methyl ethyl ketone, and polymerization initiation. A mixture of 232.4 parts by mass of 2,2'-azobis (methyl isobutyrate) as an agent was sequentially added dropwise over 180 minutes. After the dropping, the temperature was maintained at 96 ° C. for 230 minutes, diluted with ethyl acetate so that the solid content was 62% by mass, and then cooled to obtain a solution of the (meth) acrylic copolymer B1.

[Manufacturing Example B2]
In Production Example B1, the mixture dropped into the reactor was used as a (meth) acrylic monomer having a carboxy group in an amount of 180 parts by mass of acrylic acid (AA) [with respect to the total mass of the (meth) acrylic copolymer B2. Equivalent to 10.0 mass%, equivalent to 18.0 mol% with respect to the (meth) acrylic copolymer B2], and 1620 parts by mass of t-butyl methacrylate (t-BMA) as other monomers [(meth) acrylic Equivalent to 90.0% by mass with respect to the total mass of the system copolymer B2, equivalent to 82.0 mol% with respect to the (meth) acrylic copolymer B2], 180.6 parts by mass of toluene, 180.6 parts by mass of methyl ethyl ketone , And the same operation as in Production Example B1 except that the mixture was changed to a mixture of 232.4 parts by mass of 2,2'-azobis (methyl isobutyrate) as the polymerization initiator, and the (meth) acrylic copolymer was obtained. A solution of B2 was obtained.

[Manufacturing Example B3]
In Production Example B1, 180 parts by mass of 2-hydroxyethyl methacrylate (2HEMA) [(meth) acrylic copolymer B3 as a (meth) acrylic monomer having a hydroxyl group is added to the mixture dropped into the reactor. Equivalent to 10.0 mass% with respect to, 9.9 mol% with respect to the (meth) acrylic copolymer B3], and 1620 parts by mass of t-butyl acrylate (t-BA) as other monomers [(meth) ) Equivalent to 90.0% by mass with respect to the total mass of the acrylic copolymer B3, equivalent to 90.1 mol% with respect to the (meth) acrylic copolymer B3], 180.6 parts by mass of toluene, 180.6 parts by mass of methyl ethyl ketone The same operation as in Production Example B1 was carried out except that the mixture was changed to a mixture of 232.4 parts by mass of 2,2'-azobis (methyl isobutyrate) as a polymerization initiator, and the (meth) acrylic copolymer was used. A solution of polymer B3 was obtained.

[Manufacturing Example B4]
In Production Example B1, the mixture dropped into the reactor was used as another monomer in an amount of 100 parts by mass of t-butyl methacrylate (t-BMA) [(meth) acrylic copolymer B4 with respect to the total mass. Equivalent to 0% by mass, equivalent to 100.0 mol% with respect to the (meth) acrylic copolymer B4], 180.6 parts by mass of toluene, 180.6 parts by mass of methyl ethyl ketone, and 2,2'-azobis as a polymerization initiator ( A solution of the (meth) acrylic copolymer B4 was obtained in the same manner as in Production Example B1 except that the mixture was changed to a mixture of 232.4 parts by mass of methyl isobutyrate).

[Manufacturing Example B5]
70 parts by mass of ethyl acetate, 300 parts by mass of methyl ethyl ketone, ABN-V (2,2'-azobis (2,4-dimethylvalero)) in a reactor equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer. Nitrile)) 0.25 parts by mass of the mixture was charged and kept at reflux temperature (80 ° C.) for 10 minutes. Next, in this reactor, 59 parts by mass of 2-hydroxyethyl methacrylate (2HEMA) as a (meth) acrylic monomer having a hydroxyl group [10.0 with respect to the total mass of the (meth) acrylic copolymer B5. Equivalent to mass%, equivalent to 10.8 mol% with respect to (meth) acrylic copolymer B5], and 531 parts by mass of t-butyl methacrylate (t-BMA) as other monomers [(meth) acrylic copolymer 90.0% by mass with respect to the total mass of B5, 89.2 mol% with respect to the (meth) acrylic copolymer B5], 110% by mass of ethyl acetate, ABN-V (2,2'-azobis) 2,4-Dimethylvaleronitrile)) 4 parts by mass of the mixture was sequentially added dropwise over 120 minutes. After dropping at 83 ° C. for 60 minutes after dropping, a mixture of 80 parts by mass of ethyl acetate and 1.5 parts by mass of ABN-V (2,2'-azobis (2,4-dimethylvaleronitrile)) was added over 30 minutes. It was dropped sequentially. After the dropping, the temperature was maintained at 84 ° C. for 90 minutes and then cooled to obtain a solution of the (meth) acrylic copolymer B5.

Among the (meth) acrylic copolymers B1 to B5 obtained above, the (meth) acrylic copolymers B1 to B3 are (meth) acrylic monomers having at least one of a hydroxyl group and a carboxy group. It is included in the specific (meth) acrylic copolymer B in the present invention because it contains a structural unit derived from the above and has a weight average molecular weight of 40,000 to 20,000.

Monomer composition (unit: mass%) of (meth) acrylic copolymers B1 to B5, structural units derived from (meth) acrylic monomer having a hydroxyl group in (meth) acrylic copolymer B, and Total content b (unit: mol%) of constituent units derived from (meth) acrylic monomer having a carboxy group, weight average molecular weight (Mw, unit: 10,000), and glass transition temperature (Tg, unit: ° C.) ) Is shown in Table 2.
In Table 2, "t-BMA" is "t-butyl methacrylate", "t-BA" is "t-butyl acrylate", "AA" is "acrylic acid", and "2HEMA" is "2-hydroxyethyl methacrylate". ".

[Preparation of adhesive composition]
<Example 1>
A solution of 192.3 parts by mass (solid content: 76.9 parts by mass) of the (meth) acrylic copolymer A1 produced in Production Example A1 and a (meth) acrylic copolymer produced in Production Example B1. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 1.

<Example 2>
178.5 parts by mass (solid content: 71.4 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B1. 46.1 parts by mass (solid content: 28.6 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 2.

<Example 3>
156.3 parts by mass (solid content: 62.5 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B1. 60.5 parts by mass (solid content: 37.5 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 3.

<Example 4>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B2. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B2 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 4.

<Example 5>
A solution of 192.3 parts by mass (solid content: 76.9 parts by mass) of the (meth) acrylic copolymer A2 produced in Production Example A2 and the (meth) acrylic copolymer produced in Production Example B1. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 5.

<Example 6>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A3 produced in Production Example A3 and the (meth) acrylic copolymer produced in Production Example B1. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 6.

<Example 7>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B3. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B3 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 7.

<Example 8>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B1. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B1 was mixed, and TETRAD-X [trade name, epoxy compound, Mitsubishi Gas Chemicals Co., Ltd.] was used as a cross-linking agent for the obtained solution. )] 0.6 parts by mass (solid content: 0.03 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Example 8.

<Comparative example 1>
Coronate (registered trademark) L [trade name, isocyanate compound, Tosoh] was used as a cross-linking agent for 250 parts by mass (solid content: 100 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare a pressure-sensitive adhesive composition of Comparative Example 1.

<Comparative example 2>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A4 produced in Production Example A4 and the (meth) acrylic copolymer produced in Production Example B4. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B4 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare a pressure-sensitive adhesive composition of Comparative Example 2.

<Comparative example 3>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A5 produced in Production Example A5 and the (meth) acrylic copolymer produced in Production Example B1. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B1 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare a pressure-sensitive adhesive composition of Comparative Example 3.

<Comparative example 4>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A5 produced in Production Example A5 and the (meth) acrylic copolymer produced in Production Example B2. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B2 was mixed, and the obtained solution was subjected to a copolymer (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Comparative Example 4.

<Comparative example 5>
192.3 parts by mass (solid content: 76.9 parts by mass) of the solution of the (meth) acrylic copolymer A1 produced in Production Example A1 and the (meth) acrylic copolymer produced in Production Example B5. 37.3 parts by mass (solid content: 23.1 parts by mass) of the solution of B5 and coronate (registered trademark) L [trade name, isocyanate compound, Tosoh (trade name)) were mixed with the obtained solution as a cross-linking agent. Co., Ltd.] 7.51 parts by mass (solid content: 3.38 parts by mass) was added and mixed to prepare the pressure-sensitive adhesive composition of Comparative Example 5.

[Preparation of adhesive sheet for evaluation]
The pressure-sensitive adhesive composition prepared above is applied onto a silicone-treated PET film (trade name: film binar, thickness: 100 μm, Fujimori Kogyo Co., Ltd.) after drying to a coating amount of 25 g / m ^2. After applying the pressure-sensitive adhesive composition as described above, the pressure-sensitive adhesive composition was dried at 100 ° C. for 1 minute using a hot air dryer to form a pressure-sensitive adhesive layer. Next, soft vinyl chloride (trade name: 00178M7, containing 30% by mass of an adipic acid-based plasticizer, thickness: 75 μm, Nippon Carbide) as a base material was contained on the surface of the pressure-sensitive adhesive layer of the PET film on which the pressure-sensitive adhesive layer was formed. An adhesive sheet for evaluation was obtained by sticking it on one side of Kogyo Co., Ltd. and curing it in an environment of 23 ° C. and a relative humidity of 50% for 7 days.

[Evaluation]
1. 1. Measurement of Adhesive Strength in Room Temperature Environment The evaluation adhesive sheet prepared above was cut into 25 mm × 150 mm. Next, the silicone-treated PET film of the cut evaluation adhesive sheet was peeled off, and the adhesive layer was SUS (stainless steel) in an environment of room temperature (23 ° C.) and relative humidity of 50% using a 2 kg rubber roller. It was crimped to a steel plate to prepare a test sample. After leaving this test sample in an environment of 23 ° C. and 50% relative humidity for 24 hours, the adhesive strength when the evaluation adhesive sheet is peeled off from the SUS plate together with the adhesive layer is measured by A & D Co., Ltd. -Measurement was performed using an And-D single column type material tester STA-1225 under the conditions of a peeling angle of 180 ° and a peeling speed of 0.3 m / min in an environment of 23 ° C. and a relative humidity of 50%. The results are shown in Table 3.

2. 2. Evaluation of Adhesive Retaining Ability in High Temperature Environment By measuring the adhesive strength after curing in a high temperature (95 ° C) environment and comparing it with the adhesive strength in a normal temperature (23 ° C) environment, adhesion containing a plasticizer Evaluate whether the decrease in the adhesive strength of the pressure-sensitive adhesive layer is suppressed even in a high-temperature environment where the plasticizer easily migrates from the material to the pressure-sensitive adhesive layer (that is, whether it has the adhesive strength retaining ability even in a high-temperature environment). did. Specifically, the test sample prepared in the above "1. Measurement of adhesive strength in a normal temperature environment" was left to stand in an environment of 23 ° C. and a relative humidity of 50% for 24 hours, and then 96 in an environment of 95 ° C. After curing for hours, it was left to stand again in an environment of 23 ° C. and 50% relative humidity for 24 hours. The adhesive strength of the test sample after being left to stand when the evaluation adhesive sheet is peeled off from the SUS plate together with the adhesive layer (that is, the adhesive strength after curing in a high temperature environment) is measured by A & D Co., Ltd. as a measuring device. The measurement was performed using a single column type material tester STA-1225 of A & D under the conditions of a peeling angle of 180 ° and a peeling speed of 0.3 m / min in an environment of 23 ° C. and a relative humidity of 50%. Then, the rate of decrease in the adhesive strength when the adhesive strength after curing in a high temperature environment is compared with the above adhesive strength in a normal temperature environment is calculated, and the adhesive strength holding ability in a high temperature environment is calculated according to the following evaluation criteria. Was evaluated. The results are shown in Table 3.
If the evaluation result is "A", "B", or "C", it is judged that the evaluation result is within the practically acceptable range.

-Evaluation criteria-
A: The rate of decrease in adhesive strength is less than 20%.
B: The rate of decrease in adhesive strength is 20% or more and less than 30%.
C: The rate of decrease in adhesive strength is 30% or more and less than 50%.
D: The rate of decrease in adhesive strength is 50% or more.

3. 3. Measurement of Adhesive Strength in Low Temperature Environment The evaluation adhesive sheet prepared above was cut into 25 mm × 150 mm. Next, the silicone-treated PET film of the cut evaluation pressure-sensitive adhesive sheet was peeled off, and the pressure-sensitive adhesive layer was BA (bright-annealed)-treated using a 2 kg rubber roller in an environment of 5 ° C. Hereinafter, it was crimped so as to be in contact with the surface of the “BA-SUS plate”) to prepare a test sample. After leaving this test sample in an environment of 5 ° C. for 1 minute, the adhesive strength when the evaluation adhesive sheet was peeled off from the BA-SUS plate together with the adhesive layer was measured by A & D Co., Ltd. as a measuring device. Using the day's single column type material tester STB-1225, the measurement was performed under the conditions of a peeling angle of 180 ° and a peeling speed of 0.3 m / min in an environment of 5 ° C. The results are shown in Table 3.
If the evaluation result is "A", "B", or "C", it is judged that the evaluation result is within the practically acceptable range.

-Evaluation criteria-
A: The maximum adhesive strength exceeds 20 N / 25 mm.
B: The maximum adhesive strength exceeds 10 N / 25 mm and is 20 N / 25 mm or less.
C: The maximum adhesive strength exceeds 5N / 25mm and is 10N / 25mm or less.
D: The maximum adhesive strength is 5 N / 25 mm or less.

In Table 3, "-" means that the corresponding component is not blended.
In Table 3, "a structural unit derived from a (meth) acrylic monomer having a hydroxyl group and a structural unit derived from a (meth) acrylic monomer having a carboxy group in the (meth) acrylic copolymer A. A structural unit derived from a (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer B and a (meth) acrylic single amount having a carboxy group with respect to the total content a (unit: mol%). The ratio of the total content rate b (unit: molar%) of the constituent units derived from the body (total content rate b / total content rate a) "is" the ratio of the total content rate b to the total content rate a [b / a]. Is written.

As shown in Table 3, all of the pressure-sensitive adhesive layers obtained from the pressure-sensitive adhesive compositions of Examples 1 to 8 have excellent adhesive strength retention ability in a high temperature environment and adhesive strength in a low temperature environment. Was also excellent.
On the other hand, the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of Comparative Example 1 containing only the specific (meth) acrylic-based copolymer A as the (meth) acrylic-based copolymer is a specific (meth) acrylic-based copolymer. Compared with the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of Example (for example, Example 1) containing both the polymer A and the specific (meth) acrylic copolymer B, in a high temperature environment. The adhesive strength retention ability was significantly inferior.
Obtained from the pressure-sensitive adhesive composition of Comparative Example 2 in which the (meth) acrylic copolymer A has both a hydroxyl group and a carboxy group, and the (meth) acrylic copolymer B has neither a hydroxyl group nor a carboxy group. The adhesive layer had a low ability to retain adhesive strength in a high temperature environment.
The pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of Comparative Example 3 in which the (meth) acrylic copolymer A does not have a carboxy group is an example in which the (meth) acrylic copolymer A has a carboxy group (for example). The adhesive strength in a low temperature environment was significantly inferior to that of the adhesive layer obtained from the adhesive composition of Example 1).
From the pressure-sensitive adhesive composition of Comparative Example 4 containing a (meth) acrylic copolymer A having a hydroxyl group and no carboxy group and a (meth) acrylic copolymer B having a carboxy group. The obtained pressure-sensitive adhesive layer contains Examples (for example, Example 4) containing a (meth) acrylic copolymer A having a carboxy group and a (meth) acrylic copolymer B having a carboxy group. The adhesive strength in a low temperature environment was significantly inferior to that of the adhesive layer obtained from the adhesive composition of. In addition, the adhesive strength retention ability in a high temperature environment was also low.
The pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of Comparative Example 5 in which the weight-average molecular weight of the (meth) acrylic copolymer B is 60,000 has a weight-average molecular weight of 0 for the (meth) acrylic-based copolymer B. The adhesive strength in a low temperature environment was significantly inferior to that of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of Example (for example, Example 1) in the range of 40,000 to 20,000. ..

Claims (6)

A (meth) acrylic copolymer A containing a structural unit derived from a (meth) acrylic monomer having a carboxy group and having a weight average molecular weight of 200,000 to 2 million,
A (meth) acrylic copolymer B containing a structural unit derived from a (meth) acrylic monomer having at least one of a hydroxyl group and a carboxy group and having a weight average molecular weight of 5,000 to 20,000.
Crosslinker and
Contains,
The total content of the structural unit derived from the (meth) acrylic monomer having a hydroxyl group and the structural unit derived from the (meth) acrylic monomer having a carboxy group in the (meth) acrylic copolymer B b (Unit: mol%) is derived from the structural unit derived from the (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer A and the (meth) acrylic monomer having a carboxy group. More than the total content a (unit: molar%) of the constituent units
The glass transition temperature of the (meth) acrylic copolymer A is -80 ° C to -60 ° C, and the glass transition temperature of the (meth) acrylic copolymer B is 75 ° C to 130 ° C. Yes,
The cross-linking agent is either an isocyanate compound having an isocyanate group or an epoxy compound having an epoxy group.
When the cross-linking agent is an isocyanate compound having an isocyanate group, the content of the cross-linking agent is 100 parts by mass of the total amount of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B. 2 to 5 parts by mass,
When the cross-linking agent is an epoxy compound having an epoxy group, the content of the cross-linking agent is 100 parts by mass of the total amount of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B. The pressure-sensitive adhesive composition for a film, which is 0.01 parts by mass to 0.05 parts by mass. The total content a of the structural units derived from the (meth) acrylic monomer having a hydroxyl group and the structural unit derived from the (meth) acrylic monomer having a carboxy group in the (meth) acrylic copolymer A. Derived from the structural unit derived from the (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic copolymer B and the (meth) acrylic monomer having a carboxy group with respect to (unit: mol%). The pressure-sensitive acrylic composition for a film according to claim 1, wherein the ratio of the total content rate b (unit: mol%) of the constituent units is more than 1 and 3 or less. The film pressure-sensitive adhesive composition according to claim 1 or 2, wherein the (meth) acrylic copolymer B contains a structural unit derived from a (meth) acrylic monomer having a hydroxyl group. The ratio of the content of the (meth) acrylic copolymer A to the total content of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B is 0. The adhesive composition for a film according to any one of claims 1 to 3, which is 5 to 0.8. The film pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth) acrylic copolymer A contains a structural unit derived from 2-ethylhexyl acrylate. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition for a film according to any one of claims 1 to 5.