JP7081817B2 - Adhesive composition for optical member protective film and optical member protective film - Google Patents

Description

The present invention relates to an adhesive composition for an optical member protective film and an optical member protective film.

In order to protect the surface of various articles, a protective film provided with an adhesive layer is widely used. In particular, protective films are often used in various optical members represented by polarizing plates.

For example, Patent Document 1 describes (A) a (meth) acrylic polymer having a glass transition temperature of −40 ° C. or lower, which is obtained by copolymerizing at least a (meth) acrylic acid alkyl ester and a functional group-containing monomer, (B) ( It contains a (meth) acrylic polymer containing a meta) acrylic acid alkyl ester as a main component and having a glass transition temperature of 80 ° C. or higher, and (C) a cross-linking agent. Disclosed is a pressure-sensitive adhesive for a protective sheet obtained by subjecting a crosslinkable composition containing 5 to 20 parts by weight to a crosslink reaction so as to have a gel content of 80% or more.
Further, Patent Document 2 describes 100 parts by mass of a polymer (A) having a glass transition temperature of less than 0 ° C., a weight average molecular weight of 1000 or more and less than 50,000, and a (meth) acrylic having a glass transition temperature of 30 to 300 ° C. A pressure-sensitive adhesive composition containing 0.05 to 3 parts by mass of the system polymer (B) and an organopolysiloxane compound (C) having a specific structure having a polyoxyalkylene chain is disclosed.
Further, Patent Document 3 describes a (meth) acrylic polymer having a hydroxy group and having an acid value of 0 mgKOH / g or more and less than 16 mgKOH / g, and an alkylene oxide having an acid value of 0.1 mgKOH / g or more and 40 mgKOH / g or less. A pressure-sensitive adhesive composition containing a chain-containing (meth) acrylic oligomer, a polyether-modified silicone having a reactive group, a cross-linking agent, and an ionic compound is disclosed.

Japanese Unexamined Patent Publication No. 2005-146151 Japanese Unexamined Patent Publication No. 2013-216769 Japanese Unexamined Patent Publication No. 2017-128636

The adhesive composition used for the protective film used for the optical member (hereinafter, also referred to as "adhesive composition for the optical member protective film") is protected after the protective film is attached to the surface of the optical member. It is required that a pressure-sensitive adhesive layer that can be efficiently peeled off from the optical member can be formed at a stage where problems such as peeling and misalignment from the optical member are unlikely to occur and protection is no longer required for the necessary period. Here, the fact that the adhesive layer is less likely to cause problems such as peeling from the optical member and slippage is that the adhesive force measured when the protective film is peeled from the optical member at a low speed (0.3 m / min) (so-called). , Low speed peeling force). Further, the adhesive layer that can be efficiently peeled from the optical member can be evaluated by the adhesive force (so-called high-speed peeling force) measured when the protective film is peeled from the optical member at a high speed (30 m / min).

By the way, when the protective film is peeled off from the optical member, a phenomenon called zipping (hereinafter, also referred to as “zipping phenomenon”) may occur in which the protective film is peeled off without being smoothly peeled off with a crackling noise. When the zipping phenomenon occurs, streak-like defects may be confirmed on the surface of the optical member after the protective film is peeled off. Therefore, it is also required that the pressure-sensitive adhesive composition for an optical member protective film can form a pressure-sensitive adhesive layer capable of suppressing the zipping phenomenon.

Further, the pressure-sensitive adhesive composition for an optical member protective film is required to be able to form a highly transparent pressure-sensitive adhesive layer so that the appearance of the optical member can be confirmed with the protective film attached.

However, when trying to control the low-speed peeling force and the high-speed peeling force of the adhesive layer included in the protective film, both exhibit the same behavior, and it is difficult to adjust the balance between the low-speed peeling force and the high-speed peeling force.
Further, in recent years, from the viewpoint of further improving workability, the peeling speed of the protective film from the optical member tends to be faster. In addition, as the optical member becomes thinner, surface defects of the optical member due to the zipping phenomenon at the time of peeling of the protective film tend to occur more easily. The zipping phenomenon is said to occur due to the strength of the adhesive force of the adhesive layer. In general, the adhesive strength of the pressure-sensitive adhesive layer tends to increase as the peeling speed increases, so that the zipping phenomenon is likely to occur when the protective film is peeled from the optical member at high speed.
Therefore, the optical member protection capable of forming an adhesive layer having a good balance between low-speed peeling force and high-speed peeling force, less likely to cause a zipping phenomenon when peeling at high speed, and excellent transparency. It has been difficult to realize a pressure-sensitive adhesive composition for films.

The problem to be solved by the present invention is that the balance between the low-speed peeling force and the high-speed peeling force is good, the zipping phenomenon that may occur when the low-speed peeling force is peeled off is sufficiently suppressed, and the adhesive layer has excellent transparency. It is an object of the present invention to provide a pressure-sensitive adhesive composition for an optical member protective film capable of forming the above, and an optical member protective film.

Specific means for solving the problem include the following aspects.
<1> Containing a structural unit derived from n-butyl acrylate and a structural unit derived from a monomer having a hydroxyl group, the glass transition temperature is −40 ° C. or lower, and the weight average molecular weight is 200,000 or more and 2 million or less. (Meta) acrylic copolymer (A), which is in the range of
It contains a structural unit derived from n-butyl methacrylate and a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature in the range of 0 ° C. or higher and 45 ° C. or lower, and has a weight average molecular weight of 10,000 or more and 200,000. With the (meth) acrylic copolymer (B) in the following range,
Contains isocyanate-based cross-linking agents,
The content of the (meth) acrylic copolymer (B) is in the range of 1 part by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). Adhesive composition for protective film.
<2> The content of the structural unit derived from the n-butyl methacrylate in the (meth) acrylic copolymer (B) is higher than that of all the structural units of the (meth) acrylic copolymer (B). , The pressure-sensitive adhesive composition for an optical member protective film according to <1>, which is 50% by mass or more.
<3> The content of the structural unit derived from the n-butyl acrylate in the (meth) acrylic copolymer (A) is higher than that of all the structural units of the (meth) acrylic copolymer (A). , The pressure-sensitive adhesive composition for an optical member protective film according to <1> or <2>, which is 50% by mass or more.
<4> The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (A) becomes the total structural unit of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition for an optical member protective film according to any one of <1> to <3>, which is in the range of 0.7% by mass or more and 15% by mass or less.
<5> The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (B) becomes the total structural unit of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition for an optical member protective film according to any one of <1> to <4>, which is in the range of 0.7% by mass or more and 15% by mass or less.
<6> The content of the (meth) acrylic copolymer (B) is in the range of 3 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition for an optical member protective film according to any one of <1> to <5>.
<7> The optical member protective film according to any one of <1> to <6>, wherein the weight average molecular weight of the (meth) acrylic copolymer (B) is in the range of 10,000 or more and 150,000 or less. Adhesive composition for.
<8> The pressure-sensitive adhesive composition for an optical member protective film according to any one of <1> to <7>, wherein the isocyanate-based cross-linking agent is hexamethylene diisocyanate.
<9> A base material, a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition for an optical member protective film according to any one of <1> to <8>. Optical member protective film.

According to the present invention, the optics can form a pressure-sensitive adhesive layer having a good balance between low-speed peeling force and high-speed peeling force, sufficiently suppressing the zipping phenomenon that may occur when peeling at high speed, and having excellent transparency. A pressure-sensitive adhesive composition for a member protective film and an optical member protective film 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 one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
In the present specification, a combination of two or more preferred embodiments is a more preferred embodiment.
In the present specification, the amount of each component means the total amount of a plurality of kinds of substances when there are a plurality of kinds of substances corresponding to each component, unless otherwise specified.

As used herein, the term "(meth) acrylic copolymer" means that the content of the structural units derived from the monomer having a (meth) acryloyl group is the total structural unit (that is, the (meth) acrylic polymer). It means a copolymer which is 50% by mass or more of (all constituent units of).

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

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

As used herein, the term "adhesive composition" means a liquid or paste-like substance before the cross-linking reaction is completed.
As used herein, the term "adhesive layer" means a film made of a substance after the cross-linking reaction in the pressure-sensitive adhesive composition is completed.
As used herein, the term "adhesive body" refers to an optical member.

In the present specification, the "low-speed peeling force" means that the protective film attached to the adherend is peeled 180 ° from the adherend in the longitudinal direction of the protective film at a low speed (that is, 0.3 m / min). Means the adhesive strength measured in. The detailed measurement method is as shown in Examples described later.
In the present specification, the "appropriate low-speed peeling force" means an adhesive force having a strength to such an extent that defects such as peeling and slippage from the adherend are unlikely to occur.

In the present specification, the "high-speed peeling force" is measured when the protective film attached to the adherend is peeled 180 ° from the adherend in the longitudinal direction of the protective film at high speed (that is, 30 m / min). It means the adhesive strength to be applied. The detailed measurement method is as shown in Examples described later.
As used herein, the term "appropriate high-speed peeling force" means an adhesive force having a strength that allows efficient peeling from an adherend.

In the present specification, the "adhesive layer having a good balance between low-speed peeling force and high-speed peeling force" means that problems such as peeling and slippage from the adherend are unlikely to occur, and the adhesive layer is efficiently peeled from the adherend. It means an adhesive layer having an adhesive strength as strong as possible.

In the present specification, the "optical member protective film" is also simply referred to as a "protective film".

[Adhesive composition for optical member protective film]
The pressure-sensitive adhesive composition for an optical member protective film of the present invention (hereinafter, also simply referred to as “pressure-sensitive adhesive composition”) includes a structural unit derived from n-butyl acrylate and a structural unit derived from a monomer having a hydroxyl group. (Meta) acrylic copolymer (A) [hereinafter, specific (meth) acrylic copolymer, which contains, has a glass transition temperature of −40 ° C. or lower, and has a weight average molecular weight in the range of 200,000 or more and 2 million or less. Also referred to as "polymer (A)". ], A structural unit derived from n-butyl methacrylate and a structural unit derived from a monomer having a hydroxyl group, the glass transition temperature is in the range of 0 ° C. or higher and 45 ° C. or lower, and the weight average molecular weight is 10,000. The (meth) acrylic copolymer (B) in the range of 200,000 or less [hereinafter, also referred to as a specific (meth) acrylic copolymer (B)]. ] And an isocyanate-based cross-linking agent, and the content of the specific (meth) acrylic copolymer (B) is 1 mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It is in the range of 70 parts by mass or more and 70 parts by mass or less.
According to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive having a good balance between low-speed peeling force and high-speed peeling force, sufficiently suppressing the zipping phenomenon that may occur when peeling at high speed, and having excellent transparency. Layers can be formed.
Although it is not clear why the pressure-sensitive adhesive composition of the present invention may exert such an effect, the present inventors speculate as follows. However, the following speculation does not limitly interpret the pressure-sensitive adhesive composition of the present invention, but is described as an example.

The specific (meth) acrylic copolymer (B) contained in the pressure-sensitive adhesive composition of the present invention has a glass transition temperature of 0 ° C. or higher and a weight average molecular weight of 10,000 or more and 200,000 or less. .. Further, the content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The range is 70 parts by mass or less. Therefore, in the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, the specific (meth) acrylic copolymer (B) is appropriately localized near the surface (so-called interface with the adherend). It is thought that it will be localized. When the specific (meth) acrylic copolymer (B) is appropriately localized near the interface with the adherend in the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer does not become excessively wetted with the adherend. It is presumed that the layer exhibits an appropriate high speed peeling force. Further, since the glass transition temperature of the specific (meth) acrylic copolymer (B) is 45 ° C. or lower, it is considered that the pressure-sensitive adhesive layer is appropriately wetted with respect to the adherend. Therefore, in the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, it is presumed that the zipping phenomenon caused by insufficient wetting of the pressure-sensitive adhesive layer with respect to the adherend is suppressed.

The specific (meth) acrylic copolymer (A) contained in the pressure-sensitive adhesive composition of the present invention has a glass transition temperature of −40 ° C. or lower and a weight average molecular weight of 200,000 or more and 2 million or less. be. Therefore, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention exhibits an appropriate low-speed peeling force. Further, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention sufficiently suppresses the zipping phenomenon that may occur when the pressure-sensitive adhesive layer is peeled off at high speed.

The pressure-sensitive adhesive composition of the present invention contains a specific (meth) acrylic copolymer (A) and a specific (meth) acrylic copolymer (B) having different monomer compositions.
In general, a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing two or more copolymers having different monomer compositions tends to have a problem of a decrease in transparency (so-called increase in haze).
The specific (meth) acrylic copolymer (A) contained in the pressure-sensitive adhesive composition of the present invention contains a structural unit derived from n-butyl acrylate, and the specific (meth) acrylic copolymer (B) is , N-Contains building blocks derived from butyl methacrylate. Since the specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B) both contain a structural unit derived from a monomer having an n-butyl group, they are compatible with each other. Shows a tendency to be good. Therefore, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention is excellent in transparency.

The specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B) contained in the pressure-sensitive adhesive composition of the present invention are both derived from a monomer having a hydroxyl group. Since it contains a structural unit, it properly cross-links with an acrylic cross-linking agent. Therefore, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention has a good balance between the low-speed peeling force and the high-speed peeling force. Further, it is presumed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention sufficiently suppresses the zipping phenomenon that may occur when the pressure-sensitive adhesive layer is peeled off at high speed.

For the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive for a protective sheet described in Patent Document 1 (Japanese Patent Laid-Open No. 2005-146151; hereinafter the same) contains two types of (meth) acrylic polymers. However, since the glass transition temperature (Tg) of the (meth) acrylic polymer of the component (B) is 80 ° C. or higher, the adhesive layer formed is insufficiently wetted with respect to the adherend, for example, peeling off. High-speed peeling at a speed of 30 m / min does not sufficiently suppress the zipping phenomenon.
The pressure-sensitive adhesive composition described in Patent Document 2 (Japanese Unexamined Patent Publication No. 2013-216769; the same applies hereinafter) contains two types of copolymers, but is a glass of a (meth) acrylic polymer (B). Since the transition temperature (Tg) is 59 ° C. or higher, the formed pressure-sensitive adhesive layer is insufficiently wetted with respect to the adherend, as in the case of the pressure-sensitive adhesive for a protective sheet described in Patent Document 1, for example, peeling. High-speed peeling at a speed of 30 m / min does not sufficiently suppress the zipping phenomenon. Further, since the two types of copolymers contained in the pressure-sensitive adhesive composition described in Patent Document 2 have significantly different monomer compositions, the transparency of the pressure-sensitive adhesive layer is not sufficient.
The pressure-sensitive adhesive composition described in Patent Document 3 (Japanese Unexamined Patent Publication No. 2017-128636) contains two types of (meth) acrylic copolymers, but is a (meth) acrylic copolymer corresponding to an oligomer. Since the alkylene oxide chain is contained in the resin, it is considered that the wettability of the formed pressure-sensitive adhesive layer to the adherend is promoted too much, and the high-speed peeling force becomes excessively high. Therefore, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition described in Patent Document 3 does not have a good balance between the low-speed peeling force and the high-speed peeling force (see, for example, Comparative Example 16 described later).

Hereinafter, in the present specification, "specific (meth) acrylic copolymer (A) and specific (meth) acrylic copolymer (B)" are collectively referred to as "specific (meth) acrylic copolymer". It is called.

[Specific (meth) acrylic copolymer (A)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from n-butyl acrylate and a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature of −40 ° C. or lower, and has a weight average molecular weight of −40 ° C. or lower. The (meth) acrylic copolymer (A) [that is, the specific (meth) acrylic copolymer (A)] in the range of 200,000 or more and 2 million or less is included.

<Constituent unit derived from n-butyl acrylate>
The specific (meth) acrylic copolymer (A) contains a structural unit derived from n-butyl acrylate.
As used herein, the term "constituent unit derived from n-butyl acrylate" means a structural unit formed by addition polymerization of n-butyl acrylate.

The content (ratio) of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic copolymer (A) is not particularly limited.
The content (ratio) of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic copolymer (A) is, for example, the content (ratio) of the structural unit derived from the specific (meth) acrylic copolymer (A) with respect to all the structural units of the specific (meth) acrylic copolymer (A). It is preferably 40% by mass or more, more preferably 45% by mass or more, and further preferably 50% by mass or more.
The content (ratio) of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic copolymer (A) is 40 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is by mass% or more, the compatibility with the (meth) acrylic copolymer (B) becomes better, so that there is a tendency that a pressure-sensitive adhesive layer in which haze is more suppressed can be formed.
Further, the content rate (ratio) of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic copolymer (A) is, for example, the total structural unit of the specific (meth) acrylic copolymer (A). However, it is preferably 70% by mass or less.
The content (ratio) of the structural unit derived from n-butyl acrylate in the specific (meth) acrylic copolymer (A) is 70 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is mass% or less, there is a tendency that a pressure-sensitive adhesive layer having a better balance between the low-speed peeling force and the high-speed peeling force can be formed.

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

The type of the monomer having a hydroxyl group is not particularly limited.
Specific examples of the monomer having a hydroxyl group include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-. Hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1 -Dimethyl-3-hydroxybutyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3- Examples thereof include hydroxyhexyl (meth) acrylate, hydroxyalkyl (meth) acrylate such as N-hydroxyethyl (meth) acrylamide, 1,4-cyclohexanedimethanol monoacrylate, dicaprolactone 2-acryloyloxy-ethyl ether and the like.
Among these, as the monomer having a hydroxyl group, for example, hydroxyalkyl (meth) acrylate is preferable from the viewpoint of good copolymerizability with n-butyl acrylate.
The hydroxyalkyl (meth) acrylate has, for example, the number of carbon atoms from the viewpoint of good compatibility and copolymerizability with n-butyl acrylate and good reactivity with an isocyanate-based cross-linking agent. A hydroxyalkyl (meth) acrylate having a hydroxyalkyl group of 1 to 5 is preferable, and a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable.

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

The content (ratio) of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is not particularly limited, but is, for example, the specific (meth) acrylic copolymer (A). ), The range is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.7% by mass or more and 15% by mass or less, and 1% by mass or more. It is more preferably in the range of 10% by mass or less.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is 0. When it is 1% by mass or more, it means that the specific (meth) acrylic copolymer (A) positively contains a structural unit derived from a monomer having a hydroxyl group.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (A) is 20 mass with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is less than%, it tends to be possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when peeling at high speed is more sufficiently suppressed. In addition, there is a tendency to form a pressure-sensitive adhesive layer that is more transparent.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer different from n-butyl acrylate>
The specific (meth) acrylic copolymer (A) is a (meth) acrylic acid alkyl ester monomer different from n-butyl acrylate [hereinafter, another (meth) acrylic acid alkyl ester monomer (a)]. Also called. ] It is preferable to include a structural unit derived from.
The structural unit derived from the other (meth) acrylic acid alkyl ester monomer (a) contributes to the adjustment of the adhesive strength of the pressure-sensitive adhesive layer.

In the present specification, the “constituent unit derived from another (meth) acrylic acid alkyl ester monomer (a)” is an addition polymerization of another (meth) acrylic acid alkyl ester monomer (a). It means a structural unit to be formed.

The type of the other (meth) acrylic acid alkyl ester monomer (a) is not particularly limited as long as it is a (meth) acrylic acid alkyl ester monomer different from n-butyl acrylate.
As the other (meth) acrylic acid alkyl ester monomer (a), an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable.
The alkyl group of the other (meth) acrylic acid alkyl ester monomer (a) may be linear, branched or cyclic.
Further, the carbon number of the alkyl group is preferably 1 to 18 from the viewpoint of the adhesive force of the formed pressure-sensitive adhesive layer to the adherend and the adhesion to the base material of the protective film, preferably 1 to 12. It is more preferable to have.

Examples of the other (meth) acrylic acid alkyl ester monomer (a) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl methacrylate, i-butyl (meth) acrylate, and s-butyl (meth) acrylate. , T-butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n -Decil (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate and the like can be mentioned.
Among these, as the other (meth) acrylic acid alkyl ester monomer (a), for example, the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) is adjusted to −40 ° C. or lower. 2-Ethylhexyl acrylate (2EHA) is preferable from the viewpoint of ease of use.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from the other (meth) acrylic acid alkyl ester monomer (a), the other (meth) acrylic acid alkyl ester monomer Only one type of structural unit derived from (a) may be contained, or two or more types may be contained.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from another (meth) acrylic acid alkyl ester monomer (a), in the specific (meth) acrylic copolymer (A). The content (ratio) of the structural unit derived from the other (meth) acrylic acid alkyl ester monomer (a) is, for example, relative to all the structural units of the specific (meth) acrylic copolymer (A). It is preferably in the range of 10% by mass or more and 59.9% by mass or less, more preferably in the range of 15% by mass or more and 50% by mass or less, and further preferably in the range of 20% by mass or more and 40% by mass or less. preferable.

<Constituent unit derived from a monomer having a carboxy group>
The specific (meth) acrylic copolymer (A) may contain a structural unit derived from a monomer having a carboxy group.
When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group, the high-speed peeling force of the formed pressure-sensitive adhesive layer is reduced, and the low-speed peeling force and the high-speed peeling force are reduced. It tends to be better balanced with force.

As used herein, the term "constituent unit derived from a monomer having a carboxy group" means a structural unit formed by addition polymerization of a monomer having a carboxy group.

The type of the monomer having a carboxy group is not particularly limited.
Specific examples of the monomer having a carboxy group include acrylic acid (AA), methacrylic acid (MAA), crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, and ω-carboxy-polycaprolactone. Examples thereof include mono (meth) acrylate (for example, ω-carboxy-polycaprolactone (n≈2) monoacrylate), succinic acid ester (for example, 2-acryloyloxyethyl-succinic acid) and the like.
Among these, acrylic acid (AA) is preferable as the monomer having a carboxy group, for example, from the viewpoint of good reactivity with an isocyanate-based cross-linking agent.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group, the specific (meth) acrylic copolymer (A) may contain only one structural unit derived from the monomer having a carboxy group. Well, it may contain two or more kinds.

When the specific (meth) acrylic copolymer (A) contains a structural unit derived from a monomer having a carboxy group, the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is used. The content rate (ratio) of the derived structural units is preferably in the range of 0.1% by mass or more and 5% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer (A). It is more preferably in the range of 0.3% by mass or more and 3% by mass or less, and further preferably in the range of 0.5% by mass or more and 1.5% by mass or less.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is 0 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is 1% by mass or more, the high-speed peeling force of the formed pressure-sensitive adhesive layer tends to be further lowered.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (A) is 5 with respect to all the structural units of the specific (meth) acrylic copolymer (A). When it is less than the mass%, it tends to be possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when the material is peeled off at high speed is more sufficiently suppressed.

<Other building blocks>
The specific (meth) acrylic copolymer (A) is a structural unit derived from the above-mentioned structural unit, that is, n-butyl acrylate, which is an essential structural unit, within the range in which the effect of the present invention is exhibited. A structural unit derived from a monomer having a hydroxyl group, a structural unit derived from another (meth) acrylic acid alkyl ester monomer (a) which is an arbitrary structural unit, and a structural unit other than the structural unit having a carboxy group. Units (so-called other structural units) may be included.

The monomer constituting the other structural unit is not particularly limited as long as it can be copolymerized with the monomer constituting the above-mentioned structural unit.
As the monomer constituting the other structural unit, for example, it has a cyclic group represented by cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, and phenoxyethyl (meth) acrylate (meth). ) Acrylate, methoxyethyl (meth) acrylate, and alkoxyalkyl (meth) acrylate represented by ethoxyethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and Examples thereof include aromatic monovinyl represented by vinyl toluene, vinyl cyanide represented by acrylonitrile and methacrylonitrile, and vinyl esters represented by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versatic acid. In addition, various derivatives of these monomers can be mentioned.
However, when the specific (meth) acrylic copolymer (A) contains a structural unit derived from (meth) acrylate having a cyclic group, it has a cyclic group in the specific (meth) acrylic copolymer (A) (). The content (ratio) of the structural unit derived from the meta) acrylate is, for example, from the viewpoint of the transparency of the pressure-sensitive adhesive layer to be formed, with respect to all the structural units of the specific (meth) acrylic copolymer (A). It is preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 1% by mass or less, and the specific (meth) acrylic copolymer (A) has a cyclic group. It is particularly preferable that it does not contain a structural unit derived from (meth) acrylate, that is, it is 0% by mass.

<< Glass transition temperature of specific (meth) acrylic copolymer (A) >>
The glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) is −40 ° C. or lower, preferably −50 ° C. or lower, and more preferably −60 ° C. or lower.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) is −40 ° C. or lower, the high-speed peeling force does not become too high, and the balance between the low-speed peeling force and the high-speed peeling force is good. It can form a pressure-sensitive adhesive layer. In addition, it is possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when peeling at high speed is sufficiently suppressed.
The lower limit of the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) is not particularly limited, and is preferably −70 ° C. or higher from the viewpoint of adhesive strength to the adherend, for example.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) is a value obtained by converting the absolute temperature (K) obtained by calculation from the following formula 1 into the Celsius temperature (° C.).
1 / Tg = m1 / Tg1 + m2 / Tg2 + ... + m (k-1) / Tg (k-1) + mk / Tgk (Equation 1)

In the formula 1, Tg1, Tg2, ..., Tg (k-1), and Tgk are used when each monomer constituting the specific (meth) acrylic copolymer (A) is used as a homopolymer. It represents the glass transition temperature (Tg) represented by the absolute temperature (K), respectively. m1, m2, ..., m (k-1), and mk represent the mole fractions of each monomer constituting the specific (meth) acrylic copolymer (A), respectively, and m1 + m2 + ... + M (k-1) + mk = 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.

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

The "glass transition temperature (Tg) represented by the Celsius temperature (° C) when made into a homopolymer" of a typical monomer is -76 ° C for 2-ethylhexyl acrylate (2EHA) and 2-ethylhexyl methacrylate (2-ethylhexyl methacrylate). 2EHMA) is -10 ° C, n-butyl acrylate (n-BA) is -57 ° C, n-butyl methacrylate (n-BMA) is 21 ° C, t-butyl acrylate (t-BA) is 41 ° C, t-butyl. Methacrylate (t-BMA) at 107 ° C, i-butyl methacrylate (i-BMA) at 48 ° C, methyl acrylate (MA) at 5 ° C, methyl methacrylate (MMA) at 103 ° C, and isobonyl methacrylate (IBXMA) at 155 ° C. , Isobonyl acrylate (IBXA) 96 ° C, cyclohexyl methacrylate (CHMA) 56 ° C, ethyl acrylate (EA) -27 ° C, ethyl methacrylate (EMA) 42 ° C, methacrylic acid 185 ° C, 4-hydroxybutyl acrylate. (4HBA) is −39 ° C., 2-hydroxyethyl acrylate (2HEA) is −15 ° C., 2-hydroxyethyl methacrylate (2HEMA) is 55 ° C., acrylic acid (AA) is 163 ° C., isooctyl acrylate (i-OA). Is −75 ° C., dimethylaminoethyl methacrylate (DM) is 18 ° C., ω-carboxy-polycaprolactone (n≈2) monoacrylate is −30 ° C., and 2-acryloyloxyethyl-succinic acid is −40 ° C.

<< Weight average molecular weight of specific (meth) acrylic copolymer (A) >>
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A) is in the range of 200,000 or more and 2 million or less, preferably in the range of 250,000 or more and 1 million or less, and preferably 300,000 or more and 80. It is more preferably in the range of 10,000 or less, and further preferably in the range of 350,000 or more and 550,000 or less.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A) is 200,000 or more, the cohesive force tends to be easily obtained.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A) is 2 million or less, the coatability tends to be 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 1 minute to obtain a film-shaped specific (meth) acrylic copolymer (A).
(2) Using the film-shaped specific (meth) acrylic copolymer (A) obtained in (1) above and tetrahydrofuran is used, a sample solution having a solid content concentration of 0.2% by mass is obtained.
(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: TSK-GEL GMHXL (manufactured by Tosoh Corporation) connected in series 4 Column temperature: 40 ° C
Eluent: Tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL / min

<< Content of specific (meth) acrylic copolymer (A) >>
The content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and is, for example, 50% by mass or more and 99 with respect to the total solid content in the pressure-sensitive adhesive composition. The range is preferably in the range of mass% or less, more preferably in the range of 60% by mass or more and 90% by mass or less, and further preferably in the range of 70% by mass or more and 80% by mass or less.
When the content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is 50% by mass or more with respect to the total solid content in the pressure-sensitive adhesive composition, it is peeled off at high speed. There is a tendency to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur in the resin is more sufficiently suppressed.
When the content of the specific (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is 99% by mass or less with respect to the total solid content in the pressure-sensitive adhesive composition, low-speed peeling force and high speed are achieved. There is a tendency to form an adhesive layer having a better balance with the peeling force.
In the present specification, the "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a volatile component such as a solvent, and the pressure-sensitive adhesive. When the composition contains a volatile component such as a solvent, it means the mass of the residue obtained by removing the volatile component such as a solvent from the pressure-sensitive adhesive composition.

[Specific (meth) acrylic copolymer (B)]
The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from n-butyl methacrylate and a structural unit derived from a monomer having a hydroxyl group, and has a glass transition temperature in the range of 0 ° C. or higher and 45 ° C. or lower, and It contains a (meth) acrylic copolymer (B) [that is, a specific (meth) acrylic copolymer (B)] having a weight average molecular weight in the range of 10,000 or more and 200,000 or less.
Further, the content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). The range is 70 parts by mass or less.

<Constituent unit derived from n-butyl methacrylate>
The specific (meth) acrylic copolymer (B) contains a structural unit derived from n-butyl methacrylate.
As used herein, the term "constituent unit derived from n-butyl methacrylate" means a structural unit formed by addition polymerization of n-butyl methacrylate.

The content (ratio) of the structural unit derived from n-butyl methacrylate in the specific (meth) acrylic copolymer (B) is not particularly limited.
The content (ratio) of the structural unit derived from n-butyl methacrylate in the specific (meth) acrylic copolymer (B) is, for example, the content (ratio) of the structural unit derived from the specific (meth) acrylic copolymer (B) with respect to all the structural units of the specific (meth) acrylic copolymer (B). It is preferably 40% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more.
The content (ratio) of the structural unit derived from n-butyl methacrylate in the specific (meth) acrylic copolymer (B) is 40 with respect to all the structural units of the specific (meth) acrylic copolymer (B). When it is by mass% or more, the compatibility with the (meth) acrylic copolymer (A) becomes better, so that there is a tendency that a pressure-sensitive adhesive layer in which haze is more suppressed can be formed.
Further, the content rate (ratio) of the structural unit derived from n-butyl methacrylate in the specific (meth) acrylic copolymer (B) is, for example, the total structural unit of the specific (meth) acrylic copolymer (B). On the other hand, it is preferably 99.9% by mass or less, more preferably 98% by mass or less, and further preferably 97% by mass or less.
The content (ratio) of the structural unit derived from n-butyl methacrylate in the specific (meth) acrylic copolymer (B) is 99 with respect to all the structural units of the specific (meth) acrylic copolymer (B). When it is 9.9% by mass or less, it is more appropriately crosslinked with the isocyanate-based cross-linking agent, and therefore, there is a tendency that a pressure-sensitive adhesive layer having a better balance between the low-speed peeling force and the high-speed peeling force can be formed.

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

The type of the monomer having a hydroxyl group is not particularly limited.
Specific examples of the monomer having a hydroxyl group are as described above, and thus the description thereof will be omitted here.
As the monomer having a hydroxyl group, for example, hydroxyalkyl (meth) acrylate is preferable from the viewpoint of good copolymerizability with n-butyl methacrylate.
The hydroxyalkyl (meth) acrylate has, for example, a carbon number of carbon atoms from the viewpoint of good compatibility and copolymerizability with n-butyl methacrylate and good reactivity with an isocyanate-based cross-linking agent. A hydroxyalkyl (meth) acrylate having a hydroxyalkyl group of 1 to 5 is preferable, and a hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is more preferable.

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

The content (ratio) of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is not particularly limited, but is, for example, the specific (meth) acrylic copolymer (B). ), The range is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.7% by mass or more and 15% by mass or less, and 1% by mass or more. It is more preferably in the range of 10% by mass or less.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is 0. When it is 1% by mass or more, it means that the specific (meth) acrylic copolymer (B) positively contains a structural unit derived from a monomer having a hydroxyl group.
The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (B) is 20% by mass with respect to all the structural units of the specific (meth) acrylic copolymer (B). When it is less than%, there is a tendency that a pressure-sensitive adhesive layer having a better balance between the low-speed peeling force and the high-speed peeling force can be formed.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer different from n-butyl methacrylate>
The specific (meth) acrylic copolymer (B) is a (meth) acrylic acid alkyl ester monomer different from n-butyl methacrylate [hereinafter, another (meth) acrylic acid alkyl ester monomer (b)]. Also called. ] It is preferable to include a structural unit derived from.
The building blocks derived from the other (meth) acrylic acid alkyl ester monomer (b) contribute to the adjustment of the adhesive strength of the formed pressure-sensitive adhesive layer.

In the present specification, the "constituent unit derived from another (meth) acrylic acid alkyl ester monomer (b)" is an addition polymerization of another (meth) acrylic acid alkyl ester monomer (b). It means a structural unit to be formed.

The type of the other (meth) acrylic acid alkyl ester monomer (b) is not particularly limited as long as it is a (meth) acrylic acid alkyl ester monomer different from n-butyl methacrylate.
As the other (meth) acrylic acid alkyl ester monomer (b), an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable.
The alkyl group of the other (meth) acrylic acid alkyl ester monomer (b) may be linear, branched or cyclic.
Further, the carbon number of the alkyl group is preferably 1 to 18 from the viewpoint of the adhesive force of the formed pressure-sensitive adhesive layer to the adherend and the adhesion to the base material of the protective film, preferably 1 to 12. It is more preferable to have.

Examples of the other (meth) acrylic acid alkyl ester monomer (b) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl acrylate (n-BA), i-butyl (meth) acrylate, and s-. Butyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl ( Examples thereof include meta) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, and lauryl (meth) acrylate.
Among these, the other (meth) acrylic acid alkyl ester monomer (b) has good copolymerizability with, for example, n-butyl methacrylate (n-BMA) and has a glass transition temperature (Tg). ) Is suitable, and ethyl methacrylate (EMA) is preferable from the viewpoint that the desired adhesive performance can be easily obtained. Further, as the other (meth) acrylic acid alkyl ester monomer (b), for example, n-butyl acrylate (n-BA) from the viewpoint of compatibility with the specific (meth) acrylic copolymer (A). Is preferable.

When the specific (meth) acrylic copolymer (B) contains a structural unit (b) derived from another (meth) acrylic acid alkyl ester monomer, the other (meth) acrylic acid alkyl ester monomer The constituent unit (b) derived from the above may be contained in only one kind, or may contain two or more kinds.

When the specific (meth) acrylic copolymer (B) contains a structural unit derived from another (meth) acrylic acid alkyl ester monomer (b), in the specific (meth) acrylic copolymer (B). The content (ratio) of the constituent units derived from the other (meth) acrylic acid alkyl ester monomer (b) is, for example, the content (ratio) of the constituent units with respect to all the constituent units of the specific (meth) acrylic copolymer (B). It is preferably in the range of 0.1% by mass or more and 59.9% by mass or less.

<Constituent unit derived from a monomer having a carboxy group>
The specific (meth) acrylic copolymer (B) may contain a structural unit derived from a monomer having a carboxy group.
When the specific (meth) acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxy group, the high-speed peeling force of the formed pressure-sensitive adhesive layer is reduced, and the low-speed peeling force and the high-speed peeling force are reduced. It tends to be better balanced with force.

The type of the monomer having a carboxy group is not particularly limited.
Specific examples of the monomer having a carboxy group are as described above, and thus the description thereof will be omitted here.
As the monomer having a carboxy group, acrylic acid (AA) is preferable, for example, from the viewpoint of good reactivity with an isocyanate-based cross-linking agent.

When the specific (meth) acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxy group, the specific (meth) acrylic copolymer (B) may contain only one structural unit derived from the monomer having a carboxy group. Well, it may contain two or more kinds.

When the specific (meth) acrylic copolymer (B) contains a structural unit derived from a monomer having a carboxy group, the monomer having a carboxy group in the specific (meth) acrylic copolymer (B) is used. The content (ratio) of the derived structural units is preferably in the range of 0.1% by mass or more and 5% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer (B). It is more preferably in the range of 0.3% by mass or more and 3% by mass or less, and further preferably in the range of 0.5% by mass or more and 1.5% by mass or less.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (B) is 0 with respect to all the structural units of the specific (meth) acrylic copolymer (B). When it is 1% by mass or more, there is a tendency that a pressure-sensitive adhesive layer having a better balance between low-speed peeling force and high-speed peeling force can be formed.
The content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer (B) is 5 with respect to all the structural units of the specific (meth) acrylic copolymer (B). When it is less than the mass%, it tends to be possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when the material is peeled off at high speed is more sufficiently suppressed.

<Other building blocks>
The specific (meth) acrylic copolymer (B) is a structural unit derived from the above-mentioned structural unit, that is, n-butyl methacrylate, which is an essential structural unit, within the range in which the effect of the present invention is exhibited. A structural unit derived from a monomer having a hydroxyl group, a structural unit derived from another (meth) acrylic acid alkyl ester monomer (b) which is an arbitrary structural unit, and a structural unit other than the structural unit having a carboxy group. Units (so-called other structural units) may be included.

The monomer constituting the other structural unit is not particularly limited as long as it can be copolymerized with the monomer constituting the above-mentioned structural unit.
Specific examples of the monomers constituting the other structural units are as described above, and thus the description thereof will be omitted here.

<< Glass transition temperature of specific (meth) acrylic copolymer (B) >>
The glass transition temperature (Tg) of the specific (meth) acrylic copolymer (B) is in the range of 0 ° C. or higher and 45 ° C. or lower, preferably in the range of 5 ° C. or higher and 40 ° C. or lower, and is preferably 10 ° C. or higher and 35 ° C. or higher. It is more preferably in the range of ° C. or lower.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (B) is 0 ° C. or higher, a pressure-sensitive adhesive layer having a good balance between low-speed peeling force and high-speed peeling force can be formed.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (B) is 45 ° C. or lower, a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when peeling at high speed can be sufficiently suppressed can be formed. ..

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer (B) is calculated by the same method as the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) described above. Value.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer (B) is appropriately determined by using, for example, two or more types of monomers having different glass transition temperatures (Tg) when used as a homopolymer. Can be adjusted.

<< Weight average molecular weight of specific (meth) acrylic copolymer (B) >>
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B) is in the range of 10,000 or more and 200,000 or less, preferably in the range of 10,000 or more and 150,000 or less, and is preferably 15,000. It is more preferably in the range of 150,000 or more, and further preferably in the range of 20,000 or more and 100,000 or less.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B) is 10,000 or more, a pressure-sensitive adhesive layer having a good balance between low-speed peeling force and high-speed peeling force can be formed.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B) is 200,000 or less, it is possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when peeling at high speed is sufficiently suppressed. .. Further, since the compatibility with the specific (meth) acrylic copolymer (A) is improved, a pressure-sensitive adhesive layer having excellent transparency can be formed.

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

For the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (B), the polymerization temperature, the polymerization time, the amount of the organic solvent used, the type of the polymerization initiator, the amount of the polymerization initiator used, etc. shall be adjusted. Therefore, the desired value can be obtained.

<< Content of specific (meth) acrylic copolymer (B) >>
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 1 part by mass or more and 70 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It is a range of 3 parts or less, preferably 3 parts by mass or more and 60 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass or less.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). , A pressure-sensitive adhesive layer having a good balance between low-speed peeling force and high-speed peeling force can be formed.
The content of the specific (meth) acrylic copolymer (B) in the pressure-sensitive adhesive composition of the present invention is 70 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). , It is possible to form a pressure-sensitive adhesive layer in which the zipping phenomenon that may occur when peeling at a high speed is sufficiently suppressed. In addition, a pressure-sensitive adhesive layer having excellent transparency can be formed.

[Manufacturing method of specific (meth) acrylic copolymer]
The method for producing the specific (meth) acrylic copolymer (A) and the specific (meth) acrylic copolymer (B) [that is, the specific (meth) acrylic copolymer] is not particularly limited.
The specific (meth) acrylic copolymer is produced by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method. can.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer can be appropriately adjusted by using, for example, two or more kinds of monomers having different glass transition temperatures (Tg) when made into a homopolymer.
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer can be determined by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, and the like. , Can be set to the desired value.

As a polymerization method, solution polymerization is preferable because the treatment step is relatively simple and can be performed in a short time in preparing the pressure-sensitive adhesive composition of the present invention after production.
In solution polymerization, generally, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent to be used as needed are charged in a polymerization tank, and the reflux temperature of the nitrogen stream and / or the organic solvent is used. Heat and react for several hours with stirring. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be added sequentially.

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

In the production of the specific (meth) acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of an aromatic hydrocarbon compound, an ester compound, a ketone compound, an alcohol compound, etc. Meta) From the viewpoint of solubility of the acrylic copolymer, ease of polymerization reaction and the like, it is preferable to use toluene, ethyl acetate, methyl ethyl ketone, t-butyl alcohol and the like.

Examples of the polymerization initiator include organic peroxides and azo compounds used in ordinary solution polymerization.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, and di-2-ethylhexylperoxydi. Carbonate, t-butylperoxypivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4) -Di-t-butylperoxycyclohexyl) butane and 2,2-bis (4,4-di-t-octylperoxycyclohexyl) butane can be mentioned.
Examples of the azo compound include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile) (ABVN), and 2,2'-azobis (4-). Methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), and 2,2'-azobis (isobutyric acid) dimethyl.
At the time of the polymerization reaction, only one kind of these polymerization initiators may be used, or two or more kinds thereof may be mixed and used.

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

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

In the production of the specific (meth) acrylic copolymer, a chain transfer agent may be used, if necessary, as long as the object and effect of the present invention are not impaired.
Examples of the chain transfer agent include cyanoacetic acid, an alkyl ester compound having 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, an alkyl ester compound having 1 to 8 carbon atoms of bromoacetic acid, α-methylstyrene, anthracene, phenanthrene and fluorene. , And aromatic compounds such as 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds such as p-nitrotoluene, benzoquinone and A benzoquinone derivative typified by 2,3,5,6-tetramethyl-p-benzoquinone, a borane derivative typified by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane. , Tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and halogenated hydrocarbon compounds typified by 3-chloro-1-propene, aldehyde compounds typified by chloral and furaldehyde, alkyl having 1 to 18 carbon atoms. For mercaptan compounds, aromatic mercaptan compounds typified by thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds having 1 to 10 carbon atoms of mercaptoacetic acid, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and binen and turpinolene. Representative terpene compounds can be mentioned.

When a chain transfer agent is used in the production of the specific (meth) acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and depends on the molecular weight of the target specific (meth) acrylic copolymer. , Set as appropriate.

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

[Isocyanate-based cross-linking agent]
The pressure-sensitive adhesive composition of the present invention contains an isocyanate-based cross-linking agent.
As used herein, the term "isocyanate-based cross-linking agent" means a compound having two or more isocyanate groups in the molecule (so-called polyisocyanate compound). However, the isocyanate-based cross-linking agent in the present specification does not include a compound having an isocyanate group, a polysiloxane structure and an alkylene oxide structure. In the present specification, a compound having an isocyanate group, a polysiloxane structure and an alkylene oxide structure is referred to as a "silicone-based isocyanate compound", and details thereof will be described later.

Examples of the isocyanate-based cross-linking agent include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), and pentamethylene diisocyanate (PDI). , Isophoron diisocyanate, aliphatic or alicyclic polyisocyanate compounds such as hydrogenated additives of aromatic polyisocyanate compounds, and the like.
Examples of the isocyanate-based cross-linking agent include a dimer of the polyisocyanate compound, a trimer of the polyisocyanate compound, a pentamer of the polyisocyanate compound, and a polyisocyanate compound and a polyol compound (for example, trimetylolpropane). The adduct form of the above, the biuret form of the above isocyanate compound, and the like can also be mentioned.
Among these, hexamethylene diisocyanate (HMDI) is preferable as the isocyanate-based cross-linking agent, for example, from the viewpoint of easily developing a desired adhesive force and further suppressing haze.

As the polyisocyanate compound, a commercially available product can be used.
Examples of commercially available polyisocyanate compounds are "Coronate (registered trademark) HX", "Coronate (registered trademark) HL-S", "Coronate (registered trademark) L", and "Coronate (registered trademark) L-45E". , "Coronate® 2031", "Coronate® 2030", "Coronate® 2234", "Coronate® 2785", "Aquanate® 200", and "Aqua". Nate (registered trademark) 210 "[above, manufactured by Toso Co., Ltd.]," Sumijuru (registered trademark) N3300 "," Death Module (registered trademark) N3400 ", and" Sumijuru (registered trademark) N-75 "[ Sumika Cobestro Urethane Co., Ltd.], "Duranate (registered trademark) E-405-80T", "Duranate (registered trademark) AE700-100", "Duranate (registered trademark) 24A-100", and "Duranate (registered trademark) 24A-100". Duranate (registered trademark) TSE-100 "[above, manufactured by Asahi Kasei Co., Ltd.]," Takenate (registered trademark) D-110N "," Takenate (registered trademark) D-120N "," Takenate (registered trademark) M -631N ”,“ MT-Orester® NP1200 ”, and“ Stavio® XD-340N ”[above, manufactured by Mitsui Kagaku Co., Ltd.].

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

The content of the isocyanate-based cross-linking agent in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and is 0.1 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer. It is preferably in the range of 0.3 parts by mass or more and 7.0 parts by mass or less, and further preferably in the range of 0.5 parts by mass or more and 6.0 parts by mass or less. It is particularly preferable that the range is 1.0 part by mass or more and 5.0 parts by mass or less.
The content of the isocyanate-based cross-linking agent in the pressure-sensitive adhesive composition of the present invention is 0.1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer, that is, the pressure-sensitive adhesive composition of the present invention. Means that it positively contains an isocyanate-based cross-linking agent.
When the content of the isocyanate-based cross-linking agent in the pressure-sensitive adhesive composition of the present invention is 10.0 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer, the coating of the pressure-sensitive adhesive layer formed. There is no excessive reduction in wetting on the body and the adhesive layer tends to exhibit a more appropriate slow peeling force. In addition, the zipping phenomenon that may occur when peeling at high speed tends to be more sufficiently suppressed.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent.
The organic solvent contributes to the improvement of the coatability of the pressure-sensitive adhesive composition.
Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the above-mentioned specific (meth) acrylic copolymer.

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

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

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the above-mentioned components (so-called other components), if necessary, as long as the effects of the present invention are not impaired.
Other components include silicone-based isocyanate compounds, silicone-based compounds different from silicone-based isocyanate compounds (hereinafter, also referred to as “other silicone compounds”), ionic compounds, and specific (meth) acrylic copolymers. Polymers, cross-linking agents other than isocyanate-based cross-linking agents (eg, metal chelate-based cross-linking agents), cross-linking catalysts, tackifiers, antioxidants, colorants (eg, dyes and pigments), light stabilizers (eg, UV absorption). Agent) and the like.

<Silicone-based isocyanate compound>
The pressure-sensitive adhesive composition of the present invention may contain a compound having an isocyanate group, a polysiloxane structure and an alkylene oxide structure (that is, a silicone-based isocyanate compound) in addition to the above-mentioned isocyanate-based cross-linking agent. ..
Since the silicone-based isocyanate compound has an isocyanate group, it reacts with a cross-linking functional group in a specific (meth) acrylic copolymer to form a cross-linked structure, and is easily retained in an anchored state in the pressure-sensitive adhesive layer. .. Therefore, when the protective film is peeled off, the transfer of the contaminating component to the surface of the adherend is suppressed. Therefore, when the pressure-sensitive adhesive composition of the present invention contains a silicone-based isocyanate compound, there is a tendency that a pressure-sensitive adhesive layer having excellent stain resistance can be formed.
Further, since the silicone-based isocyanate compound has a polysiloxane structure in the molecule, it is difficult to be compatible with the specific (meth) acrylic-based copolymer and tends to be localized near the surface of the pressure-sensitive adhesive layer. Further, since the silicone-based isocyanate compound has an alkylene oxide structure in the molecule, the pressure-sensitive adhesive layer is coordinated with the antistatic agent in the same manner as the silicone compound having an alkylene oxide structure used as an antistatic aid. It tends to be localized near the surface. Therefore, the silicone-based isocyanate compound can impart excellent antistatic performance to the formed pressure-sensitive adhesive layer in a small amount.
As used herein, the term "polysiloxane structure" refers to a structure in which a siloxane group (-Si-O-) is linked.
The number of silicon atoms contained in the polysiloxane structure in the silicone-based isocyanate compound is preferably in the range of 1 to 100.

The silicone-based isocyanate compound can be obtained by reacting a silicone compound having a reactive group and having an alkylene oxide structure with an isocyanate compound (hereinafter, also referred to as “pre-reaction”).

Examples of the reactive group in the silicone compound having a reactive group and having an alkylene oxide structure include a hydroxyl group, a carboxy group, a substituted or unsubstituted amide group, a substituted or unsubstituted amino group, an epoxy group and a mercapto group. Examples thereof include reactive groups such as silicon-containing groups.
Among these, as the reactive group, for example, the reaction between the reactive group and the isocyanate group (NCO group) in the isocyanate compound is effectively promoted, and the generation of contamination on the adherend is effectively suppressed. From the viewpoint of being able to do so, hydroxyl groups are preferable.
The reactive group may be introduced at any of both ends, one end, and a side chain of the silicone compound having an alkylene oxide structure.
Here, "one end" means, for example, one end of the main chain of a silicone compound having a polysiloxane chain (main chain) having a repeating unit of a siloxane group. "Both ends" means, for example, both ends of the main chain of a silicone compound having a molecular chain (main chain) having a repeating unit of a siloxane group.

Examples of the silicone compound having a reactive group and having an alkylene oxide structure include a compound in which an alkylene oxide structure is bonded in a graft shape to a silicone chain (polysiloxane backbone) or a compound in which the alkylene oxide structure is bonded in a block shape. Can be mentioned.
Examples of the compound having an alkylene oxide structure include polyethylene oxide and polypropylene oxide having a reactive group, and may be a polyalkylene oxide in which ethylene oxide and propylene oxide are added in a block shape or at random.

The silicone compound having a reactive group and having an alkylene oxide structure has, for example, an alkylene oxide structure and an alkylene from the viewpoint of exhibiting excellent antistatic properties and effectively suppressing contamination of the adherend. It is preferably a silicone compound containing a structure in which a hydroxyl group is bonded to the end of the oxide structure (hereinafter, also referred to as “specific alkylene oxide structure-containing silicone compound”).
When the specific alkylene oxide structure-containing silicone compound has a structure in which a hydroxyl group is bonded to the end of the alkylene oxide structure, it becomes possible to exhibit more excellent stain resistance.
Silicone compounds having an alkylene oxide chain tend to interact with antistatic agents described below and localize near the surface of the pressure-sensitive adhesive layer. As a result, it is presumed that the surface resistance value on the surface of the pressure-sensitive adhesive layer is lowered. When the pressure-sensitive adhesive composition contains a silicone-based isocyanate compound, it is possible to suppress the blending amount of the antistatic agent in the pressure-sensitive adhesive composition.

From the viewpoint of imparting antistatic properties and reducing the contamination with the adherend, the specific alkylene oxide structure-containing silicone compounds include dialkylsiloxane-derived structural units and alkyl (hydroxypolyalkyleneoxyalkyl) siloxanes. It is preferably a polysiloxane compound containing the derived structural unit.
The number of carbon atoms of the alkyl group in the dialkylsiloxane is preferably 1 to 4, and more preferably 1.
Further, the carbon number of the alkylene oxide chain in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 2 to 4, more preferably 2 to 3.
The content of the alkylene oxide chain in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 1 to 100, more preferably 10 to 100.
The number of carbon atoms of the alkyl group in the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 1 to 4.

When the specific alkylene oxide structure-containing silicone compound contains a structural unit derived from a dialkylsiloxane and a structural unit derived from an alkyl (hydroxypolyalkyleneoxyalkyl) siloxane, the content of the structural unit derived from the dialkylsiloxane is 100 or less. It is preferably present, and more preferably 1 to 80. Further, the content of the structural unit derived from the alkyl (hydroxypolyalkyleneoxyalkyl) siloxane is preferably 2 to 100, more preferably 2 to 80.

The specific alkylene oxide structure-containing silicone compound is preferably a compound represented by the following general formula (3) or general formula (4) from the viewpoint of reducing adhesiveness, antistatic property and stain resistance to the adherend. ..

In the general formula (3), p is the number of repetitions of the dimethylsiloxane structural unit and represents an integer of 0 to 100. q is the number of repetitions of the methylpropylene siloxane structural unit having a polyethylene oxide chain and represents an integer of 2 to 100. a is the number of repetitions of the ethylene oxide structural unit and represents an integer of 1 to 100.
Here, when the compound represented by the general formula (3) is an aggregate of a plurality of compounds, p, q, and a are average values as an aggregate of the compounds and are rational numbers.

The number of repetitions a of the ethylene oxide structural unit is an integer of 1 to 100, and is preferably an integer of 10 to 100. When a is 1 or more, sufficient conductivity is obtained, and the antistatic effect tends to be further improved. Further, when a is 100 or less, localization is likely to occur near the surface of the pressure-sensitive adhesive layer.

The number of repetitions p of the dimethylsiloxane structural unit is an integer of 0 to 100, and is preferably an integer of 1 to 80. When p is 0 or more, the antistatic effect tends to be improved. Further, when p is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be further improved.
The number of repetitions q of the methylpropylene siloxane structural unit is an integer of 2 to 100, and is preferably an integer of 2 to 80. When q is 2 or more, sufficient conductivity is likely to be obtained, and the antistatic effect tends to be improved. Further, when q is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be further improved.

Specific examples of the compound represented by the general formula (3) include "SF-8428", "FZ-2162", "SH-3773M", "FZ-77", "FZ-2104", and "FZ-2110". , "L-7001", "L-7002", "SH-3479", etc. [above, manufactured by Toray Dow Corning Co., Ltd.].

In the general formula (4), R ¹ and R ² independently represent an alkylene group having 1 to 6 carbon atoms, c represents an integer of 10 to 80, and d represents an ethylene oxide (EO) constituent unit. It is the number of repetitions and represents an integer of 1 or more, e is the number of repetitions of the propylene oxide (PO) constituent unit and represents an integer of 0 or more, and d + e represents an integer of 1 to 30. The order of ethylene oxide and propylene oxide may be random.

Specific examples of the compound represented by the general formula (4) include "BY-16-201", "SF-8427" and the like [above, manufactured by Toray Dow Corning Co., Ltd.].

The weight average molecular weight (Mw) of the specific alkylene oxide structure-containing silicone compound is not particularly limited, but is preferably in the range of 10,000 or more and 20,000 or less, and is preferably 3,000 or more and 15,000 or less. It is more preferably in the range.
The weight average molecular weight (Mw) of the specific alkylene oxide structure-containing silicone compound is a value measured by the same method as the weight average molecular weight (Mw) of the above-mentioned specific (meth) acrylic copolymer (A).

The HLB value of the specific alkylene oxide structure-containing silicone compound is not particularly limited.
The HLB value of the specific alkylene oxide structure-containing silicone compound is, for example, 5 or more from the viewpoint of compatibility with a specific (meth) acrylic copolymer, ease of localization, and adhesiveness suitable for a protective film. The range is preferably less than 16, and more preferably 7 or more and 15 or less.

The HLB value is a measure showing the balance between hydrophilicity and hydrophobicity of a silicone compound having an alkylene oxide structure. In the present specification, the definition of the Griffin method calculated by the following formula is followed. When the silicone having an alkylene oxide structure is a commercially available product, the catalog data of the commercially available product is preferentially adopted.
HLB = {(sum of formulas of hydrophilic group part) / (molecular weight of silicone compound having alkylene oxide structure)} × 20

The specific alkylene oxide structure-containing silicone compound may be selected from the above-mentioned commercially available products, and an organic compound having an unsaturated bond and a polyethylene oxide chain is hydrosilylated with respect to the dimethylpolysiloxane backbone having silicon hydride. It may be obtained by grafting by reaction.

The isocyanate compound used for the pre-reaction of the silicone-based isocyanate compound is not particularly limited as long as it has the above-mentioned reactive group and can react with the silicone compound having an alkylene oxide structure.
Examples of such an isocyanate compound include the polyisocyanate compound which is the above-mentioned isocyanate-based cross-linking agent, and specific examples are the same as those of the specific examples of the isocyanate-based cross-linking agent.

For example, from the viewpoint of reactivity in the pre-reaction, the isocyanate compound used in the pre-reaction is at least one selected from isophorone diisocyanate or xylylene diisocyanate, and isocyanurate modified products of hexamethylene diisocyanate and polyol. Isocyanate is preferable, and at least one of isophorone diisocyanate and xylylene diisocyanate is more preferable from the viewpoint of particularly suppressing gelation during the pre-reaction described later.

For example, from the viewpoint of antistatic property, the isocyanate compound used in the pre-reaction is preferably an isocyanate compound different from the polyisocyanate compound which is the above-mentioned isocyanate-based cross-linking agent.
When the above-mentioned polyisocyanate compound which is an isocyanate-based cross-linking agent and the isocyanate compound used for the pre-reaction of the silicone-based isocyanate compound are different, the above-mentioned polyisocyanate compound which is an isocyanate-based cross-linking agent is used in the pressure-sensitive adhesive layer. Since it is difficult to be compatible with the silicone-based isocyanate compound and the silicone-based isocyanate compound is more likely to be localized on the surface of the pressure-sensitive adhesive layer, better antistatic properties tend to be obtained.

As the isocyanate compound used in the pre-reaction, only one kind may be used, or two or more kinds may be used. For example, when isophorone diisocyanate and xylylene diisocyanate are used in combination, gelation during the prereaction tends to be further suppressed.

The silicone-based isocyanate compound preferably contains a structure represented by the following structural formula (1).

In the structural formula (1), r represents an integer of 1 to 100, b represents an integer of 1 to 100, and X represents a monovalent organic group containing an isocyanate group.

The number of repetitions r of the methylpropylene siloxane structural unit is an integer of 1 to 100, and is preferably an integer of 2 to 80. When r is 1 or more, sufficient conductivity is obtained and the antistatic property tends to be improved. Further, when r is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The number of repetitions b of the ethylene oxide structural unit is an integer of 1 to 100, and is preferably an integer of 10 to 100. When b is 1 or more, sufficient conductivity is obtained and the antistatic property tends to be improved. Further, when b is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The monovalent organic group represented by X is a monovalent group obtained by removing one isocyanate group (NCO group) from the above-mentioned polyisocyanate compound (that is, a bifunctional or higher functional isocyanate compound) which is an isocyanate-based cross-linking agent. The basis of is mentioned.
Among these, the monovalent organic group represented by X is, for example, a chain-like or cyclic aliphatic polyisocyanate compound, a chain-like or a chain-like one from the viewpoint of reactivity with a specific (meth) acrylic copolymer. Isocyanate from at least one polyisocyanate compound selected from a trimer or a pentamer containing a dimer of a cyclic aliphatic polyisocyanate compound and an isocyanurate-modified form of a chain or cyclic aliphatic polyisocyanate compound. A monovalent group excluding one group is preferable, and a trimeric or 5 containing an isophorone diisocyanate, a xylylene diisocyanate, or a dimer of hexamethylene diisocyanate or hexamethylene diisocyanate, and an isocyanurate-modified product of hexamethylene diisocyanate. A monovalent group obtained by removing one isocyanate group from at least one polyisocyanate compound selected from the metric is more preferable, and a trimer containing an isocyanurate modified product of isophorone diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. A monovalent group obtained by removing one isocyanate group from at least one is more preferable, and a monovalent group obtained by removing one isocyanate group from at least one of isophorone diisocyanate and xylylene diisocyanate is particularly preferable.
The monovalent organic group represented by X is, for example, an isocyanate from another bifunctional or higher functional isocyanate compound different from the polyisocyanate compound which is the above-mentioned isocyanate-based cross-linking agent from the viewpoint of antistatic property. It is preferably a monovalent group excluding one group (NCO group).

A specific example of the structure represented by the structural formula (1) is shown below. The structure represented by the structural formula (1) is not limited to the following exemplary structure, and is not particularly limited as long as it is a structure included in the structure represented by the structural formula (1).

The silicone-based isocyanate compound is preferably at least one selected from the group consisting of the compounds represented by the general formula (1-1) and the general formula (2), for example, from the viewpoint of stain resistance, and is generally used. It is more preferable that the compound is represented by the formula (1-1).

In the general formula (1-1), p represents an integer of 0 to 100, q and r independently represent an integer of 1 to 100, a represents an integer of 1 to 100, and b represents an integer of 1 to 100. Represents an integer from 1 to 100. Further, X represents a monovalent organic group containing an isocyanate group.
Here, when the compound represented by the general formula (1-1) is an aggregate of a plurality of compounds, p, q, r, a, and b are average values as an aggregate of the compounds, and are rational numbers. Is.

The number of repetitions a of the ethylene oxide structural unit is an integer of 1 to 100, and is preferably an integer of 10 to 100. When a is 1 or more, sufficient conductivity is obtained and the antistatic property tends to be improved. Further, when a is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The number of repetitions p of the dimethylsiloxane structural unit is an integer of 0 to 100, and is preferably an integer of 1 to 80. When p is 0 or more, the antistatic property tends to be improved. Further, when p is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.
The number of repetitions q of the methylpropylene siloxane structural unit is an integer of 1 to 100, and is preferably an integer of 2 to 80. When q is 1 or more, sufficient conductivity is obtained, and the antistatic property tends to be improved. Further, when q is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

In the general formula (1-1), r and b are synonymous with r and b in the structural formula (1), and the preferable range is also the same.

In the general formula (2), R ¹ and R ² independently represent an alkylene group having 1 to 6 carbon atoms, c represents an integer of 10 to 80, and d represents an ethylene oxide (EO) structural unit. It is the number of repetitions and represents an integer of 1 or more, e is the number of repetitions of the propylene oxide (PO) structural unit and represents an integer of 0 or more, and d + e represents an integer of 1 to 30. The order of the ethylene oxide structural units and the propylene oxide structural units may be random.

In the general formula (2), the alkylene group having 1 to 6 carbon atoms represented by R ¹ or R ² is not particularly limited, and examples thereof include a methylene group, an ethylene group, a propylene group, and a butylene group.

The number of repetitions d of the ethylene oxide structural unit is preferably an integer of 1 to 100, and more preferably an integer of 10 to 100. When d is 1 or more, sufficient conductivity is obtained and the antistatic property tends to be improved. Further, when d is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The number of repetitions e of the propylene oxide structural unit is preferably an integer of 1 to 100, and more preferably an integer of 10 to 100. When e is 1 or more, sufficient conductivity is obtained and the antistatic property tends to be improved. Further, when e is 100 or less, the compatibility with other components constituting the pressure-sensitive adhesive composition is improved, and the transparency of the pressure-sensitive adhesive layer tends to be improved.

The sum of the number of repetitions d of the ethylene oxide structural unit and the number of repetitions e of the propylene oxide structural unit is more preferably an integer of 1 to 50.

Specific examples of the silicone-based isocyanate compound are shown below. The silicone-based isocyanate compound is not limited to the following exemplified compounds, and is not particularly limited as long as it is a compound included in the compound having the structure represented by the above-mentioned structural formula (1).

The method for producing the silicone-based isocyanate compound is not particularly limited, and a known production method can be applied.
For example, a predetermined amount of a silicone compound having a reactive group and an alkylene oxide structure and an isocyanate compound are put into a reaction vessel, and the mixture is uniformly stirred to cause a reaction (pre-reaction). A based isocyanate compound can be obtained.

The temperature of the pre-reaction is preferably 40 ° C to 100 ° C, more preferably 45 ° C to 95 ° C, and even more preferably 50 ° C to 95 ° C.

When the pressure-sensitive adhesive composition of the present invention contains a silicone-based isocyanate compound, the content of the silicone-based isocyanate compound in the pressure-sensitive adhesive composition is, for example, 100 parts by mass of the specific (meth) acrylic copolymer (A). , 0.1 part by mass or more, more preferably 0.2 part by mass to 3 parts by mass, and further preferably 0.3 part by mass to 2 parts by mass.
When the content of the silicone-based isocyanate compound is 0.1 part by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A), a pressure-sensitive adhesive layer having excellent stain resistance tends to be formed. be.

When the pressure-sensitive adhesive composition of the present invention contains a silicone-based isocyanate compound, the mass ratio of the silicone-based isocyanate compound to the isocyanate-based cross-linking agent [silicone-based isocyanate compound / isocyanate-based cross-linking agent] is 1/1 to 1/20. It is preferably 1/2 to 1/15, more preferably 1/3 to 1/10, and even more preferably 1/3 to 1/10.
When the mass ratio [silicone-based isocyanate compound / isocyanate-based cross-linking agent] is 1/1 or more, the specific (meth) acrylic copolymer (A) and the isocyanate-based cross-linking agent sufficiently react to form a cross-linked structure. Therefore, more appropriate adhesive force tends to be imparted to the pressure-sensitive adhesive layer.
When the mass ratio [silicone-based isocyanate compound / isocyanate-based cross-linking agent] is 1/20 or less, the isocyanate-based cross-linking agent contained in the pressure-sensitive adhesive composition does not increase too much, and the silicone-based isocyanate compound is appropriately present. Therefore, there is a tendency that an adhesive layer having excellent stain resistance can be formed.

<Other silicone compounds>
The pressure-sensitive adhesive composition of the present invention may contain at least one silicone-based compound (that is, another silicone compound) other than the silicone-based isocyanate compound as long as the effects of the present invention are not impaired.
Other silicone compounds can serve as antistatic aids.

Examples of other silicone compounds include silicone compounds having a reactive group and having an alkylene oxide structure, which are used in the pre-reaction of silicone-based isocyanate compounds.
Specific examples of other silicone compounds are the same as those of specific examples of silicone compounds having the above-mentioned reactive group and having an alkylene oxide structure, and the preferred range is also the same.

<Ionic compound>
The pressure-sensitive adhesive composition of the present invention may contain at least one ionic compound.
The ionic compound can function as an antistatic agent.

The ionic compound is not particularly limited.
Examples of the ionic compound include alkali metal salts and organic salts.
As the ionic compound, for example, at least one selected from the group consisting of alkali metal salts and organic salts is selected from the viewpoint of high ionic dissociation and easy development of excellent antistatic properties even in a small amount. preferable.

The alkali metal salt is not particularly limited as long as it is a metal salt having lithium ion (Li ⁺ ), sodium ion (Na ⁺ ), potassium ion (K ⁺ ), rubidium (Rb ⁺ ) or the like as cations.
The alkali metal salt is, for example, at least one cation selected from the group consisting of Li ⁺ , Na ⁺ , and K ⁺ , and Cl ⁻ , Br ⁻ , I ⁻ , BF _4- , PF ₆ ⁻ , SCN ⁻ , ^and ClO. From _4- ^, CF ₃ SO _3- ^, (FSO ₂ ) ₂ N- ^, (CF ₃ SO ₂ ) ₂ N- ^, (C ₂ F ₅ SO ₂ ) ₂ N- ^{, and} (CF ₃ SO ₂ ) ₃ C- It is preferably a metal salt composed of at least one anion selected from the group.
Among the alkali metal salts, for example, from the viewpoint of antistatic properties, LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ (so-called LiTFS), Li (FSO ₂ ) ₂ N, Lithium salts such as Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₃ C are preferable, and LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ ). More preferably, at least one lithium salt selected from the group consisting of SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, and Li (CF ₃ SO ₂ ) ₃ C.

Organic salts include organic cations and their counterions.
The organic salt includes, for example, an ionic solid having a melting point of 30 ° C. or higher and an ionic liquid having a melting point of less than 30 ° C.
The organic salt is preferably an ionic solid having a melting point of 30 ° C. or higher. When the melting point of the organic salt is 30 ° C. or higher, the transfer to the adherend is small and the contamination property is low, which is preferable.
Examples of the organic cation include an imidazolium cation, a pyridinium cation, an alkylpyrrolidinium cation, an ammonium cation having an organic group as a substituent, a sulfonium cation having an organic group as a substituent, and a phosphonium cation having an organic group as a substituent. Be done.
Among these, the organic cation is preferably a pyridinium cation or an imidazolium cation, for example, from the viewpoint of antistatic property.

The anion portion that becomes the counterion of the organic cation is not particularly limited, and may be either an inorganic anion or an organic anion. The anion portion that becomes the counter ion of the organic cation is preferably a fluorine-containing anion containing a fluorine atom, and more preferably a hexafluorophosphate anion (PF ₆ ⁻ ) from the viewpoint of excellent antistatic property.

Examples of the organic salt include pyridinium salt, imidazolium salt, alkylammonium salt, alkylpyrrolidinium salt, alkylphosphonium salt and the like.
Among these, the organic salt is preferably a pyridinium salt or an imidazolium salt, and more preferably a salt of a pyridinium cation, an imidazolium cation, and a fluorine-containing anion.

<Crosslink catalyst>
The pressure-sensitive adhesive composition of the present invention may contain a cross-linking catalyst.
The cross-linking catalyst is not particularly limited, and known ones can be used.
Examples of the cross-linking catalyst include organometallic compounds represented by dioctyltin dilaurate (DOTDL) and 1,3-diacetoxytetrabutylstanoxane, and tertiary amines represented by triethylenediamine and N-methylmorpholine. Examples include compounds.

[Use]
The pressure-sensitive adhesive composition of the present invention is preferably used as a protective film for protecting an optical member (so-called optical member protective film).
The pressure-sensitive adhesive composition of the present invention has a good balance between low-speed peeling force and high-speed peeling force, sufficiently suppresses zipping that may occur when peeling at high speed, and provides a pressure-sensitive adhesive layer having excellent transparency. Since it can be formed, it is suitable for applications in which a protective film is attached to an optical member.

Examples of the optical member include a member constituting a device (so-called optical device) such as an image display device and an input device, or a member used for these devices.
Specific examples of the optical member include a polarizing plate, an AG (Anti-Glare) polarizing plate, a wavelength plate, a retardation plate including a wavelength plate such as 1/2 and 1/4, a viewing angle compensation film, and an optical compensation film. Examples thereof include those used for display devices such as brightness improving films, light guide plates, reflective films, antireflection films, transparent conductive films such as ITO (Indium-Tin Oxide) films, prism sheets, lens sheets, and diffusers.
Examples of the material of the optical member include polyester resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, vinyl chloride resin, and ABS. (Acrylonitrile Butadiene Styrene) Examples thereof include resins such as resins and fluororesins.

[Optical member protective film]
The optical member protective film of the present invention includes a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the above-mentioned pressure-sensitive adhesive composition of the present invention. That is, in the protective film of the present invention, the base material and the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention are laminated.
Since the protective film of the present invention includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, after being attached to the surface of the adherend, it is peeled off from the adherend while protection is required. Problems such as slippage are unlikely to occur, protection is not required, and when peeling from the adherend, it can be peeled efficiently. In other words, the balance between the low-speed peeling force and the high-speed peeling force is good.
Further, since the protective film of the present invention includes the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, a zipping phenomenon is unlikely to occur when the protective film is peeled off from the adherend at high speed, and streaks are formed on the surface of the adherend. It is hard to cause the defect of the shape.
Further, the protective film of the present invention is excellent in transparency because it includes a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention.

The base material in the protective film of the present invention is not particularly limited as long as the pressure-sensitive adhesive layer can be formed on the base material.
Examples of the base material include polyester resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, vinyl chloride resin, ABS resin, and the like. Examples thereof include a film containing a resin such as a fluororesin.
For example, from the viewpoint of inspection and management of optical members by fluoroscopy, the base material may be a polyester resin, an acetate resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, or a polyolefin resin. , And a film containing at least one resin selected from the group consisting of acrylic resins are preferable.
Further, for example, from the viewpoint of surface protection performance, a film containing a polyester resin is preferable, and from the viewpoint of practicality, a film containing polyethylene terephthalate (PET) is particularly preferable.

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

The thickness of the base material is generally 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less.
The lower limit of the thickness of the base material is, for example, preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of the strength of the protective film.

An antistatic layer may be provided on one side or both sides of the base material. Further, even if the surface on the side where the pressure-sensitive adhesive layer of the base material is provided is subjected to surface treatment such as corona discharge treatment or plasma discharge treatment from the viewpoint of improving the adhesion between the base material and the pressure-sensitive adhesive layer. good.

The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a commonly used method can be adopted.
As a method for forming the pressure-sensitive adhesive layer on the substrate, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied on a substrate as it is or diluted with a solvent if necessary to form a coating film on the substrate. Next, the formed coating film is dried to remove the solvent, and then cured to form an adhesive layer on the substrate.
The surface of the exposed pressure-sensitive adhesive layer may be protected by a release film. The release film is not particularly limited as long as it can be easily peeled off from the surface of the pressure-sensitive adhesive layer, and examples thereof include paper and resin films having one or both sides surface-treated with a release agent. .. Examples of the resin film include a polyester film typified by a polyethylene terephthalate (PET) film. Examples of the release agent include a fluororesin, paraffin wax, silicone, a long-chain alkyl group compound and the like.
The release film protects the surface of the pressure-sensitive adhesive layer until the protective film is put into practical use, and is peeled off at the time of use.

As another method for forming the pressure-sensitive adhesive layer on the substrate, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied as it is or, if necessary, diluted with a solvent onto a release film such as a paper or resin film surface-treated with a release agent to remove the pressure-sensitive adhesive composition. A coating film is formed on the film. Then, the formed coating film is dried to remove the solvent. Next, the surface of the release film on which the pressure-sensitive adhesive layer is formed is brought into contact with the base material and pressed, and the pressure-sensitive adhesive layer is transferred to the base material to form the pressure-sensitive adhesive layer on the base material. Then, curing is performed.

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

The thickness of the pressure-sensitive adhesive layer can be appropriately set according to the adhesive strength required for the protective film, the type of the adherend (for example, the material and shape), the surface roughness of the adherend, and the like.
The thickness of the pressure-sensitive adhesive layer is generally in the range of 1 μm or more and 100 μm or less, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

The method for drying the coating film formed on the substrate or the release film is not particularly limited, and examples thereof include methods such as natural drying, heat drying, hot air drying, and vacuum drying.
The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set according to the thickness of the coating film, the amount of the organic solvent in the coating film, and the like.

Curing is performed, for example, in an environment of 23 ° C. and 50% RH for 1 to 10 days.
Curing completes the cross-linking reaction of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.

The adhesive force (so-called peeling force) of the adhesive layer when the protective film attached to the adherend is peeled 180 ° is 0 when the peeling speed is 0.3 m / min (that is, low-speed peeling). It is preferably 10 N / 25 mm or more, more preferably 0.15 N / 25 mm or more, and further preferably 0.20 N / 25 mm or more.
When the adhesive force at the time of low-speed peeling (so-called low-speed peeling force) is 0.10 N / 25 mm or more, the occurrence of peeling or slippage of the protective film tends to be further suppressed.

The adhesive force (so-called peeling force) of the adhesive layer when the protective film attached to the adherend is peeled 180 ° is 1.50 N when the peeling speed is 30 m / min (that is, high-speed peeling). It is preferably less than / 25 mm, more preferably less than 1.00 N / 25 mm, and even more preferably less than 0.50 N / 25 mm.
When the adhesive force at the time of high-speed peeling (so-called high-speed peeling force) is less than 1.50 N / 25 mm, the protective film can be peeled more efficiently from the adherend, so that workability can be further improved.

In the present specification, a pressure-sensitive adhesive layer having a good balance between low-speed peeling force and high-speed peeling force is a value obtained by dividing the value of low-speed peeling force by the value of high-speed peeling force (low-speed peeling force / high-speed peeling force). Evaluate based on.
(Low-speed peeling force / high-speed peeling force) is preferably 0.10 or more, more preferably 0.20 or more, and further preferably 0.30 or more.

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.

[Manufacturing of (meth) acrylic copolymer (A)]
[Manufacturing Example A-1]
171.0 parts by mass of ethyl acetate and 249.0 parts by mass of t-butyl alcohol were placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser.
In another container, 360.0 parts by mass of n-butyl acrylate (n-BA), 217.8 parts by mass of 2-ethylhexyl acrylate [2EHA; other acrylic acid alkyl ester monomer (a)], 4-. 18.0 parts by mass of hydroxybutyl acrylate (4HBA; monomer having a hydroxyl group) and 4.2 parts by mass of acrylic acid (AA; monomer having a carboxy group) were added and mixed to obtain a monomer mixture. ..
Of this monomer mixture, 20.0% by mass was added into the reaction vessel. Then, after replacing the air in the reaction vessel with nitrogen gas, 0.08 part by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added, and the mixture was stirred under a nitrogen atmosphere. The temperature of the contents in the reaction vessel was raised to 85 ° C. to start the initial reaction.
In the reaction vessel after the initial reaction was almost completed, 80.0% by mass of the remaining monomer mixture and a mixture of 88.0 parts by mass of ethyl acetate and 0.80 parts by mass of AIBN were added over about 2 hours. The contents in the reaction vessel were reacted while being added sequentially, and after the addition was completed, the reaction was further carried out for 2 hours to obtain a reaction product (a1).
Then, a solution prepared by dissolving 0.60 part by mass of t-butyl peroxypivalate (polymerization initiator) in 132.0 parts by mass of ethyl acetate in the reaction product (a1) in the reaction vessel was added dropwise over 1 hour. Then, after the completion of the dropping, the reaction was further carried out for 1.5 hours to obtain a reaction product (a2). The obtained reaction product (a2) was diluted with ethyl acetate to obtain a solution of the (meth) acrylic copolymer A-1 having a solid content of 45% by mass.
The term "solid content" as used herein means the remaining components obtained by removing volatile components such as a solvent from the solution of the (meth) acrylic copolymer A-1. The same applies to the following (meth) acrylic copolymers A-2 to A-10 solutions.

[Manufacturing Examples A-2 to A-10]
In Production Example A-1, the monomer composition of the (meth) acrylic copolymer (A) was changed to the monomer composition shown in Table 1, and the amount of the organic solvent used and the polymerization initiator were changed. Production Examples except that the weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) was changed to the weight average molecular weight (Mw) shown in Table 1 by adjusting at least one of the amounts used. The same operation as in A-1 was carried out to obtain solutions of (meth) acrylic copolymers A-2 to A-10 having a solid content of 45% by mass.

Monomer composition (unit: mass%) of (meth) acrylic copolymers A-1 to A-10, glass transition temperature (Tg, unit: ° C.), and weight average molecular weight [Mw, unit: 10,000 (table). Among them, "× 10 ⁴ notation)] is shown in Table 1.
The glass transition temperature (Tg) of the (meth) acrylic copolymers A-1 to A-10 is the same method as the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) described above. Calculated by. Further, the weight average molecular weight (Mw) of the (meth) acrylic copolymers A-1 to A-10 is the same as the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A) described above. It was measured by the method of.

Of the (meth) acrylic copolymers A-1 to A-10 obtained above, the (meth) acrylic copolymers A-1 to A-7 are the specific (meth) acrylic copolymers in the present invention. Corresponds to the copolymer (A).

Details of each monomer shown in Table 1 are as shown below.
"N-BA": n-butyl acrylate <other (meth) acrylic acid alkyl ester monomer (a)>
"2EHA": 2-ethylhexyl acrylate "MA": Methyl acrylate <monomer having a hydroxyl group>
"4HBA": 4-hydroxybutyl acrylate <monomer having a carboxy group>
"AA": Acrylic acid

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

[Manufacturing of (meth) acrylic copolymer (B)]
[Manufacturing Example B-1]
350.0 parts by mass of ethyl acetate and 150.0 parts by mass of t-butyl alcohol were placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser.
In another container, 577.8 parts by mass of n-butyl methacrylate (n-BMA), 18.0 parts by mass of 4-hydroxybutyl acrylate (4HBA; monomer having a hydroxyl group), and acrylic acid (AA; carboxy). A monomer having a group) 4.2 parts by mass was added and mixed to obtain a monomer mixture.
Of this monomer mixture, 20.0% by mass was added into the reaction vessel. Next, after replacing the air in the reaction vessel with nitrogen gas, 1.80 parts by mass of 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] was added, and the mixture was stirred under a nitrogen atmosphere. The temperature of the contents in the reaction vessel was raised to 85 ° C. to start the initial reaction.
In the reaction vessel after the initial reaction was almost completed, 80.0% by mass of the remaining monomer mixture and the mixture of 80.0 parts by mass of ethyl acetate and 8.0 parts by mass of AIBN were placed over about 2 hours. The contents in the reaction vessel were reacted while being added sequentially, and after the addition was completed, the reaction was further carried out for 1 hour to obtain a reaction product (b1).
Then, a solution prepared by dissolving 0.60 part by mass of t-butylperoxypivalate (polymerization initiator) in 132.0 parts by mass of ethyl acetate in the reaction product (b1) in the reaction vessel was added dropwise over 1 hour. Then, after the completion of the dropping, the reaction was further carried out for 2 hours to obtain a reaction product (b2). The obtained reaction product (b2) was diluted with ethyl acetate to obtain a solution of the (meth) acrylic copolymer B-1 having a solid content of 45% by mass.
The term "solid content" as used herein means the remaining components obtained by removing volatile components such as a solvent from the solution of the (meth) acrylic copolymer B-1. The same applies to the following (meth) acrylic copolymers B-2 to B-21 solutions.

[Production Examples B-2 to B-6, B-10 to B-12, and B-15 to B-21]
In Production Example B-1, the monomer composition of the (meth) acrylic copolymer (B) was changed to the monomer composition shown in Table 2, and the amount of the organic solvent used and the polymerization initiator were changed. Production Examples except that the weight average molecular weight (Mw) of the (meth) acrylic copolymer (B) was changed to the weight average molecular weight (Mw) shown in Table 2 by adjusting at least one of the amounts used. Perform the same operation as B-1, and the (meth) acrylic copolymers having a solid content of 45% by mass B-2 to B-6, B-10 to B-12, and B-15 to B-21. Each solution of was obtained.

[Manufacturing Examples B-7 to B-9, B-13, and B-14]
In Production Example B-1, the weight average molecular weight (Mw) of the (meth) acrylic copolymer (B) is shown in Table 2 by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used. The same operation as in Production Example B-1 was carried out except that the weight average molecular weight (Mw) was changed to the weight average molecular weight (Mw) shown in the above. , B-13, and B-14 were obtained.

Monomer composition (unit: mass%), glass transition temperature (Tg, unit: ° C.), and weight average molecular weight [Mw, unit: 10,000 (table) of (meth) acrylic copolymers B-1 to B-21. Among them, "× 10 ⁴ notation)] is shown in Table 2.
The glass transition temperature (Tg) of the (meth) acrylic copolymers B-1 to B-20 is the same method as the glass transition temperature (Tg) of the specific (meth) acrylic copolymer (A) described above. Calculated by The glass transition temperature (Tg) of the (meth) acrylic copolymer B-21 was not calculated.
The weight average molecular weight (Mw) of the (meth) acrylic copolymers B-1 to B-21 is the same as the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer (A) described above. It was measured by the method of.

Of the (meth) acrylic copolymers B-1 to B-21 obtained above, the (meth) acrylic copolymers B-1 to B-12 are the specific (meth) acrylic copolymers in the present invention. Corresponds to the copolymer (B).

Details of each monomer shown in Table 2 are as shown below.
"N-BMA": n-butyl methacrylate <other (meth) acrylic acid alkyl ester monomer (b)>
"EMA": Ethyl methacrylate "i-BMA": i-Butyl methacrylate "MMA": Methyl methacrylate "2EHMA": 2-Ethylhexyl methacrylate <Other monomers>
"CHMA": Cyclohexylmethacrylate "MePEGMA": Methoxypolyethylene glycol methacrylate (average number of moles of alkylene oxide group added: 23)
<Monomer with hydroxyl group>
"4HBA": 4-hydroxybutyl acrylate "2HEA": 2-hydroxyethyl acrylate "2HEMA": 2-hydroxyethyl methacrylate <monomer having a carboxy group>
"AA": Acrylic acid

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

[Manufacturing of silicone-based isocyanate compounds]
Takenate (registered trademark) 500 [trade name, xylylene diisocyanate (XDI), manufactured by Mitsui Kagaku Co., Ltd.] in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel. After charging 118.0 parts by mass and SH-3773M [trade name, polyether-modified silicone compound, manufactured by Toray Dow Corning Co., Ltd.] 82.0 parts by mass, and replacing the air in the flask with nitrogen gas. , The internal temperature was raised to 50 ° C. The contents in the flask were stirred for 6 hours while maintaining the internal temperature at 50 ° C. to obtain a silicone-based isocyanate compound.

[Preparation of adhesive composition]
[Example 1]
In a four-necked flask equipped with a stirring blade, a thermometer, a cooler, and a dropping funnel, 222.2 parts by mass (100 parts by mass as a solid content) of the solution of the (meth) acrylic copolymer A-1 and (100 parts by mass as a solid content). Meta) 66.6 parts by mass (30 parts by mass as solid content) of the solution of acrylic copolymer B-1 and SH-3773M [trade name, polyether-modified silicone compound, manufactured by Toray Dow Corning Co., Ltd.] 0 .30 parts by mass and 0.25 parts by mass of LiTFS [LiCF ₃ SO ₃ , manufactured by Morita Chemical Industry Co., Ltd.] were charged, and the mixture was stirred for 4 hours while keeping the liquid temperature in the flask at around 25 ° C.
Next, in the flask, as an isocyanate-based cross-linking agent, Sumijur (registered trademark) N-3300 [trade name, diluted product of hexamethylene diisocyanate (HMDI), manufactured by Sumika Cobestlor Urethane Co., Ltd.] 12 .0 parts by mass (3.00 parts by mass as a solid content) was added, and the mixture was sufficiently stirred to obtain a pressure-sensitive adhesive composition.

[Examples 2 to 18]
In Examples 2 to 18, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 3, to obtain a pressure-sensitive adhesive composition.

[Examples 19 to 34]
In Examples 19 to 34, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 4, to obtain a pressure-sensitive adhesive composition.

[Comparative Examples 1 to 16]
In Comparative Examples 1 to 16, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 5, to obtain a pressure-sensitive adhesive composition.

In Tables 3 to 5, "-" means that the corresponding component is not contained.

The details of the components shown in Tables 3 to 5 are as follows.
<Isocyanate-based cross-linking agent>
"N-3300" [Product name: Sumijuru (registered trademark) N-3300, manufactured by Sumika Covestro Urethane Co., Ltd.]: 4-fold dilution of hexamethylene diisocyanate (HMDI) trimer, solid content: 25 mass%
"L-45E" [Product name: Coronate (registered trademark) L-45E, manufactured by Tosoh Corporation]: Adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45% by mass
"N-3400" [Product name: Death Module (registered trademark) N-3400, manufactured by Sumika Covestro Urethane Co., Ltd.]: 4-fold diluted diluted product of hexamethylene diisocyanate (HMDI), solid content: 25 mass%
"D-120" [Product name: Takenate (registered trademark) D-120, manufactured by Mitsui Chemicals, Inc.]: Adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content: 75% by mass

<Other ingredients>
"SH-3773M" [trade name, manufactured by Toray Dow Corning Co., Ltd.]: polyether-modified silicone compound (having a hydroxy group as a reactive group at the end of a polyalkyleneoxy group), other silicone compounds "LiTFS" [ Morita Chemical Industry Co., Ltd.]: Lithium trifluoromethanesulfonate [LiCF ₃ SO ₃ ], ionic compound "DOTDL": Dioctyl tin dilaurate, cross-linking catalyst "Aluminum chelate" [Kawaken Fine Chemical Co., Ltd.]: Aluminum trisacetyl Acetonate, metal chelate-based cross-linking agent "TETRAD-X" [trade name: TETRAD (registered trademark) -X, manufactured by Mitsubishi Gas Chemicals Co., Ltd.]: epoxy-based cross-linking agent

[evaluation]
The following evaluation was performed using the pressure-sensitive adhesive composition prepared above.
The results are shown in Tables 6-8.

1. 1. Peeling force <Preparation of protective film for peeling force evaluation>
Application after drying on polyethylene terephthalate (PET) film as a base material [trade name: Teijin (registered trademark) Tetron (registered trademark) film, model number: G2, thickness: 38 μm, manufactured by Teijin Film Solutions Co., Ltd.] The pressure-sensitive adhesive composition was applied so that the amount was 15 g / m ² , and a coating film was formed. Then, the formed coating film was dried at 100 ° C. for 60 seconds using a hot air circulation type dryer.
Next, the exposed surface of the dried adhesive film was surface-treated with a silicone-based release agent [trade name: Film Vina (registered trademark) 100E-0010N023, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.]. It was superposed on the surface-treated surface of the above to form a laminated body. This laminate is passed through a pair of pressurized nip rolls, crimped and bonded, and then cured in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 96 hours to allow the cross-linking reaction to proceed, and the substrate / adhesive layer / peeling is performed. A protective film for evaluation of peeling force having a laminated structure of the film was obtained.

(1) Low-speed peeling force The protective film for peeling force evaluation produced above was cut into a size of 25 mm × 150 mm, and a protective film piece for peeling force evaluation was prepared.
Next, the release film was peeled off from the prepared protective film piece for evaluation of peeling force, and the surface of the pressure-sensitive adhesive layer exposed by the peeling was formed on a polyethylene terephthalate (PET) film [trade name: Cosmoshine (registered trademark) A4300, thickness: 300 μm, manufactured by Toyobo Co., Ltd.], and then crimped using a tabletop laminating machine to prepare a test sample.
This test sample was left for 24 hours in an environment with an atmospheric temperature of 23 ° C. and 50% RH. Next, a single column type material testing machine [model number: STA-1225, manufactured by A & D Co., Ltd.] was used as a measuring device, and the peeling speed was 0.3 m / in an environment of an atmospheric temperature of 23 ° C. and 50% RH. The peeling force (unit: N / 25 mm) when the protective film piece (adhesive layer / base material) for peeling force evaluation was peeled 180 ° in the long side (150 mm) direction from the PET film was measured under the condition of minutes. .. Then, the low-speed peeling force was evaluated according to the following evaluation criteria.
If the evaluation result is "AA", "A", or "B", it is judged that the low-speed peeling force is excellent.

-Evaluation criteria-
AA: The peeling force is 0.20 N / 25 mm or more.
A: The peeling force is 0.15 N / 25 mm or more and less than 0.20 N / 25 mm.
B: The peeling force is 0.10 N / 25 mm or more and less than 0.15 N / 25 mm.
C: The peeling force is less than 0.10 N / 25 mm.

(2) High-speed peeling force A test sample was obtained by the same procedure as in the above "(1) Low-speed peeling force".
This test sample was left for 24 hours in an environment with an atmospheric temperature of 23 ° C. and 50% RH. Next, a peeling tester [model number: horizontal TE-720, manufactured by Tester Sangyo Co., Ltd.] was used as a measuring device, and PET was performed under the conditions of an ambient temperature of 23 ° C. and a peeling speed of 30 m / min. The peeling force (unit: N / 25 mm) when the protective film piece (adhesive layer / base material) for evaluation of peeling force was peeled from the film by 180 ° in the long side (150 mm) direction was measured. Then, the high-speed peeling force was evaluated according to the following evaluation criteria.
If the evaluation result is "AA", "A", or "B", it is judged that the high-speed peeling force is excellent.

-Evaluation criteria-
AA: The peeling force is less than 0.50 N / 25 mm.
A: The peeling force is 0.50 N / 25 mm or more and less than 1.00 N / 25 mm.
B: The peeling force is 1.00 N / 25 mm or more and less than 1.50 N / 25 mm.
C: The peeling force is 1.50 N / 25 mm or more.

(3) Balance between low-speed peeling force and high-speed peeling force The value of the low-speed peeling force measured by the above "(1) low-speed peeling force" and the value of the low-speed peeling force measured by the above "(2) high-speed peeling force" were measured. The balance between the low-speed peeling force and the high-speed peeling force was evaluated based on the value of the high-speed peeling force.
Specifically, the balance between the low-speed peeling force and the high-speed peeling force is evaluated according to the following evaluation criteria based on the value obtained by dividing the value of the low-speed peeling force by the value of the high-speed peeling force and rounding off the third digit after the decimal point. did.
If the evaluation result is "AA", "A", or "B", it is judged that the balance between the low-speed peeling force and the high-speed peeling force is good.

-Evaluation criteria-
AA: "Low speed peeling force / high speed peeling force" is 0.30 or more.
A: "Low speed peeling force / high speed peeling force" is 0.20 or more and less than 0.30.
B: "Low speed peeling force / high speed peeling force" is 0.10 or more and less than 0.20.
C: "Low speed peeling force / high speed peeling force" is less than 0.10.

2. 2. Suppression of zipping phenomenon In the above "(2) High-speed peeling force", the presence or absence and degree of zipping sound when the protective film piece (adhesive layer / base material) for evaluating the peeling force was peeled from the PET film was confirmed. Then, the suppression of the zipping phenomenon was evaluated according to the following evaluation criteria.
When the evaluation result was "AA", "A", or "B", it was judged that the zipping phenomenon that could occur when the peeling was performed at high speed was sufficiently suppressed.

-Evaluation criteria-
AA: I can't hear any sound.
A: I can hear a faint sound.
B: I can hear a little sound.
C: I hear a loud noise.

3. 3. Transparency <Preparation of protective film for transparency evaluation>
Polyethylene terephthalate (PET) film as a base material [trade name: Cosmoshine (registered trademark) A4100, thickness: 100 μm, manufactured by Toyobo Co., Ltd.] so that the coating amount after drying is 40 g / m ² . , The pressure-sensitive adhesive composition was applied to form a coating film. Next, the formed coating film was dried at 100 ° C. for 60 seconds using a hot air circulation type dryer to form an adhesive film on the PET film.
Next, the exposed surface of the adhesive film formed on the PET film was surface-treated with a silicone-based release agent [trade name: Film Vina (registered trademark) 100E-0010N023, thickness: 100 μm, Fujimori Kogyo ( Co., Ltd.] was superposed on the surface-treated surface to form a laminated body. This laminate is passed through a pair of pressurized nip rolls, crimped and bonded, and then cured in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 96 hours to allow the cross-linking reaction to proceed, and the substrate / adhesive layer / peeling is performed. A protective film for transparency evaluation having a laminated structure of the film was obtained.

The transparency evaluation protective film produced above was cut into a size of 25 mm × 150 mm to obtain a transparency evaluation protective film piece. The release film was peeled off from the protective film piece for transparency evaluation to expose the pressure-sensitive adhesive layer, and the haze was measured. A haze meter (model number: NDH 5000SP) manufactured by Nippon Denshoku Kogyo Co., Ltd. was used for the haze measurement.
Transparency was evaluated according to the following evaluation criteria based on the measured haze value (unit:%).
If the evaluation result is "AA", "A", or "B", it is judged that the transparency is excellent.

-Evaluation criteria-
AA: The haze value is less than 1.0%.
A: The haze value is 1.0% or more and less than 1.5%.
B: The haze value is 1.5% or more and less than 2.0%.
C: The haze value is 2.0% or more.

As shown in Tables 6 and 7, it contains a structural unit derived from n-butyl acrylate and a structural unit derived from a polymer having a hydroxyl group, has a glass transition temperature of −40 ° C. or lower, and has a weight average molecular weight. The (meth) acrylic copolymer (A) [that is, the specific (meth) acrylic copolymer (A)] in the range of 200,000 or more and 2 million or less, and the constituent units derived from n-butyl methacrylate and Specific (meth) acrylic containing a structural unit derived from a polymer having a hydroxyl group, having a glass transition temperature in the range of 0 ° C. or higher and 45 ° C. or lower, and a weight average molecular weight in the range of 10,000 or higher and 200,000 or lower. The system copolymer (B) [that is, the specific (meth) acrylic copolymer (B)] and the isocyanate-based cross-linking agent are contained, and the content of the specific (meth) acrylic copolymer (B) is high. , A pressure-sensitive adhesive formed from the pressure-sensitive adhesive compositions of Examples 1 to 34, which are in the range of 1 part by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the layers had a good balance between the low-speed peeling force and the high-speed peeling force, sufficiently suppressed the zipping phenomenon that could occur when the layers were peeled at high speed, and had excellent transparency.

On the other hand, as shown in Table 8, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 containing no specific (meth) acrylic copolymer (B) has a remarkably low low-speed peeling force and a low-speed peeling force. It was confirmed that the high-speed peeling force was remarkably high and the balance between the low-speed peeling force and the high-speed peeling force was not good.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 2 in which the (meth) acrylic copolymer (A) does not contain a structural unit derived from n-butyl acrylate has a significantly high haze and is transparent. It was confirmed to be inferior.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 3 in which the (meth) acrylic copolymer (A) does not contain a structural unit derived from a monomer having a hydroxyl group has a significantly high high-speed peeling power. It was confirmed that the balance between the low-speed peeling force and the high-speed peeling force was not good.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 4 in which the glass transition temperature (Tg) of the (meth) acrylic copolymer (A) exceeds −40 ° C. has a significantly high high-speed peeling force and a low speed. It was confirmed that the balance between the peeling force and the high-speed peeling force was not good.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 5 having a weight average molecular weight of the (meth) acrylic copolymer (B) exceeding 200,000 sufficiently exhibits a zipping phenomenon that may occur when peeled at high speed. It was confirmed that it could not be suppressed. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 5 had a remarkably high haze and was inferior in transparency.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 6 in which the weight average molecular weight of the (meth) acrylic copolymer (B) is less than 10,000 has a significantly low low-speed peeling force and high-speed peeling. It was confirmed that the force was remarkably high and the balance between the low-speed peeling force and the high-speed peeling force was not good.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 7 in which the (meth) acrylic copolymer (B) does not contain a structural unit derived from n-butyl methacrylate has a significantly high haze and is transparent. It was confirmed to be inferior.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 8 in which the (meth) acrylic copolymer (B) does not contain a structural unit derived from a monomer having a hydroxyl group has a significantly high high-speed peeling power. It was confirmed that the balance between the low-speed peeling force and the high-speed peeling force was not good.

It does not contain a structural unit derived from n-butyl methacrylate and a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature (Tg) of more than 45 ° C., and has a weight average molecular weight of less than 10,000 (meth). It was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 9 containing the acrylic copolymer (B) could not sufficiently suppress the zipping phenomenon that could occur when peeled at high speed. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 9 had a remarkably high haze and was inferior in transparency.
It is formed by the pressure-sensitive adhesive composition of Comparative Example 10 which does not contain a structural unit derived from n-butyl methacrylate and contains a (meth) acrylic copolymer (B) having a glass transition temperature (Tg) of more than 45 ° C. It was confirmed that the adhesive layer could not sufficiently suppress the zipping phenomenon that could occur when the adhesive layer was peeled off at high speed. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 10 had a remarkably high haze and was inferior in transparency.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 11 in which the glass transition temperature (Tg) of the (meth) acrylic copolymer (B) exceeds 45 ° C. is a zipping phenomenon that can occur when the pressure-sensitive adhesive layer is peeled off at high speed. It was confirmed that it could not be sufficiently suppressed. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 11 had a remarkably high haze and was inferior in transparency.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 12 in which the glass transition temperature (Tg) of the (meth) acrylic copolymer (B) is less than 0 ° C. has a significantly low low-speed peeling force and It was confirmed that the high-speed peeling force was remarkably high and the balance between the low-speed peeling force and the high-speed peeling force was not good.

Formed by the pressure-sensitive adhesive composition of Comparative Example 13 in which the content of the specific (meth) acrylic copolymer (B) exceeds 70 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the applied pressure-sensitive adhesive layer could not sufficiently suppress the zipping phenomenon that could occur when the adhesive layer was peeled off at high speed. Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 13 had a remarkably high haze and was inferior in transparency.
According to the pressure-sensitive adhesive composition of Comparative Example 14, the content of the specific (meth) acrylic copolymer (B) is less than 1 part by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer (A). It was confirmed that the formed pressure-sensitive adhesive layer had a remarkably low low-speed peeling force and a remarkably high high-speed peeling force, and the balance between the low-speed peeling force and the high-speed peeling force was not good.
It was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 15 containing no isocyanate-based cross-linking agent could not sufficiently suppress the zipping phenomenon that could occur when peeled at high speed.
A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of Comparative Example 16 in which the specific (meth) acrylic copolymer (B) contains an alkylene oxide chain and does not contain a structural unit derived from a monomer having a hydroxyl group. It was confirmed that the layer had a remarkably high high-speed peeling force, and the balance between the low-speed peeling force and the high-speed peeling force was not good.

Claims (9)

It contains a structural unit derived from n-butyl acrylate and a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature of −40 ° C. or lower, and has a weight average molecular weight in the range of 200,000 or more and 2 million or less. With a certain (meth) acrylic copolymer (A),
It contains a structural unit derived from n-butyl methacrylate and a structural unit derived from a monomer having a hydroxyl group, has a glass transition temperature in the range of 0 ° C. or higher and 45 ° C. or lower, and has a weight average molecular weight of 10,000 or more and 200,000. With the (meth) acrylic copolymer (B) in the following range,
Contains isocyanate-based cross-linking agents,
The content of the (meth) acrylic copolymer (B) is in the range of 1 part by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). Adhesive composition for protective film. The content of the structural unit derived from the n-butyl methacrylate in the (meth) acrylic copolymer (B) is 50 mass with respect to all the structural units of the (meth) acrylic copolymer (B). % Or more of the pressure-sensitive adhesive composition for an optical member protective film according to claim 1. The content of the structural unit derived from the n-butyl acrylate in the (meth) acrylic copolymer (A) is 50 mass with respect to all the structural units of the (meth) acrylic copolymer (A). % Or more of the pressure-sensitive adhesive composition for an optical member protective film according to claim 1 or 2. The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (A) is higher than that of all the structural units of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition for an optical member protective film according to any one of claims 1 to 3, which is in the range of 0.7% by mass or more and 15% by mass or less. The content of the structural unit derived from the monomer having a hydroxyl group in the (meth) acrylic copolymer (B) is higher than that of all the structural units of the (meth) acrylic copolymer (B). The pressure-sensitive adhesive composition for an optical member protective film according to any one of claims 1 to 4, which is in the range of 0.7% by mass or more and 15% by mass or less. Claimed that the content of the (meth) acrylic copolymer (B) is in the range of 3 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer (A). The pressure-sensitive acrylic composition for an optical member protective film according to any one of claims 1 to 5. The pressure-sensitive adhesive for an optical member protective film according to any one of claims 1 to 6, wherein the weight average molecular weight of the (meth) acrylic copolymer (B) is in the range of 10,000 or more and 150,000 or less. Composition. The pressure-sensitive adhesive composition for an optical member protective film according to any one of claims 1 to 7, wherein the isocyanate-based cross-linking agent is hexamethylene diisocyanate. Optics comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition for an optical member protective film according to any one of claims 1 to 8. Member protection film.