JP2021147452A - Adhesive agent composition and protective tape - Google Patents

Abstract

To provide an adhesive agent composition capable of forming an adhesive agent layer that exhibits high adhesion to an adherend before UV irradiation, can be readily peeled from the adherend after UV irradiation, and hardly generates adhesive deposit to the adherend when peeling.SOLUTION: An adhesive agent composition comprises: 100 pts.mass of (meth)acrylic copolymer containing 12 to 80 mass% of a constituent unit derived from an alkyl group-containing (meth)acrylic acid alkyl ester monomer a having 8 to 24 carbon atoms and a constituent unit derived from a (meth)acrylic acid alkyl ester monomer b including a straight chain alkyl group having 4 to 7 carbons and having Tg of lower than 0°C as a single polymer, and having the content of a constituent unit derived from a monomer c (excluding monomer a) having Tg of 0°C or higher as a single polymer of 0 mass%, or over 0 mass% to 10 mass% or smaller; 25 to 95 pts.mass of a trifunctional or higher (meth)acrylate compound; and 0.1 to 10 pts.mass of a photopolymerization initiator, in which (content of the trifunctional or higher (meth)acrylate compound)/(content of the photopolymerization initiator) is 7 to 350.SELECTED DRAWING: None

Description

The present invention relates to pressure-sensitive adhesive compositions and protective tapes.

Protective tapes for processes or shipments are adhesive tapes used to protect products during transport. Protective tape has high adhesive strength so that it will not slip off when the product is transported, and low adhesive strength so that it can be easily peeled off from the product when protection is no longer required. Is required to show. As a method of achieving both of these two contradictory performances, the protective film is irradiated with active energy rays [for example, UV (ultraviolet rays)] when the product is no longer required to be protected, and the adhesive strength of the protective film is increased. The method of lowering is common, and protective tapes using this method have been reported.

For example, Patent Document 1 describes an easily peelable adhesive tape that has excellent peeling adhesive strength when attached to an adherend, but can be easily peeled off after being irradiated with active energy rays. , on at least one surface side of the substrate, temperature 25 ° C. and the storage modulus measured at frequencies 1.0Hz (G _'a25) has an active energy ray-curable layer is less than 1.0 × ¹⁰ 6 Pa Disclosed is an easily peelable adhesive tape having an adhesive layer on the surface side of the active energy ray-curable layer. Further, in Patent Document 1, the easily peelable adhesive tape is irradiated with active energy rays to cure the active energy ray-cured layer, and the storage elastic modulus (G') measured at a temperature of 25 ° C. and a frequency of 1.0 Hz. _It is described that a25) forms a cured layer of 1.0 × 10 ^{6 Pa or more.}

International Publication No. 2017/10478

By the way, in the field of electronic materials, protective tapes for processes are used in products of various sizes, from small products having a side length of 1 mm or less to large products having a side length of 20 mm or more. ing. In recent years, for the purpose of protecting products of various sizes with one type of protective tape, a soft film that can be applied as a base material for a protective film, specifically, a soft film containing an olefin resin, a urethane resin, etc. Film is used. Such a protective tape using a soft film as a base material is liable to be unintentionally deformed when peeled from the product. The pressure-sensitive adhesive layer included in the protective film is preferably hard from the viewpoint of being easily peeled off from the product. However, if the pressure-sensitive adhesive layer is too hard, the pressure-sensitive adhesive layer cannot follow the base material when the protective tape is deformed, so that adhesive residue on the product is likely to occur. As described above, with recent protective films, it has been difficult to achieve both easy peeling from the product and difficulty in causing adhesive residue on the product during peeling.

Regarding the above points, the easily peelable adhesive tape described in Patent Document 1 is intended to be easily peeled off from the product, and even attention is paid to making it difficult for adhesive residue to be generated on the product at the time of peeling. Not done.

The problem to be solved by the present invention is that it exhibits high adhesive strength to the adherend before UV irradiation, can be easily peeled from the adherend after UV irradiation, and is detached at the time of peeling. It is an object of the present invention to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer in which adhesive residue is unlikely to occur on the surface, and a protective tape.

Specific means for solving the problem include the following aspects.
<1> The structural units derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms are 12% by mass to 80% by mass based on all the structural units, and carbon. A structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) having a number of 4 to 7 linear alkyl groups and having a glass transition temperature of less than 0 ° C. when used as a homopolymer. Monomer (c) in which the glass transition temperature when made into a homopolymer is 0 ° C. or higher [However, the (meth) acrylic acid alkyl ester monomer (a) is excluded. ] Is not included, or the content of the structural unit derived from the above-mentioned monomer (c) is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units. With (meth) acrylic copolymer,
With trifunctional or higher functional (meth) acrylate compounds,
Including a photopolymerization initiator,
The content of the trifunctional or higher functional (meth) acrylate compound is 25 parts by mass to 95 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.
The content of the photopolymerization initiator is 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, and
The ratio of the content mass of the trifunctional or higher (meth) acrylate compound to the content mass of the photopolymerization initiator [the content mass of the trifunctional or higher (meth) acrylate compound / the content mass of the photopolymerization initiator] is A pressure-sensitive adhesive composition of 7 to 350.
<2> The pressure-sensitive adhesive composition according to <1>, wherein the (meth) acrylic copolymer does not contain a structural unit derived from the monomer (c).
<3> The (meth) acrylic copolymer is derived from the (meth) acrylic monomer (d) having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. Content of the structural unit derived from the (meth) acrylic monomer (d) which does not contain a structural unit or has at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. However, the pressure-sensitive adhesive composition according to <1> or <2>, which is in the range of more than 0% by mass and 2% by mass or less with respect to all the constituent units.
<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the (meth) acrylic copolymer has a weight average molecular weight of 600,000 to 3 million.
<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the trifunctional or higher functional (meth) acrylate compound is a pentafunctional or higher functional (meth) acrylate compound.
<6> A protective tape comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition according to any one of <1> to <5>.

According to the present invention, it exhibits high adhesive strength to the adherend before UV irradiation, can be easily peeled from the adherend after UV irradiation, and has adhesive residue on the adherend at the time of peeling. Provided are a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer in which is unlikely to occur, and a protective tape.

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

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

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

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

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

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention has a (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms [hereinafter, simply "(meth) acrylic acid alkyl ester monomer (a)". ) ”. ] Derived from the glass transition temperature when the constituent unit has 12% by mass to 80% by mass and a linear alkyl group having 4 to 7 carbon atoms and is a homopolymer. Is less than 0 ° C. (meth) acrylic acid alkyl ester monomer (b) [hereinafter, also simply referred to as “(meth) acrylic acid alkyl ester monomer (b)”. ], And the glass transition temperature when made into a homopolymer is 0 ° C. or higher. Monomer (c) [However, (meth) acrylic acid alkyl ester monomer (a) is excluded. Hereinafter, it is also simply referred to as “monomer (c)”. ] Is not included, or the content of the structural unit derived from the monomer (c) is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units (). Meta) acrylic copolymer [Hereinafter, also referred to as "specific (meth) acrylic copolymer". ], A trifunctional or higher functional (meth) acrylate compound, and a photopolymerization initiator, and the content of the trifunctional or higher functional (meth) acrylate compound is 100 parts by mass of the specific (meth) acrylic copolymer. On the other hand, the content of the photopolymerization initiator is 25 parts by mass to 95 parts by mass, and the content of the photopolymerization initiator is 0.1 parts by mass to 10 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. The ratio of the content mass of the trifunctional or higher functional (meth) acrylate compound to the content mass of the photopolymerization initiator [the content mass of the trifunctional or higher functional (meth) acrylate compound / the content mass of the photopolymerization initiator] is 7 to 350. be.
According to the pressure-sensitive adhesive composition of the present invention, it exhibits high adhesive strength to the adherend before UV irradiation, can be easily peeled from the adherend after UV irradiation, and is adhered at the time of peeling. It is possible to form an adhesive layer that does not easily leave adhesive residue on the body.
Although it is not clear why the pressure-sensitive adhesive composition of the present invention can exert such an effect, the present inventors speculate as follows. However, the following speculation does not limit the interpretation of the pressure-sensitive adhesive composition of the present invention, but is described as an example.
In the present specification, it is determined that the pressure-sensitive adhesive layer is less likely to leave adhesive residue on the adherend during peeling, using the storage elastic modulus (E') of the pressure-sensitive adhesive layer as an index. The storage elastic modulus (E') of the pressure-sensitive adhesive layer is an index of the flexibility of the pressure-sensitive adhesive layer. The lower the storage elastic modulus (E') of the pressure-sensitive adhesive layer, the higher the flexibility of the pressure-sensitive adhesive layer. If the pressure-sensitive adhesive layer is highly flexible, the pressure-sensitive adhesive layer follows the base material during peeling, so that adhesive residue on the adherend is unlikely to occur. From this, it is judged that the lower the storage elastic modulus (E'), the less likely it is that adhesive residue will be left on the adherend during peeling.

The pressure-sensitive adhesive composition of the present invention contains a specific (meth) acrylic copolymer, a specific ratio of a trifunctional or higher functional (meth) acrylate compound, and a specific ratio of a photopolymerization initiator, and is a specific (meth) acrylic. Since the system copolymer contains a constituent unit derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms in a specific ratio, the (meth) acrylic acid alkyl ester Due to the steric damage caused by the monomer (a), the trifunctional or higher functional (meth) acrylate compound does not excessively react during UV irradiation. Therefore, it is considered that the crosslink density of the pressure-sensitive adhesive layer after UV irradiation does not become excessively high, and the storage elastic modulus (E') of the pressure-sensitive adhesive layer becomes moderately low. Further, in the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed because the specific (meth) acrylic copolymer contains or hardly contains a structural unit derived from the monomer (c). It is considered that the storage elastic modulus (E') of the above does not become excessively high. From the above, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention exhibits high adhesive strength to the adherend before UV irradiation, and easily peels off from the adherend after UV irradiation. It is presumed that it can be formed and that adhesive residue on the adherend is unlikely to occur at the time of peeling.

[Specific (meth) acrylic copolymer]
The pressure-sensitive adhesive composition of the present invention contains 12% by mass to 80% by mass of a structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms with respect to all the structural units. A (meth) acrylic acid alkyl ester monomer (b) having a linear alkyl group having a mass% and 4 to 7 carbon atoms and having a glass transition temperature of less than 0 ° C. when used as a homopolymer. ), And the glass transition temperature when made into a homopolymer is 0 ° C. or higher. Monomer (c) [However, (meth) acrylic acid alkyl ester monomer (a) is excluded. ] Is not included, or the content of the structural unit derived from the monomer (c) is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units (). Includes meta) acrylic copolymers [ie, specific (meth) acrylic copolymers].

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms>
The specific (meth) acrylic copolymer contains 12% by mass of a structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms with respect to all the structural units. Contains ~ 80% by mass.

In the present specification, the "constituent unit derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms" has an alkyl group having 8 to 24 carbon atoms. It means a structural unit formed by addition polymerization of the (meth) acrylic acid alkyl ester monomer (a).
The "(meth) acrylic acid alkyl ester monomer (a)" in the present specification is a (meth) acrylic simple substance having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. A metric, that is, a monomer corresponding to the (meth) acrylic monomer (d) described later is not included.

The alkyl group in the (meth) acrylic acid alkyl ester monomer (a) is preferably unsubstituted.
The alkyl group in the (meth) acrylic acid alkyl ester monomer (a) may be a linear alkyl group, a branched chain alkyl group, or a cyclic alkyl group, but is a linear alkyl group or a branched chain alkyl group. Is preferable, and a linear alkyl group is more preferable.

The number of carbon atoms of the alkyl group in the (meth) acrylic acid alkyl ester monomer (a) is 8 to 24, preferably 8 to 18, more preferably 10 to 18, and 12 to 18. It is more preferable to have.
When the carbon number of the alkyl group in the (meth) acrylic acid alkyl ester monomer (a) is within the above range, it can be easily peeled from the adherend by UV irradiation, and the adherend can be easily peeled off at the time of peeling. There is a tendency to form an adhesive layer that is unlikely to leave adhesive residue on the surface. The reason is that the steric hindrance caused by the (meth) acrylic acid alkyl ester monomer (a) suppresses the excessive reaction of the trifunctional or higher functional (meth) acrylate compound during UV irradiation. This is considered to be because the crosslink density of the pressure-sensitive adhesive layer after UV irradiation does not become excessively high, and the storage elastic modulus (E') of the pressure-sensitive adhesive layer becomes moderately low.

Specific examples of the (meth) acrylic acid alkyl ester monomer (a) include n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-nonyl (meth) acrylate. , I-nonyl (meth) acrylate, n-decyl (meth) acrylate, i-decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, Cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like can be mentioned.
The (meth) acrylic acid alkyl ester monomer (a) is preferably at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and stearyl acrylate, and at least selected from lauryl acrylate and stearyl acrylate. It is more preferable that it is one kind.

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

The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) in the specific (meth) acrylic copolymer is higher than that of all the structural units of the specific (meth) acrylic copolymer. It is 12% by mass to 80% by mass, preferably 15% by mass to 80% by mass, more preferably 25% by mass to 70% by mass, and further preferably 25% by mass to 60% by mass. , 30% by mass to 60% by mass is particularly preferable.
The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) in the specific (meth) acrylic copolymer is 12 with respect to all the structural units of the specific (meth) acrylic copolymer. If it is more than% by mass, UV irradiation tends to form an adhesive layer in which adhesive residue on the adherend is unlikely to occur at the time of peeling.
The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) in the specific (meth) acrylic copolymer is 80 with respect to all the structural units of the specific (meth) acrylic copolymer. When it is less than mass%, a pressure-sensitive adhesive layer that can be easily peeled off from the adherend tends to be formed by UV irradiation.

Derived from the (meth) acrylic acid alkyl ester monomer (a) with respect to the content mass of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) described later in the specific (meth) acrylic copolymer. Ratio of the content of the structural unit to be contained [The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) / the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) The content mass] is not particularly limited, but is, for example, preferably 0.14 to 4.44, more preferably 0.25 to 1.50, and preferably 0.25 to 1.20. More preferred.
[The content mass of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) / the content mass of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (b)] is within the above range. Then, it has a good balance of high adhesive strength to the adherend before UV irradiation, excellent peelability from the adherend after UV irradiation, and excellent adhesive residue suppression property to the adherend. Adhesive layers tend to form.

<Constituent unit derived from (meth) acrylic acid alkyl ester monomer (b) having a linear alkyl group having 4 to 7 carbon atoms>
The specific (meth) acrylic copolymer has a linear alkyl group having 4 to 7 carbon atoms, and the glass transition temperature (Tg; hereinafter the same) when it is a homopolymer is less than 0 ° C. Contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer (b).
The structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) contributes to the adjustment of the adhesive force of the formed pressure-sensitive adhesive layer.

In the present specification, "a (meth) acrylic acid alkyl ester monomer having a linear alkyl group having 4 to 7 carbon atoms and having a glass transition temperature of less than 0 ° C. when used as a homopolymer (meth). The "constituent unit derived from b)" is an alkyl (meth) acrylate having a linear alkyl group having 4 to 7 carbon atoms and having a glass transition temperature of less than 0 ° C. when used as a homopolymer. It means a structural unit formed by addition polymerization of the ester monomer (b).
The "(meth) acrylic acid alkyl ester monomer (b)" in the present specification is a (meth) acrylic simple substance having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. A metric, that is, a monomer corresponding to the (meth) acrylic monomer (d) described later is not included.

The alkyl group in the (meth) acrylic acid alkyl ester monomer (b) is preferably unsubstituted.
The alkyl group in the (meth) acrylic acid alkyl ester monomer (b) has 4 to 7 carbon atoms, and is preferably 4, for example, from the viewpoint of availability.
When the number of carbon atoms of the alkyl group in the (meth) acrylic acid alkyl ester monomer (b) is within the above range, the adhesive strength of the formed pressure-sensitive adhesive layer tends to be easily adjusted.

The glass transition temperature of the (meth) acrylic acid alkyl ester monomer (b) as a homopolymer is less than 0 ° C., preferably in the range of −60 ° C. or higher and lower than 0 ° C., preferably −60 ° C. It is more preferably in the range of −10 ° C. or lower, further preferably in the range of −60 ° C. or higher and −20 ° C. or lower, and particularly preferably in the range of −60 ° C. or higher and −30 ° C. or lower.
When the glass transition temperature of the (meth) acrylic acid alkyl ester monomer (b) as a homopolymer is less than 0 ° C., the adhesive strength of the formed pressure-sensitive adhesive layer tends to be easily adjusted.

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

Specific examples of the (meth) acrylic acid alkyl ester monomer (b) include n-butyl acrylate (alkyl group carbon number: 4, glass transition temperature when homopolymerized: −57 ° C.) and the like. Be done.

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

The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) in the specific (meth) acrylic copolymer is not particularly limited, but for example, the specific (meth) acrylic copolymer It is preferably 20% by mass to 88% by mass, more preferably 20% by mass to 85% by mass, further preferably 30% by mass to 75% by mass, and 40% by mass with respect to all the constituent units. It is more preferably% to 75% by mass, and particularly preferably 40% by mass to 70% by mass.
The content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) in the specific (meth) acrylic copolymer is higher than that of all the structural units of the specific (meth) acrylic copolymer. Within the above range, the adhesive strength of the formed pressure-sensitive adhesive layer tends to be more easily adjusted to a desired value.

<Monomer (c) having a glass transition temperature of 0 ° C. or higher when used as a homopolymer [However, the (meth) acrylic acid alkyl ester monomer (a) is excluded. ] Derived from the structural unit>
The specific (meth) acrylic copolymer does not contain a structural unit derived from the monomer (c) having a glass transition temperature of 0 ° C. or higher when used as a homopolymer, or the monomer (c). ) Is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units. However, the monomer corresponding to the (meth) acrylic acid alkyl ester monomer (a) described above is not included in the monomer (c).

In the present specification, "a structural unit derived from the monomer (c) having a glass transition temperature of 0 ° C. or higher when made into a homopolymer" means that the glass transition temperature when made into a homopolymer is 0 ° C. It means a structural unit formed by addition polymerization of the above-mentioned monomer (c).
The "monomer (c)" in the present specification is a (meth) acrylic monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group, that is, which will be described later. The monomer corresponding to the (meth) acrylic monomer (d) is not included.

Specific examples of the monomer (c) include methyl acrylate (glass transition temperature when used as a homopolymer: 5 ° C.), methyl metallilate (glass transition temperature when used as a homopolymer: 103 ° C.), and ethyl. Methacrylate (glass transition temperature when homopolymer: 42 ° C), n-butyl methacrylate (glass transition temperature when homopolymer: 21 ° C), t-butyl acrylate (glass when homopolymer) Transition temperature: 41 ° C.), t-butyl metallicate (glass transition temperature when made into a homopolymer: 107 ° C.), i-butyl metallicate (glass transition temperature when made into a homopolymer: 48 ° C.), styrene (Glass transition temperature when made into a homopolymer: 90 ° C.), vinyl acetate (glass transition temperature when made into a homopolymer: 33 ° C.) and the like can be mentioned.

When the specific (meth) acrylic copolymer contains a structural unit derived from the monomer (c), it may contain only one structural unit derived from the monomer (c), 2 It may contain more than a seed.

The specific (meth) acrylic copolymer does not contain a structural unit derived from the monomer (c), or the content of the structural unit derived from the monomer (c) is a specific (meth) acrylic. It is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units of the system copolymer, and does not contain the structural unit derived from the monomer (c), or the monomer (c). The content of the structural unit derived from is preferably in the range of more than 0% by mass and 8% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer, and the monomer (c). Does not contain the structural unit derived from, or the content of the structural unit derived from the monomer (c) exceeds 0% by mass with respect to all the structural units of the specific (meth) acrylic copolymer. It is more preferably in the range of 5% by mass or less, and the content of the structural unit derived from the monomer (c) is not included, or the content of the structural unit derived from the monomer (c) is specified (meth). ) It is more preferably in the range of more than 0% by mass and 3% by mass or less with respect to all the structural units of the acrylic copolymer, and it is particularly preferable that the structural unit derived from the monomer (c) is not contained. ..
The specific (meth) acrylic copolymer does not contain a structural unit derived from the monomer (c), or the structural unit derived from the monomer (c) in the specific (meth) acrylic copolymer. When the content is in the range of more than 0% by mass and 10% by mass or less with respect to all the constituent units of the specific (meth) acrylic copolymer, glue to the adherend at the time of peeling by UV irradiation There is a tendency to form a pressure-sensitive adhesive layer that is unlikely to leave a residue.

<Constituent unit derived from a (meth) acrylic monomer (d) having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group>
The specific (meth) acrylic copolymer is a (meth) acrylic copolymer having at least one functional group (hereinafter, also referred to as “specific functional group”) selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. Polymer (d) [Hereinafter, it is also simply referred to as "(meth) acrylic monomer (d)". ] Derived from the structural unit may be included.
The "amino group" here refers to a primary amino group or a secondary amino group.

In the present specification, "a structural unit derived from a (meth) acrylic monomer (d) having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group" is a carboxy group. It means a structural unit formed by addition polymerization of a (meth) acrylic monomer (d) having at least one functional group selected from the group consisting of a hydroxyl group and an amino group.

The (meth) acrylic monomer (d) is not particularly limited as long as it has at least one functional group (that is, a specific functional group) selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. ..

Specific examples of the (meth) acrylic monomer having a carboxy group include acrylic acid, methacrylic acid, ω-carboxy-polycaprolactone monoacrylate and the like.

Specific examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth) acrylate. ) Acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) Acrylate, 1,1-dimethyl-3-hydroxybutyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2 -Ethyl-3-hydroxyhexyl (meth) acrylate and the like can be mentioned.

Specific examples of the (meth) acrylic monomer having a primary amino group include acrylamide and methacrylamide.
Specific examples of the (meth) acrylic monomer having a secondary amino group include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide and the like.
Specific examples of the (meth) acrylic monomer having a hydroxyl group and a secondary amino group include N-hydroxyethyl (meth) acrylamide and the like.

When the specific (meth) acrylic copolymer contains a structural unit derived from the (meth) acrylic monomer (d), the structural unit derived from the (meth) acrylic monomer (d) is used. Only one type may be contained, or two or more types may be contained.

The specific (meth) acrylic copolymer does not contain a structural unit derived from the (meth) acrylic monomer (d), or a structural unit derived from the (meth) acrylic monomer (d). The content of (meth) acrylic monomer (d) is preferably in the range of more than 0% by mass and 8% by mass or less with respect to all the constituent units of the specific (meth) acrylic copolymer. Does not contain the structural unit derived from, or the content of the structural unit derived from the (meth) acrylic monomer (d) is 0 with respect to all the structural units of the specific (meth) acrylic copolymer. It is more preferably in the range of more than mass% and 2% by mass or less, and does not contain a structural unit derived from the (meth) acrylic monomer (d), or is a (meth) acrylic monomer (meth). The content of the structural unit derived from d) is more preferably in the range of more than 0% by mass and 1% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer, and (meth). It is particularly preferable that the constituent unit derived from the acrylic monomer (d) is not contained.
The specific (meth) acrylic copolymer does not contain a structural unit derived from the (meth) acrylic monomer (d), or the (meth) acrylic single amount in the specific (meth) acrylic copolymer. When the content of the structural unit derived from the body (d) is in the range of more than 0% by mass and 8% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer, it is determined by UV irradiation. A pressure-sensitive adhesive layer that can be more easily peeled off from the adherend tends to be formed. The reason is considered to be that the adhesion to the adherend is further suppressed.

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

<< Weight average molecular weight of specific (meth) acrylic copolymer >>
The weight average molecular weight (Mw; hereinafter the same) of the specific (meth) acrylic copolymer is not particularly limited, but is preferably 600,000 to 3 million, preferably 700,000 to 2.5 million, for example. More preferably, it is more preferably 800,000 to 2 million, and particularly preferably 1 million to 2 million.
When the weight average molecular weight of the specific (meth) acrylic copolymer is 600,000 or more, UV irradiation tends to form an adhesive layer that is less likely to leave adhesive residue on the adherend during peeling. ..
When the weight average molecular weight of the specific (meth) acrylic copolymer is 3 million or less, the viscosity of the pressure-sensitive adhesive composition does not become too high, and the pressure-sensitive adhesive composition tends to be applied better.

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

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

The weight average molecular weight of the specific (meth) acrylic copolymer can be adjusted to a desired value 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.

<< Content of specific (meth) acrylic copolymer >>
The content of the specific (meth) acrylic copolymer in the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is, for example, 47% by mass to 80% by mass with respect to the total solid content in the pressure-sensitive adhesive composition. It is preferably 49% by mass to 80% by mass, more preferably 52% by mass to 78% by mass, and particularly preferably 52% by mass to 76% by mass.
In the present specification, the "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a solvent, and the pressure-sensitive adhesive composition contains a solvent. When included, it means the mass of the residue obtained by removing the solvent from the pressure-sensitive adhesive composition.

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

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

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

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

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

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

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

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

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

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

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

[Trifunctional or higher functional (meth) acrylate compound]
The pressure-sensitive adhesive composition of the present invention contains a trifunctional or higher functional (meth) acrylate compound. The content of the trifunctional or higher functional (meth) acrylate compound in the pressure-sensitive adhesive composition of the present invention is 25 parts by mass to 95 parts by mass with respect to 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer. The ratio of the content mass of the trifunctional or higher functional (meth) acrylate compound to the content mass of the photopolymerization initiator described later is 7 to 350.

As used herein, the term "trifunctional or higher (meth) acrylate compound" means a (meth) acrylate compound having three or more (meth) acryloyl groups in one molecule.
In the present specification, the number of (meth) acryloyl groups contained in the (meth) acrylate compound is also referred to as “the number of functional groups”.

The trifunctional or higher functional (meth) acrylate compound is preferably a pentafunctional or higher functional (meth) acrylate compound, and more preferably an octafunctional or higher functional (meth) acrylate compound.
When the pressure-sensitive adhesive composition of the present invention contains a pentafunctional or higher functional (meth) acrylate compound as a trifunctional or higher functional (meth) acrylate compound, UV irradiation causes more adhesive residue on the adherend during peeling. Adhesive layers that are unlikely to occur tend to be formed.

Examples of the trifunctional or higher functional (meth) acrylate compound include (tri / tetra / penta / hexa) (meth) acrylate, pentaerythritol (tri / tetra) (meth) acrylate, trimethylolpropane tri (meth) acrylate, and ditri. Examples thereof include (meth) acrylate compounds such as methylolpropane tetra (meth) acrylate and isocyanuric acid (meth) acrylate.
Here, "(tri / tetra / penta / hexa) (meth) acrylate" is a concept including tri (meth) acrylate, tetra (meth) acrylate, penta (meth) acrylate, and hexa (meth) acrylate. .. Further, "(tri / tetra) (meth) acrylate" is a concept including tri (meth) acrylate and tetra (meth) acrylate.
Further, examples of the trifunctional or higher functional (meth) acrylate compound include a trifunctional or higher functional urethane (meth) acrylate compound.

The double bond equivalent of the trifunctional or higher functional (meth) acrylate compound is not particularly limited, but is preferably, for example, 80 g / mol to 2000 g / mol, more preferably 80 g / mol to 1800 g / mol. It is more preferably 80 g / mol to 1500 g / mol, and particularly preferably 80 g / mol to 1300 g / mol.
When the double bond equivalent of the trifunctional or higher functional (meth) acrylate compound is 80 g / mol or more, UV irradiation tends to form an adhesive layer that is less likely to leave adhesive residue on the adherend during peeling. There is.
When the double bond equivalent of the trifunctional or higher functional (meth) acrylate compound is 2000 g / mol or less, a pressure-sensitive adhesive layer that can be more easily peeled from the adherend tends to be formed by UV irradiation.

The double bond equivalent of a trifunctional or higher (meth) acrylate compound is calculated by dividing the molecular weight of the trifunctional or higher (meth) acrylate compound by the number of double bonds of the trifunctional or higher (meth) acrylate compound. Is the value to be.

As the trifunctional or higher functional (meth) acrylate compound, a commercially available product can be used.
As an example of a commercially available product of a trifunctional or higher functional (meth) acrylate compound, "Viscoat # 802" [trade name, tripentaerythritol acrylate / mono and dipentaerythritol acrylate / polypentaerythritol acrylate mixture, number of functional groups: 8, 2 Double bond equivalent: 100 g / mol, Osaka Organic Chemical Industry Co., Ltd.], "Shikou UV-7610B" [Product name, urethane acrylate, number of functional groups: 9, double bond equivalent: 1220 g / mol, Mitsubishi Chemical Co., Ltd.] , "UA-33H" [trade name, urethane acrylate, number of functional groups: 9, double bond equivalent: 160 g / mol, Shin-Nakamura Chemical Industry Co., Ltd.], and "A-TMPT" [trade name, trimethyl propantri Acrylate, number of functional groups: 3, double bond equivalent: 100 g / mol, Shin-Nakamura Chemical Industry Co., Ltd.].

The pressure-sensitive adhesive composition of the present invention may contain only one type of trifunctional or higher functional (meth) acrylate compound, or may contain two or more types.

The content of the trifunctional or higher functional (meth) acrylate compound in the pressure-sensitive adhesive composition of the present invention is 25 parts by mass to 95 parts by mass and 30 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. It is preferably parts to 90 parts by mass, more preferably 35 parts by mass to 85 parts by mass, further preferably 40 parts by mass to 80 parts by mass, and 45 parts by mass to 75 parts by mass. Especially preferable.
When the content of the trifunctional or higher functional (meth) acrylate compound in the pressure-sensitive adhesive composition of the present invention is 25 parts by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer, it is subject to UV irradiation. There is a tendency to form an adhesive layer that can be easily peeled off from the body.
When the content of the trifunctional or higher functional (meth) acrylate compound in the pressure-sensitive adhesive composition of the present invention is 95 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer, it is peeled off by UV irradiation. At this time, there is a tendency to form an adhesive layer in which adhesive residue on the adherend is unlikely to occur.

The ratio of the content mass of the trifunctional or higher (meth) acrylate compound to the content mass of the photopolymerization initiator described later in the pressure-sensitive adhesive composition of the present invention [content mass of trifunctional or higher (meth) acrylate compound / initiation of photopolymerization The mass of the agent] is 7 to 350, preferably 7 to 300, more preferably 8 to 250, further preferably 10 to 200, and particularly preferably 20 to 100. preferable.
When [the content mass of the trifunctional or higher functional (meth) acrylate compound / the content mass of the photopolymerization initiator] is 7 or more, the pressure-sensitive adhesive layer before UV irradiation tends to show high adhesive strength to the adherend. There is.
When [the content mass of the trifunctional or higher functional (meth) acrylate compound / the content mass of the photopolymerization initiator] is 350 or less, there is a tendency that a pressure-sensitive adhesive layer that can be easily peeled off from the adherend is formed by UV irradiation. be.

[Photopolymerization initiator]
The pressure-sensitive adhesive composition of the present invention contains a photopolymerization initiator. The content of the photopolymerization initiator in the pressure-sensitive adhesive composition of the present invention is 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer.
The photopolymerization initiator contributes to the adjustment of the reaction of the trifunctional or higher functional (meth) acrylate compound described above.

The type of photopolymerization initiator is not particularly limited.
Examples of the photopolymerization initiator include a photopolymerization initiator having an oxime ester structure (so-called oxime-based photopolymerization initiator) and a photopolymerization initiator having an α-aminoalkylphenone structure (so-called α-aminoalkylphenone-based photopolymerization). Initiator), photopolymerization initiator having an α-hydroxyalkylphenone structure (so-called α-hydroxyalkylphenone-based polymerization initiator), photopolymerization initiator having an acylphosphine oxide structure (so-called acylphosphine oxide-based photoinitiator) Polymerization initiator), photopolymerization initiator having an N-phenylglycine structure (so-called N-phenylglycine-based photopolymerization initiator), photopolymerization initiator having a hexaarylbiimidazole structure (so-called hexaarylbiimidazole-based light) Polymerization initiator) and the like.

As the photopolymerization initiator, a commercially available product can be used.
Examples of commercially available photopolymerization initiators are "Omnirad® 184" [Chemical name: 1-hydroxycyclohexylphenyl ketone, IGM RESINS B. et al. V. , "Omnirad® 379EG" [Chemical name: 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone , IGM RESINS B.I. V. , "Omnirad® 907" [Chemical name: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, IGM RESINS B. et al. V. , Omnirad® 127 "[Chemical name: 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] phenyl} -2-methylpropan-1-one, IGM RESINS B. V. , "Omnirad® 369" [Chemical name: 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, IGM RESINS B. et al. V. , "Omnirad® 1173" [Chemical name: 2-hydroxy-2-methyl-1-phenylpropan-1-one, IGM RESINS B. et al. V. , "Omnirad® 651" [Chemical name: 2,2-dimethoxy-1,2-diphenylethane-1-one, IGM RESINS B. et al. V. Company], "Irgacure (registered trademark) OXE-01" [Chemical name: 1- [4- (phenylthio) phenyl] -1,2-octanedione-2- (O-benzoyloxime), BASF Japan Co., Ltd.] , "Irgacure® OXE-02" [Chemical name: 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3-yl] ethanone-1- (O-acetyloxime), BASF Japan Co., Ltd.], "Irgacure (registered trademark) OXE-03" [Chemical name: 8- [5- (2,4,6-trimethylphenyl) -11- (2-ethylhexyl) -11H-benzo [a] ] Carbonyl] [2- (2,2,3,3-tetrafluoropropoxy) phenyl] Metanon- (O-acetyloxime), BASF Japan Co., Ltd.], and "Irgacure® OXE-04" [Chemistry Name: 1- [4- [4- (2-benzofuranylcarbonyl) phenyl] thio] phenyl] -4-methyl-1-pentanone-1- (O-acetyloxime), BASF Japan Co., Ltd.] Be done.

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

The content of the photopolymerization initiator in the pressure-sensitive adhesive composition of the present invention is 0.1 part by mass to 10 parts by mass and 0.2 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. It is preferably ~ 8 parts by mass, more preferably 0.3 part by mass to 6 parts by mass, further preferably 0.5 part by mass to 5 parts by mass, and 1 part by mass to 4 parts by mass. It is particularly preferable to have.
When the content of the photopolymerization initiator 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, the adherend is exposed to UV irradiation. A pressure-sensitive adhesive layer that can be easily peeled off tends to be formed.
When the content of the photopolymerization initiator in the pressure-sensitive adhesive composition of the present invention is 10 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer, the pressure-sensitive adhesive layer before UV irradiation is covered. It tends to show high adhesive strength to the body.

[Crosslinking agent]
The pressure-sensitive adhesive composition of the present invention may contain a cross-linking agent.
The type of cross-linking agent is not particularly limited.
Examples of the cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, and a metal chelate-based cross-linking agent.
Among these, an isocyanate-based cross-linking agent is preferable as the cross-linking agent.

As used herein, the term "isocyanate-based cross-linking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate compound). Further, the "epoxy-based cross-linking agent" refers to a compound having two or more epoxy groups in one molecule (so-called bifunctional or higher functional epoxy compound). Further, the "metal chelate-based cross-linking agent" refers to a metal chelate compound that functions as a cross-linking agent.

The type of isocyanate-based cross-linking agent is not particularly limited.
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). ), Isophorone diisocyanate, an aliphatic or alicyclic polyisocyanate compound such as a hydrogenated additive of an aromatic polyisocyanate compound, and the like.
Examples of the isocyanate-based cross-linking agent include a dimer, a trimeric, or a pentamer of the polyisocyanate compound, an adduct of the polyisocyanate compound and a polyol compound such as trimethylolpropane, and a biuret of the polyisocyanate compound. The body is also mentioned.

As the isocyanate-based cross-linking agent, a commercially available product can be used.
Examples of commercially available isocyanate-based cross-linking agents include "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 " Aquanate (registered trademark) 210 "[above, Toso Co., Ltd.]," Sumijuru (registered trademark) N3300 "," Death Module (registered trademark) N3400 ", and" Sumijuru (registered trademark) N75 "[above, 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)" Trademark) TSE-100 "[above, Asahi Kasei Co., Ltd.], and" Takenate (registered trademark) D-110N "," Takenate (registered trademark) D-120N "," Takenate (registered trademark) M-631N ", Examples thereof include "MT-Orester (registered trademark) NP1200" and "Stavio (registered trademark) XD-340N" [above, Mitsui Kagaku Co., Ltd.].

The type of epoxy cross-linking agent is not particularly limited.
Examples of the epoxy-based cross-linking agent include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and the like. 1,6-Hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromo Neopentyl glycol diglycidyl ether, trimethylpropan triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipate diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) ) Isocyanurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-1,3-benzenedi (methaneamine) and the like.

As the epoxy-based cross-linking agent, a commercially available product can be used.
Examples of commercially available epoxy-based cross-linking agents include "TETRAD (registered trademark) -X" and "TETRAD (registered trademark) -C" [above, Mitsubishi Gas Chemical Company, Inc.].

The type of the metal chelate-based cross-linking agent is not particularly limited.
Examples of the metal chelate-based cross-linking agent include aluminum monoacetylacetonate bis (ethylacetate acetate), aluminum tris (ethylacetacetate), and aluminum chelate compounds typified by aluminum tris (acetylacetonate), titanium chelate compounds, and zirconium chelate. Examples include compounds and cobalt chelate compounds.

As the metal chelate-based cross-linking agent, a commercially available product can be used.
Examples of commercially available metal chelate-based cross-linking agents include "aluminum chelate A", "aluminum chelate D", and "ALCH-TR" [above, Kawaken Fine Chemicals Co., Ltd.].

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

When the pressure-sensitive adhesive composition of the present invention contains a cross-linking agent, the content of the cross-linking agent is not particularly limited, and is appropriately set according to, for example, the type of the cross-linking agent.
For example, when the pressure-sensitive adhesive composition of the present invention contains an isocyanate-based cross-linking agent as a cross-linking agent, the content of the isocyanate-based cross-linking agent is 0.1 mass by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. 10 parts by mass, more preferably 0.1 parts by mass to 5 parts by mass, further preferably 0.1 parts by mass to 2 parts by mass, and 0.1 parts by mass to 0 parts. It is particularly preferable that the amount is 5.5 parts by mass.

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

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

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

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the above-mentioned components (so-called other components), if necessary, as long as the effects of the present invention are not impaired.
Examples of other components include polymers other than the specific (meth) acrylic copolymer, cross-linking catalysts, colorants (for example, dyes and pigments), light stabilizers (for example, ultraviolet absorbers), and the like.

[Use]
The pressure-sensitive adhesive composition of the present invention exhibits high adhesive strength to the adherend before UV irradiation, can be easily peeled from the adherend after UV irradiation, and is attached to the adherend at the time of peeling. It is suitable for protective tapes because it can form an adhesive layer that does not easily leave adhesive residue. In particular, the pressure-sensitive adhesive composition of the present invention is preferably used for a protective tape used in a process or shipping.

[Protective tape]
The protective tape 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 the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, it exhibits high adhesive strength to the adherend before UV irradiation, and after UV irradiation, the adherend. It can be easily peeled off from the surface, and adhesive residue on the adherend is unlikely to occur during peeling.

The base material 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 polyethylene-based resin, polyester-based resin, acetate-based resin (for example, triacetyl cellulose resin), polyether sulfone-based resin, polycarbonate-based resin, polyamide-based resin, polyimide-based resin, and polyolefin-based resin. Examples thereof include films containing resins such as acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, fluororesins, and urethane resins.
For example, from the viewpoint that the effects of the present invention are more exerted, as the base material, a film containing at least one resin selected from the group consisting of polyolefin-based resins, vinyl chloride-based resins, and urethane-based resins is used. preferable.
For example, from the viewpoint of practicality, as the base material, a film containing a polyester resin is preferable, and a film containing polyethylene terephthalate (hereinafter, appropriately referred to as "PET") is more preferable.

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

The thickness of the base material is not particularly limited, but is generally 500 μm or less, preferably 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, and more preferably 10 μm or more, from the viewpoint of the strength of the protective tape.

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 of forming the pressure-sensitive adhesive layer on the base material, 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. Next, the formed coating film is dried to form an adhesive layer on the substrate.
In the embodiment in which the pressure-sensitive adhesive composition contains a cross-linking agent, the formed coating film is dried and then cured to form a pressure-sensitive adhesive layer on the substrate. Curing completes the cross-linking reaction of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer exposed in the protective tape of the present invention may be protected by a release film.
The release film is not particularly limited as long as it can be easily peeled from the pressure-sensitive adhesive layer. For example, a resin film having one or both sides surface-treated with a release treatment agent (so-called easy peeling treatment). Can be mentioned.
Examples of the resin film include a polyester film typified by a PET film.
Examples of the stripping agent include fluororesins, paraffin waxes, silicones, long-chain alkyl group compounds and the like.
The release film protects the surface of the pressure-sensitive adhesive layer until the protective tape 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 on a release film such as a paper or resin film that has been surface-treated with a release agent to remove the pressure-sensitive adhesive composition. A coating film is formed on the film. Next, the formed coating film is dried to form an adhesive layer on the release film. Next, the exposed surface of the formed pressure-sensitive adhesive layer is brought into contact with the base material and pressurized, and the pressure-sensitive adhesive layer is transferred to the base material to form the pressure-sensitive adhesive layer on the base material.
In the embodiment in which the pressure-sensitive adhesive composition contains a cross-linking agent, the formed coating film is dried and then cured to form a pressure-sensitive adhesive layer on the release film. Curing completes the cross-linking reaction of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.

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 base material 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 tape, the type of adherend (for example, material and shape), the surface roughness of the adherend, and the like.
The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

The method for drying the coating film formed on the base material 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.
An example of the drying condition is a condition of drying at 70 ° C. to 120 ° C. for 40 seconds to 180 seconds using a hot air dryer.

When curing is performed, for example, it is performed for 4 to 7 days in an environment with an atmospheric temperature of 20 ° C. to 35 ° C. and 50% RH.

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

[Manufacturing of (meth) acrylic copolymer]
[Manufacturing Example 1]
2-Ethylhexyl acrylate [2EHA; (meth) acrylic acid alkyl ester monomer (a)] 30.0 parts by mass, n in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux cooling tube. -Butyl acrylate [n-BA; (meth) acrylic acid alkyl ester monomer (b)] 70.0 parts by mass and ethyl acetate [organic solvent] 90.0 parts by mass were added and mixed to obtain a mixture. After that, the inside of the reactor was replaced with nitrogen. Then, the mixture in the reactor was heated to 70 ° C. with stirring, and then 2,2'-azobis (2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] was added to the mixture in the reactor. 02 parts by mass and 40.0 parts by mass of ethyl acetate were sequentially added and held for 6 hours to carry out a polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to obtain a solution of a (meth) acrylic copolymer having a solid content concentration of 16.7% by mass.

The "solid content concentration" here means the mass ratio of the (meth) acrylic copolymer to the solution of the (meth) acrylic copolymer.
The same applies to each solution of the (meth) acrylic copolymer produced in Production Examples 2 to 17.

[Production Examples 2 to 16]
In Production Examples 2 to 16, the monomer composition of the (meth) acrylic copolymer was changed to the monomer composition shown in Table 1, and the amount of the organic solvent used and the amount of the polymerization initiator used were different. The same operation as in Production Example 1 was performed except that the weight average molecular weight of the (meth) acrylic copolymer was changed to the weight average molecular weight shown in Table 1 by adjusting at least one of them, and the solid content concentration was 16. Each solution of the (meth) acrylic copolymer in an amount of 0.7% by mass was obtained.

[Manufacturing Example 17]
In Production Example 17, a solution of the (meth) acrylic copolymer was obtained according to the methods described in paragraphs [0099] and [0100] of JP-A-2017-179025.

Was prepared in Production Example 1-17 (meth) monomer composition of the acrylic copolymer (unit: mass%), and weight-average molecular weight [Mw, ten thousand (in the table, indicated as "× 10 ⁴⁾ ] Is shown in Table 1.
The weight average molecular weight (Mw) of the (meth) acrylic copolymer was measured by the same method as the above-mentioned method for measuring the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer.

Among the (meth) acrylic copolymers produced in Production Examples 1 to 17, the (meth) acrylic copolymer produced in Production Examples 1 to 14 is a specific (meth) acrylic copolymer in the present invention. Equivalent to.

Details of each monomer shown in Table 1 are as shown below.
<(Meta) Acrylic Acid Alkyl Ester Monomer (a)>
"2EHA": 2-ethylhexyl acrylate (alkyl group carbon number: 8)
"LA": Lauryl acrylate (alkyl group carbon number: 12)
"SA": Stearyl acrylate (alkyl group carbon number: 18)
<(Meta) acrylic acid alkyl ester monomer (b)>
"N-BA": n-butyl acrylate (carbon number of linear alkyl group: 4)
<Monomer (c)>
"MA": Methyl acrylate (glass transition temperature when made into a homopolymer: 5 ° C)
<(Meta) acrylic monomer (d) having a specific functional group>
"AA": Acrylic acid (specific functional group: carboxy group)
"2HEA": 2-hydroxyethyl acrylate (specific functional group: hydroxyl group)

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

[Preparation of adhesive composition]
[Example 1]
599 parts by mass (100 parts by mass as solid content) of the (meth) acrylic copolymer solution produced in Production Example 1 and Viscort # 802 [trade name, tripentaerythritol acrylate] as a trifunctional or higher functional (meth) acrylate compound. / Mono and dipentaerythritol acrylate / Polypentaerythritol acrylate mixture, number of functional groups: 8, double bond equivalent: 100 g / mol, Osaka Organic Chemical Industry Co., Ltd.] 60 parts by mass (60 parts by mass as solid content) and light Omnirad® 184 as a polymerization initiator [trade name, chemical name: 1-hydroxycyclohexylphenylketone, IGM RESINS B.I. V. Company] 1.8 parts by mass (1.8 parts by mass as solid content) and 1.8 parts by mass were sufficiently mixed to obtain the pressure-sensitive adhesive composition of Example 1.

[Examples 2 to 24]
In Example 1, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 2, to obtain each pressure-sensitive adhesive composition of Examples 2 to 24.

[Comparative Examples 1 to 8]
In Example 1, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 3, and each pressure-sensitive adhesive composition of Comparative Examples 1 to 8 was obtained.

In Tables 2 and 3, "-" in the composition column means that the corresponding component is not blended in the column.
In Tables 2 and 3, the numerical values of "parts by mass" are all solid content conversion values.
In Tables 2 and 3, "the ratio of the content mass of the trifunctional or higher (meth) acrylate compound to the content mass of the photopolymerization initiator [the content mass of the trifunctional or higher (meth) acrylate compound (X) / the start of photopolymerization". The content mass of the agent (Y)] ”was described as“ content mass ratio (X) / (Y) ”.
In Table 3, "-" described in the column of "content mass ratio (X) / (Y)" means that there is no corresponding value in that column.

Details of the components shown in Tables 2 and 3 are as shown below.
<Crosslinking agent>
"Coronate L" [Product name: Coronate (registered trademark) L, adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 75% by mass, Tosoh Corporation]
<(Meta) acrylate compound>
-3 Functional or higher (meth) acrylate compound-
"# 802" [Product name: Viscote # 802, tripentaerythritol acrylate / mono and dipentaerythritol acrylate / polypentaerythritol acrylate mixture, number of functional groups: 8, double bond equivalent: 100 g / mol, Osaka Organic Chemical Industry Co., Ltd. )]]
"UV-7610B" [Product name: Shikou UV-7610B, urethane acrylate, number of functional groups: 9, double bond equivalent: 1220 g / mol, Mitsubishi Chemical Corporation]
"A-TMPT" [Product name, trimethylolpropane triacrylate, number of functional groups: 3, double bond equivalent: 100 g / mol, Shin Nakamura Chemical Industry Co., Ltd.]
"UA-33H" [Product name, urethane acrylate, number of functional groups: 9, double bond equivalent: 160 g / mol, Shin Nakamura Chemical Industry Co., Ltd.]
-Comparative compound-
"A-200" [Product name, polyethylene glycol # 200 diacrylate, number of functional groups: 2, double bond equivalent: 150 g / mol, Shin Nakamura Chemical Industry Co., Ltd.]
<Photopolymerization initiator>
"Omnirad 184" [Product name: Omnirad (registered trademark) 184, chemical name: 1-hydroxycyclohexylphenyl ketone, IGM RESINS B.I. V. Company]

[evaluation]
The following evaluation was performed using the pressure-sensitive adhesive composition prepared above. The results are shown in Table 4.

1. 1. Measurement of adhesive strength <Preparation of adhesive sheet X>
<< If the adhesive composition does not contain a cross-linking agent >>
The surface-treated surface of the release film [trade name: Film Vina (registered trademark) 100E-0010 N0.23, thickness: 100 μm, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent has a thickness after drying. The pressure-sensitive adhesive composition was applied so as to have a thickness of 15 μm to form a coating film. Next, the formed coating film was dried using a hot air circulation type dryer under drying conditions of a drying temperature of 100 ° C. and a drying time of 1 minute to form an adhesive layer on the release film. Next, the exposed surface of the adhesive layer was superposed on a separately prepared PET film [trade name: Teijin (registered trademark) Tetron (registered trademark) film, model number: G2, thickness: 38 μm, Teijin Film Solution Co., Ltd.]. The adhesive sheet X was prepared by laminating. The produced pressure-sensitive adhesive sheet X has a laminated structure of a release film / pressure-sensitive adhesive layer / base material (PET film).

<< When the adhesive composition contains a cross-linking agent >>
The surface-treated surface of the release film [trade name: Film Vina (registered trademark) 100E-0010 N0.23, thickness: 100 μm, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent has a thickness after drying. The pressure-sensitive adhesive composition was applied so as to have a thickness of 15 μm to form a coating film. Next, the formed coating film was dried using a hot air circulation type dryer under drying conditions of a drying temperature of 100 ° C. and a drying time of 1 minute to form an adhesive film on the release film. Next, the exposed surface of the adhesive film is overlaid on a separately prepared PET film [trade name: Teijin (registered trademark) Tetron (registered trademark) film, model number: G2, thickness: 38 μm, Teijin Film Solution Co., Ltd.]. After the combination, the film was allowed to stand in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 7 days and cured to prepare an adhesive sheet X. The produced pressure-sensitive adhesive sheet X has a laminated structure of a release film / pressure-sensitive adhesive layer / base material (PET film).

(1) Before UV Irradiation The adhesive sheet X was cut, and a piece of adhesive tape for evaluation having a size of 25 mm × 150 mm was prepared. Next, the release film of the prepared adhesive tape piece for evaluation [structure: release film / adhesive layer / base material (PET film)] was peeled off, and the surface of the adhesive layer exposed by the peeling was made of stainless steel as an adherend. After laminating and adhering on the surface of a plate [trade name: SUS304 (BA), Partec Co., Ltd.] (hereinafter, appropriately referred to as "SUS"), a 2 kg roller is reciprocated once and crimped to form a laminated body. Made. The produced laminated body has a laminated structure of an adherend (SUS) / adhesive tape piece for evaluation [structure: adhesive layer / base material (PET film)]. Next, the prepared laminate was allowed to stand in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 30 minutes to prepare a test piece.
For this test piece, the adhesive force (unit: N / 25 mm) when the evaluation adhesive tape piece is peeled 180 ° in the long side (150 mm) direction from the adherend (SUS) is used as a single column type material. The measurement was carried out using a testing machine [model number: STA-1225, A & D Co., Ltd.] under the condition of an ambient temperature of 23 ° C. and a peeling speed of 300 mm / min in an environment of 50% RH. Then, the adhesive strength before UV irradiation was evaluated according to the following evaluation criteria.
If the evaluation result is "A", "B", or "C", it is determined that the adhesive layer exhibits high adhesive strength to the adherend before UV irradiation.

-Evaluation criteria-
A: The adhesive strength before UV irradiation is 2.0 N / 25 mm or more.
B: The adhesive strength before UV irradiation is 1.5 N / 25 mm or more and less than 2.0 N / 25 mm.
C: The adhesive strength before UV irradiation is 1.0 N / 25 mm or more and less than 1.5 N / 25 mm.
D: The adhesive strength before UV irradiation is less than 1.0 N / 25 mm.

(2) After UV irradiation, the adhesive sheet X was cut, and a piece of adhesive tape for evaluation having a size of 25 mm × 150 mm was prepared. Next, the release film of the prepared adhesive tape piece for evaluation [structure: release film / adhesive layer / base material (PET film)] was peeled off, and the surface of the adhesive layer exposed by the peeling was made of stainless steel as an adherend. After laminating and adhering on the surface of a plate [trade name: SUS304 (BA), Partec Co., Ltd.] (hereinafter, appropriately referred to as "SUS"), a 2 kg roller is reciprocated once and crimped to form a laminated body. Made. The produced laminated body has a laminated structure of an adherend (SUS) / adhesive tape piece for evaluation [structure: adhesive layer / base material (PET film)]. Next, the prepared laminate was allowed to stand in an environment with an atmospheric temperature of 23 ° C. and 50% RH for 30 minutes. The laminated body after standing was irradiated with UV from the base material side under the conditions of an ^{illuminance of 150 mW / cm 2} and an integrated light amount of ^{150 mJ / cm 2} using a high-pressure mercury lamp to prepare a test piece.
For this test piece, the adhesive force (unit: N / 25 mm) when the evaluation adhesive tape piece is peeled 180 ° in the long side (150 mm) direction from the adherend (SUS) is used as a single column type material. The measurement was carried out using a testing machine [model number: STA-1225, A & D Co., Ltd.] under the condition of an ambient temperature of 23 ° C. and a peeling speed of 300 mm / min in an environment of 50% RH. Then, the adhesive strength after UV irradiation was evaluated according to the following evaluation criteria.
If the evaluation result is "A", "B", or "C", it is determined that the adhesive layer can be easily peeled off from the adherend after UV irradiation.

-Evaluation criteria-
A: The adhesive strength after UV irradiation is less than 0.10 N / 25 mm.
B: The adhesive strength after UV irradiation is 0.10 N / 25 mm or more and less than 0.18 N / 25 mm.
C: The adhesive strength after UV irradiation is 0.18 N / 25 mm or more and less than 0.25 N / 25 mm.
D: The adhesive strength after UV irradiation is 0.25 N / 25 mm or more.

2. Measurement of storage elastic modulus (E') <Preparation of adhesive sheet Y>
<< If the adhesive composition does not contain a cross-linking agent >>
On the surface-treated surface of the release film A [trade name: Film Vina (registered trademark) 100E-0010 N0.23, thickness: 100 μm, high release film, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent. The pressure-sensitive adhesive composition was applied so that the thickness after drying was 25 μm, and a coating film was formed. Next, the formed coating film was dried using a hot air circulation type dryer under drying conditions of a drying temperature of 100 ° C. and a drying time of 1 minute to form an adhesive layer on the release film. Next, the exposed surface of the pressure-sensitive adhesive layer was surface-treated with a separately prepared silicone-based release treatment agent. Fujimori Kogyo Co., Ltd.] was laminated on the surface-treated surface and bonded to prepare an adhesive sheet Y. The produced pressure-sensitive adhesive sheet Y has a laminated structure of a release film A / an adhesive layer / a release film B.

<< When the adhesive composition contains a cross-linking agent >>
On the surface-treated surface of the release film A [trade name: Film Vina (registered trademark) 100E-0010 N0.23, thickness: 100 μm, high release film, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent. The pressure-sensitive adhesive composition was applied so that the thickness after drying was 25 μm, and a coating film was formed. Next, the formed coating film was dried using a hot air circulation type dryer under drying conditions of a drying temperature of 100 ° C. and a drying time of 1 minute to form an adhesive film on the release film. Next, the exposed surface of the adhesive film was surface-treated with a separately prepared silicone-based release treatment agent. Release film B [Product name: Film Vina (registered trademark) 25E-0010 BD, Thickness: 25 μm, Light release film, Fujimori After being laminated on the surface-treated surface of [Industry Co., Ltd.], it was allowed to stand in an environment of an atmospheric temperature of 23 ° C. and 50% RH for 7 days and cured to prepare an adhesive sheet Y. The produced pressure-sensitive adhesive sheet Y has a laminated structure of a release film A / an adhesive layer / a release film B.

The produced adhesive sheet Y was UV-irradiated from the release film B side using a high-pressure mercury lamp under ^{the conditions of an illuminance of 150 mW / cm 2} and an integrated light ^{intensity of 150 mJ / cm 2.} The UV-irradiated adhesive sheet Y was cut into a size of 20 mm × 300 mm, and then the release film B was peeled off. Next, on the release film A, only the pressure-sensitive adhesive layer was rolled into a columnar shape having a diameter of 5.0 mm and a height of 20 mm, which was used as a measurement sample. For this measurement sample, the storage elastic modulus (E') was measured under the following conditions using a dynamic viscoelasticity measuring device [model name: Rheogel-E4000, UBM Co., Ltd.]. Then, based on the measured value at 23 ° C., the storage elastic modulus (E') after UV irradiation was evaluated according to the following evaluation criteria.
When the evaluation result was "A", "B", or "C", it was determined that the adhesive layer was less likely to leave adhesive residue on the adherend during peeling after UV irradiation.

~conditions~
Measurement length: 10 mm
Measurement mode: Pull mode Temperature condition: 0 ° C to 60 ° C
Temperature rise rate: 5 ° C / min Frequency: 10Hz

-Evaluation criteria-
A: a storage elastic modulus after UV irradiation than 1.0 × ¹⁰ 7 Pa.
B: The storage elastic modulus after UV irradiation is 1.0 × 10 ⁷ Pa or more and ^{less than 5.0 × 10 7} Pa.
C: The storage elastic modulus after UV irradiation is 5.0 × 10 ⁷ Pa or more and ^{less than 7.0 × 10 7} Pa.
D: is the storage modulus after UV irradiation 7.0 × ¹⁰ 7 Pa or higher.

As shown in Table 4, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 24 exhibited high adhesive strength to the adherend before UV irradiation.
Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 24 showed low adhesive strength to the adherend after UV irradiation and could be easily peeled off from the adherend. ..
Further, it was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 24 had a low storage elastic modulus (E') after UV irradiation and was excellent in flexibility. From this, it is considered that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 24 is a pressure-sensitive adhesive layer in which adhesive residue on the adherend is unlikely to occur at the time of peeling.

On the other hand, in Comparative Example 1, the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) in the (meth) acrylic copolymer is less than 12% by mass with respect to all the structural units. The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition had a high storage elastic modulus (E') after UV irradiation and was inferior in flexibility. From this, it is considered that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 is a pressure-sensitive adhesive layer in which adhesive residue is likely to occur on the adherend at the time of peeling.
The pressure-sensitive adhesive layer of Comparative Example 2 in which the content of the structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) in the (meth) acrylic copolymer exceeds 80% by mass with respect to all the structural units. It was confirmed that the pressure-sensitive adhesive layer formed by the above method has high adhesive strength after UV irradiation and cannot be easily peeled off from the adherend after UV irradiation.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 3 in which the content of the trifunctional or higher functional (meth) acrylate compound is less than 25 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer is It was confirmed that the adhesive strength after UV irradiation was high and that the adhesive force could not be easily peeled off from the adherend after UV irradiation.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 4 in which the content of the trifunctional or higher functional (meth) acrylate compound exceeds 95 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer is UV. The storage elastic modulus (E') after irradiation was high, and the flexibility was inferior. From this, it is considered that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 4 is a pressure-sensitive adhesive layer in which adhesive residue is likely to occur on the adherend at the time of peeling.
A (meth) acrylate compound having a photopolymerization initiator content of less than 0.1 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer and having a trifunctionality or higher relative to the content mass of the photopolymerization initiator. The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 5 having a mass content ratio of more than 700 has high adhesive strength after UV irradiation and cannot be easily peeled off from the adherend after UV irradiation. confirmed.
The content of the photopolymerization initiator exceeds 10 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, and the content of the trifunctional or higher functional (meth) acrylate compound with respect to the content mass of the photopolymerization initiator. It was confirmed that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 6 having a ratio of less than 6 had a low adhesive force to the adherend before UV irradiation.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 7, which contains a bifunctional (meth) acrylate compound instead of the trifunctional or higher functional (meth) acrylate compound, has high adhesive strength after UV irradiation and is UV. After irradiation, it was confirmed that it could not be easily peeled off from the adherend.
A pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer of Comparative Example 8 in which the content of the structural unit derived from the monomer (c) in the (meth) acrylic copolymer exceeds 10% by mass with respect to all the structural units. Has a high storage elastic modulus (E') after UV irradiation and is inferior in flexibility. From this, it is considered that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 4 is a pressure-sensitive adhesive layer in which adhesive residue is likely to occur on the adherend at the time of peeling.

Claims (6)

The structural unit derived from the (meth) acrylic acid alkyl ester monomer (a) having an alkyl group having 8 to 24 carbon atoms is 12% by mass to 80% by mass with respect to all the structural units, and the carbon number is 4 It contains a structural unit derived from the (meth) acrylic acid alkyl ester monomer (b) having a linear alkyl group of ~ 7 and having a glass transition temperature of less than 0 ° C. when used as a homopolymer. Monomer (c) having a glass transition temperature of 0 ° C. or higher when used as a homopolymer [However, the (meth) acrylic acid alkyl ester monomer (a) is excluded. ] Is not included, or the content of the structural unit derived from the monomer (c) is in the range of more than 0% by mass and 10% by mass or less with respect to all the structural units. With (meth) acrylic copolymer,
With trifunctional or higher functional (meth) acrylate compounds,
Including a photopolymerization initiator,
The content of the trifunctional or higher functional (meth) acrylate compound is 25 parts by mass to 95 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.
The content of the photopolymerization initiator is 0.1 part by mass to 10 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer, and
A pressure-sensitive adhesive composition in which the ratio of the content mass of the trifunctional or higher functional (meth) acrylate compound to the content mass of the photopolymerization initiator is 7 to 350. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic copolymer does not contain a structural unit derived from the monomer (c). The (meth) acrylic copolymer contains a structural unit derived from the (meth) acrylic monomer (d) having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. The content of the structural unit derived from the (meth) acrylic monomer (d) which does not contain or has at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is the total. The pressure-sensitive adhesive composition according to claim 1 or 2, which is in the range of more than 0% by mass and not more than 2% by mass with respect to the constituent unit. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the (meth) acrylic copolymer has a weight average molecular weight of 600,000 to 3 million. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the trifunctional or higher functional (meth) acrylate compound is a pentafunctional or higher functional (meth) acrylate compound. A protective tape comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 5.