JPWO2017115632A1 - Composition for pressure-sensitive adhesive, pressure-sensitive adhesive layer, and pressure-sensitive adhesive sheet - Google Patents

Abstract

[Problem] The object of the present invention is to form a pressure-sensitive adhesive layer that exhibits excellent adhesive force even when adhered to polyolefin-based low-polarity materials such as polypropylene and has excellent durability under high temperature load environments Furthermore, it is providing the composition for adhesives.
[Solution] A gel comprising a (meth) acrylate polymer molecule (a) having a trithiocarbonate structure, having hydroxyl groups at both ends of the molecule, and having a structural unit derived from a carboxyl group-containing monomer (Meth) acrylic polymer (A) having a weight average molecular weight (Mw) of 300,000 to 600,000 and a molecular weight distribution (Mw / Mn) of 4.0 or less as measured by a permeation chromatography method, and one molecule 0.1 to 5 parts by mass of an isocyanate compound (B) having 2 or more isocyanate groups in it relative to 100 parts by mass of the (meth) acrylic polymer (A), and a tackifier (C And a composition for pressure-sensitive adhesives.

Description

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

In recent years, in the field of pressure-sensitive adhesives, there is a demand for highly reliable pressure-sensitive adhesives that have good adhesive strength and have excellent durability that does not peel off even under severe conditions.
In general, when sticking an adhesive mainly composed of an acrylic polymer to a polyolefin-based low-polarity material such as polyethylene or polypropylene, in order to develop a good adhesive force, an appropriate tackifier is used in the adhesive. It is necessary to add.

  For example, Patent Document 1 discloses a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a polymer component containing a specific acrylic polymer and a rosin-based tackifier resin or a terpene-based tackifier resin.

  However, by simply adding a tackifier to a conventional general acrylic polymer, an adhesive layer having sufficient durability under a load environment may not be obtained in sticking to a polyolefin-based low-polarity material. is there.

The pressure-sensitive adhesive is also required to have durability under high temperature conditions.
Patent Document 2 discloses a pressure-sensitive adhesive composition containing a specific (meth) acrylic acid ester polymer and a polyfunctional isocyanate compound. However, the weight average molecular weight of the polymers disclosed in the examples of Patent Document 2 is 70,000 to 250,000, and the durability under high temperature conditions is not sufficient.

JP, 2015-110724, A International Publication No. 2014/192492

  An object of the present invention is to provide a pressure-sensitive adhesive layer that exhibits excellent adhesive force even when adhered to a polyolefin-based low-polarity material such as polypropylene, and can form an adhesive layer having excellent durability under a high-temperature load environment. The object is to provide a pharmaceutical composition.

  The present inventors diligently studied to solve the above problems. As a result, the present inventors have found that the above problems can be solved by a pressure-sensitive adhesive composition containing a specific (meth) acrylic polymer, a specific amount of a polyfunctional isocyanate compound, and a specific tackifier, thereby completing the present invention. It was.

The present invention includes, for example, the following [1] to [6].
[1] A (meth) acrylate polymer molecule (a) having a structure represented by the formula (a1), having hydroxyl groups at both ends of the molecule, and having a structural unit derived from a carboxyl group-containing monomer (Meth) acrylic polymer (A) having a weight average molecular weight (Mw) of 300,000 to 600,000 and a molecular weight distribution (Mw / Mn) of 4.0 or less as measured by gel permeation chromatography And an isocyanate compound (B) having 2 or more isocyanate groups in one molecule, 0.1 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer (A), and a softening point of 95 ° C. or more. The composition for adhesives containing a tackifier (C).

  [2] The pressure-sensitive adhesive composition according to [1], wherein the (meth) acrylic polymer (A) is a reversible addition-fragmentation chain transfer (RAFT) polymer of a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer. object.

  [3] The (meth) acrylic polymer (A) is a polymer of a polymerizable double bond-containing monomer in which the amount of the monomer having at least one selected from a hydroxyl group and an amino group is 0.3% by mass or less. The composition for adhesives as described in [1] or [2].

  [4] The composition for pressure-sensitive adhesives according to any one of [1] to [3], wherein the (meth) acrylic acid ester polymer molecule (a) is a polymer represented by the formula (A1-1).

［式（Ａ１−１）中、Ｒ¹はそれぞれ独立に２価の有機基であり、（Ａ）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基である。］

[In Formula (A1-1), R ¹ is each independently a divalent organic group, and (A) is independently derived from a polymer of a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer. Is a valent group. ]

  [5] A pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition according to any one of [1] to [4].

  [6] A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to [5].

  According to the present invention, a pressure-sensitive adhesive layer that exhibits a good adhesive force even when adhered to a polyolefin-based low-polarity material such as polypropylene and can form an adhesive layer having excellent durability under a high temperature load environment. A pharmaceutical composition can be provided.

Hereinafter, the composition for pressure-sensitive adhesives, the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive sheet of the present invention will be described.
In the present specification, “polymer” is used to include homopolymers and copolymers, and “polymerization” is used to include homopolymerization and copolymerization.
Acrylic and methacrylic are also collectively referred to as “(meth) acrylic”.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention includes a specific (meth) acrylic polymer (A) containing a specific (meth) acrylic acid ester polymer molecule (a) (hereinafter also referred to as “polymer molecule (a)”). And an isocyanate compound (B) having two or more isocyanate groups in one molecule (hereinafter also referred to as “polyfunctional isocyanate compound (B)”) and a specific tackifier (C).

<(Meth) acrylic polymer (A)>
The (meth) acrylic polymer (A) contains a polymer molecule (a).
<(Meth) acrylic acid ester polymer molecule (a)>
The polymer molecule (a) has a structure represented by the formula (a1), has a hydroxyl group at both ends of the molecule, and has a structural unit derived from a carboxyl group-containing monomer.

重合体分子（ａ）は、式（ａ１）で表される構造（以下「トリチオカーボネート構造」ともいう。）を有する。

The polymer molecule (a) has a structure represented by the formula (a1) (hereinafter also referred to as “trithiocarbonate structure”).

  In the polymer molecule (a), hydroxyl groups at both ends of the molecule are crosslinked with the polyfunctional isocyanate compound (B) to form a crosslinked product (network polymer). Since the crosslinked body is excellent in stress relaxation properties, the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition of the present invention can maintain high constant load peelability even at high temperatures and is considered to be excellent in durability. .

  The polymer molecule (a) has a structural unit derived from a carboxyl group-containing monomer. In order for the polymer molecule (a) to have a structural unit derived from a carboxyl group-containing monomer, for example, a carboxyl group-containing monomer can be used as the polymerizable double bond-containing monomer. By having a structural unit derived from a carboxyl group-containing monomer, the reaction between the hydroxyl group of the polymer molecule (a) and the isocyanate group of the polyfunctional isocyanate compound (B) can be promoted. A pressure-sensitive adhesive layer having excellent durability can be formed. Furthermore, since the polymer molecule (a) has a structural unit derived from a carboxyl group-containing monomer, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition containing the polymer molecule (a) is made of a SUS plate or an aluminum plate. Excellent durability when attached to.

  The weight average molecular weight (Mw) of the polymer molecule (a) measured by gel permeation chromatography (GPC) is preferably 300,000 to 600,000, more preferably 320,000 to 550,000. More preferably, it is 330,000-500,000.

The molecular weight distribution (Mw / Mn) of the polymer molecule (a) is preferably 4.0 or less, more preferably 1.5 to 3.8, still more preferably 1.8 to 3.5.
Mw and Mw / Mn can be measured, for example, by the method described in Examples.

  The polymer molecule (a) is a reversible addition-cleavage of a polymerizable double bond-containing monomer such as (meth) acrylic acid ester to the compound represented by the formula (A1) (hereinafter also referred to as “compound (A1)”). A polymer obtained by polymerization by a chain transfer (RAFT) polymerization method is preferred.

式（Ａ１）中、Ｒ¹はそれぞれ独立に２価の有機基である。

In formula (A1), each R ¹ is independently a divalent organic group.

  The compound (A1) has a trithiocarbonate structure in the molecule and has hydroxyl groups at both ends of the molecule. Compound (A1) can be synthesized, for example, according to the method described in JP-A-2007-230947. By using the compound (A1) having the above structure, a telechelic structure can be formed without containing harmful organic metals.

  By performing RAFT polymerization, the repeating structural unit derived from the polymerizable double bond-containing monomer is bonded almost uniformly to both sides of the trithiocarbonate structure in the molecule, and the hydroxyl group is bonded to both ends of the molecule. A chain polymer can be obtained.

  Examples of the compound (A1) include a compound represented by the formula (A2) (hereinafter also referred to as “compound (A2)”) and a compound represented by the formula (A3) (hereinafter also referred to as “compound (A3)”). .).

  The compound (A2) has a trithiocarbonate structure in the molecule, and has one hydroxyl group at each end of the molecule. Examples of the compound (A2) include RAFT-NT manufactured by Nippon Terpene Chemical Co., Ltd.

式（Ａ２）中、Ｘはそれぞれ独立に−ＣＯＯ−、−ＣＯＮＲ³−または直接結合であり、Ｒ³はそれぞれ独立にアルキル基であり、当該アルキル基の炭素数は好ましくは１〜４、より好ましくは１〜３であり；Ｒ²はそれぞれ独立にアルキレン基であり、当該アルキレン基の炭素数は好ましくは１〜１２、より好ましくは１〜６であり；Ａｒはそれぞれ独立にフェニレン基、ナフチレン基またはフェニレン基，ナフチレン基に含まれる芳香環水素の少なくとも１つを置換基に置き換えてなる基である。置換基としては、例えば、アルキル基、アルコキシ基が挙げられる。なお、Ｘにおいて−ＣＯＯ−および−ＣＯＮＲ³−中のカルボニル基がＡｒに結合するものとする。２つのＸは同一の基であることが好ましく、２つのＲ²は同一の基であることが好ましく、２つのＲ³は同一の基であることが好ましく、２つのＡｒは同一の基であることが好ましい。

In formula (A2), each X is independently —COO—, —CONR ³ — or a direct bond, R ³ is each independently an alkyl group, and the alkyl group preferably has 1 to 4 carbon atoms. R ² is each independently an alkylene group, and the alkylene group preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms; Ar is each independently a phenylene group or naphthylene. Or a group formed by substituting at least one of the aromatic ring hydrogen contained in the phenylene group or naphthylene group with a substituent. Examples of the substituent include an alkyl group and an alkoxy group. In X, a carbonyl group in —COO— and —CONR ³ — is bonded to Ar. Two X are preferably the same group, ^two R ² are preferably the same group, two R ³ are preferably the same group, and two Ar are the same group It is preferable.

  Compound (A3) has a trithiocarbonate structure in the molecule, and two hydroxyl groups at both ends of the molecule. Examples of the compound (A3) include RAFT-DiOH manufactured by Nippon Terpene Chemical Co., Ltd.

式（Ａ３）中、ＸおよびＡｒは式（Ａ２）中の同一記号と同義であり；Ｒ⁴はそれぞれ独立にアルキレン基であり、Ｒ⁵はそれぞれ独立に直接結合またはアルキレン基であり、これらのアルキレン基の炭素数は好ましくは１〜１２、より好ましくは１〜６である。２つのＸは同一の基であることが好ましく、２つのＲ⁴は同一の基であることが好ましく、２つのＲ⁵は同一の基であることが好ましく、２つのＡｒは同一の基であることが好ましい。
化合物（Ａ１）の具体例を以下に示す。

In the formula (A3), X and Ar have the same meanings as the same symbols in the formula (A2); each R ⁴ independently represents an alkylene group, each R ⁵ independently represents a direct bond or an alkylene group, Carbon number of an alkylene group becomes like this. Preferably it is 1-12, More preferably, it is 1-6. Two X are preferably the same group, two R ⁴ are preferably the same group, two R ⁵ are preferably the same group, and two Ar are the same group It is preferable.
Specific examples of the compound (A1) are shown below.

ＲＡＦＴ重合において、化合物（Ａ１）の存在下、重合性二重結合含有モノマーを重合させる。化合物（Ａ１）の使用量は、重合性二重結合含有モノマーの総量１００質量部に対して、通常０．０５〜２０質量部、好ましくは０．０５〜１０質量部である。化合物（Ａ１）の使用量が前記範囲の下限値以上であれば反応制御が容易であり、前記範囲の上限値以下であれば得られる重合体の重量平均分子量を上記範囲に調整することが容易である。

In RAFT polymerization, a polymerizable double bond-containing monomer is polymerized in the presence of the compound (A1). The usage-amount of a compound (A1) is 0.05-20 mass parts normally with respect to 100 mass parts of total amounts of a polymerizable double bond containing monomer, Preferably it is 0.05-10 mass parts. If the amount of the compound (A1) used is not less than the lower limit of the range, the reaction control is easy, and if it is not more than the upper limit of the range, it is easy to adjust the weight average molecular weight of the resulting polymer to the above range. It is.

  For example, the compound represented by the formula (A1-1) reacts so that a polymerizable double bond-containing monomer is inserted between a sulfur atom in the compound (A1) and a methylene group adjacent to the sulfur atom. Combined (hereinafter also referred to as “polymer (A1-1)”), specific examples include a polymer represented by formula (A2-1) or formula (A3-1) (hereinafter referred to as “polymer (A2-1)”). "Also referred to as" polymer (A3-1) ").

式（Ａ１−１）中、Ｒ¹は式（Ａ１）中の同一記号と同義であり、（Ａ）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In formula (A1-1), R ¹ is synonymous with the same symbol in formula (A1), and (A) is derived from a polymer of a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer. It is a divalent group (polymer chain of a polymerizable double bond-containing monomer).

式（Ａ２−１）中、Ｘ、Ｒ²およびＡｒは式（Ａ２）中の同一記号と同義であり、（Ａ）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In the formula (A2-1), X, R ² and Ar have the same meanings as the same symbols in the formula (A2), and (A) represents the weight of the polymerizable double bond-containing monomer including the carboxyl group-containing monomer. It is a divalent group derived from a coalescence (polymer chain of a polymerizable double bond-containing monomer).

式（Ａ３−１）中、Ｘ、Ｒ⁴、Ｒ⁵およびＡｒは式（Ａ３）中の同一記号と同義であり、（Ａ）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In the formula (A3-1), X, R ⁴ , R ⁵ and Ar have the same meanings as the same symbols in the formula (A3), and (A) each independently contains a polymerizable double bond containing a carboxyl group-containing monomer. It is a divalent group derived from a monomer polymer (polymer chain of a polymerizable double bond-containing monomer).

  In formulas (A1-1) to (A3-1), A (a divalent group derived from a polymer) may be either a homopolymer structure or a copolymer structure of a polymerizable double bond-containing monomer, Further, the copolymer structure may be either a random copolymer structure of a polymerizable double bond-containing monomer or a block copolymer structure.

  In the above A (divalent group derived from a polymer) in the formulas (A1-1) to (A3-1), the number of repeating structural units derived from the polymerizable double bond-containing monomer is the number of the polymer molecule (a). Mw is a number within the above range.

  The block copolymer structure is obtained by, for example, adding a polymerizable double bond-containing monomer to the compound (A1) and performing the first RAFT polymerization, and adding an additional polymerizable double bond to the obtained polymer. It can be obtained by adding a monomer and performing the second RAFT polymerization. Here, an example of a two-component block structure has been described, but a three-component block structure may be used, and is not particularly limited. For example, Formula (A1-2), specifically, a polymer represented by Formula (A2-2) or Formula (A3-2) (hereinafter referred to as “polymer (A1-2)”, “polymer (A2-2)”. And “polymer (A3-2)”).

式（Ａ１−２）中、Ｒ¹は式（Ａ１）中の同一記号と同義であり、（Ａ¹）および（Ａ²）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In formula (A1-2), R ¹ has the same meaning as the same symbol in formula (A1), and (A ¹ ) and (A ² ) are each independently a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer It is a divalent group (polymer chain of a polymerizable double bond-containing monomer) derived from the polymer.

式（Ａ２−２）中、Ｘ、Ｒ²およびＡｒは式（Ａ２）中の同一記号と同義であり、（Ａ¹）および（Ａ²）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In formula (A2-2), X, R ² and Ar have the same meanings as the same symbols in formula (A2), and (A ¹ ) and (A ² ) are each independently a polymerizable group containing a carboxyl group-containing monomer. It is a divalent group (polymer chain of a polymerizable double bond-containing monomer) derived from a polymer of a heavy bond-containing monomer.

式（Ａ３−２）中、Ｘ、Ｒ⁴、Ｒ⁵およびＡｒは式（Ａ３）中の同一記号と同義であり、（Ａ¹）および（Ａ²）はそれぞれ独立にカルボキシル基含有モノマーを含む重合性二重結合含有モノマーの重合体に由来する２価の基（重合性二重結合含有モノマーの重合体鎖）である。

In formula (A3-2), X, R ⁴ , R ⁵ and Ar have the same meanings as the same symbols in formula (A3), and (A ¹ ) and (A ² ) each independently contain a carboxyl group-containing monomer. It is a divalent group (polymer chain of a polymerizable double bond-containing monomer) derived from a polymer of a polymerizable double bond-containing monomer.

  As the polymer molecule (a), when the polymer chain of the polymerizable double bond-containing monomer has a block copolymer structure, for example, polymers (A1-2) to (A3-2), The resulting composition for pressure-sensitive adhesives has a good balance of hydrophobicity-hydrophilicity, flexibility-rigidity, etc. depending on the purpose.

  The RAFT polymer having the above structure has a soft segment derived from the polymer chain of the polymerizable double bond-containing monomer. Therefore, since the isocyanate group of the polyfunctional isocyanate compound (B) tends to approach the terminal hydroxyl group of the RAFT polymer, the formation of urethane bonds is considered to proceed efficiently.

The polymer molecule (a) can be used alone or in combination of two or more.
The (meth) acrylic polymer (A) may further contain a polymer other than the polymer molecule (a) in addition to the polymer molecule (a). Examples of the polymer other than the polymer molecule (a) include a by-product of RAFT polymerization when the polymer molecule (a) is produced by RAFT polymerization.

The content of the polymer molecule (a) in the (meth) acrylic polymer (A) is not particularly defined as long as the polymer molecule (a) is contained in the (meth) acrylic polymer (A).
The (meth) acrylic polymer (A) is obtained by, for example, RAFT polymerization.

The (meth) acrylic polymer (A) is preferably a RAFT polymer of a polymerizable double bond-containing monomer including a carboxyl group-containing monomer.
The polymerizable double bond-containing monomer used to form the (meth) acrylic polymer (A) is the same as the polymerizable double bond-containing monomer used to form the polymer molecule (a). It is preferable. That is, the polymer molecule (a) and a polymer other than the polymer molecule (a) contained in the (meth) acrylic polymer (A) are formed from the same polymerizable double bond-containing monomer. It is preferably a coalescence.

  Mw measured by GPC of (meth) acrylic polymer (A) is 300,000 to 600,000, preferably 320,000 to 550,000, more preferably 330,000 to 500,000. By using the acrylic polymer (A) having Mw in the above range, an adhesive layer excellent in durability under a high temperature load environment can be obtained.

  Mw / Mn of the (meth) acrylic polymer (A) is 4.0 or less, preferably 1.5 to 3.8, more preferably 1.8 to 3.5. The (meth) acrylic polymer (A) having a Mw / Mn in the above range has a uniform molecular weight and a small number of low molecular weight substances, so that the resulting crosslinked product is excellent in heat resistance and peels off a pressure sensitive adhesive sheet from low temperature to high temperature conditions. Contamination of the adherend due to the low molecular weight material at the time can be suppressed.

Mw and Mw / Mn can be measured, for example, by the method described in Examples.
Content of the (meth) acrylic polymer (A) in the composition for adhesives is 10-95 mass% normally in 100 mass% of compositions for adhesives.

<Polymerizing double bond-containing monomer>
The (meth) acrylic polymer (A) containing the polymer molecule (a) can be obtained by, for example, RAFT polymerization of the polymerizable double bond-containing monomer. As the polymerizable double bond-containing monomer, at least a (meth) acrylic acid ester and a carboxyl group-containing monomer are used. However, functional group-containing (meth) acrylates such as carboxyl group-containing (meth) acrylate, hydroxyl group-containing (meth) acrylate, and amino group-containing (meth) acrylate are excluded from the (meth) acrylic acid ester.

  In addition, as the polymerizable double bond-containing monomer, at least one selected from functional group-containing monomers other than carboxyl groups and copolymerizable monomers other than these can be used.

<(Meth) acrylic acid ester>
Since the polymer molecule (a) has a structural unit derived from (meth) acrylic acid ester, (meth) acrylic acid ester is used as the polymerizable double bond-containing monomer.
Examples of the (meth) acrylic acid ester include alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, alkoxypolyalkylene glycol mono (meth) acrylate, alicyclic group, and aromatic ring-containing (meth) acrylate.

  It is preferable that carbon number of the alkyl group in alkyl (meth) acrylate is 1-20. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, and iso-butyl ( (Meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, Decyl (meth) acrylate, undeca (meth) acrylate, lauryl (meth) acrylate, oleyl (meth) acrylate, n-stearyl (meth) acrylate, iso-stearyl (meth) acrylate, dide (Meth) acrylate.

  Examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl ( Examples include meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

  Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, ethoxydiethylene glycol mono (meth) acrylate, And methoxytriethylene glycol mono (meth) acrylate.

  Examples of the alicyclic group or aromatic ring-containing (meth) acrylate include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate.

The (meth) acrylic acid ester can be used alone or in combination of two or more.
The amount of the (meth) acrylic acid ester used is usually 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more with respect to 100% by mass of the total polymerizable double bond-containing monomer.

In the case of forming a block copolymer structure in the RAFT polymerization method, for example, in the polymers (A1-2) to (A3-2), the polymerizable double bond-containing monomer that forms each of A ¹ and A ² is It is preferable that each of them contains different types of monomers selected from (meth) acrylic acid esters.

<Carboxyl group-containing monomer>
Since the polymer molecule (a) has a structural unit derived from a carboxyl group-containing monomer, a carboxyl group-containing monomer is used as the polymerizable double bond-containing monomer.

  Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloyloxyethyl ester succinate, and ω-carboxypolycaprolactone mono (meth) acrylate. Carboxyl group-containing (meth) acrylates such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid.

The carboxyl group-containing monomer can be used alone or in combination of two or more.
The used amount of the carboxyl group-containing monomer is usually 0.5 to 15% by mass, preferably 1 to 12% by mass, more preferably 3 to 10% by mass with respect to 100% by mass of the total polymerizable double bond-containing monomer. is there.

<Functional group-containing monomer other than carboxyl group>
Examples of functional group-containing monomers other than carboxyl groups include acid group-containing monomers other than carboxyl groups, hydroxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, nitrogen-based heterocyclic-containing monomers, and cyano group-containing monomers. . Examples of the acid group other than the carboxyl group include an acid anhydride group, a phosphoric acid group, and a sulfuric acid group.

  Examples of acid group-containing monomers other than carboxyl groups include acid anhydride group-containing monomers such as phthalic anhydride and maleic anhydride; phosphate group-containing monomers such as (meth) acrylic monomers having a phosphate group in the side chain A sulfuric acid group-containing monomer such as a (meth) acrylic monomer having a sulfuric acid group in the side chain.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( Examples include hydroxyl group-containing (meth) acrylates such as (meth) acrylate.

  Examples of the amino group-containing monomer include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

  Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and N-hexyl (meth) acrylamide. Examples of the nitrogen heterocycle-containing monomer include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The functional group-containing monomer can be used alone or in combination of two or more.
In the synthesis of the polymer molecule (a), a monomer containing a functional group other than a carboxyl group may be used, but a copolymer of a monomer containing a functional group such as a hydroxyl group or an amino group that is highly reactive with an isocyanate group In this case, due to isocyanate crosslinking, the sites other than both ends of the molecule are crosslinked, and the free ends are increased by a certain amount, so that the durability of the resulting pressure-sensitive adhesive layer may be lowered. Therefore, from the viewpoint of improving durability, the amount of the monomer having at least one selected from a hydroxyl group and an amino group is preferably 0.3% by mass or less with respect to 100% by mass of the total polymerizable double bond-containing monomer. More preferably, it is 0.1% by mass or less.
The polymer molecule (a) preferably has no structural unit derived from a monomer containing a functional group having reactivity with an isocyanate group.

<Copolymerizable monomer>
Examples of copolymerizable monomers include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, and other alkyl styrenes, fluorostyrene, chlorostyrene, bromostyrene, dibromo. Examples thereof include styrene monomers such as styrene, iodinated styrene, nitrostyrene, acetylstyrene, and methoxystyrene, and vinyl acetate.
The copolymerizable monomer can be used alone or in combination of two or more.

<Polymerization initiator>
RAFT polymerization is preferably performed in the presence of a polymerization initiator. Examples of the polymerization initiator include ordinary organic polymerization initiators, specifically, peroxides such as benzoyl peroxide and lauroyl peroxide, and 2,2′-azobisisobutyronitrile. An azo compound is mentioned. Among these, an azo compound is preferable.

  Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2′-azobis (2-cyclopropyl). Propionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile) 2- (carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis ( N, N'-dimethyleneisobutylamidine), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2,2'-azobi (Isobutyramide) dihydrate, 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis (2-cyanopropanol), dimethyl-2,2′-azobis (2-methylpropionate), 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide].

The polymerization initiator can be used alone or in combination of two or more.
The usage-amount of a polymerization initiator is 0.001-2 mass part normally with respect to 100 mass parts of polymerizable double bond containing monomers, Preferably it is 0.002-1 mass part. By using the polymerization initiator within the above range, the Mw of the (meth) acrylic polymer (A) can be adjusted within an appropriate range.

<Polymerization conditions>
The reaction temperature in the RAFT polymerization method is usually 60 to 120 ° C., preferably 70 to 110 ° C., and is usually performed in an inert gas atmosphere such as nitrogen gas. The reaction can be performed under any conditions, and is usually performed at normal pressure. Moreover, reaction time is 1 to 20 hours normally, Preferably it is 2 to 14 hours. Regarding polymerization conditions, for example, JP-A-2007-230947 and JP-A-2011-52057 can be referred to.

  In RAFT polymerization, the reaction is usually carried out without using a reaction solvent, but a reaction solvent may be used if necessary. Examples of the reaction solvent include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; cyclopentane, cyclohexane and cycloheptane. Cycloaliphatic hydrocarbons such as cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; chloroform, carbon tetrachloride, Halogenated hydrocarbons such as 1,2-dichloroethane and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate and methyl propionate; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexane Ketones such as non; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide and sulfolane Can be mentioned. These solvents can be used alone or in combination of two or more.

<Polyfunctional isocyanate compound (B)>
The polyfunctional isocyanate compound (B) is an isocyanate compound having two or more isocyanate groups in one molecule. The number of isocyanate groups in one molecule of the polyfunctional isocyanate compound (B) is preferably 2 to 8, more preferably 3 to 5. When the number of isocyanate groups is within the above range, it is preferable from the viewpoint of the crosslinking reaction efficiency between the polymer molecule (a) and the isocyanate compound, and the availability.

  Examples of the diisocyanate compound having 2 isocyanate groups in one molecule include aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl. Examples include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include alicyclic rings having 7 to 30 carbon atoms such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylylene diisocyanate. Group diisocyanates. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

  Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4 ', 4 "-triphenylmethane triisocyanate.

  Examples of the isocyanate compound include multimers (for example, dimers or trimers, biurets, and isocyanurates) and derivatives (for example, polyhydric alcohols) of the above isocyanate compounds having 2 or 3 isocyanate groups. Addition reaction product with two or more diisocyanate compounds) and polymer. Examples of the polyhydric alcohol in the derivative include trivalent or higher alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight polyhydric alcohols; high molecular weight polyhydric alcohols such as polyether polyols, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

  Examples of such isocyanate compounds include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or tolylene diisocyanate biuret or isocyanurate, trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate. Reaction product (for example, a trimolecular adduct of tolylene diisocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a trimolecular adduct of hexamethylene diisocyanate), a polyether polyisocyanate, Polyester polyisocyanate is mentioned.

The polyfunctional isocyanate compound (B) can be used alone or in combination of two or more.
Content of the polyfunctional isocyanate compound (B) in the composition for adhesives is 0.1-5 mass parts with respect to 100 mass parts of (meth) acrylic polymer (A), Preferably it is 0.5-4 mass. Part, more preferably 1 to 3 parts by mass. When the content of the compound (B) is in the above range, the cohesiveness of the resulting composition does not decrease, and the pressure-sensitive adhesive layer is excellent in the balance of adhesive properties of the resulting composition and excellent in durability. Can be obtained. In particular, it is preferable to use the compound (B) at the lower limit value or more because the reaction rate between the terminal hydroxyl group and the isocyanate group is improved, and the adhesive performance can be exhibited because it is sufficiently cured.

<Tackfire (C)>
Since the composition for pressure-sensitive adhesives of the present invention contains a tackifier (C), it can form a pressure-sensitive adhesive layer that exhibits good adhesive force even when adhered to a polyolefin-based low polarity material such as polypropylene. .

  The softening point of the tackifier (C) is 95 ° C. or higher, more preferably 95 to 150 ° C. If the tackifier (C) has a softening point within the above range, the pressure-sensitive adhesive layer has an appropriate tackiness and is excellent in heat resistance, so that a pressure-sensitive adhesive layer excellent in durability in a high-temperature environment can be obtained. Therefore, it is preferable. The softening point can be measured, for example, by differential scanning calorimetry (DSC) from 23 ° C. to 180 ° C. at a heating rate of 5 ° C. per minute.

Examples of the tackifier (C) include rosin compounds such as rosin ester resins; terpene compounds such as terpene phenol resins.
Examples of the rosin ester resin include disproportionated rosin ester resin, hydrogenated rosin ester resin, and polymerized rosin ester resin.

  Examples of the disproportionated rosin ester resin include super ester A-100 (manufactured by Arakawa Chemical Industries, softening point 95 to 105 ° C.) and super ester A-115 (manufactured by Arakawa Chemical Industries, softening point 108 to 120 ° C.). ), Superester A-125 (Arakawa Chemical Industries, softening point 120-130 ° C.). Examples of the hydrogenated rosin ester resin include Pine Crystal KE-604 (Arakawa Chemical Industries, softening point 124-134 ° C.), Pine Crystal KE-140 (Arakawa Chemical Industries, softening point 130-150 ° C.). Is mentioned. Examples of the polymerized rosin ester resin include Pencel A (Arakawa Chemical Industries, softening point 100 ° C. or higher), Pencel C (Arakawa Chemical Industries, softening point 117-127 ° C.), Pencel D-125 (Arakawa Chemical). Industrial company, softening point 120-130 ° C), Pencel D-135 (Arakawa Chemical Industries, softening point 130-140 ° C), Pencel D-160 (Arakawa Chemical Industries, softening point 150-165 ° C) Can be mentioned.

Examples of the terpene phenol resin include YS Polystar G150 (manufactured by Yasuhara Chemical, softening point 145 to 155 ° C.), YS Polystar G125 (manufactured by Yashara Chemical, softening point 120 to 130 ° C.), YS Polystar T100 (manufactured by Yashara Chemical, softening). 95-105 ° C), YS Polystar T115 (Yasuhara Chemical Co., softening point 110-120 ° C), YS Polystar T130 (Yasuhara Chemical Co., softening point 125-135 ° C), YS Polystar T145 (Yasuhara Chemical Co., softening point 140) -150 ° C), Tamanol 80L (Arakawa Chemical Industries, softening point 145-160 ° C), Tamanoru 901 (Arakawa Chemical Industries, softening point 120-135 ° C).
These tackifiers (C) may be used alone or in combination of two or more.

  The content of the tackifier (C) in the pressure-sensitive adhesive composition is usually 5 to 50 parts by mass, preferably 8 to 40 parts by mass, more preferably 100 parts by mass of the (meth) acrylic polymer (A). 10 to 30 parts by mass. When the content of the tackifier (C) is in the above range, the pressure-sensitive adhesive layer has an appropriate tackiness and is excellent in adhesive strength to olefinic low-polarity materials.

<Additive>
The pressure-sensitive adhesive composition of the present invention is an organic solvent, an antistatic agent, an ultraviolet absorber, an antioxidant, and a tackifying resin other than the above (C) as long as the effects of the present invention are not impaired in addition to the above components. 1 type (s) or 2 or more types selected from a plasticizer, an antifoaming agent, a filler, a stabilizer, a softening agent, and a wettability adjusting agent may be contained.

  As the organic solvent, the reaction solvent described in the “polymerization conditions” column of RAFT polymerization can be used. For example, a polymer solution containing a (meth) acrylic polymer (A) and a reaction solvent obtained by RAFT polymerization, a polyfunctional isocyanate compound (B) and a tackifier (C) are mixed to prepare a pressure-sensitive adhesive composition. Can be prepared. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 0 to 90% by mass, preferably 10 to 80% by mass.

(Adhesive layer)
The pressure-sensitive adhesive layer of the present invention is a polyfunctional (meth) acrylic polymer (A) containing a (meth) acrylic acid ester polymer molecule (a) by crosslinking the above-mentioned pressure-sensitive adhesive composition. It can be obtained by crosslinking with an isocyanate compound (B). The pressure-sensitive adhesive layer thus obtained exhibits a good adhesive force even when adhered to a polyolefin-based low-polarity material such as polypropylene, and has excellent durability under a high-temperature load environment.

The thickness of the pressure-sensitive adhesive layer is usually 3 to 100 μm, preferably 5 to 50 μm.
The pressure-sensitive adhesive layer has a gel fraction of preferably 20 to 90% by mass, more preferably 30 to 80% by mass, from the viewpoint of suppressing distortion of the polarizing plate, improving cohesive force, adhesive force, and removability. Preferably it is 40-70 mass%.

  The conditions for forming the pressure-sensitive adhesive layer are as follows. For example, the said composition is apply | coated on a support body or a separator, and normally 60-120 degreeC, Preferably it is 70-110 degreeC, and is normally dried for 1 to 5 minutes, Preferably it is 2 to 4 minutes, and forms a coating film.

  The pressure-sensitive adhesive layer is preferably formed under the following conditions. After applying the composition on a support or separator and applying the support or separator on the coating film formed under the above conditions, usually 3 days or more, preferably 7 to 10 days, usually 5 to 60 ° C., It is preferably cured under an environment of 15 to 40 ° C., usually 30 to 70% RH, preferably 40 to 70% RH. When crosslinking is performed under the aging conditions as described above, a crosslinked body (network polymer) can be efficiently formed.

  Examples of the support and the separator include polyester films such as polyethylene terephthalate, plastic films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; nonwoven fabrics; and paper separators.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer made of the above-described pressure-sensitive adhesive composition. This pressure-sensitive adhesive sheet preferably has a base material, and may have a separator on the pressure-sensitive adhesive layer. Examples of the pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer, a base material, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on both surfaces of the base material, the base material, and one of the base materials. Examples thereof include a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on the surface, and a pressure-sensitive adhesive sheet having a separator attached to a surface of the pressure-sensitive adhesive sheet that is not in contact with the base material.

  The thickness of the pressure-sensitive adhesive layer is usually 3 to 100 μm, preferably 5 to 80 μm. Although the film thickness of a base material and a separator is not specifically limited, Usually, 10-100 micrometers, Preferably it is 25-50 micrometers.

  Examples of the substrate and the separator include polyester films such as polyethylene terephthalate, plastic films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; non-woven fabrics; and paper separators.

  The pressure-sensitive adhesive sheet of the present invention exhibits a good pressure-sensitive adhesive force even when adhered to a polyolefin-based low-polarity material such as polyethylene and polypropylene, and has excellent durability under a high temperature load environment.

  Therefore, the pressure-sensitive adhesive sheet of the present invention can be widely used as an industrial pressure-sensitive adhesive sheet, but it can be used for a nonwoven fabric double-sided tape and a double-sided tape for laminating urethane foam, particularly used in automobile interiors and inside electronic devices. it can.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. In the following description of Examples and the like, “part” means “part by mass” unless otherwise specified.
Each measured value in the examples was determined by the following method.

[Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)]
About the (meth) acrylic polymer, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) by standard polystyrene conversion were calculated | required by the gel permeation chromatography (GPC) method on the following conditions.
・ Measurement device: HLC-8120GPC (manufactured by Tosoh Corporation)
-GPC column configuration: The following five columns (all manufactured by Tosoh Corporation)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5) TSK-GEL G2500HXL
Sample Concentration: As will be 1.0 mg / cm ^3, diluting and mobile phase solvent with tetrahydrofuran: tetrahydrofuran Flow rate: 1.0 cm ³ / min
-Column temperature: 40 ° C

[Measurement of heating residue]
1 g of a (meth) acrylic polymer solution was put into a precisely weighed tin plate (mass: n1), and the total mass (n2) was precisely weighed, followed by heating at 105 ° C. for 3 hours. Thereafter, the tin plate was allowed to stand in a desiccator at room temperature for 1 hour, then weighed again, and the total mass (n3) after heating was measured. The heating residue was calculated from the following formula using the obtained mass measurement values (n1 to n3).
Heating residue (mass%) = 100 × [mass after heating (n3-n1) / mass before heating (n2-n1)]

<Acrylic polymer>
[Production Example A1]
In a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer and a reflux condenser, n-butyl acrylate 44 parts, 2-ethylhexyl acrylate 50 parts, acrylic acid 6 parts, and bis [4- {ethyl- (2- Hydroxyethyl) aminocarbonyl} -benzyl] trithiocarbonate (manufactured by Nippon Terpene Chemical Co., Ltd.) (hereinafter also referred to as “RAFT agent-1”) 0.1 part was charged while introducing nitrogen gas into the flask. The contents of were heated to 80 ° C.

  After visually confirming that the RAFT agent was dissolved, 0.02 part of 2,2′-azobisisobutyronitrile (hereinafter also referred to as “AIBN”) was added to the flask under stirring. Heating and cooling were performed for 1 hour so that the temperature of the contents could be maintained at 80 ° C. Next, 100 parts of ethyl acetate was added dropwise over 1 hour while maintaining the temperature of the contents in the flask at 80 ° C., and then heating and cooling were performed so that the temperature of the contents in the flask could be maintained at 80 ° C. Finally, 20 parts of ethyl acetate was added.

  As described above, a polymer solution containing the acrylic polymer (A1) was obtained. The molecular weight measured by GPC for the acrylic polymer (A1) contained in the obtained polymer solution was Mw: 380,000 and Mw / Mn: 2.4. The heating residue of the obtained polymer solution was 45% by mass.

[Production Examples A2 and B1 to B4]
In Production Example A1, a polymer solution containing acrylic polymers (A2) and (B1) to (B4) was obtained in the same manner as in Production Example 1 except that the component composition was changed as described in Table 1. In Production Example B1, 60 parts of ethyl acetate was added dropwise over 1 hour while maintaining the temperature of the contents in the flask at 80 ° C., and finally 20 parts were added.
Each component described in Table 1 is as shown below.
BA: n-butyl acrylate 2-EHA: 2-ethylhexyl acrylate 2-HEA: 2-hydroxyethyl acrylate AA: acrylic acid RAFT agent-1: bis [4- {ethyl- (2-hydroxyethyl) aminocarbonyl} -benzyl ] Trithiocarbonate RAFT agent-2: S, S-dibenzyltrithiocarbonate

<Adhesive composition and double-sided PSA sheet>
[Example 1]
A polymer solution containing the acrylic polymer (A1) obtained in Production Example A1 was mixed with D-125 (Arakawa Chemical Industries, softening point 120 to 130 ° C.) as a tackifier. This mixture was mixed with L-45 (manufactured by Soken Chemical Co., Ltd., tolylene diisocyanate crosslinking agent, about 3 isocyanate groups in one molecule) as an isocyanate compound to obtain a pressure-sensitive adhesive composition. In addition, it mixed in the ratio (all are solid content ratio) in which the compounding quantity of D-125 with respect to 100 parts of acrylic polymers (A1) becomes 30 parts, and the compounding quantity of L-45 becomes 2.0 parts.

  After removing the foam, the pressure-sensitive adhesive composition was applied on a paper separator (EKR-80D) that had been peeled off using a doctor blade so that the thickness after drying would be 65 μm. The solvent was removed by drying for a minute. The obtained pressure-sensitive adhesive coating film was bonded to both sides of a 38 μm-thick nonwoven substrate and aged for 7 days in an environment of 23 ° C. and 65% RH. Paper separator / pressure-sensitive adhesive layer / non-woven fabric substrate / pressure-sensitive adhesive layer / A double-sided pressure-sensitive adhesive sheet comprising a paper separator and having a total tape thickness of 140 μm excluding the paper separators on both sides was obtained.

[Examples 2 and 3 and Comparative Examples 1 to 6]
In Example 1, the composition for adhesives and the double-sided adhesive sheet were obtained like Example 1 except having changed the composition component as described in Table 1.
The tackifiers listed in Table 1 are as shown below.
D-125: Rosin tackifier (Arakawa Chemical Co., Ltd., trade name: Pencel D-125, softening point: 120 to 130 ° C.)
T145: Terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name: YS Polyster T145, softening point: 140-150 ° C.)
A-75: Rosin tackifier (Arakawa Chemical Co., Ltd., trade name: Superester A-75, softening point: 70-80 ° C.)

<Evaluation>
[Gel fraction]
About 0.1 g of the pressure-sensitive adhesive layer obtained in Examples and the like was collected in a sampling bottle, 30 mL of ethyl acetate was added and shaken for 4 hours, and then the contents of this sample bottle were filtered through a 200-mesh stainless steel wire mesh. The residue on the wire mesh was dried at 100 ° C. for 2 hours, and the dry mass was measured. The gel fraction of the pressure-sensitive adhesive layer was determined by the following formula.
Gel fraction (% by mass) = (dry mass / adhesive layer sampling mass) × 100 (%)

[High temperature constant load test]
Under the conditions of 23 ° C. and 50% RH, one paper separator of the double-sided PSA sheet obtained in Examples and the like was peeled off, and a polyethylene terephthalate film having a thickness of 25 μm was lined on the exposed PSA layer surface. Thereafter, the other paper separator was peeled off, and the exposed adhesive surface was pressure-bonded to a polypropylene plate using a 2 kg roller. The affixing area was 20 mm wide × 50 mm. 20 minutes after sticking, the temperature was kept at 110 ° C. for 20 minutes under dry conditions, and then a load of 100 g was applied vertically in the direction of 90 ° with respect to the adhesive layer surface, and the peel length (mm) after 60 minutes was measured. When the test piece dropped from the polypropylene plate within the measurement time, the time required for the drop was measured. When dropped, it was described as “falling”.

Claims (6)

A (meth) acrylate polymer molecule (a) having a structure represented by the formula (a1), having a hydroxyl group at both ends of the molecule, and having a structural unit derived from a carboxyl group-containing monomer; (Meth) acrylic polymer (A) having a weight average molecular weight (Mw) measured by gel permeation chromatography method of 300,000 to 600,000 and a molecular weight distribution (Mw / Mn) of 4.0 or less;
0.1 to 5 parts by mass of the isocyanate compound (B) having 2 or more isocyanate groups in one molecule with respect to 100 parts by mass of the (meth) acrylic polymer (A),
A pressure-sensitive adhesive composition comprising a tackifier (C) having a softening point of 95 ° C or higher.

  The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic polymer (A) is a reversible addition-fragmentation chain transfer (RAFT) polymer of a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer.   The (meth) acrylic polymer (A) is a polymer of a polymerizable double bond-containing monomer in which the amount of a monomer having at least one selected from a hydroxyl group and an amino group is 0.3% by mass or less. The composition for adhesives of 1 or 2. The composition for pressure-sensitive adhesives according to any one of claims 1 to 3, wherein the (meth) acrylic acid ester polymer molecule (a) is a polymer represented by the formula (A1-1).

[In Formula (A1-1), R ¹ is each independently a divalent organic group, and (A) is independently derived from a polymer of a polymerizable double bond-containing monomer containing a carboxyl group-containing monomer. Is a valent group. ]   The adhesive layer obtained from the composition for adhesives of any one of Claims 1-4.   A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to claim 5.