KR102418362B1 - (meth)acrylic tri-block copolymer and manufacturing method thereof, pressure-sensitive adhesive composition, and pressure-sensitive adhesive sheet - Google Patents

Abstract

[assignment]
About the adhesive composition containing the (meth)acrylic block copolymer, the adhesive physical property with respect to various to-be-adhered bodies is further improved.
[Solution]
The (meth)acrylic triblock copolymer (A) obtained by RAFT polymerization using the RAFT agent shown in Formula (a1). [In formula (a1), R is a monovalent organic group having neither a hydroxyl group, a carboxyl group, nor an amino group, and two R's may be the same as or different from each other.]

Description

(meth)acrylic tri-block copolymer and manufacturing method thereof, pressure-sensitive adhesive composition, and pressure-sensitive adhesive sheet

The present invention relates to a (meth)acrylic tri-block copolymer and a method for producing the same, a pressure-sensitive adhesive composition, and a pressure-sensitive adhesive sheet.

In the field of adhesives, there is a demand for a pressure-sensitive adhesive composition having good adhesive properties with respect to retention, tack, and the like. Patent Documents 1 to 4 describe a pressure-sensitive adhesive composition containing a (meth)acrylic block copolymer obtained by a living radical polymerization method. In particular, Patent Document 1 describes a pressure-sensitive adhesive composition containing a (meth)acrylic block copolymer obtained by RAFT polymerization using a reversible addition cleavage chain transfer (RAFT) agent. However, the pressure-sensitive adhesive composition containing such a block copolymer needs further improvement in terms of physical properties of adhesion to various types of adherends.

Japanese Patent Application Laid-Open No. 2014-208762 Japanese Patent Application Laid-Open No. 10-008013 Japanese Patent Laid-Open No. 2001-348553 Japanese Patent Laid-Open No. 2016-023237

An object of the present invention is to further improve the adhesive properties of the pressure-sensitive adhesive composition containing the (meth)acrylic block copolymer to various adherends.

MEANS TO SOLVE THE PROBLEM The present inventors earnestly examined in order to solve the said subject. As a result, it discovered that the said subject could be solved by the (meth)acrylic-type triblock copolymer which has the following structures, and came to complete this invention.

The present invention is, for example, the following [1] to [11].

[1] The (meth)acrylic triblock copolymer (A) obtained by RAFT polymerization using the RAFT agent shown in Formula (a1).

[In formula (a1), R is a monovalent organic group having neither a hydroxyl group, a carboxyl group nor an amino group, and two R's may be the same as or different from each other.]

[2] The (meth)acrylic triblock copolymer (A) according to the above [1], wherein R in the formula (a1) is a hydrocarbon group, an acyl group, an acyloxy group or an acyloxyalkyl group.

[3] The (meth)acrylic triblock copolymer according to [1] or [2], wherein the weight average molecular weight (Mw) measured by the GPC method is 30,000 to 600,000, and the molecular weight distribution (Mw / Mn) is 1.5 to 5.0 coalescence (A).

[4] Block A-block B-block A has a tri-block structure, block B has a divalent structure represented by -S-C(=S)-S-, in 100% by mass of copolymer (A), block The (meth)acrylic triblock copolymer (A) according to any one of [1] to [3], wherein the total content of A is 5 to 40 mass% and the content of block B is 95 to 60 mass%.

[5] The content of the structural unit derived from the reactive functional group-containing monomer is 0.5 to 15 mass% in 100% by mass of the total structural units, and 95% by mass or more of the 100% by mass of the total structural units derived from the reactive functional group-containing monomer is block A The (meth)acrylic tri-block copolymer (A) according to the above [4] present in the.

[6] A pressure-sensitive adhesive composition comprising the (meth)acrylic tri-block copolymer (A) according to any one of [1] to [5].

[7] The pressure-sensitive adhesive composition according to the above [6], further comprising a curing agent (B).

[8] An adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to [6] or [7].

[9] Step 1 of polymerizing a polymerizable double bond-containing monomer using a RAFT agent represented by the formula (a1), and a polymerizable double bond-containing monomer different from the monomer composition in Step 1 to the polymer obtained in Step 1 A (meth)acrylic tri-block copolymer (A) in which one or both of the monomer used in step 1 and the monomer added in step 2 contain (meth)acrylic acid ester (A) ) manufacturing method.

[10] The method for producing the (meth)acrylic tri-block copolymer (A) according to the above [9], wherein the polymer obtained in step 1 has a weight average molecular weight (Mw) of 3,000 to 40,000 as measured by GPC method.

[11] The (meth)acrylic tri-block copolymer according to [9] or [10], wherein 95% by mass or more of the above monomer is used in Step 1 among 100% by mass of the reactive functional group-containing monomer that can be used in Steps 1 and 2 Method for producing the coalescence (A).

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition having excellent adhesion properties to various types of adherends, and it is possible to provide a (meth)acrylic tri-block copolymer suitable as a component of the composition.

Hereinafter, the (meth)acrylic tri-block copolymer of the present invention and its manufacturing method, the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive sheet will be described in detail including suitable aspects.

In this specification, "polymer" is used in the meaning containing a homopolymer and a copolymer, and "polymerization" is used in the meaning containing homopolymerization and copolymerization. In addition, acryl and methacryl are collectively referred to as "(meth)acryl".

In the present specification, a copolymer having at least a structural unit derived from (meth)acrylic acid ester is also referred to as a “(meth)acrylic copolymer”, and in the copolymer, 70 mass of raw material monomers used to form the copolymer % or more is preferably (meth)acrylic acid ester.

In this specification, the reversible addition cleavage chain transfer is also described as "RAFT".

[( meta ) acrylic try block copolymer (A)]

The (meth)acrylic tri-block copolymer (A) of the present invention is a RAFT polymerization using the RAFT agent represented by the formula (a1), specifically, for RAFT polymerization of a polymerizable double bond-containing monomer containing at least (meth)acrylic acid ester. obtained by

In formula (a1), R is a monovalent organic group which does not have any of a hydroxyl group, a carboxyl group, and an amino group. Although two R may be mutually the same or different, it is preferable that it is the same group from a synthetic point.

Since R does not have the above-listed functional groups (hydroxyl group, carboxyl group and amino group), the obtained copolymer also does not have the above-mentioned functional group at the molecular terminal derived from the RAFT agent.

Examples of the monovalent organic group include a hydrocarbon group such as an alkyl group, an aryl group, and an aralkyl group, an acyl group represented by R ¹ -C(=O)-, and an acyl group represented by R ¹ -C(=O)-O-. and an acyloxyalkyl group represented by an oxy group and R ¹ -C(=O)-OR ² -. R ¹ is an alkyl group, and R ² is an alkylene group. Among these, an acyl group, an acyloxy group, and an acyloxyalkyl group are preferable from the viewpoint that the RAFT agent tends to become liquid at room temperature and thus has excellent handling properties and excellent adhesion properties to various high-polarity or low-polarity adherends are obtained. do.

Specific examples of each group in the monovalent organic group are as follows. Carbon number of an alkyl group is 1-12 normally, Preferably it is 1-6, For example, a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group are mentioned. Carbon number of an aryl group is 6-18 normally, Preferably it is 6-12, For example, a phenyl group and a naphthyl group are mentioned. Carbon number of an aralkyl group is 7-18 normally, Preferably it is 7-12, For example, a benzyl group and a phenethyl group are mentioned. Carbon number of an acyl group and an acyloxy group is 2-8 normally, Preferably it is 2-6, For example, an acetyl group and an acetyloxy group are mentioned. Carbon number of an acyloxyalkyl group is 3-8 normally, Preferably it is 3-6, For example, an acetyloxymethyl group is mentioned.

As a RAFT agent shown in Formula (a1), the compound shown below is mentioned, for example.

The said RAFT agent has a trithiocarbonate structure in a molecule|numerator, and does not have a hydroxyl group, a carboxyl group, and an amino group in said R. The said RAFT agent can be synthesize|combined according to the method described in Unexamined-Japanese-Patent No. 2007-230947, for example.

The copolymer (A) preferably has a tri-block structure of block A-block B-block A. Here, the block B has a bivalent structure represented by -S-C(=S)-S-. In such an aspect, for example, a sea-island structure in which block A becomes an island and block B becomes an ocean, a gyroid structure or a cylinder structure can be formed, and an appropriate cohesive force can be imparted to the pressure-sensitive adhesive. preferred in

In 100 mass% of copolymer (A), the total content of block A is preferably 5 to 40 mass%, more preferably 10 to 30 mass%, and the content of block B is preferably 95 to 60 mass%, more Preferably it is 90-70 mass %.

Content of the structural unit derived from a reactive functional group containing monomer in 100 mass % of all structural units of a copolymer (A) becomes like this. Preferably it is 0.5-15 mass %, More preferably, it is 0.8-12 mass %, More preferably, it is 1- It is 10 mass %. The structural unit amount can be calculated from, for example, the amount of each monomer used and the residual amount of each monomer based on gas chromatography analysis of the polymer solution after polymerization. In such an aspect, an adhesive can take an appropriate crosslinking form, and it is preferable at the point which is excellent in various adhesive physical properties. In addition, all structural units of a copolymer (A) are all structural units derived from a raw material monomer.

Copolymer (A) WHEREIN: It is preferable that 95 mass % or more exists in block A out of 100 mass % of all structural units derived from a reactive functional group containing monomer, More preferably, it is 98 mass % or more. If it is such an aspect, since the reactive functional group is localizing in the block A, hardening is quick and the aging period of an adhesive composition can be shortened.

A copolymer (A) is represented by a following formula, for example.

In the above formula, R has the same symbol and the same meaning as in formula (a1), Ap is each independently a divalent group derived from the polymer of the polymerizable double bond-containing monomer (polymer chain of the polymerizable double bond-containing monomer), Bp are each independently a divalent group derived from the polymer of the polymerizable double bond-containing monomer (polymer chain of the polymerizable double bond-containing monomer).

In the above formula, Ap corresponds to the above-mentioned block A, and -Bp-S-C(=S)-S-Bp- corresponds to the above-mentioned block B. At least one block of blocks A and B also preferably has a structural unit derived from (meth)acrylic acid ester in both blocks.

By using the copolymer (A) of the present invention, it is possible to obtain a pressure-sensitive adhesive composition having good adhesive properties (eg, holding power, tack) to various adherends such as high-polarity materials and polyolefin-based low-polar materials.

《 polymeric Double bond-containing monomers >>

The raw material monomer of the copolymer (A) is a polymerizable double bond-containing monomer containing at least (meth)acrylic acid ester. As the polymerizable double bond-containing monomer, for example, (meth)acrylic acid ester not having the following reactive functional group, a monomer having at least one of the following reactive functional groups (hereinafter also referred to as “reactive functional group-containing monomer”), copolymerizable other than these monomers and monomers. Examples of the reactive functional group include an acid group, a hydroxyl group, an amino group, an amide group, a cyano group, and a nitrogen-based heterocycle.

As the (meth)acrylic acid ester having no reactive functional group, for example, alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, alkoxy polyalkylene glycol mono (meth) acrylate, alicyclic or aromatic ring containing ( meth) acrylate.

It is preferable that carbon number of the alkyl group in alkyl (meth)acrylate is 1-20. As alkyl (meth)acrylate, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, n-butyl (meth)acrylate , iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Octyl (meth) acrylate, iso-octyl (meth) acrylate, nonyl (meth) acrylate, iso- nonyl (meth) acrylate, decyl (meth) acrylate, iso-decyl (meth) acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and iso-stearyl (meth)acrylate are mentioned.

As alkoxyalkyl (meth)acrylate, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate Acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate are mentioned.

As alkoxy polyalkylene glycol mono(meth)acrylate, for example, methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol Col mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, and methoxytriethylene glycol mono(meth)acrylate are mentioned.

As the alicyclic group or aromatic ring-containing (meth)acrylate, for example, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate , benzyl (meth)acrylate, and phenyl (meth)acrylate.

The (meth)acrylic acid ester may be used alone or in combination of two or more.

The amount of the (meth)acrylic acid ester not having a reactive functional group is usually 70% by mass or more, preferably 80% by mass or more, among 100% by mass of all polymerizable double bond-containing monomers excluding reactive functional group-containing monomers, more preferably is 90 mass % or more.

Examples of the reactive functional group-containing monomer include an acid group-containing monomer, a hydroxyl group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a cyano group-containing monomer, and a nitrogen-based heterocycle-containing monomer.

As an acidic radical in an acidic radical containing monomer, a carboxyl group, an acid anhydride group, a phosphoric acid group, and a sulfuric acid group are mentioned, for example. As the acid group-containing monomer, for example, (meth)acrylic acid β-carboxyethyl, (meth)acrylic acid 5-carboxypentyl, succinic acid mono(meth)acryloyloxyethyl ester, ω-carboxypolycaprolactone mono(meth)acrylate Carboxyl group-containing monomers, such as unsaturated carboxylic acids, such as carboxyl group containing (meth)acrylates, such as (meth)acrylic acid, itaconic acid, a crotonic acid, a fumaric acid, and maleic acid; acid anhydride group-containing monomers such as maleic anhydride; Phosphoric acid group-containing monomers, such as a (meth)acrylic-type monomer which has a phosphoric acid group in a side chain; Sulfate group-containing monomers, such as a (meth)acrylic-type monomer which has a sulfuric acid group in a side chain, are mentioned.

As a hydroxyl-containing monomer, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate is, for example. and hydroxyl group-containing (meth)acrylates such as 8-hydroxyoctyl (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, N-hexyl (meth)acrylamide, etc. of (meth)acryl-type amides are mentioned. As a cyano group containing monomer, cyano (meth)acrylate and (meth)acrylonitrile are mentioned, for example. As a nitrogen-type heterocyclic-containing monomer, vinyl pyrrolidone, (meth)acryloyl morpholine, and vinyl caprolactam are mentioned, for example.

Among the reactive functional group-containing monomers, at least one selected from a carboxyl group-containing monomer and a hydroxyl group-containing monomer is preferable from the viewpoint of crosslinking reactivity with a crosslinking agent (B1) described later.

The reactive functional group-containing monomer can be used individually by 1 type or in 2 or more types.

The usage-amount of a reactive functional group containing monomer is 0.5-15 mass % normally, Preferably it is 0.8-12 mass %, More preferably, it is 1-10 mass % in 100 mass % of all polymerizable double bond containing monomers. When using at least 1 sort(s) chosen from a carboxyl group containing monomer and a hydroxyl group containing monomer, it is preferable that these total amounts exist in the said range.

Examples of the copolymerizable monomer include a styrene-based monomer and a vinyl-based monomer. Examples of the styrene-based monomer include styrene, α-methylstyrene; alkyl styrenes such as methyl styrene, dimethyl styrene and octyl styrene; halogenated styrenes such as fluorostyrene, chlorostyrene and bromostyrene; In addition, nitrostyrene, acetylstyrene, and methoxystyrene are mentioned. As a vinyl-type monomer, vinyl acetate is mentioned, for example.

A copolymerizable monomer can be used individually by 1 type or 2 or more types.

《 Product made in RAFT 》

RAFT polymerization WHEREIN: A polymerizable double bond containing monomer is superposed|polymerized in presence of the RAFT agent shown by Formula (a1). The usage-amount of the RAFT agent shown in Formula (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. In such an aspect, reaction control is easy, and it is easy to adjust the weight average molecular weight of the copolymer obtained to the range mentioned later.

"polymerization initiator 》

RAFT polymerization is preferably performed in the presence of a polymerization initiator. Examples of the polymerization initiator include ordinary organic polymerization initiators, and specific examples thereof include peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile. . Among these, an azo compound is preferable.

As the azo compound, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azo Bis (2-cyclopropylpropionitrile), 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(isobutyl Amide) dihydrate, 4,4'-azobis (4-cyanopentanic acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methyl) propionate) and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide].

A polymerization initiator can be used individually by 1 type or 2 or more types.

The usage-amount of a polymerization initiator is 0.001-2 mass parts normally with respect to 100 mass parts of total amounts of a polymerizable double bond containing monomer, Preferably it is 0.002-1 mass part. In such an aspect, it is easy to adjust the weight average molecular weight of the copolymer obtained to the range mentioned later.

《Polymerization solvent》

Although bulk polymerization which does not use a polymerization solvent may be sufficient as RAFT polymerization, you may use a polymerization solvent for RAFT polymerization as needed.

As a polymerization solvent, For example, aromatic hydrocarbons, such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane and chlorobenzene; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether and diphenyl ether; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; Sulfoxides, such as dimethyl sulfoxide and a sulfolane, are mentioned.

The polymerization solvent can be used individually by 1 type or in 2 or more types.

《Polymerization Conditions》

In the method for producing the copolymer (A) of the present invention, for example, step 1 (first RAFT polymerization) of polymerizing a polymerizable double bond-containing monomer using a RAFT agent represented by formula (a1) and step 1 It has the process 2 (2nd RAFT polymerization) which further adds and superposes|polymerizes a polymerizable double bond containing monomer different from the monomer composition in process 1 to the obtained polymer. It is preferable that one or both of the said monomer used in process 1 and the said monomer added in process 2 contain (meth)acrylic acid ester, and all contain (meth)acrylic acid ester.

In addition, as for the polymerizable double bond-containing monomer different from the monomer composition in step 1, the monomer composition added in step 2 with respect to the monomer composition used in step 1 depends on the type of monomer and (in each step, multiple types of monomers are used and added). ) means excluding the same case including the ratio. For example, the monomer common to the monomer used in the step 1 and the addition monomer in the step 2 may be contained. Moreover, even if the monomer used in step 1 and the monomer added in step 2 are the same, a plurality of types of monomers are used and added, respectively, and the ratio in the monomer used in step 1 (eg, methyl acrylate 90wt%, butylacryl rate) and the ratio in the monomer added in step 2 (eg, methyl acrylate 10 wt%, butyl acrylate 90 wt%) may be different.

In RAFT polymerization, polymerization proceeds by reacting so that a polymerizable double bond-containing monomer as a raw material monomer is inserted between a sulfur atom in the RAFT agent represented by the formula (a1) and a methylene group adjacent to the sulfur atom.

The reaction temperature in the RAFT polymerization method is usually 60 to 120°C, preferably 70 to 110°C, and is usually carried out in an inert gas atmosphere such as nitrogen gas. This reaction can be carried out under any conditions of normal pressure, pressurization and reduced pressure, and is usually carried out at normal pressure. Moreover, reaction time is 1-20 hours normally, Preferably it is 2-14 hours. These conditions may be applied to process 1 and process 2, respectively. About polymerization conditions, Unexamined-Japanese-Patent No. 2007-230947 and Unexamined-Japanese-Patent No. 2011-52057 can be referred, for example.

Preferably the weight average molecular weight (Mw) measured by GPC method of the polymer obtained in process 1 is 3,000-40,000, More preferably, it is 5,000-38,000, More preferably, it is 8,000-36,000.

Further, out of 100 mass% of the reactive functional group-containing monomers usable in Steps 1 and 2, 95% by mass or more, particularly 98% by mass or more of the reactive functional group-containing monomer is preferably used in Step 1. In such an aspect, since the reactive functional group is localized in the block A, curing is quick and the aging period of the pressure-sensitive adhesive composition can be shortened.

The amount ratio of the monomer used in Step 1 and Step 2 is not particularly limited, and for example, is appropriately set according to the amount ratio of the block A and block B in the copolymer (A) as the target product. For example, the amount of the polymerizable double bond-containing monomer added in the step 2 with respect to 100 parts by mass of the polymer obtained in the step 1 is preferably 150 to 1900 parts by mass, more preferably 233 to 900 parts by mass.

[Physical properties of copolymer (A)]

The weight average molecular weight (Mw) of the copolymer (A) measured by the gel permeation chromatography method (GPC method) is preferably 30,000 to 600,000, more preferably 50,000 to 550,000, still more preferably 80,000 to 500,000 to be. Since sufficient cohesive force is provided to an adhesive composition in such an aspect, it is preferable from a viewpoint of the durable improvement in high temperature dry conditions and high temperature, high humidity conditions.

The molecular weight distribution (Mw/Mn) of a copolymer (A) becomes like this. Preferably it is 1.5-5.0, More preferably, it is 1.5-4.8, More preferably, it is 1.7-4.5. If it is such an aspect, while the crosslinked body and/or hardening body obtained are excellent in heat resistance, the contamination of the to-be-adhered body at the time of adhesive sheet peeling can be suppressed.

The molecular weight and molecular weight distribution can be measured under the conditions described in Examples.

The glass transition temperature (Tg) of the copolymer (A) is preferably less than 0°C, more preferably -70 to -20°C, still more preferably -60 to -30°C. When Tg exists in the said range, it is preferable from a viewpoint of the adhesiveness to the to-be-adhered body of an adhesive layer. Moreover, it is excellent in the cohesion force of an adhesive layer as Tg is more than the said lower limit, and it is preferable from a viewpoint of a durable improvement. Tg of a copolymer (A) is computable from the formula of Tg and Fox of the homopolymer of each monomer, for example. As for Tg of the homopolymer of each monomer, the value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003) can be used, for example.

In one embodiment, the Tg of block A is preferably -30 to 150 °C, more preferably -20 to 120 °C, and the Tg of block B is preferably -80 to -40 °C, more preferably is -75 to -50 °C. Tg of each block is also computable from the formula of Tg and Fox of the homopolymer of each monomer, for example.

For a monomer whose Tg is not described in the above literature, for example, the Tg of a homopolymer synthesized under the following conditions is measured under the following conditions. 100 parts by mass of a monomer and 100 parts by mass of an ethyl acetate solvent were put into a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, and the temperature was raised to 80° C. while introducing nitrogen gas. Next, 0.1 mass part of 2,2'- azobisisobutyronitrile is added, and polymerization reaction is performed at 80 degreeC in nitrogen gas atmosphere for 6 hours. The obtained homopolymer is sealed in a simple airtight pan. Using a differential scanning calorimeter (DSC), increase the temperature at 10 °C/min under a nitrogen stream and measure the thermal change, draw a graph between “heat absorption” and “temperature”, and describe the characteristic inflection observed at this time as a glass transition do it with In addition, the value obtained by the midpoint method from the DSC curve is used for Tg.

[Adhesive composition]

The adhesive composition of this invention contains the above-mentioned (meth)acrylic-type triblock copolymer (A). It is preferable that the adhesive composition of this invention further contains a hardening|curing agent (B) according to a use.

[( meta ) acrylic try block copolymer (A)]

Content of (meth)acrylic-type triblock copolymer (A) is 60 mass % or more in 100 mass % of solid content of an adhesive composition, Preferably it is 65 mass % or more, More preferably, it is 70 mass % or more. In addition, 100 mass % may be sufficient as the upper limit of the said content of a copolymer (A), and when another component is also contained in solid content, it is determined with content of another component. If it is such an aspect, it is preferable at the point which can adjust various adhesive physical properties, such as a holding power and a tack, arbitrarily. Solid content refers to components other than a solvent normally.

[curing agent (B)]

It is preferable that the adhesive composition of this invention further contains a hardening|curing agent (B). By crosslinking the copolymer (A) with the curing agent (B) and/or curing the composition, a crosslinked product and/or a cured product can be formed, and an adhesive layer excellent in heat resistance can be obtained.

The pressure-sensitive adhesive composition of the present invention may be either a thermosetting system or an active energy ray curing system.

The kind of the curing agent (B) is appropriately selected depending on the reactive functional group that can be introduced into the copolymer (A) and the curing system of the pressure-sensitive adhesive composition. For example, when the acrylic copolymer (A) has a reactive functional group, a crosslinking agent (B1) capable of crosslinking reaction with the functional group such as an isocyanate compound, an epoxy compound, or a metal chelate compound can be used. Moreover, as a hardening|curing agent (B), polyfunctional (meth)acrylate (B2) can also be used, for example.

As the isocyanate compound, an isocyanate compound in which the number of isocyanate groups in one molecule is 2 or more is usually used, and the number of isocyanate groups is preferably 2 to 8, more preferably 3 to 6 . When the number of isocyanate groups exists in the said range, it is preferable at the point of the point of the crosslinking reaction efficiency of a copolymer (A) and an isocyanate compound, and the point which maintains the softness|flexibility of an adhesive layer.

As a diisocyanate compound whose number of isocyanate groups in 1 molecule is 2, aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate are mentioned, for example. As aliphatic diisocyanate, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diiso Aliphatic diisos having 4 to 30 carbon atoms, such as cyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate and cyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated tolylene diisocyanate. C7-30 alicyclic diisocyanate, such as nitrate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylylene diisocyanate, is mentioned. As aromatic diisocyanate, for example, phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate and C8-30 aromatic diisocyanate, such as diphenylmethane diisocyanate and diphenyl propane diisocyanate.

Examples of the isocyanate compound in which the number of isocyanate groups in one molecule is 3 or more 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. have.

Moreover, as an isocyanate compound, the number of isocyanate groups is 2 or 3 or more, for example, a multimer (for example, a dimer or trimer, a biuret body, an isocyanurate body), a derivative|guide_body of the said isocyanate compound. (For example, an addition reaction product of a polyhydric alcohol and two or more molecules of diisocyanate compound) and a polymer are mentioned. Examples of the polyhydric alcohol in the derivative include trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol as low molecular weight polyhydric alcohols; Examples of the high molecular weight polyhydric alcohol include polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

As such an isocyanate compound, for example, a trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate, or tolylene diisocyanate. Biuret form or isocyanurate form, reaction product of trimethylolpropane with tolylene diisocyanate or xylylene diisocyanate (for example, tolylene diisocyanate or xylylene diiso trimolecular adduct of cyanate), reaction product of trimethylolpropane with hexamethylene diisocyanate (e.g. trimolecular adduct of hexamethylene diisocyanate), polyetherpolyiso Cyanate and polyester polyisocyanate are mentioned.

Among the isocyanate compounds, xylylene diisocyanate-based and hexamethylene diisocyanate-based crosslinking agents are preferable from the viewpoint of egg yolk denaturation, and tolylene diisocyanate-based crosslinking agents are preferred from the viewpoint of stress relaxation properties. desirable. Examples of the xylylene diisocyanate-based crosslinking agent include xylylene diisocyanate and its multimers, derivatives, and polymers; Examples of the hexamethylene diisocyanate-based crosslinking agent include hexamethylene diisocyanate and its multimers, derivatives, and polymers; Examples of the tolylene diisocyanate-based crosslinking agent include tolylene diisocyanate and its multimers, derivatives, and polymers.

Examples of the epoxy compound include compounds having two or more epoxy groups in the molecule, for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, Glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylol propane triglycidyl ether, diglycidyl aniline, diamine glycidylamine, N, N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diamineglycidylaminomethyl) are mentioned.

As the metal chelate compound, for example, a compound in which a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium is coordinated with an alkoxide, acetylacetone, ethyl acetoacetate, etc. can be heard Specific examples include aluminum isopropylate, aluminum secondary rebutylate, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

Examples of the polyfunctional (meth)acrylate (B2) include di, tri, or polyalkylene glycol-di(meth)acrylate, alkanedioldi(meth)acrylate, and bisphenol-based di(meth)acrylate. , polyol poly (meth) acrylate more than trifunctional, polyurethane di (meth) acrylate, and polyurethane poly (meth) acrylate.

A hardening|curing agent (B) can be used individually by 1 type or 2 or more types.

The pressure-sensitive adhesive composition of the present invention contains the curing agent (B) in an amount of usually 0.01 to 25 parts by mass, preferably 0.05 to 20 parts by mass, more preferably 0.1 to 15 parts by mass with respect to 100 parts by mass of the copolymer (A). do.

In one embodiment, the composition contains the crosslinking agent (B1) in an amount of preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 4.0 parts by mass, still more preferably 0.1 to 100 parts by mass of the copolymer (A). It contains in the range of 3.0 mass parts. Or in another embodiment, the composition contains the polyfunctional (meth)acrylate (B2) with respect to 100 parts by mass of the copolymer (A), preferably 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass part, More preferably, it contains in 0.1-10 mass parts. Such an aspect is preferable because an appropriate degree of crosslinking and curing can be achieved and excellent adhesion properties can be realized.

[ light curing initiator (C)]

The pressure-sensitive adhesive composition of the present invention may further contain a photoinitiator (C). For example, the composition which contains polyfunctional (meth)acrylate (B2) at least as a hardening|curing agent (B), and further contains a photoinitiator (C) is preferable as an active energy ray hardening system adhesive composition.

Examples of the photopolymerization initiator (C) include a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzophenone-based photoinitiator, a ketal-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and an acylphosphine oxide-based photopolymerization initiator. , Specific examples of these initiators include compounds listed in paragraphs [0023] to [0027] of Japanese Patent Application Laid-Open No. 2009-013361.

A photoinitiator (C) can be used individually by 1 type or 2 or more types.

In one embodiment, the pressure-sensitive adhesive composition of the present invention contains, for example, 0.1 to 200 parts by mass, preferably 10 to 150 parts by mass, of the photopolymerization initiator (C) with respect to 100 parts by mass of the polyfunctional (meth)acrylate (B2). , More preferably, it contains in the range of 20-100 mass parts.

[Additive (D)]

The pressure-sensitive adhesive composition of the present invention is a (meth)acrylic polymer other than the copolymer (A), tackifying resin, silane coupling agent, antistatic agent, antioxidant, light stabilizer, You may contain the 1 type(s) or 2 or more types of additives chosen from a metal corrosion inhibitor, a plasticizer, a crosslinking promoter, surfactant, and a rework agent.

[Organic solvent (E)]

It is preferable that the adhesive composition of this invention contains an organic solvent (E) in order to adjust the applicability|paintability. The adhesive composition of this invention WHEREIN: Content of an organic solvent (E) is 30-90 mass % normally, Preferably it is 40-90 mass %. As an organic solvent (E), the solvent enumerated as a polymerization solvent mentioned above is mentioned.

The organic solvent (E) can be used individually by 1 type or in 2 or more types.

[Preparation of adhesive composition]

The adhesive composition of this invention can be prepared by mixing said each component by a conventionally well-known method, for example. For example, an adhesive composition can be prepared by mixing the solution containing the copolymer (A) obtained by the synthesis|combination of a copolymer (A), and another component.

[Adhesive sheet]

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention.

The pressure-sensitive adhesive sheet includes, for example, a double-sided pressure-sensitive adhesive sheet having only the above-mentioned pressure-sensitive adhesive layer, a substrate, and an adhesive layer formed on both surfaces of the substrate, and at least one pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, a double-sided pressure-sensitive adhesive sheet, a substrate and , a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on one surface of the base material, and a pressure-sensitive adhesive sheet in which a peeling-treated cover film is affixed to a surface in the pressure-sensitive adhesive layer of these pressure sensitive adhesive sheets that is not in contact with the base material.

The thickness of an adhesive layer is 5-200 micrometers normally from a viewpoint of adhesive performance maintenance, Preferably it is 10-100 micrometers. Moreover, the gel fraction of an adhesive layer is from a viewpoint of cohesion force, adhesive force, and re-peelability, Preferably it is 10-98 mass %, More preferably, it is 20-95 mass %, More preferably, it is 30-90 mass %.

For example, by advancing crosslinking and/or curing reaction in the pressure-sensitive adhesive composition of the present invention, the above-mentioned pressure-sensitive adhesive layer is obtained by crosslinking the copolymer (A) with a crosslinking agent (B1) in any one embodiment.

The formation conditions of an adhesive layer are as follows, for example. The pressure-sensitive adhesive composition of the present invention is applied on a substrate, support or cover film. When the composition contains a solvent, it is usually dried at 50 to 150° C., preferably at 60 to 100° C., usually for 1 to 10 minutes, preferably for 2 to 7 minutes to remove the solvent. A coating film is formed as mentioned above.

As a method for applying the pressure-sensitive adhesive composition, a known method, for example, a spin coat method, a knife coat method, a roll coat method, a bar coat method, a blade coat method, a die coat method, or a gravure coat method, is applied to a predetermined thickness. A drying method may be used.

In the case of a thermosetting pressure-sensitive adhesive composition, the coating film is usually 3 days or more, preferably 7 to 10 days, usually 5 to 60° C., preferably 15 to 40° C. and usually 30 to 70% RH, preferably It may be cured in an environment of 40 to 70% RH. When crosslinking is performed under the above aging conditions, a crosslinked product (network polymer) can be efficiently formed.

In the case of an active energy ray hardening system adhesive composition, an adhesive can be obtained by irradiating an active energy ray to the said coating film. As an active energy ray, an ultraviolet-ray, a visible light, and an electron beam are mentioned, for example, An ultraviolet-ray is preferable. As irradiation conditions of an active energy ray, the accumulated light quantity is 300-3000 mJ/cm< ² > normally.

In addition, the aging and active energy ray irradiation are preferably performed in a state in which the coating film is sandwiched by a substrate, a support, or a cover film in order to block contact of air with the coating film.

As a base material, a support body, and a cover film, a plastic film, a foam base material, a nonwoven fabric, paper, and flat yarn cloth are mentioned, for example. As a plastic film, For example, polyester films, such as a polyethylene terephthalate; Polyolefin films, such as polyethylene, a polypropylene, and an ethylene- vinyl acetate copolymer, are mentioned. As the foam substrate, for example, a foam substrate obtained using an olefin resin such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, a foam substrate obtained using polystyrene, polyurethane using The foam base material obtained using the foam base material obtained, the foam base material obtained using polyvinyl chloride, the foam base material obtained using the (meth)acrylic-type rubber, the foam base material obtained using other elastomer etc. are mentioned. Examples of the nonwoven fabric include nonwoven fabrics obtained using chemical fibers such as manila hemp, wood pulp, rayon, acetate fibers, polyester fibers, polyvinyl alcohol fibers and polyamide fibers, and mixtures of two or more thereof. Examples of the flat yarn fabric include those in which polyethylene flat yarns and polypropylene yarns are woven, and those in which a resin film is laminated on the surface. Although the thickness of a base material, a support body, and a cover film is not specifically limited, For example, it is 5-150 micrometers.

〔purpose〕

The adhesive sheet of this invention is excellent in the balance of adhesive force and rework property.

The pressure-sensitive adhesive sheet of the present invention has good adhesive properties for adhesion to a high-polarity material or a polyolefin-based low-polarity material. Examples of the polyolefin-based low-polar material include polyethylene and polypropylene. Accordingly, the pressure-sensitive adhesive sheet of the present invention can be widely used as an industrial pressure-sensitive adhesive sheet, and in particular, can be used for bonding non-woven double-sided tapes and urethane foams used in the interior of automobiles and electronic devices.

(Example)

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples. In the following description, "part" represents "part by mass" unless otherwise specified.

Each measurement value in an Example was calculated|required with the following method.

〔heating leftover measurement〕

1 g of the polymer solution was put into the precisely weighed tin plate dish (mass: n1) and the total mass (n2) was precisely weighed, followed by heating at 150°C for 3 hours. Thereafter, the tin plate was left still in a desiccator at room temperature for 1 hour, then precisely weighed again, and the total mass (n3) after heating was measured. The heating residue was computed from the following formula using the obtained mass measurement values (n1-n3).

Heating residue (mass %) = 100 x [mass after heating (n3-n1)/mass before heating (n2-n1)]

[Weight Average Molecular Weight (Mw) and Molecular Weight Distribution (Mw/Mn)]

About the (meth)acrylic copolymer, Mw and Mw/Mn by standard polystyrene conversion were calculated|required by GPC method on the following conditions.

・Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)

·GPC column configuration: the following 5 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: diluted with tetrahydrofuran to 1.0mg/cm ³

· Mobile phase solvent: tetrahydrofuran

Flow rate: 1.0cm ³ /min

·Column temperature: 40℃

[ Example A1]

In a flask equipped with a stirring device, nitrogen gas introduction tube, thermometer and reflux cooling tube, 90 g of methyl acrylate (MA), 10 g of acrylic acid (AA), 30 g of ethyl acetonitrile and 1.0 g of RAFT agent 1 represented by the following formula were placed, The contents of the flask were heated to 80° C. while introducing nitrogen gas into the flask.

Next, 0.02 g of 2,2'-azobisisobutyronitrile was added into the flask under stirring, and heating and cooling were performed for 1 hour so that the temperature of the contents in the flask could be maintained at 80°C.

Then, heating and cooling were performed for 10 hours so that the temperature of the content in a flask could be maintained at 80 degreeC, and 20 g of ethyl acetate was added finally.

A polymer solution containing an acrylic polymer (A') was obtained as described above. The heating residue of the obtained polymer solution was about 65 mass %. Mw of the acrylic polymer (A') contained in the obtained polymer solution was 25,000.

Separately prepare a flask equipped with a stirring device, nitrogen gas introduction tube, thermometer, and reflux cooling tube, put a polymer solution containing acrylic polymer (A') so that the solid content of the acrylic polymer (A') becomes 15 g, and then , 85 g of n-butyl acrylate (BA) and 50 g of ethyl acetate were put, and the contents of the flask were heated to 80°C while introducing nitrogen gas into the flask.

Next, 0.02 g of 2,2'-azobisisobutyronitrile was added into the flask under stirring, and heating and cooling were performed for 1 hour so that the temperature of the contents in the flask could be maintained at 80°C.

Then, heating and cooling were performed for 10 hours so that the temperature of the content in a flask could be maintained at 80 degreeC, and 20 g of ethyl acetate was added finally.

A polymer solution containing an acrylic polymer (A1) was obtained as described above. The heating residue of the obtained polymer solution was about 52 mass %. About the acrylic polymer (A1) contained in the obtained polymer solution, Mw was 170,000 and Mw/Mn was 2.1.

[ Example A2]

A polymer solution containing an acrylic polymer (A2) was obtained in the same manner as in Example A1 except that 4-hydroxybutyl acrylate (4HBA) was used instead of the acrylic acid (AA) shown in Table 1.

[ comparative example A1]

85 g of n-butyl acrylate (BA), 13.5 g of methyl acrylate (MA), 1.5 g of acrylic acid (AA), and 100 g of ethyl acetate were placed in a flask equipped with a stirring device, nitrogen gas introduction tube, thermometer and reflux cooling tube, The contents of the flask were heated to 80° C. while introducing nitrogen gas into the flask.

Next, 0.05 g of 2,2'-azobisisobutyronitrile was added to the flask under stirring, and heating and cooling were performed for 1 hour so that the temperature of the contents in the flask could be maintained at 80°C.

Subsequently, heating and cooling were performed for 10 hours so that the temperature of the content in the flask could be maintained at 80 degreeC, and finally, it diluted with ethyl acetate, and the copolymer solution containing copolymer (RA1) was prepared. Mw of the obtained copolymer (RA1) was 240,000, and Mw/Mn was 4.5.

[ comparative example A2]

A polymer solution containing an acrylic polymer (RA2) was obtained in the same manner as in Comparative Example A1 except that 4-hydroxybutyl acrylate (4HBA) was used instead of the acrylic acid (AA) shown in Table 1.

<Adhesive composition and adhesive sheet>

[ Example B1, B2 and comparative example B1, B2]

The polymer solution obtained in Examples etc. was used as a non-crosslinking adhesive composition. Further, the polymer solution obtained in Examples etc. and M-5A, E-50C or L-45 (all manufactured by Soken Chemical Co., Ltd.) as a crosslinking agent are mixed so that the solid content concentration of the crosslinking agent becomes the amount shown in Table 1, and ethyl acetate was appropriately diluted to obtain a pressure-sensitive adhesive composition for crosslinking.

After the air bubbles are removed from the pressure-sensitive adhesive composition, using a doctor blade, apply a 50 μm thick polyethylene terephthalate (PET) film on the corona-treated surface to have a dry film thickness of 50 μm, and dry at 90° C. for 5 minutes The solvent was removed. The obtained adhesive coating film was pasted together to the PET separator by which the peeling process was carried out, 23 degreeC and under 65 %RH environment, it aged for 7 days, and the adhesive sheet was obtained.

<Evaluation>

[ retention exam〕

Under 23 degreeC and 50% RH conditions, the PET separator of the adhesive sheet obtained in Examples etc. was peeled off, the adhesive layer exposed on the SUS board was affixed, 3 reciprocating 2 kg rollers were made and it crimped|bonded. The affixing area was 20 mm x 20 mm. 20 minutes after application at 80 ° C and dry conditions, a load of 500 g in an uncrosslinked system and a load of 1 kg in a crosslinked system in a direction parallel to the surface of the pressure-sensitive adhesive layer were applied in a direction parallel to the surface of the pressure-sensitive adhesive layer, and the distance shifted from the original position 1 hour after the start of the application of the load ( mm) was measured. In addition, when the sheet|seat fell within the measurement time, the fall time was described. In addition, in the E-50C addition system, a holding force test was also performed on the sheet prepared without the above-mentioned 7-day aging period and the sheet after 2 days and 3 days after the above-mentioned aging.

[ probe tack test]

The PET separator of the adhesive sheet obtained in Examples etc. was peeled off, and the probe tack of the exposed adhesive layer was measured. The probe was made of SUS with a diameter of 5 mm, the contact time was 1 second, the probe speed was 1 cm/sec, and the load was 20 g.

[Gel fraction]

The PET separator was peeled off from the pressure-sensitive adhesive sheet obtained in the same manner as in Examples, etc., except that it was produced using a peel-treated PET separator instead of the PET film. After adding and shaking for 4 hours, the contents of the sample bottle were filtered through a 200-mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100° C. for 2 hours to measure the dry mass. The gel fraction of the adhesive was calculated|required by the following formula. For the E-50C addition system, the gel fraction was calculated for the sheet prepared without the 7-day aging period and the sheet after 2 days and 3 days after aging.

・Gel fraction (%) = (dry mass / adhesive collection mass) x 100 (%)

Example A1 Example A2 Comparative Example A1 Comparative Example A2 (meth)acrylic copolymer sign A1 A2 RA1 RA2 block A MA 13.5 wt%
AA 1.5wt%
(Mw:25,000) MA 13.5 wt%
4HBA 1.5wt%
(Mw:36,000) block B BA 85wt% BA 85wt% random BA 85wt%
MA 13.5 wt%
AA 1.5wt% BA 85wt%
MA 13.5 wt%
AA 1.5wt% Mw 170,000 217,000 240,000 270,000 Mw/Mn 2.1 2.3 4.5 4.8 Example B1 Example B2 Comparative Example B1 Comparative Example B2 (meth)acrylic copolymer A1 A2 RA1 RA2 unbridged retention 0.2mm 1.0mm fall immediately fall immediately Crosslinking agent M-5A (0.2wt% added) retention 0.25mm fall 10 minutes fall 15 minutes fall immediately Crosslinking agent E-50C (0.5wt% added) retention 0.1mm 0.05mm probe tag 16[N/5mmφ] 10.9 [N/5mmφ] Crosslinking agent L-45 (added 0.5wt%) retention 0.1mm 0.1mm probe tag 12[N/5mmφ] 7.4 [N/5mmφ]

M-5A: Aluminum chelate-based crosslinking agent

E-50C: Epoxy crosslinking agent

L-45: isocyanate-based crosslinking agent

Table 2 Example B1, Comparative Example B1 Aging properties of the E-50C addition system immediately after application 2 days 3 days Example B1 gel fraction 86.6% 86.8% 86.9% retention 0.15mm 0.1mm 0.1mm Comparative Example B1 gel fraction 0% 64.2% 87.1% retention fall 13 minutes 0.15mm 0.05mm

※ Immediately after application: Measurement of “immediately after application and drying at 90℃ for 5 minutes”

The pressure-sensitive adhesive sheets of Examples B1 and B2 prepared from the copolymers of Examples A1 and A2 were compared with the pressure-sensitive adhesive sheets of Comparative Examples B1 and B2 prepared from the copolymers of Comparative Examples A1 and A2. Since the cohesive force is high, even if it is uncrosslinked, it has sufficient holding force. Moreover, although the copolymer of Example A1 and Comparative Example A1 has the same monomer composition, when it has a structure in which the reactive functional group is localized like Example A1, the adhesive sheet excellent in aging property is obtained.

Claims (11)

The (meth)acrylic triblock copolymer (A) obtained by RAFT polymerization using the RAFT agent shown in Formula (a1).

[In formula (a1), R is a monovalent organic group having neither a hydroxyl group, a carboxyl group, nor an amino group, and two R's may be the same as or different from each other.] The (meth)acrylic tri-block copolymer (A) according to claim 1, wherein R in the formula (a1) is a hydrocarbon group, an acyl group, an acyloxy group or an acyloxyalkyl group. The (meth)acrylic triblock according to claim 1 or 2, wherein the weight average molecular weight (Mw) measured by GPC method is 30,000 to 600,000, and the molecular weight distribution (Mw/Mn) is 1.5 to 5.0. Copolymer (A). 3. The method according to claim 1 or 2, having a tri-block structure of block A-block B-block A,
Block B has a bivalent structure represented by -SC(=S)-S-,
In 100 mass % of copolymer (A), the total content of block A is 5-40 mass %, and content of block B is 95-60 mass %, The (meth)acrylic-type triblock copolymer (A) characterized by the above-mentioned. The content of the structural unit derived from the reactive functional group-containing monomer in 100% by mass of the total structural units according to claim 4 is 0.5 to 15% by mass, and 95% by mass or more in 100% by mass of the total structural units derived from the reactive functional group-containing monomer A (meth)acrylic tri-block copolymer (A), characterized in that it exists in the block A. A pressure-sensitive adhesive composition containing the (meth)acrylic tri-block copolymer (A) according to claim 1 or 2. The pressure-sensitive adhesive composition according to claim 6, further comprising a curing agent (B). The adhesive sheet which has an adhesive layer formed from the adhesive composition of Claim 6. A polymerizable double bond-containing monomer different from the monomer composition in step 1 is further added to the polymer obtained in step 1 and step 1 of polymerizing the polymerizable double bond-containing monomer using the RAFT agent represented by the formula (a1) A method for producing a (meth)acrylic tri-block copolymer (A) in which one or both of the monomer used in step 1 and the monomer added in step 2 contain (meth)acrylic acid ester in step 2 of polymerization .

[In formula (a1), R is a monovalent organic group having neither a hydroxyl group, a carboxyl group, nor an amino group, and two R's may be the same as or different from each other.] The method for producing a (meth)acrylic tri-block copolymer (A) according to claim 9, wherein the polymer obtained in step 1 has a weight average molecular weight (Mw) of 3,000 to 40,000 as measured by GPC method. 11. The method according to claim 9 or 10, wherein out of 100 mass % of the reactive functional group-containing monomer that can be used in steps 1 and 2, 95 mass% or more of the reactive functional group-containing monomer is used in step 1 (meta) Method for producing an acrylic tri-block copolymer (A).