KR102371911B1 - (meth)acrylic 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-type copolymer obtained by RAFT polymerization using a RAFT agent, the storage stability and sticking reliability with respect to various to-be-adhered bodies are improved further.
[Solution]
The (meth)acrylic 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 copolymer and manufacturing method thereof, pressure-sensitive adhesive composition, and pressure-sensitive adhesive sheet

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

In the field of pressure-sensitive adhesives, there is a demand for a pressure-sensitive adhesive composition having good adhesion and excellent durability that the pressure-sensitive adhesive sheet does not peel off even in a severe situation. Patent Documents 1 and 2 describe a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer obtained by RAFT polymerization using various reversible addition cleavage chain transfer (RAFT) agents. However, the adhesive composition containing such a copolymer needs further improvement in terms of storage stability and sticking reliability to various to-be-adhered bodies.

Japanese Patent Laid-Open No. 2003-041224 Japanese Patent Laid-Open No. 2014-208762

An object of the present invention is to further improve storage stability, static load resistance to peeling resistance to various types of adherends, and adhesion reliability of a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer obtained by RAFT polymerization using a RAFT agent.

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 copolymer which has the following structures, and came to complete this invention.

The present invention is, for example, the following [1] to [5].

[1] The (meth)acrylic 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] A (meth)acrylic copolymer (A) having a group represented by formula (a2) at a molecular terminal.

[In formula (a2), R is a monovalent organic group having neither a hydroxyl group, a carboxyl group nor an amino group.]

[3] A pressure-sensitive adhesive composition comprising the (meth)acrylic copolymer (A) according to the above [1] or [2], a curing agent (B), and a tackifying resin (C).

[4] An adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the above [3].

[5] The manufacturing method of the (meth)acrylic-type copolymer (A) which has the process of superposing|polymerizing (meth)acrylic acid ester 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.]

ADVANTAGE OF THE INVENTION According to this invention, the (meth)acrylic-type copolymer which is excellent in storage stability obtained by RAFT polymerization using a RAFT agent, and the static-load peeling resistance with respect to various to-be-adhered bodies and the adhesive composition excellent in sticking reliability can be provided.

Hereinafter, the (meth)acrylic copolymer of this invention and its manufacturing method, an adhesive composition, and an adhesive sheet are demonstrated in detail including suitable aspect.

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 copolymer (A)]

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

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 they are the same group from a synthetic point.

Since R does not have the functional groups listed above (hydroxyl group, carboxyl group and amino group), the obtained copolymer also does not have the functional groups listed above in the molecular terminal derived from the RAFT agent. Therefore, since the copolymer does not have a highly reactive molecular terminal functional group, it is possible to improve the storage stability of the copolymer solution, the pressure-sensitive adhesive composition containing the copolymer, and the pressure-sensitive adhesive formed from the composition.

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 is excellent in handling properties, and excellent adhesion reliability to various types of high or low polarity to be adhered is 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.

In RAFT polymerization, polymerization proceeds by reacting such that a polymerizable double bond-containing monomer containing (meth)acrylic acid ester is inserted between a sulfur atom in the RAFT agent and a methylene group adjacent to the sulfur atom. A copolymer (A) contains the copolymer shown by a following formula, for example.

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

Said Ap may be either a random copolymer structure or a block copolymer structure of a polymerizable double bond-containing monomer. For the block copolymer structure, for example, a polymerizable double bond-containing monomer is added to the RAFT agent and subjected to first RAFT polymerization, and a polymerizable double bond-containing monomer having a composition different from that of the monomer is added to the obtained polymer. It can be obtained by adding it and performing 2nd RAFT polymerization.

The (meth)acrylic copolymer (A) according to the second present invention has a group represented by formula (a2) at the molecular terminal, and in one embodiment, a divalent trivalent group represented by -SC(=S)-S- It further has a thiocarbonate structure.

In formula (a2), R is a monovalent organic group which does not have any of a hydroxyl group, a carboxyl group, and an amino group, and the specific example and suitable example of the said organic group are the same as the organic group demonstrated by Formula (a1).

In the following description, if there is no distinction in particular with respect to the (meth)acrylic copolymer (A) according to the first and second present invention, "(meth)acrylic copolymer (A)" or " (of the present invention) copolymer (A)" etc.

By using the copolymer (A) of this invention, it is excellent in storage stability, and the adhesive composition which exhibits the outstanding peeling resistance (sticking reliability) which is excellent in not peeling off from a to-be-adhered body even in a harsh environment can be obtained.

《 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. Examples of the polymerizable double bond-containing monomer include (meth)acrylic acid esters not having the following functional groups, monomers having at least one of the following functional groups (hereinafter also referred to as “functional group-containing monomers”), and copolymerizable monomers other than these monomers. can Examples of the functional group include an acid group, a hydroxyl group, an amino group, an amide group, a cyano group, and a nitrogen-based heterocycle.

As (meth)acrylic acid ester which does not have the said functional group, for example, alkyl (meth)acrylate, alkoxyalkyl (meth)acrylate, alkoxy polyalkylene glycol mono(meth)acrylate, alicyclic group or aromatic ring containing (meth) ) acrylates.

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 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 functional group is usually 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, among 100% by mass of all polymerizable double bond-containing monomers excluding the functional group-containing monomer. mass % or more.

Examples of the 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 a 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)acrylic amides. 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 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 the crosslinking agent (B1) described later.

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

The usage-amount of a functional group containing monomer is 0.1-10 mass % normally in 100 mass % of all polymerizable double bond containing monomers, Preferably it is 0.5-8 mass %, More preferably, it is 1-5 mass %. 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 》

In the first invention, and preferably also in the second invention, in the RAFT polymerization, the polymerizable double bond-containing monomer is polymerized in the presence of the RAFT agent represented by the 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; and sulfoxides such as dimethyl sulfoxide and sulfolane.

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

《Polymerization Conditions》

The manufacturing method of the (meth)acrylic-type copolymer (A) of this invention has the process of superposing|polymerizing (meth)acrylic acid ester by RAFT polymerization using the RAFT agent shown in Formula (a1), for example. You may use other polymerizable double bond containing monomers with the said (meth)acrylic acid ester.

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. About polymerization conditions, Unexamined-Japanese-Patent No. 2007-230947 and Unexamined-Japanese-Patent No. 2011-52057 can be referred, for example.

[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 50,000 to 1,000,000, more preferably 100,000 to 900,000, still more preferably 150,000 to 800,000 am. Since sufficient cohesive force is provided to an adhesive composition in such an aspect, it is preferable from a viewpoint of the durability 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 1.5-6.0, More preferably, it is 1.5-5.0, 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 cohesive 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.

For a monomer whose Tg is not described in the above document, 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 reactor 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 (meth)acrylic-type copolymer (A) mentioned above. The pressure-sensitive adhesive composition of the present invention may further contain a curing agent (B); You may further contain tackifying resin (C).

[( meta ) acrylic copolymer (A)]

The content of the (meth)acrylic copolymer (A) is usually 60% by mass or more, preferably 65 to 99% by mass, more preferably 70 to 97% by mass, still more preferably in 100% by mass of the solid content of the pressure-sensitive adhesive composition. is 70 to 95 mass %. Such an aspect is preferable at the point that the adhesive force with respect to various to-be-adhered bodies can be adjusted 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 functional group to 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 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-triisocyanatebenzene, and 4,4',4''-triphenylmethane triisocyanate. there is.

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, the 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 (e.g. 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 thereof 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 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 adhesive properties can be realized.

[Tackifying Resin (C)]

It is preferable that the adhesive composition of this invention contains tackifying resin (C). In this case, a pressure-sensitive adhesive layer having better adhesive strength not only in high-polarity materials such as SUS substrates but also in adhesion to polyolefin-based low-polar materials such as polyethylene and polypropylene, specifically, a pressure-sensitive adhesive layer exhibiting high static load peeling resistance can be formed

Examples of the tackifying resin (C) include rosin-based tackifying resins such as rosin ester-based resins, terpene-based tackifying resins such as terpene phenol-based resins, styrene-based tackifying resins, and alicyclic saturated hydrocarbon resins, A rosin ester-based resin is preferable.

The rosin ester-based resin is a resin obtained by esterifying a rosin-based resin with alcohol. Examples of the rosin-based resin include a rosin resin containing a resin acid such as abietic acid as a main component, a disproportionated rosin resin and a hydrogenated rosin resin, and a dimer (polymerized rosin resin) of a resin acid such as abietic acid. . Examples of the alcohol include polyhydric alcohols such as ethylene glycol, glycerin, and pentaerythritol.

A resin obtained by esterifying a rosin resin is a rosin ester resin, a resin obtained by esterifying a disproportionated rosin resin is a disproportionated rosin ester resin, a resin obtained by esterifying a hydrogenated rosin resin is a hydrogenated rosin ester resin, and a polymerized rosin resin is an ester. The converted resin is a polymerized rosin ester resin.

The terpene phenol-based resin is a resin obtained by polymerizing terpene in the presence of phenol.

The softening temperature of tackifying resin (C) becomes like this. Preferably it is 70-170 degreeC, More preferably, it is 100-170 degreeC. According to such an aspect, an adhesive layer has suitable tackiness, is excellent in heat resistance, and is excellent in the durability in a high temperature environment, and the adhesive layer is obtained. The softening temperature can be measured by the JISK2207 round ball method.

Examples of the disproportionated rosin ester resin include Super Ester A75 (75° C.), Super Ester A100 (100° C.), Super Ester A115 (115° C.), and Super Ester A125 (125° C.). Examples of the hydrogenated rosin ester resin include Fine Crystal KE-359 (100° C.) and Ester Gum H (70° C.). Examples of the polymerized rosin ester resin include Pencel D-135 (135°C), Pencel D-125 (125°C), and Pencel D-160 (160°C). The above products are manufactured by Arakawa Chemical Co., Ltd., and the temperature in parentheses is the softening temperature.

Examples of the terpene-based tackifying resin include YS polyester G150 (150°C), YS polyester T100 (100°C), YS polyester G125 (125°C), YS polyester T115 (115°C), YS polyester T145 ( 145 degreeC) and YS polyester T130 (130 degreeC) are mentioned. The above products are manufactured by Yasuhara Chemical Co., Ltd., and the temperature in parentheses is the softening temperature.

As styrene tackifying resin, FMR-0150 (145 degreeC), FTR-6100 (100 degreeC), FTR-6110 (110 degreeC), FTR-6125 (125 degreeC), FTR-7100 (100 degreeC), FTR, for example, are -8120 (120 degreeC), FTR-0100 (100 degreeC), FTR-2120 (120 degreeC), and FTR-2140 (145 degreeC) are mentioned. The above products are manufactured by Mitsui Chemicals Co., Ltd., and the temperature in parentheses is the softening temperature. Moreover, SX-100 (100 degreeC, Yasuhara Chemical Co., Ltd. product) is also mentioned.

Examples of the alicyclic saturated hydrocarbon resin include Arcon P-90 (90° C.), Arcon P-100 (100° C.), Arcon P-115 (115° C.), Arcon P-125 (125° C.), Arcon M-90 ( 90°C), Arcon M-100 (100°C), Arcon M-115 (115°C), and Arcon M-135 (135°C). The above products are manufactured by Arakawa Chemical Co., Ltd., and the temperature in parentheses is the softening temperature.

Tackifying resin (C) can be used individually by 1 type or 2 or more types.

The adhesive composition of this invention is 5-50 mass parts with respect to 100 mass parts of copolymer (A) of tackifying resin (C), Preferably it is 8-40 mass parts, More preferably, 10-30 mass parts contained within the range. In such an aspect, the pressure-sensitive adhesive layer has an appropriate tackiness and is excellent in the static load peeling resistance to the polyolefin-based low-polar material.

[ light curing initiator (D)]

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

Examples of the photopolymerization initiator (D) include a benzoin ether-based photoinitiator, an acetophenone-based photoinitiator, 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 (D) 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 (D) 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 (E)]

The pressure-sensitive adhesive composition of the present invention is a (meth)acrylic polymer other than the copolymer (A) in the range that does not impair the effects of the present invention other than the above components, a silane coupling agent, an antistatic agent, an antioxidant, a light stabilizer, a metal corrosion inhibitor, a plasticizer , a crosslinking accelerator, a surfactant, and a rework agent may contain one or more additives.

[Organic solvent (F)]

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

The organic solvent (F) 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.

In the present invention, a pressure-sensitive adhesive composition is prepared immediately using a solution containing the synthesized copolymer (A), and the displacement distance when the holding force test described in the example is performed on the double-sided adhesive sheet formed under the conditions described in the example After storing the initial value and the solution containing the synthesized copolymer (A) in a sealed container at 60 ° C / dry conditions for 1 month, the pressure-sensitive adhesive composition is prepared, and the double-sided pressure-sensitive adhesive sheet formed under the conditions described in Examples All the values of the displacement distance in the holding force test are usually 0 to 2.0 mm, preferably 0 to 1.5 mm, and more preferably 0 to 1.0 mm. When the result of the holding force test is this range, the flow in the shear direction at the time of heating is suppressed, and it is judged that it is a reliable adhesive layer with respect to a heat|fever. Moreover, the copolymer (A) of this invention, the adhesive composition, and the adhesive formed from this are excellent in storage stability.

[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 cohesive 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 the gel fraction, for example, about 0.1 g from the pressure-sensitive adhesive layer is collected in a sampling bottle, 30 mL of ethyl acetate is added and shaken for 4 hours, the contents of the sample bottle are filtered through a 200-mesh stainless steel wire mesh, and the residue on the wire mesh is dried at 100° C. for 2 hours to measure the dry mass, and it can be obtained by the following formula.

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

For example, by advancing the crosslinking and/or curing reaction in the adhesive composition of this invention, the said adhesive layer is obtained by bridge|crosslinking a 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, it is possible to efficiently form a crosslinked product (network polymer).

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 the 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 adhesive sheet of this invention exhibits high static load peeling resistance with respect to a high polarity material or a polyolefin type 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 can be particularly 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, n-butyl acrylate (BA) 78 g, 2-ethylhexyl acrylate (2EHA) 20 g, acrylic acid (AA) 2 g, hydroxyethyl acrylate (HEA) 0.5 g and 0.15 g of the RAFT agent 1 represented by the following formula was 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, while maintaining the temperature of the contents in the flask at 80°C, 60 g of ethyl acetate was added dropwise over 1 hour, and after that, heating and cooling were performed for 10 hours so that the temperature of the contents in the flask could be maintained at 80°C, and finally, ethyl acetate 20 g was added.

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 %. With respect to the acrylic polymer (A1) contained in the obtained polymer solution, Mw was 250,000 and Mw/Mn was 2.1.

[ Example A2, comparative example A1~A2]

Except having changed the RAFT agent as described in Table 1, it carried out similarly to Example A1, and obtained the polymer solution containing an acrylic polymer (A2), an acrylic polymer (RA1), or an acrylic polymer (RA2).

<Adhesive composition and adhesive sheet>

[ Example B1-B2 and comparative example B1~B2]

Table 1 shows the polymer solution obtained in Examples and the like, L-45 (manufactured by Soken Chemical Co., Ltd.) as an isocyanate-based crosslinking agent, and Pencel D-160 (manufactured by Arakawa Chemicals Co., Ltd.) as a tackifying resin. It mixed with the solid content ratio shown to, it diluted suitably with ethyl acetate, and obtained the adhesive composition.

The pressure-sensitive adhesive composition was applied to a dry film thickness of 65 µm on a paper separator (EKR-78D, thickness 115 µm) subjected to peeling using a doctor blade after the bubbles were removed, and the solvent was removed by drying at 80 ° C. for 2 minutes. The obtained pressure-sensitive adhesive coating film was pasted on both sides of a nonwoven fabric substrate having a thickness of 38 μm, and aged at 23 ° C. and 65% RH for 7 days under an environment, to obtain a double-sided pressure-sensitive adhesive sheet consisting of a paper separator / adhesive layer / nonwoven substrate / adhesive layer / paper separator.

<Evaluation>

[ retention test〕

Under 23 degreeC and 50%RH conditions, the paper separator of one side of the double-sided adhesive sheet obtained in Examples etc. was peeled off, and the PET film with a thickness of 25 micrometers was applied to the exposed adhesive layer surface. Then, the other paper separator was peeled off, the exposed adhesive layer was affixed to the SUS board, 2 kg of rollers were made to make 3 reciprocation, and it crimped|bonded. The affixing area was 20 mm x 20 mm. After 20 minutes from application, a load of 1 kg is applied in a direction parallel to the pressure-sensitive adhesive layer surface at 80° C. and dry conditions, and the displacement (mm) from the original position 1 hour after the start of load application is measured, and this is the initial stage of the holding force test. valued it In addition, after storing the polymer solution obtained in Examples etc. in a sealed container at 60 ° C./dry condition for 1 month, a pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet were prepared in the same manner as above, and the deviation distance (mm) in the holding force test was measured. The same amount of a crosslinking agent as that of the pressure-sensitive adhesive composition prepared with the polymer solution not stored above is added to the pressure-sensitive adhesive composition prepared after the polymer solution is stored at 60° C./dry for one month.

Moreover, the addition amount of a crosslinking agent is set so that the initial value of the shift|offset|difference distance in the said holding force test in each Example and a comparative example may be set to 0.3 mm. The values of the holding force test and the static load peel test under these conditions were compared.

[ dead load Peel test]

Under 23 degreeC and 50%RH conditions, the paper separator of one side of the double-sided adhesive sheet obtained in Examples etc. was peeled off, and the PET film with a thickness of 25 micrometers was applied to the exposed adhesive layer surface. Then, the other paper separator was peeled off, the exposed adhesive layer was affixed to a polypropylene (PP) board or SUS board with a thickness of 1 mm, and it crimped|bonded by making 3 reciprocating 2 kg rollers. The affixing area was 20 mm width x 50 mm. 20 minutes after sticking, from the PET film side at 80°C and dry conditions, in the case of SUS plate, a load of 200 g, and in the case of PP plate, a load of 100 g was applied in the direction of 90° with respect to the pressure-sensitive adhesive layer surface, and 1 The peeling length (mm) after time was measured.

Example A1 Example A2 Comparative Example A1 Comparative Example A2 (meth)acrylic type
copolymer
(Acrylic Polymer) sign A1 A2 RA1 RA2 Monomer composition BA/2EHA/AA/HEA=78/20/2/0.5 RATF 1 0.15 RATF 2nd 0.135 RATF 3 0.072 RATF 4th 0.14 Mw 250,000 250,000 250,000 250,000 Mw/Mn 2.1 2.1 2.1 2.1 Example B1 Example B2 Comparative Example B1 Comparative Example B2 (meth)acrylic type
copolymer A1 100 copies A2 100 copies RA1 100 copies RA2 100 copies crosslinking agent L-45 1.7 parts Part 2.6 Part 2.4 1.0 copies tackifying resin D-160 25 copies 25 copies 25 copies 25 copies holding force test Early 0.3mm 0.3mm 0.3mm 0.3mm 60℃/1 month 0.3mm 0.5mm 0.5mm fall Static load peel test SUS 80℃/200g 3.5mm 1.0mm 10.0mm 6.0mm PP 80℃/100g 8.5mm 9.5mm 17.5mm 13.0mm

The double-sided pressure-sensitive adhesive sheets of Examples B1 and B2 were satisfactory in both the holding force test and the static load peel test.

The double-sided pressure-sensitive adhesive sheet of Comparative Example B1 was prepared from an acrylic polymer prepared using RAFT agent 3 which does not have groups such as acyl group, acyloxy group and acyloxyalkyl group. The result was inferior to Examples B1 and B2.

The double-sided pressure-sensitive adhesive sheet of Comparative Example B2 prepared from an acrylic polymer prepared using RAFT agent 4 having a hydroxyl group at the terminal fell in the holding force test after storage for one month under 60°C/dry conditions. During storage, a transesterification reaction occurs in the system, and the hydroxyl group present at the end of the polymer moves to the inside of the polymer, which lowers the reactivity with the crosslinking agent compared to the polymer before storage, and the amount of crosslinking agent equal to the initial value of the retention test This is thought to be because the crosslinking reaction did not proceed sufficiently.

Claims (5)

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

[In formula (a1), R is an alkyl group having 1 to 12 carbon atoms or an acyloxyalkyl group having 3 to 8 carbon atoms represented by R ¹ -C(=O)-OR ² -, R ¹ is an alkyl group, R ² is an alkylene group, and two R may be the same as or different from each other.] The (meth)acrylic copolymer (A) which has the group represented by Formula (a2) at the molecular terminal.

[In formula (a2), R is an alkyl group having 1 to 12 carbon atoms, or an acyloxyalkyl group having 3 to 8 carbon atoms represented by R ¹ -C(=O)-OR ² -, R ¹ is an alkyl group, R ² is an alkylene group.] The adhesive composition containing the (meth)acrylic copolymer (A) of Claim 1 or 2, a hardening|curing agent (B), and tackifying resin (C). The adhesive sheet which has an adhesive layer formed from the adhesive composition of Claim 3. The manufacturing method of the (meth)acrylic-type copolymer (A) which has the process of superposing|polymerizing (meth)acrylic acid ester by RAFT polymerization using the RAFT agent shown in Formula (a1).

[In formula (a1), R is an alkyl group having 1 to 12 carbon atoms or an acyloxyalkyl group having 3 to 8 carbon atoms represented by R ¹ -C(=O)-OR ² -, R ¹ is an alkyl group, R ² is an alkylene group, and two R may be the same as or different from each other.]