JP2003268334A - Adhesive composition and adhesive sheet using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high solid adhesive composition that can be coated with a low viscosity, and an adhesive sheet in which the surface of the adhesive layer is flat and smooth. <P>SOLUTION: The adhesive composition mainly comprises an acrylic polymer which is obtained by radical polymerization in the presence of an oligomer or a polymer having ≥3 nitroxy radicals in a molecule. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same, and in particular,
The present invention relates to an acrylic pressure-sensitive adhesive composition having a low viscosity even when made into a high solid, and a pressure-sensitive adhesive sheet having a smooth pressure-sensitive adhesive layer surface.

[0002]

2. Description of the Related Art Conventionally, an organic solvent has been indispensable as a diluting liquid when applying an acrylic pressure-sensitive adhesive. However, since organic solvents have problems such as environmental pollution, adverse effects on the health of workers, and danger of ignition, reduction in the amount used is required.

However, when the amount of the organic solvent used in the conventional acrylic pressure-sensitive adhesive is reduced, the viscosity of the pressure-sensitive adhesive increases, the coatability deteriorates, and the surface of the pressure-sensitive adhesive layer becomes uneven (skin skin). Problem occurs.

The present invention has been made in view of such circumstances, and even when the amount of the organic solvent used at the time of coating the pressure-sensitive adhesive is small, that is, even when it is made into a high solid, it is coated with a low viscosity. An object of the present invention is to provide a pressure-sensitive adhesive composition that can be used, and a pressure-sensitive adhesive sheet having a smooth pressure-sensitive adhesive layer surface.

[0005]

In order to achieve the above-mentioned object, firstly, the present invention relates to an acrylic polymer which is radically polymerized in the presence of an oligomer or polymer having three or more nitroxy radical groups in one molecule. Provided is a pressure-sensitive adhesive composition mainly composed of coalescence (claim 1).

In the pressure-sensitive adhesive composition (claim 1),
The nitroxy radical group contained in the oligomer or polymer is 2,2,6,6-tetramethylpiperidine-
It is preferably derived from 1-oxyl (hereinafter abbreviated as "TEMPO") or its derivative (claim 2).

In the pressure-sensitive adhesive composition (claims 1 and 2), the weight average molecular weight of the oligomer or polymer is preferably 500 to 300,000 (claim 3).

In the pressure-sensitive adhesive composition (claims 1 to 3), it is preferable that the acrylic polymer has a star-shaped or comb-shaped structure, and the weight average molecular weight of the branched polymer chain is 1000 or more (claims). Item 4).

The pressure-sensitive adhesive composition (claims 1 to 4) may contain the acrylic polymer having a polar group and a crosslinking agent capable of reacting with the polar group (claim 5). .

Secondly, the present invention provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition (claims 1 to 5) formed on a substrate.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. [Adhesive composition] The adhesive composition according to the present invention mainly comprises a (meth) acrylic acid ester (B) in the presence of an oligomer or a polymer (A) having three or more nitroxy radical groups in one molecule. The main component is an acrylic polymer (C) obtained by radical polymerization as a constituent monomer unit, and may optionally contain other component (D).

The oligomer or polymer (A) having three or more nitroxy radical groups in one molecule can react with the compound (a1) having a nitroxy radical group and the compound (a1) having a nitroxy radical group. Obtained by reacting with the compound (a2).

A compound having a nitroxy radical group (a
1) includes the following general formula:

[Chemical 1] (In the formula, R ₁ , R ₂ , R ₃ and R ₄ are each a linear or branched alkyl group having 1 to 10 carbon atoms or 5 to 10 carbon atoms.
Which are cyclic hydrocarbon groups, and may be the same or different. ), A nitroxyl radical structure represented by, for example, a bis (tert-butyl) nitroxide structure, 2,2,4,4-tetramethylazetidine-1-
A compound having an oxyl structure, a 2,2,4,4-tetramethyloxazolidine-3-oxyl structure, a 2,2,5,5-tetramethylpyrrolidine-1-oxyl structure, a TEMPO structure, and the like, further comprising a compound ( Examples thereof include compounds having a functional group capable of reacting with a2), such as a hydroxyl group, a carboxyl group, an amino group, an epoxy group and a nitrile group. Among these compounds (a1), 4-hydroxy-TE is considered in consideration of reactivity, stability, availability, and the like.
It is preferred to use TEMPO derivatives such as MPO.

The compound (a2) is a compound (a2) capable of reacting with one molecule of the compound (a2) in a ratio of 3 or more molecules, that is, a functional group capable of reacting with a functional group of the compound (a1). The compound having three or more is not particularly limited as long as it has an unsaturated group capable of forming an oligomer or polymer, or a compound forming an oligomer or polymer.

Examples of such a compound (a2) include, for example, three or more hydroxyl groups, carboxyl groups, epoxy groups, amino groups, halogenated alkyl groups and isocyanate groups which can easily undergo a nucleophilic substitution reaction in one molecule. And a derivative thereof, an oligomer or a polymer having these functional groups, and the like.

Examples of the compound containing three or more hydroxyl groups in one molecule include trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol and the like. The oligomer or polymer having a hydroxyl group can be obtained by polymerizing a compound having a polymerizable unsaturated bond and a hydroxyl group in the molecule as a comonomer. Examples of such comonomers include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, vinyl alcohol and the like.

Compounds containing three or more carboxyl groups in one molecule include nitrilotriacetic acid, ethylenediaminetetraacetic acid, hexamethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, 1,
2,3,4-butanetetracarboxylic acid, tetrahydrofuran-2r, 3t, 4t, 5c-tetracarboxylic acid and the like can be mentioned. Further, the oligomer or polymer having a carboxyl group can be obtained by polymerizing a compound having a polymerizable unsaturated bond and a carboxyl group in the molecule as a comonomer. Such comonomers include acrylic acid, methacrylic acid, itaconic acid, 4
-Vinylbenzoic acid and the like can be mentioned.

Compounds containing three or more epoxy groups in one molecule include tris (2,3-epoxypropyl) isocyanurate, 4,4'-methylenebis (N, N-diglycidylaniline), N, N. -Diglycidyl-4-glycidyloxyaniline, triphenylolmethane triglycidyl ether, trimethylolpropane triglycidyl ether and the like can be mentioned. The oligomer or polymer having an epoxy group can be obtained by polymerizing a compound having a polymerizable unsaturated bond and an epoxy group in the molecule as a comonomer. Examples of such a comonomer include glycidyl methacrylate and the like.

The compounds containing three or more amino groups in one molecule include 2,4,6-triaminopyrimidine, 2,
4,6-triamino-5-nitrosopyridine, tris (2-aminomethyl) amine, N, N, N ′, N′-tetrakis (3-aminopropyl) -1,4-butanediamine trimethylolpropane and the like can be mentioned. be able to.
The oligomer or polymer having an amino group can be obtained by polymerizing a compound having a polymerizable unsaturated bond and an amino group in the molecule as a comonomer.
4-Vinylaniline etc. can be mentioned as such a comonomer.

The compounds containing three or more halogenated alkyl groups in one molecule include 1,3-dichloro-2- (chloromethyl) -2-methylpropane and 1,1,1-tris (chloromethyl). Propane, cyanuric chloride, 2,4,6-tris (bromomethyl) mesitylene,
Examples thereof include tetrakis (2,3-dibromopropyl) isocyanurate, pentaerythrityl tetrachloride, pentaerythrityl tetrabromide, 1,2,4,5-tetrakis (bromomethyl) benzene, and hexakis (bromomethyl) benzene. Further, an oligomer or polymer having a halogenated alkyl group that can easily undergo a nucleophilic substitution reaction can be obtained by polymerizing a compound having a polymerizable unsaturated bond and a halogenated alkyl group in the molecule as a comonomer. Examples of such comonomers include 4-vinylbenzyl chloride and methyl-2- (bromomethyl) acrylate.

The compound containing three or more isocyanate groups in one molecule can be obtained by reacting the above-mentioned compound having a hydroxyl group, a carboxyl group or an amino group with an organic polyvalent isocyanate compound. As the organic polyvalent isocyanate compound, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3
-Xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate , Isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-
A diisocyanate etc. can be mentioned. Further, the oligomer or polymer having an isocyanate group is
It can be obtained by polymerizing a compound having a polymerizable unsaturated bond and an isocyanate group in the molecule as a comonomer. 2-Isocyanatoethylmethacrylate etc. can be mentioned as such a comonomer.

The reaction between the compound (a1) and the compound (a2) may be carried out by a conventional method, for example, 6 to 6 in an organic solvent.
Both can be made to react by heating at 40-120 degreeC for 24 hours.

In the oligomer or polymer (A) obtained by reacting the compound (a1) with the compound (a2), the number of nitroxy radical groups in one molecule is 3 or more, preferably 3 to 30. is there.

The number of nitroxy radical groups in one molecule is 3
When the number is less than the above, the acrylic polymer (C) does not have a star-shaped structure or a comb-shaped structure, and the obtained pressure-sensitive adhesive composition does not exhibit the intended effect. On the other hand, when the number of nitroxy radical groups in one molecule exceeds 30, it becomes difficult to control radical polymerization, and it becomes difficult to polymerize the monomer to a desired molecular weight.

The acrylic polymer (C) has a (meth) acrylic acid ester (B) as a main constituent monomer unit,
It may be a homopolymer or a copolymer thereof.

Examples of the (meth) acrylic acid ester (B) include (meth) acrylic acid cycloalkyl ester, (meth) acrylic acid benzyl ester, and (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms. Etc. are used. Among these, (meth) acrylic acid alkyl ester in which the alkyl group has 1 to 18 carbon atoms, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate,
Butyl acrylate, butyl methacrylate, etc. are used.

When the (meth) acrylic acid ester (B) is copolymerized with another monomer, examples of the other monomer include vinyl acetate, styrene, acrylonitrile, acrylamide, acrylic acid, methacrylic acid, acrylic acid 2 -Hydroxyethyl, glycidyl methacrylate, 4-hydroxybutyl acrylate, etc. can be used.

For polymerization of the acrylic polymer (C), a radical polymerization initiator is used together with the compound (a1) having a nitroxy radical group. Examples of the radical polymerization initiator include thermal polymerization initiation type and photopolymerization initiation type, but are not particularly limited, and examples thereof include benzoyl peroxide, paramenthane hydroperoxide, cumene hydroperoxide and the like. Initiators, azobisisobutyronitrile, 2,2'-di (2-hydroxyethyl) azobisisobutyronitrile and other azo initiators, potassium persulfate, sodium persulfate and other persulfate initiators, etc. Can be used.

The amount of the radical polymerization initiator used is preferably 0.01 to 2% by weight based on the total amount of the monomers. When the amount of the radical polymerization initiator used is less than 0.01% by weight, the polymerization rate is remarkably slowed, and when the amount of the radical polymerization initiator used exceeds 2% by weight, it becomes difficult to control the polymerization.

The amount of the oligomer or polymer (A) used for radical polymerization of the acrylic polymer (C) is preferably 50 to 300% by weight of the above radical polymerization initiator. The amount of oligomer or polymer (A) used is 5
If it is less than 0% by weight, the acrylic polymer (C) does not have a star-shaped or comb-shaped structure, and the resulting pressure-sensitive adhesive composition does not exhibit the intended effect. On the other hand, when the amount of the oligomer or polymer (A) used is more than 300% by weight, the polymerization rate is remarkably reduced and the desired acrylic polymer (C) cannot be obtained.

Polymerization of the acrylic polymer (C) may be carried out by a conventional method. For example, a radical polymerization initiator and an oligomer or polymer (A) are added to a monomer, and the temperature is maintained at 60 to 180 ° C. for 6 to 48 hours. Polymerization is carried out by heating.

The acrylic polymer (C) thus obtained has a star-shaped or comb-shaped structure. The acrylic polymer (C) having such a star-shaped or comb-shaped structure becomes a spherical polymer, and since the spherical polymer can be monodispersed in a solvent, the acrylic polymer (C) is the main component. It is considered that the pressure-sensitive adhesive composition can be coated with a low viscosity even when made into a high solid.

The weight average molecular weight of the branched polymer chain of the acrylic polymer (C) having a star-shaped or comb-shaped structure is 100.
It is preferably 0 or more, and particularly preferably 5000 to 100,000. When the weight average molecular weight of the branch polymer chain of the acrylic polymer (C) is less than 1000, all the cohesive failure occurs during the evaluation of adhesive performance, and the intended adhesive sheet cannot be obtained.

On the other hand, the weight average molecular weight of the acrylic polymer (C) as a whole is preferably 3,000 or more, and particularly preferably 10,000 to 1,000,000. The weight average molecular weight of the entire acrylic polymer (C) is 3,000.
If the amount is less than the above, cohesive failure occurs during the evaluation of adhesive performance, and the intended adhesive sheet cannot be obtained.

The pressure-sensitive adhesive composition according to the present invention contains the above acrylic polymer (C) as a main component, but may contain other component (D) if desired. Other ingredients (D)
Examples thereof include various components such as a crosslinking agent, an ultraviolet absorber, an antistatic agent, an antioxidant, a filler, a plasticizer, a pigment and a dye.

When the acrylic polymer (C) has a polar group such as a hydroxyl group, a carboxyl group, an amino group, an epoxy group and an isocyanate group, it is preferable to contain a crosslinking agent capable of reacting with the polar group. In this case, by cross-linking the acrylic polymer (C) with a cross-linking agent, the adhesive force and cohesive force of the obtained adhesive sheet can be controlled.

As the crosslinking agent, the above-mentioned organic polyvalent isocyanate compound, organic polyvalent epoxy compound, metal chelate compound, organic polyvalent imine compound and the like can be used.

Specific examples of the organic polyvalent isocyanate compound include 2,4-tolylene diisocyanate and 2,6-
Tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, reaction products of these organic polyvalent isocyanate compounds and polyhydric alcohols (for example, trimethylolpropane tris (4-methyl) -3-isocyanatophenyl carbamate), trimethylolpropane adduct hexamethylene diisocyanate, etc.) and the like.

Specific examples of the organic polyepoxy compound include bisphenol A type epoxy compound, bisphenol F type epoxy compound, 1,3-bis (N, N-diglycidylaminomethyl) benzene and 1,3-bis (N). , N
-Diglycidylaminomethyl) toluene, N, N,
Examples thereof include N ', N'-tetraglycidyl-4,4'-diaminodiphenylmethane.

Specific examples of the metal chelate compound include coordination compounds of polyvalent metals such as trisethylacetoacetate aluminum, ethylacetoacetate aluminum diisopropylate, and trisacetylacetonatoaluminum.

Specific examples of the organic polyvalent imine compound include:
N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate , N, N′-toluene-2,4-bis (1-aziridinecarboxamide) triethylenemelamine and the like.

The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer (C).

When the pressure-sensitive adhesive composition obtained as described above is applied, an organic solvent such as toluene, ethyl acetate, 2-butanone, and isopropanol is usually added to the pressure-sensitive adhesive composition to give the viscosity of the coating agent. Is adjusted to 100 to 10000 cps, preferably 500 to 3000 cps. By adjusting the viscosity of the coating agent in such a range, it is possible to improve the coatability and form a smooth pressure-sensitive adhesive layer whose surface does not become orange-skin.

The amount of the organic solvent added is 100
10 to 200 parts by weight, especially 50 to 15 parts by weight
It is preferably 0 part by weight. Conventionally, adhesive composition 10
The amount of the organic solvent added is generally 200 to 0 parts by weight.
Considering that the amount was 500 parts by weight, it can be said that the pressure-sensitive adhesive composition can be applied with a low viscosity even if the amount of the organic solvent added is reduced, that is, even if it is made high solid. .

[Adhesive Sheet] The adhesive sheet according to the present invention has a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive composition formed on a substrate, and a release sheet on the pressure-sensitive adhesive layer, if necessary. May be attached.

The pressure-sensitive adhesive layer is formed by coating the coating composition of the above-mentioned pressure-sensitive adhesive composition with a gravure coater, a die coater, a reverse coater,
It can be formed by coating on a substrate with a general coating machine such as a kiss roll coater, a knife coater, or a roll knife coater and drying. The thickness of the pressure-sensitive adhesive layer is usually 1 to 100 μm, preferably 5 to 50 μm.
The degree can be appropriately changed depending on the application of the pressure-sensitive adhesive sheet.

The base material for forming the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film,
Polyvinyl chloride film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate copolymer film, ionomer resin film, ethylene (meth) acrylic acid copolymer film, ethylene (meth) acrylic acid ester copolymer A film, a polystyrene film, a polycarbonate film, a crosslinked film or a laminated film thereof, or the like can be used. The thickness of the substrate is usually 6 to 300 μm, preferably 12 to 200 μm.
Although it is about m, it can be appropriately changed depending on the application of the pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet according to the present invention may have various shapes such as a tape shape, a label shape, and a shape similar to that of the pressure-sensitive adhesive object, depending on the application of the pressure-sensitive adhesive sheet.

[0049]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[Production Example 1] (Production of TEMPO derivative a) Trimethylolpropane adduct hexamethylene diisocyanate (Coronate HL, MW638 manufactured by Nippon Polyletan Industry Co., Ltd.) 1 g (1.
57 mmol) with hydroxy TEMPO (Lanca
3-fold molar amount of MW172) manufactured by Ster Co., 0.81 g
(4.71 mmol) was added, and the mixture was reacted in toluene at 40 ° C. for 7 hours to obtain a trifunctional TEMPO derivative a.

[Production Example 2] (Production of TEMPO derivative b) 1 g (5.41 mm) of cyanuric chloride (MW185 manufactured by Aldrich)
ol), hydroxy TEMPO (Lancaster)
Manufactured by MW172, 3 times the molar amount 2.79 g (16.2 g)
3 mmol) and added in nitrobenzene at 120 ° C for 12
The reaction was carried out for a time to obtain a trifunctional TEMPO derivative b.

[Production Example 3] (Production of TEMPO derivative c) 1 g of hexamethylene diisocyanate trimer having isocyanurate ring (Coronate EH, MW504, manufactured by Nippon Polyletan Industry Co., Ltd.)
(1.98 mmol), hydroxy TEMPO (La
ncaster, MW172) 3 times the molar amount 1.0
2 g (5.94 mmol) was added and reacted in toluene at 40 ° C. for 7 hours to obtain a trifunctional TEMPO derivative c.

[Production Example 4] (Production of TEMPO derivative d) 0.5 g (1.97) of dipentaerythritol (MW254 manufactured by Aldrich)
Toluene diisocyanate (manufactured by Aldrich Co., MW174) was added in a 6-fold molar amount to 2.06 g (11.
82 mmol) was added and reacted in tetrahydrofuran at 60 ° C. for 7 hours, and then hydroxy TEMPO (Lanc
aster, MW172, 2.03 g (11.82)
mmol) and further reacted at 60 ° C. for 7 hours, 6
A functional TEMPO derivative d was obtained.

[Production Example 5] (Production of TEMPO derivative e) Polybutadiene having carboxyl groups at both ends (CTB (1 manufactured by Goodrich Co.)
300 × 162), MW4000) 5g (1.25mm)
ol), a trimethylolpropane adduct hexamethylene diisocyanate (Coronate HL, MW638 manufactured by Nippon Polyretan Kogyo Co., Ltd.) is used in a double molar amount (1.6 g, 2.
5 mmol) and reacted in toluene at 40 ° C. for 4 hours, and then 0.86 g (5 mmol) of hydroxy TEMPO (manufactured by Lancaster, MW172) was added and further reacted at 40 ° C. for 7 hours to give a tetrafunctional TEMPO derivative. e was obtained.

[Production Example 6] (Production of TEMPO derivative f) Butyl acrylate 90
Hydroxyl TEMPO (manufactured by Lancaster, MW172) was added to 100 g of a copolymer (weight ratio 90:10) of 10 g (64.52 mmol) of 10 g (645.52 mmol) of isocyanatoethyl methacrylate (manufactured by Aldrich, MW155).
Is equivalent to isocyanate ethyl methacrylate (11.
2 g, 64.52 mmol) added, and in toluene at 40 ° C.
After reacting for 12 hours, a polyfunctional TEMPO derivative f was obtained.

[Example 1] 100 g of butyl acrylate
And 1 g of the TEMPO derivative a obtained in Production Example 1 and benzoi
0.7g of Ruperoxide was added, and at 95 ° C under nitrogen.
Polymerize for 2 hours at 130 ° C for 15 hours to give an adhesive
I got A. Weight of the branched polymer chain in the obtained adhesive A
Gel permeation chromatography (Tosoh Corporation)
Column: TSKgelGMH_XL* TSK gelGM
H_XL* TSKgel G2000H _XL, Measurement conditions: 4
When measured with 0 ° C / THF 1 ml / min)
The weight average molecular weight of the mer chain was 35,000.

Example 2 100 g of butyl acrylate
To 0.5 g of the TEMPO derivative b obtained in Production Example 2 and 0.7 g of benzoyl peroxide were added to
Polymerization was performed at 2 ° C. for 2 hours and at 130 ° C. for 15 hours to obtain adhesive B. When the weight average molecular weight of the branch polymer chain in the obtained pressure-sensitive adhesive B was measured in the same manner as in Example 1, the weight average molecular weight of the branch polymer chain was 37,000.

[Example 3] 100 g of butyl acrylate
To which was added 0.9 g of the TEMPO derivative c obtained in Production Example 3 and 0.7 g of benzoyl peroxide, and the mixture was heated to 95% under nitrogen.
Polymerization was performed at 2 ° C. for 2 hours and at 130 ° C. for 15 hours to obtain adhesive C. When the weight average molecular weight of the branch polymer chain in the obtained pressure-sensitive adhesive C was measured in the same manner as in Example 1, the weight average molecular weight of the branch polymer chain was 33,000.

Example 4 100 g of butyl acrylate
Was added to 1 g of the TEMPO derivative d obtained in Production Example 4 and 0.7 g of benzoyl peroxide, and the mixture was polymerized under nitrogen at 95 ° C. for 2 hours and at 130 ° C. for 15 hours to obtain an adhesive D. When the weight average molecular weight of the branched polymer chain in the obtained pressure-sensitive adhesive D was measured in the same manner as in Example 1,
The weight average molecular weight of the branched polymer chain was 33,000.

Example 5 100 g of butyl acrylate
To which was added 3.8 g of the TEMPO derivative e obtained in Production Example 5 and 0.7 g of benzoyl peroxide, and the mixture was heated to 95% under nitrogen.
Polymerization was performed at 2 ° C. for 2 hours and at 130 ° C. for 15 hours to obtain adhesive E. When the weight average molecular weight of the branch polymer chain in the obtained pressure-sensitive adhesive E was measured in the same manner as in Example 1, the weight average molecular weight of the branch polymer chain was 40,000.

Example 6 300 g of butyl acrylate
Was added to 4 g of the TEMPO derivative f obtained in Production Example 6 and 2.1 g of benzoyl peroxide, and polymerization was performed under nitrogen at 95 ° C. for 2 hours and at 130 ° C. for 15 hours to obtain a pressure-sensitive adhesive F. The weight average molecular weight of the branched polymer chain in the obtained pressure-sensitive adhesive F was measured in the same manner as in Example 1,
The weight average molecular weight of the branched polymer chain was 35,000.

Example 7 To 95 g of butyl acrylate and 5 g of 4-hydroxybutyl acrylate, 1 g of the TEMPO derivative d obtained in Preparation Example 4 and 0.7 g of benzoyl peroxide were added, and the mixture was kept at 95 ° C. for 2 hours under nitrogen for 1 hour.
Polymerization was performed at 30 ° C. for 15 hours to obtain adhesive G.
When the weight average molecular weight of the branch polymer chain in the obtained adhesive G was measured in the same manner as in Example 1, the weight average molecular weight of the branch polymer chain was 35,000.

Example 8 285 g of butyl acrylate
And 15 g of 4-hydroxybutyl acrylate, 4 g of the TEMPO derivative f obtained in Production Example 6 and 2.1 g of benzoyl peroxide were added, and polymerization was carried out under nitrogen at 95 ° C. for 2 hours and at 130 ° C. for 15 hours to give a tack. Agent H was obtained. When the weight average molecular weight of the branch polymer chain in the obtained pressure-sensitive adhesive H was measured in the same manner as in Example 1, the weight average molecular weight of the branch polymer chain was 37,000.

[Example 9] Pressure-sensitive adhesive G obtained in Example 7
To 100 parts by weight, 5 parts by weight of trimethylolpropane adduct hexamethylene diisocyanate (Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to give an adhesive I.
And

Example 10 To 100 parts by weight of the pressure-sensitive adhesive H obtained in Example 8, 5 parts by weight of trimethylolpropane adduct hexamethylene diisocyanate (Coronate HL manufactured by Nippon Polyurethane Industry Co., Ltd.) was added, and the pressure-sensitive adhesive was added. J.

Comparative Example 1 100 g of butyl acrylate
2,2-azobisisobutyronitrile (AIBN)
0.07 g was added, and the mixture was added to ethyl acetate under nitrogen at 60 ° C for 12
Polymerization was carried out over a period of time to obtain adhesive K.

Test Example Adhesive A1 produced in Example 1
100g of toluene as a solvent is added to 00g,
The viscosity (cps) of the obtained coating agent was measured using an E-type viscometer. A polyethylene terephthalate film as a base material (thickness: 50 μm)
It was coated on the above with a knife coater and dried at 100 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 30 μm. Regarding the smoothness of the surface state of this pressure-sensitive adhesive layer, the image clarity (%) was measured using an image clarity measuring device (ICM-1DP manufactured by Gas Tester Co., Ltd.)
Was measured.

With respect to the adhesives B to K obtained in Examples 2 to 10 and Comparative Example 1, the viscosity and the image clarity were measured in the same manner as the adhesive A. Table 1 shows each measurement result.

[0069]

[Table 1]

As is clear from Table 1, Examples 1-10
Regarding the adhesives A to J obtained in 1., the viscosity of the coating agent is lower than that of the adhesive K obtained in Comparative Example 1, and the image clarity of the surface of the adhesive layer is high, that is, the adhesives The surface of the layer was smooth.

[0071]

EFFECTS OF THE INVENTION According to the present invention, a pressure-sensitive adhesive composition which can be applied with a low viscosity even when it is made into a high solid, and a pressure-sensitive adhesive sheet having a smooth pressure-sensitive adhesive layer surface are obtained.

Claims (6)

[Claims] 1. A pressure-sensitive adhesive composition containing, as a main component, an acrylic polymer radical-polymerized in the presence of an oligomer or polymer having three or more nitroxy radical groups in one molecule. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the nitroxy radical group contained in the oligomer or polymer is derived from 2,2,6,6-tetramethylpiperidine-1-oxyl or a derivative thereof. object. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the oligomer or polymer has a weight average molecular weight of 500 to 300,000. 4. The acrylic polymer has a star-shaped or comb-shaped structure, and the weight average molecular weight of its branched polymer chain is 10
It is 00 or more, The adhesive composition in any one of Claims 1-3. 5. The method according to claim 1, comprising the acrylic polymer having a polar group and a cross-linking agent capable of reacting with the polar group.
The pressure-sensitive adhesive composition according to any one of 4 above. 6. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to claim 1 formed on a substrate.