JP6793631B2 - Adhesive composition for heat-resistant adhesive film used for masking, adhesive for heat-resistant adhesive film used for masking, heat-resistant adhesive film for masking - Google Patents

Description

The present invention is heat-adhesive film for the PSA composition used in the masking, heat adhesive film for adhesive to be used for masking, relates resistant adhesive film for masking, in particular, used for masking the remaining amount of the polymerization initiator is reduced The present invention relates to a pressure-resistant adhesive film pressure-sensitive adhesive composition, a heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive used for masking , and a masking heat-resistant pressure-sensitive adhesive film.

Flexible printed wiring (FPC) boards are used in information terminal electronic devices such as mobile phones. In recent years, the thickness of laminated boards including FPC boards has been reduced by improving the performance of circuits and reducing the size and weight of electronic devices. Miniaturization is progressing. As a result, the strength of the laminated plate is lowered and it is easily damaged. Therefore, in order to prevent the damage, it is necessary to protect the laminated plate with a protective film during the manufacturing process. However, since it is exposed to a high temperature during the manufacturing process, the adhesive layer of the protective film may adhere to the laminated plate, and the laminated plate may be damaged when the protective film is peeled off, or contamination due to adhesive residue may occur. In addition, since the adhesive strength may decrease and floating may occur at a high temperature, there is a problem that the protective film cannot exhibit sufficient protective ability. In order to solve these problems, the following adhesive / adhesive compositions have been proposed.

For example, a pressure-sensitive adhesive composition containing a (meth) acrylic polymer having an alkenyl group in the side chain and a cross-linking agent having a siloxane bond and at least two hydrosilyl groups in the molecule is disclosed (Patent). Reference 1).

A pressure-sensitive adhesive composition containing a pressure-sensitive adhesive polymer having a hydroxyl group and a cross-linking accelerator which is a metal organic compound containing at least one metal selected from tin, zinc, lead, and bismuth, and further containing a volatile acid. , And a removable adhesive tape using this pressure-sensitive adhesive composition is disclosed (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2010-235845 JP-A-2002-241732

However, in the technique disclosed in Patent Document 1, pressure-sensitive adhesion containing a (meth) acrylic polymer having an alkenyl group in the side chain and a cross-linking agent having a siloxane bond and at least two hydrosilyl groups in the molecule. An agent composition is used. For example, after adding 0.24 parts by weight of azobisisobutyronitrile (polymerization initiator), the reaction is carried out at 60 ° C. for only 24 hours, and the residual polymerization initiator is present. Adhesion contamination may occur after the heat-resistant process, as a large amount may remain in the calculation. In addition, the heat resistance at higher temperatures is inferior, and adhesive residue may occur.

Further, the technique disclosed in Patent Document 2 is a pressure-sensitive adhesive containing a pressure-sensitive adhesive polymer having a hydroxyl group and a cross-linking accelerator which is a metal organic compound containing at least one metal selected from tin, zinc, lead and bismuth. A removable pressure-sensitive adhesive tape obtained by cross-linking the composition with an isocyanate cross-linking agent. For example, during the production of a pressure-sensitive adhesive, a benzoyl peroxide-based initiator (Niper BMT-K40, manufactured by Nippon Oil & Fats Co., Ltd.) 0.36. Since the reaction was carried out at 86 ° C. for only 4 hours after the addition of parts by weight, and there is a possibility that a large amount of residual polymerization initiator remains in the calculation, adherent contamination may occur after the heat resistance process. .. In addition, the added cross-linking accelerator and volatile acid may cause adherent contamination.

As described above, in any of the pressure-sensitive adhesive compositions, as will be described later, the bonds in the pressure-sensitive adhesive layer are formed by the radicals generated by the decomposition of the residual polymerization initiator in the pressure-sensitive adhesive layer, especially in a high temperature environment. There is a problem of being cleaved, and it is difficult to prevent the above problem only by adjusting the degree of cross-linking (for example, improving the degree of cross-linking with a cross-linking accelerator or cross-linking with a hydrosilyl group). is there.

In view of the above circumstances, the present invention provides a heat-resistant adhesive film pressure-sensitive adhesive composition used for masking in which the residual amount of the polymerization initiator is reduced, a heat-resistant pressure- resistant adhesive film pressure-sensitive adhesive used for masking , and a masking heat-resistant pressure-sensitive adhesive film. It is the purpose.

As a result of investigating the problem that the adherend is contaminated as described above, especially in a high temperature environment, the present inventors did not break the chemical bond or the physical bond of the pressure-sensitive adhesive only by heat in the high-temperature heat-resistant process. , The polymerization initiator remaining in the pressure-sensitive adhesive, oxygen in the resin, and nitrogen oxides in the air generate radicals, and the radicals attack the chemical bonds in the pressure-sensitive adhesive to break the chemical bonds and physical bonds. I found out what caused it.

Then, the present inventors diligently studied in order to solve the above problem, and focused on the polymerization initiator remaining in the pressure-sensitive adhesive. As a result, even after the polymerization reaction is almost completed and the consumption of the polymerization initiator is completed, the remaining polymerization initiator is decomposed by heating (decomposition to a state where it does not function as a polymerization initiator) by intentionally continuing heating. ), Recalling that the amount of the polymerization initiator remaining in the finally obtained polymer, the acrylic resin, is reduced.

Therefore, as a result of further studies from the above viewpoints, the present inventors have used an acrylic resin adjusted to have a content much smaller than the content of the polymerization initiator that normally remains in a high temperature environment. However, the present invention has been found that the adherend is not contaminated, the adhesive performance is sufficiently high, the aging period for producing the adhesive film is short, and the efficiency is economically high.

Further, when the content concentration of the polymerization initiator in the polymerization reaction solution of the acrylic resin is below a certain value, heating at a temperature higher than the 10-hour half-life temperature of the polymerization initiator for 2 hours or more is obtained. We have found that the residual amount of the polymerization initiator in the acrylic resin to be obtained can be effectively reduced to obtain a pressure-resistant pressure-resistant pressure-sensitive adhesive film suitable for use as a pressure-sensitive adhesive, and the present invention has been reached. did.

<< Abstract of the present invention >>
That is, the present invention is a pressure-sensitive adhesive composition in which the polymerization component [I] is polymerized in the presence of an azo-based polymerization initiator and contains an acrylic resin and a cross-linking agent, wherein the acrylic resin is (meth). an acrylic resin polymer component [I] is polymerized containing as a main component an alkyl ester monomer of acrylic acid (a1), the polymer component [I] is one having hydroxyl group and hydroxyl groups in one molecule It contains 5 to 20 % by weight of the monomer (a2) and 0.05 to 5 % by weight of the nitrogen atom-containing monomer (a3), and the weight average molecular weight of the acrylic resin is 300,000 to 2 million (however). , 300,000 is excluded.), The azo polymerization initiator-containing concentration of the acrylic resin is 280 ppm or less, and the cross-linking agent is contained in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the acrylic resin. The pressure-resistant adhesive film pressure-sensitive adhesive composition used for masking has a gel content of 90 to 100 % of the pressure-sensitive adhesive obtained by cross-linking the present pressure-sensitive adhesive composition (hereinafter referred to as "heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive composition"). (Sometimes) is the first gist.

Further, the second gist is a heat- resistant adhesive film adhesive (hereinafter sometimes referred to as "adhesive") used for masking obtained by curing the heat-resistant adhesive film adhesive composition of the first gist. The third gist is a heat-resistant adhesive film for masking (hereinafter sometimes referred to as "heat-resistant adhesive film") having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive .

The "heat-resistant adhesive film" in the present invention conceptually includes a heat-resistant adhesive sheet, a heat-resistant adhesive film, and a heat-resistant adhesive tape.

Thus, the present invention is a polymerization component [I] is a pressure-sensitive adhesive composition containing a polymerized acrylic resin and a crosslinking agent in the presence of an azo-based polymerization initiator, the acrylic resin, ( Meta) An acrylic resin obtained by polymerizing a polymerization component [I] containing an acrylic acid alkyl ester-based monomer (a1) as a main component, and the above-mentioned polymerization component [I] has one hydroxyl group in one molecule. 5 an acid group-containing monomer (a2) 20 wt% and a nitrogen atom-containing monomer (a3) is contained 0.05 to 5 wt%, the weight-average molecular weight of the acrylic resin is 300,000 to 2,000,000 (However, 300,000 is excluded.) The azo polymerization initiator-containing concentration of the acrylic resin is 280 ppm or less, and the cross-linking agent is contained in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the acrylic resin. The gel content of the pressure-sensitive adhesive obtained by cross-linking the present pressure-sensitive adhesive composition is 90 to 100 % . Therefore, the heat-resistant adhesive film using the adhesive made of the adhesive composition containing the acrylic resin and the cross-linking agent does not contaminate the adherend even when used in a high temperature environment, and is adhesive. The performance is sufficiently high, the aging period for adhesive film production is short, and it is economically efficient. Therefore, the pressure-resistant adhesive film composition for heat-resistant pressure-sensitive adhesive films containing an acrylic resin and a cross-linking agent of the present invention is used, for example, for heat-resistant processes such as flexible printed circuit board applications. Specifically, it is useful for masking applications in heat-resistant processes and fixing applications in heat-resistant processes. The acrylic resin is a reaction solution when a polymerization component [I] containing a (meth) acrylic acid alkyl ester-based monomer as a main component is polymerized in the presence of an azo-based polymerization initiator to produce an acrylic resin. It can be produced by heating the azo-based polymerization initiator at a temperature higher than the 10-hour half-life temperature for 2 hours or more in a state where the content concentration of the initiator is 300 ppm or less.

Then, in the above production, when polymerization is carried out in the presence of an antioxidant in addition to the polymerization initiator, the heat resistance of the pressure-sensitive adhesive is further improved.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.
In the present specification, (meth) acrylic means acrylic or methacrylic, (meth) acryloyl means acryloyl or methacrylic, and (meth) acrylate means acrylate or methacrylate. Further, as described above, the "film" conceptually includes a sheet, a film, and a tape.

In the present invention, the acrylic resin for heat-resistant adhesive film (hereinafter, may be simply referred to as "acrylic resin") uses a polymerization component [I] containing a (meth) acrylic acid alkyl ester-based monomer as a main component. , This is obtained by polymerizing in the presence of an azo-based polymerization initiator.

<Polymerization component [I]>
In the present invention, the polymerization component [I] is obtained by polymerizing the polymerization component [I] (monomer component) containing the (meth) acrylic acid alkyl ester-based monomer (a1) as a main component, and is obtained by polymerizing the above-mentioned polymerization. components other monomer components other than the above (a1) contained in the [I], hydroxyl group-containing monomer having one hydroxyl group in a molecule other than below the nitrogen atom-containing monomer (a3) (a2), nitrogen atom A monomer appropriately selected from the contained monomer (a3) and the other polymerizable monomer (a4) is contained. The "main component" containing the (meth) acrylic acid alkyl ester-based monomer (a1) as a main component is specifically that the (meth) acrylic acid alkyl ester-based monomer (a1) is a polymerization component. [I] It means that it is usually contained in an amount of 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more, based on the total amount of (monomer component). The upper limit is usually 100% by weight.

[(Meta) Acrylic Acid Alkylate Monomer (a1)]
Examples of the (meth) acrylic acid alkyl ester-based monomer (a1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, and tert-butyl (meth). Meta) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl acrylate, isodecyl (meth) acrylate, lauryl (meth) ) (Meta) acrylic acid alkyl esters such as acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, iso-stearyl (meth) acrylate; alicyclic group (meth) such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. ) Acrylate ester and the like can be mentioned. In the case of the (meth) acrylic acid alkyl ester, the number of carbon atoms of the alkyl group is usually 1 to 20, particularly preferably 1 to 12, further preferably 1 to 8, particularly 4 to 8. These can be used alone or in combination of two or more.

[Hydroxyl (except nitrogen atom-containing monomer (a3)) one having hydroxyl group-containing monomer (a2) in one molecule]
Hydroxyl group-containing monomer having one hydroxyl group in the molecule (a2) is, be other than the nitrogen atom-containing monomer (a3) described below, these can be used either alone or in combination ..

In order to improve the heat resistance of the pressure-sensitive adhesive, it is necessary that the pressure-sensitive adhesive film is sufficiently cross-linked. For that purpose, there is a functional group that is cross-linked in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film, and this functional group is sufficient. Sufficient heat resistance will not be exhibited unless the film is crosslinked. From this, it is preferable that the pressure-resistant adhesive film of the present invention has a functional group in the acrylic resin, and the functional group is most preferably a hydroxyl group, and as described above, one molecule has one hydroxyl group. A hydroxyl group-containing monomer is used. Therefore, a pressure-sensitive adhesive having no functional group as a reaction point is not preferable because the heat resistance is insufficient and the adherend is contaminated.

Examples of the hydroxyl group-containing monomer having one hydroxyl group in one molecule include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, and 6-hydroxyhexyl ( (Meta) acrylic acid hydroxyalkyl esters such as meta) acrylates and 8-hydroxyoctyl (meth) acrylates; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylates; diethylene glycol (meth) acrylates and polyethylene glycol (meth) Oxyalkylene-modified monomer such as acrylate; In addition, primary hydroxyl group-containing monomer such as 2-acryloyloxyethyl 2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3- Secondary hydroxyl group-containing monomers such as chloro2-hydroxypropyl (meth) acrylate; Tertiary hydroxyl group-containing monomers such as 2,2-dimethyl2-hydroxyethyl (meth) acrylate can be mentioned. Among these, (meth) acrylic acid hydroxyalkyl ester is preferable from the viewpoint of copolymerizability and polarity, and in particular, it is easy to react with a cross-linking agent and has few impurities such as di (meth) acrylic acid ester and is easy to polymerize. From the point of view, it is preferable to use 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or 4-hydroxybutyl acrylate. Further, it is preferable to use two or more kinds of hydroxyl group-containing monomers in combination because the crosslinked structure can be made dense and the heat resistance is improved. From this point, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferable. Is to be used together.

Content of the hydroxyl group-containing monomer (a2) having one hydroxyl group in the molecule, the polymerizable component (monomer component) [I] is 5 to 20% by weight relative to the total, good Mashiku the 5 It is 15% by weight, more preferably 7 to 13% by weight. If the content ratio of the hydroxyl group-containing monomer (a2) having one hydroxyl group in one molecule is too large, the adhesive strength tends to decrease, and if it is too small, the crosslink density tends to decrease and the adherend contamination resistance tends to decrease. There is.

[Nitrogen atom-containing monomer (a3)]
The nitrogen atom-containing monomer (a3) may be a monomer containing a nitrogen atom, and may be, for example, an amino group-containing monomer, an amide group-containing monomer, a nitrogen-based heterocyclic ring-containing monomer, or a cyano group-containing monomer. Examples thereof include monomers, imide group-containing monomers, and betaine monomers. Among them, a monomer having a high basicity showing a catalytic activity is preferable, and for example, a monomer selected from a substituted amino group-containing monomer, a substituted amide group-containing monomer, and a nitrogen-based heterocyclic ring-containing monomer is preferable. Substituted amino group-containing monomers are preferred. Moreover, as these monomers, (meth) acrylic monomers are preferable. These nitrogen atom-containing monomers (a3) can be used alone or in combination of two or more.

The amino group-containing monomer may be a polymerizable monomer having an ethylenically unsaturated double bond and an amino group (unsubstituted or substituted amino group), for example, aminomethyl (meth) acrylate. Aminoalkyl (meth) acrylate such as aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, aminoisopropyl (meth) acrylate and N such as N- (t-butyl) aminoethyl (meth) acrylate. − Alkylaminoalkyl (meth) acrylic acid ester, etc. Monosubstituted amino group-containing (meth) acrylic acid ester;
(Meta) of N, N-dialkylaminoalkyl such as N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate Disubstituted amino group-containing (meth) acrylic acid ester such as acrylic acid ester;
Dialkylaminoalkyl (meth) acrylamide such as N, N-dimethylaminopropyl (meth) acrylamide, quaternized salts of these amino group-containing monomers, etc.;
Amino group-containing styrenes such as p-aminostyrene;
Styrenes having a dialkylamino group such as 3- (dimethylamino) styrene and dimethylaminomethylstyrene; dialkylaminoalkylvinyl ethers such as N, N-dimethylaminoethyl vinyl ether and N, N-diethylaminoethyl vinyl ether;
Allylamine, 4-diisopropylamino-1-butene, trans-2-butene-1,4-diamine, 2-vinyl-4,6-diamino-1,3,5-triazine and the like are used.

The amide group-containing monomer may be a polymerizable monomer having an ethylenically unsaturated double bond and an amide group (a group having an amide bond), and may be, for example, (meth) acrylamide: N-methyl (meth) acrylamide: N-methyl. Meta) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide, N-isobutyl (meth) acrylamide, N-s- Butyl (meth) acrylamide, N-t-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, diacetone (meth) acrylamide, N, N'-methylenebis (meth) acrylamide, N- (1,1-dimethyl) N-alkyl (meth) acrylamide such as -3-oxobutyl) (meth) acrylamide:
N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (Meta) acrylamide, N, N-diisobutyl (meth) acrylamide, N, N-di (s-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide, N, N-dipentyl (Meta) acrylamide, N, N-dihexyl (meth) acrylamide, N, N-diheptyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N, N-diallyl (meth) acrylamide, N, N-ethyl N, N-dialkyl (meth) acrylamide such as methyl acrylamide:
Dialkylaminoalkyl (meth) acrylamide such as N, N-dimethylaminopropyl (meth) acrylamide:
Substituted amide group-containing monomers such as N-vinylacetamide, N-vinylformamide, (meth) acrylamide ethylethyleneurea, and (meth) acrylamide-t-butylsulfonic acid;
Hydroxy group-containing (meth) acrylamides such as N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-methylolpropane (meth) acrylamide;
Alkoxy group-containing (meth) acrylamide such as N-methoxymethyl (meth) acrylamide and N- (n-butoxymethyl) (meth) acrylamide;
Examples thereof include quaternized salts of these amide group-containing monomers.

The nitrogen-based heterocycle-containing monomer may be any polymerizable monomer having an ethylenically unsaturated double bond and a nitrogen-based heterocycle (a heterocycle having a nitrogen atom as a ring constituent element), for example. N-Methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazin, N-vinylpyrazine, N-vinylpyrrole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylimidazole, 1-vinylimidazole, 4-vinylpyridine, 2-vinylpyridine, 2-vinylpyrazine, N-vinyl-2-pyrrolidone, N-vinylcarbazole, N-vinylphthalimide, 2- N-vinyl-based monomer such as vinyl-2H-indazole;
N-allyl-based monomers such as N-allylmorpholin;
N- (meth) acryloyl morpholine, N- (meth) acryloyl pyrrolidone, N- (meth) acryloyl piperidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl aziridine, aziridini N- (meth) acryloyl-based monomer such as ruethyl (meth) acrylate;
A quaternized salt of a nitrogen-based heterocyclic-containing monomer obtained by reacting the above-mentioned monomer with a known quaternizing agent such as alkyl halide, benzyl halide, alkyl or aryl sulfonic acid or dialkyl sulfate; 4 -Methyl-5-vinylthiazole and the like can be mentioned.

The cyano group-containing monomer may be a polymerizable monomer having an ethylenically unsaturated double bond and a cyano group, and examples thereof include acrylonitrile and methacrylonitrile.

The imide group-containing monomer may be a polymerizable monomer having an ethylenically unsaturated double bond and an imino group, and may be, for example, maleimide, N-cyclohexylmaleimide, N-isopropylmaleimide, or N-laurylmaleimide. , N-phenylmaleimide, isopropylmaleimide and other maleimide-based monomers;
N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, itaconimide, etc. Quantum;
Examples thereof include succinimide-based monomers such as N- (meth) acryloyl oxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

Examples of the betaine-containing monomer include N- (3-sulfopropyl) -N-acryloyloxyethyl-N, N-dimethylammonium betaine, and N- (3-sulfopropyl) -N-methacryloylamide propyl-. N, N-dimethylammonium betaine, N- (3-carboxymethyl) -N-methacryloylamide propyl-N, N-dimethylammonium betaine, N- (3-sulfopropyl) -N-methacryloyloxyethyl-N, N- Examples thereof include dimethylammonium betaine, N-carboxymethyl-N-methacryloyloxyethyl-N, and N-dimethylammonium betaine.

Among these nitrogen atom-containing monomers (a3), amino group-containing monomers and amide group-containing monomers are preferable in terms of copolymerizability with other monomers and cross-linking promoting effect, and the amino group-containing monomer is preferable. Of particular preference are N, N-dimethylaminoethyl (meth) acrylate (dimethylaminoethyl (meth) acrylate), N, N-diethylaminoethyl (meth) acrylate (diethylaminoethyl methacrylate), which contain the above amide group. Particularly preferred as the monomer are N, N-dimethylaminopropyl (meth) acrylamide [dimethylaminopropyl (meth) acrylamide] and N, N-dimethyl (meth) acrylamide [dimethyl (meth) acrylamide].

More preferably, dimethylaminoethyl (meth) acrylate, dimethylaminopropylacrylamide, dimethylacrylamide, and diethylaminoethyl methacrylate are used in terms of copolymerizability with other monomers, cross-linking promoting effect, and availability as a raw material. is there.

The content ratio of the nitrogen atom-containing monomer (a3) is 0.05 to 5 % by weight , preferably 0.05 to 2 % by weight, particularly preferably 0.05 % by weight , based on the entire polymerization component (monomer component) [I]. It is 0.05 to 1% by weight . If the content ratio of the nitrogen atom-containing monomer (a3) is too large, the molecular weight tends to decrease during polymerization or the pressure-sensitive adhesive tends to be colored, and if it is too small, it tends to be difficult to obtain a sufficient catalytic effect.

[Other polymerizable monomers (a4)]
The other polymerizable monomer (a4) is a monomer other than the above-mentioned (a1), (a2) and (a3) monomers, and is, for example, phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth). ) Acrylate, phenoxydiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, styrene, α-methylstyrene and other monomers containing one aromatic ring; 2-methoxyethyl (meth) acrylate, 2 -Ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate , Ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol-polypropylene glycol-mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, steer Monomer containing an alkoxy group or an oxyalkylene group such as loxypolyethylene glycol mono (meth) acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, Examples thereof include vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyltrimethylammonium chloride, and dimethylallyl vinyl ketone. Preferably, the homopolymer is a monomer having a glass transition temperature (Tg) of 0 ° C. or higher. These other polymerizable monomers (a4) may be used alone or in combination of two or more.

The content ratio of the other polymerizable monomer (a4) is preferably 0 to 80% by weight, particularly preferably 0 to 50% by weight, still more preferably 0 to 0, based on the entire polymerization component (monomer component) [I]. It is 30% by weight. If the content ratio of the other polymerizable monomer (a4) is too large, the heat resistance tends to decrease or the adhesive strength tends to decrease.

[Hard monomer (X)]
Among the above-mentioned monomer components (a1) to (a4), the hard monomer (X) having a glass transition temperature of −30 ° C. or higher is specifically mentioned, for example, the (meth) acrylic acid ester-based monomer (a1). Among them, iso-butyl acrylate, tert-butyl acrylate, ethyl acrylate, methyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, and methacrylic. Examples thereof include iso-butyl acid, tert-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl (meth) acrylate.
Examples of the nitrogen atom-containing monomer (a3) include acryloyl morpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylaminopropyl acrylamide.
Among the other polymerizable monomers (a4), phenoxyethyl acrylate, styrene and the like can be mentioned.

Among these hard monomers (X), methyl (meth) acrylate, ethyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, butyl methacrylate, and propyl methacrylate are preferable. Used, particularly preferably methyl (meth) acrylate.

[Polymer initiator]
The polymerization initiator used in the radical polymerization in the production method of the acrylic resin, for example, 2, 2'-azobis (2-methylbutyronitrile) (67 ° C.), 2,2'-azobisisobutyronitrile Nitrile (65 ° C), (1-phenylethyl) azodiphenylmethane (58 ° C), 2,2'-azobis (2,4-dimethylvaleronitrile) (52 ° C), 2,2'-azobis (2-cyclopropyl) Specific examples thereof include azo-based polymerization initiators such as propionitrile (49.6 ° C.) and 2,2'-azobis (4-methoxy 2,4-dimethylvaleronitrile) (30 ° C.). The numerical values in parentheses following each compound name are the 10-hour half-life temperature of each compound.

In the present invention, the preferred 10-hour half-life temperature of the polymerization initiator is preferably 100 ° C. or lower, more preferably 90 ° C. or lower, still more preferably 80 ° C. or lower, and most preferably 70 ° C. or lower.

In the method for producing an acrylic resin, the amount of the polymerization initiator used in the entire polymerization reaction is usually 0.001 to 10 parts by weight, preferably 0.005 to 5 parts by weight, based on 100 parts by weight of the polymerization component [I]. It is by weight, particularly preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.5 parts by weight. If the amount of the polymerization initiator used is too small, it is difficult to obtain the effect of the addition, and if the amount used is too large, it is uneconomical.

In the method for producing an acrylic resin, in the polymerization reaction, other additives such as an antioxidant can be appropriately used together with the polymerization component [I] and the polymerization initiator.

[Antioxidant]
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, aminoether-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.

Examples of the phenolic antioxidant include 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, and 2,6-dicyclohexyl-4-methylphenol. , 2,6-diisopropyl-4-ethylphenol, 2,6-di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol, 2,6-dicyclohexyl- 4-n-octylphenol, 2-isopropyl-4-methyl-6-t-butylphenol, 2-t-butyl-4-ethyl-6-t-octylphenol, 2-isobutyl-4-ethyl-6-t-hexylphenol , 2-Cyclohexyl-4-n-butyl-6-isopropylphenol, styrene mixed cresol, DL-α-tocopherol, stearyl-β- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, etc. Monocyclic phenol compound; 2,2'-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 4,4'-thiobis (3-) Methyl-6-t-butylphenol), 2,2'-thiobis (4-methyl-6-t-butylphenol), 4,4'-methylenebis (2,6-di-t-butylphenol), 2,2'- Methylenebis [6- (1-methylcyclohexyl) -p-cresol], 2,2'-ethylidenebis (4,6-di-t-butylphenol), 2,2'-butylidenebis (2-t-butyl-4- Methylphenol), 3,6-dioxaoctamethylenebis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate], triethylene glycolbis [3- (3-t-butyl-5) -Methyl-4-hydroxyphenyl) propionate], 1,6-hexanediolbis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2'-thiodiethylenebis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate] and other bicyclic phenol compounds; 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane , 1,3,5-Tris (2,6-dimethyl-3-hydroxy-4-t-butylbenzyl) isocyanurate, 1,3,5-Tris [(3,5-di-t-butyl-4-4) Hydroxyphenyl) propionyloxyethyl] a Socianurate, tris (4-t-butyl-2,6-dimethyl-3-hydroxybenzyl) isocyanurate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-) Tricyclic phenol compound such as 4-hydroxybenzyl) benzene; tetracyclic phenol compound such as tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane; bis (3,5) Phosphor-containing phenolic compounds such as −di-t-butyl-4-hydroxybenzylphosphonate) calcium, bis (3,5-di-t-butyl-4-hydroxybenzylphosphonate) nickel, etc. it can.

Examples of the amine-based antioxidant include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2,2. , 6,6-Tetramethylpiperidin Ethanol polycondensate, N, N', N'', N'''-tetrakis- [4,6-bis- {butyl- (N-methyl-2,2,6) , 6-Tetramethylpiperidin-4-yl) amino} -triazine-2-yl] -4,7-diazadecan-1,10-diamine, dibutylamine, 1,3,5-triazine, N, N'-bis Polycondensate of (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine) and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) Imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4 -Butanetetracarboxylate, 2,2,6,6-tetramethyl-4-piperidylbenzoate, bis- (1,2,6,6-pentamethyl-4-pepyridyl) -2- (3,5-di-t) -Butyl-4-hydroxybenzyl) -2-n-butylmalonate, bis- (N-methyl-2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,1'-(1,2'-(1,2) -Ethandiyl) bis (3,3,5,5-tetramethylpiperazinone), (mixed 2,2,6,6-tetramethyl-4-piperidyl / tridecyl) -1,2,3,4-butane Tetracarboxylate, (mixed 1,2,2,6,6-pentamethyl-4-piperidyl / tridecyl) -1,2,3,4-butanetetracarboxylate, mixed [2,2,6,6- Tetramethyl-4-piperidyl / β, β, β', β'-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethyl] -1,2, 3,4-Butanetetracarboxylate, mixed [1,2,2,6,6-pentamethyl-4-piperidyl / β, β, β', β'-tetramethyl-3,9- [2,4 8,10-Tetraoxaspiro (5,5) undecane] diethyl] -1,2,3,4-butante Tracarboxylate, N, N'-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino]- 6-Chloro-1,3,5-triazine condensate, poly [6-N-morpholyl-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4) -Piperidil) imino] hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl) imide], N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) hexa Examples thereof include a condensate of methylenediamine and 1,2-dibromoethane, N- (2,2,6,6-tetramethyl-4-piperidyl) -2-methyl and the like.

Examples of the aminoether-based antioxidant include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate and bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate. , Bis (1-methoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-ethoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1 -Propoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-butoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-pentyroxy-2) , 2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-hexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-heptyroxy-2,2,6 , 6-Tetramethyl-4-piperidyl) sebacate, bis (1-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-nonyloxy-2,2,6,6-tetra Methyl-4-piperidyl) sebacate, bis (1-decaniloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-dodecyloxy-2,2,6,6-tetramethyl-4- Piperidil) Sevacate and the like.

Examples of the phosphorus-based antioxidant include triphenylphosphite, diphenylisodecylphosphite, phenyldiisodecylphosphite, and 4,4'-butylidene-bis (3-methyl-6-t-butylphenylditridecyl) phos. Fight, Cyclic Neopentane Tetraylbis (Nonylphenyl) Phenylphosphite, Cyclic Neopentanetetraylbis (Dinonylphenyl) Hosphite, Cyclic Neopentantetrayl Tris (Nonylphenyl) Hosphite, Cyclic Neopentanetetra Iltris (dinonylphenyl) phosphite, 10- (2,5-dihydroxyphenyl) -10H-9-oxa-10-phosphaphenanthrene-10-oxide, diisodecylpentaerythritol diphosphite, tris (2,4-) Di-t-butylphenyl) phosphite and the like can be mentioned.

Examples of the sulfur-based antioxidant include dilaurylthiodipropionate, ditridecylthiodipropionate, distearylthiodipropionate, pentaerythritol tetrakis (3-dodecylthiopropionate), and 4,4-thiobis. (2-Triary Butyl-5-Methylphenol) Bis-3- (dodecylthio) propionate, dimyristyl-3,3'-thiodipropionate, lauryl-stearyl-3,3'-thiodipropionate, neopentanetetra Iltetrakis (3-laurylthiopropionate) and the like can be mentioned.
Each of these antioxidants may be used alone or in combination of two or more.

Of these, it is preferable to use a phenolic antioxidant, and particularly preferably a hindered phenolic antioxidant. As the hindered phenolic antioxidant, pentaerythritol ester of β- (3,5-di-t-butyl-4-hydroxyphenyl) propionic acid (Irganox 1010, manufactured by BASF Japan Ltd.) is preferable. More preferably, a phenolic antioxidant and at least one of a phosphorus-based antioxidant and a sulfur-based antioxidant are used in combination. In the case of the above combined use, the combined use ratio (weight ratio) is preferably 10 to 2000 parts by weight, preferably 10 to 2000 parts by weight, for at least one of the phosphorus-based antioxidant and the sulfur-based antioxidant with respect to 100 parts by weight of the phenol-based antioxidant. Is 50 to 500 parts by weight.

The blending amount of the antioxidant is preferably 0.01 to 20 parts by weight, particularly preferably 0.03 to 10 parts by weight, based on 100 parts by weight of the acrylic resin obtained by using the polymerization component [I]. It is more preferably 0.05 to 5 parts by weight, particularly preferably 0.08 to 3 parts by weight, and most preferably 0.1 to 2 parts by weight. The above-mentioned antioxidant may be added at the time of polymerization, or may be added separately after the completion of polymerization.

[Manufacturing of acrylic resin]
In the acrylic resin, the actually measured residual initiator amount (polymerization initiator-containing concentration) is 280 ppm or less in the acrylic resin. It is more preferably 240 ppm or less, further preferably 180 ppm or less, particularly preferably 125 ppm or less, and most preferably 80 ppm or less. The amount of the residual initiator is preferably small, but the lower limit is usually 0.1 ppm.
This measured value is based on the value measured using LC-MS / MS [LC device: manufactured by Shimadzu Corporation, LC-10A; MS device: Applied Biosystems API3000].

In the present invention, such an acrylic resin can be produced by polymerizing using the polymerization component [I] containing the (meth) acrylic acid alkyl ester-based monomer (a1) as appropriate. In the above polymerization, conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and a method of partially polymerizing using these methods and then adding a monomer or an initiator to polymerize after coating. It can be done by the method. For example, a polymerization component [I] containing a (meth) acrylic acid alkyl ester-based monomer (a1) and a polymerization initiator are mixed or dropped in an organic solvent to polymerize under predetermined polymerization conditions. Among these polymerization methods, a method of solution radical polymerization, massive polymerization, partial polymerization, then addition of a monomer or an initiator and polymerization after coating is preferable, and more preferably solution radical polymerization, partial polymerization, and then monomer or initiation. It is a method of adding an agent and polymerizing after coating, and most preferably solution radical polymerization.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, n-propyl alcohol and isopropyl alcohol. Examples thereof include aliphatic alcohols, acetone, methyl ethyl ketone, methyl isobutyl ketone, and ketones such as cyclohexanone. Among these solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are preferable from the viewpoints of ease of polymerization reaction, effect of chain transfer, ease of drying when coating an adhesive, and safety. More preferably, ethyl acetate, acetone and methyl ethyl ketone are preferable.

The polymerization component [I] may be charged by any of a batch charging method, a multi-stage split charging method, or a charging method. In the case of split preparation in multiple stages, it is usually sufficient to prepare in 2 to 4 stages, preferably in 3 stages. In the case of the preparation by these three steps, 90 to 99.5% by weight of the total polymerized component [I] may be charged in the first step, and the remaining 10 to 0.1% by weight may be charged in the second and subsequent steps. .. Specifically, it is preferable to charge 0.01 to 5% by weight of the total amount of the functional group monomer (a2) in the polymerization component [I] in the second and subsequent stages.

As in the case of the polymerization component [I], the method for charging the polymerization initiator may be a batch charging method, a multi-step split charging method, or any charging method. In the case of division in multiple stages, it is usually sufficient to prepare in 2 to 4 stages, preferably in 3 stages. In the case of charging in these three stages, 10 to 80% by weight of the total amount of the polymerization initiator may be charged in the first stage, and 20 to 90% by weight may be charged in the second and subsequent stages. As described above, in the case of charging in a multi-step division, it is preferable to use a polymerization initiator having a 10-hour half-life temperature of 100 ° C. or less as the polymerization initiator in the second and subsequent steps.

As a method of adding the above-mentioned polymerization initiator, for example, the addition of the first-stage polymerization initiator may be added before the addition of the polymerization component [I], or the addition of the polymerization component [I] is completed. It may be added later, and at the same time as the polymerization component [I] is dropped, it is dissolved in the polymerization component [I], or a polymerization initiator is separately dissolved in a solvent and dropped at the same time as the polymerization component [I]. May be good.

The polymerization temperature in the above polymerization reaction is usually 50 to 95 ° C, preferably 65 to 90 ° C. The polymerization time in the polymerization reaction (that is, the time until the start of drive-in heating described later) is not particularly limited, but is 2 hours or more, preferably 3 hours or more, more preferably 4 hours after the last addition of the polymerization initiator. The above is particularly preferably 5 hours or more.

In the present invention , in the above method for producing an acrylic resin, a heating operation (to a temperature higher than the 10-hour half-life temperature of the polymerization initiator) after a state in which the concentration of the polymerization initiator in the reaction solution is calculated to be 300 ppm or less is achieved. The heating operation) is defined as "driving heating" for thermally decomposing the polymerization initiator.

Then, in the start of the drive-in heating, which is the heating operation, specifically, the content concentration of the initiator in the reaction solution is calculated to be 300 ppm or less, and the reaction rate of the polymerization component [I] is 80%. In the above state, it is preferable to carry out drive-in heating. The reaction rate of the polymerization component [I] is particularly preferably 85% or more, further preferably 90% or more, and particularly preferably 95% or more. The upper limit of the reaction rate is usually 100%. The reaction rate of the polymerization component [I] can be measured and confirmed, for example, as follows.
For the reaction rate of the polymerization component [I], that is, the reaction rate (%) of the acrylic resin, 1 g of a sample of the target resin whose reaction rate is to be confirmed is precisely weighed on an aluminum foil, and a ket (infrared dryer, The solid content during the reaction is calculated from the remaining amount after heating at 185 W (height 5 cm) for 45 minutes, and the reaction rate is calculated from the monomer content (solid content when it is assumed that all the monomers have reacted) by the following formula. Can be calculated.
Reaction rate (%) = [(solid content during reaction) / (monomer content)] x 100

Then, as described above, the drive-in heating temperature must be higher than the 10-hour half-life temperature of the polymerization initiator. For example, a temperature 10 ° C. or higher higher than the 10-hour half-life temperature of the polymerization initiator is particularly preferable, and a temperature 15 ° C. or higher higher is even more preferable. The higher the driven heating temperature, the more preferable it is, but since it is not possible to heat above the boiling point of the reaction solution at normal pressure, it is usually about 100 ° C. at the highest. Therefore, specifically, the drive-in heating temperature is usually 50 to 95 ° C, preferably 65 to 90 ° C, and particularly preferably 70 to 90 ° C. That is, it is preferable to set the final residual polymerization initiator amount (concentration) calculated from the reaction temperature, the reaction time, and the blended polymerization initiator amount to be smaller.

The time required for the drive-in heating (that is, the time from the time when the concentration of the polymerization initiator in the reaction solution becomes 300 ppm or less in the calculated value to the end of the reaction) needs to be 2 hours or more. It is preferably 3 hours or more, particularly preferably 4 hours or more, still more preferably 5 hours or more, and usually there is no particular upper limit, but economically it is 48 hours or less. That is, it is preferable to set the final residual polymerization initiator amount (concentration) calculated from the reaction temperature, the reaction time, and the blended polymerization initiator amount to be smaller.

In the acrylic resin obtained by the above production method using the above polymerization component [I], in order to obtain a pressure-sensitive adhesive which has particularly high adhesive strength and is preferable for use in fixing applications, the glass transition temperature of the acrylic resin (Tg) is preferably −40 ° C. or higher. It is particularly preferably −35 ° C. or higher, and the upper limit is preferably 40 ° C. or lower, particularly preferably 10 ° C. or lower, still more preferably 0 ° C. or lower, and particularly preferably −10 ° C. or lower. If the glass transition temperature (Tg) is too low, the adhesive strength tends to decrease, and if it is too high, the adhesive sheet tends to be difficult to fit with the adherend and floats. Therefore, in order to set the glass transition temperature (Tg), it is preferable to use the combination [hard monomer (X)] of the above-mentioned polymerization component [I].

On the other hand, in the acrylic resin obtained by using the above-mentioned polymerization component [I], the adhesive strength is particularly low, the increase in the adhesive strength after heat resistance is small, and in order to obtain a preferable adhesive for use in surface protection applications, acrylic The glass transition temperature (Tg) of the based resin is preferably −30 ° C. or lower. It is particularly preferably −35 ° C. or lower, further preferably −40 ° C. or lower, particularly preferably −45 ° C., particularly preferably −50 ° C. or lower, and the lower limit is usually −100 ° C. If the glass transition temperature (Tg) is too high, the adhesive strength becomes too high and the adherend is damaged, and the increase in the adhesive strength after the heat resistance treatment also increases, which tends to increase the risk of the adherend being damaged. There is.

Ｔg ：重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ）
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ）
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ）
Ｗa ：モノマーＡの重量分率
Ｗb ：モノマーＢの重量分率
Ｗn ：モノマーＮの重量分率
（ただし、Ｗa＋Ｗb＋・・・＋Ｗn＝１である。） The glass transition temperature (Tg) of the acrylic resin is calculated by the following Fox formula.

Tg: Glass transition temperature of polymer (K)
Tga: Glass transition temperature (K) of homopolymer of monomer A
Tgb: Glass transition temperature (K) of homopolymer of monomer B
Tgn: Glass transition temperature (K) of homopolymer of monomer N
Wa: Weight fraction of monomer A Wb: Weight fraction of monomer B Wn: Weight fraction of monomer N (where Wa + Wb + ... + Wn = 1)

The weight average molecular weight of the acrylic resin is 300,000 to 2,000,000 (excluding 300,000.), Good Mashiku is 300000-1000000. If the weight average molecular weight is too small, the heat resistance tends to decrease and the adherend contamination resistance tends to decrease, and if it is too large, a large amount of diluting solvent is required, which tends to be unfavorable in terms of coatability and cost. ..

The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin is preferably 20 or less, particularly preferably 15 or less, further preferably 10 or less, and particularly preferably 7 or less. If the degree of dispersion is too high, the heat resistance of the pressure-sensitive adhesive layer is lowered, and foaming or the like tends to occur easily. The lower limit of the dispersity is usually 1.1 for manufacturing reasons.

The above weight average molecular weight is a weight average molecular weight converted to standard polystyrene molecular weight, and is used in high performance liquid chromatography (manufactured by Nippon Waters Co., Ltd., "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ^7, separation range: 100-2 × 10 ^7, theoretical plate number: 10,000 plates / the filler material: styrene - divinylbenzene polymer, filler particle It is measured by using three series having a diameter (diameter: 10 μm), and the number average molecular weight is also measured by the same method. The degree of dispersion is obtained from the weight average molecular weight and the number average molecular weight.

The viscosity (mPa · s (25 ° C.)) of the acrylic resin is preferably 10 to 500,000 mPa · s (25 ° C.), particularly preferably 100 to 100,000 mPa · s (25 ° C.) at 25 ° C. is there. If the viscosity is too low, the pressure-sensitive adhesive composition tends to drip or repel from the base material during coating, making coating difficult. If the viscosity is too high, the pressure-sensitive adhesive composition tends to thicken when the cross-linking agent is blended. Construction tends to be difficult. If coating becomes difficult due to the thickening of the pressure-sensitive adhesive composition, it may be diluted to reduce the solid content concentration, if necessary. Viscosity can be measured according to the 4.5.3 rotational viscometer method of JIS K5400 (1990).

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention contains the acrylic resin as an essential component, and by cross-linking the acrylic resin, it becomes, for example, a pressure-resistant adhesive film. When cross-linking the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition further contains a cross-linking agent.

Examples of the above-mentioned cross-linking agent include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, oxazoline-based cross-linking agents, melamine-based cross-linking agents, aldehyde-based cross-linking agents, and amine-based cross-linking agents. Among these, isocyanate-based cross-linking agents are preferably used in terms of improving the adhesion of the heat-resistant adhesive film to the base material and the reactivity with the base polymer.

Examples of the isocyanate-based cross-linking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalenediocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof. Examples thereof include an adduct form of and a polyol compound such as trimethylolpropane, a bullet form of these polyisocyanate compounds, and an isocyanurate form. Among these, isocyanurate of hexamethylene diisocyanate, burette of hexamethylene diisocyanate, 2,4-tolylene diisocyanate and / or adduct of 2,6-tolylene diisocyanate and trimethylpropane, 2 , 4-Tolylene diisocyanate and / or 2,6-tolylene diisocyanate isocyanurate, tetramethylxylylene diisocyanate and trimethylpropane adduct are preferable, and hexamethylene diisocyanate isocyanurate or burette is most preferable. Is preferable.

Examples of the epoxy-based cross-linking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. , Trimethylol Propane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, 1,3'-bis (N, N-diglycidyl aminomethyl) cyclohexane, N , N, N', N'-tetraglycidyl-m-xylene diamine and the like.

Examples of the aziridine-based cross-linking agent include tetramethylolmethane-tri-β-aziridinyl propionate, trimethylolpropane-tri-β-aziridinyl propionate, and N, N'-diphenylmethane-4,4. Examples thereof include'-bis (1-aziridine carboxylamide) and N, N'-hexamethylene-1,6-bis (1-aziridine carboxylamide).

Examples of the oxazoline-based cross-linking agent include 2,2'-bis (2-oxazoline), 1,2-bis (2-oxazoline-2-yl) ethane, and 1,4-bis (2-oxazoline-2-yl). Il) butane, 1,8-bis (2-oxazoline-2-yl) butane, 1,4-bis (2-oxazoline-2-yl) cyclohexane, 1,2-bis (2-oxazoline-2-yl) Bisoxazoline compounds containing aliphatic or aromatic compounds such as benzene, 1,3-bis (2-oxazoline-2-yl) benzene, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, Addition polymerization of 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, etc. Examples thereof include one or more polymers of sex oxazoline.

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resin. ..

Examples of the aldehyde-based cross-linking agent include glioxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardaldehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine-based cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, and polyamide.

The above-mentioned cross-linking agent may be used alone or in combination of two or more.

The content of the cross-linking agent is usually 1 to 20 parts by weight, preferably 2 to 20 parts by weight, and particularly preferably 5 to 15 parts by weight with respect to 100 parts by weight of the acrylic resin. If the amount of the above-mentioned cross-linking agent is too small, the cohesive force of the pressure-sensitive adhesive tends to decrease, which tends to cause adhesive residue. If the amount of the cross-linking agent is too large, the cross-linking of the pressure-sensitive adhesive proceeds too much and the adhesive strength decreases. It tends to float between the surface and the surface.

The cross-linking reaction of the pressure-sensitive adhesive composition can also be carried out by irradiating with active energy rays. As the active energy rays, for example, far ultraviolet rays, ultraviolet rays, near ultraviolet rays, rays such as infrared rays, electromagnetic waves such as X-rays and γ-rays, electron beams, proton rays, neutron rays and the like can be used. Curing by ultraviolet irradiation is advantageous because of the availability and price of the irradiation device. In this case, it is preferable to blend a polyfunctional (meth) acrylate. Examples of the polyfunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate and ethylene oxide-modified trimethylolpropane tri (meth) acrylate. , Pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerin polyglycidyl ether poly (meth) acrylate and the like. Cross-linking by irradiation with active energy rays is preferably used in combination with cross-linking with a cross-linking agent.

The pressure-sensitive adhesive composition of the present invention further comprises an antioxidant, a plasticizer, a filler, an antistatic agent, a pigment, a diluent, an antioxidant, an ultraviolet absorber, and an ultraviolet stabilizer as long as the effects of the present invention are not impaired. , Other additives such as antistatic resin may be further contained, and these additives may be used alone or in combination of two or more. In particular, antioxidants are effective in maintaining the stability of the pressure-sensitive adhesive layer. In addition to these additives, a small amount of impurities and the like contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition may be contained.

As the antioxidant, the same antioxidant as described above, which is appropriately used in the polymerization reaction, is used. Further, the blending amount of the antioxidant is also set in the same manner as described above.

The pressure-sensitive adhesive composition of the present invention contains an acrylic resin as a main component. Here, the term "main component" means that the acrylic resin is usually contained in an amount of 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, based on the total amount of the pressure-sensitive adhesive composition. means. The upper limit is usually 99.9% by weight.

In addition, the pressure-sensitive adhesive composition of the present invention preferably contains substantially no acid, which can reduce corrosion of adherends such as metals. Here, "substantially free of acid" specifically means that the acid value is preferably 5 mgKOH / g or less, particularly preferably 1 mgKOH / g or less, and further preferably 0.1 mgKOH / g or less. means.

The gel fraction of the pressure-sensitive adhesive composition is formed by crosslinking the pressure-sensitive adhesive of the present invention is 9 0-100%, good Mashiku is 97 to 100%, particularly preferably 98% to 100%. If the gel fraction is too low, the cohesive force of the adhesive is reduced, leaving adhesive residue, which tends to cause contamination of the adherend.

The gel fraction of the pressure-sensitive adhesive is adjusted to the above range by, for example, adjusting the type and amount of the cross-linking agent, adjusting the composition ratio of the hydroxyl groups in the composition, and the like. In addition, the ratio of the cross-linking agent and the amount of functional groups needs to be balanced because the gel fraction changes due to each interaction.

The gel fraction is a measure of the degree of cross-linking, and is calculated by, for example, the following method. That is, a pressure-sensitive adhesive sheet (without a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, a polyethylene terephthalate film) as a base material is wrapped with a 200-mesh SUS wire mesh, and 23 in toluene. The gel fraction is defined as the weight percentage of the insoluble adhesive component remaining in the wire mesh after immersion at ° C. for 24 hours. However, the weight of the base material is subtracted from the calculation.

The adhesive strength of the pressure-sensitive adhesive obtained by cross-linking the pressure-sensitive adhesive composition of the present invention is preferably 0.01 N / 25 mm or more, particularly preferably 0.05 N, when it has a particularly high adhesive strength and is preferable for use in fixed applications. It is / 25 mm or more, more preferably 0.5 N / 25 mm or more, and particularly preferably 0.8 N / 25 mm or more. The adhesive strength is particularly low, the increase in adhesive strength after heat resistance is small, and the adhesive strength of the pressure-sensitive adhesive preferable for use in surface protection applications is preferably 5.0 N / 25 mm or less, particularly preferably 1.00 N / 25 mm or less. More preferably, it is 0.50 N / 25 mm or less, and particularly preferably 0.20 N / 25 mm or less. Further, the adhesive strength after heat resistance is preferably 20.0 N / 25 mm or less, particularly preferably 10.00 N / 25 mm or less, further preferably 5.00 N / 25 mm or less, and particularly preferably 2.00 N / 25 mm or less. The adhesive strength is 180 ° peel strength (N / 25 mm) obtained according to the test method of [adhesive strength] in the examples described later.

In the present invention, the heat-resistant pressure-sensitive adhesive film of the present invention can be obtained by laminating and forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition on a film as a base material.
Examples of the base material on which the pressure-sensitive adhesive layer is laminated include a single-layer or laminated film made of a metal, a polyester-based resin, a polyfluorinated ethylene-based resin, a polyimide and its derivative, an epoxy resin, and the like, and has heat resistance. Polyimide films and polyester films are more preferable from the viewpoint of convenience in actual use. Specific examples thereof include aromatic polyimide films such as DuPont's trade name "Kapton" and polyethylene naphthalate films such as "Theonex". For the heat-resistant adhesive film, it is preferable to further provide a release film on the surface of the pressure-sensitive adhesive layer opposite to the base material. When the heat-resistant adhesive film is put into practical use, the release film is peeled off and used. As the release film, a silicon-based release film, an olefin-based release film, a fluorine-based release film, a long-chain alkyl-based release film, and an alkyd-based release film can be used.

In producing the heat-resistant adhesive film, as a method of cross-linking the pressure-sensitive adhesive composition of the present invention, [1] the pressure-resistant adhesive film pressure-sensitive adhesive composition is applied onto a substrate, dried, and then a release film is applied. Examples thereof include a method of laminating and aging treatment, and [2] a method of applying an adhesive composition for a heat-resistant adhesive film on a release film, drying it, and then laminating a base material and performing an aging treatment. .. Among these, the method [2] is preferable in terms of not damaging the base material, workability and stable production.

Here, the aging treatment of the pressure-resistant adhesive film usually requires aging at a high temperature for a long time, but in the present invention, a nitrogen atom-containing monomer is used to lower the temperature and shorten the temperature. The aging process can be completed in time.

The aging treatment is carried out in order to balance the sticky physical properties, and the aging conditions are such that the temperature is usually 0 to 150 ° C, preferably 10 to 100 ° C, particularly preferably 20 to 80 ° C, and the time is It is usually less than 30 days, preferably less than 14 days, particularly preferably less than 7 days, and specifically, it can be carried out under conditions such as, for example, 3 to 10 days at 23 ° C. and 1 to 7 days at 40 ° C. ..

When applying the pressure-sensitive adhesive composition of the present invention, it is preferable to dilute the pressure-sensitive adhesive composition with a solvent and apply it, and the dilution concentration is preferably 5 to 60% by weight, particularly preferably 10 to 30% by weight. %. The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive film pressure-sensitive adhesive composition, and for example, an ester solvent such as methyl acetate, ethyl acetate, methyl acetoacetate, or ethyl acetoacetate. Ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate, methyl ethyl ketone, and toluene are preferably used from the viewpoints of solubility, dryness, price, and the like.

Further, the pressure-sensitive adhesive composition can be applied by a conventional method such as roll coating, die coating, gravure coating, comma coating, screen printing or the like.

The thickness of the pressure-sensitive adhesive layer in the heat-resistant adhesive film is preferably 3 to 300 μm, more preferably 5 to 100 μm, particularly preferably 7 to 50 μm, and even more preferably 10 to 30 μm. If the pressure-sensitive adhesive layer is too thin, the adhesive properties tend to be difficult to stabilize, and if it is too thick, the entire heat-resistant adhesive film tends to be too thick, resulting in poor usability.

Resistant pressure-sensitive adhesive film of the invention, for example, as a heat-adhesive film for temporary surface protection (masking) for temporarily surface protection circuit board and electronic components such as semiconductors and the FPC board, it is possible to take advantage. In addition, one o'clock surface protected with the surface protection Applications in the manufacturing process of the optical product as an (masked) for heat adhesive fill beam, can be utilized. In addition, it is used for other applications used in a process in which heat is applied to the adhesive sheet and the adherend.

Examples of the adherend to be adhered to the heat-resistant adhesive film of the present invention include a base material of the following materials.

Metal plate or metal foil such as aluminum, copper, iron, stainless steel, magnesium, nickel, titanium;
Polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer, and ester acrylate;
Polyethylene, chlorinated polyethylene, chlorosulphonized polyethylene, ethylene propylene rubber, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-isobutyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacryl Polyethylene resins such as acid copolymers, ionomers, polypropylenes, polyaromers, polybutylenes, and polymethylpentene;
Polyvinyl fluoride resin such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluorinated ethylene, ethylene-4 ethylene fluoride copolymer;
Polystyrene, poly-α-methylstyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer;
Acrylics such as polyalkyl (meth) acrylates such as polymethylmethacrylate, ethylpolymethacrylate, ethylpolyacrylate, and butyl polyacrylate, methylmethacrylate-styrene copolymers, and methylmethacrylate-α-methylstyrene copolymers. resin;
Polyvinyl chloride, plasticized polyvinyl chloride, ABS modified polyvinyl chloride, post-chlorinated polyvinyl chloride, polyvinyl chloride-acrylic resin alloy, vinyl chloride-propylene copolymer, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride Polyvinyl chloride polymer such as vinylidene and its derivatives;
Polyvinyl acetate, polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyvinyl acetate such as vinylon, and derivatives thereof;
Polyvinyl methyl ether, polyvinyl methyl ketone;
Polyethers such as polyformaldehyde, acetal copolymers, polyethylene oxides, polypropylene oxides, chlorinated polyethers, phenoxy resins, polyphenylene oxides;
Fluorescent resins such as polyterolafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, chlorotrifluoroethylene-vinylidene fluoride copolymer;
Polycarbonate, Polycarbonate ABS Alloy;
Nylon (polyamide) such as nylon, nylon-6, nylon-6,6, nylon-6 / 6,6 copolymer, nylon-6,10, nylon-6,12, nylon-11, nylon-12;
Butadiene-styrene copolymer, butadiene plastic;
Polyimide and its derivatives, polysulfone, polyphenylene sulfide, high acrylonitrile copolymer;
Silicone resin, semi-inorganic and inorganic polymers;
Phenolic resins such as phenolic resins, phenol-furfural resins, modified phenolic resins and their derivatives;
Formalin resins such as furan resin, xylene resin, aniline resin, and acetone formaldehyde resin;
Unsaturated polyester and alkyd resin;
Epoxy resins such as bisphenol type epoxy resin, epoxy resin composite material, alicyclic epoxy resin, epoxy novolak, biphenyl type epoxy resin, epoxy acrylate;
Polyurethane, urethane foam, polyurethane such as urethane acrylate;
Allyl resins such as diallyl phthalate resin, triallyl cyanurate resin, polyallyl sulfone, allyl diglycol carbonate, polyallyl ether, polyarylate;
Cellulose-based resins such as cellulosic plastics, cellulose acetate, cellulosic propionate, cellulosic acetate butyrate, ethyl cellulose, nitrocellulose and cellulose.

In particular, as a heat-resistant material, a metal plate or metal foil such as aluminum, copper, iron, stainless steel, magnesium, nickel, titanium, etc .; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer, etc. , Polyester resin such as ester acrylate; Polyfluoroethylene resin such as polyvinylidene, polyvinylidene, polytetrafluoride, ethylene-4ethylene copolymer; polyimide and its derivative; bisphenol type epoxy resin, Examples thereof include epoxy resin composite materials, alicyclic epoxy resins, epoxy novolacs, biphenyl type epoxy resins, and epoxy resins such as epoxy acrylates.

The heat-resistant adhesive film obtained by using the pressure-sensitive adhesive composition used for masking of the present invention is used as a carrier film for a process such as a printed circuit board, particularly a flexible printed circuit board; curls, wrinkles, and contamination of a film or foil having a heating process. Protective film for prevention; Protective film for solder plating on printed circuit boards; Insulation and heat-resistant protective film for heat-resistant transformers; Masking film during solder reflow process of electronic circuit boards; Various temporary fixing and component protection films; Through applications such as sealing films of the hole can be mentioned, and can be widely used in masking applications general requiring heat.

Explaining how to use the Masking heat-resistant adhesive film of the present invention. First, the heat-resistant adhesive film for masking of the present invention is attached to the surface of the adherend. Examples of the sticking means include a rubber roller and the like. Then, the adherend masking withstand heat adhesive film is stuck 170 ° C. or higher, preferably 175 ° C. or higher, particularly preferably subjected to 180 ° C. or more heating steps. After the heating step is completed, the Masking heat-resistant adhesive film its peeling from the adherend surface.

Masking resistant adhesive film of the present invention, after use in a high temperature, hardly occurs contamination when peeled from the adherend, and since adhesive performance sufficiently high, effective temporary protection of the adherend surface is there.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the example, "part" and "%" mean a weight standard.

[Example 1]
<Manufacturing of acrylic resin (A-1)>
80 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 91 .85 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 7 parts, dimethylaminoethyl acrylate (DMAEA: a3) 0.15 parts and 2,2-azobisisobutyronitrile (AIBN) 0.06 parts The dropping of the mixed mixture was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added. Further, 7 hours after the start of the reaction, a solution prepared by dissolving 0.1 part of pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] in 10.0 parts of ethyl acetate was added. Then, it reacted for another 3 hours.

Ten hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-1). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 81 ° C. In addition, the time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 98.4%.

[Example 2]
<Manufacturing of acrylic resin (A-2)>
80 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 91 .85 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 7 parts, dimethylaminoethyl acrylate (DMAEA: a3) 0.15 parts and 2,2-azobisisobutyronitrile (AIBN) 0.06 parts The dropping of the mixed mixture was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-2). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 81 ° C. In addition, the time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 98.4%.

[Example 3]
<Manufacturing of acrylic resin (A-3)>
100 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux cooler, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 41 .85 parts, methyl acrylate (MA: a1) 50 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 7 parts, dimethylaminoethyl acrylate (DMAEA: a3) 0.15 parts and 2,2-azobisiso Dropping of a mixture obtained by mixing and dissolving 0.06 part of butylnitrile (AIBN) was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-3). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 80 ° C. The time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 99.3%.

[Example 4]
<Manufacturing of acrylic resin (A-4)>
60 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux cooler, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 35 , Methyl acrylate (MA: a1) 54.50 parts, 2-Hydroxyethyl acrylate (2-HEA: a2) 9 parts, Dimethylaminoethyl acrylate (DMAEA: a3) 0.5 parts and 2,2-azobisiso Dropping of a mixture obtained by mixing and dissolving 0.3 part of butylnitrile (AIBN) was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, a solution prepared by dissolving 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN in 8.0 part of ethyl acetate was added, and 5 hours after the start of the reaction, 4-hydroxy was added. A solution prepared by dissolving 0.2 part of butyl acrylate (4HBA: a2) and 0.04 part of AIBN in 8.0 part of ethyl acetate was added. Further, 7 hours after the start of the reaction, a solution prepared by dissolving 0.1 part of pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] in 10.0 parts of ethyl acetate was added. Then, it reacted for another 2 hours.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-4). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 82 ° C. The time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 99.6%.

[Example 5]
<Manufacturing of acrylic resin (A-5)>
80 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 87 .85 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 11 parts, dimethylaminopropyl acrylamide (DMAPAA: a3) 0.15 parts and 2,2-azobisisobutyronitrile (AIBN) 0.06 parts The dropping of the mixture in which the mixture was mixed and dissolved was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added. Further, 7 hours after the start of the reaction, a solution prepared by dissolving 0.1 part of pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] in 10.0 parts of ethyl acetate was added. Then, it reacted for another 3 hours.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-5). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 80 ° C. In addition, the time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 98.6%.

[Example 6]
<Manufacturing of acrylic resin (A-6)>
80 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 91 .85 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 7 parts, dimethylaminopropyl acrylamide (DMAPAA: a3) 0.15 parts and 2,2-azobisisobutyronitrile (AIBN) 0.06 parts The dropping of the mixture in which the mixture was mixed and dissolved was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added. Further, 7 hours after the start of the reaction, a solution prepared by dissolving 0.1 part of pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] in 10.0 parts of ethyl acetate was added. Then, it reacted for another 3 hours.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-6). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 81 ° C. In addition, the time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 98.7%.

[Example 7]
<Manufacturing of acrylic resin (A-7)>
70 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux cooler, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 35 , Methyl acrylate (MA: a1) 54.80 parts, 2-Hydroxyethyl acrylate (2-HEA: a2) 9 parts, Dimethylaminoethyl acrylate (DMAEA: a3) 0.2 parts and 2,2-azobisiso Dropping of a mixture obtained by mixing and dissolving 0.3 part of butylnitrile (AIBN) was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, a solution prepared by dissolving 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN in 8.0 part of ethyl acetate was added, and 5 hours after the start of the reaction, 4-hydroxy was added. A solution prepared by dissolving 0.2 part of butyl acrylate (4HBA: a2) and 0.04 part of AIBN in 8.0 part of ethyl acetate was added. Further, 7 hours after the start of the reaction, a solution prepared by dissolving 0.1 part of pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] in 10.0 parts of ethyl acetate was added. Then, it reacted for another 2 hours.

Further, 10 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A-7). The time from the last addition of the polymerization initiator to the end of the reaction was 5 hours, and the reaction temperature was 80 ° C. The time required for drive-in heating was 3 hours. The reaction rate of the polymerized component at the start of drive-in heating was 99.6%.

[Comparative Example 1]
<Manufacturing of acrylic resin (A'-1)>
80 parts of ethyl acetate was placed in a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, and the temperature was raised while stirring. When the temperature reached 78 ° C., butyl acrylate (BA: a1) 91 .85 parts, 2-hydroxyethyl acrylate (2-HEA: a2) 7 parts, dimethylaminoethyl acrylate (DMAEA: a3) 0.15 parts and 2,2-azobisisobutyronitrile (AIBN) 0.06 parts The dropping of the mixed mixture was started. The start of this dropping is defined as the reaction start time. The mixture was added dropwise over 2 hours. Three hours after the start of the reaction, 0.8 part of 4-hydroxybutyl acrylate (4HBA: a2) and 0.05 part of AIBN were dissolved in 6.0 parts of ethyl acetate, and a solution was added. A solution prepared by dissolving 0.2 parts of butyl acrylate (4HBA: a2) and 0.06 parts of AIBN in 6.0 parts of ethyl acetate was added.

Further, 7 hours after the start of the reaction, the mixture was diluted with ethyl acetate so that the solid content became 40% to obtain a 40% solution of the acrylic resin (A'-1). The time from the last addition of the polymerization initiator to the end of the reaction was 2 hours, and the reaction temperature was 81 ° C.

Composition (polymerization component) of acrylic resin (A-1 to 7, A'-1) obtained in Examples 1 to 7 and Comparative Example 1 and acrylic resin component (heating residue) after drive-in heating. Table 1 below shows the viscosity of the obtained acrylic resin, the total reaction time, the time required for the drive-in reaction, and the polymerization initiator used during the drive-in reaction. Further, the weight average molecular weight (Mw), dispersity (Mw / Mn), and glass transition temperature of the obtained acrylic resin (A-1 to 7, A'-1) were measured and calculated according to the above-mentioned method, and the results thereof were measured and calculated. The results are shown in Table 2 below.

Production conditions for acrylic resin using the polymerization component [I] in Examples 1 to 7 and Comparative Example 1 [Residual amount of each polymerization initiator at each time, each temperature, 5 hours, 7 hours, and reaction end time. (Concentration) and drive-in heating time] are also shown in Table 3 below.

As shown in Table 3 above, in Examples 1 to 7, the amount (concentration) of the residual polymerization initiator was calculated to be 300 ppm or less in the 7 hours from the start of the reaction, and it took another 3 hours from that point. The driving reaction was carried out. Therefore, the amount of the residual polymerization initiator at the end of the reaction of the acrylic resin was calculated to be 7 to 22 ppm.

On the other hand, in Comparative Example 1, the acrylic resin was produced by a normal polymerization reaction without driving-in heating, and the final amount of the residual polymerization initiator (calculated value) at the end was as high as 150 ppm. It was.

The amount of residual polymerization initiator (calculated value) (ppm) at the end shown in Table 3 above is the amount of residual polymerization initiator (parts by weight) calculated based on the following calculation formulas (1) to (3). ) Was used, and the calculation was performed according to the following formula (4).

The A value, B value, and D value in the above calculation formulas (1) to (3) are shown in Table 4 below.

The calculation method of the A value, B value, and D value is shown below. That is, as shown below, the coefficient of the power approximation formula is calculated from the logarithm of the polymerization initiator temperature and the half-life temperature using the least squares method. The relationship between the temperature (H) and the half-life time (T) when AIBN is used as the polymerization initiator is shown in Table 5 below.
Since the half-life time T = A × 10 ^B × (reaction temperature H) ^D , log (T) = log (A × 10 ^B ) + Dlog (H)

The amount of the polymerization initiator can be actually measured according to the following as well as the above calculated value. -Sample preparation After dissolving the acrylic resin solution in acetone, it was reprecipitated with acetonitrile, and the supernatant was used for measurement by LC-MS / MS.
-LC-MS / MS measurement conditions LC device: manufactured by Shimadzu Corporation, LC-10A
MS device: Applied Biosystems API3000
Column: Inertsil ODS-3 (GL Science, 2.1 x 100 mm, 3 μm)
Temperature 40 ° C
Eluent: 5 mM ammonium formate aqueous solution / acetonitrile = 60/40 (0 minutes) → 0/100 (5 minutes) → 0/100 (6 minutes), 0.2 mL / min
Injection volume: 3 μL
Detection: ESI (+), MRM m / z 182 (M + NH4) / 86, Dwell = 0.5 seconds DP, CE, CAD = 15,8,3

In the present invention, the residual amount of the polymerization initiator is measured by using LC-MS / MS, which is a kind of LC-MS, but this is because the radical polymerization initiator is an unstable substance and is heated. This is because it is detected by GC-MS or the like with a value smaller than the actual residual amount of the polymerization initiator, and accurate measurement cannot be performed. Therefore, it is necessary to measure by LC-MS in order to evaluate the measured residual amount of the polymerization initiator. Further, it is more preferable to measure by LC-MS / MS, which has particularly good measurement sensitivity.

When the remaining amount of the polymerization initiator (the amount of the initiator at the end) of Example 2 and Comparative Example 1 in Table 3 is actually measured, it can be seen that there is a correlation with the theoretical value (calculated value). That is, it can be seen that the calculation based on this half-life is valid and well represents the actual remaining amount of the polymerization initiator.

[Examples 8 to 20, Comparative Examples 2 to 3]
<Making heat-resistant adhesive film>
Each acrylic resin solution obtained as described above is mixed with a cross-linking agent (isocyanurate of hexamethylene diisocyanate: Coronate HX, burette of hexamethylene diisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.) in the amounts shown in Table 6 below. : Asahi Kasei Chemicals Co., Ltd., Duranate 24A-100), and antioxidant pentaerythritol tetrakis [β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (BASF Japan Co., Ltd., Irganox 1010) was blended (Examples 10, 12, 16 and Comparative Example 2), further diluted with ethyl acetate to a solid content concentration of 33.3%, and then dried to a thickness of about 25 μm. , A polyimide film as a base material (manufactured by Toray DuPont, Kapton: thickness 25 μm) was applied, and dried at 100 ° C. for 2 minutes. Then, a release-treated polyethylene terephthalate (PET) film was attached to the coated surface to protect it, and the film was cured in an atmosphere at a temperature of 40 ° C. for 7 days to prepare a heat-resistant adhesive film.

Further, for measuring the gel fraction, each acrylic resin solution is applied to the release-treated PET film (thickness 38 μm) in the same manner as above, and the heat-resistant adhesive layer without a base material is applied in the same manner as in the above operation. Got

[Confirmation of cross-linking agent reaction]
Regarding the cross-linking reaction of the obtained heat-resistant adhesive film, the peak of the residual isocyanate group was confirmed by infrared spectroscopy. As a measuring device, an FT-IR Nicolet 380FT-IR manufactured by Thermoelectron was used, and the number of scans was 32 by the ATR method. Then, the presence or absence of a peak of 2200 to 2300 cm ^-1 , which is an absorption peak of the isocyanate group, and the size of the peak were evaluated. As a result, no peak was confirmed in all the examples and comparative examples.

[Adhesive force]
A heat-resistant adhesive film with a size of 25 mm x 100 mm was pressure-bonded to a stainless steel plate (SUS304BA plate) as an adherend in an atmosphere of 23 ° C. x 50% relative humidity with 2 reciprocating 2 kg rubber rollers, and 23 ° C. x relative humidity. After leaving it for 30 minutes in a 50% atmosphere, 180 ° peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min.

[Adhesive strength after heat resistance treatment]
A heat-resistant adhesive film with a size of 25 mm x 100 mm was pressure-bonded to a stainless steel plate (SUS304BA plate) as an adherend under an atmosphere of 23 ° C. x 50% relative humidity with two reciprocating 2 kg rubber rollers, and each heat-resistant process temperature (SUS304BA plate) It was left at 180 ° C. and 200 ° C. for 5 hours. Then, after returning to 23 ° C. and allowing to stand for another 3 hours, 180 ° peel strength (N / 25 mm) was measured at a peeling speed of 300 mm / min.

[Adhesive residue]
Using the obtained heat-resistant adhesive film, a test piece having a size of 25 mm × 100 mm was prepared (cut out), and this test piece was pressure-bonded to an adherend (SUS304BA plate) by reciprocating a 2 kg roller twice. The film was left at the temperature (180 ° C., 200 ° C.) and time (5 hours) shown in Table 7 to return to 23 ° C. Further, after leaving it for 2 hours in an atmosphere of 23 ° C. and 50% relative humidity, the state of the adherend surface after 180 ° peeling at a peeling speed of 300 mm / min was visually observed and evaluated according to the following criteria.
◯: No contamination was confirmed.
Δ: There was some cloudiness, but no contamination was confirmed.
X: Contamination was confirmed.

[Gel fraction]
The gel fraction was calculated for the obtained heat-resistant adhesive layer. That is, the heat-resistant adhesive layer to be the test piece is wrapped with a 200-mesh SUS wire mesh, immersed in toluene at 23 ° C. for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the wire mesh is defined as the gel fraction. did.
These results are shown in Table 7 below.

Further, using the heat-resistant adhesive films of Examples 12 to 16, 19, and 20, the adhesive strength and adhesive residue after the heat-resistant treatment at 250 ° C. were measured and evaluated according to the following method. The results are shown in Table 8 below.

[Adhesive strength after heat resistance treatment]
A heat-resistant adhesive film with a size of 25 mm x 100 mm was pressure-bonded to a stainless steel plate (SUS304BA plate) as an adherend under an atmosphere of 23 ° C. x 50% relative humidity with 2 reciprocating 2 kg rubber rollers, and 5 at 250 ° C. I left it for a while. Then, after returning to 23 ° C. and allowing to stand for another 3 hours, 180 ° peel strength (N / 25 mm) was measured at a peeling speed of 300 mm / min.

[Adhesive residue]
Using the obtained heat-resistant adhesive film, a test piece having a size of 25 mm × 100 mm was prepared (cut out), and this test piece was pressure-bonded to an adherend (SUS304BA plate) by reciprocating a 2 kg roller twice, and 250 After leaving at ° C. for 5 hours, the temperature was returned to 23 ° C. Further, after leaving it for 2 hours in an atmosphere of 23 ° C. and 50% relative humidity, the state of the adherend surface after 180 ° peeling at a peeling speed of 300 mm / min was visually observed and evaluated according to the following criteria.
◯: No contamination was confirmed.
Δ: There was some cloudiness, but no contamination was confirmed.
X: Contamination was confirmed.

From the above results, Examples 8 to 20 using an acrylic resin having a small residual amount of the polymerization initiator are subjected to any heat resistance treatment of 180 ° C. × 5 hours and 200 ° C. × 5 hours (in addition, Examples 12 to 12). It is clear that 16th, 19th, and 20th have no adhesive residue even after heat-resistant treatment at 250 ° C. for 5 hours) and are suitable for use in the heat-resistant process. On the other hand, Comparative Examples 2 and 3 using an acrylic resin having a large residual amount of the polymerization initiator are not suitable for use in the heat-resistant process because contamination due to the adhesive residue was confirmed. .. In Examples 12 to 14, 19 and 20, the adhesive strength is 0.8 N / 25 mm or more even after 0.5 hours of pasting, and the adhesive strength is high, which is preferable for fixing applications. Further, Examples 8 to 11 and 15 to 18 have a low adhesive strength of less than 2.0 N / 25 mm even when heated after 200 ° C. × 5 hours, and can be said to be preferable because they are easily peeled off as a surface protection application.

Further, in the above-mentioned Example, AIBN was used as the polymerization initiator, but instead of this, an azo-based polymerization initiator other than AIBN, which is the above-mentioned other polymerization initiator, was used in the same manner as in the above-mentioned Example. An acrylic resin was prepared to prepare a heat-resistant adhesive film. Then, as a result of performing various evaluations in the same manner as described above, good results were obtained, which were substantially the same as in the case of AIBN.

Adhesive composition containing a specific acrylic resin and the crosslinking agent of the present invention, widely used in masking Applications General requiring resistance heat, suitably used as an adhesive layer-forming material of the heat-adhesive film for Masking be able to.

Claims (4)

The polymerization component [I] is a pressure-sensitive adhesive composition containing an acrylic resin and a cross-linking agent polymerized in the presence of an azo-based polymerization initiator, and the acrylic resin is a (meth) acrylic acid alkyl ester-based monomer. (a1) an acrylic resin polymer component [I] is polymerized containing as a main component, the polymerization component [I] is hydroxyl group-containing monomer having one hydroxyl group in each molecule (a2) It contains 5 to 20 % by weight and 0.05 to 5 % by weight of a nitrogen atom-containing monomer (a3), and the weight average molecular weight of the acrylic resin is 300,000 to 2,000,000 (excluding 300,000). ), The azo polymerization initiator-containing concentration of the acrylic resin is 280 ppm or less, and the cross-linking agent is contained in an amount of 1 to 20 parts by weight based on 100 parts by weight of the acrylic resin. A pressure-resistant pressure-sensitive adhesive film pressure-sensitive adhesive composition used for masking, wherein the gel content of the pressure-sensitive adhesive obtained by cross-linking the material is 90 to 100 % . The pressure-resistant pressure-resistant adhesive film pressure-sensitive adhesive composition used for masking according to claim 1, which contains an antioxidant. A pressure-resistant pressure-resistant adhesive film pressure-sensitive adhesive used for masking, which is obtained by curing the pressure-sensitive adhesive composition according to claim 1 or 2. A heat-resistant adhesive film for masking, which has an adhesive layer made of the adhesive according to claim 3.