JP2013032504A - Adhesive composition for heat-resistant adhesive film, adhesive for heat-resistant adhesive film produced by crosslinking the same, and use for the adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for heat-resistant adhesive film which hardly stains an adherend when the film is peeled off from the adherend after being used under high temperature, has a sufficient adhesive property, and is economically efficient because the aging period during film production is short, and also to provide an adhesive for heat-resistant adhesive film produced by crosslinking the same and uses for the adhesive.SOLUTION: The adhesive composition for a heat-resistant adhesive film includes an acrylic resin (A) which is obtained by copolymerizing a monomer component [I] including a nitrogen atom-containing monomer (a1) and has a glass transition temperature of ≥-40°C. The adhesive for heat-resistant adhesive film is made by crosslinking the adhesive composition containing a crosslinking agent (B). The heat-resistant adhesive film, such as a heat-resistant adhesive masking film, is characterized in that the film is covered with an adhesive layer containing the adhesive. Methods for using the heat-resistant masking adhesive film are also provided.

Description

  The present invention relates to a pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive film, a pressure-sensitive adhesive for a heat-resistant pressure-sensitive adhesive film obtained by crosslinking the same, and a use of this pressure-sensitive adhesive. Contamination hardly occurs when peeled off, the adhesive performance is sufficiently high, and the aging period at the time of film production is short, so the adhesive composition used for the heat-resistant adhesive film is economically efficient, and is crosslinked. The present invention relates to a pressure-sensitive adhesive for heat-resistant pressure-sensitive adhesive films and uses of the pressure-sensitive adhesive.

  Flexible printed wiring (FPC) substrates are used in information terminal electronic devices such as mobile phones. In recent years, thinning of laminates including FPC substrates has become possible due to higher circuit performance and smaller and lighter electronic devices. Miniaturization is progressing. As a result, since the strength of the laminated plate is reduced and is easily damaged, it is necessary to protect the laminated plate with a protective film during the manufacturing process in order to prevent the damage. However, since it is exposed to a high temperature during the production process, the adhesive layer of the protective film may adhere to the laminated board, and the laminated board may be damaged when the protective film is peeled off or may be contaminated by adhesive residue. In addition, since the adhesive strength may be reduced and float may occur at high temperatures, there is a problem that sufficient protective ability as a protective film cannot be exhibited. In order to solve these problems, the following techniques are disclosed.

  Patent Document 1 discloses that a hydroxyl group-containing acrylic resin having a weight average molecular weight of 450,000 to 1,500,000 and an isocyanate-based crosslinking agent, an isocyanate in the isocyanate-based crosslinking agent relative to the amount of hydroxyl group in the hydroxyl group-containing acrylic resin. In the range of 0.6 to 1.6 times (molar ratio), the hydroxyl group-containing acrylic resin and the isocyanate-based crosslinking agent and the non-hydroxy group-containing acrylic resin with respect to 100 parts by weight of the hydroxyl group-containing acrylic resin. A pressure-sensitive adhesive composition that is reactive and contains 3 to 20 parts by weight of an ester compound having a formula weight or a number average molecular weight of 300 to 1500 is disclosed.

  Patent Document 2 discloses a pressure-sensitive adhesive composition for a heat-resistant fine-adhesive film or sheet that is laminated to a film or sheet such as an FPC base material and reinforces the film or sheet. A heat-resistant slightly pressure-sensitive adhesive composition characterized in that an acrylic resin and an isocyanate resin and a metal chelating agent are blended is disclosed.

JP 2007-327036 A JP 2003-261849 A

  However, in the technique of Patent Document 1, since a low molecular weight compound having a number average molecular weight of 300 to 1500 is used, the compound itself may be a causative substance of the adherend, and the pressure-sensitive adhesive The layer may cause a decrease in cohesive force at a high temperature, and the adhesive may remain on the adherend surface.

  Moreover, in the technique of patent document 2, since the metal chelating agent is used, a metal ion may become a causative substance of a to-be-adhered body. In addition, the crosslinking by the metal chelate is different from the crosslinking by the covalent bond such as isocyanate or epoxy, and is the crosslinking by the ionic bond. Therefore, the bond is easily dissociated and the heat resistance at a higher temperature is inferior and the adhesive residue may be generated.

  Furthermore, since it takes a long time to age these pressure-sensitive adhesive compositions, there is also a problem that they are not economically efficient.

  Therefore, in the present invention, under such a background, after use at high temperature, it is difficult to cause contamination when peeled from the adherend surface, the adhesive performance is sufficiently high, and the aging period during film production is also high. An object of the present invention is to provide a pressure-sensitive adhesive composition used for a heat-resistant pressure-sensitive adhesive film that is economically efficient because it is short, a pressure-sensitive adhesive for a heat-resistant pressure-sensitive adhesive film obtained by crosslinking the composition, and use of the pressure-sensitive adhesive.

  By using an acrylic resin having a glass transition temperature higher than usual as an acrylic resin for forming the pressure-sensitive adhesive layer, and further using a monomer having an effect of promoting crosslinking as a monomer component of the acrylic resin, The present inventors have found that the above problems can be solved, and have completed the present invention.

  That is, the gist of the present invention includes an acrylic resin (A) obtained by polymerizing the monomer component [I] containing the nitrogen atom-containing monomer (a1) and having a glass transition temperature of −40 ° C. or higher. The present invention relates to a pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive films.

  The gist of the present invention also relates to a heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film.

  Furthermore, the gist of the present invention relates to a heat-resistant adhesive film having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive for heat-resistant adhesive film on the film, particularly to a heat-resistant adhesive film for masking.

  Further, the gist of the present invention is that the masking heat-resistant adhesive film is attached to the surface of the adherend and subjected to a heating step of 170 ° C. or higher, and then the masking heat-resistant adhesive film is peeled off from the surface of the adherend. The present invention relates to a method for using a heat-resistant adhesive film.

  The “adhesive film” in the present invention conceptually includes an adhesive sheet, an adhesive film, and an adhesive tape.

  In the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention, the glass transition temperature (Tg) when a homopolymer is used as compared with butyl acrylate and 2-ethylhexyl acrylate, which are alkyl acrylates used in general pressure-sensitive adhesives. By using a high monomer, the entire glass transition temperature (Tg) can be set to -40 ° C. or higher, whereby the cohesive force of the pressure-sensitive adhesive layer in the heat-resistant pressure-sensitive adhesive film can be increased. Moreover, bridge | crosslinking can be accelerated | stimulated by using a nitrogen atom containing monomer (a1), and this can further raise the cohesion force of an adhesive layer. Due to these effects, even after the heat-resistant adhesive film attached to the surface of the adherend is exposed to a high temperature, adherend contamination such as adhesive residue hardly occurs when the heat-resistant adhesive film is peeled off.

  In general, if the degree of cross-linking of the pressure-sensitive adhesive is increased, adhesive residue is less likely to be generated, but instead, the pressure-sensitive adhesive layer becomes more cohesive, making it difficult for the pressure-sensitive adhesive layer to conform to the adherend and adhesion. It decreases and the adhesive strength decreases. Therefore, if a heat-resistant adhesive film using a pressure-sensitive adhesive with only a high degree of crosslinking is used, the heat-resistant adhesive film will float when exposed to high temperatures, and the adherend There is a problem that the surface is contaminated or the adherend cannot be fixed sufficiently.

  In the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention, adherence contamination can be prevented by controlling not only the degree of crosslinking but also the glass transition temperature (Tg) of the pressure-sensitive adhesive composition. It becomes difficult to produce the malfunction which becomes too low and cannot fully fix to the to-be-adhered body surface.

  In addition, the pressure-sensitive adhesive composition containing a polymer obtained by polymerizing a monomer containing an acid group to promote crosslinking causes corrosion to a metal adherend such as an FPC board, resulting in problems in the final product. There is a possibility to make it. On the other hand, the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention comprises an acrylic resin (A) obtained by polymerizing a monomer component [I] containing a basic nitrogen atom-containing monomer (a1). Since it contains, the possibility of corrosion of a metal adherend is reduced.

  According to the pressure-sensitive adhesive composition for heat-resistant adhesive film of the present invention and the pressure-sensitive adhesive for heat-resistant film obtained by crosslinking the same, it is difficult to cause contamination when peeled off from the adherend surface after being used at a high temperature. The performance is sufficiently high and the aging period at the time of film production is short, so that a heat-resistant adhesive film such as a heat-resistant adhesive film for masking can be produced economically and efficiently. Moreover, according to the usage method of the heat-resistant adhesive film for masking of this invention, the adherend surface is protected with respect to a heating process of 170 degreeC or more, and can peel from an adherend surface.

The present invention will be described in detail below, but these show examples of desirable embodiments.
In the present specification, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate. The “film” conceptually includes a sheet, a film, and a tape.

  The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive films of the present invention comprises an acrylic resin (A). The acrylic resin (A) used in the present invention is obtained by polymerizing the monomer component [I] containing the nitrogen atom-containing monomer (a1) as an essential component, and is contained in the monomer component [I]. As another monomer component, a monomer appropriately selected from the (meth) acrylic acid ester monomer (a2), the functional group-containing monomer (a3), and the other polymerizable monomer (a4) is contained.

  The nitrogen atom-containing monomer (a1) may be any monomer containing a nitrogen atom. For example, an amino group-containing monomer, an amide group-containing monomer, a nitrogen-based heterocyclic ring-containing monomer, a cyano group-containing monomer. Examples thereof include monomers, imide group-containing monomers, and betaine monomers. Among them, a highly basic monomer exhibiting catalytic activity is preferable, 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. Amino group-containing monomers are preferred. These monomers are preferably (meth) acrylic monomers. The nitrogen atom-containing monomer (a1) can be used alone or in combination of two or more.

The amino group-containing monomer may be any polymerizable monomer having an ethylenically unsaturated double bond and an amino group (unsubstituted or substituted amino group). For example, aminomethyl (meth) acrylate, ( N-methine such as aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, aminoalkyl (meth) acrylate such as aminoisopropyl (meth) acrylate and N- (t-butyl) aminoethyl (meth) acrylate Monosubstituted amino group-containing (meth) acrylic acid esters such as alkylaminoalkyl (meth) acrylic acid esters;
N, N-dialkylaminoalkyl (meth) such as N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylate Disubstituted amino group-containing (meth) acrylic acid esters such as acrylic acid esters;
Dialkylaminoalkyl (meth) acrylamides such as N, N-dimethylaminopropyl (meth) acrylamide, quaternized salts of these amino group-containing monomers, and the like;
amino group-containing styrenes such as p-aminostyrene;
Styrenes having a dialkylamino group such as 3- (dimethylamino) styrene and dimethylaminomethylstyrene; dialkylaminoalkyl vinyl 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 any polymerizable monomer having an ethylenically unsaturated double bond and an amide group (group having an amide bond). For example, (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, Ns-butyl (Meth) acrylamide, Nt-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, diacetone (meth) acrylamide, N, N′-methylenebis (meth) acrylamide, N- (1,1-dimethyl-) N-alkyl (meth) acrylamids such as 3-oxobutyl) (meth) acrylamide Do:
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) (Meth) acrylamide, N, N-diisobutyl (meth) acrylamide, N, N-di (s-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide, N, N-dipentyl (Meth) acrylamide, N 2, 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) acrylamides such as methylacrylamide:
Dialkylaminoalkyl (meth) acrylamides such as N, N-dimethylaminopropyl (meth) acrylamide:
Substituted amide group-containing monomers such as N-vinylacetamide, N-vinylformamide, (meth) acrylamide ethylethyleneurea, (meth) acrylamide t-butylsulfonic acid;
Hydroxyl group-containing (meth) acrylamides such as N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylolpropane (meth) acrylamide;
Alkoxy group-containing (meth) acrylamides such as N-methoxymethyl (meth) acrylamide and N- (n-butoxymethyl) (meth) acrylamide;
These include quaternized salts of these amide group-containing monomers.

The nitrogen-based heterocyclic ring-containing monomer may be any polymerizable monomer having an ethylenically unsaturated double bond and a nitrogen-based heterocyclic ring (a heterocyclic ring having a nitrogen atom as a ring constituent element). -Methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, N-vinyl pyrrole, N-vinyl oxazole, N-vinyl morpholine, N-vinyl caprolactam, N -Vinylpyrrolidone, N-vinylimidazole, 1-vinylimidazole, 4-vinylpyridine, 2-vinylpyridine, 2-vinylpyrazine, N-vinyl-2-pyrrolidone, N-vinylcarbazole, N-vinylphthalimide, N-vinyl N-vinyl-based single quantities such as 2-pyrrolidone and 2-vinyl-2H-indazole ;
N-allylic monomers such as N-allylmorpholine;
N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylaziridine, N- (meth) acryloylaziridine, aziridini N- (meth) acryloyl monomers such as ruethyl (meth) acrylate;
A quaternized salt of a nitrogen-based heterocycle-containing monomer obtained by allowing a known quaternizing agent such as alkyl halide, benzyl halide, alkyl or arylsulfonic acid or dialkyl sulfate to act on the above monomer; 4 -Methyl-5-vinylthiazole and the like.

  The cyano group-containing monomer may be any 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 any polymerizable monomer having an ethylenically unsaturated double bond and an imino group, such as maleimide, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, Maleimide monomers such as N-phenylmaleimide and isopropylmaleimide;
Itacimide imides such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl leuconacimide, N-lauryl itaconimide, itaconimide Mer;
Examples thereof include succinimide monomers such as N- (meth) acryloyloxymethylene 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, N- (3-sulfopropyl) -N-methacryloylamidopropyl-N. , N-dimethylammonium betaine, N- (3-carboxymethyl) -N-methacryloylamidopropyl-N, N-dimethylammonium betaine, N- (3-sulfopropyl) -N-methacryloyloxyethyl-N, N-dimethyl Examples include ammonium betaine and N-carboxymethyl-N-methacryloyloxyethyl-N, N-dimethylammonium betaine.

Among these nitrogen atom-containing monomers (a1), amino group-containing monomers and amide group-containing monomers are preferred from the viewpoints of copolymerizability with other monomers and cross-linking promotion effects. Particularly preferred are (meth) acrylic acid N, N-dimethylaminoethyl (dimethylaminoethyl (meth) acrylate), (meth) acrylic acid N, N-diethylaminoethyl (diethylaminoethyl methacrylate), and an amide group-containing monomer. Particularly preferred are N, N-dimethylaminopropyl (meth) acrylamide (dimethylaminopropyl (meth) acrylamide) and N, N-dimethyl (meth) acrylamide (dimethyl (meth) acrylamide).
More preferred are dimethylaminoethyl acrylate, dimethylaminopropyl acrylamide, dimethyl acrylamide, and diethylaminoethyl methacrylate from the viewpoints of copolymerization with other monomers, crosslinking promotion effect, and availability as raw materials.

The content ratio of the nitrogen atom-containing monomer (a1) is preferably 0.001 to 30% by weight, particularly preferably 0.005 to 5% by weight, and still more preferably 0.01 to 0%, based on the entire monomer component [I]. 2% by weight.
If the content ratio of the nitrogen atom-containing monomer (a1) is too large, the molecular weight tends to decrease during polymerization or the pressure-sensitive adhesive tends to be colored. If the content is too small, the catalytic effect tends to be insufficient.

  The (meth) acrylic acid ester monomer (a2) used in the present invention is a monomer excluding the nitrogen atom-containing monomer (a1), and includes, for example, methyl (meth) acrylate, ethyl (meth) acrylate, and n-butyl. (Meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meta ) (Meth) acrylic acid alkyl esters such as acrylate, iso-octyl acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, iso-stearyl (meth) acrylate; Kurohekishiru (meth) acrylate, isobornyl (meth) alicyclic acrylates such as (meth) acrylic acid ester. In the case of (meth) acrylic acid alkyl ester, the alkyl group preferably has 1 to 20, particularly 1 to 12, more preferably 1 to 8, and particularly preferably 4 to 8 carbon atoms. These can be used alone or in combination of two or more.

Among such (meth) acrylic acid alkyl ester monomers (a2), 2-ethylhexyl (meth) acrylate and butyl (meth) acrylate are preferable (particularly preferably butyl (meth) acrylate), and more preferably butyl (meth) acrylate. Further, it is preferable to polymerize a monomer having a glass transition temperature (Tg) of −20 ° C. or higher (particularly preferably 0 ° C. or higher).
The monomer having a glass transition temperature (Tg) of −20 ° C. or higher when such a homopolymer is used is preferably methyl (meth) acrylate, particularly excellent in heat-resistant removability and high adhesive strength, and particularly preferably methyl acrylate. It is.

The content ratio of the (meth) acrylic acid ester monomer (a2) is preferably 10 to 99% by weight, particularly preferably 20 to 98% by weight, more preferably 40 to 97% by weight, based on the whole monomer component [I]. %.
If the content ratio of the (meth) acrylic acid ester monomer (a2) is too small, the adhesive strength tends to be lowered.

  The functional group-containing monomer (a3) used in the present invention is a monomer containing a functional group that can become a crosslinking point by reacting with the below-mentioned crosslinking agent (B), and other than the above (a1) and (a2) monomers For example, a hydroxyl group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, a glycidyl group-containing monomer, and the like can be used, and these can be used alone or in combination of two or more. Among these, a hydroxyl group-containing monomer is preferably used in that a crosslinking reaction can be efficiently performed.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meta ) Acrylic acid hydroxyalkyl ester such as acrylate; Caprolactone-modified 2-hydroxyethyl (meth) acrylate and other caprolactone-modified monomers; Diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate and other oxyalkylene-modified monomers; Primary hydroxyl group-containing monomers such as leuoxyethyl 2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate Rate, secondary hydroxyl group-containing monomers such as 3-chloro-2-hydroxypropyl (meth) acrylate; may be mentioned 2,2-dimethyl-2-hydroxyethyl (meth) tertiary hydroxyl group-containing monomers such as acrylates.
Among these, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxybutyl acrylate are preferably used.
Moreover, it is preferable to use two or more kinds of hydroxyl group-containing monomers in view of increasing the cross-linking structure and improving the heat resistance, and it is particularly preferable to use 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate in combination. It is.

  Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

  Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, allyl glycidyl (meth) acrylate, and the like.
These functional group-containing monomers (a3) may be used alone or in combination of two or more.

The content ratio of the functional group-containing monomer (a3) is preferably 1 to 30% by weight, particularly preferably 2 to 20% by weight, and further preferably 3 to 10% by weight with respect to the whole monomer component [I].
If the content ratio of the functional group-containing monomer (a3) is too large, the adhesive strength tends to decrease, and if it is too small, the degree of crosslinking tends to decrease and the adherend contamination resistance tends to decrease.

  The other polymerizable monomer (a4) is a monomer other than the monomers (a1), (a2), and (a3), and examples thereof include phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth). Monomers containing one aromatic ring such as acrylate, phenoxydiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, styrene, α-methylstyrene; 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, methoxytri Tylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethyleneglycol-polypropyleneglycol-mono (meth) acrylate, lauroxypolyethyleneglycolmono Monomers containing alkoxy groups or oxyalkylene groups such as (meth) acrylate and stearoxypolyethylene glycol mono (meth) acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, Alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate Examples thereof include esters, dialkyl esters of fumaric acid, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, and the like. Preferably, it is a monomer having a glass transition temperature (Tg) of the homopolymer of 0 ° C. or higher. These monomers (a4) may be used alone or in combination of two or more.

The content of the other polymerizable monomer (a4) is preferably 0 to 80% by weight, particularly preferably 0 to 50% by weight, more preferably 0 to 30% by weight, based on the entire monomer component [I]. .
When there is too much content rate of this other polymerizable monomer (a4), there exists a tendency for heat resistance to fall or for adhesive force to fall.

In the present invention, as described later, the acrylic resin (A) has a glass transition temperature (Tg) of −40 ° C. or higher, and is obtained by polymerizing the monomers (a1) to (a4) ( As long as the glass transition temperature (Tg) of A) is −40 ° C. or higher, the glass transition temperature (Tg) when the monomers (a1) to (a4) are homopolymers is not particularly limited. It is preferable to use a monomer having a glass transition temperature (Tg) of 0 ° C. or higher when a homopolymer is used.
For example, in the case where two or more types of (meth) acrylic acid ester monomers (a2) are used in combination, a monomer having a glass transition temperature (Tg) of 0 ° C. or more when a homopolymer is used with respect to the entire monomer (a2) Preferably 15 to 80% by weight, more preferably 20 to 75% by weight.

  The acrylic resin (A) can be produced by appropriately selecting and polymerizing the monomer components (a1) to (a4). Such polymerization can be carried out by conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization. For example, in an organic solvent, a polymerization monomer such as nitrogen atom-containing monomer (a1), (meth) acrylic acid ester monomer (a2), functional group-containing monomer (a3), other polymerizable monomer (a4), polymerization start The agent is mixed or dropped and polymerized at reflux or at 50 to 90 ° C. for 2 to 20 hours.

  Examples of the organic solvent used for the polymerization include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, fats such as n-propyl alcohol and isopropyl alcohol. Group alcohols, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  As the polymerization initiator used for such radical polymerization, azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are usual radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, di- Specific examples thereof include peroxide polymerization initiators such as t-butyl peroxide and cumene hydroperoxide.

  The acrylic resin (A) in the present invention has a glass transition temperature (Tg) of −40 ° C. or higher, preferably −40 to + 40 ° C., more preferably −35 to + 35 ° C., particularly preferably −35 to + 10 ° C. Particularly preferred is −35 to 0 ° C. If the glass transition temperature (Tg) is too low, the heat-resistant adhesive film will be inferior in heat resistance, and if it is too high, the adhesive force will be reduced, and the heat-resistant adhesive film will tend to be incompatible with the adherend and float.

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） Ｗa ：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗb ：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗn ：モノマーＮの重量分率
（Ｗa＋Ｗb＋・・・＋Ｗn＝１） The glass transition temperature (Tg) is calculated from the following Fox equation.

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

  The weight average molecular weight of the acrylic resin (A) is preferably 100,000 to 2,500,000, particularly preferably 200,000 to 2,200,000, and more preferably 300,000 to 2,000,000. If the weight average molecular weight is too small, the heat resistance tends to decrease and the adherend contamination resistance tends to decrease. If it is too large, a large amount of diluent solvent is required, which tends to be undesirable in terms of coating properties and cost. .

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

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in a high performance liquid chromatography (The Japan Waters company, "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plate / piece, filler material: styrene-divinylbenzene polymer, filler particle The number average molecular weight is also measured by the same method. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight.

  The viscosity (mPa · s (25 ° C.)) of the acrylic resin (A) is preferably 10 to 500,000 (mPa · s (25 ° C.)), particularly preferably 100 to 100,000 (mPa · s (25 ° C.)). ° C)). If the viscosity is too low, the pressure-sensitive adhesive composition may sag or repel from the substrate at the time of coating, and the coating tends to be difficult. Tend to be difficult. In addition, when application | coating becomes difficult by the thickening of a composition, you may dilute and reduce solid content concentration as needed. The viscosity can be measured according to the 4.5.3 rotational viscometer method of JIS K5400 (1990).

  The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention contains the acrylic resin (A) as an essential component, and becomes a pressure-sensitive adhesive for heat-resistant pressure-sensitive adhesive film by crosslinking it. When the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film is crosslinked, the pressure-sensitive adhesive composition further contains a crosslinking agent (B).

  Examples of the crosslinking agent (B) include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, oxazoline crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, and amine crosslinking agents. Among these, an isocyanate-based crosslinking agent is 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 crosslinking 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-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof And adducts of a polyol compound such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds. Among these, in terms of heat resistance, isocyanurate of hexamethylene diisocyanate, 2,4-tolylene diisocyanate and / or adduct of 2,6-tolylene diisocyanate and trimethylol propane, 2,4-tolylene diisocyanate and An isocyanurate of 2,6-tolylene diisocyanate and an adduct of tetramethylxylylene diisocyanate and trimethylolpropane are preferred.

  Examples of the epoxy crosslinking 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. , Trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, 1,3′-bis (N, N-diglycidylaminomethyl) cyclohexane, N , N, N ′, N′-tetraglycidyl-m-xylenediamine and the like.

  Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. '-Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like can be mentioned.

  Examples of the oxazoline-based crosslinking agent include 2,2′-bis (2-oxazoline), 1,2-bis (2-oxazolin-2-yl) ethane, and 1,4-bis (2-oxazoline-2-). Yl) butane, 1,8-bis (2-oxazolin-2-yl) butane, 1,4-bis (2-oxazolin-2-yl) cyclohexane, 1,2-bis (2-oxazolin-2-yl) Bisoxazoline compounds containing aliphatic or aromatic such as benzene, 1,3-bis (2-oxazolin-2-yl) benzene, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl- Examples thereof include one or more polymers of addition polymerizable oxazoline such as 2-oxazoline.

  Examples of the melamine-based crosslinking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexaptoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, and melamine resin. .

  Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

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

  Moreover, these crosslinking agents (B) may be used independently and may use 2 or more types together.

  In general, the content of the crosslinking agent (B) is preferably 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, particularly 100 parts by weight of the acrylic resin (A). The amount is preferably 2 to 20 parts by weight, particularly preferably 5 to 15 parts by weight. If the amount of the crosslinking agent (B) is too small, the cohesive force of the pressure-sensitive adhesive tends to decrease and causes a residue, and if too large, the pressure-sensitive adhesive is excessively cross-linked and the pressure-sensitive adhesive strength decreases. There is a tendency that floating occurs between the surface and the surface of the body.

  In addition, a crosslinking reaction can also be performed by irradiating an active energy ray. In this case, it is preferable to blend polyfunctional (meth) acrylate. Examples of such polyfunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane tri (meth) acrylate, penta Examples include erythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and glycerin polyglycidyl ether poly (meth) acrylate. In addition, it is preferable to use together the bridge | crosslinking by active energy ray irradiation with the bridge | crosslinking by a crosslinking agent.

  The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention further includes an antioxidant, a plasticizer, a filler, an antistatic agent, a pigment, a diluent, an anti-aging agent, and an ultraviolet absorber as long as the effects of the present invention are not impaired. , UV stabilizers, tackifier resins and other additives may be further contained, and these additives may be used alone or in combination of two or more. Particularly, the antioxidant is used in the adhesive layer. It is effective to keep stability. In addition to the additive, 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.

  The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive films of the present invention preferably contains an acrylic resin (A) as a main component. As used herein, “main component” means that the acrylic resin (A) 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. It means to do. The upper limit is usually 99.9% by weight.

  Moreover, it is preferable that the adhesive composition for heat-resistant adhesive films of this invention does not contain an acid substantially, and can reduce corrosion of to-be-adhered bodies, such as a metal. 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, more preferably 0.1 mgKOH / g or less. means.

  The gel fraction of the pressure-sensitive adhesive film for heat-resistant pressure-sensitive adhesive film obtained by crosslinking the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention is usually 40 to 100%, preferably 60 to 100%, particularly preferably 80 to 100%. More preferably, it is 90 to 100%, and particularly preferably 97 to 100%. When the gel fraction is too low, the cohesive force of the pressure-sensitive adhesive is lowered, and a residue remains, which tends to cause adherend contamination.

  In addition, in adjusting the gel fraction of an adhesive to the said range, it is achieved by adjusting the kind and quantity of a crosslinking agent, adjusting the composition ratio of the hydroxyl group in a composition, etc., for example. Moreover, since the gel fraction changes with each interaction, the ratio between the crosslinking agent and the functional group amount needs to be balanced.

  The gel fraction is a measure of the degree of crosslinking, and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (not provided with a separator) in which a pressure-sensitive adhesive layer is formed on a polymer sheet (for example, polyethylene terephthalate film or the like) as a base material is wrapped with a 200-mesh SUS wire mesh, and 23 in toluene. The weight percentage of the insoluble pressure-sensitive adhesive component immersed in the wire mesh at 24 ° C. for 24 hours is defined as the gel fraction. However, the weight of the substrate is calculated by subtracting.

  The adhesive strength of the heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive obtained by crosslinking the heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive composition of the present invention is preferably 0.01 N / 25 mm or more, particularly preferably 0.05 N / 25 mm or more, and still more preferably. 0.5 N / 25 mm or more, particularly preferably 0.8 N / 25 mm or more. In addition, adhesive force is 180 degree | times peel strength (N / 25mm) obtained according to the test method of [adhesive strength] in the below-mentioned Example.

  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 obtained by crosslinking the pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive film on a film that is 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 metal, polyester resin, polyfluorinated ethylene resin, polyimide and derivatives thereof, epoxy resin, and the like. From the viewpoint of convenience in actual use, a polyimide film is preferable, and a polyester film is more preferable. The heat-resistant adhesive film is preferably provided with 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 to practical use, the release film is peeled off and used. As the release film, a silicon release film, an olefin release film, a fluorine release film, a long-chain alkyl release film, and an alkyd release film can be used.

  Regarding the method for crosslinking the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film of the present invention in producing the heat-resistant pressure-sensitive adhesive film, [1] After applying the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film on a substrate and drying it , A method of pasting a release film and performing an aging treatment, [2] An adhesive composition for a heat-resistant adhesive film is applied on a release film and dried, and then a base material is pasted to perform an aging treatment. The method of performing is mentioned. Among these, the method [2] is preferable from the viewpoint of not damaging the substrate, workability and stable production.

Here, the aging treatment of a pressure-sensitive adhesive film usually imparted with heat resistance usually requires aging at a high temperature for a long time, but in the present invention, the use of a nitrogen atom-containing monomer makes it possible to achieve a lower temperature and a shorter temperature. The aging process can be completed in time.
The aging treatment is carried out to balance the physical properties of the adhesive. As the aging conditions, the temperature is usually 0 to 150 ° C., preferably 10 to 100 ° C., particularly preferably 20 to 80 ° C., and the time is Usually, it is less than 30 days, preferably less than 14 days, particularly preferably less than 7 days. Specifically, it can be carried out, for example, at 23 ° C. for 3 to 10 days, at 40 ° C. for 1 to 7 days, etc. .

  When applying the pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film, it is preferable to dilute and apply the pressure-sensitive adhesive composition to a solvent. The dilution concentration is preferably 5 to 60% by weight, particularly preferably 10 to 30% by weight. %. In addition, the solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition for heat-resistant adhesive film, for example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, ethyl acetoacetate, A ketone solvent such as acetone, methyl ethyl ketone and methyl isobutyl ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent 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, drying property, price, and the like.

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

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

The heat-resistant adhesive film of the present invention is used as a temporary surface protection (masking) heat-resistant adhesive film for temporarily protecting a circuit board such as an FPC board, or temporarily holds and reinforces a product during a manufacturing process. It can be utilized as a heat-resistant adhesive film for temporary fixing for fixing for the purpose.
Examples of the adherend to which the heat resistant adhesive film is to be attached include base materials made of the following materials.

Metal plates or metal foils such as aluminum, copper, iron, stainless steel, magnesium, nickel, titanium;
Polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer, ester acrylate;
Polyethylene, chlorinated polyethylene, chlorosulfonated polyethylene, ethylene propylene rubber, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-isobutyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid Polyolefin resins such as acid copolymers, ionomers, polypropylene, polyallomer polybutylene, polymethylpentene;
Polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer;
Polystyrene, polyalphamethyl styrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene-acrylate copolymer;
Acrylics such as polyalkyl (meth) acrylates such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate, methyl methacrylate-styrene copolymers, and methyl methacrylate-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, polychlorinated Polyvinyl chloride polymers such as vinylidene and derivatives thereof;
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 copolymer, polyethylene oxide, polypropylene oxide, chlorinated polyether, phenoxy resin, polyphenylene oxide;
Fluorinated resins such as polyterolafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, chlorotrifluoroethylene-vinylidene fluoride copolymer;
Polycarbonate, polycarbonate ABS alloy; nylon, nylon-6, nylon-6,6, nylon-6 / 6,6 copolymer, nylon-6,10, nylon-6,12, nylon-11, nylon-12, etc. Nylon (polyamide);
Butadiene-styrene copolymer, butadiene plastic;
Polyimide and its derivatives, polysulfone, polyphenylene sulfide, high acrylonitrile copolymer;
Silicon resins, 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, acetone formaldehyde resin;
Unsaturated polyester and alkyd resin;
Epoxy resins such as bisphenol type epoxy resin, epoxy resin composite material, alicyclic epoxy resin, epoxy novolac, biphenyl type epoxy resin, epoxy acrylate;
Polyurethanes such as polyurethane, urethane foam, urethane acrylate;
Allyl resins such as diallyl phthalate resin, triallyl cyanurate resin, polyallyl sulfone, allyl diglycol carbonate, polyallyl ether, polyarylate;
Cellulosic resins such as cellulose plastic, cellulose acetate, cellulose propionate, cellulose acetate butyrate, ethyl cellulose, nitrocellulose and celluloid.

  In particular, heat-resistant materials include aluminum, copper, iron, stainless steel, magnesium, nickel, titanium and other metal plates or metal foils; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer Polyester resins such as ester acrylates; polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymers; polyimides and derivatives thereof; bisphenol-type epoxy resins, Examples include epoxy resin composite materials, alicyclic epoxy resins, epoxy novolacs, biphenyl type epoxy resins, and epoxy resins such as epoxy acrylate.

  Examples of the use of the heat-resistant adhesive film obtained using the pressure-sensitive adhesive composition for heat-resistant adhesive films of the present invention include carrier films for processes such as printed boards, particularly flexible printed boards; curls of films and foils with heating processes, wrinkles, Protective film for preventing contamination; protective film for soldering printed circuit boards; insulating film for heat-resistant transformers, etc .; film for masking during solder reflow process of electronic circuit boards; Examples include applications such as through-hole sealing films, and it can be widely used in general masking applications requiring heat resistance and temporary fixing applications.

The usage method of the heat-resistant adhesive film for masking among the heat-resistant adhesive films of this invention is demonstrated. First, the heat-resistant adhesive film for masking of the present invention is attached to the surface of the adherend. As a sticking means, a rubber roller etc. are mentioned, for example. Next, the adherend to which the heat-resistant adhesive film is attached is subjected to a heating step at 170 ° C. or higher, preferably 175 ° C. or higher, particularly preferably 180 ° C. or higher. After the heating step is completed, the heat-resistant masking pressure-sensitive adhesive film is peeled off from the adherend surface.
The heat-resistant pressure-sensitive adhesive film for masking of the present invention is effective for temporary protection of the adherend surface because it is hardly contaminated when it is peeled off from the adherend after being used at a high temperature, and the adhesive performance is sufficiently high. .

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. In the examples, “parts” and “%” mean weight basis.

  First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin, a dispersion degree, a glass transition temperature, and a viscosity, it measured according to the above-mentioned method.

[Method for producing acrylic resin (A)]
<Examples for production>
[Production Example A-1]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 4-hydroxybutyl acrylate (a3: 4HBA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-1).

[Production Example A-2]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , Methyl methacrylate (a2: MMA) 30 parts, 2-hydroxyethyl acrylate (a3: 2HEA) 4 parts, dimethylaminoethyl acrylate (a1: DMAEA) 0.2 part and azobisisobutyronitrile (AIBN) 0.036 The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-2).

[Production Example A-3]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl methacrylate (a3: 2HEMA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl methacrylate (a3: 2HEMA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-3).

[Production Example A-4]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 74.8 parts of butyl acrylate (a2: BA). 20 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl methacrylate (a3: 2HEMA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl methacrylate (a3: 2HEMA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-4).

[Production Example A-5]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 130 parts of ethyl acetate was charged, and the temperature was raised while stirring. When the temperature reached 78 ° C., 40 parts of butyl acrylate (a2: BA), methyl Acrylate (a2: MA) 54.8 parts, 2-hydroxyethyl methacrylate (a3: 2HEMA) 4 parts, dimethylaminoethyl acrylate (a1: DMAEA) 0.2 part and azobisisobutyronitrile (AIBN) 0.06 The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.11 part of AIBN was dissolved in 1 part of 2-hydroxyethyl methacrylate (a3: 2HEMA) and 12 parts of ethyl acetate, and then ethyl acetate and Dilution with toluene gave a 40% solution of acrylic resin (A-5).

[Production Example A-6]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl methacrylate (a3: 2HEMA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-6).

[Production Example A-7]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 90 parts of ethyl acetate was charged, and the temperature was increased while stirring. When the temperature reached 78 ° C., 40 parts of butyl acrylate (a2: BA), methyl Acrylate (a2: MA) 54.8 parts, 2-hydroxyethyl acrylate (a3: 2HEA) 4 parts, dimethylaminoethyl acrylate (a1: DMAEA) 0.2 part and azobisisobutyronitrile (AIBN) 0.06 The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.11 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 12 parts of ethyl acetate, and then ethyl acetate and Dilution with toluene gave a 40% solution of acrylic resin (A-7).

[Production Example A-8]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.2 part of dimethylaminopropylacrylamide (a1: DMAPAA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-8).

[Production Example A-9]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.2 part of dimethylacrylamide (a1: DMAA) and 0.036 part of azobisisobutyronitrile (AIBN) The mixed and dissolved mixture was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-9).

[Production Example A-10]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.2 part of diethylaminoethyl methacrylate (a1: DEAEMA) and 0.036 part of azobisisobutyronitrile (AIBN) Was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-10).

[Production Example A-11]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.2 part of dimethylaminopropylacrylamide (a1: DMAPAA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-11).

[Production Example A-12]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 64.5 parts of butyl acrylate (a2: BA) , 30 parts of methyl methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.5 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-12).

[Production Example A-13]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 62.8 parts of butyl acrylate (a2: BA). , 30 parts of methyl methacrylate (a2: MMA), 6 parts of 2-hydroxyethyl acrylate (a3: 2HEA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.036 of azobisisobutyronitrile (AIBN) The mixture in which the parts were mixed and dissolved was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A-13).

  Table 1 shows the content of each polymerization component in Production Examples A-1 to A-13 for Examples. The weight-average molecular weight, dispersity, and glass transition temperature of the obtained acrylic resins (A-1 to A-13) are shown in Table 1. Table 2 summarizes the solid content and viscosity.

* DMAEA: Dimethylaminoethyl acrylate (a1)
DMAPAA: dimethylaminopropylacrylamide (a1)
DMAA: Dimethylacrylamide (a1)
DEAEMA: diethylaminoethyl methacrylate (a1)
BA: Butyl acrylate (a2)
MMA: Methyl methacrylate (a2)
MA: methyl acrylate (a2)
2HEA: 2-hydroxyethyl acrylate (a3)
2HEMA: 2-hydroxyethyl methacrylate (a3)
4HBA: 4-hydroxybutyl acrylate (a3)

<Production example for comparison>
[Production Example A′-1]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, and the temperature was raised while stirring. When the temperature reached 78 ° C., 65 parts of butyl acrylate (a2: BA), methyl A mixture of 30 parts of methacrylate (a2: MMA), 4 parts of 4-hydroxybutyl acrylate (a3: 4HBA) and 0.036 parts of azobisisobutyronitrile (AIBN) was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A′-1).

[Production Example A′-2]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, and the temperature was raised while stirring. When the temperature reached 78 ° C., 65 parts of butyl acrylate (a2: BA), methyl A mixture of 30 parts of methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl acrylate (a3: 2HEA) and 0.036 parts of azobisisobutyronitrile (AIBN) was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl acrylate (a3: 2HEA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A'-2).

[Production Example A′-3]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of ethyl acetate was charged, and the temperature was raised while stirring. When the temperature reached 78 ° C., 65 parts of butyl acrylate (a2: BA), methyl A mixture of 30 parts of methacrylate (a2: MMA), 4 parts of 2-hydroxyethyl methacrylate (a3: 2HEMA) and 0.036 parts of azobisisobutyronitrile (AIBN) was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.08 part of AIBN was dissolved in 1 part of 2-hydroxyethyl methacrylate (a3: 2HEMA) and 14.8 parts of ethyl acetate. Dilution with ethyl and toluene gave a 40% solution of acrylic resin (A'-3).

[Production Example A′-4]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 80 parts of ethyl acetate was charged, the temperature was increased while stirring, and when the temperature reached 78 ° C., 94.8 parts of butyl acrylate (a2: BA) 4 parts of 4-hydroxybutyl acrylate (a3: 4HBA), 0.2 part of dimethylaminoethyl acrylate (a1: DMAEA) and 0.06 part of azobisisobutyronitrile (AIBN) were mixed and dissolved for 2 hours. Dripped over. Further, during the polymerization, polymerization was carried out for 7 hours while sequentially adding a polymerization catalyst solution in which 0.11 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 12 parts of ethyl acetate, and then ethyl acetate and Dilution with toluene gave a 40% solution of acrylic resin (A′-4).

[Production Example A′-5]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 43 parts of ethyl acetate and 15 parts of acetone were charged, and the temperature was raised while stirring. When the temperature reached 68 ° C., 2-ethylhexyl acrylate (a2: 2EHA) 94.8 parts, 4-hydroxybutyl acrylate (a3: 4HBA) 4 parts, dimethylaminoethyl acrylate (a1: DMAEA) 0.2 part and azobisisobutyronitrile (AIBN) 0.03 part are mixed and dissolved. The resulting mixture was added dropwise over 2 hours. Further, during the polymerization, the polymerization catalyst solution in which 0.096 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 20 parts of ethyl acetate was successively added for 7 hours, and then ethyl acetate and Dilution with toluene gave a 40% solution of acrylic resin (A′-5).

[Production Example A′-6]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser, 80 parts of ethyl acetate was charged, the temperature was increased while stirring, and when 78 ° C was reached, 95 parts of butyl acrylate (a2: BA), 4 A mixture of 4 parts of hydroxybutyl acrylate (a3: 4HBA) and 0.06 part of azobisisobutyronitrile (AIBN) was added dropwise over 2 hours. Further, during the polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.11 part of AIBN was dissolved in 1 part of 4-hydroxybutyl acrylate (a3: 4HBA) and 12 parts of ethyl acetate. Dilution gave a 40% solution of acrylic resin (A′-6).

  Table 3 shows the content of each monomer component in Production Examples A′-1 to A′-6 for Comparative Examples, and the weight-average molecular weight and dispersity of the obtained acrylic resins (A′-1 to A′-6). Table 4 shows the glass transition temperature, solid content, and viscosity.

* DMAEA: Dimethylaminoethyl acrylate (a1)
BA: Butyl acrylate (a2)
2EHA: 2-ethylhexyl acrylate (a2)
MMA: Methyl methacrylate (a2)
2HEA: 2-hydroxyethyl acrylate (a3)
2HEMA: 2-hydroxyethyl methacrylate (a3)
4HBA: 4-hydroxybutyl acrylate (a3)

The following were used as the crosslinking agent.
・ Crosslinking agent (B-1)
Isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., “Coronate HX”)
・ Crosslinking agent (B-2)
Isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., “Coronate L55E”)

<Examples 1-16 and Comparative Examples 1-6>
In the acrylic resin solution obtained above, a crosslinking agent was blended, and further, using ethyl acetate, in Examples 1-9, 11-16, and Comparative Examples 1-6, the solid content concentration was 33.3%. In Example 10, after diluting to a solid content concentration of 20%, it was applied to a polyethylene terephthalate (PET) film (thickness 38 μm) as a base material so that the thickness after drying was about 25 μm, and at 100 ° C. for 2 minutes. Dried. Thereafter, a PET film that had been subjected to a release treatment was adhered to the coated surface for protection, and the film was cured for 7 days in an atmosphere at a temperature of 40 ° C. to obtain a heat-resistant adhesive film.

The following evaluation was performed about the heat-resistant adhesive film obtained in said Examples 1-16 and Comparative Examples 1-6, and it put together in Table 5 and 6, respectively.
The release-treated PET film was peeled off when performing various measurement tests.

[Confirmation of cross-linking agent reaction]
About the crosslinking reaction of the obtained heat-resistant adhesive film, the peak of the residual isocyanate group was confirmed using infrared spectroscopy. As a measuring instrument, FT-IR Nicolet 380FT-IR manufactured by Thermo Electron Co., Ltd. was used. The number of scans was measured 32 times by the ATR method. Evaluation was based on the presence and size of a peak at 2200 to 2300 cm ⁻¹ , which is an absorption peak of an isocyanate group.
A: No peak was confirmed.
Δ: A slight peak was confirmed.
X: A peak was clearly confirmed.

[Gel fraction]
The gel fraction was calculated for the obtained heat-resistant adhesive film. That is, the test piece was wrapped with a 200-mesh SUS metal mesh, immersed in toluene at 23 ° C. for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the metal mesh was defined as the gel fraction. However, the weight of the substrate is subtracted.

[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 the adherend (SUS304BA plate) by reciprocating a 2 kg roller twice, as shown in the following table. It was left at the temperature and time described in 5 and 6 and returned to 23 ° C. Further, after being left for 2 hours in an atmosphere of 23 ° C. and 50% relative humidity, the appearance of the adherend surface after 180 ° peeling was observed at a peeling speed of 300 mm / min, and evaluated according to the following criteria.
○: No contamination was confirmed.
Δ: Slight contamination was confirmed.
X: Contamination was clearly confirmed.

〔Adhesive force〕
The above heat-resistant adhesive film of 25 mm x 100 mm is pressure-applied to a stainless steel plate (SUS304BA plate) as an adherend in an atmosphere of 23 ° C and relative humidity of 50% with two reciprocations of 2 kg rubber rollers, and 30 minutes under the same atmosphere. After standing, 180 degree peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min, and evaluated according to the following criteria.
(Evaluation)
◎: 0.5N / 25mm or more ○: 0.05N / 25mm or more, less than 0.5N / 25mm △: 0.01N / 25mm or more, less than 0.05N / 25mm ×: Less than 0.01N / 25mm

  As shown in Table 5, the heat-resistant adhesive films of Examples 1 to 16 were hardly contaminated when peeled from the adherend surface after high-temperature treatment, and the adhesive performance was sufficiently high. Moreover, since the remaining of the crosslinking agent could not be confirmed after curing for 7 days in an atmosphere at a temperature of 40 ° C., it can be seen that the aging period at the time of film production can be shortened and the production efficiency is economically good.

  On the other hand, as shown in Table 6, in the heat resistant adhesive films of Comparative Examples 1 to 4 and 6, slight contamination was confirmed even by heating at 180 ° C. for 1 hour. Contamination was over the entire surface. Contamination was clearly confirmed in all cases of heating at 180 ° C. for 5 hours. In addition, it can be seen that the heat resistant adhesive films of Comparative Examples 1, 2, 3 and 6 are not completed in the cross-linking after 7 days of curing in an atmosphere at a temperature of 40 ° C., and the production efficiency is not good.

  The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive films of the present invention can be suitably used for heat-resistant pressure-sensitive adhesive films that are widely used in general masking applications and temporary fixing applications that require heat resistance, in particular, heat-resistant pressure-sensitive adhesive films for masking.

Claims (8)

  A heat resistance characterized by comprising an acrylic resin (A) obtained by polymerizing a monomer component [I] containing a nitrogen atom-containing monomer (a1) and having a glass transition temperature of -40 ° C or higher. An adhesive composition for an adhesive film.   The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film according to claim 1, wherein the content of the nitrogen atom-containing monomer (a1) in the monomer component [I] is 0.001 to 30% by weight.   3. The pressure-sensitive adhesive composition for heat-resistant pressure-sensitive adhesive film according to claim 1, wherein the monomer component [I] contains a hydroxyl group-containing monomer.   The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive film according to any one of claims 1 to 3, which is substantially free of an acid.   The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive film according to claim 1, wherein the pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive film contains a crosslinking agent (B) and is crosslinked.   A heat-resistant adhesive film comprising an adhesive layer containing the adhesive for a heat-resistant adhesive film according to claim 5 on the film.   A heat-resistant adhesive film for masking, comprising an adhesive layer containing the pressure-sensitive adhesive for heat-resistant adhesive film according to claim 5 on the film.   The heat-resistant adhesive film for masking according to claim 7 is attached to the surface of the adherend, and after being subjected to a heating step at 170 ° C. or higher, the heat-resistant adhesive film for masking is peeled off from the surface of the adherend. How to use heat-resistant adhesive film for masking.