JP6701727B2 - Adhesive composition, adhesive obtained by crosslinking this, adhesive for masking film, adhesive for heat resistant adhesive film, heat resistant adhesive film for masking - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive obtained by crosslinking the same, a masking film pressure-sensitive adhesive, a heat-resistant pressure-sensitive adhesive film pressure-sensitive adhesive, and a masking heat-resistant pressure-sensitive adhesive film. A pressure-sensitive adhesive composition that can be used for a heat-resistant pressure-sensitive adhesive film for masking and the like, which has excellent quick-curing property and heat resistance, a pressure-sensitive adhesive for heat-resistant pressure-sensitive film comprising the pressure-sensitive adhesive, and the pressure-sensitive adhesive. The present invention relates to a heat-resistant adhesive film for masking, which comprises an adhesive layer consisting of

  Conventionally, a re-peelable pressure-sensitive adhesive film has been used for temporarily fixing and protecting members when processing various members. In recent years, for example, circuit boards such as flexible printed wiring (FPC) boards and ITO. It is used as an adhesive film for masking for temporarily protecting the surface of a transparent electrode layer, and an adhesive film for surface protection of flat panel displays and touch panels. Since the manufacturing process of the FPC substrate and the ITO transparent electrode layer includes a process of being exposed to high temperature, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film adheres to the laminated plate, and when the pressure-sensitive adhesive film is peeled off, the FPC substrate and the ITO transparent electrode layer Laminates may be damaged or stains may develop due to adhesive residue. Therefore, even after the high temperature step, it is required that the adhesive can be peeled off with a light force without peeling after the peeling.

  As a pressure-sensitive adhesive composition used for such a heat-resistant pressure-sensitive adhesive sheet, for example, in Patent Document 1, even under high temperature conditions, when peeled from an adherend, contamination is unlikely to occur, and the pressure-sensitive adhesive performance is sufficiently high. Furthermore, as a pressure-sensitive adhesive composition that is preferably used for a heat-resistant pressure-sensitive adhesive sheet having a short aging period during film production, it is obtained by polymerizing a monomer component containing a nitrogen atom-containing monomer, and has a glass transition temperature of -40°C or higher. A pressure-sensitive adhesive composition containing a certain acrylic resin is disclosed.

  However, in the technique of Patent Document 1, in order to balance the pressure-sensitive adhesive properties of the pressure-sensitive adhesive, it is necessary to perform an aging treatment for a certain period of time after the pressure-sensitive adhesive sheet is manufactured, until the pressure-sensitive adhesive composition is crosslinked in the aging step. In some cases, fine irregularities of the base film or the separator are transferred to the pressure-sensitive adhesive layer, and it may not be possible to obtain a pressure-sensitive adhesive film having a smooth pressure-sensitive adhesive layer surface. When the pressure-sensitive adhesive sheet is used for surface protection of an optical film such as a flat panel display or a touch panel, the fine unevenness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is transferred to the optical film that is the adherend, which reduces visibility. Problems can occur.

  Here, in Patent Document 2, as a pressure-sensitive adhesive pressure-sensitive adhesive composition that satisfies the required physical properties of the pressure-sensitive adhesive for a surface protection film and can shorten the curing time without shortening the pot life, An acrylic pressure-sensitive adhesive composition including an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer having a reactive hydroxyl group, a dialkylacetylacetone tin complex catalyst, and an isocyanate compound is disclosed.

  However, in the technique of Patent Document 2, although it has a heat resistance of 70° C. in terms of heat resistance, the heat resistance under higher temperature conditions may be poor, and adhesive residue may occur. Further, in recent years, the toxicity problem of organotin compounds has been pointed out, and especially tributyltin contained in dibutyltin dilaurate is feared as an endocrine disrupting substance.

JP, 2013-32504, A JP, 2008-13634, A

  Therefore, under such a background, the present invention does not contain an organotin compound, has a sufficient pot life, is excellent in immediate curability, and has a small increase in adhesive strength after being used under high temperature conditions. Another object of the present invention is to provide a pressure-sensitive adhesive composition that can be peeled off with a small force and is unlikely to cause contamination when peeled off from an adherend, and that can be used for a heat-resistant pressure-sensitive adhesive film for masking.

  Further, the present invention provides a pressure-sensitive adhesive obtained by crosslinking this pressure-sensitive adhesive composition, a pressure-sensitive adhesive for a masking film comprising the pressure-sensitive adhesive, a pressure-sensitive adhesive for a heat-resistant pressure-sensitive adhesive film comprising the pressure-sensitive adhesive, and a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive. Another object of the present invention is to provide a heat-resistant adhesive film for masking, which has on the film.

  However, as a result of intensive studies by the present inventors, in a pressure-sensitive adhesive composition containing an acrylic resin having a hydroxyl group and an isocyanate cross-linking agent, further contains a zinc compound that is rarely used in pressure-sensitive adhesive compositions. It was found that by doing so, a pressure-sensitive adhesive composition that solves the above problems can be obtained, and the present invention was completed.

  This is because the pressure-sensitive adhesive composition of the present invention has a zinc compound having a reactivity that is not too high, as compared with a commonly used metal compound such as zirconium or aluminum having an action of promoting a crosslinking reaction of an isocyanate crosslinking agent, Since it has a moderate reactivity, it is presumed that immediate curability can be achieved without reducing the pot life.

That is, the gist of the present invention, the acrylic resin having hydroxyl groups (A), an isocyanate crosslinking agent (B), zinc compound (C), and a pressure-sensitive adhesive composition containing a crosslinking retarder (D) The zinc compound (C) is an alkoxide zinc compound or a zinc chelate compound, and the content of the zinc compound (C) is 0.01 to 15 parts by weight with respect to 100 parts by weight of the acrylic resin (A) having a hydroxyl group. it relates adhesive composition characterized in that it is part.

  Further, the gist of the present invention is a pressure-sensitive adhesive characterized in that the pressure-sensitive adhesive composition of the present invention is crosslinked, a masking film pressure-sensitive adhesive comprising the pressure-sensitive adhesive of the present invention, the pressure-sensitive adhesive of the present invention The present invention also relates to a pressure-sensitive adhesive for heat-resistant adhesive film, which is characterized by comprising an agent, and a heat-resistant adhesive film for masking, which comprises an adhesive layer comprising the adhesive of the present invention on the film.

  According to the pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive obtained by cross-linking the same, since it has a very good pot life while having a sufficient pot life, it is possible to form a base film or separator having fine irregularities. It is possible to form a smooth adhesive layer surface without transferring the uneven shape, and further, after using under high temperature conditions, it is unlikely to cause contamination when peeled from the adherend and peels with a small force. It is possible to produce a heat-resistant adhesive film for masking which can

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, but these show one example of preferred embodiments. In this specification, (meth)acryl means acryl or methacryl, (meth)acryloyl means acryloyl or methacryloyl, and (meth)acrylate means acrylate or methacrylate.
Further, in the present invention, the “adhesive film” conceptually includes an adhesive sheet, an adhesive film and an adhesive tape.

  The acrylic resin (A) having a hydroxyl group used in the present invention is obtained by polymerizing a polymerization component containing a (meth)acrylic acid ester monomer (a1) and a hydroxyl group-containing monomer (a2) as essential components. If necessary, the functional group-containing monomer (a3) other than the hydroxyl group and the other polymerizable monomer (a4) can be appropriately contained as a polymerization component.

  The (meth)acrylic acid ester-based monomer (a1) used in the present invention is a (meth)acrylate having an aliphatic or alicyclic alkyl ester. The number of carbon atoms of the alkyl in the alkyl ester is usually 1 to 20, preferably 1 to 12, and particularly preferably 1 to 8. If the carbon number is too large, contamination of the adherend after the heating step tends to increase.

Specifically, for example, methyl (meth)acrylate, ethyl (meth)acrylate, 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(meth)acrylate, iso-octyl acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate, cetyl(meth)acrylate, stearyl( Aliphatic (meth)acrylic acid alkyl esters such as (meth)acrylate and iso-stearyl (meth)acrylate; alicyclic (meth)acrylic acid alkyl esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate Can be mentioned.
Preferred (meth)acrylic acid ester-based monomers (a1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate. , N-propyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.
These may be used alone or in combination of two or more.

The content of the (meth)acrylic acid ester-based monomer (a1) in the polymerization component is usually 40 to 99.99% by weight, preferably 45 to 99.9% by weight, particularly preferably 50 to 99% by weight. Is. If the content is too low, the adhesive force after the heating step tends to be too high, and if it is too high, the adherend contamination after the heating step tends to increase.
In addition, after the heating step, the content of the (meth)acrylic acid alkyl ester-based monomer having an alkyl group having 1 to 8 carbon atoms in the (meth)acrylic acid ester-based monomer (a1) is 80% by weight or more. It is preferable that it is excellent in staining of adherends, particularly preferably 85% by weight or more, further preferably 90% by weight or more, and particularly preferably 95% by weight or more.

Examples of the hydroxyl group-containing monomer (a2) include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-. Acrylic hydroxyalkyl esters such as hydroxyoctyl (meth)acrylate; caprolactone modified monomers such as caprolactone modified 2-hydroxyethyl (meth)acrylate; oxyalkylene modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; other , 2-acryloyloxyethyl-2-hydroxyethylphthalic acid and other primary hydroxyl group-containing monomers; 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth) Examples thereof include secondary hydroxyl group-containing monomers such as acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl2-hydroxyethyl (meth)acrylate.
Among the above-mentioned hydroxyl group-containing monomers, it is preferable to use 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate because of their excellent reactivity with the isocyanate crosslinking agent (B).
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, and in particular, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth). ) It is preferable to use acrylate together.

  The content of the hydroxyl group-containing monomer (a2) in the polymerization component is preferably 0.1 to 30% by weight, more preferably 0.5 to 25% by weight, and particularly preferably 1 to 20% by weight. If the content is too low, the degree of crosslinking tends to decrease, and the contamination of the adherend tends to increase. If it is too high, the adhesive strength immediately after application tends to be too high.

  As the hydroxyl group-containing monomer used in the present invention, it is also preferable to use a di(meth)acrylate content ratio of 0.5% or less, more preferably 0.2% or less, especially Is preferably 0.1% or less.

  Examples of the functional group-containing monomer (a3) other than the hydroxyl group-containing monomer include a carboxyl group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, a glycidyl group-containing monomer, an amino group-containing monomer, and an amide group-containing monomer. Can be mentioned.

  Examples of the carboxyl group-containing monomer include (meth)acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamon bark. Acids and the like can be mentioned, and among them, (meth)acrylic acid is preferably used, but when used for a metal substrate, it is preferable not to contain a carboxyl group from the viewpoint of corrosion prevention.

  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 their alkylene oxide adducts.

  Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allylglycidyl (meth)acrylate.

  Examples of the amino group-containing monomer include monomers having an ethylenically unsaturated double bond and an amino group (unsubstituted or substituted amino group), and examples thereof include aminomethyl (meth)acrylate and aminoethyl (meth)acrylate. (Meth) of N-alkylaminoalkyl such as aminoalkyl (meth)acrylate such as aminopropyl (meth)acrylate and aminoisopropyl (meth)acrylate and N-alkylaminoalkyl such as N-(t-butyl)aminoethyl (meth)acrylate Mono-substituted amino group-containing (meth)acrylic acid esters such as acrylic acid esters; N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N (meth)acrylic acid -Disubstituted amino group-containing (meth)acrylic acid ester such as N,N-dialkylaminoalkyl (meth)acrylic acid ester such as dimethylaminopropyl; Dialkylaminoalkyl such as N,N-dimethylaminopropyl (meth)acrylamide (Meth)acrylamide, quaternized salts of these amino group-containing monomers, and the like; amino group-containing styrenes such as p-aminostyrene; and dialkylamino groups such as 3-(dimethylamino)styrene and dimethylaminomethylstyrene. Styrenes; 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 can be mentioned.

  Examples of the amide group-containing monomer include monomers having an ethylenically unsaturated double bond and an amide group (group having an amide bond), and examples thereof include (meth)acrylamide; N-methyl(meth)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, N -T-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, diacetone (meth)acrylamide, N,N'-methylenebis(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl) (meth ) N-alkyl(meth)acrylamides such as 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)(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,N-dihexyl(meth)acrylamide, N,N-diheptyl(meth)acrylamide, N,N-dioctyl(meth)acrylamide, N,N -N,N-dialkyl(meth)acrylamides such as diallyl(meth)acrylamide, N,N-ethylmethylacrylamide; dialkylaminoalkyl(meth)acrylamides such as N,N-dimethylaminopropyl(meth)acrylamide; N-vinyl Substituted amide group-containing monomers such as acetamide, N-vinylformamide, (meth)acrylamideethylethyleneurea, (meth)acrylamide t-butylsulfonic acid; N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide A hydroxyl group-containing (meth)acrylamide such as N-methylolpropane (meth)acrylamide; an alkoxy group-containing (meth)acrylamide such as N-methoxymethyl (meth)acrylamide, N-(n-butoxymethyl)(meth)acrylamide; Examples thereof include quaternized salts of these amide group-containing monomers.

These functional group-containing monomers (a2) may be used alone or in combination of two or more.
Among these, in the present invention, from the viewpoint of the effect of promoting crosslinking, it is preferable to contain a functional group-containing monomer containing a nitrogen atom, particularly preferably an amino group-containing monomer, an amide group-containing monomer, more preferably dimethylamino. Ethyl (meth)acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl (meth)acrylamide, dimethyl (meth)acrylamide, particularly preferably dimethylaminopropyl acrylamide.

  The content of the functional group-containing monomer (a3) other than the hydroxyl group in the polymerization component is usually 0.001 to 30% by weight, preferably 0.01 to 20% by weight, particularly preferably 0.05 to 15% by weight. %. If the content is too low, the degree of crosslinking tends to decrease, and the contamination of the adherend tends to increase. If it is too high, the adhesive strength immediately after application tends to be too high.

  When the amino group-containing monomer and/or the amide group-containing monomer is contained as the functional group-containing monomer (a3) other than the hydroxyl group, the content ratio of the monomer in the polymerization component is preferably 0.001 to 30% by weight, It is particularly preferably 0.005 to 5% by weight, further preferably 0.01 to 2% by weight. If the content is too large, the molecular weight tends to decrease during the polymerization, or the pressure-sensitive adhesive tends to be colored, and if it is too small, a sufficient effect of promoting crosslinking cannot be obtained.

Examples of the other copolymerizable monomer (a4) include, for example,
One fragrance such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, styrene and α-methylstyrene. A monomer containing a ring;
Biphenyloxy structure-containing (meth)acrylic acid ester-based monomers such as biphenyloxyethyl (meth)acrylate;
Alkoxy such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polypropylene glycol mono (meth)acrylate Group or a monomer containing an oxyalkylene group;
Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride , Methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone and the like.
These may be used alone or in combination of two or more.

  The content of the other copolymerizable monomer (a4) in the polymerization component is usually 0 to 40% by weight, preferably 0.001 to 30% by weight, particularly preferably 0.01 to 25% by weight. . If the content is too large, the adhesive property tends to deteriorate.

  In the polymerization of the acrylic resin (A) having a hydroxyl group, conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be adopted. For example, in an organic solvent, the (meth)acrylic acid ester-based monomer (a1), the hydroxyl group-containing monomer (a2), and optionally a functional group-containing monomer (a3) other than a hydroxyl group, and other copolymerizable monomers ( A polymerization component containing a4) and a polymerization initiator are mixed or added dropwise, and polymerization is carried out at reflux or at 50 to 90° C. for 2 to 20 hours.

  The weight average molecular weight of the hydroxyl group-containing acrylic resin (A) of the present invention is usually 100,000 to 2,500,000, preferably 200,000 to 2,200,000, and particularly preferably 400,000 to 2,000,000. If the weight average molecular weight is too low, the heat resistance of the pressure-sensitive adhesive layer tends to decrease, and the contamination of the adherend tends to increase.If it is too high, a large amount of diluting solvent is required, which is disadvantageous in terms of coatability and cost. Tends to be.

  The degree of dispersion (weight average molecular weight/number average molecular weight) of the acrylic resin (A) having a hydroxyl group is, for example, usually 20 or less, preferably 15 or less, particularly preferably 10 or less, and the lower limit is usually 1 .1. If the dispersity is too high, the heat resistance of the pressure-sensitive adhesive layer tends to decrease, and foaming or the like tends to occur.

The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene molecular weight, and is used for high performance liquid chromatography (manufactured by Japan Waters, "Waters 2695 (main body)" and "Waters 2414 (detector)") in a column. : Shodex GPC KF-806L (Exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , theoretical plate number: 10,000 plates/piece, filler material: styrene-divinylbenzene copolymer, filler It is measured by using three series of (particle size: 10 μm), and the same method can be used for the number average molecular weight. The dispersity is calculated from the weight average molecular weight and the number average molecular weight.
In addition, the polymer may be derivatized at the time of measurement, and the type of eluent may be appropriately changed.

  Further, the glass transition temperature of the acrylic resin (A) having a hydroxyl group is usually −80 to 0° C., preferably −75 to −5° C., and particularly preferably −70 to −10° C. If the glass transition temperature is too high, the adhesive force after the heating step tends to be high, and if the glass transition temperature is too low, the heat resistance tends to decrease and the adherend contamination tends to increase.

The glass transition temperature is calculated from the following Fox equation.

  The pressure-sensitive adhesive composition of the present invention preferably contains the acrylic resin (A) having a hydroxyl group in an amount of 30 to 99% by weight, particularly preferably 40 to 97% by weight, and further preferably, based on the total amount of the adhesive composition. It is 50 to 95% by weight.

  It is important that the pressure-sensitive adhesive composition of the present invention contains an isocyanate cross-linking agent (B) as a cross-linking agent in terms of high reactivity and improved heat resistance.

Examples of the isocyanate-based crosslinking agent (B) include, for example,
Aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, tolidine diisocyanate, xylylene diisocyanate and tetramethyl xylylene diisocyanate;
Aliphatic diisocyanates such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, dimer acid diisocyanate, norbornene diisocyanate, trans-cyclohexane diisocyanate, hydrogenated tolylene diisocyanate;
Aliphatic isocyanates such as hexamethylene diisocyanate;
Etc.,
Further examples include adducts of these polyisocyanate compounds and polyol compounds such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds.

  Among them, the isocyanurate form of hexamethylene diisocyanate, 2,4-tolylene diisocyanate and/or 2,6-tolylene diisocyanate and trimethylolpropane are small in that the adhesive strength after heating is small and the heat-resistant stain resistance is good. And adducts of 2,4-tolylene diisocyanate and/or 2,6-tolylene diisocyanate, and adducts of tetramethylxylylene diisocyanate and trimethylolpropane.

  The content of the isocyanate cross-linking agent (B) is 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, and particularly preferably 2 to 100 parts by weight of the acrylic resin (A) having a hydroxyl group. 25 parts by weight. If the content of such an isocyanate-based crosslinking agent is too large, the crosslinking of the pressure-sensitive adhesive will proceed too much, and the adhesive strength will decrease, so that there is a tendency to cause floating between the surface of the adherend and too little, The cohesive force of the agent tends to decrease, and the heat-resistant stain resistance tends to decrease.

Further, in the present invention, other cross-linking agents usually used in the pressure-sensitive adhesive composition can be used in combination within the range not impairing the object of the present invention.
Examples of such a crosslinking agent include an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, an oxazoline-based crosslinking agent, a melamine-based crosslinking agent, an aldehyde-based crosslinking agent, and an amine-based crosslinking agent.

  It is important for the pressure-sensitive adhesive composition of the present invention to contain the zinc compound (C) from the viewpoint of achieving both pot life and immediate curability and obtaining a smooth pressure-sensitive adhesive layer.

Examples of the zinc compound (C), and alkoxide zinc compound A alcohol formed by bonding, acetylacetone, it is necessary β- diketone compounds such as ethyl acetoacetate is a zinc chelate compound formed by coordinating Specifically, zinc propoxide, zinc butoxide, zinc acetyl acetate, zinc ethyl acetoacetate, zinc acetyl acetonate, and the like, in the present invention, from the viewpoint of achieving both sufficient pot life and immediate curability, Preference is given to using zinc acetylacetonate.

In addition, as said zinc compound (C), commercially available Matsumoto Fine Chemical Co., Ltd. "X-1301", Tokyo Chemical Industry Co., Ltd. "bis (2,4-pentanedionato) zinc (II).
," King Industries, Inc. For example, “K-KAT 670” manufactured by K.K.

The content of the zinc compound (C) is to the acrylic resin (A) 100 parts by weight of having a hydroxyl group 0. It is from 01 to 15 parts by weight. If the content of the zinc compound (C) is too small, the immediate curability tends to decrease, and if it is too large, the metal tends to precipitate.

The content ratio (weight ratio) (C)/(B) of the isocyanate cross-linking agent (B) and the zinc compound (C) (solid content conversion) is preferably 0.0001 to 10, and more preferably. It is 0.001 to 1.0, and particularly preferably 0.002 to 0.5.
If the content of the zinc compound (C) is too large with respect to the content of the isocyanate crosslinking agent (B), the metal tends to be deposited.
If the amount is too small, the immediate curability is insufficient, and a smooth surface of the pressure-sensitive adhesive layer tends not to be obtained.

In addition, the pressure-sensitive adhesive composition of the present invention needs to contain a crosslinking retarder (D), which is preferable from the viewpoint of extending pot life and improving coatability.

Examples of the crosslinking retarder (D) include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate, acetylacetone, and 2,4-hexanedione. , Β-diketones such as benzoylacetone. These are keto-enol tautomeric compounds, and by protecting the zinc compound (C), the catalytic activity of the zinc compound in a solution state is reduced, and the viscosity of the pressure-sensitive adhesive composition after formulation is excessively increased or gelled. Can be suppressed and the pot life of the pressure-sensitive adhesive composition can be extended.
Among these, acetylacetone is preferably used as the crosslinking retarder (D) from the viewpoint of the balance between pot life and quick curability.
These crosslinking retardants (D) can be used alone or in combination of two or more.

  As the crosslinking retarder (D), commercially available products such as "acetylacetone" manufactured by Daicel Co., Ltd., "acetylacetone" manufactured by Tokyo Kasei Kogyo, "acetylacetone" manufactured by Wako Pure Chemical Industries, "acetylacetone" manufactured by Kishida Chemical Co., Ltd., and the like may be used. .

Since the crosslinking retarder (D) has an effect of suppressing crosslinking, which is opposite to the crosslinking promoting effect of the zinc compound (C), the ratio of the crosslinking retarder (D) to the zinc compound (C) is set appropriately. Preferably.
In order to extend the pot life of the pressure-sensitive adhesive composition and not impair the immediate curability, the content ratio (weight ratio) of the crosslinking retarder (D) and the zinc compound (C) (solid content equivalent) is zinc. Compound (C): Crosslinking retarder (D) is preferably in the range of 0.01:1 to 15:1, more preferably 0.1:1 to 13:1, and particularly preferably 0. 0.5:1 to 10:1.
If the content of the cross-linking retarder (D) is too small with respect to the content of the zinc compound (C), the pot life tends to be short and the coatability tends to deteriorate, while if it is too large, the immediate curability tends to deteriorate. There is.

  The pressure-sensitive adhesive composition of the present invention further contains an antistatic agent, an antioxidant, a plasticizer, a filler, a pigment, a diluent, an antiaging agent, an ultraviolet absorber, an ultraviolet stabilizer within a range that does not impair the effects of the present invention. Further, additives such as tackifying resins may be further contained, and these additives may be used alone or in combination of two or more kinds. In particular, the antioxidant is effective in maintaining the stability of the pressure-sensitive adhesive layer. The content of the antioxidant when blended is not particularly limited, but is preferably 0.01 to 5% by weight. It should be noted that, in addition to the additive, a small amount of impurities and the like contained in the raw materials for manufacturing the constituent components of the pressure-sensitive adhesive composition may be contained.

The gel fraction of the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition of the present invention with the isocyanate crosslinking agent (B) is usually 40 to 100%, preferably 60 to 100%, particularly preferably 80 to 100%. It is more preferably 85 to 100%, and particularly preferably 90 to 100%.
If the gel fraction is too low, the cohesive force of the pressure-sensitive adhesive will be reduced, leaving adhesive residue, which tends to cause contamination of the adherend.

  The gel fraction is a measure of the degree of crosslinking, and is calculated by the following method, for example. That is, an adhesive sheet (without a separator) formed by forming an adhesive layer on a polymer sheet (for example, a polyethylene terephthalate film) serving as a base material is wrapped with a 200-mesh SUS wire mesh, and then placed in It is immersed at 24° C. for 24 hours, and the weight percentage of the insoluble pressure-sensitive adhesive component remaining in the wire netting is taken as the gel fraction. However, the weight of the base material is subtracted.

  The pressure-sensitive adhesive composition of the present invention shows a slight to low tackiness (about 2 N/25 mm or less) by cross-linking with a cross-linking agent to form a pressure-sensitive adhesive, and temporarily protects the surface of an adherend. Therefore, it is preferably used as a pressure-sensitive adhesive for a masking film or a pressure-sensitive adhesive for a heat-resistant pressure-sensitive adhesive film, which is bonded to an adherend for a short period (several hours to several days).

  In the present invention, a masking film, a heat-resistant pressure-sensitive adhesive film is prepared by preparing a pressure-sensitive adhesive for a masking film or a heat-resistant pressure-sensitive adhesive film from the pressure-sensitive adhesive composition, and forming a pressure-sensitive adhesive layer on the film which is a substrate. Alternatively, a heat-resistant adhesive film for masking (hereinafter sometimes collectively referred to as an adhesive film) can be obtained. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is the above-mentioned pressure-sensitive adhesive composition crosslinked with the isocyanate crosslinking agent (B).

  Examples of the substrate on which the pressure-sensitive adhesive layer is laminated include a film having a single layer or a laminated structure made of metal, polyester resin, polyfluorinated ethylene resin, polyimide and its derivatives, epoxy resin, or the like. In the masking film, heat-resistant adhesive film or masking heat-resistant adhesive film, it is preferable to further provide a release film on the surface of the adhesive layer opposite to the substrate. When the masking film, heat-resistant adhesive film or heat-resistant adhesive film for masking is put to 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, or an alkyd-based release film can be used.

  Regarding the method for producing the above-mentioned pressure-sensitive adhesive film, [1] a method of applying a pressure-sensitive adhesive composition on a substrate, drying, and then laminating a release film, and performing aging treatment, [2] release film Examples include a method in which the pressure-sensitive adhesive composition is applied on the above, dried, and then a base material is attached, and an aging treatment is performed. Among these, the method [1] is preferable in terms of improving the adhesion to the substrate, workability and stable production.

  The above-mentioned aging treatment is carried out in order to balance the pressure-sensitive adhesive properties, and the conditions for aging are usually a temperature of 0 to 150° C., preferably 10 to 100° C., particularly preferably 20 to 80° C., and a time of It is usually 30 days or less, preferably 14 days or less, particularly preferably 7 days or less, and specifically, it can be carried out under the conditions of, for example, 23° C. for 3 to 10 days and 40° C. for 1 to 7 days. .

  The pressure-sensitive adhesive film, which has been imparted with heat resistance, usually requires an aging treatment in order to allow the crosslinking reaction to proceed sufficiently, but in the present invention, by containing the zinc compound, it has excellent immediate curability. Therefore, it is possible to form a smooth pressure-sensitive adhesive layer surface without transferring fine irregularities to the pressure-sensitive adhesive layer during aging.

  At the time of applying the pressure-sensitive adhesive composition, it is preferable to dilute the pressure-sensitive adhesive composition in a solvent before coating, and the dilution concentration is preferably 5 to 60% by weight, particularly preferably 10 to 50% by weight. The solvent is not particularly limited as long as it can dissolve the pressure-sensitive adhesive composition, and examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate; acetone, methyl ethyl ketone, A ketone solvent such as methyl isobutyl ketone; an aromatic solvent such as toluene or xylene; an alcohol solvent such as methanol, ethanol or propyl alcohol can be used. Among these, ethyl acetate, methyl ethyl ketone, and toluene are preferably used in terms 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 pressure-sensitive adhesive film is usually 5 to 300 μm, preferably 5 to 50 μm, and particularly preferably 10 to 30 μm. If this pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive properties tend to be difficult to stabilize, and if it is too thick, the pressure-sensitive adhesive film as a whole tends to be too thick, resulting in poor usability.

  As the adherend of the adhesive film, it is preferable to use a base material of a material having heat resistance, for example, a metal plate or metal foil such as aluminum, copper, iron, stainless steel, magnesium, nickel, titanium; polyethylene terephthalate, Polyester resin such as polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate/isophthalate copolymer, ester acrylate; polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-4 fluoroethylene copolymer, etc. Polyfluorinated ethylene resin; polyimide and its derivatives; bisphenol type epoxy resin, epoxy resin composite material, alicyclic epoxy resin, epoxy novolac, biphenyl type epoxy resin, epoxy resin such as epoxy acrylate, and the like.

  The adhesive strength of the adhesive layer of the adhesive film is appropriately adjusted depending on the material of the adherend and the like, but when it is attached to, for example, a SUS-BA plate, a hard-coated PET film, glass, or a polyimide film. Of the adhesive strength immediately after coating (before aging) is preferably 0.01 to 1.0 N/25 mm, particularly preferably 0.05 to 0.5 N/25 mm, further preferably 0.1 to 0. It is 0.3 N/25 mm.

  The adhesive strength of the adhesive layer of the adhesive film after aging is preferably 0.01 to 1.0 N/25 mm, particularly preferably 0.05 to 0.5 N/25 mm, and further preferably 0.1. Is about 0.3 N/25 mm.

  Further, the adhesive strength of the adhesive layer of the adhesive film after heating is preferably 0.01 to 1.2 N/25 mm, particularly preferably 0.05 to 0.6 N/25 mm, and further preferably 0.1 to It is 0.3 N/25 mm.

Obtained using the pressure-sensitive adhesive composition of the present invention, a masking film, a heat-resistant pressure-sensitive adhesive film or a heat-resistant pressure-sensitive adhesive film for masking, even after use under high temperature conditions, hardly cause contamination when peeled from the adherend, and Since it can be peeled off with a small force, for example, a masking adhesive film for temporarily protecting the surface of a circuit board such as an FPC board or an ITO transparent electrode layer, which requires heat resistance, or a product during the manufacturing process. It can be used for general temporary fixing applications for temporary fixing and holding.
Further, the pressure-sensitive adhesive composition of the present invention has immediate curability, and since the fine irregularities of the release film are difficult to be transferred to the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer, it is for a protective film for a display such as a flat panel display or a touch panel. Even when used as, it is possible to prevent a decrease in visibility due to unevenness.

  The heat-resistant pressure-sensitive adhesive film for masking obtained by using the pressure-sensitive adhesive composition of the present invention may be used by attaching the heat-resistant pressure-sensitive adhesive film for masking to the surface of an adherend and usually at 100°C or higher (preferably 110°C or higher, particularly The heating method is preferably 120° C. or higher, more preferably 130° C. or higher), and then the heat-resistant adhesive film for masking is peeled off from the surface of the adherend.

  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 addition, "%" and "part" in the examples mean weight basis.

<Production of acrylic resin (A) solution>
[Production Example 1: Acrylic resin (A-1)]
In a reactor equipped with a thermometer, a stirrer, a dropping funnel, and a reflux condenser, 74.2 parts of ethyl acetate was charged, and the temperature was raised with stirring. When the temperature reached about 80°C, 91.85 parts of butyl acrylate (BA) was added. , Hydroxyethyl acrylate (HEA) 7.0 parts, dimethylaminopropyl acrylamide (DMAPAA) 0.15 parts, azobisisobutyronitrile (AIBN) 0.06 parts, ethyl acetate 6.0 parts by mixing and mixing The liquid was added dropwise over 2 hours. Further, during the polymerization, a mixed solution of 0.3 part of ethyl acetate mixed with 0.8 part of 4-hydroxybutyl acrylate (4HBA), a mixed solution of 0.3 part of ethyl acetate mixed with 0.05 part of AIBN, A mixed solution of 0.3 parts of ethyl acetate and 0.2 parts of 4HBA, and finally a mixed solution of 0.3 parts of ethyl acetate and 0.05 parts of AIBN were sequentially added, and the mixture was refluxed at the temperature of 7.5. After refluxing for an hour, the mixture was diluted with ethyl acetate to obtain a 42% solution of acrylic resin (A-1).

<Isocyanate cross-linking agent (B)>
(B-1)
Hexamethylene diisocyanate trimer ("Coronate HX" manufactured by Nippon Polyurethane Industry Co., Ltd.)

<Metal compound>
[Zinc compound (C)]
(C-1)
Zinc acetylacetonate ("X-1301" manufactured by Matsumoto Fine Chemical Co., solid content concentration 19%)

[Metal compound other than zinc]
(C'-1: zirconium compound)
Zirconium tetraacetylacetonate ("ZC-700" manufactured by Matsumoto Fine Chemical Co., solid content concentration 20%)
(C'-2: Aluminum compound)
Tris(2,4-pentanedionato)aluminum (III) ("Narsem Aluminum" manufactured by Nippon Kagaku Sangyo Co., Ltd., solid content concentration 100%)
(C'-3: tin compound)
Dibutyltin dilaurate (manufactured by Kishida Chemical Co., Ltd.)
(C'-4: tin compound)
Dialkylacetylacetone tin complex solution: 30 parts of acetylacetone was added to 10 parts of a 1% solution of dibutyltin dilaurate (DBTL) dissolved in toluene to prepare a catalyst solution containing 0.25% by weight of dialkylacetylacetone tin complex.

<Crosslink retarder (D)>
・(D-1)
Acetylacetone

<Example 1>
[Preparation of adhesive composition]
With respect to 100 parts of the solid content of the acrylic resin (A-1) obtained above, 11.8 parts of the isocyanate cross-linking agent (B-1) and 0.1 part of the zinc compound (C-1) ( 20 parts of acetylacetone (D-1) was blended to prepare a pressure-sensitive adhesive composition.

[Pot life]
The pot life of the pressure-sensitive adhesive composition prepared above was evaluated by the following method.
After the pressure-sensitive adhesive composition was prepared, the pressure-sensitive adhesive composition was placed in a storage bottle and placed in a constant temperature water bath at 25° C., and the viscosity of the pressure-sensitive adhesive composition after 1 hour was measured with a B-type viscometer at 25° C.×1 minute. After that, it was further placed in a constant temperature water bath at 25° C., and after 8 hours from the adjustment, the viscosity was measured at 25° C. for 1 minute with a B-type viscometer and evaluated according to the following criteria.
(Evaluation criteria)
◯... Viscosity after 8 hours is less than 2 times the viscosity after 1 hour. Δ... Viscosity after 8 hours is 2 times or more and less than 3 times the viscosity after 1 hour. ..Viscosity after 8 hours is 3 times or more than that after 1 hour

[Preparation of adhesive film]
The pressure-sensitive adhesive composition prepared above was applied to a PET film (thickness 38 μm) as a base material so that the thickness of the spreading agent layer after drying was about 25 μm, and then dried at 150° C. for 2 minutes. After that, a release-treated PET film was attached to the coated surface to protect the pressure-sensitive adhesive layer, and a pressure-sensitive adhesive film was produced.
The following evaluation was performed using the obtained adhesive film. The results are shown in Table 1.

[Instant curability]
A 25 mm×100 mm test piece was prepared using the adhesive film after 3 hours had elapsed from the preparation of the adhesive film, the release film was peeled off, and then a 25 μm-thick polyimide film (Toray -Dupont "Kapton 100H") is adhered to the polyimide film surface of the adherend under pressure of 2 kg rubber roller 2 reciprocations under the atmosphere of 23°C and relative humidity of 50%, and under the same atmosphere, 30 After leaving for a minute, the 180-degree peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min, and evaluated according to the following criteria.
It should be noted that the smaller the peel strength value is, the more the adhesive layer is crosslinked, and it can be seen that the crosslinking is advanced in a short time such as 3 hours after the production of the adhesive film. Therefore, it can be judged that the surface of the pressure-sensitive adhesive layer is smooth without transferring the fine unevenness of the release-treated PET film.
(Evaluation criteria)
○: less than 0.3 N/25 mm △: 0.3 N/25 mm or more, less than 0.5 N/25 mm ×... 0.5 N/25 mm or more

〔Heat-resistant〕
<Adhesive strength: before heating>
After subjecting the adhesive film obtained above to aging treatment at 40° C. for 7 days, a 25 mm×100 mm test piece was prepared, the release film was peeled off, and a 25 μm-thick polyimide film was placed on a stainless steel plate (SUS304BA plate). (Toray DuPont's "Kapton 100H") is adhered to the polyimide film surface of the adherend under pressure of 2 kg rubber roller 2 reciprocations under the atmosphere of 23°C and relative humidity of 50%. After being left for 30 minutes at 180° C., the 180° peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min, and evaluated according to the following criteria.
(Evaluation criteria)
◯: less than 0.3 N/25 mm Δ: 0.3 N/25 mm or more, less than 0.5 N/25 mm ×... 0.5 N/25 mm or more

<Adhesive strength: After heating>
After the adhesive film obtained above was aged at 40° C. for 7 days, a 25 mm×100 mm test piece was prepared, the release film was peeled off, and a 25 μm-thick polyimide film was placed on a stainless steel plate (SUS304BA plate). (Toray DuPont's "Kapton 100H") is adhered to the polyimide surface of the adherend under pressure of 2 kg rubber roller 2 reciprocations under the atmosphere of 23°C and relative humidity of 50%. It was left for 30 minutes. Then, it was exposed to the condition of 150° C. for 1.5 hours and then returned to 23° C. Furthermore, after leaving it for 2 hours in an atmosphere of 23° C. and a relative humidity of 50%, a 180° peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min and evaluated according to the following criteria.
(Evaluation criteria)
○: less than 0.3 N/25 mm △: less than 0.3 N/25 mm, less than 0.6 N/25 mm x: more than 0.6 N/25 mm

[Heat resistant stain resistance]
After subjecting the adhesive film obtained above to aging treatment at 40° C. for 7 days, a 25 mm×100 mm test piece was prepared, and a 25 μm thick polyimide film (“Kapton 100H” manufactured by Toray-Dupont Co., Ltd.) was formed on a stainless plate (SUS304BA plate). )) was adhered to the adherend under pressure of two round trips of a 2 kg rubber roller in an atmosphere of 23° C. and a relative humidity of 50%, and left for 30 minutes in the same atmosphere. Then, it was exposed to the condition of 150° C. for 1.5 hours and then returned to 23° C. After being left in an atmosphere of 23° C. and a relative humidity of 50% for 2 hours, the state of the adherend surface after peeling 180 degrees at a peeling speed of 300 mm/min was observed and evaluated according to the following criteria.
(Evaluation criteria)
◯: Almost no adhesive residue or sticking trace was confirmed ×: Peeling of the substrate interface was confirmed

[Appearance of adhesive layer surface]
After subjecting the pressure-sensitive adhesive film obtained above to aging treatment at 40° C. for 7 days, the release film of the pressure-sensitive adhesive film was peeled off, and platinum was deposited on the pressure-sensitive adhesive layer surface at 30 mA for 40 seconds with a JFC-1600 auto fine coater. Let After that, the surface of the pressure-sensitive adhesive layer on which platinum was vapor-deposited was observed with a microscope (VHX-900 (model number) manufactured by Keyence Corporation), and evaluated according to the following criteria.
(Evaluation criteria)
O: Almost no surface irregularities were confirmed.
Δ: Some irregularities on the surface were confirmed.
X: Many irregularities on the surface were confirmed.

<Example 2, Comparative Examples 1 to 5>
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the respective components of the pressure-sensitive adhesive composition were mixed in the proportions shown in Table 1 to prepare a pressure-sensitive adhesive film. The same evaluation as in Example 1 was performed using the obtained pressure-sensitive adhesive composition and pressure-sensitive adhesive film. The results are shown in Table 1.

  In the pressure-sensitive adhesive compositions of Examples 1 and 2 having the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition containing the isocyanate-based cross-linking agent (B) as the cross-linking agent and the zinc-based compound (C) as the cross-linking catalyst in the specified amounts, The rate of increase in adhesive strength from 8 hours to 8 hours is low, that is, it has a sufficient pot life. In the adhesive film, the adhesive strength of the adhesive film is low 3 hours after preparation, and the appearance of the coating film is Good, that is, excellent in quick-curing property, and does not become excessively adhesive even after being exposed to a high temperature condition of 150° C. for 1.5 hours, and peels from an adherend with a small force. It can be seen that it is possible to prevent the contamination from occurring when peeled from the adherend.

On the other hand, Comparative Example 1 containing no zinc compound was inferior in immediate curability, unevenness was observed on the surface of the pressure-sensitive adhesive layer, and inferior in appearance. Furthermore, the adhesive strength after heating was high, and the light releasability was poor.
Further, in Comparative Examples 2 to 5 using metal compounds other than zinc (zirconium compound, aluminum compound, tin compound), the viscosity increase rate of the pressure-sensitive adhesive composition was high and the pot life was not sufficient, or 3 It can be seen that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film has a high adhesive force over time, and unevenness is observed in the coating film, that is, the immediate curability is poor.

  The pressure-sensitive adhesive composition of the present invention is a heat-resistant pressure-sensitive adhesive film for masking for performing masking or fixing in a heating step included in a manufacturing process of a circuit board such as an FPC board or a touch panel-related member such as an ITO transparent electrode, or a flat panel display. It can be suitably used for an adhesive film for surface protection such as a touch panel and a touch panel.

Claims (7)

A pressure-sensitive adhesive composition containing an acrylic resin (A) having a hydroxyl group, an isocyanate crosslinking agent (B), a zinc compound (C) , and a crosslinking retardant (D) ,
The zinc compound (C) is a zinc alkoxide compound or a zinc chelate compound,
Content of a zinc compound (C) is 0.01-15 weight part with respect to 100 weight part of acrylic resin (A) which has a hydroxyl group, The adhesive composition characterized by the above-mentioned.   Content of an isocyanate type crosslinking agent (B) is 0.5-40 weight part with respect to 100 weight part of acrylic resin (A) which has a hydroxyl group, The adhesive composition of Claim 1 characterized by the above-mentioned. .   The content ratio (weight ratio) (C)/(B) of the isocyanate-based cross-linking agent (B) and the zinc compound (C) (solid content equivalent) is 0.0001 to 0.5. The pressure-sensitive adhesive composition according to 1 or 2. Adhesive pressure-sensitive adhesive composition according to any one of claims 1 to 3 is characterized by comprising cross-linked by an isocyanate crosslinking agent (B). A masking film pressure-sensitive adhesive comprising the pressure-sensitive adhesive according to claim 4 . An adhesive for a heat-resistant adhesive film, comprising the adhesive according to claim 4 . A heat-resistant pressure-sensitive adhesive film for masking, comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to claim 4 on a film.