JP6562131B1 - Adhesive and adhesive sheet - Google Patents

Abstract

A pressure-sensitive adhesive layer formed from an acrylic pressure-sensitive adhesive is superior in resistance at a higher temperature (180 to 260 ° C.) than before and can suppress contamination of an adherend after the pressure-sensitive adhesive layer is peeled off. And providing an adhesive sheet. The pressure-sensitive adhesive according to the present invention is a pressure-sensitive adhesive used for forming a pressure-sensitive adhesive layer of 5 to 15 μm, and has a weight average molecular weight of 6.0 × 10 5 to 1.00 × 10 6 by GPC analysis. A (meth) acrylic copolymer (A) and an epoxy curing agent (B), and the (meth) acrylic copolymer (A) is a functional group capable of crosslinking with the epoxy curing agent (B). In the molecular weight distribution curve having a unit derived from a reactive functional group-containing monomer having a group, and the molecular weight distribution curve obtained by the GPC analysis, the content of the oligomer component having a molecular weight of 1,000 to 20,000 is represented by the molecular weight distribution curve. The total area is 5% or less. [Selection figure] None

Description

  The present invention relates to an acrylic pressure-sensitive adhesive and a pressure-sensitive adhesive sheet.

  Conventionally, pressure-sensitive adhesive sheets have been widely used as surface protection sheets and fixing means for various members. For example, pressure-sensitive adhesive sheets are frequently used as surface protection sheets for flat panel displays (FPD) such as liquid crystal displays (LCD) and organic electroluminescent displays (OELD), and touch panel displays. Moreover, the adhesive sheet is utilized as a surface protection sheet of electronic components, such as optical members, such as a polarizing plate, and a printed circuit board, or for household appliances and a nameplate fixing use.

As an adhesive used for such an adhesive sheet, for example, an acrylic copolymer having a weight average molecular weight of 100,000 to 300,000, a solvent, a tackifier resin, a crosslinking agent having an epoxy group, and a metal chelate crosslinking An acrylic pressure-sensitive adhesive containing a predetermined amount of each agent is disclosed (Patent Document 1). Further, it contains a polydiorganosiloxane having one or more alkenyl groups, R ₃ SiO _1/2 units and SiO _4/2 units, and the molar ratio of R ₃ SiO _1/2 units to SiO _4/2 units is 0.5. -1.5 polyorganosiloxane (R is a monovalent hydrocarbon group having 1 to 10 carbon atoms in the alkyl group), polyorganohydrogensiloxane, reaction inhibitor, curing catalyst required for the addition reaction, A silicone pressure-sensitive adhesive composition containing an isocyanuric acid derivative has been disclosed (Patent Document 2).

JP 2008-120970 A JP 2017-179056 A

  The pressure-sensitive adhesive sheet is required to have a good holding power with respect to the adherend and to be able to peel well without leaving any adhesive on the adherend. Furthermore, in recent years, from the viewpoint of reducing manufacturing costs and reducing environmental burdens, surface protection sheets used for protecting members from contact with each manufacturing equipment, member processing, or conveyance during the manufacturing process, and after product completion It is being demanded that a surface protective sheet for protecting a product from conveyance associated with shipment is used in combination with the same pressure-sensitive adhesive sheet. However, when the manufacturing process includes a high-temperature step (for example, 180 to 260 ° C.), the adhesive strength of the adhesive sheet increases, and thus there is a problem that adhesive residue is likely to occur when the adhesive layer is peeled from the adherend. . For this reason, when it becomes a high temperature environment at the time of manufacture etc., the silicone adhesive like patent document 2 which is excellent in heat resistance is used instead of the acrylic adhesive like patent document 1. FIG. However, although the silicone-based pressure-sensitive adhesive is excellent in durability in a high temperature environment, there is a problem that adherence contamination is likely to occur in addition to the problem that the cost is increased due to the material.

  The present invention has been made in view of the above background, and in an adhesive layer formed from an acrylic adhesive, it is superior in resistance at a higher temperature (180 to 260 ° C.) than before and peels off the adhesive layer. It aims at providing the adhesive and adhesive sheet which can suppress the adherend contamination after having done.

As a result of intensive studies by the present inventor, it has been found that the problems of the present invention can be solved in the following modes, and the present invention has been completed.
[1]: (Meth) acrylic copolymer (A) having a weight average molecular weight of 6.0 × 10 ^{5 to} 1.00 × 10 ⁶ by gel permeation chromatography analysis;
Containing an epoxy curing agent (B),
The (meth) acrylic copolymer (A) has a unit derived from a reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B), and obtained by the gel permeation chromatography analysis. In the obtained molecular weight distribution curve, the pressure-sensitive adhesive in which the content of oligomer components having a molecular weight of 1,000 to 20,000 is 5% or less with respect to the total area of the molecular weight distribution curve.
[2]: Furthermore, an antioxidant (C) is contained,
The antioxidant (C) is the pressure-sensitive adhesive according to [1], which is a semi-hindered phenol-based antioxidant.
[3]: The pressure-sensitive adhesive according to [1] or [2], further comprising a polymerization inhibitor (D).
[4]: The (meth) acrylic copolymer (A) has 65 to 99% by mass of units derived from a (meth) acrylic acid ester having an alkyl group having 8 to 18 carbon atoms. [3] The pressure-sensitive adhesive according to any one of [3].
[5]: A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to any one of [1] to [4].
[6] The pressure-sensitive adhesive sheet according to [5], wherein the pressure-sensitive adhesive layer is 5 to 15 μm.

  According to the present invention, the pressure-sensitive adhesive layer formed from an acrylic pressure-sensitive adhesive is superior in resistance at a higher temperature (180 to 260 ° C.) than before and suppresses adherend contamination after the pressure-sensitive adhesive layer is peeled off. It is possible to provide an excellent pressure-sensitive adhesive and a pressure-sensitive adhesive sheet.

  Hereinafter, an example of an embodiment to which the present invention is applied will be described. The numerical values specified in this specification are values obtained by the method disclosed in the embodiment or examples. It should be noted that other embodiments are also included in the scope of the present invention as long as they meet the spirit of the present invention. Moreover, the adhesive sheet of this invention is synonymous with an adhesive film, an adhesive tape, and an adhesive label. Moreover, unless otherwise mentioned, the various compounding components in the pressure-sensitive adhesive can be used independently or in combination of two or more. Further, (meth) acryl means acryl or methacryl, and (meth) acrylate means acrylate or methacrylate.

<Adhesive>
The pressure-sensitive adhesive of this embodiment is used for forming a pressure-sensitive adhesive layer, and this pressure-sensitive adhesive layer is bonded to an adherend such as glass and peeled off from the adherend at a desired timing. It is preferably used as an application. The pressure-sensitive adhesive of the present embodiment includes a (meth) acrylic copolymer (A) having a weight average molecular weight (Mw) of 6.0 × 10 ^{5 to} 1.00 × 10 ⁶ by gel permeation chromatography (GPC) analysis, and And an epoxy curing agent (B). This (meth) acrylic copolymer (A) has a unit derived from a reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B), and was obtained by the GPC analysis. In the molecular weight distribution curve, the content of an oligomer component having a molecular weight of 1,000 to 20,000 (hereinafter also simply referred to as “oligomer component”) is set to 5% or less with respect to the total area of the molecular weight distribution curve. The pressure-sensitive adhesive layer is cured by promoting crosslinking between the (meth) acrylic copolymer (A) and the epoxy curing agent (B) in the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present embodiment. A crosslinked structure derived from an epoxy group is formed.

  In addition, although the adhesive of this embodiment is a composition which mix | blended multiple types of material containing a (meth) acryl copolymer (A) and an epoxy-type hardening | curing agent (B), in an adhesive, ) A plurality of blending components including the acrylic copolymer (A) and the epoxy curing agent (B) may not be clearly present as independent components. That is, the pressure-sensitive adhesive of this embodiment contains a reaction product obtained by partially crosslinking the (meth) acrylic copolymer (A) and the epoxy curing agent (B), or ( In some cases, a reaction product obtained by partially reacting a plurality of blending components including the (meth) acrylic copolymer (A) and the epoxy curing agent (B) may be included. Crosslinking basically proceeds by a curing process, but such a reaction product or a crosslinked structure may be partially contained before the curing process.

  After the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present embodiment is bonded to the adherend, the paste is applied to the adherend even if it is placed in a high temperature environment of about 180 to 260 ° C. and then peeled off from the adherend. The phenomenon in which the rest is generated can be significantly suppressed. By using the acrylic pressure-sensitive adhesive of this embodiment instead of the silicone pressure-sensitive adhesive having high temperature resistance, it is possible to effectively prevent adherend contamination while reducing costs. Hereinafter, each component of the adhesive of this embodiment is explained in full detail.

[(Meth) acrylic copolymer (A)]
As described above, the (meth) acrylic copolymer (A) has a Mw by GPC analysis in the range of 6.0 × 10 ^{5 to} 1.00 × 10 ⁶ , and a molecular weight distribution curve obtained by this GPC analysis. The content of the oligomer component having a molecular weight of 1,000 to 20,000 is 5% or less with respect to the total area of the molecular weight distribution curve. The total area of the molecular weight distribution curve here refers to the area of the area between the differential molecular weight distribution curve calculated from GPC and the baseline of the differential molecular weight distribution curve, and the horizontal axis represents the molecular weight (logarithmic value) and the vertical axis. This is the value when the axis is the differential value.

By setting Mw of the (meth) acrylic copolymer (A) to 600,000 or more, the heat resistance can be effectively improved. Further, by setting the Mw to 1 million or less, it becomes possible to improve the coating property for forming the pressure-sensitive adhesive layer and to effectively exhibit good wettability. A more preferable range of Mw of the (meth) acrylic copolymer (A) is 7.0 × 10 ^{5 to} 9.0 × 10 ⁵ , and a more preferable range is 7.5 × 10 ^{5 to} 8.5 × 10 ^5. It is.

Mw of the (meth) acrylic copolymer (A) is 6.0 × 10 ^{5 to} 1.00 × 10 ⁶ , and the content of the oligomer component is based on the total area of the molecular weight distribution curve obtained by GPC analysis The pressure-sensitive adhesive layer is 180 to 260 in spite of being an acrylic pressure-sensitive adhesive by setting it to 5% or less and further curing by crosslinking in the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive so as to form an epoxy-based crosslinked structure. Even after peeling from the adherend after being exposed to a high temperature region of about ° C, the adhesive residue on the adherend can be remarkably improved. The content of the oligomer component is preferably 4.5% or less, more preferably 3.5% or less, and more preferably 2.5% with respect to the total area of the molecular weight distribution curve obtained by GPC analysis. More preferably, it is as follows.

  The (meth) acrylic copolymer (A) can be obtained by polymerizing two or more kinds of monomers that form monomer units constituting the (meth) acrylic copolymer (A), and can be crosslinked with the epoxy-based curing agent (B) as the monomer. A reactive functional group-containing monomer having a functional group is essential. The functional group of the monomer derived from the reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B) serves as a base point for crosslinking with the epoxy curing agent (B).

  The functional group in the reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B) is preferably a carboxy group. That is, it is preferable to use a carboxy group-containing monomer as the reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B).

  The carboxy group-containing monomer is a monomer having a (meth) acryloyl group or a vinyl group and having a carboxy group. Specific examples include (meth) acrylic acid, β-carboxyethyl (meth) acrylate, itaconic acid, crotonic acid, maleic acid, fumaric acid, p-carboxybenzyl acrylate, ethylene oxide modification (ethylene oxide addition moles) : (2-18) phthalic acid acrylate and succinic acid monohydroxyethyl acrylate, among which acrylic acid and methacrylic acid are preferred.

  The reactive functional group-containing monomer is preferably contained in an amount of 1.0 to 8.0% by mass and more preferably 1.5 to 5.0% by mass in 100% by mass of the monomer mixture. By including 1.0 to 8.0% by mass, the crosslink density when the pressure-sensitive adhesive layer is cured is made appropriate, and the adhesive strength and removability of the cured pressure-sensitive adhesive layer are easily compatible.

  The (meth) acrylic copolymer (A) has a (meth) acrylic unit copolymerizable with a reactive functional group-containing monomer. As a unit constituting such a (meth) acrylic copolymer (A), a unit derived from a (meth) acrylic acid ester is preferable. The alkyl group in the (meth) acrylic acid ester may be linear or branched.

  (Meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, (meth ) N-pentyl acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, Iso-octyl (meth) acrylate, n-nonyl (meth) acrylate, iso-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-isodecyl (meth) acrylate, (meth) acrylic acid n-dodecyl, isomyristyl (meth) acrylate, n-tridecyl (meth) acrylate, n-teto (meth) acrylate Decyl, (meth) acrylate, stearyl, (meth) isostearyl acrylate.

  Among (meth) acrylic acid esters, a (meth) acrylic acid ester having 8 to 18 carbon atoms in the alkyl group is preferably used from the viewpoint of more effectively expressing high-temperature resistance. By setting this range, the adhesive residue on the adherend when the pressure-sensitive adhesive layer and the adherend were peeled was suppressed, and the balance between the holding force and the peel force between the pressure-sensitive adhesive layer and the adherend was combined. An adhesive is obtained. More preferably, it is a (meth) acrylic acid ester having 8 to 14 carbon atoms in the alkyl group, and more preferably a (meth) acrylic acid ester having 8 to 10 carbon atoms.

  In the (meth) acrylic copolymer (A), the content of units derived from a (meth) acrylic acid ester having 8 to 18 carbon atoms in the alkyl group is 65 to 99% by mass with respect to all monomers. It is preferable. By setting it as this range, the balance of adhesive force and cohesive force becomes good, and an adhesive having excellent heat resistance after crosslinking can be provided. As for content of the unit derived from the (meth) acrylic acid ester whose carbon number of an alkyl group is 8 or more and 18 or less, a more preferable range is 75-99 mass%, More preferably, it is 85-99 mass%.

  From the viewpoint of more effectively increasing the resistance at high temperatures (180 to 260 ° C.), the (meth) acrylic copolymer (A) contains a (meth) acrylic acid ester having an alkyl group with less than 8 carbon atoms. The amount is preferably less than 32% by mass, more preferably less than 16% by mass, and particularly preferably 0% by mass. By setting the content of the (meth) acrylic acid ester having less than 8 carbon atoms in the alkyl group to be less than 32% by mass, the high temperature resistance can be more remarkably improved. The reason is considered to be that the formation of oligomer components could be suppressed by not using a monomer having a short side chain (side group) alkyl chain. That is, it is considered that by suppressing the formation of the oligomer component, it was possible to suppress the adhesive residue at high temperatures and to reduce the increase in adhesive strength.

  The (meth) acrylic copolymer (A) can also use other monomers other than those described above. Other monomers should just be a monomer which does not impair the adhesive force and cohesion force of an adhesive layer. Examples include hydroxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, imide group-containing monomers, aromatic ring-containing monomers, alkoxy (poly) alkylene oxide-containing monomers, and other vinyl monomers.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth) (Meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, polyethylene glycol Mono (meth) acrylic acid ester, polypropylene glycol mono (meth) acrylic acid ester, glycol mono (meth) acrylic acid ester such as 1,4-cyclohexanedimethanol mono (meth) acrylic acid ester, caprolactone modified (meth) acrylic Ester, N- hydroxymethyl (meth) acrylamide, N- hydroxyethyl (meth) acrylamide such as N- hydroxyalkyl (meth) acrylamide. Among these, 2-hydroxyethyl (meth) acrylate is preferable.

Examples of the amino group-containing monomer include aminomethyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylate.
Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, (Meth) acrylamide compounds such as N-dimethylaminopropyl (meth) acrylamide, diacetone (meth) acrylamide, N- (butoxymethyl) acrylamide; and heterocyclic rings such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine Compounds and the like.
Examples of the imide group-containing monomer include N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, and N-octylitaconimide. N-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) An acryloyl-8-oxyoctamethylene succinimide is mentioned.
Other vinyl monomers include, for example, vinyl acetate, styrene, methyl styrene, vinyl toluene, and acrylonitrile.
In addition, known polyfunctional (meth) acrylic acid compounds such as polyethylene glycol di (meth) acrylate and neopentyl glycol adipate di (meth) acrylate are included in other vinyl monomers.

  Examples of the aromatic ring-containing monomer include phenoxyethyl acrylate, benzyl acrylate, phenoxydiethylene glycol (meth) acrylate, and (meth) acrylate ethylene oxide-modified nonylphenol.

  Alkoxy (poly) alkylene oxide-containing monomers include, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylic acid Examples include esters, methoxypolypropylene glycol (meth) acrylic acid esters, ethoxypolypropylene glycol (meth) acrylic acid esters, phenoxypolyethylene glycol (meth) acrylic acid esters, and phenoxypolypropylene glycol (meth) acrylic acid esters.

  Other vinyl monomers include, but are not limited to, vinyl acetate and acrylonitrile.

  The glass transition temperature of the (meth) acrylic copolymer (A) is preferably −68 to −40 ° C. The pressure-sensitive adhesive sheet in which a polymer in this temperature range is crosslinked with an epoxy curing agent has an effect of suppressing adhesive residue at a high temperature. More preferably, it is -68--55 degreeC, More preferably, it is -68--60 degreeC.

(Synthesis method)
The (meth) acrylic copolymer (A) can be obtained by adding a polymerization initiator to the monomer mixture and appropriately selecting a known production method such as solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. Among these, solution polymerization is preferable from the viewpoint of easy adjustment of the contents of the Mw and oligomer components of the acrylic copolymer (A).

  Solvents used for solution polymerization include, for example, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, and isopropanol. Preferably, ethyl acetate is more preferable. Solvents can be used alone or in combination of two or more.

  The solution polymerization is preferably performed by adding about 0.001 to 1% by mass of a polymerization initiator to 100% by mass of the monomer mixture. The polymerization can be performed, for example, at a temperature of about 50 to 90 ° C. for 3 hours or more and less than 8 hours in an inert gas atmosphere such as nitrogen. By making it less than 8 hours, the increase in an oligomer component can be suppressed effectively.

  Examples of the initiator include azo compounds and peroxides. Examples of the peroxide include alkyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-Butylcumyl peroxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethyl Cyclohexane, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxy Organic peroxides such as Sobuchireto, potassium persulfate, sodium persulfate, inorganic peroxides such as ammonium persulfate.

  Examples of the azo compound include 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 ′. -Azobis (2-methylbutyronitrile), 4,4'-azobis-4-cyanovaleric acid ammonium (amine) salt, 2,2'-azobis (2-methylamidooxime) dihydrochloride, 2,2 '-Azobis (2-methylbutanamidooxime) dihydrochloride tetrahydrate, 2,2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] -propionamide} 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] and the like.

  Among these, an azo compound is preferable from the viewpoint of suppressing the amount of oligomer component generated. The initiator is preferably used in an amount of 0.01 to 0.20% by mass with respect to 100% by mass of the monomer. Moreover, in order to adjust Mw, you may use a chain transfer agent.

  In the polymerization of the (meth) acrylic copolymer (A), the molecular weight increases as the polymerization progresses, but as the polymerization proceeds to some extent, the viscosity of the solution increases and the monomer concentration in the solution decreases. . Along with this, the proportion of oligomer components increases. The acrylic pressure-sensitive adhesive is obtained by polymerizing a resin, using the solvent used for polymerization as it is, and adjusting the solid content concentration with the solvent for viscosity adjustment, and adding a curing agent thereto to obtain a pressure-sensitive adhesive. For this reason, it is sufficiently polymerized so that no monomer component remains in the acrylic copolymer after polymerization. As described above, the acrylic resin obtained in such a manner that the monomer component does not remain is included in an amount exceeding 5% even if the oligomer component having a molecular weight of 1,000 to 20,000 is estimated to be small.

  In this embodiment, in order to make this oligomer component 5% or less, the polymerization is completed before the oligomer component increases while adjusting the polymerization time and polymerization conditions by GPC measurement. This condition can be easily adjusted by performing GPC measurement during the polymerization. As a result of extensive studies by the inventor, the acrylic copolymer (A) is obtained by terminating the reaction when the monomer component reaches 25,000 to 15,000 ppm with respect to all charged monomers in the polymerization step. It was found that the oligomer component (component having a molecular weight of 1,000 to 20,000) can be adjusted to 5% or less. As described above, the solution polymerization can be performed at 50 to 90 ° C. for 3 hours or more and less than 8 hours, but a more preferable polymerization temperature is 70 to 80 ° C., and the reaction time is about 3 to 5 hours.

  Unreacted monomers remaining after the polymerization can be removed by volatilization in the heat drying step when forming the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is preferably heated and air-dried after coating so that the solvent and the unreacted monomer are sufficiently volatilized. What is necessary is just to change heating air drying conditions suitably according to the film thickness of an adhesive layer. From the viewpoint of improving the high temperature resistance at high temperatures (180 to 260 ° C.) while having excellent adhesiveness and peelability, the thickness of the pressure-sensitive adhesive layer is preferably in the range of 5 to 15 μm. By setting it within this range, it is easy to remove the unreacted monomer component. The removal of the unreacted monomer component is not limited to the case where the unreacted monomer is not substantially contained in the pressure-sensitive adhesive layer. The content of the unreacted monomer component in the pressure-sensitive adhesive layer is preferably 15,000 ppm or less, more preferably 10,000 ppm or less, and particularly preferably substantially not contained.

  When the pressure-sensitive adhesive layer is thicker than 15 μm to about 200 μm, a step of removing the monomer is performed at the stage where the acrylic copolymer (A) before forming the pressure-sensitive adhesive is polymerized in order to increase the high temperature resistance. It is preferable. For example, before adding an epoxy-type hardening | curing agent (B), after adding the polymerization inhibitor mentioned later, the solution used for superposition | polymerization may be heated and a monomer and a solvent may be distilled off. Although the manufacturing process increases, it can be suitably applied to a thick film adhesive layer.

[Epoxy curing agent (B)]
The epoxy curing agent (B), which is an essential component of the pressure-sensitive adhesive of the present embodiment, functions as a crosslinking agent for the (meth) acrylic copolymer (A). By constructing a cross-linked structure in the pressure-sensitive adhesive layer, it is possible to combine the properties of the wettability to the adherend and the removability at high temperatures.

  Epoxy curing agents (B) are ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, poly Tetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane tri Glycidyl ether, pentaerythritol polyglycidyl ether, Bitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and the like can be mentioned. Among these, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane and N, N, N ′, N′-tetraglycidyl-m-xylylenediamine containing four epoxy groups are preferable. Moreover, in a commercial item, "TETRAD-C" and "TETRAD-X" (made by Mitsubishi Gas Chemical Company) are preferable.

  It is preferable that an epoxy-type hardening | curing agent (B) contains 0.25-8 mass% with respect to 100 mass% of acrylic copolymers (A). By setting it within this range, the cohesive strength is high and it is possible to prevent the adhesive residue and the adhesive strength from increasing at high temperatures. A more preferable range is 0.3 to 5% by mass, and more preferably 0.6 to 3% by mass.

  A metal chelate may be used in combination with the epoxy curing agent (B). The metal chelate is a coordination compound of a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium and acetylacetone or ethyl acetoacetate. Examples of the metal chelate compound include aluminum ethyl acetoacetate / diisopropylate, aluminum trisacetylacetonate, aluminum trisethylacetoacetate, aluminum bisethylacetoacetate / monoacetylacetonate, titanium acetylacetonate, titanium tetraacetylacetonate, Examples thereof include titanium ethyl acetoacetate, titanium-1,3-propanedioxybis (ethyl acetoacetate), zirconium tetraacetyl acetonate, zirconium monoacetyl acetonate, zirconium ethyl acetoacetate and the like.

  It is preferable that a metal chelate contains 0.1-5 mass% with respect to 100 mass% of acrylic copolymers (A). When 0.1 to 5% by mass is contained, it becomes easy to balance the cohesive force and adhesive force of the adhesive layer.

  As described above, the pressure-sensitive adhesive of this embodiment can form a crosslinked structure derived from an epoxy group by a crosslinking reaction. By combining the above-mentioned (meth) acrylic copolymer (A) with a crosslinked structure derived from an epoxy group, heat resistance can be significantly improved compared to a crosslinked structure having a urethane bond using an isocyanate group. it can.

[Antioxidant (C)]
The pressure-sensitive adhesive of this embodiment can contain an antioxidant (C) as an optional component. Examples of the antioxidant (C) include phosphite antioxidants, hindered phenol antioxidants, semi-hindered phenol antioxidants, and less hindered phenol antioxidants.

  Specific examples of the phosphite antioxidant include, for example, ADK STAB PEP series (manufactured by ADEKA).

  The semi-hindered phenol-based antioxidant has a phenol structure, and one of the ortho positions of the OH group (phenolic hydroxyl group) constituting the phenol structure is a bulky group (for example, t-butyl group), and the other An antioxidant in which is a methyl group. As a specific example, for example, 3,9-bis [2- {3- (3-tertiarybutyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4, 8,10-tetraoxaspiro [5,5] undecane (for example, trade name “ADEKA STAB AO-80”, manufactured by ADEKA), ethylene bis (oxyethylene) bis [3- (5-tert-butyl-hydroxy-m -Tolyl) propionate] (for example, trade name “Irganox 245”, manufactured by BASF), triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] (for example, product Name "Adeka Stub AO-70", manufactured by ADEKA).

  The hindered phenol-based antioxidant is an antioxidant having a phenol structure, wherein one of the ortho positions of the phenolic hydroxyl group is a bulky group (for example, a t-butyl group) and the other is hydrogen. . Specific examples include 1,1,3-tris- (2-methyl-4-hydroxy-5-tertiarybutylphenyl) butane (for example, trade name “ADK STAB AO-30” manufactured by ADEKA), 4,4. '-Butylidenebis (6-t-butyl-3-methylphenol) (for example, trade name “Adeka Stub AO-40”, manufactured by ADEKA), 4,4′-thiobis (6-t-butyl-3-methylphenol) (For example, trade name “Sumilyzer WX-R”, manufactured by Sumitomo Chemical Co., Ltd.).

  The hindered phenol-based antioxidant is an antioxidant having a phenol structure, and both of the ortho positions of the phenolic hydroxyl group are bulky groups (for example, t-butyl group). For example, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl) -4-hydroxyphenyl) propionamide], benzenepropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy, C7-C9 side chain alkyl ester, 3,3 ′, 3 ″, 5 , 5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-creso , Calcium diethylbis [[[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] phosphonate], 4,6-bis (octylthiomethyl) -o-cresol, 4,6 -Bis (dodecylthiomethyl) -o-cresol, hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris (3,5-di- tert-Butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, reaction of N-phenylbenzenamine with 2,4,4-trimethylpentene Product, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol, triethyl Glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxy) Phenyl) propionate], 2,6-di-tert-butyl-p-cresol, 2,2′-ethylidene-bis (4,6-di-tert-butylphenol), 1,3,5-tris (3,5 -Di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 5 -Di-tert-butyl-4-hydroxyhydrocinnamate, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionylo Xyl] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,3,5-tris (2,6-dimethyl-4-tert-butyl-3 -Hydroxybenzyl) isocyanurate, 3,5-di (3,5-di-tert-butyl-4-hydroxybenzyl) mesitol, 3,6-dioxaoctamethylenebis (3-methyl-5-tert-butyl) -4-hydroxyhydrocinnamate), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-tris [2- (3,5-di- -Tert-butyl-4-hydroxyhydrocinnamoyloxy) ethyl] isocyanurate, thiodiethylenebis (3,5-di-tert-butyl-4-hydroxyhydrocinnamer ), Tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, n-octadecyl 3di-n-octadecyl 3,5-di-tert-butyl-4-hydroxy Examples include benzyl phosphonate and octadecyl-3- (3,5-t-butyl-4-hydroxyphenyl) propionate.

  Among these, from the viewpoint of quickly capturing radicals, a semi-hindered phenol-based antioxidant or a less hindered phenol-based antioxidant is preferable, and a semi-hindered phenol-based antioxidant is more preferable. By using a semi-hindered phenolic antioxidant as the antioxidant (C), it is possible to suppress the adhesive residue on the adherend when the pressure-sensitive adhesive layer that has undergone the high temperature process is peeled off from the adherend, and high temperature resistance It will be better.

  The content of the antioxidant (C) is preferably 0.1 to 1.0% by mass, and preferably 0.2 to 0.6% by mass with respect to 100% by mass of the (meth) acrylic copolymer. It is more preferable.

[Polymerization inhibitor (D)]
The pressure-sensitive adhesive of this embodiment can contain a polymerization inhibitor (D) as an optional component. High temperature resistance is improved by adding a polymerization inhibitor (D) to the pressure-sensitive adhesive. The reason is considered to be that the unreacted monomer remaining after the polymerization step can be appropriately prevented from polymerizing and forming an oligomer. By using the polymerization inhibitor (D) together with the antioxidant (C), the effect of high temperature resistance of the pressure-sensitive adhesive layer can be enhanced. Particularly preferred is the combined use of an antioxidant (C) and a polymerization inhibitor (D) of a semi-hindered antioxidant.

  The polymerization inhibitor (D) plays a role of inhibiting radical polymerization. Specifically, any phenolic, amine-based, phosphorus-based, or sulfur-based effect can be used without particular limitation, but a phenolic type is preferably used. For example, hydroquinone, methoquinone (MEHQ: hydroquinone monomethyl ether), p-benzoquinone, phenothiazine, mono-t-butylhydroquinone, catechol, pt-butylcatechol, benzoquinone, 2,5-di-t-butylhydroquinone, anthraquinone 2,6-di-t-butylhydroxytoluene (BHT) and the like.

  The content of the polymerization inhibitor (D) is preferably 0.001 to 1.0% by mass with respect to 100% by mass of the (meth) acrylic copolymer (A), and 0.01 to 0.5% by mass. % Is more preferable.

  The pressure-sensitive adhesive of this embodiment may contain a solvent. As the solvent, the solvent used for solution polymerization of the (meth) acrylic copolymer (A) may be used as it is, a different solvent may be used, or a mixed solvent thereof may be used.

[Others]
In addition, the adhesive of this embodiment may contain another component in the range which can solve the subject of this invention. For example, tackifying resins, seed resins, curing catalysts, silane coupling agents, oils, softeners, dyes, pigments, antioxidants, UV absorbers, weathering stabilizers, fillers, anti-aging agents and antistatic agents, etc. You may mix | blend. Examples of tackifying resins include rosin resins, terpene resins, alicyclic hydrocarbon resins, aliphatic petroleum resins, aromatic petroleum resins, and alkylphenol formaldehyde resins (oil-based phenol resins).

  The pressure-sensitive adhesive of this embodiment is a coating for forming a pressure-sensitive adhesive layer by dissolving or dispersing an acrylic copolymer (A), a curing agent (B), and other additives in an appropriate solvent. It is preferable to adjust the solid content concentration so that the liquid has an appropriate viscosity.

[Application example]
The pressure-sensitive adhesive of this embodiment is particularly suitable as a pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer for forming surface protective sheets for various members represented by FPDs such as LCD and OELD, and touch panel displays. According to this embodiment, since it is excellent in high-temperature resistance, the pressure-sensitive adhesive sheet used for protecting the member from each manufacturing equipment or conveyance in the manufacturing process, and product protection until the user uses the product after completion of the product It is possible to use the pressure-sensitive adhesive sheet in combination with the same pressure-sensitive adhesive sheet. Since the pressure-sensitive adhesive of this embodiment is an acrylic pressure-sensitive adhesive, it is possible to improve adherend contamination that is a problem with silicone-based pressure-sensitive adhesives. The pressure-sensitive adhesive of this embodiment can be suitably used as a pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer having a thickness of 5 to 15 μm in order to achieve high temperature resistance.

  Examples of the adherend to which the adhesive layer is bonded include SUS (stainless steel), glass, and plastic film. Examples of the plastic film include polymethyl methacrylate (PMMA) and polycarbonate. Also suitable are olefins such as polypropylene and polyethylene.

  In addition, the adhesive of this invention can be applied besides the said use according to a use or the characteristic calculated | required. For example, it can be suitably used as a pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer other than the above film thickness. In the case of a thick film exceeding 15 μm to about 200 μm, a step of removing the monomer is performed at the stage where the acrylic copolymer (A) before forming the pressure-sensitive adhesive is polymerized in order to increase the high temperature resistance more effectively. It is preferable. Although the manufacturing process increases, it can be suitably applied to a thick film adhesive layer.

  General labels and seals, adhesive optical films, paints, elastic wall materials, waterproof coating materials, flooring materials, tackifiers, adhesives, adhesives for laminated structures, sealing agents, molding materials, surface modification Coating agents, binders (magnetic recording media, ink binders, casting binders, fired brick binders, graft materials, microcapsules, glass fiber sizing, etc.), high solid paints, thermosetting elastomers, microcellular, fiber processing agents, sound absorbing materials , Damping materials, surfactants, gel coating agents, resins for artificial marble, impact modifiers for artificial marble, resins for inks, films (laminate adhesives, protective films, etc.), resins for laminated glass, reactive diluents As raw materials for various molding materials, elastic fibers, artificial leather, synthetic leather, etc., and various resin additives and their raw materials It can be used as useful to.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of this embodiment includes a base material and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention. The pressure-sensitive adhesive sheet may be formed with a laminate other than the pressure-sensitive adhesive layer and the substrate. The pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive on a substrate and drying it. Alternatively, it can be formed by applying a pressure-sensitive adhesive on a peelable sheet and drying to form a pressure-sensitive adhesive layer, and then bonding the pressure-sensitive adhesive layer and the substrate together. In applying the pressure-sensitive adhesive, the viscosity described above can be appropriately adjusted by adding the solvent described in the solution polymerization.

  The substrate is preferably, for example, cellophane, plastic, rubber, foam, fabric, rubber-impregnated fabric, resin-impregnated fabric, glass and wood in addition to polyvinyl chloride. The effect of can be demonstrated. The shape of the substrate can be selected from a plate shape and a film shape, but a film shape that is easy to handle is preferable. The substrate can be used alone or in combination of two or more.

  Examples of the plastic include polyolefins such as polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate, polynorbornene , Polyarylate, polyacryl, polyphenylene sulfide, polystyrene, polyamide, and polyimide.

  The method of applying the adhesive is not particularly limited, and examples thereof include Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, and spin coater. It is done. It is preferable to perform a drying process at the time of coating. The drying device is not particularly limited, and examples thereof include a hot air dryer, an infrared heater, and a pressure reduction method. The drying temperature is usually about 60 to 160 ° C. It is preferable that the film thickness after drying of the adhesive layer in the adhesive sheet of this embodiment shall be 5-15 micrometers.

  An adhesive sheet can also be formed in both surfaces other than the aspect formed in the single side | surface of a base material. On the pressure-sensitive adhesive layer, a peelable sheet may be laminated until just before use. As the release sheet, for example, a known release paper or release film obtained by coating a release agent on paper such as high-quality paper or a plastic film can be used. The thickness of the peelable sheet is usually about 10 μm to 200 μm.

  By using the pressure-sensitive adhesive sheet of the present embodiment, in the acrylic pressure-sensitive adhesive, the adhesive residue of the adherend after high temperature aging of about 180 to 260 ° C. can be drastically improved, and high-temperature resistance can be improved. . The contamination of the adherend can be effectively prevented while reducing the cost instead of the silicone-based pressure-sensitive adhesive having high temperature resistance.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the examples, “parts” means “parts by mass”, and “%” means “% by mass”. Moreover, the values other than the solvent are non-volatile content conversion values.

[Measurement of weight average molecular weight (Mw) and oligomer component of acrylic copolymer (A)]
The weight average molecular weight of the acrylic copolymer (A) is Mw in terms of polystyrene determined by gel permeation chromatography (GPC) analysis, and GPC measurement conditions are as follows.
Apparatus: SHIMADZU Prominence (manufactured by Shimadzu Corporation)
Column: three SHODEXLF-804 (manufactured by Showa Denko KK) connected in series,
Detector: differential refractive index detector,
Solvent: tetrahydrofuran (THF),
Flow rate: 0.5 mL / min,
Solvent temperature: 40 ° C.
Sample concentration: 0.1%
Sample injection volume: 100 μL.
Moreover, the oligomer component content rate (%) of the acrylic copolymer (A) is an area of a molecular weight of 1,000 to 20,000 in the differential molecular weight distribution curve in GPC measurement as a ratio to the total area of the molecular weight distribution curve. Asked.

(Synthesis of acrylic copolymer (A))
<Synthesis Example 1>
Using a polymerization apparatus equipped with a stirrer, a thermometer, a dropping tube, and a reflux condenser, 99 parts of 2-ethylhexyl acrylate, 1.0 part of acrylic acid, 100 parts of ethyl acetate, and 0.1 part of AIBN were each in a reaction vessel. The remaining half amount was added dropwise from the dropping tube over 1 hour under reflux in a nitrogen atmosphere, and then further copolymerized for 6 hours. After completion of the reaction, the reaction mixture was cooled to obtain an acrylic copolymer solution having an Mw of 650,000 and a nonvolatile content of 50%.

<Synthesis Examples 2-14>
As shown in Table 1, an acrylic copolymer solution was obtained in the same manner as in Synthesis Example 1 except that the types of monomers, polymerization solvents and additives, the number of parts by mass, and the reaction time were changed.

<Example 1>
Prepare an acrylic copolymer solution described in Synthesis Example 1, add 5 parts of TETRAD-X MEK solution (concentration 5%) as an epoxy curing agent (B) to 100 parts of non-volatile content, and after sufficient stirring The adhesive was obtained. Using a comma coater, the resulting pressure-sensitive adhesive was coated on a 25 μm thick PI film (Kapton 100H: manufactured by Toray DuPont) to a dry thickness of 10 μm, and dried at 120 ° C. for 3 minutes. After that, a 38 μm thick release liner (SP-PET38: manufactured by Mitsui Chemicals, Inc.) was attached to the pressure-sensitive adhesive layer and aged for 7 days at room temperature in this state to obtain a pressure-sensitive adhesive sheet. Moreover, when the area of the oligomer component (molecular weight 1,000 to 20,000) was determined with respect to the total area of the molecular weight distribution curve obtained by GPC analysis, it was 4.5%.

<Examples 2 to 13>
As shown in Table 2, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the types of monomers, solvents, additives, and the like and the number of parts by mass were changed.

<Comparative Example 1>
An acrylic copolymer solution described in Synthesis Example 11 was prepared, and 5 parts of a TETRAD-X MEK solution (concentration 5%) was added as an epoxy curing agent (B) to 100 parts of the non-volatile content. The adhesive was obtained. Using a comma coater, the resulting pressure-sensitive adhesive was coated on a 25 μm thick PI film (Kapton 100H: manufactured by Toray DuPont) to a dry thickness of 10 μm, and dried at 120 ° C. for 3 minutes. After that, a 38 μm thick release liner (SP-PET38: manufactured by Mitsui Chemicals, Inc.) was attached to the pressure-sensitive adhesive layer and aged for 7 days at room temperature in this state to obtain a pressure-sensitive adhesive sheet.

<Comparative Examples 2-5>
As shown in Table 2, a pressure-sensitive adhesive sheet was prepared in the same manner as in Comparative Example 1 except that the acrylic copolymer (A), the epoxy curing agent (B), and the coating film thickness were changed.

About the adhesive sheet of the said Examples 1-13 and Comparative Examples 1-5, adhesive force and heat resistance were evaluated. The results are shown in Table 2. However, Examples 1 and 4 to 12 are read as Reference Examples 1 and 4 to 12.

<Adhesive strength>
The release paper is peeled off from the 10 cm × 25 mm coated product test piece, the pressure-sensitive adhesive layer is pasted on a polished stainless steel (SUS) plate, and after reciprocating with a 2 kg roll, the peel rate is 300 mm / min after 24 hours. The adhesive force was measured under the condition of a peeling angle of 180 °. The unit is N / 25 mm.

<Heat resistance>
After peeling the release paper from the 10 cm × 25 mm coated specimen, sticking the adhesive layer to a polished stainless steel (SUS) plate, press-bonding once with a 2 kg roll, and then letting it stand for 30 seconds at 250 ° C., Left at room temperature for 1 hour. The adhesive force of the sample was measured under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 °, and the appearance was confirmed. The unit of adhesive strength is N / 25 mm. About heat resistance, it represents with the following abbreviations.
S: No adhesive residue and suppression of adhesive strength increase. The increase in adhesive strength ([adhesive strength after aging of SUS plate at 250 ° C. × 30 seconds] − [adhesive strength after aging of SUS plate at normal temperature × 24 hours] (hereinafter the same)) is 0.1 N / 25 mm or less.
A: No increase in adhesive strength and no increase in adhesive strength. Increase in adhesive strength is over 0.1 N / 25 mm and below 0.2 N / 25 mm.
B: There is no adhesive residue and slightly suppresses an increase in adhesive strength. Increase in adhesive strength is over 0.2N / 25mm and below 0.3N / 25mm.
C: No adhesive residue, but slightly increased adhesive strength. Increase in adhesive strength exceeds 0.3 N / 25 mm and 0.4 N / 25 mm or less.
D: No adhesive residue but increased adhesive strength. (Practical is possible) Adhesive strength increase exceeds 0.4 N / 25 mm and 0.5 N / 25 mm or less.
NG1: There is adhesive residue.
NG2: There is peeling.

The meanings of the abbreviations in Tables 1 and 2 are as follows.
BA: Butyl acrylate 2EHA: 2-ethylhexyl acrylate AA: Acrylic acid HEA: 2-Hydroxyethyl acrylate Adekastab AO-40: Phenolic antioxidant manufactured by ADEKA (reshindered type)
ADK STAB AO-80: Phenolic antioxidant manufactured by ADEKA (semi-hindered type)
ADK STAB PEP-36: Phosphite antioxidant manufactured by ADEKA TDI-TMP: Trimethylolpropane adduct of tolylene diisocyanate TETRAD-X: Multifunctional epoxy resin manufactured by Mitsubishi Gas Chemical Company, Inc.

  As shown in Comparative Example 1, the pressure-sensitive adhesive having a weight average molecular weight of less than 600,000 did not have sufficient heat resistance. Moreover, as shown in Comparative Example 2, the adhesive having an oligomer component area exceeding 5% had adhesive residue on the adherend and was contaminated. Moreover, when an isocyanate type hardening | curing agent was used as a hardening | curing agent, as shown in the comparative example 3, the adhesive force raise after a heating was large and generation | occurrence | production of the adhesive residue was confirmed.

  On the other hand, in this example, it was possible to suppress an increase in adhesive strength in a high temperature region (180 to 260 ° C.), to suppress adhesive residue, and to confirm that there was no problem with the adherend appearance after peeling. .

Claims (7)

(Meth) acrylic copolymer (A) having a weight average molecular weight of 6.0 × 10 ^{5 to} 1.00 × 10 ⁶ by gel permeation chromatography analysis;
An epoxy curing agent (B),
Containing an antioxidant (C) including a semi-hindered phenolic antioxidant,
The (meth) acrylic copolymer (A) has a unit derived from a reactive functional group-containing monomer having a functional group capable of crosslinking with the epoxy curing agent (B), and obtained by the gel permeation chromatography analysis. In the obtained molecular weight distribution curve, the pressure-sensitive adhesive in which the content of the oligomer component having a molecular weight of 1,000 to 20,000 is 3.5% or less with respect to the total area of the molecular weight distribution curve. A 10 μm pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive according to claim 1 is attached to a polished stainless steel plate, and after two reciprocating pressures with a 2 kg roll, a peeling speed of 300 mm / min and a peeling angle of 180 ° are obtained 24 hours later. Adhering to the polished stainless steel plate with a 10 μm pressure-sensitive adhesive layer formed using the above-mentioned pressure-sensitive adhesive, the pressure-sensitive adhesive strength measured under the above conditions was 1 reciprocating with a 2 kg roll, and then treated at 250 ° C. for 30 seconds. The pressure-sensitive adhesive according to claim 1, wherein the increase in adhesive strength is 0.3 N / 25 mm or less when measured under conditions of a peeling speed of 300 mm / min and a peeling angle of 180 ° after standing at room temperature for 1 hour.   Furthermore, the adhesive of Claim 1 or 2 containing a polymerization inhibitor (D).   The (meth) acrylic copolymer (A) has 75 to 99 mass% of units derived from a (meth) acrylic acid ester having 8 to 18 carbon atoms in the alkyl group. The adhesive as described.   The pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the (meth) acrylic copolymer (A) has a glass transition temperature of -68 to -40 ° C.   The adhesive sheet containing a base material and the adhesive layer formed from the adhesive in any one of Claims 1-5.   The pressure-sensitive adhesive sheet according to claim 6, wherein the pressure-sensitive adhesive layer is 5 to 15 μm.