JP2011202126A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet that gives out a suppressed amount of gas and is excellent in adhesive force.SOLUTION: The adhesive sheet comprises a supporting base material and, provided on one surface or both surfaces thereof, an adhesive agent layer mainly composed of an acrylic resin, where the outgas amount from the adhesive agent layer is at most 20 ng/cmwhen heated at 120°C for 1 hr.

Description

  The present invention relates to an adhesive sheet used for an electronic member or an optical member.

  Conventionally, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition is formed on one side or both sides of a supporting substrate has been widely used in various fields. In the above-mentioned pressure-sensitive adhesive layer, those that exhibit strong adhesiveness are usually provided with adhesive force by introducing a large amount of acid, but do not use acid due to problems such as corrosion of the adhesive object (acid-free) Many applications are also required. Especially for electronic component applications, not only good adhesiveness, but also the generation of gas that causes malfunctions is suppressed, and the suppression of gas generation does not corrode electronic components and cause poor appearance. There is a need for an adhesive sheet with a layer.

  The information label used for bonding to the electronic member, particularly the precision electronic member, the adhesive for fixing the electronic member, and the adhesive sheet are based on the premise that no foreign matter such as dust is generated, but included in the adhesive. Gases (outgases) derived from low molecular weight components, low boiling point volatile components, polymerization initiators and residual solvents are also a kind of foreign matter, and these cause malfunction of electronic members. That is, since the inside of an electronic device provided with a precise electronic member becomes a high temperature atmosphere when used, it is necessary to keep the amount of gas generated in such an atmosphere low. As a method for reducing the amount of such outgas generation, a method has been proposed in which an acrylic copolymer containing no acidic group is used as an adhesive (see Patent Document 1). In addition, by using an acrylic copolymer that does not contain a carboxyl group, it is possible to achieve low metal adhesion and low outgassing, and a method of exhibiting high adhesive force by copolymerizing a morpholine unsaturated compound. It has been proposed (see Patent Document 2).

JP 2003-268335 A JP 2008-222967 A

  However, a pressure-sensitive adhesive using an acrylic polymer into which a functional group other than an acidic group such as a hydroxyl group as in Patent Document 1 is used is sufficient depending on the application although a low-outgas type pressure-sensitive adhesive sheet can be obtained to some extent. Further, the adhesive strength was insufficient because no acidic group was introduced. In addition, the pressure-sensitive adhesive using an acrylic copolymer that does not contain a carboxyl group as in the above-mentioned Patent Document 2 can reduce the outgas generation amount to some extent. The effect was not yet satisfactory.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a pressure-sensitive adhesive sheet that suppresses the generation of gas and has excellent adhesive strength.

Therefore, the present inventors have conducted extensive studies on the physical properties of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet that causes gas generation for the purpose of preventing various harmful effects caused by gas generation. As a result, when the pressure-sensitive adhesive layer was formed using a pressure-sensitive adhesive mainly composed of an acrylic resin, the amount of outgas from the pressure-sensitive adhesive layer was 20 ng / cm under severe conditions of heating at 120 ° C. for 1 hour. ^{If the} amount is ² or less, the amount of outgas generated is sufficiently suppressed, so that the amount of generated gas is small, and it has been found that various adverse effects caused by outgas can be effectively prevented. Reached.

That is, the gist of the present invention is a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive mainly composed of an acrylic resin on one or both sides of a support base material, and the above-mentioned when heated at 120 ° C. for 1 hour. The amount of outgas from the pressure-sensitive adhesive layer is 20 ng / cm ² or less.

  The pressure-sensitive adhesive layer having such physical properties is, for example, a specific product obtained by polymerizing a copolymer component (a) not containing a compound having an acidic group in the presence of a functional group-containing polymerization initiator (b). When the pressure-sensitive adhesive composition [I] containing the acrylic resin (A) and the crosslinking agent (B) is formed using the pressure-sensitive adhesive crosslinked with the crosslinking agent (B), the amount of outgas generated is effective. Is suppressed. The reason will be described in detail below.

  First, as a result of examining the generation factors of gas generation, (1) In the polymerization reaction of acrylic resin, residual monomers, low molecular weight components generated during the reaction, unreacted polymerization initiators, etc. as volatile components in the adhesive It exists, and this is the cause of gas generation. (2) The knowledge that gas is generated when the acid component in the pressure-sensitive adhesive decomposes other constituents was obtained. As a result of further research on the pressure-sensitive adhesive layer forming material based on such knowledge, when the functional group-containing polymerization initiator (b) is used in the polymerization reaction of the acrylic resin, the generation amount of outgas is suppressed. I found out. That is,

(1) In a normal acrylic resin polymerization reaction, even when a functional group-containing monomer is used as a constituent monomer, a certain amount of functional group-free low molecular weight components are generated. Since this low molecular weight component not containing functional groups does not have a functional group, it cannot react with the cross-linking agent and is not taken into the cross-linking structure of the pressure-sensitive adhesive. There is a case.
In the present invention, for example, when a functional group-containing polymerization initiator is used, a functional group is always introduced into the constituent monomer that has reacted with the polymerization initiator during the polymerization reaction. It contains a functional group.
Therefore, the low molecular weight component having a functional group can react with the cross-linking agent and is taken into the cross-linked structure, so that the residual low molecular weight component after cross-linking can be reduced, and as a result, generation of outgas is suppressed.

(2) In the polymerization reaction of a normal acrylic resin, not all polymerization initiators are used in the polymerization reaction and the polymerization initiator may remain, and this remaining polymerization initiator is used as a volatile component. It may cause outgassing.
In the present invention, for example, when a functional group-containing polymerization initiator is used, the remaining polymerization initiator reacts with the cross-linking agent via the functional group and is taken into the cross-linked structure. It becomes possible to reduce.
In addition, in terms of reactivity with the crosslinking agent, when comparing the functional group of the polymer side chain of the acrylic resin and the functional group of the polymerization initiator, the functional group of the polymerization initiator having a low molecular weight preferentially reacts. It is assumed that most of the remaining polymerization initiator reacts with the crosslinking agent.
Therefore, for example, even when a carboxyl group-containing functional group is used, it is considered that there is almost no adverse effect due to the carboxyl group of the remaining polymerization initiator. Since the amount is very small, the adverse effect is presumed to be small.

  Thus, for example, an acrylic resin (A) obtained by polymerizing a copolymer component (a) not containing a compound having an acidic group in the presence of a functional group-containing polymerization initiator (b), and a crosslinking agent ( When the pressure-sensitive adhesive composition [I] containing B) is used and the pressure-sensitive adhesive composition [I] is formed by using the pressure-sensitive adhesive crosslinked with the crosslinking agent (B), the amount of outgas generated Can be suppressed, and excellent adhesive properties can be obtained.

Thus, the pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive mainly composed of an acrylic resin on one or both sides of a support substrate, and the pressure-sensitive adhesive layer when heated at 120 ° C. for 1 hour. From which the outgas amount is 20 ng / cm ² or less. For this reason, as a result of the suppression of gas generation, it is possible to effectively prevent various adverse effects in various applications, for example, appearance defects due to corrosion of electronic members and the like by suppressing the gas generation.

  And the specific acrylic resin (A) which the said adhesive layer polymerizes the copolymerization component (a) which does not contain the compound which has an acidic group in presence of a functional group containing polymerization initiator (b), and When the pressure-sensitive adhesive composition [I] containing the cross-linking agent (B) is formed by cross-linking with the cross-linking agent (B), the amount of outgas generated is effectively suppressed and excellent pressure-sensitive adhesive properties are imparted. Is done.

  When the acrylic resin (A) has a weight average molecular weight of 100,000 to 2,000,000, an effect of securing general adhesive properties and improving coating workability can be obtained.

The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.

The pressure-sensitive adhesive sheet of the present invention has a configuration in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive mainly composed of an acrylic resin is provided on one side or both sides of a support substrate. And it is an adhesive sheet from which the amount of outgas from the said adhesive layer at the time of heating at 120 degreeC for 1 hour will be 20 ng / cm < ² > or less.

  In the present invention, “main component” means that the acrylic resin is usually 50% by weight or more, preferably with respect to the pressure-sensitive adhesive layer forming material [for example, pressure-sensitive adhesive composition [I] described later]. Means 60% by weight or more, more preferably 70% by weight or more. The upper limit is usually 99.9% by weight.

The measurement condition for the amount of outgas from the pressure-sensitive adhesive layer is to heat at 120 ° C. for 1 hour, but the amount of outgas generated under such high temperature and long time heating conditions is 20 ng / cm ² or less. This is a feature of the present invention. Especially preferably, it is 15 ng / cm < ² > or less, More preferably, it is 10 ng / cm < ² > or less. Of course, the lower limit of the outgas amount is preferably as small as possible. If the amount of generated outgas is too large, for example, when this pressure-sensitive adhesive sheet is used for an electronic member, malfunction may occur, or the electronic member may be corroded to cause poor appearance.

In addition, the amount of outgas in this invention is measured on condition of the following.
[Measurement condition]
An adhesive is applied to one side of a 25 μm thick polyethylene terephthalate (PET) film so that the thickness after drying is 25 μm, and dried by heating at 100 ° C. for 2 minutes to produce an adhesive sheet with an adhesive layer.
The pressure-sensitive adhesive sheet is cut into a size of 20 cm ² , sealed in a vial, and then 1 ml of gas when heated at 120 ° C. for 1 hour is subjected to gas chromatography (GC) measurement.
In addition, qualitative analysis of each peak is performed from head speed method gas chromatography / mass spectrometry measurement (HS-GC / MS).
Next, 1 μl of an acetone solution containing a known concentration of decane is provided, and head space method gas chromatography measurement (HS-GC) is performed in the same manner, thereby creating a calibration curve. Based on the obtained calibration curve, the outgas amount (ng / cm ² ) is determined from each peak of the adhesive headspace gas chromatography measurement (HS-GC).

  Examples of the support substrate include metal foils such as aluminum, copper, and iron; polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer; polyethylene, polypropylene, polymethyl Polyolefin resins such as pentene; Polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluorinated ethylene; Polyamides such as nylon 6, nylon 6, and 6; Polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, Ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, vinyl polymers such as polyvinyl alcohol and vinylon; cellulose resins such as cellulose triacetate and cellophane; polymethyl methacrylate, polymeta Acrylic resins such as ethyl laurate, polyethyl acrylate, and polybutyl acrylate; synthetic resin films or sheets such as polystyrene, polycarbonate, polyarylate, polyimide, paper such as fine paper, glassine paper, glass fiber, natural fiber, A monolayer or a multilayer selected from synthetic fibers and the like can be mentioned.

  The said adhesive layer consists of an adhesive which has acrylic resin as a main component. The adhesive layer is more specifically, for example, a pressure-sensitive adhesive composition [I] containing a specific acrylic resin (A) and a crosslinking agent (B) is crosslinked by the crosslinking agent (B). What is formed.

  The specific acrylic resin (A) does not include a compound having an acidic group, which includes the (meth) acrylic acid alkyl ester monomer (a1) and the monomer (a2) having a functional group other than the acidic group. It can be obtained by using the copolymer component (a) and polymerizing them in the presence of the functional group-containing polymerization initiator (b).

  In the present invention, (meth) acrylic acid is acrylic acid or methacrylic acid, (meth) acryl is acrylic or methacrylic, (meth) acryloyl is acryloyl or methacryloyl, and (meth) acrylate is acrylate or Each means methacrylate.

  As said (meth) acrylic-acid alkylester type | system | group monomer (a1), carbon number of an alkyl group is 1-20 normally, Especially 1-12, Furthermore, 1-8, It is especially 4-8. Specifically, 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, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (Meth) acrylate, isobornyl (meth) ac Rate, and the like. These may be used alone or in combination of two or more.

  Among the above (meth) acrylic acid alkyl ester monomers (a1), n-butyl (meth) acrylate, 2-ethylhexyl (meta) in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials. ) Acrylate is preferably used, and more preferably n-butyl (meth) acrylate is used in terms of excellent heat resistance.

  The content of the (meth) acrylic acid alkyl ester monomer (a1) is preferably 50 to 99.9% by weight, particularly preferably 60 to 99.%, based on the entire copolymer component (a). It is 8% by weight, more preferably 70 to 99.7% by weight, particularly preferably 80 to 99.6% by weight. When the content of the (meth) acrylic acid alkyl ester monomer (a1) is too large, the amount of the monomer having a functional group is decreased, and the cohesive force tends to be insufficient. When the content is too small, the pressure-sensitive adhesive is hard. There is a tendency to become too tacky and lack of tack.

  Examples of the monomer (a2) having a functional group other than the acidic group include a hydroxyl group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a glycidyl group-containing monomer, an acetoacetyl group-containing monomer, and an isocyanate group-containing monomer. It is done. Among these, the functional group other than the acidic group is preferably at least one selected from a hydroxyl group, an amino group, an amide group, and a glycidyl group in terms of reactivity with the crosslinking agent. Among these, a hydroxyl group-containing monomer is preferably used in terms of efficient crosslinking reaction.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( Hydroxyalkyl esters of acrylic acid such as (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, 2- Primary hydroxyl group-containing monomers such as acryloyloxyethyl 2-hydroxyethylphthalic acid and N-methylol (meth) acrylamide; 2-hydroxypropyl (meth) acrylic acid Secondary, such as rate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro 2-hydroxypropyl (meth) acrylate, 2-hydroxy3-phenoxypropyl (meth) acrylate Hydroxyl group-containing monomers: Tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth) acrylate can be mentioned.

  Among the above hydroxyl group-containing monomers, a primary hydroxyl group-containing monomer is preferable in terms of excellent reactivity with a crosslinking agent. Furthermore, it is particularly preferable to use 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl acrylate because there are few impurities such as di (meth) acrylate and the production is easy.

  Examples of the amino group-containing monomer include t-butylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

  Examples of the amide group-containing monomer include acrylamide, methacrylamide, N-methylacrylamide, N, N-dimethylacrylamide, N-methylmethacrylamide, N, N-dimethylmethacrylamide, N-methylolacrylamide, and N-methylolmethacrylate. Examples thereof include amide and diacetone acrylamide.

  Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, allyl glycidyl (meth) acrylate, and the like.

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

Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.
These functional group-containing monomers (a2) may be used alone or in combination of two or more.

  The content of the functional group-containing monomer (a2) is preferably 0.1 to 30% by weight, particularly preferably 0.2 to 20% by weight, more preferably based on the entire copolymerization component (a). Is 0.3 to 10% by weight, particularly preferably 0.4 to 5% by weight. When there is too much content of a functional group containing monomer (a2), there exists a tendency for the glass transition temperature of an adhesive to become high too much and it will become difficult to manufacture, and when too small, there exists a tendency for cohesive force to be insufficient.

  Furthermore, as copolymerization components other than the above (a1) and (a2), phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, ethoxylated o-phenyl (meth) acrylate, phenoxydiethylene glycol ( Aromatic ring-containing monomers such as (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, styrene, α-methylstyrene, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3- Methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meta Acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethyleneglycol-polypropyleneglycol-mono (meth) acrylate, lauroxypolyethyleneglycol mono (meth) acrylate, Ether chain-containing (meth) acrylic ester monomers such as stearoxy polyethylene glycol mono (meth) acrylate, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene , Vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate, dialkyl fumarate Le, allyl alcohol, acrylic chloride, methyl vinyl ketone, N- acrylamidomethyl trimethylammonium chloride, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, can be used (meth) acryloyl morpholine. These may be used alone or in combination of two or more.

  In general, the content of the ethylenically unsaturated monomer is preferably 40% by weight or less based on the entire copolymerization component. More preferably, it is 30% by weight or less. That is, if the content of the ethylenically unsaturated monomer is too large, the pressure-sensitive adhesive may become too hard, and it is difficult to obtain good pressure-sensitive adhesive properties.

  The above-mentioned (a1) and (a2), and further a copolymer component (a) containing an ethylenically unsaturated monomer and not containing a compound having an acidic group are blended at a predetermined ratio, and this is combined with a functional group-containing polymerization. An acrylic resin can be produced by copolymerizing in the presence of the initiator (b) according to various polymerization methods. Examples of the polymerization method include solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization. For example, by mixing or dropping the copolymer component (a) and the functional group-containing polymerization initiator (b) in an organic solvent, and performing a polymerization reaction at reflux or 50 to 98 ° C. for 2 to 20 hours. An acrylic resin can be produced.

  Examples of the functional group-containing polymerization initiator (b) include 4,4′-azobis-4-cyanovaleric acid (ACVA), 2,2′-azobis [N- (2-carboxyethyl) -2-methyl, Carboxyl group-containing polymerization initiators such as propionamide, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis Hydroxyl-containing polymerization such as {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide] Examples thereof include an initiator, an amino group-containing polymerization initiator, and a cyano group-containing polymerization initiator. These may be used alone or in combination of two or more. Of these, carboxyl group-containing polymerization initiators and hydroxyl group-containing polymerization initiators are preferable, carboxyl group-containing polymerization initiators are particularly preferable, and 4,4′-azobis-4-cyano is more preferable from the viewpoint of availability of products. Valeric acid (ACVA) is preferably used. The functional group-containing polymerization initiator (b) is also preferably an azo polymerization initiator from the viewpoint of solubility in a solvent.

  As a compounding quantity of the said functional group containing polymerization initiator (b), it is preferable that it is 0.001-10 weight part with respect to 100 weight part of said copolymerization components (a), Most preferably, it is 0.005. 5 parts by weight, more preferably 0.01 to 3 parts by weight. If the amount of the functional group-containing polymerization initiator (b) is too large, the molecular weight tends to be too low and the cohesive force tends to be insufficient, and if too small, the molecular weight tends to be too high and the production tends to be difficult.

  And the ratio [(b) / (a2)] of the functional group amount of the functional group-containing polymerization initiator (b) to the functional group amount of the monomer (a2) having a functional group other than the acidic group is: It is preferable that (b) / (a2) = 0.0001 to 1 in terms of molar ratio. Especially preferably, it is 0.0005-0.8, More preferably, it is 0.001-0.5. If the molar ratio [(b) / (a2)] is too small outside the above range, the molecular weight of the acrylic resin (A) tends to be too high, and the production tends to be difficult, and the molar ratio [(b) / (A2)] is too large outside the above range, the molecular weight of the acrylic resin (A) tends to be too small and the cohesive force tends to be insufficient.

  Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; esters such as methyl acetate, ethyl acetate and butyl acetate; aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol; acetone, Examples thereof include ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, which can be appropriately selected according to the monomer used. These solvents are used alone or in combination of two or more.

  About the weight average molecular weight of acrylic resin (A) obtained, it is 100,000-2 million normally, Preferably it is 200,000-1,800,000, Most preferably, it is 300,000-1,500,000. If the weight average molecular weight is too small, the cohesive force may be insufficient. If the weight average molecular weight is too large, a large amount of diluent solvent is required, which tends to be undesirable in terms of coating properties and cost.

The weight-average molecular weight of the acrylic resin (A) is a weight-average molecular weight in terms of standard polystyrene molecular weight. High-performance liquid chromatography (manufactured by Waters, Japan, “Waters 2695 (main body)” and “Waters 2414 (detector)”). ), 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 weight Measured by using three series of coalesced, filler particle size: 10 μm).

  The pressure-sensitive adhesive composition [I] is prepared by blending the acrylic resin (A) thus prepared and the crosslinking agent (B), and the pressure-sensitive adhesive is subjected to crosslinking treatment under predetermined conditions such as heating. Used as.

  Examples of the crosslinking agent (B) include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a melamine crosslinking agent, an aldehyde crosslinking agent, an amine crosslinking agent, and a metal chelate crosslinking agent. . Among these, an isocyanate-based crosslinking agent is preferably used from the viewpoint of improving the adhesion with the support substrate and the reactivity with the base polymer.

  Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof And adducts of polyol compounds such as trimethylolpropane, and burettes and isocyanurates of these polyisocyanate compounds.

  Examples of the epoxy crosslinking agent include N, N, N ′, N′-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, 1, 6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, etherene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, Pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycid In addition to ruether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, resorcinating ricidyl ether, bisphenol-S-diglycidyl ether, 2 epoxy groups in the molecule And epoxy resins having at least two.

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

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

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

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

  Examples of the metal chelate-based crosslinking agent include aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium, zirconium, and other multimetallic acetylacetone and acetoacetyl ester coordination compounds. It is done.

  And these crosslinking agents (B) are used individually or in combination of 2 or more types.

  The content of the crosslinking agent (B) is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, particularly preferably 100 parts by weight of the acrylic resin (A). Is 0.1 to 2.5 parts by weight. If the content of the cross-linking agent (B) is too small, the cohesive force tends to be insufficient, and sufficient durability tends to be difficult to obtain. Conversely, if the content of the cross-linking agent (B) is too high, the content is flexible. This is because there is a tendency that the properties and adhesive strength are lowered and it becomes difficult to use for various applications.

  Furthermore, the pressure-sensitive adhesive composition [I] includes an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resin, rosin, rosin ester, and hydrogenated rosin as long as the effects of the present invention are not impaired. Tackifiers such as esters, phenol resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, colorants, fillers, anti-aging agents, UV absorbers Various additives such as functional dyes, and compounds that cause coloration or discoloration upon irradiation with ultraviolet rays or radiation can be blended. In addition to the above additives, a small amount of impurities contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition [I] may be contained. What is necessary is just to set these addition amounts suitably so that the desired physical property may be obtained.

  The pressure-sensitive adhesive sheet of the present invention can be produced, for example, using the pressure-sensitive adhesive composition [I] as follows. First, the pressure-sensitive adhesive composition [I] is applied to one side or both sides of a supporting base so as to have a predetermined thickness, and is crosslinked by heating and drying to form a pressure-sensitive adhesive layer. Next, a pressure-sensitive adhesive sheet can be produced by attaching a release sheet to the pressure-sensitive adhesive layer surface as necessary. In addition, the obtained pressure-sensitive adhesive sheet is subjected to an aging treatment as necessary, and then, when used, the release sheet is peeled from the pressure-sensitive adhesive layer and used. In this way, a pressure-sensitive adhesive sheet is obtained in which a pressure-sensitive adhesive layer is formed on one side or both sides of the support substrate, and a release sheet is provided on the pressure-sensitive adhesive layer surface as necessary.

  As the release sheet, for example, various synthetic resin sheets exemplified for the support substrate, paper, cloth, non-woven fabric and the like can be used.

  In coating the pressure-sensitive adhesive composition [I], the pressure-sensitive adhesive composition [I] is preferably diluted with a solvent and applied, and the dilution concentration is preferably 5 to 75% by weight, particularly preferably. 10 to 60% by weight. The solvent may be any solvent that dissolves the pressure-sensitive adhesive composition [I]. Examples thereof include ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone, methyl ethyl ketone, and methyl isobutyl. A ketone solvent such as ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate, methyl ethyl ketone, and toluene are preferably used from the viewpoints of solubility, drying property, price, and the like.

  Moreover, as a coating method of said adhesive composition [I], if it is a general coating method, it will not specifically limit, For example, roll coating, die coating, gravure coating, comma coating, screen printing etc. Method.

  And as said heat drying conditions, what is necessary is just to be able to dry adhesive composition [I], For example, the conditions for about 1 to 5 minutes are mentioned at 50-150 degreeC.

  The aging treatment is carried out to balance the physical properties of the adhesive. As aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. What is necessary is just to carry out on conditions, such as 1 day-20 days at 40 degreeC, and 1 day-7 days at 40 degreeC.

  Thus, the pressure-sensitive adhesive composition [I] used in the present invention is crosslinked to form a pressure-sensitive adhesive layer.

  In the present invention, the gel fraction of the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition [I] is preferably 20 to 100%, particularly preferably 30 to 99% from the viewpoint of durability. More preferably, it is 40 to 97%, particularly preferably 50 to 95%. If the gel fraction is too low, durability tends to be insufficient due to insufficient cohesive force. If the gel fraction is too high, cohesive force tends to increase too much, and the adhesion tends to be insufficient.

  In adjusting the gel fraction of the pressure-sensitive adhesive layer to the above range, for example, it is achieved by adjusting the type and amount of the crosslinking agent (B), adjusting the composition ratio of the functional groups in the composition, and the like. Is done. Moreover, since the gel fraction changes by each interaction, it is necessary to balance each ratio of the said crosslinking agent (B) and functional group amount.

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

  As for the thickness of the adhesive layer in the adhesive sheet obtained, 5-250 micrometers is preferable normally, More preferably, it is 5-150 micrometers, Most preferably, it is 5-100 micrometers. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive physical properties tend to be difficult to stabilize, and if it is too thick, drying becomes difficult and the amount of outgas tends to increase.

  Thus, although the thickness of the whole adhesive sheet obtained is set suitably according to a use, it is preferable to set to the range of 30-300 micrometers, for example. Moreover, it is preferable to set the thickness of a support base material in the range of 15-125 micrometers.

  When using the pressure-sensitive adhesive sheet of the present invention, as the type of adherend, for example, articles having various metal surfaces; polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate copolymer; Polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; Polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluorinated ethylene; Polyamides such as nylon 6, nylon 6, and 6; Polyvinyl chloride, Polyvinyl chloride / Vinyl acetate copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, vinyl polymers such as polyvinyl alcohol and vinylon; cellulose resins such as cellulose triacetate and cellophane; Methyl Le acid, polyethyl methacrylate, polyethyl acrylate, acrylic resins such as polybutyl acrylate; polystyrene, polycarbonate, polyarylate, synthetic resin films such as polyimide, sheet or plate and the like.

  The article having the metal surface has a metal surface, and the pressure-sensitive adhesive sheet is bonded at least partially (partially or entirely) directly to the metal surface. In an article having such a metal surface, the adherend to which the pressure-sensitive adhesive sheet is bonded (sometimes referred to as a “metal face-containing adherend”) has at least a partial metal face. There is no particular limitation. In such a metal surface-containing adherend, the part where the metal surface is formed is not particularly limited as long as it is a part where the adhesive sheet can be directly attached, and may be an outer surface, Further, it may be an inner surface or the like. When a plurality of metal surfaces are formed on one metal surface-containing adherend, these plurality of metal surfaces may be surfaces formed of the same metal material or formed of different metal materials. It may be a surface.

  The metal surface in the metal surface-containing adherend may be the surface of a metal surface-containing adherend formed of a metal material, or on the surface of a base material (or structure) formed of various materials. It may be the surface of the formed metal layer (in particular, the surface of the metal thin film layer). In any case, the metal surface may be a surface made of a metal material.

  The metal layer such as the metal thin film layer can be formed on a predetermined portion of the surface of the base material (or structure) made of various materials. In such a metal layer, the thickness of the metal thin film layer can be appropriately selected according to the type of the metal surface-containing adherend, and may be, for example, 0.1 μm or more. The upper limit of the thickness of the metal thin film layer is not particularly limited as long as it is generally regarded as a thin film layer.

  The metal material for forming the metal surface is not particularly limited. For example, a metal material made of a single metal such as aluminum, silver, gold, copper, iron, titanium, platinum, or nickel; a gold alloy (for example, gold-copper) Alloy), copper alloy [eg, copper-zinc alloy (brass), copper-aluminum alloy, etc.), aluminum alloy (eg, aluminum-molybdenum alloy, aluminum-tantalum alloy, aluminum-cobalt alloy, aluminum-chromium alloy, aluminum) -Titanium alloys, aluminum-platinum alloys, etc.), nickel alloys (for example, nickel-chromium alloys, copper-nickel alloys, zinc-nickel alloys, etc.), metal materials made of various alloys such as tin alloys and stainless steels. These metal materials can be used alone or in combination of two or more.

  Note that the metal material may be a metal material containing only a metal element, or a metal material containing a non-metal element together with a metal element [for example, metal oxide, hydroxide, halide (chloride, etc.) And metal compounds such as oxo acid salts (nitrate, sulfate, phosphate, carbonate, etc.).

  Specifically, as the metal surface-containing adherend, for example, a window material having a metal surface (such as a metal thin film layer surface) at least partially, a member for constituting the window material, or a metal thin film layer An optical product having an electromagnetic wave shielding layer formed by the above, or a member for constituting the optical product. Examples of the optical product having an electromagnetic wave shielding layer include optical devices such as an electronic display (plasma display), optically recordable discs (optical recording discs) such as digital universal discs, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis unless otherwise specified.

[Example 1]
"Preparation of acrylic resin solution"
A reactor equipped with a thermometer, stirrer, dropping funnel and reflux condenser was charged with 40 parts of ethyl acetate, heated with stirring to 78 ° C., then 88 parts of butyl acrylate (a1), methyl acrylate (a1) 10 parts, a mixture of 0.12 part of 4,4'-azobis-4-cyanovaleric acid (b) (ACVA) as a functional group-containing polymerization initiator in 2 parts of 2-hydroxyethyl acrylate (a2) Added dropwise over 2 hours. Further, during polymerization, polymerization was carried out for 7 hours while successively adding a polymerization catalyst solution in which 0.01 part of ACVA was dissolved in 10 parts of ethyl acetate, and then diluted with ethyl acetate to obtain an acrylic resin [weight average molecular weight (Mw ) 850,000] was prepared. In addition, regarding the measurement of the weight average molecular weight (Mw) of acrylic resin, it measured according to the above-mentioned method.

  Next, 3 parts of 55% isocyanate crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L55E) was added to the acrylic resin solution to prepare an adhesive composition [I].

"Production of adhesive sheet"
A polyethylene terephthalate (PET) film having a thickness of 25 μm (manufactured by Panac Corp., Lumirror T-25) was used as a supporting substrate. On the other hand, a 25 μm-thick polyethylene terephthalate (PET) film (manufactured by Panac, SEPA100) was used as the release sheet. And the said adhesive composition [I] is apply | coated to the single side | surface of the said support base material (PET film) using an applicator so that the thickness after drying may be set to 25 micrometers, and it heat-drys at 100 degreeC for 2 minutes, and bridge | crosslinks. To form an adhesive layer. Subsequently, the adhesive sheet was produced by bonding the release sheet (PET film) to the adhesive layer surface.

[Example 2, Comparative Examples 1-2]
"Adjustment of acrylic resin"
The monomer components (copolymerization components) and polymerization initiators shown in Table 1 below were used in the amounts shown in the same table. Other than that was carried out similarly to Example 1, and produced the 35% solution of acrylic resin. Moreover, the weight average molecular weight (Mw) of each acrylic resin was measured according to the above-mentioned method, and the result is combined with Table 1 mentioned later, and is shown.

  Next, 3 parts of 55% isocyanate crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., Coronate L55E) was added to the acrylic resin solution to prepare an adhesive composition [I].

"Production of adhesive sheet"
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the pressure-sensitive adhesive composition [I].

  Using each pressure-sensitive adhesive sheet thus obtained, the gel fraction was measured according to the following method, and characteristic evaluation (outgas amount, adhesive strength) was performed according to the following method. The results are also shown in Table 1 below.

[Gel fraction]
After cutting each pressure-sensitive adhesive sheet (PET film with pressure-sensitive adhesive layer) to 40 × 40 mm, the release sheet is peeled off and the pressure-sensitive adhesive layer side is bonded to a 50 × 100 mm SUS mesh sheet (200 mesh), The sample was folded from the center with respect to the longitudinal direction of the SUS mesh sheet, wrapped in a sample, and then the gel fraction was measured by weight change when immersed in a sealed container containing 250 g of toluene at 23 ° C. for 24 hours. .

[Outgas amount]
The pressure-sensitive adhesive sheet was cut into a size of 20 cm ² , sealed in a vial, and then 1 ml of gas when heated at 120 ° C. for 1 hour was subjected to gas chromatography (GC) measurement. In addition, the qualitative analysis of each peak was performed from the head space method gas chromatography / mass spectrometry measurement (HS-GC / MS). Next, 1 μl of an acetone solution containing a known concentration of decane was provided, and head space method gas chromatography measurement (HS-GC) was performed in the same manner, thereby preparing a calibration curve. Based on the obtained calibration curve, the outgas amount (ng / cm ² ) was determined from each peak of the headspace method gas chromatography measurement (HS-GC) of each adhesive.

〔Adhesive force〕
Each pressure-sensitive adhesive sheet was cut to prepare a test piece having a size of 25 mm × 120 mm, and then the release sheet was peeled off from the test piece. Subsequently, this was crimped | bonded by the method of making a 2kg roller reciprocate once to the stainless steel plate as a to-be-adhered body. Then, after leaving for 24 hours, 180 ° peeling force at a peeling speed of 0.3 m / min was measured in an atmosphere of 23 ° C. × 50% RH, and this was defined as adhesive strength.

From the above results, the example product in which the outgas amount was suppressed to 20 ng / cm ² or less even under the severe condition of heating at 120 ° C. for 1 hour had an appropriate adhesive force and had a problem. It was not.

On the other hand, the comparative product in which a large amount of gas was generated with an outgas amount exceeding 20 ng / cm ² had no problem in adhesive strength, but a large amount of outgas was generated as described above. At that time, it was a problem.

  The pressure-sensitive adhesive sheet of the present invention is useful for, for example, information labels and electronic member fixing sheets.

Claims (7)

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer mainly composed of an acrylic resin on one side or both sides of a supporting substrate, wherein the amount of outgas from the pressure-sensitive adhesive layer when heated at 120 ° C. for 1 hour is It is 20 ng / cm < ² > or less, The adhesive sheet characterized by the above-mentioned. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition [I] containing the following (A) and (B) with a crosslinking agent (B).
(A) A copolymer component (a) containing the following (a1) and (a2) and not containing a compound having an acidic group is polymerized in the presence of a functional group-containing polymerization initiator (b). Acrylic resin.
(A1) (Meth) acrylic acid alkyl ester monomer.
(A2) A monomer having a functional group other than an acidic group.
(B) Crosslinking agent.   The ratio [(b) / (a2)] of the functional group amount of the functional group-containing polymerization initiator (b) to the functional group amount of the monomer (a2) having a functional group other than an acidic group is in molar ratio. (B) / (a2) = 0.0001 to 1. The pressure-sensitive adhesive sheet according to claim 2.   The pressure-sensitive adhesive sheet according to claim 2 or 3, wherein the acrylic resin (A) has a weight average molecular weight of 100,000 to 2,000,000.   The functional group of the monomer (a2) having a functional group other than the acidic group is at least one selected from the group consisting of a hydroxyl group, an amino group, an amide group, and a glycidyl group. The pressure-sensitive adhesive sheet described in 1.   The pressure-sensitive adhesive sheet according to any one of claims 2 to 5, wherein the functional group contained in the functional group-containing polymerization initiator (b) is a carboxyl group or a hydroxyl group.   The pressure-sensitive adhesive sheet according to any one of claims 2 to 6, wherein the functional group-containing polymerization initiator (b) is an azo polymerization initiator.