JP5738967B2 - Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheets using the same - Google Patents

Description

  The present invention relates to an acrylic pressure-sensitive adhesive composition. More specifically, the present invention relates to an antistatic pressure-sensitive adhesive composition and pressure-sensitive adhesive sheets using the same. In particular, the pressure-sensitive adhesive sheets of the present invention are used for plastic products and the like that are likely to generate static electricity, and in particular, optical plates such as polarizing plates, wave plates, optical compensation films, light diffusion sheets, and reflective sheets used in liquid crystal displays. It is useful as a surface protective film used for the purpose of protecting the member surface.

  In recent years, when optical components and electronic components are transported and mounted on a printed circuit board, the individual components are often transported depending on a state of being wrapped with a predetermined sheet or affixed to an adhesive tape. Among these, surface protective films are particularly widely used in the field of optical and electronic components.

  The surface protective film is generally used for the purpose of sticking to a body to be protected through an adhesive applied to the side of the protective film and preventing scratches and dirt generated during processing and transportation of the body to be protected. For example, a panel of a liquid crystal display is formed by bonding an optical member such as a polarizing plate or a wave plate to a liquid crystal cell via an adhesive.

  For these optical members to be bonded to the liquid crystal cell, a protective film is bonded via an adhesive for the purpose of preventing scratches and dirt. And this protective film peels and is removed in the stage which became unnecessary.

  In general, since the protective film and the optical member are made of a plastic material, they have high electrical insulation, and generate static electricity during friction and peeling. Therefore, static electricity is generated when the protective film is peeled off from the optical member such as a polarizing plate. If voltage is applied to the liquid crystal while the static electricity generated at this time remains, the alignment of the liquid crystal molecules is lost. However, there is a problem that the panel is lost. Furthermore, the presence of static electricity has a problem of sucking dust and debris and causing a sticking problem due to the suction action of the adherend that occurs when sticking the adhesive tape. Therefore, various antistatic treatments are applied to the surface protective film in order to solve the above problems.

  So far, as an attempt to suppress the electrostatic charge described above, a surface protective film (see, for example, Patent Document 1) in which an antistatic layer is provided on one side of a plastic film has been disclosed. However, in such a surface protection film, since the surface protection film itself is subjected to antistatic treatment, the surface protection film side can be prevented from being charged, but cannot be prevented from being charged to the adherend and protected from the adherend. When the film is peeled off, the adherend is charged.

  In addition, a method is disclosed in which a low molecular surfactant is added to the pressure-sensitive adhesive, and the surfactant is transferred from the pressure-sensitive adhesive to the adherend to prevent charging (for example, see Patent Document 2). However, in such a method, the added low-molecular surfactant is likely to bleed on the pressure-sensitive adhesive surface, and there is a concern that the adherend is contaminated when applied to a protective film. Therefore, when the adhesive to which a low molecular surfactant is added is applied to the protective film for an optical member, there is a problem that particularly the optical properties of the optical member are impaired.

  Moreover, the adhesive sheet (for example, refer patent document 3) which made the adhesive layer contain the antistatic agent is disclosed. In such pressure-sensitive adhesive sheets, an antistatic agent comprising a polyether polyol compound and an alkali metal salt is added to the acrylic pressure-sensitive adhesive in order to suppress bleeding of the antistatic agent on the surface of the pressure-sensitive adhesive. However, even if such adhesive sheets are used, the bleed phenomenon such as an antistatic agent is unavoidable. As a result, when it is actually applied to a surface protection film, the bleed phenomenon occurs when the treatment is performed under time or high temperature conditions. Therefore, there is a problem that a phenomenon that the surface protective film partially lifts from the adherend occurs.

  As described above, none of these problems can still be solved in a balanced manner, and in the technical fields related to optical and electronic components, where electrostatic charging and contamination are particularly serious problems, antistatic properties It cannot respond to further improvement requests for surface protection films.

JP 11-256116 A JP-A-9-165460 JP-A-6-128539

  Therefore, the object of the present invention is to prevent the problem of the conventional antistatic pressure-sensitive adhesive sheets, and to prevent the charge to an uncharged adherend when it is peeled off. It is an object to provide an antistatic pressure-sensitive adhesive composition with reduced adhesion and excellent adhesion reliability, and an antistatic pressure-sensitive adhesive sheet using the same.

  In order to achieve the above object, the present inventors have made extensive studies on the monomer component that is the main component of the pressure-sensitive adhesive composition. As a result, the present inventors comprise a (meth) acrylic polymer having an acid value of 1.0 or less. By using the pressure-sensitive adhesive composition, it is possible to prevent the static charge on the non-static adherend when it is peeled off, and the anti-adhesive adhesive with excellent adhesion reliability, with reduced contamination on the adherend. The present inventors have found that an agent composition can be obtained and have completed the present invention.

  That is, the pressure-sensitive adhesive composition of the present invention comprises a (meth) acrylic polymer mainly comprising a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, and an alkali metal salt. The acid value of the (meth) acrylic polymer is 1.0 or less.

  The (meth) acrylic polymer in the present invention refers to an acrylic polymer and / or a methacrylic polymer, and (meth) acrylate refers to an acrylate and / or methacrylate.

  According to the pressure-sensitive adhesive composition of the present invention, as shown in the results of the examples, by using a pressure-sensitive adhesive composition consisting of a (meth) acrylic polymer having an acid value of 1.0 or less, It is possible to prevent electrification of the adherend that is not prevented, to reduce contamination on the adherend, and to have excellent adhesion reliability. Although the details of the reason why the crosslinked product of the pressure-sensitive adhesive composition exhibits such properties are not clear, by using a (meth) acrylic polymer having an acid value of 1.0 or less, a phase with an alkali metal salt is used. It is presumed that it contributes to a well-balanced interaction such as solubility, conductivity, etc., and thus enables good adhesive properties and charging properties to be aligned.

  In the pressure-sensitive adhesive composition of the present invention, a (meth) acrylic polymer having an acid value of 1.0 or less is used. The acid value of the (meth) acrylic polymer in the present invention means the number of mg of potassium hydroxide required to neutralize free fatty acid, resin acid, etc. contained in 1 g of a sample. In the (meth) acrylic polymer skeleton, there are a large number of carboxyl groups and sulfonate groups that have a large interaction with the alkali metal salt, so that ionic conduction is hindered and excellent antistatic ability to the adherend is obtained. It is estimated that there was not. Therefore, in the present invention, it is necessary to use a (meth) acrylic polymer which does not substantially contain an acrylate and / or methacrylate having a carboxyl group and / or a sulfonate group as a structural unit, The acid value must be: In the case of a (meth) acrylic polymer exceeding 1.0, an excellent antistatic ability to the adherend may not be obtained.

  In the present invention, in order to exert an effect as a pressure-sensitive adhesive composition, at least a constituent component is a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, an alkali metal salt, and a vinyl monomer having a functional group. It is what.

  In the present invention, an alkali metal salt is included. By using an alkali metal salt to obtain a compatible and well-balanced interaction with a (meth) acrylic polymer, etc., it is possible to prevent static charge on an uncharged adherend when peeled. It is possible to obtain a pressure-sensitive adhesive composition having excellent adhesion reliability with reduced contamination to the surface.

  Examples of the alkali metal salt used in the above include metal salts composed of lithium, sodium, and potassium, and among them, a particularly high dissociable lithium salt is preferable.

  Moreover, in this invention, the (meth) acrylic-type polymer which further contains the (meth) acrylic-type monomer which has a hydroxyl group as a structural component is used. By using a (meth) acrylic monomer having a hydroxyl group, it becomes easy to control the crosslinking of the pressure-sensitive adhesive composition, and in turn, it becomes easy to control the balance between improvement of wettability by flow and reduction of adhesive strength in peeling. . Further, unlike the above-described carboxyl group or sulfonate group, which can generally act as a crosslinking site, a hydroxyl group can be suitably used in terms of antistatic properties because it has a moderate interaction with an alkali metal salt.

  On the other hand, the pressure-sensitive adhesive layer of the present invention is formed by crosslinking the pressure-sensitive adhesive composition described above. A pressure-sensitive adhesive sheet having more excellent heat resistance can be obtained by appropriately adjusting the structural unit, the structural ratio, the selection of the crosslinking agent, the addition ratio, and the like of the (meth) acrylic polymer.

  The pressure-sensitive adhesive sheet of the present invention is characterized in that a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition described above is formed on a support. According to the pressure-sensitive adhesive sheets of the present invention, since the pressure-sensitive adhesive composition is provided with a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition having the above-described effects, it is possible to prevent charging to an adherend that is not antistatic when peeled. Thus, pressure-sensitive adhesive sheets having excellent adhesion reliability with reduced contamination to the adherend are obtained. For this reason, in particular, it becomes very useful as an antistatic surface protective film in the technical field related to optical and electronic parts, in which electrostatic charging and contamination are particularly serious problems.

  Further, the pressure-sensitive adhesive sheets of the present invention have a 180 ° peel adhesive strength (tensile speed of 10 m / min) at 23 ° C. × 50% HR with respect to a saponified triacetyl cellulose film of 0.1 to 6 N / 25 mm. Is more preferable, 0.2 to 4 N / 25 mm is more preferable, and 0.4 to 3 N / 25 mm is particularly preferable. The saponified triacetyl cellulose film in the present invention means, for example, a film obtained by immersing a triacetyl cellulose film in a 60 ° C. sodium hydroxide aqueous solution (10 wt%) for 1 minute. 180 ° peel adhesive strength refers to peel adhesive strength (N / 25 mm) at 23 ° C. × 50% HR at a tensile speed of 10 m / min. When the peel adhesive strength is less than 0.1 N / 25 mm, the protective tape is easily peeled off from the adherend other than during the peeling step, and the protective function for the adherend is impaired. On the other hand, if the thickness exceeds 6 N / 25 mm, the protective tape is difficult to peel off from the adherend, and the peelability when the protective tape is no longer necessary is inferior. Further, the adherend is damaged by the peeling process. It is not preferable.

  When the pressure-sensitive adhesive composition of the present invention is applied to a protective film, an acrylate having an alkyl group having 4 or more carbon atoms is preferably used as a main component. By using an acrylate having an alkyl group having 4 or more carbon atoms as a main component, a 180 ° peel adhesive strength (tensile speed of 10 m / min) at 23 ° C. × 50% HR to a saponified triacetyl cellulose film is 0. It becomes easy to adjust so that it may become 1-6N / 25mm.

  Furthermore, when the pressure-sensitive adhesive composition of the present invention is applied to a surface protective film, the plastic substrate used for the protective film is more preferably subjected to antistatic treatment. By subjecting the plastic substrate to an antistatic treatment, it is possible to more effectively reduce the stripping voltage on the adherend, and further to obtain an excellent antistatic ability. Examples of the antistatic treatment include a method of applying an antistatic resin or a conductive polymer composed of an antistatic agent and a resin component, a conductive resin containing a conductive substance, a method of depositing or plating a conductive substance, etc. Can be given.

  In the present invention, by selecting and using the (meth) acrylic polymer having an acid value of 1.0 or less as described above, an acrylic pressure-sensitive adhesive composition that conventionally has a polyether polyol compound as an essential component (for example, , See Patent Document 3). Furthermore, in the pressure-sensitive adhesive composition of the present invention, since there is no need to use a polyether polyol compound, there is no problem that the surface protective film partially floats due to the bleeding phenomenon caused by such components as described above. Excellent adhesion reliability is exhibited even when treatment is performed over time or under high temperature conditions.

Schematic configuration diagram of potential measurement unit used for measurement of peeling voltage in Examples etc.

  Hereinafter, embodiments of the present invention will be described in detail.

  The pressure-sensitive adhesive composition of the present invention comprises a (meth) acrylic monomer having a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms as a main component (that is, a component having the highest content among resin structural units). In the pressure-sensitive adhesive composition containing a polymer and an alkali metal salt, the acid value of the (meth) acrylic polymer is 1.0 or less.

  The (meth) acrylic polymer used in the present invention is not particularly limited as long as it is a (meth) acrylic polymer having adhesive properties corresponding to those described above.

  Although the (meth) acrylic-type monomer which has a C1-C14 alkyl group in this invention is used, the (meth) acrylic-type monomer which has a C4-C14 alkyl group is preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate and the like can be mentioned, among which n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate and the like are preferably used.

  Other polymerizable monomers other than the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms include a polymerizable monomer for adjusting the glass transition point and peelability of the (meth) acrylic polymer. It can be used within a range not impairing the effects of the present invention. These monomers may be used alone or in combination, but the total content is preferably 0 to 50% by weight in the monomer component of the (meth) acrylic monomer.

  Other polymerizable monomers used in the (meth) acrylic polymer can be used without particular limitation as long as they are components other than acrylate and / or methacrylate having a carboxyl group or a sulfonate group. Among them, acrylates and / or methacrylates having a hydroxyl group are more preferably used because crosslinking can be easily controlled.

  The (meth) acrylic polymer in the present invention uses a (meth) acrylic polymer having an acid value of 1.0 or less, preferably 0.8 or less, and more preferably 0.6 or less. preferable. Specifically, for example, an acrylic polymer obtained by copolymerizing 2-ethylhexyl acrylate and acrylic acid as an acrylic polymer having a carboxyl group is exemplified. In this case, the total amount of 2-ethylhexyl acrylate and acrylic acid is 100 parts by weight. On the other hand, acrylic acid is 0.13 parts by weight or less.

  In the present invention, a (meth) acrylic monomer having a hydroxyl group can be used. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( (Meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, vinyl alcohol, allyl alcohol 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like.

  In the case where the (meth) acrylic monomer having a hydroxyl group described above is included, the (meth) acrylic monomer having a hydroxyl group is 0.5 to 10 with respect to 100 parts by weight of all the structural units of the (meth) acrylic polymer. It is preferable that it is a weight part, and it is more preferable that it is 1-8 weight part.

  Furthermore, in the present invention, as an optional component other than the above hydroxyl group-containing monomer, it has a cohesive strength and heat resistance improving ability such as cyano group-containing monomers such as acrylonitrile, vinyl esters such as vinyl acetate, and aromatic vinyl compounds such as styrene. Monomers, amide group-containing monomers such as acrylamide and diethylacrylamide, amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, glycidyl (meth) acrylate, Monomers having a functional group that functions as an adhesive strength improvement or a crosslinking base, such as epoxy group-containing monomers such as allyl glycidyl ether, vinyl ethers such as N-acryloylmorpholine and vinyl ethyl ether, can be used as appropriate. These compounds may be used alone or in combination of two or more.

  The (meth) acrylic polymer used in the present invention has a weight average molecular weight of 100,000 to 5,000,000, preferably 200,000 to 4,000,000, more preferably 300,000 to 3,000,000. When the weight average molecular weight is less than 100,000, the adhesive strength at the time of peeling increases due to the improvement of wettability to the polarizing plate, which may cause damage to the polarizing plate in the peeling process. There is a tendency for adhesive residue to occur due to the reduced cohesive force. On the other hand, when the weight average molecular weight exceeds 5,000,000, the fluidity of the polymer decreases and the wettability to the polarizing plate becomes insufficient, and the swelling generated between the polarizing plate and the pressure-sensitive adhesive composition layer of the surface protective film is reduced. There is a tendency to cause. A weight average molecular weight means what was obtained by measuring by GPC (gel permeation chromatography).

  The glass transition temperature (Tg) of the (meth) acrylic polymer is 0 ° C. or lower, preferably −10 ° C. or lower. When the glass transition temperature is higher than 0 ° C., the polymer is difficult to flow and the wetting to the polarizing plate is insufficient, and there is a tendency to cause blisters generated between the polarizing plate and the pressure-sensitive adhesive composition layer of the surface protective film. is there. In addition, the glass transition temperature (Tg) of a (meth) acrylic-type polymer can be adjusted in the said range by changing the monomer component and composition ratio to be used suitably.

  The polymerization method of the (meth) acrylic polymer used in the present invention is not particularly limited, and it can be polymerized by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization or the like. In addition, the obtained copolymer may be any of a random copolymer, a block copolymer, and the like.

Examples of the alkali metal salt used in the present invention include a metal salt composed of lithium, sodium, and potassium. Specifically, a cation composed of Li ⁺ , Na ⁺ , K ⁺ , and a Cl ⁻ , Br ⁻ , I ⁻ , A metal salt composed of an anion composed of BF ₄ ⁻ , PF ₆ ⁻ , SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₃ C ⁻ Preferably used. Among these, lithium salts such as LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (CF ₃ SO ₂ ) ₃ C are preferably used. These alkali metal salts may be used alone or in combination of two or more.

  About the compounding quantity of the alkali metal salt used in the said adhesive composition, it is preferable to mix | blend 0.01-5 weight part of alkali metal salt with respect to 100 weight part of (meth) acrylic-type polymers, 0.05 It is more preferable to add ~ 3 parts by weight. If the amount is less than 0.01 parts by weight, sufficient charging characteristics may not be obtained. On the other hand, if the amount is more than 5 parts by weight, contamination of the adherend tends to increase, such being undesirable.

  As the crosslinking agent used in the present invention, an isocyanate compound, an epoxy compound, a melamine resin, an aziridine derivative, a metal chelate compound, and the like are used. Of these, isocyanate compounds and epoxy compounds are particularly preferably used mainly from the viewpoint of obtaining an appropriate cohesive force. These compounds may be used alone or in combination of two or more.

  Examples of the isocyanate compound include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate, alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate, and 2,4-tolylene diisocyanate. , 4,4′-diphenylmethane diisocyanate, aromatic isocyanates such as xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane / hexa Methylene diisocyanate trimer adduct (trade name Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), Isocyanine of hexamethylene diisocyanate Over door body (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) and isocyanate adducts and the like. These compounds may be used alone or in combination of two or more.

  Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine (trade name: TETRAD-X, manufactured by Mitsubishi Gas Chemical Company), and 1,3-bis (N, N-dioxy). And glycidylaminomethyl) cyclohexane (trade name: TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.). These compounds may be used alone or in combination of two or more.

  Examples of the melamine resin include hexamethylol melamine. Examples of the aziridine derivative include a commercially available product name HDU (manufactured by Mutual Pharmaceutical Company), a product name TAZM (manufactured by Mutual Pharmaceutical Company), and a product name TAZO (manufactured by Mutual Pharmaceutical Company). These compounds may be used alone or in combination of two or more.

  Examples of the metal chelate compound include aluminum, iron, tin, titanium, and nickel as metal components, and acetylene, methyl acetoacetate, and ethyl lactate as chelate components. These compounds may be used alone or in combination of two or more.

  The content of the crosslinking agent used in the present invention is preferably 0.01 to 15 parts by weight with respect to 100 parts by weight of the (meth) acrylic (co) polymer, and 0.5 to 10 parts by weight. More preferably it is contained. When the content is less than 0.01 part by weight, the crosslinking formation by the crosslinking agent becomes insufficient, the cohesive force of the pressure-sensitive adhesive composition becomes small, and sufficient heat resistance may not be obtained, and the adhesive residue There is a tendency to cause. On the other hand, when the content exceeds 15 parts by weight, the cohesive force of the polymer is large, the fluidity is lowered, the wettability to the polarizing plate becomes insufficient, and it occurs between the polarizing plate and the pressure-sensitive adhesive composition layer. There is a tendency to cause dandruff. These crosslinking agents may be used alone or in combination of two or more.

  In the present invention, a polyfunctional monomer having two or more radiation-reactive unsaturated bonds can be added as a crosslinking agent. In such a case, the pressure-sensitive adhesive composition is crosslinked by irradiating with radiation or the like. As a polyfunctional monomer having two or more radiation-reactive unsaturated bonds in one molecule, for example, it can be crosslinked (cured) by irradiation with radiation such as vinyl group, acryloyl group, methacryloyl group, vinylbenzyl group. Examples thereof include polyfunctional monomers having two or more radiation reactivity of one kind or two or more kinds. As the polyfunctional monomer, generally, those having 10 or less radiation-reactive unsaturated bonds are preferably used. These compounds may be used alone or in combination of two or more.

  Specific examples of the polyfunctional monomer include, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 1,6 hexane. Examples thereof include diol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, divinylbenzene, N, N′-methylenebisacrylamide and the like.

  The amount of the polyfunctional monomer used is appropriately selected depending on the balance with the (meth) acrylic polymer to be crosslinked, and further depending on the intended use as the pressure-sensitive adhesive sheet. In general, in order to obtain sufficient heat resistance by the cohesive force of the acrylic pressure-sensitive adhesive, it is preferably blended at 0.1 to 30 parts by weight with respect to 100 parts by weight of the (meth) acrylic polymer. Moreover, it is more preferable to mix | blend at 10 weight part or less with respect to 100 weight part of (meth) acrylic-type polymers from the point of a softness | flexibility and adhesiveness.

  Examples of the radiation include ultraviolet rays, laser rays, α rays, β rays, γ rays, X rays, electron rays, and the like, and ultraviolet rays are preferably used from the viewpoints of controllability, good handleability, and cost. More preferably, ultraviolet rays having a wavelength of 200 to 400 nm are used. Ultraviolet rays can be irradiated using an appropriate light source such as a high-pressure mercury lamp, a microwave excitation lamp, or a chemical lamp. In addition, when using an ultraviolet-ray as a radiation, a photoinitiator is added to an acrylic adhesive.

  The photopolymerization initiator may be any substance that generates radicals or cations by irradiating ultraviolet rays having an appropriate wavelength that can trigger the polymerization reaction according to the type of the radiation-reactive component.

  As radical photopolymerization initiators, for example, benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, methyl o-benzoylbenzoate-p-benzoin ethyl ether, benzoin isopropyl ether, α-methylbenzoin, benzyldimethyl ketal, trichloro Acetophenones such as acetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4′-isopropyl-2-methylpropiophenone, etc. Propiophenones, benzophenone, methylbenzophenone, p-chlorobenzophenone, benzophenones such as p-dimethylaminobenzophenone, 2-chlorothioxanthone, 2-ethylthio Thioxanthones such as xanthone and 2-isopropylthioxanthone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)- Examples include acylphosphine oxides such as (ethoxy) -phenylphosphine oxide, benzyl, dibenzosuberone, α-acyloxime ester, and the like. These compounds may be used alone or in combination of two or more.

  Examples of the cationic photopolymerization initiator include onium salts such as aromatic diazonium salts, aromatic iodonium salts, and aromatic sulfonium salts, organometallic complexes such as iron-allene complexes, titanocene complexes, and arylsilanol-aluminum complexes, nitro Examples thereof include benzyl ester, sulfonic acid derivative, phosphoric acid ester, phosphoric acid ester, phenol sulfonic acid ester, diazonaphthoquinone, and N-hydroxyimide sulfonate. These compounds may be used alone or in combination of two or more. The photopolymerization initiator is usually added in an amount of 0.1 to 10 parts by weight and preferably 0.2 to 7 parts by weight with respect to 100 parts by weight of the acrylic polymer.

  It is also possible to use a photoinitiated polymerization aid such as amines in combination. Examples of the photoinitiator include 2-dimethylaminoethylbenzoate, dimethylaminoacetophenone, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid isoamyl ester, and the like. These compounds may be used alone or in combination of two or more. It is preferable to mix | blend 0.05-10 weight part with respect to 100 weight part of (meth) acrylic-type polymers, and, as for a polymerization start adjuvant, it is more preferable to mix | blend in the range of 0.1-7 weight part.

  The pressure-sensitive adhesive composition of the present invention may contain other additives. For example, a filler, a colorant, a pigment, a surfactant, a plasticizer, a tackifier, a low molecular weight polymer and the like are appropriately used. Can be used.

  On the other hand, the pressure-sensitive adhesive layer of the present invention is obtained by crosslinking the pressure-sensitive adhesive composition as described above. Moreover, the surface protective film of this invention forms this adhesive layer on a support body. At that time, the pressure-sensitive adhesive composition is generally crosslinked after application of the pressure-sensitive adhesive composition, but the pressure-sensitive adhesive layer comprising the crosslinked pressure-sensitive adhesive composition can be transferred to a support film or the like. is there.

In the case where a photopolymerization initiator as an optional component is added as described above, the pressure-sensitive adhesive composition is applied directly on the object to be protected, or after being applied to one or both sides of the support substrate, An adhesive layer can be obtained by light irradiation. Usually, the pressure-sensitive adhesive layer is obtained by irradiating ultraviolet rays having an illuminance of 1 to 200 mW / cm ² at a wavelength of 300 to 400 nm and photopolymerizing them with a light amount of about 400 to 4000 mJ / cm ² .

  The method for forming the pressure-sensitive adhesive layer on the film is not particularly limited. For example, the pressure-sensitive adhesive composition is applied to a support film, and the polymerization solvent is dried and formed to form the pressure-sensitive adhesive layer on the support film. Produced. Thereafter, curing may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction. In addition, when a pressure-sensitive adhesive composition is applied on a support film to produce a surface protective film, one or more solvents other than the polymerization solvent are newly added to the composition so that the surface protective film can be uniformly applied on the support film. May be added.

  Furthermore, the adhesive used in the protective film of the present invention includes various conventionally known tackifiers and surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, ultraviolet absorbers, polymerization inhibitors, A silane coupling agent, an inorganic or organic filler, a powder such as a metal powder or a pigment, a conventionally known various additives such as particles and foils can be appropriately added depending on the use.

  The pressure-sensitive adhesive sheets of the present invention are variously made of a plastic film such as a polyester film or a porous material such as paper or nonwoven fabric so that the thickness of the pressure-sensitive adhesive is usually 3 to 100 μm, preferably about 5 to 50 μm. It is applied and formed on one side or both sides of the support to form a sheet or tape.

  The support constituting the surface protective film is preferably a resin film having heat resistance and solvent resistance and flexibility. When the support has flexibility, the pressure-sensitive adhesive composition can be applied by a roll coater or the like, and can be wound into a roll.

  Examples of the resin forming the support film as the support include polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, polyfluoroethylene, and other fluorine-containing resins, nylon, and cellulose. be able to.

  In addition, in order to improve the adhesiveness between an adhesive layer and a support film, you may perform corona treatment etc. on the surface of a support film. Moreover, you may perform a back surface process to a support film.

  The present invention is useful for various surface protective films, masking tapes, re-peelable labels and the like because the resulting pressure-sensitive adhesive layer can be easily peeled at high speed and has excellent wettability. In particular, the surface protective film of the present invention is useful as a surface protective film for an optical member such as a polarizing plate, and in particular, excellent wettability due to flow and excellent resistance to an optical member whose surface is subjected to anti-glare treatment. High speed peelability becomes effective.

  Particularly in the case of a surface protective film, a plastic substrate is used as a support. The plastic substrate is not particularly limited as long as it can be formed into a sheet shape or a film shape. For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene Polyolefin films such as propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer, polyethylene terephthalate, polyethylene naphthalate, poly Polyester film such as butylene terephthalate, polyacrylate film, polystyrene film, nylon 6, nylon 6,6, polyamide film such as partially aromatic polyamide, polyvinyl chloride film, polyvinylidene chloride film, polycarbonate Such as ball titanate film, and the like.

  The thickness of the film is usually about 5 to 200 μm, preferably about 10 to 100 μm. The adhesive layer bonding surface of the film may be appropriately treated with a release agent such as a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, silica powder, or the like.

  In the saponification treatment of the film or the like in the present invention, a known method can be appropriately used as a saponification treatment method.

  On one side of the plastic base, if necessary, release with silicone, fluorine, long chain alkyl or fatty acid amide, release with silica powder, antifouling treatment, acid treatment, alkali treatment, primer Easy adhesion treatment such as treatment, corona treatment, plasma treatment, and ultraviolet treatment can also be performed.

  The pressure-sensitive adhesive sheets of the present invention are obtained by applying the pressure-sensitive adhesive to a plastic substrate so that the thickness is usually 3 to 100 μm, preferably about 5 to 50 μm. As a method for coating and forming an adhesive, a known method used for the production of an adhesive tape is used. Specifically, for example, a roll coat, a gravure coat, a reverse coat, a roll brush, a spray coat, an air knife coat method, etc. can give.

  In the pressure-sensitive adhesive sheets of the present invention, a separator can be bonded to the pressure-sensitive adhesive surface for the purpose of protecting the pressure-sensitive adhesive surface as necessary. As a base material constituting the separator, there are paper and plastic film, but a plastic film is preferably used from the viewpoint of excellent surface smoothness. The film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer. Examples thereof include a coalesced film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

  In addition, the plastic substrate used in the present invention is more preferably an antistatic treatment. The antistatic treatment applied to the plastic substrate is not particularly limited, but there are a method of providing an antistatic layer on at least one side of a commonly used substrate and a method of kneading a type antistatic agent into a plastic substrate. Used. As a method of providing an antistatic layer on at least one surface of a base material, a method of applying an antistatic resin or a conductive polymer composed of an antistatic agent and a resin component, a conductive resin containing a conductive substance, or a conductive substance is used. Examples of the method include vapor deposition or plating.

  Antistatic agents contained in the antistatic resin include cationic antistatic agents having cationic functional groups such as quaternary ammonium salts, pyridinium salts, primary, secondary and tertiary amino groups, and sulfonic acids Anionic antistatic agents having an anionic functional group such as salts, sulfate esters, phosphonates and phosphate esters, alkylbetaines and derivatives thereof, imidazolines and derivatives thereof, and amphoteric antistatic agents such as alanine and derivatives thereof , Nonionic antistatic agents such as amino alcohol and derivatives thereof, glycerin and derivatives thereof, polyethylene glycol and derivatives thereof, and monomers having the above-mentioned cationic, anionic and zwitterionic ion conductive groups Or the ion conductive polymer obtained by copolymerization is mention | raise | lifted. These compounds may be used alone or in combination of two or more.

  As a cationic type antistatic agent, for example, it has a quaternary ammonium group such as alkyltrimethylammonium salt, acyloylamidopropyltrimethylammonium methosulfate, alkylbenzylmethylammonium salt, acylcholine chloride, polydimethylaminoethyl methacrylate (meth) Examples thereof include acrylate copolymers, styrene copolymers having quaternary ammonium groups such as polyvinylbenzyltrimethylammonium chloride, and diallylamine copolymers having quaternary ammonium groups such as polydiallyldimethylammonium chloride. These compounds may be used alone or in combination of two or more.

  Examples of the anionic antistatic agent include alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate ester salt, alkyl ethoxy sulfate ester salt, alkyl phosphate ester salt, and sulfonic acid group-containing styrene copolymer. These compounds may be used alone or in combination of two or more.

  Examples of zwitterionic antistatic agents include alkylbetaines, alkylimidazolium betaines, and carbobetaine graft copolymers. These compounds may be used alone or in combination of two or more.

  Nonionic antistatic agents include, for example, fatty acid alkylolamide, di (2-hydroxyethyl) alkylamine, polyoxyethylene alkylamine, fatty acid glycerin ester, polyoxyethylene glycol fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid Examples thereof include esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl ethers, polyethylene glycols, polyoxyethylene diamines, copolymers composed of polyethers, polyesters and polyamides, and methoxypolyethylene glycol (meth) acrylates. These compounds may be used alone or in combination of two or more.

  Examples of the conductive polymer include polyaniline, polypyrrole, polythiophene and the like.

  Examples of the conductive material include tin oxide, antimony oxide, indium oxide, cadmium oxide, titanium oxide, zinc oxide, indium, tin, antimony, gold, silver, copper, aluminum, nickel, chromium, titanium, iron, cobalt, Examples include copper iodide, and alloys or mixtures thereof.

  As the resin component used for the antistatic resin and the conductive resin, general-purpose resins such as polyester, acrylic, polyvinyl, urethane, melamine, and epoxy are used. In the case of a polymer type antistatic agent, it is not necessary to contain a resin component. Further, the antistatic resin component can contain a methylol- or alkylol-containing melamine-based, urea-based, glyoxal-based, acrylamide-based compound, epoxy compound, or isocyanate-based compound as a crosslinking agent.

  The antistatic layer can be formed by, for example, diluting the antistatic resin, conductive polymer, or conductive resin with a solvent such as an organic solvent or water, and applying and drying the coating liquid on a plastic substrate. It is formed.

  Examples of the organic solvent used for forming the antistatic layer include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol, n-propanol, and isopropanol. can give. These solvents may be used alone or in combination of two or more.

  As a coating method in forming the antistatic layer, a known coating method is appropriately used. Specifically, for example, roll coating, gravure coating, reverse coating, roll brush, spray coating, air knife coating, impregnation and curtain coating are used. The law is raised.

  The thickness of the antistatic resin layer, the conductive polymer, and the conductive resin is usually about 0.01 to 5 μm, preferably about 0.03 to 1 μm.

  Examples of the method for depositing or plating the conductive material include vacuum deposition, sputtering, ion plating, chemical vapor deposition, spray pyrolysis, chemical plating, and electroplating.

  The thickness of the conductive material layer is usually 20 to 10,000 mm, preferably 50 to 5000 mm.

  As the kneading type antistatic agent, the above antistatic agent is appropriately used. The compounding amount of the kneading type antistatic agent is 20% by weight or less, preferably 0.05 to 10% by weight based on the total weight of the plastic substrate. The kneading method is not particularly limited as long as the antistatic agent can be uniformly mixed with the resin used for the plastic substrate. For example, a heating roll, a Banbury mixer, a pressure kneader, a biaxial kneader, or the like can be used. Used.

  The pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet using the present invention are used particularly for plastic products and the like that are likely to generate static electricity, and in particular, polarizing plates, wave plates, optical compensation films, light used for liquid crystal displays and the like. It can be used as a surface protective film used for the purpose of protecting the surface of an optical member such as a diffusion sheet or a reflection sheet.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described, but the present invention is not limited to these. In addition, the evaluation item in an Example etc. measured as follows.

<Measurement of weight average molecular weight of acrylic polymer>
The weight average molecular weight of the produced polymer was measured by GPC (gel permeation chromatography).

Device: HLC-8220GPC, manufactured by Tosoh Corporation
column:
Sample column: manufactured by Tosoh Corporation, TSK guard column Super HZ-H (1) + TSK gel Super HZM-H (2)
Reference column; manufactured by Tosoh Corporation, TSKgel Super H-RC (1)
Flow rate: 0.6ml / min
Injection volume: 10 μl
Column temperature: 40 ° C
Eluent: THF
Injection sample concentration: 0.2% by weight
Detector: differential refractometer The weight average molecular weight was calculated in terms of polystyrene.

<Measurement of glass transition temperature (Tg)>
The glass transition temperature Tg (° C.) was determined by the following formula using the following literature values as the glass transition temperature Tg _n (° C.) of the homopolymer of each monomer.

Formula: 1 / (Tg + 273) = Σ [W _n / (Tg _n +273)] (where Tg (° C.) is the glass transition temperature of the copolymer, W _n (−) is the weight fraction of each monomer, Tg _n (° C.) represents the glass transition temperature of the homopolymer of each monomer, and n represents the type of each monomer.)
2-ethylhexyl acrylate: -70 ° C
2-hydroxyethyl acrylate: -15 ° C
Butyl acrylate: -55 ° C
Acrylic acid: 106 ° C

  In addition, as a reference value, “Synthesis / design of acrylic resin and development of new application” (published by Central Management Development Center Publishing Department) was referred.

<Measurement of acid value>
The acid value was measured using an automatic titration device (COM-550, manufactured by Hiranuma Sangyo Co., Ltd.) and obtained from the following formula.

A = {(Y−X) × f × 5.611} / M
A: Acid value Y: Titration volume of sample solution (ml)
X: Titration volume of a solution containing only 50 g of mixed solvent (ml)
f: Factor of titration solution M: Weight of polymer sample (g)
The measurement conditions are as follows.

  Sample solution: About 0.5 g of a polymer sample was dissolved in 50 g of a mixed solvent (weight ratio: toluene / 2-propanol / distilled water = 50 / 49.5 / 0.5) to obtain a sample solution.

Titration solution: 2-propanol potassium hydroxide solution (0.1N, manufactured by Wako Pure Chemical Industries, Ltd., for petroleum product neutralization value test)
Electrode: Glass electrode; GE-101, Comparative electrode; RE-201
Measurement mode: Petroleum product neutralization number test 1

<Measurement of peeling band voltage of polarizing plate>
A protective film is cut to a size of 70 mm in width and 130 mm in length, the separator is peeled off, and then a polarizing plate (manufactured by Nitto Denko Co., Ltd.) bonded to an acrylic plate having a thickness of 1 mm, a width of 70 mm, and a length of 100 mm that has been previously neutralized. SEG1425EWVAGS2B, size: width 70 mm, length 100 mm) The surface was crimped with a hand roller so that one end of the surface protruded 30 mm. After being left for one day in an environment of 23 ° C. × 50% RH, a sample was set at a predetermined position as shown below. One end protruding 30 mm was fixed to an automatic winder and peeled so that the peeling angle was 150 ° and the peeling speed was 3 m / min. The potential of the polarizing plate surface generated at this time was measured with a potential measuring device (KSD-0103, manufactured by Kasuga Denki Co., Ltd.) fixed at a predetermined position. The measurement was performed in an environment of 23 ° C. × 50% RH.

<Evaluation of occurrence of floating>
After a sample obtained by laminating a pressure-sensitive adhesive sheet on a polarizing plate (manufactured by Nitto Denko Corporation, SEG1425EWVAGS2B) at a pressure of 0.25 MPa is cut to a size of 30 mm in width and 30 mm in length, and the separator bonded to the polarizing plate side is peeled off An evaluation sample was prepared by pressure bonding with a hand roller to a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., water edge polish) having a thickness of 1.3 mm, a width of 65 mm, and a length of 165 mm. The evaluation sample was allowed to stand in an environment of 23 ° C. for one day, and then autoclaved for 40 minutes in an environment of 50 ° C. × 5 atm. Then, after standing for 2 hours in an environment of 80 ° C., it was visually confirmed whether or not the pressure-sensitive adhesive sheet was lifted from the polarizing plate.

If no floating is observed: ○
When floating is observed: ×

<Measurement of adhesive strength>
A 90 μm-thick triacetyl cellulose film (Fuji Photo Film, Fujitac) was cut to a width of 70 mm and a length of 100 mm, immersed in a 60 ° C. aqueous sodium hydroxide solution (10% by weight) for 1 minute, and then with distilled water. Washed to prepare an adherend. The above adherend was allowed to stand for 1 day in an environment of 23 ° C. × 50% RH, and then an adhesive sheet cut to a size of 25 mm in width and 100 mm in length was laminated at a pressure of 0.25 MPa to prepare an evaluation sample. After standing for 30 minutes after lamination, the adhesive strength when peeled at a peeling speed of 10 m / min peeling angle of 180 ° was measured with a universal tensile tester. The measurement was performed in an environment of 23 ° C. × 50% RH.

<Preparation of (meth) acrylic polymer>
[Acrylic polymer (A)]
200 parts by weight of 2-ethylhexyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, and 2,2′-azobisiso as a polymerization initiator in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser Charge 0.4% by weight of butyronitrile and 312 parts by weight of ethyl acetate, introduce nitrogen gas while gently stirring, and perform a polymerization reaction for about 6 hours while maintaining the liquid temperature in the flask at around 65 ° C. A polymer (A) solution (40% by weight) was prepared. The acrylic polymer (A) had a weight average molecular weight of 500,000, a glass transition temperature (Tg) of −68 ° C., and an acid value of 0.0.

[Acrylic polymer (B)]
200 parts by weight of butyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, and 2,2′-azobisisobutyroyl as a polymerization initiator in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser 0.4 parts by weight of nitrile and 625 parts by weight of ethyl acetate were added, nitrogen gas was introduced while gently stirring, and the polymerization temperature was kept at around 65 ° C. for about 6 hours to carry out a polymerization reaction. B) A solution (25% by weight) was prepared. The acrylic polymer (B) had a weight average molecular weight of 540,000, a glass transition temperature (Tg) of −54 ° C., and an acid value of 0.0.

[Acrylic polymer (C)]
In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 200 parts by weight of 2-ethylhexyl acrylate, 1-hydroxycyclohexyl phenyl ketone as a polymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) ) 0.1 part by weight, 0.1 part by weight of benzylmethyl ketal (Ciba Specialty Chemicals, Irgacure 651) was charged, nitrogen gas was introduced with gentle stirring, and a high pressure mercury lamp (Toshiba Lighting & Technology, SHL) The polymerization reaction was carried out for about 3 minutes by irradiating with UV rays of −100 UVQ-2) to prepare an acrylic polymer (C) solution that was a partially polymerized product (syrup shape) with a polymerization rate of 10%. The acrylic polymer (C) had a weight average molecular weight of 2.2 million, a glass transition temperature (Tg) of −70 ° C., and an acid value of 0.0.

[Acrylic polymer (D)]
200 parts by weight of 2-ethylhexyl acrylate, 8 parts by weight of acrylic acid, and 2,2′-azobisisobutyronitrile as a polymerization initiator in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube and a condenser 0.4 parts by weight and 312 parts by weight of ethyl acetate were added, nitrogen gas was introduced while gently stirring, and the polymerization temperature was kept at around 65 ° C. for about 6 hours to carry out an acrylic polymer (D ) A solution (40% by weight) was prepared. The acrylic polymer (D) had a weight average molecular weight of 540,000, a glass transition temperature (Tg) of −66 ° C., and an acid value of 29.5.

[Acrylic polymer (E)]
200 parts by weight of 2-ethylhexyl acrylate, 0.4 parts by weight of acrylic acid, 3.6 parts by weight of 2-hydroxyethyl acrylate, polymerization started in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser 2,2'-azobisisobutyronitrile 0.43 parts by weight and ethyl acetate 312 parts by weight were introduced as agents, nitrogen gas was introduced with gentle stirring, and the liquid temperature in the flask was kept at around 65 ° C. A polymerization reaction was performed for about 6 hours to prepare an acrylic polymer (E) solution (40% by weight). The acrylic polymer (E) had a weight average molecular weight of 560,000, a glass transition temperature (Tg) of −66 ° C., and an acid value of 1.3.

<Preparation of antistatic agent>
[Antistatic agent solution (a)]
A four-necked flask equipped with a stirring blade, a thermometer, and a cooler was charged with 5 parts by weight of lithium perchlorate and 45 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was reduced to 25. The mixture was stirred for about 2 hours while maintaining at around 0 ° C. to prepare an antistatic agent solution (a) (10% by weight).

[Antistatic agent solution (b)]
A four-necked flask equipped with a stirring blade, a thermometer, and a condenser was charged with 5 parts by weight of lithium iodide and 45 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was 25 ° C. The mixture was stirred and stirred for about 2 hours to prepare an antistatic agent solution (b) (10% by weight).

[Antistatic agent solution (c)]
A four-necked flask equipped with a stirring blade, thermometer, and condenser is charged with 0.2 parts by weight of lithium perchlorate, 9.8 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000), and 10 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring, and the mixture was stirred for about 2 hours while maintaining the liquid temperature in the flask at around 80 ° C. to prepare an antistatic agent solution (c) (50 wt%).

[Antistatic agent solution (d)]
A four-necked flask equipped with a stirring blade, a thermometer, and a condenser was charged with 0.1 parts by weight of lithium iodide, 9.9 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000), and 10 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring, and the mixture was stirred for about 2 hours while maintaining the liquid temperature in the flask at around 80 ° C. to prepare an antistatic agent solution (d) (50 wt%).

<Preparation of antistatic treated polyethylene terephthalate film>
Antistatic agent solution by diluting 10 parts by weight of antistatic agent (manufactured by Solvex, Microsolver RMd-142, main components: tin oxide and polyester resin) with a mixed solvent consisting of 30 parts by weight of water and 70 parts by weight of methanol Adjusted. The obtained antistatic agent solution was applied onto a polyethylene terephthalate (PET) film (thickness 38 μm) using a Meyer bar and dried at 130 ° C. for 1 minute to remove the solvent and remove the antistatic layer (thickness). And an antistatic treated polyethylene terephthalate film was produced.

<Example 1>
[Adjustment of adhesive solution]
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, 2 parts by weight of the antistatic agent solution (a) is added to 100 parts by weight of this solution, and trimethylolpropane / trimethyl is used as a crosslinking agent. Add 1.1 parts by weight of a diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and 0.6 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst and keep it at around 25 ° C. The mixture was stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (1).

[Preparation of adhesive sheet]
The acrylic pressure-sensitive adhesive solution (1) was applied to the surface opposite to the antistatic treatment surface of the antistatic treatment polyethylene terephthalate film prepared as described above, heated at 110 ° C. for 3 minutes, and a thickness of 20 μm. An adhesive layer was formed. Next, a silicone-treated surface of a polyethylene terephthalate film (thickness 25 μm) having a silicone treatment on one side was bonded to the surface of the pressure-sensitive adhesive layer to produce a pressure-sensitive adhesive sheet.

<Example 2>
[Adjustment of adhesive solution]
An acrylic pressure-sensitive adhesive solution (2) was prepared in the same manner as in Example 1 except that 1 part by weight of the antistatic agent solution (b) was used instead of 2 parts by weight of the antistatic agent solution (a). did.

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (2) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Example 3>
[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 2 except that a polyethylene terephthalate film (thickness: 38 μm) that had not been subjected to antistatic treatment was used in place of the antistatic-treated polyethylene terephthalate film.

<Example 4>
[Adjustment of adhesive solution]
The acrylic polymer (B) solution (25% by weight) is diluted to 20% by weight with ethyl acetate, 1 part by weight of the antistatic agent solution (b) is added to 100 parts by weight of this solution, and trimethylolpropane / trimethyl is used as a crosslinking agent. Add 1.1 parts by weight of a diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and 0.6 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst and keep it at around 25 ° C. The mixture was stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (3).

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (3) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Example 5>
[Adjustment of adhesive solution]
After adding 0.5 parts by weight of lithium iodide to 100 parts by weight of the acrylic polymer (C) solution and keeping it at around 25 ° C. for about 2 hours, the mixture is stirred for about 2 hours, and then trimethylolpropane triacrylate as a polyfunctional monomer. 1.5 parts by weight, 0.1 part by weight of benzylmethyl ketal (manufactured by Ciba Specialty Chemicals, Irgacure 651) as a polymerization initiator is added and kept at around 25 ° C., and mixed and stirred for about 1 minute to prepare an acrylic adhesive An agent solution (4) was prepared.

[Preparation of adhesive sheet]
The said acrylic adhesive solution (4) was apply | coated to the surface opposite to the antistatic treatment surface of the antistatic treatment polyethylene terephthalate film produced as mentioned above, and the 20-micrometer-thick adhesive layer was formed. Next, a silicone-treated surface of a polyethylene terephthalate film (thickness 25 μm) having a silicone treatment on one side was bonded to the surface of the pressure-sensitive adhesive layer. This film sheet was irradiated with ultraviolet rays (illuminance 37 mW / cm ² , light amount 660 mJ / cm ² ) with a high-pressure mercury lamp (Ushio Electric Co., Ltd., UVL-4000-N) to produce an adhesive sheet.

<Example 6>
[Adjustment of adhesive solution]
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, 0.6 parts by weight of the antistatic agent solution (b) is added to 100 parts by weight of this solution, and hexamethylene diisocyanate as a crosslinking agent. 0.4 part by weight of isocyanurate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX) and 0.4 part by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst, and kept at around 25 ° C., about 1 Mixing and stirring were performed for a minute to prepare an acrylic pressure-sensitive adhesive solution (5).

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (5) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Comparative Example 1>
[Adjustment of adhesive solution]
The acrylic polymer (D) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, 1 part by weight of the antistatic agent solution (b) is added to 100 parts by weight of this solution, and 1,3-bis is used as a crosslinking agent. (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, TETRAD-C) 0.8 part by weight, trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) 0.3 parts by weight was added and kept at around 25 ° C., and mixed and stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (6).

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (6) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Comparative Example 2>
[Adjustment of adhesive solution]
The acrylic polymer (E) solution (25% by weight) is diluted to 20% by weight with ethyl acetate, 1 part by weight of the antistatic agent solution (b) is added to 100 parts by weight of this solution, and trimethylolpropane / trimethyl is used as a crosslinking agent. Add 1.1 parts by weight of a diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and 0.6 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst and keep it at around 25 ° C. The mixture was stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (7).

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (7) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Comparative Example 3>
[Adjustment of adhesive solution]
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, 100 parts by weight of this solution is mixed with 4 parts by weight of the antistatic agent solution (c), and trimethylolpropane / trimethyl is used as a crosslinking agent. Add 0.53 parts by weight of diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) and 0.4 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst and keep it at around 25 ° C. The mixture was stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (8).

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (8) was used in place of the acrylic pressure-sensitive adhesive solution (1).

<Comparative Example 4>
[Adjustment of adhesive solution]
An acrylic pressure-sensitive adhesive solution (9) was prepared in the same manner as in Example 1 except that 4 parts by weight of the antistatic agent solution (d) was used instead of 4 parts by weight of the antistatic agent solution (c). did.

[Preparation of adhesive sheet]
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (9) was used instead of the acrylic pressure-sensitive adhesive solution (1).

  In accordance with the above method, peeling voltage measurement, evaluation of occurrence of lifting, and peel adhesive strength measurement of the produced pressure-sensitive adhesive sheet were performed. The obtained results are shown in Table 1.

  From the results of Table 1 above, when the pressure-sensitive adhesive composition prepared according to the present invention was used (Examples 1 to 6), the withstand voltage to the polarizing plate was suppressed in any of the Examples, and the pressure-sensitive adhesive composition was floated. It became clear that there was no outbreak. On the other hand, in Comparative Examples 1 and 2 using the pressure-sensitive adhesive composition made of an acrylic polymer having an acid value greater than 1, no occurrence of lifting was observed, but the peeling withstand voltage to the polarizing plate was high. It became. Moreover, in Comparative Examples 3 to 4 using an antistatic agent containing a polyether polyol compound, the peeling withstand voltage to the polarizing plate was kept low, but the occurrence of lifting was observed. Therefore, in all of the comparative examples, it is impossible to achieve both the suppression of the peeling withstand voltage to the polarizing plate as the adherend and the suppression of the occurrence of floating, and it is not suitable for the pressure-sensitive adhesive composition for the pressure-sensitive adhesive sheet. It became clear.

  Moreover, it turns out that the adhesive sheet of Examples 1-4 of this invention has a 180 degree peel adhesive force in the range of 0.1-6 N / 25mm, and is an adhesive sheet applicable as an object for protective films.

Claims (5)

In the pressure-sensitive adhesive composition containing a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms as a main component, an alkali metal salt, and a crosslinking agent,
The acid value of the (meth) acrylic polymer is 1.0 or less,
The (meth) acrylic polymer does not contain an acrylic copolymer having a hydroxyl group and an alkylene oxide chain in the side chain,
Furthermore, it does not contain polyether polyol,
The alkali metal salt is a lithium salt;
The alkali metal contains 0.01 to 5 parts by weight with respect to 100 parts by weight of the (meth) acrylic polymer,
The crosslinking agent is at least one of an isocyanate compound, an epoxy compound, a melamine resin, an aziridine derivative, and a metal chelate compound;
The pressure-sensitive adhesive composition comprising 0.01 to 10 parts by weight of the crosslinking agent with respect to 100 parts by weight of the (meth) acrylic polymer.   A pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1 formed on one or both sides of a support.   The pressure-sensitive adhesive sheet according to claim 3, wherein the 180 ° peel adhesive strength at 23 ° C x 50% HR with respect to the saponified triacetylcellulose film is 0.1 to 6 N / 25 mm.   The pressure-sensitive adhesive sheet according to claim 3 or 4, wherein a plastic base material subjected to antistatic treatment is used as the support.

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