JP2005314476A - Adhesive composition, adhesive sheet and surface-protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antistatic adhesive composition causing no corrosion even if adhesive face directly contacts with metals, and giving excellent antistaticity to a non-antistatic adherend in releasing, and to provide antistatic adhesive sheets and surface-protective films each using the composition. <P>SOLUTION: The adhesive composition comprises a (meth)acrylic polymer based on that having 1-14C alkyl groups and a polyether polyol compound. In this adhesive composition, the the acid value of the (meth)acrylic polymer is ≤1.0. This adhesive composition also contains an alkali metal salt treated with an anion-adsorbing compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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, pressure-sensitive adhesive sheets and a surface protective film using the same. In particular, the surface protective film of the present invention is used in plastic products and the like that are likely to generate static electricity, and in particular, antistatic pressure-sensitive adhesive sheets and surface protective films in applications that require corrosion resistance, such as electronic devices. Useful as.

  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. 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, LiClO ₄ shown in such a proposal is highly corrosive and may corrode the metal when the adhesive surface directly touches the metal. In particular, as a use application of the protective film for optical members, there are many examples in which the outer peripheral portion of the optical member is applied to a liquid crystal module fixed with a metal fixing frame called stainless steel or aluminum called “bezel”. In applications, it has been found that there is a possibility that the “bezel” may be deteriorated due to corrosion by the above-mentioned pressure-sensitive adhesive component, and there are restrictions on application.

As described above, none of these problems can still be solved in a balanced manner, and in the technical field related to electronic equipment where static charge and corrosion are particularly serious problems, antistatic surfaces It is difficult to respond to further improvement requests for protective films.
JP 11-256116 A JP-A-9-165460 JP-A-6-128539

  Therefore, in light of such circumstances, the object of the present invention is to prevent corrosion even when the adhesive surface is in direct contact with metals, and to provide excellent antistatic properties to an uncharged adherend during peeling. It is an object to provide an antistatic pressure-sensitive adhesive composition having the above, an antistatic pressure-sensitive adhesive sheet and a surface protective film using the same.

  In order to achieve the above object, the present inventors have made extensive studies on the base polymer and antistatic component as the main components of the pressure-sensitive adhesive composition, and as a result, (meth) acrylic polymers having an acid value of 1.0 or less. , And an adhesive composition containing an alkali metal salt treated with an anion-adsorptive compound, it is possible to prevent the adherend from being charged when peeled, and to prevent the anticorrosiveness of the adherend from being reduced. The present inventors have found that a pressure-sensitive adhesive composition can be obtained and have completed the present invention.

  That is, in the pressure-sensitive adhesive composition containing a (meth) acrylic polymer having as a main component a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, and a polyether polyol compound, the (meth) acrylic The acid value of the polymer is 1.0 or less, and an alkali metal salt treated with an anion-adsorbing compound is included.

  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 Examples, a pressure-sensitive adhesive containing a (meth) acrylic polymer having an acid value of 1.0 or less and an alkali metal salt treated with an anion-adsorbing compound By using the composition, even if the adhesive surface is in direct contact with metals, corrosion does not occur, and the antistatic property to the adherend during peeling is excellent. Although the details of the reason why the crosslinked product of the pressure-sensitive adhesive composition exhibits such properties are not clear, it was treated with a (meth) acrylic polymer having an acid value of 1.0 or less and an anion-adsorbing compound. By using a pressure-sensitive adhesive composition containing an alkali metal salt, it contributes to a balanced interaction such as compatibility with the alkali metal salt and conductivity, and an anion of the alkali metal salt considered to be the main factor of corrosion. It is presumed that removal makes it possible to have good adhesion characteristics, charging characteristics, and inhibition of corrosion.

  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 structure, the presence of a large number of carboxyl groups and sulfonate groups that have a large interaction with the alkali metal salt prevents ionic conduction and provides excellent antistatic ability to the adherend. 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 1.0 or less. In the case of a (meth) acrylic polymer exceeding 1.0, an excellent antistatic ability to the adherend may not be obtained.

  The pressure-sensitive adhesive composition in the present invention is characterized by containing an alkali metal salt treated with an anion-adsorbing compound. By subjecting the alkali metal salt to an anion adsorption treatment with an anion adsorbing compound, it is possible to suppress corrosion when the pressure-sensitive adhesive layer is in direct contact with metals. Although it is not clear why the occurrence of corrosion can be suppressed by such anion adsorption treatment, it is possible to suppress the occurrence of corrosion by removing the anion of the alkali metal salt, which is thought to contribute to corrosion, with an anion adsorbent. Guessed.

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

  The anion-adsorbing compound in the present invention means a compound having an ability to adsorb anions by anion adsorption treatment, and a hydrotalcite compound mainly composed of magnesium and aluminum can be preferably used. It is given as a thing.

  Further, in the present invention, a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms as a main component and a polyether in order to exert an effect as an adhesive composition A polyol compound is at least a constituent component.

  By using a (meth) acrylic polymer whose main component is a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms, the balance of compatibility with the alkali metal salt and the excellent adhesive properties are aligned. Presumed to have contributed.

  In addition, by containing the above polyether polyol compound, it is possible to obtain a compatible and well-balanced interaction with alkali metal salts and (meth) acrylic polymers, etc., thereby preventing the adherend from being peeled when peeled. Can be obtained.

  In the present invention, a (meth) acrylic polymer further containing a (meth) acrylic monomer having a hydroxyl group as a constituent component is used. By using a (meth) acrylic monomer having a hydroxyl group, it becomes easier to control the crosslinking of the pressure-sensitive adhesive composition, and in turn, it becomes easier 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 as described above. A surface protective film having more excellent heat resistance can be obtained by appropriately adjusting the constitutional unit, constitutional ratio, selection of the crosslinking agent, 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 one side or both sides of a support. According to the pressure-sensitive adhesive sheets of the present invention, since the pressure-sensitive adhesive composition obtained by crosslinking the pressure-sensitive adhesive composition exhibiting the above-described effects is provided, it is possible to prevent charging of the adherend when peeled, and to adhere to the adherend. The pressure-sensitive adhesive sheets are reduced in corrosiveness. For this reason, it becomes very useful as an antistatic pressure-sensitive adhesive sheet in a technical field related to electronic equipment, in which electrostatic charge and corrosion are particularly serious problems.

  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.

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

  The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition comprising a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms as a main component, and a polyether polyol compound. The acid value of the (meth) acrylic polymer is 1.0 or less, and an alkali metal salt treated with an anion-adsorbing compound is included.

  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, etc. are used suitably.

  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 mentioned. In this case, the total amount of 2-ethylhexyl acrylate and acrylic acid is 100 wt. Part of 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, Examples thereof include 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. These hydroxyl group-containing monomers may be used alone or in combination of two or more.

  In the case of including the (meth) acrylic monomer having the hydroxyl group described above, the (meth) acrylic monomer having a hydroxyl group is 0.1 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 this invention, you may use another polymerizable monomer as arbitrary components other than the said hydroxyl group containing monomer. Other polymerizable monomers include, for example, components for improving cohesion and heat resistance such as sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, and carboxyl group-containing monomers. , An acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, an epoxy group-containing monomer, N-acryloylmorpholine, a vinyl ether monomer, etc. be able to. These monomer compounds may be used alone or in admixture of two or more. However, when an acrylate and / or methacrylate having an acid functional group such as a carboxyl group, a sulfonic acid group, or a phosphoric acid group is used, it is necessary to adjust the acid value of the acrylic polymer to 1.0 or less.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth). Examples include acryloyloxynaphthalene sulfonic acid.

  Examples of the phosphate group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

  Examples of the cyano group-containing monomer include acrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethyl styrene, α-methyl styrene, and the like.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

  Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

  Examples of the amide group-containing monomer include acrylamide and diethyl acrylamide.

  Examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and the like.

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

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  In the present invention, the (meth) acrylic polymer has a (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms in an amount of 50 to 100% by weight, more preferably 70 to 100% by weight, based on all monomer components. It is used.

  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 is lowered 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).

  Moreover, although the glass transition temperature (Tg) of the said (meth) acrylic-type polymer is normally -100 degreeC or more, it is preferable that it is -90 degreeC-0 degreeC, and it is -80 degreeC--10 degreeC. More preferably. 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.

  In the present invention, an alkali metal salt treated with an anion-adsorbing compound is used. Examples of the anion-adsorptive compound include inorganic ion exchangers such as hydrotalcite compounds mainly composed of magnesium and aluminum, zirconium-based compounds, antimony-based compounds, bismuth-based compounds, and magnesium-aluminum-based compounds. Especially, the hydrotalcite compound which can perform the adsorption process of an anion efficiently can be mentioned as what can be used suitably. Specific examples of the hydrotalcite compound include, for example, Kyoward 500, Kyoward 1000, Kyoward 2000 (manufactured by Kyowa Chemical Industry Co., Ltd.), and the like. These compounds may be used alone or in combination of two or more.

  About the compounding quantity of the said anion adsorptive compound, it is preferable to mix | blend alkali metal salt 0.05-5 equivalent with respect to 1 equivalent of alkali metal salt to adsorb | suck, and mix | blend 0.1-2 equivalent. More preferred. If the amount is less than 0.05 equivalent, the anion adsorption treatment may be insufficient, and a sufficient corrosion prevention effect may not be obtained. The prevention effect does not increase.

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 said alkali metal salt, 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, and mix | blending 0.05-3 weight part. Is more preferable. 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 a method of anion adsorption treatment with the anion-adsorbing compound used in the present invention, a known method can be appropriately used in the conventional anion adsorption treatment. Specifically, for example, an anion-adsorptive compound is added to an organic solvent in which an alkali metal salt is dissolved, and the anion-adsorptive compound is dissolved in an organic solvent in which a polyether polyol compound and an alkali metal salt are dissolved. Examples thereof include a method of adding an anion and adsorbing the anion. These methods may be used alone or in combination of two or more.

  The organic solvent used for the adsorption treatment is not particularly limited as long as it can dissolve the polyether polyol compound and / or the alkali metal salt. Examples thereof include ethyl acetate, tetrahydrofuran, methanol, ethanol, isopropanol and the like. These organic solvents may be used alone or in combination of two or more.

  As the treatment conditions for the adsorption treatment, the treatment is performed at a temperature of 20 ° C. to 100 ° C., preferably 30 ° C. to 90 ° C., for 10 minutes to 240 minutes, preferably 30 minutes to 120 minutes.

  On the other hand, the anion-adsorbing compound in the present invention is usually removed after the adsorption treatment. The removal of the anion-adsorbing compound after the adsorption treatment is performed, for example, by removing the adsorption treatment solution by allowing the adsorption treatment solution to stand, or by removing the adsorption treatment solution with a filter medium such as a depth type filter or a screen type filter. And the method of separating and removing by filtration. These methods may be used alone or in combination of two or more.

  In the pressure-sensitive adhesive composition of the present invention, a polyether polyol is added for the purpose of further improving the antistatic effect on the adherend.

  The polyether polyol is not particularly limited as long as it is a polymer polyol having an ether group. For example, polyethylene glycol, polypropylene glycol (diol type), polypropylene glycol (triol type), polytetramethylene ether glycol, and the above derivatives And a copolymer. Among these, polypropylene glycol (diol type) and polypropylene glycol (triol type) are particularly preferably used. These polyether polyols may be used alone or in combination of two or more.

  As the molecular weight of the polyether polyol, those having a number average molecular weight of 10,000 or less, preferably 200 to 5,000 are suitably used. When the molecular weight is 10,000 or more, the contamination of the adherend increases.

  The amount of the polyether polyol is 1 to 50 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of the acrylic polymer. If the amount is less than 1 part by weight, sufficient charging characteristics cannot be obtained, and if it exceeds 50 parts by weight, contamination of the adherend increases.

  In the adhesive composition of this invention, it can be set as the adhesive layer excellent in heat resistance by bridge | crosslinking the said adhesive composition suitably. As a crosslinking means, for example, there is a method in which a compound capable of reacting with an amino group, an amide group, a hydroxyl group or the like introduced as a crosslinking base point in an acrylic polymer structure is used as a crosslinking agent.

  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, 2,4-tolylene diisocyanate, Aromatic isocyanates such as 4,4′-diphenylmethane diisocyanate and xylylene diisocyanate, trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane / hexamethylene Diisocyanate trimer adduct (trade name Coronate HL, manufactured by Nippon Polyurethane Industry Co., Ltd.), isocyanurate of hexamethylene diisocyanate 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-diglycidyl). Aminomethyl) 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 parts 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. 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 is insufficient, and the adhesiveness tends to be insufficient. 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 include diol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, divinylbenzene, and N, N′-methylenebisacrylamide.

  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.

  Examples of radical photopolymerization initiators include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, o-benzoylbenzoic acid methyl-p-benzoin ethyl ether, benzoin isopropyl ether, α-methylbenzoin, benzyl dimethyl 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 blended 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-dimethylaminoethyl benzoate, 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.

  Further, the pressure-sensitive adhesive composition of the present invention may contain other known additives such as powders such as colorants and pigments, surfactants, plasticizers, tackifiers, Molecular weight polymer, surface lubricant, leveling agent, antioxidant, corrosion inhibitor, light stabilizer, UV absorber, polymerization inhibitor, silane coupling agent, inorganic or organic filler, metal powder, particulate, foil It can be added appropriately depending on the purpose of using the product.

  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. The pressure-sensitive adhesive sheets of the present invention are formed by forming such a pressure-sensitive adhesive layer on a support. 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 is transferred to a support such as a support film. Is also possible.

In the case of adding a photopolymerization initiator as an optional component as described above, the pressure-sensitive adhesive composition is applied directly on the adherend, 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 pressure-sensitive adhesive sheets is not particularly limited. For example, the pressure-sensitive adhesive composition is applied to a support such as a support film, and the polymerization solvent is dried and removed to support the pressure-sensitive adhesive layer. It is produced by forming on top. Thereafter, curing may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction. Further, when the pressure-sensitive adhesive composition is coated on a support to produce a pressure-sensitive adhesive sheet, the composition contains at least one polymerization solvent other than the polymerization solvent so that it can be uniformly coated on a support such as a support film. A new solvent may be added.

  Furthermore, the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive sheets of the present invention includes various conventionally known tackifiers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, ultraviolet absorbers, polymerization agents. Add appropriately according to the use of various conventionally known additives such as inhibitors, silane coupling agents, inorganic or organic fillers, powders such as metal powders and pigments, particles and foils. I can do it.

  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 pressure-sensitive adhesive sheet is preferably a support film such as a resin film having heat resistance and solvent resistance and flexibility. When the support film 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 that forms the support include polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, polyfluoroethylene, and other fluorine-containing resins, nylon, and cellulose.

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

  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.

  As a method for coating and forming the pressure-sensitive adhesive composition in the present invention, known methods used for the production of pressure-sensitive adhesive tapes are used. Specifically, for example, roll coating, gravure coating, reverse coating, roll brush, spray Examples thereof include a coating method and an air knife coating method.

  The surface protective film of the present invention can be bonded to the surface of the pressure-sensitive adhesive layer 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, sulfates, phosphonates and phosphates, amphoteric antistatics such as alkylbetaines and derivatives thereof, imidazolines and derivatives thereof, and alanines 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. These conductive polymers may be used alone or in combination of two or more.

  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. In addition, the antistatic resin component may contain a methylol- or alkylol-containing melamine-based, urea-based, glyoxal-based, acrylamide-based compound, epoxy compound, or isocyanate 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.

  Further, as the kneading type antistatic agent, the above antistatic agents are 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 surface protective film using the present invention are used in plastic products and the like that are particularly prone to generate static electricity, and in particular, polarizing plates, wave plates, optical compensation films, light used in 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 thereto. 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)]
(Wherein Tg (° C.) is the glass transition temperature of the copolymer, W _n (−) is the weight fraction of each monomer, T g _n (° C.) is the glass transition temperature of the homopolymer of each monomer, and n is each monomer. Represents the type of
2-ethylhexyl acrylate: -70 ° C
2-hydroxyethyl acrylate: -15 ° C
Acrylic acid: 106 ° C
In addition, as a reference value, we referred to “Synthesis / design of acrylic resin and development of new applications” (published by Central Management Development Center Publishing Department).

<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-propanolic 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>
The surface 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 (Nitto Denko Corporation) 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. Manufactured, SEG1425EWVAGS2B, size: width 70 mm, length 100 mm) was pressed with a hand roller so that one end protruded 30 mm from the surface. 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 10 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.

<Corrosive evaluation>
The surface protective film was cut into a size of 30 mm in width and 80 mm in length, and pressure-bonded to an aluminum foil having a width of 50 mm and a length of 100 mm with a hand roller to obtain an evaluation sample. This evaluation sample was left in an environment of 60 ° C. × 90% RH for one day, and then the protective film was peeled off from the aluminum foil, and the aluminum foil surface was visually observed and evaluated.

If no discoloration was observed: ○
If discoloration is observed: ×

<Measurement of adhesive strength>
A 80 μm thick triacetylcellulose film (Fuji Photo Film, Fujitac) was cut to a width of 70 mm and a length of 100 mm, immersed in an aqueous solution of sodium hydroxide (10 wt%) at 60 ° C. 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 a surface protective film cut to a size of 25 mm in width and 80 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 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 charged, 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. ) A solution (40% by weight) was prepared. The acrylic polymer (B) had a weight average molecular weight of 540,000, a glass transition temperature (Tg) of −66 ° C., and an acid value of 30.

<Preparation of antistatic agent>
[Antistatic agent solution (a)]
A four-necked flask equipped with a stirring blade, a thermometer, and a nitrogen gas introduction tube was charged with 2.0 parts by weight of lithium iodide and 40 parts by weight of ethyl acetate, and nitrogen gas was introduced and dissolved while gently stirring. Thereafter, 4.0 parts by weight of a hydrotalcite compound (manufactured by Kyowa Chemical Industry Co., Ltd., Kyoward 500) is further added to the flask, and the mixture is stirred for about 2 hours while maintaining the liquid temperature in the vicinity of 80 ° C. Subsequently, it kept at 25 degreeC vicinity, and left still for 2 hours, The supernatant liquid in a flask was extract | collected, and the adsorption processing solution (1) was obtained. To 30 g of this adsorption treatment solution (1) (5% by weight), 4.0 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000) is added to obtain an antistatic agent solution (a) (16.2% by weight). Prepared.

[Antistatic agent solution (b)]
In a four-necked flask equipped with a stirring blade, a thermometer, and a nitrogen gas introduction tube, 4.0 parts by weight of lithium perchlorate and 80 parts by weight of ethyl acetate were charged, and nitrogen gas was introduced and dissolved while gently stirring. Thereafter, 8.0 parts by weight of a hydrotalcite compound (Kyowa Kagaku Kogyo Co., Ltd., Kyoward 500) is further added to the flask, and the mixture is stirred for about 2 hours while keeping the liquid temperature in the vicinity of 80 ° C. Subsequently, it kept at 25 degreeC vicinity, and left still for 2 hours, The supernatant liquid in a flask was extract | collected, and the adsorption processing solution (2) was obtained. An antistatic agent solution (b) (12.3 wt%) was prepared by adding 5.0 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000) to 60 g of this adsorption treatment solution (2) (5 wt%). did.

[Antistatic agent solution (c)]
A four-necked flask equipped with a stirring blade, a thermometer, and a nitrogen gas introduction tube was charged with 0.5 parts by weight of lithium iodide, 9.5 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000), and 10 parts by weight of ethyl acetate. Then, nitrogen gas was introduced while gently stirring, and the mixture was stirred for about 2 hours while keeping the liquid temperature in the vicinity of 80 ° C. to prepare an antistatic agent solution (c) (50% by weight).

[Antistatic agent solution (d)]
In a four-necked flask equipped with a stirring blade, a thermometer, and a nitrogen gas inlet tube, 0.2 parts by weight of lithium perchlorate, 9.8 parts by weight of polypropylene glycol (diol type, number average molecular weight 2000), 10 parts by weight of ethyl acetate Was added with nitrogen gas while gently stirring, and the mixture was stirred for about 2 hours while keeping the liquid temperature in the vicinity of 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 (E) was adjusted. The obtained antistatic agent solution (e) 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 prevent the antistatic. A layer (thickness 0.2 μm) was formed to produce an antistatically treated polyethylene terephthalate film.

<Example 1>
(Preparation of adhesive solution)
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 6.8 parts by weight of the antistatic agent solution (a) (16.2% by weight) is added to 100 parts by weight of this solution. 25 parts by adding 0.4 parts by weight of isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX) as a crosslinking agent and 0.4 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst Mixing and stirring was performed for about 1 minute while keeping the temperature around 0 ° C. to prepare an acrylic pressure-sensitive adhesive solution (1).

[Production of surface protective film]
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, the surface of the pressure-sensitive adhesive layer was laminated with a silicone-treated surface of a polyethylene terephthalate film (thickness 25 μm) that had been subjected to silicone treatment on one side to produce a surface protective film.

<Example 2>
(Preparation of adhesive solution)
The acrylic pressure-sensitive adhesive solution (2) was prepared in the same manner as in Example 1 except that 13 parts by weight of the antistatic agent solution (b) was used instead of 6.8 parts by weight of the antistatic agent solution (a). Was prepared.

[Production of surface protective film]
A surface protective film was produced 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).

<Comparative Example 1>
(Preparation of adhesive solution)
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and isocyanurate of hexamethylene diisocyanate as a crosslinking agent (100% by weight, Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) Add 0.8 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a cross-linking catalyst and keep it at around 25 ° C. for about 1 minute to mix and stir the acrylic adhesive solution (3) Was prepared.

[Production of surface protective film]
A surface protective film was produced 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).

<Comparative Example 2>
(Preparation of adhesive solution)
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 4.0 parts by weight of the antistatic agent solution (c) (50% by weight) is added to 100 parts by weight of this solution. 0.53 parts by weight of trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) as an agent, and 0.4 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst In addition, the mixture was stirred at about 25 ° C. for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (4).

[Production of surface protective film]
A surface protective film was produced in the same manner as in Example 1 except that the acrylic pressure-sensitive adhesive solution (4) was used instead of the acrylic pressure-sensitive adhesive solution (1).

<Comparative Example 3>
(Preparation of adhesive solution)
An acrylic pressure-sensitive adhesive solution (in the same manner as in Example 1 except that 4.0 parts by weight of the antistatic agent solution (d) was used instead of 6.8 parts by weight of the antistatic agent solution (a). 5) was prepared.

[Production of surface protective film]
A surface protective film was produced 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 4>
(Preparation of adhesive solution)
The acrylic polymer (B) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 6.8 parts by weight of the antistatic agent solution (a) (16.2% by weight) is added to 100 parts by weight of this solution. , 0.7 parts by weight of 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, TETRAD-C) as a cross-linking agent, trimethylolpropane / tolylene diisocyanate trimer adduct ( Nippon Polyurethane Industry Co., Ltd., Coronate L) 0.27 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).

[Production of surface protective film]
A surface protective film was produced 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).

  According to the above method, the peeled surface voltage measurement of the produced surface protective film, the evaluation of the occurrence of corrosion, and the adhesive force measurement were performed. The obtained results are shown in Table 1.

上記表１の結果より、本発明によって作製された粘着剤組成物を用いた場合（実施例１〜２）、全実施例において被着体である偏光板への剥離帯電圧が抑制され、かつ、腐食の発生もないことが明らかとなった。これに対して、アルカリ金属塩およびポリプロピレングリコールのいずれも含まない場合（比較例１）、およびベースポリマーの酸価が１をこえるものである場合（比較例４）のいずれにおいても、腐食の発生は見られなかったが、偏光板への剥離帯電圧が高い結果となった。また、ハイドロタルサイトを用いていない場合（比較例２〜３）、いずれにおいても偏光板への剥離帯電圧は低く抑えられているが、腐食の発生が生じる結果となった。したがって、比較例ではいずれも、被着体である偏光板への剥離帯電圧の抑制、ならびに腐食の発生の抑制を両立することができない結果となり、表面保護フィルム用の粘着剤組成物には適さないことが明らかとなった。

From the results of Table 1 above, when the pressure-sensitive adhesive composition prepared according to the present invention was used (Examples 1 and 2), the stripping voltage to the polarizing plate as the adherend was suppressed in all Examples, and It was revealed that there was no corrosion. On the other hand, the occurrence of corrosion both when the alkali metal salt and polypropylene glycol are not included (Comparative Example 1) and when the base polymer has an acid value exceeding 1 (Comparative Example 4). Was not observed, but the peeling voltage to the polarizing plate was high. Further, when hydrotalcite was not used (Comparative Examples 2 to 3), the stripping voltage to the polarizing plate was kept low in any case, but the corrosion occurred. Therefore, in all of the comparative examples, it is impossible to achieve both suppression of the stripping voltage to the polarizing plate as the adherend and suppression of the occurrence of corrosion, which is suitable for the pressure-sensitive adhesive composition for the surface protective film. It became clear that there was no.

  Moreover, it turns out that the surface protection film of Examples 1-2 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 a protective film use.

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

Claims (7)

  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 and a polyether polyol compound, the (meth) acrylic polymer A pressure-sensitive adhesive composition comprising an alkali metal salt having an acid value of 1.0 or less and treated with an anion-adsorbing compound.   The pressure-sensitive adhesive composition according to claim 1, wherein the alkali metal salt is a lithium salt.   The pressure-sensitive adhesive composition according to claim 1, wherein the anion-adsorptive compound is a hydrotalcite compound.   The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylic polymer further contains a (meth) acrylic monomer having a hydroxyl group as a constituent component.   The adhesive layer formed by bridge | crosslinking the adhesive composition in any one of Claims 1-4.   A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to claim 1 on one side or both sides on a support. A pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to any one of claims 1 to 4 is formed on one side or both sides on a support made of a plastic substrate subjected to antistatic treatment. Characteristic surface protective film.

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