JP5235021B2 - Adhesive composition, adhesive sheet, and surface protective film - Google Patents

Description

  The present invention relates to an acrylic resin composition. More specifically, the present invention relates to an antistatic pressure-sensitive adhesive composition and pressure-sensitive adhesive sheets using the same. The pressure-sensitive adhesive sheets of the present invention are used for plastic products and the like that are likely to generate static electricity. Especially, it is useful as a surface protective film used for the purpose of protecting the surface of an optical member such as a polarizing plate, a wave plate, a retardation plate, an optical compensation film, a reflection sheet, and a brightness enhancement film used in a liquid crystal display. .

  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 protected body via an adhesive applied to the surface protective film side, and preventing scratches and dirt generated during processing and transportation of the protected body. 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 surface protective film is bonded via an adhesive for the purpose of preventing scratches and dirt. And this surface protection film peels and is removed in the stage which became unnecessary.

  In general, since the surface 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. Accordingly, static electricity is generated even when the surface protective film is peeled off from the optical member such as a polarizing plate. When a voltage is applied to the liquid crystal while the static electricity generated at this time remains, the orientation of the liquid crystal molecules is changed. There is a problem that the panel is lost and 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 a sucking action of an object to be protected that occurs when sticking adhesive tapes. 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 the surface to be protected cannot be prevented from being charged. When the protective film is peeled off, the object to be protected is charged.

  In addition, a method is disclosed in which a low molecular surfactant is added to an adhesive, and the surfactant is transferred from the adhesive to an object to be protected to prevent charging (for example, see Patent Document 2). However, in such a method, the added low molecular surfactant easily bleeds to the surface of the pressure-sensitive adhesive, and when applied to a surface protective film, there is a concern about contamination of the object to be protected. Therefore, since it has a problem of impairing the optical characteristics of the optical member, application in a technical field related to optical / electronic parts in which contamination becomes a particularly serious problem is not preferable.

  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, the exemplified alkali metal salt is blended in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer, and these pressure-sensitive adhesive compositions are used as a surface protective film. When it is applied to the optical member, there is a problem that the optical member is contaminated by the treatment with time or at a high temperature, which is not sufficient.

  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 is difficult to respond to further improvement requests for surface protection films.

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

  In light of the circumstances as described above, the present invention reduces contamination of a protected body when applied to a surface protective film such as a plastic product, and the protected body is not antistatic when the surface protective film is peeled off. It is an object of the present invention to provide an antistatic pressure-sensitive adhesive composition capable of preventing antistatic properties, an antistatic pressure-sensitive adhesive sheet using the same, and a surface protective film.

  In order to achieve the above object, the present inventors have conducted intensive studies on the main component of the pressure-sensitive adhesive composition (that is, the monomer component having the highest content in the resin composition). By using a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group as a main component and having an acid value of 1.0 or less, it is possible to produce an object that is not antistatic when peeled off. It has been found that an antistatic pressure-sensitive adhesive composition can be obtained which can be prevented from being charged and the contamination of an object to be protected is reduced, and the present invention has been completed.

  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 6 to 14 carbon atoms, a polyether polyol compound and an alkali metal salt. The pressure-sensitive adhesive composition contains an acid value of the (meth) acrylic polymer of 1.0 or less, and less than 0.1 part by weight of the alkali metal with respect to 100 parts by weight of the (meth) acrylic polymer. It is characterized by.

  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, the main component is a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms, and the acid value is 1.0 or less. By using a pressure-sensitive adhesive composition comprising a (meth) acrylic polymer, it is possible to prevent the object to be protected from being charged when it is peeled off, and to reduce the contamination of the object to be protected. Although the details of the reason why the surface protective film exhibits such properties are not clear, the main component is a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms, and the acid value is 1.0 or less. By using a certain (meth) acrylic polymer, it contributes to a balanced interaction such as compatibility with the alkali metal salt and the polyether polyol compound, and conductivity, thereby suppressing contamination of the protected object, It is presumed that the charging characteristics can be arranged side by side.

  The pressure-sensitive adhesive composition according to the present invention is characterized by using a (meth) acrylic polymer containing a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms as a main component. By using such a (meth) acrylic polymer, excellent charging characteristics can be obtained even when the blending amount of the alkali metal salt is less than 0.1 parts by weight, and contamination of the protected object can be reduced.

  Moreover, in the adhesive composition in this invention, the (meth) acrylic-type polymer whose acid value of a (meth) acrylic-type polymer is 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 protected object 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 1.0 or less. A (meth) acrylic polymer exceeding 1.0 may not provide an excellent antistatic ability for the protected object.

  In the present invention, in order to exert an effect as an adhesive composition, a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms as a main component, a polyether polyol compound, An alkali metal salt and a vinyl monomer having a functional group are at least constituent components.

  In the present invention, an alkali metal salt is included. Surface protection film that can achieve anti-static to the object that is not anti-static when peeled by obtaining compatibility and well-balanced interaction with (meth) acrylic polymer using alkali metal salt Can be obtained.

  Moreover, in this invention, content of the alkali metal salt in the said adhesive composition is less than 0.1 weight part with respect to 100 weight part of said (meth) acrylic-type polymers, It is characterized by the above-mentioned. By setting the content of the alkali metal salt to less than 0.1 parts by weight, it is possible to obtain a surface protective film in which contamination of the protected object by the alkali metal salt is reduced.

  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.

  In the present invention, a polyether polyol compound is included. By using a polyether polyol compound to obtain a compatible and well-balanced interaction with alkali metal salts and (meth) acrylic polymers, etc., antistatic to non-antistatic objects when peeled Can be obtained, and a surface protective film with reduced contamination to the protected body can be obtained.

  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. . Furthermore, unlike the above-mentioned carboxyl group and sulfonate group, which can generally act as a crosslinking site, the hydroxyl group has an appropriate interaction with the alkali metal salt and the polyether polyol compound, so that it is also preferably used in terms of antistatic properties. be able to.

  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.

  Among them, an isocyanurate-modified product of isocyanate obtained by isocyanate-modified isocyanate such as hexamethylene diisocyanate or tolylene diisocyanate is preferably used as a crosslinking agent. By using an isocyanurate-modified product of isocyanate, it becomes easy to control the balance between the adhesive strength and the stripping voltage characteristics.

  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 is provided with a pressure-sensitive adhesive layer obtained by crosslinking the above-described pressure-sensitive adhesive composition, it is possible to prevent the object to be protected from being charged when peeled off. Thus, pressure-sensitive adhesive sheets with reduced contamination to the protected body are obtained. For this reason, it becomes very useful as an antistatic pressure-sensitive adhesive sheet in the technical field related to optical and electronic components, in particular, where electrostatic charging and corrosiveness 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 to the protected body and to obtain a material having 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. According to the surface protective film of the present invention, since the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition having the above-described effects is provided, it is possible to prevent the object to be protected from being charged when peeled off. Thus, a surface protective film with reduced contamination to the object to be protected is 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.

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 includes a (meth) acrylic polymer mainly composed of a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms, a pressure-sensitive adhesive containing a polyether polyol compound and an alkali metal salt. In the agent composition, the acid value of the (meth) acrylic polymer is 1.0 or less, and contains less than 0.1 part by weight of the alkali metal with respect to 100 parts by weight of the (meth) acrylic polymer. It is characterized by that.

  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 monomer having an alkyl group having 6 to 14 carbon atoms in the present invention is used, a (meth) acrylic monomer having an alkyl group having 7 to 13 carbon atoms is preferred. For example, 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. Among them, 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 and the like are preferably used.

  Other polymerizable monomers other than the (meth) acrylic monomer having an alkyl group having 6 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, 2- Examples thereof include 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 0.1 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 0.5-8 weight part.

  Furthermore, in the present invention, as an optional component other than the above hydroxyl group-containing monomer, it has the ability to improve cohesive strength and heat resistance, 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 can be polymerized by known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and alternating copolymerization. In addition, the obtained copolymer may be any of a random copolymer, a block copolymer, and the like.

  The polyether polyol compound in the present invention is not particularly limited as long as it is a polymer polyol having an ether group, and a known polymer polyol can be appropriately used. Specific examples include polyethylene glycol, polypropylene glycol (diol type), polypropylene glycol (triol type), polytetramethylene ether glycol, and the above derivatives and copolymers. Among these, polypropylene glycol (diol type) and polypropylene glycol (triol type) are particularly preferably used. These compounds may be used alone or in combination of two or more.

  As the molecular weight of the polyether polyether compound, those having a number average molecular weight of 10,000 or less, preferably 200 to 5,000 are suitably used. When the number average molecular weight exceeds 10,000, the contamination tends to deteriorate. The number average molecular weight is obtained by measuring by GPC (gel permeation chromatography).

  Moreover, as a compounding quantity of the said polyether polyol compound, it is 1-50 weight part with respect to 100 weight part of (meth) acrylic-type polymers, Preferably it is 3-20 weight part. 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 protected object tends to 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 ⁺ , Cl ⁻ , Br ⁻ , I _{^{-, BF 4 -, PF 6}} -, SCN -, ClO 4 -, CF 3 SO 3 -, (CF 3 SO 2) 2 N -, (CF 3 SO 2) 3 C - metal composed become more anions A salt is 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 less than 0.1 weight part of alkali metal salt with respect to 100 weight part of (meth) acrylic-type polymers. Furthermore, it is more preferable to mix | blend 0.01-0.09 weight part, and it is more preferable to mix | blend 0.05-0.08 weight part. 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 0.1 parts by weight, contamination to the protected body 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.

  Among the above isocyanate compounds, in particular, from the viewpoint of controlling the balance between adhesive strength and peeling voltage characteristics, isocyanurate-modified isocyanate (trade name Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) Isocyanate-modified isocyanate of tolylene diisocyanate An isocyanurate modified product (trade name Coronate 2030, manufactured by Nippon Polyurethane Industry Co., Ltd.) is a suitable example.

  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, and 0.5 to 10 parts by weight, with respect to 100 parts by weight of the (meth) acrylic polymer. It is more preferable. 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 to be used is appropriately selected depending on the balance with the (meth) acrylic polymer to be crosslinked and further depending on the intended use as a surface protective film. 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, 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 sheets of the present invention are 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 film. 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, pressure-sensitive adhesive sheets are 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 the pressure-sensitive adhesive composition is coated on a support film to produce pressure-sensitive adhesive sheets, one or more solvents other than the polymerization solvent are newly added to the composition so that the pressure-sensitive adhesive composition can be uniformly coated on the support film. 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 surface protective film of the present invention is obtained by crosslinking the pressure-sensitive adhesive composition. 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 surface protective film of the present invention is a variety of plastic films such as polyester film, porous materials such as paper and nonwoven fabric, etc., 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 film constituting the surface protective film is preferably 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 forming the support film 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 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 surface protective film obtained by the present invention is useful for masking tapes, re-peelable labels, and the like. In particular, the surface protective film of the present invention is useful as a surface protective film for an optical member or the like whose surface is anti-glare-treated in a concavo-convex shape, and is beneficial for antistatic properties to a protected body and a reduction effect of contamination to a coated body. Act on.

  In the present invention, a plastic substrate is preferably used as the 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.

  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 surface protective film of the present invention is obtained by coating and forming the above-mentioned pressure-sensitive adhesive on a plastic substrate so that the thickness is usually 3 to 100 μm, preferably about 5 to 50 μm. As a method for forming and applying the pressure-sensitive adhesive, a known method used for producing a surface protective film is used. Specific examples include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and the like.

  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, 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. 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, for example, 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 may contain, for example, a methylol- or alkylol-containing melamine-based, urea-based, glyoxal-based, or acrylamide-based compound, an epoxy compound, or an isocyanate compound as a crosslinking agent.

  As a method for forming the antistatic layer, for example, the above-mentioned antistatic resin, conductive polymer, or conductive resin is diluted with a solvent such as an organic solvent or water, and this coating solution is applied to a plastic substrate and dried. Formed with.

  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. Specific examples include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, impregnation and curtain coating methods.

  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 surface protective film using the present invention is used for plastic products that are particularly prone to generate static electricity, and in particular, polarizing plates, wave plates, retardation plates, optical compensation films, reflective sheets, used for liquid crystal displays, etc. It can be used as a surface protective film used for the purpose of protecting the surface of an optical member such as a brightness enhancement film.

  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
Sample 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
Isononyl acrylate: -82 ° C
Butyl acrylate: -55 ° C
Ethyl acrylate: -22 ° C
2-hydroxyethyl acrylate: -15 ° 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 number Y: Titration volume of sample solution (ml)
X: Titration volume of a solution containing only 50 g of mixed solvent (ml)
f; Factor M of the titration solution; 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>
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.

<Evaluation of contamination of protected objects>
The prepared surface protective film was cut into a size of 30 mm in width and 80 mm in length, and the separator was peeled off, followed by pressure bonding to a polarizing plate (manufactured by Nitto Denko Corporation, SEG1425EWVAGS2B, size: width 70 mm, length 100 mm) with a hand roller. did. After being left for one day in an environment of 23 ° C. × 50% RH, the surface protective film was peeled off from the stainless steel plate by hand, and the state of contamination on the stainless steel plate surface at that time was visually observed. The evaluation criteria are as follows.

If no contamination was found: ○
If contamination is found: ×

<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 leaving the laminate for 30 minutes, the adhesive strength when peeled at a peeling speed of 30 m / minute and a 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 isononyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, 2,2′-azobisisobutyrate 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 parts by weight of nitrile 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. (B) 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 −80 ° C., and an acid value of 0.0.

[Acrylic polymer (C)]
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. C) A solution (25% by weight) was prepared. The acrylic polymer (C) had a weight average molecular weight of 550,000, a glass transition temperature (Tg) of −54 ° C., and an acid value of 0.0.

[Acrylic polymer (D)]
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, 180 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of ethyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, 2 as a polymerization initiator Charge 0.4 parts by weight of 2'-azobisisobutyronitrile and 340 parts by weight of ethyl acetate, introduce nitrogen gas with gentle stirring, and maintain the liquid temperature in the flask at around 65 ° C for about 6 hours of polymerization. Reaction was performed and the acrylic polymer (D) solution (38 weight%) was adjusted. The acrylic polymer (D) had a weight average molecular weight of 650,000, a glass transition temperature (Tg) of −64 ° C., and an acid value of 0.0.

[Acrylic polymer (E)]
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 100 parts by weight of 2-ethylhexyl acrylate, 100 parts by weight of ethyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, 2 as a polymerization initiator Charge 2'-azobisisobutyronitrile (0.4 parts by weight) and ethyl acetate (486 parts by weight), introduce nitrogen gas with gentle stirring, and maintain the liquid temperature in the flask at around 65 ° C for about 6 hours of polymerization. Reaction was performed and the acrylic polymer (E) solution (30 weight%) was adjusted. The acrylic polymer (E) had a weight average molecular weight of 620,000, a glass transition temperature (Tg) of −47 ° C., and an acid value of 0.0.

[Acrylic polymer (F)]
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 a polymerization reaction. ) A solution (40% by weight) was prepared. The acrylic polymer (F) 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 (G)]
200 parts by weight of 2-ethylhexyl acrylate, 3.6 parts by weight of 2-hydroxyethyl acrylate, 0.4 parts by weight of acrylic acid, 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 (G) solution (40% by weight). The acrylic polymer (G) 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 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 keeping the liquid temperature in the vicinity of 80 ° C. to prepare an antistatic agent solution (a) (50 wt%).

[Antistatic agent solution (b)]
A four-necked flask equipped with a stirring blade, thermometer, and condenser is charged with 0.1 parts by weight of lithium perchlorate, 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 (b) (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>
(Preparation of adhesive solution)
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 2.6 parts by weight of the antistatic agent solution (a) (50% by weight) is added to 100 parts by weight of this solution. Hexamethylene diisocyanate isocyanurate body (Nihon Polyurethane Industry Co., Ltd., Coronate HX) 0.6 parts by weight as the agent, and dibutyltin dilaurate (1% by weight ethyl acetate solution) 0.4 parts by weight as the crosslinking catalyst The mixture was stirred and stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (1). In the acrylic pressure-sensitive adhesive solution (1), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[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 protective film.

<Example 2>
(Preparation of adhesive solution)
The acrylic pressure-sensitive adhesive solution (A) (40% by weight) was replaced with 100 parts by weight of a solution diluted to 20% by weight with ethyl acetate, and the acrylic pressure-sensitive adhesive solution (B) (40% by weight) was replaced with ethyl acetate. An acrylic pressure-sensitive adhesive solution (2) was prepared in the same manner as in Example 1 except that 100 parts by weight of the solution diluted to 20% by weight was used. In the acrylic pressure-sensitive adhesive solution (2), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[Preparation of adhesive sheet]
A 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).

<Example 3>
(Preparation of adhesive solution)
The acrylic polymer (A) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 1.6 parts by weight of the antistatic agent solution (b) (50% by weight) is added to 100 parts by weight of this solution. Add 0.4 parts by weight of isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX) as an agent, and add 0.4 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst. The mixture was stirred and stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (3). In the acrylic pressure-sensitive adhesive solution (1), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.040 parts by weight.

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

<Comparative Example 1>
(Preparation of adhesive solution)
Instead of the acrylic pressure-sensitive adhesive solution (A) (40% by weight) diluted to 20% by weight with ethyl acetate, the acrylic pressure-sensitive adhesive solution (C) (25% by weight) was diluted with ethyl acetate. An acrylic pressure-sensitive adhesive solution (4) was prepared in the same manner as in Example 1 except that 100 parts by weight of the solution diluted to 20% by weight was used. In the acrylic pressure-sensitive adhesive solution (4), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[Preparation of adhesive sheet]
A protective film was produced in the same manner as in Example 1 except that the acrylic adhesive solution (4) was used instead of the acrylic adhesive solution (1).

<Comparative Example 2>
(Preparation of adhesive solution)
The acrylic polymer (D) solution (38% by weight) is diluted to 20% by weight with ethyl acetate, and 2.6 parts by weight of the antistatic agent solution (b) (50% by weight) is added to 100 parts by weight of this solution. Add 0.4 parts by weight of isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate HX) as an agent, and add 0.4 parts by weight of dibutyltin dilaurate (1% by weight ethyl acetate solution) as a crosslinking catalyst. The mixture was stirred and stirred for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (5). In the acrylic pressure-sensitive adhesive solution (1), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[Preparation of adhesive sheet]
A 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 3>
(Preparation of adhesive solution)
Instead of the acrylic pressure-sensitive adhesive solution (D) (38 wt%) diluted to 20 wt% with ethyl acetate in 100 parts by weight, the acrylic pressure-sensitive adhesive solution (E) (30 wt%) was diluted with ethyl acetate. An acrylic pressure-sensitive adhesive solution (6) was prepared in the same manner as in Comparative Example 2, except that 100 parts by weight of the solution diluted to 20% by weight was used. In the acrylic pressure-sensitive adhesive solution (6), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[Preparation of adhesive sheet]
A 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).

<Comparative Example 4>
(Preparation of adhesive solution)
The acrylic polymer (F) solution (40% by weight) is diluted to 20% by weight with ethyl acetate, and 2.6 parts by weight of the antistatic agent solution (a) (50% by weight) is added to 100 parts by weight of this solution. 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, TETRAD-C) as an agent, trimethylolpropane / tolylene diisocyanate trimer adduct (Nippon Polyurethane) Koronate L, manufactured by Kogyo Co., Ltd. (0.3 parts by weight) was added, and the mixture was stirred at about 25 ° C. for about 1 minute to prepare an acrylic pressure-sensitive adhesive solution (7). In the acrylic pressure-sensitive adhesive solution (7), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

[Preparation of adhesive sheet]
A protective film was produced in the same manner as in Example 1 except that the acrylic adhesive solution (7) was used in place of the acrylic adhesive solution (1).

<Comparative Example 5>
(Preparation of adhesive solution)
Instead of the acrylic pressure-sensitive adhesive solution (A) (40% by weight) diluted to 20% by weight with ethyl acetate, the acrylic pressure-sensitive adhesive solution (G) (40% by weight) was diluted with ethyl acetate. An acrylic pressure-sensitive adhesive solution (8) was prepared in the same manner as in Example 1 except that 100 parts by weight of the solution diluted to 20% by weight was used. In addition, in the acrylic adhesive solution (8), the compounding quantity of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.065 parts by weight.

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

<Comparative Example 6>
(Preparation of adhesive solution)
Example 1 except that 4.0 parts by weight of the antistatic agent solution (a) (50% by weight) was used instead of 2.6 parts by weight of the antistatic agent solution (a) (50% by weight). An acrylic pressure-sensitive adhesive solution (9) was prepared by the same method. In addition, in the acrylic adhesive solution (9), the blending amount of the alkali metal salt (lithium salt) with respect to 100 parts by weight of the acrylic polymer was 0.10 parts by weight.

[Preparation of adhesive sheet]
A protective film was produced 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-described method, the protective film and tape produced were subjected to stripping voltage measurement, evaluation of contamination, and measurement of adhesive strength. 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 3), the stripping voltage to the polarizing plate was suppressed in any Example, and It became clear that the reduction effect was also excellent. On the other hand, Comparative Examples 1 to 3 using an adhesive composition comprising a (meth) acrylic polymer having a (meth) acrylic monomer having an alkyl group having less than 6 carbon atoms as a component, and an acid value larger than 1. In Comparative Examples 4 and 5 using the pressure-sensitive adhesive composition made of an acrylic polymer, no contamination was observed, but the stripping voltage to the polarizing plate was high. Further, in Comparative Example 6 using the pressure-sensitive adhesive composition in which the alkali metal salt was blended in an amount of 0.1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, the stripping voltage to the polarizing plate was kept low. As a result, the polarizing plate was contaminated. Therefore, in the comparative examples, it is clear that both the suppression of the peeling voltage to the polarizing plate which is the object to be protected and the suppression of the occurrence of contamination cannot be achieved at the same time, which is not suitable for the surface protective film. became.

  Moreover, the protective film of Examples 1-3 of this invention has a 180 degree peel adhesive force in the range of 0.1-6 N / 25mm, and it turns out that it is an adhesive sheet applicable as an object for protective films.

Claims (7)

Having A alkyl group (meth) Ru consists acrylic monomers chromatography (meth) acrylic polymer, in Po Li polyether polyol compound and a pressure-sensitive adhesive composition comprising an alkali metal salt,
The (meth) acrylic monomer having an alkyl group consists only of a (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms,
The (meth) acrylic monomer having an alkyl group having 6 to 14 carbon atoms is 50% by weight or more of the constituent components of the (meth) acrylic polymer,
The (meth) an acid value of the acrylic polymer is 1.0 or less, the relative (meth) 100 parts by weight of the acrylic polymer, Ri Na contained less than the alkali metal 0.1 part by weight,
Pressure-sensitive adhesive composition wherein the alkali metal salt and wherein the lithium salt der Rukoto. 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 pressure-sensitive adhesive composition according to claim 1 or 2 , wherein the pressure-sensitive adhesive composition contains an isocyanurate-modified product of an isocyanate compound as a crosslinking agent. The adhesive layer formed by bridge | crosslinking the adhesive composition in any one of Claims 1-3 . Pressure-sensitive adhesive sheet characterized by comprising forming on one side or both sides of the support an adhesive layer formed by crosslinking a pressure-sensitive adhesive composition according to any one of claims 1-3. A pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to any one of claims 1 to 3 is formed on one side or both sides on a support made of a plastic substrate subjected to antistatic treatment. Characteristic surface protective film. An optical member comprising the surface protective film according to claim 6 bonded thereto.

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