CN103242753A - Adhesive composition, adhesive film and surface-protective adhesive film - Google Patents

Abstract

The present invention relates to an adhesive composition, an adhesive film, and a surface protection film. The present invention provides an adhesive composition, an adhesive film using the same, and a surface protective film, the adhesive composition, the adhesive film and the surface protective film using the same have excellent antistatic properties, and have Corrosive, low pollution. In an adhesive composition containing a (meth)acrylic polymer mainly composed of a (meth)acrylate monomer with an alkyl group of C1 to C14 carbon atoms, an ion having a melting point of 30°C or higher is contained. Sexual compounds. In addition, in an adhesive composition containing a (meth)acrylic polymer mainly composed of a (meth)acrylic acid ester monomer having an alkyl group having C1 to C14 carbon atoms, the (meth)acrylic The polymer has an acid value of 30 or less and contains an ionic compound having a melting point of 30° C. or higher.

Description

Adhesive composition, adhesive film and surface protection film

technical field

The present invention provides an adhesive composition having antistatic properties, and an adhesive film in which an adhesive layer having antistatic properties is formed on at least one surface of a resin film using the adhesive composition, and the surface protective film. The adhesive films and surface protection films according to the invention have particularly excellent antistatic properties. Therefore, the surface protective film of the present invention can be used for the purpose of protecting the surface of an optical film such as a polarizing plate, retardation plate, antireflection film, etc., which use a plastic film that easily generates static electricity as a component.

Background technique

Conventionally, in the manufacturing process of optical films such as polarizing plates, retardation plates, and antireflection films constituting liquid crystal displays, a surface protective film is temporarily bonded to the surface of the optical film. When assembling an optical film into a liquid crystal display, the surface protection film is peeled and removed from an optical film. The surface protection film for protecting the surface of the optical film is used only in the manufacturing process, so it is also called a process film.

The surface protection film used in the process of manufacturing an optical film has an adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film. Moreover, the peeling-processed peeling film for protecting this adhesive layer was bonded on the upper surface of an adhesive layer before bonding to an optical film.

In addition, for optical films such as polarizing plates, phase difference plates, and anti-reflection films, optical evaluations involving display capabilities, chromaticity, contrast, and contamination of liquid crystal display panels, etc. Therefore, the necessary performance for the surface protection film is that no air bubbles or impurities are attached to the adhesive layer.

Furthermore, in recent years, excellent antistatic performance that prevents static electricity from being generated when the surface protection film is peeled off from an optical film such as a polarizing plate, a retardation film, and an antireflection film is required. This is because when the pressure-sensitive adhesive layer is peeled off from the adherend, the electrical control circuit of the liquid crystal display may malfunction due to static electricity generated during peeling.

In addition, there is a demand for a corrosion-resistant adhesive combination that does not corrode even when an optical film such as a polarizing plate, retardation film, or antireflection film is bonded to a metallic adherend such as a bezel. thing.

Furthermore, when the surface protective film is peeled off from an optical film such as a polarizing plate, a retardation film, and an antireflection film as an adherend, it is required that the adherend is not contaminated, that is, no adhesive residue is generated.

In this way, in recent years, from the viewpoint of ease of use suitable for the use of surface protection films, as the required performance for the adhesive layer constituting the surface protection film, it is required that: (1) have excellent antistatic performance; (2) have Corrosion resistance; (3) Prevent the occurrence of adhesive residue, etc.

However, although each of these (1) to (3) individually required performances as required performances for the adhesive layer constituting the surface protection film can be satisfied, it is very difficult to simultaneously satisfy the requirements in the adhesive layer of the surface protection film. All required properties of (1) to (3) required.

For example, regarding having excellent antistatic performance, a method of kneading an antistatic agent into a base film has been shown as a method of imparting antistatic performance to a surface protection film. As antistatic agents, for example, (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, primary to tertiary amino groups; (b) having sulfonate groups, sulfate ester groups, Anionic antistatic agents based on anionic groups such as phosphate and phosphonate groups; (c) amphoteric antistatic agents such as amino acids and aminosulfuric acid esters, (d) amino alcohols, glycerin, polyethylene glycol (e) polymer antistatic agents obtained by increasing the molecular weight of the above-mentioned antistatic agents, etc. (Patent Document 1).

In addition, in recent years, it has been proposed not only to include such an antistatic agent in a base film or to apply it on the surface of a base film, but also to directly contain such an antistatic agent in an adhesive layer.

In addition, as a conventional antistatic agent, an alkali metal salt is used. For example, Patent Document 2 discloses that as an ionic substance in a (meth)acrylic polymer, an alkali metal salt selected from perchloric acid and a compound selected from perchloric acid are used. One of alkaline earth metal salts, alkali metal salts of organoboron complexes, and alkaline earth metal salts of organoboron complexes. However, since an adhesive composition containing an antistatic agent composed of an alkali metal salt has metal corrosion properties, corrosion occurs when the adherend is a metal. Therefore, there is a need for an adhesive composition having corrosion resistance while having excellent antistatic properties.

In addition, regarding the prevention of adhesive residues, for example, it has been proposed to mix an isocyanate compound curing agent and a specific silicate oligomer into an acrylic resin in an amount of 0.0001 to 10 parts by weight with respect to 100 parts by weight of an acrylic resin. adhesive composition (Patent Document 3).

In Patent Document 3, an alkyl acrylate having an alkyl group of about 2 to 12 carbon atoms, an alkyl methacrylate having an alkyl group of about 4 to 12 carbon atoms are used as main monomer components, for example, Other functional group-containing monomer components such as carboxyl group-containing monomers can be contained. Generally, it is preferable to contain 50% by weight or more of the above-mentioned main monomers, and the content of monomer components containing functional groups is desirably 0.001 to 50% by weight, preferably 0.001 to 25% by weight, more preferably 0.01 to 25% by weight. Since the adhesive composition described in Patent Document 3 has little change in cohesion and adhesive force over time even under high temperature or high temperature and high humidity, and also shows an excellent effect in adhesive force to curved surfaces, In addition, no blistering or peeling of the adhesive occurred.

In general, when the adhesive layer is made flexible, adhesive residue tends to occur. That is, it is easy to make peeling difficult and rebonding difficult at the time of erroneous bonding. Therefore, it is necessary to cross-link monomers having functional groups such as carboxyl groups on the main agent to make the adhesive layer have a certain hardness and prevent the occurrence of adhesive residue.

In addition, the following proposals are known for preventing occurrence of adhesive residue. An acrylic pressure-sensitive adhesive layer obtained by using a copolymer of an alkyl (meth)acrylate having an alkyl group having 7 or less carbon atoms and a copolymer compound containing a carboxyl group as a main component, and subjecting it to a cross-linking treatment with a cross-linking agent After a long time has elapsed after bonding the adhesive layer, the transfer of the adhesive to the adherend side and the adhesive force to the adherend increase over time. In order to solve this problem, an adhesive (pressure-sensitive adhesive) is known in which an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms and an alcoholic A copolymer of a copolymerizable compound of a hydroxyl group is obtained by crosslinking treatment with a crosslinking agent (Patent Document 4).

Adhesives such as those obtained by mixing a small amount of a copolymer of an alkyl (meth)acrylate and a carboxyl group-containing copolymerizable compound in the same copolymer as above, and crosslinking it with a crosslinking agent have also been proposed. obtained by processing. However, when these adhesives are used for the surface protection of plastic plates with low surface tension and smooth surfaces, peeling phenomena such as floating may occur due to heating during processing or storage.

[Prior art literature]

[Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 11-070629

[Patent Document 2] Japanese Patent Laid-Open No. 2006-199873

[Patent Document 3] Japanese Patent Application Laid-Open No. 8-199130

[Patent Document 4] Japanese Patent Laid-Open No. 63-225677

Contents of the invention

[Problem to be solved by the invention]

Conventional adhesive compositions having antistatic performance have used alkali metal salts as antistatic agents to be contained in applications requiring excellent antistatic performance. However, if an alkali metal salt is used, corrosion occurs when the adherend is metal. In addition, the conventional surface protection film cannot satisfy the required performance required for the pressure-sensitive adhesive layer used in the surface protection film because of its contaminating property to the adherend.

The present invention takes advantage of the foregoing. An object of the present invention is to provide an adhesive composition having excellent antistatic performance, corrosion resistance, and low staining property, an adhesive film using the same, and a surface protection film.

[method to solve the problem]

The adhesive composition of the present invention contains an ionic compound having a melting point of 30° C. or higher, has corrosion resistance, and obtains excellent antistatic performance as a technical idea. Moreover, since the (meth)acrylic-type monomer which has a hydroxyl group is contained, the adhesive composition with little adhesive residue and low staining property can be obtained. By using such an adhesive composition, it is possible to provide an adhesive composition having excellent antistatic performance, corrosion resistance, and low contamination, an adhesive film and a surface protection film using the same.

In order to solve the above-mentioned problems, the present invention provides an adhesive composition comprising (meth)acrylic acid ester monomers whose main components are C1-C14 carbon atoms in the alkyl group. The adhesive composition of the product contains an ionic compound with a melting point of 30°C or higher.

In addition, the present invention provides an adhesive composition, which contains (meth)acrylic polymer mainly composed of (meth)acrylic acid ester monomers whose carbon atoms in the alkyl group are C1-C14. In the mixture composition, the (meth)acrylic polymer has an acid value of 30 or less and contains an ionic compound having a melting point of 30° C. or higher.

The aforementioned (meth)acrylic polymer preferably contains a (meth)acrylic monomer having a hydroxyl group.

Moreover, this invention provides the adhesive film which formed the adhesive layer which crosslinked the said adhesive composition on one surface or both surfaces of a resin film.

In addition, the present invention provides a surface protection film obtained by forming an adhesive layer obtained by crosslinking the aforementioned adhesive composition on one surface of a resin film, After drawing with a ballpoint pen on the surface protective film bonded to the adherend via the pressure-sensitive adhesive layer, it was peeled off from the adherend without transfer of contamination to the adherend.

The aforementioned surface protection film is preferably used as a surface protection film of a polarizing plate. Furthermore, it is preferable to perform antistatic and antifouling treatments on the surface of the aforementioned resin film opposite to the side on which the aforementioned pressure-sensitive adhesive layer is formed.

[Invention effect]

According to the present invention, it is possible to provide an adhesive composition having excellent antistatic performance, corrosion resistance to an adherend, and low contamination, and an adhesive film and a surface protection film formed using the same.

Detailed ways

Next, the present invention will be described based on preferred embodiments.

In the adhesive composition of the present invention, in an adhesive composition containing a (meth)acrylic polymer whose main component is a (meth)acrylic acid ester monomer with an alkyl group having C1 to C14 carbon atoms Contains ionic compounds with a melting point of 30°C or higher.

In addition, the adhesive composition of the present invention is combined with an adhesive containing a (meth)acrylic polymer mainly composed of a (meth)acrylic acid ester monomer having an alkyl group having C1 to C14 carbon atoms. In the product, the (meth)acrylic polymer has an acid value of 30 or less and contains an ionic compound having a melting point of 30° C. or higher.

As a (meth)acrylate monomer whose alkyl group has C1 to C14 carbon atoms, there are listed: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, ( Isopropyl methacrylate, Butyl (meth)acrylate, Isobutyl (meth)acrylate, Pentyl (meth)acrylate, Hexyl (meth)acrylate, Heptyl (meth)acrylate, ( Octyl methacrylate, Isooctyl (meth)acrylate, 2-Ethylhexyl (meth)acrylate, Nonyl (meth)acrylate, Isononyl (meth)acrylate, Acrylic acid (meth) Decyl ester, Undecyl (meth)acrylate, Lauryl (meth)acrylate, Tridecyl (meth)acrylate, Myristyl (meth)acrylate, (Meth) ) cyclopentyl acrylate, (meth)cyclohexyl acrylate, etc. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. The weight ratio of the (meth)acrylate monomer whose alkyl group has C1 to C14 carbon atoms to the (meth)acrylic polymer is preferably 50 to 100%.

The (meth)acrylic polymer preferably contains a (meth)acrylic monomer having a hydroxyl group. Examples of (meth)acrylic monomers having a hydroxyl group include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, Hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; N-hydroxy(meth)acrylamide, N-methylol(meth)acrylamide, N-hydroxyethyl Hydroxyl-containing (meth)acrylamides, such as (meth)acrylamide, etc.

The (meth)acrylic polymer may contain a copolymerizable monomer having a carboxyl group. Examples of carboxyl group-containing copolymerizable monomers include: (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate Esters etc.

In addition, the (meth)acrylic polymer may contain copolymerized vinyl monomers other than the above. Examples of other copolymerized vinyl monomers include aromatic group-containing (meth)acrylates such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, styrene, acrylamide, etc. , acrylonitrile, methyl vinyl ether, ethyl vinyl ether, vinyl acetate, vinyl chloride and other vinyl monomers.

However, if acidic monomers such as carboxyl group-containing monomers (hereinafter referred to as acidic monomers) are excessively added, there is a possibility that corrosion may increase due to these acids. Therefore, the acid value of the (meth)acrylic polymer is preferably 30 or less.

Here, the "acid value" is one of the indicators showing the acid content, and it is expressed in mg of potassium hydroxide required to neutralize 1 g of a polymer having an acidic component.

In order to impart antistatic performance, the adhesive composition of the present invention preferably contains an antistatic agent. The antistatic agent is preferably solid at normal temperature (for example, 30° C.), more specifically, an ionic compound with a melting point of 30° C. or higher. Since such an antistatic agent has a lower melting point than an alkali metal salt and has a long-chain alkyl group, it is presumed to have a high affinity with an acrylic copolymer.

The ionic compound having a melting point of 30° C. or higher is an ionic compound having a cation and an anion, and the following compounds are exemplified: the cation is a pyridinium cation, an imidazolium cation, a pyrimidinium cation, a pyrazolium cation, a pyrrolium cation, Nitrogenous cations such as ammonium cations, or phosphonium cations, sulfonium cations, etc., and anions such as hexafluorophosphate (PF ₆ ^- ), thiocyanate (SCN ^- ), alkylbenzenesulfonate (RC ₆ H ₄ SO ₃ ^- ), perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ^- ) and other inorganic or organic anion compounds. A substance having a melting point of 30°C or higher can be obtained by selecting the chain length of the alkyl group or the position and number of substituents. The cation is preferably a quaternary nitrogen-containing onium cation, and examples include: quaternary pyridinium cations such as 1-alkylpyridinium (the carbon atom at the 2-6 position may have a substituent or may be unsubstituted), and 1,3-dioxane Quaternary imidazolium cations such as imidazolium (the carbon atoms at positions 2, 4, and 5 may be substituted or unsubstituted), quaternary ammonium cations such as tetraalkylammonium groups, and the like. The melting point of the ionic compound is preferably 30 to 80°C. An alkyl group, an aryl group, etc. are mentioned as a substituent which a cation may have. Since the above-mentioned ionic compound is not an alkali metal salt, it can solve the problem that the alkali metal salt in the prior art has metal corrosion.

The main agent (meth)acrylic polymer used in the adhesive composition of the present invention can be a (meth)acrylate monomer with one or more carbon atoms of the alkyl group being C1~C14 As a main component, other monomers are added as needed, and polymerized to synthesize. The polymerization method of the (meth)acrylic polymer is not particularly limited, and suitable polymerization methods such as solution polymerization and emulsion polymerization can be used.

The adhesive composition of the present invention preferably crosslinks the adhesive polymer when forming the adhesive layer. As a method for causing the crosslinking reaction, the adhesive composition may contain a known crosslinking agent, or may be crosslinked by photocrosslinking such as ultraviolet rays (UV). Examples of the crosslinking agent include isocyanate compounds with difunctional or trifunctional groups or more, epoxy compounds with difunctional or trifunctional group or more, acrylate compounds with difunctional or trifunctional groups or more, metal chelate compounds, and the like.

In addition, as other components, silane coupling agents, antioxidants, surfactants, crosslinking accelerators, plasticizers, fillers, hardening accelerators, hardening inhibitors, processing aids, antiaging agents, etc. can be mixed appropriately known additives. These additives can be used alone or in combination of two or more.

The surface resistivity of the adhesive layer obtained by crosslinking the aforementioned adhesive composition is preferably 5.0×10 ⁺¹⁰ Ω/□ or less. In addition, the peeling voltage of the pressure-sensitive adhesive layer is preferably ±0 to 1 kV. In addition, in the present invention, the "±0~1kV" means 0~-1kV and 0~+1kV, that is, -1~+1kV. When the surface resistivity is large, the performance of releasing static electricity due to charging during peeling is poor. Therefore, by making the surface resistivity sufficiently small, the peeling charge voltage accompanying the static electricity generated when the adhesive layer is peeled off from the adherend can be reduced. , To suppress the impact on the electrical control circuit of the adherend, etc.

The gel fraction of the adhesive layer obtained by crosslinking the adhesive composition of the present invention (crosslinked adhesive) is preferably 95 to 100%. In this way, due to the high gel fraction, the adhesive force at the time of low-speed peeling can not become too large, the elution of unpolymerized monomers or oligomers from the copolymer can be reduced, and the anti-pollution property, high temperature and high humidity can be improved. Durability, inhibits contamination of adherends.

The adhesive film of the present invention is an adhesive film in which an adhesive layer obtained by crosslinking the adhesive composition of the present invention is formed on one or both surfaces of a resin film. In addition, the surface protection film of the present invention is a surface protection film in which an adhesive layer obtained by crosslinking the adhesive composition of the present invention is formed on one surface of a resin film. Since the adhesive composition of the present invention has excellent antistatic performance, and has corrosion resistance to the adherend, and has low pollution, therefore, the surface protection film of the present invention is attached to the adherend, that is, use After the ballpoint pen was drawn on the surface protection film through the adhesive layer, it was peeled off from the adherend, and there was no transfer contamination to the adherend. Therefore, the surface protection film of this invention can be used suitably as the use of the surface protection film of a polarizing plate.

Resin films, such as a polyester film, etc. can be used as a base film of an adhesive layer, and the peeling film (separator) which protects an adhesive surface.

In the substrate film, on the surface of the resin film opposite to the side where the adhesive layer is formed, anti-pollution treatment with silicone-based, fluorine-based mold release agents or coating agents, silica particles, etc. can be implemented; Antistatic treatment by coating or kneading of an antistatic agent.

In the release film, the surface of the pressure-sensitive adhesive layer on the side to be bonded to the adhesive surface is subjected to a mold release treatment with a silicone-based or fluorine-based mold release agent or the like.

In the case of a surface protection film for optics such as a surface protection film for polarizing plates, the base film and the adhesive layer preferably have sufficient transparency.

Example

Hereinafter, the present invention will be specifically described based on examples.

<Preparation of Adhesive Composition>

[Example 1]

Nitrogen was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen. Then, 100 parts by weight of 2-ethylhexyl acrylate, 5.0 parts by weight of 2-hydroxyethyl acrylate, and 100 parts by weight of a solvent (ethyl acetate) were added to the reaction device. Then, 0.1 weight part of azobisisobutyronitrile was dripped as a polymerization initiator over 2 hours, and it was made to react at 65 degreeC for 8 hours, and the acrylic-type copolymer solution was obtained. A part of the acrylic copolymer was used as a measurement sample of the acid value described below.

To this acrylic copolymer solution, 1.5 parts by weight of 1-octylpyridinium hexafluorophosphate, 1.5 parts by weight of Coronet HX (isocyanurate body of hexamethylene diisocyanate compound), 1.5 parts by weight of dilauric acid di 0.02 parts by weight of octyltin were stirred and mixed to obtain the adhesive composition of Example 1.

[Examples 2 to 4 and Comparative Examples 1 to 3]

The compositions of monomers and additives were set as described in Table 1, except that, in the same manner as the adhesive composition of Example 1 above, the adhesive compositions of Examples 2 to 4 and Comparative Examples 1 to 3 were obtained. Adhesive composition.

Here, (A) acrylic monomer, (B) hydroxyl monomer, (C) acidic monomer are added to the reaction device before polymerization of the acrylic copolymer solution, and then added to the acrylic copolymer solution after polymerization (D) Isocyanate (NCO) crosslinking agent, (E) crosslinking accelerator, (F) antistatic agent as additives.

In Table 1, the mixing ratio of each component is enclosed in parentheses, and represents the numerical value of the required parts by weight with the total of (A) group being 100 parts by weight. In addition, Table 2 shows the compound names corresponding to the abbreviations of the components used in Table 1. Coronet (registered trademark) HX, the same HL and the same L-45 are trade names of Nippon Polyuretan Industry Co., Ltd., and Takenet (registered trademark) D-140N is a trade name of Mitsui Chemicals Corporation. Regarding the compound names of the isocyanate (NCO) crosslinking agents in Table 2, HDI, IPDI, and TMP mean hexamethylene diisocyanate, isophorone diisocyanate, and trimethylolpropane, respectively.

[Table 1]

[Table 2]

＜Preparation of surface protection film＞

After coating the adhesive composition of Example 1 on a release film formed of a silicone resin-coated polyethylene terephthalate (PET) film, the solvent was removed by drying at 90°C to obtain The thickness of the adhesive layer is an adhesive sheet of 25 μm. Then, the adhesive sheet was transferred to the opposite side of the antistatic and antifouling treated side of polyethylene terephthalate (PET) film having antistatic and antifouling treatment on one side to obtain a The surface protection film of Example 1 of the laminated structure of anti-pollution-treated PET film/adhesive layer/release film (silicone resin-coated PET film)".

[Examples 2 to 4 and Comparative Examples 1 to 3]

Using the adhesive composition of Examples 2 to 4 and Comparative Examples 1 to 3 respectively instead of the adhesive composition of Example 1, except that, in the same manner as the surface protection film of Example 1 above, Example 2 was obtained. ~4 and the surface protective film of Comparative Examples 1~3.

＜Test method and evaluation＞

After aging the surface protection films in Examples 1 to 4 and Comparative Examples 1 to 3 in an atmosphere of 23°C and 50% RH for 7 days, peel off the release film (silicone resin-coated PET film), and expose the adhesive film. After the substance of the agent layer is pasted on the aluminum foil, it is placed in a high-temperature and high-humidity atmosphere of 60°C and 90%RH for 48 hours, and then it is used as a corrosion measurement sample.

Furthermore, the surface protective film with the exposed adhesive layer was attached to the surface of the polarizing plate attached to the liquid crystal cell through the adhesive layer, and after standing for 1 day, it was subjected to an autoclave at 50° C., 5 atmospheres, and 20 minutes. After treatment, it was further left at room temperature for 12 hours, and the material obtained above was used as a test sample for adhesion and peeling voltage.

<Measurement method of acid value>

For the acid value of acrylic copolymers, a sample was dissolved in a solvent (a mixture of diethyl ether and ethanol at a volume ratio of 2:1), using a potentiometric automatic titration device (manufactured by Kyoto Denshi Kogyo, AT-610), using 0.1 of the above Potentiometric titration device, carry out potentiometric titration with potassium hydroxide ethanol solution with a concentration of about 0.1 mol/l, and measure the amount of potassium hydroxide ethanol solution required to neutralize the sample. Then, the acid value was calculated|required by the following formula.

Acid value = (B × f × 5.611) / S

B = the amount of 0.1mol/l potassium hydroxide ethanol solution used in the titration (ml)

f=factor of 0.1mol/l potassium hydroxide ethanol solution

S=mass of the solid component of the sample (g)

＜Measurement of Adhesive Strength＞

The following peel strength is used as the adhesive force: Measured by peeling the test sample obtained above (a surface protective film with a width of 25 mm on the surface of the polarizing plate) using a tensile tester at a tensile speed of 30 m/min in a direction of 180° Peel strength (N/25mm).

<Measurement method of peeling voltage>

When the test sample obtained above was peeled off at a tensile speed of 30 m/min at 180°, the voltage (charged voltage) generated by charging the polarizer was measured using a high-precision electrostatic sensor SK-035, SK-200 (manufactured by Keyence Co., Ltd.), The maximum value of the measured value was taken as the stripping voltage (kV).

＜Evaluation method of corrosion＞

After attaching the sample to the aluminum foil, it was left for 48 hours under high temperature and high humidity conditions of 60°C×90%RH. Then, the sample was peeled off from the aluminum foil, the surface of the aluminum foil was visually confirmed, and it evaluated by the following reference|standard.

◯: Discoloration on the surface of the aluminum foil was not confirmed.

Δ: Partial discoloration of the surface of the aluminum foil was confirmed.

×: Discoloration of the surface of the aluminum foil was confirmed.

<Evaluation method of pollution>

After drawing with a ballpoint pen (load 500 g, reciprocating 3 times) on the surface protection film of the test sample obtained above, it was left to stand at 70° C. for 24 hours. The surface protective film was peeled off from the polarizing plate, and the surface of the polarizing plate was observed to confirm that there was no transfer of contamination to the polarizing plate, and the following criteria were used for evaluation.

◯: Contamination was not transferred to the polarizing plate.

Δ: Transfer of contamination to at least a part was confirmed along the trajectory drawn by the ballpoint pen.

X: Transfer contamination was confirmed along the trajectory drawn by the ballpoint pen, and the adhesive was also detached from the adhesive surface.

[table 3]

Table 3 shows the results of the tests and evaluations.

In Examples 1 to 4 in which an ionic compound having a melting point of 30° C. or higher was used as an antistatic agent, a substance having excellent antistatic performance, corrosion resistance to an adherend, and low staining property was formed.

In Comparative Example 1 in which lithium perchlorate was used as the antistatic agent, a highly corrosive and somewhat highly polluting substance was formed.

In Comparative Example 2, in which lithium bis(trifluoromethanesulfonyl)imide was used as the antistatic agent, and the acid value of the acrylic polymer of the binder was high, the peeling voltage was high, the antistatic performance was poor, and the staining property was poor. High, slightly corrosive substances.

In Comparative Example 3 in which lithium trifluoromethanesulfonate was used as the antistatic agent, a slightly more corrosive and slightly more polluting substance was formed.

Therefore, the surface protection films of Comparative Examples 1 to 3 could not simultaneously satisfy (1) excellent antistatic performance, (2) corrosion resistance, and (3) prevent occurrence of adhesive residue.

Claims (10)

1. An adhesive composition comprising an adhesive combination of (meth)acrylic polymers containing (meth)acrylic polymers whose main component is a (meth)acrylic acid ester monomer with the number of carbon atoms of the alkyl group being C1 to C14 It contains ionic compounds with a melting point above 30°C. 2. An adhesive composition, which is combined with an adhesive (meth)acrylic polymer whose main component is a (meth)acrylic polymer containing a (meth)acrylic ester monomer whose carbon number is C1 to C14. In the product, the (meth)acrylic polymer has an acid value of 30 or less and contains ionic compounds with a melting point of 30°C or higher. 3. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic polymer contains a (meth)acrylic monomer having a hydroxyl group. 4. An adhesive film comprising an adhesive layer formed by crosslinking the adhesive composition according to claim 1 or 2 on one or both surfaces of a resin film. 5. An adhesive film comprising an adhesive layer formed by crosslinking the adhesive composition according to claim 3 on one or both surfaces of a resin film. 6. A surface protection film, which is a surface protection film obtained by forming an adhesive layer on one side of a resin film, and the adhesive layer is obtained by making the adhesive composition according to claim 1 or 2 Obtained by cross-linking, after being drawn with a ballpoint pen on the surface protective film attached to the adherend through the above-mentioned adhesive layer, it is peeled off from the adherend, and there is no transfer of contamination to the adherend. 7. A surface protection film obtained by forming an adhesive layer on one side of a resin film obtained by crosslinking the adhesive composition according to claim 3 As a result, after drawing with a ballpoint pen on the surface protection film bonded to an adherend via the pressure-sensitive adhesive layer, it was peeled off from the adherend without transfer of contamination to the adherend. 8. The surface protection film according to claim 6, which is used as a surface protection film of a polarizing plate. 9. The surface protection film according to claim 6, which is subjected to antistatic and antifouling treatments on the surface of the resin film opposite to the side where the adhesive layer is formed. 10. The surface protection film according to claim 8, which is subjected to antistatic and antifouling treatments on the surface of the resin film opposite to the side where the adhesive layer is formed.