TWI655265B - Adhesive composition, adhesive film and surface protective film - Google Patents

Abstract

The present invention provides an adhesive composition, an adhesive film, and a surface protective film which have excellent antistatic properties, excellent balance of adhesion at the peeling speed in low-speed regions and high-speed regions, and excellent durability and reworkability. An antistatic agent-containing adhesive composition comprising an acrylic polymer containing a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 10 carbon atoms as a main component, and polymerized with respect to 100 parts by weight of an acrylic polymer. The product contains 85 to 98.5 parts by weight of an alkyl (meth) acrylate, 0.1 to 15 parts by weight of a hydroxyl-containing copolymerizable monomer, 0.1 to 2 parts by weight of a carboxyl-containing copolymerizable monomer, and 0.1 to 5 parts by weight of a crosslinking agent, the acid value of the acrylic polymer is 0.01 to 8.0, the antistatic agent is an ionic compound having a melting point of 30 to 50 ° C, and the adhesive composition contains a polyether-modified silicone Compound.

Description

Adhesive composition, adhesive film and surface protective film

The invention relates to an adhesive composition having antistatic performance, and an adhesive film using the adhesive composition to form an adhesive layer having antistatic performance on at least one side of a resin film, and a surface protection film.

In addition, the present invention relates to a surface protection film used in a manufacturing step of a liquid crystal display. More specifically, the present invention relates to an adhesive composition for a surface protection film adhered to the surface of an optical member such as a polarizing plate, a retardation plate, and an anti-reflection film constituting a liquid crystal display, and a surface protection using the adhesive composition. membrane.

Conventionally, in the manufacturing steps of optical members such as a polarizing plate, a retardation plate, and an antireflection film, which are members constituting a liquid crystal display, a surface protective film for temporarily protecting the surface of the optical member is stuck. This surface protection film is used only in the step of manufacturing an optical member, and when the optical member is assembled to a liquid crystal display, it is peeled off from the optical member and removed. Since such a surface protective film for protecting the surface of an optical member is used only in a manufacturing step, it is also commonly referred to as a "step film".

For the surface protective film used in such a step of manufacturing an optical member, a polyethylene terephthalate (PET) tree having optical transparency is used. An adhesive layer is formed on one side of the lipid film. A release film, which has been subjected to a release treatment, for protecting the adhesive layer is pasted on the adhesive layer until it is attached to the optical member.

In addition, for optical components such as polarizing plates, retardation plates, and anti-reflection films, products with optical evaluation such as display ability, hue, contrast, and impurity incorporation of liquid crystal display panels are applied in a state where a surface protective film is bonded. Inspection, so as a performance requirement for the surface protection film, it is required that the adhesive layer does not contain bubbles and no impurities.

In addition, in recent years, when the surface protective film is peeled from optical members such as a polarizing plate, a retardation plate, and an anti-reflection film, peeling static electricity caused by static electricity generated when the adhesive layer is peeled from an adherend may affect The failure of the electrical control circuit of the liquid crystal display, therefore, the adhesive layer is required to have excellent antistatic performance.

In addition, when a surface protective film is adhered to an optical member such as a polarizing plate, a retardation plate, or an anti-reflection film, for various reasons, the surface protective film may be temporarily peeled off and the surface protective film may be affixed again. In this case, the surface protection film is required to have a characteristic (reworkability) that is easily peeled off from the optical member of the adherend. In addition, at this time, it is required that the adhesive layer of the surface protective film does not contaminate the adherend, that is, it is required that no so-called adhesive residue phenomenon occurs.

In addition, when the surface protective film is peeled from the final optical member such as a polarizing plate, a retardation plate, or an antireflection film, it is required to be able to peel off the surface protection film quickly. That is, it is required that the change in the adhesive force due to the peeling speed is small in order to be able to peel off quickly even in the case of high-speed peeling.

As described above, in recent years, from the viewpoint of easy handling when using a surface protective film, the adhesive layer constituting the surface protective film is required to have the following properties: (1) Achieving the balance of adhesive force at the peeling speed in the low speed region and the high speed region; (2) preventing the occurrence of adhesive residue; (3) having excellent antistatic performance; and (4) having reprocessing (ReWork) performance.

However, even if the performance requirements for the adhesive layer constituting the surface protective film can be individually satisfied, that is, even if the individual performance requirements in the above (1) to (4) can be satisfied, the adhesive layer requiring the surface protective film is also satisfied at the same time. All the performance requirements of (1) to (4) are very difficult issues.

In this specification, the "low speed region" refers to a region where the peeling speed is around 0.3 m / min; the "high speed region" refers to a region where the peeling speed is around 30 m / min.

For example, the following suggestions are known about (1) achieving a balance of adhesive force at the peeling speed in the low speed region and the high speed region, and (2) preventing the occurrence of adhesive residues.

It is prepared by using a copolymer of an alkyl (meth) acrylate having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound as a main component and subjecting it to a crosslinking treatment with a crosslinking agent. In the acrylic adhesive layer, when the adhesive is adhered for a long time, there is a problem that the adhesive moves to the adherend and adheres to the adherend, and the adhesion force to the adherend increases with time. . In order to avoid this problem, there is known a technical solution provided with an adhesive layer using an (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and an alcoholic hydroxyl group. An adhesive layer obtained by copolymerizing a copolymer of a polymerizable compound and subjecting it to a crosslinking treatment with a crosslinking agent (Patent Document 1).

In addition, there is also proposed a technical solution provided with an adhesive layer, which is prepared by blending a small amount of (methyl) in the same copolymer as the above. An adhesive layer comprising a copolymer of an alkyl acrylate and a copolymerizable compound containing a carboxyl group and cross-linking it with a cross-linking agent. However, when it is used for the surface protection of a plastic plate or the like having a low surface tension and a smooth surface, it has problems of peeling such as separation due to heating during processing or storage, and high-speed peeling in the field of manual operation. The problem of poor re-peelability.

In order to solve these problems, an adhesive composition is proposed. The adhesive composition is: (a) an alkyl (meth) acrylate having an alkyl group having 8 to 10 carbon atoms as a main component (methyl ) To 100 parts by weight of an alkyl acrylate, b) 1 to 15 parts by weight of a carboxyl group-containing copolymerizable compound, and c) 3 to 100 parts by weight of a vinyl group of an aliphatic carboxylic acid having 1 to 5 carbon atoms. An ester composition to obtain a copolymer of a monomer mixture, and an adhesive composition obtained by blending a cross-linking agent having a carboxyl group or more equivalent of the component b) to the copolymer (Patent Document 2).

In the adhesive composition described in Patent Document 2, no peeling phenomenon such as separation occurs during processing or storage, and the adhesive force does not increase significantly over time, so that the re-peelability is excellent. In addition, even long-term storage, especially long-term storage in a high-temperature environment, it can be re-peeled with a small force. At this time, the adhesive does not remain on the adherend, and it can be removed even at high speeds. The force is then stripped.

In addition, as for the excellent antistatic performance of (3), as a method for imparting antistatic properties to a surface protective film, a method of mixing an antistatic agent into a base film, etc. have been proposed. As the antistatic agent, for example, (a) various cationic antistatic agents having a class 4 ammonium salt, a pyridinium salt, and a class 1 to 3 amino group; (b) a sulfonate group and a sulfate ester group , Phosphate ester, phosphonate, etc. Anionic antistatic agent based on anionic groups; (c) amphoteric antistatic agents such as amino acids and amino sulfates; (d) nonionic antistatic agents such as amino alcohols, glycerols, and polyethylene glycols; ( e) A polymer-type antistatic agent obtained by polymerizing the antistatic agent as described above (Patent Document 3).

In addition, in recent years, proposals have been made to include such an antistatic agent in a base film or directly include it in an adhesive layer instead of coating the surface of the base film.

In addition, regarding (4) reworkability, for example, an adhesive composition is proposed. The adhesive composition is composed of 100 to 10 parts by weight of a curing agent and 0.0001 to 10 parts by weight of an isocyanate compound and 100 parts by weight of an acrylic resin. Obtained from a specific silicate oligomer (Patent Document 4).

Patent Document 4 describes that a main monomer is an alkyl acrylate having an alkyl group having about 2 to 12 carbon atoms, an alkyl methacrylate having an alkyl group having about 4 to 12 carbon atoms, and the like. The component may contain, for example, a monomer component containing another functional group such as a carboxyl group-containing monomer. Generally speaking, it is preferable that the above-mentioned main monomer is contained in an amount of 50% by weight or more, and the content of the monomer component containing a functional group is preferably 0.001 to 50% by weight, preferably 0.001 to 25% by weight, and more preferably 0.01 to 25 weight%. Such an adhesive composition described in Patent Document 4 has a small change in cohesive force and adhesive force over time even under high temperature or high temperature and humidity, and shows excellent effects on the adhesive force of curved surfaces. Processability.

In general, when the adhesive layer is soft, adhesive residue is liable to occur, and reworkability is also easily reduced. That is, it is difficult to peel off after erroneous bonding, and it is difficult to re-adhere. From this point of view, in order to make it reworkable, it is necessary to crosslink a monomer having a functional group such as a carboxyl group to the main agent so that the adhesive layer has a certain hardness.

In the conventional technology, as a performance requirement for the adhesive layer constituting the surface protective film, it has been required to have (1) the balance of the adhesion force at the peeling speed in the low-speed region and the high-speed region; (2) the prevention of adhesion Occurrence of agent residues; (3) having excellent antistatic properties; and (4) having reprocessing properties. However, even if the performance requirements of individual items in (1) to (4) above can be individually met, all the performance requirements required for the adhesive layer of the surface protection film cannot be met.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 63-225677

[Patent Document 2] Japanese Unexamined Patent Publication No. 11-256111

[Patent Document 3] Japanese Patent Application Laid-Open No. 11-070629

[Patent Document 4] Japanese Unexamined Patent Publication No. 8-199130

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an excellent antistatic performance, an excellent balance of adhesion at a peeling speed in a low speed region and a high speed region, and excellent durability and reworkability. Adhesive composition, adhesive film and surface protective film.

In order to solve the above problems, the present invention provides an adhesive composition, which is an adhesive composition containing an antistatic agent, wherein the adhesive composition contains a (methyl group having an alkyl group having 4 to 10 carbon atoms ) Acrylic polymer with alkyl acrylate as the main component, The acrylic polymer contains 85 to 98.5 parts by weight of the main component (alkyl) (meth) acrylate, 0.1 to 15 parts by weight of a hydroxyl-containing copolymerizable monomer, and 0.1 to 2 parts with respect to 100 parts by weight of the acrylic polymer. The carboxyl group-containing copolymerizable monomer and 0.1 to 5 parts by weight of a cross-linking agent, the acrylic polymer has an acid value of 0.01 to 8.0, and the antistatic agent is an ionic compound having a melting point of 30 to 50 ° C. The adhesive composition contains a polyether-modified silicone compound.

The main component (alkyl) (meth) acrylate is preferably selected from the group consisting of butyl (meth) acrylate, isobutyl (meth) acrylate, amyl (meth) acrylate, and (meth) Hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, ( One or more of the compound group consisting of isononyl (meth) acrylate and decyl (meth) acrylate.

The hydroxyl-containing copolymerizable monomer is preferably selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 4 (meth) acrylic acid. -Hydroxybutyl ester, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acryl At least one or more members of the compound group consisting of amidine.

The carboxyl-containing copolymerizable monomer is selected from the group consisting of (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 2- (meth) acrylic acid. Ethyl hexahydrophthalic acid, 2- (meth) acryloxypropylhexahydrophthalic acid, 2- (meth) acryloxyethyl phthalic acid, 2- (formyl) ) Acrylic acid ethoxyethyl succinic acid, 2- (meth) acrylic acid oxyethyl maleic acid, carboxy polycaprolactone mono (meth) acrylate, 2- (meth) acrylic acid oxy B One or more of the compound group consisting of tetrahydrophthalic acid.

The polyether-modified silicone compound is preferably a polyether-modified silicone compound having an HLB value of 7 to 12.

The crosslinking agent is preferably a trifunctional or higher isocyanate compound.

In addition, the present invention provides an adhesive film formed by forming an adhesive layer on one or both sides of a resin film, and the adhesive layer is formed by cross-linking the aforementioned adhesive composition.

In addition, the present invention provides a surface protection film formed by forming an adhesive layer on one side of a resin film, and the adhesive layer is formed by cross-linking the aforementioned adhesive composition.

Based on the present invention, all the properties required for the adhesive layer of the surface protection film that cannot be solved in the prior art can be satisfied. Moreover, excellent antistatic properties can be obtained and the occurrence of adhesive residues can be prevented.

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

The adhesive composition of the present invention is an adhesive composition containing an antistatic agent, and is characterized in that the adhesive composition includes a (meth) acrylic alkyl group having an alkyl group having 4 to 10 carbon atoms. The acrylic polymer having an ester as a main component contains 85 to 98.5 based on 100 parts by weight of the acrylic polymer. This main component is an alkyl (meth) acrylate, 0.1 to 15 parts by weight of a hydroxyl-containing copolymerizable monomer, 0.1 to 2 parts by weight of a carboxyl-containing copolymerizable monomer, and 0.1 to 5 parts by weight. Acid value of the acrylic polymer is 0.01 to 8.0, the antistatic agent is an ionic compound having a melting point of 30 to 50 ° C, and the adhesive composition contains a polyether-modified silicone compound .

The alkyl (meth) acrylate as a main component is preferably an alkyl (meth) acrylate containing an alkyl group having 4 to 10 carbon atoms, and is preferably selected from butyl (meth) acrylate Ester, isobutyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate One or more compounds selected from the group consisting of esters, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and decyl (meth) acrylate.

The content of the alkyl (meth) acrylate as a main component is preferably 85 to 98.5 parts by weight based on 100 parts by weight of the acrylic polymer.

Examples of the hydroxyl-containing copolymerizable monomer include hydroxyalkyl (meth) acrylates, (meth) acrylamidoamines containing a hydroxyl group, and the like.

The above-mentioned hydroxyl-containing copolymerizable monomer is preferably selected from the group consisting of 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Composed of 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide At least one or more of the compound groups.

The content of the copolymerizable monomer containing a hydroxyl group is preferably 0.1 to 15 parts by weight based on 100 parts by weight of the acrylic polymer.

The carboxyl-containing copolymerizable monomer is preferably selected from the group consisting of (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 2- (meth) acrylic acid. Ethyl hexahydrophthalic acid, 2- (meth) acryloxypropylhexahydrophthalic acid, 2- (meth) acryloxyethyl phthalic acid, 2- (formyl) ) Acrylic acid ethoxyethyl succinic acid, 2- (meth) acrylic acid oxyethyl maleic acid, carboxy polycaprolactone mono (meth) acrylate, 2- (meth) acrylic acid oxy One or more of the compound group consisting of ethyltetrahydrophthalic acid.

The content of the carboxyl group-containing copolymerizable monomer is preferably 0.1 to 2 parts by weight based on 100 parts by weight of the acrylic polymer.

In the adhesive composition of the present invention, it is preferable that the adhesive polymer is crosslinked when the adhesive layer is formed. As a method for initiating the crosslinking reaction, crosslinking may be performed by photocrosslinking such as ultraviolet (UV), but it is preferred that the adhesive composition contains a crosslinking agent.

Examples of the crosslinking agent include difunctional or trifunctional or higher isocyanate compounds, difunctional or trifunctional or higher epoxides, difunctional or trifunctional or higher acrylate compounds, metal chelate compounds, and the like. Among them, polyisocyanate compounds (difunctional or trifunctional or higher isocyanate compounds) are preferred, and trifunctional or higher isocyanate compounds are more preferred.

The content of the cross-linking agent relative to 100 parts by weight of the acrylic polymer is preferably 0.1 to 5 parts by weight.

The trifunctional or higher isocyanate compound may be a polyisocyanate compound having at least three or more isocyanate (NCO) groups in one molecule. Polyisocyanate compounds include aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, and alicyclic isocyanates. The present invention may be any of them. Specific examples of the polyisocyanate compound include aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI). ; Diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), dimethyldiphenylene diisocyanate (TOID), toluene diisocyanate (TDI ) And other aromatic isocyanate compounds.

Examples of the trifunctional or higher isocyanate compounds include biuret-modified or isocyanurate-modified diisocyanates (compounds having two NCO groups in one molecule), and trimethylol groups. Adducts (polyol modified products) and the like of trivalent or higher polyhydric alcohols (compounds having at least three or more OH groups in one molecule) such as propane (TMP) or glycerol.

In order to impart antistatic properties, 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, the antistatic agent is an ionic compound having a melting point of 30 to 50 ° C. The antistatic agent may be a quaternary ammonium salt type ionic compound containing an acrylium group.

Since these antistatic agents have a low melting point and have a long-chain alkyl group, it is presumed that they have high affinity with acrylic polymers.

The antistatic agent as an ionic compound having a melting point of 30 to 50 ° C is an ionic compound having a cation and an anion. Examples of the cation include pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, and pyrrolidinium. (pyrrolidinium), an ammonium cation such as a nitrogen-containing cation or a phosphonium cation, sulfonium cation, the anion is phosphate hexafluoride (PF ₆ ^-), thiocyanate (SCN ^-), alkylbenzene sulphonate (RC ₆ H ₄ SO ₃ ^-), perchlorate (ClO ₄ ^- compound) of an inorganic or organic anion ^-), borate tetrafluoride (BF _4. A compound having a melting point of 30 to 50 ° C can be obtained by selecting the chain length of the alkyl group, the position and number of the substituents, and the like. The cation is preferably a 4th order nitrogen-containing onium cation, and examples include 1-alkylpyridinium (the carbon atom at the 2 to 6 position may or may not have a substituent), a fourth-order pyridinium cation, and the like, 1,4-dialkylimidazolium (4, 5 and 5 carbon atoms may or may not have a substituent) and other fourth-order imidazolium cations, etc. .

The content of the antistatic agent as an ionic compound having a melting point of 30 to 50 ° C. is preferably 0.1 to 5.0 parts by weight based on 100 parts by weight of the acrylic polymer.

The quaternary ammonium salt-type ionic compound containing acrylfluorenyl group is an ionic compound having a cation and an anion, and examples thereof include a (meth) acryloxyalkyltrialkylammonium (R ₃ N ⁺ - _{C n H 2n -OCOCQ = CH 2} , where, Q = H or CH _3, R = alkyl) ammonium 4 stage like containing (meth) Bing Xixi group, a phosphate hexafluoride anion (PF ₆ ^- ), thiocyanate (SCN ^-), organic sulfonate (RSO ₃ ^-), perchlorate (ClO ₄ ^-), borate tetrafluoride (BF ₄ ^-), (PEI) containing the root of F (R ^F ₂ compound) of an inorganic or organic anion, ^- N. (PEI) containing a root of F (R ^F ₂ N ^-) of R & lt ^F, include trifluoromethanesulfonic acyl, sulfo pentafluoroethyl acyl group such as a perfluoroalkyl sulfonic acyl, sulfo-fluoro-acyl. (PEI) containing F as the root include bis (fluorosulfonyl acyl) (PEI) root [(FSO _{2) 2} N ^-], bis (trifluoromethanesulfonyl acyl) (PEI) root [(CF ₃ SO _{2) 2} N ^-], bis (pentafluoroethane sulfonyl acyl) (PEI) root _{[(C 2 F 5 SO 2)} 2 N - etc.] bis sulfo acyl (PEI) root.

It is preferable that the aforementioned quaternary ammonium salt type ionic compound containing acrylfluorene group is copolymerized with 0.1 to 5.0% by weight in the acrylic polymer.

As a specific example of the antistatic agent, there is no particular limitation, but Specific examples of the ionic compound having a melting point of 30 to 50 ° C include 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, and 3-methyl 1-dodecylpyridinium hexafluorophosphate, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, and the like.

In addition, as a specific example of the above-mentioned quaternary ammonium salt-type ionic compound containing an acrylium group, dimethylaminomethyl (meth) acrylate hexafluorophosphate methyl salt [(CH ₃ ) ₃ N ⁺ _{CH 2 OCOCQ = CH 2 ‧PF 6} -, where, Q = H or CH _3], dimethylaminoethyl (meth) acrylate, bis (trifluoromethanesulfonyl acyl) (PEI) salt [methyl ( ^{_{CH 3) 3 N + (CH}} 2) 2 OCOCQ = CH 2 ‧ (CF 3 SO 2) 2 N -, where, Q = H or CH _3], dimethylaminomethyl (meth) acrylate, bis ( Fluorosulfonyl) fluorenimine methyl salt [(CH ₃ ) ₃ N ⁺ CH ₂ OCOCQ = CH ₂ ‧ (FSO ₂ ) ₂ N ⁻ , where Q = H or CH ₃ ] and the like.

The adhesive composition of the present invention contains a polyether-modified silicone compound. The polyether-modified silicone compound is a silicone compound having a polyether group. In addition to the normal silicone unit [-SiR ¹ ₂ -O-], it also contains a silicone unit having a polyether group [ -SiR ¹ (R ² O (R ³ O) _n R ⁴ ) -O-]. Here, R ¹ represents one or two or more alkyl or aryl groups, R ² and R ³ represent one or two or more alkylene groups, R ⁴ represents one or two or more alkyl groups, fluorenyl groups, and the like ( Terminal group). Examples of the polyether group include polyoxyalkylene groups such as polyoxyethylene groups [(C ₂ H ₄ O) _n ] and polyoxypropylene groups [(C ₃ H ₆ O) _n ].

The polyether-modified silicone compound is preferably a polyether-modified silicone compound having an HLB value of 7 to 12. The content of the polyether-modified silicone compound relative to 100 parts by weight of the acrylic polymer is preferably 0.01 to 0.5 parts by weight. More preferably, it is 0.1 to 0.5 parts by weight.

HLB refers to, for example, the hydrophilic-lipophilic balance (ratio of hydrophilicity and lipophilicity) specified in JIS K3211 (surfactant term).

The polyether-modified siloxane compound can be obtained, for example, by a method of grafting an organic compound having an unsaturated bond and a polyoxyalkylene group to a polyorganosiloxane having a silane group by a hydrosilylation reaction. Obtained from the main chain. Specific examples include a dimethylsiloxane-methyl (polyoxyethylene) siloxane copolymer, a dimethylsiloxane-methyl (polyoxyethylene) siloxane-methyl (polyoxyethylene) (Propylene oxide) silicone copolymer, dimethylsiloxane-methyl (polyoxypropylene) silicone copolymer, and the like.

By blending the polyether-modified silicone compound with the adhesive composition, the adhesive force and reworkability of the adhesive can be improved.

The adhesive composition of the present invention may contain a crosslinking inhibitor. Examples of the crosslinking inhibitor include methyl ethyl acetate, ethyl ethyl acetate, octyl ethyl acetate, oleyl ethyl acetate, lauryl ethyl acetate, stearyl ethyl acetate, and the like. β-ketoesters, β-diketones such as acetoacetone, 2,4-hexanedione, and benzophenone acetone. These are ketoenol tautomeric compounds. In an adhesive composition using a polyisocyanate compound as a cross-linking agent, by blocking the isocyanate group of the cross-linking agent, the adhesive composition can be suppressed after the cross-linking agent is added. Excessive increase in viscosity or gelation can extend the shelf life of the adhesive composition.

The aforementioned cross-linking inhibitor is preferably a ketoenol tautomeric compound, and particularly preferably is at least one selected from the group consisting of acetone and ethyl acetate.

When the crosslinking inhibitor is added, the content of the crosslinking inhibitor relative to 100 parts by weight of the acrylic polymer is preferably 1.0 to 5.0 weight. Serving.

The adhesive composition of the present invention may contain a crosslinking catalyst. When a polyisocyanate compound is used as the crosslinking agent, the crosslinking catalyst may be any substance that acts as a catalyst for the reaction between the acrylic polymer and the crosslinking agent (crosslinking reaction). Examples of the crosslinking catalyst include amine compounds such as tertiary amines, organic tin compounds, organic lead compounds, and organic zinc compounds such as organic zinc compounds.

Examples of the tertiary amine include trialkylamine, N, N, N ', N'-tetraalkyldiamine, N, N-dialkylamino alcohol, triethylenediamine, Phthaloline derivatives Derivatives, etc.

Examples of the organotin compound include dialkyltin oxide, fatty acid salts of dialkyltin, and fatty acid salts of tin (II).

The crosslinking catalyst is preferably an organotin compound, and particularly preferably at least one selected from the group consisting of dioctyltin oxide and dioctyltin dilaurate.

When the crosslinking catalyst is added, the content of the crosslinking catalyst is preferably 0.01 to 0.5 parts by weight based on 100 parts by weight of the acrylic polymer.

The adhesive composition of the present invention may contain a polyether compound. The polyether compound is a compound having a polyalkylene oxide, and examples thereof include polyether polyols such as polyalkylene glycols and derivatives thereof. Examples of the alkylene group included in the polyalkylene glycol and the polyalkyleneoxy group include, but are not limited to, ethylene, propylene, and butylene. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of the polyalkylene glycol copolymer include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, and polypropylene glycol-polybutylene glycol. Alcohol, polyethylene glycol-polypropylene glycol-polybutylene glycol, etc. The copolymer may be a block copolymer or a random copolymer.

Examples of the polyalkylene glycol derivative include polyoxyalkylene alkyl ethers such as polyoxyalkylene monoalkyl ether and polyoxyalkylene dialkyl ether, and polyoxyalkylene mono Polyoxyalkylene alkenyl ethers such as alkenyl ether, polyoxyalkylene dienyl ether, polyoxyalkylene monoaryl ethers, polyoxyalkylene diaryl ethers, etc. Ethers, polyoxyalkylene alkyl phenyl ethers, polyoxyalkylene glycol monofatty acid esters, polyoxyalkylene glycol difatty acid esters and other polyoxyalkylene glycol fatty acid esters, polyoxidized Alkylene sorbitan fatty acid esters, polyoxyalkylene alkylamines, polyoxyalkylene diamines, and the like.

Here, examples of the alkyl ether in the polyalkylene glycol derivative include lower alkyl ethers such as methyl ether and diethyl ether, and higher alkyl ethers such as dodecyl ether and octadecyl ether. Examples of the alkenyl ether in the polyalkylene glycol derivative include vinyl ether, allyl ether, and oleyl ether. Examples of the fatty acid ester in the polyalkylene glycol derivative include saturated fatty acid esters such as acetates and stearates, and unsaturated fatty acid esters such as (meth) acrylates and oleates. .

The polyether compound is preferably a compound containing ethylene oxide, and more preferably a compound containing polyoxyethylene.

When the polyether compound has a polymerizable functional group, it may be copolymerized with a (meth) acrylic polymer. The polymerizable functional group is preferably a vinyl functional group such as a (meth) acryl group, a vinyl group, or an allyl group. Examples of the polyether compound having a polymerizable functional group include polyalkylene glycol mono (meth) acrylate, polyalkylene glycol di (meth) acrylate, and alkoxy polyalkylene di Alcohol (meth) acrylate, polyalkylene glycol monoallyl ether, polyalkylene di Alcohol diallyl ether, alkoxy polyalkylene glycol allyl ether, polyalkylene glycol monovinyl ether, polyalkylene glycol divinyl ether, alkoxy polyalkylene glycol vinyl ether Wait.

Further, as other components, a copolymerizable (meth) acrylic acid monomer containing an alkylene oxide, a (meth) acrylamide monomer, a dialkyl-substituted acrylamide monomer, Known additives such as surfactants, curing accelerators, plasticizers, fillers, curing inhibitors, processing aids, anti-aging agents, and antioxidants. These may be used alone or in combination of two or more.

The (meth) acrylic acid alkyl ester having an alkyl group having 4 to 10 carbon atoms, and a copolymerizable monomer containing a hydroxyl group and a copolymerizable monomer containing a carboxyl group can be copolymerized to synthesize and be used as the adhesive of the present invention. Acrylic polymer as the main component of the agent composition. The polymerization method of the acrylic polymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.

In the acrylic polymer, a polyalkylene glycol mono (meth) acrylate monomer, a hydroxyl group-containing nitrogen-containing vinyl monomer, and an alkoxy group-containing (meth) acrylic acid alkyl group may be used. Other monomers, such as an ester monomer and a quaternary ammonium salt type ionic compound containing an acrylium group, are copolymerized.

The adhesive composition of the present invention can be formulated by blending a cross-linking agent, an antistatic agent, and any appropriate additives with the acrylic polymer.

The acid value of the acrylic polymer is preferably 0.01 to 8.0. Thereby, it is possible to improve the contamination property and the performance of preventing the occurrence of an adhesive residue phenomenon.

Here, the "acid value" is one of the indicators showing the acid content, and is expressed in mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

It is preferable that the adhesive force of the adhesive layer formed by cross-linking the aforementioned adhesive composition at a peeling speed of 0.3 m / min in the low-speed region is 0.05 to 0.1 N / 25 mm, and the peeling speed in the high-speed region is 30 m / min. Adhesive force is 1.0N / 25mm or less. As a result, a small change in the adhesive force with the peeling speed can be obtained, and the peeling can be performed quickly even in the case of high-speed peeling. In addition, even when the surface protection film is temporarily peeled for re-adhesion, an excessive force is not required, and it is easy to peel from the adherend.

The surface resistivity of the adhesive layer obtained by cross-linking the adhesive composition is preferably 5.0 × 10 ⁺¹¹ Ω / □ or less, and the peeling static voltage is ± 0 to 0.5 kV. In addition, in the present invention, “± 0 to 0.5 kV” means “0 to −0.5 kV” and “0 to +0.5 kV”, that is, “−0.5 to +0.5 kV”. In the case where the surface resistivity of the adhesive layer is large, when the surface protective film is peeled off, the adhesive layer has poor performance in discharging static electricity generated by charging. By making the surface resistivity of the adhesive layer sufficiently small, it is possible to reduce the peeling static voltage caused by static electricity generated when the adhesive layer is peeled from the adherend, and to suppress the influence on the electrical control circuit and the like of the adherend.

The gel fraction of the adhesive layer (crosslinked adhesive) obtained by crosslinking the adhesive composition of the present invention is preferably 95 to 100%. Because the gel fraction is so high, the adhesive force does not become too large at low peel speeds, reducing the phenomenon of dissolution of unpolymerized monomers or oligomers from acrylic polymers, which can improve reworkability and high temperature. / Durability under high humidity and suppresses contamination by adherends.

The adhesive film of the present invention is formed by forming an adhesive layer on one or both sides of a resin film, and the adhesive layer is formed by crosslinking the adhesive composition of the present invention. The surface protection film of the present invention is an adhesive formed on one side of a resin film. The adhesive layer is formed by crosslinking the adhesive composition of the present invention. In the adhesive composition of the present invention, each component of the acrylic polymer is well-balanced, so it has excellent antistatic performance and balance of adhesive force at a peeling speed in a low speed region and a high speed region. excellent. In addition, it has excellent durability and reworkability (after drawing on a surface protective film with an adhesive pen through an adhesive layer, it does not transfer contamination to the adherend). Therefore, it can be preferably used as a surface protective film for a polarizing plate, a retardation plate, or an antireflection film.

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

For the base film, the surface of the resin film opposite to the side where the adhesive layer is formed can be protected with a silicone-based, fluorine-based release agent or coating agent, or silica particles. The antifouling treatment may be an antistatic treatment by applying or mixing an antistatic agent.

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

[Example]

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

<Production of acrylic polymer>

[Example 1]

Nitrogen was introduced into a reaction device equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, thereby replacing the air in the reaction device with nitrogen. Then, 90 parts by weight of 2-ethylhexyl acrylate, 9 parts by weight of 8-hydroxyoctyl acrylate, and 1.0 parts by weight of acrylic acid were added to the reaction device, and 60 was added simultaneously. Part by weight of solvent (ethyl acetate). Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was reacted at 65 ° C for 6 hours to obtain acrylic acid used in Example 1 with a weight average molecular weight of 500,000. Like polymer solution 1. A part of the acrylic polymer was taken and used as an acid value measurement sample described later.

[Examples 2 to 6 and Comparative Examples 1 to 3]

Except that the composition of each monomer was adjusted as shown in (A) to (C) in Table 1, the same operation was performed as the acrylic polymer solution 1 used in Example 1 above to obtain the samples used in Examples 2 to 6 and the acrylic polymer solutions in Comparative Examples 1 to 3.

In addition, in Tables 1 and 2, (A) is an alkyl (meth) acrylate as a main component, (B) is a copolymerizable monomer containing a hydroxyl group, and (C) is a copolymerizable property containing a carboxyl group. monomer.

<Manufacturing of adhesive composition and surface protective film>

[Example 1]

To the acrylic polymer solution 1 of Example 1 prepared as described above, 2.0 parts by weight of 1-octylpyridinium dodecylbenzenesulfonate and 0.1 parts by weight of KF-351A (HLB = 12 Polyether-modified silicone compound) and stirred, then 1.0 part by weight of Coronate HX (isocyanurate of hexamethylene diisocyanate compound) was added and stirred and mixed to obtain the adhesive composition of Example 1 Thing. This adhesive composition was coated on a release film composed of a silicone resin-coated polyethylene terephthalate (PET) film, and then dried at 90 ° C to remove the solvent to obtain an adhesive layer. An adhesive sheet having a thickness of 25 μm.

Then, prepare a polyethylene terephthalate (PET) film with antistatic treatment and antifouling treatment on one side, and transfer the adhesive sheet to the polyethylene terephthalate (PET) film. On the opposite side of the surface subjected to the antistatic treatment and the antifouling treatment, a PET film / adhesive layer / release film (a PET film coated with a silicone resin) ) ". The surface protective film of Example 1 having a laminated structure.

[Examples 2 to 6 and Comparative Examples 1 to 3]

The surface protection films of Examples 2 to 6 and Comparatives 1 to 3 were obtained in the same manner as in the surface protective film of Example 1 except that the composition of each additive was adjusted as shown in (D) to (F) of Table 2. membrane.

In Tables 1 and 2, (D) is a crosslinking agent, (E) is an antistatic agent, and (F) is a polyether-modified silicone compound.

In Table 1, the numerical values in parentheses all indicate the numerical values of the weight parts of each component obtained by setting the total weight of the groups (A) to (C) to 100 parts by weight. In addition, the compound names corresponding to the abbreviations of the respective components used in Table 1 are shown in Table 2. In addition, Coronate (registered trademark) HX, Coronate HL, and Coronate L are trade names of Nippon Polyurethane Industry Co., Ltd., and Takenate (registered trademark) D-140N, D-127N, D -110N and D-120N are trade names of Mitsui Chemicals Co., Ltd., and KF-351A, KF-352A, KF-353, KF-640, and X-22-6191 are trade names of Shin-Etsu Chemical Co., Ltd.

<Test method and evaluation>

After the surface protective films of Examples 1 to 6 and Comparative Examples 1 to 3 were aged at 23 ° C and 50% RH for 7 days, the release film (PET film coated with silicone resin) was peeled off to make adhesion. The agent layer was exposed and used as a sample for measuring surface resistivity.

Furthermore, the exposed surface protection film of the adhesive layer was bonded to the surface of the polarizing plate pasted on the liquid crystal cell through the adhesive layer, and after being left for 1 day, the autoclave treatment was performed at 50 ° C and 5 atmospheres for 20 minutes. It was further left at room temperature for 12 hours, and the surface protection film thus obtained was used as a sample for measuring the adhesive force, peeling static voltage, reworkability, and durability.

<Acid value>

Acid value of acrylic polymer: Dissolve the sample in a solvent (a solvent in which diethyl ether and ethanol are mixed at a volume ratio of 2: 1), and use an automatic potentiometric titration device (AT-610, Kyoto Electronics Industry Co., Ltd.) (Manufactured), potentiometric titration with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol / L, and the amount of potassium hydroxide ethanol solution required for neutralizing the sample was measured. Then, the acid value was obtained by the following formula.

Acid value = (B × f × 5.611) / S

B = 0.1 mol / L potassium hydroxide ethanol solution used in titration (mL)

f = 0.1mol / L coefficient of potassium hydroxide ethanol solution

S = mass of solid content of sample (g)

<Adhesion>

Using a tensile tester, the measurement sample obtained above was peeled in a 180 ° direction at a peeling speed (0.3 m / min) in a low speed region and a peeling speed (30 m / min) in a high speed region (a 25 mm wide surface protective film A sample obtained by bonding to the surface of a polarizing plate), the peeling strength was measured, and the peeling strength was used as the adhesive force.

<Surface resistivity>

After aging, before attaching to the polarizing plate, peel off the release film (PET film coated with silicone resin) to expose the adhesive layer. Use a resistivity meter (trade name: "Hiresta UP-HT450", stock) The company's Mitsubishi Chemical Analytech Co., Ltd.) measured the surface resistivity of the adhesive layer.

<Peel Static Voltage>

A high-precision electrostatic sensor (models SK-035 and SK-200, manufactured by Keyence Corporation) was used to measure the tensile speed of the measurement sample obtained above at a speed of 30 m / min. When 180 ° peeling was performed, the voltage (static voltage) generated when the polarizing plate was charged was used, and the maximum value of the measured value was taken as the peeling static voltage.

<Reworkability>

After drawing on the surface protective film of the measurement sample obtained above with a ball pen (load of 500 g, three times back and forth), the surface protective film was peeled from the polarizing plate, and the surface of the polarizing plate was observed to confirm that no contamination was transferred to the polarizing plate. Evaluation of reworkability Criterion: When the pollution is not transferred to the polarizing plate, it is evaluated as “○”; when it is confirmed that the trace traced along the ballpoint pen is transferred at least locally, it is evaluated as “△”; when it is confirmed that there is pollution shifted along the trace traced by the ballpoint pen In addition, when detachment of the adhesive was also confirmed from the surface of the adhesive, it was evaluated as “×”. The reworkability was evaluated based on the above criteria.

<Durability>

After leaving the measurement sample obtained at 60 ° C and 90% RH for 250 hours, the sample was taken out and placed at room temperature for another 12 hours. Then, the adhesive force was measured, and it was confirmed that there was no obvious difference compared with the initial adhesive force. increase. Criteria for evaluating durability: When the adhesion after the test is 1.5 times or less the initial adhesion, it is evaluated as "○", and when it exceeds 1.5 times, it is evaluated as "X". The durability was evaluated according to the above criteria.

The evaluation results are shown in Table 3. Further, the surface resistivity by "mE + n" to represent "m × 10 ^{+ n"} (where, m is an arbitrary real numbers, n-is a positive integer).

For the surface protection films of Examples 1 to 6, the adhesive force at a peeling speed of 0.3 m / min in the low-speed region was 0.05 to 0.1 N / 25 mm, and the adhesive force at a peeling speed of 30 m / min in the high-speed region was 1.0. Below N / 25mm, surface resistivity is below 5.0 × 10 ⁺¹¹ Ω / □, and peeling static voltage is ± 0 ~ 0.5kV. In addition, after drawing on a surface protective film with a ballpoint pen through an adhesive layer, there was no transfer of contamination to the adherend, and the durability after being left for 250 hours in an environment of 60 ° C and 90% RH was also excellent.

That is, all of the following performance requirements are met at the same time: (1) the balance of the adhesive force at the peeling speed in the low speed region and the high speed region is achieved; (2) the occurrence of adhesive residue is prevented; ; And (4) has reworkability.

The surface protective film of Comparative Example 1 may be due to too few (meth) acrylic acid alkyl esters as main components, too many hydroxyl-containing copolymerizable monomers, and no copolymerizable monomers having a carboxyl group. Because the HLB value of the polyether-modified silicone compound is too small, the adhesive force at the peeling speed of 0.3 m / min in the low-speed region is small, the surface resistivity and the peeling static voltage are high, and the durability is poor.

In the surface protective film of Comparative Example 2, the copolymerizable monomer containing a carboxyl group was too much with respect to the (meth) acrylic acid alkyl ester of the main component, so that the expiration date became too short and cross-linking was performed before coating. , So coating cannot be performed.

The surface protection film of Comparative Example 3 may be due to the absence of a carboxyl-containing copolymerizable monomer, a cross-linking agent, and an antistatic agent, and the HLB value of the polyether-modified silicone compound was too small. Adhesion at a peeling speed of 0.3 m / min in a low speed region and adhesive force at a peeling speed of 30 m / min in a high speed region are excessive, surface resistivity and peeling static voltage are high, and reworkability and durability are poor.

As described above, in the surface protective films of Comparative Examples 1 to 3, it was impossible to simultaneously fill Meet all of the following performance requirements: (1) Achieving a balance of adhesion at peel speeds in the low-speed and high-speed regions; (2) Preventing the occurrence of adhesive residues; (3) Excellent antistatic performance; and (4) ) Has reworkability.

Claims (7)

An adhesive composition is an adhesive composition containing an acrylic polymer, an antistatic agent, and a cross-linking agent. The acrylic polymer comprises the following (A), (B), and (C). Polymerized copolymer: (A) 90 to 98.5 parts by weight of one or more alkyl (meth) acrylates having an alkyl group having 4 to 10 carbon atoms, (B) a copolymerizable monomer containing a hydroxyl group 0.1 to 9.5 parts by weight in total, and 0.1 to 2 parts in weight in (C) one or more copolymerizable monomers containing a carboxyl group, excluding alkane having 4 to 10 carbon atoms with respect to (A) 100 parts by weight of alkyl (meth) acrylate, 0.1 to 6.0 parts by weight of the (B) hydroxyl-containing copolymerizable monomer, and (B) ) A polymer in which the total amount of 8-hydroxyoctyl acrylate, 6-hydroxyhexyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate is 0 to 2.5 parts by weight, based on the above (A) to (C) ) Is contained in a proportion of 100 parts by weight in total, and the (A) alkyl (meth) acrylate having an alkyl group having 4 to 10 carbon atoms contains (meth) in a proportion of 50 parts by weight or more Acid, isooctyl acrylate, or (meth) acrylate, 2-ethylhexyl acrylate, the antistatic agent is an ionic compound having a melting point of 30 ~ 50 ℃. For example, the adhesive composition of claim 1 in which the (A) alkyl (meth) acrylate having an alkyl group having 4 to 10 carbon atoms is selected from the group consisting of butyl (meth) acrylate Ester, isobutyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate One or more compounds selected from the group consisting of esters, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and decyl (meth) acrylate. For example, the adhesive composition of claim 1 or 2, wherein the (B) hydroxyl-containing copolymerizable monomer is selected from the group consisting of (meth) acrylic acid 8-hydroxyoctyl ester and (meth) acrylic acid 6-hydroxyhexyl ester, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acryl At least one or more of a compound group consisting of amine and N-hydroxyethyl (meth) acrylamide. For example, the adhesive composition of claim 1 or 2, wherein the (C) carboxyl-containing copolymerizable monomer is selected from the group consisting of (meth) acrylic acid, carboxyethyl (meth) acrylate, ( Carboxypentyl methacrylate, 2- (meth) acryloxyethyl hexahydrophthalic acid, 2- (meth) acryloxypropyl hexahydrophthalic acid, 2- (formyl) ) Acrylic acid ethyl phthalate, 2- (meth) acrylic acid ethyl succinic acid, 2- (meth) acrylic acid ethyl maleic acid, carboxy polycaprolactone mono One or more of the compound group consisting of (meth) acrylate and 2- (meth) acryloxyethyltetrahydrophthalic acid. For example, the adhesive composition according to item 1 or 2 of the patent application scope further includes a polyether-modified silicone compound having an HLB value of 7 to 12, and the cross-linking agent is a trifunctional or more isocyanate compound. An adhesive film is formed by forming an adhesive layer on one or both sides of a resin film, and the adhesive layer is formed by crosslinking the adhesive composition according to any one of claims 1 to 5 of the patent application scope. . A surface protection film is formed by forming an adhesive layer on one side of a resin film, and the adhesive layer is obtained by cross-linking the adhesive composition according to any one of claims 1 to 5.