TWI630268B - 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 that have excellent antistatic properties, excellent balance of adhesion at peel speeds 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 100 parts by weight of the aforementioned acrylic The polymer contains 85 to 99.5 parts by weight of the aforementioned main component (alkyl) (meth) acrylate, 0.5 to 15 parts by weight of a hydroxyl-containing copolymerizable monomer, and 0.1 to 5 parts by weight of a crosslinking agent. The agent is an ionic compound having a melting point of 30 to 50 ° C.

Description

Adhesive composition, adhesive film and surface protective film

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

The adhesive film and surface protection film of the present invention have particularly excellent antistatic performance. Therefore, it is applied to the surface of an optical film such as a polarizing plate, a retardation plate, an anti-reflection film, etc., using a plastic film that easily generates static electricity as a constituent member to protect the surface.

Conventionally, in the manufacturing steps of optical members such as polarizing plates, retardation plates, and anti-reflection films, which are members constituting a liquid crystal display, a surface protection film for temporary protection is stuck on the surface of the optical member. This surface protection film is only used in the step of manufacturing optical members, when the optical member is inserted into a liquid crystal display When removing it, it is removed from the optical member. 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".

In the surface protection film used in such a step of manufacturing an optical member, an adhesive layer is formed on one surface of a polyethylene terephthalate (PET) resin film having optical transparency. 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 there are no bubbles and no impurities in the adhesive layer.

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, from the final polarizer, retarder, anti-reflection film and other optical components When peeling a surface protection film, it is required to be able to peel 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 protection film, the adhesive layer constituting the surface protection film is required to have the following properties: (1) to achieve a balance of adhesion at the peeling speed of the low speed region and the high speed region; (2) prevent the occurrence of adhesive residues; (3) have excellent antistatic properties; and (4) have rework properties.

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 which uses an alkane having 8 to 10 carbon atoms. An adhesive layer comprising a copolymer of a (meth) acrylic acid alkyl ester and a copolymerizable compound having an alcoholic hydroxyl group and cross-linking it with a crosslinking agent (Patent Document 1).

In addition, a technical solution is provided in which an adhesive layer is provided, which is prepared by blending a small amount of a (meth) acrylic acid alkyl ester with a copolymerizability containing a carboxyl group in the same copolymer as above. An adhesive layer made of a copolymer of compounds 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 amine group; (b) a sulfonate group and a sulfate salt Anionic antistatic agents such as anionic groups such as amino groups, phosphate ester groups, phosphonate groups; (c) amphoteric antistatic agents such as amino acids, amino sulfates; (d) amino alcohols, glycerols And nonionic antistatic agents such as polyethylene glycols; (e) Polymer-type antistatic agents obtained by polymerizing the above-mentioned antistatic agents with high molecular weight (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, the adhesive layer constituting the surface protection film is required to have the following properties: to achieve a balance of adhesive force at the peeling speed in the low-speed region and the high-speed region; to have excellent antistatic performance; However, even if the performance requirements of individual items in (1) to (4) above can be met, respectively, all the performance requirements of (1) to (4) 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 Patent Application Laid-Open 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-mentioned problems, the present invention provides an adhesive composition, which is an adhesive composition containing an antistatic agent, wherein the adhesive composition includes a (methyl ) An acrylic polymer having an alkyl acrylate as a main component contains 85 to 99.5 parts by weight of the main component (alkyl) (meth) acrylate and 0.5 to 15 parts by weight based on 100 parts by weight of the acrylic polymer. Part of a hydroxyl-containing copolymerizable monomer and 0.1 to 5 parts by weight of a cross-linking agent. The antistatic agent is an ionic compound having a melting point of 30 to 50 ° C.

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-hydroxybutyl (meth) acrylate. Ester, 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 in the composition.

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 made of the aforementioned adhesive The composition is crosslinked.

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 a surface protection film that cannot be solved by conventional techniques can be satisfied.

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, wherein the adhesive composition contains an alkyl (meth) acrylate having an alkyl group having 4 to 10 carbon atoms as a main component. The acrylic polymer contains 85 to 99.5 parts by weight of the aforementioned main component, which is an alkyl (meth) acrylate, and 0.5 to 15 parts by weight of a copolymerizable polymer with respect to 100 parts by weight of the acrylic polymer. The monomer and the crosslinking agent in an amount of 0.1 to 5 parts by weight. The antistatic agent is an ionic compound having a melting point of 30 to 50 ° C.

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 more preferably selected from (meth) Butyl acrylate, isobutyl (meth) acrylate, amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylic acid Isooctyl, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate More than one compound group.

The content of the alkyl (meth) acrylate as a main component is preferably 85 to 99.5 parts by weight based on 100 parts by weight of the acrylic polymer.

Examples of the hydroxyl-containing copolymerizable monomer include 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and (methyl) ) Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl acrylate; N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (methyl (Meth) acrylamide and the like containing (meth) acrylamide 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 hydroxyl-containing copolymerizable monomer is preferably 0.5 to 15 parts by weight based on 100 parts by weight of the acrylic polymer.

In the adhesive composition of the present invention, it is preferred that the adhesive composition 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 classifications of aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, and alicyclic isocyanates, and 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 glycerin.

The adhesive composition of the present invention contains an ionic compound having a melting point of 30 to 50 ° C as an antistatic agent. 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 pyrrole. alkyl bromide (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 ^-), alkyl benzene sulfonate inorganic or organic compound anion ^{_{(RC 6 H 4 SO 3 -}} ), perchlorate (ClO ₄ ^{- -),} borate tetrafluoride (BF _4). The compound is preferably solid at normal temperature (for example, 30 ° C), and 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 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 a cation is (meth) acryloxyalkyltrialkylammonium (R ₃ N ⁺ -C _n H _2n -OCOCQ = CH ₂ , where Q = H or CH ₃ , R = alkyl) and other quaternary ammonium containing (meth) acrylfluorenyl, the anion is phosphate hexafluoride (PF ₆ ^-), thiocyanate (the SCN ^-), organic sulfonate (RSO ₃ ^-), perchlorate (ClO ₄ ^-), borate tetrafluoride (BF ₄ ^-), the F-containing root (PEI) (R compound) of an inorganic or organic anions ^{- F} ₂ 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.

The quaternary ammonium salt type ionic compound containing the propylene sulfonium group is preferably copolymerized in the acrylic polymer in an amount of 0.1 to 5.0% by weight.

Specific examples of the antistatic agent are not particularly limited, but specific examples of the ionic compound having a melting point of 30 to 50 ° C. include 1-octylpyridinium dodecylbenzenesulfonate and 1-deca Dialkylpyridine thiocyanate, 3-methyl-1-dodecylpyridinium hexafluorophosphate, 1-dodecylpyridine dodecylbenzenesulfonate, 4-methyl- 1-octylpyridinium hexafluorophosphate and the like.

Moreover, 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) methyl salt ^{_{[(CH 3) 3 N + (}} CH 2) 2 OCOCQ = CH 2 ˙ (CF 3 SO 2) 2 N -, where, Q = H or CH _3], dimethyl aminomethyl (meth) acrylate, bis (acyl-fluoro-sulfo) methyl acyl imide 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 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 tautomers, which are combined in polyisocyanates By blocking the isocyanate group of the cross-linking agent in the adhesive composition which is used as a cross-linking agent, the phenomenon of excessive increase in viscosity or gelation of the adhesive composition after the cross-linking agent is mixed can be suppressed, and the adhesion can be extended. The shelf life of the agent 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 parts by weight.

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 in the reaction (crosslinking reaction) between the acrylic polymer and the crosslinking agent. 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-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. In addition, when added, 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 polyether compound. Make 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, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol. 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. .

Preferably, the polyether compound is ethylene oxide-containing The compound is more preferably a compound containing a polyoxyethylene group.

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 glycol diallyl ether, alkoxy polyalkylene glycol allyl ether, polyalkylene glycol mono Vinyl ether, polyalkylene glycol divinyl ether, alkoxy polyalkylene glycol vinyl ether, and the like.

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.

By copolymerizing a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 10 carbon atoms and a copolymerizable monomer containing a hydroxyl group, it is possible to synthesize acrylics used as a main agent of the adhesive composition of the present invention. polymer. 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. In addition, the acrylic polymer may not be It contains, for example, an acidic copolymerizable monomer such as a carboxyl group-containing copolymerizable monomer.

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.

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 the peeling speed in the low-speed region, which reduces the phenomenon of dissolution of unpolymerized monomers or oligomers from the acrylic polymer, which can improve reworkability, Durability at high temperature / humidity and suppresses adherends Pollution.

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. In addition, the surface protection film of the present invention is formed by forming an adhesive layer on one side of a resin film, and 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 used preferably as a surface protective film for a polarizing plate.

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 is 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]

To a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen introduction tube Nitrogen was introduced into the reactor, and the air in the reactor was replaced with nitrogen. Then, 95 parts by weight of 2-ethylhexyl acrylate and 5 parts by weight of 8-hydroxyoctyl acrylate were added to the reaction device, and 60 parts by weight of a solvent (ethyl acetate) were simultaneously added. 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 having a weight average molecular weight of 500,000. Like polymer solution 1.

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

Except that the monomer composition was adjusted as shown in (A) to (B) in Table 1, the same operation was performed as for the acrylic polymer solution 1 used in Example 1 to obtain Examples 2 to 6. And the acrylic polymer solution in Comparative Examples 1 to 3.

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

<Manufacturing of adhesive composition and surface protective film>

[Example 1]

To the acrylic polymer solution 1 of Example 1 manufactured as described above, 1.5 parts by weight of 1-octylpyridinium dodecylbenzenesulfonate was added and stirred, and then 1.5 parts by weight of Coronate HX (six The isocyanurate of the methylene diisocyanate compound) was then stirred and mixed to obtain the adhesive composition of Example 1. 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 surface, and transfer the adhesive sheet to the polyethylene terephthalate The surface of the polyethylene glycol ester (PET) film opposite to the surface subjected to antistatic treatment and antifouling treatment was obtained. (Silicon resin-coated PET film) The surface protective film of Example 1 having a laminated structure.

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

Except that the composition of each additive was adjusted as shown in (C) to (D) of Table 1, the surface protection film of Example 1 was operated in the same manner to obtain the surface protection of Examples 2 to 6 and Comparatives 1 to 3. membrane.

In Tables 1 and 2, (C) is a crosslinking agent, and (D) is an antistatic agent.

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 (B) 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 are trade names of Mitsui Chemicals 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 left at 50 ° C for one day. The autoclave treatment was performed at 5 ° C and 5 atm for 20 minutes, and further left at room temperature for 12 hours. The surface protection film thus obtained was used as a sample for measuring adhesion, peeling static voltage, reworkability, and durability.

<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 and before bonding 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", Mitsubishi Chemical Analysis) Technology Co., Ltd. (manufactured by 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 criteria for reworkability: "○" was evaluated when contamination was not transferred to the polarizing plate; The track traced by the ball pen was evaluated as “Δ” when contamination was transferred at least locally; it was evaluated as “×” when it was confirmed that there was a transfer of pollution along the track traced by the ball pen and the release of the adhesive was also confirmed from the surface of the adhesive. 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. N / 25mm or less; surface resistivity is 5.0 × 10 ⁺¹¹ Ω / □ or less, peeling static voltage is ± 0 ~ 0.5kV; and after drawing on a surface protective film with an adhesive pen through an adhesive layer, It is also contaminated by adherend transfer and has excellent durability after being left for 250 hours in an environment of 60 ° C and 90% RH.

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 protection film of Comparative Example 1 may be due to too few (meth) acrylic acid alkyl esters as main components and too many hydroxyl-containing copolymerizable monomers, and the peeling speed in the low-speed region was 0.3 m / min. The adhesive force is small, the surface resistivity and peeling static voltage are high, and the durability is poor.

In the surface protection film of Comparative Example 2, the low-speed region of the main component may be due to too few (meth) acrylic acid alkyl esters as main components, too many hydroxyl-containing copolymerizable monomers, and no antistatic agent. Adhesion at a peeling speed of 0.3 m / min is small, surface resistivity and peeling static voltage are high, and durability is poor.

For the surface protection film of Comparative Example 3, it may be because it does not contain a cross-linking agent and an antistatic agent, and its peeling speed at a low speed region of 0.3 m / min and its peeling speed at a high speed region of 30 m / min The adhesive strength is too high, the surface resistivity and the peeling static voltage are high, and the reworkability and durability are poor.

As described above, in the surface protective films of Comparative Examples 1 to 3, all of the following performance requirements cannot be satisfied at the same time: (1) Obtaining the peeling speed in the low speed region and the high speed region Balance of adhesive force under the temperature; (2) preventing the occurrence of adhesive residue; (3) having excellent antistatic performance; and (4) having reprocessing performance.

Claims (6)

An adhesive composition is an adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent. The acrylic polymer does not contain an acidic comonomer and does not contain an alkylene oxide. In the state of a copolymerizable (meth) acrylic monomer, an alkyl (meth) acrylate having an alkyl group having 4 to 10 carbon atoms is used as a main component, and 100 parts by weight of the acrylic polymer is polymerized. Copolymer containing 85 to 99.5 parts by weight of the main component (alkyl) (meth) acrylate and 0.5 to 15 parts by weight of a copolymerizable monomer containing a hydroxyl group, compared to the acrylic polymer 100 parts by weight, the adhesive composition contains 0.1 to 5 parts by weight of the cross-linking agent, and the cross-linking agent is selected from the group consisting of a difunctional or trifunctional or higher isocyanate compound, a difunctional or higher trifunctional ring One or more of the group consisting of an oxide, a difunctional or trifunctional acrylate compound, and a metal chelate. The antistatic agent is a cation having a melting point of 30 to 50 ° C and a solid at a temperature of 30 ° C. Anion ionization Composition, the cationic nitrogen-containing group is a cation, phosphonium cation and sulfonium cation selected from the group consisting of the anion is selected from the group consisting of phosphate hexafluoride (PF ₆ ^-), thiocyanate ( SCN ^-), alkyl sulfonate ^{_{(RC 6 H 4 SO 3 -}} ), (ClO 4 perchlorate ^-) or borate tetrafluoride (BF ₄ ^- group) consisting of one. For example, the adhesive composition according to item 1 of the patent application range, wherein the main component (alkyl) (meth) acrylate is selected from the group consisting of (meth) acrylate, Amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate One or more of the compound group consisting of an ester, nonyl (meth) acrylate, isononyl (meth) acrylate, and decyl (meth) acrylate. For example, the adhesive composition of claim 1 or 2, wherein the hydroxyl-containing copolymerizable monomer is selected from the group consisting of 8-hydroxyoctyl (meth) acrylate and 6-hydroxy (meth) acrylate Hexyl ester, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N -At least one or more members of the compound group consisting of hydroxyethyl (meth) acrylamide. For example, the adhesive composition according to item 1 or 2 of the patent application scope, wherein the crosslinking 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 cross-linking the adhesive composition according to any one of claims 1 to 4 of the scope of patent application. The gel fraction of the adhesive layer obtained by cross-linking the adhesive composition is 95 to 100%. A surface protection film is formed by forming an adhesive layer on one side of a resin film, and the adhesive layer is formed by cross-linking the adhesive composition according to any one of claims 1 to 4 of the scope of patent application.