TWI544048B - Adhesive composition and surface protective film - Google Patents

Description

Adhesive composition and surface protective film

The present invention relates to a surface protective film used in a manufacturing step of a liquid crystal display. More specifically, the present invention relates to an adhesive composition for a surface protective film used for protecting the surface of an optical member constituting a polarizing plate or a phase difference plate of a liquid crystal display, and a surface protective film using the same.

In the manufacturing process of an optical member such as a polarizing plate or a phase difference plate which is a member constituting a liquid crystal display, a surface protective film is attached to temporarily protect the surface of the optical member. Such a surface protective film is used only in the step of manufacturing an optical member, and when the optical member is incorporated in a liquid crystal display, it is peeled off from the optical member and removed. Such a surface protective film for protecting the surface of the optical member is used only in the manufacturing step. Therefore, it is also generally referred to as a step film.

Such a surface protective film used in the step of producing an optical member is formed by forming an adhesive layer on one side of a polyethylene terephthalate (PET) resin film having optical transparency. The surface protective film is bonded to the optical member until it is bonded to the optical member, and the release film for protecting the adhesive layer from being adhered to the adhesive layer.

In addition, since the optical member such as the polarizing plate or the retardation film is in contact with the surface protective film, the product inspection is performed with optical evaluation such as display performance, chromaticity, contrast, and impurity incorporation of the liquid crystal display panel. As a required property for the surface protective film, it is required that no bubbles or impurities are attached to the adhesive layer.

In addition, when the surface protective film is peeled off from an optical member such as a polarizing plate or a retardation plate, peeling electrification occurs due to static electricity generated when the adhesive layer is peeled off from the adherend, and the electrical control circuit of the liquid crystal display is broken. affected. Therefore, the adhesive layer must have excellent antistatic properties.

In addition, when the surface protective film is bonded to an optical member such as a polarizing plate or a retardation plate, the surface protective film is temporarily peeled off and the surface protective film is reattached for various reasons. In this case, an optical member which is easily removed from the adherend is required. Peeling (reworkability).

Further, when the surface protective film is finally peeled off from an optical member such as a polarizing plate or a phase difference plate, it is required to be peeled off quickly. That is, in order to peel off quickly by high-speed peeling, it is required that the adhesive force changes little with the peeling speed.

In recent years, in order to obtain the required performance of the adhesive layer constituting the surface protective film, it is required to obtain (1) balance of adhesion in the low-speed peeling region and the high-speed peeling region, and (2) prevention of occurrence of adhesive residue, (3) ) has excellent antistatic properties, and (4) has reworkability. The surface protective film is easy to use by having such properties.

However, although the required performance for the adhesive layer constituting the surface protective film, that is, the required performance of each of (1) to (4), and the required performance of the adhesive layer of the surface protective film are satisfied (1) )~(4) All performance requirements are very difficult.

For example, the following proposals are known regarding (1) obtaining the balance of the adhesive force in the low-speed peeling region and the high-speed peeling region, and (2) preventing the occurrence of the adhesive residue.

An acrylic adhesive prepared by crosslinking a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound as a main component and crosslinking the mixture with a crosslinking agent In the case where the layer adheres for a long period of time, the adhesive adheres to the side of the adherend and adheres, and the adhesion to the adherend increases sharply with time. problem. In order to avoid this problem, it is known to provide an article provided with an adhesive layer which is obtained by copolymerization of an alkyl (meth)acrylate having an alkyl group having a carbon number of 8 to 10 and having an alcoholic hydroxyl group. The copolymer of the compound is obtained by crosslinking treatment with a crosslinking agent (Patent Document 1).

And an article provided with an adhesive layer in which a small amount of a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound is mixed in the same copolymer as described above, and a crosslinking agent is used. It is obtained by cross-linking treatment. 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, there is a problem that peeling occurs due to heating during processing or storage, or poor removability by manual high-speed peeling. The problem.

In order to solve these problems, an adhesive composition is proposed which is based on a) 100 parts by weight of an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms as a main component. To the alkyl (meth)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 ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms In addition, a copolymer of the monomer mixture is obtained, and a crosslinking agent having an equivalent weight or more with respect to the carboxyl group of the component b) is obtained in the copolymer (Patent Document 2).

The adhesive composition described in Patent Document 2 does not have a peeling phenomenon such as floating during processing or storage, and the adhesion is not greatly increased over time, and therefore the removability is excellent. Moreover, even if it is stored for a long period of time, especially in a high-temperature environment, it can be peeled off with a small force. In this case, no adhesive remains on the adherend, and a small force can be applied at the time of high-speed peeling. Stripped.

In addition, (3) excellent antistatic performance, as a method of imparting antistatic property to the surface protective film, a method of kneading an antistatic agent to a base film, and the like are exemplified. As antistatic Examples of the agent include (a) various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a first to third amino group; (b) a sulfonate group and a sulfate group. An anionic antistatic agent such as an anionic group such as a phosphate group or a phosphonate group; (c) an amphoteric antistatic agent such as an amino acid or an aminosulfate; (d) an amine alcohol or a glycerin system A nonionic antistatic agent such as a polyethylene glycol system; (e) a polymer type antistatic agent obtained by polymerizing an antistatic agent as described above (Patent Document 3).

Further, in recent years, it has been proposed not only to include such an antistatic agent in a base film or to apply it to a surface of a base film, but also to directly form an adhesive agent layer with an antistatic agent.

Further, regarding (4) reworkability, for example, an adhesive composition is proposed which is obtained by mixing an isocyanate-based compound in an amount of 0.0001 to 10 parts by weight based on 100 parts by weight of the acrylic resin in the acrylic resin. It is obtained with a specific phthalate oligomer (Patent Document 4).

In Patent Document 4, an alkyl acrylate having an alkyl group having a carbon number of 2 to 12 or an alkyl methacrylate having an alkyl group having a carbon number of 4 to 12 or the like is a main monomer component, and may be contained. For example, a monomer component containing another functional group such as a carboxyl group-containing monomer. In general, it is preferable to contain 50% by weight or more of the above-mentioned main monomer, and it is preferable that the content of the monomer component containing a functional group is 0.001 to 50% by weight, more preferably 0.001 to 25% by weight, and most preferably 0.01%. 25 wt%. The adhesive composition described in Patent Document 4 has a small change in cohesive force and adhesion over time even under high temperature or high temperature and high humidity, and exhibits an excellent effect on the curved surface adhesion force, so that it has reworkability.

In general, when the adhesive layer is made into a soft property, the adhesive residue tends to occur, and the reworkability is also liable to lower. In other words, it is easy to cause detachment and detachment is difficult, and it is difficult to reattach. Therefore, in order to have reworkability, it is necessary to crosslink a monomer having a functional group such as a carboxyl group to the main agent to form a certain hardness of the adhesive layer.

[Advanced technical literature] (Patent Literature)

(Patent Document 1) Japanese Patent Laid-Open Publication No. SHO 63-225677

(Patent Document 2) Japanese Patent Laid-Open No. Hei 11-256111

(Patent Document 3) Japanese Patent Laid-Open No. Hei 11-070629

(Patent Document 4) Japanese Patent Laid-Open No. Hei 8-199130

In the prior art, as a required performance for an adhesive layer constituting the surface protective film, it is required to (1) obtain a balance of adhesion in a low-speed peeling region and a high-speed peeling region; (2) prevent adhesion of an adhesive; (3) ) has excellent antistatic properties; and (4) has reworkability. However, although the required performance of each of (1) to (4) can be satisfied, it is difficult to satisfy all the required performances of (1) to (4) required for the adhesive layer of the surface protective film. Not achievable.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide (1) balance between adhesion in a low-speed peeling region and a high-speed peeling region, (2) prevention of occurrence of adhesive residue, (3) excellent antistatic property, and (4) An adhesive composition and a surface protective film having all the required properties of reworkability.

In order to solve the above problems, the present invention provides an adhesive composition comprising (A) a (meth) acrylate monomer having an alkyl group having a carbon number of C4 to C10, (B) a copolymerizable monomer having a hydroxyl group, And (C) a copolymer of a carboxyl group-containing copolymerizable monomer, further containing (D) a trifunctional or higher isocyanate compound, (E) a crosslinking retarder, (F) a crosslinking catalyst, and (G) an antibiotic Electrostatic agent, (H) polyether modified oxoxane compound.

The above (B) hydroxyl group-containing copolymerizable single system is selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. a group of compounds consisting of 2-hydroxyethyl acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide At least one or more; preferably, based on 100 parts by weight of the (A) alkyl group having a C4 to C10 alkyl group carbon number, containing 0.1 to 5.0 parts by weight of the above (B) hydroxyl group-containing monomer The monomer can be copolymerized, and in the above (B) hydroxyl group-containing copolymerizable monomer, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, or (meth)acrylic acid 4 The total amount of the -hydroxybutyl ester is 0 to 0.9 parts by weight.

The (C) carboxyl group-containing copolymerizable single system is at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth) acrylate, and carboxypentyl (meth) acrylate. Preferably, the (C)-containing (A) alkyl group has a carbon number of C4 to C10 (meth) acrylate monomer, and contains 0.35 to 1.0 part by weight of the above (C) carboxyl group-containing copolymerizable single sheet. body.

The (D) trifunctional or higher isocyanate compound is selected from the group consisting of a trimer isocyanate of a hexamethylene diisocyanate compound, a trimer isocyanate of an isophorone diisocyanate compound, and an addition object of a hexamethylene diisocyanate compound. At least one or more of the compound groups of the addition substances of the isophorone diisocyanate compound are preferably contained in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of the above-mentioned copolymer. Isocyanate compound.

The (G) antistatic agent is preferably an ionic compound having a content of the above-mentioned copolymer of 0.5 to 5.0 parts by weight and a melting point of 30 to 80 ° C, or 1.0 to 5.0 in the above copolymer. A quaternary ammonium salt type acrylic monomer having a weight % copolymerization and a melting point of 30 to 80 ° C.

The (H) polyether modified siloxane compound is preferably a polyether modified siloxane compound having an HLB value of 7 to 12, and contains 0.01 to 0.5 parts by weight based on 100 parts by weight of the above copolymer. H) Polyether modified oxirane compound.

The (E) crosslinking retarder is preferably a ketoenol tautomer compound, and contains 1.0 to 5.0 parts by weight of the above (E) crosslinking retarder per 100 parts by weight of the above copolymer.

The (F) catalyst is preferably an organotin compound, and 0.01 to 0.5 part by weight of the above (F) catalyst is contained per 100 parts by weight of the copolymer.

Preferably, the adhesive layer obtained by crosslinking the above adhesive composition has an adhesive force of 0.3 to 0.1 N/25 mm at a low-speed peeling region of 0.3 m/min, and an adhesive force of 1.0 N/min at a high-speed peeling region of 30 m/min. 25mm or less.

It is preferable that the surface resistivity of the adhesive layer obtained by crosslinking the above-mentioned adhesive composition is 5.0 × 10 ^{+ 10} Ω / □ or less, and the peeling tape voltage is ± 0 to 1 kV.

Moreover, the present invention provides an adhesive film in which the adhesive composition obtained by crosslinking the above-mentioned adhesive composition is formed on one surface or both surfaces of the resin film.

Moreover, the present invention provides a surface protective film in which an adhesive layer obtained by crosslinking the above-mentioned adhesive composition is formed on one surface of a resin film, and is formed by penetrating the surface of the adhesive film with a ball pen. Transfer pollution to the adherend.

The above surface protective film can be used as a surface protective film for a polarizing plate.

It is preferable to carry out antistatic and antifouling treatment on the opposite side of the above-mentioned resin film on the side of the above-mentioned adhesive layer.

According to the present invention, it is possible to simultaneously satisfy (1) balance of adhesion in a low-speed peeling region and a high-speed peeling region, (2) prevention of occurrence of adhesive residue, (3) excellent antistatic property, and (4) Adhesive composition with all required properties of reworkability And surface protection film.

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

The adhesive composition of the present invention is characterized in that the main component is a (meth) acrylate monomer having (A) an alkyl carbon number of C4 to C10, (B) a hydroxyl group-containing copolymerizable monomer, and (C) a copolymer of a carboxyl group-containing copolymerizable monomer, and further comprising (D) a trifunctional or higher isocyanate compound, (E) a crosslinking retarder, (F) a crosslinking catalyst, and (G) an antistatic agent. (H) Polyether modified oxirane compound.

Examples of the (meth) acrylate monomer having (A) an alkyl group having a carbon number of C4 to C10 include butyl (meth)acrylate, isobutyl (meth)acrylate, and amyl (meth)acrylate. Hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylic acid An oxime ester, an isodecyl (meth) acrylate, an oxime (meth) acrylate or the like.

Examples of the (B) hydroxyl group-containing copolymerizable monomer include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl methacrylate, N-hydroxy(methyl) acrylamide, N-methylol (meth) acrylamide, N-hydroxyl A hydroxyl group-containing (meth) acrylamide such as a (meth) acrylamide or the like.

Preferably, it is selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, N At least one or more of the group consisting of hydroxy (meth) acrylamide, N-methylol (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide.

The (B) (4) hydroxyl group-containing copolymerizable monomer is preferably contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the (A) alkyl group having a C4 to C10 alkyl group carbon number. .

Further, in (B) a hydroxyl group-containing copolymerizable monomer, a total of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate The amount is preferably less than 1 part by weight (may not be contained), and is preferably 0 to 0.9 part by weight.

(C) The carboxyl group-containing copolymerizable monomer is preferably at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth) acrylate, and carboxypentyl (meth) acrylate. .

The (meth) acrylate monomer having a C4 to C10 carbon number per 100 parts by weight of the (A) alkyl group preferably contains 0.35 to 1.0 part by weight of (C) a carboxyl group-containing copolymerizable monomer.

The (C) trifunctional or higher isocyanate compound may be a polyisocyanate compound having at least three or more isocyanate (NCO) groups in one molecule, and examples thereof include hexamethylene diisocyanate and isophorone diisocyanate. Biuret modification or trimerization of diisocyanate (diamine having 2 NCO groups in one molecule) such as diphenylmethane diisocyanate, phenylene diisocyanate or decyl diisocyanate An addition object (polyol modified substance) of a trivalent or higher polyhydric alcohol (a compound having at least three or more OH groups in one molecule) such as trimethylolpropane or glycerol.

(D) The trifunctional or higher isocyanate compound is a polyisocyanate compound having at least three or more isocyanate (NCO) groups in one molecule, and particularly preferably a trimer isocyanate selected from a hexamethylene diisocyanate compound, and isophor. Adduct of a trimeric isocyanate (trimer) or hexamethylene diisocyanate compound of a keto diisocyanate compound At least one or more of a compound composition of a body, an isophorone diisocyanate compound, a biuret of a hexamethylene diisocyanate compound, and a biuret body of an isophorone diisocyanate compound. The (D) trifunctional or higher isocyanate compound is preferably contained in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of the copolymer.

The adhesive composition of the present invention may further contain (E) a crosslinking retarder.

Examples of the (E) crosslinking retarding agent include methyl ethyl acetate, ethyl acetate, octyl acetate, oleyl acetate, lauryl acetate, and stearyl acetate. Or a β-ketoester, or a β-diketone such as acetamidine, 2,4-hexanedione or benzamidine. These are ketoenol tautomer compounds, and in the adhesive composition using a polyisocyanate compound as a crosslinking agent, by blocking the isocyanate group of the crosslinking agent, the composition of the adhesive after the crosslinking agent is mixed can be suppressed. The excessive viscosity of the material rises or gels, prolonging the pot life of the adhesive composition.

(E) The crosslinking retardation agent is preferably a ketoenol tautomer compound, and particularly preferably at least one selected from the group consisting of acetamidineacetone and ethyl acetoacetate.

It is preferred to contain 1.0 to 5.0 parts by weight of the (E) crosslinking retarder relative to 100 parts by weight of the copolymer.

The adhesive composition of the present invention may further contain (F) a crosslinking catalyst. In the case where the polyisocyanate compound is used as the crosslinking agent, the (F) crosslinking catalyst may be a substance that functions as a catalyst for the reaction (crosslinking reaction) of the copolymer and the crosslinking agent. An amine compound such as a tertiary amine, an organometallic compound such as an organotin compound, an organic lead compound or an organic zinc compound is obtained.

Examples of the tertiary amine include a trialkylamine, N,N,N',N'-tetraalkyldiamine, N,N-dialkylamino alcohol, and triethylenediamine. Phenanthene derivative Derivatives, etc.

Examples of the organotin compound include dialkyl tin oxides and dialkyl tin salts. Fatty acid salt, fatty acid salt of stannous, and the like.

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

It is preferred to contain 0.01 to 0.5 part by weight of the (F) crosslinking catalyst with respect to 100 parts by weight of the copolymer.

(G) The antistatic agent is preferably a substance which is solid at normal temperature (for example, 30 ° C), and more specifically, preferably contains 0.5 to 5.0 parts by weight and has a melting point with respect to 100 parts by weight of the above copolymer. An ionic compound of 30 to 80 ° C or a 4-stage ammonium salt type acrylic monomer copolymerized at 1.0 to 5.0% by weight in the above copolymer and having a melting point of 30 to 80 ° C. In the present invention, as the (G) antistatic agent, (G1) an ionic compound having a melting point of 30 to 80 ° C or a (G2) 4-grade ammonium salt type acrylic acid having a melting point of 30 to 80 ° C is added to the copolymer. The monomers are copolymerized in the copolymer. Since these (G) antistatic agents have a low melting point and a long-chain alkyl group, it is presumed that the affinity with the acrylic acid copolymer is high.

The ionic compound having a melting point of (G1) of 30 to 80 ° C is an ionic compound having a cation and an anion, and examples thereof include a pyridine cation, an imidazolium cation, a pyrimidine cation, and a pyrazolium cation. a nitrogen-containing phosphonium cation such as a pyrrolidine cation or an ammonium cation; or a compound such as a phosphonium cation or a sulfonium cation; the anion is a hexafluorophosphate (PF ₆ ^- ), a thiocyanate (SCN ^- ), an alkyl group A compound of an inorganic or organic anion such as benzenesulfonate (RC ₆ H ₄ SO ₃ ^- ), perchlorate (ClO ₄ ^- ), or tetrafluoroborate (BF ₄ ^- ). A material having a melting point of 30 to 80 ° C can be obtained by selecting the chain length of the alkyl group or the position and number of the substituent. The cation is preferably a 4-stage nitrogen-containing phosphonium cation, and examples thereof include a 4-alkylpyridinium cation such as a 1-alkylpyridinium group (a carbon atom having 2 to 6 carbon atoms may be substituted or unsubstituted), and 1,3. a 4-stage imidazolium cation such as a dialkylimidazolium (a carbon atom at the 2, 4 or 5 position may have a substituent or may be unsubstituted), or a 4- to ammonium cation such as a tetraalkylammonium group.

The (G2) fourth-order ammonium salt type acrylic monomer having a melting point of 30 to 80 ° C is an ionic compound having a cation and an anion, and examples thereof include the following compounds: a cation is a (meth) propylene decyloxyalkyl group A quaternary ammonium compound containing an alkyl amide (R ₃ N ⁺ -C _n H _2n -OCOCQ=CH ₂ , wherein Q=H or CH ₃ , R=alkyl), etc., an anion Hexafluorinated phosphate (PF ₆ ^- ), thiocyanate (SCN ^- ), organic sulfonate (RSO ₃ ^- ), perchlorate (ClO ₄ ^- ), tetrafluoroborate (BF ₄ ^- ) A compound of an inorganic or organic anion.

Specific examples of the (G) antistatic agent are not particularly limited, but examples thereof include 1-octylpyridinium hexafluorophosphate, 1-mercaptopyridinium hexafluorophosphate, and 2-methyl- 1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecylpyridinium ten Dialkylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, dimethylaminomethyl acrylate hexafluorophosphate methyl salt ((CH ₃ ) ₃ N ⁺ CH ₂ OCOCH =CH ₂ ‧PF ₆ ^- ) and so on.

(H) Polyether modified siloxane compound is a siloxane compound having a polyether group, in addition to a general siloxane unit (-SiR ¹ ₂ -O-), a siloxane 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 groups or aryl groups, R ² and R ³ represent one or two or more kinds of alkylene groups, and R ⁴ represents one or two or more kinds of alkyl groups and hydrazines. Base or the like (end group). The polyether group may, for example, be a polyoxyalkylene group such as a polyoxyalkylene group ((C ₂ H ₄ O) _n ) or a polyoxylated propyl group ((C ₃ H ₆ O) _n ).

(H) a polyether modified siloxane compound is a polyether modified siloxane compound having an HLB value of 7 to 12, preferably 0.01 to 0.5 part by weight based on 100 parts by weight of the above copolymer. H) Polyether modified oxirane compound. More preferably, it is 0.1 to 0.5 parts by weight.

The HLB system is a hydrophilic-lipophilic balance (ratio of hydrophilicity to lipophilicity) prescribed in, for example, JIS K3211 (in the form of a surfactant).

The polyether modified oxoxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group by a hydrogenation oximation reaction for a polyorganosiloxane chain having a decyl group. Specifically, dimethyl oxa oxide can be mentioned. Methyl (polyoxyalkylene) oxirane copolymer, dimethyloxane. Methyl (polyoxy-extended ethyl) decane. Methyl (polyoxylated propyl) oxirane copolymer, dimethyl oxa oxide. A methyl (polyoxylated propyl) alkane copolymer or the like.

The adhesion and reworkability of the adhesive can be improved by mixing the (H) polyether modified oxoxane compound into the adhesive composition.

Further, as another component, a copolymerizable (meth)acrylic monomer, a (meth)acrylamide monomer, a dialkyl-substituted acrylamide monomer, which contains an alkylene oxide, may be appropriately mixed. A well-known additive such as a surfactant, a hardening accelerator, a plasticizer, a filler, a hardening retarder, a processing aid, an anti-aging agent, an antioxidant, and the like. These may be used alone or in combination of two or more.

The copolymer of the main component used in the adhesive composition of the present invention can be obtained by (A) a (meth) acrylate monomer having an alkyl group having a carbon number of C4 to C10, and (B) a copolymerizable monomer having a hydroxyl group. The body and (C) a carboxyl group-containing copolymerizable monomer are polymerized and synthesized. The polymerization method of the copolymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.

In the case of using the (G2) fourth-order ammonium salt type acrylic monomer as the (G) antistatic agent, the copolymer of the main component used in the adhesive composition of the present invention can be obtained by using (A) an alkane a (meth) acrylate monomer having a carbon number of C4 to C10, (B) a copolymerizable monomer having a hydroxyl group, (C) a copolymerizable monomer having a carboxyl group, and a 4-grade ammonium salt of (G2) The acrylic monomer is synthesized by polymerization.

By mixing (D) a trifunctional or higher isocyanate compound in the above copolymer The adhesive of the present invention can be produced by using (E) a crosslinking retarder, (F) a crosslinking catalyst, (G) an antistatic agent, (H) a polyether modified siloxane compound, and further suitable additives. Composition. Further, when the (G2) fourth-order ammonium salt type acrylic monomer having a melting point of 30 to 80 ° C is polymerized in the copolymer of the main component, it is not related to whether or not the (G) antistatic agent is further added to the copolymer. .

Preferably, the adhesive layer obtained by crosslinking the above adhesive composition has an adhesive force of 0.3 to 0.1 N/25 mm at a low-speed peeling region of 0.3 m/min, and an adhesive force of 1.0 N/min at a high-speed peeling region of 30 m/min. 25mm or less. As a result, it is possible to obtain a performance in which the adhesive force changes little with the peeling speed, and even if it is peeled off at a high speed, rapid peeling can be performed. Further, in order to re-bond, when the surface protective film is temporarily peeled off, excessive force is not required, and it is easy to peel off from the adherend.

It is preferable that the surface resistivity of the adhesive layer obtained by crosslinking the above-mentioned adhesive composition is 5.0 × 10 ^{+ 10} Ω / □ or less, and the peeling tape voltage is ± 0 to 1 kV. Further, in the present invention, the above "±0 to 1 kV" means 0 to -1 kV and 0 to +1 kV, that is, -1 to +1 kV. When the surface resistivity is large, the performance of static electricity generated by charging during peeling is poor. Therefore, by sufficiently reducing the surface resistivity, it is possible to reduce the generation of static electricity generated when the adhesive layer is peeled off from the adherend. The stripping voltage is applied to suppress the influence on the electrical control circuit of the adherend.

The adhesive layer (adhesive after crosslinking) obtained by crosslinking the adhesive composition of the present invention preferably has a gel fraction of 95 to 100%. As described above, since the gel fraction is high, the adhesive force in the low-speed peeling region can be prevented from becoming excessively large, and the elution of the unpolymerized monomer or oligomer from the copolymer can be reduced, and the durability in reworkability and high-temperature and high-humidity can be improved. To inhibit the contamination of the adherend.

The adhesive film of the present invention is obtained by crosslinking the adhesive composition of the present invention. The agent layer is formed on one side or both sides of the resin film. Further, the surface protective film of the present invention is obtained by crosslinking an adhesive layer formed of the adhesive composition of the present invention on a surface protective film on one surface of a resin film. In the adhesive composition of the present invention, the components of the above (A) to (H) are mixed in a good balance, and at the same time, (1) the balance of adhesion in the low-speed peeling region and the high-speed peeling region can be satisfied, and (2) Prevents the occurrence of adhesive residue, (3) has excellent antistatic properties, and (4) has reworkability (it is not transferred to the adherend after being drawn on the surface protective film with the pen atom interposed between the above adhesive layers) All required performance of pollution). Therefore, it can be suitably used for the use of the surface protective film of a polarizing plate.

As the base film of the adhesive layer or the release film (separator) for protecting the adhesive surface, a resin film such as a polyester film or the like can be used.

In the base film, the anti-fouling treatment using a polyfluorene-based or fluorine-based release agent, a coating agent, cerium oxide fine particles or the like can be performed on the opposite side of the resin film on the side of the adhesive layer; Antistatic treatment such as application or mixing of an electrostatic agent.

In the release film, a release treatment is performed on a surface on the side where the adhesive layer and the adhesive surface are bonded by a polyfluorene-based or fluorine-based release agent.

[Examples]

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

<Manufacture of Acrylic Polymers> [Example 1]

Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen. Then, 100 parts by weight of 2-ethylhexyl acrylate, 0.9 parts by weight of 8-hydroxyoctyl acrylate, 0.5 parts by weight of acrylic acid, and 60 parts of a solvent (ethyl acetate) were placed in the reaction apparatus. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and it was inverted at 65 °C. The acrylic copolymer solution 1 used in Example 1 having a weight average molecular weight of 500,000 was obtained over 6 hours.

[Examples 2 to 9 and Comparative Examples 1 to 9]

Examples 2 to 9 and Comparative Examples were obtained in the same manner as in the acrylic copolymer solution 1 used in the above Example 1, except that the composition of the monomers was set as described in (A) to (C) of Table 1. The acrylic copolymer solution used in 1~9.

<Manufacture of Adhesive Composition and Surface Protective Film> [Example 1]

As described above, 1.5 parts by weight of 1-octylpyridinium hexafluorophosphate, KF-351A (polyether of HLB=12) was added to the produced acrylic copolymer solution 1 (in which the acrylic copolymer was 100 parts by weight). 0.1 parts by weight of a modified oxoxane compound, and 2.5 parts by weight of acetamidine acetone, and stirred, then added 1.5 parts by weight of CORONATE HX (trimeric isocyanate of hexamethylene diisocyanate compound), dioctyltin dilaurate 0.02 After the parts by weight, the mixture was stirred and mixed to obtain the adhesive composition of Example 1. The adhesive composition was applied onto a release film composed of a polyoxyethylene resin coated polyethylene terephthalate (PET) film, and then dried at 90 ° C to remove the solvent to obtain an adhesive layer. Adhesive sheet having a thickness of 25 μm.

Then, the adhesive sheet is transferred to a single-sided antistatic and antifouling polyethylene terephthalate (PET) film through the antistatic and antifouling treatment surface to obtain "antistatic and antifouling treatment". The surface protective film of Example 1 of the laminated structure of the PET film/adhesive layer/release film (polyoxyxene-coated PET film).

[Examples 2 to 9 and Comparative Examples 1 to 9]

The composition of the additive was set as described in (D) to (H) of Table 1, except that the surface protective films of Example 1 were obtained in the same manner as in Examples 2 to 9 and Comparative Examples 1 to 9. Surface protection film.

In Table 1, the mixing ratio of each component is a numerical value which shows the weight part obtained by the total of (A) group as 100 weight part by the bracket. Further, Table 2 shows the compound names of the respective component numbers used in Table 1. In addition, CORONATE (registered trademark) HX and HL are trade names of Japan POLYURETHANE Industrial Co., Ltd., TAKENATE (registered trademark) D-140N is the trade name of Mitsui Chemicals Co., Ltd., 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>

The surface protective films of Examples 1 to 9 and Comparative Examples 1 to 9 were aged for 7 days in an environment of 23° C. and 50% RH, and then the release film (PET film coated with polyoxymethylene resin) was peeled off to expose adhesion. The agent layer was used as a test sample for gel fraction and surface resistivity.

Further, the surface protective film exposing the adhesive layer is adhered to the surface of the polarizing plate adhered to the liquid crystal cell via the adhesive layer, and left for 1 day, and then subjected to a high pressure of 50 ° C, 5 atm, and 20 minutes. The kettle was treated and further allowed to stand at room temperature for 12 hours, and the thus obtained was used as a test sample of adhesion, peeling tape voltage and durability.

<gel fraction>

After the aging was completed, the quality of the test sample attached to the polarizing plate was accurately measured, and after immersing in toluene for 24 hours, it was filtered through a metal mesh of 200 mesh. Then, after drying the filtrate at 100 ° C for 1 hour, the quality of the residue was accurately measured, and the gel fraction of the adhesive layer (adhesive after crosslinking) was calculated from the following formula.

Gel fraction (%) = insoluble mass (g) / adhesive mass (g) × 100

<adhesion>

The test sample obtained above was peeled off at a low speed (0.3 m/min) and a high speed (30 m/min) in a 180° direction using a tensile tester (a surface protective film of 25 mm width was attached to the surface of the polarizing plate), and the peel strength was measured. This is used as adhesion.

<surface resistance>

After aging, before peeling on the polarizing plate, the release film (polyoxyphthalocene-coated PET film) was peeled off to expose the surface of the adhesive layer, and the adhesive layer was measured using a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Corporation ANALYTECH). Surface resistance.

<Peel strip voltage>

When the test sample obtained as described above was peeled off at a tensile speed of 180° at 30 m/min, The high-voltage electrostatic sensors SK-035 and SK-200 (manufactured by KEYENCE Co., Ltd.) were used to set the voltage (band voltage) generated by the polarizing plate, and the maximum value of the measured value was used as the peeling band voltage.

<reworkability>

After drawing on the surface protective sheet of the test sample obtained above by a ballpoint pen, the surface protective sheet was peeled off from the polarizing plate, and the surface of the polarizing plate was observed to confirm that no contamination was transferred to the polarizing plate. The evaluation target criterion was evaluated as "○" in the case where no contamination was transferred to the polarizing plate, and it was confirmed that "X" was evaluated as a case where the trajectory drawn by the atomic pen was transferred to at least a part of the contamination.

<Durability>

The test sample obtained above was placed in an environment of 60 ° C and 90% RH for 250 hours, and then taken out at room temperature. After further standing for 12 hours, the adhesion was measured to confirm that there was no significant increase compared with the initial adhesion. . The evaluation target was evaluated as "○" when the adhesive strength after the test was 1.5 times or less of the initial adhesive force, and "x" when it was more than 1.5 times.

The evaluation results are shown in Table 3. Further, the surface resistivity is marked by a method in which "m × 10 ^{+ n} " is expressed as "mE + n" (where m is an arbitrary real number and n is a positive integer).

The surface protective films of Examples 1 to 9 had an adhesive force of 0.3 to 0.1 N/25 mm at a low-speed peeling region of 0.3 m/min, and an adhesive force of 30 nm/min at a high-speed peeling region of 1.0 N/25 mm or less. Further, the surface resistivity was 5.0 × 10 ^{+ 10} Ω / □ or less, and the peeling tape voltage was ± 0 to 1 kV. Further, it is excellent in durability after being placed in a 60 ° C, 90% RH environment for 250 hours by drawing the adhesive layer on the surface protective sheet with a ball pen.

That is, it satisfies (1) the balance of the adhesion in the low-speed peeling zone and the high-speed peeling zone, (2) prevention of the occurrence of adhesive residue, (3) excellent antistatic property, and (4) rework performance. All required performance.

The surface protective film of Comparative Example 1 may have a low adhesion rate of 0.3 m/min in the low-speed peeling region due to excessive (B) hydroxyl group-containing monomer.

In the surface protective film of Comparative Example 2, the (B) hydroxyl group-containing monomer is too small, (D) the isocyanate compound is excessive, and the (H) polyether modified siloxane compound has an excessively small HLB value, so the low-speed peeling region is 0.3 m. The adhesive force of /min and the adhesive force of 30 m/min in the high-speed peeling region become excessively large, the peeling tape voltage becomes high, the reworkability and durability are deteriorated, and the gel fraction is lowered.

In the surface protective film of Comparative Example 3, there may be a case where (B) a hydroxyl group-containing monomer is excessive, (C) an acid-containing monomer is excessive, and (H) a polyether-modified oxirane compound has an excessive HLB value, so that the low-speed peeling region is excessive. Low adhesion at 0.3m/min, high surface resistivity, high stripping voltage, poor reworkability and durability.

In the surface protective film of Comparative Example 4, since the (C) acid-containing monomer was too small, the adhesion at a low-speed peeling region of 0.3 m/min was low, and durability was poor.

In the surface protective film of Comparative Example 5, since (B) the monomer having a hydroxyl group is excessive and (D) the isocyanate compound is too small, the adhesion at a low-speed peeling region of 0.3 m/min and the adhesive force at a high-speed peeling region of 30 m/min may be changed. If it is too large, the peeling tape voltage becomes high, the reworkability and durability are deteriorated, and the gel fraction is lowered.

The surface protective film of Comparative Example 6 may be because there is no mixing (E) crosslinking retarder and (F) too much crosslinking catalyst, so the use period is too short, and crosslinking is performed before coating, and coating is impossible. .

The surface protective film of Comparative Example 7 may have a low-speed peeling region of 0.3 because it contains MA having a C1 alkyl group in (A) a (meth) acrylate monomer having an alkyl group, and no mixed (F) crosslinking catalyst. The adhesion of m/min and the high-speed peeling zone have an excessive adhesion of 30 m/min, a high surface resistivity, a high peeling strip voltage, and poor reworkability and durability.

In the surface protective film of Comparative Example 8, since the (G) antistatic agent was too small and the (H) polyether modified siloxane compound was not mixed, the adhesion at a low-speed peeling region of 0.3 m/min and the high-speed peeling region of 30 m/ The adhesion of min is too large, the surface resistivity is high, the stripping voltage is high, and the reworkability is poor.

In the surface protective film of Comparative Example 9, the (G) antistatic agent may have a melting point of less than 30 ° C (liquid at normal temperature) and (H) polyether modified oxoxane compound, so the low-speed peeling region is 0.3 m/ The adhesion of min is low, the stripping voltage is high, and the durability is poor.

As described above, in the surface protective films of Comparative Examples 1 to 9, it is impossible to simultaneously satisfy (1) the balance of the adhesive force in the low-speed peeling region and the high-speed peeling region, (2) prevention of the occurrence of the adhesive residue, and (3) excellent Antistatic properties, and (4) all required performance with reworkability.

Claims (12)

An adhesive composition comprising an acrylic acid copolymer characterized in that the acrylic copolymer is selected from a (meth) acrylate monomer having a C4 to C10 alkyl carbon number relative to 100 parts by weight of (A) alkyl group. 50 parts by weight or more of one of a compound group consisting of butyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; (B) a copolymerizable single group containing a hydroxyl group 0.1 to 5.0 parts by weight of the compound; and (C) a copolymer of 0.35 to 1.0 part by weight of a carboxyl group-containing copolymerizable monomer, and the above-mentioned adhesive composition further contains (D) a trifunctional or higher isocyanate Compound, (E) cross-linking retarder of ketoenol tautomerization compound, (F) cross-linking catalyst, (G) antistatic agent, (H) polyether modified oxirane having an HLB value of 7-12 The compound (B) having a hydroxyl group-containing copolymerizable single system is selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide Group to compound is at least one or more of the antistatic agent based ionic compound having a melting point 30 ~ 80 ℃ of. The adhesive composition of claim 1, wherein the (B) (C) hydroxyl group having a (C) alkyl group having a C4 to C10 alkyl group has a hydroxyl group In the copolymerizable monomer, the total amount of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate is 0 to 0.9 parts by weight (wherein It is also allowed to contain no 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate). The adhesive composition according to claim 1 or 2, wherein the (C) carboxyl group-containing copolymerizable single system is selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypenta At least one or more of the compound groups composed of the group (meth) acrylate. The adhesive composition according to claim 1 or 2, wherein the (D) trifunctional or higher isocyanate compound is selected from the group consisting of a trimer isocyanate of a hexamethylene diisocyanate compound and an isophorone diisocyanate compound. An adduct of a trimeric isocyanate, a hexamethylene diisocyanate compound, an addition of an isophorone diisocyanate compound, a biuret of a hexamethylene diisocyanate compound, At least one or more of the compound composition of the biuret of the isophorone diisocyanate compound; and the above adhesive composition contains 0.5 to 5.0 parts by weight of the above (D) 3 with respect to 100 parts by weight of the above copolymer. A functional or higher isocyanate compound. The adhesive composition according to claim 1 or 2, wherein the (G) antistatic agent is contained in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of the copolymer, and the melting point is 30. Ionic compound at ~80 °C. The adhesive composition according to claim 1 or 2, wherein the adhesive composition contains 0.01 to 0.5 part by weight of the above (H) polyether modified oxime relative to 100 parts by weight of the above copolymer. Alkane compound. The adhesive composition according to claim 1 or 2, wherein the (E) ketoenol tautomer compound crosslinking crosslinking agent is based on 100 parts by weight of the above copolymer, the adhesive composition It contains 1.0 to 5.0 parts by weight of the above (E) crosslinking retarder. The adhesive composition according to claim 1 or 2, wherein the (F) cross-linking catalyst organotin compound contains 0.01 to 0.5 with respect to 100 parts by weight of the above copolymer. The above (F) cross-linking catalyst is added in parts by weight. An adhesive film formed by crosslinking an adhesive composition according to any one of claims 1 to 8 on one or both sides of a resin film. A surface protective film which is one of claims 1 to 8 The adhesive layer obtained by crosslinking the adhesive composition is formed on one side of the resin film, and is not contaminated by the adherend after being drawn on the surface protective film with the atomic pen interposed therebetween. The surface protective film of claim 10 is used as a surface protective film for a polarizing plate. The surface protective film of claim 10, wherein the resin film is formed on the opposite side of the adhesive layer side, and an antistatic and antifouling treatment is performed.