TWI545167B - Adhesive composition, adhesive film and surface protective film - Google Patents

Description

Adhesive composition, adhesive film 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 a surface protective film for bonding the surface of an optical member such as a polarizing plate or a retardation film which constitutes a liquid crystal display, and for protecting an optical member such as a polarizing plate or a phase difference plate. Adhesive composition, and a surface protective film using the same.

In the manufacturing steps of an optical member such as a polarizing plate or a phase difference plate for constituting a liquid crystal display device, a surface protective film is temporarily bonded to the surface of the optical member. When the optical member is assembled in the liquid crystal display, the surface protective film is peeled off from the optical member and removed. The surface protective film for protecting the surface of the optical member is used only in the manufacturing step. Therefore, it is also called a step film.

The surface protective film used in the step of producing an optical member has an adhesive layer formed on one surface of an optically transparent polyethylene terephthalate (PET) resin film. Further, the release film for protecting the adhesive layer from being peeled off is bonded to the upper surface of the adhesive layer until it is bonded to the optical member.

In addition, in the optical member such as the polarizing plate or the retardation film, the product inspection of the optical evaluation accompanying the display capability, chromaticity, contrast, and impurity incorporation of the liquid crystal display panel is performed in a state in which the surface protective film is bonded. The necessary performance for the surface protective film is that no bubbles or impurities adhere to the adhesive layer.

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 may be temporarily peeled off and the surface protective film may be reattached for various reasons. At this time, a surface protective film which can be easily peeled off from the optical member of the adherend (having heavy workability) is desired.

Further, when the surface protective film is peeled off from an optical member such as a polarizing plate or a phase difference plate, it is required to be peeled off quickly. It is required that even high-speed peeling can be quickly peeled off, and the influence on the peeling speed of the adhesive force is small.

In recent years, in order to obtain the required performance of the adhesive layer constituting the surface protective film and to be easy to use when using the surface protective film, it is required to obtain (1) the balance of adhesion in low-speed peeling and high-speed peeling, (2) ) Prevents the occurrence of adhesive residue, and (3) Has heavy workability.

However, although the respective required performances of the above (1) to (3) can be satisfied, it is extremely difficult to have all the required performances of (1) to (3) required in the adhesive layer of the surface protective film. of.

For example, the following proposals are known regarding (1) obtaining an adhesive balance in low-speed peeling and high-speed peeling; and (2) preventing occurrence of 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. If it takes a long time after the bonding, there is a problem that the adhesive moves toward the adherend side, and the adhesion to the adherend increases with time. In order to prevent this problem, an adhesive (pressure-sensitive adhesive) is known which uses an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group. The copolymer is obtained by crosslinking treatment with a crosslinking agent (Patent Document 1).

And proposed the following adhesives, etc.: a small amount of blending in the same copolymer as above (A A copolymer of an alkyl acrylate and a carboxyl group-containing copolymerizable compound is obtained by crosslinking a crosslinking 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, there is a problem of peeling due to floating due to heating during processing or storage, or a high-speed peeling by manual peeling. The problem of poor removability.

In order to solve such problems, an adhesive composition is proposed, which comprises (a) 100 parts by weight of an alkyl (meth)acrylate having an alkyl group having 8 to 10 carbon atoms as a main component. (b) 1 to 15 parts by weight of a carboxyl group-containing copolymerizable compound, and (c) 3 to 100 parts by weight of an aliphatic carboxylic acid having 1 to 5 carbon atoms; A copolymer of a monomer mixture obtained by a vinyl ester is obtained by blending a copolymer having a carboxyl group equivalent or more with respect to the carboxyl group of the component (b) in the copolymer (Patent Document 2).

The adhesive composition described in Patent Document 2 does not cause peeling such as floating during processing or storage, and the adhesion time rises little, and the removability is excellent, even for long-term storage, especially Long-term storage in a high-temperature environment can also be peeled off with a small force. At this time, no adhesive remains on the adherend, and it can be peeled off with a small force even at the time of high-speed peeling.

Further, (3) has a rework property, for example, an adhesive composition is proposed, which is a hardener in which an isocyanate compound is blended in an acrylic resin, and is 0.0001 to 10 parts by weight based on 100 parts by weight of the acrylic resin. Specific citrate oligomer (Patent Document 3).

In Patent Document 3, 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, or the like is used as a main monomer component, and for example, A monomer component containing another functional group in a monomer such as a carboxyl group. In general, it is preferred to contain 50% by weight or more of the above-mentioned main monomer, and further, it is desirable to contain a monomer component having a functional group. The content is 0.001 to 50% by weight, preferably 0.001 to 25% by weight, and preferably 0.01 to 25% by weight. The adhesive composition described in Patent Document 3 has a small change in cohesive force and adhesive force over time even under high temperature or high temperature and high humidity, and exhibits an excellent effect in adhesion to a curved surface. Heavy work.

In general, when the adhesive layer is made into a soft property, the adhesive residue tends to occur, and the workability is also liable to lower. That is, it is difficult to peel off and re-attach when it is erroneously bonded. Therefore, it is necessary to crosslink a monomer having a functional group such as a carboxyl group to a host agent, and to form a certain hardness of the adhesive layer to have a reworkability.

[Previous 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 8-199130

In the prior art, as a required performance for the adhesive layer constituting the surface protective film, it is desired to achieve adhesion balance and rework performance in low-speed peeling and high-speed peeling, but although it is possible to satisfy each of the required performances, it is not possible. Meet all the required properties required in the adhesive layer of the surface protective film.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide an adhesive composition and a surface protective film which are excellent in adhesion balance in low-speed peeling and high-speed peeling, and excellent in durability and rework performance.

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, and (B) a copolymerizable monomer having a hydroxyl group. And (C) an acrylic polymer comprising a carboxyl group-containing copolymerizable monomer and (D) a polyalkylene glycol mono(meth)acrylate monomer copolymer, further comprising (E)3 An isocyanate compound having a functional group or more, (F) a crosslinking inhibitor, (G) a crosslinking catalyst, and (H) a polyether modified siloxane compound, wherein the acrylic polymer has an acid value of 0.01 to 8.0.

The above (B) hydroxyl group-containing copolymerizable monomer is selected from the group consisting of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (A) a group of compounds consisting of 2-hydroxyethyl acrylate, N-hydroxy(meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide At least one or more of them; preferably, the (A) (B)-containing (B)-containing (A) (C)-containing (C)-containing (meth) acrylate monomer having 0.1 to 5.0 parts by weight of the above (B) a copolymerizable monomer of a hydroxyl group, and among the above (B) hydroxyl group-containing copolymerizable monomers, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, (meth)acrylic acid The total content of 4-hydroxybutyl ester is 0 to 0.9 parts by weight.

The above (C) carboxyl group-containing copolymerizable monomer is selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2-(methyl) propylene oxime Ethyl hexahydrophthalic acid, 2-(methyl) propylene methoxypropyl hexahydrophthalic acid, 2-(methyl) propylene methoxyethyl phthalate, 2-(A Acryloxyethyl succinic acid, 2-(methyl) propylene oxiranyl ethyl maleic acid, carboxy polycaprolactone mono (meth) acrylate, 2-(methyl) propylene decyloxy At least one or more of the group consisting of ethyltetrahydrophthalic acid; preferably a (meth) acrylate single having a C4 to C10 carbon number relative to 100 parts by weight of the above (A) alkyl group , containing 0.35 to 1.0 part by weight of the above (C) carboxyl group-containing copolymerizable single body.

The above (D) polyalkylene glycol mono(meth) acrylate monomer is selected from the group consisting of polyalkylene glycol mono(meth) acrylate and methoxy polyalkylene glycol (meth) acrylate. At least one of an ester and an ethoxylated polyalkylene glycol (meth) acrylate; preferably a C4 to C10 (methyl) group of the above (A) alkyl group with respect to 100 parts by weight An acrylate monomer containing 1 to 20 parts by weight of the above (D) polyalkylene glycol mono(meth)acrylate monomer.

The above (E) trifunctional or higher isocyanate compound is an isocyanurate body selected from a hexamethylene diisocyanate compound, an isocyanurate body of an isophorone diisocyanate compound, and hexamethylene diisocyanate. At least an adduct of the compound, an adduct of an isophorone diisocyanate compound, a biuret of a hexamethylene diisocyanate compound, and a biuret composed of a biuret compound of an isophorone diisocyanate compound One or more; preferably, 0.5 to 5.0 parts by weight of the above (E) trifunctional or higher isocyanate compound is contained per 100 parts by weight of the copolymer.

The (H) 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 copolymer. (H) Polyether modified oxoxane compound.

The above (F) crosslinking inhibitor is a ketoenol tautomer compound, and preferably contains 1.0 to 5.0 parts by weight of the above (F) crosslinking inhibitor with respect to 100 parts by weight of the above copolymer.

The (G) crosslinking catalyst is an organotin compound, and preferably contains 0.01 to 0.5 part by weight of the above (G) crosslinking catalyst based on 100 parts by weight of the copolymer.

Preferably, the adhesive layer obtained by crosslinking the above-mentioned adhesive composition has an adhesive force of 0.05 to 0.1 N/25 mm at a low-speed peeling speed of 0.3 m/min, and an adhesive force of 1.0 at a high-speed peeling speed of 30 m/min. N/25mm or less.

Further, the present invention provides an adhesive film which is formed on one or both sides of a resin film. An adhesive film obtained by bonding an adhesive layer obtained by crosslinking the above adhesive composition is formed.

Further, the present invention provides a surface protective film in which a surface protective film of an adhesive layer obtained by crosslinking the above-mentioned adhesive composition is formed on one surface of a resin film, and the surface protective film is passed through the adhesive layer to be a ballpoint pen After being painted on the surface protective film, it will not be contaminated by the transfer of the adhesive.

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

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

According to the present invention, it is possible to satisfy all the properties required in the adhesive layer such as the surface protective film in the prior art. In addition, excellent performance for preventing the occurrence of adhesive residue is obtained. Specifically, the performance of preventing the occurrence of adhesive residue can be further improved.

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

The adhesive composition of the present invention is mainly composed of a (meth) acrylate monomer having (A) an alkyl group having a carbon number of C4 to C10, (B) a hydroxyl group-containing copolymerizable monomer, and (C) An acrylic polymer containing a copolymerizable monomer of a carboxyl group and a copolymer of (D) a polyalkylene glycol mono(meth)acrylate monomer, further containing (E) 3 functional groups or more An isocyanate compound, (F) a crosslinking inhibitor, (G) a crosslinking catalyst, and (H) a polyether modified siloxane compound, the acid value of the above acrylic polymer is 0.01 to 8.0.

(A) (meth) acrylate monomer having an alkyl group having C4 to C10 carbon atoms Examples thereof include butyl (meth)acrylate, isobutyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, and (meth)acrylic acid. Octyl ester, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, decyl (meth)acrylate, and 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 acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl A (hydroxy)-containing (meth) acrylamide such as acrylamide or the like.

It is preferably 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 a compound 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) (C)-C10-C10 (meth) acrylate monomer. body.

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 content is preferably less than 1 part by weight (may not be contained), and preferably 0 to 0.9 parts by weight.

(C) The carboxyl group-containing copolymerizable monomer is preferably selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2-(methyl) propylene oxime Ethyl hexahydrophthalic acid, 2-(methyl) propylene methoxy propyl hexahydrophthalic acid, 2-(methyl) propylene methoxyethyl phthalic acid, carboxy polyene At least one of a group consisting of ester mono(meth)acrylate and 2-(meth)acryloxyethyltetrahydrophthalic acid the above.

(C) a carboxyl group-containing copolymerizable monomer is preferably contained in an amount of from 0.35 to 1.0 part by weight based on 100 parts by weight of the (A) alkyl group having a C4 to C10 (meth) acrylate monomer. More preferably, it contains 0.35 to 0.6 parts by weight.

As the (D) polyalkylene glycol mono(meth)acrylate monomer, it may be a compound in which a hydroxyl group is esterified as a (meth) acrylate among a plurality of hydroxyl groups of the polyalkylene glycol . Since the (meth) acrylate group becomes a polymerizable group, it can be copolymerized with the main agent polymer. The other hydroxyl group may be maintained as OH, or may be an alkyl ether such as methyl ether or diethyl ether or a saturated carboxylic acid ester such as acetate.

Examples of the alkylene group which the polyalkylene glycol has are an exoethyl group, a propyl group, a butyl group, and the like, but are not limited thereto. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethyl diol, poly propyl diol, and polybutylene glycol. Examples of the copolymer of the polyalkylene glycol include a polyethylene glycol-polypropylene glycol, a polyethylene glycol-polybutylene glycol, and a poly(propylidene glycol)-polymer. Stretching butyl diol, polyethyl propylene glycol - poly propylene glycol - polybutylene glycol, etc., the copolymer may be a block copolymer or a random copolymer.

As the (D) polyalkylene glycol mono(meth) acrylate monomer, preferably selected from polyalkylene glycol mono(meth) acrylate, methoxy polyalkylene glycol (A) At least one of acrylate and ethoxylated polyalkylene glycol (meth) acrylate.

More specifically, polyethyl epoxide-mono (meth) acrylate, poly propyl diol-mono (meth) acrylate, polybutylene butyl diol - mono (meth) acrylic acid Ester, polyethyl epoxide - poly propyl diol - mono (meth) acrylate, polyethyl propylene glycol - polybutylene diol - mono (meth) acrylate, poly propyl Glycol-polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-polybutylene glycol-mono(meth)acrylate; methoxy Gather Ethylene glycol-(meth)acrylate, methoxypolypropyl diol-(meth) acrylate, methoxy-polybutylene glycol-(meth) acrylate, methoxy -Polyethyl diol-poly propyl diol-(meth) acrylate, methoxy-polyethyl diol-polybutylene glycol-(meth) acrylate, methoxy -Polypropylene glycol-polybutylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol-(methyl Acrylate; ethoxylated polyethylene glycol-(meth)acrylate, ethoxylated polypropylene glycol-(meth)acrylate, ethoxylated butyl glycol-(A) Acrylate, ethoxy-polyethyl diol-poly propylene glycol-(meth) acrylate, ethoxy-polyethyl ethane-polybutylene glycol-(A) Acrylate, ethoxy-poly-propyl diol-polybutylene glycol-(meth) acrylate, ethoxy-polyethyl diol-poly propylene glycol-polycondensation Butylene glycol-(meth) acrylate and the like.

It is preferred to contain 1 to 20 parts by weight of the above (D) polyalkylene glycol with respect to 100 parts by weight of the (A) alkyl group having a C4 to C10 (meth) acrylate monomer. Mono (meth) acrylate monomer.

The (E) trifunctional or higher isocyanate compound may have at least three or more isocyanate (NCO) groups in one molecule, and examples thereof include hexamethylene diisocyanate and isophorone diisocyanate. Biuret modified or isocyanuric acid of diisocyanate (compound having two NCO groups in one molecule) such as diphenylmethane diisocyanate, phenylene diisocyanate or xylylene diisocyanate An adduct (polyol modified body) of a trivalent or higher polyvalent alcohol (a compound having at least three or more OH groups in one molecule) such as an ester modified product, trimethylolpropane or glycerin.

The (E) trifunctional or higher isocyanate compound is a polyisocyanate compound having at least three or more isocyanate (NCO) groups in one molecule, and particularly preferably an isocyanurate selected from a hexamethylene diisocyanate compound. Isocyanurate body, isocyanurate body of isophorone diisocyanate compound, adduct body of hexamethylene diisocyanate compound, isophorone diiso At least one or more of the group consisting of an adduct of a cyanate compound, a biuret of a hexamethylene diisocyanate compound, and a biuret of an isophorone diisocyanate compound. The (E) trifunctional or higher isocyanate compound is preferably 0.5 to 5.0 parts by weight based on 100 parts by weight of the copolymer.

Examples of the (F) crosslinking inhibitor include methyl ethyl acetate, ethyl acetate, octyl acetate, oleyl acetate, lauryl acetate, and stearyl acetate. A β-ketoester such as an ester, or a β-diketone such as acetamidineacetone, 2,4-hexanedione or benzamidineacetone. These are ketoenol tautomer compounds, and in the adhesive composition using a polyisocyanate compound as a crosslinking agent, by blocking the isocyanate group having a crosslinking agent, the adhesive composition after the crosslinking agent is mixed can be suppressed. The excessive viscosity rises or gels, prolonging the shelf life of the adhesive composition.

(F) The crosslinking inhibitor is preferably a ketoenol tautomer compound, and particularly preferably at least one selected from the group consisting of ethyl acetate and ethyl acetate.

It is preferred to contain 1.0 to 5.0 parts by weight of (F) a crosslinking inhibitor with respect to 100 parts by weight of the copolymer.

In the case where the polyisocyanate compound is used as the crosslinking agent, the (G) crosslinking catalyst may be a substance which functions as a catalyst in the reaction (crosslinking reaction) between the copolymer and the crosslinking agent, and may be exemplified by An amine compound such as a tertiary amine, an organometallic compound such as an organotin compound, an organic lead compound or an organozinc compound.

As the tertiary amine, there may be mentioned: a trialkylamine, N,N,N',N'-tetraalkyldiamine, N,N-dialkylamino alcohol, tri-ethylenediamine, morpholine Derivatives, oxazine derivatives, and the like.

Examples of the organotin compound include a dialkyl tin oxide, a fatty acid salt of a dialkyl tin, a fatty acid salt of stannous, and the like.

(G) a crosslinking catalyst is preferably an organotin compound, particularly preferably selected from the group consisting of dioctyl oxide. At least one or more of the group consisting of tin and dioctyltin dilaurate.

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

(H) Polyether modified oxoxane compound is a polyether-based oxoxane compound, in addition to a conventional siloxane unit (-SiR ¹ ₂ -O-), a polyether-based oxirane unit ( -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 polyoxyethylene group ((C ₂ H ₄ O) _n ) or a polyoxypropylene group ((C ₃ H ₆ O) _n ).

The (H) polyether modified siloxane compound is preferably a polyether modified siloxane compound having an HLB value of 7 to 12. Further, it is preferred to contain 0.01 to 0.5 part by weight of the above (H) polyether modified siloxane compound with respect to 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 part by weight.

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

The polyether modified siloxane 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 methoxyoxane can be mentioned. Methyl (polyethylene oxide) alkane copolymer, dimethyl methoxy alkane. Methyl (polyoxyethylene) oxirane. Methyl (polyoxypropylene) siloxane copolymer, dimethyl methoxy alkane. A methyl (polyoxypropylene) siloxane copolymer or the like.

The adhesion and reworkability of the adhesive can be improved by blending the (H) polyether modified siloxane compound to the adhesive composition.

Further, as other components, a copolymerizable (meth)acrylic monomer containing an alkylene oxide, a (meth)acrylamide monomer, and a dialkyl-substituted C may be appropriately blended. A well-known additive such as an aniline monomer, a surfactant, a hardening accelerator, a plasticizer, a filler, a hardening inhibitor, a processing aid, an anti-aging agent, an antioxidant, an antistatic agent, and the like. These may be used alone or in combination of two or more.

As an antistatic agent, an ionic compound is mentioned. Further, it is also possible to impart antistatic properties by copolymerizing with an ionic acrylic monomer in the copolymer of the main component.

The copolymer of the main component used in the adhesive composition of the present invention can be obtained by polymerizing (A) a (meth) acrylate monomer having an alkyl group having a C4 to C10 carbon number, and (B) a hydroxyl group-containing copolymer. A polymerizable monomer, (C) a carboxyl group-containing copolymerizable monomer, and (D) a polyalkylene glycol mono(meth)acrylate monomer are 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.

The adhesive composition of the present invention can be modified by blending (E) a trifunctional or higher isocyanate compound, (F) a crosslinking inhibitor, (G) a crosslinking catalyst, (H) polyether in the above copolymer. The siloxane compound is further prepared by appropriately adding an optional additive.

The copolymer is preferably an acrylic polymer, preferably an acrylic monomer containing 50 to 100% by weight of a (meth) acrylate monomer, (meth)acrylic acid, or (meth) acrylamide. body.

Further, the acid value of the acrylic polymer is preferably from 0.01 to 8.0. Thereby, the contamination property can be improved, and the performance of preventing the occurrence of the adhesive residue can be improved.

Here, the "acid value" is one of the indexes indicating the acid content, and indicates the number of mg of potassium hydroxide required to neutralize 1 g of the carboxyl group-containing polymer.

Preferably, the adhesive layer obtained by crosslinking the above adhesive composition has an adhesive force of 0.05 to 0.1 N/25 mm at a low-speed peeling speed of 0.3 m/min, and an adhesive force of 1.0 at a high-speed peeling speed of 30 m/min. N/25mm or less. Thereby, 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, it can be peeled off quickly. and, In order to re-attach, when the surface protective film is temporarily peeled off, excessive force is not required, and it is also easy to peel off from 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%. Thus, since the gel fraction is high, the adhesive force at the low-speed peeling speed can be prevented from becoming excessively large, the dissolution of the unpolymerized monomer or oligomer from the copolymer is lowered, and the durability in the workability, high temperature, high humidity and high humidity is improved. Sex, inhibiting the contamination of the adherend.

The adhesive film of the present invention is formed by crosslinking an adhesive composition of the present invention on one or both sides of a resin film. Further, the surface protective film of the present invention is a surface protective film in which an adhesive layer obtained by crosslinking the adhesive composition of the present invention is formed on one surface of a resin film. The adhesive composition of the present invention has excellent balance of adhesion at a low-speed peeling speed and a high-speed peeling speed because the components of the above (A) to (H) are blended in a well-balanced manner, and durability and reworkability ( The ballpoint pen is excellent in the transfer of the above-mentioned adhesive layer on the surface protective film without causing contamination of the adherend. Therefore, the surface protective film of the present invention can be suitably used as a surface protective film for a polarizing plate.

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

In the base film, an antifouling treatment by an anthrone, a fluorine-based release agent or a coating agent, cerium oxide microparticles or the like may be applied to the opposite side of the resin film on which the adhesive layer is formed; Antistatic treatment by coating or kneading of an antistatic agent.

In the release film, a release treatment is applied to the surface which is bonded to the adhesive surface of the pressure-sensitive adhesive layer by an fluorenone-based or fluorine-based release agent.

[Examples]

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

<Preparation of Acrylic Copolymer> [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, 3 parts by weight of polyethylene glycol monoacrylate, and a solvent (acetic acid B) were added to the reaction apparatus. Ester) 60 parts by weight. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise thereto over 2 hours, and the mixture was reacted at 65 ° C for 6 hours to obtain an acrylic copolymer used in Example 1 having a weight average molecular weight of 500,000. Solution 1. A part of the acrylic copolymer was sampled and used as a sample for measuring an acid value to be described later.

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

Except that the composition of the monomer was set as described in (A) to (D) of Table 1, the same procedure as in the acrylic copolymer solution 1 used in the above Example 1 was carried out, and Example 2 was obtained. 9 and the acrylic copolymer solution used in Comparative Examples 1 to 9.

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

According to the acrylic copolymer solution 1 prepared above (in which the acrylic copolymer is 100 parts by weight), 0.1 part by weight of KF-351A (polyether modified oxirane compound of HLB=12) and 2.5 parts by weight of acetamidine acetone are added. After stirring, 1.5 parts by weight of CORONATE HX (isocyanurate body of hexamethylene diisocyanate compound) and 0.02 parts by weight of dioctyltin dilaurate were added and stirred and mixed to obtain an adhesive composition of Example 1. Things. Applying the adhesive composition to a bismuth ketone resin coated polyethylene terephthalate (PET) film After leaving the film, the solvent was removed by drying at 90 ° C to obtain an adhesive sheet having an adhesive layer thickness of 25 μm.

Then, the adhesive sheet is transferred to the opposite side of the antistatic and antifouling treatment surface of the antistatic and antifouling polyethylene terephthalate (PET) film on one side, thereby obtaining "antistatic and The antifouling PET film/adhesive layer/release film (anthracene resin-coated PET film) was deposited under the surface protective film of Example 1.

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

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

In Table 1, the mixing ratio of each component is expressed by parentheses in a numerical value of 100 parts by weight of the total weight of the group (A). Further, the compound names corresponding to the respective component abbreviations used in Table 1 are shown in Table 2. In addition, CORONATE HX (registered trademark) is the trade name of Nippon Polyurethane Industry Co., Ltd. as HL, and Takenate D-140N (registered trademark) is the trade name of Mitsui Chemicals Co., Ltd., DURANATE 24A-100 (registered trademark) is the trade name of Asahi Kasei Chemicals Corporation, KF-351A, KF-352A, KF-353, KF-640 and X-22-6191 are Shin-Etsu Chemical Co., Ltd. Product name.

<Test method and evaluation>

The surface protective films of Examples 1 to 9 and Comparative Examples 1 to 9 were looped at 23 ° C and 50% RH. After aging for 7 days, the release film (anthraquinone resin-coated PET film) was peeled off to expose the material of the adhesive layer as a test sample of the gel fraction.

Further, the surface protective film exposing the adhesive layer is bonded to the surface of the polarizing plate bonded to the liquid crystal cell through the adhesive layer, and left for 1 day, and then subjected to autoclaving at 50 ° C, 5 atm, and 20 minutes. After further standing at room temperature for 12 hours, the material obtained above was used as a test sample for adhesion and durability.

<acid value>

The acid value of the acrylic polymer is obtained by dissolving a sample in a solvent (a substance obtained by mixing diethyl ether and ethanol in a volume ratio of 2:1), using a potential difference automatic titrator (manufactured by Kyoto Electronics Industrial Co., Ltd., AT-610), using 0.1. The potentiometric titration apparatus described above was subjected to potentiometric titration with a potassium hydroxide ethanol solution having a concentration of about 0.1 mol/l, and the amount of the potassium hydroxide ethanol solution required for neutralizing the sample was measured. Then, the acid value was obtained by the following formula.

Acid value = (B × f × 5.611) / S

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

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

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

<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 mass 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 peel strength measured as follows was used as the adhesive force: the test sample obtained above was peeled off in the 180° direction at a low speed peeling speed (0.3 m/min) and a high speed peeling speed (30 m/min) using a tensile tester (in polarized light) The surface of the board was bonded to a surface protective film having a width of 25 mm) and the peel strength measured was measured.

<Reworkability>

After drawing on a surface protective film of the test sample obtained above by a ballpoint pen (loading weight: 500 g, reciprocating three times), the surface of the polarizing plate was observed from the surface protective film of the polarizing plate, and it was confirmed that no contamination was transferred to the polarizing plate. The evaluation target was evaluated as "○" when no contamination was transferred to the polarizing plate, and it was confirmed that the contamination was traced along at least a part of the trajectory drawn by the ballpoint pen as "△", and it was confirmed that the contamination was traced along the trajectory drawn by the ballpoint pen. The case where the adhesive was detached on the surface of the agent was evaluated as "x".

<Durability>

The test sample obtained above was allowed to stand 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, and it was confirmed 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.

The surface protective film of Examples 1 to 9 has an adhesive force of 0.05 to 0.1 N/25 mm at a low-speed peeling speed of 0.3 m/min, and an adhesive force of 1.0 N/25 mm or less at a high-speed peeling speed of 30 m/min, which is penetrated by a ballpoint pen. After the adhesive layer was drawn on the surface protective film, it was not contaminated by the adherend, and was excellent in durability when placed in an environment of 60 ° C and 90% RH for 250 hours.

That is, (1) the balance of the adhesion in the low-speed peeling speed and the high-speed peeling speed is obtained; (2) the occurrence of the adhesive residue is prevented; and (3) the rework performance is satisfied, and all the required performance is also satisfied.

The surface protective film of Comparative Example 1 seems to contain no (D) polyalkylene glycol mono(meth)acrylate monomer, and the adhesion at a low-speed peeling speed of 0.3 m/min is low, and the workability is low. Also slightly worse.

In the surface protective film of Comparative Example 2, it is considered that (B) the monomer having a hydroxyl group is too small, (D) the polyalkylene glycol mono(meth)acrylate monomer is too small, and (E) the isocyanate compound is excessive (H). The HLB value of the polyether modified siloxane compound is too small, and the adhesion at a low-speed peeling speed of 0.3 m/min and the adhesion at a high-speed peeling speed of 30 m/min become excessive, and the workability and durability are deteriorated. The gel fraction becomes lower.

In the surface protective film of Comparative Example 3, it is considered that (B) the monomer having a hydroxyl group is excessive, (C) the acid-containing monomer is excessive, and (D) the polyalkylene glycol mono(meth)acrylate monomer is excessively large. (H) The HLB value of the polyether modified siloxane compound is too large, and the acid value of the acrylic polymer is high, and the adhesion at a low-speed peeling speed of 0.3 m/min is low, and the workability and durability are poor.

In the surface protective film of Comparative Example 4, it was found that the (C) acid-containing monomer was too small, and the (D) polyalkylene glycol mono(meth)acrylate monomer was not contained, and the low-speed peeling speed was 0.3 m/ The adhesion under min is low, and the workability and durability are poor.

In the surface protective film of Comparative Example 5, it is considered that (B) the monomer having a hydroxyl group is excessive, (C) the acid-containing monomer is excessive, and (D) the polyalkylene glycol mono(meth)acrylate monomer is too small. (E) The isocyanate compound is too small, and the acid value of the acrylic polymer is high, and the adhesive force at a low-speed peeling speed of 0.3 m/min and the adhesive force at a high-speed peeling speed of 30 m/min become excessive, heavy workability, and durability. The variation is poor and the gel fraction is low.

The surface protective film of Comparative Example 6 was similar to the fact that the (F) crosslinking inhibitor was not mixed, so that the storage period was too short, and crosslinking was performed before coating, and coating was impossible.

The surface protective film of Comparative Example 7 seems to contain MA having a C1 alkyl group in (A) a (meth) acrylate monomer having an alkyl group, (B) a monomer having a hydroxyl group, and no (D) poly Alkyl glycol mono(meth)acrylate monomer, unmixed (G) cross-linking catalyst, and adhesion at a low-speed peeling speed of 0.3 m/min and adhesion at a high-speed peeling speed of 30 m/min Excessively large, heavy work and poor durability.

In the surface protective film of Comparative Example 8, the (D) polyalkylene glycol mono(meth)acrylate monomer was excessively mixed, and the (H) polyether modified oxoxane compound was not mixed, and the low-speed peeling speed was caused. The adhesion at 0.3m/min and the high-speed peeling speed at 30m/min are too strong and the reworkability is slightly poor.

In the surface protective film of Comparative Example 9, it seems that the (D) polyalkylene glycol mono(meth)acrylate monomer and (H) polyether modified rhodium oxide compound are not excessive, and the low-speed peeling speed is caused. The adhesion at 0.3m/min is low, the workability is slightly poor, 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 at the low-speed peeling speed and the high-speed peeling speed; (2) the prevention of the occurrence of the adhesive residue; and (3) All required performance such as heavy work performance.

Claims (12)

An adhesive composition comprising an acrylic polymer, characterized in that the acrylic polymer is a (meth) acrylate single having a C4 to C10 (A) alkyl group having a carbon number of (A). 0.1 to 5.0 parts by weight of (B) a hydroxyl group-containing copolymerizable monomer, 0.35 to 1.0 part by weight of (C) a carboxyl group-containing copolymerizable monomer, and 1 to 20 parts by weight of (D) poly An acrylic polymer obtained by copolymerizing a copolymer of an alkyl diol mono(meth) acrylate monomer, wherein the adhesive composition further contains (E) a trifunctional or higher isocyanate compound, and (F) a ketoenol tautomer compound as a crosslinking inhibitor, (G) a crosslinking catalyst, (H) a polyether modified oxirane compound having an HLB value of 7 to 12, and an acid value of 0.01 of the above acrylic polymer ~8.0, the above (B) hydroxyl group-containing copolymerizable monomer 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-methylol (meth) acrylamide, N-hydroxyethyl (meth) propylene oxime At least one or more of the group consisting of amines. The adhesive composition according to claim 1, wherein the (B) hydroxyl group is contained in the above (A) (A) alkyl group having a C4 to C10 alkyl group. Among the copolymerizable monomers, the total content of 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate is 0 to 0.9 parts by weight. (Where, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, or 4-hydroxybutyl (meth)acrylate) is also not allowed. The adhesive composition according to claim 1 or 2, wherein the (C) carboxyl group-containing copolymerizable monomer is selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth) acrylate, and carboxy pentane. (meth) acrylate, 2-(methyl) propylene methoxyethyl hexahydrophthalic acid, 2-(methyl) propylene methoxy propyl hexahydrophthalic acid, 2- (A) Acetylene Oxyethyl phthalic acid, 2-(methyl) propylene methoxyethyl succinic acid, 2-(methyl) propylene methoxyethyl maleic acid, carboxy polycaprolactone mono (methyl) At least one or more of the group consisting of acrylate and 2-(meth)acryloxyethyltetrahydrophthalic acid. The adhesive composition according to claim 1 or 2, wherein the (D) polyalkylene glycol mono(meth)acrylate monomer is selected from the group consisting of polyalkylene glycol mono(methyl) At least one or more of an acrylate, a methoxy-polyalkylene glycol (meth) acrylate, and an ethoxy-polyalkylene glycol (meth) acrylate. The adhesive composition according to claim 1 or 2, wherein the (E) trifunctional or higher isocyanate compound is an isocyanurate or isophorone selected from a hexamethylene diisocyanate compound. An isocyanurate body of a diisocyanate compound, an adduct body of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a biuret body of a hexamethylene diisocyanate compound, and a different Buddha At least one or more of the group of compounds having a biuret composition of the ketone diisocyanate compound; and 0.5 to 5.0 parts by weight of the above (E) trifunctional or higher isocyanate compound per 100 parts by weight of the copolymer. The adhesive composition of claim 1 or 2, wherein 0.01 to 0.5 part by weight of the polyether modified (H) having a HLB value of 7 to 12 is contained with respect to 100 parts by weight of the copolymer. Oxyalkane compound. The adhesive composition of claim 1 or 2, wherein 1.0 to 5.0 parts by weight of the above (F) ketoenol tautomer is used as a crosslinking inhibitor with respect to 100 parts by weight of the above copolymer. Compound. The adhesive composition according to claim 1 or 2, wherein the (G) crosslinking catalyst is an organotin compound; and 0.01 to 0.5 parts by weight of the above (G) is contained with respect to 100 parts by weight of the copolymer. cross Co-catalyst. The adhesive composition according to claim 1 or 2, wherein the adhesive layer obtained by crosslinking the adhesive composition has an adhesive force at a low-speed peeling speed of 0.3 m/min of 0.05 to 0.1 N/25 mm. The adhesive force at a high-speed peeling speed of 30 m/min is 1.0 N/25 mm or less. An adhesive film comprising an adhesive layer formed by crosslinking an adhesive composition according to any one of claims 1 to 9 on one or both sides of a resin film. A surface protective film formed on one surface of a resin film with a surface protective film of an adhesive layer obtained by crosslinking an adhesive composition of claim 1 or 2, wherein the surface protective film is passed through the adhesive layer After being drawn on the surface protective film with a ballpoint pen, it will not be contaminated by the transfer of the adhesive. The surface protective film of claim 11 is used as a surface protective film for a polarizing plate.