KR102200707B1 - Adhesive composition and surface-protective film - Google Patents

Abstract

The present invention provides a pressure-sensitive adhesive composition and a surface protective film having an excellent balance of adhesive force in a low-speed peeling speed and a high-speed peeling speed, excellent adhesion performance having stain resistance, and excellent antistatic performance without deteriorating with time. (A) A (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in an alkyl group, (B) a copolymerizable monomer containing a hydroxyl group, and (C) a copolymerizable monomer containing a carboxyl group, have an acid value of 0.1 to 1.0 It contains the acrylic polymer of the copolymer, and (A) contains 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more in 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group, The crosslinking agent (D) is a trifunctional or higher isocyanate compound, and the antistatic agent is an ionic compound having a melting point of 25 to 50°C having an anion having a number of fluorine atoms of F7 or more.

Description

Pressure-sensitive adhesive composition and surface protective film TECHNICAL FIELD [ADHESIVE COMPOSITION AND SURFACE-PROTECTIVE FILM}

The present invention relates to a pressure-sensitive adhesive composition and a surface protective film containing an antistatic agent. More specifically, by sticking to a polarizing plate constituting a liquid crystal display, a pressure-sensitive adhesive composition for a surface protective film used to protect the surface of the polarizing plate and does not deteriorate with time and has excellent antistatic performance, and surface protection using the same It is a film.

Conventionally, in a manufacturing process of an optical member such as a polarizing plate, which is a member constituting a liquid crystal display, a surface protection film for temporarily protecting the surface of the optical member is attached. Such a surface protection film is used only in the process of manufacturing an optical member, and is removed by peeling from the optical member when the optical member is attached to a liquid crystal display. Since the surface protective film for protecting the surface of such an optical member is used only in a manufacturing process, it may be generally called a eutectic film.

As described above, in the surface protective film used in the process of manufacturing an optical member, an adhesive layer is formed on one side of a polyethylene terephthalate (PET) resin film having optical transparency. A release film subjected to a release treatment for protecting the pressure-sensitive adhesive layer is bonded on the pressure-sensitive adhesive layer until it is bonded to the optical member.

Further, an optical member such as a polarizing plate is subjected to a product inspection accompanying optical evaluation such as display capability, color, contrast, and foreign matter mixing of the liquid crystal display panel in a state in which the surface protection film is attached thereto. For this reason, as a required performance for the surface protective film, it is required that the pressure-sensitive adhesive layer has no air bubbles or foreign matter, and the low molecular weight component of the pressure-sensitive adhesive composition, that is, has stain resistance.

In addition, when peeling the surface protective film from an optical member such as a polarizing plate, there is a concern that the peeling charge caused by static electricity generated when the adhesive layer is peeled from the adherend affects the failure of the electric control circuit of the liquid crystal display. . For this reason, it is required that the pressure-sensitive adhesive layer has excellent antistatic performance.

In addition, in recent years, as a polarizer protective layer (sometimes referred to as a protective film) of a polarizing plate, in addition to the conventional triacetyl cellulose (TAC), acrylic resins such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), etc. The use of materials that are liable to cause peeling charge when peeling the surface protective film of a polarizing plate, such as a polyester resin, a cyclic olefin-based polymer, and a polycarbonate, is expanding. For this reason, it is required that the antistatic performance required for the pressure-sensitive adhesive layer for a surface protective film of a polarizing plate is superior to the conventional one.

Further, when finally peeling the surface protective film from an optical member such as a polarizing plate, it is required to be able to peel quickly. In order to be able to quickly peel even by so-called high-speed peeling, it is required that the adhesive force has little change also by the peeling speed.

As described above, in recent years, as required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (1) balancing the adhesive force in a low-speed peeling rate and a high-speed peeling rate, (2) having fouling resistance, (3) Excellent antistatic performance and the like are required from the viewpoint of ease of use in using the surface protection film.

However, although each of these (1) to (3), which is the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, can satisfy the individual required performance, (1) to (1) to the pressure-sensitive adhesive layer of the surface protective film are required. It was a very difficult task to satisfy all the required performances of (3) at the same time.

In order to solve such a problem, for example, (1) balancing the adhesive force in the low-speed peeling speed and the high-speed peeling speed, (2) having stain resistance, and (3) excellent antistatic performance are as follows: The same proposal is known.

(1) Regarding the balance of adhesive force in the low-speed peeling rate and the high-speed peeling rate, a copolymer of a (meth)acrylate alkyl ester having an alkyl group having 7 or less carbon atoms and a copolymerizable compound containing a carboxyl group is used as a main component, and this is a crosslinking agent. In the acrylic pressure-sensitive adhesive layer obtained by cross-linking treatment with, there is a problem that the pressure-sensitive adhesive adheres to the adherend side when adhered for a long period of time, and the increase in the adhesive strength to the adherend with time is large. In order to avoid this, it is known that a copolymer of a (meth)acrylate alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group is used, and a pressure-sensitive adhesive layer is crosslinked with this crosslinking agent ( Patent Document 1).

Further, it is proposed that a small amount of a copolymer of an alkyl (meth)acrylate and a copolymerizable compound containing a carboxyl group is blended in the same copolymer as described above, and a pressure-sensitive adhesive layer is formed by crosslinking this with a crosslinking agent. However, these have low surface tension and are used to protect the surface of a plastic plate with a smooth surface, which may cause peeling phenomena such as lifting by heating during processing or storage. There was also a problem of poor sex.

In order to solve these problems, a) 100 parts by weight of an alkyl (meth)acrylate containing 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 copolymerizable compound containing a carboxyl group A pressure-sensitive adhesive composition comprising a copolymer of a monomer mixture obtained by adding parts and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms, and a crosslinking agent equivalent to or more than the carboxyl group of the component b). It has been proposed (Patent Document 2).

In the pressure-sensitive adhesive composition described in Patent Document 2, no peeling phenomenon such as lifting occurs during processing or storage, and the increase in adhesion over time is small, and the re-peelability is excellent, and long-term storage, especially in a high-temperature atmosphere Even if it is stored, it is said that it can be peeled again with a small force, and at that time, no adhesive residue is generated on the adherend, and even when peeling is performed at a high speed, it can be peeled again with a small force.

In addition, (2) for those having fouling resistance, 0 parts by mass or more and less than 0.5 parts by mass of a carboxyl group-containing monomer, 0.6 to 9 parts by mass of a hydroxy group-containing (meth)acrylic monomer, and 99.4 to 90.5 parts by mass of a (meth)acrylic acid ester monomer. 100 parts by mass of a (meth)acrylic copolymer having a weight average molecular weight of 100,000 or more and less than 1 million; And a pressure-sensitive adhesive composition containing 0.1 to 5 parts by mass of a carbodiimide crosslinking agent (Patent Document 3).

In the pressure-sensitive adhesive composition described in Patent Document 3, a carbodiimide-based crosslinking agent is used as a crosslinking agent for a (meth)acrylic copolymer having a specific composition. For this reason, it is possible to provide the pressure-sensitive adhesive layer with a crosslinked structure capable of following shrinkage due to pressure and temperature during autoclave treatment. For this reason, the pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive composition can suppress and prevent foaming even under high temperature and high pressure conditions (in the case of autoclave treatment), has excellent adherend contamination resistance, and is also excellent in transparency.

In addition, as for (3) excellent antistatic performance, as a method for imparting antistatic properties to the surface protective film, a method of mixing an antistatic agent into a base film, etc. are disclosed. Examples of the antistatic agent include (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and first to tertiary amino groups, (b) sulfonate groups, sulfate ester bases, and phosphoric acid. Anionic antistatic agents having anionic groups such as ester bases and phosphonic acid groups, (c) amphoteric antistatic agents such as amino acid and amino sulfuric acid esters, (d) ratios of amino alcohols, glycerin, polyethylene glycols, etc. On-the-fly antistatic agents, (e) polymer-type antistatic agents in which the above antistatic agents have been made high molecular weight are disclosed (Patent Document 4).

In addition, in recent years, it has been proposed to contain such an antistatic agent in a base film or to contain it directly in the pressure-sensitive adhesive layer without being applied to the surface of the base film.

In addition, as an antistatic pressure-sensitive adhesive composition obtained by dispersing a salt having an anion having a fluoro group and a sulfonyl group, the salt having an anion having a fluoro group and a sulfonyl group is a polyether ester containing a polyether group in the main chain. An antistatic pressure-sensitive adhesive composition, characterized in that it is dispersed in a dissolved state in a plasticizer, is disclosed (Patent Document 5).

In the pressure-sensitive adhesive composition described in Patent Document 5, an ester formed of an alcohol having a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group as a plasticizer and an alcohol having a non-cyclic hydrocarbon group having 1 to 20 carbon atoms, or the unsaturated acyclic type It is disclosed to use a plasticizer comprising an ester in which the unsaturated group in the hydrocarbon group is epoxidized. The mono or dicarboxylic acid having such a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to that of an acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer, thereby improving compatibility with the antistatic pressure-sensitive adhesive composition, It is said that bleed-out is suppressed because it is preferably held in the plasticizer acrylic antistatic pressure-sensitive adhesive composition.

Japanese Laid-Open Patent Publication No. 63-225677 Japanese Laid-Open Patent Publication No. Hei 11-256111 Japanese Unexamined Patent Publication No. 2011-122054 Japanese Laid-Open Patent Publication No. Hei 11-070629 Japanese Unexamined Patent Publication No. 2014-118469

As described above, in the prior art, as required performance for the pressure-sensitive adhesive layer constituting the surface protective film, balance of adhesive strength in low-speed peeling speed and high-speed peeling speed, having stain resistance, and excellent antistatic performance are required. Has been. However, although it was possible to satisfy each individual required performance, all the required performance required for the pressure-sensitive adhesive layer of the surface protection film could not be satisfied at the same time.

The present invention has been made in view of the above circumstances, has excellent balance of adhesive force in low-speed peeling speed and high-speed peeling speed, and has excellent adhesion performance having stain resistance, and does not deteriorate with time and has excellent antistatic performance, and It makes it a subject to provide a surface protection film.

In the pressure-sensitive adhesive composition having antistatic performance and the surface protective film using the same, the relationship between the antistatic performance and the stain resistance to the adherend is a relationship of a trade-off, and it is extremely important to improve the stain resistance while maintaining the antistatic performance. It was difficult.

By the way, the inventors of the present invention have a copolymer obtained by copolymerizing a copolymerizable monomer containing a carboxyl group, a polyether-containing silicone compound, and an anion having a number of fluorine atoms of F7 or more (for example, nonafluorobutanesulfonate anion). It has been found that a pressure-sensitive adhesive composition containing an antistatic agent composed of an ionic compound having a melting point of 25°C or higher can solve this problem.

In order to solve the above problems, the present invention is a pressure-sensitive adhesive composition containing an antistatic agent and a crosslinking agent, wherein the pressure-sensitive adhesive composition contains (A) a (meth)acrylic acid ester monomer having C1-C18 alkyl groups, and (B) a hydroxyl group. An acrylic polymer of a copolymer having an acid value of 0.1 to 1.0 obtained by copolymerization of the copolymerizable monomer and (C) a copolymerizable monomer containing a carboxyl group, wherein the acrylic polymer has C1 to C18 in the (A) alkyl group. Consisting of containing 70 parts by weight or more of 2-ethylhexyl acrylate in 100 parts by weight of the (meth)acrylic acid ester monomer, the glass transition temperature of the acrylic polymer is 0° C. or less, and the crosslinking agent (D) 3 An isocyanate compound having a functional or higher function, and the antistatic agent is an ionic compound having a melting point of 25 to 50° C. consisting of an anion having an anion having an anion having a number of fluorine atoms of F7 or more, and the pressure-sensitive adhesive composition further comprising (E) a crosslinking retarder, (F) A pressure-sensitive adhesive composition comprising a crosslinking catalyst other than a tin compound as a crosslinking catalyst is provided.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition for a surface protective film bonded to a polarizer protective layer of a polarizing plate, wherein the polarizer protective layer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, In addition, it is preferable that the surface treatment applied to the surface of the polarizer protective layer of the polarizing plate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment.

The anion of the ionic compound is C ₆ F ₅ (CF ₂ ) _n COO ^― , C ₆ F ₅ (CF ₂ ) _n SO ₃ ^― , C ₆ F ₅ (CF ₂ ) _n O ^― , C ₆ F ₅ O ( CF ₂ ) _n SO ₃ ^― , (C ₆ F ₅ CO) ₂ N ^― , (C ₆ F ₅ CO) ₃ C ^― , (C ₆ F ₅ SO ₂ ) ₂ N ^― , (C ₆ F ₅ SO ₂ ) ₃ C ^― , (C ₆ F ₅ OSO ₂ ) ₂ N ^― , (C ₆ F ₅ OSO ₂ ) ₃ C ^― , (C ₆ F ₅ ) ₄ B ^― , CF ₃ (CF ₂ ) ₃ SO ₃ ^― It is preferable that at least one selected from the group is contained as an anion, and the ionic compound is contained as an essential component in a ratio of 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.

The cation of the ionic compound is pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, lithium, It is one type selected from the group consisting of morpholinium, and it is preferable to contain the ionic compound as an essential component in a ratio of 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.

The surface resistivity of the pressure-sensitive adhesive layer crosslinked with the pressure-sensitive adhesive composition is 1.0×10 ⁺¹² Ω/□ or less, and the peeling of the pressure-sensitive adhesive layer to a low-refractive-index layer formed using a composition for forming a low-refractive-index layer containing a fluorine compound The voltage is in the range of -0.3 to +0.3 kV, and the adhesive force of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition to the polarizing plate at a low speed of 0.3 m/min is 0.04 to 0.2 N/25 mm, and high-speed peeling It is preferable that the adhesive force at a speed of 30 m/min is 2.0 N/25 mm or less.

(B) The copolymerizable monomer containing a hydroxyl group is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (Meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) is at least one selected from the group consisting of acrylamide,

The (A) alkyl group contains 0.1 to 10 parts by weight of a copolymerizable monomer containing a hydroxyl group relative to 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms,

The (C) copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-( Meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylmaleic acid, carboxypoly It is at least one or more selected from the group of compounds consisting of caprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid,

It is preferable that the (A) alkyl group contains 0.01 to 0.5 parts by weight of a copolymerizable monomer containing a carboxyl group with respect to 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms. .

The (E) crosslinking retardant is a ketoenol tautomer compound, and the (E) crosslinking retardant is contained in an amount of 0.1 to 300 parts by weight based on 100 parts by weight of the acrylic polymer, and the (F) crosslinking The catalyst is at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound, and the ratio of 0.001 to 0.5 parts by weight of the (F) crosslinking catalyst with respect to 100 parts by weight of the acrylic polymer It is composed of, and the (E) / (F) is preferably 80 to 1000 parts by weight.

It is preferable that the pressure-sensitive adhesive composition contains a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight average molecular weight of 10000 or less in a proportion of 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the acrylic polymer.

The pressure-sensitive adhesive composition has a weight average molecular weight obtained by copolymerizing a (meth)acrylic acid ester monomer having 1 to 18 carbon atoms of an alkyl group and a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer with respect to 100 parts by weight of the acrylic polymer. It is preferable to contain a copolymer of more than 10,000 and 300,000 or less in a proportion of 0.1 to 5.0 parts by weight.

The polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer has an average repetition number of 3 to 14 alkylene oxide constituting the polyalkylene glycol chain, and in the polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer The diester content is 0.2% or less, and as the polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer, polyalkylene glycol mono (meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, ethoxypoly Consisting of at least one or more selected from the group consisting of alkylene glycol (meth)acrylate in a ratio of 1 to 50 parts by weight of 100 parts by weight of the copolymer having a weight average molecular weight of more than 100,000 and less than 300,000 desirable.

In addition, the present invention provides a pressure-sensitive adhesive film, wherein a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is laminated on one side of a resin film.

In addition, the present invention provides a surface protective film in which the adhesive film is used.

In addition, the present invention provides a surface protective film for a polarizing plate in which the adhesive film is used.

Further, the present invention provides an optical film in which a pressure-sensitive adhesive layer in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is laminated on at least one surface of an optical film is formed.

In addition, the present invention provides the pressure-sensitive adhesive film having antistatic treatment and antifouling treatment on one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed.

The pressure-sensitive adhesive composition according to the present invention has excellent adhesive performance and does not deteriorate with time, and has excellent peeling antistatic performance, compared to the conventional pressure-sensitive adhesive composition for a surface protective film.

In particular, the surface protection film according to the present invention includes an antifouling layer containing a fluorine compound, or a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound, in which an adherend is laminated on the surface of an optical film. In the case of the adherend having, compared to the surface protective film according to the prior art, it has excellent adhesion performance, does not deteriorate with time, and has excellent peeling antistatic performance. That is, the surface protective film according to the present invention has a remarkable effect on both antistatic performance and stain resistance.

That is, the pressure-sensitive adhesive composition according to the present invention and the surface protective film using the same have excellent adhesive performance, no deterioration over time, and excellent peeling antistatic performance, and thus have extremely high industrial value.

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

The pressure-sensitive adhesive composition of this embodiment is a pressure-sensitive adhesive composition containing an antistatic agent and a crosslinking agent, wherein the pressure-sensitive adhesive composition is copolymerizable containing (A) a (meth)acrylic acid ester monomer having an alkyl group having C1 to C18 carbon atoms, and (B) a hydroxyl group. A monomer and (C) an acrylic polymer of a copolymer having an acid value of 0.1 to 1.0 obtained by copolymerizing a copolymerizable monomer containing a carboxyl group, wherein the acrylic polymer has C1 to C18 in the (A) alkyl group (meta) Made by containing 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more among 100 parts by weight of the acrylic acid ester monomer, the glass transition temperature of the acrylic polymer is 0°C or less, and the crosslinking agent is (D) an isocyanate having a trifunctional or higher function. A compound, wherein the antistatic agent is an ionic compound having a melting point of 25 to 50° C. consisting of an anion having an anion having an anion having a number of fluorine atoms of F7 or more, and the pressure-sensitive adhesive composition further comprises (E) a crosslinking retardant, and (F) It is characterized by containing a crosslinking catalyst other than a tin compound as a crosslinking catalyst.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment is a main polymer of the pressure-sensitive adhesive composition, and has a glass transition temperature of 0°C or less. Further, the acrylic polymer is preferably a copolymer containing (A) a (meth)acrylic acid ester monomer having an alkyl group having C1 to C18 as a main component.

(A) Examples of (meth)acrylic acid ester monomers having C1 to C18 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and isobutyl. (Meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylic Rate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (Meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth) ) Acrylate, etc. are mentioned. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic.

The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment contains (A) 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more in 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group. It is preferably made.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (B) a copolymerizable monomer containing a hydroxyl group. (B) As a copolymerizable monomer containing a hydroxyl group, 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy Ethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, etc. desirable.

It is preferable to contain (B) a copolymerizable monomer containing a hydroxyl group in a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the alkyl group, and 1.6 It is more preferable to contain it in the ratio of -8.5 weight part, and it is especially preferable to contain it in 2.1-7.5 weight part ratio.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (C) a copolymerizable monomer containing a carboxyl group. (C) As a copolymerizable monomer containing a carboxyl group, (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2- (Meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylmaleic acid, carboxy It is preferable that it is at least 1 type selected from the compound group consisting of polycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyltetrahydrophthalic acid, etc.

The (A) alkyl group preferably contains 0.01 to 0.5 parts by weight of a copolymerizable monomer containing a carboxyl group relative to 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms, and 0.01 It is more preferably contained in a proportion of -0.45 parts by weight, and particularly preferably contained in a proportion of 0.01 to 0.4 parts by weight.

The method for producing the acrylic polymer to be contained in the pressure-sensitive adhesive composition according to the present embodiment is not particularly limited, and a known polymerization method such as a solution polymerization method or an emulsion polymerization method can be appropriately used. The weight average molecular weight of the acrylic polymer copolymer is, for example, 50 to 3 million. It is preferable that the acid value of the acrylic polymer is 0.1 to 1.0. For this reason, stain resistance can be improved. Here, "acid value" is one of the indexes showing the content of an acid, and is expressed by the number of mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

The pressure-sensitive adhesive composition according to the present embodiment contains (G) an antistatic agent. The antistatic agent (G) of the present embodiment is an ionic compound composed of an anion and a cation having an anion having a number of fluorine atoms of F7 or more. This ionic compound has a melting point of 25 to 50°C, and is preferably a solid at room temperature (for example, 25°C). It is preferable to contain the ionic compound as an essential component in a ratio of 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.

In addition, when it is necessary to increase the antistatic performance of the pressure-sensitive adhesive layer and reduce the lower limit of the surface resistivity to 1.0×10 ⁺¹⁰ Ω/□ or less, the ionic compound is 0.01 to 15 parts by weight based on 100 parts by weight of the acrylic polymer. It is more preferable to contain it in a weight part ratio.

Examples of the anion of the ionic compound include C ₆ F ₅ (CF ₂ ) _n COO ^― , C ₆ F ₅ (CF ₂ ) _n SO ₃ ^― , C ₆ F ₅ (CF ₂ ) _n O ^― , C ₆ F ₅ O(CF ₂ ) _n SO ₃ ^― , (C ₆ F ₅ CO) ₂ N ^― , (C ₆ F ₅ CO) ₃ C ^― , (C ₆ F ₅ SO ₂ ) ₂ N ^― , (C ₆ F ₅ SO ₂ ) ₃ C ^― , (C ₆ F ₅ OSO ₂ ) ₂ N ^― , (C ₆ F ₅ OSO ₂ ) ₃ C ^― , (C ₆ F ₅ ) ₄ B ^― , CF ₃ (CF ₂ ) ₃ SO ₃ ^― At least one or more selected from the group consisting of may be mentioned. Here, n is an integer of 1 or more.

Examples of the cation of the ionic compound include pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, At least one or more selected from the group consisting of lithium and morpholinium may be mentioned.

(G) Specific examples of the antistatic agent include methyltrioctylammonium tris(pentafluorobenzenesulfonyl)methide salt, 3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, 1 -Ethyl-3-methylimidazolium tetrakis(pentafluorophenyl)borate salt, 1-butyl-1-methylpiperidinium bis(pentafluorobenzenesulfonyl)imide salt, and the like.

The pressure-sensitive adhesive composition according to the present embodiment further contains (D) a trifunctional or higher isocyanate compound as a crosslinking agent. (D) Examples of trifunctional or higher isocyanate compounds include biuret modified products and isocyanates of diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. And adducts with trivalent or higher polyols such as an anurate modified product, trimethylolpropane, and glycerin. (D) As the ratio of the trifunctional or higher isocyanate compound, the ratio of 0.01 to 5 parts by weight relative to 100 parts by weight of the acrylic polymer is mentioned, for example.

The pressure-sensitive adhesive composition according to the present embodiment may contain (E) a crosslinking retarder. (E) As a crosslinking retardant, β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone, 2,4-hexane Β-diketones, such as dione and benzoyl acetone, are mentioned. These are ketoenol tautomer compounds, and in a pressure-sensitive adhesive composition comprising a polyisocyanate compound as a crosslinking agent, by blocking an isocyanate group possessed by the crosslinking agent, excessive viscosity increase or gelation of the pressure-sensitive adhesive composition after blending of the crosslinking agent is suppressed, and the pressure-sensitive adhesive composition Pot life can be extended. (E) The crosslinking retardant is preferably a ketoenol tautomer compound, and particularly preferably at least one or more selected from the group of compounds consisting of acetylacetone and ethyl acetoacetate. It is preferable to contain (E) a crosslinking retardant in an amount of 0.1 to 300 parts by weight based on 100 parts by weight of the acrylic polymer.

The pressure-sensitive adhesive composition according to the present embodiment may contain a crosslinking catalyst other than a tin compound as (F) a crosslinking catalyst. (F) The crosslinking catalyst may be a material that functions as a catalyst for the reaction (crosslinking reaction) of the copolymer and the crosslinking agent when the polyisocyanate compound is used as a crosslinking agent. Examples of the crosslinking catalyst other than the tin compound include amine compounds such as tertiary amines, metal chelate compounds, organic lead compounds, and organometallic compounds such as organic zinc compounds.

(F) As a metal chelate compound of a crosslinking catalyst, it is a compound in which one or more polydentate ligand L bonded to a central metal atom M. The metal chelate compound may or may not have at least one monodentate ligand X bonded to the metal atom M. Specific examples of the metal chelate compound include tris (2,4-pentanedionate) iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris Acetylacetonate, zirconium tetrakisacetylacetonate, tris (2,4-hexanedionate) iron (III), bis (2,4-hexanedionate) zinc, tris (2,4-hexanedionate) titanium, Tris (2,4-hexanedionate) aluminum, tetrakis (2,4-hexanedionate) zirconium, and the like.

(F) As the crosslinking catalyst, it is preferable that it is at least one or more metal chelate compounds selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound. It is preferable to contain the (F) crosslinking catalyst in an amount of 0.001 to 0.5 parts by weight based on 100 parts by weight of the acrylic polymer.

Since the (E) crosslinking retardant has an effect of suppressing crosslinking as opposed to the (F) crosslinking catalyst, it is preferable to appropriately set the ratio of the (E) crosslinking retardant and (F) the crosslinking catalyst. In order to lengthen the pot life of the pressure-sensitive adhesive composition and improve storage stability, it is preferable that the ratio of (E)/(F) by weight is 80 to 1000. Here, the weight part ratio of (E)/(F) is a value of the quotient obtained by dividing the weight part of (E) by the weight part of (F).

The pressure-sensitive adhesive composition according to the present embodiment may contain (H) a polyether-modified siloxane compound as an optional component. (H) The polyether-modified siloxane compound is a siloxane compound having a polyether group, and in addition to the usual 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 is one or two or more alkyl or aryl groups, R ² and R ³ are one or two or more alkylene groups, and R ⁴ is one or two or more alkyl or acyl groups (terminal groups). Show. Examples of the polyether group include polyoxyalkylene groups such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] or a polyoxypropylene group [(C ₃ H ₆ O) _n ]. In the siloxane unit having a polyether group, the terminal of the polyether group may be an OH group (R ⁴ =H in the above formula).

(H) The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 6 to 12. In addition, with respect to 100 parts by weight of the acrylic polymer, (H) polyether-modified siloxane compound is preferably contained in an amount of 0.01 to 0.5 parts by weight, more preferably 0.02 to 0.35 parts by weight, more preferably 0.02 to 0.25 parts by weight. It is particularly preferred to be. The HLB value is, for example, a hydrophilic lipophilic balance (hydrophilic lipophilicity ratio) defined by JIS K3211 (terminal surfactant).

The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group to a polyorganosiloxane main chain having a silicon hydride group by a hydrosilylation reaction. Specifically, dimethylsiloxane/methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxyethylene) siloxane/methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxypropylene) siloxane polymer, etc. Can be mentioned.

(H) By blending the polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the adhesive strength and rework performance of the pressure-sensitive adhesive layer can be improved. (H) It is preferable that the weight average molecular weight of the polyether-modified siloxane compound is 10000 or less. From the viewpoint of compatibility with an acrylic polymer, a low HLB value and a low molecular weight provide good compatibility, but a polyether-modified siloxane compound with a low molecular weight has a relatively high HLB value and excellent antistatic properties even if the compatibility with the polymer is slightly low. Is obtained.

As an optional component, the pressure-sensitive adhesive composition according to the present embodiment is a weight average molecular weight obtained by copolymerizing a (meth)acrylic acid ester monomer having 1 to 18 carbon atoms in an alkyl group and (I) a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer. You may contain this copolymer of more than 100,000 and 300,000 or less (hereinafter referred to as "copolymer B") as an antistatic aid. Copolymer B is preferably contained in a proportion of 0.1 to 5.0 parts by weight, more preferably 0.1 to 3.5 parts by weight, and more preferably contained in a proportion of 0.1 to 2.5 parts by weight, based on 100 parts by weight of the acrylic polymer. It is particularly preferred.

(I) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer may be a compound in which one of the plurality of hydroxyl groups of the polyalkylene glycol is esterified as a (meth)acrylic acid ester. Since the (meth)acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the acrylic polymer. Polyalkylene glycol mono(meth)acrylate in which other hydroxyl groups remain OH, or alkoxypolyalkylene glycol mono(meth)acrylate in which other hydroxyl groups have been converted to alkyl ether may be used.

The polyalkylene glycol constituting the polyalkylene glycol chain may be a glycol compound having one or two or more alkylene groups. For example, polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-poly Propylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol, and the like.

(I) It is preferable that the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of 3 to 14 of the alkylene oxide constituting the polyalkylene glycol chain. "Average repeat number of alkylene oxide" means (I) in the portion of the "polyalkylene glycol chain" contained in the molecular structure of the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, the alkylene oxide unit is It is the number of repeated averages. In addition, it is preferable that the diester content in the (I) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 0.2% or less. The "diester content in a monomer" is the content rate (weight%) of polyalkylene glycol di(meth)acrylic acid ester contained in (I) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

(I) As the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol(meth)acrylate, ethoxypolyalkylene glycol (meth) ) It is preferably at least one or more selected from the group consisting of acrylates. The ratio of the (I) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer in the copolymer B is preferably 1 to 50 parts by weight, and 2 to 35 parts by weight, based on 100 parts by weight of the copolymer B. The proportion of parts is more preferable, and the proportion of 2 to 25 parts by weight is particularly preferable.

As monomers other than the (I) polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer copolymerized to the copolymer B, a (meth)acrylic acid ester monomer having C1 to 18 carbon atoms in the alkyl group and a copolymerizable monomer containing a hydroxyl group At least one or more of such as may be mentioned. Specific examples of these monomers include (meth)acrylic monomers exemplified in the above (A) and (B), respectively. The monomer copolymerized with the copolymer B may be different from the monomer copolymerized with the acrylic polymer. Copolymer B does not need to copolymerize a copolymerizable monomer containing a carboxyl group.

The pressure-sensitive adhesive composition of the present embodiment is not limited to the additives described above, and known additives such as a surfactant, a curing accelerator, a plasticizer, a filler, a curing retardant, a processing aid, an anti-aging agent, and an antioxidant may be appropriately blended. These may be used alone or in combination of two or more.

The pressure-sensitive adhesive composition of this embodiment is preferable as the pressure-sensitive adhesive composition for surface protective films bonded to the polarizer protective layer of a polarizing plate. Here, the polarizer protective layer of the polarizing plate may be one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film. Here, TAC is an abbreviation of triacetyl cellulose, PMMA is polymethyl methacrylate, and PET is an abbreviation of polyethylene terephthalate.

Further, the surface treatment applied to the surface of the polarizer protective layer of the polarizing plate may be one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. Here, AG refers to anti-glare, LR refers to low reflection, and AR refers to anti-reflection.

In the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment, the surface resistivity of the pressure-sensitive adhesive layer is preferably 1.0×10 ⁺¹² Ω/□ or less, more preferably 5.0×10 ⁺¹¹ Ω/□ or less, and 1.0×10 ⁺¹¹ Ω/□ It is particularly preferable that it is the following. When the surface resistivity is large, the ability to escape static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend is inferior. For this reason, by making the surface resistivity sufficiently small, the peeling electrification voltage caused by static electricity generated when the pressure-sensitive adhesive layer is peeled from the adherend is reduced, and it is possible to suppress the influence on the adherend.

The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment has a peeling electrification voltage of -0.3 to +0.3 kV with respect to the low-refractive-index layer formed by using the composition for forming a low-refractive-index layer containing a fluorine compound. It is desirable to be internal. As a fluorine compound used in the composition for forming a low refractive index layer, a fluorinated copolymer such as one or two or more polymers such as fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates, and silanes containing a fluorinated alkyl group Condensation products, such as a compound, are mentioned. In the fluorinated copolymer, in addition to a fluorinated monomer, a non-fluorinated monomer such as olefins, vinyl ethers, and (meth)acrylates may be copolymerized. The low refractive index layer may be combined with a high refractive index layer or the like to form an antireflection layer.

With respect to the polarizing plate of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of the present embodiment, the adhesive strength at a low speed of 0.3 m/min is 0.04 to 0.2 N/25 mm, and the adhesive strength at a high speed of 30 m/min is 2.0 N/ It is preferable that it is 25 mm or less, and it is more preferable that the adhesive force at a high-speed peeling speed of 30 m/min is 0.2 to 1.6 N/25 mm. For this reason, the performance in which the adhesive force is less changed by the peeling speed is obtained, and it becomes possible to peel quickly even by high-speed peeling. In addition, even when once peeling the surface protective film for re-adhesion, it does not require excessive force and is easy to peel from the adherend.

The gel fraction of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of the present embodiment is preferably 95 to 100%, and more preferably 97 to 100%. By such a high gel fraction, the adhesive strength does not become excessive at a low-speed peeling rate, the elution of unpolymerized monomers or oligomers from the copolymer is reduced, and the rework property and durability at high temperatures and high humidity are improved. Pollution can be suppressed.

The pressure-sensitive adhesive film of this embodiment is formed by forming a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition of the present embodiment on one side or both sides of a resin film. In addition, the surface protection film of this embodiment is a surface protection film formed by forming an adhesive layer formed by crosslinking the adhesive composition of this embodiment on one surface of a resin film. The pressure-sensitive adhesive composition of the present embodiment has excellent antistatic performance, has excellent balance of adhesive strength in low-speed peeling speed and high-speed peeling speed, and has stain resistance. For this reason, it can be used suitably as the use of the surface protection film of a polarizing plate.

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

Antistatic treatment and antifouling treatment may be applied on one surface of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed. Examples of the antistatic treatment include application or mixing of an antistatic agent. Examples of the antifouling treatment include treatment with a silicone-based or fluorine-based releasing agent or coating agent, and silica fine particles. The release film may be subjected to a release treatment with a silicone-based, fluorine-based, or long-chain alkyl-based releasing agent or the like on the side of the side that matches the adhesive surface of the pressure-sensitive adhesive layer.

Further, by laminating the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment on at least one surface of the optical film, an optical film in which the pressure-sensitive adhesive layer is formed can be obtained. As an optical film, a polarizing film, a retardation film, an antireflection film, an anti-glare (anti-glare) film, an ultraviolet absorbing film, an infrared absorbing film, an optical compensation film, a brightness improving film, etc. are mentioned. Devices to which the optical member is applied include a liquid crystal panel, an organic EL panel, and a touch panel.

In the case of an optical surface protective film and an adhesive film such as a surface protective film for a polarizing plate, it is preferable that the base film and the adhesive layer have sufficient transparency.

Example

Hereinafter, the present invention will be described in detail with reference to examples.

<Preparation of acrylic polymer solution>

[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 apparatus was replaced with nitrogen gas. Then, a solvent (ethyl acetate) was added to the reaction apparatus together with 90 parts by weight of 2-ethylhexyl acrylate, 10 parts by weight of methyl acrylate, 5.5 parts by weight of 8-hydroxyoctyl acrylate, and 0.2 parts by weight of acrylic acid. Thereafter, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65° C. for 6 hours to obtain an acrylic polymer solution used in Example 1.

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

The composition of the monomers was the same as the acrylic polymer solution used in Example 1, except that the composition of the monomers were the same as those described in Table 1 (A) to (C), respectively, and used in Examples 2 to 6 and Comparative Examples 1 to 3 An acrylic polymer solution was obtained.

<Preparation of adhesive composition and surface protective film>

[Example 1]

With respect to the acrylic polymer solution of Example 1 prepared as described above, 2.0 parts by weight of a crosslinking agent (coronate HX), 9 parts by weight of a crosslinking retarder (acetylacetone), 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), and charging 0.9 parts by weight of inhibitor (methyltrioctylammonium tris (pentafluorobenzenesulfonyl) methide salt), 0.05 parts by weight of polyether-modified siloxane compound (HLB=7), 0.2 parts by weight of copolymer B-1 (molecular weight 150,000) It was added and mixed with stirring to obtain the pressure-sensitive adhesive composition of Example 1. After applying this pressure-sensitive adhesive composition onto a release film (silicone resin coated PET film), the solvent was removed by drying at 90°C to obtain a pressure-sensitive adhesive layer having a thickness of 20 μm. Thereafter, the pressure-sensitive adhesive layer on which the release film was formed is transferred to the surface of the base film (antistatic and antifouling treated PET film on one side) opposite to the antistatic and antifouling treatment side, and the ``base film/adhesive layer The surface protective film of Example 1 which has a lamination structure of "/release film" was obtained.

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

The surface of Examples 2 to 6 and Comparative Examples 1 to 3 was carried out in the same manner as the surface protection film of Example 1, except that the composition of the additive was as described in Table 1 (D) to (H) and the copolymer B, respectively. A protective film was obtained.

In Table 1, the weight part of each component was calculated|required as 100 weight part of the total of (A) C1-C18 (meth)acrylic acid ester monomers of the alkyl group.

Here, in Table 1, in each column of (D), (E), (F), (G), (H), and (Copolymer B), the content ratio of each component (weight Part) is indicated by the numerical value in parentheses (　).

In addition, the compound names of the abbreviations of each component used in Table 1 are shown in Tables 2-3. Table 2 also includes the compound names of the abbreviated symbols of monomers other than the (I) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer among the component monomers of the copolymer B shown in Table 3. Meanwhile, Coronate (registered trademark) HX, HL, and L are brand names of Tosoh Corporation, and Takenate (registered trademark) D-140N is a brand name of Mitsui Chemicals Corporation.

(G) Among the antistatic agents, all of G-1 to G-4 are ionic compounds which have an anion having a number of fluorine atoms of F7 or more and are solid at a melting point of 25°C or more. G-5 is an ionic compound that has an anion having an F5 number of fluorine atoms and is solid at a melting point of 25°C or higher.

(H) Among the polyether-modified siloxane compounds, all of H-1 to H-6 have a weight average molecular weight of 10000 or less.

(I) Among the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers, I-1 to I-3 have a diester content of 0.2% or less in a monomer, and I-4 have a diester content of 0.8% in a monomer. In addition, n in the column of group (I) of Table 3 is a numerical value showing the average repeat number of alkylene oxide.

<Test method and evaluation>

The surface protective films in Examples 1 to 6 and Comparative Examples 1 to 3 were aged for 7 days in an atmosphere of 23°C and 50% RH, respectively, and then evaluated by the following test method.

<Test method of adhesive force>

The surface protective film obtained by peeling the release film and exposing the pressure-sensitive adhesive layer was bonded to the surface of the polarizing plate via the pressure-sensitive adhesive layer, left to stand for 1 day, and then subjected to autoclave treatment at 50° C., 5 atm, for 20 minutes, and an additional 12 at room temperature. What was left to stand for a time was used as a measurement sample for adhesion. The obtained measurement sample was peeled at a low speed (0.3 m/min) or a high speed (30 m/min) using a tensile tester in the 180° direction, and the measured peel strength was taken as the adhesive force.

Here, the polarizer protective layer of the polarizing plate is one selected from the group consisting of triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET).

Further, in the LR polarizing plate and the AG-LR polarizing plate, the surface of the polarizer protective layer of the polarizing plate is a composition containing a fluorine compound and has been subjected to a low-reflection surface treatment.

<Test method of surface resistivity>

After aging the surface protection film, before bonding to the polarizing plate, the release film is peeled to expose the pressure-sensitive adhesive layer, and the surface resistivity of the pressure-sensitive adhesive layer is measured using a resistivity meter Hyresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech). I did.

<Test method of peeling large voltage>

The surface protective film from which the release film was peeled to expose the pressure-sensitive adhesive layer was bonded to a polarizing plate having a low-refractive-index layer formed using a composition for forming a low-refractive-index layer containing a fluorine compound on the adherend. When the surface protection film is peeled 180° at a tensile speed of 30 m/min, the voltage (high voltage) generated by charging the adherend is measured using high-precision electrostatic sensors SK-035, SK-200 (manufactured by Keyence Corporation). , The maximum value of the measured value was taken as the peeling voltage.

<Test method for fouling resistance>

The polarizing plate subjected to the low-reflection (LR) surface treatment on one side of the glass plate was bonded through an adhesive layer (double-sided adhesive tape) using a bonding machine. Then, the surface protection film was pasted on the surface of the said polarizing plate using a bonding machine. After storage over a period of 3 days and 30 days in an environment of 23°C and 50% RH, the surface protective film was peeled off, and the contamination state of the surface of the polarizing plate was visually observed. As for the stain resistance judgment criteria, "○" was evaluated for the surface of the polarizing plate without contamination, "Δ" when there was slight contamination, and "×" when there was contamination.

Table 4 shows the evaluation results for the surface protective films in Examples 1 to 6 and Comparative Examples 1 to 3. The "surface resistivity" was expressed by the method of making "m×10 ⁺ⁿ ""mE+n" (where m is an arbitrary real value and n is a positive integer). The column of "polarizer protective layer of polarizing plate" represents the material and surface treatment of the polarizer protective layer of the polarizing plate used in the adhesion test. Plain of "surface treatment" means untreated.

The surface protective films of Examples 1 to 6 had an adhesive strength of 0.04 to 0.2 N/25 mm to a polarizing plate as an adherend at a low-speed peeling rate of 0.3 m/min, and an adhesive strength of 2.0 N/25 mm at a high-speed peeling speed of 30 m/min. It is as follows, and the adhesion performance was excellent.

In addition, in the surface protective films of Examples 1 to 6, the surface resistivity of the pressure-sensitive adhesive layer is 1.0×10 ⁺¹² Ω/□ or less, and for a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound, The peeling voltage of the pressure-sensitive adhesive layer was in the range of -0.3 to +0.3 kV, and the antistatic performance was excellent.

In addition, the surface protective films of Examples 1 to 6 were not contaminated with respect to the polarizing plate as an adherend even after storage over a period of 3 and 30 days, and were excellent in stain resistance.

That is, from the evaluation results shown in Table 4 for the surface protective films of Examples 1 to 6, it is demonstrated that the subject of the present invention could be solved.

In the surface protective film of Comparative Example 1, the ratio of 2EHA is as small as 50 parts by weight in 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group in the acrylic polymer contained in the adhesive composition. In addition, (C) a copolymerizable monomer containing a carboxyl group is not copolymerized. In addition, in the pressure-sensitive adhesive composition according to the surface protective film of Comparative Example 1, the antistatic agent contains an anion of F5 whose number of fluorine atoms is less than F7. For this reason, the surface protective film of Comparative Example 1 had a high adhesive force of the pressure-sensitive adhesive layer, high peeling voltage, and poor stain resistance.

In addition, the surface protective film of Comparative Example 2 had an acid value of the acrylic polymer contained in the pressure-sensitive adhesive composition exceeding 1.0, and the stain resistance was poor.

In addition, in the surface protective film of Comparative Example 3, the antistatic agent contained in the pressure-sensitive adhesive composition contained an anion of F5 whose number of fluorine atoms was less than F7, and the stain resistance was poor.

Thus, in the surface protective film of Comparative Examples 1 to 3, the subject of the present invention could not be solved.

Claims (9)

As a pressure-sensitive adhesive composition containing an antistatic agent and a crosslinking agent,
The pressure-sensitive adhesive composition
(A) a (meth)acrylic acid ester monomer having C1 to C18 in the alkyl group,
(B) a copolymerizable monomer containing a hydroxyl group, and
(C) contains an acrylic polymer copolymerized with a copolymerizable monomer containing a carboxyl group,
The (A) alkyl group contains 0.1 to 10 parts by weight of a copolymerizable monomer containing a hydroxyl group relative to 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms, and the (C ) It is made by containing a copolymerizable monomer containing a carboxyl group in a ratio of 0.01 to 0.5 parts by weight,
The acrylic polymer is made by containing 2-ethylhexyl acrylate in a ratio of 70 parts by weight or more, among 100 parts by weight of the (meth)acrylic acid ester monomer having C1 to C18 carbon atoms in the (A) alkyl group,
The glass transition temperature of the acrylic polymer is 0°C or less,
The crosslinking agent (D) is a trifunctional or higher isocyanate compound,
The antistatic agent is an ionic compound having a melting point of 25 to 50° C. consisting of an anion having an anion having a number of fluorine atoms of F7 or more and an anion,
A pressure-sensitive adhesive composition comprising the ionic compound in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the acrylic polymer. The method of claim 1,
The anion of the ionic compound is C ₆ F ₅ (CF ₂ ) _n COO ^― , C ₆ F ₅ (CF ₂ ) _n SO ₃ ^― , C ₆ F ₅ (CF ₂ ) _n O ^― , C ₆ F ₅ O ( CF ₂ ) _n SO ₃ ^― , (C ₆ F ₅ CO) ₂ N ^― , (C ₆ F ₅ CO) ₃ C ^― , (C ₆ F ₅ SO ₂ ) ₂ N ^― , (C ₆ F ₅ SO ₂ ) ₃ C ^― , (C ₆ F ₅ OSO ₂ ) ₂ N ^― , (C ₆ F ₅ OSO ₂ ) ₃ C ^― , (C ₆ F ₅ ) ₄ B ^― and CF ₃ (CF ₂ ) ₃ SO ₃ ^― (where , n is an integer of 1 or more), wherein the pressure-sensitive adhesive composition is one selected from the group consisting of. The method according to claim 1 or 2,
The cation of the ionic compound is pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methyllium, lithium, Pressure-sensitive adhesive composition, characterized in that one selected from the group consisting of morpholinium. The method according to claim 1 or 2,
(B) The copolymerizable monomer containing a hydroxyl group is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (Meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) is at least one selected from the group consisting of acrylamide,
The (C) copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-( Meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethylphthalic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylmaleic acid, carboxypoly A pressure-sensitive adhesive composition, characterized in that it is at least one selected from the group of compounds consisting of caprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition further comprises (E) a crosslinking retardant and (F) a crosslinking catalyst,
(E) the crosslinking retardant is a ketoenol tautomer compound,
Consisting of containing 0.1 to 300 parts by weight of the (E) crosslinking retardant based on 100 parts by weight of the acrylic polymer,
The (F) crosslinking catalyst is at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound,
It is made by containing the (F) crosslinking catalyst in a proportion of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The pressure-sensitive adhesive composition, characterized in that the ratio of the (E) / (F) by weight is 80 to 1000. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition has a weight average molecular weight obtained by copolymerizing a (meth)acrylic acid ester monomer having 1 to 18 carbon atoms of an alkyl group and a polyalkylene glycol chain-containing mono (meth)acrylic acid ester monomer with respect to 100 parts by weight of the acrylic polymer. An adhesive composition comprising a copolymer of more than 10,000 and 300,000 or less in a proportion of 0.1 to 5.0 parts by weight. An adhesive film, wherein an adhesive layer obtained by crosslinking the adhesive composition of claim 1 or 2 is laminated on one side of a resin film. The surface protective film in which the adhesive film of claim 7 is used. An optical film in which a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of claim 1 or 2 is laminated on at least one surface of the optical film.