JP7152569B2 - AG-treated surface protective film for polarizing plates - Google Patents

Description

The present invention relates to a surface protective film for polarizing plate. More specifically, at low peeling speed and high peeling speed, the balance of adhesive strength is excellent, the adhesion to the polarizing plate is excellent despite the low adhesive strength, durability and reworkability, and antistatic performance It also relates to a surface protective film for a polarizing plate which is also excellent in

2. Description of the Related Art Conventionally, in the manufacturing process of optical members such as polarizing plates and retardation plates, which are members constituting liquid crystal displays, surface protective films are adhered to temporarily protect the surfaces of the optical members. Such a surface protective film is used only in the process of manufacturing the optical member, and is peeled off and removed from the optical member when the optical member is incorporated into the liquid crystal display. Such a surface protective film for protecting the surface of an optical member is generally called a process film because it is used only in the manufacturing process.

The surface protective film used in the process of manufacturing the optical member is an optically transparent polyethylene terephthalate (PET) resin film having an adhesive layer formed on one side thereof. A peel-treated release film for protecting the pressure-sensitive adhesive layer is laminated on the pressure-sensitive adhesive layer.
In addition, optical members such as polarizing plates and retardation plates are subjected to product inspection with optical evaluation such as display ability, hue, contrast, foreign matter contamination, etc. As a required performance for the surface protective film, it is required that the pressure-sensitive adhesive layer is free of air bubbles and foreign substances.
In recent years, when peeling off the surface protective film from optical members such as polarizing plates and retardation plates, the static electricity generated when the adhesive layer is peeled off by the adherend causes peeling electrification, which is caused by the electrical control of liquid crystal displays. There is a concern that it may affect the failure of the circuit, and excellent antistatic performance is required for the pressure-sensitive adhesive layer.
In addition, when a surface protective film is attached to an optical member such as a polarizing plate or a retardation plate, the surface protective film may be peeled off and then re-applied for various reasons. In addition, it is required to be easily peeled off from the optical member of the adherend (reworkability).
Moreover, when the surface protective film is finally peeled off from the optical members such as the polarizing plate and the retardation plate, it is required to be able to be quickly peeled off. It is required that the adhesive force does not change much with the peeling speed so that the adhesive can be quickly peeled even by so-called high-speed peeling.

Thus, in recent years, the required performance for the pressure-sensitive adhesive layer that constitutes the surface protective film is (i) a balance of adhesive strength at low peeling speed and high peeling speed, and (ii) excellent Antistatic performance, (iii) reworkability, etc. are required from the viewpoint of ease of use in using the surface protection film.

For example, (i) the following proposals are known for balancing adhesive force at low peeling speed and high peeling speed.

An acrylic pressure-sensitive adhesive comprising, as a main component, a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group of 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound, and cross-linked with a cross-linking agent. In the case of the layer, there is a problem that the pressure-sensitive adhesive is transferred to the adherend when adhered for a long period of time, and the adhesive force to the adherend greatly increases with time. In order to avoid this, a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group was used and crosslinked with a crosslinking agent. One having an adhesive layer is known (Patent Document 1).
Also, the same copolymer as above is mixed with a small amount of a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound, and a pressure-sensitive adhesive layer is provided by cross-linking this with a cross-linking agent. etc., have been proposed. However, when these materials are used to protect the surface of plastic plates with low surface tension and smooth surfaces, they cause problems such as floating and peeling due to heating during processing and storage. There is also a problem of poor re-peelability at the time of peeling.

In order to solve these problems, a) 100 parts by weight of a (meth)acrylic acid alkyl ester mainly composed of a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms, and b) a carboxyl group-containing 1 to 15 parts by weight of a copolymerizable compound and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms are added to the copolymer of the monomer mixture, the above b ) has been proposed a pressure-sensitive adhesive composition containing a cross-linking agent in an equivalent amount or more to the carboxyl groups of the component (Patent Document 2).
The pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as lifting during processing or storage, and furthermore, the increase in adhesive strength over time is small and the re-peelability is excellent, so that it can be stored for a long period of time. In particular, even after long-term storage in a high-temperature atmosphere, it can be re-peeled with a small force, leaving no adhesive residue on the adherend, and even when high-speed stripping is performed, it can be re-peeled with a small force.

As for (ii) excellent antistatic performance, a method of kneading an antistatic agent into a base film is disclosed as a method for imparting antistatic performance to a surface protective film. Antistatic agents include, for example, (a) quaternary ammonium salts, pyridinium salts, various cationic antistatic agents having cationic groups such as primary to tertiary amino groups, (b) sulfonic acid groups, sulfuric acid Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases and phosphonate bases, (c) amphoteric antistatic agents such as amino acid-based and amino sulfate ester-based agents, (d) amino alcohol-based and glycerin-based , a nonionic antistatic agent such as polyethylene glycol, and (e) a polymeric antistatic agent obtained by increasing the molecular weight of the above antistatic agent (Patent Document 3).
In recent years, it has been proposed to incorporate such an antistatic agent into the base film, or directly into the pressure-sensitive adhesive layer instead of applying it to the surface of the base film.

In addition, (iii) reworkability, for example, in the acrylic resin, an isocyanate compound curing agent and a specific silicate oligomer are mixed in 0.0001 to 10 parts by weight with respect to 100 parts by weight of the acrylic resin. An agent composition has been proposed (Patent Document 4).
In Patent Document 4, an acrylic acid alkyl ester having an alkyl group having about 2 to 12 carbon atoms or a methacrylic acid alkyl ester having an alkyl group having about 4 to 12 carbon atoms is used as a main monomer component. can contain other functional group-containing monomer components. In general, it is preferable to contain 50% by weight or more of the main monomer, and the content of the functional group-containing monomer component is 0.001 to 50% by weight, preferably 0.001 to 25% by weight, more preferably It states that it is desired to be 0.01 to 25% by weight. Such a pressure-sensitive adhesive composition described in Patent Document 4 shows little change over time in cohesive strength and adhesive strength even under high temperature or high temperature and high humidity conditions, and exhibits excellent adhesive strength to curved surfaces. It is said to have reworkability.
In general, if the pressure-sensitive adhesive layer is made to have a soft property, adhesive residue tends to occur and reworkability tends to deteriorate. That is, it is difficult to peel off and re-adhering is likely to be difficult when adhered by mistake. For this reason, it is considered necessary to crosslink the main agent with a monomer having a functional group such as a carboxyl group to give the pressure-sensitive adhesive layer a certain degree of hardness in order to impart reworkability.

JP-A-63-225677 JP-A-11-256111 JP-A-11-070629 JP-A-8-199130

2. Description of the Related Art In recent years, the screen size of various displays such as liquid crystal displays has rapidly increased. However, as the screen size of the liquid crystal display increases, a new problem arises in the process of manufacturing the members of the liquid crystal display. For example, the following problems have arisen with respect to surface protective films for polarizing plates that are adhered to the surfaces of polarizing plates to protect the polarizing plates.
In the prior art, in the manufacturing process of a polarizing plate, which is a member of a liquid crystal display, after bonding a surface protective film to a polarizing plate, which is an adherend, the surface protective film is required to be easily peeled off from the polarizing plate. On the other hand, this demand has been met by reducing the adhesive force of the adhesive layer formed on the surface protective film.
However, if the adhesive strength of the pressure-sensitive adhesive layer is reduced to make it easier to peel off the surface protective film from the adherend, the adhesion of the surface protective film to the polarizing plate will decrease. When the size of the polarizing plate is increased compared to the conventional one, there arises a problem that the surface protective film is peeled off at the edge of the polarizing plate.

The present invention has been made in view of the above circumstances, and has an excellent balance of adhesive force at low peeling speed and high peeling speed, and good adhesion to polarizing plates despite low adhesive force. An object of the present invention is to provide a surface protective film for a polarizing plate which is excellent in durability, reworkability and antistatic performance.

In order to solve the above-mentioned problems, the present invention provides a polarized light in which a pressure-sensitive adhesive layer is formed on one side of a resin film by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent. In the plate surface protection film, the acrylic polymer comprises (A) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18 and (B) a copolymer containing a hydroxyl group. At least one polymerizable monomer, (C) at least one copolymerizable monomer containing a carboxyl group, and (D) at least one polyalkylene glycol mono(meth)acrylate monomer. and (E) at least one nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth)acrylate monomer not containing a hydroxyl group, wherein the cross-linking agent is a trifunctional isocyanate compound, the pressure-sensitive adhesive composition further contains (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, and is attached to a polarizing plate subjected to AG treatment, width 25 mm × The polarizing plate surface protective film cut to a length of 35 mm is subjected to a load of 500 g and left to stand for 24 hours in an atmosphere of 23°C. To provide a surface protective film for a polarizing plate.

The present invention also provides a surface protective film for a polarizing plate, in which a pressure-sensitive adhesive layer obtained by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent is formed on one side of a resin film. The acrylic polymer contains (A) a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18, and (B) a hydroxyl group. A total of 2 to 10 parts by weight of at least one copolymerizable monomer and 0.05 to 0.3 parts by weight of (C) a total of at least one copolymerizable monomer containing a carboxyl group. and (D) a total of 3 to 40 parts by weight of at least one or more polyalkylene glycol mono(meth)acrylate monomers, and (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) A total of 0.1 to 20 parts by weight of at least one or more acrylate monomers is made of a copolymer obtained by copolymerizing, the cross-linking agent is a trifunctional isocyanate compound, and the pressure-sensitive adhesive composition further comprises , (F) a polyether-modified siloxane having an HLB value of 7 to 12 with respect to a total of 100 parts by weight of (A) at least one (meth)acrylic acid ester monomer having a C4 to C18 alkyl group. It contains at least one or more compounds in a total amount of 0.001 to 0.5 parts by weight, and is attached to a polarizing plate that has been subjected to AG treatment. A surface protective film for a polarizing plate, characterized in that there is no displacement in a shear holding force test for a polarizing plate, in which the surface protective film for a polarizing plate is left standing for 24 hours in an atmosphere at a temperature of 23° C. under a load of 500 g. offer.

The (D) polyalkylene glycol mono(meth)acrylate monomer is selected from the group of compounds consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkyleneglycol (meth)acrylate, and ethoxypolyalkyleneglycol (meth)acrylate. At least one or more selected alkylene oxides constituting the polyalkylene glycol chain have an average repeating number of 3 to 14, the diester content in the monomer is 0.2% or less, and the water content is 0.2%. It is preferably 1% or less, and preferably has a solubility in water of 2% or less in a haze value in a 20% aqueous solution.

(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, and N-hydroxyethyl(meth)acrylamide.

(C) the copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, It is preferably at least one selected from the compound group consisting of carboxypolycaprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid.

The trifunctional isocyanate compound is an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a burette of a hexamethylene diisocyanate compound, and isophorone diisocyanate. buret form of compound, isocyanurate form of tolylene diisocyanate compound, isocyanurate form of xylylene diisocyanate compound, isocyanurate form of hydrogenated xylylene diisocyanate compound, adduct form of tolylene diisocyanate compound, adduct form of xylylene diisocyanate compound, It is preferably at least one selected from the compound group consisting of adducts of hydrogenated xylylene diisocyanate compounds.

The (J) antistatic agent is added to the pressure-sensitive adhesive composition with respect to a total of 100 parts by weight of at least one (A) alkyl group having a carbon number of C4 to C18 (meth)acrylic acid ester monomer It is preferably an ionic compound that is solid at 25°C and has a melting point of 25°C to 50°C, which is contained 0.01 to 5.0 parts by weight.

The pressure-sensitive adhesive layer has an adhesive strength of 0.04 to 0.2 N/25 mm at a low peel speed of 0.3 m/min and an adhesive strength of 2.0 N at a high peel speed of 30 m/min. /25 mm or less.

The pressure-sensitive adhesive layer preferably has a surface resistivity of 9.0×10 ⁺¹¹ Ω/□ or less and a peeling electrification voltage of ±0 to 0.5 kV.

It is preferable that one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed is subjected to antistatic treatment and antifouling treatment.

According to the present invention, at a low peeling speed and a high peeling speed, the balance of adhesive force is excellent, the adhesive force to the polarizing plate is good even though the adhesive force is small, and the durability, reworkability, and chargeability are improved. It is possible to provide a surface protective film for a polarizing plate with excellent anti-reflection performance.

The present invention will be described below based on preferred embodiments.
The surface protective film for a polarizing plate of the present invention is a polarizing plate in which a pressure-sensitive adhesive layer is formed on one side of a resin film by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent. In the plate surface protection film, the acrylic polymer comprises (A) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18 and (B) a copolymer containing a hydroxyl group. At least one polymerizable monomer, (C) at least one copolymerizable monomer containing a carboxyl group, and (D) at least one polyalkylene glycol mono(meth)acrylate monomer. and (E) at least one nitrogen-containing vinyl monomer or alkoxy group-containing alkyl (meth)acrylate monomer not containing a hydroxyl group, wherein the cross-linking agent is a trifunctional isocyanate compound, the pressure-sensitive adhesive composition further contains (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, and is attached to a polarizing plate subjected to AG treatment, width 25 mm × The polarizing plate surface protective film cut to a length of 35 mm is subjected to a load of 500 g and left to stand for 24 hours in an atmosphere of 23°C. It is a surface protection film for polarizing plates.

In the surface protective film for polarizing plate of the present invention, a pressure-sensitive adhesive layer is formed on one side of a resin film by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent. A surface protective film for a polarizing plate, wherein the acrylic polymer comprises (A) a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18, (B) a total of 2 to 10 parts by weight of at least one copolymerizable monomer containing a hydroxyl group; 05 to 0.3 parts by weight, (D) a total of 3 to 40 parts by weight of at least one or more polyalkylene glycol mono(meth)acrylate monomers, and (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or A copolymer obtained by copolymerizing a total of 0.1 to 20 parts by weight of at least one or more alkoxy group-containing alkyl (meth)acrylate monomers, wherein the cross-linking agent is a trifunctional isocyanate compound, The pressure-sensitive adhesive composition further comprises (F) an HLB value of 7 with respect to a total of 100 parts by weight of at least one (A) alkyl group having a C4 to C18 (meth)acrylic acid ester monomer. 12 polyether-modified siloxane compounds in total at a ratio of 0.001 to 0.5 parts by weight, and bonded to a polarizing plate subjected to AG treatment, width 25 mm × length The surface protective film for a polarizing plate cut to a size of 35 mm is subjected to a load of 500 g and left to stand for 24 hours in an atmosphere at a temperature of 23°C. It is a surface protective film for polarizing plates.

(A) Examples of (meth)acrylic acid ester monomers having alkyl groups of C4 to C18 carbon atoms include butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate ) acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, myristyl (meth)acrylate , isomyristyl (meth)acrylate, cetyl (meth)acrylate, isocetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate and the like.

(B) Examples of copolymerizable monomers containing hydroxyl groups include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate. hydroxyalkyl (meth)acrylates such as , and hydroxyl group-containing (meth)acrylamides such as N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide.
8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) ) at least one compound selected from the compound group consisting of acrylamide and N-hydroxyethyl (meth)acrylamide.
(A) at least one (meth)acrylic acid ester monomer in which the alkyl group has a carbon number of C4 to C18, with respect to a total of 100 parts by weight, (B) at least one copolymerizable monomer containing a hydroxyl group It is preferable to contain the above total in a proportion of 2 to 10 parts by weight, more preferably in a proportion of 3.5 to 10 parts by weight, particularly in a proportion of 4.2 to 10 parts by weight. preferable.

(C) a copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2 - (meth) acryloyloxypropyl hexahydrophthalate, 2-(meth) acryloyloxyethyl phthalate, 2-(meth) acryloyloxyethyl succinate, 2-(meth) acryloyloxyethyl maleate, carboxy It is preferably at least one selected from the compound group consisting of polycaprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid.
(A) with respect to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer in which the alkyl group has C4 to C18 carbon atoms, (C) at least one copolymerizable monomer containing a carboxyl group It is preferable to contain the total of seeds or more in a proportion of 0.05 to 0.3 parts by weight, more preferably 0.05 to 0.25 parts by weight, and 0.05 to 0.2 parts by weight Part ratio is particularly preferred.

The (D) polyalkylene glycol mono(meth)acrylic acid ester monomer may be a compound in which one hydroxyl group among the plurality of hydroxyl groups of 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 main polymer. Other hydroxyl groups may be OH as they are, alkyl ethers such as methyl ether and ethyl ether, saturated carboxylic acid esters such as acetic acid esters, and the like.
The alkylene group possessed by the polyalkylene glycol includes, but is not limited to, an ethylene group, a propylene group, a butylene group, and the like. The polyalkylene glycol may be a copolymer of two or more polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol. Copolymers of polyalkylene glycol include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol and the like. It may be a block copolymer or a random copolymer.

(D) The polyalkylene glycol mono(meth)acrylic acid ester monomer preferably has an average repeating number of 3 to 14 for the alkylene oxide constituting the polyalkylene glycol chain. The "average number of repeating alkylene oxides" is the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion contained in the molecular structure of the (D) polyalkylene glycol mono(meth)acrylate monomer. be.

(D) Polyalkylene glycol mono(meth)acrylic acid ester monomer has a diester content of 0.2% or less, a water content of 0.1% or less, and solubility in water , the haze value in a 20% aqueous solution is preferably 2% or less.
The "diester content in the monomer" is the content (% by weight) of the polyalkylene glycol di(meth)acrylate contained in the (D) polyalkylene glycol mono(meth)acrylate monomer.
The "moisture content" is the content (% by weight) of water contained in the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer.
The “haze value in a 20% aqueous solution state” is the haze value (%) of an aqueous solution of 20% by weight of (D) polyalkylene glycol mono(meth)acrylic acid ester monomer. That is, the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer not only has water solubility (solubility in water) enough to form a 20% aqueous solution, but also has a low haze value (%) in a 20% aqueous solution. (less white turbidity).
In this specification, the haze value of a 20% aqueous solution is a value measured by a haze meter after putting the aqueous solution into a quartz cell with an optical path length of 10 mm. This index was introduced to select a highly hydrophilic monomer that provides a solution without white turbidity even at a high concentration as the degree of hydrophilicity of the (D) polyalkylene glycol mono(meth)acrylate monomer. is.

(D) polyalkylene glycol mono(meth)acrylic acid ester monomer, selected from the group of compounds consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkyleneglycol (meth)acrylate, and ethoxypolyalkyleneglycol (meth)acrylate; At least one or more are preferably selected.
More specifically, polyethylene glycol-mono (meth) acrylate, polypropylene glycol-mono (meth) acrylate, polybutylene glycol-mono (meth) acrylate, polyethylene glycol-polypropylene glycol-mono (meth) acrylate, polyethylene glycol-poly Butylene glycol-mono(meth)acrylate, polypropylene glycol-polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-polybutylene glycol-mono(meth)acrylate; methoxypolyethylene glycol-(meth)acrylate, methoxypolypropylene glycol -(meth)acrylate, methoxypolybutylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polybutylene glycol-(meth)acrylate, methoxy-polypropylene glycol-polybutylene Glycol-(meth)acrylate, methoxy-polyethyleneglycol-polypropyleneglycol-polybutyleneglycol-(meth)acrylate; ethoxypolyethyleneglycol-(meth)acrylate, ethoxypolypropyleneglycol-(meth)acrylate, ethoxypolybutyleneglycol-(meth)acrylate Acrylate, ethoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polybutylene glycol-(meth)acrylate, ethoxy-polypropylene glycol-polybutylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polypropylene glycol -polybutylene glycol-(meth)acrylate and the like.

(A) With respect to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having a C4 to C18 alkyl group, at least (D) a polyalkylene glycol mono(meth)acrylic acid ester monomer The total content of one or more is preferably 3 to 40 parts by weight, more preferably 3 to 30 parts by weight, and particularly preferably 5 to 30 parts by weight.

The acrylic polymer can further contain (E) at least one of nitrogen-containing vinyl monomers not containing hydroxyl groups or alkoxy group-containing alkyl (meth)acrylate monomers. Among (E), (E-1) nitrogen-containing vinyl monomers include vinyl monomers containing an amide bond, vinyl monomers containing an amino group, and vinyl monomers having a nitrogen-containing heterocyclic structure. More specifically, N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl Cyclic nitrogen vinyl compounds having an N-vinyl-substituted heterocyclic structure such as pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-vinyllauryrolactam; N-( meth) acryloylmorpholine, N-(meth)acryloylpiperazine, N-(meth)acryloylaziridine, N-(meth)acryloylazetidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth) ) Cyclic nitrogen vinyl compounds having an N-(meth)acryloyl-substituted heterocyclic structure, such as acryloylazepane and N-(meth)acryloylazocane; N-cyclohexylmaleimide, N-phenylmaleimide, etc., nitrogen atoms and Cyclic nitrogen vinyl compounds having a heterocyclic structure having an ethylenically unsaturated bond in the ring; (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nt-butyl(meth) Unsubstituted or monoalkyl-substituted (meth)acrylamide such as acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropylacrylamide, N,N-diisopropyl (meth)acrylamide ) acrylamide, N,N-dibutyl (meth)acrylamide, N-ethyl-N-methyl (meth)acrylamide, N-methyl-N-propyl (meth)acrylamide, N-methyl-N-isopropyl (meth)acrylamide, etc. Dialkyl-substituted (meth)acrylamide; N,N-dimethylaminomethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-dimethylaminoisopropyl (meth) acrylate, N,N-dimethylaminobutyl (meth) acrylate, N,N-diethylaminomethyl (meth) acrylate, N,N-diethylaminoethyl (meth) acrylate, N-ethyl-N-methylaminoethyl (meth) ) acrylate, N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl (meth)acrylate t) acrylates, dialkylamino (meth)acrylates such as N,N-dibutylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate; N,N-dimethylaminopropyl (meth)acrylamide, N,N- Diethylaminopropyl (meth)acrylamide, N,N-dipropylaminopropyl (meth)acrylamide, N,N-diisopropylaminopropyl (meth)acrylamide, N-ethyl-N-methylaminopropyl (meth)acrylamide, N-methyl- N,N-dialkyl-substituted aminopropyl (meth)acrylamides such as N-propylaminopropyl (meth)acrylamide, N-methyl-N-isopropylaminopropyl (meth)acrylamide; N-vinylformamide, N-vinylacetamide, N- N-vinylcarboxylic acid amides such as vinyl-N-methylacetamide; N-methoxymethyl (meth)acrylamide, N-ethoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetoneacrylamide, N, N - (meth)acrylamides such as methylenebis(meth)acrylamide; unsaturated carboxylic acid nitriles such as (meth)acrylonitrile; and the like.

As the nitrogen-containing vinyl monomer (E-1), those containing no hydroxyl group are preferable, and those containing neither hydroxyl group nor carboxyl group are more preferable. Such monomers include the monomers exemplified above, for example, acrylic monomers containing N,N-dialkyl-substituted amino groups and N,N-dialkyl-substituted amide groups; N-vinyl-2-pyrrolidone, N-vinyl N-vinyl-substituted lactams such as caprolactam and N-vinyl-2-piperidone; N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine are preferred.

Among (E), (E-2) alkoxy group-containing alkyl (meth)acrylate monomers include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-isopropoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 2-propoxypropyl (meth)acrylate, 2-isopropoxy Propyl (meth)acrylate, 2-butoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 3-propoxypropyl (meth)acrylate, 3-isopropoxypropyl (meth)acrylate Acrylates, 3-butoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, 4-propoxybutyl (meth)acrylate, 4-isopropoxybutyl (meth)acrylate, 4- butoxybutyl (meth)acrylate and the like.
These alkoxy group-containing alkyl(meth)acrylate monomers have a structure in which the alkyl group atoms in the alkyl(meth)acrylate are substituted with alkoxy groups.

(A) relative to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer in which the alkyl group has C4 to C18 carbon atoms, (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl The total of at least one (meth) acrylate monomer is preferably contained in a proportion of 0.1 to 20 parts by weight, more preferably in a proportion of 0.3 to 10 parts by weight, and 0.3 to A content of 8 parts by weight is particularly preferred. (E-1) Nitrogen-containing vinyl monomers containing no hydroxyl groups and (E-2) alkoxy group-containing alkyl (meth)acrylate monomers may be used singly or in combination of two or more.

The pressure-sensitive adhesive composition according to the present invention may contain (F) a polyether-modified siloxane compound having an HLB value of 7-12. 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 groups 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 groups or acyl groups. etc. (end group). The polyether group includes polyoxyalkylene groups such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a polyoxypropylene group [(C ₃ H ₆ O) _n ].

(A) With respect to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C18, (F) a polyether-modified siloxane compound having an HLB value of 7 to 12 It is preferable to contain at least one or more in a total amount of 0.001 to 0.5 parts by weight. More preferably, it is 0.01 to 0.5 parts by weight. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) defined, for example, in JIS K3211 (surfactant terms).

A 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 through a hydrosilylation reaction. Specifically, dimethylsiloxane/methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxyethylene) siloxane/methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxypropylene) A siloxane polymer etc. are mentioned. The HLB value of the polyether-modified siloxane compound can be adjusted by selecting the ratio of polyether groups to siloxane groups. (F) By incorporating a polyether-modified siloxane compound having an HLB value of 7 to 12 into the adhesive composition, the adhesive strength and rework performance of the adhesive can be improved.

The trifunctional isocyanate compound may be at least one or two or more selected from polyisocyanate compounds having three isocyanate (NCO) groups in one molecule. Polyisocyanate compounds are classified into aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, alicyclic isocyanates, and the like, and any of them may be used.

Examples of the trifunctional isocyanate compound include bifunctional isocyanate compounds (compounds having two NCO groups in one molecule), burette-modified products and isocyanurate-modified products, trimethylolpropane (TMP), glycerin, and other trivalent or higher valent compounds. Examples thereof include adducts (polyol-modified products) with polyols (compounds having at least 3 or more OH groups in one molecule).

Examples of the trifunctional isocyanate compound include an isocyanurate of a hexamethylene diisocyanate compound, an isocyanurate of an isophorone diisocyanate compound, an adduct of a hexamethylene diisocyanate compound, an adduct of an isophorone diisocyanate compound, a burette of a hexamethylene diisocyanate compound, and isophorone diisocyanate. buret form of compound, isocyanurate form of tolylene diisocyanate compound, isocyanurate form of xylylene diisocyanate compound, isocyanurate form of hydrogenated xylylene diisocyanate compound, adduct form of tolylene diisocyanate compound, adduct form of xylylene diisocyanate compound, It is preferably at least one selected from the compound group consisting of adducts of hydrogenated xylylene diisocyanate compounds.
(A) The total of at least one trifunctional isocyanate compound is 0.1 per 100 parts by weight in total of at least one (meth)acrylic acid ester monomer having a C4 to C18 alkyl group. It is preferably contained in a proportion of up to 10 parts by weight, more preferably in a proportion of 0.1 to 6 parts by weight.

The cross-linking catalyst may be any substance that functions as a catalyst for the reaction (cross-linking reaction) between the acrylic polymer and the cross-linking agent when a polyisocyanate compound is used as the cross-linking agent, and is an amine-based compound such as a tertiary amine. , metal chelate compounds, organic tin compounds, organic lead compounds, organic zinc compounds and the like.
Tertiary amines include trialkylamines, N,N,N',N'-tetraalkyldiamines, N,N-dialkylaminoalcohols, triethylenediamine, morpholine derivatives, piperazine derivatives and the like.

A metal chelate compound is a compound in which one or more polydentate ligands L are bonded to a central metal atom M. The metal chelate compound may or may not have one or more monodentate ligands X bound to the metal atom M. For example, when the general formula of a metal chelate compound having one metal atom M is represented by M(L) _m (X) _n , m≧1 and n≧0. When m is 2 or more, m L may be the same ligand or different ligands. When n is 2 or more, n Xs may be the same ligand or different ligands.

Metal atoms M include Fe, Ni, Mn, Cr, V, Ti, Ru, Zn, Al, Zr, Sn and the like.
Examples of the multidentate ligand L include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate and stearyl acetoacetate, acetylacetone (also known as 2,4-pentanedione), β-diketones such as 2,4-hexanedione and benzoylacetone. These are keto-enol tautomeric compounds, which in the polydentate ligand L may be deprotonated enolates of enols (eg acetylacetonate).
The monodentate ligand X includes halogen atoms such as chlorine and bromine atoms, acyloxy groups such as pentanoyl, hexanoyl, 2-ethylhexanoyl, octanoyl, nonanoyl, decanoyl, dodecanoyl and octadecanoyl group, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, alkoxy group such as butoxy group, and the like.

Specific examples of metal chelate compounds include tris(2,4-pentanedionato)iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris Acetylacetonate, zirconium tetrakisacetylacetonate, tris(2,4-hexanedionato)iron(III), bis(2,4-hexanedionato)zinc, tris(2,4-hexanedionato)titanium, tris (2,4-hexanedionato)aluminum, tetrakis(2,4-hexanedionato)zirconium and the like.

Examples of organic tin compounds include dialkyltin oxides, dialkyltin fatty acid salts, stannous fatty acid salts, and the like.
The cross-linking catalyst is preferably a metal chelate compound or an organic tin compound. As metal chelate compounds, aluminum chelate compounds, titanium chelate compounds, iron chelate compounds, tin chelate compounds and the like are preferable. The organic tin compound is preferably at least one compound selected from the compound group consisting of dioctyltin oxide and dioctyltin dilaurate.
(A) The total amount of at least one crosslinking catalyst is added to 0.001 to 0.001 to 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C18. It is preferably contained at a rate of 5 parts by weight.

Ketoenol tautomeric compounds include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, acetylacetone, 2,4-hexanedione, and benzoylacetone. and β-diketones such as The ketoenol tautomer compound blocks the isocyanate group of the cross-linking agent in the pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, thereby preventing excessive viscosity increase of the pressure-sensitive adhesive composition after blending the cross-linking agent. Gelation can be suppressed and the pot life of the pressure-sensitive adhesive composition can be extended.
The keto-enol tautomeric compound is preferably at least one selected from the group of compounds consisting of acetylacetone and ethyl acetoacetate.
(A) A total of at least one kind of ketoenol tautomer compound is added to 0.00 parts per 100 parts by weight in total of at least one kind of (meth)acrylic acid ester monomer in which the number of carbon atoms in the alkyl group is from C4 to C18. It is preferably contained in a proportion of 1 to 300 parts by weight, more preferably in a proportion of 1.0 to 30.0 parts by weight.

Since the keto-enol tautomer compound has the effect of suppressing cross-linking, contrary to the cross-linking catalyst, it is preferable to appropriately set the ratio of the keto-enol tautomer compound to the cross-linking catalyst. In order to prolong the pot life of the adhesive composition and improve the storage stability, the weight ratio of the crosslinking catalyst to the ketoenol tautomer compound (ketoenol tautomer compound/crosslinking catalyst) is 70 to 1000. is preferred.

(J) The antistatic agent is preferably an ionic compound that has a melting point of 25 to 50°C and is solid at 25°C.
In the present invention, as (J) an antistatic agent, an ionic compound that has a melting point of 25 to 50°C and is solid at 25°C is added to the adhesive composition. Since these antistatic agents (J) have low melting points and long-chain alkyl groups, they are presumed to have high affinity with acrylic polymers.

(J) Antistatic agents include ionic compounds that are solid at 25° C. and have a melting point of 25 to 50° C. contained in the adhesive composition.

The ionic compound that has a melting point of 25 to 50° C. and is solid at 25° C. is an ionic compound having a cation and an anion, wherein the cation is pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, nitrogen _- containing onium cations such as pyrrolidinium cations and ammonium cations, phosphonium cations ^, sulfonium cations ^, etc., and salt (RC ₆ H ₄ SO ₃ ⁻ ), perchlorate (ClO ₄ ⁻ ), tetrafluoroborate (BF ₄ ⁻ ), bis(fluorosulfonyl)imide salt (FSI), bis(trifluoromethanesulfonyl) Compounds that are inorganic or organic anions such as imide salts (TFSI) and trifluoromethanesulfonates (TF) can be mentioned. It is preferably solid at room temperature (for example, 25° C.), and a melting point of 25 to 50° C. can be obtained by selecting the chain length of the alkyl group, the position and number of substituents, and the like. The cation is preferably a quaternary nitrogen-containing onium cation, such as quaternary pyridinium cations such as 1-alkylpyridinium (the carbon atoms at positions 2 to 6 may be substituted or unsubstituted), and 1, quaternary imidazolium cations such as 3-dialkylimidazolium (carbon atoms at positions 2, 4 and 5 may be substituted or unsubstituted); quaternary ammonium cations such as tetraalkylammonium; .
(A) an ionic compound solid at 25 ° C. with a melting point of 25 to 50 ° C. with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer in which the number of carbon atoms in the alkyl group is C4 to C18; It is preferable to contain at least one or more in a total amount of 0.01 to 5.0 parts by weight.

Specific examples of the (J) antistatic agent are not particularly limited, but specific examples of ionic compounds that have a melting point of 25 to 50°C and are solid at 25°C include 1-octylpyridinium hexafluoride Phosphate, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1- dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate and the like.

Furthermore, as other components, copolymerizable (meth)acrylic monomers containing alkylene oxide, (meth)acrylamide monomers, dialkyl-substituted acrylamide monomers, surfactants, curing accelerators, plasticizers, fillers, curing retarders , processing aids, anti-aging agents, and antioxidants. These are used alone or in combination of two or more.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present invention includes (A) at least one (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C4 to C18, and (B) a copolymer containing a hydroxyl group. It comprises a copolymer obtained by copolymerizing at least one or more polymerizable monomers with (C) at least one or more copolymerizable monomers containing a carboxyl group. The acrylic polymer comprises (A) at least one (meth)acrylic acid ester monomer having an alkyl group of C4 to C18 carbon atoms, and (B) at least one copolymerizable monomer containing a hydroxyl group. (C) at least one copolymerizable monomer containing a carboxyl group, (D) at least one polyalkylene glycol mono(meth)acrylate monomer, and (E) no hydroxyl group It may be a copolymer obtained by copolymerizing at least one of nitrogen-containing vinyl monomers and alkoxy group-containing alkyl (meth)acrylate monomers. The polymerization method of the acrylic polymer is not particularly limited, and an appropriate polymerization method such as solution polymerization or emulsion polymerization can be used.
The pressure-sensitive adhesive composition of the present invention further comprises the above acrylic polymer, (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, a trifunctional isocyanate compound as a cross-linking agent, and an antistatic agent. , a solid ionic compound at 25.degree.

When producing an acrylic polymer, it is preferable to carry out a polymerization reaction under anhydrous conditions, such as solution polymerization using an anhydrous organic solvent, in order to reduce contamination of water in the pressure-sensitive adhesive composition. In particular, since the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer is highly hydrophilic, it is preferable to use one having a low moisture content.
In order to avoid increasing the viscosity of the pressure-sensitive adhesive composition, each monomer used in the production of the main acrylic polymer should be a polyfunctional (bifunctional or higher) monomer that can function as a cross-linking agent. preferably reduced. In particular, (D) polyalkylene glycol mono(meth)acrylic acid ester monomer has a low diester content because the corresponding diester content is a di(meth)acrylic acid ester of a bifunctional monomer.

The acrylic polymer contains 50 to 100 parts by weight of acrylic monomers such as (meth)acrylic acid ester monomers, (meth)acrylic acid, and (meth)acrylamides with respect to 100 parts by weight of the acrylic polymer. It is preferably contained in proportion.
Also, the acid value of the acrylic polymer is preferably 0.01 to 8.0. As a result, it is possible to improve the staining property and improve the adhesive residue prevention performance.
Here, the "acid value" is one index of the acid content, and is expressed in mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition has an adhesive strength to the polarizing plate of 0.04 to 0.2 N/25 mm at a low peel speed of 0.3 m/min, and 0.04 to 0.2 N/25 mm at a high speed peel speed. It is preferable that the adhesive strength at a peeling speed of 30 m/min is 2.0 N/25 mm or less. As a result, it is possible to obtain a performance in which the adhesive strength does not change much depending on the peeling speed, and it is possible to peel off quickly even with high-speed peeling. Moreover, when the surface protective film is once peeled off for reattachment, it is easy to peel off from the adherend without requiring excessive force.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition preferably has a surface resistivity of 9.0×10 ⁺¹¹ Ω/□ or less and a peel electrostatic voltage of ±0 to 0.5 kV. In the present invention, "±0 to 0.5 kV" means 0 to -0.5 kV and 0 to +0.5 kV, that is, -0.5 to +0.5 kV. If the surface resistivity is high, the performance of releasing static electricity generated by electrification during peeling is inferior. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage caused by the static electricity generated when the adhesive layer is peeled off by the adherend is reduced, and the electric control circuit of the adherend is not affected. can be suppressed.

The gel fraction of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is preferably 95 to 100%. Due to such a high gel fraction, the adhesive strength does not become excessive at low peeling speeds, and the elution of unpolymerized monomers or oligomers from the acrylic polymer is reduced. Durability is improved, and contamination of adherends can be suppressed.

A pressure-sensitive adhesive film can be obtained by forming a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one or both sides of a resin film. Further, the surface protective film for polarizing plate of the present invention is a surface protective film in which a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is formed on one side of a resin film. The surface protective film for a polarizing plate of the present invention does not shift in a shear holding force test when attached to a polarizing plate, and has good adhesion to the polarizing plate despite having a small adhesive force, durability, and reworkability. Excellent antistatic performance. Therefore, it can be suitably used as a surface protection film for polarizing plates. Examples of polarizing plates include glare, plain (general purpose), and antiglare (AG). Protective film materials for the surface of the polarizing plate include TAC films (triacetyl cellulose compounds), acrylic films, and the like.

Test conditions for the shear holding force include, for example, a load (weight mass) of 500 g, an environmental temperature of 23° C., and a standing time of 24 hours. This test condition is suitable as a guideline for judging whether the adhesion of the surface protective film to the polarizing plate is good. The contact area (dimension) of the polarizing plate surface protective film to the polarizing plate, which is the adherend in the shear holding force test, is 25 mm×35 mm. The details of the test method (apparatus, etc.) may conform to, for example, the holding power test of JIS Z 0237 (adhesive tape/adhesive sheet test method).

A resin film such as a polyester film can be used as the resin film that serves as the base material of the pressure-sensitive adhesive layer and the release film (separator) that protects the pressure-sensitive adhesive surface.
On the side of the resin film that serves as the base material, which is opposite to the side on which the pressure-sensitive adhesive layer is formed, a silicone-based or fluorine-based release agent or coating agent, an antifouling treatment using silica fine particles, etc., and an antistatic agent are applied. can be applied or kneaded to prevent static electricity.
The release film is subjected to release treatment with a silicone-based or fluorine-based release agent or the like on the side of the release film that is to be matched with the adhesive surface of the adhesive layer.

EXAMPLES The present invention will be specifically described below with reference to Examples.

<Production of acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 8.0 parts by weight of 8-hydroxyoctyl acrylate, 0.1 parts by weight of acrylic acid, polypropylene glycol monoacrylate (average number of repeating alkylene oxides constituting the polyalkylene glycol chain) was added to the reactor. n = 12, diester content in monomer is 0.1%, solubility in water is 0.8%, water content is 0.05%) 8 parts by weight, N- 60 parts by weight of a solvent (ethyl acetate) was added along with 1 part by weight of vinylpyrrolidone. After that, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and allowed to react at 65° C. for 6 hours to give an acrylic polymer solution having a weight average molecular weight of 500,000 used in Example 1. Obtained. A portion of the acrylic polymer was sampled and used as a sample for acid value measurement, which will be described later.
[Examples 2 to 8 and Comparative Examples 1 to 4]
Examples 2 to 8 and Comparative An acrylic polymer solution used in Examples 1-4 was obtained.

<Production of pressure-sensitive adhesive composition and surface protection film>
[Example 1]
For the acrylic polymer solution of Example 1 produced as described above, 0.05 parts by weight of a polyether-modified siloxane compound (HLB value is 7), 1.0 parts by weight of 1-octylpyridinium hexafluorophosphate, After adding 8.5 parts by weight of acetylacetone and stirring, 4.0 parts by weight of Coronate HX (isocyanurate form of hexamethylene diisocyanate compound) and 0.1 part by weight of titanium trisacetylacetonate were added and mixed by stirring. was obtained. After applying this adhesive composition on a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, the solvent is removed by drying at 90 ° C., and the thickness of the adhesive layer is 25 μm. got a sheet.
After that, the pressure-sensitive adhesive sheet is transferred to the opposite side of the antistatic and antifouling treated side of the polyethylene terephthalate (PET) film having one side antistatic and antifouling treated. A surface protective film of Example 1 having a laminated structure of "PET film/adhesive layer/release film (silicone resin-coated PET film)" was obtained.
[Examples 2 to 8 and Comparative Examples 1 to 4]
Examples 2 to 8 and Comparative Examples 1 to 2 were prepared in the same manner as the surface protective film of Example 1 above, except that the compositions of the additives were each as described in (F) to (J) in Table 2. 4 surface protective film was obtained.

In Tables 1 and 2, the compounding ratio of each component is indicated by enclosing the numerical values in parentheses in parts by weight obtained based on the total of Group (A) being 100 parts by weight.
In addition, Tables 3 and 4 show the compound names of the abbreviations of the components used in Tables 1 and 2. Coronate (registered trademark) HX, HL and L are trade names of Nippon Polyurethane Industry Co., Ltd. Takenate (registered trademark) D-140N, D-127N, D-110N and D-120N are Mitsui Chemicals, Inc. The company's product name. Regarding group (D) in Table 3, the numerical value of "n" is the average repeating number of alkylene oxides constituting the polyalkylene glycol chain. The numerical value of "diester" is the diester content (%) in the monomer. The numerical value of "moisture content" is the moisture content (%). The numerical value of "haze" is the haze value (%) in a 20% aqueous solution state.

<Test method and evaluation>
After aging the surface protective films in Examples 1 to 8 and Comparative Examples 1 to 4 in an atmosphere of 23 ° C. and 50% RH for 7 days, the release film (silicone resin-coated PET film) was peeled off, and the pressure-sensitive adhesive The exposed layer was used as a measurement sample for gel fraction and surface resistivity.
Furthermore, the surface protective film with the adhesive layer exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell via the adhesive layer, left for one day, and then left at 50° C. for 20 minutes at 5 atm. After being autoclaved and allowed to stand at room temperature for 12 hours, the adhesive strength, peeling electrification voltage, shear holding power (displacement), reworkability and durability were measured. The polarizing plate of the adherend is a polarizing plate having an AG-treated surface.

<Gel fraction>
After aging, the mass of the pressure-sensitive adhesive layer separated from the measurement sample before being attached to the polarizing plate is accurately measured, immersed in toluene for 24 hours, and then filtered through a 200-mesh wire 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 layer after cross-linking) was calculated from the following formula.
Gel fraction (%) = mass of insoluble portion (g)/mass of adhesive layer (g) x 100

<Adhesive strength>
The measurement sample obtained above (a surface protective film with a width of 25 mm was laminated on the surface of a polarizing plate whose surface was subjected to AG treatment) was measured in a 180 ° direction using a tensile tester at a low peel speed ( 0.3 m/min) and a high peel speed (30 m/min), and the measured peel strength was taken as the adhesive strength (N/25 mm).

<Surface resistivity>
After aging, before bonding to the polarizing plate, the release film (silicone resin-coated PET film) is peeled off to expose the adhesive layer, and a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytic Tech) is used. The surface resistivity (Ω/□) of the adhesive layer was measured.

<Peeling electrification voltage>
When the measurement sample obtained above is peeled 180° at a tensile speed of 30 m/min, the voltage (charged voltage) generated by charging the polarizing plate whose surface is AG-treated is measured by the high-precision electrostatic sensor SK. -035 and SK-200 (manufactured by KEYENCE CORPORATION), and the maximum value of the measured values was taken as the peeling electrification voltage (kV).
<Shear holding force for polarizing plate>
A surface protective film (adhesive layer thickness: 20 μm) cut to a size of 25 mm in width and 35 mm in length is attached to a polarizing plate whose surface has been subjected to AG treatment, and the film is attached to the polarizing plate in an atmosphere at a temperature of 23°C. A load of 500 g was applied to the combined surface protective film, and the displacement (mm) of the surface protective film was measured after the film was left for 24 hours.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ballpoint pen (load 500 g, 3 reciprocations), the surface protective film was peeled off from the polarizing plate and the surface of the polarizing plate was observed. Confirmed no migration. The evaluation target criteria are "○" when there is no contamination transfer to the polarizing plate, "△" when contamination transfer is confirmed at least partially along the trace traced with the ballpoint pen, and along the trace traced with the ballpoint pen. A case where transfer of contamination was confirmed and separation of the adhesive from the surface of the adhesive was also confirmed was evaluated as "x".

<Durability>
After leaving the measurement sample obtained above in an atmosphere of 60 ° C. and 90% RH for 250 hours, taking it out to room temperature and leaving it for another 12 hours, the adhesive strength is measured and compared with the initial adhesive strength. It was confirmed that there was no significant increase. As for the evaluation target criteria, when the adhesive strength after the test was 1.5 times or less of the initial adhesive strength, it was evaluated as "good", and when it exceeded 1.5 times, it was evaluated as "poor".

Table 5 shows the evaluation results. In addition, the surface resistivity was expressed by a method of setting "m×10 ⁺ⁿ " to "mE+n" (where m is an arbitrary real number and n is a positive integer).
Further, the misalignment shown in Table 5 indicates the measured value of the misalignment (mm) of the surface protective film in the shear holding force test for the polarizing plate.

The surface protective films of Examples 1 to 8 had an adhesive strength of 0.04 to 0.2 N/25 mm at a low peeling speed of 0.3 m / min to the polarizing plate of the adherend, and high speed peeling. The adhesive strength at a speed of 30 m/min is 2.0 N/25 mm or less, the surface resistivity is 9.0 × 10 ⁺¹¹ Ω/□ or less, the peeling electrification voltage is ±0 to 0.5 kV, and the load is 500 g. After leaving at 23 ° C. x 24 hours at 23 ° C. × 24 hours, there was no shift, and after tracing the surface protective film with a ballpoint pen through the adhesive layer, there was no transfer of contamination to the adherend, 60 ° C., 90% RH It was also excellent in durability when left in the atmosphere for 250 hours.
That is, (1) good adhesion to the polarizing plate despite low adhesive strength, (2) durability, (3) reworkability, and (4) excellent antistatic performance, satisfying all the required performances, fulfilled at the same time.

In the surface protective film of Comparative Example 1, (C) the copolymerizable monomer containing a carboxyl group is excessive, the acrylic polymer does not contain (D) a polyalkylene glycol mono(meth)acrylic acid ester monomer, and the adhesive The agent composition (F) does not contain a polyether-modified siloxane compound having an HLB value of 7 to 12, (G) contains too little trifunctional isocyanate compound, and (J) does not contain an antistatic agent. The adhesive strength at a peel speed of 0.3 m / min and a high peel speed of 30 m / min is too large, the surface resistivity and peel electrification voltage are high, there is a deviation in the shear holding force test, and reworkability and durability are poor. was inferior.

In the surface protective film of Comparative Example 2, (C) the copolymerizable monomer containing a carboxyl group is too small, the diester content of the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer is large, and the moisture content is is high, the solubility in water is low, and the HLB value of (F) the polyether-modified siloxane compound is excessive, so the adhesive strength at a low peeling speed of 0.3 m / min and a high peeling speed of 30 m / min It was too large, the surface resistivity and peeling electrification voltage were high, there was deviation in the shear holding force test, and the durability was poor.

In the surface protection film of Comparative Example 3, the acrylic polymer does not contain (B) a copolymerizable monomer containing a hydroxyl group, (C) contains an excessive amount of a copolymerizable monomer containing a carboxyl group, and (D) Polyalkylene glycol mono(meth)acrylic acid ester monomer diester content is high, water content is high, and water solubility is low, resulting in a low gel fraction and a low peeling speed of 0.3 m/min. The adhesive strength at a speed of 30 m/min was very large, and even though the surface resistivity was low, the peeling electrification voltage was high and the reworkability was poor.

In the surface protective film of Comparative Example 4, the HLB value of (F) the polyether-modified siloxane compound was excessively large, and there was deviation in the shear holding force test.

Thus, in the surface protective films of Comparative Examples 1 to 4, (1) good adhesion to the polarizing plate despite low adhesive strength, (2) durability, (3) reworkability, and (4) ) It was not possible to simultaneously satisfy all the required performances of excellent antistatic performance.

The surface protective film for a polarizing plate according to the present invention has a problem in the prior art. Since the adhesion strength decreases, the surface protective film peels off at the edge of the polarizing plate when the size of the polarizing plate becomes larger than before as the screen size of the liquid crystal display increases. is solved, the industrial utility value is great.

Claims (2)

An AG-treated surface protective film for a polarizing plate,
A pressure-sensitive adhesive layer is formed on one side of a resin film by cross-linking a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an antistatic agent,
The acrylic polymer is
(A) a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C4 to C18;
(B) a total of 2 to 10 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(C) a total of 0.05 to 0.3 parts by weight of at least one copolymerizable monomer containing a carboxyl group;
(D) a total of 3 to 40 parts by weight of at least one or more polyalkylene glycol mono(meth)acrylate monomers;
(E) A copolymer obtained by copolymerizing a total of 1 to 5 parts by weight of at least one nitrogen-containing vinyl monomer containing no hydroxyl group without copolymerizing an alkoxy group-containing alkyl (meth)acrylate monomer . consists of
(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)acrylamide, at least one selected from the group of compounds,
(C) the copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, At least one selected from the group of compounds consisting of carboxypolycaprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid,
The cross-linking agent is a trifunctional isocyanate compound,
The pressure-sensitive adhesive composition further includes (F) an HLB value with respect to a total of 100 parts by weight of at least one (A) alkyl group having a C4 to C18 (meth)acrylic acid ester monomer having a carbon number of C4 to C18 containing at least one or more of 7 to 12 polyether-modified siloxane compounds in a proportion of 0.001 to 0.5 parts by weight;
A load of 500 g is applied to the polarizing plate surface protective film cut to a size of 25 mm in width and 35 mm in length, which is attached to the polarizing plate subjected to the AG treatment, and left to stand for 24 hours in an atmosphere at a temperature of 23°C. A surface protective film for a polarizing plate subjected to an AG treatment, characterized in that there is no displacement in a shear holding force test for a polarizing plate. 2. The AG-treated surface protection for a polarizing plate according to claim 1, wherein one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed is subjected to antistatic treatment and antifouling treatment. the film.