JP6525321B2 - Surface protection film for polarizing plate - Google Patents

Description

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

  Conventionally, in the process of manufacturing an optical member such as a polarizing plate or a retardation 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 protective film is used only in the process of manufacturing the optical member, and is peeled off from the optical member when the optical member is incorporated into the liquid crystal display. A surface protection film for protecting the surface of such an optical member is generally used only as a process film because it is used only in the manufacturing process.

As described above, the surface protection film used in the process of manufacturing the optical member has the pressure-sensitive adhesive layer formed on one side of the optically transparent polyethylene terephthalate (PET) resin film, but it is bonded to the optical member Until then, a release-treated release film for protecting the pressure-sensitive adhesive layer is laminated on the pressure-sensitive adhesive layer.
In addition, optical members such as a polarizing plate and a retardation plate are subjected to product inspection with optical evaluation such as display ability, hue, contrast, and contamination of a liquid crystal display plate in a state where a surface protection film is attached. As performance requirements for the surface protective film, it is required that no air bubbles or foreign matter adhere to the pressure-sensitive adhesive layer.
Also, in recent years, when the surface protective film is peeled off from an optical member such as a polarizing plate or a retardation plate, the peeling charge caused by the static electricity generated when the adherend peels off the pressure sensitive adhesive layer is the electrical control of the liquid crystal display There is a concern that it may affect circuit failure, and excellent antistatic performance is required for the pressure-sensitive adhesive layer.
Moreover, when bonding a surface protection film to optical members, such as a polarizing plate and a phase difference plate, the surface protection film may be once peeled off for various reasons, and the surface protection film may be stuck again. There is a demand for removability from the optical member of the adherend (reworkability).
In addition, when the surface protective film is finally peeled off from an optical member such as a polarizing plate or a retardation plate, it is required that the film can be peeled quickly. In order to be able to peel off quickly even by so-called high-speed peeling, it is required that the adhesive force has little change even by the peeling speed.

  Thus, in recent years, as the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (i) balance of adhesion at low peeling speed and high peeling speed, (ii) excellent Antistatic performance, (iii) reworkability and the like are required in terms of ease of use in using the surface protective film.

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

An acrylic adhesive comprising a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound as a main component, which is crosslinked with a crosslinking agent. In the layer, there has been a problem that the adhesive transfers to the adherend side when adhering 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, using 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, this is crosslinked with a crosslinking agent. What provided the adhesive layer is known (patent document 1).
In addition, a small amount of a copolymer of a (meth) acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound is blended with the same copolymer as described above, and a pressure-sensitive adhesive layer obtained by crosslinking with a crosslinking agent is provided. Etc have been proposed. However, when used for surface protection such as a plastic plate having a low surface tension and a smooth surface, these may cause peeling phenomena such as floating due to heating during processing or storage, and high speed in a manual area. There is also a problem that the removability at the time of peeling is inferior.

In order to solve these problems, a) 100 parts by weight of (meth) acrylic acid alkyl ester mainly composed of (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms, b) carboxyl group-containing In the copolymer of a monomer mixture obtained by adding 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, b A pressure-sensitive adhesive composition has been proposed in which a crosslinking agent is blended in an equivalent amount or more to the carboxyl group of the component) (Patent Document 2).
The pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as floating at the time of processing, storage, etc., moreover, the increase in adhesion with time is small and the removability is excellent. In particular, even if stored for a long time in a high temperature atmosphere, it can be peeled again with a small force, and at that time, no adhesive residue occurs on the adherend, and even when high speed peeling is performed, it can be peeled again with a small force.

Moreover, (ii) About the outstanding antistatic performance, the method of kneading an antistatic agent in a base film etc. are shown as a method for providing antistatic performance to a surface protection film. As the antistatic agent, for example, (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups, (b) sulfonic acid groups, sulfuric acid Anionic antistatic agent having an anionic group such as ester base, phosphoric ester base, phosphonic acid base, (c) amphoteric antistatic agent such as amino acid type, amino sulfuric acid ester type, (d) amino alcohol type, glycerin type And non-ionic antistatic agents such as polyethylene glycols, (e) high-molecular-weight antistatic agents obtained by increasing the molecular weight of the above-described antistatic agents, and the like (Patent Document 3).
Further, in recent years, it has been proposed that such an antistatic agent is not contained in the base film or directly contained in the pressure-sensitive adhesive layer, instead of being applied to the surface of the base film.

For (iii) reworkability, for example, an adhesive in which a curing agent of an isocyanate compound and a specific silicate oligomer are blended in an amount of 0.0001 to 10 parts by weight with respect to 100 parts by weight of an acrylic resin. An agent composition has been proposed (Patent Document 4).
In Patent Document 4, acrylic acid alkyl ester having 2 to 12 carbon atoms of alkyl group or methacrylic acid alkyl ester having 4 to 12 carbon atoms of alkyl group is used as a main monomer component, for example, a carboxyl group-containing monomer And other functional group-containing monomer components can be included. Generally, 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, and more preferably It is said that 0.01 to 25% by weight is desired. Such a pressure-sensitive adhesive composition described in Patent Document 4 exhibits a small change in cohesion and adhesion with the passage of time even under high temperature or high temperature and high humidity, and exhibits excellent effects on adhesion to a curved surface, It is said to have reworkability.
In general, when the pressure-sensitive adhesive layer has a soft property, adhesive residue is easily generated and reworkability is easily reduced. That is, when it pastes by mistake, it is hard to exfoliate and it becomes easy to become difficult to reattach. From this, it is considered necessary to make the pressure-sensitive adhesive layer have a certain hardness by crosslinking the monomer having a functional group such as a carboxyl group to the main agent, in order to give reworkability.

Japanese Patent Application Laid-Open No. 63-225677 Japanese Patent Application Laid-Open No. 11-256111 Japanese Patent Application Laid-Open No. 11-070629 JP-A-8-199130

In recent years, the screen size of various displays such as liquid crystal displays has been rapidly developed. However, with the increase in screen size of liquid crystal displays, new problems have occurred in the process of manufacturing members of liquid crystal displays. For example, the following problems have occurred with respect to a surface protective film for a polarizing plate for bonding to the surface of the polarizing plate to protect the polarizing plate.
In the prior art, in the process of manufacturing a polarizing plate which is a member of a liquid crystal display, after bonding a surface protection film to a polarizing plate as an adherend, when peeling off the surface protection film from the polarizing plate, On the other hand, this demand has been satisfied by reducing the adhesive strength of the pressure-sensitive adhesive layer formed on the surface protective film.
However, if the adhesive strength of the pressure-sensitive adhesive layer is reduced to make it easy to peel off the surface protective film from the adherend, the adhesion of the surface protective film to the polarizing plate is reduced. When the size of the area is increased compared to the prior art, there arises a problem that the surface protective film is peeled off at the end of the polarizing plate.

  The present invention has been made in view of the above-described circumstances, and has a good balance of adhesion at a low peeling speed and a high peeling speed, and good adhesion to a polarizing plate despite small adhesion. It is an object of the present invention 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 subject, in the present invention, a polarization formed by forming a pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent, and an antistatic agent on one side of a resin film A surface protection film for a plate, wherein the acrylic polymer contains 100 parts by weight of a total of at least one or more (meth) acrylic acid ester monomers having (C) alkyl group having a carbon number of C4 to C18; ) 2 to 10 parts by weight of a total of at least one or more copolymerizable monomers containing a hydroxyl group, and a total of at least one or more of a copolymerizable monomer (C) containing a carboxyl group 0.3 parts by weight, 3 to 40 parts by weight of a total of at least one or more kinds of (D) polyalkylene glycol mono (meth) acrylic acid ester monomers, and (E) containing no hydroxyl group Consists copolymer copolymerized with 0.1 to 20 parts by weight of at least one or more of the total of-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer, wherein the (D) a polyalkylene glycol mono ( At least one or more selected from the group of compounds consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, ethoxypolyalkylene glycol (meth) acrylate, and meta) acrylic acid ester monomers And the average repetition number of the alkylene oxide constituting the polyalkylene glycol chain is 3 to 14, the diester content in the monomer is 0.2% or less, the water content is 0.1% or less, and water Solubility in water is 20% in aqueous solution Haze value is not more than 2%, the crosslinking agent is trifunctional a isocyanate compound, the pressure-sensitive adhesive composition, wherein (A) the number of carbon atoms in the alkyl group is a C 4 -C 18 (meth) acrylic acid ester monomer A solid compound at 25 ° C. having a melting point of 25 to 50 ° C. in a proportion of 0.01 to 5.0 parts by weight based on 100 parts by weight of at least one or more of The pressure-sensitive adhesive composition further comprises (F) relative to 100 parts by weight of at least one or more of (meth) acrylic acid ester monomers having a C4 to C18 carbon number of the (A) alkyl group. A total of at least one or more of polyether modified siloxane compounds having an HLB value of 7 to 12 is contained in a proportion of 0.001 to 0.5 parts by weight, and they are bonded to a polarizing plate subjected to AG treatment, Width 25 The surface protection film for polarizing plate cut into dimensions of mm × length 35 mm is loaded with a load of 500 g and left for 24 hours in an atmosphere at a temperature of 23 ° C. Provided is a surface protective film for polarizing plate, which is characterized.

  The (B) hydroxyl group-containing copolymerizable monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate It is preferable that it is at least 1 sort (s) or more selected from the compound group which consists of N-hydroxy (meth) acrylamide, N- hydroxymethyl (meth) acrylamide, and N- hydroxyethyl (meth) acrylamide.

  The (C) carboxyl group-containing copolymerizable monomer is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, It is preferable that it is at least 1 type or more selected from the compound group which consists of a carboxy polycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxy ethyl tetrahydro phthalic 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, an isophorone diisocyanate Buret body of compound, isocyanurate body of tolylene diisocyanate compound, isocyanurate body of xylylene diisocyanate compound, isocyanurate body of hydrogenated xylylene diisocyanate compound, adduct body of tolylene diisocyanate compound, adduct body of xylylene diisocyanate compound, An adduct of a hydrogenated xylylene diisocyanate compound Selected from, it is preferably at least 1 or more.

  The pressure-sensitive adhesive layer has an adhesion of 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min to the polarizing plate, and an adhesion of 2.0 N at a high peeling speed of 30 m / min. It is preferable that it is / 25 mm or less.

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

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

  According to the present invention, at a low peeling speed and a high peeling speed, the balance of adhesion is excellent, and although the adhesion is small, the adhesion to the polarizing plate is good, and the durability, reworkability, and charging The surface protection film for polarizing plates excellent in prevention performance can be provided.

Hereinafter, the present invention will be described based on preferred embodiments.
The surface protective film for polarizing plate of the present invention is a polarized light comprising a pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent, and an antistatic agent on one side of a resin film. A surface protection film for a plate, wherein the acrylic polymer comprises (A) at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18 and (B) a hydroxyl group. At least one or more of polymerizable monomers, (C) at least one or more copolymerizable monomers containing a carboxyl group, and at least one or more of (D) polyalkylene glycol mono (meth) acrylate monomers And (E) at least at least a nitrogen-containing vinyl monomer having no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer. The cross-linking agent is a trifunctional isocyanate compound, and the pressure-sensitive adhesive composition further includes (F) a polyether-modified 7 to 12 HLB value. A load of 500 g is applied to the surface protective film for a polarizing plate cut into a dimension of 25 mm wide × 35 mm long and bonded to a polarizing plate containing a siloxane compound and subjected to an AG treatment, at a temperature of 23 ° C. It is a surface protection film for polarizing plates characterized by having no shift in a shear holding power test on a polarizing plate, which is left to stand for 24 hours in an atmosphere of

  In the surface protective film for a polarizing plate of the present invention, a pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent, and an antistatic agent is formed on one side of a resin film. The surface-protective film for polarizing plate, wherein the acrylic polymer contains 100 parts by weight in total of at least one or more of (meth) acrylic acid ester monomers having a C4 to C18 carbon number of the (A) alkyl group, (B) 2 to 10 parts by weight of a total of at least one or more copolymerizable monomers containing a hydroxyl group, and (C) a total of at least one or more of copolymerizable monomers containing a carboxyl group is 0. (E) containing 5 to 0.3 parts by weight, 3 to 40 parts by weight of a total of at least one or more kinds of (D) polyalkylene glycol mono (meth) acrylic acid ester monomers, and (E) a hydroxyl group A copolymer obtained by copolymerizing 0.1 to 20 parts by weight of a total of at least one or more kinds of nitrogen-containing vinyl monomers or alkoxy group-containing alkyl (meth) acrylate monomers, and the cross-linking agent is trifunctional It is an isocyanate compound, and the carbon number of the (A) alkyl group is at least one of a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers of the (A) alkyl group. F) A total of at least one or more of polyether modified siloxane compounds having an HLB value of 7 to 12 is contained at a ratio of 0.001 to 0.5 parts by weight, and is bonded to a polarizing plate subjected to AG treatment A load of 500 g is applied to the surface protective film for a polarizing plate cut into dimensions of 25 mm wide × 35 mm long, and released for 24 hours in an atmosphere at a temperature of 23 ° C. It is a surface protection film for a polarizing plate characterized by having no shift in a shear holding power test on a polarizing plate, which is carried out.

  (A) As the (meth) acrylic acid ester monomer having a C4 to C18 carbon number of the alkyl group, 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, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl Meta) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate, isomyristyl (meth) acrylate, cetyl (meth) acrylate, isocetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate etc. Be

(B) As a copolymerizable monomer containing a hydroxyl group, 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate And hydroxy-containing (meth) acrylamides such as N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide and the like.
8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) It is preferable that it is at least 1 sort (s) or more selected from the compound group which consists of acrylamide and N- hydroxyethyl (meth) acrylamide.
(B) At least one copolymerizable monomer having a hydroxyl group (B) with respect to a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having (C) alkyl group of C4 to C18 The total of the above is preferably contained in the proportion of 2 to 10 parts by weight, more preferably 3.5 to 10 parts by weight, and particularly preferably 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) acryloyloxyethyl hexahydrophthalic acid, 2 -(Meth) acryloyloxypropylhexahydrophthalic acid, 2- (Meth) acryloyloxyethyl phthalic acid, 2- (Meth) acryloyloxyethylsuccinic acid, 2- (Meth) acryloyloxyethylmaleic acid, carboxy It is preferable that it is at least 1 or more types selected from the compound group which consists of a polycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxy ethyl tetrahydro phthalic acid.
(C) at least one copolymerizable monomer containing a carboxyl group with respect to 100 parts by weight in total of at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18 It is preferable to contain the total of species or more in a proportion of 0.05 to 0.3 parts by weight, more preferably in a proportion of 0.05 to 0.25 parts by weight, 0.05 to 0.2 parts by weight It is particularly preferable to contain in the proportion of parts.

(D) The polyalkylene glycol mono (meth) acrylic acid ester monomer may be a compound in which one hydroxyl group is esterified as a (meth) acrylic acid ester among a plurality of hydroxyl groups possessed by the polyalkylene glycol. Since the (meth) acrylic ester group becomes a polymerizable group, it can be copolymerized with the main agent polymer. The other hydroxyl group may be OH as it is, and may be an alkyl ether such as methyl ether or ethyl ether, or a saturated carboxylic acid ester such as acetic acid ester.
As an alkylene group which polyalkylene glycol has, although an ethylene group, a propylene group, a butylene group etc. are mentioned, it is not limited to these. The polyalkylene glycol may be a copolymer of two or more polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol. Examples of the polyalkylene glycol copolymer include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol and the like, and the copolymer is It may be a block copolymer or a random copolymer.

  The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer preferably has an average repeating number of 3 to 14 of alkylene oxide constituting a polyalkylene glycol chain. The “average number of repetitions of alkylene oxide” is the average number of repeating alkylene oxide units in the “polyalkylene glycol chain” portion included in the molecular structure of (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is there.

(D) As the polyalkylene glycol mono (meth) acrylic acid ester monomer, the diester content in the monomer is 0.2% or less, the water content is 0.1% or less, and the solubility in water is The haze value in a 20% aqueous solution state is preferably 2% or less.
The "diester component 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 "water 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 the aqueous solution in the state where a 20% by weight aqueous solution of (D) polyalkylene glycol mono (meth) acrylate monomer is used. That is, (D) the polyalkylene glycol mono (meth) acrylic acid ester monomer not only has water solubility (solubility in water) to be a 20% aqueous solution but also has a low haze value (%) in a 20% aqueous solution Needs (less whitening).
In the present specification, the haze value of a 20% aqueous solution is a value measured by a haze meter by placing the aqueous solution in a quartz cell with an optical path length of 10 mm. This indicator is introduced to select a highly hydrophilic monomer which can obtain a solution free of white turbidity even at high concentration as the degree of hydrophilicity of (D) polyalkylene glycol mono (meth) acrylic acid ester monomer It is.

(D) As the polyalkylene glycol mono (meth) acrylic acid ester monomer, from the compound group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate and ethoxypolyalkylene glycol (meth) acrylate It is preferable that it is at least one or more 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, methoxy polybutylene 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-polyethylene glycol-polypropylene glycol-polybutylene glycol -(Meth) acrylate; ethoxy polyethylene glycol-(meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, ethoxy polybutylene glycol (meth) 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 - such as (meth) acrylate.

  (D) At least one of (C) polyalkylene glycol mono (meth) acrylic acid ester monomers with respect to a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having C4 to C18 alkyl group carbon atoms It is preferable to contain the total of 1 or more types in the ratio of 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 may further contain at least one of a nitrogen-containing vinyl monomer (R) not containing a hydroxyl group (E) or an alkoxy group-containing alkyl (meth) acrylate monomer. Among (E), as the (E-1) nitrogen-containing vinyl monomer, a vinyl monomer containing an amide bond, a vinyl monomer containing an amino group, a vinyl monomer having a nitrogen-containing heterocyclic structure and the like can be mentioned. More specifically, N-vinyl-2-pyrrolidone, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrazine, 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-vinyl lauryl lactam; Meth) acryloyl morpholine, N- (meth) acryloyl piperazine, N- (meth) acryloyl aziridine, N- (meth) acryloyl azetidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl piperidine, N- (meth) ) Acryloyl azepane, N-(Meta) a Cyclic nitrogen vinyl compounds having an N- (meth) acryloyl-substituted heterocyclic structure such as lyoylazocan; and heterocyclic rings having a nitrogen atom and an ethylenically unsaturated bond such as N-cyclohexyl maleimide, N-phenyl maleimide, etc. in the ring Cyclic nitrogen vinyl compounds having a formula structure; unsubstituted or monoalkyl-substituted (meth) acrylamides such as (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-butyl (meth) acrylamide ) Acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide , N-ethyl-N-methyl (meth) group N-methyl-N-propyl (meth) acrylamide, N-methyl-N-isopropyl (meth) acrylamide and like dialkyl substituted (meth) acrylamides; 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 Ta) Dialkylamino (meth) acrylates such as acrylate, N, N-dibutylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, etc .; 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 and the like; N-vinylformamide, N-vinylaceto , N-vinylcarboxylic acid amides such as N-vinyl-N-methylacetamide; N-methoxymethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide And (meth) acrylamides such as N, N-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 no hydroxyl group and carboxyl group are more preferable. As such a monomer, monomers exemplified above, for example, acrylic monomers containing N, N-dialkyl-substituted amino group or N, N-dialkyl-substituted amido group; 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) acryloyl morpholine and N- (meth) acryloyl pyrrolidine are preferable.

Among (E), as the (E-2) alkoxy group-containing alkyl (meth) acrylate monomer, 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 Meta) acrylate, 3-butoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, 4-propoxybutyl (meth) acrylate, 4-isopropoxybutyl (meth) acrylate, 4-butoxybutyl (meth) acrylate etc. are mentioned.
These alkoxy group-containing alkyl (meth) acrylate monomers have a structure in which an atom of the alkyl group in the alkyl (meth) acrylate is substituted with an alkoxy group.

  (E) A nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl which does not contain a hydroxyl group (E) with respect to a total of 100 parts by weight of at least one or more kinds of (meth) acrylate monomers having C4 to C18 carbon atoms It is preferable to contain the total of at least one or more of (meth) acrylate monomers in a proportion of 0.1 to 20 parts by weight, and more preferably 0.3 to 10 parts by weight, and 0.3 to 30 parts by weight. It is particularly preferable to contain 8 parts by weight. The nitrogen-containing vinyl monomer (E-1) having no hydroxyl group and the (E-2) alkoxy group-containing alkyl (meth) acrylate monomer may be used alone 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 to 12. Polyether-modified siloxane compound is a siloxane compound having a polyether group, in addition to the normal siloxane units [-SiR ¹ ₂ -O-], siloxane units having polyether groups [-SiR ^{1 (R} 2 O ( R ³ O) _n R ⁴ ) -O-]. Here, R ¹ represents one or more alkyl groups or aryl groups, R ² and R ³ represent one or more alkylene groups, R ⁴ represents one or more alkyl groups or an acyl group Etc. (terminal group). Polyether group includes polyoxyalkylene groups such as polyoxyethylene group [(C ₂ H ₄ O) _n ] and polyoxypropylene group [(C ₃ H ₆ O) _n ].

  (A) A polyether-modified siloxane compound having an HLB value of 7 to 12 with respect to a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18 It is preferable to contain at least one or more of the total 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, for example, a hydrophilic / lipophilic balance (hydrophilic / lipophilic ratio) defined in JIS K 3211 (term of surfactant) or the like.

  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) A siloxane polymer etc. are mentioned. The HLB value of the polyether-modified siloxane compound can be adjusted by selecting the ratio of the polyether group to the siloxane group. (F) The adhesion and rework performance of the pressure-sensitive adhesive can be improved by blending a polyether-modified siloxane compound having an HLB value of 7 to 12 into the pressure-sensitive adhesive composition.

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

  As a trifunctional isocyanate compound, a biuret modified product of a bifunctional isocyanate compound (a compound having two NCO groups in one molecule), an isocyanurate modified product, a trivalent or higher trivalent compound such as trimethylolpropane (TMP) or glycerin, etc. Examples include adducts (polyol-modified products) with polyols (compounds having at least 3 or more OH groups in one molecule).

As trifunctional isocyanate compounds, isocyanurates of hexamethylene diisocyanate, isocyanurates of isophorone diisocyanate, adducts of hexamethylene diisocyanate, adducts of isophorone diisocyanate, adducts of hexamethylene diisocyanate, buret of hexamethylene diisocyanate, isophorone diisocyanate Buret body of compound, isocyanurate body of tolylene diisocyanate compound, isocyanurate body of xylylene diisocyanate compound, isocyanurate body of hydrogenated xylylene diisocyanate compound, adduct body of tolylene diisocyanate compound, adduct body of xylylene diisocyanate compound, Compounds consisting of adducts of hydrogenated xylylene diisocyanate compounds Selected from in, it is preferably at least 1 or more.
(A) The total of at least one trifunctional isocyanate compound is 0.1 for a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having a C4 to C18 alkyl group carbon number It is preferable to contain by the ratio of -10 weight part, and it is more preferable to contain by the ratio of 0.1-6 weight part.

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

The 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 bonded to the metal atom M. For example, when 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 X may be the same ligand or different ligands.

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

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

Examples of the organic tin compound include dialkyl tin oxide, fatty acid salts of dialkyl tin, and fatty acid salts of stannous tin.
The crosslinking catalyst is preferably a metal chelate compound or an organotin compound. As a metal chelate compound, an aluminum chelate compound, a titanium chelate compound, an iron chelate compound, a tin chelate compound, etc. are preferable. The organic tin compound is preferably at least one selected from the group consisting of dioctyl tin oxide and dioctyl tin dilaurate.
(A) The total of at least one or more crosslinking catalysts is 0.001 to 0 with respect to a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18. It is preferable to contain in the ratio of 5 weight part.

Examples of keto-enol tautomeric compounds include β-keto esters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, stearyl acetoacetate, acetylacetone, 2,4-hexanedione, benzoylacetone And β-diketones. In the pressure-sensitive adhesive composition using a polyisocyanate compound as a crosslinking agent, the keto-enol tautomer compound blocks the isocyanate group possessed by the crosslinking agent, thereby causing an excessive increase in viscosity of the pressure-sensitive adhesive composition after compounding the crosslinking agent or It is possible to suppress gelation and extend the pot life of the pressure-sensitive adhesive composition.
The keto-enol tautomeric compound is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate.
(A) The total of at least one or more kinds of keto enol tautomer compounds is 0. 0 to a total of 100 parts by weight of at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18. It is preferable to contain in the ratio of 1-300 weight part, and the ratio of 1.0-30.0 weight part is more preferable.

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

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

  (J) As an antistatic agent, the ionic compound solid at 25 degreeC of 25-50 degreeC of melting | fusing point contained in an adhesive composition is mentioned.

The ionic compound which is solid at 25 ° C. and has a melting point of 25 to 50 ° C. is an ionic compound having a cation and an anion, and the cation is pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, Nitrogen-containing onium cations such as pyrrolidinium cation and ammonium cation, phosphonium cation and sulfonium cation etc., and the anion is hexafluorophosphate (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), alkylbenzene sulfonic acid Salt (RC ₆ H ₄ SO ₃ ⁻ ), Perchlorate (ClO ₄ ⁻ ), Tetrafluoroborate (BF ₄ ⁻ ), Bis (fluorosulfonyl) imide salt (FSI), Bis (trifluoromethanesulfonyl) Imide salt (TFSI), trifluoromethane sulfonate (T ) Inorganic or compound which is an organic anions such. It is preferably solid at normal temperature (for example, 25 ° C.), and one having a melting point of 25 to 50 ° C. can be obtained by selecting the chain length of the alkyl group, the position of the substituent, the number and the like. The cation is preferably a quaternary nitrogen-containing onium cation, and is a quaternary pyridinium cation such as 1-alkylpyridinium (the carbon atoms at positions 2 to 6 may have a substituent or may not be substituted), or 1, Quaternary imidazolium cations such as 3-dialkylimidazolium (the carbon atoms at positions 2, 4 and 5 may have a substituent or not) and quaternary ammonium cations such as tetraalkyl ammonium and the like can be mentioned. .
(A) A solid ionic compound having a melting point of 25 to 50 ° C. and a solid temperature of 25 ° C. relative to a total of 100 parts by weight of at least one or more kinds of (meth) acrylate monomers having an alkyl group of C4 to C18 It is preferable to contain at least one or more of the total in a proportion of 0.01 to 5.0 parts by weight.

  Specific examples of the antistatic agent (J) are not particularly limited, and specific examples of the ionic compound solid at 25 ° C. and having a melting point of 25 to 50 ° C. include, for example, 1-octylpyridinium hexafluoride Phosphate, 1-nonyl pyridinium hexafluorophosphate, 2-methyl-1-dodecyl pyridinium hexafluorophosphate, 1-octyl pyridinium dodecyl benzene sulfonate, 1-dodecyl pyridinium thiocyanate, 1- Examples include dodecyl pyridinium dodecyl benzene sulfonate, 4-methyl-1-octyl pyridinium hexafluorophosphate and the like.

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

The acrylic polymer used in the pressure-sensitive adhesive composition of the present invention is a copolymer containing (A) at least one or more kinds of (meth) acrylic acid ester monomers having an alkyl group of C4 to C18 and (B) a hydroxyl group. It consists of a copolymer obtained by copolymerizing at least one or more of a polymerizable monomer and at least one or more of a (C) carboxyl group-containing copolymerizable monomer. In addition, the acrylic polymer is at least one kind of (A) alkyl group, at least one kind of (meth) acrylic acid ester monomer having C4 to C18 carbon number, and (B) at least one kind of copolymerizable monomer containing a hydroxyl group. And (C) at least one or more of copolymerizable monomers having a carboxyl group, (D) at least one of polyalkylene glycol mono (meth) acrylate monomers, and (E) no hydroxyl group It may be a copolymer obtained by copolymerizing at least one or more of a nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer. The polymerization method of the acrylic polymer is not particularly limited, and appropriate polymerization methods such as solution polymerization and emulsion polymerization can be used.
The pressure-sensitive adhesive composition of the present invention further comprises (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, a trifunctional isocyanate compound as a crosslinking agent, and the above-mentioned acrylic polymer as an antistatic agent. It can be prepared by blending an ionic compound which is solid at 25 ° C. and a melting point of 25 to 50 ° C., and further, an optional additive.

At the time of production of the acrylic polymer, in order to reduce the mixing of water into the adhesive composition, it is preferable to carry out the polymerization reaction under anhydrous conditions such as solution polymerization using an anhydrous organic solvent. In particular, since the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is high in hydrophilicity, it is preferable to use one having a low water content.
Each monomer used in the preparation of the main component acrylic polymer can minimize the amount of polyfunctional (difunctional or higher) monomer capable of functioning as a crosslinking agent in order to avoid the viscosity increase of the pressure-sensitive adhesive composition. It is preferable to reduce. In particular, as the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, since the corresponding diester is a di (meth) acrylic acid ester of a difunctional monomer, it is preferable to use one having a low diester content.

The acrylic polymer comprises 50 to 100 parts by weight of (meth) acrylic acid ester monomer, (meth) acrylic acid, acrylic monomers such as (meth) acrylamides, etc., per 100 parts by weight of the acrylic polymer. It is preferable to include in proportion.
The acid value of the acrylic polymer is preferably 0.01 to 8.0. As a result, the stain resistance can be improved, and the adhesive residue generation performance can be improved.
Here, the "acid value" is one of the indices representing the content of the acid, and is represented by the number of mg of potassium hydroxide required to neutralize 1 g of the polymer containing a carboxyl group.

  The adhesion of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition to the polarizing plate is such that the adhesion at a low peeling speed of 0.3 m / min is 0.04 to 0.2 N / 25 mm, and is high speed The adhesion at a peeling speed of 30 m / min is preferably 2.0 N / 25 mm or less. This makes it possible to obtain a performance in which the adhesive strength is less changed even by the peeling speed, and it is possible to peel rapidly even by high-speed peeling. In addition, even when the surface protective film is once peeled off for re-sticking, it does not require an excessive force and is easily peeled off from the adherend.

The surface resistivity of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition is preferably 9.0 × 10 ⁺¹¹ Ω / □ or less, and the peeling voltage is preferably ± 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 large, the performance to release the static electricity generated by charging during peeling is inferior. For this reason, by making the surface resistivity sufficiently low, the peeling-off voltage generated with the static electricity generated when the adherend peels off the pressure-sensitive adhesive layer is reduced, which affects the electric control circuit of the adherend, etc. Can be suppressed.

  The gel fraction of the pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition is preferably 95 to 100%. Thus, by virtue of the high gel fraction, the adhesion does not become excessive at a low peeling speed, and the elution of the unpolymerized monomer or oligomer from the acrylic polymer is reduced, and reworkability and high temperature / high humidity are achieved. Durability is improved, and contamination of the adherend can be suppressed.

  A pressure-sensitive adhesive film is obtained by forming a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one side or both sides of a resin film. Moreover, the surface protective film for polarizing plates of this invention is a surface protective film in which the adhesive layer which bridge | crosslinked the said adhesive composition is formed in the single side | surface of a resin film. The surface protective film for a polarizing plate of the present invention has no displacement in a shear holding power test when it is bonded to a polarizing plate, and it has good adhesion to the polarizing plate despite its small adhesive strength, durability, and rework And excellent in antistatic performance. For this reason, it can be conveniently used as a use of the surface protection film of a polarizing plate. As a polarizing plate, glare, plane (general purpose), anti-glare (AG) etc. are mentioned. As a protective film material of the surface of a polarizing plate, a TAC system film (a triacetyl cellulose type compound), an acrylic film, etc. are mentioned.

  As a test condition of the shear holding power, for example, a load (weight of weight) 500 g, an environmental temperature of 23 ° C., and a standing time of 24 hours may be mentioned. This test condition is suitable as a judgment guideline that the adhesion of the surface protective film to the polarizing plate is good. As a contact area (dimension) of the surface protection film for polarizing plates with respect to the polarizing plate which is a to-be-adhered body of a shear holding strength test, 25 mm x 35 mm is mentioned. The details (apparatus etc.) of the test method 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 a resin film as a base material of the pressure-sensitive adhesive layer, or as a peeling film (separator) for protecting the adhesive surface.
The resin film as the base material is a resin film on the side opposite to the side on which the pressure-sensitive adhesive layer is formed, and the antifouling treatment with silicone type, fluorine type mold release agent or coating agent, silica fine particles, etc., antistatic agent Can be subjected to antistatic treatment by coating or kneading.
The release film is subjected to a release treatment with a silicone-based or fluorine-based release agent or the like on the side of the release film to be combined with the adhesive surface of the pressure-sensitive adhesive layer.

  Hereinafter, the present invention will be specifically described by way of 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 air in the reactor with nitrogen gas. Thereafter, in a reaction apparatus, 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 repeating number of alkylene oxide constituting polyalkylene glycol chain) n = 12, the diester content in the monomer is 0.1%, the solubility in water is 20%, the haze value in an aqueous solution state is 0.8%, the water content is 0.05%), 8 parts by weight, N− 60 parts by weight of a solvent (ethyl acetate) was added together with 1 part by weight of vinyl pyrrolidone. Thereafter, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator is dropped over 2 hours, reacted at 65 ° C. for 6 hours, and an acrylic polymer solution used in Example 1 having a weight average molecular weight of 500,000. Obtained. A part of the acrylic polymer was collected and used as a measurement sample of the acid value described later.
[Examples 2 to 8 and Comparative Examples 1 to 4]
Examples 2 to 8 and comparison are the same as the acrylic polymer solution used in Example 1 above except that the composition of the monomers is as described in Table 1 (A) to (E) respectively. The acrylic polymer solution used in Examples 1 to 4 was obtained.

<Production of Pressure-Sensitive Adhesive Composition and Surface Protective Film>
Example 1
0.05 parts by weight of a polyether-modified siloxane compound (HLB value: 7) and 1.0 parts by weight of 1-octylpyridinium hexafluorophosphate with respect to the acrylic polymer solution of Example 1 produced as described above, After adding 8.5 parts by weight of acetylacetone and stirring, 4.0 parts by weight of Coronate HX (isocyanurate of hexamethylene diisocyanate compound) and 0.1 parts by weight of titanium trisacetylacetonate are added and mixed by stirring. The adhesive composition of The pressure-sensitive adhesive composition is applied onto a release film made of a silicone resin-coated polyethylene terephthalate (PET) film and then dried at 90 ° C. to remove the solvent, and the pressure-sensitive adhesive layer has a thickness of 25 μm. I got a sheet.
After that, the adhesive sheet is transferred on one surface opposite to the antistatic and antifouling treated surface of the polyethylene terephthalate (PET) film which has been subjected to antistatic and antifouling treatment, and the antistatic and antifouling treatment is performed. The surface protection film of Example 1 which has a laminated structure of “PET film / adhesive layer / release film (PET film coated with silicone resin)” was obtained.
[Examples 2 to 8 and Comparative Examples 1 to 4]
Examples 2 to 8 and Comparative Examples 1 to 4 are the same as the surface protection film of Example 1 except that the composition of the additive is as described in Table 2 (F) to (J), respectively. A surface protection film of 4 was obtained.

In Tables 1 and 2, the compounding ratio of each component is shown in parentheses with the numerical value of the part by weight determined based on 100 parts by weight of the total of the group (A).
In addition, the compound names of the abbreviations of the respective components used in Tables 1 and 2 are shown in Tables 3 and 4. 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, D-120N are Mitsui Chemical Co., Ltd. It is a trade name of the company. In the group (D) of Table 3, the numerical value of "n" is the average number of repetitions of alkylene oxide constituting the polyalkylene glycol chain. The numerical value of "diester" is the diester content (%) in the monomer. The numerical value of "water" is the water content (%). The numerical value of "haze" is the haze value (%) in a 20% aqueous solution state.

<Test method and evaluation>
The surface protective films in Examples 1 to 8 and Comparative Examples 1 to 4 are aged for 7 days in an atmosphere of 23 ° C. and 50% RH, and then the release film (PET film coated with silicone resin) is peeled off to obtain an adhesive The exposed layer was used as a measurement sample of gel fraction and surface resistivity.
Furthermore, the surface protection film in which the pressure-sensitive adhesive layer is exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell through the pressure-sensitive adhesive layer, and left for 1 day. A sample subjected to an autoclave treatment and left at room temperature for a further 12 hours was used as a measurement sample of the adhesive strength, peel voltage, shear holding power (displacement), reworkability and durability. The polarizing plate of the adherend is a polarizing plate whose surface is subjected to an AG treatment.

<Gel fraction>
After the end of aging, the mass of the pressure-sensitive adhesive layer separated from the measurement sample before bonding to the polarizing plate is accurately measured, and after being immersed in toluene for 24 hours, it is filtered through a 200 mesh wire mesh. Thereafter, the filtrate was dried at 100 ° C. for 1 hour, and then the mass of the residue was accurately measured, and the gel fraction of the pressure-sensitive adhesive layer (pressure-sensitive adhesive layer after crosslinking) was calculated from the following formula.
Gel fraction (%) = insoluble part mass (g) / mass of adhesive layer (g) x 100

<Adhesiveness>
Using a tensile tester in the direction of 180 °, the measurement sample obtained above (a 25 mm wide surface protection film attached to the surface of an AG-treated polarizing plate) was peeled off at a low speed using a tensile tester ( Peeling was performed at 0.3 m / min) and a high-speed peeling speed (30 m / min), and the measured peeling strength was taken as the adhesive strength (N / 25 mm).

<Surface resistivity>
After aging, before bonding to a polarizing plate, the release film (PET film coated with silicone resin) is peeled off to expose an adhesive layer, and using a resistivity meter HIRESTA UP-HT450 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) The surface resistivity (Ω / □) of the pressure-sensitive adhesive layer was measured.

<Peeling voltage>
When the measurement sample obtained above is peeled 180 ° at a tensile speed of 30 m / min, the voltage (voltage drop) generated by charging the polarizing plate whose surface is subjected to AG treatment is a high accuracy electrostatic sensor SK It measured using-035 and SK-200 (made by Keyence, Inc.), and made the maximum value of the measured value the peeling zone voltage (kV).
<Shear holding power to polarizing plate>
The surface protection film (pressure-sensitive adhesive layer thickness is 20 μm) cut into dimensions of 25 mm in width × 35 mm in length is attached to the polarizing plate subjected to AG treatment on the surface, and 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 after left for 24 hours was measured.

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

<Durability>
The measurement sample obtained above is left at room temperature for 250 hours under an atmosphere of 60 ° C., 90% RH, taken out to room temperature, and left for a further 12 hours, after which the adhesive strength is measured and it is clear compared with the initial adhesive strength. It confirmed that there was no increase. Evaluation target criteria evaluated the case where the adhesive force after a test is 1.5 times or less of initial stage adhesive force as "(circle)", and the case where it exceeded 1.5 times as "x".

Table 5 shows the evaluation results. The surface resistivity is represented by a method in which “m × 10 ^{+ n} ” is “mE + n” (where, m is an arbitrary real number and n is a positive integer).
Moreover, the shift described in Table 5 indicates the measured value of the shift (mm) of the surface protective film in the test of the shear holding power to the polarizing plate.

The surface protective films of Examples 1 to 8 have a tackiness of 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min with respect 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 voltage is ± 0 to 0.5 kV, and the load is 500 g There is no shift in the shear holding power test after standing at 23 ° C for 24 hours, and after the surface protection film is traced with a ballpoint pen through the adhesive layer, there is no migration of contamination on the adherend, 60 ° C, 90% RH The durability was also excellent when left for 250 hours under the atmosphere.
That is, (1) the adhesion to the polarizing plate is good despite the small adhesive strength, (2) durability, (3) reworkability, and (4) excellent antistatic performance, all the required performances, I am satisfied at the same time.

  In the surface protection film of Comparative Example 1, the copolymerizable monomer containing (C) a carboxyl group is excessive, and the acrylic polymer does not contain the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, and adhesion is Agent composition does not contain (F) a polyether-modified siloxane compound having an HLB value of 7 to 12, (G) a trifunctional isocyanate compound is too small, and (J) does not contain an antistatic agent. The adhesion at a high peeling speed of 30 m / min, with a peeling speed of 0.3 m / min, is too large, the surface resistivity and peeling band voltage are high, there is a gap in the shear holding power test, reworkability and durability It was inferior.

  The surface protection film of Comparative Example 2 has a small amount of (C) carboxyl group-containing copolymerizable monomer, a large amount of diester of (D) polyalkylene glycol mono (meth) acrylate monomer, and a moisture content Is low, the solubility in water is low, and the HLB value of the (F) polyether-modified siloxane compound is too high, so the adhesion 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 the peeling electrostatic voltage were high, there was a gap in the shear retention test, and the durability was inferior.

  In the surface protection film of Comparative Example 3, the acrylic polymer does not contain the copolymerizable monomer containing (B) a hydroxyl group, and (C) the copolymerizable monomer containing a carboxyl group is excessive, (D) Peeling at high speed with a low peeling rate of 0.3 m / min, with a low gel fraction due to the high content of diester of polyalkylene glycol mono (meth) acrylic acid ester monomer, high water content and low water solubility The adhesion at a speed of 30 m / min was very large, and even if the surface resistivity was low, the peel voltage was high and the reworkability was inferior.

  In the surface protective film of Comparative Example 4, the HLB value of the (F) polyether-modified siloxane compound was too large, and there was a gap in the shear retention test.

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

  The surface protective film for polarizing plate according to the present invention is a problem of the prior art, and when the surface protective film is easily peeled off from the adherend by reducing the adhesive force of the pressure-sensitive adhesive layer, the surface protective film for polarizing plate Since the adhesion is reduced, the surface protective film may be peeled off at the end of the polarizing plate when the size of the polarizing plate is increased as compared to the prior art along with the enlargement of the liquid crystal display. Industrial use value is great because it

Claims (3)

A surface protective film for polarizing plate, wherein an adhesive layer obtained by crosslinking an adhesive composition containing an acrylic polymer, a crosslinking agent, and an antistatic agent is formed on one side of a resin film,
The acrylic polymer is
(A) 100 parts by weight of a total of at least one or more of (meth) acrylic acid ester monomers having a C4 to C18 carbon number of an alkyl group,
(B) 2 to 10 parts by weight of a total of at least one or more kinds of copolymerizable monomers containing a hydroxyl group,
(C) 0.05 to 0.3 parts by weight of a total of at least one or more copolymerizable monomers containing a carboxyl group,
(D) 3 to 40 parts by weight of a total of at least one or more kinds of polyalkylene glycol mono (meth) acrylic acid ester monomers,
(E) 0.1 to 20 parts by weight of a total of at least one or more of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer,
And a copolymer obtained by copolymerizing
The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate and ethoxypolyalkylene glycol (meth) acrylate. The average repetition number of the selected alkylene oxide constituting the polyalkylene glycol chain is 3 to 14, the diester content in the monomer is 0.2% or less, and the water content is at least 0. 1% or less, and the solubility in water is 2% or less in terms of the haze value in a 20% aqueous solution state,
The crosslinker is a trifunctional isocyanate compound,
The pressure-sensitive adhesive composition has a melting point as the antistatic agent with respect to 100 parts by weight in total of at least one or more kinds of (meth) acrylic acid ester monomers having (C) alkyl group of C4 to C18. The ionic compound solid at 25 ° C. to 25 ° C. and containing 0.01 to 5.0 parts by weight of the ionic compound,
The pressure-sensitive adhesive composition further has a (F) HLB value relative to a total of 100 parts by weight of at least one or more of (meth) acrylic acid ester monomers having C4 to C18 carbon atoms of the (A) alkyl group. A total of at least one or more of 7 to 12 polyether-modified siloxane compounds is contained in a proportion of 0.001 to 0.5 parts by weight,
A load of 500 g is applied to the surface protective film for a polarizing plate cut to dimensions of 25 mm wide × 35 mm long bonded to a polarizing plate subjected to AG treatment, and left for 24 hours in an atmosphere at a temperature of 23 ° C. A surface protective film for a polarizing plate characterized in that there is no deviation in a shear holding power test for the polarizing plate. The (B) hydroxyl group-containing copolymerizable monomer is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate At least one selected from the group consisting of N-hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide,
The (C) carboxyl group-containing copolymerizable monomer is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxypolycaprolactone mono (meth) acrylate, 2- (meth) acryloyloxyethyl selected from among the group of compounds consisting of ethyl tetrahydrophthalic acid, polarization according to claim 1, characterized in that at least one Surface protection film for boards. The surface protection film for polarizing plates of Claim 1 or 2 in which the antistatic process and the antifouling | stain-resistant process are carried out on the opposite side to the side in which the said adhesive layer was formed in the single side | surface of the said resin film.