JP6926264B2 - Surface protective film for polarizing plates that has been subjected to AG treatment - Google Patents

Description

The present invention relates to a surface protective film for a polarizing plate. More specifically, at low-speed peeling speed and high-speed peeling speed, the balance of adhesive strength is excellent, and despite the low adhesive strength, the adhesion to the polarizing plate is excellent, and durability, reworkability, and antistatic performance are excellent. Also related to an excellent surface protective film for polarizing plates.

Conventionally, in the manufacturing process of optical members such as polarizing plates and retardation plates, which are members constituting a liquid crystal display, a surface protective film for temporarily protecting the surface of the optical members 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 and removed when the optical member is incorporated into the liquid crystal display. Since such a surface protective film for protecting the surface of the optical member is used only in the manufacturing process, it is also generally called a process film.

The surface protective film used in the process of manufacturing the optical member in this way has an adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film, and is bonded to the optical member. Up to, a release-treated release film for protecting the pressure-sensitive adhesive layer is bonded onto the pressure-sensitive adhesive layer.
In addition, optical members such as polarizing plates and retardation plates are inspected with optical evaluations such as the display capacity, hue, contrast, and foreign matter contamination of the liquid crystal display plate with the surface protective film attached. As the required performance of the surface protective film, it is required that no air bubbles or foreign substances adhere to the pressure-sensitive adhesive layer.
Further, 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 generated by the static electricity generated when the adherend peels off the adhesive layer is electrically controlled by the liquid crystal display. There is concern that it may affect circuit failure, and excellent antistatic performance is required for the adhesive layer.
Further, when the 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 reattached for various reasons. It is required that it be easily peeled off from the optical member of the adherend (reworkability).
Further, 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 to be able to peel off quickly. It is required that the adhesive strength does not change much depending on the peeling speed so that the peeling can be performed quickly even by so-called high-speed peeling.

As described above, in recent years, as the required performance for the pressure-sensitive adhesive layer constituting the surface protective film, (i) balancing the adhesive strength at a low peeling speed and a high peeling speed, (ii) excellent. Antistatic performance, (iii) reworkability, etc. are required from the viewpoint of ease of use when using the surface protective film.

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

An acrylic pressure-sensitive adhesive whose main component is a copolymer of a (meth) acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymer compound, which is crosslinked with a crosslinking agent. In the layer, there is a problem that the adhesive is transferred to the adherend side when the adhesive is adhered for a long period of time, and the adhesive force to the adherend is greatly increased 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 copolymer compound having an alcoholic hydroxyl group was used, and this was crosslinked with a crosslinking agent. Those provided with an adhesive layer are known (Patent Document 1).
Further, a copolymer of 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 copolymer, and a pressure-sensitive adhesive layer obtained by cross-linking the copolymer with a cross-linking agent is provided. Etc. have been proposed. However, when these are used to protect the surface of plastic plates with low surface tension and a smooth surface, there is a problem that peeling phenomena such as floating occur due to heating during processing and storage, and at high speeds, which is a manual work area. There is also a problem that the re-peelability at the time of peeling is inferior.

In order to solve these problems, a) 100 parts by weight of a (meth) acrylic acid alkyl ester containing a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms as a main component, b) a carboxyl group is contained. The above b is added to a 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. A pressure-sensitive adhesive composition in which an equivalent amount or more of a cross-linking agent is added to the carboxyl group of the component) has been proposed (Patent Document 2).
The pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as floating during processing or storage, and also has a small adhesive strength with time and is excellent in re-peelability, and is stored for a long period of time. In particular, even if it is stored for a long period of time in a high temperature atmosphere, it can be re-peeled with a small force, and at that time, no adhesive residue is generated on the adherend, and even when high-speed peeling is performed, it can be re-peeled with a small force.

Further, regarding (ii) excellent antistatic performance, a method of kneading an antistatic agent into the base film is shown as a method for imparting antistatic performance to the surface protective film. Examples of the antistatic agent include (a) various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and a primary to tertiary amino group, and (b) a sulfonic acid base and a sulfuric acid. Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases, and phosphonic acid bases, (c) amphoteric antistatic agents such as amino acid-based and aminosulfate-based, (d) aminoalcohol-based, and glycerin-based. , Nonionic antistatic agents such as polyethylene glycol type, (e) high molecular weight antistatic agents obtained by increasing the molecular weight of the above antistatic agents, and the like are disclosed (Patent Document 3).
Further, in recent years, it has been proposed that such an antistatic agent is contained in the base film, or is directly contained in the pressure-sensitive adhesive layer instead of being applied to the surface of the base film.

Regarding (iii) reworkability, for example, a pressure-sensitive adhesive in which an isocyanate-based compound curing agent and a specific silicate oligomer are mixed in an acrylic resin in an amount of 0.0001 to 10 parts by weight based on 100 parts by weight of the acrylic resin. Agent compositions have 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, a methacrylate alkyl ester having an alkyl group having about 4 to 12 carbon atoms, or the like is used as a main monomer component, and for example, a carboxyl group-containing monomer or the like. Other functional group-containing monomer components can be included. Generally, it is preferable to contain the above main monomer in an amount of 50% by weight or more, 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 0.001 to 25% by weight. It is said that it is desired to be 0.01 to 25% by weight. The pressure-sensitive adhesive composition described in Patent Document 4 has a small change in cohesive force and adhesive force with time even under high temperature or high temperature and high humidity, and exhibits an excellent effect on the adhesive force on a curved surface. It is said to have reworkability.
In general, when the pressure-sensitive adhesive layer has a soft property, adhesive residue is likely to occur, and the reworkability is likely to decrease. That is, when they are attached by mistake, they are difficult to peel off, and it is easy to reattach them. From this, it is considered necessary to crosslink a monomer having a functional group such as a carboxyl group with the main agent to make the pressure-sensitive adhesive layer have a certain hardness in order to have reworkability.

Japanese Unexamined Patent Publication No. 63-225677 Japanese Unexamined Patent Publication No. 11-256111 Japanese Unexamined Patent Publication No. 11-070629 Japanese Unexamined Patent Publication No. 8-199130

In recent years, the screen size of various displays such as liquid crystal displays has been rapidly increasing. However, with the increase in the screen size of the liquid crystal display, a new problem has arisen in the process of manufacturing the member of the liquid crystal display. For example, the following problems have arisen with respect to a surface protective film for a polarizing plate, which is attached to the surface of the polarizing plate to protect the polarizing plate.
In the prior art, in the manufacturing process of a polarizing plate which is a member of a liquid crystal display, when the surface protective film is attached to a polarizing plate which is an adherend and then the surface protective film is peeled off from the polarizing plate, there is a demand for easy peeling. 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 force of the pressure-sensitive adhesive layer is reduced so that the surface protective film can be easily peeled off from the adherend, the adhesion of the surface protective film to the polarizing plate is reduced. When the size of the polarizing plate is increased as compared with the conventional one, there is a problem that the surface protective film is peeled off at the end portion 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 a low peeling speed and a high peeling speed, and has a good adhesive force to a polarizing plate even though the adhesive force is small. Therefore, it is an object of the present invention to provide a surface protective film for a polarizing plate having excellent durability, reworkability, and antistatic performance.

In order to solve the above problems, in the present invention, a polarizing agent 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. A surface protective film for plates, wherein the acrylic polymer contains at least one (A) alkyl group (meth) acrylic acid ester monomer having C4 to C18 carbon atoms and (B) a hydroxyl group. At least one or more polymerizable monomers, (C) at least one copolymerizable monomer containing a carboxyl group, and (D) at least one polyalkylene glycol mono (meth) acrylic acid ester monomer. And (E) a copolymer obtained by copolymerizing at least one of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer, and the cross-linking agent is a trifunctional isocyanate. It is a compound, and 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, having a width of 25 mm ×. The surface protective film for a polarizing plate 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 at a temperature of 23 ° C.. Provided is a surface protective film for a polarizing plate.

Further, the present invention is a surface protective film for a polarizing plate, wherein 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 100 parts by weight and (B) a hydroxyl group in total of at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C4 to C18 carbon atoms. The total of at least one copolymerizable monomer is 2 to 10 parts by weight, and the total of at least one copolymerizable monomer (C) containing a carboxyl group is 0.05 to 0.3 parts by weight. And (D) at least one or more polyalkylene glycol mono (meth) acrylic acid ester monomers in total of 3 to 40 parts by weight, and (E) a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth). The cross-linking agent is a trifunctional isocyanate compound, and the pressure-sensitive adhesive composition is further composed of a copolymer obtained by copolymerizing at least one or more kinds of acrylate monomers with 0.1 to 20 parts by weight. (F) Polyether-modified siloxane having an HLB value of 7 to 12 with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C4 to C18 carbon atoms in the (A) alkyl group. A total of at least one of the compounds was contained in a proportion of 0.001 to 0.5 parts by weight, and the mixture was cut into a size of 25 mm in width × 35 mm in length, which was bonded to an AG-treated polarizing plate. A surface protective film for a polarizing plate characterized in that there is no deviation in a shear holding force test on a polarizing plate, which is carried out by applying a load of 500 g to the surface protective film for a polarizing plate and leaving it to stand for 24 hours in an atmosphere at a temperature of 23 ° C. offer.

The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is selected from a group of compounds consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. The average number of repetitions of the alkylene oxide constituting the polyalkylene glycol chain of at least one selected is 3 to 14, the diester content in the monomer is 0.2% or less, and the water content is 0. It is preferable that the haze value is 1% or less and the solubility in water is 2% or less in a 20% aqueous solution state.

The copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or 2-hydroxyethyl (meth) acrylate. , N-Hydroxy (meth) acrylamide, N-hydroxymethyl (meth) acrylamide, and N-hydroxyethyl (meth) acrylamide, which are preferably at least one selected from the group of compounds.

The copolymerizable monomer containing the (C) carboxyl group is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (Meta) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, It is preferably at least one selected from the group of compounds consisting of carboxypolycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.

The trifunctional isocyanate compound is an isocyanurate form of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct form of a hexamethylene diisocyanate compound, an adduct form of an isophorone diisocyanate compound, a bullet body of a hexamethylene diisocyanate compound, and an isophorone diisocyanate. Bullet of compound, isocyanurate of tolylene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, adduct of tolylene diisocyanate compound, adduct of xylylene diisocyanate compound, It is preferable that at least one selected from the compound group consisting of an adduct of a hydrogenated xylylene diisocyanate compound.

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

The adhesive force of the pressure-sensitive adhesive layer on the polarizing plate at a low speed of 0.3 m / min is 0.04 to 0.2 N / 25 mm, and the pressure of the pressure-sensitive adhesive layer at a high speed of 30 m / min is 2.0 N. It is preferably / 25 mm or less.

It is preferable that the surface resistivity of the pressure-sensitive adhesive layer is 9.0 × 10 ^{+ 11} Ω / □ or less, and the peeling band voltage is ± 0 to 0.5 kV.

It is preferable that one side of the resin film is subjected to antistatic treatment and antifouling treatment on the side 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 adhesive force is excellent, the adhesive force to the polarizing plate is good despite the small adhesive force, and the durability, reworkability, and charging are good. It is possible to provide a surface protective film for a polarizing plate having excellent prevention performance.

Hereinafter, the present invention will be described based on preferred embodiments.
The surface protective film for a polarizing plate of the present invention is polarized by forming 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 on one side of a resin film. A surface protective film for plates, wherein the acrylic polymer contains at least one (A) alkyl group (meth) acrylic acid ester monomer having C4 to C18 carbon atoms and (B) a hydroxyl group. At least one or more polymerizable monomers, (C) at least one copolymerizable monomer containing a carboxyl group, and (D) at least one polyalkylene glycol mono (meth) acrylic acid ester monomer. And (E) a copolymer obtained by copolymerizing at least one of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkoxy group-containing alkyl (meth) acrylate monomer, and the cross-linking agent is a trifunctional isocyanate. It is a compound, and 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 an AG-treated polarizing plate, having a width of 25 mm ×. The surface protective film for a polarizing plate 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 at a temperature of 23 ° C.. This is a surface protective film for a polarizing plate.

Further, in the surface protective film for a polarizing plate of the present invention, 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 the resin film. A surface protective film for a polarizing plate, wherein the acrylic polymer has 100 parts by weight in total of at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C4 to C18 carbon atoms. The total of (B) at least one copolymerizable monomer containing a hydroxyl group is 2 to 10 parts by weight, and the total of (C) at least one copolymerizable monomer containing a carboxyl group is 0. 05 to 0.3 parts by weight, 3 to 40 parts by weight of the total of at least one or more of (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, and (E) nitrogen-containing vinyl monomer containing no hydroxyl group or The cross-linking agent is a trifunctional isocyanate compound, which comprises a copolymer obtained by copolymerizing at least one or more alkoxy group-containing alkyl (meth) acrylate monomers with 0.1 to 20 parts by weight. The pressure-sensitive adhesive composition further has a (F) HLB value of 7 with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C4 to C18 carbon atoms in the (A) alkyl group. A total of at least one or more of the polyether-modified siloxane compounds of ~ 12 was contained in a proportion of 0.001 to 0.5 parts by weight, and the mixture was bonded to an AG-treated polarizing plate, having a width of 25 mm and a length of 25 mm. 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 for 24 hours in an atmosphere at a temperature of 23 ° C., which is characterized in that there is no deviation in a shear holding force test on the polarizing plate. A surface protective film for a polarizing plate.

Examples of the (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms include butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and heptyl (meth). ) 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 (meth) acrylate, octadecyl (meth) acrylate, myristyl (meth) acrylate. , Isomyristyl (meth) acrylate, cetyl (meth) acrylate, isosetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate and the like.

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

(C) Copolymerizable monomers containing a carboxyl group are (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2 -(Meta) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, carboxy It is preferably at least one selected from the group of compounds consisting of polycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.
At least one of the copolymerizable monomers containing the (C) carboxyl group with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms. The total of the seeds or more is preferably contained 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, preferably 0.05 to 0.2 parts by weight. It is particularly preferable to contain it in a proportion of parts.

The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer may be a compound in which one hydroxyl group of the plurality of hydroxyl groups of the polyalkylene glycol is esterified as a (meth) acrylic acid ester. Since the (meth) acrylic acid ester group becomes a polymerizable group, it can be copolymerized with the main polymer. The other hydroxyl group may be OH as it is, or may be an alkyl ether such as methyl ether or ethyl ether, a saturated carboxylic acid ester such as an acetate ester, or the like.
Examples of the alkylene group contained in the polyalkylene glycol include, but are not limited to, an ethylene group, a propylene group, and a butylene group. The polyalkylene glycol may be a copolymer of two or more kinds of polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of the copolymer 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.

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

The (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 state is preferably 2% or less.
The “diester content in the monomer” is the content (% by weight) of the polyalkylene glycol di (meth) acrylic acid ester contained in the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer.
The "moisture content" is the water content (% by weight) contained in the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer.
The "haze value in a 20% aqueous solution state" is a haze value (%) of the aqueous solution in a state where the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is an aqueous solution of 20% by weight. That is, the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer not only has water solubility (solubility in water) enough to be a 20% aqueous solution, but also has a low haze value (%) in the 20% aqueous solution. It needs to be (less cloudy).
In the present specification, the haze value of the 20% aqueous solution is a value measured by a haze meter in which the aqueous solution is placed in a quartz cell having an optical path length of 10 mm. This index was introduced as the degree of hydrophilicity of the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer to select a highly hydrophilic monomer capable of obtaining a solution without white turbidity even at a high concentration. Is.

The polyalkylene glycol mono (meth) acrylic acid ester monomer (D) is selected from the compound group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. It is preferably at least one 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-polyethylene glycol-polybutylene glycol-mono (meth) acrylate; methoxypolyethylene glycol- (meth) acrylate, methoxypolyethylene glycol -(Meta) acrylate, methoxypolyethylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, methoxy-polyethylene glycol-polybutylene Glycol- (meth) acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol- (meth) acrylate; ethoxypolyethylene glycol- (meth) acrylate, ethoxypolyethylene glycol- (meth) acrylate, ethoxypolybutylene glycol- (meth) Acrylate, ethoxy-polyethylene glycol-polyethylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polybutylene glycol- (meth) acrylate, ethoxy-polyethylene glycol-polypropylene glycol -Polybutylene glycol- (meth) acrylate and the like.

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

The acrylic polymer can further contain at least one of (E) a hydroxyl group-free nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl (meth) acrylate monomer. Among (E), examples of the (E-1) nitrogen-containing vinyl monomer include a vinyl monomer containing an amide bond, a vinyl monomer containing an amino group, and a vinyl monomer 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-vinylmorpholin, N-vinylcaprolactam, N-vinyllauryllolactum; Meta) acryloyl morpholine, N- (meth) acryloyl piperazine, N- (meth) acryloyl azidine, N- (meth) acryloyl azetidine, N- (meth) acryloyl pyrrolidine, N- (meth) acryloyl piperidine, N- (meta) ) Cyclic nitrogen-vinyl compounds having a heterocyclic structure of N- (meth) acryloyl substitution, such as acryloyl azepan and N- (meth) acryloyl azocan; A cyclic nitrogen-vinyl compound having a heterocyclic structure having an ethylene-based unsaturated bond in the ring; (meth) acrylamide, N-methyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-t-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, 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 (Meta) acrylate, N, N-dimethylaminobutyl (meth) acrylate, N, N-diethylaminomethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N-ethyl-N-methylaminoethyl (meth) ) Acrylic, N-methyl-N-propylaminoethyl (meth) acrylate, N-methyl-N-isopropylaminoethyl (me) Dialkylamino (meth) acrylates such as t) acrylate, 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 -(Meta) acrylamides such as methylenebis (meth) acrylamide; unsaturated carboxylic acid nitriles such as (meth) acrylonitrile; and the like.

The nitrogen-containing vinyl monomer (E-1) preferably does not contain a hydroxyl group, and more preferably does not contain a hydroxyl group or a carboxyl group. Examples of such a monomer include acrylic monomers containing the above-exemplified monomers such as 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) acryloylpyrrolidin are preferred.

Among (E), examples of the (E-2) alkoxy group-containing alkyl (meth) acrylate monomer include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and 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, 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 can be mentioned.
These alkoxy group-containing alkyl (meth) acrylate monomers have a structure in which the alkyl group atom in the alkyl (meth) acrylate is substituted with an alkoxy group.

(A) A hydroxyl group-free nitrogen-containing vinyl monomer or an alkoxy group-containing alkyl with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms. The total content of at least one (meth) acrylate monomer is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight, and 0.3 to 20 parts by weight. It is particularly preferable to contain it in a proportion of 8 parts by weight. (E-1) A nitrogen-containing vinyl monomer containing no hydroxyl group and (E-2) an alkyl (meth) acrylate monomer containing an alkoxy group can be used alone or in combination of two or more.

The pressure-sensitive adhesive composition according to the present invention can contain (F) a polyether-modified siloxane compound having an HLB value of 7 to 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-], the siloxane unit having a polyether group [-SiR ¹ (R ² O (R 2 O)). It has R ³ O) _n R ⁴ ) -O-]. Here, R ¹ is one or more alkyl groups or aryl groups, R ² and R ³ are one or more alkylene groups, and R ⁴ is one or more alkyl groups or acyl groups. Etc. (terminal groups). Examples of the polyether group include a polyoxyalkylene group such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a 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 (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms. It is preferable that the total of at least one type is contained in a proportion 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 K3211 (surfactant term) and 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 on 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) Examples thereof include a siloxane polymer. 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) By blending a polyether-modified siloxane compound having an HLB value of 7 to 12 into the pressure-sensitive adhesive composition, the pressure-sensitive adhesive strength and rework performance of the pressure-sensitive 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, but any of them may be used.

Examples of the trifunctional isocyanate compound include a bullet-modified compound of a bifunctional isocyanate compound (a compound having two NCO groups in one molecule), an isocyanurate-modified compound, and a trivalent or higher valent or higher such as trimethylolpropane (TMP) and glycerin. Examples thereof include an adduct (modified polyol) with a polyol (a compound having at least 3 or more OH groups in one molecule).

Examples of the trifunctional isocyanate compound include isocyanurates of hexamethylene diisocyanate compounds, isocyanurates of isophorone diisocyanate compounds, adducts of hexamethylene diisocyanate compounds, adducts of isophorone diisocyanate compounds, bullets of hexamethylene diisocyanate compounds, and isophorone diisocyanates. Bullet of compound, isocyanurate of tolylene diisocyanate compound, isocyanurate of xylylene diisocyanate compound, isocyanurate of hydrogenated xylylene diisocyanate compound, adduct of tolylene diisocyanate compound, adduct of xylylene diisocyanate compound, It is preferable that at least one selected from the compound group consisting of an adduct of a hydrogenated xylylene diisocyanate compound.
(A) The total of at least one or more trifunctional isocyanate compounds is 0.1 with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms. It is preferably contained in a proportion of 10 parts by weight, more preferably 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 the polyisocyanate compound is used as the cross-linking agent, and is an amine-based compound such as a tertiary amine. , Organometallic compounds such as metal chelate compounds, organic tin compounds, organic lead compounds, and organic zinc compounds.
Examples of the tertiary amine include trialkylamine, N, N, N', N'-tetraalkyldiamine, N, N-dialkylaminoalcohol, triethylenediamine, morpholine derivative, piperazine derivative and the like.

The metal chelate compound is a compound in which one or more polydentate ligands L are bonded to the central metal atom M. The metal chelate compound may or may not have one or more bidentate ligands X that bind 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 may be different ligands. When n is 2 or more, n Xs 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.
Examples of the polydentate ligand L include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetic acid, lauryl acetoacetic acid, and stearyl acetoacetic acid, and acetylacetone (also known as 2,4-pentandione). Examples thereof include β-diketones such as 2,4-hexanedione and benzoylacetone. These are keto-enol tautomeric compounds and may be enol-deprotonated enolates (eg, acetylacetonate) in the polydentate ligand L.
The monodentate ligand X includes halogen atoms such as chlorine atom and bromine atom, pentanoyl group, hexanoyl group, 2-ethylhexanoyl group, octanoyl group, nonanoyl group, decanoyyl group, dodecanoyl group, octadecanoyl group and other acyloxy. Examples thereof include an alkoxy group such as a group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group and a butoxy group.

Specific examples of the metal chelate compound include tris (2,4-pentandionato) iron (III), iron trisacetylacetonate, titaniumtrisacetylacetonate, rutheniumtrisacetylacetonate, zinc bisacetylacetonate, and aluminum tris. Acetylacetonate, Zirconite Tetrakis Acetylacetonate, Tris (2,4-Hexanedionate) Iron (III), Bis (2,4-Hexane Zionato) Zinc, Tris (2,4-Hexane Zionato) Titanium, Tris Examples thereof include (2,4-hexane dionat) aluminum and tetrakis (2,4-hexane dionate) zirconium.

Examples of the organic tin compound include dialkyltin oxide, a fatty acid salt of dialkyltin, and a fatty acid salt of first tin.
The cross-linking catalyst is preferably a metal chelate compound or an organic tin compound. As the metal chelate compound, an aluminum chelate compound, a titanium chelate compound, an iron chelate compound, a tin chelate compound and the like are preferable. The organic tin compound is preferably at least one selected from the compound group consisting of dioctyl tin oxide and dioctyl tin dilaurate.
(A) For a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18, the total of at least one of the cross-linking catalysts is 0.001 to 0. It is preferably contained in a proportion of 5 parts by weight.

Examples of the ketoenol tether compound include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetic acid, lauryl acetoacetic acid, and stearyl acetoacetic acid, acetylacetone, 2,4-hexanedione, and benzoylacetone. Etc., β-diketone and the like. In a pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, the ketoenol tether compound compound blocks the isocyanate group contained in the cross-linking agent, thereby causing an excessive increase in the viscosity of the pressure-sensitive adhesive composition after the compounding of the cross-linking agent. Gelation can be suppressed and the pot life of the pressure-sensitive adhesive composition can be extended.
The keto-enol tautomer compound is preferably at least one selected from the compound group consisting of acetylacetone and ethyl acetoacetate.
(A) A total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18, and 0. It is preferably contained in a proportion of 1 to 300 parts by weight, more preferably 1.0 to 30.0 parts by weight.

Since the keto-enol tautomer compound has an effect of suppressing cross-linking as opposed 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 pressure-sensitive adhesive composition and improve the storage stability, the weight ratio (keto-enol tautomer compound / cross-linking catalyst) of the cross-linking catalyst to the keto-enol tautomer compound is 70 to 1000. Is preferable.

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

Examples of the (J) antistatic agent include an ionic compound contained in the pressure-sensitive adhesive composition having a melting point of 25 to 50 ° C. and a solid at 25 ° C.

An ionic compound having a melting point of 25 to 50 ° C. and a solid at 25 ° C. is an ionic compound having a cation and an anion, and the cations are pyridinium cation, imidazolium cation, pyrimidinium cation, pyrazolium cation, and the like. pyrrolidinium cation, and nitrogen-containing onium cations such as ammonium cations, phosphonium cation, sulfonium cation or the like, anions, hexafluorophosphate (PF 6 ^_-), thiocyanate (SCN ^-), alkyl benzene sulfonic acid salt ^{_{(RC 6 H 4 SO 3 -}} ), perchlorate (ClO ₄ ^-), tetrafluoroborate (BF ₄ ^-), bis (fluorosulfonyl) imide salt (FSI), bis (trifluoromethanesulfonyl) Examples thereof include compounds that are inorganic or organic anions such as imide salt (TFSI) and trifluoromethanesulfonate (TF). 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 of the substituent, the number of substituents, 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 atom at the 2nd to 6th positions may have a substituent or is unsubstituted), or 1, Examples thereof include a quaternary imidazolium cation such as 3-dialkylimidazolium (the carbon atom at the 2, 4 and 5 positions may have a substituent or not substituted), a quaternary ammonium cation such as tetraalkylammonium, and the like. ..
(A) An ionic compound having a melting point of 25 to 50 ° C. and a solid at 25 ° C. with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having an alkyl group having C4 to C18 carbon atoms. It is preferable that the total of at least one kind is contained in a proportion of 0.01 to 5.0 parts by weight.

Specific examples of the (J) antistatic agent are not particularly limited, but specific examples of an ionic compound having a melting point of 25 to 50 ° C. and a solid at 25 ° C. are, for example, 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 can be mentioned.

Further, as other components, a copolymerizable (meth) acrylic monomer containing an alkylene oxide, a (meth) acrylamide monomer, a dialkyl-substituted acrylamide monomer, a surfactant, a curing accelerator, a plasticizer, a filler, and a curing retarder , Processing aids, antioxidants, antioxidants and other known additives 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 contains at least one (meth) acrylic acid ester monomer having (A) alkyl groups having C4 to C18 carbon atoms and (B) a hydroxyl group. It is composed of a copolymer obtained by copolymerizing at least one kind of polymerizable monomer and at least one kind of copolymerizable monomer containing (C) a carboxyl group. Further, the acrylic polymer is (A) at least one kind of (meth) acrylic acid ester monomer having C4 to C18 carbon atoms and (B) at least one kind of copolymerizable monomer containing a hydroxyl group. The above, (C) at least one copolymerizable monomer containing a carboxyl group, (D) at least one polyalkylene glycol mono (meth) acrylic acid ester monomer, and (E) no hydroxyl group. It may be a copolymer obtained by copolymerizing at least one 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 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, a (F) 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. It can be prepared by blending a solid ionic compound having a melting point of 25 to 50 ° C. and 25 ° C., and an optional additive as appropriate.

When producing an acrylic polymer, it is preferable to carry out the polymerization reaction under anhydrous conditions such as solution polymerization using an anhydrous organic solvent in order to reduce the mixing of water into the pressure-sensitive adhesive composition. In particular, since the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer has high hydrophilicity, it is preferable to use one having a low water content.
Each monomer used in the production of the base acrylic polymer should have as much polyfunctional (bifunctional or higher) monomer as possible, which can function as a cross-linking agent, in order to avoid an increase in the viscosity of the pressure-sensitive adhesive composition. It is preferable to reduce it. In particular, as the (D) polyalkylene glycol mono (meth) acrylic acid ester monomer, since the corresponding diester content is a di (meth) acrylic acid ester of a bifunctional monomer, it is preferable to use one having a low diester content.

The acrylic polymer contains 50 to 100 parts by weight of an acrylic monomer such as (meth) acrylic acid ester monomer, (meth) acrylic acid, and (meth) acrylamide with respect to 100 parts by weight of the acrylic polymer. It is preferable to include it in a proportion.
The acid value of the acrylic polymer is preferably 0.01 to 8.0. As a result, it is possible to improve the contaminating property and improve the performance of preventing the generation of adhesive residue.
Here, the "acid value" is one of the indexes showing 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 adhesive force of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition with respect to the polarizing plate is as high as 0.04 to 0.2 N / 25 mm at a low peeling speed of 0.3 m / min. The adhesive strength at a peeling speed of 30 m / min is preferably 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 quickly peel even by high-speed peeling. Further, since it is reattached, even when the surface protective film is once peeled off, it does not require an excessive force and can be easily peeled off from the adherend.

It is preferable that the surface resistivity of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is 9.0 × 10 ^{+ 11} Ω / □ or less, and the peeling band voltage is ± 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 of releasing static electricity generated by charging at the time of peeling is inferior. Therefore, by sufficiently reducing the surface resistivity, the peeling band voltage generated by the static electricity generated when the adherend peels off the adhesive layer is reduced, which affects the electric control circuit of the adherend. Can be suppressed.

The gel fraction of the pressure-sensitive adhesive layer formed 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 a low peeling speed, the elution of unpolymerized monomers or oligomers from the acrylic polymer is reduced, and the reworkability and high temperature / high humidity are satisfied. Durability is improved and contamination of the adherend can be suppressed.

A pressure-sensitive adhesive film can be obtained by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition on one side or both sides of a resin film. Further, the surface protective film for a 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 has no deviation in a shear holding force test when it is attached to a polarizing plate, and has good adhesion to a polarizing plate despite its small adhesive force, and has good durability and rework. It has excellent properties and antistatic performance. Therefore, it can be suitably used as a surface protective film for a polarizing plate. Examples of the polarizing plate include glare, plain (general purpose), anti-glare (AG) and the like. Examples of the protective film material on the surface of the polarizing plate include a TAC film (triacetyl cellulose compound) and an acrylic film.

Examples of the shear holding force test conditions include a load (mass of the weight) of 500 g, an environmental temperature of 23 ° C., and a standing time of 24 hr. This test condition is suitable as a guideline for determining that the surface protective film has good adhesion to the polarizing plate. The contact area (dimensions) of the surface protective film for a polarizing plate with respect to the polarizing plate which is the adherend of the shear holding force test is 25 mm × 35 mm. The details of the test method (device, etc.) may be based on, for example, the holding force test of JIS Z 0237 (adhesive tape / adhesive sheet test method).

As the resin film used as the base material of the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface, a resin film such as a polyester film can be used.
The resin film used as the base material has a silicone-based or fluorine-based mold release agent or coating agent, an antifouling treatment with silica fine particles, and an antistatic agent on the opposite side of the resin film from the side on which the pressure-sensitive adhesive layer is formed. Antistatic treatment can be applied by coating or kneading.
The release film is subjected to a mold release treatment with a silicone-based or fluorine-based mold release agent or the like on the surface of the pressure-sensitive adhesive layer that is combined with the adhesive surface.

Hereinafter, the present invention will be specifically described with reference to Examples.

<Manufacturing of acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction pipe, and the air in the reactor was replaced with nitrogen gas. After that, 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, and polypropylene glycol monoacrylate (average number of repetitions of alkylene oxide constituting the polyalkylene glycol chain) were added to the reaction apparatus. n = 12, diester content in monomer is 0.1%, solubility in water is 0.8% in a 20% aqueous solution state, 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 vinylpyrrolidone. Then, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours and reacted at 65 ° C. for 6 hours to obtain an acrylic polymer solution having a weight average molecular weight of 500,000 and used in Example 1. Obtained. A part of the acrylic polymer was collected and used as a sample for measuring the acid value described later.
[Examples 2 to 8 and Comparative Examples 1 to 4]
Comparison with Examples 2 to 8 in the same manner as the acrylic polymer solution used in Example 1 above, except that the composition of the monomers is as described in Tables 1 (A) to (E). The acrylic polymer solution used in Examples 1 to 4 was obtained.

<Manufacturing of adhesive composition and surface protective film>
[Example 1]
0.05 parts by weight of a polyether-modified siloxane compound (HLB value: 7), 1.0 part 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 compound of hexamethylene diisocyanate compound) and 0.1 parts by weight of titanium trisacetylacetoneate are added and stirred and mixed. The pressure-sensitive adhesive composition of the above was obtained. This pressure-sensitive adhesive composition is applied onto a release film made of a polyethylene terephthalate (PET) film coated with a silicone resin, 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 to the surface opposite to the antistatic and antifouling treated polyethylene terephthalate (PET) film on one surface, and "antistatic and antifouling treated". A surface protective film of Example 1 having 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 8 are similar to the surface protective film of Example 1 above, except that the compositions of the additives are as described in Table 2 (F) to (J), respectively. The surface protective film of No. 4 was obtained.

In Tables 1 and 2, the compounding ratio of each component is shown by enclosing the numerical value of the part by weight obtained by assuming that the total of the group (A) is 100 parts by weight.
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., and Takenate (registered trademark) D-140N, D-127N, D-110N and D-120N are Mitsui Chemicals Co., Ltd. The product name of the company. With respect to group (D) in Table 3, the numerical value of "n" is the average number of repetitions of the alkylene oxide constituting the polyalkylene glycol chain. The numerical value of "diester" is the diester content (%) in the monomer. The numerical value of "moisture" is the moisture content (%). The numerical value of "haze" is the haze value (%) in the state of a 20% aqueous solution.

<Test method and evaluation>
The surface protective films of Examples 1 to 8 and Comparative Examples 1 to 4 were aged at 23 ° C. and 50% RH for 7 days, and then the release film (silicone resin coated PET film) was peeled off to obtain an adhesive. The exposed layer was used as a sample for measuring the gel fraction and the surface resistance.
Further, the surface protective film on which the pressure-sensitive adhesive layer is exposed is attached to the surface of the polarizing plate attached to the liquid crystal cell via the pressure-sensitive adhesive layer, left for 1 day, and then left at 50 ° C., 5 atm for 20 minutes. The sample which was autoclaved and left at room temperature for another 12 hours was used as a measurement sample of adhesive strength, peeling zone voltage, shear holding power (deviation), reworkability and durability. The polarizing plate of the adherend is a polarizing plate whose surface is AG-treated.

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

<Adhesive strength>
The measurement sample obtained above (a 25 mm wide surface protective film bonded to the surface of a polarizing plate whose surface has been AG-treated) is subjected to a low peeling speed (a low peeling speed () using a tensile tester in the 180 ° direction. Peeling was performed at 0.3 m / min) and a high peeling speed (30 m / min), and the measured peel strength was defined as the adhesive strength (N / 25 mm).

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

<Peeling band voltage>
When the measurement sample obtained above is peeled 180 ° at a tensile speed of 30 m / min, the voltage (voltage band) generated by charging the AG-treated polarizing plate on the surface is measured by the high-precision electrostatic sensor SK. The measurement was performed using -035 and SK-200 (manufactured by Keyence Co., Ltd.), and the maximum value of the measured values was defined as the peeling band voltage (kV).
<Shear holding force against polarizing plate>
A surface protective film (thickness of the adhesive layer is 20 μm) cut to a size of 25 mm in width × 35 mm in length is attached to a polarizing plate whose surface has been subjected to AG treatment, 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 deviation (mm) of the surface protective film after being left for 24 hours was measured.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ball pen (load 500 g, 3 reciprocations), the surface protective film is peeled off from the polarizing plate, the surface of the polarizing plate is observed, and the polarizing plate is contaminated. It was confirmed that there was no migration. The evaluation target criteria are "○" when there is no contamination transfer on the polarizing plate, "△" when contamination transfer is confirmed at least in part along the trajectory traced with the ballpoint pen, and along the trajectory traced with the ballpoint pen. When the transfer of contamination was confirmed and the detachment of the adhesive was confirmed from the surface of the adhesive, it was evaluated as "x".

<Durability>
The measurement sample obtained above was left to stand in an atmosphere of 60 ° C. and 90% RH for 250 hours, then taken out to room temperature, left to stand for another 12 hours, and then the adhesive strength was measured and clearly compared with the initial adhesive strength. It was confirmed that there was no significant increase. The evaluation target criteria were evaluated as "◯" when the adhesive strength after the test was 1.5 times or less of the initial adhesive strength, and as "x" when it exceeded 1.5 times.

Table 5 shows the evaluation results. The surface resistivity is expressed by a method in which "m × 10 ^{+ n} " is set to "mE + n" (where m is an arbitrary real number and n is a positive integer).
Further, the deviation shown in Table 5 shows the measured value of the deviation (mm) of the surface protective film in the test of the shear holding force with respect to the polarizing plate.

The surface protective films of Examples 1 to 8 have an adhesive force 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 perform high-speed peeling. Adhesive strength at a speed of 30 m / min is 2.0 N / 25 mm or less, surface resistance is 9.0 x 10 ^{+ 11} Ω / □ or less, peeling band voltage is ± 0 to 0.5 kV, and load is 500 g. In the shear holding force test after leaving at 23 ° C for 24 hours, there was no deviation, and after tracing the surface protective film with a ball pen through the adhesive layer, there was no contamination transfer to the adherend, and the temperature was 60 ° C, 90% RH. It was also excellent in durability when left in an atmosphere for 250 hours.
That is, (1) the adhesive strength is small, but the adhesion to the polarizing plate is good, (2) durability, (3) reworkability, and (4) antistatic performance are excellent, and all required performances are satisfied. Meet at the same time.

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

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

In the surface protective film of Comparative Example 3, the acrylic polymer does not contain (B) a copolymerizable monomer containing a hydroxyl group, and (C) has an excess of copolymerizable monomers containing a carboxyl group, and (D) Since the polyalkylene glycol mono (meth) acrylic acid ester monomer has a high diester content, a high water content, and low solubility in water, the gel content is low and the peeling speed is as low as 0.3 m / min, which is a high speed. The adhesive strength at a speed of 30 m / min was very large, the peeling band voltage was high even if the surface resistance was low, 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 excessive, and there was a deviation in the shear holding force test.

As described above, in the surface protective films of Comparative Examples 1 to 4, (1) the adhesive strength is small, but the adhesive strength to the polarizing plate is good, (2) durability, (3) reworkability, and (4). ) It was not possible to meet all the required performances of excellent antistatic performance at the same time.

The surface protective film for a polarizing plate according to the present invention has been a subject of the prior art, and when the adhesive force of the pressure-sensitive adhesive layer is reduced so that the surface protective film can be easily peeled off from the adherend, the surface protective film with respect to the polarizing plate of the surface protective film can be easily peeled off. Since the adhesion is reduced, the surface protective film is peeled off at the end of the polarizing plate when the size of the polarizing plate is increased as compared with the conventional one as the screen of the liquid crystal display is increased. The industrial utility value is great because it solves the problem.

Claims (2)

A surface protective film for a polarizing plate that has been subjected to an AG treatment 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 the resin film. And
The acrylic polymer
(A) The total of at least one (meth) acrylic acid ester monomer having C4 to C18 carbon atoms in the alkyl group is 100 parts by weight.
(B) The total of at least one or more copolymerizable monomers containing a hydroxyl group is 2 to 10 parts by weight.
(C) The total of at least one or more copolymerizable monomers containing a carboxyl group is 0.05 to 0.3 parts by weight.
(D) The total of at least one or more polyalkylene glycol mono (meth) acrylic acid ester monomers is 3 to 40 parts by weight.
(E) A total of at least one or more of a nitrogen-containing vinyl monomer containing no hydroxyl group or an alkyl (meth) acrylate monomer containing an alkoxy group is 0.1 to 20 parts by weight.
Consists of a copolymer of
2-Ethylhexyl (meth) acrylate and isooctyl (meth) acrylate in a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C4 to C18 carbon atoms in the (A) alkyl group. Is contained in an amount of 50 parts by weight or less, or one selected from the compound group consisting of 2-ethylhexyl (meth) acrylate and isooctyl (meth) acrylate in an amount of more than 50 parts by weight and 100 parts by weight or less.
The pressure-sensitive adhesive composition is trifunctional as the cross-linking agent with respect to a total of 100 parts by weight of at least one (meth) acrylic acid ester monomer having C4 to C18 carbon atoms in the (A) alkyl group. The total of at least one or more of the (F) polyether-modified siloxane compounds having an HLB value of 7 to 12 and containing 0.1 to 6 parts by weight of the isocyanate compound is 0.001 to 0.5. Ri Na contained in a ratio of parts by weight,
The copolymerizable monomer containing the (B) hydroxyl group is 8-hydroxyoctyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or 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.
The copolymerizable monomer containing the (C) carboxyl group is (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (Meta) acryloyloxypropyl hexahydrophthalic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl maleic acid, At least one selected from the group of compounds consisting of carboxypolycaprolactone mono (meth) acrylate and 2- (meth) acryloyloxyethyl tetrahydrophthalic acid.
The (D) polyalkylene glycol mono (meth) acrylic acid ester monomer is selected from a group of compounds consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxypolyalkylene glycol (meth) acrylate. The average number of repetitions of the alkylene oxide constituting the polyalkylene glycol chain of at least one selected is 3 to 14, the diester content in the monomer is 0.2% or less, and the water content is 0. polarizing plate surface protective film AG processing shall be the characteristics were subjected to 1% or less. Wherein the one surface of the resin film, the opposite surface to the pressure-sensitive adhesive layer is formed side, antistatic treatment and AG treatment subjected polarizing plates for surface protection according to claim 1, antifouling treatment is the film.