JP7207961B2 - Adhesive composition, and adhesive film and surface protective film using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition that can be suitably used for surface protection films such as surface protection films for polarizing plates, and pressure-sensitive adhesive films and surface protection films using the same. More specifically, a pressure-sensitive adhesive composition capable of achieving both antistatic performance and anti-fouling performance while having well-balanced adhesive strength at low peeling speed and high peeling speed, and the same. It relates to providing a pressure-sensitive adhesive film and a surface protection film using.

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

A surface protective film used in the process of manufacturing such an optical member has an adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film. In addition, a release film that has undergone a release treatment is attached to the surface of the adhesive layer of the surface protective film in order to protect the adhesive layer until it is attached to an optical member.
Then, the optical member such as the polarizing plate, with the surface protective film attached thereto, undergoes a product inspection accompanied by optical evaluations of the display ability, hue, contrast, foreign matter contamination, etc. of the liquid crystal display plate. For this reason, the performance required for the surface protective film is that the pressure-sensitive adhesive layer should not contain air bubbles or foreign matter, and that adhesion of the low-molecular-weight components of the pressure-sensitive adhesive composition to the surface of the adherend can be reduced. , is required to have antifouling performance.
In addition, when the surface protective film is peeled off from the optical member such as the polarizing plate, the static electricity generated when the adhesive layer is peeled off from the adherend will cause peeling electrification, which will affect the failure of the electric control circuit of the liquid crystal display. is concerned. Therefore, the pressure-sensitive adhesive layer of the surface protective film is required to have excellent antistatic performance.
Furthermore, in recent years, in addition to triacetyl cellulose (TAC), which has been conventionally used as a protective layer (sometimes called a protective film) for the polarizer of the polarizing plate, an acrylic film such as polymethyl methacrylate (PMMA) has been used. The use of materials such as resins, polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonates, which tend to cause peeling electrification when the surface protective film of the polarizing plate is peeled off, is expanding. Therefore, it is required that the antistatic performance required for the pressure-sensitive adhesive layer for the surface protective film of the polarizing plate is superior to that of the conventional ones.
Moreover, when the surface protective film is finally peeled off from the optical member such as the polarizing plate, it is required to be able to peel off quickly. It is required that the adhesive force does not change much with the peeling speed so that the adhesive can be quickly peeled even by so-called high-speed peeling.

Thus, in recent years, the pressure-sensitive adhesive layer that constitutes the surface protective film has been required to (1) balance the adhesive force at low peeling speed and high peeling speed, and (2) stain resistance performance. and (3) excellent antistatic performance are required from the viewpoint of ease of use in using the surface protective film.
However, regarding the required performance for the adhesive layer constituting the surface protective film, although each of these (1) to (3) can satisfy the individual required performance, the adhesive layer of the surface protective film is required ( It was a very difficult task to simultaneously satisfy all the required performances of 1) to (3).

In order to solve such problems, for example, (1) balance adhesive force at low peel speed and high peel speed, (2) have stain resistance performance, and (3) The following proposals are known for having excellent antistatic performance.

(1) With regard to balancing adhesive force at low peeling speed and high peeling speed, (meth)acrylic acid alkyl ester having an alkyl group having 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound In an acrylic pressure-sensitive adhesive layer that is mainly composed of a copolymer with and cross-linked with a cross-linking agent, the pressure-sensitive adhesive will transfer to the adherend when adhered for a long period of time. There is a problem that the adhesive force to the body increases significantly over time. In order to avoid this, a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group was used and crosslinked with a crosslinking agent. , a pressure-sensitive adhesive layer having a gel fraction of 60% or more, and a surface protection member having the pressure-sensitive adhesive layer are known (Patent Document 1).
However, the pressure-sensitive adhesive layer described in Patent Literature 1 has the problem that the adhesive strength to the adherend increases over time, which is not completely resolved.
In addition, a small amount of a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymer compound was blended with the same copolymer as above, and a pressure-sensitive adhesive layer was provided by cross-linking this with a cross-linking agent. things are known. However, when these pressure-sensitive adhesive layers are used to protect the surface of plastic plates with low surface tension and smooth surfaces, they cause problems such as peeling when heated during processing or storage. There is also the problem that the adhesive strength at a high peeling speed is large and the removability is poor.

In order to solve these problems, a) 100 parts by weight of a (meth)acrylic acid alkyl ester mainly composed of a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms, and b) a carboxyl group-containing 1 to 15 parts by weight of a copolymerizable compound and c) 3 to 100 parts by weight of a vinyl ester of an aliphatic carboxylic acid having 1 to 5 carbon atoms are added to the copolymer of the monomer mixture, the above b ) has been proposed a pressure-sensitive adhesive composition containing a cross-linking agent in an equivalent amount or more to the carboxyl groups of the component (Patent Document 2).
The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition described in Patent Document 2 does not cause a peeling phenomenon such as lifting during processing or storage, and furthermore, the adhesive strength increases little over time and can be reused. It has excellent releasability, and can be re-peeled with little force even after long-term storage, especially in a high-temperature atmosphere. It is said that it can be re-peeled by force.
However, in the adhesive layer obtained by cross-linking the adhesive composition described in Patent Document 2, the gel fraction of the adhesive layer in Examples 1 to 3 is all 90%, and the adhesive strength at a low peeling speed. becomes excessively large, and unpolymerized monomers or oligomers tend to elute from the pressure-sensitive adhesive layer. In addition, Patent Document 2 does not describe antistatic performance and stain resistance performance, and a pressure-sensitive adhesive layer having excellent antistatic performance and stain resistance performance when a material that is prone to peel electrification is used as an adherend. There was a problem that it was difficult to improve

In addition, (2) having stain resistance performance, 0 parts by mass or more and less than 0.5 parts by mass of a carboxyl group-containing monomer, 0.6 to 9 parts by mass of a hydroxy group-containing (meth)acrylic monomer, and 99.5 parts by mass. 100 parts by mass of a (meth)acrylic copolymer consisting of 4 to 90.5 parts by mass of a (meth)acrylic acid ester monomer and having a weight average molecular weight of 100,000 or more and less than 1,000,000; and 0.1 of a carbodiimide-based cross-linking agent. A pressure-sensitive adhesive composition containing ∼5 parts by weight has been disclosed (Patent Document 3).
The pressure-sensitive adhesive composition described in Patent Document 3 is characterized by using a carbodiimide-based cross-linking agent as a cross-linking agent for a (meth)acrylic copolymer having a specific composition. This makes it possible to provide a pressure-sensitive adhesive layer having a crosslinked structure capable of following shrinkage due to pressure and temperature during autoclaving. For this reason, the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition described in Patent Document 3 can suppress or prevent foaming even under high temperature and high pressure conditions (during autoclave treatment), and has excellent stain resistance. It is said that it is excellent in transparency.
However, although the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition described in Patent Document 3 has improved stain resistance performance, it is difficult to balance the adhesive force at low and high peel speeds. It has not been possible to achieve both excellent adhesive performance and antistatic performance, and it remains a problem to be solved.

As for (3) having excellent antistatic performance, a method of kneading an antistatic agent into a base film is known as a method for imparting antistatic properties to a surface protective film. Antistatic agents include, for example, (a) quaternary ammonium salts, pyridinium salts, various cationic antistatic agents having cationic groups such as primary to tertiary amino groups, (b) sulfonic acid groups, sulfuric acid Anionic antistatic agents having anionic groups such as ester bases, phosphate ester bases and phosphonate bases, (c) amphoteric antistatic agents such as amino acid-based and amino sulfate ester-based agents, (d) amino alcohol-based and glycerin-based , a polyethylene glycol-based nonionic antistatic agent, and (e) a polymeric antistatic agent obtained by increasing the molecular weight of the above antistatic agent (Patent Document 4).
However, in the surface protection film described in Patent Document 4, although there is a description about imparting antistatic performance related to the adhesion of dust to the adherend, there is no solution to achieve both excellent adhesive performance and stain resistance performance. It is not described and remains as a problem to be solved.

Also, in recent years, it has been proposed to directly incorporate an antistatic agent into the pressure-sensitive adhesive layer instead of incorporating it into the substrate film or coating it on the surface of the substrate film. For example, antistatic properties characterized in that a salt having an anion having a fluoro group and a sulfonyl group is dissolved and dispersed in a polyether ester plasticizer containing a polyether group in the main chain An adhesive composition has been disclosed (Patent Document 5).
In the adhesive composition described in Patent Document 5, a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group and an alcohol having an acyclic hydrocarbon group having 1 to 20 carbon atoms are used as plasticizers. or an ester in which the unsaturated group in said unsaturated acyclic hydrocarbon group is epoxidized. Such a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to that of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer. The compatibility with the antistatic pressure-sensitive adhesive composition is improved, and it is preferably retained in the plasticizer acrylic antistatic pressure-sensitive adhesive composition, so that bleeding out is suppressed.
However, in the pressure-sensitive adhesive layer obtained by cross-linking the antistatic pressure-sensitive adhesive composition described in Patent Document 5, although there is a disclosure of technology for improving antistatic performance and bleed-out, the peeling speed is low and the peeling speed is high. does not describe that excellent adhesive performance can be obtained by balancing adhesive strength, and the problem of obtaining a pressure-sensitive adhesive layer having excellent adhesive performance remains.

JP-A-63-225677 JP-A-11-256111 JP 2011-122054 A JP-A-11-070629 JP 2014-118469 A

As described above, the performance requirements for the pressure-sensitive adhesive layer that constitutes the surface protective film are (1) a balance of adhesive strength at low and high peeling speeds, and (2) stain resistance. , and (3) to have excellent antistatic performance, there is no prior art that solves the problem of simultaneously achieving the above.
In addition, conventionally, the relationship between the antistatic performance of the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition having antistatic performance and the surface protective film using the same and the contamination resistance performance to the adherend are in a trade-off relationship, and it has been difficult to improve anti-fouling performance while maintaining antistatic performance.
Furthermore, in recent years, the number of types of adherend materials to which surface protective films are laminated has increased, and the surface-treated state of adherends has also diversified. It is becoming more and more difficult to balance adhesion and (2) to have antifouling performance, particularly at the above-mentioned (1) low peel speed and high peel speed. .

The present invention has been made in view of the above circumstances, and has a well-balanced adhesive strength at a low peeling speed and a high peeling speed, and achieves both antistatic performance and stain resistance performance. It is an object of the present invention to provide a pressure-sensitive adhesive composition capable of achieving a desired temperature, and a pressure-sensitive adhesive film and a surface protection film using the same.

The inventors of the present invention have found that a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a cross-linking agent as a pressure-sensitive adhesive composition for use in a surface protective film for a polarizing plate. By reexamining the type of the copolymerized compound, especially in the above (1) low-speed peeling speed and high-speed peeling speed, it is necessary to balance the adhesive force and (2) to have stain resistance performance. We worked diligently to improve the issue of achieving a balance between
As a result, among the (A) alkyl (meth)acrylates having C1 to C10 alkyl groups, 2-ethylhexyl acrylate and monofunctional methacrylates whose homopolymer glass transition temperature (Tg) is 0° C. or higher The inventors have found that the above problems (1) and (2) can be solved at the same time by defining the content ratio with the monomer in a specific range. It is completed.

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive composition containing a first acrylic polymer, a cross-linking agent, and an ionic compound, wherein the first acrylic polymer comprises (A ) a total of 100 parts by weight of at least two or more alkyl (meth)acrylates having C1 to C10 alkyl groups, and (B) a total of 1 or more of at least one copolymerizable monomer containing a hydroxyl group. an acid value obtained by copolymerizing 0 to 6.0 parts by weight and 0.01 to 0.6 parts by weight of (C) a total of at least one copolymerizable monomer containing a carboxyl group; is 0.1 to 1.0 and the weight average molecular weight is more than 300,000 and less than 1,000,000, and the (A) alkyl (meth)acrylate in which the number of carbon atoms in the alkyl group is C1 to C10. 50 parts by weight or more of 2-ethylhexyl acrylate and one or more monofunctional methacrylate monomers whose homopolymer Tg is 0 ° C. or higher in 100 parts by weight of the total of at least two or more of 5 to 40 parts by weight. parts by weight, and the pressure-sensitive adhesive composition contains, as the cross-linking agent, a trifunctional or higher isocyanate compound, a cross-linking retarder, and a cross-linking catalyst other than a tin compound as a cross-linking catalyst. To provide a pressure-sensitive adhesive composition characterized by:

A pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is laminated on one side of a polyester film having a thickness of 38 μm to a thickness of 15 μm. When peeling the surface protective film from the polarizing plate, the adhesive strength at a low peeling speed of 0.3 m/min is 0.01 to 0.1 N/25 mm, and the adhesive strength at a high peeling speed of 30 m/min. is preferably 1.0 N/25 mm or less.

The monofunctional methacrylate monomer whose homopolymer Tg is 0° C. or higher is selected from n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, and methyl methacrylate. It is preferably one or more selected from the group of compounds.

The pressure-sensitive adhesive composition further contains a second acrylic polymer, and the second acrylic polymer comprises (a) at least a (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18 Copolymerizing one or more, (b) at least one copolymerizable monomer containing a hydroxyl group, and (c) at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. and the pressure-sensitive adhesive composition contains (A) the total of at least two alkyl (meth)acrylates having C1 to C10 alkyl groups, It is preferable to contain the second acrylic polymer in a proportion of 0.1 to 5.0 parts by weight.

The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer that is used in a surface protective film for a polarizing plate, and the protective layer of the polarizer of the polarizing plate is a TAC-based film or a PMMA-based film. , one selected from the group consisting of PET-based films, and the surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate is untreated, AG treatment, LR treatment, AR treatment, It is preferably one selected from the group consisting of AG-LR treatment and AG-AR treatment.

The ionic compound is an ionic compound having a melting point of 25 to 80° C., the cation of the ionic compound is pyridinium, and the pressure-sensitive adhesive composition contains 100 parts by weight of the first acrylic polymer. , the ionic compound is preferably contained as an essential component in a proportion of 0.01 to 10 parts by weight.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition has a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less,
The pressure-sensitive adhesive layer has a peeling electrostatic voltage in the range of +0.3 to −0.3 kV with respect to the low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound,
The surface base material is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and the surface treatment applied to the surface of the surface base material is untreated, AG-treated, After being attached to a polarizing plate selected from the group consisting of LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment, it was left in an atmosphere of 60° C. and 90% RH for 2 days and then taken out. It is preferable that there is no contamination when the film is peeled off after one day has passed.

(B) the copolymerizable monomer containing a hydroxyl group is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate , N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, at least one selected from the group of compounds,
(C) the copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, It is preferably at least one selected from the compound group consisting of carboxypolycaprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid.

The cross-linking retarder is a ketoenol tautomer compound, and contains 0.1 to 300 parts by weight of the cross-linking retarder with respect to 100 parts by weight of the first acrylic polymer, The crosslinking catalyst is at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound, and with respect to 100 parts by weight of the first acrylic polymer, It is preferable that the cross-linking catalyst is contained in a ratio of 0.001 to 0.5 parts by weight, and the weight part ratio of the cross-linking retarder/cross-linking catalyst is 80-1000.

The adhesive composition contains a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight average molecular weight of 10,000 or less with respect to 100 parts by weight of the first acrylic polymer, and 0.01 to 0.5 It is preferably contained in a proportion of parts by weight.

The second acrylic polymer contains (a) a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18, and (b) a copolymer containing a hydroxyl group. A total of 2.0 to 12.0 parts by weight of at least one or more polymerizable monomers, and a total of 1 to 30 parts by weight of at least one (c) polyalkylene glycol chain-containing mono(meth)acrylate monomer. and a copolymer having a weight average molecular weight of more than 300,000 and 800,000 or less, and the (B ) Value of total parts by weight of at least one or more copolymerizable monomers containing a hydroxyl group (B-1), and the second acrylic polymer contained in the total 100 parts by weight of the second acrylic polymer The ratio (b-1)/(B-1) of the total weight of at least one or more copolymerizable monomers containing a hydroxyl group (b-1) is 1.0 It is preferably in the range of ~2.0.

The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeating number of 3 to 14 for the alkylene oxide constituting the polyalkylene glycol chain, and the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. The diester content is 0.2% or less, and the polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers include polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxy polyalkylene At least one selected from the group consisting of glycol (meth)acrylates is preferably contained in a proportion of 1 to 50 parts by weight based on 100 parts by weight of the second acrylic polymer.

The present invention also provides a pressure-sensitive adhesive film comprising a pressure-sensitive adhesive layer obtained by cross-linking the above-described pressure-sensitive adhesive composition laminated on one side of a resin film.

The present invention also provides a surface protective film using the pressure-sensitive adhesive film described above.

The present invention also provides a surface protective film for polarizing plates, which uses the pressure-sensitive adhesive film described above.

The present invention also provides an optical film with a pressure-sensitive adhesive layer, in which a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is laminated on at least one surface of an optical film.

The present invention also provides an adhesive film in which one surface of the resin film opposite to the side on which the adhesive layer is formed is subjected to antistatic treatment and antifouling treatment.

In the pressure-sensitive adhesive composition according to the present invention, the first acrylic polymer comprises (A) at least two alkyl (meth)acrylates in which the alkyl group has C1 to C10 carbon atoms. A total of 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of a monofunctional methacrylate monomer having a homopolymer Tg of 0° C. or more is contained. As a result, even in a surface protective film for a polarizing plate using PMMA as a base material, (1) the adhesive force is balanced between the low-speed peeling speed and the high-speed peeling speed, and (2) stain resistance. It can be compatible with having performance.
In addition, in the pressure-sensitive adhesive composition according to the present invention, containing one or more monofunctional methacrylate monomers having a homopolymer Tg of 0° C. or higher is effective for (1) a low peeling speed and a high peeling speed. , the reason why it contributes to balancing the adhesive strength and (2) having stain resistance performance is not clear. A possible reason is that these methacrylate monomers do not have polar functional groups, such as carboxyl or amide groups, or long chain alkyl groups greater than C10, yet yield polymers with high Tg. The reason for this is presumed to be that the adhesion performance in the crosslinked state can be greatly improved, and that the affinity with methyl methacrylate, which is the main component of the PMMA-based film, is improved.

The present invention will be described below based on preferred embodiments.
The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition containing an acrylic polymer, a cross-linking agent, and an ionic compound, wherein the acrylic polymer is
(A) a total of 100 parts by weight of at least two or more alkyl (meth)acrylates in which the number of carbon atoms in the alkyl group is C1 to C10;
(B) a total of 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(C) a total of 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group;
is an acrylic polymer composed of a copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1,000,000,
Of the total 100 parts by weight of at least two or more alkyl (meth)acrylates (A) in which the alkyl group has a carbon number of C1 to C10, 50 parts by weight or more of 2-ethylhexyl acrylate, and the Tg of the homopolymer is 0 ° C. or higher containing a total of one or more monofunctional methacrylate monomers in a proportion of 5 to 40 parts by weight,
The pressure-sensitive adhesive composition is characterized by containing an isocyanate compound having a functionality of 3 or more as the cross-linking agent, a cross-linking retarder, and a cross-linking catalyst other than a tin compound as the cross-linking catalyst.

The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment is the main polymer of the pressure-sensitive adhesive composition, and may be referred to as the first acrylic polymer when distinguished from the second acrylic polymer described later. The first acrylic polymer is an acrylic polymer having a glass transition temperature (Tg) of 0° C. or lower. The first acrylic polymer is preferably (A) a copolymer mainly composed of an alkyl (meth)acrylate in which the alkyl group has C1 to C10 carbon atoms.

(A) Examples of alkyl (meth)acrylates in which the alkyl group has C1 to C10 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate and the like. The alkyl group of these alkyl (meth)acrylates may be either acyclic (linear or branched) or cyclic (monocyclic or polycyclic).

The first acrylic polymer comprises 50 parts by weight or more of 2-ethylhexyl acrylate out of 100 parts by weight of the total of (A), and a monofunctional methacrylate monomer having a homopolymer Tg of 0° C. or higher. It is preferable to contain the total of the above in a proportion of 5 to 40 parts by weight.
Further, 2-ethylhexyl acrylate is preferably contained at a rate of 50 parts by weight or more, more preferably at a rate of 60 parts by weight or more, out of 100 parts by weight of the total of (A), and 70 parts by weight. It is particularly preferable to contain at a ratio of 1 part or more.
Further, among the (A) alkyl (meth)acrylates in which the number of carbon atoms in the alkyl group is C1 to C10, monofunctional methacrylate monomers having a Tg of 0° C. or higher include n-butyl methacrylate, isobutyl methacrylate, and s-butyl methacrylate. , t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, methyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, dicyclopenta methacrylate One or more selected from the compound group consisting of Among these monofunctional methacrylate monomers having a Tg of 0° C. or higher, methacrylate monomers in which the alkyl group has a carbon number of C1 to C6 are preferred, and methacrylate monomers in which the alkyl group has a carbon number of C1 to C4 are more preferred. One or more selected from the group consisting of n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate and methyl methacrylate is particularly preferred.
In addition, the total of one or more monofunctional methacrylate monomers having a Tg of 0 ° C. or higher is preferably contained in a proportion of 5 to 40 parts by weight based on 100 parts by weight of the total of (A). It is more preferably contained in a proportion of up to 40 parts by weight, and particularly preferably in a proportion of 10 to 35 parts by weight. In the following description, when a monomer is simply referred to as Tg, it may refer to the Tg of a homopolymer.

Examples of the (B) hydroxyl group-containing copolymerizable monomer used in the first acrylic polymer include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, etc. At least one selected from the group of compounds It is preferable that it is above.
The first acrylic polymer contains 1.0 to 6.0 parts by weight of (B) a total of at least one copolymerizable monomer containing a hydroxyl group with respect to 100 parts by weight of the total of (A). parts by weight, more preferably 2.0 to 6.0 parts by weight, and more preferably 2.5 to 5.5 parts by weight. is particularly preferred.

The (C) carboxyl group-containing copolymerizable monomer used in the first acrylic polymer includes (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, 2-(meth) Acryloyloxyethylhexahydrophthalate, 2-(meth)acryloyloxypropylhexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-( At least one compound selected from a group of compounds consisting of meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, etc. preferable.
The first acrylic polymer, with respect to 100 parts by weight of the total of (A), (C) the total of at least one copolymerizable monomer containing a carboxyl group is 0.01 to 0.6 It is preferably contained at a rate of 0.01 to 0.5 parts by weight, and more preferably at a rate of 0.01 to 0.4 parts by weight. is particularly preferred.

The method for producing the first acrylic polymer is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. The first acrylic polymer preferably has a weight average molecular weight of more than 300,000 and less than 1,000,000. Also, the acid value of the first acrylic polymer is preferably 0.1 to 1.0. This can improve antifouling performance. Here, the "acid value" is one index of the acid content, and is expressed in mg of potassium hydroxide required to neutralize 1 g of a polymer containing a carboxyl group.

The pressure-sensitive adhesive composition according to this embodiment contains (G) an antistatic agent. (G) the antistatic agent of the present embodiment is preferably an ionic compound having a melting point of 25 to 80°C. The ionic compound is preferably solid at room temperature. Normal temperature is, for example, a temperature of less than 25°C, and specifically, it is preferably an ionic compound that is solid at 23°C. The pressure-sensitive adhesive composition according to the present embodiment preferably contains the ionic compound in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the first acrylic polymer as an essential component. .

Examples of the anion of the ionic compound include hexafluorophosphate (PF ₆ ⁻ ), thiocyanate (SCN ⁻ ), perchlorate (ClO ₄ ⁻ ), and tetrafluoroborate (BF ₄ ⁻ ). inorganic anions such as carboxylates (RCOO ⁻ ), sulfonates (RSO ₃ ⁻ ), alkoxide or phenoxide salts (RO ⁻ ), organic imide salts (R ₂ N ⁻ ), methide salts (R ₃ C ⁻ ), Examples include organic anions such as organic borate salts (R ₄ B ⁻ ). R included in each general formula of an organic anion is an organic group that may have fluorine substitution. Examples of the organic group include at least one of an alkyl group, an alkoxy group, an aromatic group (aryl group, aralkyl group, etc.), an aliphatic or aromatic carbonyl group, an aliphatic or aromatic sulfonyl group, and the like. Some or all of the hydrogen atoms in the organic group contained in the anion may be substituted with one or more halogen atoms such as fluorine atoms.

Examples of the cation of the ionic compound include one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, and morpholinium. The cation of the ionic compound is preferably pyridinium. Some or all of the hydrogen atoms in the organic group contained in the cation may be substituted with one or more halogen atoms such as fluorine atoms.
When the anion and/or cation of the ionic compound contains an organic group such as an alkyl group, an ionic compound having a melting point of 25 to 80° C. can be obtained by selecting the chain length of the alkyl group, the position and number of substituents, etc. be able to.

Specific examples of the ionic compound include, for example, 1-octylpyridinium hexafluorophosphate, 1-nonylpyridinium hexafluorophosphate, 2-methyl-1-dodecylpyridinium hexafluorophosphate, 3 -methyl-1-dodecylpyridinium hexafluorophosphate, 1-octylpyridinium dodecylbenzenesulfonate, 1-dodecylpyridinium thiocyanate, 1-dodecylpyridinium dodecylbenzenesulfonate, 4-methyl-1-octylpyridinium hexafluorophosphate, 1-nonylpyridinium 2-iodobenzenesulfonate, 4,5-diiodo-1-butyl-3-methylimidazolium hexafluorophosphate, 2-methyl-1-dodecylpyridinium 2 - iodobenzenesulfonate, 4,5-diiodo-1-butyl-3-methylimidazolium 3-iodobenzenesulfonate, 1-octyl-2-methylpyridinium trifluoromethanesulfonate salt, 1,2,3- Trimethylimidazolium pentafluoroethanesulfonate salt, 1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate salt, 1-hexyl-4-methylpyridinium pentafluoroethanesulfonate salt, 1-octyl-3-methylpyridinium trifluoromethanesulfonate salt, n-octylpyridinium trifluoromethanesulfonate salt, 1-propyl-3-methylpyridinium nonafluorobutanesulfonate salt, 3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, methyltrioctylammonium tris(pentafluorobenzenesulfonyl)methide salt, 1-ethyl-3-methylimidazolium tetrakispentafluorophenylborate salt, 1-butyl-1-methylpiperidinium bis(pentafluorobenzenesulfonyl)imide salt and the like.

The pressure-sensitive adhesive composition according to this embodiment further contains a tri- or more functional isocyanate compound as (D) a cross-linking agent. Trifunctional or higher isocyanate compounds include, for example, buret-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, trimethylolpropane, and glycerin. Examples thereof include adducts with polyols having a valence of 3 or more. (D) The ratio of the trifunctional or higher isocyanate compound that is the cross-linking agent is, for example, preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the first acrylic polymer. More preferably, it is contained in a proportion of 0.1 to 6 parts by weight.

The pressure-sensitive adhesive composition according to this embodiment may contain (E) a cross-linking retarder. (E) Crosslinking retarders include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, acetylacetone, 2,4-hexanedione, and benzoylacetone. and β-diketones such as These are ketoenol tautomer compounds, and in a pressure-sensitive adhesive composition using a polyisocyanate compound as a cross-linking agent, (D) by blocking the isocyanate group of the cross-linking agent, the pressure-sensitive adhesive composition after blending the cross-linking agent It is possible to suppress excessive viscosity increase and gelation of the product and extend the pot life of the pressure-sensitive adhesive composition. (E) The cross-linking retarder is preferably at least one selected from the compound group consisting of acetylacetone and ethyl acetoacetate. It is preferable to contain (E) a cross-linking retarder in a proportion of 0.1 to 300 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

The pressure-sensitive adhesive composition according to this embodiment may contain a cross-linking catalyst other than the tin compound as (F) a cross-linking catalyst. (F) The cross-linking catalyst may be any substance that functions as a catalyst for the reaction (cross-linking reaction) between the acrylic polymer and the cross-linking agent when a polyisocyanate compound is used as the cross-linking agent. (F) As the cross-linking catalyst, a metal chelate compound is preferred. A metal chelate compound is a compound in which one or more polydentate ligands L are bonded to a central metal atom M. The metal chelate compound may or may not have one or more monodentate ligands X bound to the metal atom M. Specific examples of metal chelate compounds include tris(2,4-pentanedionato)iron (III), iron trisacetylacetonate, titanium trisacetylacetonate, ruthenium trisacetylacetonate, zinc bisacetylacetonate, aluminum tris Acetylacetonate, zirconium tetrakisacetylacetonate, tris(2,4-hexanedionato)iron(III), bis(2,4-hexanedionato)zinc, tris(2,4-hexanedionato)titanium, tris (2,4-hexanedionato)aluminum, tetrakis(2,4-hexanedionato)zirconium and the like.

(F) The cross-linking catalyst is preferably at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds. It is preferable that the cross-linking catalyst (F) is contained at a ratio of 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the first acrylic polymer.

Since (E) the cross-linking retarder has the effect of suppressing cross-linking, contrary to the (F) cross-linking catalyst, the ratio between (E) the cross-linking retarder and (F) the cross-linking catalyst can be appropriately set. preferable. In order to prolong the pot life of the adhesive composition and improve the storage stability, the weight part ratio of (E)/(F) is preferably 80 to 1000, more preferably 80 to 700. 80 to 300 is particularly preferred. Here, the weight part ratio of (E)/(F) is a quotient value obtained by dividing the weight part of (E) by the weight part of (F).

The pressure-sensitive adhesive composition according to this embodiment may contain (H) a polyether-modified siloxane compound as an optional component. (H) _The polyether ^- modified siloxane compound is ^a siloxane compound having a polyether group. ² O(R ³ O) _n R ⁴ )—O—]. Here, R ¹ is one or two or more alkyl groups or aryl groups, R ² and R ³ are one or two or more alkylene groups, and R ⁴ is one or two or more alkyl groups or acyl groups. etc. (end group). The polyether group includes polyoxyalkylene groups such as a polyoxyethylene group [(C ₂ H ₄ O) _n ] and a polyoxypropylene group [(C ₃ H ₆ O) _n ]. In the siloxane unit having a polyether group, the end of the polyether group may be an OH group (R ⁴ =H in the general formula above).

(H) The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 6-12. In addition, it is preferable that (H) the polyether-modified siloxane compound is contained in a proportion of 0.01 to 0.5 parts by weight, and 0.02 to 0.35 parts by weight, with respect to 100 parts by weight of the first acrylic polymer. It is more preferably contained at a rate of 0.02 to 0.25 parts by weight, and particularly preferably at a rate of 0.02 to 0.25 parts by weight. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) defined, for example, in JIS K3211 (surfactant terms).
A polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group to a polyorganosiloxane main chain having a silicon hydride group through a hydrosilylation reaction. Specifically, dimethylsiloxane/methyl (polyoxyethylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxyethylene) siloxane/methyl (polyoxypropylene) siloxane copolymer, dimethylsiloxane/methyl (polyoxypropylene) A siloxane polymer etc. are mentioned.

By incorporating (H) the polyether-modified siloxane compound into the adhesive composition, the adhesive strength and rework performance of the adhesive layer can be improved. (H) The weight average molecular weight of the polyether-modified siloxane compound is preferably 10,000 or less. From the viewpoint of compatibility with acrylic polymers, the lower the HLB value and the lower the molecular weight, the better the compatibility. Excellent antistatic property can be obtained even if the compatibility with is slightly low.

The pressure-sensitive adhesive composition according to this embodiment may contain a second acrylic polymer as an optional component. The adhesive composition further contains a second acrylic polymer obtained by copolymerizing a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, thereby improving the compatibility between the ionic compound and the acrylic polymer. and can further improve antistatic performance and antifouling performance. The second acrylic polymer comprises (a) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18 and (b) at least one copolymerizable monomer containing a hydroxyl group. A copolymer obtained by copolymerizing at least one of (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer and at least one of (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers.

Examples of the (a) (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C1 to C18 used in the second acrylic polymer include methyl (meth)acrylate, ethyl (meth)acrylate, and n-propyl (meth)acrylate. acrylates, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl ( meth) acrylate and the like. The alkyl group of (a) may be either acyclic (linear or branched) or cyclic (monocyclic or polycyclic).
The (a) (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C1 to C18 used in the second acrylic polymer is the (A) alkyl group having a carbon number of C1 used in the first acrylic polymer. It is also possible to select the same compounds or proportions as the -C10 alkyl (meth)acrylates.
Alternatively, (a) may contain a compound different from (A). Moreover, even if the monomers are the same compound, the ratio in (a) may differ from the ratio in (A). For example, the second acrylic polymer may be a copolymer in which alkyl methacrylate is not copolymerized. In addition, the second acrylic polymer may be a copolymer in which a (meth)acrylic acid ester monomer having an alkyl group having a carbon number of C11 to C18 is not copolymerized, or the second acrylic polymer However, it may contain a (meth)acrylic acid ester monomer having an alkyl group of C11 to C18 carbon atoms.

Examples of the (b) hydroxyl-containing copolymerizable monomer used in the second acrylic polymer include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 2-hydroxyethyl (meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, etc. At least one selected from the group of compounds It is preferable that it is above.
The second acrylic polymer contains (b) a hydroxyl group with respect to a total of 100 parts by weight of at least one (a) (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18. It is preferable to contain at least one or more copolymerizable monomers in a proportion of 2.0 to 12.0 parts by weight, more preferably 3.0 to 12.0 parts by weight. , 4.0 to 12.0 parts by weight.
(b) a hydroxyl group-containing copolymerizable monomer used in the second acrylic polymer is the same compound or proportion as the (B) hydroxyl group-containing copolymerizable monomer used in the first acrylic polymer. can also be selected. Alternatively, (b) may contain a compound different from (B). Moreover, even if the monomers are the same compound, the ratio in (b) may differ from the ratio in (B).

The second acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment contains (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer. In the adhesive composition of the present embodiment, the second acrylic polymer containing the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer functions as an antistatic adjuvant.
The first acrylic polymer may be a copolymer in which a polyalkylene glycol chain-containing mono(meth)acrylic ester monomer is not copolymerized, or a poly(polyethylene) similar to the second acrylic polymer. It is also possible to copolymerize an alkylene glycol chain-containing mono(meth)acrylate monomer.
The amount of the second acrylic polymer is 0.00 parts per 100 parts by weight of the total of at least two alkyl (meth)acrylates (A) having C1 to C10 alkyl groups used in the first acrylic polymer. It is preferably contained in a proportion of 1 to 5.0 parts by weight, more preferably in a proportion of 0.1 to 3.5 parts by weight, and is contained in a proportion of 0.1 to 2.5 parts by weight. is particularly preferred.

(C) Polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer, among a plurality of hydroxyl groups of polyalkylene glycol, one hydroxyl group is esterified as a (meth) acrylic acid ester may be used. . Since the (meth)acrylate group becomes a polymerizable group, it can be copolymerized with the second acrylic polymer. It may be a polyalkylene glycol mono(meth)acrylate in which other hydroxyl groups remain OH, or an alkoxypolyalkylene glycol mono(meth)acrylate in which other hydroxyl groups are converted to alkyl ethers. Since polyalkylene glycol mono(meth)acrylate corresponds to (c), it is not classified as (B) or (b) even if it contains a hydroxyl group.

The polyalkylene glycol constituting the polyalkylene glycol chain may be a glycol compound having one or more alkylene groups, and examples thereof include polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene glycol, and polyethylene. Glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, polyethylene glycol-polypropylene glycol-polybutylene glycol and the like are included.

(c) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer preferably has an average repeating number of 3 to 14 for the alkylene oxide constituting the polyalkylene glycol chain. The “average number of repeating alkylene oxides” refers to the average number of repeating alkylene oxide units in the “polyalkylene glycol chain” portion contained in the molecular structure of the (c) polyalkylene glycol chain-containing mono(meth)acrylate monomer. is a number.
Further, the diester content in the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is preferably 0.2% or less. The “diester content in the monomer” is the content (% by weight) of the polyalkylene glycol di(meth)acrylate contained in the (c) polyalkylene glycol chain-containing mono(meth)acrylate monomer.

(c) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkyleneglycol (meth)acrylate, and ethoxypolyalkyleneglycol (meth)acrylate. It is preferably at least one or more selected from.
The second acrylic polymer contains (c) polyalkylene glycol with respect to 100 parts by weight of the total of at least one (a) alkyl group having C1 to C18 (meth)acrylic acid ester monomers having C1 to C18 carbon atoms. The chain-containing mono (meth) acrylic acid ester monomer is preferably contained in a proportion of 1 to 30 parts by weight, more preferably in a proportion of 2 to 30 parts by weight, and contained in a proportion of 5 to 25 parts by weight. is particularly preferred.

The method for producing the second acrylic polymer is not particularly limited, and known polymerization methods such as a solution polymerization method and an emulsion polymerization method can be used as appropriate. The second acrylic polymer is preferably a copolymer having a weight average molecular weight of more than 300,000 and 800,000 or less. The weight average molecular weight of the second acrylic polymer may be about the same as the weight average molecular weight of the first acrylic polymer, or may be larger or smaller than the weight average molecular weight of the first acrylic polymer.
The second acrylic polymer may have (D) a functional group capable of reacting with a cross-linking agent. The second acrylic polymer may be a copolymer in which a copolymerizable monomer containing a carboxyl group is not copolymerized, or a copolymer containing the same carboxyl group as the first acrylic polymer. It is also possible to copolymerize polymerizable monomers. (D) A cross-linking agent may participate in cross-linking between the first acrylic polymer and the second acrylic polymer.

The value of the total parts by weight of at least one or more copolymerizable monomers containing a hydroxyl group (B) contained in the first acrylic polymer with respect to the total of 100 parts by weight of the first acrylic polymer (B-1) and the value of the total parts by weight of at least one copolymerizable monomer containing a hydroxyl group (b) contained in the second acrylic polymer with respect to the total 100 parts by weight of the second acrylic polymer (b- The ratio (b-1)/(B-1) to 1) is preferably in the range of 1.0 to 2.0.

The pressure-sensitive adhesive composition of the present embodiment is not limited to the additives described above, and may include known additives such as surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, anti-aging agents, and antioxidants. may be appropriately blended. These can be used alone or in combination of two or more.

The pressure-sensitive adhesive composition of this embodiment is suitable as a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, which is used for a surface protective film for polarizing plates. The pressure-sensitive adhesive layer of the surface protective film may be attached to the protective layer of the polarizer of the polarizing plate. Here, the protective layer of the polarizer of the polarizing plate may be at least one selected from the group consisting of TAC-based films, PMMA-based films, and PET-based films. Here, TAC is an abbreviation for triacetyl cellulose, PMMA for polymethyl methacrylate, and PET for polyethylene terephthalate.
Further, the surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate is at least selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. It may be one or more. Here, AG is anti-glare, LR is low reflection, and AR is anti-reflection.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment preferably has a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less, more preferably 5.0×10 ⁺¹¹ Ω/□. It is more preferably 1.0×10 ⁺¹¹ Ω/□ or less, particularly preferably 1.0×10 +11 Ω/□ or less. If the surface resistivity is high, the performance of releasing static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend is inferior. Therefore, by sufficiently reducing the surface resistivity, the peeling electrification voltage caused by the static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend is reduced, and the effect on the adherend is suppressed. can be done.

The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment has a peeling electrification voltage of the pressure-sensitive adhesive layer with respect to the low refractive index layer formed using the composition for forming a low refractive index layer containing a fluorine compound. is preferably in the range of +0.3 to -0.3 kV. As the fluorine compound used in the composition for forming the low refractive index layer, one or more fluorine-containing copolymers such as fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates are polymerized. Condensates such as polymers and silane compounds containing fluorinated alkyl groups can be mentioned. In addition to fluorinated monomers, the fluorine-containing copolymer may be copolymerized with non-fluorinated monomers such as olefins, vinyl ethers and (meth)acrylates. The low refractive index layer may constitute an antireflection layer in combination with a high refractive index layer or the like.

When measuring the peeling electrification voltage for the low refractive index layer, examples of substrates for forming the low refractive index layer on the surface include PMMA substrates and TAC substrates. In addition, the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment has a peeling electrostatic voltage of +0.3 to -0.3 to a plain layer having no treatment on the surface of the PMMA substrate and the TAC substrate. It is preferably in the range of 3 kV.

After the pressure-sensitive adhesive layer is attached to an adherend such as a polarizing plate, it is allowed to stand for 2 days (48 hours) in an atmosphere with a temperature of 60° C. and a humidity of 90% RH. It is preferable that there is no contamination when peeled off. Examples of the adherend include a polarizing plate in which a protective layer is laminated on a polarizer and the surface of the protective layer is subjected to a low-reflection surface treatment with a composition containing a fluorine compound. The composition containing the fluorine compound used for the low-reflection surface treatment may be the same as or different from the above resin composition for forming the low refractive index layer containing the fluorine compound. Examples of the protective layer and surface treatment include the protective layer of the polarizer and the surface treatment applied to the surface thereof.

A surface protective film obtained by laminating an adhesive layer obtained by cross-linking the adhesive composition of the present embodiment to a thickness of 15 μm on one side of a polyester film having a thickness of 38 μm was attached to the surface of the polarizing plate. After that, when the surface protective film is peeled off from the polarizing plate, the adhesive strength at a low peeling speed of 0.3 m/min is 0.01 to 0.1 N/25 mm, and at a high peeling speed of 30 m/min. is preferably 1.0 N/25 mm or less, and more preferably 0.2 to 1.6 N/25 mm at a high peeling speed of 30 m/min. As a result, it is possible to obtain a performance in which the adhesive strength does not change much depending on the peeling speed, and it is possible to peel off quickly even with high-speed peeling. Moreover, when the surface protective film is once peeled off for reattachment, it is easy to peel off from the adherend without requiring excessive force.

The gel fraction of the pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment is preferably 95 to 100%, more preferably 97 to 100%. Due to the high gel fraction of the adhesive layer, the adhesive strength at low peeling speeds does not become excessive, and the elution of unpolymerized monomers or oligomers from the copolymer is reduced, resulting in reworkability and high-temperature adhesion.・Durability at high humidity is improved, and contamination of the adherend can be suppressed.

The pressure-sensitive adhesive film of the present embodiment is obtained by forming a pressure-sensitive adhesive layer formed by cross-linking the pressure-sensitive adhesive composition of the present embodiment on one side or both sides of a resin film. Moreover, the surface protective film of this embodiment is a surface protective film which forms the adhesive layer which bridge|crosslinks the adhesive composition of this embodiment on the single side|surface of the resin film. The pressure-sensitive adhesive composition of the present embodiment has excellent antistatic performance, excellent balance of adhesive strength at low and high peeling speeds, and stain resistance performance. Therefore, it can be suitably used as a surface protection film for polarizing plates.

A resin film such as a polyester film can be used as the base film of the pressure-sensitive adhesive layer and the release film (separator) for protecting the pressure-sensitive adhesive surface.
Antistatic treatment and antifouling treatment may be performed on one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed. Examples of the antistatic treatment include coating and kneading of an antistatic agent. Examples of antifouling treatment include treatment with a silicone-based or fluorine-based release agent or coating agent, silica fine particles, or the like. The release film may be subjected to release treatment with a release agent such as a silicone-based, fluorine-based, or long-chain alkyl-based release agent on the side of the release film that is to be matched with the adhesive surface of the adhesive layer.

Moreover, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition of the present embodiment on at least one surface of an optical film. Examples of optical films include polarizing films, retardation films, antireflection films, antiglare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, brightness enhancement films, and the like. Devices to which the optical member is applied include liquid crystal panels, organic EL panels, touch panels, and the like.
In the case of optical surface protective films and pressure-sensitive adhesive films such as surface protective films for polarizing plates, the base film and pressure-sensitive adhesive layer preferably have sufficient transparency.

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

<Production of first acrylic polymer>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube to replace the air in the reactor with nitrogen gas. A solvent (ethyl acetate) was then added to the reactor along with 70 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of n-butyl methacrylate, 5.5 parts by weight of 8-hydroxyoctyl acrylate, and 0.2 parts by weight of acrylic acid. Thereafter, 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 a first acrylic polymer used in Example 1.
[Examples 2 to 6 and Comparative Examples 1 to 4]
Example 2 was prepared in the same manner as the first acrylic polymer solution used in Example 1 above, except that the monomer compositions were set as shown in (A), (B), and (C) in Table 1. 1 to 6 and Comparative Examples 1 to 4 were obtained.
The first acrylic polymer used in Examples 1 to 6 and Comparative Examples 1 to 4 was a copolymer having a weight average molecular weight of more than 300,000 and less than 1,000,000.

<Production of pressure-sensitive adhesive composition and surface protective film>
[Example 1]
2.0 parts by weight of a cross-linking agent (Coronate HX), 9 parts by weight of acetylacetone, and 0.1 part by weight of a cross-linking catalyst (titanium trisacetylacetonate) are added to the first acrylic polymer solution of Example 1 prepared as described above. , antistatic agent (3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt) 0.9 parts by weight, polyether-modified siloxane compound (HLB = 7) 0.05 parts by weight, 2-ethylhexyl acrylate and 8- 0.2 parts by weight of a copolymer having a weight average molecular weight (Mw) of 600,000 obtained by copolymerizing hydroxyoctyl acrylate and methoxypolyethylene glycol acrylate (n=8) at a weight ratio of 100:8:15 was added. The pressure-sensitive adhesive composition of Example 1 was obtained by stirring and mixing. After coating this adhesive composition on a release film (silicone resin-coated PET film), the solvent was removed by drying at 90° C. to obtain an adhesive layer with a thickness of 20 μm. After that, the adhesive layer with a release film is transferred to the surface opposite to the antistatic and antifouling treated surface of the base film (PET film with antistatic and antifouling treatment on one side), A surface protective film of Example 1 having a laminated structure of "base film/adhesive layer/releasing film" was obtained.
[Examples 2 to 6 and Comparative Examples 1 to 4]
Examples 2 to 2 were prepared in the same manner as in the surface protective film of Example 1 above, except that the compositions of the additives were set as described in (D) to (H) and (J) in Tables 1 and 2, respectively. 6 and Comparative Examples 1 to 4 were obtained.
In addition, in the surface protective films of Examples 1 to 6 and Comparative Examples 1 to 4, the gel fractions of the adhesive layers were all within the range of 95 to 100%.

In Tables 1 and 2, parts by weight of each component were determined based on 100 parts by weight of (A) the total of alkyl (meth)acrylates having alkyl groups of C1 to C10 carbon atoms.
In Tables 1 and 2, in each column of (B) to (H) and (J), the acrylic polymer is 100 parts by weight, and the content ratio (parts by weight) of each component is shown in parentheses ( ). Indicated.
In addition, Table 3 shows the abbreviated compound names of the components (A) to (H) used in Tables 1 and 2. Coronate (registered trademark) HX, HL and L are trade names of Tosoh Corporation, and Takenate (registered trademark) D-140N, D-127N and D-110N are trade names of Mitsui Chemicals, Inc. .

Among the (G) antistatic agents, G-1 to G-4 are ionic compounds that have a melting point of 25° C. or higher and 80° C. or lower and are solid at room temperature. G-5 is an ionic compound that has a melting point of over 80° C. and is solid at room temperature. Further, among the (H) polyether-modified siloxane compounds, the weight average molecular weights of H-1 to H-6 are 10,000 or less.

Table 4 shows the composition and molecular weight (Mw) of the monomers constituting the second acrylic polymer shown in column (J) of Table 2. In addition, Table 5 shows the compound names of the abbreviations of the components used in Table 4. In Table 4, the parts by weight of each component were determined based on the total of (a) being 100 parts by weight. Furthermore, in each column of (b) to (c), the content ratio (parts by weight) determined based on the total of 100 parts by weight of the second acrylic polymer is shown in parentheses ( ).

Among the (c) polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomers, I-1 to I-3 are monomers having a diester content of 0.2 wt% or less, and I-4 has a diester content of 0. .8 wt % monomer. The value of n indicates the average repeating number of alkylene oxide.

<Test method and evaluation>
The surface protective films in Examples 1 to 6 and Comparative Examples 1 to 4 were each aged in an atmosphere of 23° C. temperature and 50% RH for 7 days, and then evaluated by the following test methods.

<Test method for adhesive force>
After peeling off the release film and exposing the adhesive layer, the surface protective film is attached to the surface of the polarizing plate via the adhesive layer, left to stand for one day, and then autoclaved at 50 ° C., 5 atmospheres, and 20 minutes. The treated sample was left at room temperature for an additional 12 hours and used as a test sample for adhesive strength. The obtained measurement sample was peeled off at a low speed (0.3 m/min) or a high speed (30 m/min) using a tensile tester in the direction of 180°, and the peel strength measured was taken as the adhesive strength.
Here, the protective layer of the polarizer of the polarizing plate is polymethylmethacrylate (PMMA) with an AG-LR treated layer.

<Method for testing surface resistivity>
After aging the surface protective film and before laminating it to the polarizing plate, the release film is peeled off to expose the adhesive layer, and the adhesive layer is measured using a resistivity meter Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytic Tech). was measured.

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

<Test method for stain resistance performance>
A polarizing plate subjected to a low reflection (LR) surface treatment was laminated on one side of a glass plate via an adhesive layer (double-sided adhesive tape) using a laminating machine. After that, a surface protective film was bonded to the surface of the polarizing plate using a bonding machine. After bonding to the adherend, it was left for 2 days (48 hours) in an atmosphere with a temperature of 60° C. and a humidity of 90% RH. The contamination state of the surface of was observed visually. As the evaluation criteria for the stain resistance performance, the surface of the polarizing plate was evaluated as "good" when not soiled, "fair" when slightly soiled, and "poor" when soiled.

Table 6 shows the evaluation results of the surface protective films in Examples 1-6 and Comparative Examples 1-4. “Surface resistivity” was expressed by a method of “m×10 ⁺ⁿ ” being “mE+n” (where m is an arbitrary real number and n is a positive integer).
The column of "Stain resistance performance" shows the material (TAC, PMMA, PET) and surface treatment (untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment) of the polarizer protective layer of the polarizing plate used in the test. ). "Plain" in "surface treatment" means untreated.

The surface protective films of Examples 1 to 6 had an adhesive strength of 0.01 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min to the polarizing plate as an adherend, and a high peeling speed. Since the adhesive strength at 30 m/min was 1.0 N/25 mm or less, the adhesive performance was excellent by balancing the adhesive strength at low peeling speed and high peeling speed.
Further, in the surface protective films of Examples 1 to 6, the pressure-sensitive adhesive layer has a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less, and a composition for forming a low refractive index layer containing a fluorine compound is used. The peeling electrostatic voltage of the pressure-sensitive adhesive layer was in the range of +0.3 to -0.3 kV with respect to the low refractive index layer formed by the above method, and the antistatic performance was excellent.
Furthermore, the surface protective films of Examples 1 to 6 were left in an atmosphere of 60 ° C. and 90% RH for 48 hours after being attached to the adherend, and were removed from the atmosphere for 1 day. There was no staining on the various polarizing plates to which it was attached, and the staining resistance was also excellent.
That is, the evaluation results shown in Table 6 demonstrate that the surface protective films of Examples 1 to 6 were able to solve the problems of the present invention.

The surface protection film of Comparative Example 1 (where the monofunctional methacrylate monomer copolymerized with the first acrylic polymer had a Tg of less than 0° C.) had poor antifouling performance on adherends other than TAC.
In addition, the surface protective film of Comparative Example 2 (excessive hydroxyl group-containing monomer copolymerized with the first acrylic polymer) had a large adhesive force at a low peeling speed, and had poor stain resistance against PMMA. .
In addition, the surface protection film of Comparative Example 3 (the first acrylic polymer does not contain a methacrylate monomer having a Tg of 0 ° C. or higher, the proportion of the carboxyl group-containing monomer is excessive, and the melting point of the antistatic agent is 80 ° C. Excess) had high adhesive strength at high peel speed, high peel electrification voltage, and poor anti-fouling performance.
In addition, the surface protective film of Comparative Example 4 (Tables 1 and 2, except that the component (A) of Comparative Example 4 does not contain a methacrylate monomer having a Tg of 0 ° C. or higher, the components (B) to ( H) and (J) are the same.) Compared with the surface protective film of Example 3, the adhesive strength at a high peeling speed is high, the peeling electrification voltage is high, and the stain resistance performance against PMMA was bad.
From the performance comparison between the surface protective film of Comparative Example 4 and the surface protective film of Example 3, in the adhesive composition according to the present invention, the monofunctional methacrylate monomer whose homopolymer Tg is 0° C. or higher The inclusion of more than one species contributes to (1) balancing adhesion at low and high peel speeds, and (2) having anti-fouling performance. became clear,
Further, as described above, the surface protective films of Comparative Examples 1 to 4 could not solve the problems of the present invention.

Claims (17)

A pressure-sensitive adhesive composition comprising a first acrylic polymer, a cross-linking agent, and an ionic compound,
The first acrylic polymer is
(A) a total of 100 parts by weight of at least two or more alkyl (meth)acrylates in which the number of carbon atoms in the alkyl group is C1 to C10;
(B) a total of 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(C) a total of 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group;
is an acrylic polymer composed of a copolymer having an acid value of 0.1 to 1.0 and a weight average molecular weight of more than 300,000 and not more than 1,000,000,
Of the total 100 parts by weight of at least two or more alkyl (meth)acrylates (A) in which the alkyl group has a carbon number of C1 to C10, 50 parts by weight or more of 2-ethylhexyl acrylate, and the Tg of the homopolymer is 0 ° C. or higher containing a total of one or more monofunctional methacrylate monomers in a proportion of 5 to 40 parts by weight,
The ionic compound is an ionic compound having a melting point of 25 to 80° C.,
A pressure-sensitive adhesive composition characterized in that the pressure-sensitive adhesive composition contains a trifunctional or higher isocyanate compound as the cross-linking agent, a cross-linking retarder, and a cross-linking catalyst other than a tin compound as a cross-linking catalyst. A pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition is laminated on one side of a polyester film having a thickness of 38 μm to a thickness of 15 μm. When peeling the surface protective film from the polarizing plate, the adhesive strength at a low peeling speed of 0.3 m/min is 0.01 to 0.1 N/25 mm, and the adhesive strength at a high peeling speed of 30 m/min. is 1.0 N/25 mm or less, the pressure-sensitive adhesive composition according to claim 1. The monofunctional methacrylate monomer whose homopolymer Tg is 0° C. or higher is selected from n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, ethyl methacrylate, and methyl methacrylate. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the adhesive composition is one or more selected from the group of compounds. The pressure-sensitive adhesive composition further contains a second acrylic polymer,
The second acrylic polymer is
(a) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18;
(b) at least one copolymerizable monomer containing a hydroxyl group;
(c) a copolymer obtained by copolymerizing at least one or more polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers,
The pressure-sensitive adhesive composition contains 0.00 of the second acrylic polymer with respect to 100 parts by weight of the total of at least two alkyl (meth)acrylates (A) having alkyl groups of C1 to C10 carbon atoms. 4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, which is contained in a proportion of 1 to 5.0 parts by weight. The pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, which is used in a surface protective film for a polarizing plate,
The protective layer of the polarizer of the polarizing plate is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and is applied to the surface of the protective layer of the polarizer of the polarizing plate. Any one of claims 1 to 4, wherein the surface treatment applied is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. 1. The pressure-sensitive adhesive composition according to claim 1. the cation of the ionic compound is pyridinium,
A claim characterized in that the pressure-sensitive adhesive composition contains, as an essential component, the ionic compound in a proportion of 0.01 to 10 parts by weight with respect to 100 parts by weight of the first acrylic polymer. Item 6. The pressure-sensitive adhesive composition according to any one of items 1 to 5. The pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition has a surface resistivity of 1.0×10 ⁺¹² Ω/□ or less,
The pressure-sensitive adhesive layer has a peeling electrostatic voltage in the range of +0.3 to −0.3 kV with respect to the low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound,
The surface base material is one selected from the group consisting of a TAC-based film, a PMMA-based film, and a PET-based film, and the surface treatment applied to the surface of the surface base material is untreated, AG-treated, After being attached to a polarizing plate selected from the group consisting of LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment, it was left in an atmosphere of 60° C. and 90% RH for 2 days and then taken out. 7. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, which is free from contamination when peeled off after one day has passed. (B) the copolymerizable monomer containing a hydroxyl group is 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate , N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, at least one selected from the group of compounds,
(C) the copolymerizable monomer containing a carboxyl group is (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, Any one of claims 1 to 7, wherein at least one compound is selected from the group of compounds consisting of carboxypolycaprolactone mono(meth)acrylate and 2-(meth)acryloyloxyethyltetrahydrophthalic acid. 1. The pressure-sensitive adhesive composition according to item 1. The cross-linking retarder is a ketoenol tautomer compound,
Containing 0.1 to 300 parts by weight of the cross-linking retarder with respect to 100 parts by weight of the first acrylic polymer,
The crosslinking catalyst is at least one metal chelate compound selected from the group consisting of an aluminum chelate compound, a titanium chelate compound, and an iron chelate compound,
Containing 0.001 to 0.5 parts by weight of the crosslinking catalyst with respect to 100 parts by weight of the first acrylic polymer,
The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the weight part ratio of the cross-linking retarder/cross-linking catalyst is 80-1000. The adhesive composition contains a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight average molecular weight of 10,000 or less with respect to 100 parts by weight of the first acrylic polymer, and 0.01 to 0.5 10. The pressure-sensitive adhesive composition according to any one of claims 1 to 9, which is contained in a proportion of parts by weight. The second acrylic polymer is
(a) With respect to a total of 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18,
(b) a total of 2.0 to 12.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(c) a copolymer having a weight average molecular weight of more than 300,000 and not more than 800,000, obtained by copolymerizing 1 to 30 parts by weight of at least one polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer in total; can be,
The value of the total parts by weight of at least one or more copolymerizable monomers containing a hydroxyl group (B) contained in the first acrylic polymer with respect to the total 100 parts by weight of the first acrylic polymer (B- 1) and the total weight parts of at least one or more copolymerizable monomers containing a hydroxyl group (b) contained in the second acrylic polymer, relative to the total 100 weight parts of the second acrylic polymer. 5. The pressure-sensitive adhesive composition according to claim 4, wherein the ratio (b-1)/(B-1) to the value (b-1) is within the range of 1.0 to 2.0. The polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer has an average repeating number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14,
The diester content in the polyalkylene glycol chain-containing mono(meth)acrylate monomer is 0.2% or less,
The polyalkylene glycol chain-containing mono (meth) acrylic acid ester monomer is selected from the group consisting of polyalkylene glycol mono (meth) acrylate, methoxypolyalkylene glycol (meth) acrylate, and ethoxy polyalkylene glycol (meth) acrylate. 12. The pressure-sensitive adhesive composition according to claim 4 or 11, wherein at least one kind is contained in a ratio of 1 to 50 parts by weight based on 100 parts by weight of the second acrylic polymer. A pressure-sensitive adhesive film comprising a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition according to any one of claims 1 to 12 and laminated on one side of a resin film. A surface protection film using the pressure-sensitive adhesive film according to claim 13 . A surface protection film for a polarizing plate, using the pressure-sensitive adhesive film according to claim 13 . An optical film with a pressure-sensitive adhesive layer, which is obtained by laminating a pressure-sensitive adhesive layer obtained by cross-linking the pressure-sensitive adhesive composition according to any one of claims 1 to 12 on at least one surface of an optical film. 14. The pressure-sensitive adhesive film according to claim 13, wherein one side of the resin film opposite to the side on which the pressure-sensitive adhesive layer is formed is subjected to antistatic treatment and antifouling treatment.