JP7747835B2 - Pressure-sensitive adhesive composition, and pressure-sensitive adhesive film, surface protection film, and pressure-sensitive adhesive layer-attached optical film using the same - Google Patents

Description

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 to pressure-sensitive adhesive films and surface protection films that use the same. More specifically, the present invention relates to a pressure-sensitive adhesive composition that has balanced adhesive strength at both low and high peel speeds and is capable of achieving both antistatic performance and stain resistance, and to providing pressure-sensitive adhesive films and surface protection films that use the same.

Conventionally, in the manufacturing process of optical components such as polarizing plates, which are components that make up liquid crystal displays, a surface protection film is applied to temporarily protect the surface of the optical component. Such surface protection films are used only in the process of manufacturing the optical component, and are peeled off and removed from the optical component when the optical component is incorporated into an LCD display. Because such surface protection films for protecting the surface of optical components are used only in the manufacturing process of optical components, they are also commonly referred to as process films.

The surface protection film used in the process of producing such optical components has a pressure-sensitive adhesive layer formed on one side of an optically transparent polyethylene terephthalate (PET) resin film, and a release-treated release film is attached to the surface of the pressure-sensitive adhesive layer of the surface protection film to protect the pressure-sensitive adhesive layer until it is attached to the optical component.
Optical components such as polarizing plates, with the surface protection film attached, undergo product inspections that involve optical evaluation of the display performance, hue, contrast, and inclusion of foreign matter of the liquid crystal display panel. For this reason, the performance requirements for the surface protection film include the absence of air bubbles or foreign matter in the pressure-sensitive adhesive layer and the ability to reduce adhesion of low-molecular-weight components of the pressure-sensitive adhesive composition to the surface of the adherend, i.e., contamination resistance.
Furthermore, when peeling a surface protection film from an optical component such as a polarizing plate, there is concern that the static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend may cause peeling electrification, which could lead to malfunctions in the electrical control circuits of liquid crystal displays. For this reason, the pressure-sensitive adhesive layer of a surface protection film is required to have excellent antistatic properties.
Furthermore, in recent years, in addition to the conventionally used triacetyl cellulose (TAC), materials that are likely to cause peel electrification when the surface protective film of a polarizing plate is peeled off, such as acrylic resins such as polymethyl methacrylate (PMMA), polyester resins such as polyethylene terephthalate (PET), cyclic olefin polymers, and polycarbonates, have been increasingly used as protective layers (sometimes called protective films) for polarizers of polarizing plates. For this reason, the antistatic performance required for pressure-sensitive adhesive layers for surface protective films of polarizing plates needs to be superior to that of conventional materials.
Furthermore, when the surface protection film is finally peeled off from an optical component such as a polarizing plate, it is required to be able to be peeled off quickly, i.e., it is required that the adhesive strength does not change much depending on the peeling speed so that it can be peeled off quickly even at high speeds.

Thus, in recent years, in terms of ease of use when using a surface protection film, the adhesive layer constituting the surface protection film is required to (1) balance adhesive strength at low and high peel speeds, (2) have anti-fouling properties, and (3) have excellent antistatic properties.
However, while it is possible to satisfy each of the required performances (1) to (3) for the pressure-sensitive adhesive layer constituting the surface protection film, it has been an extremely difficult task to simultaneously satisfy all of the required performances (1) to (3) required for the pressure-sensitive adhesive layer of the surface protection film.

To solve these problems, for example, the following proposals have been proposed to (1) balance adhesive strength at low and high peel speeds, (2) provide stain resistance, and (3) provide excellent antistatic properties.

(1) With regard to balancing adhesive strength at low and high peeling speeds, an acrylic pressure-sensitive adhesive layer, which is mainly composed of a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group with 7 or less carbon atoms and a carboxyl group-containing copolymerizable compound and crosslinked with a crosslinking agent, has the problem that the pressure-sensitive adhesive transfers to the adherend after long-term adhesion, and the adhesive strength to the adherend increases significantly over time. To avoid this, a pressure-sensitive adhesive layer with a gel fraction of 60% or more, which uses a copolymer of a (meth)acrylic acid alkyl ester having an alkyl group with 8 to 10 carbon atoms and a copolymerizable compound having an alcoholic hydroxyl group and crosslinked with a crosslinking agent, and a surface protection member provided with this pressure-sensitive adhesive layer are known (Patent Document 1).
However, the pressure-sensitive adhesive layer described in Patent Document 1 has a problem in that it does not completely solve the problem of the adhesive strength to the adherend increasing over time.
Also, known is a pressure-sensitive adhesive layer prepared by blending a small amount of a copolymer of (meth)acrylic acid alkyl ester and a carboxyl group-containing copolymerizable compound with the above-mentioned copolymer, and crosslinking the copolymer with a crosslinking agent.However, when these pressure-sensitive adhesive layers are used for protecting the surface of a plastic plate or the like that has a low surface tension and a smooth surface, they have the problem of peeling phenomenon such as lifting due to heating during processing or storage, and the problem of poor removability due to the large adhesive strength at the high peeling speed that is the range of manual work.

In order to solve these problems, a pressure-sensitive adhesive composition has been proposed in which a copolymer of a monomer mixture obtained by adding a) 100 parts by weight of a (meth)acrylic acid alkyl ester containing as the main component a (meth)acrylic acid alkyl ester having an alkyl group having 8 to 10 carbon atoms, b) 1 to 15 parts by weight of a carboxyl group-containing 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, is blended with a crosslinking agent in an amount equivalent to or greater than the amount of the carboxyl groups of the above-mentioned b) component (Patent Document 2).
In the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition described in Patent Document 2, peeling phenomena such as lifting do not occur during processing or storage, and further, the adhesive strength increases little over time, resulting in excellent removability, and the layer can be removably peeled with little force even after long-term storage, particularly long-term storage under a high-temperature atmosphere, without leaving any adhesive residue on the adherend, and can be removably peeled with little force even when peeled at high speed.
However, in the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition described in Patent Document 2, the gel fraction of the pressure-sensitive adhesive layer in Examples 1 to 3 was 90%, and the adhesive strength at low peel speeds was prone to become excessive, and unpolymerized monomers or oligomers were prone to elution from the pressure-sensitive adhesive layer. Furthermore, Patent Document 2 does not describe antistatic performance and stain resistance, and there was a problem in that it was difficult to improve the pressure-sensitive adhesive layer to have excellent antistatic performance and stain resistance when the adherend was a material that was prone to generating static electricity upon peeling.

Furthermore, with regard to (2) stain resistance, a pressure-sensitive adhesive composition has been disclosed that contains 100 parts by mass of a (meth)acrylic copolymer having a weight-average molecular weight of 100,000 or more and less than 1,000,000, which is composed of 0 part by mass or more and less than 0.5 part by mass of a carboxyl group-containing monomer, 0.6 to 9 parts by mass of a hydroxy group-containing (meth)acrylic monomer, and 99.4 to 90.5 parts by mass of a (meth)acrylic acid ester monomer; and 0.1 to 5 parts by mass of a carbodiimide crosslinking agent (Patent Document 3).
The pressure-sensitive adhesive composition described in Patent Document 3 is characterized by using a carbodiimide-based crosslinking agent as a crosslinking agent for a (meth)acrylic copolymer of a specific composition. This makes it possible to provide a pressure-sensitive adhesive layer having a crosslinked structure that can adapt to shrinkage due to pressure and temperature during autoclave treatment. Therefore, the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition described in Patent Document 3 is capable of suppressing or preventing foaming even under high-temperature and high-pressure conditions (during autoclave treatment), and is said to have excellent contamination resistance and transparency.
However, in the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition described in Patent Document 3, although the stain resistance performance is improved, it has not been possible to simultaneously achieve excellent adhesive performance by balancing adhesive strength at low and high peel speeds and antistatic performance, and this remains a problem to be solved.

Regarding (3) excellent antistatic performance, a method of kneading an antistatic agent into a substrate film is known as a method for imparting antistatic properties to a surface protective film. Examples of antistatic agents disclosed include (a) various cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups, (b) anionic antistatic agents having anionic groups such as sulfonate groups, sulfate groups, phosphate groups, and phosphonate groups, (c) amphoteric antistatic agents such as amino acid-based and amino sulfate-based, (d) nonionic antistatic agents such as amino alcohol-based, glycerin-based, and polyethylene glycol-based, and (e) polymer-type antistatic agents obtained by increasing the molecular weight of the above-mentioned antistatic agents (Patent Document 4).
However, although the surface protection film described in Patent Document 4 describes imparting antistatic properties related to the adhesion of dirt to the adherend, it does not describe a solution for achieving both excellent adhesive properties and contamination resistance, and this remains a problem that needs to be solved.

In recent years, it has been proposed to incorporate an antistatic agent directly into a pressure-sensitive adhesive layer, rather than incorporating it into a substrate film or applying it to the surface of a substrate film. For example, Patent Document 5 discloses an antistatic pressure-sensitive adhesive composition characterized in that a salt having an anion having a fluoro group and a sulfonyl group is dispersed in a dissolved state in a polyether ester plasticizer containing a polyether group in the main chain.
The pressure-sensitive adhesive composition described in Patent Document 5 discloses the use of a plasticizer consisting of an ester formed from a mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group and an alcohol having an acyclic hydrocarbon group of 1 to 20 carbon atoms, or an ester in which the unsaturated group in the unsaturated acyclic hydrocarbon group has been epoxidized. Such mono- or dicarboxylic acid having a saturated or unsaturated acyclic hydrocarbon group has a carbon number close to the carbon number of the acrylic monomer constituting the acrylic copolymer used in the pressure-sensitive adhesive layer, which improves compatibility with the antistatic pressure-sensitive adhesive composition and allows the plasticizer to be suitably retained in the acrylic antistatic pressure-sensitive adhesive composition, thereby suppressing bleed-out.
However, although Patent Document 5 discloses a technique for improving antistatic performance and bleed-out in a pressure-sensitive adhesive layer obtained by crosslinking an antistatic pressure-sensitive adhesive composition, it does not disclose that excellent adhesive performance can be obtained by balancing adhesive strength at low and high peel speeds, and the problem of obtaining a pressure-sensitive adhesive layer with excellent adhesive performance remains.

Japanese Patent Application Publication No. 63-225677 Japanese Patent Application Publication No. 11-256111 JP 2011-122054 A Japanese Patent Application Publication No. 11-070629 JP 2014-118469 A

As described above, there is no prior art that solves the problem of simultaneously achieving the following required properties for the pressure-sensitive adhesive layer that constitutes a surface protection film: (1) balancing adhesive strength at low and high peel speeds, (2) having contamination resistance, and (3) having excellent antistatic properties.
Furthermore, conventionally, there has been a trade-off between the antistatic performance of a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition with antistatic properties and the anti-contamination performance of the adherend in a surface protection film using the same, and it has been difficult to improve the anti-contamination performance while maintaining the antistatic performance.
Furthermore, in recent years, the types of materials of the adherends to which surface protection films are attached have increased, and the surface treatment conditions of the adherends have become more diverse. As a result, it has become increasingly difficult for the pressure-sensitive adhesive layer constituting the surface protection film to balance adhesive strength with all adherends, particularly at the above-mentioned (1) low and high peel speeds, and (2) to have contamination resistance.

The present invention was made in consideration of the above circumstances, and aims to provide a pressure-sensitive adhesive composition that has balanced adhesive strength at both low and high peel speeds, and that is capable of achieving both antistatic performance and stain resistance, as well as a pressure-sensitive adhesive film and a surface protection film that use the same.

The inventors of the present invention have reconsidered the type of compound to be copolymerized with an acrylic polymer in an adhesive composition used in a surface protection film for polarizing plates, the adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, and have worked diligently to improve the above-mentioned problem of achieving both (1) a balance of adhesive strength at both low and high peel speeds, and (2) contamination resistance.
As a result, it was found that the above problems (1) and (2) can be simultaneously solved by specifying the content ratio of 2-ethylhexyl acrylate and a monofunctional methacrylate monomer, the homopolymer of which has a glass transition temperature (Tg) of 0°C or higher, within a specific range among (A) alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10. The present invention was also completed by providing a pressure-sensitive adhesive composition that further contains an antistatic agent.

In order to solve the above problems, the present invention provides a pressure-sensitive adhesive composition comprising a first acrylic polymer, a crosslinking agent, and an ionic compound, wherein the first acrylic polymer is a copolymer of (A) 100 parts by weight of at least two or more alkyl (meth)acrylates having an alkyl group carbon number of C1 to C10, (B) 1.0 to 6.0 parts by weight of at least one or more copolymerizable monomers containing a hydroxyl group, and (C) 0.01 to 0.6 parts by weight of at least one or more copolymerizable monomers containing a carboxyl group, and has an acid value of 0.1 to 1.0 and a weight-average molecular weight of more than 300,000. The adhesive composition is an acrylic polymer consisting of a copolymer of more than 1 million carbon atoms, and contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher out of a total of 100 parts by weight of (A) at least two alkyl (meth)acrylates whose alkyl groups have carbon atoms of C1 to C10. The adhesive composition also contains a tri- or higher functional isocyanate compound as the crosslinking agent, a crosslinking retarder, and a crosslinking catalyst other than a tin compound as the crosslinking catalyst.

When a surface protection film is formed by laminating a 15 μm thick adhesive layer obtained by crosslinking the adhesive composition onto one side of a 38 μm thick polyester film and then laminating the film to the surface of a polarizing plate, the adhesive strength at a low peeling speed of 0.3 m/min when peeled from the polarizing plate is preferably 0.01 to 0.1 N/25 mm, and 1.0 N/25 mm or less at a high peeling speed of 30 m/min when peeled from the polarizing plate.

It is preferable that the monofunctional methacrylate monomer having a homopolymer Tg of 0°C or higher is 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.

The pressure-sensitive adhesive composition preferably further contains a second acrylic polymer, which is a copolymer obtained by copolymerizing (a) at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C1 to C18, (b) at least one copolymerizable monomer having a hydroxyl group, and (c) at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, and the pressure-sensitive adhesive composition preferably contains 0.1 to 5.0 parts by weight of the second acrylic polymer per 100 parts by weight of the total of the at least two or more (A) alkyl (meth)acrylates having an alkyl group carbon number of C1 to C10.

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

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

the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 1.0 × 10 ⁺¹² Ω/□ or less;
the peeling electrification voltage of the pressure-sensitive adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound is within the range of +0.3 to −0.3 kV;
It is preferable that the surface substrate is one selected from the group consisting of a TAC film, a PMMA film, and a PET film, and the surface treatment applied to the surface of the surface substrate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment, and then the film is attached to a polarizing plate, left to stand for two days in an atmosphere at a temperature of 60°C and a humidity of 90% RH, removed, and then peeled off after one day has passed, resulting in no contamination.

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

It is preferable that the crosslinking retarder is a keto-enol tautomer compound, and that the crosslinking retarder is contained in a proportion of 0.1 to 300 parts by weight per 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 aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds, and that the crosslinking catalyst is contained in a proportion of 0.001 to 0.5 parts by weight per 100 parts by weight of the first acrylic polymer; and the weight ratio of the crosslinking retarder to the crosslinking catalyst is 80 to 1000.

The pressure-sensitive adhesive composition preferably contains 0.01 to 0.5 parts by weight of a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight-average molecular weight of 10,000 or less per 100 parts by weight of the first acrylic polymer.

The second acrylic polymer is a copolymer having a weight average molecular weight of more than 300,000 and not more than 800,000, obtained by copolymerizing 2.0 to 12.0 parts by weight of (b) at least one or more copolymerizable monomers containing a hydroxyl group and 1 to 30 parts by weight of (c) at least one mono(meth)acrylic acid ester monomer containing a polyalkylene glycol chain with 100 parts by weight of (a) at least one or more (meth)acrylic acid ester monomers having an alkyl group carbon number of C1 to C18, and the ratio (b-1)/(B-1) of the total parts by weight of the at least one or more copolymerizable monomers containing a hydroxyl group (B-1) contained in the first acrylic polymer relative to 100 parts by weight of the first acrylic polymer to the total parts by weight of the at least one or more copolymerizable monomers containing a hydroxyl group (b-1) contained in the second acrylic polymer relative to 100 parts by weight of the second acrylic polymer is preferably within the range of 1.0 to 2.0.

Preferably, the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of 3 to 14 alkylene oxides constituting the polyalkylene glycol chain, the diester content in the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 0.2% or less, and the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer contains at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate in an amount of 1 to 50 parts by weight per 100 parts by weight of the second acrylic polymer.

The present invention also provides an adhesive film characterized by having an adhesive layer formed by crosslinking the above-mentioned adhesive composition laminated on one side of a resin film.

The present invention also provides a surface protection film that uses the above-mentioned adhesive film.

The present invention also provides a surface protection film for polarizing plates that uses the above-mentioned adhesive film.

The present invention also provides an optical film with a pressure-sensitive adhesive layer, which comprises an optical film and a pressure-sensitive adhesive layer formed by crosslinking the above-mentioned pressure-sensitive adhesive composition laminated on at least one surface of the optical film.

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

In the pressure-sensitive adhesive composition according to the present invention, the first acrylic polymer contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0° C. or higher, out of a total of 100 parts by weight of (A) at least two or more alkyl (meth)acrylates whose alkyl groups have carbon atoms of C1 to C10. This makes it possible, particularly in a surface protection film for polarizing plates using PMMA as a base material, to simultaneously achieve (1) a balance of adhesive strength at both low and high peel speeds, and (2) stain resistance.
It is not clear why the inclusion of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0° C. or higher in the pressure-sensitive adhesive composition of the present invention contributes to (1) balancing adhesive strength at low and high peel speeds and (2) providing stain resistance. Possible reasons for this are thought to be that these methacrylate monomers produce polymers with high Tg despite not having polar functional groups such as carboxyl groups or amide groups, or long-chain alkyl groups exceeding C10, thereby significantly improving adhesive performance in the crosslinked state, and also improving affinity with methyl methacrylate, the main component of PMMA-based films.

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 crosslinking agent, and an ionic compound, wherein the acrylic polymer is
(A) 100 parts by weight of a total of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10;
(B) 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(C) 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group;
an acrylic polymer comprising 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,
(A) contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher, out of a total of 100 parts by weight of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10;
The pressure-sensitive adhesive composition is characterized by containing a tri- or higher functional isocyanate compound as the crosslinking agent, a crosslinking retarder, and a crosslinking catalyst other than a tin compound as the crosslinking catalyst.

The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment is the main polymer of the pressure-sensitive adhesive composition, and is sometimes referred to as the first acrylic polymer when distinguishing it from the second acrylic polymer described below. The first acrylic polymer is an acrylic polymer having a glass transition temperature (Tg) of 0°C or lower. Furthermore, the first acrylic polymer is preferably a copolymer whose main component is (A) an alkyl (meth)acrylate whose alkyl group has a carbon number of C1 to C10.

(A) Examples of alkyl (meth)acrylates having an alkyl group with a carbon number of 1 to 10 include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, 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, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. The alkyl groups in these alkyl (meth)acrylates may be either acyclic (straight-chain or branched) or cyclic (monocyclic or polycyclic).

The first acrylic polymer preferably contains, relative to 100 parts by weight of the total of (A), 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of a total of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher.
Furthermore, 2-ethylhexyl acrylate is preferably contained in an amount of 50 parts by weight or more, more preferably 60 parts by weight or more, and particularly preferably 70 parts by weight or more, of a total of 100 parts by weight of (A).
Furthermore, among (A) alkyl (meth)acrylates in which the alkyl group has a carbon number of C1 to C10, examples of the monofunctional methacrylate monomer having a Tg of 0°C or higher include 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, methyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, and dicyclopentamethacrylate. 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, methacrylate monomers in which the alkyl group has a carbon number of C1 to C4 are more preferred, and 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 are particularly preferred.
The total amount of one or more monofunctional methacrylate monomers having a Tg of 0°C or higher is preferably 5 to 40 parts by weight, more preferably 8 to 40 parts by weight, and particularly preferably 10 to 35 parts by weight, out of 100 parts by weight of the total of (A). In the following description, when the Tg of a monomer is simply referred to, it may refer to the Tg of the homopolymer.

The hydroxyl group-containing copolymerizable monomer (B) used in the first acrylic polymer is preferably at least one selected from the group consisting of 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, and the like.
The first acrylic polymer preferably contains at least one kind of copolymerizable monomer (B) containing a hydroxyl group in a proportion of 1.0 to 6.0 parts by weight, more preferably 2.0 to 6.0 parts by weight, and particularly preferably 2.5 to 5.5 parts by weight, per 100 parts by weight of the total of (A).

The carboxyl group-containing copolymerizable monomer (C) used in the first acrylic polymer is preferably at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, and the like.
The first acrylic polymer preferably contains 0.01 to 0.6 parts by weight, more preferably 0.01 to 0.5 parts by weight, and particularly preferably 0.01 to 0.4 parts by weight of at least one copolymerizable monomer (C) containing a carboxyl group, relative to 100 parts by weight of the total of (A).

The method for producing the first acrylic polymer is not particularly limited, and any known polymerization method, such as solution polymerization or emulsion polymerization, can be used as appropriate. The first acrylic polymer preferably has a weight-average molecular weight of more than 300,000 and not more than 1,000,000. The acid value of the first acrylic polymer is preferably 0.1 to 1.0. This improves stain resistance. Here, "acid value" is an index representing the acid content and is expressed as the number of milligrams of potassium hydroxide required to neutralize 1 g of a polymer containing carboxyl groups.

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

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

The cation of the ionic compound may be 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. The organic group contained in the cation may have some or all of the hydrogen atoms 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 the substituents, etc.

Specific examples of the ionic compound include 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, and 4,5-diiodo-1-butyl-3-methylimidazolium 3-Iodobenzenesulfonate salt, 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 Examples include bis(pentafluorobenzenesulfonyl)imide salts.

The pressure-sensitive adhesive composition according to this embodiment further contains a trifunctional or higher isocyanate compound (D) as a crosslinking agent. Examples of trifunctional or higher isocyanate compounds include biuret-modified or isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, as well as adducts with trivalent or higher polyols such as trimethylolpropane and glycerin. The proportion of the trifunctional or higher isocyanate compound (D) as a crosslinking agent is preferably 0.1 to 10 parts by weight, and more preferably 0.1 to 6 parts by weight, per 100 parts by weight of the first acrylic polymer.

The pressure-sensitive adhesive composition of this embodiment may contain a crosslinking retarder (E). Examples of the crosslinking retarder (E) include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, as well as β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. These are keto-enol tautomer compounds, and in pressure-sensitive adhesive compositions using a polyisocyanate compound as a crosslinking agent, blocking the isocyanate groups of the crosslinking agent (D) can suppress excessive viscosity increase and gelation of the pressure-sensitive adhesive composition after the crosslinking agent is added, thereby extending the pot life of the pressure-sensitive adhesive composition. The crosslinking retarder (E) is preferably at least one selected from the group consisting of acetylacetone and ethyl acetoacetate. The crosslinking retarder (E) is preferably contained in an amount of 0.1 to 300 parts by weight per 100 parts by weight of the first acrylic polymer.

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

The crosslinking catalyst (F) is preferably at least one metal chelate compound selected from the group consisting of aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds. The crosslinking catalyst (F) is preferably contained in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the first acrylic polymer.

In contrast to the crosslinking catalyst (F), the crosslinking retarder (E) has the effect of inhibiting crosslinking, so it is preferable to appropriately set the ratio of the crosslinking retarder (E) to the crosslinking catalyst (F). To extend the pot life of the PSA composition and improve its storage stability, the weight ratio of (E)/(F) is preferably 80 to 1000, more preferably 80 to 700, and particularly preferably 80 to 300. Here, the weight ratio of (E)/(F) is the quotient obtained by dividing the weight parts of (E) by the weight parts of (F).

The pressure-sensitive adhesive composition according to this embodiment may contain (H) a polyether-modified siloxane compound as an optional component. The (H) polyether-modified siloxane compound is a siloxane compound having a polyether group, and in addition to the usual siloxane unit [—SiR ¹ ₂ —O—], has a siloxane unit having a polyether group [—SiR ¹ (R ² O(R ³ O) _n R ⁴ )—O—]. Here, R ¹ represents one or more alkyl or aryl groups, R ² and R ³ represent one or more alkylene groups, and R ⁴ represents one or more alkyl groups, acyl groups, or the like (terminal groups). Examples of the polyether group include 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 terminal of the polyether group may be an OH group (R ⁴ =H in the above general formula).

The polyether-modified siloxane compound (H) is preferably a polyether-modified siloxane compound having an HLB value of 6 to 12. The polyether-modified siloxane compound (H) is preferably contained in an amount of 0.01 to 0.5 parts by weight, more preferably 0.02 to 0.35 parts by weight, and particularly preferably 0.02 to 0.25 parts by weight, per 100 parts by weight of the first acrylic polymer. The HLB value is the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) as defined, for example, in JIS K3211 (Surfactant Terminology).
The polyether-modified siloxane compound can be obtained, for example, by grafting an organic compound having an unsaturated bond and a polyoxyalkylene group onto a polyorganosiloxane main chain having a silicon hydride group by a hydrosilylation reaction.Specific examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxypropylene)siloxane polymer, etc.

By incorporating (H) a polyether-modified siloxane compound into the pressure-sensitive adhesive composition, the adhesive strength and rework performance of the pressure-sensitive adhesive layer can be improved. The weight-average molecular weight of (H) the polyether-modified siloxane compound is preferably 10,000 or less. From the perspective of compatibility with acrylic polymers, the lower the HLB value and the lower the molecular weight, the better the compatibility. However, if the polyether-modified siloxane compound has a low molecular weight, it can achieve excellent antistatic properties even if it has a relatively high HLB value and somewhat low compatibility with the polymer.

The pressure-sensitive adhesive composition according to this embodiment may contain a second acrylic polymer as an optional component. When the pressure-sensitive adhesive composition further contains a second acrylic polymer copolymerized with a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer, the compatibility between the ionic compound and the acrylic polymer is improved, thereby further improving antistatic performance and stain resistance. Examples of the second acrylic polymer include copolymers of (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, and (c) at least one polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

Examples of (a) (meth)acrylic acid ester monomers having an alkyl group with a carbon number of 1 to 18 used in the second acrylic polymer include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, 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, and isooctyl (meth)acrylate. Examples of the alkyl group (a) include methyl (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, and cyclohexyl (meth)acrylate. The alkyl group (a) may be acyclic (straight-chain or branched) or cyclic (monocyclic or polycyclic).
It is also possible to select the same compound or ratio of (a) the (meth)acrylic acid ester monomer in which the alkyl group has a carbon number of C1 to C18 used in the second acrylic polymer and (A) the alkyl (meth)acrylate in which the alkyl group has a carbon number of C1 to C10 used in the first acrylic polymer.
Alternatively, (a) may contain a compound different from (A). Furthermore, even if the monomers are the same compound, the proportion in (a) may be different from the proportion in (A). For example, the second acrylic polymer may be a copolymer in which alkyl methacrylate is not copolymerized. Furthermore, the second acrylic polymer may be a copolymer in which a (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C11 to C18 is not copolymerized, or the second acrylic polymer may contain a (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C11 to C18.

The (b) copolymerizable monomer containing a hydroxyl group used in the second acrylic polymer is preferably at least one selected from the group consisting of 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, and the like.
The second acrylic polymer preferably contains 2.0 to 12.0 parts by weight, more preferably 3.0 to 12.0 parts by weight, and particularly preferably 4.0 to 12.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group, relative to 100 parts by weight of the at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18.
The hydroxyl group-containing copolymerizable monomer (b) used in the second acrylic polymer may be the same compound or in the same proportion as the hydroxyl group-containing copolymerizable monomer (B) used in the first acrylic polymer. Alternatively, (b) may contain a compound different from (B). Furthermore, even if the monomers are the same compound, the proportion in (b) may be different from the proportion 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 pressure-sensitive adhesive composition of the present embodiment, the second acrylic polymer containing (c) a 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 acid ester monomer is not copolymerized, or it may be copolymerized with the same polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer as the second acrylic polymer.
The second acrylic polymer is preferably contained in an amount of 0.1 to 5.0 parts by weight, more preferably 0.1 to 3.5 parts by weight, and particularly preferably 0.1 to 2.5 parts by weight, relative to 100 parts by weight in total of the at least two or more alkyl (meth)acrylates (A) whose alkyl group has a carbon number of C1 to C10 and are used in the first acrylic polymer.

(c) The polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer may be a compound in which one of the multiple hydroxyl groups of a polyalkylene glycol is esterified as a (meth)acrylic acid ester. Because the (meth)acrylic acid ester group serves as a polymerizable group, it can be copolymerized with a second acrylic polymer. It may be a polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group remains OH, or an alkoxy polyalkylene glycol mono(meth)acrylate in which the other hydroxyl group is converted to an alkyl ether. Since polyalkylene glycol mono(meth)acrylate falls under (c), it is not classified as (B) or (b) even if it contains a hydroxyl group.

The polyalkylene glycol that makes up the polyalkylene glycol chain may be any glycol compound having one or more alkylene groups, such as polyethylene glycol, polypropylene glycol, polybutylene glycol, polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol.

It is preferable that the average number of repeating alkylene oxides constituting the polyalkylene glycol chain of (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is 3 to 14. 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 (c) the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.
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" refers to the content (wt%) of polyalkylene glycol di(meth)acrylic acid ester contained in the (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer.

The (c) polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is preferably at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate.
The second acrylic polymer preferably contains 1 to 30 parts by weight, more preferably 2 to 30 parts by weight, and particularly preferably 5 to 25 parts by weight of (c) a polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer relative to 100 parts by weight of the total of (a) at least one (meth)acrylic acid ester monomer having an alkyl group with a carbon number of C1 to C18.

The method for producing the second acrylic polymer is not particularly limited, and any known polymerization method such as solution polymerization or emulsion polymerization 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 not more than 800,000. The weight-average molecular weight of the second acrylic polymer may be approximately 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 a functional group capable of reacting with the crosslinking agent (D). The second acrylic polymer may be a copolymer in which a copolymerizable monomer containing a carboxyl group has not been copolymerized, or may be a copolymer in which a copolymerizable monomer containing a carboxyl group similar to that of the first acrylic polymer has been copolymerized. The crosslinking agent (D) may be involved in crosslinking between the first acrylic polymer and the second acrylic polymer.

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

The adhesive composition of this embodiment may contain, in addition to the additives described above, known additives such as surfactants, cure accelerators, plasticizers, fillers, cure retarders, processing aids, antioxidants, and antioxidants, as appropriate. These may 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 used in a surface protection film for a polarizing plate. The pressure-sensitive adhesive layer of the surface protection film may be attached to a protective layer of a 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 a TAC-based film, a PMMA-based film, and a PET-based film. Here, TAC is an abbreviation for triacetyl cellulose, PMMA is an abbreviation for polymethyl methacrylate, and PET is an abbreviation for polyethylene terephthalate.
The surface of the protective layer of the polarizer of the polarizing plate may be subjected to at least one surface treatment selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment, where AG stands for anti-glare, LR stands for low reflection, and AR stands for anti-reflection.

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

The adhesive layer obtained by crosslinking the adhesive composition of this embodiment preferably exhibits a peel electrification voltage in the range of +0.3 to -0.3 kV relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound. Examples of fluorine compounds used in the composition for forming a low refractive index layer include fluorine-containing copolymers, which are polymers of one or more of fluorinated olefins, fluorinated vinyl ethers, and fluorinated alkyl (meth)acrylates, as well as condensates of fluorinated alkyl group-containing silane compounds. The fluorine-containing copolymer may be copolymerized with a fluorinated monomer and a non-fluorinated monomer, such as an olefin, vinyl ether, or (meth)acrylate. The low refractive index layer may be combined with a high refractive index layer to form an antireflection layer.

When measuring the peeling electrification voltage for a low refractive index layer, examples of substrates on which a low refractive index layer is formed include PMMA substrates and TAC substrates. Furthermore, the adhesive layer crosslinked with the adhesive composition of this embodiment preferably exhibits a peeling electrification voltage in the range of +0.3 to -0.3 kV relative to a plain layer on a PMMA substrate or TAC substrate that has not been treated in any way.

It is preferable that the pressure-sensitive adhesive layer is not contaminated when it is attached to an adherend such as a polarizing plate, left in an atmosphere at a temperature of 60°C and a humidity of 90% for two days (48 hours), removed from the atmosphere, and peeled off one day later. An example of an adherend is 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 a fluorine compound used for the low-reflection surface treatment may be the same as or different from the resin composition containing a fluorine compound used to form the low-refractive index layer described above. Examples of protective layers and surface treatments include the protective layer of the polarizer described above and the surface treatment applied to its surface.

A surface protection film formed by laminating a 15 μm thick adhesive layer obtained by crosslinking the adhesive composition of this embodiment to one side of a 38 μm thick polyester film is adhered to the surface of a polarizing plate. When the surface protection film is then peeled from the polarizing plate, the adhesive strength at a low peeling speed of 0.3 m/min is preferably 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. This results in performance in which the adhesive strength varies little with peeling speed, enabling rapid peeling even at high peeling speeds. Furthermore, when the surface protection film is peeled off for re-application, it is easy to peel from the adherend without requiring excessive force.

The gel fraction of the adhesive layer obtained by crosslinking the adhesive composition of this embodiment is preferably 95 to 100%, and more preferably 97 to 100%. Such a high gel fraction in the adhesive layer prevents excessive adhesive strength at slow peel speeds, reduces elution of unpolymerized monomers or oligomers from the copolymer, improves reworkability and durability at high temperatures and high humidity, and suppresses contamination of the adherend.

The adhesive film of this embodiment comprises an adhesive layer formed on one or both sides of a resin film, the adhesive layer being formed by crosslinking the adhesive composition of this embodiment. The surface protection film of this embodiment comprises an adhesive layer formed on one side of a resin film, the adhesive layer being formed by crosslinking the adhesive composition of this embodiment. The adhesive composition of this embodiment has excellent antistatic properties, an excellent balance of adhesive strength at both low and high peel speeds, and also exhibits stain resistance. Therefore, it can be suitably used as a surface protection film for polarizing plates.

As the base film of the pressure-sensitive adhesive layer and the release film (separator) that protects the adhesive surface, a resin film such as a polyester film can be used.
One surface of the resin film, opposite to the surface on which the pressure-sensitive adhesive layer is formed, may be subjected to an antistatic treatment and an antifouling treatment. Examples of the antistatic treatment include coating or kneading an antistatic agent. Examples of the 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 a release treatment with a silicone-based, fluorine-based, or long-chain alkyl-based release agent on the surface that faces the adhesive surface of the pressure-sensitive adhesive layer.

Furthermore, an optical film with a pressure-sensitive adhesive layer can be obtained by laminating a pressure-sensitive adhesive layer obtained by crosslinking 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, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancing films. Examples of devices to which optical members are applied include liquid crystal panels, organic EL panels, and touch panels.
In the case of optical surface protection films such as surface protection films for polarizing plates and pressure-sensitive adhesive films, the substrate film and pressure-sensitive adhesive layer preferably have sufficient transparency.

The present invention will be explained in detail below using 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, and the air inside the reactor was replaced with nitrogen gas. Then, 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, 0.2 parts by weight of acrylic acid, and a solvent (ethyl acetate) were added to the reactor. Then, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was allowed to react at 65°C for 6 hours, yielding a first acrylic polymer used in Example 1.
[Examples 2 to 6 and Comparative Examples 1 to 4]
The first acrylic polymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as the first acrylic polymer solution used in Example 1, except that the monomer compositions were changed to those shown in (A), (B), and (C) in Table 1, respectively.
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 not more than 1,000,000.

<Production of Pressure-Sensitive Adhesive Composition and Surface Protection Film>
[Example 1]
To the first acrylic polymer solution of Example 1 prepared as described above, 2.0 parts by weight of a crosslinker (Coronate HX), 9 parts by weight of acetylacetone, 0.1 parts by weight of a crosslinking catalyst (titanium trisacetylacetonate), 0.9 parts by weight of an antistatic agent (3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt), 0.05 parts by weight of a polyether-modified siloxane compound (HLB = 7), and 0.2 parts by weight of a copolymer having a weight average molecular weight (Mw) of 600,000, obtained by copolymerizing 2-ethylhexyl acrylate, 8-hydroxyoctyl acrylate, and methoxypolyethylene glycol acrylate (n = 8) in a weight ratio of 100:8:15, were added and mixed with stirring to obtain a pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was applied to a release film (a silicone resin-coated PET film) and then dried at 90 ° C. to remove the solvent, yielding a pressure-sensitive adhesive layer having a thickness of 20 μm. Thereafter, an adhesive layer with a release film was transferred to the side of the base film (a PET film with one side treated for antistatic and antifouling properties) opposite the side treated for antistatic and antifouling properties, thereby obtaining the surface protection film of Example 1 having a laminated structure of "base film/adhesive layer/release film."
[Examples 2 to 6 and Comparative Examples 1 to 4]
The surface protection films of Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as the surface protection film of Example 1 above, except that the compositions of the additives were changed as shown in (D) to (H) and (J) in Tables 1 and 2, respectively.
In the surface protection films of Examples 1 to 6 and Comparative Examples 1 to 4, the gel fraction of the pressure-sensitive adhesive layer was in the range of 95 to 100%.

In Tables 1 and 2, the parts by weight of each component were calculated based on 100 parts by weight of the total of (A) alkyl (meth)acrylates having an alkyl group with carbon numbers of C1 to C10.
In Tables 1 and 2, in each of the columns (B) to (H) and (J), the content (parts by weight) of each component is shown by the numerical value in parentheses ( ), with the acrylic polymer being 100 parts by weight.
The compound names of the abbreviations of the components (A) to (H) used in Tables 1 and 2 are shown in Table 3. 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.

Of the (G) antistatic agents, G-1 to G-4 have a melting point of 25°C or higher and 80°C or lower, and are ionic compounds that are solid at room temperature. G-5 has a melting point above 80°C and is an ionic compound that is solid at room temperature. Furthermore, of the (H) polyether-modified siloxane compounds, H-1 to H-6 have a weight average molecular weight of 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. Table 5 shows the compound names of the abbreviations for each component used in Table 4. In Table 4, the parts by weight of each component were calculated with the total of (a) being 100 parts by weight. Furthermore, in each of columns (b) to (c), the content ratio (parts by weight) calculated with the total of the second acrylic polymer being 100 parts by weight is shown in parentheses ( ).

(c) Of the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomers, I-1 to I-3 are monomers with a diester content of 0.2 wt% or less, and I-4 is a monomer with a diester content of 0.8 wt%. The value of n indicates the average repeat number of alkylene oxides.

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

<Adhesive strength test method>
The release film was peeled off to expose the adhesive layer, and the surface protection film was then attached to the surface of a polarizing plate via the adhesive layer. After leaving it for one day, it was autoclaved at 50°C and 5 atmospheres for 20 minutes and then left at room temperature for a further 12 hours to prepare a sample for measuring adhesive strength. The obtained sample was peeled in the 180° direction at a low speed (0.3 m/min) or a high speed (30 m/min) using a tensile tester, and the peel strength was measured and defined as adhesive strength.
Here, the protective layer of the polarizer of the polarizing plate is polymethyl methacrylate (PMMA) having an AG-LR treated layer.

<Surface resistivity test method>
After aging the surface protection film and before bonding it to a polarizing plate, the release film was peeled off to expose the pressure-sensitive adhesive layer, and the surface resistivity of the pressure-sensitive adhesive layer was measured using a resistivity meter, Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech).

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

<Test method for stain resistance>
A polarizing plate that had been subjected to low reflection (LR) surface treatment was bonded to one side of a glass plate via a pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive tape) using a laminating machine. Then, a surface protective film was bonded to the surface of the polarizing plate using a laminating machine. After bonding to the adherend, the polarizing plate was left in an atmosphere at a temperature of 60°C and a humidity of 90% RH for 2 days (48 hours). After removing from the atmosphere, the surface protective film was peeled off and the state of contamination on the surface of the polarizing plate was visually observed. The evaluation criteria for contamination resistance were as follows: no contamination on the surface of the polarizing plate was evaluated as "○", slight contamination was evaluated as "△", and contamination was evaluated as "×".

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

The surface protection films of Examples 1 to 6 had an adhesive strength of 0.01 to 0.1 N/25 mm at a low peel speed of 0.3 m/min to the adherend (polarizing plate), and an adhesive strength of 1.0 N/25 mm or less at a high peel speed of 30 m/min, and therefore had excellent adhesive performance due to a balance of adhesive strength at low and high peel speeds.
Furthermore, the surface protection films of Examples 1 to 6 had a surface resistivity of the pressure-sensitive adhesive layer of 1.0 × 10 ⁺¹² Ω/□ or less, and the peeling electrification voltage of the pressure-sensitive adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound was in the range of +0.3 to −0.3 kV, and thus had excellent antistatic performance.
Furthermore, the surface protection films of Examples 1 to 6 were attached to the substrate, and then left for 48 hours in an atmosphere at a temperature of 60°C and a humidity of 90% RH. Even after being removed from the atmosphere and one day had passed, there was no contamination of the various polarizing plates that were the substrate, and the surface protection films of Examples 1 to 6 also had excellent contamination resistance.
That is, the evaluation results shown in Table 6 demonstrate that the surface protection films of Examples 1 to 6 were able to solve the problems of the present invention.

The surface protection film of Comparative Example 1 (in which the Tg of the monofunctional methacrylate monomer copolymerized with the first acrylic polymer was less than 0° C.) had poor stain resistance to adherends other than TAC.
Furthermore, the surface protection film of Comparative Example 2 (containing an excess of hydroxyl group-containing monomer copolymerized with the first acrylic polymer) had a high adhesive strength at a low peel speed and poor stain resistance against PMMA.
Furthermore, the surface protection film of Comparative Example 3 (in which the first acrylic polymer did not contain a methacrylate monomer with a Tg of 0°C or higher, the proportion of carboxyl group-containing monomers was excessive, and the melting point of the antistatic agent exceeded 80°C) had a large adhesive strength at a high peel speed, a high peel charging voltage, and poor contamination resistance.
Furthermore, the surface protection film of Comparative Example 4 (which in Tables 1 and 2 is identical to the components (B) to (H) and (J) of Example 3, except that the component (A) of Comparative Example 4 does not contain a methacrylate monomer having a Tg of 0°C or higher) had a higher adhesive strength at a high peel speed, a higher peel electrification voltage, and poorer stain resistance to PMMA than the surface protection film of Example 3.
From the comparison of the performance of the surface protection film of Comparative Example 4 with that of Example 3, it became clear that the inclusion of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher in the pressure-sensitive adhesive composition according to the present invention contributes to achieving both (1) a balance of adhesive strength at low and high peel speeds and (2) stain resistance.
Furthermore, the surface protection films of Comparative Examples 1 to 4 were unable to solve the problems of the present invention.

Claims (16)

A pressure-sensitive adhesive composition comprising a first acrylic polymer, a crosslinking agent, and an ionic compound,
The first acrylic polymer is
(A) 100 parts by weight of a total of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10;
(B) 1.0 to 6.0 parts by weight of at least one copolymerizable monomer containing a hydroxyl group;
(C) 0.01 to 0.6 parts by weight of at least one copolymerizable monomer containing a carboxyl group;
an acrylic polymer comprising 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,
(A) contains 50 parts by weight or more of 2-ethylhexyl acrylate and 5 to 40 parts by weight of one or more monofunctional methacrylate monomers having a homopolymer Tg of 0°C or higher, out of a total of 100 parts by weight of at least two or more alkyl (meth)acrylates having an alkyl group with a carbon number of C1 to C10;
the ionic compound has a melting point of 25 to 80°C,
the pressure-sensitive adhesive composition contains a tri- or higher functional isocyanate compound as the crosslinking agent,
A pressure-sensitive adhesive composition characterized in that, when a surface protection film is laminated to a surface of a polarizing plate, in which a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition is laminated to a thickness of 15 μm on one side of a polyester film having a thickness of 38 μm, and the surface protection film is then peeled 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. 2. The pressure-sensitive adhesive composition according to claim 1 , wherein the monofunctional methacrylate monomer having a homopolymer Tg of 0°C or higher is at least one 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. the pressure-sensitive adhesive composition further comprises 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 polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer,
3. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition contains 0.1 to 5.0 parts by weight of the second acrylic polymer per 100 parts by weight of the total of at least two or more alkyl (meth)acrylates (A) having an alkyl group with a carbon number of C1 to C10. the pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer used in a surface protection film for a polarizing plate,
The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein 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 the surface treatment applied to the surface of the protective layer of the polarizer of the polarizing plate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, characterized in that the cation of the ionic compound is pyridinium, and the pressure-sensitive adhesive composition contains the ionic compound as an essential component in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the first acrylic polymer. the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 1.0 × 10 ⁺¹² Ω/□ or less;
the peeling electrification voltage of the pressure-sensitive adhesive layer relative to a low refractive index layer formed using a composition for forming a low refractive index layer containing a fluorine compound is within the range of +0.3 to −0.3 kV;
6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the surface substrate 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 substrate is one selected from the group consisting of untreated, AG treatment, LR treatment, AR treatment, AG-LR treatment, and AG-AR treatment. 7. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive composition is adhered to a polarizing plate, left to stand for two days in an atmosphere at a temperature of 60°C and a humidity of 90% RH, removed, and then peeled off after one day has passed. the (B) hydroxyl group-containing copolymerizable monomer is at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide;
The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the (C) carboxyl group-containing copolymerizable monomer is at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalate. the pressure-sensitive adhesive composition contains a crosslinking retarder and a crosslinking catalyst other than a tin compound;
the crosslinking retarder is a keto-enol tautomer compound;
The crosslinking retarder is contained in an amount of 0.1 to 300 parts by weight relative 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 aluminum chelate compounds, titanium chelate compounds, and iron chelate compounds;
the crosslinking catalyst is contained in an amount of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the first acrylic polymer,
8. The pressure-sensitive adhesive composition according to claim 1, wherein the weight ratio of the crosslinking retarder to the crosslinking catalyst is 80 to 1000. The pressure-sensitive adhesive composition according to any one of claims 1 to 8, characterized in that the pressure-sensitive adhesive composition contains 0.01 to 0.5 parts by weight of a polyether-modified siloxane compound having an HLB value of 6 to 12 and a weight-average molecular weight of 10,000 or less per 100 parts by weight of the first acrylic polymer. The second acrylic polymer is
(a) per 100 parts by weight of at least one (meth)acrylic acid ester monomer having an alkyl group carbon number of C1 to C18,
(b) 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;
4. The pressure-sensitive adhesive composition according to claim 3, wherein a ratio (b-1)/(B-1) of a total part by weight of the at least one or more hydroxyl group-containing copolymerizable monomers (B) contained in the first acrylic polymer relative to a total of 100 parts by weight of the first acrylic polymer to a total part by weight of the at least one or more hydroxyl group-containing copolymerizable monomers (b) contained in the second acrylic polymer relative to a total of 100 parts by weight of the second acrylic polymer is within a range of 1.0 to 2.0. the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has an average repeat number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14,
the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer has a diester content of 0.2% or less,
11. The pressure-sensitive adhesive composition according to claim 3 or 10, wherein the polyalkylene glycol chain-containing mono(meth)acrylic acid ester monomer is at least one selected from the group consisting of polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate, in an amount of 1 to 50 parts by weight per 100 parts by weight of the second acrylic polymer. An adhesive film characterized by having an adhesive layer formed by crosslinking the adhesive composition described in any one of claims 1 to 11 laminated on one side of a resin film. A surface protection film using the adhesive film described in claim 12. A surface protection film for polarizing plates, using the adhesive film described in claim 12. An optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition described in any one of claims 1 to 11 laminated on at least one surface of the optical film. The adhesive film according to claim 12, wherein one side of the resin film opposite the side on which the adhesive layer is formed is subjected to an antistatic treatment and an antifouling treatment.