JP7843304B2 - Antistatic surface protective film and optical film - Google Patents

Description

This invention relates to an antistatic surface protection film that is laminated to the surface of optical components such as polarizing plates, phase difference plates, and lens films for displays (hereinafter sometimes referred to as optical films). More specifically, it provides an antistatic surface protection film that minimizes contamination of the adherend and has excellent peel-resistant antistatic performance without deterioration over time.

When manufacturing and transporting optical films such as polarizing plates, phase difference plates, lens films for displays, anti-reflective films, hard coat films, and transparent conductive films for touch panels, as well as optical products such as displays using these films, a surface protection film is laminated to the surface of the optical film to prevent surface contamination and scratches in subsequent processes. To improve work efficiency by eliminating the need to peel off and re-lamin the surface protection film, the visual inspection of the optical film is sometimes performed with the surface protection film still attached to the optical film.
Conventionally, surface protection films, which have an adhesive layer on one side of a base film, have been commonly used in the manufacturing process of optical products to prevent scratches and dirt from adhering. The surface protection film is laminated to the optical film via an adhesive layer with low tackiness. The reason for using a low-tack adhesive layer is to allow the surface protection film to be easily peeled off when used and removed from the surface of the optical film, and to prevent the adhesive from adhering to and remaining on the optical film of the product to which it is attached (i.e., preventing the occurrence of adhesive residue).

In recent years, during the production process of liquid crystal display panels, there have been a small number of cases where the peeling voltage generated when the surface protective film laminated onto the optical film is peeled off has caused damage to circuit components such as driver ICs that control the display screen of the liquid crystal display panel, as well as damage to the orientation of liquid crystal molecules.
Furthermore, in order to reduce the power consumption of liquid crystal display panels, the driving voltage of the liquid crystal material has been decreasing, and consequently, the breakdown voltage of the driver IC has also decreased. Recently, there has been a demand to keep the delamination zone voltage within the range of +0.7kV to -0.7kV.
Therefore, in order to prevent problems caused by a high peel voltage when peeling the surface protection film from the optical film to which it is adhered, a surface protection film has been proposed that uses an adhesive layer containing an antistatic agent to suppress the peel voltage.

For example, Patent Document 1 discloses a surface protection film using an adhesive comprising an alkyltrimethylammonium salt, a hydroxyl group-containing acrylic polymer, and a polyisocyanate.
Furthermore, Patent Document 2 discloses an adhesive composition comprising an ionic liquid and an acrylic polymer with an acid value of 1.0 or less, and adhesive sheets using the same.
Furthermore, Patent Document 3 discloses an adhesive composition comprising an acrylic polymer, a polyether polyol compound, and an alkali metal salt treated with an anion-adsorbing compound, and a surface protective film using the same.
Furthermore, Patent Document 4 discloses an adhesive composition comprising an ionic liquid, an alkali metal salt, and a polymer with a glass transition temperature of 0°C or lower, and a surface protective film using the same.
Furthermore, Patent Documents 5 and 6 indicate that polyether-modified silicone is mixed into the adhesive layer of a surface protective film.

Japanese Patent Publication No. 2005-131957 Japanese Patent Publication No. 2005-330464 Japanese Patent Publication No. 2005-314476 Japanese Patent Publication No. 2006-152235 Japanese Patent Publication No. 2009-275128 Patent No. 4537450

In the above-mentioned Patent Documents 1 to 4, an antistatic agent is added to the adhesive layer. However, as the thickness of the adhesive layer increases, and as time passes, the amount of antistatic agent that migrates from the adhesive layer to the substrate to which the surface protective film is laminated increases. Furthermore, in optical films such as LR (Low Reflective) polarizers and AG (Anti-Glare)-LR polarizers, the surface of the optical film is treated with anti-fouling agents such as silicone compounds or fluorine compounds. Therefore, the peel voltage when peeling the surface protective film used for such optical films from the laminated optical film becomes high.

Furthermore, when polyether-modified silicone is mixed into the adhesive layer, as described in Patent Documents 5 and 6, it is difficult to fine-tune the adhesive strength of the surface protection film. Also, because polyether-modified silicone is mixed into the adhesive layer, changes in the coating and drying conditions of the adhesive composition on the base film subtly alter the surface properties of the adhesive layer on which the surface protection film is formed. Moreover, from the viewpoint of protecting the surface of the optical film, the thickness of the adhesive layer cannot be made extremely thin. Therefore, it is necessary to increase the amount of polyether-modified silicone added to the adhesive layer according to its thickness, which consequently makes the adherend surface more susceptible to contamination, and changes in adhesive strength and contamination resistance to the adherend over time.

In recent years, with the spread of 3D displays (stereoscopic displays), some optical films such as polarizers have an FPR (Film Patterned Retarder) film laminated to their surface. The FPR film is applied after the surface protective film that was previously laminated to the optical film (such as a polarizer) is removed. However, if the surface of the optical film (such as a polarizer) is contaminated with the adhesive or antistatic agent used in the surface protective film, the FPR film may not adhere properly. Therefore, surface protective films used in this application require materials that minimize contamination of the substrate.

On the other hand, some LCD panel manufacturers employ a method for evaluating the contamination properties of surface protective films on the substrate. This method involves peeling off the surface protective film laminated to an optical film such as a polarizing plate, re-laminating it with air bubbles incorporated, heat-treating it under predetermined conditions, and then peeling off the surface protective film and observing the substrate surface. In this evaluation method, even if the surface contamination of the substrate is minute, if there is a difference in surface contamination between the area where air bubbles were incorporated and the area where the adhesive of the surface protective film was in contact, it will remain as a trace of the air bubbles (sometimes called an air bubble stain). Therefore, this is a very strict evaluation method for assessing the contamination properties of the substrate surface. In recent years, there has been a demand for surface protective films that do not have problems with contamination properties on the substrate surface even under such strict evaluation conditions. However, conventional surface protective films using an adhesive layer containing an antistatic agent have had difficulty solving this problem.

Therefore, there is a need for surface protection films used in optical films that minimize contamination of the substrate and whose contamination properties do not change over time. Furthermore, there is a demand for surface protection films that exhibit a low peel voltage when peeling from the substrate.

The inventors of this invention have diligently considered how to solve this problem.
To minimize contamination of the substrate and reduce the change in antistatic performance over time, it is necessary to reduce the amount of antistatic agent added, which is suspected to be the cause of contamination of the substrate. However, when the amount of antistatic agent added is reduced, the peel voltage when peeling the surface protective film from the substrate increases. The inventors of the present invention investigated a method to keep the peel voltage low when peeling the surface protective film from the substrate without increasing the absolute amount of antistatic agent added. As a result, they found that instead of adding and mixing the antistatic agent into the adhesive composition to form an adhesive layer, by applying an appropriate amount of antistatic agent to the surface of the adhesive layer after coating and drying the adhesive composition to laminate the adhesive layer, the peel voltage when peeling the surface protective film from the optical film substrate can be kept low, thus completing the present invention.

This invention has been made in view of the above circumstances, and aims to provide an antistatic surface protective film that exhibits minimal contamination of the adherend and has excellent peel-resistant antistatic performance without deterioration over time.

To solve the above problems, the antistatic surface protection film of the present invention is based on the technical concept of applying an appropriate amount of liquid silicone compound and antistatic agent at 20°C to the surface of the adhesive layer after coating and drying an adhesive composition to form an adhesive layer. This minimizes contamination of the adherend and reduces the peel voltage when peeling from the adherend, which is an optical film.

To solve the above problems, the present invention provides a release film for an antistatic surface protection film, in which an antistatic agent can be transferred only to the surface of the adhesive layer of an antistatic surface protection film having an adhesive layer formed on one side of a base film, wherein the adhesive layer is formed by crosslinking an adhesive composition containing an acrylic polymer and a crosslinking agent, and the acrylic polymer is copolymerized with (A) at least one (meth)acrylic acid ester monomer having C4 to C18 C in the alkyl group, (B) copolymerizable monomer containing a hydroxyl group, and at least one selected from a copolymerizable monomer group consisting of (C) copolymerizable monomer containing a carboxyl group, (D) polyalkylene glycol mono(meth)acrylic acid ester monomer, and (E) nitrogen-containing vinyl monomer that does not contain a hydroxyl group or alkyl (meth)acrylate monomer that does not contain a hydroxyl group. The present invention provides a release film for an antistatic surface protection film, characterized in that it is made of a copolymer, the crosslinking agent is a bifunctional or more isocyanate compound, the release film for the antistatic surface protection film has a release layer containing an antistatic agent laminated on one side of a resin film, the release layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a polyether-modified silicone as a liquid silicone compound at 20°C, and the antistatic agent, the polyether-modified silicone and the antistatic agent are contained in a ratio of 5 to 100 parts by weight of solids per 100 parts by weight of solids of the release agent mainly composed of dimethylpolysiloxane, and when the release film for the antistatic surface protection film is laminated to the surface of the adhesive layer via the release layer, the silicone compound and the antistatic agent of the release layer can be transferred only to the surface of the adhesive layer.

Furthermore, it is preferable that the copolymerizable monomer containing the hydroxyl group (B) is at least one compound 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.

Furthermore, it is preferable that the copolymerizable monomer containing the (C) carboxyl group is at least one compound selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid.

Furthermore, it is preferable that the (D) polyalkylene glycol mono(meth)acrylic acid ester monomer is at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate.

Furthermore, it is preferable that the acrylic polymer contains at least one of the following copolymerizable monomers: (E) nitrogen-containing vinyl monomers that do not contain hydroxyl groups, or alkyl (meth)acrylate monomers containing alkoxy groups.

Furthermore, as the (F) isocyanate compound with two or more functions, the bifunctional isocyanate compound is an acyclic aliphatic isocyanate compound produced by reacting a diisocyanate compound with a diol compound, the diisocyanate compound is an aliphatic diisocyanate selected from the group of compounds consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, and the diol compound is 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypiva The trifunctional isocyanate compound is preferably composed of one compound selected from the group consisting of phosphate, polyethylene glycol, and polypropylene glycol, and preferably consists of an isocyanurate form of a hexamethylene diisocyanate compound, an isocyanurate form of an isophorone diisocyanate compound, an adduct form of a hexamethylene diisocyanate compound, an adduct form of an isophorone diisocyanate compound, a burette form of a hexamethylene diisocyanate compound, an adduct form of an isophorone diisocyanate compound, an isocyanurate form of a tolylene diisocyanate compound, an isocyanurate form of a xylylene diisocyanate compound, an isocyanurate form of a hydrogenated xylylene diisocyanate compound, an adduct form of a tolylene diisocyanate compound, an adduct form of a xylylene diisocyanate compound, and an adduct form of a hydrogenated xylylene diisocyanate compound.

Furthermore, it is preferable that the adhesive composition contains an (I) polyether-modified siloxane compound having an HLB value of 7 to 15.

Furthermore, it is preferable that the silicone compound in the release agent layer is a polyether-modified silicone.

Furthermore, it is preferable that the antistatic agent in the release agent layer is an alkali metal salt.

Furthermore, in order to solve the above problems, the present invention provides a substrate film made of a transparent resin on one side, comprising: (A) at least one (meth)acrylic acid ester monomer having C4 to C18 C in its alkyl group; and a group of copolymerizable monomers, consisting of: (B) copolymerizable monomers containing a hydroxyl group; (C) copolymerizable monomers containing a carboxyl group; (D) polyalkylene glycol mono(meth)acrylic acid ester monomer; and (E) nitrogen-containing vinyl monomer or alkyl (meth)acrylate monomer containing an alkoxy group that does not contain a hydroxyl group. The present invention provides an antistatic surface protective film comprising an adhesive layer made of an acrylic polymer copolymer containing at least one monomer selected from a group of copolymerizable monomers, and a release film having a release layer containing an antistatic agent laminated on one side of a resin film, laminated sequentially so that the adhesive layer and the release layer are in contact, wherein the release layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a silicone compound that is liquid at 20°C, and an antistatic agent, and the release band voltage of the adhesive layer is ±0.6 kV or less.

Furthermore, it is preferable that the silicone compound in the release agent layer is a polyether-modified silicone.

Furthermore, it is preferable that the antistatic agent in the release agent layer is an alkali metal salt.

Furthermore, the present invention provides an optical film formed by laminating the above-mentioned antistatic surface protective film.

Furthermore, the present invention provides an optical component to which the above-mentioned antistatic surface protective film is laminated.

The antistatic surface protection film of the present invention causes minimal contamination of the adherend, and its low contamination properties do not change over time. Furthermore, according to the present invention, even if the adherend surface of the adherend is an optical film such as an LR polarizer or an AG-LR polarizer that has been treated with an anti-fouling agent such as a silicone compound or a fluorine compound, the peel voltage generated when peeling the antistatic surface protection film from the adherend can be kept low, and an antistatic surface protection film with excellent peel-and-static performance that does not deteriorate over time can be provided.
The antistatic surface protection film of the present invention can reliably protect the surface of optical films, thereby improving productivity and yield.

This is a cross-sectional view illustrating the concept of the antistatic surface protective film of the present invention. This is a cross-sectional view showing the antistatic surface protective film of the present invention with the release film removed. This is a cross-sectional view showing one embodiment of the optical component of the present invention.

The present invention will be described in detail below based on embodiments.
Figure 1 is a conceptual cross-sectional view of the antistatic surface protection film of the present invention. In this antistatic surface protection film 10, an adhesive layer 2 is formed on one side of a transparent base film 1. A release film 5, which has a release agent layer 4 formed on the surface of a resin film 3, is laminated to the surface of this adhesive layer 2.

The base film 1 used in the antistatic surface protection film 10 according to the present invention is a base film made of a transparent and flexible resin. This allows the optical component to be visually inspected while the antistatic surface protection film is laminated to the optical component. Preferably, the transparent resin film used as the base film 1 is a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate. In addition to polyester films, films made of other resins can also be used as long as they have the necessary strength and optical suitability. The base film 1 may be an unoriented film or a uniaxially or biaxially stretched film. Furthermore, the stretching ratio of the stretched film and the orientation angle of the axial shape formed during crystallization of the stretched film may be controlled to specific values.
The thickness of the base film 1 used in the antistatic surface protective film 10 according to the present invention is not particularly limited, but for example, a thickness of about 12 to 100 μm is preferred, and a thickness of about 20 to 50 μm is easier to handle and therefore more preferred.
Furthermore, if necessary, an anti-fouling layer to prevent surface soiling, an antistatic layer, a hard coat layer to prevent scratches, etc., can be provided on the surface opposite to the side of the base film 1 where the adhesive layer 2 is formed. In addition, the surface of the base film 1 may be subjected to easy-adhesion treatments such as surface modification by corona discharge or application of an anchor coating agent.

Furthermore, the adhesive layer 2 used in the antistatic surface protection film 10 according to the present invention is not particularly limited as long as it adheres to the surface of the adherend, can be easily peeled off after use, and does not easily contaminate the adherend. However, considering durability after lamination to optical films, it is common to use an acrylic adhesive made by crosslinking (meth)acrylate copolymers.

In particular, an acrylic adhesive layer is preferred in which the main component of the acrylic adhesive is an acrylic polymer copolymer comprising (A) at least one (meth)acrylic acid ester monomer having C4 to C18 carbon atoms in the alkyl group, and at least one selected from the copolymerizable monomer group consisting of (B) copolymerizable monomers containing a hydroxyl group, (C) copolymerizable monomers containing a carboxyl group, (D) polyalkylene glycol mono(meth)acrylic acid ester monomer, and (E) nitrogen-containing vinyl monomer or alkyl(meth)acrylate monomer containing an alkoxy group that does not contain a hydroxyl group.
Furthermore, in addition to the acrylic polymer, an adhesive layer comprising an adhesive composition containing (F) a bifunctional or more isocyanate compound, (G) a crosslinking accelerator, and (H) a ketoenol tautomer compound is preferable.

(A) Examples of (meth)acrylic acid ester monomers with C4 to C18 in the alkyl group include butyl (meth)acrylate, isobutyl (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, isodecyl (meth)acrylate, and undecyl Examples include methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, myristyl methacrylate, isomiristyl methacrylate, cetyl methacrylate, isocetyl methacrylate, stearyl methacrylate, isostearyl methacrylate, and others.
When the total amount of the acrylic polymer in the copolymer is 100 parts by weight, it is preferable that (A) the copolymer contains 50 to 95 parts by weight of (meth)acrylic acid ester monomers having C4 to C18 carbon atoms in the alkyl group.

(B) Examples of copolymerizable monomers containing hydroxyl groups include hydroxyalkyl (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate, as well as hydroxyl group-containing (meth)acrylamides such as N-hydroxy (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide.
Preferably, it is at least one compound 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.
When the total amount of the acrylic polymer copolymer is 100 parts by weight, it is preferable that the copolymerizable monomer containing the hydroxyl group (B) is contained in a proportion of 0.1 to 10 parts by weight.

(C) Preferably, the copolymerizable monomer containing a carboxyl group is at least one selected from the group of compounds consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid.
When the total amount of the acrylic polymer copolymer is 100 parts by weight, it is preferable that the copolymerizable monomer containing the (C) carboxyl group is contained in a proportion of 0 to 1.0 part by weight. In the adhesive layer according to the present invention, the adhesive composition does not need to contain the copolymerizable monomer containing the (C) carboxyl group.

(D) The polyalkylene glycol mono(meth)acrylic acid ester monomer can be any compound in which one of the multiple hydroxyl groups of the polyalkylene glycol is esterified as a (meth)acrylic acid ester. Since the (meth)acrylic acid ester group is a polymerizable group, it can be copolymerized with the main polymer. The other hydroxyl groups may remain as OH groups, or they may be alkyl ethers such as methyl ether or ethyl ether, or saturated carboxylic acid esters such as acetate esters, etc.
The alkylene groups in polyalkylene glycol include, but are not limited to, ethylene groups, propylene groups, and butylene groups. The polyalkylene glycol may be a copolymer of two or more polyalkylene glycols, such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. Examples of polyalkylene glycol copolymers include polyethylene glycol-polypropylene glycol, polyethylene glycol-polybutylene glycol, polypropylene glycol-polybutylene glycol, and polyethylene glycol-polypropylene glycol-polybutylene glycol, and the copolymer may be a block copolymer or a random copolymer.
(D) The polyalkylene glycol mono(meth)acrylic acid ester monomer preferably has an average repeating number of alkylene oxides constituting the polyalkylene glycol chain of 3 to 14. The "average repeating number of alkylene oxides" is the average number of repeating alkylene oxide units in the "polyalkylene glycol chain" portion included in the molecular structure of (D) polyalkylene glycol mono(meth)acrylic acid ester monomer.

(D) The polyalkylene glycol mono(meth)acrylic acid ester monomer is preferably at least one selected from polyalkylene glycol mono(meth)acrylate, methoxypolyalkylene glycol (meth)acrylate, and ethoxypolyalkylene glycol (meth)acrylate.
More specifically, polyethylene glycol-mono(meth)acrylate, polypropylene glycol-mono(meth)acrylate, polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-mono(meth)acrylate, polyethylene glycol-polybutylene glycol-mono(meth)acrylate, polypropylene glycol-polybutylene glycol-mono(meth)acrylate, polyethylene glycol-polypropylene glycol-polybutylene glycol-mono(meth)acrylate; methoxypolyethylene glycol-(meth)acrylate, methoxypolypropylene glycol-(meth)acrylate, methoxypolybutylene glycol-(meth)acrylate, methoxypolyethylene glycol-polypropylene glycol-(meth)acrylate, methoxypolyethylene glycol Examples include polybutylene glycol-(meth)acrylate, methoxy-polypropylene glycol-polybutylene glycol-(meth)acrylate, methoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol-(meth)acrylate; ethoxypolyethylene glycol-(meth)acrylate, ethoxypolypropylene glycol-(meth)acrylate, ethoxypolybutylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polypropylene glycol-(meth)acrylate, ethoxy-polyethylene glycol-polybutylene glycol-(meth)acrylate, ethoxy-polypropylene glycol-polybutylene glycol-(meth)acrylate, and ethoxy-polyethylene glycol-polypropylene glycol-polybutylene glycol-(meth)acrylate.
When the total amount of the acrylic polymer copolymer is 100 parts by weight, it is preferable that the (D) polyalkylene glycol mono(meth)acrylic acid monomer is contained in a proportion of 0 to 50 parts by weight. In the adhesive layer according to the present invention, the adhesive composition does not need to contain the (D) polyalkylene glycol mono(meth)acrylic acid monomer.

The acrylic polymer preferably contains, as part of the copolymerizable monomer group, at least one of (E) nitrogen-containing vinyl monomers that do not contain hydroxyl groups or alkyl (meth)acrylate monomers containing alkoxy groups.

Among (E), (E-1) nitrogen-containing vinyl monomers include vinyl monomers containing amide bonds, vinyl monomers containing amino groups, and vinyl monomers having a nitrogen-containing heterocyclic structure. More specifically, these include N-vinyl-2-pyrrolidone, N-vinylpyrrolidone, methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-vinyllaurillolactam, and other vinyl monomers having an N-vinyl-substituted heterocyclic structure. Cyclic nitrogen vinyl compounds; cyclic nitrogen vinyl compounds having an N-(meth)acryloyl-substituted heterocyclic structure, such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperazine, N-(meth)acryloylaziridine, N-(meth)acryloylazetidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylpiperidine, N-(meth)acryloylazepane, and N-(meth)acryloylazokane. ;cyclic nitrogen vinyl compounds having a heterocyclic structure with a nitrogen atom and an ethylene-based unsaturated bond in the ring, such as N-cyclohexylmaleimide and N-phenylmaleimide; unsubstituted or monoalkyl-substituted (meth)acrylamides such as (meth)acrylamide, N-methyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-t-butyl(meth)acrylamide; dialkyl-substituted (meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropylacrylamide, N,N-diisopropyl(meth)acrylamide, N,N-dibutyl(meth)acrylamide, N-ethyl-N-methyl(meth)acrylamide, N-methyl-N-propyl(meth)acrylamide, and N-methyl-N-isopropyl(meth)acrylamide; N,N-dimethylaminomethyl(meth) Dialkylamino(meth)acrylates such as acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-dimethylaminoisopropyl (meth)acrylate, N,N-dimethylaminobutyl (meth)acrylate, N,N-diethylaminomethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N-ethyl-N-methylaminoethyl (meth)acrylate, N-methyl-N-propylaminoethyl (meth)acrylate, N-methyl-N-isopropylaminoethyl (meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate; N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, N,N-dipropyl Examples include N,N-dialkyl-substituted aminopropyl (meth)acrylamides such as minopropyl (meth)acrylamide, N,N-diisopropylaminopropyl (meth)acrylamide, N-ethyl-N-methylaminopropyl (meth)acrylamide, N-methyl-N-propylaminopropyl (meth)acrylamide, and N-methyl-N-isopropylaminopropyl (meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinylformamide, N-vinylacetamide, and N-vinyl-N-methylacetamide; (meth)acrylamides such as N-methoxymethyl (meth)acrylamide, N-ethoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetone acrylamide, and N,N-methylenebis(meth)acrylamide; and unsaturated carboxylic acid nitriles such as (meth)acrylonitrile.

(E-1) Nitrogen-containing vinyl monomers are preferably those that do not contain hydroxyl groups, and more preferably those that do not contain both hydroxyl and carboxyl groups. Suitable monomers include those exemplified above, for example, acrylic monomers containing N,N-dialkyl-substituted amino groups or N,N-dialkyl-substituted amide groups; N-vinyl-substituted lactams such as N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinyl-2-piperidone; and N-(meth)acryloyl-substituted cyclic amines such as N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

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

When the total amount of the acrylic polymer copolymer is 100 parts by weight, it is preferable that it contains (E-1) nitrogen-containing vinyl monomer without hydroxyl groups or (E-2) alkyl (meth)acrylate monomer containing alkoxy groups in a proportion of 0 to 20 parts by weight. (E-1) nitrogen-containing vinyl monomer without hydroxyl groups and (E-2) alkyl (meth)acrylate monomer containing alkoxy groups can each be used individually or in combination of two or more types. In the adhesive layer according to the present invention, the adhesive composition does not necessarily have to contain (E) nitrogen-containing vinyl monomer without hydroxyl groups or alkyl (meth)acrylate monomer containing alkoxy groups.

(F) The isocyanate compound with two or more functions may be at least one or more selected from polyisocyanate compounds having at least two or more isocyanate (NCO) groups in one molecule. Polyisocyanate compounds can be classified into aliphatic isocyanates, aromatic isocyanates, acyclic isocyanates, and alicyclic isocyanates, and any of these may be used. Specific examples of polyisocyanate compounds include aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and trimethylhexamethylene diisocyanate (TMDI), and aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hydrogenated xylylene diisocyanate (H6XDI), dimethyl diphenyl diisocyanate (TOID), and tolylene diisocyanate (TDI).
Examples of isocyanate compounds with three or more functions include bifunctional isocyanate compounds (compounds having two NCO groups in one molecule), such as bifunctional isocyanate compounds, isocyanurate compounds, and adduct compounds (polyol-modified compounds) with trivalent or higher polyols (compounds having at least three OH groups in one molecule) such as trimethylolpropane (TMP) and glycerin.
(F) As the isocyanate compound with two or more functions, it is also possible to use only a (F-1) trifunctional isocyanate compound or only a (F-2) bifunctional isocyanate compound. Furthermore, it is also possible to use a combination of a (F-1) trifunctional isocyanate compound and a (F-2) bifunctional isocyanate compound.

Furthermore, the (F-1) trifunctional isocyanate compound used in the present invention is selected from the (F-1-1) first aliphatic isocyanate compound group, which consists of the isocyanurate form of a hexamethylene diisocyanate compound, the isocyanurate form of an isophorone diisocyanate compound, the adduct form of a hexamethylene diisocyanate compound, the adduct form of an isophorone diisocyanate compound, the burette form of a hexamethylene diisocyanate compound, and the burette form of an isophorone diisocyanate compound. It is preferable to include at least one of the above and at least one selected from the second aromatic isocyanate compound group (F-1-2), which consists of isocyanurate forms of tolylene diisocyanate compounds, isocyanurate forms of xylylene diisocyanate compounds, isocyanurate forms of hydrogenated xylylene diisocyanate compounds, adduct forms of tolylene diisocyanate compounds, adduct forms of xylylene diisocyanate compounds, and adduct forms of hydrogenated xylylene diisocyanate compounds. It is preferable to use the first aliphatic isocyanate compound group (F-1-1) and the second aromatic isocyanate compound group (F-1-2) in combination. In this invention, by using a combination of (F-1-1) a trifunctional isocyanate compound, which is selected from the first aliphatic isocyanate compound group, and (F-1-2) a trifunctional isocyanate compound, which is selected from the second aromatic isocyanate compound group, the balance of adhesive strength in the low-speed peeling region and the high-speed peeling region can be further improved.

Furthermore, the (F-1) trifunctional isocyanate compound preferably comprises at least one compound selected from the (F-1-1) first aliphatic isocyanate compound group and at least one compound selected from the (F-1-2) second aromatic isocyanate compound group, in a total amount of 0.5 to 5.0 parts by weight per 100 parts by weight of the copolymer. The mixing ratio of at least one compound selected from the (F-1-1) first aliphatic isocyanate compound group and at least one compound selected from the (F-1-2) second aromatic isocyanate compound group is preferably within the weight range of (F-1-1):(F-1-2) 10%:90% to 90%:10%.

Furthermore, the (F-2) bifunctional isocyanate compound used in the present invention is preferably an acyclic aliphatic isocyanate compound, which is a compound produced by reacting a diisocyanate compound with a diol compound.
For example, when a diisocyanate compound is represented by the general formula "O=C=N-X-N=C=O" (where X is a divalent group) and a diol compound is represented by the general formula "HO-Y-OH" (where Y is a divalent group), a compound produced by reacting a diisocyanate compound with a diol compound is, for example, a compound represented by the following general formula Z.

[General formula Z]
O=C=N-X-(NH-CO-O-Y-O-CO-NH-X) _n -N=C=O

Here, n is a non-negative integer. When n is 0, the general formula Z represents "O=C=N-X-N=C=O". The bifunctional acyclic aliphatic isocyanate compound may include a compound where n is 0 in the general formula Z (an unreacted diisocyanate compound with respect to the diol compound), but it is preferable to include a compound where n is a non-negative integer as an essential component. The bifunctional acyclic aliphatic isocyanate compound may also be a mixture of multiple compounds where n in the general formula Z is different.

Diisocyanate compounds represented by the general formula "O=C=N-X-N=C=O" are aliphatic diisocyanates. X is preferably an acyclic, aliphatic divalent group. The aliphatic diisocyanate is preferably one or more compounds selected from the group consisting of tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

The diol compound represented by the general formula "HO-Y-OH" is an aliphatic diol. Y is preferably an acyclic, aliphatic divalent group. The diol compound is preferably one or more compounds selected from the group consisting of 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, polyethylene glycol, and polypropylene glycol.

The weight ratio (F-1/F-2) of the (F-1) trifunctional isocyanate compound to the (F-2) bifunctional isocyanate compound is preferably 1 to 90. It is also preferable that the amount of the (F) bifunctional or more isocyanate compound is 0.1 to 10 parts by weight per 100 parts by weight of the acrylic polymer.

(G) The crosslinking accelerator for the metal chelate compound can be any substance that functions as a catalyst for the reaction (crosslinking reaction) between the copolymer and the crosslinking agent when a polyisocyanate compound is used as the crosslinking agent. Examples include amine compounds such as tertiary amines, metal chelate compounds, organotin compounds, organolead compounds, organozinc compounds, and other organometallic compounds. In this invention, metal chelate compounds and organotin compounds are preferred as crosslinking accelerators.

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

Examples of metal atoms M include Fe, Ni, Mn, Cr, V, Ti, Ru, Zn, Al, Zr, and Sn.
Examples of polydentate ligand L 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 (also known as 2,4-pentanedione), 2,4-hexanedione, and benzoylacetone. These are ketoenol tautomer compounds, and in the case of polydentate ligand L, the enol may be deprotonated enolates (e.g., acetylacetonate).
Examples of monodentate ligand X include halogen atoms such as chlorine and bromine atoms, acyloxy groups such as pentanoyl, hexanoyl, 2-ethylhexanoyl, octanoyl, nonanoyl, decanoyl, dodecanoyl, and octadecanoyl groups, and alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, and butoxy groups.

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

Examples of organotin compounds include dialkyltin oxides, fatty acid salts of dialkyltin, and fatty acid salts of stannous tin. Conventionally, dibutyltin compounds have been widely used, but in recent years, concerns have been raised about the toxicity of organotin compounds, and tributyltin (TBT), contained in dibutyltin compounds, is particularly concerning as an endocrine disruptor. From a safety standpoint, long-chain alkyltin compounds such as dioctyltin compounds are preferred. Specific examples of organotin compounds include dioctyltin oxide and dioctyltin dilaurate. While Sn compounds can be used provisionally, in light of the trend towards requiring safer substances in the future, it is preferable to use metal chelate compounds such as Al, Ti, and Fe, which are safer than Sn.
In the adhesive composition according to the present invention, it is preferable that the metal chelating compound includes at least one selected from the group consisting of aluminum chelating compounds, titanium chelating compounds, iron chelating compounds, and tin chelating compounds (provided that TBT is not included).
(G) The crosslinking accelerator of the metal chelate compound is preferably present in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the copolymer.

Examples of (H) ketoenol tautomer compounds 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. In adhesive compositions using polyisocyanate compounds as crosslinking agents, these compounds block the isocyanate groups of the crosslinking agent, thereby suppressing excessive viscosity increases and gelation of the adhesive composition after the addition of the crosslinking agent, and extending the pot life of the adhesive composition.
(H) The ketoenol tautomer compound is preferably present in an amount of 0.1 to 200 parts by weight per 100 parts by weight of the copolymer.

(H) Ketoenol tautomer compounds have an inhibitory effect on crosslinking, in contrast to the crosslinking promoter effect of (G) metal chelate compounds. Therefore, it is preferable to appropriately set the ratio of (H) ketoenol tautomer compounds to the crosslinking promoter effect of (G) metal chelate compounds. To extend the pot life of the adhesive composition and improve storage stability, the weight ratio of (G):(H) is preferably in the range of 1:1 to 1:300, more preferably 1:30 to 1:300, and most preferably 1:80 to 1:300.

The adhesive composition may optionally contain (I) a polyether-modified siloxane compound. (I) The polyether-modified siloxane compound is a siloxane compound having a polyether group, and in addition to the usual siloxane unit [-SiR ¹ ₂ -O-], it 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 groups or aryl groups, R ² and R ³ represent one or more alkylene groups, and R ⁴ represents one or more alkyl groups or acyl groups (terminal groups). Examples of polyether groups include polyoxyethylene groups [(C ₂ H ₄ O) _n ] and polyoxyalkylene groups such as polyoxypropylene groups [(C ₃ H ₆ O) _n ].

(I) The polyether-modified siloxane compound is preferably a polyether-modified siloxane compound having an HLB value of 7 to 15. Furthermore, it is preferable that the polyether-modified siloxane compound is present in an amount of 0.01 to 1.0 parts by weight per 100 parts by weight of the copolymer. More preferably, it is 0.1 to 0.5 parts by weight.
HLB refers to the hydrophilic-lipophilic balance (hydrophilic-lipophilic ratio) as defined in standards such as JIS K3211 (surfactant terminology).

(I) Polyether-modified siloxane compounds can be obtained, for example, by grafting an organic compound having unsaturated bonds and polyoxyalkylene groups onto a polyorganosiloxane main chain having silicon hydride groups via a hydrosilylation reaction. Specifically, examples include dimethylsiloxane-methyl(polyoxyethylene)siloxane copolymer, dimethylsiloxane-methyl(polyoxyethylene)siloxane-methyl(polyoxypropylene)siloxane copolymer, and dimethylsiloxane-methyl(polyoxypropylene)siloxane polymer.
(I) By incorporating a polyether-modified siloxane compound into the adhesive composition, the adhesive strength and rework performance of the adhesive can be improved. If the adhesive composition does not contain a polyether-modified siloxane compound, the cost will be lower.

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

The copolymer of the main component used in the adhesive composition of the present invention can be synthesized by copolymerizing (A) at least one (meth)acrylic acid ester monomer having C4 to C18 C in its alkyl group with at least one selected from the copolymerizable monomer group consisting of (B) copolymerizable monomers containing a hydroxyl group, (C) copolymerizable monomers containing a carboxyl group, (D) polyalkylene glycol mono(meth)acrylic acid ester monomer, and (E) nitrogen-containing vinyl monomer or alkyl(meth)acrylate monomer containing an alkoxy group that does not contain a hydroxyl group. The polymerization method of the copolymer is not particularly limited, and any suitable polymerization method such as solution polymerization or emulsion polymerization can be used.
The adhesive composition of the present invention can be prepared by blending the above copolymer with (F) a bifunctional or more isocyanate compound, (G) a crosslinking promoter of a metal chelate compound, (H) a ketoenol tautomer compound, and any other additives as appropriate.

The copolymer is preferably an acrylic polymer, and more preferably contains 50 to 100% by weight of an acrylic monomer such as (meth)acrylic acid ester monomer, (meth)acrylic acid, or (meth)acrylamide.
Furthermore, the acid value of the acrylic polymer is preferably 0.01 to 8.0. This improves stain resistance and enhances the ability to prevent adhesive residue.
Here, "acid value" is one of the indicators that represents the acid content, and is expressed as the number of mg of potassium hydroxide required to neutralize 1 g of polymer containing carboxyl groups.

Preferably, the adhesive layer formed by crosslinking the aforementioned adhesive composition has an adhesive strength of 0.05 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min, and an adhesive strength of 1.0 N/25 mm or less at a high peeling speed of 30 m/min. This results in a performance where the adhesive strength does not change significantly with peeling speed, and allows for quick peeling even at high speeds. Furthermore, when removing the surface protective film for reapplication, excessive force is not required, making it easy to peel from the adherend.

Preferably, the adhesive layer formed by crosslinking the adhesive composition has a surface resistivity of 5.0 × 10 ^{+ 12} Ω/□ or less, and a peel band voltage of "±0.6 kV or less". In this invention, "±0.6 kV or less" means 0 to -0.6 kV and 0 to +0.6 kV, i.e., -0.6 to +0.6 kV. If the surface resistivity is high, the performance of dissipating static electricity generated by charging during peeling is poor. By making the surface resistivity sufficiently low, the peel band voltage generated by static electricity when the adherend peels off the adhesive layer can be reduced, and it is possible to suppress the effect on the electrical control circuit of the adherend, etc.

The gel fraction of the adhesive layer (adhesive after crosslinking) formed by crosslinking the adhesive composition of the present invention is preferably 95 to 100%. This high gel fraction prevents excessive adhesion at low peeling speeds, reduces the elution of unpolymerized monomers or oligomers from the copolymer, improves reworkability and durability at high temperatures and humidity, and suppresses contamination of the adherend.

The adhesive film of the present invention is formed by creating an adhesive layer on one or both sides of a resin film, which is formed by crosslinking the adhesive composition of the present invention. The surface protection film of the present invention is a surface protection film formed by creating an adhesive layer on one side of a resin film, which is formed by crosslinking the adhesive composition of the present invention. Because the adhesive composition of the present invention contains a well-balanced blend of components (A) to (H) above, it possesses excellent antistatic properties, a superior balance of adhesive strength at both low and high peeling speeds, and excellent durability and reworkability (no contamination transfer to the adherend after tracing the surface protection film with a ballpoint pen via the adhesive layer). Therefore, it can be suitably used as a surface protection film for polarizing plates.

The thickness of the adhesive layer 2 used in the antistatic surface protection film 10 according to the present invention is not particularly limited, but for example, a thickness of about 5 to 40 μm is preferred, and a thickness of about 10 to 30 μm is more preferred. It is preferable that the adhesive layer 2 has a weak adhesive force, with a peel strength (adhesion) of about 0.03 to 0.3 N/25 mm, when peeling the antistatic surface protection film from the adherend, as this provides excellent operability when peeling the antistatic surface protection film from the adherend. Furthermore, it is preferable that the peel force of the release film 5 from the adhesive layer 2 is 0.2 N/50 mm or less, as this provides excellent operability when peeling the release film 5 from the antistatic surface protection film 10.

Furthermore, the release film 5 used in the antistatic surface protection film 10 according to the present invention has a release agent layer 4 formed on one side of the resin film 3, using a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a silicone-based compound that is liquid at 20°C, and an antistatic agent.

Examples of resin film 3 include polyester film, polyamide film, polyethylene film, polypropylene film, and polyimide film, but polyester film is particularly preferred due to its excellent transparency and relatively low cost. The resin film may be an unoriented film or a uniaxially or biaxially oriented film. Furthermore, the stretching ratio of the stretched film and the orientation angle of the axial shape formed during crystallization of the stretched film may be controlled to specific values.
The thickness of the resin film 3 is not particularly limited, but a thickness of about 12 to 100 μm is preferred, and a thickness of about 20 to 50 μm is easier to handle and therefore more preferable.
Furthermore, if necessary, the surface of the resin film 3 may be subjected to easy-adhesion treatments such as surface modification by corona discharge or application of an anchor coating agent.

The release agent mainly composed of dimethylpolysiloxane that constitutes the release agent layer 4 includes known silicone-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. Examples of commercially available addition reaction type silicone-based release agents include KS-776A, KS-847T, KS-779H, KS-837, KS-778, KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, and LTC-310 (manufactured by Toray Dow Corning Co., Ltd.). Examples of commercially available condensation reaction type products include SRX-290 and SYLOFF-23 (manufactured by Toray Dow Corning Co., Ltd.). Examples of commercially available cationic polymerization products include TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available radical polymerization products include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

Examples of liquid silicone compounds at 20°C that constitute the release agent layer 4 include polyether-modified silicone, alkyl-modified silicone, and carbinol higher fatty acid ester-modified silicone. In the present invention, in order to improve the antistatic properties of the surface of the adhesive layer, a liquid silicone compound at 20°C that is compatible with the release agent layer mainly composed of dimethylpolysiloxane is used. Among the modified silicone compounds, polyether-modified silicone is preferred for the applications of the present invention. The polyether chain in polyether-modified silicone is composed of ethylene oxide, propylene oxide, etc., and by selecting, for example, the molecular weight of polyethylene oxide used in the side chain, physical properties such as compatibility with the silicone release agent and antistatic effect can be adjusted.
Other commercially available polyether-modified silicones include, for example, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-642 (manufactured by Shin-Etsu Chemical Co., Ltd.), SH8400, SH8700, SF8410 (manufactured by Toray Dow Corning Co., Ltd.), TSF-4440, TSF-4441, TSF-4445, TSF-4446, TSF-4450 (manufactured by Momentive Performance Materials, Inc.), and BYK-300, BYK-306, BYK-307, BYK-320, BYK-325, BYK-330 (manufactured by Bic Chemie Inc.).
The amount of liquid silicone compound added at 20°C to a release agent mainly composed of dimethylpolysiloxane will vary depending on the type of silicone compound and its degree of compatibility with the release agent. However, it should be set considering the desired peel voltage, contamination of the substrate, and adhesive properties when peeling the antistatic surface protective film from the substrate.

The antistatic agent constituting the release agent layer 4 is preferably one that disperses well in the release agent solution mainly composed of dimethylpolysiloxane and does not inhibit the hardening of the release agent mainly composed of dimethylpolysiloxane. Alkali metal salts are suitable as such antistatic agents.

Examples of alkali metal salts include metal salts composed of lithium, sodium, and potassium. Specifically, metal salts composed of cations consisting of Li ⁺ , Na ⁺ , ^and K ⁺ _, and anions _consisting of Cl- ^, _Br- ^{, I- , BF4-} , _{PF6- , SCN-} , _ClO4- , ^CF3SO3- , ( _CF3SO2 ) _2N- ^, ( _{C2F5SO2 )} ^{2N- ,} _and ( _CF3SO2 ) _{3C- are} preferably used ^. In particular, _{lithium salts such as LiBr, LiI, LiBF₄, LiPF₄, LiSCN, LiClO₄, LiCF₃SO₃, Li(CF₃SO₂)₂N , Li ( C₂F₅SO₂ ) ₂N , and Li ( CF₃SO₂} ) _₃C are preferably used. These alkali metal salts may be used individually or in mixtures of two or _more . Compounds containing a polyoxyalkylene structure may be added to stabilize the ionic substance.
The amount of antistatic agent added to a release agent mainly composed of dimethylpolysiloxane varies depending on the type of antistatic agent and its affinity for the release agent, but it should be set considering the desired peel voltage when peeling the antistatic surface protective film from the substrate, the degree of contamination on the substrate, and the adhesive properties.

There are no particular limitations on the method of mixing the release agent, which mainly consists of dimethylpolysiloxane, with the polyether-modified silicone and the antistatic agent. Any method is acceptable, such as adding the polyether-modified silicone and antistatic agent to the dimethylpolysiloxane-based release agent, mixing them, and then adding and mixing a catalyst for curing the release agent; diluting the dimethylpolysiloxane-based release agent with an organic solvent beforehand, then adding and mixing the polyether-modified silicone, antistatic agent, and catalyst for curing the release agent; or diluting the siloxane-based release agent with an organic solvent beforehand, adding and mixing the catalyst, and then adding and mixing the polyether-modified silicone and antistatic agent. Furthermore, if necessary, adhesion enhancers such as silane coupling agents or materials that support the antistatic effect, such as compounds containing polyoxyalkylene groups, may be added.

The mixing ratio of the release agent, primarily composed of dimethylpolysiloxane, to the polyether-modified silicone and antistatic agent is not particularly limited, but a ratio of approximately 5 to 100 units of solids of the polyether-modified silicone and antistatic agent per 100 units of solids of the release agent primarily composed of dimethylpolysiloxane is preferable. If the amount of polyether-modified silicone and antistatic agent added (in terms of solids) is less than 5 units per 100 units of solids of the release agent primarily composed of dimethylpolysiloxane, the amount of antistatic agent transferred to the surface of the adhesive layer will be reduced, making it difficult for the adhesive to exhibit its antistatic function. Furthermore, if the amount of polyether-modified silicone and antistatic agent added (in terms of solids) exceeds 100 units per 100 units of solids of the release agent primarily composed of dimethylpolysiloxane, the release agent primarily composed of dimethylpolysiloxane will be transferred to the surface of the adhesive layer along with the polyether-modified silicone and antistatic agent, potentially reducing the adhesive properties of the adhesive.

The method for forming the adhesive layer 2 on the base film 1 and the method for laminating the release film 5 to the antistatic surface protection film 10 according to the present invention may be carried out by known methods and is not particularly limited. Specifically, examples include (1) a method of applying a resin composition for forming the adhesive layer 2 to one side of the base film 1, drying it to form the adhesive layer, and then laminating the release film 5; and (2) a method of applying a resin composition for forming the adhesive layer 2 to the surface of the release film 5, drying it to form the adhesive layer, and then laminating the base film 1. Any of these methods may be used.

Furthermore, the adhesive layer 2 on the surface of the base film 1 can be formed by known methods. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Meyer bar coating, and air knife coating can be used.

Similarly, the release agent layer 4 on the resin film 3 can be formed using a known method. Specifically, known coating methods such as gravure coating, Meyer bar coating, and air knife coating can be used.

Figure 2 is a cross-sectional view showing the antistatic surface protective film of the present invention after the release film has been peeled off.
When the release film 5 is peeled off from the antistatic surface protection film 10 shown in Figure 1, a portion of the liquid silicone-based compound and antistatic agent (reference numeral 7) contained in the release agent layer 4 of the release film 5, which are liquid at 20°C, are transferred (adhered) to the surface of the adhesive layer 2 of the antistatic surface protection film 10. Therefore, in Figure 2, the liquid silicone-based compound and antistatic agent transferred to the surface of the adhesive layer 2 of the antistatic surface protection film, which are liquid at 20°C, are schematically shown as spots labeled reference numeral 7.
In the antistatic surface protection film according to the present invention, when the antistatic surface protection film 11, which has had the release film shown in Figure 2 peeled off, is bonded to an adherend, the silicone-based compound and antistatic agent, which are liquid at 20°C and transferred to the surface of the adhesive layer 2, come into contact with the surface of the adherend. As a result, the peel voltage when peeling the antistatic surface protection film from the adherend again can be kept low.

Figure 3 is a cross-sectional view showing an embodiment of the optical component of the present invention.
The release film 5 is peeled off from the antistatic surface protective film 10 of the present invention, exposing the adhesive layer 2, and the film is then bonded to the optical component 8, which is the object to be adhered to, via the adhesive layer 2.
Specifically, Figure 3 shows an optical component 20 to which the antistatic surface protection film 10 of the present invention is laminated. Examples of optical components include polarizing plates, phase difference plates, lens films, polarizing plates that also function as phase difference plates, and polarizing plates that also function as lens films. Such optical components are used as components of optical systems for liquid crystal display devices such as liquid crystal display panels, and various instruments. Examples of optical components also include optical films such as anti-reflective films, hard coat films, and transparent conductive films for touch panels. In particular, the antistatic surface protection film can be suitably used as a laminate to the anti-fouling treated surface of optical films such as low-reflection polarizing plates (LR polarizing plates) and anti-glare low-reflection polarizing plates (AG-LR polarizing plates), whose surfaces are treated with anti-fouling agents such as silicone compounds or fluorine compounds.
According to the optical component of the present invention, when the antistatic surface protective film 10 is peeled off from the adherend, the peeling voltage can be suppressed to a sufficiently low level. Therefore, there is no risk of damaging circuit components such as driver ICs, TFT elements, and gate line drive circuits, thereby increasing production efficiency in the process of manufacturing liquid crystal display panels and the like, and maintaining the reliability of the production process.

Next, the present invention will be further explained with reference to examples.

<Manufacturing of adhesive compositions>
[Example 1]
Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube to replace the air in the reactor with nitrogen gas. Then, 100 parts by weight of 2-ethylhexyl acrylate, 3.0 parts by weight of 8-hydroxyoctyl acrylate, 10 parts by weight of polypropylene glycol monoacrylate (average repeat number n=12 of alkylene oxides constituting the polyalkylene glycol chain) were added to the reactor along with 60 parts by weight of solvent (ethyl acetate). Subsequently, 0.1 parts by weight of azobisisobutyronitrile was added dropwise over 2 hours as a polymerization initiator, and the reaction was carried out at 65°C for 6 hours to obtain the acrylic copolymer solution of Example 1 with a weight-average molecular weight of 500,000. To this acrylic copolymer solution, 8.5 parts by weight of acetylacetone was added and stirred, and then 2.0 parts by weight of Coronate HX (isocyanurate of a hexamethylene diisocyanate compound) and 0.1 parts by weight of titanium trisacetylacetonate were added and stirred to obtain the adhesive composition of Example 1.

[Examples 2-6 and Comparative Examples 1-2]
Except for the composition of the adhesive composition of Example 1 being as described in Tables 1 and 2, the adhesive compositions of Examples 2 to 6 and Comparative Examples 1 to 2 were obtained in the same manner as in Example 1.

Tables 1 and 2 are two separate tables showing the mixing ratios of each component. In both tables, the values in parts by weight are shown in parentheses, calculated with the total of group (A) set at 100 parts by weight. Tables 3 and 4 show the compound names of the abbreviated symbols used for each component in Tables 1 and 2. Note that Coronate® HX, HL, and L are product names of Nippon Polyurethane Industry Co., Ltd., Takenate® D-140N, D-127N, and D-110N are product names of Mitsui Chemicals, Inc., and Desmodule® N3400 is a product name of Sumika Bayer Urethane Co., Ltd.

<Synthesis of bifunctional isocyanate compounds>
The bifunctional isocyanate compounds in Synthesis Examples 1 and 2 were synthesized by the following method. As shown in Tables 5 and 6, diisocyanate and diol compounds were mixed in a molar ratio of NCO/OH = 16 and reacted at 120°C for 3 hours. Then, unreacted diisocyanate was removed under reduced pressure using a thin-film evaporator to obtain the desired bifunctional isocyanate compounds.

<Manufacturing of antistatic surface protective film>
[Example 1]
A coating for forming the release agent layer of Example 1 was prepared by mixing 5 parts by weight of addition-type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 0.15 parts by weight of polyether-modified silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SH8400), 5 parts by weight of 10% lithium perchlorate ethyl acetate solution, 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 catalyst) and stirring. The coating for forming the release agent layer of Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm using a meyer bar so that the thickness after drying was 0.2 μm, and the film was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Example 1.
The adhesive composition of Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm to a dry thickness of 20 μm, and then dried in a hot air circulating oven at 100°C for 2 minutes to form an adhesive layer. Subsequently, the release layer (silicone-treated surface) of the release film of Example 1 prepared above was laminated to the surface of this adhesive layer. The resulting adhesive film was kept warm in a 40°C environment for 5 days to cure the adhesive, and the antistatic surface protective film of Example 1 was obtained.

[Examples 2-6]
The antistatic surface protective films of Examples 2 to 6 were obtained in the same manner as in Example 1, except that the adhesive composition of Example 1 was replaced with the adhesive compositions of Examples 2 to 6, respectively.

[Comparative Example 1]
A coating for forming the release agent layer of Comparative Example 1 was prepared by mixing 5 parts by weight of addition-type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 95 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.05 parts by weight of platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212 catalyst) and stirring. The coating for forming the release agent layer of Comparative Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm using a meyer bar so that the thickness after drying would be 0.2 μm, and the film was dried in a hot air circulating oven at 120°C for 1 minute to obtain the release film of Comparative Example 1.
The adhesive composition of Comparative Example 1 was applied to the surface of a polyethylene terephthalate film with a thickness of 38 μm to a dry thickness of 20 μm, and then dried in a hot air circulating oven at 100°C for 2 minutes to form an adhesive layer. Subsequently, the release layer (silicone-treated surface) of the release film of Comparative Example 1, prepared as described above, was laminated to the surface of this adhesive layer. The resulting adhesive film was kept warm in a 40°C environment for 5 days to cure the adhesive, and the antistatic surface protective film of Comparative Example 1 was obtained.

[Comparative Example 2]
The antistatic surface protective film of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that the adhesive composition of Comparative Example 1 was replaced with the adhesive composition of Comparative Example 2.

Table 7 shows the composition and thickness of the release agent layer in the antistatic surface protective films of Examples 1-6 and Comparative Examples 1 and 2.

<Testing Methods and Evaluation>
The surface protective films from Examples 1 to 6 and Comparative Examples 1 and 2 were aged for 7 days in an atmosphere of 23°C and 50% RH. After that, the release film (silicone resin-coated PET film) was peeled off to expose the adhesive layer, and these were used as samples for surface resistivity measurement.
Furthermore, this surface protection film with the adhesive layer exposed was bonded to the surface of a polarizing plate attached to a liquid crystal cell via the adhesive layer, left for one day, then autoclaved at 50°C and 5 atmospheres for 20 minutes, and left at room temperature for another 12 hours. This was used as a sample for measuring adhesive strength, peel voltage, and reworkability.

<Adhesive strength>
The sample obtained above (a 25 mm wide surface protective film laminated onto the surface of a polarizing plate) was peeled off in the 180° direction using a tensile testing machine at a low peeling speed (0.3 m/min) and a high peeling speed (30 m/min), and the measured peel strength was defined as the adhesive strength.

<Surface resistivity>
After aging, before bonding to the polarizing plate, the release film (silicone resin-coated PET film) was peeled off to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter, Hi-Resta UP-HT450 (manufactured by Mitsubishi Chemical Analytec).

<Strip voltage>
The voltage (band voltage) generated when the polarizing plate becomes charged during the peeling of the sample obtained above at a tensile speed of 30 m/min at 180° was measured using high-precision electrostatic sensors SK-035 and SK-200 (manufactured by Keyence Corporation), and the maximum value of the measured value was defined as the peeled band voltage.

<Reworkability>
After tracing the surface protective film of the measurement sample obtained above with a ballpoint pen (load 500g, 3 back-and-forth strokes), the surface protective film was peeled off the polarizing plate and the surface of the polarizing plate was observed to confirm that there was no contamination transfer to the polarizing plate. The evaluation criteria were as follows: "○" if there was no contamination transfer to the polarizing plate, "△" if contamination transfer was confirmed at least partially along the traced path of the ballpoint pen, and "×" if contamination transfer was confirmed along the traced path of the ballpoint pen and the adhesive was also confirmed to have detached from the adhesive surface.

Table 8 shows the evaluation results. Surface resistivity is expressed using the formula "mE + n" instead of "m × 10 ^{+ n} " (where m is an arbitrary real number and n is a positive integer).

The following can be seen from the measurement results shown in Table 8.
The antistatic surface protection films of Examples 1 to 6 according to the present invention have appropriate adhesive strength, do not contaminate the surface of the adherend, and have a low peel voltage when the antistatic surface protection film is peeled off from the adherend.
On the other hand, the antistatic surface protection film of Comparative Example 1, in which a silicone compound and an antistatic agent were added to the adhesive layer, had a low and good surface resistivity of the adhesive layer, but due to its high adhesive strength, the peel voltage was high and its reworkability was poor. In Comparative Example 2, although it had moderate adhesive strength, the high surface resistivity of the adhesive layer resulted in a high peel voltage and poor reworkability.
In other words, in Comparative Examples 1 and 2, where a silicone compound and an antistatic agent were mixed in the adhesive, it was difficult to achieve both a reduction in the release voltage and contamination of the adherend. On the other hand, in Examples 1 to 6, where a silicone compound and an antistatic agent were added to the release agent layer and then transferred to the surface of the adhesive layer, a small amount of additive was sufficient to reduce the release voltage, resulting in no contamination of the adherend and a good antistatic surface protective film.

The antistatic surface protection film of the present invention can be used, for example, to protect the surface of optical films such as polarizers, phase difference plates, and lens films for displays, as well as various other optical components, in production processes. In particular, when used as an antistatic surface protection film for optical films such as LR polarizers and AG-LR polarizers whose surfaces have been treated with anti-fouling agents such as silicone compounds or fluorine compounds, the amount of static electricity generated when peeling the film from the adherend can be reduced.
The antistatic surface protective film of the present invention has great industrial value because it causes minimal contamination of the adherend, does not deteriorate over time, and possesses excellent peel-resistant antistatic properties, thereby improving the yield of the production process.

1…Base film, 2…Adhesive layer, 3…Resin film, 4…Release layer, 5…Release film, 7…Liquid silicone compound and antistatic agent at 20°C, 8…Substrate (optical component), 10…Antistatic surface protection film, 11…Antistatic surface protection film with release film removed, 20…Optical component with antistatic surface protection film laminated to it.

Claims (2)

An antistatic surface protection film having an adhesive layer formed on one side of a base film, with a release film laminated on the adhesive layer,
The adhesive layer is formed by crosslinking an adhesive composition containing an acrylic polymer and a crosslinking agent.
The acrylic polymer is a copolymer obtained by copolymerizing (A) at least one (meth)acrylic acid ester monomer having C4 to C18 carbon atoms in its alkyl group, (B) a copolymerizable monomer containing a hydroxyl group, and at least one selected from a copolymerizable monomer group consisting of (C) a copolymerizable monomer containing a carboxyl group, (D) a polyalkylene glycol mono(meth)acrylic acid ester monomer, and (E) a nitrogen-containing vinyl monomer that does not contain a hydroxyl group or an alkoxy-group-containing alkyl (meth)acrylate monomer that does not contain a hydroxyl group.
The crosslinking agent is a bifunctional or more isocyanate compound.
The aforementioned release film is formed by laminating a release agent layer containing an antistatic agent on one side of a resin film.
The aforementioned release agent layer is formed from a resin composition containing a release agent mainly composed of dimethylpolysiloxane, a polyether-modified silicone as a liquid silicone compound at 20°C, and an antistatic agent.
An antistatic surface protective film characterized in that the silicone compound and the antistatic agent contained in the release agent layer are transferred only to the surface of the adhesive layer, the interior of the adhesive layer does not contain the antistatic agent, the adhesive strength of the adhesive layer is 0.05 to 0.1 N/25 mm at a low peeling speed of 0.3 m/min, the adhesive strength of the adhesive layer is 1.0 N/25 mm or less at a high peeling speed of 30 m/min, the surface resistivity of the adhesive layer is 3.41 × 10 ^{+ 11} Ω/□ or less, and the peel band voltage of the adhesive layer is ±0.6 kV or less. An optical film using the antistatic surface protective film described in claim 1.