TWI679113B - Surface-protective film and optical component attached with the same - Google Patents

Abstract

The invention provides a surface protection film and an optical element using the surface protection film. The surface protection film can be used for an optical film with unevenness on the surface, and has less pollution to the adherend and low pollution to the adherend. It has excellent peeling and antistatic properties without changing with time. The surface protection film (10) forms a binder layer (2) containing an ionic compound as an antistatic agent on one surface of a substrate film (1) made of a transparent resin, and the binder layer ( 2) A release film (5) having a release agent layer (4) is bonded to the release agent layer (4), and the release agent layer (4) is composed of an alkali metal salt and a silicone resin-based release agent, and the alkali metal salt component is removed from the release film. The static voltage is reduced when the adhesive layer is transferred to the surface of the adhesive layer and the adhesive layer is peeled from the adherend.

Description

Surface protection film and optical element with the film

The present invention relates to a surface protection film that is bonded to the surface of an optical element (hereinafter sometimes referred to as an optical film) such as a polarizing plate, a retardation plate, and a lens film for a display. In more detail, the present invention provides a surface protection film and an optical element to which the surface protection film is bonded. The surface protection film has less contamination of an adherend, and has excellent peeling and antistatic properties without deterioration over time. performance.

When manufacturing and transporting optical films such as polarizing plates, retardation plates, display lens films, anti-reflection films, hard coating films, and transparent conductive films for touch panels, and optical products such as displays using these, The surface of the film is adhered to a surface protection film to prevent surface contamination and damage in subsequent steps. In order to save the time of peeling off the surface protective film and then bonding, and improve the working efficiency, the visual inspection of the optical film as a product may be performed directly in a state where the surface protective film is bonded to the optical film.

For a long time, in the manufacturing steps of optical products, in order to prevent damage or adhesion of dirt, a surface protective film having an adhesive layer provided on one surface of a base film is generally used. Surface protective film is applied via an adhesive layer with weak adhesion It is attached to the optical film. The reason why the adhesive layer has a weak adhesive force is that when the used surface protective film is peeled off from the surface of the optical film, it can be easily peeled off, and the adhesive does not remain on the optical film product as an adherend. (Ie prevent the generation of residual glue).

In recent years, in the production steps of liquid crystal display panels, although the number of occurrences is small, there are still the following phenomena: the peeling static voltage generated when the surface protective film bonded to the optical film is peeled off and removed A phenomenon in which circuit elements such as a driving IC that controls a display screen of a liquid crystal display panel is damaged, and alignment of liquid crystal molecules is damaged.

In addition, in order to reduce the power consumption of the liquid crystal display panel, the driving voltage of the liquid crystal material is reduced, and the destruction voltage of the driving IC is also reduced accordingly. Recently, efforts have been made to make the peeling static voltage within a range of +0.7 kV to -0.7 kV.

In addition, conventional polarizers are composed of a polarizer made of polyvinyl alcohol (PVA) impregnated with iodine, and a triacetam cellulose film (TAC film) is bonded with a water-based adhesive to protect the polarizer. To manufacture polarizing plates, but in recent years, polarizing plates using acrylic films, cyclic polyolefin films, and polyester films instead of TAC films have also started to be used; polarizing plates using ultraviolet curing adhesives instead of water-based adhesives . A change in the constituent material of the polarizing plate causes a problem that the peeling static voltage generated when the surface protective film is peeled off is higher than that when a polarizing plate having a conventional structure is used.

In addition, in recent years, with the spread of 3D displays (stereoscopic displays), FPR (Film Patterned Retarder) films are sometimes bonded to the surface of optical films such as polarizers. After peeling off the surface protection film attached to the surface of an optical film such as a polarizing plate, the FPR film was attached. but, If the surface of an optical film such as a polarizer is contaminated with an adhesive or an antistatic agent for a surface protection film, there is a problem that the FPR film is difficult to adhere. Therefore, for the surface protection film for this application, a film with less contamination to the adherend is required.

On the other hand, in some liquid crystal panel manufacturers, as a method for evaluating the contamination of a surface protection film to an adherend, the following method is used to peel off the surface protection film attached to an optical film such as a polarizing plate to The air bubbles were mixed again in a state where they were mixed, and heat treatment was performed under predetermined conditions. Then, the surface protective film was peeled off, and the surface of the adherend was observed. In this evaluation method, even if the surface of the adherend is contaminated in a small amount, if the surface contamination of the adherend differs between the part where the air bubbles are mixed and the part of the surface protective film that is in contact with the adhesive, the air bubble trace (with (Also known as bubble spots). Therefore, as an evaluation method of the contamination property to the surface of an adherend, it becomes a very strict evaluation method. In recent years, a surface protective film has been sought, and the surface protective film has no problem in the contamination of the surface of an adherend even in a result determined by such a strict evaluation method.

A surface protection film has been proposed. When the surface protection film is peeled off from an optical film as an adherend, in order to prevent an unfavorable condition caused by a high peeling static voltage, a low peeling static voltage is used and a protective film is used. Adhesive layer of electrostatic agent.

For example, Patent Document 1 discloses a surface protective film using a binder composed of an alkyltrimethylammonium salt, a hydroxyl-containing acrylic polymer, and a polyisocyanate.

In addition, Patent Document 2 discloses an adhesive composition and an adhesive sheet using the adhesive composition. The adhesive composition is made of an ionic liquid. And an acrylic polymer having an acid value of 1.0 or less.

In addition, Patent Literature 3 discloses an adhesive composition and a surface protection film using the adhesive composition, the adhesive composition being made of an acrylic polymer, a polyether polyol compound, or an anion-adsorbing compound treated Alkali metal salt composition.

In addition, Patent Document 4 discloses an adhesive composition and a surface protective film using the adhesive composition. The adhesive composition is composed of an ionic liquid, an alkali metal salt, and a glass transition temperature of 0 ° C or lower. Polymer composition.

Prior art literature

Patent literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-131957

Patent Document 2: Japanese Patent Application Laid-Open No. 2005-330464

Patent Document 3: Japanese Patent Application Laid-Open No. 2005-314476

Patent Document 4: Japanese Patent Application Laid-Open No. 2006-152235

In the surface protection films described in the aforementioned Patent Documents 1 to 4, an antistatic agent is added inside the adhesive layer. Therefore, the thicker the adhesive layer, or the longer it takes to adhere to the adherend, the greater the amount of antistatic agent transferred from the adhesive layer to the adherend for the adherend to which the surface protective film is attached. More trends. When the amount of the antistatic agent transferred to the adherend is increased, there is a possibility that the appearance quality of the optical film as an adherend is deteriorated, or the adhesiveness of the FPR film may be reduced when the FPR film is bonded.

In this way, in order to reduce the change with time of the antistatic agent transferred from the adhesive layer to the adherend, if the thickness of the adhesive layer is made thinner, another problem occurs. For example, in the case of an optical film having unevenness on the surface such as an anti-glare polarizing plate used for anti-glare, the adhesive cannot follow the unevenness on the surface of the optical film and mix air bubbles; The adhesion area with the adhesive is reduced to reduce the adhesive force, and the surface protective film is lifted and peeled off during use.

In addition, in order to reduce the change with time of the antistatic agent transferred from the adhesive layer to the adherend, if the amount of the antistatic agent added to the adhesive layer is reduced, there is a risk of the following phenomenon: peeling and removing The phenomenon that the peeling static voltage increases during the surface protection film increases, the circuit elements such as the driver IC are destroyed, or the alignment of the liquid crystal molecules is destroyed.

The present invention has been made in view of the above circumstances, and a technical problem thereof is to provide a surface protection film and an optical element using the surface protection film. The surface protection film is a surface protection film for an optical film. The surface protection The film can be used even for an optical film having unevenness on the surface, the pollution to the adherend is very small, and the contamination of the adherend does not change with time, and even if the component of the polarizing plate (TAC film) is replaced Changing to an acrylic film or a polyester film, and changing the water-based adhesive to a UV-curable adhesive) can also suppress the peeling static voltage when peeling the surface protective film to a low level.

In order to solve the technical problem, the inventors of the present application have conducted earnest research.

First, in order to reduce the contamination of the adherend and to reduce the contamination change with time, it is necessary to reduce the amount of the antistatic agent presumed to contaminate the adherend. but When the amount of the antistatic agent is reduced, the peeling static voltage when the surface protective film is peeled from the adherend increases. Therefore, the inventors of the present application have studied a method of suppressing the peeling static voltage when the surface protective film is peeled from the adherend to be low without increasing the amount of the antistatic agent added.

After researching the content, the inventors of the present application found that an antistatic agent is added to the adhesive composition to a degree that does not contaminate the adherend, and the adhesive composition is coated and dried on one surface of the substrate. After the adhesive layer is laminated, an appropriate amount of an antistatic agent is applied to the surface of the adhesive layer. Accordingly, the peeling static voltage when the surface protective film is peeled from the optical film as an adherend can be suppressed to a low level, and it is difficult to contaminate the adherend, and the present invention has been completed.

The technical idea of the surface protection film of the present invention is to apply and dry an adhesive composition containing an antistatic agent to a degree that does not contaminate the adherend, and after laminating the adhesive layer, give the surface of the adhesive layer an appropriate amount of antistatic. The agent suppresses the contamination property of the adherend to low contamination properties, and suppresses the peeling static voltage when peeling from the optical film as the adherend to be low.

In order to solve the above-mentioned technical problems, the present invention provides a surface protection film characterized in that an adhesive layer containing an ionic compound as an antistatic agent is formed on one surface of a substrate film made of a resin having transparency, and The release film of the release agent layer is bonded to the adhesive layer via the release agent layer. The release agent layer contains an alkali metal salt and a silicone resin-based release agent, and components of the alkali metal salt are removed from the release film. The static voltage is reduced when the adhesive layer is transferred to the surface of the adhesive layer and the adhesive layer is peeled from the adherend.

Furthermore, it is preferred that the ionic compound is not an alkali metal salt.

In addition, it is preferable that the adhesive layer is formed by crosslinking a (meth) acrylate copolymer.

In addition, a surface protection film having a surface potential of +0.7 kV to -0.7 kV when peeled from an optical film as an adherend is provided.

In addition, the peeling force when peeling the release film from the adhesive layer is preferably 0.005 to 0.3 N / 50 mm.

The present invention also provides an optical element to which the surface protection film is bonded.

The surface protective film of the present invention is a surface protective film for an optical film, and can be used even for an optical film having unevenness on the surface. In addition, the surface protection film of the present invention has very little pollution to the adherend, and is a surface protection film that does not change the contamination of the adherend with time. Furthermore, the present invention can provide a surface protection film and an optical element using the same. Even if the surface protection film of the present invention is a constituent element of a polarizing plate, it changes (from a TAC film to an acrylic film or a cyclic polyolefin film). Or polyester film, from an aqueous adhesive to an ultraviolet-curable adhesive), the peeling static voltage when the surface protective film is peeled off is still kept low.

According to the surface protection film of the present invention, the amount of static electricity generated when peeling from an adherend can be reduced, and the time-dependent change of the peeling antistatic performance and the pollution to the adherend are small. Therefore, an improvement in productivity and yield can be expected. improve.

1‧‧‧ substrate film

2‧‧‧ Adhesive layer

3‧‧‧ resin film

4‧‧‧ peeling agent layer

5‧‧‧ peeling film

7‧‧‧Antistatic agent

8‧‧‧ Adhered body (optical element)

10‧‧‧ surface protective film

11‧‧‧ peel off the surface protection film of the release film

20‧‧‧ Optical element with surface protection film

FIG. 1 is a schematic cross-sectional view of a surface protective film of the present invention; FIG. 2 is a cross-sectional view showing a state where a release film is peeled from the surface protective film of the present invention; and FIG. 3 is a view showing a surface of the present invention A cross-sectional view of one embodiment of a protective film bonded to an optical element.

Hereinafter, this invention is demonstrated in detail based on embodiment.

FIG. 1 is a schematic cross-sectional view of a surface protection film of the present invention. This surface protection film 10 has an antistatic agent-containing adhesive layer 2 formed on one surface of a transparent base film 1. A release film 5 is laminated on the surface of the adhesive layer 2, and the release film 5 forms a release agent layer 4 containing an antistatic agent 7 on the surface of the resin film 3.

As the base film 1 used for the surface protection film 10 of the present invention, a base film made of a resin having transparency and flexibility is used. In this manner, the appearance inspection of the optical element can be performed in a state where the surface protective film is bonded to the optical element as an adherend. As the film made of a transparent resin used as the base film 1, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and polyethylene terephthalate are suitably used. Polyester film such as butanediol diformate. In addition to a polyester film, a film made of another resin may be used as long as it has a desired strength and has optical characteristics. The base film 1 may be a non-stretched film, or may be a uniaxially or biaxially stretched film. The stretching ratio of the stretched film and the alignment angle in the axial direction formed by the crystallization of the stretched film may be controlled to specific values.

The thickness of the base film 1 used for the surface protection film 10 of the present invention is not particularly limited For example, a thickness of about 12 to 100 μm is preferable, and a thickness of about 20 to 75 μm is preferable because it is easy to handle.

In addition, if necessary, an antifouling layer, an antistatic layer, a hard coat layer, or the like that prevents surface contamination can be provided on the opposite side of the surface on which the adhesive layer 2 is formed on the base film 1. In addition, the surface of the base film 1 may be subjected to an easy-adhesion treatment such as surface modification by corona discharge and application of a tackifier.

In addition, the adhesive layer 2 used in the surface protection film 10 of the present invention is not particularly limited as long as it is adhered to the surface of the adherend, can be easily peeled off after use, and it is difficult to contaminate the adherent of the adherend. In consideration of durability after bonding to an optical film, an adhesive obtained by crosslinking a (meth) acrylate copolymer is usually used.

Examples of the (meth) acrylate copolymer include a main monomer such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate, and acrylonitrile and vinyl acetate. , Comonomers such as methyl methacrylate, ethyl acrylate, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, N-hydroxymethacrylamide, etc. Copolymer made from copolymerizing monomers. The (meth) acrylic acid ester copolymer may have both the main monomer and other monomers as (meth) acrylic acid esters. As a monomer other than the main monomer, it may contain one or two or more kinds of (meth) acrylic acid esters. Monomer.

In the (meth) acrylate copolymer, a compound containing a polyoxyalkylene group may be copolymerized or mixed. Examples of the compound containing a copolymerizable polyoxyalkylene group include polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, and methoxypolyethylene glycol (400). Acrylate, methoxy polyethylene glycol (400) methacrylate, polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxy polypropylene glycol (400) acrylate, methyl Oxypolypropylene glycol (400) methacrylate and the like. By copolymerizing these polyoxyalkylene group-containing monomers with the main monomer and functional monomer of the (meth) acrylic acid ester copolymer, a binder composed of a polyoxyalkylene group-containing copolymer can be obtained.

The polyoxyalkylene group-containing compound that can be mixed in the (meth) acrylate copolymer is preferably a (meth) acrylate copolymer containing a polyoxyalkylene group, and more preferably a (meth) acrylate containing a polyoxyalkylene group. Polymer of acrylic monomers, for example, polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, and methoxypolyethylene glycol (400) acrylic acid Esters, methoxy polyethylene glycol (400) methacrylate, polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxy polypropylene glycol (400) acrylate, methoxy Polymers such as polypropylene glycol (400) methacrylate. By mixing these polyoxyalkylene group-containing compounds with the (meth) acrylate copolymer, a binder to which a polyoxyalkylene group-containing compound is added can be obtained.

Examples of the curing agent added to the adhesive layer 2 include a isocyanate compound, an epoxy compound, a melamine compound, and a metal chelate as a crosslinking agent that crosslinks the (meth) acrylate copolymer. Examples of the thickener include rosin, coumarone indene, terpene, petroleum, and phenol.

The adhesive layer 2 contains an antistatic agent. Examples of the antistatic agent contained in the adhesive layer 2 include surfactants, ionic liquids, alkali metal salts, Metal oxides, metal fine particles, conductive polymers, carbon, carbon nanotubes, etc. are preferably other than alkali metal salts in terms of transparency, affinity for (meth) acrylic polymers, and contamination by adherends, etc. The ionic compound and the like are particularly preferably an ionic compound which is solid at a temperature of 25 ° C.

In addition, various resins can be added to the antistatic agent of the adhesive layer 2. Examples of the resin added to the antistatic agent include polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl butyral resins, polyvinyl alcohol resins, and polyvinyl acetate resins. , Cellulose resin, silicone resin, fluororesin, etc.

The antistatic agent contained in the adhesive layer 2 need not be concentrated on the surface of the adhesive layer 2, and can be uniformly dissolved or dispersed in the adhesive layer 2.

An ionic compound refers to an ionic liquid composed of an anion and a cation, and has an ionic liquid that is liquid at normal temperature and an ionic solid that is solid at normal temperature. Examples of the cationic moiety include organic cations and inorganic cations such as cyclic sulfonium ions such as imidazolium ions, pyridinium ions, ammonium ions, sulfonium ions, and sulfonium ions. Further, as the anionic moiety include ^{_{C n H 2n + 1 COO -}} , C n F 2n + 1 COO -, NO 3 -, C n F 2n + 1 SO 3 -, (C n F 2n + 1 SO 2 _{^{) 2 N -, (C n}} F 2n + 1 SO 2) 3 C -, PO 4 3-, AlCl 4 -, Al 2 Cl 7 -, ClO 4 -, BF 4 -, PF 6 -, AsF 6 -, SbF ₆ ^- and other organic or inorganic anions.

The thickness of the antistatic agent-containing adhesive layer 2 used in the surface protective film 10 of 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. Since the workability when peeling the surface protection film from the adherend is excellent, it is preferable that the peel strength (adhesive force) of the surface protection film to the surface of the adherend is about 0.03 to 0.3N / 25mm, Adhesive layer 2 with weak adhesion. In addition, from the viewpoint of excellent operability when peeling the peeling film 5 from the surface protective film 10, the peeling force of the peeling film 5 from the adhesive layer 2 is preferably 0.005 to 0.3 N / 50 mm.

In addition, the release film 5 used in the surface protection film 10 of the present invention has a release agent layer 4 containing a silicone resin release agent and an antistatic agent 7 which does not react with the release agent, laminated on one surface of the resin film 3.

Examples of the resin film 3 include a polyester film, a polyimide film, a polyethylene film, a polypropylene film, and a polyimide film. A polyester film is preferred in terms of excellent transparency and low cost. The resin film may be a non-stretched film or a film which is uniaxially or biaxially stretched. The stretching ratio of the stretched film and the alignment angle in the axial direction formed by the crystallization of the stretched film may be controlled to specific values.

The thickness of the resin film 3 is not particularly limited. For example, a thickness of about 12 to 100 μm is preferable, and a thickness of about 20 to 50 μm is easy to handle, and thus it is more preferable.

In addition, if necessary, the surface of the resin film 3 may be subjected to an easy-adhesion treatment such as surface modification by corona discharge and application of a tackifier.

The silicone resin-based release agent constituting the release agent layer 4 is a release agent mainly composed of polydimethylsiloxane, and examples thereof include addition reaction type, condensation reaction type, cation polymerization type, and radical polymerization. Type (radical polymerization type) and other known silicone-based release agents. Examples of products that are commercially available as addition reaction type silicone resin strippers include KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (Shin-Etsu Chemical Industry Co., Ltd. (Stock) system), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, LTC-310 (Dow Corning Toray (shares) system) and so on. Examples of products that are commercially available as condensation reaction types include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray). Examples of products sold on the market as a cationic polymerization type include TPR-66501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials), X62-7622 (manufactured by Shin-Etsu Chemical Industry (Stock)) . As a product which is marketed as a radical polymerization type, X62-7205 (made by Shin-Etsu Chemical Industry Co., Ltd.) etc. are mentioned, for example.

As the antistatic agent constituting the release agent layer 4, it is preferable that the dispersant has a dimethylpolysiloxane as a main component, has good dispersibility, and does not hinder a release agent containing a dimethylpolysiloxane as a main component. Curing. Further, in order to transfer from the release agent layer 4 to the surface of the adhesive layer 2 and impart an antistatic effect to the adhesive layer, an antistatic agent that does not react with a release agent containing dimethylpolysiloxane as a main component is preferred. As such an antistatic agent, an alkali metal salt is suitable.

Examples of the alkali metal salt include metal salts formed of lithium, sodium, and potassium. Specifically, for example, may be suitably selected from Li ^+, Na ^+, K ⁺ is a cation selected from ^{Cl -, Br -, I -} , BF4 -, PF6 -, SCN -, ClO 4 -, CF 3 SO _{^{3 -, (CF 3 SO 2}} ) 2 N -, (C 2 F 5 SO 2) 2 N -, (CF 3 SO 2) 3 C - anions consisting of a metal salt. Among them, LiBr, LiI, LiBF ₄ , LiPF ₆ , LiSCN, LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₃ C and other lithium salts. These alkali metal salts may be used singly or in combination of two or more kinds. In order to stabilize the ionic substance, a compound containing a polyoxyalkylene structure may be added.

The addition amount of the antistatic agent of the release agent containing dimethyl polysiloxane as a main component varies depending on the type of the antistatic agent or the degree of affinity with the release agent. It may be set in consideration of a desired peeling static voltage when peeling the surface protective film from the adherend, contamination to the adherend, adhesion characteristics, and the like.

The release agent layer 4 may be a release agent layer 4 composed of a mixture of a release agent containing dimethylpolysiloxane as a main component and an antistatic agent which does not react with the release agent. The mixing method of the peeling agent which has dimethyl polysiloxane as a main component and an antistatic agent is not specifically limited. Either of the following methods: a method of adding an antistatic agent to a release agent containing dimethylpolysiloxane as a main component, and adding and mixing the catalyst for curing the release agent after mixing; using dimethylpolysiloxane A method in which a stripping agent having a main component is diluted with an organic solvent in advance, and an antistatic agent and a curing agent for curing the stripping agent are added and mixed. , The method of adding and mixing catalyst, and then adding and mixing antistatic agent. In addition, if necessary, materials such as an adhesion promoter such as a silane coupling agent, or a polyoxyalkylene group-containing compound may be added to assist the antistatic effect.

The mixing ratio of the release agent containing dimethyl polysiloxane as the main component and the antistatic agent is not particularly limited. With respect to 100 parts by weight of the solid content of the release agent containing dimethyl polysiloxane as the main component, The proportion of the antistatic agent in terms of solid content is preferably about 5 to 100 parts by weight. The antistatic agent is added to the surface of the adhesive layer when the solid content of the antistatic agent is less than 5 parts by weight relative to 100 parts by weight of the solid content of the release agent containing dimethylpolysiloxane as a main component. The transfer amount becomes smaller, making it difficult to exert an antistatic function in the adhesive. In addition, with respect to 100 parts by weight of the solid content of the release agent containing dimethylpolysiloxane as a main component, if the solid content of the antistatic agent is added in an amount exceeding 100 parts by weight, the antistatic agent and the Dimethyl polysiloxane as main The component release agent is simultaneously transferred to the surface of the adhesive layer, so there is a possibility that the adhesive properties of the adhesive are reduced.

The method of forming the adhesive layer 2 containing an antistatic agent on the base film 1 of the surface protection film 10 of the present invention, and the method of bonding the release film 5 can be performed by known methods, and are not particularly limited. Specifically, the following methods can be enumerated: (1) coating and drying a resin composition for forming an adhesive layer 2 containing an antistatic agent on one surface of the base film 1 to form an adhesive layer; A method for bonding a release film 5; (2) coating and drying a resin composition for forming an adhesive layer 2 containing an antistatic agent on the surface of the release film 5 to form a bonding agent layer, and then bonding a base film 1 method, etc .; any one of the above methods can be used.

The formation of the adhesive layer 2 containing an antistatic agent on the surface of the base film 1 can be performed by a known method. Specifically, a reverse coating method, a comma coating method, a gravure coating method, a slot die coating method, and a wire bar coating method (Meyer bar) can be used. coating), air knife coating, and other known coating methods.

In addition, the formation of the release agent layer 4 on the resin film 3 can also be performed by a known method. Specifically, known coating methods such as a gravure coating method, a bar coating method, and an air knife coating method can be used.

The surface potential of the surface protective film 10 of the present invention having the above-mentioned structure when peeled from the optical film as an adherend is preferably +0.7 kV to -0.7 kV. Furthermore, the surface potential is more preferably +0.5 kV to -0.5 kV, and particularly preferably +0.1 kV to -0.1 kV. This surface potential can be adjusted by increasing or decreasing the type, addition amount, and the like of the antistatic agent 7 contained in the adhesive layer 2 and the antistatic agent 7 contained in the release agent layer 4. To the surface protection film 10 from light as an adherend After considering the surface contamination of the optical film as an adherend after the academic film is peeled off, the type and amount of the antistatic agent 7 of the adhesive layer 2 and the antistatic agent 7 of the release agent layer 4 may be adjusted.

Fig. 2 is a cross-sectional view showing a state where the release film is peeled from the surface protective film of the present invention.

By peeling the release film 5 from the surface protection film 10 shown in FIG. 1, a part of the antistatic agent (symbol 7) contained in the release agent layer 4 of the release film 5 is transferred to (attached to) the surface protection film. 10 of the surface of the adhesive layer 2. Therefore, in FIG. 2, the antistatic agent adhered to the surface of the adhesive layer 2 of the surface protective film is indicated schematically by a spot (circle) of symbol 7. The components of the antistatic agent 7 are transferred from the release film 5 to the surface of the adhesive layer 2. Therefore, compared with the adhesive layer 2 before the transfer, the peeling time when the adhesive layer 2 is peeled from the adherend is smaller. The voltage drops. The peeling static voltage when the adhesive layer is peeled from the adherend can be measured by a known method. For example, after the surface protective film is attached to an adherend such as a polarizing plate, the surface protective film is peeled at a peeling speed of 40 m per minute using a high-speed peel tester (manufactured by Tester Industries), and a surface potential meter (Keyence ( Co., Ltd.) The surface potential of the surface of the adherend was measured every 10 ms, and the maximum value of the absolute value of the surface potential at this time was taken as the peeling static voltage (kV).

In the surface protective film of the present invention, when the surface protective film 11 in a state where the release film is peeled off as shown in FIG. 2 is bonded to an adherend, the antistatic agent transferred to the surface of the adhesive layer 2 Make contact with the surface of the adherend. Accordingly, the peeling static voltage when the surface protective film is peeled from the adherend can be suppressed to be low again.

FIG. 3 is a cross-sectional view showing an example in which the surface protective film of the present invention is bonded to an optical element.

The surface protective film 10 of the present invention is in a state in which the release film 5 is peeled off and the adhesive layer 2 is exposed (surface protective film 11 in FIG. 2), and the optical element 8 as an adherend is bonded via the adhesive layer 2. on.

That is, FIG. 3 shows the optical element 20 to which the surface protective film 11 is bonded, and the surface protective film 11 is in a state where the release film 5 is peeled from the surface protective film 10 of the present invention. Examples of the optical element include optical films such as a polarizing plate, a retardation plate, a lens film, a polarizing plate also serving as a retardation plate, and a polarizing plate also serving as a lens film. Such an optical element can be used as a structural element such as a liquid crystal display device such as a liquid crystal display panel, and various optical devices such as measuring instruments. Examples of the optical element include optical films such as antireflection films, hard coat films, and transparent conductive films for touch panels.

When the surface protection film 11 in a state where the release film 5 is peeled from the antistatic surface protection film 10 of the present invention is peeled off from the optical element (optical film) as an adherend, the peeling static voltage can be sufficiently suppressed to Lower. Therefore, there is no possibility of destroying circuit elements such as a driving IC, a TFT element, and a gate line driving circuit, and it is possible to improve the production efficiency in the step of manufacturing the liquid crystal display panel and ensure the reliability of the production step.

Examples

Next, the present invention will be further described through examples.

(Example 1)

(Production of surface protective film)

5 parts by weight of addition reaction type silicone resin (Dow Corning Toray (Stock), trade name: SRX-345), 0.75 parts by weight of lithium bis (fluorosulfonyl) imide, 95 parts by weight of a 1: 1 mixed solvent of toluene and ethyl acetate, 0.05 weight A part of a platinum catalyst (produced by Dow Corning Toray Co., Ltd., trade name: SRX-212) was blended, stirred and mixed to prepare a coating material for forming the release agent layer of Example 1. The coating material forming the release agent layer of Example 1 was coated on a surface of a polyethylene terephthalate film having a thickness of 38 μm with a wire rod so that the thickness after drying was 0.2 μm. The hot air circulation type oven was dried for 1 minute, and the peeling film of Example 1 was obtained.

On the other hand, a binder is composed of a copolymer of 80 parts by weight of 2-ethylhexyl acrylate, 17 parts by weight of methoxypolyethylene glycol (400) methacrylate, and 3 parts by weight of 2-hydroxyethyl acrylate. Based on 100 parts by weight of a 40% ethyl acetate solution of the adhesive, stir and mix 0.2 parts by weight of 1-nonyl pyridinium hexafluoride phosphate and 2 parts by weight of an isocyanate curing agent (CORONATE (registered trademark) HX manufactured by Tosoh Corporation), and the adhesive of Example 1 was prepared.

The prepared adhesive was coated on the surface of a polyethylene terephthalate film having a thickness of 38 μm so that the thickness after drying was 20 μm, and then dried in a hot air circulation oven at 100 ° C. for 2 minutes. Form an adhesive layer. Then, on the surface of this adhesive layer, the release agent layer (silicone resin treated surface) of the release film of Example 1 produced as described above was bonded. The obtained adhesive film was held in an environment at 40 ° C. for 5 days to cure the adhesive to obtain a surface protection film of Example 1.

(Example 2)

The surface of Example 2 was obtained in the same manner as in Example 1 except that the thickness of the coating material forming the release agent layer in Example 1 was 0.1 μm after drying. Protective film.

(Example 3)

Except that the addition reaction type silicone resin of Example 1 was made by Dow Corning Toray Co., Ltd., trade name: SRX-211, and lithium bistrifluoromethanesulfonimide was used instead of lithium bissulfonimide. In the same manner as in Example 1, a surface protection film of Example 3 was obtained.

(Comparative example 1)

5 parts by weight of an addition reaction type silicone resin (manufactured by Dow Corning Toray Co., Ltd., trade 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 a platinum catalyst (Dow Corning Toray Co., Ltd., trade name: SRX-212) was blended, stirred and mixed to prepare a coating material for forming the release agent layer of Comparative Example 1. The coating material forming the release agent layer of Comparative Example 1 was coated on the surface of a polyethylene terephthalate film having a thickness of 38 μm with a wire rod so that the thickness after drying was 0.2 μm, and hot air at 120 ° C. was used. Dry in a loop oven for 1 minute to obtain a release film of Comparative Example 1.

On the other hand, the adhesive of Example 1 was coated on the surface of a polyethylene terephthalate film having a thickness of 38 μm so that the thickness after drying was 20 μm, and then a 100 ° C. hot air loop type was used. Dry in an oven for 2 minutes to form an adhesive layer. Then, the release agent layer (silicone resin-treated surface) of the release film of Comparative Example 1 produced as described above was bonded to the surface of the adhesive layer. The obtained adhesive film was held in an environment at 40 ° C. for 5 days to cure the adhesive to obtain a surface protection film of Comparative Example 1.

(Comparative example 2)

In addition to not adding 1-nonylpyridinium hexafluoride phosphate to the binder, In addition, in the same manner as in Example 1, a surface protection film of Comparative Example 2 was obtained.

(Comparative example 3)

A surface protection film of Comparative Example 3 was obtained in the same manner as in Example 1 except that lithium bisfluorosulfimide was used instead of the 1-nonylpyridinium hexafluorophosphate of Example 1.

The methods and results of the evaluation tests are shown below.

<Method for measuring peeling force of release film>

A sample of the surface protective film was cut into a width of 50 mm and a length of 150 mm. In a test environment of 23 ° C. × 50% RH, a tensile tester was used at a peeling speed of 300 mm / min in a direction of 180 ° to measure the strength when peeling the peeling film, and this was taken as the peeling force of the peeling film (N / 50mm).

(Surface resistivity of antistatic agent layer)

After the release film was peeled from the sample of the antistatic surface protection film, it was measured using a high-performance high-resistance meter (Hiresta (registered trademark) -UP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) under a voltage of 100 V and a measurement time of 30 seconds. Surface resistivity of the antistatic agent layer (Ω / □).

<Method for measuring adhesive force of surface protective film>

An anti-glare and low-reflection polarizer (AG-LR polarizer) with an acrylic film bonded to a polarizer (an iodine-containing polyvinyl alcohol film) using a UV-curable adhesive was used as an adherend. This polarizing plate was bonded to the surface of the glass plate with a bonding machine. Then, a surface protective film having a width of 25 mm was bonded to the acrylic film on the surface of the polarizing plate, and then stored in a test environment at 23 ° C. × 50% RH for 1 day. Then, using a tensile tester, the strength at the time of peeling the surface protective film was measured at a peeling speed of 300 mm / min in a direction of 180 °, and this was defined as Adhesion (N / 25mm).

<Method for measuring peeling static voltage of surface protective film>

An anti-glare and low-reflection polarizer (AG-LR polarizer) with an acrylic film bonded to a polarizer (an iodine-containing polyvinyl alcohol film) using a UV-curable adhesive was used as an adherend. This polarizing plate was bonded to the surface of the glass plate with a bonding machine. Then, a 25 mm-wide surface protective film was bonded to the acrylic film on the surface of the polarizing plate, and stored in a test environment at 23 ° C. × 50% RH for 1 day. Then, the surface protective film was peeled at a peeling speed of 40 m per minute using a high-speed peel tester (manufactured by Tester Industries), and the surface potential of the surface of the polarizing plate was measured every 10 ms using a surface potential meter (manufactured by Keyence). The maximum value of the absolute value of the surface potential at this time was taken as the peeling static voltage (kV).

<A method for confirming the surface contamination of a surface protective film>

An anti-glare low-reflection polarizing plate (AG-LR polarizing plate) with an acrylic film bonded to a polarizer (polyvinyl alcohol film containing iodine) using a UV-curable adhesive was used as an adherend. This polarizing plate was bonded to the surface of a glass plate with a bonding machine. Then, an acrylic film on the surface of the polarizing plate was bonded and cut into a surface protective film having a width of 25 mm, and then stored in a test environment at 23 ° C. × 50% RH for 3 days and 30 days. Then, the surface protective film was peeled off, and the surface of the polarizing plate was visually observed for contamination to confirm the surface contamination. As a criterion for determining the surface contamination property, a case where no pollution transfer occurred on the polarizing plate was (○), and a case where pollution transfer was confirmed on the polarizing plate was (×).

The measurement results of the obtained surface protective films of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1. "2EHA" means 2-ethylhexyl acrylate, "HEA" means 2-hydroxyethyl acrylate, "# 400G" means methoxypolyethylene glycol (400) methacrylate, and "AS agent (1) "Means lithium bisfluorosulfimide," AS agent (2) "means lithium bistrifluoromethanesulfonylimide," AS agent (3) "means 1-nonylpyridinium hexafluorophosphate," SRX "-345" means SRX-345, "SRX-211" means SRX-211, and "SRX212" means platinum catalyst SRX-212. In addition, "1.5E10" of the surface resistivity means 1.5 × 10 ¹⁰ .

From the measurement results shown in Table 1, it can be known that the surface protective films of Examples 1 to 3 of the present invention have a moderate adhesive force and have no pollution to the surface of the adherend. In addition, even if the adherend is a polarizing plate using an acrylic film, the peeling static voltage when peeling the surface protective film from the adherend is low.

On the other hand, Comparative Example 1 in which no antistatic agent was added to the release agent layer The surface protection film of Comparative Example 2 and the surface protection film of Comparative Example 2 in which no antistatic agent was added to the adhesive layer had a high peeling static voltage when the surface protection film was peeled from the adherend. In addition, for the surface protection film of Comparative Example 3 using the same type of antistatic agent in the adhesive layer and the release agent layer, the peeling static voltage when the surface protection film was peeled from the adherend was low, which was good, but After peeling, contamination of the adherend increases.

That is, it is difficult for the surface protective films of Comparative Examples 1 to 3 to achieve both a reduction in peeling static voltage and a low contamination property to an adherend. On the other hand, for the surface protection films of Examples 1 to 3 in which different types of antistatic agents were added to the adhesive layer and the release agent layer, the effect of reducing the peeling static voltage was high, and there was no contamination of the adherend. Obtain a good surface protective film.

Industrial applicability

The surface protective film of the present invention can be used in the production steps of optical films such as polarizing plates, retardation plates, lens films, anti-reflection films, hard coating films, and transparent conductive films, and various other optical elements. The surface of the optical element is protected. In addition, the surface protection film of the present invention has a low amount of static electricity when it is peeled from the adherend, and the time-dependent change of the peeling antistatic performance and less pollution to the adherend can improve the yield of the production step. The use value is great.

Claims (5)

A surface protection film characterized in that an ionic compound containing an ionic compound as an antistatic agent which is solid at a temperature of 25 ° C. and is not an alkali metal salt is formed on one surface of a substrate film made of a resin having transparency. An adhesive layer, a release film having a release agent layer bonded to the adhesive layer via the release agent layer, the release agent layer containing an alkali metal salt and a silicone resin-based release agent, and components of the alkali metal salt The static peeling voltage when the adhesive film is transferred from the release film to the surface of the adhesive layer and when the adhesive layer is peeled from the adherend is reduced. The surface protection film according to item 1 of the scope of patent application, wherein the adhesive layer is formed by crosslinking a (meth) acrylate copolymer. For example, the surface protection film according to item 1 or 2 of the patent application scope is characterized in that the surface potential when peeled from the optical film as an adherend is +0.7 kV to -0.7 kV. The surface protection film according to any one of claims 1 or 2, wherein a peeling force when the peeling film is peeled from the adhesive layer is 0.005 to 0.3 N / 50 mm. An optical element is formed by laminating a surface protection film according to any one of claims 1 to 4 of the scope of patent application.