TW201702078A - Surface-protective film and optical component attached with the same - Google Patents

Abstract

The present invention provides a surface-protective film and an optical component uses the same. The surface-protective film may be applied to an optical film with irregular surface, makes little pollution to an adhered body, the low pollution toward the adhered body does not change over time and has excellent antistatic properties during peeling without deterioration over time. In the surface-protective film (10), an adhesive agent layer (2) containing an ionic compound which serve as an antistatic agent is formed on one surface of a substrate film (1) composed of a transparent resin. Peel film (5) containing peel agent layer (4) is adhered to the adhesive agent layer (2). The peel agent layer (4) is formed of alkali metal salts and silicone peel agent. The alkali metal salts transfer from the peel film to the surface of the adhesive agent layer, decreasing the peel voltage during peeling the adhesive agent layer from the adhered body.

Description

Surface protection film and optical component to which the film is attached

The present invention relates to a surface protective film which is bonded to a surface of an optical element (hereinafter sometimes referred to as an optical film) such as a polarizing plate, a phase difference plate, or a lens film for a display. More specifically, the present invention provides a surface protective film and an optical element to which the surface protective film is bonded, the surface protective film having less contamination to the adherend, and having excellent peeling and antistatic property without deterioration over time. performance.

In the optical product such as an optical film such as a polarizing plate, a phase difference plate, a lens film for a display, an antireflection film, a hard coat film, or a transparent conductive film for a touch panel, and an optical product such as a display using the same, The surface protective film is applied to the surface of the film to prevent surface contamination and damage in subsequent steps. In the appearance inspection of the optical film of the product, the time for bonding the surface protective film is removed and the work efficiency is improved, and the surface protective film may be directly bonded to the optical film.

For the long term, in the manufacturing step of an optical product, in order to prevent damage or adhesion of dirt, a surface protective film having a layer of a binder provided on one surface of the substrate film is generally used. The surface protective film is pasted via a layer of adhesive with weak adhesion It is combined with an optical film. When the adhesive layer is used as a weak adhesive force, it is easy to peel off when the used surface protective film is peeled off from the surface of the optical film, and the adhesive does not adhere to the optical film product as the adherend. Upper (ie prevent the generation of residual glue).

In the production process of the liquid crystal display panel, in the production process of the liquid crystal display panel, the number of occurrences is small, but it is also caused by the peeling static voltage generated when the surface protective film attached to the optical film is peeled off and removed. The circuit element such as the driver IC that controls the display screen of the liquid crystal display panel is broken and the alignment of the liquid crystal molecules is damaged.

Further, in order to reduce the power consumption of the liquid crystal display panel, the driving voltage of the liquid crystal material becomes low, and the breakdown voltage of the driving IC also becomes low. Recently, it has been attempted to make the peeling static voltage in the range of +0.7 kV to -0.7 kV.

Further, the conventional polarizing plate is bonded to a triacetyl cellulose film (TAC film) with a water-based adhesive to protect the polarizer on both sides of a polarizer made of polyvinyl alcohol (PVA) impregnated with iodine. In order to manufacture a polarizing plate, in recent years, the following polarizing plates have also been used: a polarizing plate using an acrylic film, a cyclic polyolefin film, a polyester film instead of a TAC film, and a polarizing plate using an ultraviolet curing type adhesive instead of an aqueous adhesive. . The 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 increased as compared with the case of using a polarizing plate having a conventional configuration.

Further, in recent years, with the spread of 3D displays (stereoscopic displays), an FPR (Film Patterned Retarder) film may be bonded to the surface of an optical film such as a polarizing plate. After the surface protective film attached to the surface of the optical film such as a polarizing plate is peeled off, the FPR film is bonded. but, When the surface of the optical film such as a polarizing plate is contaminated with a binder or an antistatic agent for the surface protective film, there is a problem that the FPR film is hard to be bonded. Therefore, for the surface protective film for this use, a film having less contamination of the adherend is sought.

On the other hand, in some liquid crystal panel manufacturers, as a method for evaluating the staining property of the adherend by the surface protective film, the surface protective film attached to the optical film such as a polarizing plate is first peeled off by the following method. The state in which the air bubbles were mixed was adhered again, and heat treatment was performed under predetermined conditions, and then the surface protective film was peeled off to observe the surface of the adherend. In this evaluation method, even if the surface of the adherend is contaminated with a small amount, if the portion in which the bubble is mixed and the portion of the surface protective film that is in contact with the binder is contaminated by the surface of the adherend, the bubble trace is present. Also known as the form of bubble spots. Therefore, as a method of evaluating the contamination of the surface of the adherend, this is a very strict evaluation method. In recent years, a surface protective film which does not have a problem in the staining property on the surface of the adherend even in the results judged by such a strict evaluation method has been sought.

A surface protective film is proposed in which a peeling static voltage is suppressed to a low level and is contained in order to prevent a problem caused by a high peeling static voltage when the surface protective film is peeled off from the optical film as the adherend. A layer of adhesive for the electrostatic agent.

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

Further, in Patent Document 2, a binder composition and an adhesive sheet using the same, which are composed of an ionic liquid, are disclosed. It is composed of an acrylic polymer having an acid value of 1.0 or less.

Further, Patent Document 3 discloses a bonding composition and a surface protective film using the same, which is treated with an acrylic polymer, a polyether polyol compound, and an anion-adsorbing compound. It is composed of an alkali metal salt.

Further, Patent Document 4 discloses a binder composition and a surface protective film using the same, wherein the binder composition has an ionic liquid, an alkali metal salt, and a glass transition temperature of 0 ° C or less. Polymer composition.

Prior art literature

Patent literature

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

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

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

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

In the surface protection film described in the above Patent Documents 1 to 4, an antistatic agent is added to the inside of the binder layer. Therefore, the thicker the thickness of the adhesive layer or the longer the time after bonding to the adherend, the more the amount of the antistatic agent transferred from the adhesive layer to the adherend for the adherend to which the surface protective film is bonded More trends. When the amount of the antistatic agent to be transferred to the adherend is increased, the appearance quality of the optical film as the adherend may be lowered, or the adhesion of the FPR film may be lowered when the FPR film is bonded.

Thus, in order to reduce the temporal change of the antistatic agent transferred from the adhesive layer to the adherend, if the thickness of the adhesive layer is made thin, another problem arises. For example, in the case of an optical film having irregularities on the surface of an anti-glare-treated polarizing plate for anti-glare, the binder cannot follow the irregularities on the surface of the optical film to mix air bubbles; The bonding area with the binder is reduced to lower the bonding force, and the surface protective film is lifted and peeled off during use.

Further, in order to reduce the change over time of the antistatic agent transferred from the binder layer to the adherend, if the amount of the antistatic agent added to the binder layer is reduced, there is a risk of causing the following phenomenon: peeling off The peeling static voltage generated when the surface protective film is increased, the circuit element such as the driver IC is broken, or the alignment of the liquid crystal molecules is broken.

The present invention has been made in view of the above circumstances, and a technical problem thereof is to provide a surface protective film which is a surface protective film for an optical film, and a surface protective film using the surface protective film, the surface protective film The film can be used even for an optical film having irregularities on the surface, and the contamination to the adherend is extremely small, and the contamination to the adherend does not change over time, and even if the constituent elements of the polarizing plate are replaced (TAC film) When the acrylic film or the polyester film is changed to an ultraviolet curable adhesive, the peeling static voltage at the time of peeling off the surface protective film can be suppressed to be low.

In order to solve the above-described technical problems, the inventors of the present application have conducted serious research.

First, in order to reduce the contamination of the adherend and to reduce the temporal change of the contamination, it is necessary to reduce the amount of the antistatic agent estimated to be a contaminated adherend. but When the amount of the antistatic agent to be added is reduced, the peeling static voltage when the surface protective film is peeled off from the adherend is increased. Then, the inventors of the present invention have studied a method of suppressing the peeling static voltage when the surface protective film is peeled off from the adherend without lowering the amount of the antistatic agent to be added.

The present inventors have found that an antistatic agent which does not contaminate the adherend is added to the adhesive composition, and the binder composition is applied and dried on one side of the substrate. After laminating the adhesive layer, an appropriate amount of an antistatic agent is applied to the surface of the adhesive layer. Thus, the peeling static voltage when the surface protective film is peeled off from the optical film as the adherend is suppressed to be low, and it is difficult to contaminate the adherend, and the present invention has been completed.

The technical concept of the surface protective film of the present invention is to apply an appropriate amount of antistatic to the surface of the adhesive layer by laminating and drying the adhesive composition containing the antistatic agent to the extent that it does not contaminate the adherend. In addition, the contamination of the adherend is suppressed to be low-contamination, and the peeling static voltage when peeling off from the optical film as the adherend is suppressed to be low.

In order to solve the above problems, the present invention provides a surface protective film comprising a binder layer containing an ionic compound as an antistatic agent on one surface of a substrate film made of a resin having transparency. The release film of the release agent layer is bonded to the adhesive layer via the release agent layer, and the release agent layer contains an alkali metal salt and a silicone resin release agent, and the alkali metal salt component is removed from the release film The surface of the adhesive layer is transferred to the surface of the adhesive layer, and the peeling static voltage when the adhesive layer is peeled off from the adherend is lowered.

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

Further, it is preferred that the binder layer be formed by crosslinking a (meth) acrylate copolymer.

Further, a surface protective film having a surface potential of from +0.7 kV to -0.7 kV when peeled off from the optical film as the adherend is provided.

Further, it is preferable that the peeling force when the release film is peeled off from the adhesive layer is 0.005 to 0.3 N/50 mm.

Further, the present invention provides an optical element to which the surface protective film is attached.

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 irregularities on its surface. Further, the surface protective film of the present invention has very little contamination of the adherend, and is a surface protective film which does not change with time when the contamination of the adherend is changed. Further, the present invention can provide a surface protective film and an optical element using the same, and the surface protective film of the present invention changes even in a constituent element of the polarizing plate (from a TAC film to an acrylic film, a cyclic polyolefin film) Or the polyester film changes from an aqueous binder to an ultraviolet-curable adhesive, and the peeling static voltage at the time of peeling off a surface protection film is suppressed low.

According to the surface protection film of the present invention, the amount of static electricity generated when peeling off from the adherend can be reduced, and the change in the antistatic property over time and the contamination on the adherend are small, so that productivity improvement and yield can be expected. improve.

1‧‧‧Base film

2‧‧‧Binder layer

3‧‧‧ resin film

4‧‧‧ Stripper layer

5‧‧‧Release film

7‧‧‧Antistatic agent

8‧‧‧Adhered body (optical component)

10‧‧‧Surface protection film

11‧‧‧ peeling off the surface protective film of the release film

20‧‧‧Optical components with surface protection film

1 is a schematic cross-sectional view showing a surface protective film of the present invention; FIG. 2 is a cross-sectional view showing a state in which a release film is peeled off 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 the protective film attached to the optical element.

Hereinafter, the present invention will be described in detail based on the embodiments.

Fig. 1 is a schematic cross-sectional view showing a surface protective film of the present invention. The surface protection film 10 is formed with a pressure-sensitive adhesive layer 2 containing an antistatic agent on the surface of one surface of the transparent base film 1. A release film 5 is bonded to the surface of the adhesive layer 2, and the release film 5 has a release agent layer 4 containing an antistatic agent 7 formed 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 formed of a resin having transparency and flexibility is used. In this manner, the appearance of the optical element can be inspected by attaching the surface protective film to the optical element as the adherend. As the film composed of the transparent resin used as the base film 1, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polyparaphenylene is preferably used. A polyester film such as butylene glycol dicarboxylate. In addition to the 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 a film which is uniaxially or biaxially stretched. Further, 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 substrate film 1 used for the surface protective film 10 of the present invention is not particularly The limitation is, for example, preferably a thickness of about 12 to 100 μm, and a thickness of about 20 to 75 μm is more preferable because it is easy to handle.

Further, an antifouling layer for preventing surface contamination, an antistatic layer, a damage-resistant hard coat layer, or the like may be provided on the opposite side surface of the surface of the base film 1 on which the adhesive layer 2 is formed, as needed. Further, on the surface of the base film 1, an easy adhesion treatment such as surface modification by a corona discharge or application of a tackifier can be applied.

Further, the adhesive layer 2 used for the surface protective 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 is difficult to contaminate the adhesive of the adherend. A binder obtained by crosslinking a (meth) acrylate copolymer is usually used in consideration of durability and the like after bonding to an optical film.

Examples of the (meth) acrylate copolymer include main monomers such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isodecyl acrylate, and acrylonitrile and vinyl acetate. , comonomers such as methyl methacrylate and ethyl acrylate, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, N-methylol acrylamide, etc. A copolymer obtained by copolymerization of a monomer. The (meth) acrylate copolymer may be a (meth) acrylate as a main monomer and other monomers, and may be a monomer other than the main monomer, and may contain one or more kinds of (meth) acrylates. Monomer.

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

The polyoxyalkylene group-containing compound which can be mixed in the (meth) acrylate copolymer is preferably a polyoxyalkylene group-containing (meth) acrylate copolymer, more preferably a polyoxyalkylene group (A) The polymer of the acrylic monomer may, for example, be polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, methoxy polyethylene glycol (400) acrylic acid. Ester, methoxy polyethylene glycol (400) methacrylate, polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxy polypropylene glycol (400) acrylate, methoxy A polymer such as polypropylene glycol (400) methacrylate. By mixing these polyoxyalkylene group-containing compounds with the (meth) acrylate copolymer, a binder to which a compound containing a polyoxyalkylene group is added can be obtained.

The crosslinking agent to crosslink the (meth) acrylate copolymer as the curing agent to be added to the binder layer 2 may, for example, be an isocyanate compound, an epoxy compound, a melamine compound or a metal chelate compound. Further, examples of the tackifier include rosin, coumarone indene, terpene, petroleum, and phenol.

The adhesive layer 2 contains an antistatic agent. Examples of the antistatic agent contained in the binder layer 2 include surfactants, ionic liquids, and alkali metal salts. Metal oxides, metal fine particles, conductive polymers, carbon, carbon nanotubes, and the like are preferably selected from the group consisting of alkali metal salts, such as transparency, affinity for (meth)acrylic polymers, and contamination of adherends. As the ionic compound or the like, an ionic compound which is solid at a temperature of 25 ° C is particularly preferable.

Further, various resins may be added to the antistatic agent of the adhesive layer 2. Examples of the resin to be added to the antistatic agent include a polyester resin, a polyamide resin, a polyurethane resin, a polyolefin resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, and a polyvinyl acetate resin. , cellulose resin, epoxy resin, fluororesin, and the like.

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

The ionic compound is composed of an anion and a cation, and has an ionic liquid which is liquid at normal temperature and an ionic solid which is solid at normal temperature. Examples of the cationic moiety include an organic cation such as a cyclic sulfonium ion such as an imidazolium ion, a pyridinium ion, an ammonium ion, a cerium ion, or a cerium ion, or an inorganic cation. Further, examples of the anion 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 ^- , An organic anion or an inorganic anion of SbF ₆ ^- .

The thickness of the antistatic agent-containing adhesive layer 2 used for the surface protection film 10 of the present invention is not particularly limited, but is preferably, for example, a thickness of about 5 to 40 μm, and more preferably a thickness of about 10 to 30 μm. Since the handleability at the time of peeling off the surface protection film from the adherend is excellent, it is preferable that the peeling strength (bonding force) of the surface protective film to the surface of the adherend is about 0.03 to 0.3 N/25 mm. Adhesive layer 2 with weak adhesion. Further, from the viewpoint of excellent workability when the release film 5 is peeled off from the surface protection film 10, the peeling force from the adhesive layer 2 of the release film 5 is preferably 0.005 to 0.3 N/50 mm.

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

The resin film 3 is exemplified by a polyester film, a polyamide film, a polyethylene film, a polypropylene film, a polyimide film, and the like, and is preferably a polyester film from the viewpoint of being excellent in transparency and being inexpensive. The resin film may be a non-stretched film or a film which is uniaxially or biaxially stretched. Further, 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, and is, for example, preferably about 12 to 100 μm, and more preferably about 20 to 50 μm.

Further, an easy adhesion treatment such as surface modification by corona discharge or application of a tackifier may be applied to the surface of the resin film 3 as needed.

The silicone resin-based release agent constituting the release agent layer 4 is a release agent containing polydimethyl methoxyoxane as a main component, and examples thereof include an addition reaction type, a condensation reaction type, a cationic polymerization type, and a radical polymerization. A known silicone resin-based release agent such as a radical polymerization type. As a product which is commercially available as an addition reaction-type epoxy resin-based release agent, for example, KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (Shin-Etsu Chemical Industry) (share) system), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, LTC-310 (Dow Corning) Toray (share) system, etc. Examples of the product which is commercially available as a condensation reaction type include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray Co., Ltd.). Examples of the product which is commercially available as a cationic polymerization type include TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). . As a product which is commercially available as a radical polymerization type, for example, X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like are mentioned.

The antistatic agent constituting the release agent layer 4 preferably has a good dispersibility for a release agent solution containing dimethyl polysiloxane as a main component, and does not inhibit a release agent containing dimethyl polyoxymethane as a main component. Cured. Further, in order to transfer from the release agent layer 4 to the surface of the binder layer 2 and to impart an antistatic effect to the binder layer, an antistatic agent which does not react with a release agent containing dimethylpolysiloxane as a main component is preferable. As such an antistatic agent, an alkali metal salt is suitable.

The alkali metal salt may, for example, be a metal salt formed of lithium, sodium or potassium. Specifically, for example, a cation selected from Li ⁺ , Na ⁺ , K ⁺ and a group selected from Cl ^- , Br ^- , I ^- , BF4 ^- , PF6 _- , SCN ^- , ClO ₄ ^- , CF ₃ SO may be suitably used. a metal salt composed of an anion of ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- . 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) are particularly preferably used. 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. For the stabilization of the ionic substance, a compound containing a polyoxyalkylene structure may be added.

The amount of the antistatic agent added to 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 suffices to set the peeling static voltage, the staining property to the adherend, the bonding property, and the like which are desired when the surface protective film is peeled off from the adherend.

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 method of mixing the release agent containing dimethyl polysiloxane as a main component and the antistatic agent is not particularly limited. Any of the following methods may be: adding an antistatic agent to a release agent containing dimethyl polysiloxane as a main component, and adding and mixing a catalyst for curing the release agent after mixing; using dimethyl polyoxyalkylene A method in which a release agent containing a main component is diluted with an organic solvent, and an antistatic agent and a catalyst for curing a release agent are added; and a release agent containing dimethyl polysiloxane as a main component is diluted in an organic solvent in advance. , a method of adding and mixing a catalyst, and then adding and mixing an antistatic agent. Further, a material which assists an antistatic effect such as a patch accelerator such as a decane coupling agent or a compound containing a polyoxyalkylene group may be added as needed.

The mixing ratio of the release agent containing dimethyl polysiloxane as a main component and the antistatic agent is not particularly limited, and the solid content of the release agent containing dimethylpolysiloxane as a main component is 100 parts by weight. The antistatic agent is preferably a ratio of about 5 to 100 parts by weight based on the solid content. The antistatic agent is applied to the surface of the binder layer in an amount of less than 5 parts by weight based on 100 parts by weight of the solid component of the release agent containing dimethylpolysiloxane as a main component, if the solid content of the antistatic agent is less than 5 parts by weight. The amount of transfer is reduced, and it is difficult to exhibit an antistatic function in the binder. In addition, the solid content of the release agent containing dimethyl polysiloxane as a main component is 100% by weight, and if the solid content of the antistatic agent is more than 100 parts by weight, the antistatic agent is Dimethyl polyoxane as the main The release agent of the component is simultaneously transferred to the surface of the binder layer, so there is a possibility that the bonding property of the binder is lowered.

The method of forming the adhesive layer 2 containing the 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 carried out by a known method, and are not particularly limited. Specifically, the following method is exemplified: (1) coating and drying a resin composition for forming a binder layer 2 containing an antistatic agent on one surface of the base film 1, and forming a binder layer, a method of bonding the release film 5; (2) coating and drying a resin composition for forming the adhesive layer 2 containing an antistatic agent on the surface of the release film 5, forming a binder layer, and bonding the substrate film The method of 1 or the like; any of the above methods may be used.

Further, the formation of the adhesive layer 2 containing the antistatic agent on the surface of the base film 1 can be carried out 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. Known coating methods such as coating) and air knife coating.

Further, the formation of the release agent layer 4 on the resin film 3 can also be carried out by a known method. Specifically, a known coating method such as a gravure coating method, a bar coating method, or an air knife coating method can be used.

The surface potential of the surface protective film 10 of the present invention having the above-described configuration when peeled off from the optical film as the adherend is preferably +0.7 kV to -0.7 kV. Further, the surface potential is more preferably +0.5 kV to -0.5 kV, and particularly preferably +0.1 kV to -0.1 kV. The surface potential can be adjusted by increasing or decreasing the type and amount of the antistatic agent 7 contained in the adhesive layer 2 and the antistatic agent 7 contained in the release agent layer 4. For the surface protective film 10 from the light as an adherend In consideration of the surface contamination of the optical film as the adherend after the peeling of the film, the type 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 in which a release film is peeled off from the surface protection film of the present invention.

By peeling off 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 (attached) to the surface protective film. 10 of the surface of the adhesive layer 2. Therefore, in Fig. 2, an antistatic agent adhering to the surface of the adhesive layer 2 of the surface protective film is schematically indicated by a spot (circle) of the symbol 7. The component of the antistatic agent 7 is transferred from the release film 5 to the surface of the adhesive layer 2, whereby the peeling of the adhesive layer 2 is removed from the adherend as compared with the adhesive layer 2 before transfer. The voltage is reduced. Further, the peeling static voltage when the adhesive layer is peeled off from the adherend can be measured by a known method. For example, after the surface protective film is bonded to an adherend such as a polarizing plate, the surface protective film is peeled off at a peeling speed of 40 m per minute using a high-speed peeling tester (manufactured by Tester Co., Ltd.) while using a surface potential meter (Keyence ( 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 defined as the peeling static voltage (kV).

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

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

The surface protection 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 (the surface protection film 11 in FIG. 2), and is bonded to the optical element 8 as an adherend via the adhesive layer 2 on.

In other words, Fig. 3 shows an optical element 20 to which the surface protective film 11 is bonded, and the surface protective film 11 is in a state in which the release film 5 is peeled off from the surface protective film 10 of the present invention. Examples of the optical element include an optical film such as a polarizing plate, a phase difference plate, a lens film, a polarizing plate which also serves as a phase difference plate, and a polarizing plate which also serves as a lens film. Such an optical element can be used as a constituent element of a liquid crystal display device such as a liquid crystal display panel or an optical device such as various measuring instruments. In addition, examples of the optical element include an optical film such as an antireflection film, a hard coat film, and a transparent conductive film for a touch panel.

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

Example

Next, the present invention will be further described by way of examples.

(Example 1)

(Production of surface protective film)

5 parts by weight of addition reaction type epoxy resin (Dow Corning Toray) (stock), trade name: SRX-345), 0.75 parts by weight of Lithium bis (fluorosulfonyl) imide, 95 parts by weight of 1:1 mixed solvent of toluene and ethyl acetate, 0.05 weight A platinum catalyst (manufactured by Dow Corning Toray Co., Ltd., trade name: SRX-212) was blended, and stirred and mixed to prepare a coating material which forms the release agent layer of Example 1. The coating material forming the release agent layer of Example 1 was applied to the surface of a polyethylene terephthalate film having a thickness of 38 μm by a wire bar so as to have a thickness of 0.2 μm after drying, and 120 ° C was used. The hot air circulating oven was dried for 1 minute to obtain a release film of Example 1.

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. And mixing 0.2 parts by weight of 1-nonyl pyridinium hexafluoride phosphate and 2 parts by weight of an isocyanate curing agent with respect to 100 parts by weight of a 40% ethyl acetate solution of the binder (CORONATE (registered trademark) HX manufactured by Tosoh Corporation), the binder of Example 1 was prepared.

On the surface of the polyethylene terephthalate film having a thickness of 38 μm, the prepared binder was applied so as to have a thickness of 20 μm after drying, and then dried in a hot air circulating oven at 100 ° C for 2 minutes. A layer of adhesive is formed. Then, a release agent layer (oxygenated resin-treated surface) of the release film of Example 1 produced above was bonded to the surface of the adhesive layer. The obtained bonded film was kept at 40 ° C for 5 days to cure the adhesive, and the surface protective film of Example 1 was obtained.

(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 of Example 1 was set to 0.1 μm. Protective film.

(Example 3)

The addition reaction type oxime resin of Example 1 was prepared by Dow Corning Toray Co., Ltd., trade name: SRX-211, and lithium bistrifluoromethanesulfonimide was used instead of lithium difluorosulfonimide. The surface protective film of Example 3 was obtained in the same manner as in Example 1.

(Comparative Example 1)

5 parts by weight of an addition reaction type oxiran 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 part 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 applied to the surface of a polyethylene terephthalate film having a thickness of 38 μm by a wire bar so as to have a thickness of 0.2 μm after drying, and a hot air of 120 ° C was used. The film was dried 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 applied to the surface of a polyethylene terephthalate film having a thickness of 38 μm so as to have a thickness of 20 μm after drying, and then a hot air loop type of 100 ° C was used. The oven was dried for 2 minutes to form a layer of adhesive. Then, a release agent layer (oxygenated resin-treated surface) of the release film of Comparative Example 1 prepared above was bonded to the surface of the adhesive layer. The obtained bonded film was kept at 40 ° C for 5 days to cure the adhesive, and the surface protective film of Comparative Example 1 was obtained.

(Comparative Example 2)

In addition to not adding 1-mercaptopyridinium hexafluorophosphate to the binder Further, a surface protective film of Comparative Example 2 was obtained in the same manner as in Example 1.

(Comparative Example 3)

A surface protective film of Comparative Example 3 was obtained in the same manner as in Example 1 except that lithium difluorosulfonimide was used instead of the 1-mercaptopyridinium hexafluorophosphate salt of Example 1.

Hereinafter, the method and result of the evaluation test are shown.

<Method for Measuring Peel Force of Release Film>

The 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, the strength at the time of peeling off the release film was measured by a tensile tester at a peeling speed of 300 mm/min in a direction of 180°, and this was used as a peeling force of the release film (N). /50mm).

(surface resistivity of the antistatic agent layer)

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

<Method for Measuring the Bonding Force of Surface Protective Film>

A polarizing plate (AG-LR polarizing plate) which is subjected to an anti-glare and low-reflection treatment with an acrylic film and a UV-curable adhesive is used as a adherend on a polarizing mirror (an iodine-containing polyvinyl alcohol film). The polarizing plate was attached to the surface of the glass plate by a bonding machine. Then, the surface protective film cut into 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 of 23 ° C × 50% RH for 1 day. Then, using a tensile tester, the strength at the time of peeling off the surface protective film was measured in a direction of 180° at a peeling speed of 300 mm/min, and it was taken as Bonding force (N/25mm).

<Method for Measuring Peeling Static Voltage of Surface Protective Film>

A polarizing plate (AG-LR polarizing plate) which is subjected to an anti-glare and low-reflection treatment with an acrylic film and a UV-curable adhesive is used as a adherend on a polarizing mirror (an iodine-containing polyvinyl alcohol film). The polarizing plate was attached to the surface of the glass plate by a bonding machine. Thereafter, a surface protective film cut to a width of 25 mm was bonded to an acrylic film on the surface of the polarizing plate, and then stored in a test environment of 23 ° C × 50% RH for one day. Then, the surface protective film was peeled off at a peeling speed of 40 m per minute using a high-speed peeling tester (manufactured by Tester Co., Ltd.), and the surface potential of the surface of the polarizing plate was measured every 10 ms using a surface potential meter (manufactured by Keyence Co., Ltd.). The maximum value of the absolute value of the surface potential at this time is taken as the peeling static voltage (kV).

<Method for Confirming Surface Contamination of Surface Protective Film>

A polarizing plate (AG-LR polarizing plate) which is subjected to an anti-glare low-reflection treatment with an acrylic film and a UV-curable adhesive is used as a adherend on a polarizing mirror (an iodine-containing polyvinyl alcohol film). The polarizing plate was attached to the surface of the glass plate by a bonding machine. Then, a surface protective film cut to a width of 25 mm was attached to an acrylic film on the surface of the polarizing plate, and then stored in a test environment of 23 ° C × 50% RH for 3 days and 30 days. Then, the surface protective film was peeled off to visually observe the surface of the polarizing plate for contamination, and the surface contamination was confirmed. As a criterion for determining the surface contamination property, the case where no contamination is transferred on the polarizing plate is (○), and the case where contamination transfer is confirmed on the polarizing plate is (×).

The measurement results of the surface protective films of the obtained 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, "AS agent (1) "Indicating lithium difluorosulfonimide, "AS agent (2)" means lithium bistrifluoromethanesulfonimide, "AS agent (3)" means 1-mercaptopyridinium hexafluorophosphate, "SRX"-345" represents SRX-345, "SRX-211" represents SRX-211, and "SRX212" represents platinum catalyst SRX-212. Further, "1.5E10" of the surface resistivity means 1.5 × 10 ¹⁰ .

From the measurement results shown in Table 1, it is understood that the surface protective films of Examples 1 to 3 of the present invention have an appropriate adhesive force and are free from contamination on the surface of the adherend. Further, even if the adherend is a polarizing plate using an acrylic film, the peeling static voltage when the surface protective film is peeled off 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 in which the surface protective film and the antistatic agent were not added to the adhesive layer increased the peeling static voltage when the surface protective film was peeled off from the adherend. Further, in the surface protective film of Comparative Example 3 in which the same type of antistatic agent was used for the adhesive layer and the release agent layer, the peeling static voltage when the surface protective film was peeled off from the adherend was low, which was good, but After peeling, the contamination of the adherend is increased.

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

Industrial applicability

The surface protective film of the present invention can be used for lamination in production steps such as a polarizing plate, a retardation film, a lens film, an antireflection film, a hard coat film, an optical film such as a transparent conductive film, and other various optical elements. The surface is protected by the optical element or the like. Further, the amount of static electricity generated when the surface protective film of the present invention is peeled off from the adherend is low, and the temporal change of the peeling antistatic property and the contamination to the adherend are small, so that the yield of the production step can be improved, and industrially, The value of utilization is large.

1‧‧‧Base film

2‧‧‧Binder layer

3‧‧‧ resin film

4‧‧‧ Stripper layer

5‧‧‧Release film

7‧‧‧Antistatic agent

10‧‧‧Surface protection film

Claims (6)

A surface protective film characterized in that a binder layer containing an ionic compound as an antistatic agent is formed on one surface of a base film composed of a resin having transparency, and a release film having a release agent layer is passed through a release agent layer is bonded to the adhesive layer, the release agent layer containing an alkali metal salt and a silicone resin release agent, and a component of the alkali metal salt is transferred from the release film to the adhesive layer On the surface, the peeling static voltage when the adhesive layer is peeled off from the adherend is lowered. The surface protective film according to claim 1, wherein the ionic compound is not an alkali metal salt. The surface protective film according to claim 1 or 2, wherein the adhesive layer is formed by crosslinking a (meth) acrylate copolymer. The surface protective film according to any one of claims 1 to 3, wherein the surface potential when peeled off from the optical film as the adherend is +0.7 kV to -0.7 kV. The surface protection film according to any one of claims 1 to 4, wherein a peeling force when the release film is peeled off from the adhesive layer is 0.005 to 0.3 N/50 mm. An optical element obtained by laminating a surface protective film according to any one of claims 1 to 5.