Antistatic surface protection film for optical films

Abstract

To provide an antistatic surface protective film for an optical film that is a peeling sheet for an antistatic surface protective film for causing little contamination on an adherend, and having excellent peeling antistatic performance without degradation with time, which enables a peeling sheet to be easily peeled during use.SOLUTION: An antistatic surface protective film 10 for an optical film obtained by bonding a peeling sheet 5 for an antistatic surface protective film capable of transferring an antistatic agent onto a surface of an adhesive layer 2 of an antistatic surface protective film having an adhesive layer 2 formed on one surface of a base material film 1, in which the peeling sheet 5 for the antistatic surface protective film is obtained by laminating a peeling agent containing dimethyl polysiloxane as a main component, and a peeling agent layer 4 formed of a resin composition containing an antistatic agent 7 on one surface of a base material 3, and the base material 3 is formed of one kind selected from the group consisting of polyethylene laminate woodfree paper, polyethylene laminate art paper and polyethylene laminate craft paper.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an antistatic surface protective film that is attached to the surface of an optical component (hereinafter, sometimes referred to as an optical film) such as a polarizing plate, a retardation plate, a lens film for a display, etc. More specifically, the present invention provides an antistatic surface protective film that causes little contamination of an adherend, does not deteriorate over time, and has excellent peel-off antistatic performance, and the release sheet of which can be easily peeled off during use. [Background technology]

[0002] When optical films such as polarizing plates, retardation plates, lens films for displays, anti-reflection films, hard coat films, transparent conductive films for touch panels, and other optical products such as displays using the same are manufactured and transported, a surface protective film is attached to the surface of the optical film to prevent the surface from being soiled or scratched in later processes. In order to improve work efficiency by eliminating the need to peel off the surface protective film and then reattach it, the appearance inspection of the optical film, which is a product, is sometimes performed with the surface protective film attached to the optical film. Conventionally, a surface protection film having a pressure-sensitive adhesive layer on one side of a base film has been generally used in the manufacturing process of optical products to prevent scratches and dirt from adhering. The surface protection film is attached to an optical film via a pressure-sensitive adhesive layer having a weak adhesive strength. The pressure-sensitive adhesive layer has a weak adhesive strength so that the used surface protection film can be easily peeled off when peeled off and removed from the surface of the optical film, and the pressure-sensitive adhesive does not adhere to and remain on the optical film of the product, which is the adherend (so-called, to prevent the occurrence of adhesive residue).

[0003] In recent years, during the production process of liquid crystal display panels, there have been rare cases where the peeling charge voltage that is generated when peeling off and removing the surface protection film that has been laminated on top of the optical film has destroyed circuit components such as driver ICs that control the display screen of the liquid crystal display panel, or damaged the alignment of liquid crystal molecules. In addition, in order to reduce the power consumption of liquid crystal display panels, the driving voltage of liquid crystal materials has been lowered, and as a result, the breakdown voltage of driver ICs has also been lowered. Recently, there has been a demand for the peeling electrification voltage to be within the range of +0.7kV to -0.7kV. For this reason, in order to prevent problems caused by high peeling electrification voltage when peeling the surface protection film from the adherend, an adhesive layer containing an antistatic agent for keeping the peeling electrification voltage low has been proposed.

[0004] For example, Patent Document 1 discloses a surface protection film that uses a pressure-sensitive adhesive made of an alkyltrimethylammonium salt, a hydroxyl group-containing acrylic polymer, and a polyisocyanate. Furthermore, Patent Document 2 discloses a pressure-sensitive adhesive composition comprising an ionic liquid and an acrylic polymer having an acid value of 1.0 or less, and pressure-sensitive adhesive sheets using the same. Furthermore, Patent Document 3 discloses an adhesive composition comprising an acrylic polymer, a polyether polyol compound, and an alkali metal salt treated with an anion-adsorbing compound, and a surface protection film using the same. Furthermore, Patent Document 4 discloses a pressure-sensitive adhesive composition comprising an ionic liquid, an alkali metal salt, and a polymer having a glass transition temperature of 0° C. or lower, and a surface protection film using the same. Furthermore, Patent Document 5 discloses a pressure-sensitive adhesive composition comprising an acrylic copolymer, an alkylene oxide chain-containing acrylic copolymer, and an alkali metal salt, and a surface protection film using the same. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-131957 A [Patent Document 2] JP 2005-330464 A [Patent Document 3] JP 2005-314476 A [Patent Document 4] JP 2006-152235 A [Patent Document 5] JP 2009-275128 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the above Patent Documents 1 to 5, an antistatic agent is added inside the adhesive layer, but the thicker the adhesive layer is, and the more time passes, the more the amount of antistatic agent that migrates from the adhesive layer to the adherend to which the surface protection film is attached increases. In addition, in optical films such as LR (Low Reflective) polarizing plates and AG (Anti Glare)-LR polarizing plates, the surface of the optical film is treated for anti-contamination with silicone compounds, fluorine compounds, etc., so that the peeling electrification voltage increases when the surface protection film used for such optical films is peeled off from the optical film that is the adherend.

[0007] In recent years, with the spread of 3D displays (stereoscopic displays), there are some in which an FPR (Film Patterned Retarder) film is laminated to the surface of an optical film such as a polarizing plate. The FPR film is laminated after peeling off the surface protective film that was laminated to the surface of the optical film such as a polarizing plate. However, if the surface of the optical film such as a polarizing plate is contaminated by the adhesive or antistatic agent used in the surface protective film, there is a problem that the FPR film is difficult to adhere to. For this reason, surface protective films used for such applications are required to be ones that cause little contamination to the adherend.

[0008] On the other hand, some liquid crystal panel manufacturers have adopted a method for evaluating the fouling property of a surface protective film on an adherend, in which the surface protective film attached to an optical film such as a polarizing plate is once peeled off, reattached in a state in which air bubbles are mixed in, heat-treated under a specified condition, and then the surface protective film is peeled off to observe the surface of the adherend. In this evaluation method, even if the surface contamination of the adherend is small, if there is a difference in the surface contamination of the adherend between the part where the air bubbles are mixed in and the part where the adhesive of the surface protective film was in contact, the trace of the air bubbles (sometimes called air bubble stains) remains. Therefore, this is a very strict evaluation method for evaluating the fouling property on the surface of the adherend. In recent years, there has been a demand for a surface protective film that does not have a problem with fouling property on the surface of the adherend even in the results of such a strict evaluation method. However, it has been difficult to solve this problem with a surface protective film using an adhesive layer containing an antistatic agent, which has been proposed in the past.

[0009] For this reason, there is a need for a surface protection film for use with an optical film that causes very little contamination of an adherend and that does not change with time with respect to the contamination of the adherend.Furthermore, there is a need for a surface protection film that suppresses the peeling electrification voltage when peeled off from an adherend.

[0010] In addition, in conventional surface protection films, a release film (in this case, the substrate of the release film is a resin film) is often attached to protect the adhesive layer (a release film is also used in the examples of Patent Documents 1 to 5). However, when a release film is used to protect the adhesive layer, the substrate film of the surface protection film is also a resin film, so when peeling the release film from the surface protection film, it is difficult to provide a "trigger" for peeling the release film, and the release film is difficult to peel off. For this reason, there are cases where an adhesive tape such as a pick-up tape is attached to both the substrate film surface and the release film surface of the surface protection film, and the pick-up tape is gripped to peel the release film from the film.

[0011] In addition, when the surface protection film is bonded to an optical component such as an optical film as an adherend using a roll-to-roll process, the release film only needs to be peeled off the first time. However, when cut sheet-like surface protection films are to be attached to an adherend, the release film must be peeled off from the surface protection film for each piece of surface protection film cut, and therefore the release film must be easy to peel off.

[0012] Furthermore, when the surface protection film is cut and attached to the adherend, the cut surface protection film is generally distributed in a stacked state of several tens to several hundreds of sheets, and in a process in which the surface protection film is used, each surface protection film is picked up one by one from a stack of multiple stacked surface protection films and used. Therefore, when the substrate of the release sheet used in the surface protection film is a resin film, when multiple surface protection films are stacked, the substrate film and the substrate of the release sheet that are in contact with each other are both resin films, and therefore they come into close contact with each other. Therefore, when the surface protection films are picked up one by one from the surface protection films supplied in a stacked state, a problem occurs in that two or more films are picked up at the same time. Furthermore, when the base material of the surface protection film is a resin film, the cutting process of the surface protection film is difficult due to poor cushioning, and there is a problem that if the cutting conditions are made strict so as to obtain a clean cut surface, the cutting blade wears out quickly.

[0013] The present inventors have conducted extensive research into solving these problems. In order to reduce contamination of the adherend and to reduce the change over time in antistatic performance, it is necessary to reduce the amount of antistatic agent added, which is presumed to be the cause of contamination of the adherend. However, when the amount of antistatic agent added is reduced, the peeling electrification voltage increases when the surface protective film is peeled off from the adherend. The present inventors have studied a method for suppressing the peeling electrification voltage when the surface protective film is peeled off from the adherend without increasing the absolute amount of the antistatic agent added. As a result, it was found that the peeling electrification voltage can be suppressed low when the surface protective film is peeled off from the adherend, that is, the optical film, by applying an appropriate amount of an antistatic agent component to the surface of the adhesive layer after laminating the adhesive layer by coating and drying the adhesive composition, rather than adding and mixing an antistatic agent into the adhesive composition to form an adhesive layer. In addition, it was found that the peeling electrification voltage can be suppressed low when the surface protective film is peeled off from the optical film, which is the adherend, by using a release sheet containing paper to protect the adhesive layer of the surface protective film, and the release sheet can be easily peeled off, and the present invention was completed.

[0014] The present invention has been made in consideration of the above circumstances, and has an object to provide an antistatic surface protective film that causes little contamination of an adherend, does not deteriorate over time, and has excellent peel-off antistatic performance, and from which the release sheet can be easily peeled off when in use. [Means for solving the problem]

[0015] In order to solve the above problems, the technical concept of the antistatic surface protection film of the present invention is to apply an appropriate amount of antistatic agent to the surface of the adhesive layer after coating and drying an adhesive composition to laminate the adhesive layer, thereby minimizing the contamination of the adherend and minimizing the peel electrification voltage when peeled off from the adherend, that is, the optical film.

[0016] In order to solve the above problems, the present invention provides an antistatic surface protection film comprising a pressure-sensitive adhesive layer formed on one side of a substrate film made of a transparent resin and a release sheet bonded to the surface of the pressure-sensitive adhesive layer, characterized in that the release sheet has a release agent layer formed on one side of the substrate from a resin composition containing a release agent mainly composed of dimethylpolysiloxane and an antistatic agent.

[0017] The substrate is preferably a substrate containing paper.

[0018] The antistatic agent is preferably an alkali metal salt.

[0019] The pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive layer formed by crosslinking a (meth)acrylate copolymer.

[0020] The present invention also provides an optical film obtained by laminating the above-mentioned antistatic surface protective film with the release sheet removed.

[0021] The present invention also provides an optical component in which the above-mentioned antistatic surface protective film is laminated with the release sheet removed. Effect of the Invention

[0022] The antistatic surface protective film of the present invention has a release sheet that is easy to peel off during use, causes little contamination of the adherend, and does not change with time in its low contamination properties. Furthermore, according to the present invention, even if the adherend is an optical film such as an LR polarizing plate or an AG-LR polarizing plate whose surface has been treated with an anti-contamination treatment using a silicone compound or a fluorine compound, the antistatic surface protective film can be once attached to the adherend and then peeled off from the adherend with a low electrostatic charge voltage that occurs when peeled off, and an antistatic surface protective film having excellent antistatic properties upon peeling off without deterioration with time can be provided. According to the antistatic surface protective film of the present invention, the surface of an optical film can be reliably protected, and therefore the productivity and yield can be improved. [Brief description of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view illustrating the concept of an antistatic surface protective film of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a state in which the release sheet has been peeled off from the antistatic surface protective film of the present invention. [Diagram 3] FIG. 1 is a cross-sectional view showing one embodiment of an optical component according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the present invention will be described in detail based on the embodiments. Fig. 1 is a cross-sectional view showing the concept of the antistatic surface protective film of the present invention. This antistatic surface protective film 10 has an adhesive layer 2 formed on one surface of a transparent substrate film 1. A release sheet 5 having a release agent layer 4 formed on the surface of a substrate 3 is attached to the surface of this adhesive layer 2.

[0025] The base film 1 used in the antistatic surface protective film 10 according to the present invention is made of a transparent and flexible resin. This allows the appearance inspection of the optical component to be performed while the antistatic surface protective film is attached to the optical component to be adhered. The film made of a transparent resin used as the base film 1 is preferably a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate. In addition to polyester films, films made of other resins can also be used as long as they have the necessary strength and optical suitability. The base film 1 may be a non-stretched film or a uniaxially or biaxially stretched film. In addition, the stretching ratio of the stretched film and the axial orientation angle formed by the crystallization of the stretched film may be controlled to a specific value. The thickness of the substrate film 1 used in the antistatic surface protection film 10 according to the present invention is not particularly limited, but is preferably about 12 to 100 μm, and more preferably about 20 to 50 μm for ease of handling. If necessary, an antifouling layer for preventing surface staining, an antistatic layer, a hard coat layer for preventing scratches, etc. may be provided on the surface of the base film 1 opposite to the surface on which the pressure-sensitive adhesive layer 2 is formed. The surface of the base film 1 may also be subjected to an easy-adhesion treatment such as surface modification by corona discharge or application of an anchor coating agent.

[0026] Furthermore, the adhesive layer 2 used in the antistatic surface protection film 10 of the present invention is not particularly limited as long as it adheres to the surface of the adherend, can be easily peeled off after use, and is unlikely to contaminate the adherend. However, taking into consideration durability after application to an optical film, it is common to use an acrylic adhesive obtained by crosslinking a (meth)acrylate copolymer.

[0027] Examples of the (meth)acrylate copolymer include copolymers obtained by copolymerizing a main monomer such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, etc. with a comonomer such as acrylonitrile, vinyl acetate, methyl methacrylate, ethyl acrylate, etc., and a functional monomer such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, N-methylol methacrylamide, etc. In the (meth)acrylate copolymer, the main monomer and the comonomer may all be (meth)acrylates, or the comonomer may contain one or more types of monomers other than (meth)acrylates.

[0028] In addition, a compound containing a polyoxyalkylene group may be copolymerized or mixed with the (meth)acrylate copolymer. Examples of copolymerizable compounds containing a polyoxyalkylene group include polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, methoxypolyethylene glycol (400) acrylate, methoxypolyethylene glycol (400) methacrylate, polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxypolypropylene glycol (400) acrylate, and methoxypolypropylene glycol (400) methacrylate. By copolymerizing these monomers containing a polyoxyalkylene group with the main monomer or functional monomer of the (meth)acrylate copolymer, a pressure-sensitive adhesive consisting of a copolymer containing a polyoxyalkylene group can be obtained.

[0029] As the compound containing a polyoxyalkylene group that can be mixed with the (meth)acrylate copolymer, a (meth)acrylate copolymer containing a polyoxyalkylene group is preferable, and a polymer of a (meth)acrylic monomer containing a polyoxyalkylene group is more preferable, and examples thereof include polymers of polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, methoxypolyethylene glycol (400) acrylate, methoxypolyethylene glycol (400) methacrylate, polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxypolypropylene glycol (400) acrylate, and methoxypolypropylene glycol (400) methacrylate. By mixing these compounds containing a polyoxyalkylene group with the (meth)acrylate copolymer, a pressure-sensitive adhesive to which a compound containing a polyoxyalkylene group is added can be obtained.

[0030] Examples of the curing agent added to the adhesive layer 2 include crosslinking agents that crosslink the (meth)acrylate copolymer, such as isocyanate compounds, epoxy compounds, melamine compounds, metal chelate compounds, etc. Examples of the tackifier include rosin-based, coumarone-indene-based, terpene-based, petroleum-based, and phenol-based agents.

[0031] The thickness of the adhesive layer 2 used in the antistatic surface protective film 10 according to the present invention is not particularly limited, but is preferably about 5 to 40 μm, and more preferably about 10 to 30 μm. The adhesive layer 2 preferably has a weak adhesive strength, that is, a peel strength (adhesive strength) of the antistatic surface protective film to the surface of the adherend of about 0.03 to 0.3 N / 25 mm, because this provides excellent operability when peeling the antistatic surface protective film from the adherend. In addition, the peel strength when peeling the release sheet 5 from the adhesive layer 2 is preferably 0.2 N / 50 mm or less, because this provides excellent operability when peeling the release sheet 5 from the antistatic surface protective film 10.

[0032] In addition, the release sheet 5 used in the antistatic surface protective film 10 according to the present invention has a release agent layer 4 formed on one side of the substrate 3, the release agent being mainly composed of dimethylpolysiloxane, and using a resin composition containing an antistatic agent.

[0033] The substrate 3 is a substrate containing paper, and may be either paper alone or paper laminated with other materials such as plastic. Specifically, examples of paper alone include fine paper, art paper, craft paper, clay-coated paper, and glassine paper, while examples of paper laminated with other materials such as plastic include polyethylene-laminated fine paper, polyethylene-laminated art paper, and polyethylene-laminated craft paper. The thickness of the base material 3 is not particularly limited, but is preferably about 30 to 200 μm, and more preferably about 50 to 150 μm for ease of handling. If necessary, the surface of the base material 3 may be subjected to surface modification by flame treatment or corona discharge, or a filler may be applied to prevent the release agent from penetrating into the paper.

[0034] The workability when peeling off the release sheet from the antistatic surface protective film is improved by using a substrate containing paper as the substrate 3. The antistatic surface protective film 10 according to the present invention comprises a substrate film 1, an adhesive layer 2, and a release sheet 5. In general, when peeling off a release sheet from a surface protection film, the surface protection film is slightly bent and deformed while rubbing the side of the surface protection film with the pad of a finger, and the edge of the release sheet is hooked with the pad of a finger to create a "trigger" for peeling off the release sheet. After the "trigger" for peeling off the release sheet from the surface protection film is created, the "trigger" part of the release sheet can be grasped and peeled off. When the member protecting the adhesive layer of the surface protection film is a release film using a base film of the same material as the base film, even if the surface protection film is slightly bent and deformed, the base film and the release film are deformed together, making it difficult to create a "trigger", and therefore it is not easy to peel off the release film. In contrast, the antistatic surface protective film 10 according to the present invention uses a base material containing paper for the base material 3 of the release sheet 5, and therefore the stiffness (elastic modulus) of the base film 1 and the release sheet 5 differ, making it easier to peel the release sheet from the antistatic surface protective film. This improves the efficiency of the work of peeling the release sheet from the antistatic surface protective film and attaching it to an optical component.

[0035] Depending on the type of optical member that is the adherend of the antistatic surface protective film according to the present invention and the application of the film, the antistatic surface protective film may not be laminated to the optical member by roll-to-roll, but may be laminated to the optical member by cutting the antistatic surface protective film into a sheet of a predetermined size. In this case, the antistatic surface protective film is cut to a predetermined size in advance, and from a stack of multiple overlapping antistatic surface protective films, each antistatic surface protective film is picked up one by one, the release sheet is peeled off, and the film is laminated to the optical member. When the member for protecting the adhesive layer of the antistatic surface protective film is a release film using a resin film, when a plurality of antistatic surface protective films are stacked, the base film in contact with the base film of the release film is both a resin film, and they are in close contact with each other. Therefore, when the antistatic surface protective films are picked up one by one from the antistatic surface protective films supplied in a stacked state, a problem occurs in which two or more sheets are picked up together. By using a base material containing paper as the base material of the release sheet, the paper layer of the base material of the release sheet, which has a surface made of a material different from that of the base film, comes into contact with the base film, and the problem of two or more antistatic surface protective films being picked up together can be prevented. Furthermore, since the number of times the release sheet is peeled off from the antistatic surface protective film is the same as the number of sheets of antistatic surface protective film cut, by using the antistatic surface protective film of the present invention, which has excellent workability in peeling off the release sheet, it is possible to improve work efficiency.

[0036] The release agent mainly composed of dimethylpolysiloxane constituting the release agent layer 4 includes known silicone-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. Examples of products commercially available as addition reaction type silicone-based release agents include KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.), SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, and LTC-310 (manufactured by Dow Corning Toray Co., Ltd.). Examples of products commercially available as condensation reaction type release agents include SRX-290 and SYLOFF-23 (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available cationic polymerization products include TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials, Inc.), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available radical polymerization products include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0037] The antistatic agent constituting the release agent layer 4 is preferably one that has good dispersibility in the release agent solution mainly composed of dimethylpolysiloxane and does not inhibit the hardening of the release agent mainly composed of dimethylpolysiloxane. An alkali metal salt is suitable as such an antistatic agent.

[0038] Examples of the alkali metal salt include metal salts of lithium, sodium, and potassium. + , Na + , K + and a cation consisting of Cl - , Br - , I - , BF4 - , PF6 - , SCN - , ClO4 - , CF3SO3 - , (CF3SO2)2N - , (C2F5SO2)2N -, (CF3SO2)3C - Metal salts composed of anions consisting of the above are preferably used. Among them, lithium salts such as LiBr, LiI, LiBF4, LiPF6, LiSCN, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(C2F5SO2)2N, and Li(CF3SO2)3C are particularly preferably used. These alkali metal salts may be used alone or in combination of two or more. In order to stabilize the ionic substance, a compound containing a polyoxyalkylene structure may be added. The amount of antistatic agent added to a release agent containing dimethylpolysiloxane as a main component varies depending on the type of antistatic agent and the degree of affinity with the release agent, but can be set taking into consideration the desired peeling electrification voltage, contamination of the adherend, adhesion characteristics, etc. when the antistatic surface protection film is peeled off from the adherend.

[0039] There is no particular limitation on the method of mixing the release agent mainly composed of dimethylpolysiloxane with the antistatic agent. Any method may be used, such as a method of adding an antistatic agent to a release agent mainly composed of dimethylpolysiloxane, mixing, and then adding and mixing a catalyst for hardening the release agent, a method of diluting a release agent mainly composed of dimethylpolysiloxane with an organic solvent in advance, and then adding and mixing an antistatic agent and a catalyst for hardening the release agent, or a method of diluting a release agent mainly composed of siloxane with an organic solvent in advance, adding and mixing a catalyst, and then adding and mixing an antistatic agent. In addition, if necessary, a material that assists the antistatic effect, such as an adhesion improver such as a silane coupling agent or a compound containing a polyoxyalkylene group, may be added.

[0040] The mixing ratio of the release agent mainly composed of dimethylpolysiloxane and the antistatic agent is not particularly limited, but the ratio of the antistatic agent as a solid content is preferably about 5 to 100 to 100 to 100 of the solid content of the release agent mainly composed of dimethylpolysiloxane. If the amount of the antistatic agent added in terms of solid content is less than 5 to 100 of the solid content of the release agent mainly composed of dimethylpolysiloxane, the amount of the antistatic agent transferred to the surface of the adhesive layer is also reduced, making it difficult for the adhesive to exhibit its antistatic function. In addition, if the amount of the antistatic agent added in terms of solid content exceeds 100 to 100 of the solid content of the release agent mainly composed of dimethylpolysiloxane, the release agent mainly composed of dimethylpolysiloxane is also transferred to the surface of the adhesive layer together with the antistatic agent, which may reduce the adhesive properties of the adhesive.

[0041] The method for forming the adhesive layer 2 on the base film 1 of the antistatic surface protective film 10 according to the present invention and the method for laminating the release sheet 5 may be performed by known methods and are not particularly limited. Specifically, examples of the method include (1) a method in which a resin composition for forming the adhesive layer 2 is applied to one side of the base film 1, dried to form an adhesive layer, and then laminating the release sheet 5, and (2) a method in which a resin composition for forming the adhesive layer 2 is applied to the surface of the release sheet 5, dried to form an adhesive layer, and then laminating the base film 1, and any of these methods may be used.

[0042] The pressure-sensitive adhesive layer 2 may be formed on the surface of the base film 1 by a known method. Specifically, known coating methods such as reverse coating, comma coating, gravure coating, slot die coating, Mayer bar coating, and air knife coating can be used.

[0043] Similarly, the release agent layer 4 may be formed on the substrate 3 by a known method. Specifically, known coating methods such as gravure coating, Mayer bar coating, and air knife coating can be used.

[0044] The antistatic surface protective film 10 according to the present invention having the above configuration preferably has a surface potential of +0.7 kV to -0.7 kV when it is attached to an optical film as an adherend with the release sheet 5 removed and then peeled off from the optical film. More preferably, the surface potential is +0.5 kV to -0.5 kV, and particularly preferably, the surface potential is +0.1 kV to -0.1 kV.

[0045] FIG. 2 is a cross-sectional view showing the antistatic surface protective film of the present invention with the release sheet removed. By peeling off the release sheet 5 from the antistatic surface protection film 10 shown in Fig. 1, the component of the antistatic agent (reference numeral 7) contained in the release agent layer 4 of the release sheet 5 is transferred to the surface of the adhesive layer 2 of the antistatic surface protection film 10 and is present only on the surface of the adhesive layer. Therefore, in Fig. 2, the component of the antistatic agent transferred to the surface of the adhesive layer 2 of the antistatic surface protection film 11 in a state in which the release sheet has been peeled off is shown diagrammatically by spots reference numeral 7. In the antistatic surface protective film according to the present invention, when the antistatic surface protective film 11 from which the release sheet has been peeled off as shown in Fig. 2 is attached to an adherend, the components of the antistatic agent present only on the surface of the pressure-sensitive adhesive layer 2 come into contact with the surface of the adherend, thereby making it possible to keep the peeling electrification voltage low when the antistatic surface protective film is peeled off from the adherend again.

[0046] FIG. 3 is a cross-sectional view showing an embodiment of an optical component according to the present invention. The release sheet 5 is peeled off from the antistatic surface protective film 10 of the present invention, and in a state where the pressure-sensitive adhesive layer 2 is exposed, the film is attached to an optical component 8 as an adherend via the pressure-sensitive adhesive layer 2 . That is, FIG. 3 shows an optical component 20 to which an antistatic surface protective film 11 is attached in a state in which the release sheet is peeled off from the antistatic surface protective film 10 of the present invention. Examples of optical components include optical films such as a polarizing plate, a retardation plate, a lens film, a polarizing plate that also serves as a retardation plate, and a polarizing plate that also serves as a lens film. Such optical components are used as components of liquid crystal display devices such as liquid crystal display panels, optical devices for various instruments, and the like. Examples of optical components include optical films such as antireflection films, hard coat films, and transparent conductive films for touch panels. In particular, the antistatic surface protective film can be suitably used as an antistatic surface protective film that is attached to the antifouling treated surface of optical films such as low reflection polarizing plates (LR polarizing plates) and antiglare low reflection polarizing plates (AG-LR polarizing plates) whose surfaces are antifouling treated with silicone compounds, fluorine compounds, or the like. According to the optical component of the present invention, when the antistatic surface protective film 11 with the release sheet removed is peeled off from the adherend, that is, the optical component (optical film), the peeling electrification voltage can be suppressed to a sufficiently low level, so that there is no risk of damaging circuit components such as driver ICs, TFT elements, and gate line driving circuits, and the production efficiency in the process of manufacturing liquid crystal display panels, etc. can be improved and the reliability of the production process can be maintained. EXAMPLES

[0047] The present invention will now be further described with reference to examples. Example 1 (Preparation of antistatic surface protection film) Addition reaction type silicone (Dow Corning Toray Co., Ltd., product name: SRX-211) 10 parts by weight, lithium bis(fluorosulfonyl)imide 1.0 part by weight, toluene and ethyl acetate 1:1 mixed solvent 90 parts by weight, platinum catalyst (Dow Corning Toray Co., Ltd., product name: SRX-212) 0.06 parts by weight were mixed and stirred to prepare a coating material for forming the release agent layer of Example 1. One side of a fine paper with a basis weight of 53 g was laminated so that the polyethylene layer was 20 μm thick to prepare polyethylene laminated fine paper. The coating material for forming the release agent layer of Example 1 was applied to the polyethylene layer surface of the polyethylene laminated fine paper with a Mayer bar so that the thickness after drying was 0.5 μm, and the coating material was dried in a hot air circulating oven at 130° C. for 1 minute to obtain a release sheet of Example 1. On the other hand, 100 parts by weight of a 40% ethyl acetate solution of the adhesive polymer of Example 1, which was a copolymer of 90 parts by weight of 2-ethylhexyl acrylate, 7 parts by weight of methoxypolyethylene glycol (400) methacrylate, and 3 parts by weight of 2-hydroxyethyl acrylate, was stirred and mixed with 2 parts by weight of an isocyanate-based curing agent (Coronate (registered trademark) HX manufactured by Tosoh Corporation) to prepare the adhesive composition of Example 1. The prepared adhesive composition of Example 1 was applied to 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 circulating oven at 100° C. for 2 minutes to form an adhesive layer. Then, the release sheet of Example 1 prepared above was attached to the surface of this adhesive layer via the release layer (silicone-treated surface) to obtain a laminated film. The obtained laminated film was kept warm in an environment of 40° C. for 5 days to harden the adhesive layer, and an antistatic surface protection film of Example 1 was obtained.

[0048] Example 2 The antistatic surface protection film of Example 2 was obtained in the same manner as Example 1, except that the addition reaction type silicone of Example 1 was changed to KS-847H manufactured by Shin-Etsu Chemical Co., Ltd., the platinum catalyst was changed to CAT PL-50T manufactured by Shin-Etsu Chemical Co., Ltd., the amount added was 0.1 parts by weight, and lithium bis(trifluoromethanesulfonyl)imide was used instead of lithium bis(fluorosulfonyl)imide.

[0049] Comparative Example 1 A surface protection film not having peel-off antistatic properties was obtained in the same manner as in Example 1, except that lithium bis(fluorosulfonyl)imide in Example 1 was not used.

[0050] Comparative Example 2 10 parts by weight of addition reaction type silicone (manufactured by Dow Corning Toray Co., Ltd., product name: SRX-211), 90 parts by weight of a 1:1 mixed solvent of toluene and ethyl acetate, and 0.06 parts by weight of a platinum catalyst (manufactured by Dow Corning Toray Co., Ltd., product name: SRX-212) were mixed and stirred / mixed to prepare a coating material for forming the release agent layer of Comparative Example 2. One side of a piece of fine paper with a basis weight of 53 g was laminated with polyethylene to a thickness of 20 μm to prepare polyethylene laminated fine paper. The coating material for forming the release agent layer of Comparative Example 2 was applied to the polyethylene side of the polyethylene laminated fine paper using a Mayer bar to a thickness of 0.5 μm after drying, and the coating material was dried in a hot air circulating oven at 130° C. for 1 minute to obtain a release sheet of Comparative Example 2. On the other hand, 100 parts by weight of a 40% ethyl acetate solution of the adhesive polymer of Example 1 was mixed with 3 parts by weight of a 10% ethyl acetate solution of lithium bis(fluorosulfonyl)imide and 2 parts by weight of an isocyanate-based curing agent (Tosoh Corporation's Coronate (registered trademark) HX) to prepare an adhesive composition of Comparative Example 2. The adhesive composition was applied to 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 for 2 minutes in a hot air circulating oven at 100 ° C. to form an adhesive layer. Thereafter, the release sheet of Comparative Example 2 prepared above was attached to the surface of this adhesive layer via the release layer (silicone-treated surface) to obtain a laminated film. The obtained laminated film was kept warm in an environment of 40 ° C. for 5 days to cure the adhesive layer, and an antistatic surface protection film of Comparative Example 2 was obtained.

[0051] The evaluation test methods and results are shown below. The surface protection films used in the evaluation test methods were antistatic surface protection films in Examples 1 and 2 and Comparative Example 2, and a surface protection film not having peel-off antistatic properties in Comparative Example 1. <Method of measuring the peel strength of the release sheet> A sample of the surface protection film was cut to a width of 50 mm and a length of 150 mm. Under a test environment of 23°C x 50% RH, a tensile tester was used to measure the strength when the release sheet was peeled off in a 180° direction at a peeling speed of 300 mm / min, and this was taken as the peel strength of the release sheet (N / 50 mm).

[0052] <Method for measuring adhesive strength of surface protection film> An anti-glare low reflection treated polarizing plate (AG-LR polarizing plate) was attached to the surface of the glass plate using a laminating machine with double-sided adhesive tape. After that, a surface protection film cut to a width of 25 mm and with the release sheet removed was attached to the surface of the polarizing plate, and then stored for one day under a test environment of 23°C x 50% RH. After that, the strength was measured when the surface protection film was peeled off in the direction of 180° at a peeling speed of 300 mm / min using a tensile tester, and this was taken as the adhesive strength (N / 25 mm).

[0053] (Method for measuring surface resistivity of adhesive layer) After peeling the release sheet from the surface protection film sample, the surface resistivity (Ω / □) of the adhesive layer was measured using a high-performance high resistivity meter (Hiresta (registered trademark)-UP manufactured by Mitsubishi Chemical Analytech Co., Ltd.) under conditions of an applied voltage of 100 V and a measurement time of 30 seconds.

[0054] <Method for measuring the peeling electrification voltage of surface protection film> An anti-glare low reflection treated polarizing plate (AG-LR polarizing plate) was attached to the surface of a glass plate with a double-sided adhesive tape using a laminating machine. Then, a surface protection film cut to a width of 25 mm and with the release sheet peeled off was attached to the surface of the polarizing plate, and the film was stored for one day under a test environment of 23°C x 50% RH. Then, the surface protection film was peeled off at a peeling speed of 40 m per minute using a high-speed peeling tester (manufactured by Tester Sangyo Co., Ltd.), and the surface potential of the polarizing plate surface was measured every 10 ms using a surface potential meter (manufactured by Keyence Corporation). The maximum absolute value of the surface potential was taken as the peeling electrification voltage (kV).

[0055] <Method for checking surface contamination of surface protection film> An anti-glare low reflection treated polarizing plate (AG-LR polarizing plate) was attached to the surface of the glass plate with a double-sided adhesive tape using a laminating machine. After that, a surface protection film cut to a width of 25 mm and with the release sheet removed was attached to the surface of the polarizing plate, and the plate was stored for 3 days and 30 days under a test environment of 23°C x 50% RH. After that, the surface protection film was peeled off, and the contamination of the surface of the polarizing plate was visually observed. As the criterion for judging the surface contamination, the case where there was no contamination transfer to the polarizing plate was marked as (○), and the case where contamination transfer was confirmed to the polarizing plate was marked as (×).

[0056] The results of measurements of the obtained antistatic surface protection films of Examples 1 and 2, the surface protection film of Comparative Example 1 not having peelable antistatic properties, and the antistatic surface protection film of Comparative Example 2 are shown in Table 1. "2EHA" means 2-ethylhexyl acrylate, "HEA" means 2-hydroxyethyl acrylate, "#400G" means methoxypolyethylene glycol (400) methacrylate, "AS agent (1)" means lithium bis(fluorosulfonyl)imide, "AS agent (2)" means lithium bis(trifluoromethanesulfonyl)imide, "SRX-211" means SRX-211, "KS-847H" means KS-847H, "SRX212" means platinum catalyst SRX-212, and "PL-50T" means platinum catalyst CAT PL-50T. The surface resistivity "4.7E10" is 4.7×10 10 "Over-range" means exceeding the measurement limit of the measuring instrument, and is 1.0×10 13 This means Ω / □ or more.

[0057] [Table 1]

[0058] The measurement results shown in Table 1 reveal the following: The antistatic surface protection films of Examples 1 and 2 according to the present invention have appropriate adhesive strength, do not contaminate the surface of the adherend, and have a low peeling electrification voltage when peeled off from the adherend after being attached to the adherend. On the other hand, in the case of the surface protection film of Comparative Example 1, which did not have peel-off antistatic performance and in which no antistatic agent was added to the release agent layer, the peel-off electrification voltage was high when the surface protection film was peeled off from the adherend after it was once attached to the adherend. Furthermore, the antistatic surface protection film of Comparative Example 2, in which an antistatic agent was added to the adhesive layer, had a low and favorable peeling electrification voltage when the antistatic surface protection film was once attached to an adherend and then peeled off from the adherend, but caused a lot of contamination of the adherend after peeling. That is, it is difficult to achieve both a reduction in peeling electrification voltage and staining properties on the adherend in the surface protection film of Comparative Example 1 that does not have peeling antistatic performance, and the antistatic surface protection film of Comparative Example 2. On the other hand, in the antistatic surface protection films of Examples 1 and 2 in which an antistatic agent is added to the release agent layer of the release sheet, and then the antistatic agent is transferred to the surface of the pressure-sensitive adhesive layer, and the component of the antistatic agent is present only on the surface of the pressure-sensitive adhesive layer, the addition of a small amount of the antistatic agent has the effect of reducing peeling electrification voltage, and there is no staining on the adherend, and a good antistatic surface protection film was obtained. [Industrial Applicability]

[0059] The antistatic surface protective film of the present invention can be used, for example, in the production process of optical films such as polarizing plates, retardation plates, and lens films for displays, as well as various other optical components, to protect the surfaces of the optical components, etc. In particular, even when used as an antistatic surface protective film for optical films such as LR polarizing plates and AG-LR polarizing plates, the surfaces of which have been anti-soiling treated with silicone compounds, fluorine compounds, etc., the amount of static electricity generated can be reduced when peeled off from the adherend after being once attached to the adherend. The antistatic surface protective film of the present invention has a release sheet that is easy to peel off during use, causes little contamination of the substrate, and has excellent antistatic performance upon peeling without deterioration over time, thereby improving the workability and yield of the production process and having extremely high industrial utility. [Explanation of symbols]

[0060] Reference Signs List 1...base material film, 2...adhesive layer, 3...base material, 4...release agent layer, 5...release sheet, 7...antistatic agent, 8...adherend (optical component), 10...antistatic surface protective film, 11...antistatic surface protective film with release sheet removed, 20...optical component with antistatic surface protective film bonded thereto.

Claims

1. An antistatic surface protective film for an optical film, comprising a base film made of a resin and an adhesive layer formed on one side of the base film, and a release sheet for the antistatic surface protective film, to which an antistatic agent can be transferred, attached to the surface of the adhesive layer, the release sheet for antistatic surface protective film is obtained by laminating a release agent layer formed of a resin composition containing a release agent mainly composed of dimethylpolysiloxane and an antistatic agent on one side of a substrate, the substrate being a paper-containing substrate made of one type selected from the group consisting of polyethylene-laminated fine paper, polyethylene-laminated art paper, and polyethylene-laminated kraft paper; The release sheet for antistatic surface protective film is attached to the surface of the pressure-sensitive adhesive layer via the release agent layer to form a laminated film, and the laminated film is cut into sheets of a predetermined size in order to be attached to an optical film of a predetermined size, and the antistatic agent in the release agent layer can be transferred to the surface of the pressure-sensitive adhesive layer. The release sheet for antistatic surface protective film is peeled from the laminated film, and the antistatic surface protective film is attached to an adherend via the pressure-sensitive adhesive layer, and then a peeling electrification voltage is reduced when the pressure-sensitive adhesive layer is peeled from the adherend, and the peeling electrification voltage when the pressure-sensitive adhesive layer is peeled from the adherend, which is the optical film of the predetermined size, is +0.7 kV to -0.7 kV as measured by the peeling electrification voltage measurement method described below. [Method for measuring peeling electrification voltage] An anti-glare low reflection treated polarizing plate (AG-LR polarizing plate) was bonded as the optical film to the surface of a glass plate with a double-sided adhesive tape using a laminating machine, and an antistatic surface protective film cut to a width of 25 mm and having the release sheet peeled off was bonded to the surface of the optical film, and the film was then stored for one day under a test environment of 23°C x 50% RH. The antistatic surface protective film was peeled off at a peeling speed of 40 m per minute while the surface potential of the optical film was measured every 10 ms. The maximum absolute value of the surface potential was defined as the peeling electrification voltage (kV).

2. 2. The antistatic surface protective film for an optical film according to claim 1, wherein the antistatic agent is an alkali metal salt.

3. 3. The antistatic surface protection film for an optical film according to claim 1, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer formed by crosslinking a (meth)acrylate copolymer.

Images