JP6761885B2 - Manufacturing method of antistatic surface protective film - Google Patents

Description

The present invention relates to a surface protective film attached to the surface of an optical component (hereinafter, may be referred to as an optical film). More specifically, the present invention relates to a surface protective film having less contamination on the adherend and the stainability on the adherend does not change with time, and an optical component using the same. Further, the present invention protects the surface even if the constituent member of the polarizing plate, which is an optical component, is replaced (change from TAC film to acrylic film or polyester film, change from water-based adhesive to ultraviolet curable adhesive). It is an object of the present invention to provide a surface protective film in which a peeling band voltage at the time of peeling a film is suppressed to a low level, and an optical component to which the film is bonded.
The optical component in the present invention refers to a polarizing plate, a retardation plate, a lens film for a display, and the like.

Manufactures and transports optical films such as polarizing plates, retardation plates, lens films for displays, antireflection films, hard coat films, transparent conductive films for touch panels, and optical products such as displays using them. In this case, a surface protective film is attached to the surface of the optical film to prevent the surface from being soiled or scratched in a subsequent step. The appearance inspection of the optical film, which is a product, may be performed with the surface protective film attached to the optical film in order to save the trouble of peeling off the surface protective film and attaching it again to improve work efficiency.

Conventionally, a surface protective film having an adhesive layer provided on one side of a base film has been generally used in the manufacturing process of an optical product in order to prevent the adhesion of scratches and stains. The surface protective film is attached to the optical film via an adhesive layer having a slight adhesive strength. The reason why the adhesive layer has a slight adhesive strength is that when the used surface protective film is peeled off from the surface of the optical film and removed, the adhesive layer can be easily peeled off, and the adhesive is an adherend. This is to prevent the adhesive from adhering to the optical film and remaining (so-called adhesive residue is prevented).

In recent years, in the production process of a liquid crystal display panel, a driver for controlling the display screen of a liquid crystal display by a peeling band voltage generated when the surface protective film bonded on the optical film is peeled off and removed. Although the number of occurrences is small, the phenomenon that circuit parts such as ICs are destroyed and the phenomenon that the orientation of liquid crystal molecules is damaged are occurring.
Further, in order to reduce the power consumption of the liquid crystal display panel, the driving voltage of the liquid crystal material is getting lower, and the breaking voltage of the driver IC is also getting lower accordingly. Recently, it has been required to set the peeling band voltage within the range of +0.7 kV to −0.7 kV.

Further, in the conventional polarizing plate, a triacetyl cellulose film (TAC film) is adhered to both sides of a polarizing element made of polyvinyl alcohol (PVA) impregnated with iodine with an aqueous adhesive to protect the polarizing element. However, in recent years, polarizing plates using acrylic film, cyclic polyolefin film or polyester film instead of TAC film, and polarizing plates using ultraviolet curable adhesive instead of water-based adhesive have also been used. It has become. Due to the change in the constituent material of the polarizing plate, there is a problem that the peeling band voltage generated when the surface protective film is peeled off and removed becomes higher than that when the polarizing plate having the conventional structure is used.

Further, in recent years, with the spread of 3D displays (stereoscopic displays), there is a film in which an FPR (Film Patterned Renderer) film is attached to the surface of an optical film such as a polarizing plate. After peeling off the surface protective film attached to the surface of the optical film such as a polarizing plate, the FPR film is attached. However, if the surface of an optical film such as a polarizing plate is contaminated with an adhesive or an antistatic agent used for the surface protective film, there is a problem that the FPR film is difficult to adhere. Therefore, the surface protective film used for this purpose is required to have less contamination on the adherend.

On the other hand, in some liquid crystal panel makers, as a method of evaluating the contamination of the surface protective film on the adherend, the surface protective film attached to the optical film such as a polarizing plate is once peeled off and air bubbles are mixed. A method is adopted in which the reattached film is heat-treated under predetermined conditions, and then the surface protective film is peeled off to observe the surface of the adherend. In such an evaluation method, even if the surface contamination of the adherend is very small, the difference in the surface contamination of the adherend is between the portion where the air bubbles are mixed and the portion where the adhesive of the surface protective film is in contact. If there is, it remains as a trace of bubbles (sometimes called bubble stains). Therefore, it is a very strict evaluation method as a method for evaluating the contamination of the surface of the adherend. In recent years, there has been a demand for a surface protective film that can pass the judgment by such a strict evaluation method and has extremely little contamination on the surface of the adherend.

After the surface protective film is attached to the optical film that is the adherend, the peel band voltage is set to prevent problems caused by the high peel band voltage that occurs when the surface protective film is peeled from the adherend. A surface protective film using an adhesive layer containing an antistatic agent has been proposed to keep it low.

For example, Patent Document 1 discloses a surface protective film using a pressure-sensitive adhesive composed of an alkyltrimethylammonium salt, a hydroxyl group-containing acrylic polymer, and a polyisocyanate.
Further, Patent Document 2 discloses a pressure-sensitive adhesive composition composed of an ionic liquid and an acrylic polymer having an acid value of 1.0 or less, and pressure-sensitive adhesive sheets using the same.
Further, Patent Document 3 discloses an adhesive composition composed of an acrylic polymer, a polyether polyol compound, an alkali metal salt treated with an anion-adsorbing compound, and a surface protective film using the same.
Further, Patent Document 4 discloses an adhesive composition composed of an ionic liquid, an alkali metal salt, a polymer having a glass transition temperature of 0 ° C. or lower, and a surface protective film using the same.

Japanese Unexamined Patent Publication No. 2005-131957 Japanese Unexamined Patent Publication No. 2005-330464 Japanese Unexamined Patent Publication No. 2005-314476 Japanese Unexamined Patent Publication No. 2006-152235

In the surface protective films described in Patent Documents 1 to 4, an antistatic agent is added to the inside of the pressure-sensitive adhesive layer. Therefore, the thicker the pressure-sensitive adhesive layer and the more time elapses after the pressure-sensitive adhesive layer is attached to the adherend, the more the pressure-sensitive adhesive layer adheres to the adherend to which the surface protective film is attached. The amount of antistatic agent transferred to the body tended to increase. Further, when the amount of the antistatic agent transferred to the adherend is increased, the appearance quality of the optical film which is the adherend is deteriorated, or the adhesiveness of the FPR film is deteriorated when the FPR film is attached. there's a possibility that.

If the thickness of the pressure-sensitive adhesive layer is reduced in order to reduce the time-dependent change of the antistatic agent that migrates from the pressure-sensitive adhesive layer to the adherend, another problem arises. For example, when it is used for an optical film having an uneven surface such as a polarizing plate treated with anti-glare to prevent glare, the adhesive layer cannot follow the unevenness on the surface of the optical film and air bubbles are mixed in, or for optical use. Since the adhesive area between the film and the adhesive layer is reduced, the adhesive strength is reduced, and there is a problem that the surface protective film floats or peels off during use.

Further, if the amount of the antistatic agent added to the pressure-sensitive adhesive layer is reduced in order to reduce the time-dependent change of the antistatic agent that migrates from the pressure-sensitive adhesive layer to the adherend, the surface protective film is peeled off from the adherend. There is a risk that the peeling band voltage generated when the film is removed will increase, causing a phenomenon in which circuit components such as a driver IC are destroyed or a phenomenon in which the orientation of liquid crystal molecules is damaged.

The present invention has been made in view of the above circumstances, and is a surface protective film to be bonded to the surface of an optical film, and can be bonded to an optical film having an uneven surface. It is an object of the present invention to provide a surface protective film having very little contamination on an adherend and having a low antifouling property on an adherend over time, and an optical component using the same.
Further, the present invention protects the surface even if the constituent member of the polarizing plate, which is an optical component, is replaced (change from TAC film to acrylic film or polyester film, change from water-based adhesive to ultraviolet curable adhesive). An object of the present invention is to provide a surface protective film in which a peeling band voltage at the time of peeling a film is suppressed to a low level, and an optical component using the same.

The present inventors have conducted diligent studies to solve these problems. It is necessary to reduce the content of the antistatic agent, which is presumed to be the cause of contaminating the adherend, in order to reduce the contamination of the adherend with time and the change of the contaminated property with time. However, when the content of the antistatic agent is reduced, the peeling band voltage when the surface protective film is peeled from the adherend becomes high.
Therefore, the present inventors have studied a method of suppressing the peeling band voltage when the surface protective film is peeled from the adherend without increasing the content of the antistatic agent.

The present inventors first apply an antistatic agent-free pressure-sensitive adhesive composition to one side of a base material, dry it, laminate a pressure-sensitive adhesive layer, and contain an antistatic agent on the other side of the base material. A surface protective film in which a release agent layer was laminated was prepared. After that, the surface protective film is wound into a roll so that the pressure-sensitive adhesive layer is on the inside, so that the components of the antistatic agent contained in the release agent layer are transferred to the surface of the pressure-sensitive adhesive layer. Then, it was in a state of being present only on the surface of the pressure-sensitive adhesive layer. It was found that the peeling band voltage at the time of peeling from the adherend after the surface protective film is once attached to the optical film which is the adherend is suppressed to a low level, and the adherend is not easily contaminated. , The present invention has been completed.

In the surface protective film of the present invention, an antistatic agent-free pressure-sensitive adhesive composition is applied and dried on one side of a base material to laminate an adhesive layer, and the other side of the base material contains an antistatic agent. After laminating the release agent layer, the surface protective film is wound so that the pressure-sensitive adhesive layer is on the inside to form a roll, so that the surface of the pressure-sensitive adhesive layer is charged with the charge contained in the release agent layer. The components of the inhibitor are transferred. According to the present invention, when the surface protective film wound in a roll shape is rewound from the roll shape and attached to the adherend, the stain resistance to the adherend is suppressed to a low level, and the adherend is used. The technical idea is to keep the peeling band voltage low when peeling the surface protection film from a certain optical film.

In order to solve the above problems, in the present invention, a release agent layer is formed on one surface of a base film made of a transparent resin, and an adhesive layer is formed on the other surface of the base film. A surface protective film formed, wherein the surface protective film is a roll body formed by winding in a roll shape with the pressure-sensitive adhesive layer inside, and the release agent layer is formed in the radial direction of the roll body. The pressure-sensitive adhesive layer is in contact with the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is an acrylic type obtained by cross-linking a pressure-sensitive adhesive composition containing a (meth) acrylate copolymer obtained by copolymerizing a compound containing a polyoxyalkylene group. A pressure-sensitive adhesive layer, wherein the release agent layer contains an antioxidant made of an alkali metal salt and a silicone-based release agent, and the antistatic agent made of the alkali metal salt contained in the release agent layer. The component 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, and the surface protective film of the roll body is rewound from the roll body. The adhesive strength of the surface protective film to the surface of the adherend, which was measured based on the following "method for measuring the adhesive strength of the surface protective film", was 0.03 when the adhesive was attached to the adherend. Provided is a surface protective film characterized by being ~ 0.3N / 25mm.

-Method of measuring the adhesive strength of the surface protective film: An anti-glare low-reflection treated polarizing plate (AG-) in which an acrylic film is attached to a polarizing element (polyvinyl alcohol film containing iodine) using an ultraviolet curable adhesive. The LR polarizing plate) is used as the adherend, and the polarizing plate is bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine, and then on the acrylic film on the surface of the polarizing plate. After laminating the surface protective film cut to a width of 25 mm, the surface protective film was stored in a test environment of 23 ° C. × 50% RH for 1 day, and then using a tensile tester at a peeling rate of 180 ° / min. In the direction, the strength when the surface protective film is peeled off is measured, and this is defined as the adhesive force (N / 25 mm).

Further, it is preferable that the surface potential at the time of peeling the pressure-sensitive adhesive layer from the optical film which is an adherend is +0.7 kV to −0.7 kV.

Further, it is preferable that the base film is wound in a roll shape with the pressure-sensitive adhesive layer inside so that the release agent layer and the pressure-sensitive adhesive layer are in contact with each other.

The present invention also provides an optical component in which the surface protective film is bonded to the surface protective film via the pressure-sensitive adhesive layer.

The surface protective film of the present invention is a surface protective film that is bonded to the surface of an optical film, and can also be bonded to an optical film having an uneven surface.
Further, according to the present invention, it is possible to provide a surface protective film which has very little contamination on the adherend and whose stainability on the adherend does not change with time, and an optical component using the same.
Further, according to the present invention, the constituent members of the polarizing plate, which is an optical component, are changed (change from TAC film to acrylic film, cyclic polyolefin film or polyester film, change from water-based adhesive to ultraviolet curable adhesive). Even so, it is possible to provide a surface protective film in which the peeling band voltage at the time of peeling the surface protective film is suppressed to a low level, and an optical component using the same.
Further, the surface protective film wound in a roll shape of the present invention is a surface protective film in which the base film is wound in a roll shape with the pressure-sensitive adhesive layer inside so that the release agent layer and the pressure-sensitive adhesive layer are in contact with each other. The component of the antistatic agent composed of the alkali metal salt is transferred from the release agent layer to the surface of the pressure-sensitive adhesive layer and exists only on the surface of the pressure-sensitive adhesive layer.
That is, in the present invention, after the surface protective film rewound from the surface protective film wound in a roll shape is attached to the adherend, the peeling band voltage when the surface protective film is peeled off from the adherend is reduced. In addition, since the peeling antistatic performance changes with time and the adherend is less contaminated, the productivity of the optical component which is the adherend can be improved and the yield can be improved. ..

It is a conceptual cross-sectional view which showed the surface protection film in the state of being wound in a roll shape of this invention. It is a conceptual cross-sectional view showing the state which the release agent layer and the pressure-sensitive adhesive layer are in contact with each other in the state where the surface protection film of this invention is wound in a roll shape. It is sectional drawing which shows one of the Examples which attached the surface protection film of this invention to an optical component.

Hereinafter, the present invention will be described in detail based on the embodiments.
FIG. 1 is a conceptual cross-sectional view showing the surface protective film 10 in a rolled state of the present invention. The surface protective film 10 in a rolled state shown on the right side of FIG. 1 is a surface protective film 5 according to the present invention wound in a roll shape with the adhesive layer 4 inside (surface protective film). 5 rolls). Further, the left side of FIG. 1 is a conceptual cross-sectional view showing the surface protective film 5 rewound from the roll shape in the arrow direction enlarged in the thickness direction.

The surface protective film 5 has a release agent layer 2 containing an antistatic agent 3 made of an alkali metal salt on one surface of the transparent base film 1, and adheres to the other surface of the base film 1. The agent layer 4 is formed. The release agent layer 2 is provided on one surface of the base film 1, and the surface protective film 5 having the pressure-sensitive adhesive layer 4 is brought into contact with the release agent layer 2 and the pressure-sensitive adhesive layer 4 on the other surface of the base film. As described above, by winding the pressure-sensitive adhesive layer 4 inside in a roll shape, the components of the antistatic agent 3 contained in the release agent layer 2 are transferred to the surface of the pressure-sensitive adhesive layer 4, and the pressure-sensitive adhesive layer 4 A surface protective film 10 in a rolled state, which exists only on the surface, can be obtained.

As the base film 1 used for the surface protective film 5 according to the present invention, a base film made of a transparent and flexible resin is used. As a result, the appearance inspection of the optical component can be performed with the surface protective film 5 attached to the optical component which is an adherend. As the film made of a transparent resin used as the base film 1, a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate is preferably used. In addition to the polyester film, a film made of another resin can be used as long as it has the required strength and optical suitability. The base film 1 may be a non-stretched film or a uniaxially or biaxially stretched film. Further, the draw 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 base film 1 used for the surface protective film 5 according to the present invention is not particularly limited, but is preferably about 12 to 100 μm, and more easily handled if the thickness is about 20 to 75 μm. preferable.
Further, if necessary, the surface of the base film 1 may be subjected to an easy adhesion treatment such as surface modification by corona discharge or application of an anchor coating agent.

Further, the release agent layer 2 formed on the surface protective film 5 according to the present invention is formed by using a release agent containing an antistatic agent 3 made of an alkali metal salt. As the release agent, a silicone-based release agent is preferably used.

Examples of the silicone-based release agent include known silicone-based release agents such as addition reaction type, condensation reaction type, cationic polymerization type, and radical polymerization type. Products commercially available as addition reaction type silicone release agents include, for example, KS-776A, KS-847T, KS-779H, KS-837, KS-778, KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.). , SRX-211, SRX-345, SRX-357, SD7333, SD7220, SD7223, LTC-300B, LTC-350G, LTC-310 (manufactured by Toray Dow Corning Co., Ltd.) and the like. Examples of products commercially available as a condensation reaction type include SRX-290 and SYLOFF-23 (manufactured by Toray Dow Corning Co., Ltd.). Products commercially available as cationically polymerized types include, for example, TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials), X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). ) And so on. Examples of products commercially available as a radical polymerization type include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

As the antistatic agent 3 contained in the release agent layer 2, it is preferable that the antistatic agent 3 has good dispersibility in the silicone-based release agent solution and does not inhibit the curing of the silicone-based release agent. Further, the component of the antistatic agent 3 contained in the release agent layer 2 is transferred to the surface of the pressure-sensitive adhesive layer 4 in contact with the release agent layer 2, and the antistatic function is transferred to the surface of the pressure-sensitive adhesive layer 4. An antistatic agent that does not react with the silicone-based release agent is preferable. Alkali metal salts are suitable as such antistatic agents.

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

The amount of the antistatic agent added to the silicone-based release agent varies depending on the type of the antistatic agent and the degree of affinity with the silicone-based release agent, but is desired when the surface protective film is peeled off from the adherend. It may be set in consideration of the band voltage, the contamination with the adherend, the adhesive property, and the like. The mixing ratio (weight ratio) of the silicone-based release agent and the antistatic agent is preferably, for example, a ratio of 5 to 100 as the solid content of the antistatic agent with respect to the solid content of 100 of the silicone-based release agent. It is a value, more preferably a ratio of 5 to 60. When the amount of the antistatic agent added in terms of solid content is less than 5 with respect to the solid content of 100 of the silicone-based release agent, the amount of transfer of the antistatic agent to the surface of the pressure-sensitive adhesive layer is also small, and the pressure-sensitive adhesive It becomes difficult for the antistatic function to be exhibited. Further, when the amount of the antistatic agent added in terms of solid content exceeds 100 with respect to the solid content of 100 of the silicone-based release agent, the components of the silicone-based release agent as well as the antistatic agent are added to the surface of the pressure-sensitive adhesive layer. Since it is transferred, it may reduce the adhesive properties of the adhesive.

The release agent layer 2 is composed of at least a silicone-based release agent and an antistatic agent that does not react with the release agent. The method of mixing the silicone-based release agent and the antistatic agent is not particularly limited. A method in which an antistatic agent is added to a silicone-based release agent and mixed, and then a catalyst for curing the release agent is added and mixed. The silicone-based release agent is diluted with an organic solvent in advance, and then the antistatic agent and the release agent are used. Any method may be used, such as a method of adding and mixing a curing catalyst, a method of diluting a silicone-based release agent with an organic solvent in advance, a method of adding and mixing a catalyst, and then a method of adding and mixing an antistatic agent. Further, the release agent layer 2 imparts printability such as an adhesion improver such as a silane coupling agent, a material assisting an antistatic effect such as a compound containing a polyoxyalkylene group, and a cellulosic compound, if necessary. It may contain a material for adjusting slipperiness, a material for adjusting slipperiness, and the like.

The release agent layer 2 may be formed on the surface of the base film 1 by a known method. Specifically, known coating methods such as gravure coating, Mayer bar coating, and air knife coating can be used.

In the pressure-sensitive adhesive layer 4 formed on the surface protective film 5 according to the present invention, the component of the antistatic agent 3 contained in the release agent layer 2 does not exist inside the pressure-sensitive adhesive layer 4 (other than the surface). , Exists only on the surface of the pressure-sensitive adhesive layer 4. As a result, it is possible to suppress changes in the peeling antistatic performance of the surface protective film 5 over time and contamination of the adherend.
The pressure-sensitive adhesive layer 4 formed on the surface protective film 5 according to the present invention may be a pressure-sensitive adhesive layer that adheres to the surface of the adherend, can be easily peeled off after use, and does not easily contaminate the adherend. However, it is not particularly limited. Considering that the surface protective film 5 according to the present invention is required to have durability after being bonded to an optical film, the acrylic pressure-sensitive adhesive layer is formed by cross-linking a (meth) acrylate copolymer. Is preferable.

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

Further, a compound containing a polyoxyalkylene group may be copolymerized or mixed with the (meth) acrylate copolymer. Examples of the copolymerizable polyoxyalkylene group-containing compound include polyethylene glycol (400) monoacrylic acid ester, polyethylene glycol (400) monomethacrylic acid ester, methoxypolyethylene glycol (400) acrylate, and methoxypolyethylene glycol (400) methacrylate. , Polypropylene glycol (400) monoacrylic acid ester, polypropylene glycol (400) monomethacrylic acid ester, methoxypolypropylene glycol (400) acrylate, methoxypolypropylene glycol (400) methacrylate and the like. By copolymerizing these polyoxyalkylene group-containing monomers with the main monomer or functional monomer of the (meth) acrylate copolymer, a pressure-sensitive adhesive composed of the polyoxyalkylene group-containing copolymer is obtained. be able to.

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 (meth) acrylic containing a polyoxyalkylene group. Polymers of based monomers are more preferred, for example, polyethylene glycol (400) monoacrylic acid ester, polyethylene glycol (400) monomethacrylic acid ester, methoxypolyethylene glycol (400) acrylate, methoxypolyethylene glycol (400) methacrylate, polypropylene glycol ( Examples thereof include polymers such as monoacrylic acid ester, polypropylene glycol (400) monomethacrylic acid ester, methoxypolypropylene glycol (400) acrylate, and methoxypolypropylene glycol (400) methacrylate. By mixing these polyoxyalkylene group-containing compounds with the (meth) acrylate copolymer, a pressure-sensitive adhesive to which the polyoxyalkylene group-containing compound is added can be obtained.

Examples of the curing agent added to the pressure-sensitive adhesive layer 4 include isocyanate compounds, epoxy compounds, melamine compounds, and metal chelate compounds as cross-linking agents for cross-linking the (meth) acrylate copolymer. Examples of the tackifier include rosin-based, marron inden-based, terpene-based, petroleum-based, and phenol-based.

The thickness of the pressure-sensitive adhesive layer 4 formed on the surface protective film 5 according to the present invention is not particularly limited, but is preferably, for example, about 5 to 40 μm, and more preferably about 10 to 30 μm. The adhesive layer 4 having a slight adhesive strength, in which the peel strength (adhesive strength) of the surface protective film to the surface of the adherend is about 0.03 to 0.3 N / 25 mm, is from the adherend to the surface. It is preferable because it is excellent in operability when peeling off the protective film.

The method for forming the pressure-sensitive adhesive layer 4 on the base film 1 of the surface protective film 5 according to the present invention may be a known method and is not particularly limited. 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.

The surface protective film 5 according to the present invention having the above configuration preferably has a surface potential of +0.7 kV to −0.7 kV when the pressure-sensitive adhesive layer 4 is peeled off from the optical film as an adherend. .. Further, the surface potential is more preferably +0.5 kV to −0.5 kV, and the surface potential is particularly preferably +0.2 kV to −0.2 kV. This surface potential can be adjusted by adjusting the type of antistatic agent 3 contained in the release agent layer 2, the amount added, and the like. The type and amount of the antistatic agent 3 added to the release agent layer 2 in consideration of the surface contamination of the optical film which is the adherend after the surface protective film 5 is peeled off from the optical film which is the adherend. Should be adjusted.

FIG. 2 is a conceptual cross-sectional view showing a state in which the release agent layer 2 and the pressure-sensitive adhesive layer 4 are in contact with each other in a state where the surface protective film 5 of the present invention is wound in a roll shape. A release agent layer 2 containing an antistatic agent 3 is formed on one surface of the base film 1, and an adhesive layer 4 containing no antistatic agent 3 is formed on the other surface of the base film 1. By forming the surface protective film 5 in a state of being wound in a roll shape with the adhesive layer 4 inside, the release agent layer 2 and the adhesive layer 4 are formed in the radial direction of the roll body. Is in contact with. As a result, a part of the components of the antistatic agent (reference numeral 3) contained in the release agent layer 2 is transferred to the surface of the pressure-sensitive adhesive layer 4. FIG. 3 shows a state in which the surface protective film 5 unwound from the surface protective film 10 wound in a roll shape thus obtained is attached to the optical component 6. By transferring the components of the antistatic agent 3 from the release agent layer 2 to the surface of the pressure-sensitive adhesive layer 4, the surface protective film 5 can be compared with the pressure-sensitive adhesive layer 4 before the components of the antistatic agent 3 are transferred. The peeling band voltage when the surface protective film 5 is peeled from the adherend after being bonded to the adherend is reduced. The peeling band voltage when the surface protective film 5 of FIG. 1 is peeled from the adherend can be measured by a known method. For example, after the surface protective film 5 is attached to an adherend such as a polarizing plate, the surface protective film 5 is peeled off at a peeling speed of 40 m / min using a high-speed peeling tester (manufactured by Tester Sangyo). When the surface potential of the surface of the film is measured every 10 ms using a surface electrometer (manufactured by Keyence Co., Ltd.), the maximum value of the absolute value of the surface potential is measured as the peeling band voltage (kV).

In the surface protective film 10 wound in a roll shape according to the present invention, the surface protective film 5 rewound from the roll shape was transferred to the surface of the pressure-sensitive adhesive layer 4 when it was attached to the adherend. The antistatic agent 3 comes into contact with the surface of the adherend. As a result, the peeling band voltage when the surface protective film 5 is peeled off from the adherend again can be suppressed to a low level. Further, in the surface protective film 10 in a rolled state according to the present invention, since the release agent layer 2 is on the outside and the pressure-sensitive adhesive layer 4 is on the inside, the surface of the pressure-sensitive adhesive layer 4 is in the rolled state. , Protected without being exposed. Even after the surface protective film 5 is rewound from the roll shape, the release agent layer 2 is integrated with the base film 1, so that the release agent layer 2 does not need to be removed or discarded.

FIG. 3 is a cross-sectional view showing an optical component 7 with a surface protective film as one of examples in which the surface protective film 5 of the present invention is attached to an optical component. The optical component 7 with a surface protective film is an optical component 6 which is an adherend of the surface protective film 5 of the present invention, which is unwound from the surface protective film 10 in a rolled state and is an adherend through the pressure-sensitive adhesive layer 4. It can be obtained by pasting on. Examples of the optical component 6 include an optical film 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 constituent members of liquid crystal display devices such as liquid crystal display panels, optical system devices of various instruments, and the like. Further, examples of the optical component include an optical film such as an antireflection film, a hard coat film, and a transparent conductive film for a touch panel.

The surface protective film 5 of the present invention is unwound from the surface protective film 10 in a rolled state, attached to an optical component (optical film) which is an adherend, and then the surface protective film 5 is attached to the adherend. When peeling off the film, the peeling band voltage can be suppressed to a sufficiently low level. Therefore, there is no risk of damaging circuit components such as driver ICs, TFT elements, and gate wire drive circuits, and production efficiency in the process of manufacturing a liquid crystal display panel or the like can be improved, and reliability of the production process can be maintained.

Next, the present invention will be described in more detail by way of examples.

(Example 1)
(Preparation of surface protection film)
Addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345) 5 parts by weight, lithium bis (fluorosulfonyl) imide 0.75 parts by weight, 95 parts by weight of a 1: 1 mixed solvent of toluene and ethyl acetate A part and a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212) were mixed by 0.05 parts by weight, stirred and mixed to prepare a coating material forming the release agent layer of Example 1.
On the other hand, with respect to 100 parts by weight of a 40% ethyl acetate solution of a pressure-sensitive adhesive composed of 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. Two parts by weight of an isocyanate-based curing agent (Coronate (registered trademark) HX manufactured by Toso Co., Ltd.) was stirred and mixed to prepare the pressure-sensitive adhesive composition of Example 1.
The paint forming the release agent layer of Example 1 is applied to the surface of a polyethylene terephthalate film having a thickness of 38 μm with a Mayer bar so that the thickness after drying becomes 0.2 μm, and a hot air circulation oven at 120 ° C. Was dried for 1 minute to form a release agent layer. Next, the prepared pressure-sensitive adhesive composition was applied to the surface of the polyethylene terephthalate film on which the release agent layer was not formed so that the thickness after drying was 20 μm, and then in a hot air circulation oven at 100 ° C. for 2 minutes. It was dried to form an adhesive layer. After that, the obtained film having a release agent layer formed on one surface of the base film and an adhesive layer formed on the other surface is subjected to an adhesive so that the release agent layer and the adhesive layer are in contact with each other. It was rolled into a roll with the layer inside. The obtained roll-shaped adhesive film was kept warm in an environment of 40 ° C. for 5 days, and the adhesive layer was cured to obtain a surface protective film in a roll-shaped wound state of Example 1.

(Example 2)
In the same manner as in Example 1, the surface protective film in a rolled state of Example 2 was formed in the same manner as in Example 1 except that the thickness of the paint forming the release agent layer of Example 1 after drying was 0.1 μm. Obtained.

(Example 3)
The addition reaction type silicone of Example 1 was manufactured by Toray Dow Corning Co., Ltd., and the product name was SRX-211, except that lithium bis (trifluoromethanesulfonyl) imide was used instead of lithium bis (fluorosulfonyl) imide. In the same manner as in Example 1, a surface protective film in a rolled state of Example 3 was obtained.

(Comparative Example 1)
A surface protective film in a rolled state of Comparative Example 1 was obtained in the same manner as in Example 1 except that lithium bis (fluorosulfonyl) imide as an antistatic agent was not added.

(Comparative Example 2)
Instead of adding lithium bis (fluorosulfonyl) imide to the release agent, 0.67 parts by weight of lithium bis (fluorosulfonyl) imide was added to 100 parts by weight of the 40% ethyl acetate solution on the pressure-sensitive adhesive side. , A surface protective film in a rolled state of Comparative Example 2 was obtained in the same manner as in Example 1.

The methods and results of the evaluation test are shown below.
<Measurement method of deploying force of surface protective film>
From the surface protective film wound in a roll shape, a sample of the unwound surface protective film is cut out in a state where two layers are overlapped, and cut into a width of 50 mm and a length of 150 mm. Under a test environment of 23 ° C. x 50% RH, the strength at the time of peeling was measured in the direction of 180 ° at a peeling speed of 300 mm / min using a tensile tester, and this was used as the unfolding force of the surface protective film (N / 50 mm).

(Surface resistivity of release agent layer and adhesive layer)
The surface resistivity (Ω / □) of the release agent layer and the pressure-sensitive adhesive layer of the surface protective film sample rewound from the roll shape is measured by a high-performance high resistivity meter (HIRESTA (registered trademark) manufactured by Mitsubishi Chemical Analytech). The measurement was performed using UP) under the conditions of an applied voltage of 100 V and a measurement time of 30 seconds.

<Measurement method of adhesive strength of surface protective film>
An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) obtained by laminating an acrylic film on a polarizing element (polyvinyl alcohol film containing iodine) using an ultraviolet curable adhesive was used as an adherend. .. This polarizing plate was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Then, a surface protective film cut to a width of 25 mm was attached onto 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, the strength when the surface protective film was peeled off was measured in the direction of 180 ° at a peeling speed of 300 mm / min using a tensile tester, and this was defined as the adhesive strength (N / 25 mm).

<Measurement method of peeling band voltage of surface protective film>
An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) obtained by laminating an acrylic film on a polarizing element (polyvinyl alcohol film containing iodine) using an ultraviolet curable adhesive was used as an adherend. .. This polarizing plate was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Then, a surface protective film cut to a width of 25 mm was attached onto 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, while peeling the surface protective film at a peeling speed of 40 m / min using a high-speed peeling tester (manufactured by Tester Sangyo), the surface potential of the polarizing plate surface was measured using a surface electrometer (manufactured by Keyence Co., Ltd.). The maximum value of the absolute value of the surface potential when measured every 10 ms was defined as the stripping band voltage (kV).

<How to check the surface contamination of the surface protection film>
An anti-glare low-reflection treated polarizing plate (AG-LR polarizing plate) obtained by laminating an acrylic film on a polarizing element (polyvinyl alcohol film containing iodine) using an ultraviolet curable adhesive was used as an adherend. .. This polarizing plate was bonded to the surface of the glass plate with a double-sided adhesive tape using a bonding machine. Then, a surface protective film cut to a width of 25 mm was attached onto the 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, and the presence or absence of contamination on the surface of the polarizing plate was visually observed to confirm the surface contamination property. As a criterion for determining surface contamination, the case where no contamination was transferred to the polarizing plate was evaluated as (◯), and the case where the transfer of contamination was confirmed on the polarizing plate was evaluated as (x).

Table 1 shows the measurement results of the obtained surface protective films of Examples 1 to 3 and Comparative Examples 1 and 2 in a rolled state. "2EHA" is 2-ethylhexyl acrylate, "HEA" is 2-hydroxyethyl acrylate, "# 400G" is methoxypolyethylene glycol (400) methacrylate, and "AS agent (1)" is lithium bis (fluorosulfonyl). ) Imid, "AS agent (2)" is lithium bis (trifluoromethanesulfonyl) imide, "SRX-345" is SRX-345, "SRX-111" is SRX-221, and "SRX212" is platinum. Each means catalyst SRX-212. In addition, the surface resistivity of "4.2 E11" means 4.2 x 10 ¹¹ , and "overrange" means that the measurement limit of the measuring machine is exceeded, and 1.0 x 10 ¹³ Ω / □ or more. means.

From the measurement results shown in Table 1, the following can be seen.
The surface protective films of Examples 1 to 3 according to the present invention in a rolled state have appropriate adhesive strength when rewound from the roll shape and are used, and stain the surface of the adherend. Absent. Moreover, even if the adherend is a polarizing plate using an acrylic film, the peeling band voltage at the time of peeling from the adherend after the surface protection film is once attached to the adherend is low.
On the other hand, as for the surface protective film in the state of being wound in a roll shape in Comparative Example 1 in which the antistatic agent was not added to the release agent layer, the surface protective film rewound from the roll shape was once attached to the adherend. After fitting, the peeling band voltage when peeling from the adherend became high. Further, instead of containing the antistatic agent in the release agent layer, the surface protective film in the state of being wound in a roll shape in Comparative Example 2 in which the pressure-sensitive adhesive layer contains an antistatic agent is wound from a roll shape. The peeling zone voltage when the returned surface protective film is once attached to the adherend and then peeled off from the adherend is low and good, but the adherend is contaminated after the surface protective film is peeled off. Has increased.
That is, it is difficult for the surface protective films of Comparative Examples 1 and 2 in the state of being wound in a roll shape to achieve both reduction of the peeling band voltage and low contamination on the adherend. On the other hand, the surface protective film in the rolled state of Examples 1 to 3 in which the antistatic agent was added to the release agent layer and the component of the antistatic agent was transferred only to the surface of the pressure-sensitive adhesive layer was a release band. The balance between the reduction of voltage and the low pollution property to the adherend was good.

The surface protective film of the present invention is used in, for example, in the production process of polarizing plates, retardation plates, lens films, antireflection films, hard coat films, optical films such as transparent conductive films, and various other optical components. , Can be used to protect the surface by sticking to the surface of the optical component or the like. Further, the surface protective film of the present invention can suppress the peeling band voltage generated when the surface protective film is peeled off from the adherend after being attached to an optical component (optical film) which is an adherend, and also , The peeling antistatic performance changes with time and the adherend is less contaminated, the yield of the production process can be improved, and the industrial utility value is great.

1 ... Base film, 2 ... Release agent layer, 3 ... Antistatic agent, 4 ... Adhesive layer, 5 ... Surface protective film, 6 ... Optical component (optical film), 7 ... Optical component with surface protective film, 10 ... A surface protective film wound in a roll shape.

Claims (1)

A release agent layer containing an antistatic agent composed of an alkali metal salt and a silicone-based release agent is formed on one surface of a base film made of a transparent resin.
After forming a pressure-sensitive adhesive layer formed by cross-linking a pressure-sensitive adhesive composition containing a (meth) acrylate copolymer obtained by copolymerizing a compound containing a polyoxyalkylene group on the other surface of the base film,
The base film is included in the release agent layer by winding the base film in a roll shape with the pressure-sensitive adhesive layer inside so that the release agent layer and the pressure-sensitive adhesive layer are in contact with each other. A method for producing an antistatic surface protective film, which comprises transferring a component of an antistatic agent composed of an alkali metal salt only to the surface of the pressure-sensitive adhesive layer.

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