JP2019218549A - Production method of antistatic surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be able to adhere to an optical film having an uneven surface, to have less contamination on an adherend, and to be excellent in that the low contamination property to an adherend does not change with time and does not deteriorate with time. Provided is a method for producing an antistatic surface protective film having peeling antistatic performance. SOLUTION: A release agent layer 2 containing an antistatic agent 3 made of an alkali metal salt and a silicone-based release agent is formed on one surface of a base film 1 made of a transparent resin, and a base material is formed. After forming a pressure-sensitive adhesive layer 4 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 film 1, a base material is formed. The alkali metal contained in the release agent layer 2 is formed by winding the film 1 in a roll shape with the pressure-sensitive adhesive layer 4 inside so that the release agent layer 2 and the pressure-sensitive adhesive layer 4 are in contact with each other. The component of the antistatic agent 3 made of salt is transferred only to the surface of the pressure-sensitive adhesive layer 4. [Selection diagram] Fig. 1

Description

The present invention relates to a surface protection film that is bonded to a surface of an optical component (hereinafter, also referred to as an optical film). More specifically, the present invention relates to a surface protective film that causes less contamination to an adherend and does not change its contamination property over time, and an optical component using the same. In addition, the present invention provides a method for protecting the surface even if the components of the polarizing plate as an optical component are replaced (change from a TAC film to an acrylic film or a polyester film, or from an aqueous adhesive to an ultraviolet curable adhesive). An object of the present invention is to provide a surface protective film in which a peeling voltage at the time of peeling a film is suppressed low, and an optical component to which the surface protective 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.

  Manufacture and transport optical films such as polarizers, retarders, lens films for displays, anti-reflection 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 stained or damaged in a later step. The appearance inspection of the optical film, which is a product, may be performed with the surface protective film adhered to the optical film in order to remove the surface protective film and increase the work efficiency by eliminating the labor for laminating again.

  2. Description of the Related Art Conventionally, a surface protection film provided with an adhesive layer on one surface of a substrate film has been generally used in a process of manufacturing an optical product in order to prevent adhesion of scratches and dirt. The surface protective film is bonded to the optical film via a slightly adhesive pressure-sensitive adhesive layer. The adhesive layer is made to have a slight adhesive strength because, when the used surface protection film is peeled off from the surface of the optical film and removed, the adhesive can be easily peeled off, and the adhesive is applied to the product to be adhered. This is to prevent the adhesive film from adhering and remaining on the optical film (so-called adhesive residue is prevented from being generated).

In recent years, in the production process of liquid crystal display panels, a driver for controlling a display screen of a liquid crystal display by a peeling voltage generated when a surface protective film bonded on an optical film is peeled off and removed. A phenomenon in which a circuit component such as an IC is destroyed and a phenomenon in which the alignment of liquid crystal molecules is damaged are occurring although the number of occurrences is small.
Further, in order to reduce the power consumption of the liquid crystal display panel, the driving voltage of the liquid crystal material has been lowered, and accordingly, the breakdown voltage of the driver IC has also been lowered. Recently, it has been required that the peeling voltage be within the range of +0.7 kV to -0.7 kV.

  A conventional polarizing plate is formed by bonding a triacetyl cellulose film (TAC film) with an aqueous adhesive to both sides of a polarizer made of polyvinyl alcohol (PVA) impregnated with iodine to protect the polarizer. In recent years, instead of using a TAC film, a polarizing plate using an acrylic film, a cyclic polyolefin film or a polyester film, or a polarizing plate using an ultraviolet-curing adhesive instead of an aqueous adhesive has also been used. It has become like that. Due to a change in the constituent material of the polarizing plate, there is also a problem that a peeling electrostatic voltage generated when the surface protective film is peeled off and removed becomes higher than when a polarizing plate having a conventional structure is used.

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

  On the other hand, some liquid crystal panel manufacturers evaluate the contamination of the surface protective film on the adherend by peeling off the surface protective film pasted on the optical film such as a polarizing plate once and introducing air bubbles. In this state, a heat treatment is performed on the re-bonded product under a predetermined condition, and then the surface protective film is peeled off and the surface of the adherend is observed. In such an evaluation method, even if the surface contamination of the adherend is minute, the difference in the surface contamination of the adherend between the part where the air bubbles are mixed and the part where the adhesive of the surface protective film is in contact with the adhesive. If there is, it remains as a mark of air bubbles (sometimes referred to as air bubble spots). Therefore, a very strict evaluation method is used 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 determination by such a strict evaluation method and that has very little contamination on the surface of the adherend.

  After bonding the surface protective film to the optical film as the adherend, the peeling voltage is applied to prevent a problem caused by a high peeling voltage, which occurs when the surface protecting film is peeled from the adherend. A surface protective film using a pressure-sensitive adhesive layer containing an antistatic agent to keep the film low has been proposed.

For example, Patent Document 1 discloses a surface protective film using an adhesive composed of an alkyltrimethylammonium salt, a hydroxyl group-containing acrylic polymer, and polyisocyanate.
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.
Patent Document 3 discloses an adhesive composition comprising an alkali metal salt treated with an acrylic polymer, a polyether polyol compound, and an anion-adsorbing compound, and a surface protective film using the same.
Patent Document 4 discloses a pressure-sensitive adhesive composition comprising 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.

JP 2005-131957 A JP-A-2005-330364 JP 2005-314476 A JP 2006-152235 A

  In the surface protection films described in Patent Documents 1 to 4, an antistatic agent is added inside the pressure-sensitive adhesive layer. Therefore, as the thickness of the pressure-sensitive adhesive layer increases, and as the elapsed time after bonding to the adherend passes, the pressure-sensitive adhesive layer adheres to the adherend to which the surface protective film has been bonded. The amount of the antistatic agent transferred to the body tended to increase. Further, when the amount of the antistatic agent transferred to the adherend increases, the appearance quality of the optical film as the adherend decreases, or when the FPR film is bonded, the adhesiveness of the FPR film decreases. there's a possibility that.

  Another problem arises when the thickness of the pressure-sensitive adhesive layer is reduced in order to reduce the change with time of the antistatic agent transferred from the pressure-sensitive adhesive layer to the adherend. For example, when used for an optical film with an uneven surface such as a polarizing plate that has been subjected to anti-glare treatment to prevent glare, bubbles may not be able to follow the unevenness of the surface of the optical film and bubbles may be mixed in. The adhesion area between the film and the pressure-sensitive adhesive layer is reduced, so that the adhesive strength is reduced, and there is a problem that the surface protective film floats or peels off during use.

  Also, in order to reduce the change with time of the antistatic agent migrating from the pressure-sensitive adhesive layer to the adherend, if the amount of the antistatic agent added to the pressure-sensitive adhesive layer is reduced, the surface protective film is peeled from the adherend. There is a danger that the peeling voltage generated when removing the semiconductor chip by removal increases, and a phenomenon that a circuit component such as a driver IC is destroyed or a phenomenon that the alignment of liquid crystal molecules is damaged occurs.

The present invention has been made in view of the above circumstances, and is a surface protection film to be bonded to the surface of an optical film, which can be bonded to an optical film having irregularities on the surface. It is an object of the present invention to provide a surface protective film that has very little contamination on an adherend and does not change in low contamination on an adherend over time, and an optical component using the same.
In addition, the present invention provides a method for protecting the surface even if the components of the polarizing plate as an optical component are replaced (change from a TAC film to an acrylic film or a polyester film, or from an aqueous adhesive to an ultraviolet curable adhesive). It is an object of the present invention to provide a surface protection film in which a peeling voltage at the time of peeling a film is suppressed low, and an optical component using the same.

The present inventors have conducted intensive studies to solve these problems. In order to reduce the contamination of the adherend and reduce the change with time of the contamination, it is necessary to reduce the content of the antistatic agent which is presumed to be the cause of the contamination of the adherend. However, when the content of the antistatic agent is reduced, the peeling voltage at the time of peeling the surface protective film from the adherend increases.
Therefore, the present inventors have studied a method for suppressing the peeling voltage when peeling the surface protective film from the adherend without increasing the content of the antistatic agent.

  The present inventors first applied a pressure-sensitive adhesive composition containing no antistatic agent, dried and laminated an adhesive layer on one surface of the substrate, and contained an antistatic agent on the other surface of the substrate. The surface protection film which laminated | stacked the release agent layer to perform was produced. Thereafter, the surface protective film is wound into a roll shape such that the pressure-sensitive adhesive layer is on the inside, whereby the components of the antistatic agent contained in the release agent layer are transferred to the surface of the pressure-sensitive adhesive layer. As a result, only the surface of the pressure-sensitive adhesive layer was present. After this surface protective film is once bonded to an optical film, which is an adherend, it has been found that the peeling electrostatic voltage when peeling from the adherend is suppressed low, and that the adherend is hardly contaminated. Thus, the present invention has been completed.

  The surface protective film of the present invention, on one side of the substrate, a pressure-sensitive adhesive composition containing no antistatic agent is applied and dried to laminate an adhesive layer, and the other surface of the substrate contains an antistatic agent. After laminating the release agent layer, the surface protective film is wound into a roll shape so that the pressure-sensitive adhesive layer is on the inside, so that the surface of the pressure-sensitive adhesive layer has a charge contained in the release agent layer. The components of the inhibitor are transferred. The present invention, when the surface protective film wound in a roll shape is unwound from the roll shape and bonded to an adherend, the contamination on the adherend is suppressed to a low level, and The technical idea is to suppress the peeling voltage when peeling the surface protective film from a certain optical film.

  In order to solve the above problems, the present invention has a release agent layer formed on one surface of a substrate film made of a transparent resin, and an adhesive layer on the other surface of the substrate film. A surface protective film formed, wherein the surface protective film is a roll body wound in a roll shape with the pressure-sensitive adhesive layer inside, and the release agent layer in a radial direction of the roll body. And the pressure-sensitive adhesive layer are in contact with each other, and the pressure-sensitive adhesive layer is formed by crosslinking a pressure-sensitive adhesive composition containing a (meth) acrylate copolymer obtained by copolymerizing a compound containing a polyoxyalkylene group. An adhesive layer, wherein the release agent layer contains an antistatic agent composed of an alkali metal salt and a silicone-based release agent, and the antistatic agent composed of the alkali metal salt contained in the release agent layer. The ingredient is The component of the antistatic agent is transferred to the surface of the adhesive layer only in the surface of the pressure-sensitive adhesive layer, and the surface protective film of the roll is unwound from the roll to adhere to the adherend. When adhered to, the adhesive strength of the surface protective film to the surface of the adherend, measured based on the "method for measuring adhesive strength of surface protective film" described below, is 0.03 to 0.3 N / 25 mm is provided.

A method for measuring the adhesive strength of the surface protective film: a polarizing plate (AG-A) having an anti-glare and low-reflection treatment, in which an acrylic film is bonded to a polarizer (polyvinyl alcohol film containing iodine) using an ultraviolet curable adhesive. LR polarizing plate) as the adherend, 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 film was stored in a test environment of 23 ° C. × 50% RH for 1 day, and then peeled at 180 ° at a peeling rate of 300 mm / min using a tensile tester. In the direction, the strength when the surface protective film was peeled was measured, and this was defined as the adhesive strength (N / 25 mm).

  Further, it is preferable that the surface potential when the pressure-sensitive adhesive layer is peeled off from the optical film as the 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 above-mentioned surface protective film is bonded via the pressure-sensitive adhesive layer.

The surface protective film of the present invention is a surface protective film bonded to the surface of an optical film, and can be bonded to an optical film having irregularities on the surface.
Further, according to the present invention, it is possible to provide a surface protective film that causes very little contamination on an adherend and does not change its contamination property over time, and an optical component using the same.
Furthermore, according to the present invention, the constituent members of the polarizing plate, which is an optical component, change (change from a TAC film to an acrylic film, a cyclic polyolefin film or a polyester film, or change from a water-based adhesive to an ultraviolet curable adhesive). Even so, it is possible to provide a surface protection film in which the peeling voltage when peeling off the surface protection film is suppressed, and an optical component using the same.
Further, the surface protective film wound into a roll of the present invention, a substrate film, such that the release agent layer and the adhesive layer are in contact with each other, the surface protective film wound in a roll shape with the adhesive layer inside. Wherein the component of the antistatic agent comprising the alkali metal salt is transferred from the release agent layer to the surface of the pressure-sensitive adhesive layer, and is present only on the surface of the pressure-sensitive adhesive layer.
That is, in the present invention, after laminating the surface protective film unwound from the surface protective film wound into a roll to the adherend, the peeling voltage when the surface protective film is peeled from the adherend is reduced. In addition, since there is little change with time of the antistatic property for peeling and contamination to the adherend, it has a feature that the productivity of the optical component as the adherend and the yield can be improved. .

FIG. 2 is a conceptual cross-sectional view showing a surface protective film in a state of being wound into a roll according to the present invention. It is a conceptual sectional view showing the state where the release agent layer and the pressure-sensitive adhesive layer were in contact with each other in a state where the surface protective film of the present invention was wound in a roll shape. It is sectional drawing which shows one of the Examples which stuck the surface protective film of this invention to an optical component.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is a conceptual sectional view showing a surface protective film 10 in a state of being wound into a roll according to the present invention. The surface protection film 10 in the state of being wound into a roll as shown on the right side of FIG. 1 is obtained by winding the surface protection film 5 according to the present invention into a roll with the pressure-sensitive adhesive layer 4 inside (the surface protection film). 5 roll body). The left side of FIG. 1 is a conceptual sectional view showing the surface protective film 5 unwound from the roll shape in the direction of the arrow, 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 a transparent substrate film 1, and an adhesive layer on the other surface of the substrate film 1. The agent layer 4 is formed. The surface protective film 5 having the release agent layer 2 on one surface of the base film 1 and the adhesive layer 4 on the other surface of the base film is brought into contact with the release agent layer 2 and the adhesive layer 4. As described above, by winding the 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 adhesive layer 4. The surface protective film 10 existing only on the surface and wound in a roll is obtained.

As the base film 1 used for the surface protection film 5 according to the present invention, a base film made of a resin having transparency and flexibility is used. Thereby, the appearance inspection of the optical component can be performed in a state where the surface protection film 5 is bonded to the optical component as the adherend. As the film made of a resin having transparency used as the base film 1, a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and 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 necessary strength and optical suitability. The base film 1 may be a non-stretched film or a uniaxially or biaxially stretched film. Further, the stretching ratio of the stretched film and the orientation angle in the axial direction formed along with the crystallization of the stretched film may be controlled to specific values.
The thickness of the base film 1 used for the surface protective film 5 according to the present invention is not particularly limited, but for example, a thickness of about 12 to 100 μm is preferable, and a thickness of about 20 to 75 μm is easy to handle. preferable.
If necessary, the surface of the base film 1 may be subjected to a surface modification by corona discharge or an easy adhesion treatment such as application of an anchor coating agent.

  The release agent layer 2 formed on the surface protection film 5 according to the present invention is formed using a release agent containing an antistatic agent 3 composed of an alkali metal salt. As the release agent, a silicone release agent is preferably used.

  Examples of the silicone-based release agent include known silicone-based release agents such as an addition reaction type, a condensation reaction type, a cationic polymerization type, and a radical polymerization type. Products commercially available as addition-reaction silicone-based release agents include, for example, 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, LTC-310 (manufactured by Toray Dow Corning Co., Ltd.). Examples of commercially available products of the condensation reaction type include SRX-290 and SYLOFF-23 (manufactured by Toray Dow Corning Co., Ltd.). Products commercially available as a cationic polymerization type include, for example, TPR-6501, TPR-6500, UV9300, VU9315, UV9430 (manufactured by Momentive Performance Materials, Inc.), X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.) ). Examples of products commercially available as a radical polymerization type include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.).

  The antistatic agent 3 contained in the release agent layer 2 preferably has good dispersibility in a silicone release agent solution and does not hinder the curing of the silicone release agent. Further, the component of the antistatic agent 3 contained in the release agent layer 2 is transferred to the surface of the adhesive layer 4 which is in contact with the release agent layer 2, and the surface of the adhesive layer 4 has an antistatic function. In order to impart an antistatic property, an antistatic agent that does not react with the silicone-based release agent is preferred. As such an antistatic agent, an alkali metal salt is preferable.

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

  The amount of the antistatic agent to be 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 the desired release when the surface protective film is released from the adherend. What is necessary is just to set in consideration of charged voltage, the contamination property with respect to an adherend, the adhesive property, etc. 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 a solid content of the antistatic agent with respect to 100 of the solid content of the silicone-based release agent. Value, and more preferably a ratio of 5 to 60. When the addition amount of the antistatic agent in terms of solid content is less than 5 relative to 100 of the solid content of the silicone-based release agent, the amount of the antistatic agent transferred to the surface of the pressure-sensitive adhesive layer also decreases, and It is difficult to exhibit the antistatic function. When the amount of the antistatic agent in terms of solids exceeds 100 relative to the solids of the silicone-based release agent, the components of the silicone-based release agent together with the antistatic agent are also added to the surface of the pressure-sensitive adhesive layer. Because of the transfer, there is a possibility that the adhesive property of the adhesive is reduced.

  The release agent layer 2 includes 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 mixed. 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 in an organic solvent in advance, adding and mixing a catalyst, and then 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 for assisting an antistatic effect such as a compound containing a polyoxyalkylene group, and a cellulose compound as necessary. And a material for adjusting the slipperiness.

  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, Meyer bar coating, and air knife coating can be used.

In the pressure-sensitive adhesive layer 4 formed on the surface protection 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 (other than the surface) of the pressure-sensitive adhesive layer 4. Exists only on the surface of the pressure-sensitive adhesive layer 4. Thereby, it is possible to suppress a change with time in the anti-peeling property of the surface protective film 5 and contamination of the adherend.
The pressure-sensitive adhesive layer 4 formed on the surface protective film 5 according to the present invention is 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. It is not particularly limited. Considering that the durability after bonding the surface protective film 5 according to the present invention to the optical film is required, it is an acrylic pressure-sensitive adhesive layer obtained by crosslinking a (meth) acrylate copolymer. Is preferred.

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

  Further, a compound containing a polyoxyalkylene group may be copolymerized or mixed with the (meth) acrylate copolymer. Examples of the compound containing a copolymerizable polyoxyalkylene group include polyethylene glycol (400) monoacrylate, polyethylene glycol (400) monomethacrylate, methoxypolyethylene glycol (400) acrylate, and methoxypolyethylene glycol (400) methacrylate. And polypropylene glycol (400) monoacrylate, polypropylene glycol (400) monomethacrylate, methoxy polypropylene glycol (400) acrylate, and methoxy polypropylene glycol (400) methacrylate. An adhesive comprising a polyoxyalkylene group-containing copolymer is obtained by copolymerizing these polyoxyalkylene group-containing monomers with the main monomer or functional monomer of the (meth) acrylate copolymer. be able to.

  As the compound containing a polyoxyalkylene group which can be mixed with the (meth) acrylate copolymer, a (meth) acrylate copolymer containing a polyoxyalkylene group is preferable, and a (meth) acryl containing a polyoxyalkylene group is preferred. Polymers of the system monomers are more preferable. For example, 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, methoxypolypropylene Polymers, such as 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 has been added can be obtained.

  Examples of the curing agent added to the pressure-sensitive adhesive layer 4 include a crosslinking agent for crosslinking the (meth) acrylate copolymer, such as an isocyanate compound, an epoxy compound, a melamine compound, and a metal chelate compound. Examples of the tackifier include rosin, coumarone-indene, terpene, petroleum, and phenol.

  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, for example, preferably about 5 to 40 μm, more preferably about 10 to 30 μm. 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, and the adhesive layer 4 having a slight adhesive strength is determined from the adherend to the surface. It is preferable because the operability when peeling the protective film is excellent.

  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, Meyer 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, amount and the like of the antistatic agent 3 contained in the release agent layer 2. The type and amount of the antistatic agent 3 in the release agent layer 2 in consideration of the surface contamination of the optical film as the adherend after the surface protective film 5 is peeled from the optical film as the adherend. Can be adjusted.

  FIG. 2 is a conceptual cross-sectional view showing a state where the release agent layer 2 and the pressure-sensitive adhesive layer 4 are in contact with each other in a state where the surface protection 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 a 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 protection film 5 thus formed into a surface protection film 10 wound in a roll with the pressure-sensitive adhesive layer 4 inside, the release agent layer 2 and the pressure-sensitive adhesive layer 4 in the radial direction of the roll body. Is in contact with. Thereby, a part of the component 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 protection film 5 drawn out from the surface protection film 10 wound in a roll shape thus obtained is bonded to the optical component 6. The components of the antistatic agent 3 are transferred from the release agent layer 2 to the surface of the pressure-sensitive adhesive layer 4, so that the surface protection film 5 can be compared with the pressure-sensitive adhesive layer 4 before transferring the components of the antistatic agent 3. After bonding to the adherend, the peeling voltage at the time of peeling the surface protective film 5 from the adherend is reduced. In addition, the peeling electrostatic voltage at the time of peeling the surface protective film 5 of FIG. 1 from the adherend can be measured by a known method. For example, after bonding the surface protective film 5 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). The maximum value of the absolute value of the surface potential when the surface potential of the body surface is measured every 10 ms using a surface potentiometer (manufactured by Keyence Corporation) is measured as a peeling voltage (kV).

  In the surface protective film 10 wound into a roll according to the present invention, the surface protective film 5 rewound from the roll was transferred to the surface of the pressure-sensitive adhesive layer 4 when the surface protective film 5 was bonded to an adherend. The antistatic agent 3 comes into contact with the surface of the adherend. Thereby, the peeling voltage when peeling the surface protection film 5 from the adherend again can be suppressed low. Further, in the surface protective film 10 wound in a roll shape according to the present invention, since the release agent layer 2 is on the outside and the adhesive layer 4 is on the inside, the surface of the adhesive layer 4 is in a roll state. , Protected without being exposed. Since the release agent layer 2 is integrated with the base film 1 even after the surface protection film 5 is unwound from the roll, removal and disposal of the release agent layer 2 are unnecessary.

  FIG. 3 is a cross-sectional view showing an optical component 7 with a surface protection film as one of examples in which the surface protection film 5 of the present invention is bonded to an optical component. The optical component 7 with the surface protection film is drawn out from the surface protection film 10 in a state where the surface protection film 5 of the present invention is wound in a roll shape, and the optical component 6 as an adherend is passed through the adhesive layer 4. Obtained by laminating. Examples of the optical component 6 include optical films such as a polarizing plate, a retardation plate, a lens film, a polarizing plate also serving as a retardation plate, and a polarizing plate also serving as a lens film. Such an optical component is used as a constituent member of a liquid crystal display device such as a liquid crystal display panel, an optical system device of various instruments, and the like. Examples of the optical component include optical films such as an antireflection film, a hard coat film, and a transparent conductive film for a touch panel.

  After the surface protective film 5 of the present invention is unwound from the surface protective film 10 wound in a roll, and is bonded to an optical component (optical film) as an adherend, the surface protective film 5 is removed from the adherend. When peeling is removed, the peeling voltage can be suppressed sufficiently low. Therefore, there is no possibility that circuit components such as a driver IC, a TFT element, and a gate line driving circuit will be destroyed, and the production efficiency in the process of manufacturing a liquid crystal display panel or the like can be increased, and the reliability of the production process can be maintained.

  Next, the present invention will be described in more detail with reference to examples.

(Example 1)
(Preparation of surface protection film)
5 parts by weight of addition reaction type silicone (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-345), 0.75 parts by weight of lithium bis (fluorosulfonyl) imide, 95 parts by weight of a 1: 1 mixed solvent of toluene and ethyl acetate And 0.05 parts by weight of a platinum catalyst (manufactured by Toray Dow Corning Co., Ltd., product name: SRX-212) were mixed, stirred and mixed to prepare a coating material for forming the release agent layer of Example 1.
On the other hand, based on 90 parts by weight of 2-ethylhexyl acrylate, 7 parts by weight of methoxypolyethylene glycol (400) methacrylate, and 100 parts by weight of a 40% ethyl acetate solution of an adhesive comprising a copolymer of 3 parts by weight of 2-hydroxyethyl acrylate, An adhesive composition of Example 1 was prepared by stirring and mixing 2 parts by weight of an isocyanate-based curing agent (Coronate (registered trademark) HX manufactured by Tosoh Corporation).
A 38 μm thick polyethylene terephthalate film surface was coated with a paint for forming a release agent layer of Example 1 using a Mayer bar so as to have a dry thickness of 0.2 μm, and a hot air circulating oven at 120 ° C. For 1 minute to form a release agent layer. Next, the prepared pressure-sensitive adhesive composition is applied to the surface of the polyethylene terephthalate film on which the release agent layer is not formed so that the thickness after drying becomes 20 μm, and then the coated composition is heated in a hot-air circulation oven at 100 ° C. for 2 minutes. It was dried to form an adhesive layer. Thereafter, the obtained film in which a release agent layer is formed on one surface of the base film and an adhesive layer is formed on the other surface, so that the release agent layer and the adhesive layer are in contact with each other, The layer was wound in a roll with the layer inside. The obtained pressure-sensitive adhesive film wound into a roll was kept at 40 ° C. for 5 days to cure the pressure-sensitive adhesive layer, thereby obtaining a surface protective film wound in a roll of Example 1.

(Example 2)
Except that the thickness after drying of the paint for forming the release agent layer of Example 1 was changed to 0.1 μm, the surface protective film in a state of being wound into a roll of Example 2 was prepared in the same manner as in Example 1. Obtained.

(Example 3)
The addition reaction type silicone of Example 1 was manufactured by Toray Dow Corning Co., Ltd. under the trade name of SRX-211, except that lithium bis (trifluorosulfonyl) imide was replaced with lithium bis (trifluoromethanesulfonyl) imide. In the same manner as in Example 1, a surface protective film wound in a roll shape in Example 3 was obtained.

(Comparative Example 1)
A surface protective film wound in a roll 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, except that 0.67 parts by weight of lithium bis (fluorosulfonyl) imide was added to the adhesive side with respect to 100 parts by weight of a 40% ethyl acetate solution. In the same manner as in Example 1, a surface protective film wound in a roll shape of Comparative Example 2 was obtained.

Hereinafter, the method and results of the evaluation test will be described.
<Measurement method for developing force of surface protective film>
A sample of the unwound surface protection film is cut out from the rolled surface protection film in a state of two layers, and cut into a width of 50 mm and a length of 150 mm. Under a test environment of 23 ° C. × 50% RH, the strength at the time of peeling was measured in a direction of 180 ° at a peeling speed of 300 mm / min using a tensile tester, and this was measured for the developing force (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 protection film sample unwound from the roll shape was measured using a high-performance high resistivity meter (Hyresta (registered trademark) manufactured by Mitsubishi Chemical Analytech Co., Ltd.) (UP) using an applied voltage of 100 V and a measurement time of 30 seconds.

<Method of measuring adhesive strength of surface protective film>
An antiglare low-reflection polarizing plate (AG-LR polarizing plate) in which an acrylic film was bonded to a polarizer (a polyvinyl alcohol film containing iodine) using an ultraviolet-curable adhesive was used as an adherend. . This polarizing plate was bonded to the surface of a glass plate with a double-sided adhesive tape using a bonding machine. Thereafter, a surface protective film cut to a width of 25 mm was bonded to the acrylic film on the surface of the polarizing plate, and then stored for one day in a test environment of 23 ° C. × 50% RH. Thereafter, the strength when the surface protective film was peeled was measured in a 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 voltage of surface protective film>
An antiglare low-reflection polarizing plate (AG-LR polarizing plate) in which an acrylic film was bonded to a polarizer (a polyvinyl alcohol film containing iodine) using an ultraviolet-curable adhesive was used as an adherend. . This polarizing plate was bonded to the surface of a glass plate with a double-sided adhesive tape using a bonding machine. Thereafter, a surface protective film cut to a width of 25 mm was bonded to the acrylic film on the surface of the polarizing plate, and then stored for one day in a test environment of 23 ° C. × 50% RH. Then, the surface potential of the polarizing plate surface was measured using a surface potentiometer (manufactured by Keyence Corporation) while peeling off the surface protective film at a peeling speed of 40 m / min using a high-speed peeling tester (manufactured by Tester Sangyo). The maximum value of the absolute value of the surface potential measured every 10 ms was defined as the peeling voltage (kV).

<Method of confirming surface contamination of surface protective film>
An antiglare low-reflection polarizing plate (AG-LR polarizing plate) in which an acrylic film was bonded to a polarizer (a polyvinyl alcohol film containing iodine) using an ultraviolet-curable adhesive was used as an adherend. . This polarizing plate was bonded to the surface of a glass plate with a double-sided adhesive tape using a bonding machine. Thereafter, a surface protective film cut to a width of 25 mm was bonded to the acrylic film on the surface of the polarizing plate, and stored for 3 days and 30 days in a test environment of 23 ° C. × 50% RH. Thereafter, 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. As a criterion for determining the surface contamination, a case where no contamination was transferred to the polarizing plate was indicated by (○), and a case where contamination was transferred to the polarizing plate was confirmed (×).

Table 1 shows the measurement results of the obtained surface protective films of Examples 1 to 3 and Comparative Examples 1 and 2 which were wound into a roll. "2EHA" is 2-ethylhexyl acrylate, "HEA" is 2-hydroxyethyl acrylate, "# 400G" is methoxypolyethylene glycol (400) methacrylate, and "AS agent (1)" is lithium bis (fluorosulfonyl). ) Imide, "AS agent (2)" is lithium bis (trifluoromethanesulfonyl) imide, "SRX-345" is SRX-345, "SRX-211" is SRX-211 and "SRX212" is platinum. The catalyst SRX-212 means each. Further, “4.2E11” of the surface resistivity is 4.2 × 10 ¹¹ , and “over range” means that the measurement limit of the measuring machine is exceeded, and 1.0 × 10 ¹³ Ω / □ or more. means.

The following can be seen from the measurement results shown in Table 1.
The surface protection film in the state of being wound into a roll of Examples 1 to 3 according to the present invention has an appropriate adhesive force when used after being rewound from the roll, and contamination on the surface of the adherend is reduced. Absent. In addition, even when the adherend is a polarizing plate using an acrylic film, the peel protection voltage is low when the surface protective film is once adhered to the adherend and then peeled off from the adherend.
On the other hand, the surface protective film wound in a roll of Comparative Example 1 in which the antistatic agent was not added to the release agent layer was obtained by applying the surface protective film rewound from the roll to the adherend once. After the combination, the peeling electrostatic voltage at the time of peeling from the adherend increased. Further, in place of containing the antistatic agent in the release agent layer, the surface protective film in the state of being wound into a roll in Comparative Example 2 in which the antistatic agent was contained in the pressure-sensitive adhesive layer was wound from a roll. Once the returned surface protective film is once adhered to the adherend, the peeling voltage when peeling off the adherend is low and good, but contamination of the adherend after peeling off the surface protective film Increased.
That is, it is difficult for the surface protective films of Comparative Examples 1 and 2 wound in a roll shape to achieve both a reduction in the peeling voltage and a low contamination property on the adherend. On the other hand, the surface protection film in the state wound in a roll of Examples 1 to 3 in which an antistatic agent was added to the release agent layer and the components of the antistatic agent were transferred only to the surface of the pressure-sensitive adhesive layer was a release band. The compatibility between the reduction of the voltage and the low contamination of the adherend was good.

  The surface protective film of the present invention is, for example, a polarizing plate, a retardation plate, a lens film, an antireflection film, a hard coat film, an optical film such as a transparent conductive film, and other, in the production process of various optical components and the like It can be used to protect the surface by bonding to the surface of the optical component or the like. In addition, the surface protective film of the present invention can suppress the peeling electrostatic voltage generated when the surface protective film is peeled off from the adherend after being bonded to the optical component (optical film) as the adherend, and In addition, there is little change with time in the antistatic property of peeling and contamination on the adherend, and the yield of the production process can be improved, which is of great industrial utility value.

DESCRIPTION OF SYMBOLS 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 protection film wound in a roll.

Claims (1)

On one surface of a substrate film made of a resin having transparency, an antistatic agent made of an alkali metal salt and a release agent layer containing a silicone-based release agent are formed,
After forming a pressure-sensitive adhesive layer formed by crosslinking 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 being wound into a roll to form a roll so that the pressure-sensitive adhesive layer is on the 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, wherein a component of the antistatic agent comprising an alkali metal salt is transferred only to the surface of the pressure-sensitive adhesive layer.

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