JP2005200607A - Surface protecting film for optical use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protecting film for optical uses, which is prepared by forming an antifouling treatment layer on one side of a polyester film and by forming an adhesive layer on the other side of the polyester film, further having an antistatic layer, wherein the antifouling treatment layer is a homogeneous layer and can retain an antistatic effect even when wiping off the matters stuck thereon. <P>SOLUTION: The protecting film for optical uses is prepared by forming the antifouling treatment layer on one side of an polyester film and by forming the adhesive layer on the other side of the polyester film, wherein the polyester film is subjected to no surface treatment. The antistatic layer composed of a material containing an antistatic agent and a polyester-based binder, is formed between the polyester film and the adhesive layer, and the adhesive layer is composed of an acrylic adhesive containing an acrylic polymer having an acid as a functional group, an epoxy-based crosslinking agent and an isocyanate crosslinking agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical surface protective film. The optical surface protective film of the present invention is used for protecting various optical film surfaces such as polarizing plates and retardation plates. Further, it is used to protect various image display devices such as a liquid crystal display device and other organic EL display devices and PDPs by sticking to the surface of the liquid crystal display plate.

  Specifically, the optical surface protective film protects the optical film when the optical film manufacturer such as a polarizing plate is shipped, and manufactures a display device (liquid crystal module) when manufacturing the image display device such as a liquid crystal display device. It is used for the purpose of protecting the optical film during the process, and further for the purpose of protecting the optical film in various steps.

  An optical film such as a polarizing plate is used for the liquid crystal display panel. A surface protective film is generally attached to the surface of the polarizing plate in order to protect the surface of the polarizing plate until the liquid crystal cell is assembled. Conventionally, the surface protective film has a biaxially stretched polyester film (polyethylene terephthalate film or the like) having a light-peelable pressure-sensitive adhesive layer that is releasably attached to the polarizing plate surface. As the pressure-sensitive adhesive layer, for example, many layers formed by applying an acrylic pressure-sensitive adhesive have been used.

  An optical film such as a polarizing plate is used as an optical film with an adhesive provided with an adhesive layer. When applying a surface protection film to such an optical film with an adhesive and punching it in a laminated state, a polarizing plate or the like is used on the back side of the surface protective film (the opposite side provided with the adhesive layer). Adhesives used are attached. Therefore, an antifouling treatment layer is provided on the back side of the surface protective film for facilitating the removal of the adhesive and the like. Moreover, the surface protection film is generally provided with an antistatic layer for preventing static electricity on the back side of the surface protection film. The antistatic layer is usually provided between the film substrate and the antifouling layer (see Patent Document 1).

However, in the surface protective film provided with the antifouling treatment layer and the antistatic layer on the back side, when wiping off the material attached to the antifouling treatment layer, the antistatic layer may be wiped off at the same time. There was a problem that the surface protective film had no antistatic effect.
JP 2001-209039 A

  The present invention is an optical surface protective film having an antifouling treatment layer on one side of a polyester film and an adhesive layer on the opposite side, and further having an antistatic layer, and is a uniform layer as an antifouling treatment layer It is an object of the present invention to provide an optical surface protective film that can maintain an antistatic effect even when it is wiped off what has adhered to the antifouling treatment layer.

  Another object of the present invention is to provide an optical film with an optical surface protective film to which the optical surface protective film is attached. Furthermore, an object of the present invention is to provide an image display device with an optical surface protective film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by an optical surface protective film shown below, and have solved the present invention.

That is, the present invention is an optical surface protection film in which an antifouling treatment layer is provided on one side of the polyester film, and an adhesive layer is provided on the opposite side,
The polyester film is not subjected to surface treatment,
An antistatic layer formed of a material containing an antistatic agent and a polyester-based binder is provided between the polyester film and the pressure-sensitive adhesive layer.
The present invention relates to an optical surface protective film, wherein the pressure-sensitive adhesive layer is formed of an acrylic polymer containing an acid as a functional group, and an acrylic pressure-sensitive adhesive containing an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent.

  In order to solve the above-mentioned problems, the present inventors tried to provide an antistatic layer between the polyester film and the pressure-sensitive adhesive layer. However, the adhesion between the polyester film and the antistatic layer is not sufficient, and the antistatic effect cannot be maintained. On the other hand, in order to improve the adhesion between the polyester film and the antistatic layer, when the surface of the polyester film is subjected to a corona treatment or the like, the polyester film itself is charged by the corona treatment or the like, and the antifouling treatment is performed. The layer cannot be applied uniformly. Therefore, the effect of both the antifouling treatment layer and the antistatic layer cannot be maintained simply by providing the antistatic layer between the polyester film and the pressure-sensitive adhesive layer.

  As a result of the above studies, the present inventors have developed the optical surface protective film. The optical surface protective film of the present invention uses a base material that is not subjected to a surface treatment such as a corona treatment as a polyester film. Thereby, a uniform antifouling treatment layer can be applied. On the other hand, by forming an antistatic layer with a material containing an antistatic agent and a polyester binder, it is possible to improve the adhesion between the antistatic layer and the polyester film even if the polyester film is not surface-treated. The antistatic effect can be maintained even when the material attached to the antifouling layer is wiped off. Furthermore, the adhesion between the antistatic layer and the pressure-sensitive adhesive layer is formed by forming a pressure-sensitive adhesive layer with an acrylic pressure-sensitive adhesive containing an acrylic polymer containing an acid as a functional group and an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. The antistatic effect can be maintained. Such a pressure-sensitive adhesive layer can be designed to have good peelability.

  The optical surface protective film is suitably used for various optical films, but is particularly suitable for protecting the surface of a polarizing plate.

  The present invention also relates to an optical film with an optical surface protective film, wherein the optical surface protective film is attached to an optical film.

  Furthermore, the present invention relates to an image display device with an optical surface protective film, wherein the optical surface protective film is attached to an image display device.

  Hereinafter, the optical surface protective film of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical surface protective film of the present invention is provided with an antifouling treatment layer 2 on one side of a polyester film 1 that has not been subjected to a surface treatment, and an adhesive layer 3 on the opposite side. An antistatic layer 4 is provided between the polyester film 1 and the pressure-sensitive adhesive layer 3. The optical surface protective film of the present invention can be used as a sheet.

  The polyester film 1 is not subjected to surface treatment such as corona treatment. Examples of the polyester include polyethylene terephthalate and polyethylene naphthalate. Of these, polyethylene terephthalate is preferred. A stretched product such as a uniaxial or biaxial polyester film can also be used. The thickness of the polyester film is not particularly limited, but is preferably about 10 to 200 μm, particularly preferably 20 to 50 μm.

  For the formation of the antifouling treatment layer 2, various antifouling treatment agents such as a long-chain alkyl type and a silicone type can be appropriately used. Long-chain alkyl antifouling treatment agents include long-chain alkyl acrylate copolymers, long-chain alkyl vinyl ester copolymers, long-chain alkyl vinyl ether copolymers, long-chain alkyl acrylamide copolymers, maleic acid It is preferable to use a long-chain alkyl derivative copolymer, a long-chain alkyl esterified product of a hydroxyl group-containing polymer, a long-chain alkyl carbamate of a hydroxyl group-containing polymer, and the like. preferable. As the silicone-based antifouling treatment agent, either a condensation type silicone type or an addition type silicone type can be used.

  The antifouling treatment agent is diluted with a solvent such as toluene, ethyl acetate, or methyl ethyl ketone, and then applied to the polyester film 1 and dried to form the antifouling treatment layer 2. The thickness (dry film thickness) of the antifouling treatment layer 2 is not particularly limited, but is preferably about 10 to 1000 nm, particularly preferably 10 to 500 nm.

  The antistatic layer 4 is formed of an antistatic material containing an antistatic agent and a polyester binder. By using the polyester-based binder, the obtained antistatic layer 4 can improve the adhesion even to the polyester film 1 that has not been subjected to a surface treatment such as a corona treatment.

  As the antistatic agent, various materials known as antistatic agents for polymer materials can be used. For example, cationic (for example, quaternary ammonium salt type, phosphonium salt type, sulfonium salt type, etc.), anionic type (carboxylic acid type, sulfonate type, sulfate type, phosphate type, phosphite type, etc.), amphoteric ion type (sulfo type) Various interfaces of betaine type, alkyl betaine type, alkyl imidazolium betaine type) or nonionic type (polyhydric alcohol derivative, β-cyclodextrin inclusion compound, sorbitan fatty acid monoester / diester, polyalkylene oxide derivative, amine oxide, etc.) Activating agent: single weight of a monomer having an ion conductive group of cationic type (quaternary ammonium salt etc.), amphoteric ion type (betaine compound etc.), anion type (sulfonate salt etc.) or nonionic type (glycerin etc.) Copolymer or co-weight of the monomer and other monomers Polymer having ion conductivity such as a polymer having a site derived from an acrylate or methacrylate having a quaternary ammonium base; a type in which a hydrophilic polymer such as a polyethylene methacrylate copolymer is alloyed with an acrylic resin or the like Permanent antistatic agent: acetylene black, ketjen black, natural graphite, artificial graphite, titanium black, zinc oxide, tin oxide, tin-coated titanium oxide, nickel flakes, phosphorus-doped tin oxide, antimony-doped tin oxide, etc. And the like. Among these antistatic agents, conductive fillers of metal compounds such as tin oxide and acrylic polymers containing quaternary ammonium salts are preferably used from the viewpoint of antistatic performance.

  The polyester binder is not particularly limited, and a polyester binder obtained by dehydrating and condensing various polybasic acid components and polyol components by a known means can be used.

  Polybasic acid components include aromatic dibasic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 5-sulfo (salt) isophthalic acid; succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid Aliphatic dibasic acids such as decane dicarboxylic acid, dodecanedioic acid, eicosane diacid, octadecanedicarboxylic acid; hexahydrophthalic acid, methylhexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid Alicyclic dibasic acids such as fumaric acid, dimer acid, α-, ω-1,2-polybutadienedicarboxylic acid, 7,12-dimethyl-7,11-octadecadien-1,18-dicarboxylic acid, etc. Dibasic acid having an unsaturated double bond or its hydride, 8,9-diphenylhexadecanedioic acid, trimellitic acid Polybasic acids other than the above can be mentioned. Examples of the polybasic acid component include acid anhydrides of the polybasic acid component and reactive derivatives such as dimethyl terephthalate.

  Examples of the polyol component include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol. 1,6-hexanediol, 1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol -L, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, α-, ω-1,2-polybutadiene glycol, bisphenol A, bisphenol F or a hydride thereof.

  In addition, the polyester resin may contain lactones, such as caprolactone, and hydroxycarboxylic acids, such as 4-hydroxybenzoic acid, in part or all. The weight average molecular weight of the polyester resin is not particularly limited, but is preferably 1000 to 10,000.

  The blending amount of the antistatic agent with respect to the polyester binder is usually 50 to 400 parts by weight, preferably 100 to 300 parts by weight with respect to 100 parts by weight of the polyester binder.

  The antistatic layer 4 is formed by diluting an antistatic material containing an antistatic agent and a polyester binder with a solvent such as water or alcohol, and then applying and drying the polyester film 1 to form the antistatic layer 4. To do. The thickness (dry film thickness) of the antistatic layer 4 is not particularly limited, but is preferably about 50 to 500 nm, particularly preferably 80 to 300 nm.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 3 is an acrylic pressure-sensitive adhesive containing an acrylic polymer containing an acid as a functional group, and an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in view of the balance of transparency, cohesiveness, and release characteristics. Is used.

  The acrylic polymer contains a monomer containing an alkyl (meth) acrylate and an acid as a monomer unit. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. These can be used alone or in combination.

  Moreover, as a monomer containing an acid, carboxyl group-containing monomers, such as (meth) acrylic acid, itaconic acid, maleic acid, or these anhydrides can be illustrated. The monomer containing an acid gives a reaction point by crosslinking or the like. The ratio of the monomer containing an acid is about 1 to 10 parts by weight, preferably 2 to 6 parts by weight, based on 100 parts by weight of alkyl (meth) acrylate.

  In addition, in order to further impart polarity to the resulting acrylic polymer, hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; amide group-containing monomers such as N-methylolacrylamide Cyano group-containing monomers such as (meth) acrylonitrile; epoxy group-containing monomers such as glycidyl (meth) acrylate; vinyl esters such as vinyl acetate; styrene monomers such as styrene and α-methylstyrene Etc. can be used as copolymerization monomers.

  The polymerization method for the acrylic polymer is not particularly limited, and a known polymerization method such as solution polymerization, emulsion polymerization, suspension polymerization, or UV polymerization can be employed. The acrylic polymer preferably has a weight average molecular weight of about 300,000 to 2.5 million.

  As the crosslinking agent, an epoxy crosslinking agent and an isocyanate crosslinking agent are used in combination. The epoxy crosslinking agent imparts cohesiveness to the pressure-sensitive adhesive layer 3, and the isocyanate crosslinking agent is used to impart adhesion to the antistatic layer 4. Only with the isocyanate-based crosslinking agent, the cohesiveness of the pressure-sensitive adhesive layer 3 cannot be maintained, and there is a possibility of heavy peeling or adhesive residue. Moreover, only with an epoxy-type crosslinking agent, adhesiveness with the antistatic layer 4 using a polyester-type binder cannot be obtained.

  As an epoxy type crosslinking agent, a polyfunctional epoxy compound is used, and various compounds having two or more epoxy groups in the molecule are included. Typical examples include sorbitol tetraglycidyl ether, trimethylolpropane glycidyl ether, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidyl-m-xylenediamine, and triglycidyl-p-aminophenol. It is done. The number of blended parts of the epoxy crosslinking agent is generally about 1 to 8 parts by weight with respect to 100 parts by weight of the acrylic polymer, although it depends on the amount of acid introduced into the acrylic polymer and the structure of the epoxy crosslinking agent. Is preferably 1-6 parts by weight.

  Moreover, as an isocyanate type crosslinking agent, a polyfunctional isocyanate compound is used, and various compounds having two or more isocyanate groups in the molecule are included. Typical examples thereof include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate and the like. What is necessary is just to mix | blend the compounding part number of an isocyanate type crosslinking agent in the grade which does not affect an adhesive physical property, Generally about 0.2-3 weight part with respect to 100 weight part of acrylic polymers, Furthermore, 0.5 ˜2 parts by weight is preferred.

  In addition, for acrylic adhesives, crosslinking agents other than those exemplified above (polyamine compounds, melamine resins, urea resins), tackifiers, plasticizers, fillers, antioxidants, ultraviolet absorbers, silane coupling agents, etc. Can also be used as appropriate.

  The method for forming the pressure-sensitive adhesive layer 3 is not particularly limited. For example, a method in which a pressure-sensitive adhesive solution is applied to a release liner such as a polyester film treated with silicone, dried, and then transferred to the antistatic layer 4 formed on the polyester film 1. (Transfer method), a method of directly applying and drying an adhesive solution to the antistatic layer 4 formed on the polyester film 1 (direct copying method), a method by coextrusion, and the like. Among these methods, the direct copy method is particularly preferable in order to further improve the adhesion with the antistatic layer 4. The thickness (dry film thickness) of the pressure-sensitive adhesive layer 3 is not particularly limited, but is usually about 5 to 60 μm, preferably 5 to 40 μm. The pressure-sensitive adhesive layer 3 of the optical surface protective film of the present invention can be protected by temporarily attaching a separator or the like until practical use, if necessary.

  Hereinafter, the optical surface protective film of the present invention will be described in more detail based on examples, but the present invention is not limited thereto. In each example, both parts and% are based on weight.

Example 1
(Base material)
An untreated polyethylene terephthalate film (Mitsubishi Chemical Polyester Co., Ltd., Diafoil T100 # 38) having a thickness of 38 μm was used.

(Anti-fouling treatment layer)
On one side of the untreated polyethylene terephthalate film, a 0.3% toluene solution of a long-chain alkyl polymer (on the other hand, Oil & Fat Industries Co., Ltd., Pyroyl 1010) was applied so that the dry film thickness was 50 nm, and 130 ° C. And dried for 30 seconds to form an antifouling treatment layer.

(Antistatic layer)
On the opposite side of the untreated polyethylene terephthalate film on which the antifouling treatment layer is formed, a 5% mixed solution of an antistatic layer forming material containing a polyester binder and tin oxide (manufactured by Solvex, Microsolver RW-922) (Water / methanol = 3/7) was applied so that the dry film thickness was 300 nm, and dried at 130 ° C. for 30 seconds to form an antistatic layer.

(Adhesive layer)
In ethyl acetate, 100 parts of 2-ethylhexyl acrylate and 3 parts of acrylic acid are copolymerized to 35% on a monomer basis to obtain a solution containing an acrylic polymer having a weight average molecular weight of 500,000 (polystyrene equivalent). It was. To this solution, 100 parts of an acrylic polymer (dry weight), 4 parts of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrad C) and an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L) A pressure-sensitive adhesive solution was prepared by blending 1 part and further adding ethyl acetate to adjust the solid content concentration to 20%. The pressure-sensitive adhesive solution was applied on the antistatic layer so as to have a dry film thickness of 25 μm, and dried at 140 ° C. for 2 minutes to form a pressure-sensitive adhesive layer, thereby obtaining a surface protective film.

Example 2
In Example 1, the surface protection film was obtained according to Example 1 except having made the dry film thickness of the adhesive layer into 30 micrometers.

Example 3
In Example 1, a surface protective film was obtained according to Example 1 except that the dry film thickness of the antistatic layer was 100 nm.

Example 4
In Example 1, the surface protection film was obtained according to Example 1 except having changed the compounding of the crosslinking agent used for the adhesive solution into 3 parts of the epoxy crosslinking agent and 2 parts of the isocyanate crosslinking agent.

Comparative Example 1
In Example 1 (base material), a 38 μm-thick corona-treated polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Co., Ltd., Diafoil T100C # 38) was used. A surface protective film was obtained according to Example 1 except that an antistatic layer was formed.

Comparative Example 2
Example 1 is the same as Example 1 except that an antistatic layer forming material containing an acrylic binder and tin oxide (Microsolver LS-110, manufactured by Solvex Co., Ltd.) was used to form the antistatic layer. A surface protective film was obtained accordingly.

Comparative Example 3
In Example 1, the surface protection film was obtained according to Example 1 except that the crosslinking agent used in the adhesive solution was changed to 4 parts of the epoxy crosslinking agent and no isocyanate crosslinking agent was added. It was.

Comparative Example 4
In Example 1, the surface protection film was obtained according to Example 1 except that the crosslinking agent used in the adhesive solution was changed to 4 parts of the isocyanate crosslinking agent and no epoxy crosslinking agent was blended. It was.

[Evaluation methods]
About the surface protection film obtained by the Example and the comparative example, evaluation was implemented with the following method. The results are shown in Table 1.

<Uniformity of antifouling treatment layer>
With the antifouling treatment layer of the surface protective film facing upward, it was confirmed whether the antifouling treatment layer was uniformly applied while holding the fluorescent light in the dark room. The case where the coating was uniformly applied was good, and the case where the coating unevenness occurred was judged as defective.

<Adhesion>
The surface protective film was cut into a length of 10 cm and a width of 5 cm. Next, the pressure-sensitive adhesive layer and the antistatic layer were scratched with a cutter so as not to scratch the base material in the vertical direction at the center in the vertical direction. The cellophane tape was affixed with a hand roller so as to straddle the scratch, and then removed and then affixed and removed again 20 times. Within 20 operations, when the adhesive layer or antistatic layer was not peeled off, it was good, and when it was peeled off, it was bad.

<Peelability>
A surface protective film was attached to the surface of a polarizing plate (AGSI) manufactured by Nitto Denko Corporation at room temperature with a laminator (linear pressure: 78.5 N / cm, speed: 0.3 m / min), and 3 ° C. at 3 ° C. After pasting and storing for days, it was left at room temperature for 2 hours. Thereafter, the 180 peel adhesive strength at 10 m / min and the actual peel feeling were examined.

  From the viewpoint of surface protection, the adhesive strength is preferably 0.1 N / 25 mm or more, more preferably 0.2 N / 25 mm or more. On the other hand, from the viewpoint of peelability, the adhesive strength is preferably 0.6 N / 25 mm or less, more preferably 0.5 N / 25 mm or less.

It is an example of sectional drawing of the surface protection film for optics of this invention.

Explanation of symbols

1 Polyester film not subjected to surface treatment 2 Antifouling treatment layer 3 Adhesive layer 4 Antistatic layer

Claims (4)

An anti-stain treatment layer on one side of the polyester film, an optical surface protection film provided with an adhesive layer on the opposite side,
The polyester film is not subjected to surface treatment,
An antistatic layer formed of a material containing an antistatic agent and a polyester-based binder is provided between the polyester film and the pressure-sensitive adhesive layer.
An optical surface protective film, wherein the pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive containing an acrylic polymer containing an acid as a functional group and an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent.   The optical surface protective film according to claim 1, which is used for protecting the surface of a polarizing plate.   An optical film with an optical surface protective film, wherein the optical surface protective film according to claim 1 or 2 is affixed to the optical film. An image display device with an optical surface protective film, wherein the optical surface protective film according to claim 1 or 2 is attached to the image display device.

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