TWI479513B - Surface protective film for transparent conductive film and transparent conductive film using the same - Google Patents

Description

Surface protective film for transparent conductive film and transparent conductive film using the same

The present invention relates to a surface protective film for a transparent conductive film and a transparent conductive film using the same, wherein the surface protective film for a transparent conductive film is bonded to a transparent conductive film having a transparent conductive film formed on one surface of a substrate. Other users and users. More specifically, the present invention provides a surface protective film for a transparent conductive film and a transparent conductive film using the same, wherein the surface of the adhesive surface to be bonded to the formed adhesive layer is smooth, even if it is adhered to transparent The conductive film also has excellent handleability, and is improved in the production process of the transparent conductive film. In the processing step, the appearance of the surface protective film is disadvantageous.

In the technical fields of touch panels, electronic papers, electromagnetic shielding materials, various sensors, liquid crystal panels, organic ELs, and solar cells, transparent conductive films have been widely used as transparent electrodes and the like. The transparent conductive film is a transparent conductive film in which a transparent conductive film such as an ITO (indium tin oxide compound) transparent conductive film, a ZnO-based transparent conductive film, or a conductive polymer is formed on one surface of the substrate (hereinafter also There is a case where it is simply referred to as "conductive film".

Further, in the manufacturing step of the transparent electrode for a touch panel, it is transparent to the ITO transparent conductive film or the ZnO-based transparent conductive film formed of a metal oxide compound. a plurality of heating steps such as a crystallization step of a metal oxide film subjected to an annealing treatment, a printing step of a resist, an etching treatment step, a forming step of a wiring circuit using a silver paste, a printing step of an insulating layer, a press step, and the like, Or liquid processing steps. In the transparent electrode manufacturing step, in order to prevent contamination or damage on the opposite side surface of the surface on which the transparent conductive film is formed in the transparent conductive film, a surface protective film for a transparent conductive film is bonded and used.

In the manufacturing process of the transparent electrode, the annealing treatment, the formation of the wiring circuit using the silver paste, and the like are performed at a temperature of about 150° C., so that the protective film for the transparent conductive film is required to have heat resistance.

In addition, various proposals have been made for a protective film for a transparent conductive film used in a transparent electrode manufacturing step such as a touch panel. For example, Patent Document 1 proposes a surface protective film for a transparent conductive film provided with a pressure-sensitive adhesive layer on a base material of a thermoplastic resin film having a melting point of 200 ° C or higher. The surface protective film for a transparent conductive film using a polyolefin resin such as polyethylene or polypropylene in the substrate is excellent in heat resistance.

Further, Patent Document 2 proposes a method for producing a surface protective film for a transparent conductive film, which is based on a polyethylene terephthalate resin and/or a polyethylene naphthalate resin. After the adhesive film is applied to one surface of the film, it is dried at a predetermined temperature, residence time, and tensile tension. After the surface protective film for a transparent conductive film obtained by the production method is bonded to the transparent conductive film, large curl does not occur even after the heating step.

Patent Document 3 proposes a protective film having a transparent conductive film on one surface of a resin film and a transparent conductive film and a protective film provided with a protective film on a surface of the resin film provided on the surface of the resin film. The film is composed of a first film and a second film, wherein the first film is heated at 150 ° C for 30 minutes. The shrinkage ratio is 0.5% or less in both the MD and TD directions; and the second film has a linear expansion coefficient of 40 ppm/° C. or less from the linear expansion coefficient of the resin film having the transparent conductive film and the protective film, and the resin is from the above resin. The first film and the second film are sequentially disposed in the film. According to the invention, it is possible to obtain a transparent conductive film which does not undergo dimensional change and curling due to heat treatment in a processing step such as touch panel formation.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-170535

[Patent Document 2] Japanese Patent No. 4342775

[Patent Document 3] Japanese Patent Laid-Open No. Hei 11-268168

In the protective film for a transparent conductive film described in Patent Document 1, a heat-resistant substrate having a resin film having a melting point of 200 ° C or higher can be used, but curling occurs after the heating step.

Further, in the protective film for a transparent conductive film described in Patent Document 2 and Patent Document 3, large curl does not occur even after the heating step, but the productivity is greatly lowered. In recent years, as the market price of transparent conductive films has been lowered, the protective film for transparent conductive films obtained by such a production method is not competitive in cost.

As described above, in the prior art, it is not possible to obtain a protective film for a transparent conductive film which can be used by being bonded to a transparent conductive film and which does not cause curling even after heat treatment.

In addition, in order to remove the protective film for a transparent conductive film, the step of producing a transparent electrode using a transparent conductive film is required to be set to be easily peeled off without causing an abrupt increase in adhesion even after heat treatment in an annealing treatment or the like. As a method of suppressing the adhesion of the adhesive without abruptly increasing the viscosity of the adhesive after the heat treatment, a method of crosslinking the resin composition of the adhesive layer at a high density is known. In general, a method of producing an adhesive layer which increases the crosslinking density is as follows. For example, on one side of a long-length base film having a length of 5 to 10,000 m, the adhesive composition is applied to a certain thickness to form a laminate, and an adhesive layer is laminated. After the layer of the adhesive layer is dried by heating to crosslink the adhesive composition, a release-treated release film is laminated on the adhesive layer. Then, a wound body of a surface protective film for a transparent conductive film wound in a roll shape can be obtained. Then, the wound body of the surface protective film obtained for the transparent conductive film is stored in a constant temperature warehouse maintained at a constant temperature for a certain period of time to carry out a curing treatment for promoting the curing reaction.

The present inventors have found that a curing process is performed on a roll of a protective film for a transparent conductive film in which a pressure-sensitive adhesive layer is laminated on one surface of a base film and a release film is peeled off on the adhesive layer. The new problem that has hitherto been unknown has led to the completion of the present invention.

A new problem in the protective film for a transparent conductive film is that a surface protective film for a transparent conductive film which is wound back from a roll is bonded to another surface of a transparent conductive film having a transparent conductive film formed on one surface of the substrate. In the production of the transparent conductive film and the processing step, the appearance of the transparent conductive film is remarkably deteriorated.

As a result of intensive studies, the inventors found that the uneven shape generated on the surface of the adhesive layer of the surface protective film for a transparent conductive film is transferred to the transparent conductive film to which a transparent conductive film is bonded. Use a surface to protect the surface of the film.

The present invention has been accomplished in view of the above circumstances. The subject of the present invention is A surface protective film for a transparent conductive film and a transparent conductive film using the same, which is bonded to the surface of the adhesive layer of the adhesive layer for the surface protective film for a transparent conductive film in a state of being wound from the wound body It is smooth and has excellent handleability even when it is bonded to a transparent conductive film, and it can also improve the manufacturing defect of the transparent conductive film.

In order to solve the above problems, the surface protective film for a transparent conductive film of the present invention has an adhesive layer laminated on one surface of a base film and a release-treated release film is laminated on the adhesive layer. By making the peeling film have a certain rigidity, deformation of unevenness on the surface of the adherend surface to be bonded to the above-mentioned adhesive layer is prevented.

In the curing of the adhesive layer of the surface protective film for a transparent conductive film according to the present invention, the adhesive layer in which the release film is bonded to the surface protective film for a transparent conductive film wound in a roll shape is prevented from being peeled off. The deformation of the film is deformed by stretching, and unevenness is generated on the surface of the adherend surface to be bonded to the adhesive layer.

In order to solve the above problems, the present invention provides a surface protective film for a transparent conductive film which is bonded to another surface of a transparent conductive film having a transparent conductive film formed on one surface of a substrate, and which is rewinded from the roll body. Forming, an adhesive layer is laminated on one surface of the flexible substrate film, and a release-treated release film is passed through the peel-treated surface layer on the surface of the adhesive surface adhered to the adhesive layer The thickness of the release film is from 50 μm to 250 μm, and the peel strength of the release film at 40 ° C is from 0.30 mN to 40 mN.

Further, the thickness of the adhesive layer is 1/20 to 1/5 of the thickness of the base film, and the storage elastic modulus of the adhesive layer at 20 ° C is 1.0 × 10 ⁵ to 8.0 × 10 ⁶ MPa.

Further, the base film of the surface protective film for a transparent conductive film is a polyethylene terephthalate resin film, and the base film has a thickness of 100 μm to 250 μm.

Moreover, the present invention provides a wound body of a surface protective film for a transparent conductive film in which the surface protective film for a transparent conductive film is wound into a roll.

Moreover, the present invention provides a transparent conductive film in which the surface protective film for a transparent conductive film is bonded to another surface of a transparent conductive film having a transparent conductive film formed on one surface of a substrate.

The surface protective film for a transparent conductive film of the present invention has a surface which is bonded to the surface of the adhesive layer of the formed adhesive layer in a state of being wound from the wound body, and has a smooth surface even if it is bonded to the transparent conductive film. Excellent operability. According to the present invention, it is possible to improve the production of the transparent conductive film. In the processing step, the surface protective film for the transparent conductive film and the transparent conductive film using the same are disadvantageous in that the surface protective film is defective in appearance.

In addition, in recent years, as the outer casing of a high-performance portable terminal such as a smart phone has become thinner, a thinner transparent conductive film is being developed. In the step of producing a transparent electrode for a touch panel, the surface protective film for a transparent conductive film of the present invention is formed on a thinned transparent conductive film even after being subjected to a heating step in a bonded state. The curl is also small. Thereby, the workability and production efficiency of the manufacturing process of the transparent electrode for touch panels can be greatly improved.

1‧‧‧Substrate film

2‧‧‧Adhesive layer

3‧‧‧Release film

4‧‧‧Adhesive film

5‧‧‧Surface protective film for transparent conductive film

6‧‧‧Substrate

6a‧‧‧One side of the substrate

6b‧‧‧Other faces of the substrate

7‧‧‧ITO (transparent conductive film)

10‧‧‧Transparent conductive film

21‧‧‧ peeling film roll

22‧‧‧The base of the substrate film

23‧‧‧Adhesive coating device

24‧‧‧ drying oven

25, 26‧‧‧ Pressing roller

27‧‧‧The roll of the surface protective film for transparent conductive film

Fig. 1 is a cross-sectional view showing an example of a surface protective film for a transparent conductive film of the present invention.

Fig. 2 is a cross-sectional view showing an example of a transparent conductive film.

3 is a cross-sectional view showing an example in which a surface protective film for a transparent conductive film of the present invention is bonded to a transparent conductive film.

4 is a schematic view showing an example of a method for producing a surface protective film for a transparent conductive film of the present invention.

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

Fig. 1 is a cross-sectional view showing an example of a surface protective film for a transparent conductive film of the present invention. The surface protective film 5 for a transparent conductive film has an adhesive film 4 in which an adhesive layer 2 is laminated on one surface of a transparent and flexible base film 1. On the surface of the adherend surface to be adhered to the adhesive layer 2, the release-treated peeling film 3 is used to pass through the peel-treated surface layer to protect the adhesive surface.

As the base film 1, a transparent and flexible resin film can be used. By using a transparent resin film, as shown in FIG. 2, the transparent conductive film of the present invention is bonded to the other surface 6b of the transparent conductive film 10 on which the transparent conductive film 7 is formed on one surface 6a of the substrate 6. In the state of the adhesive film 4 obtained by the surface protection film 5 (refer FIG. 3), the visual inspection of the transparent conductive film 10 can be performed directly. The resin film used as the base film 1 is preferably polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate or polybutylene terephthalate. A polyester film such as a glycol ester. Further, in addition to the polyester film, other types of resin films may be used as long as they have the necessary strength and optical suitability. The base film 1 is not particularly limited, and may be an unstretched film, a uniaxially or biaxially stretched film, or the like, and a base film 1 is added. Those with a low heat shrinkage rate are preferred.

Further, the thickness of the base film 1 of the surface protective film for a transparent conductive film of the present invention must be 100 μm or more. When the thickness of the base film 1 is less than 100 μm, the rigidity is weak, and workability is lowered when bonded to a thin transparent conductive film. The thickness of the base film 1 is not particularly limited, but is preferably, for example, a thickness of about 100 to 250 μm, and more preferably a thickness of about 100 to 188 μm. When the thickness of the base film 1 exceeds 300 μm, the rigidity is strong, and the surface protective film for a transparent conductive film according to the present invention is wound into a roll, and it is difficult to form a roll of the surface protective film for a transparent conductive film.

Further, depending on the need, an antifouling layer, an antistatic layer, and a scratch-resistant hard coat layer for the purpose of preventing surface contamination may be laminated on the opposite surface of the surface of the base film 1 on which the adhesive layer 2 is laminated. Adhesive treatment such as corona discharge treatment or anchor coat treatment can be applied.

In addition, as long as the adhesive layer 2 of the surface protective film for a transparent conductive film of the present invention is an adhesive having little change in adhesion before and after heat treatment, a known material can be used, and the adhesive composition is not particularly limited. Examples of the adhesive composition that can be used include a rubber-based, acrylic-based, and urethane-based composition.

As the rubber-based adhesive, an adhesive such as a tackifier, a softener, an anti-aging agent, or a filler may be added to an elastomer such as natural rubber or synthetic rubber, and a crosslinking agent may be added as needed.

As the acrylic pressure-sensitive adhesive, an adhesive having a curing agent or a tackifier added to the (meth)acrylic polymer may be used. The (meth)acrylic polymer is generally a main monomer such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate or isodecyl acrylate, and acrylonitrile, vinyl acetate, methyl methacrylate. , ethyl acrylate, etc. a polymer obtained by copolymerizing a polymonomer with a functional monomer such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate or N-methylol methacrylamide. . Examples of the curing agent include an isocyanate compound, an epoxy compound, a melamine compound, and a metal chelate compound. Examples of the tackifier include rosin, benzofuran-indene, terpene, petroleum, and phenolic.

Examples of the urethane-based pressure-sensitive adhesive include substances which change the type and composition ratio of the hard segment and the soft segment.

Examples of the anthrone-based adhesive include those in which the type and composition ratio of the polydimethylsiloxane and the fluorenone resin are changed. As the form of the curing reaction, any of an addition reaction type and a peroxide reaction type can be used.

Further, the adhesive used in the adhesive layer 2 of the surface protective film for a transparent conductive film of the present invention has heat resistance, and can easily suppress the sharp increase in the adhesive force before and after the heat treatment and the contamination of the adherend. From a low point of view, an acrylic adhesive is preferred. Further, a curing agent or a tackifier may be added to the adhesive layer as needed.

Further, an antistatic agent may be mixed in the adhesive layer 2 of the surface protective film for a transparent conductive film of the present invention as needed.

As the antistatic agent, it is preferred that the (meth)acrylic polymer is a substance which is excellent in dispersion or compatibility. Examples of the antistatic agent that can be used include a surfactant, an ionic liquid, an alkali metal salt, a metal oxide, metal fine particles, a conductive polymer, carbon, and a carbon nanotube. From the viewpoints of transparency, affinity to a (meth)acrylic polymer, etc., a surfactant, an ionic liquid, an alkali metal salt or the like is preferable. The amount of the antistatic agent to be added to the adhesive is appropriately determined in consideration of the kind of the antistatic agent and the compatibility with the base polymer. Further, in consideration of the peeling tape voltage, the contamination of the adherend, the adhesive force, and the like which are required when the surface protective film for a transparent conductive film of the present invention is peeled off from the transparent conductive film, The type and amount of antistatic agent are determined.

Further, the thickness of the adhesive layer 2 of the surface protective film for a transparent conductive film of the present invention is not particularly limited, and is, for example, preferably about 5 to 50 μm. Further, the thickness of the adhesive layer 2 is preferably about 10 to 30 μm. When the thickness of the adhesive layer 2 exceeds 50 μm, the cost of producing the surface protective film for a transparent conductive film increases, which impairs the competitiveness. Further, as described above, the thickness of the base film 1 is preferably about 100 to 250 μm. The thickness of the adhesive layer 2 of the surface protective film for a transparent conductive film of the present invention is preferably from 1/20 to 1/5 of the thickness of the base film 1.

Further, in the surface protective film for a transparent conductive film of the present invention, the peel strength on the surface of the adherend is preferably an adhesive layer having a slight adhesive force of about 0.03 to 0.3 N/25 mm. As described above, the surface protective film for a transparent conductive film having an adhesive layer having a slight adhesive property can be easily peeled off from the adherend and has excellent handleability.

Further, the surface protective film for a transparent conductive film of the present invention is not particularly limited as a material of the release film 3 to be used. The material of the release film which can be used is a polyolefin film such as a polyethylene film, a polypropylene film or a polymethylpentene film, or a release agent such as an anthrone-based release agent on the surface of a film such as a polyester film. A release film to which a release treatment is applied, a fluororesin film, a polyimide film or the like is applied. Further, it may be a material obtained by laminating a plurality of films with an adhesive or a laminated film obtained by melt-extruding a resin on a film and laminating the film. To such a single layer or laminated film, a release treatment is applied using a release agent such as an anthrone-based release agent, and a release film is obtained.

Further, in the release film 3 of the surface protective film for a transparent conductive film of the present invention, the thickness of the release film 3 is 50 μm to 250 μm, and the bending strength of the release film 3 at 40 ° C is 0.30 mN to 40 mN. The bending strength of the release film 3 is also related to the thickness of the release film 3. Although the thickness of the release film 3 is increased, the bending strength is higher, but the release film 3 is removed. The thicker the thickness, the shorter the total length of the surface protective film for a transparent conductive film can be obtained by winding the roll having the same roll diameter, and the manufacturing cost can be increased, and the thickness of the appropriate release film 3 can be derived. Further, the release film 3 is preferably a release film obtained by subjecting a single-layer polyester film to a release treatment, or a release film obtained by applying a release treatment to a film having a plurality of layers of a polyester film laminated with an adhesive.

In the surface protective film for a transparent conductive film of the present invention, the peeling film 3 preferably has a bending strength at 40 ° C of 0.30 mN to 40 mN. In the case of using the release film 3 having a flexural strength of less than 0.30 mN at 40 ° C, a release film is adhered to the surface protective film 5 for a transparent conductive film wound in a roll shape during curing of the adhesive layer 2 . The adhesive layer 2 of 3 is deformed by stretching and stretching of the release film, and irregularities are formed on the surface of the adhesive layer 2. As a result, as shown in FIG. 3, after the adhesive film 4 is bonded to the transparent conductive film 10, the uneven shape formed on the surface of the adhesive layer 2 is transferred to the surface of the transparent conductive film 10 to which the adhesive film 4 is bonded. On 6b, the transparent conductive film 10 is poor in appearance.

In addition, when the flexural strength of the release film 3 at 40 ° C is more than 40 mN, the surface protective film 5 for a transparent conductive film of the present invention is wound into a roll to form a surface protective film for a transparent conductive film. The roll of the film is difficult. The bending strength of the release film 3 can be measured in accordance with the bending repellency A method (Guller method) as specified in JIS L1096 as described later.

Further, the method of sequentially laminating the adhesive layer 2 and the release film 3 on the base film 1 is not particularly limited as long as it is carried out by a known method. Specifically, a method in which the adhesive layer 2 is applied onto the base film 1 and dried, and then the release film 3 is bonded, and the adhesive layer 2 is applied onto the release film 3 and dried and then bonded. Any method such as a method of the substrate film 1.

Further, the formation of the adhesive layer on the base film 1 can be carried out by a known method. With For the body, an inverse coating method, a comma coat method, a gravure coating method, a slit die coating method, a Mayer bar coat method, and an air knife coating method can be employed. A known coating method such as a method.

Further, a method of applying a release treatment to the release film 3 composed of a polyester film or a polyester film single-layer film or a release film 3 in which a plurality of single-layer films are laminated by an adhesive can be used. A well-known method is carried out. Specifically, a release agent may be applied to the release film 3 by a coating method such as a gravure coating method, a Meyer bar coating method, or an air knife coating method, and the release agent may be applied by heating or ultraviolet irradiation. Dry ‧ harden It is also possible to preliminarily perform corona treatment, plasma treatment, adhesion-promoting coating or the like on the release-treated film to improve the adhesion of the release agent to the film.

In addition, FIG. 3 is a schematic configuration view showing an example of a laminated film in which the adhesive film 4 of the surface protective film 5 for a transparent conductive film of the present invention is bonded to the transparent conductive film 10.

The laminated film is set such that the surface protective film 5 for a transparent conductive film of the present invention is rewinded from a wrap (symbol 27 of FIG. 4) in a slightly flat state, and the release film 3 is exposed by the adhesive layer 2 The adhesive film 4 of the adhesive surface is attached to the surface of the transparent conductive film 10. The transparent conductive film 10 (see FIG. 2) is a material in which the transparent conductive film 7 is formed on one surface 6a of the substrate 6, and specifically, polyethylene terephthalate having an ITO conductive film formed thereon is exemplified. A glycol ester film, a cyclic polyolefin film on which an ITO conductive film is formed, a polyethylene terephthalate film on which a ZnO conductive film is formed, or the like. The transparent conductive film 7 is not particularly limited as long as it has sufficient transparency and conductivity, and examples thereof include a film of a metal oxide such as ITO or ZnO, a film of a metal, and a conductive polymer film. In the technical fields of touch panels, electronic paper, electromagnetic wave shielding materials, various sensors, liquid crystal panels, organic EL, solar cells, etc., such a transparent conductive film 10 can be widely applied It is used for formation as a transparent electrode or the like. A hard coat layer (not shown) for preventing scratching may be laminated on the other surface 6b of the substrate 6 of the transparent conductive film 10.

The protective film for a transparent conductive film of the present invention can greatly improve workability and production efficiency in the production process of a transparent electrode such as a touch panel, and can reduce workability and operation even in a thin transparent conductive film. Excellent effects such as sex.

Moreover, FIG. 4 is a schematic view showing an example of a method for producing a surface protective film for a transparent conductive film of the present invention.

The roll body 21 wound from the release-treated release film 3 and the roll body 22 wound by the base film 1 are successively fed out of the release film 3 and the base film 1. The adhesive is applied to one surface of the base film 1 by an adhesive application device 23. The base film 1 coated with the adhesive is dried in a drying oven 24 to form an adhesive film 4. The surface on which the adhesive film 4 is formed with the adhesive layer is opposed to the surface on which the release film 3 is subjected to the release treatment, and is subjected to thermocompression bonding by the pressure rollers 25 and 26 to obtain a surface protective film for a transparent conductive film. . The surface protective film 5 for a transparent conductive film is wound into the winding body 27.

[Examples]

Hereinafter, the present invention will be further described based on examples.

(Preparation of Surface Protective Film for Transparent Conductive Film of Example 1)

On the one side of the biaxially stretched polyester film having a thickness of 75 μm, the coating was applied by a Meyer bar method so that the thickness of the dried fluorenone film became 0.1 μm, and the coating was formed by an addition reaction type. Ketone (relative to 100 parts by weight of Dow Corning Toray Co., Ltd., trade name: SRX-211, adding 1 part by weight of platinum catalyst SRX-212) was diluted in toluene ‧ ethyl acetate 1:1 mixed solvent obtain. Further, the film was dried and hardened in a hot air circulating oven having a temperature of 120 ° C for 1 minute to obtain a release film of Example 1. The peeling film of Example 1 obtained had a flexural strength at 40 ° C of 0.91 mN.

Further, the adhesive layer is used in an amount of 100 parts by weight based on 100% by weight of a 40% solid acrylic polymer obtained by copolymerizing butyl acrylate, 2-ethylhexyl acrylate, acrylic acid or 2-hydroxyethyl acrylate. An adhesive composition of 2.4 parts by weight of an HDI-based hardener (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: CORONATE HX ) was mixed. The above adhesive composition was applied to a polyethylene terephthalate film having a thickness of 100 μm so that the thickness of the adhesive layer after drying became 20 μm in a hot air circulating oven at a temperature of 100 ° C. Allow it to dry after two minutes. Then, the anthrone-treated surface of the release film of Example 1 prepared above was laminated and laminated on the surface of the adhesive layer to obtain a surface protective film for a transparent conductive film of Example 1.

(Preparation of Surface Protective Film for Transparent Conductive Film of Example 2)

In order to form the adhesive layer, the adhesive composition is used in an amount of 4 parts by weight based on 100 parts by weight of the acrylic polymer copolymerized with butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid. The surface of the transparent conductive film of Example 2 was obtained in the same manner as in Example 1 except that the adhesive composition of the epoxy-based hardener (trade name: TETRAD X, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used. Protective film.

(Preparation of Surface Protective Film for Transparent Conductive Film of Example 3)

A biaxially stretched polymer having a thickness of 25 μm was used to form a thickness of 25 μm using a urethane-based adhesive (manufactured by Mitsui Chemicals, trade name: TAKELAC A-505/TAKENATE A-20) so as to have a thickness of 5 μm after drying. A polyethylene terephthalate film and a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm were laminated with a coated and dried adhesive layer to form a laminated film. After the corona treatment was applied to one surface of the laminated film, an anthrone treatment was carried out in the same manner as in Example 1 to obtain a release film of Example 3. Place The peeling film of Example 3 obtained had a flexural strength at 40 ° C of 0.86 mN. Then, the transparent conductive property of Example 3 was obtained in the same manner as in Example 1 except that the release film was the release film of Example 3, and the thickness of the polyester film used as the base film was changed from 100 μm to 125 μm. A surface protective film for a film.

(Preparation of Surface Protective Film for Transparent Conductive Film of Example 4)

A release film of Example 4 was obtained in the same manner as in Example 1 except that a biaxially stretched polyester film having a thickness of 100 μm was used as the substrate of the release film. The peeling film of Example 4 obtained had a flexural strength at 40 ° C of 2.32 mN. Then, the surface protective film for a transparent conductive film of Example 4 was obtained in the same manner as in Example 1 except that the release film was the release film of Example 4.

(Preparation of Surface Protective Film for Transparent Conductive Film of Example 5)

The release film of Example 5 was obtained in the same manner as in Example 1 except that the thickness of the adhesive layer was 10 μm, and the biaxially stretched polyester film having a thickness of 50 μm was used as the base material of the release film. The peeling film of Example 5 obtained had a flexural strength at 40 ° C of 0.35 mN. Then, the surface protective film for a transparent conductive film of Example 5 was obtained in the same manner as in Example 1 except that the release film was the release film of Example 5.

(Preparation of Surface Protective Film for Transparent Conductive Film of Comparative Example 1)

A release film of Comparative Example 1 was obtained in the same manner as in Example 1 except that a biaxially stretched polyester film having a thickness of 25 μm was used as the substrate of the release film. The peeling film of Comparative Example 1 obtained had a flexural strength at 40 ° C of 0.05 mN. Then, except The surface protective film for a transparent conductive film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the release film was the release film of Comparative Example 1.

(Preparation of Surface Protective Film for Transparent Conductive Film of Comparative Example 2)

A release film of Comparative Example 2 was obtained in the same manner as in Example 1 except that a biaxially stretched polyester film having a thickness of 38 μm was used as the substrate of the release film. The peeling film of Comparative Example 2 obtained had a flexural strength at 40 ° C of 0.16 mN. The surface of the transparent conductive film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the release film was the release film of Comparative Example 2, and the adhesive composition of Example 2 was used as the adhesive composition. film.

(Preparation of Surface Protective Film for Transparent Conductive Film of Comparative Example 3)

A surface protective film for a transparent conductive film of Comparative Example 3 was obtained in the same manner as in Example 1 except that the thickness of the polyester film used as the base film was changed from 100 μm to 75 μm.

(Preparation of Surface Protective Film for Transparent Conductive Film of Comparative Example 4)

A surface protective film for a transparent conductive film of Comparative Example 4 was obtained in the same manner as in Example 1 except that the thickness of the adhesive was 40 μm.

(Preparation of Surface Protective Film for Transparent Conductive Film of Comparative Example 5)

A release film of Comparative Example 5 was obtained in the same manner as in Example 1 except that an unstretched polypropylene film having a thickness of 80 μm was used as the substrate of the release film. The peeling film of Comparative Example 5 obtained had a flexural strength at 40 ° C of 0.12 mN. Then, except The surface protective film for a transparent conductive film of Comparative Example 5 was obtained in the same manner as in Example 1 except that the release film was the release film of Comparative Example 5.

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

(Measurement of bending strength of peeling film)

The flexural strength (mN) at 40 ° C was measured according to the bending repulsive A method (Gul'll method) of JIS L1096.

The measuring device was a Gurley-type bending strength test device manufactured by Daiei Scientific Seiki Co., Ltd., model: GAS-10.

(Measurement of Initial Adhesion of Surface Protective Film for Transparent Conductive Film)

The base material for a transparent conductive film is a hard coat layer treated with a biaxially stretched polyester film having a thickness of 50 μm, or a hard coat treated PET film of an ITO film (Kimoto). Co., Ltd., trade name: KB film #50G01). The surface of the transparent conductive film cut with a thickness of 25 mm was bonded to a PET film as a substrate for a transparent conductive film and a surface coated with a hard coat layer, and then exposed to a surface of 23 ° C and 50% RH. Store for 1 hour and use it as a sample for initial adhesion measurement. Then, the strength at the time of peeling off the surface protective film for transparent conductive films at a peeling speed of 300 mm/min at a peeling speed of 300 mm/min was measured using a tensile tester, and this was set as initial adhesion (N/25 mm).

As the measuring device, a small table test device of the model: EZ-L manufactured by Shimadzu Corporation was used.

<Measurement of adhesion after heating of surface protective film for transparent conductive film>

After bonding a surface protective film of a transparent conductive film cut in a width of 25 mm to a PET film as a substrate for a transparent conductive film and applying a surface treated with a hard coat layer, The measurement was carried out in the same manner as in the measurement of the initial adhesion force, and it was set as the adhesion after heating (N/25 mm).

As the measuring device, a small table test device of the model: EZ-L manufactured by Shimadzu Corporation was used.

(Method for confirming the operability when a surface protective film for a transparent conductive film is bonded to a hard-coated PET film)

The surface protective film for a transparent conductive film (cut out from the position where the visual inspection is completed to remove the peeling film) is subjected to the appearance inspection (described later) of the surface protective film for a transparent conductive film, and is bonded to the transparent conductive material. The film-coated substrate and a hard-coated PET film (manufactured by Kimoto Co., Ltd., trade name: KB film #50G01) were subjected to a hard coat treatment surface, and then the laminate was cut into an A4 size. One corner of the four corners of the cut sample was rubbed back and forth 20 times with the film surface fanning the air. Thereafter, it was visually confirmed whether or not the hard coat-treated PET film was free from cracks and deformation. There was no fracture on the hard coat treated PET film, and the deformation was recorded as (○), and the fracture or deformation was recorded as (×).

(Method of visual inspection of surface protective film for transparent conductive film)

The coated applicator was used to prepare a roll of a surface protective film for a transparent conductive film (400 mm width × 100 m roll), and the film was kept in an oven at 40 ° C for 5 days to carry out adhesive curing. Thereafter, the surface protective film was rewinded from the roll, and the release film was removed to expose the adhesive surface, and 50 m was visually observed from the end of the surface protective film toward the long direction (a position equidistantly calculated from both ends). Sample appearance. The surface of the adhesive agent was smooth (○), the small unevenness on the surface of the adhesive was recorded (Δ), and the large unevenness on the surface of the adhesive was recorded (×).

(Appearance inspection method when a surface protective film for a transparent conductive film is bonded to a hard coat film)

The surface of the transparent conductive film for the transparent conductive film which has been subjected to the inspection of the appearance of the surface protective film for the transparent conductive film (cut from the position where the visual inspection is completed, and the material for removing the release film) is bonded to the transparent conductive film. The hard coat layer of the base material and the hard-coated PET film (manufactured by Kimoto Co., Ltd., trade name: KB film #50G01) was subjected to heat treatment at 150 ° C for 1 hour. After the protective film for a transparent conductive film was peeled off, the surface state of the hard-coated PET film was visually observed. The appearance of the hard-coated PET film was as follows (○), the small deformation in which unevenness was observed (Δ), and the large deformation in the uneven shape (×).

The measurement results of the samples are shown in Tables 1 and 2, respectively. In the "base film" and "substrate of the release film" of the tables, "125E", "100E", "75E", "50E", "38E", and "25E" each have a thickness of 125 μm and 100 μm. A polyester film of 75 μm, 50 μm, 38 μm, and 25 μm, and "80 CPP" means an unstretched polypropylene film having a thickness of 80 μm. In the "adhesive" of the table, "adhesive 1" indicates the adhesive (isocyanate cured) described in the first embodiment, and "adhesive 2" indicates the adhesive (epoxy hardened) described in the second embodiment.

The measurement results shown in Tables 1 and 2 can be judged as follows.

In the examples 1 to 5, the peeling film for the surface protective film for a transparent conductive film had a flexural strength of 0.35 to 2.32, and the change in the adhesive force was small before and after the heating step, and the unevenness of the surface of the adhesive was extremely small. In addition, the workability of the surface protective film of the transparent conductive film of the examples 1 to 5 bonded to the PET film which is the surface of the transparent conductive film and hard-coated is also excellent.

On the other hand, in Comparative Examples 1, 2, and 5, the peeling films used for the surface protective film for transparent conductive films had a low bending strength at 40 ° C of 0.05, 0.16, and 0.12, respectively. As a result, it was found that the surface protective film of the transparent conductive film of Comparative Examples 1, 2, and 5 was peeled off from the surface, and irregularities were formed on the surface of the adhesive, and it was heat-treated and treated with a hard coat layer as a substrate for a transparent conductive film. When the PET film is laminated, the uneven shape of the surface of the adhesive is transferred to the hard-coated PET film, and the appearance of the hard-coated PET film is lowered.

Further, in the surface protective film for a transparent conductive film of Comparative Example 3, the thickness of the base film is less than 100 μm, and the laminate of the surface of the transparent conductive film is bonded to the PET film treated with the hard coat layer. Sexual decline.

Further, in the surface protective film for a transparent conductive film of Comparative Example 4, the thickness of the adhesive layer was increased to 40 μm, and irregularities were also formed on the surface of the adhesive, and the substrate was used as a substrate for a transparent conductive film by heat treatment. When the hard coat-treated PET film is laminated, the uneven shape of the surface of the adhesive is transferred to the hard-coated PET film, and the appearance of the hard-coated PET film is lowered.

Further, in the surface protective films for transparent conductive films of Examples 1 to 5 and Comparative Examples 1 to 5, the storage elastic modulus of the adhesive layer used at 20 ° C was 1.0 × 10 ⁵ to 8.0 × 10 ⁶ MPa. Within the scope. Further, the storage elastic modulus of the adhesive layer was subjected to a dynamic viscoelasticity test in a linear region at a frequency of 1 Hz using a shear rheometer (manufactured by Anton Paar Co., Ltd., device name: viscoelasticity measuring device, model: MCR301). The measured value of the storage elastic coefficient was in the temperature range of -40 ° C to +150 ° C, and the value at 20 ° C was read at a temperature rising rate of 3 ° C / min, and the storage elastic modulus was obtained.

(industrial availability)

In the step of producing a transparent electrode for a touch panel, the surface protective film for a transparent conductive film of the present invention has a curl which occurs even after being subjected to a heating step in a state in which it is bonded to a thin transparent conductive film. Very small. Thereby, it can be greatly improved Workability and production efficiency of the manufacturing steps of the transparent electrode for a touch panel. Moreover, the surface protective film for a transparent conductive film of the present invention can be used as a transparent conductive material used in the technical fields of touch panels, electronic paper, electromagnetic wave shielding materials, various sensors, liquid crystal panels, organic EL, solar cells, and the like. Manufacturing of films ‧ Surface protection films for processing are widely used.

1‧‧‧Substrate film

2‧‧‧Adhesive layer

3‧‧‧Release film

4‧‧‧Adhesive film

5‧‧‧Surface protective film for transparent conductive film

Claims (3)

A surface protective film for a transparent conductive film is bonded to another surface of a transparent conductive film having a transparent conductive film formed on one surface of a substrate, and the surface protective film for the transparent conductive film is returned from the roll body. The roll is formed by laminating an adhesive layer on one side of the flexible base film, and peeling the peeled film through the peeled surface layer on the surface of the adhered surface adhered to the adhesive layer The peeling film has a thickness of 50 μm to 250 μm, and the peeling film has a flexural strength at 40° C. of 0.30 mN to 40 mN; and the base film of the surface protective film for the transparent conductive film is polyethylene terephthalate. In the ester resin film, the base film has a thickness of 100 μm to 250 μm, the thickness of the adhesive layer is 1/20 to 1/5 of the thickness of the base film, and the peel strength of the other surface as the adherend is 0.03. ~0.3N/25mm. A roll of a surface protective film for a transparent conductive film is obtained by winding a surface protective film for a transparent conductive film of the first aspect of the invention into a roll. A transparent conductive film is obtained by laminating a surface protective film for a transparent conductive film according to claim 1 of the invention, on the other surface of the transparent conductive film having the transparent conductive film formed on one surface of the substrate.