JP2005071901A - Transparent conductive laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive laminated film which has a sufficient surface resistance value for the usage of a touch panel and is superior in abrasion resistance and adhesiveness by making use of advantages that coating films can be formed at high speed while manufacturing cost is reduced concerning the transparent conductive laminated film having a large area, and by making use of advantages of the sputtering method that the coating films which have high hardness and are superior in durability can be formed at high speed. <P>SOLUTION: In the transparent conductive laminated film, a transparent conductive layer is formed via an overcoat layer composed of an oxidized silicon membrane formed by coating a sol liquid prepared by hydrolyzing an organosilicon compound on a transparent polymer film substrate of which the hardcoated layer has been installed at least on one side face, and this has a structure that an overcoat layer is laminated composed of a thin film which is transparent in a visible light region and formed by a sputtering method on the transparent conductive layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transparent conductive laminated film. More specifically, the present invention relates to a transparent conductive laminated film used as a transparent electrode such as a touch panel, a liquid crystal display element, an electroluminescence panel, an electrochromic element, a solar battery, a transparent surface heating element, an electromagnetic wave shielding film, or an antistatic film.

  A transparent conductive film in which a layer containing a transparent conductive thin film including a tin-doped indium oxide (hereinafter referred to as ITO) thin film is formed on a transparent film substrate is a vacuum deposition method, a reactive deposition method, an ion beam assisted deposition method, It is manufactured by a vacuum film forming process such as a sputtering method or an ion plating method. Among these processes, the sputtering method is most widely used for the production of transparent conductive films because it can easily cope with an increase in area. There are various means in the sputtering method. For example, an inert gas ion generated by direct current or high frequency discharge in vacuum is collided with the target surface at an accelerated speed, and atoms constituting the target are knocked out from the surface and deposited on the substrate. And a means for forming a transparent conductive layer.

  The advantages of forming a transparent conductive thin film by sputtering are that the film thickness can be easily and accurately controlled, can be formed to a uniform thickness on a large-area substrate, and the formed thin film is dense so that it is scratched. It is difficult to reduce the surface resistance, and because the sputtered transparent conductive thin film material particles are incident on the substrate with high energy, a throwing effect can be obtained and adhesion can be provided regardless of the wettability of the substrate. It is done. In addition, disadvantages include a large apparatus due to the vacuum film forming process, and a thin film forming speed that is very slow compared to the coating method, which causes an increase in manufacturing cost. Furthermore, the slow formation rate of the thin film has a problem in that the polymer film substrate is exposed to the plasma for a long time and the film is heated, causing the polymer film to be altered or wrinkled.

When a transparent conductive thin film is formed on a polymer film substrate by direct current sputtering, a transparent conductive film having a specific resistance of about 4 × 10 ^{−4 to} 5 × 10 ⁻⁴ Ω · cm can be produced. A surface resistance value of about 40 to 50Ω / □ can be realized with a film thickness of about 100 nm (Japanese Patent Laid-Open Nos. 5-241173, 8-271985, and 8-21374). However, due to the disadvantages described above, there is a problem that leads to an increase in manufacturing cost.

  In order to solve the increase in the manufacturing cost of the transparent conductive film using such a vacuum process, production of a transparent conductive film by a coating method has also been attempted. Compared with the sputtering method, the coating method is simpler and has a higher film formation rate, so the productivity is high and the manufacturing cost is low. As a method for forming a transparent conductive layer by a coating method, a conductive paint in which conductive fine particles are dispersed in a binder resin is applied to a substrate and dried, or a solution containing a metal alkoxide is hydrolyzed and polymerized. A sol-gel method in which the obtained sol is applied to a substrate to form a gel film and then heat-treated is attempted.

  In the method of forming a transparent conductive layer by applying a conductive paint containing conductive fine particles to a substrate, it was said that the conductive layer could not be formed unless a large amount of binder resin was used in the conductive paint. . For this reason, the contact between the conductive fine particles is hindered by the binder resin, and there is a problem that the resistance value of the obtained transparent conductive film becomes high, and its use is limited. When a binder resin is not used, a conductive material must be sintered at a high temperature in order to form a transparent conductive layer that can withstand practical use. There was a problem that happened.

As a method for forming a transparent conductive layer by applying a conductive paint containing conductive fine particles to a substrate, for example, in Japanese Patent Laid-Open No. 9-109259, a conductive powder and a binder resin are used on a transparent plastic film. The first step of applying and drying the conductive paint to form a conductive layer, the second step of pressing and heating the surface of the conductive layer to a mirror-finished smooth surface, pressing and heating the smooth surface A method for producing an antistatic transparent conductive film or sheet comprising a third step of laminating a treated conductive layer on a plastic plate or sheet and thermocompression bonding has been proposed. In this method, for example, when an inorganic conductive powder is used, the conductive powder is 100 to 500 parts by weight with respect to 100 parts by weight of the binder, and a large amount of binder resin is used. In this method, the surface resistance is described as about 6 × 10 ^{6 to} 7 × 10 ⁶ Ω / □, but a practical surface resistance value as a transparent conductive film for a transparent electrode cannot be realized.

  In JP-A-8-199096, a transparent conductive film is formed by coating a glass plate with a binder-free conductive film-forming coating composed of ITO powder, solvent, coupling agent, metal organic acid salt or inorganic acid salt. Although a method for forming a layer has been proposed, in this method, it is necessary to bake at a high temperature of 300 ° C. or higher after applying a conductive film-forming coating material. There is a problem of alteration.

  JP-A-9-263716 discloses an overcoat composition containing a silica sol obtained by hydrolysis of alkoxysilane and an organic polymer in a solvent on a transparent conductive layer made of a conductive powder such as ITO or ATO. A method for improving wear resistance and lowering resistance by applying and baking to form a siliceous overcoat layer has been proposed. In this method, since it is necessary to perform overcoat baking at a temperature of about 170 to 180 ° C. for 30 minutes, formation on a polymer substrate has a problem of causing deterioration of the substrate.

  As described above, the production of a transparent conductive film by a coating method has an advantage that the cost can be suppressed as compared with a vacuum film forming process, but an insulating binder component to the coating liquid in order to improve the coating film strength. If there is a limit to lowering the resistance, forming a transparent conductive film with a coating solution that does not contain a binder component requires baking at a high temperature as post-treatment to improve wear resistance. Formation becomes difficult.

  By the way, since the adhesiveness between the polymer film substrate or the hard coat layer and the transparent conductive layer is not sufficient, there is a problem that the transparent conductive layer is peeled off or missing in various processing steps for producing a transparent electrode. Moreover, when using it for the upper electrode use of a touch panel, there existed a problem which peeling will arise between a film base material and a transparent conductive layer by repeating a deformation | transformation, and an exact input cannot be performed.

  In order to solve the above problems, a method of providing an organic compound or an inorganic compound exhibiting easy adhesion as a base layer between a transparent conductive layer and a polymer film substrate has been proposed (Japanese Patent Laid-Open No. 60-13138). No. 1, JP-A-1-9729, JP-A-4-163141). However, these methods do not always have sufficient adhesion.

Regarding the method of providing sufficient adhesion between the transparent conductive layer made of a metal thin film or a conductive oxide thin film and the polymer film substrate or the hard coat layer, oxygen is used as a base layer of the transparent conductive layer on the substrate. A method of providing a deficient insulating silicon oxide layer by a vacuum process (Japanese Patent Laid-Open No. 6-320659), SiC _x , SiO _x , SiN _x , SiC _x O _y , SiC _x N _y , SiO _x N _y and A method of providing a base layer by applying an ultraviolet curable resin containing fine particles of one or more silicon compounds selected from the group consisting of SiC _x O _y N _z to a polymer film substrate No. 196871) has been proposed.

  The method of providing the insulating silicon oxide layer as a base layer is considered to increase the manufacturing cost because the insulating silicon oxide layer is formed by a vacuum process such as sputtering. Further, since it is necessary to form oxygen-deficient silicon oxide, the control of the degree of oxidation at the time of formation is very severe. Further, when silicon oxide is formed by a sputtering method, it is one of the oxides that are extremely slow in formation rate, and thus the productivity is low.

  The method of providing an undercoat layer by applying an ultraviolet curable resin containing fine particles of one or more types of silicon compounds to a polymer film substrate is obtained by applying an undercoat layer on a substrate provided with an ultraviolet curable hard coat layer. When the coating liquid of the base layer is cured, the hard coat layer is irradiated with ultraviolet rays again, so that the hard coat layer is altered and the adhesion between the substrate and the hard coat layer may be deteriorated. There is a problem that the hard coat agent that can be used is limited.

With regard to the surface resistance of transparent conductive films, surface resistance of about 1 kΩ / □ is required for recent devices such as PDAs that require low-voltage driving (Toru Motomatsu, Material Stage Vol.2 No.3 p31). (2002)). This surface resistance is a general surface resistance value (several hundreds to several tens of ohms / square) exhibited by a transparent conductive thin film formed by a vacuum process such as sputtering, and a general conductive film formed by a coating method. It is an intermediate value of the surface resistance value (about 10 ⁴ to 10 ⁶ Ω / □), whether it is a transparent conductive thin film formed by a vacuum process such as sputtering or a transparent conductive film formed by a coating method Realization is difficult.

JP-A-9-109259 JP-A-8-199096 JP-A-9-263716 JP-A-60-131238 Japanese Patent Laid-Open No. 1-9729 JP-A-4-163141 Japanese Patent Laid-Open No. 2002-196871

  The present invention has been made in order to solve the above-mentioned problems, and has the advantage of a coating method capable of suppressing the production cost of a transparent conductive film having a large area at a high speed, and has high hardness and durability. An object of the present invention is to provide a transparent conductive laminated film having a surface resistance value sufficient for touch panel use and excellent in wear resistance and adhesion, taking advantage of the sputtering method capable of forming an excellent film.

  In view of the above circumstances, as a result of intensive studies by the inventors, a transparent conductive layer is formed by a coating method, and an overcoat layer formed by a sputtering method is laminated on the transparent conductive layer. It has been found that the above-described problems can be solved by the characteristic transparent conductive laminated film.

The present invention has been made based on the following discussion in this study.
Whether a transparent conductive thin film (hereinafter referred to as a coating layer) formed by a coating method or a transparent conductive thin film (hereinafter referred to as a sputter layer) formed by a sputtering method, a conductive path is formed by contact of conductive particles with each other. Microscopically, in the sputter layer, the conductive particles are in close contact with each other while having a chemical bond, whereas in the coating layer, contact with a chemical bond is not realized. There is only sparse contact. This is the reason why the sputter layer has a lower resistance value than the coating layer.

The specific resistance of the conductive thin film is generally
ρ = 1 / (q · n · μ) (1)
(Where, ρ: specific resistance (Ω · cm), q: elementary electric charge (C), n: density of charge carriers (cm−3), μ: mobility of charge carriers (cm2 · V / s) Yes.)

  Since it is considered that the density of the charge carriers does not change greatly if the material in the conductive particles is the same in both the sputtered layer and the coated layer, the difference in the contact form of the conductive particles is reflected in the mobility μ in the equation (1). Thus, it can be concluded that there is a difference in specific resistance.

Therefore, in order to reduce the general surface resistance value of 10 ⁴ to 10 ⁶ Ω / □ of the coating layer to several kΩ, it is necessary to close contact between the conductive particles forming the coating layer. In JP-A-9-263716, an overcoat composition containing a silica sol obtained by hydrolysis of alkoxysilane and an organic polymer in a solvent is applied onto a transparent conductive layer formed by a coating method, and baked to obtain silica. A method has been proposed in which the contact of the conductive particles forming the transparent overcoat layer to form the transparent conductive layer is intimate, but there is a problem that the polymer base material cannot be used because baking at a high temperature is required. is there. Therefore, if the overcoat layer is formed by the sputtering method, not only baking is not necessary, but also the thin film formed by the sputtering method has very dense and hard characteristics, so it has better wear resistance than the coating type overcoat layer It is possible to show sex. Furthermore, since the thin film formed by the sputtering method generates a strong stress, the effect of promoting the contact between the particles forming the transparent conductive layer can be expected by this stress. This is the reason why the overcoat layer is formed by the sputtering method on the transparent conductive layer formed by the coating method proposed in the present invention.

  The reason for providing a silicon oxide film as an underlayer is that silicon oxide has good affinity with a polymer film or a transparent conductive layer, so that adhesion is enhanced as an intermediate layer between the polymer film substrate and the transparent conductive layer. Because it can be expected. The reason for using the sol-gel method to form a silicon oxide film by applying a sol prepared by hydrolyzing an organosilicon compound is that the formation speed is fast and heat treatment of the gel film is possible at a relatively low temperature. This is because the substrate is not selected.

Based on the above consideration, the present invention has been made.
That is, the present invention is a transparent substrate film, a hard coat layer provided on at least one surface thereof, a base layer provided on the hard coat layer, a transparent conductive layer provided by a coating method on the base layer, And a transparent conductive laminated film comprising an overcoat layer formed on the transparent conductive layer by a sputtering method.

  According to the present invention, the advantage of the coating method that can keep the production cost of the transparent conductive film of a large area at a high speed and the advantage of the sputtering method that can form a transparent conductive film with low resistance and excellent durability. By utilizing the above, it is possible to provide a transparent conductive laminated film having a sufficient surface resistance value for touch panel applications and having excellent wear resistance and adhesion.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing the layer structure of a transparent conductive laminated film which is a preferred embodiment of the present invention. A hard coat layer 2 from the transparent polymer film substrate 1 side, a base layer 3 made of silicon oxide formed by applying a sol prepared by hydrolyzing an organosilicon compound, and a transparent layer formed by a coating method on the outer layer It has the coating layer 4 which consists of an electroconductive thin film, and the overcoat layer 5 formed by sputtering method on it.

  The laminated film of the present invention prevents the film from being damaged by providing the hard coat layer. In addition, since a hard overcoat layer is formed by sputtering on the transparent conductive layer formed by the coating method, it has better wear resistance and is thinner than the transparent conductive film formed by the coating method. The resistance of the overcoat layer is reduced by promoting the contact between the conductive particles forming the transparent conductive layer. Furthermore, the base layer which consists of silicon oxide is provided, and the adhesiveness of a transparent conductive layer and a transparent polymer film base material is ensured.

[Transparent substrate film]
The transparent substrate film used in the present invention is preferably a plastic film. Polymers forming the plastic film include polyesters (eg, polyethylene terephthalate (PET), polyethylene naphthalate), poly (meth) acrylic (eg, polymethyl methacrylate (PMMA)), polycarbonate (PC), polystyrene, polyvinyl alcohol, Examples thereof include polyvinyl chloride, polyvinylidene chloride, polyethylene, ethylene-vinyl acetate copolymer, polyurethane, triacetate, and cellophane. Among these, PET, PC, and PMMA are preferable.

  The transparent substrate film may be an unstretched film or a stretched film depending on the type of polymer. For example, a polyester film such as a PET film is usually a biaxially stretched film, and a PC film, a triacetate film, a cellophane film and the like are usually unstretched films.

  The term “transparent” means that the transmittance in the visible light region is usually 40% or more, preferably 60% or more, more preferably 80% or more.

  The thickness of the transparent substrate film is appropriately determined depending on the use of the antireflection film, but is preferably 20 μm to 500 μm. If it is too thin, the film strength will be weak, and if it is thick, the stiffness may be large and sticking may be difficult, and 50 μm to 200 μm is more preferable. The transparent substrate film preferably transmits 40% or more of visible light, more preferably 60% or more, and still more preferably 80% or more.

  The surface of the transparent substrate film can be subjected to surface treatment on one side or both sides as desired for the purpose of improving the adhesion with the layer provided thereon. For example, corona discharge treatment, glow discharge treatment, ozone / ultraviolet irradiation treatment and the like can be mentioned. Furthermore, one or more undercoat layers can be provided. Examples of the material for the undercoat layer include copolymers such as vinyl chloride, vinylidene chloride, butadiene, (meth) acrylic acid esters and vinyl esters, and water-soluble polymers such as latex and gelatin.

[Hard coat layer]
In the present invention, the hard coat layer preferably forms a layer having transparency and appropriate hardness. The forming material is not particularly limited, and for example, a curable resin or a thermosetting resin by ionizing radiation or ultraviolet irradiation can be used. In particular, an ultraviolet irradiation curable acrylic or organic silicon resin or a thermosetting polysiloxane resin is suitable. Known resins can be used for these resins. Furthermore, it is more preferable that the refractive index of the hard coat layer is equal to or close to that of the transparent base film, but this point is not particularly necessary when the film thickness is 3 μm or more.

  In forming the hard coat layer, the coating method is not limited, but it is preferable to form the hard coat layer smoothly and uniformly.

  In this hard coat layer, transparent inorganic fine particles having an average particle diameter of 0.01 to 1 μm may be mixed and dispersed. Thereby, the crosslinking shrinkage rate as a film | membrane can be improved and the flatness of a coating film can be improved. The inorganic fine particles can enhance the adhesion at the contact portion between the hard coat layer and the transparent conductive oxide layer. As the inorganic fine particles, those having an affinity for indium, tin, and zinc contained in the transparent conductive oxide layer are preferable, and silicon dioxide particles, titanium dioxide particles, zirconium oxide particles, and aluminum oxide particles are preferable.

[Underlayer]
The underlayer is preferably formed by applying a (silicon oxide) sol solution prepared by hydrolyzing an organosilicon compound, particularly a silicon alkoxide containing tetraalkoxysilane, to a film. This sol can be prepared by dissolving an organosilicon compound in an organic solvent suitable for coating and performing hydrolysis using a certain amount of water.

This sol is preferably prepared using an organosilicon compound represented by the general formula R _a ¹ R _b ² SiX _{4- (a + b)} . Here, R ¹ and R ² are each an alkyl group, alkenyl group, allyl group, or a hydrocarbon group having a halogen group, an epoxy group, an amino group, a mercapto group, a methacryl group or a cyano group, X is an alkoxyl group, A hydrolyzable group selected from an alkoxyalkoxyl group and a halogen or acyloxy group. A and b are 0, 1 or 2, respectively, but a + b is 2 or less.

  The hydrolysis of the organosilicon compound is preferably performed by dissolving the organosilicon compound in a suitable solvent. Examples of the solvent used include alcohols such as methyl ethyl ketone, isopropyl alcohol, methanol, ethanol, methyl isobutyl ketone, ethyl acetate and butyl acetate, ketones, esters, halogenated hydrocarbons, aromatic hydrocarbons such as toluene and xylene, And mixtures thereof.

The organosilicon compound is preferably 0.1% by weight or more, more preferably 0.1 to 10% by weight in terms of SiO ₂ generated as a result of 100% hydrolysis and condensation of the organosilicon compound in the solvent. To dissolve. If the concentration of the sol in terms of SiO ₂ is less than 0.1% by weight, the formed sol film cannot sufficiently exhibit the desired characteristics, and if it exceeds 10% by weight, it is difficult to form a transparent homogeneous film. Absent. In the present invention, an organic or inorganic binder may be used in combination as long as it is within the above-mentioned solid content concentration.

  For the hydrolysis of the organosilicon compound, an amount of water necessary for hydrolysis or more than that amount is added to the solution, preferably at a temperature of 15 to 35 ° C., more preferably at a temperature of 22 to 28 ° C., preferably 0.5 It is preferably carried out by stirring for ˜48 hours, more preferably 2 to 24 hours.

  A catalyst is preferably used for the hydrolysis. These catalysts are preferably acids such as hydrochloric acid, nitric acid, sulfuric acid, and acetic acid, and these acids are preferably added so that the pH of the whole solution is 1-6. The silicon oxide sol thus obtained is colorless and transparent, is a stable liquid having a pot life of about 1 month, has good wettability with respect to the film substrate, and is excellent in applicability.

  The silicon oxide sol obtained by hydrolysis of the organosilicon compound is in a liquid state and has a viscosity in a range that can be applied to a normal coating operation, and preferably has a viscosity of 10 poise or less, more preferably 1 poise or less at an application temperature. A liquid material having a viscosity higher than this makes it difficult to form a uniform coating film.

  As a coating method, a method used in a normal coating operation can be used. For example, a spin coating method, a dip method, a spray method, a roll coater method, a meniscus coater method, a flexographic printing method, a screen printing method, a beat coater method. And a microgravure coater method. After coating, when the coating film is dried, a film made of silicon oxide is formed. The drying temperature (heat treatment temperature) is preferably 60 to 150 ° C, more preferably 80 to 110 ° C.

  The underlayer formed in this way is formed as a layer containing silicon oxide as a main component, and preferably has a thickness of 10 nm to 1 μm, more preferably 30 to 100 nm.

[Transparent conductive layer]
The transparent conductive layer is a transparent layer having conductivity. Here, the term “transparent” means that the transmittance in the visible light region is usually 40% or more, preferably 60% or more, more preferably 80% or more. This transparent conductive layer preferably contains conductive fine particles, and therefore the conductivity is shown by the conductive fine particles, and more preferably consists essentially of conductive fine particles. It is preferable from a viewpoint of electroconductivity not to contain nonelectroconductive things, such as a binder.

  The conductive fine particles are preferably conductive oxide fine particles or metal fine particles. The average particle diameter of the conductive fine particles is preferably 1 to 100 nm. If the thickness exceeds 100 nm, haze may increase. If the thickness is less than 1 nm, dispersion of fine particles may be difficult, and the surface resistance of the formed transparent conductive layer may increase rapidly.

  When the conductive fine particles are conductive oxide fine particles, the conductive oxide fine particles are tin-doped indium oxide (ITO), indium oxide, antimony-doped tin dioxide, tin dioxide, and aluminum-doped oxide. It is preferably made of at least one selected from the group consisting of zinc, zinc oxide doped with gallium, zinc oxide, and a mixture of indium oxide and zinc oxide.

  When the conductive fine particles are metal fine particles, the metal fine particles are preferably composed of at least one selected from the group consisting of gold, silver, copper, aluminum, iron, nickel, palladium, platinum, and alloys thereof. .

  Among conductive oxide fine particles, tin-doped indium oxide (ITO) fine particles having the lowest resistance among oxides are preferable. In this case, the tin content is most preferably 3 to 15 atomic% with respect to indium from the viewpoint of conductivity.

  Among the metal fine particles, fine particles containing silver are particularly preferable, and fine particles of an alloy of palladium and silver are more preferable from the viewpoint of weather resistance. In this case, the content of palladium is preferably 5 to 30% by weight. If the amount of palladium is small, the weather resistance may deteriorate, and if the amount of palladium is large, the conductivity may decrease, which is not preferable.

  The transparent conductive layer is preferably formed by applying a coating solution in which fine particles of conductive oxide are dispersed in an organic solvent or a coating solution in which fine particles of metal are dispersed in an organic solvent.

  Various organic dispersion media can be used as the dispersion medium for the conductive fine particles. For example, saturated hydrocarbons such as hexane; aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, propanol, and butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; ethyl acetate Esters such as tetrahydrofuran, dioxane and diethyl ether; amides such as N, N-dimethylformamide, N-methylpyrrolidone (NMP) and N, N-dimethylacetamide; ethylene chloride and chlorobenzene And halogenated hydrocarbons. Of these, polar dispersion media are preferred, and alcohols such as methanol and ethanol are particularly preferred because they have good dispersibility without using a dispersant. These dispersion media can be used alone or in combination of two or more. Moreover, you may use a dispersing agent by the kind of dispersion medium.

  The amount of the dispersion medium may be such that the dispersion liquid of the conductive fine particles (paint, conductive paint) has an appropriate viscosity suitable for application. Specifically, the dispersion medium is preferably about 100 to 100,000 parts by weight with respect to 100 parts by weight of the conductive fine particles, but may be appropriately changed according to the types of the conductive fine particles and the dispersion medium. Dispersion of the conductive fine particles in the dispersion medium can be performed by a known dispersion means such as a sand grinder mill method.

  Next, the conductive fine particle dispersion (coating material) is applied onto a support and dried to form a conductive fine particle-containing layer.

  The conductive fine particle dispersion (paint) can be applied onto the support by a known method. Examples thereof include a spin coating method, a dip method, a spray method, a roll coater method, a meniscus coater method, a flexographic printing method, a screen printing method, a beat coater method, a reverse roll method, and a micro gravure coater method. The drying temperature (heat treatment temperature) depends on the type of dispersion medium used for dispersion, but is preferably 60 to 150 ° C.

  Thus, when conductive fine particles are dispersed in a dispersion medium, applied, and dried, a uniform film can be easily formed. When a dispersion of these conductive fine particles is applied and dried, the fine particles form a film even if no binder is present in the dispersion.

[Overcoat layer]
An overcoat layer is provided on the transparent conductive layer thus formed. The overcoat layer is a thin film transparent in the visible light region formed by a sputtering method. Here, the term “transparent” means that the transmittance in the visible light region is usually 40% or more, preferably 60% or more, more preferably 80% or more.

  The overcoat layer is preferably at least one selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, silicon nitride, titanium nitride, and zirconium nitride.

  The thickness of the overcoat layer is preferably 10 to 100 nm. If the overcoat layer is thinner than this range, sufficient wear resistance cannot be obtained. If the overcoat layer is thicker than this range, the surface resistance is increased, which is not preferable.

  As a sputtering method, a known method such as a conventional DC magnetron method, a high-frequency magnetron method, a dual cathode magnetron method, or an electron cyclotron resonance method can be used. In particular, a dual cathode magnetron method is preferable in which two targets are arranged close to each other in one film forming chamber, and voltages are alternately applied to the two targets as an anode and a cathode at a frequency of several tens of kHz. In this method, since the target alternately becomes an anode and a cathode at a frequency of several tens of kHz, the target is not easily charged up (charge integration), and the frequency is not so high, and a high-speed film formation is possible.

  In order to form an overcoat layer made of metal oxide or metal nitride, a reactive gas (oxygen gas or nitrogen gas) is introduced into the film-forming chamber together with argon gas using a metal target as a starting material to react with the metal. A reactive sputtering method in which a gas is chemically reacted to form a metal oxide thin film or a metal nitride thin film may be used, and sputtering is performed using argon gas with an oxide sintered body or nitride sintered body target as a starting material. You may use the method to do.

  The transparent conductive laminated film of the present invention preferably has a light transmittance in the visible light region of 70% or more and a surface resistance of 500Ω / □ to 10 kΩ / □. Can be achieved.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, the characteristic of the antireflection film was evaluated by the following method.

[Electric resistance]
The surface resistance of the transparent conductive laminated film was measured using a Loresta MP (4-end needle method surface resistance meter) manufactured by Mitsubishi Chemical Corporation.

[Visible light transmittance]
The visible light transmittance of the transparent conductive laminated film is measured in the wavelength range of 380 to 780 nm by using a UV-3101PC type manufactured by Shimadzu Corporation and illuminated on the surface of the transparent conductive laminated film. Calculation was made based on JIS A5759.

[Adhesion evaluation]
A transparent knife-shaped laminated film surface is cut by 6 knives at 2 mm intervals to make 25 grids, and Nichiban Cello tape is attached on the grid, and the cello tape is peeled at 90 degree angle. The thin film on the film was visually evaluated for the number of residual grids.
Evaluation was made as follows: ◯: 25 remaining, Δ: 20-24, x: 19 or less.

[Abrasion resistance evaluation]
The abrasion resistance was evaluated by visually checking the presence or absence of scratches by pressing # 000 steel wool against the surface of the transparent conductive laminated film with a weight of 1 kg and making 10 reciprocations.
The evaluation was as follows: ○: no scratch, Δ: shallow scratch, ×: deep scratch.

[Example 1]
The transparent conductive laminated film of the present invention in which the transparent conductive layer is a film made of ITO particles and the overcoat layer is a silicon dioxide thin film was prepared. A biaxially oriented polyethylene terephthalate film (OPFW-188 μm made by Teijin DuPont Film) was used as the transparent film substrate, and a UV curable hard coat agent (JSR Desolite Z7501) was applied on one side by microgravure coating, followed by UV curing. To form a hard coat layer. At this time, the thickness of the hard coat layer was 5 μm.

  Next, a silicon oxide sol obtained by dissolving tetraethyl silicate in ethanol and hydrolyzing it with water and hydrochloric acid is applied on the hard coat layer, and heat-treated at 100 ° C. for 2 minutes. An underlying layer was formed. At this time, the film thickness of the underlayer was 100 nm.

  A coating solution obtained by adding 300 parts by weight of isopropyl alcohol to 100 parts by weight of ITO fine particles (TL-130, manufactured by Catalyst Chemical Industry Co., Ltd.) on the base layer is coated on the base layer by microgravure coating, and 150 A transparent conductive layer having a film thickness of 1.6 μm was formed by heat treatment at 2 ° C. for 2 minutes. At this time, the surface resistance was 41 kΩ / □, and the visible light transmittance was 82%.

  Further, an overcoat layer made of silicon dioxide was formed to a thickness of 20 nm on the transparent conductive layer by a dual cathode magnetron type web coater type sputtering machine. The overcoat layer was formed using a silicon dioxide target, introducing a mixed gas having a volume ratio of argon / oxygen = 99/1, and under an atmospheric pressure of 0.5 Pa.

  The transparent conductive laminated film of the present invention thus obtained had a surface resistance value of 5.3 kΩ / □ and a visible light transmittance of 87%. Moreover, as a result of evaluating adhesiveness, the number of residual grids was 25, and evaluation was (circle). As a result of evaluating the wear resistance, no scratch was observed, and the result was ◯.

[Example 2]
The same as Example 1 except that the overcoat layer was a titanium dioxide thin film. The thin film was formed by introducing a mixed gas having a volume ratio of argon / oxygen = 85/15 as a starting metal titanium target material so that the atmospheric pressure was 0.5 Pa.

  The surface resistance value and visible light transmittance before forming the overcoat layer were 41 kΩ / □ and 82%, respectively, as in Example 1. The surface resistance value after overcoat formation was 4.7 kΩ / □, and the visible light transmittance was 79%. As a result of evaluating the adhesion after the overcoat layer was formed, the number of residual grids was 25, and the evaluation was good. As a result of evaluating wear resistance, no scratch was observed, and the evaluation was good.

[Example 3]
Example 1 is the same as Example 1 except that the conductive fine particles forming the transparent conductive layer are composed of silver and palladium alloy fine particles containing 10% by weight of palladium.

  The film thickness of the transparent conductive layer was 70 nm. The surface resistance value and visible light transmittance before forming the overcoat layer were 3.3 kΩ / □ and 80%, respectively. The surface resistance value after overcoat formation was 1.6 kΩ / □, and the visible light transmittance was 78%. As a result of evaluating the adhesion after the overcoat layer was formed, the number of residual grids was 25, and the evaluation was good. As a result of evaluating wear resistance, no scratch was observed, and the evaluation was good.

[Example 4]
Example 2 is the same as Example 2 except that the conductive fine particles forming the transparent conductive layer are composed of alloy fine particles of silver and palladium containing 10% by weight of palladium.

  The surface resistance value and visible light transmittance before forming the overcoat layer are 3.3 kΩ / □ and 80%, respectively, as in Example 3. The film thickness of the transparent conductive layer is also 70 nm as in Example 3. The surface resistance value after overcoat formation was 0.85 kΩ / □, and the visible light transmittance was 74%. As a result of evaluating the adhesion after the overcoat layer was formed, the number of residual grids was 25, and the evaluation was good. As a result of evaluating wear resistance, no scratch was observed, and the evaluation was good.

[Comparative Example 1]
The same as Example 1 except that the overcoat layer is not formed. The film thickness of the transparent conductive layer, the surface resistance value, and the visible light transmittance of the transparent conductive laminated film not forming the overcoat are the same as those of the laminated film before forming the overcoat layer shown in Example 1, The values were 1.6 μm, 41 kΩ / □, and 82%, respectively. As a result of the adhesion evaluation, the number of residual grids was 21, and the evaluation was Δ. As a result of evaluating wear resistance, deep scratches were observed, and the evaluation was x. From the comparison with Example 1, it was confirmed that the overcoat layer had a function of improving the wear resistance as intended.

[Comparative Example 2]
The same as Example 3 except that no overcoat layer is formed. The film thickness of the transparent conductive layer, the surface resistance value, and the visible light transmittance of the transparent conductive laminated film not forming the overcoat are the same as the laminated film before forming the overcoat layer shown in Example 3, They were 70 nm, 3.3 kΩ / □, and 80%, respectively. As a result of the adhesion evaluation, the number of residual grids was 20, and the evaluation was Δ. As a result of evaluating the wear resistance, deep scratches were observed.

[Comparative Example 3]
Except that the overcoat layer was obtained by dissolving tetraethyl silicate in ethanol, applying water and hydrochloric acid to hydrolyze it and applying a silicon oxide sol obtained by heat treatment at 100 ° C. for 2 minutes to form a 30 nm silicon oxide film. Is the same as in Example 1.

  The transparent conductive laminated film thus obtained had a surface resistance value of 7.1 kΩ / □ and a visible light transmittance of 85%. Moreover, as a result of evaluating adhesiveness, the number of residual grids was 25, and evaluation was (circle). As a result of evaluating the wear resistance, shallow scratches were observed, and the result was Δ.

[Comparative Example 4]
The same as Comparative Example 3 except that the conductive fine particles forming the transparent conductive layer are composed of silver and palladium alloy fine particles containing 10% by weight of palladium.

  The transparent conductive laminated film thus obtained had a surface resistance value of 3.0 kΩ / □ and a visible light transmittance of 81%. Moreover, as a result of evaluating adhesiveness, the number of residual grids was 25, and evaluation was (circle). As a result of evaluating the wear resistance, shallow scratches were observed, and the result was Δ.

[Comparative Example 5]
The same as Example 1 except that the film thickness of the overcoat layer is 150 nm. The transparent conductive laminated film thus obtained had a surface resistance value of 10 ³ kΩ / □ and a visible light transmittance of 86%. Since the overcoat layer was thick, the surface resistance increased from the surface resistance of 41 kΩ / □ before the overcoat layer was formed. As a result of evaluating the adhesion, the number of residual grids was 25, and the evaluation was good. As a result of evaluating the wear resistance, no scratch was observed and the result was Δ.

[Comparative Example 6]
The same as Example 1 except that the film thickness of the overcoat layer was 5 nm. The transparent conductive laminated film thus obtained had a surface resistance value of 41 kΩ / □ and a visible light transmittance of 83%. Further, as a result of evaluating the adhesion, the number of residual grids was 18, and the evaluation was Δ. As a result of evaluating the wear resistance, deep scratches were observed, and the result was x.
The above results are summarized in a table.

  The transparent conductive laminated film of the present invention is advantageously used as a transparent electrode, an electromagnetic wave shielding film, or an antistatic film used for a touch panel, a liquid crystal display element, an electroluminescence panel, an electrochromic element, a solar cell, a transparent surface heating element, and the like. Can do.

It is a cross-sectional schematic diagram which shows an example of the layer structure of the transparent conductive laminated film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base film 2 Hard coat layer 3 Underlayer 4 Transparent conductive layer 5 Overcoat layer

Claims (9)

  A transparent base film, a hard coat layer provided on at least one surface thereof, a base layer provided on the hard coat layer, a transparent conductive layer provided on the base layer by a coating method, and a transparent conductive layer A transparent conductive laminated film comprising an overcoat layer formed thereon by a sputtering method.   The transparent conductive laminated film according to claim 1, wherein the overcoat layer comprises a thin film transparent in the visible light region.   2. The transparent conductive laminated film according to claim 1, wherein the overcoat layer comprises at least one selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, silicon nitride, titanium nitride and zirconium nitride. .   The transparent conductive laminated film according to claim 1, wherein the overcoat layer has a thickness of 10 to 100 nm.   The transparent conductive layer according to claim 1, wherein the transparent conductive layer is formed by applying a coating liquid in which fine particles of conductive oxide are dispersed in an organic solvent or a coating liquid in which fine particles of metal are dispersed in an organic solvent. the film.   Conductive oxide particles are indium oxide doped with tin (ITO), indium oxide, antimony doped tin dioxide, tin dioxide, aluminum doped zinc oxide, gallium doped zinc oxide, zinc oxide, and oxidation The transparent conductive laminated film according to claim 4, comprising at least one selected from the group consisting of a mixture of indium and zinc oxide.   The transparent conductive laminated film according to claim 4, wherein the metal fine particles comprise at least one selected from the group consisting of gold, silver, copper, aluminum, iron, nickel, palladium, platinum, and alloys thereof.   The transparent conductive laminated film of Claim 1 whose transmittance | permeability in visible region is 70% or more and whose surface resistance is 500 ohm / square-10 kohm / square.   The transparent conductive laminated film according to claim 1, wherein the underlayer is a silicon oxide layer having a thickness of 10 nm to 1 μm formed by applying a sol solution prepared by hydrolyzing an organic silicon compound.

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