JPH06103840A - Manufacture of transparent conductive substrate - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a transparent conductive substrate with low surface resistance and excellent optical properties. CONSTITUTION:A transparent conductive substrate consisting of a visible light transmissive substrate material, a transparent overcoat layer formed on the substrate material, and a transparent conductive film formed on the overcoat layer and containing conductive superfine particles is prepared by printing or applying a transparent conductive ink to a substrate, drying and then firing the ink to form the transparent conductive film, and after that forming the overcoat layer, sticking the resulting body to a substrate material with an adhesive, etc., and removing the substrate by dissolving or swelling the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a transparent conductive substrate used as a transparent electrode or the like in a touch panel, a liquid crystal device, an electroluminescent display element or the like.

[0002]

2. Description of the Related Art Generally, a transparent conductive film is made of indium-tin oxide (ITO) or tin-antimony oxide (ATO).
It can be obtained by forming an oxide such as a film on a glass or a plastic film by a sputtering method or a CVD method, but these methods require an expensive device and are difficult to obtain at low cost because of low productivity, Also, it is not suitable for obtaining a large-area film.

In order to solve these problems, therefore, there has been used a method of forming a transparent conductive circuit by printing a transparent conductive ink containing conductive ultrafine powder on a substrate and curing it.

[0004]

By the way, this transparent conductive ink uses conductive ultrafine powder as a filler, a resin such as a thermoplastic resin, a thermosetting resin or an ultraviolet curable resin as a binder, and a solvent and a small amount. It contains additives such as a dispersant. Then, after printing this transparent conductive ink on a glass or plastic film and curing (dry curing, heat curing, ultraviolet curing), conductive ultrafine powder as a filler is in contact with each other by a resin as a binder. It is fixed and becomes a conductive coating film. Therefore, when the amount of the resin used as the binder is too large, the resin intervenes between the filler particles and interferes with the contact between the particles, so that the surface resistance of the coating film increases. On the other hand, when the amount of the resin is small, the contact of the filler particles is good and the surface resistance of the coating film is lowered, but voids are generated between the particles, and the voids act as a light scattering factor and are optical properties of the coating film. The light transmittance decreases, the haze value (degree of clouding) of the coating film increases, and at the same time, the film strength and the adhesive force decrease. Therefore, although there is an optimum value for the amount of resin used as the binder, for example, if importance is attached to the resistance, the haze value of the coating film increases, resulting in an optically inadequate film. It was impossible to satisfy both the surface resistance and the optical characteristics of the.

A method is also known in which an ink containing ultrafine ITO particles is applied to a substrate such as glass and then baked at a high temperature of 500 ° C. or higher to form a transparent conductive film. However, in this method, since the ITO ultrafine particles are gently sintered at a high temperature, the surface resistance of the film is significantly reduced as compared with the above printing method performed at room temperature, but a plastic film such as polyester is used as the substrate member. In addition, since voids remain between the ITO ultrafine particles, there is a problem in the optical characteristics of the transparent conductive film as in the printing method.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a transparent conductive substrate having a low surface resistance and excellent optical characteristics. It is intended to provide a manufacturing method.

[0007]

In order to achieve the above object, the transparent conductive substrate is formed by printing or applying a transparent conductive ink on a base material, drying the transparent conductive ink, and then baking the transparent conductive ink to cure the transparent conductive film. And then forming an overcoat layer by applying an overcoat solution on this transparent conductive film, and then forming the overcoat layer with the above overcoat solution or adhesive into a substrate member that transmits visible light. The base material and the substrate member are bonded together in a state of facing each other, then the overcoat layer and / or the adhesive is cured, and after curing, the base material or a part thereof is removed by dissolution or swelling. Then, a transparent conductive film is formed on the substrate member to be manufactured.

According to the present invention, as the base material, a polyimide film or a heat resistant substrate such as glass or metal coated with polyimide is used. As the substrate member,
A plastic film such as polyester or polyether sulfone, glass or the like is used. The transparent conductive ink, indium-tin oxide or tin-disperse oxide-based ultrafine powder such as antimony oxide in a solvent,
Alternatively, a thermoplastic resin is added to and dispersed in this, and an ultraviolet curable resin or a thermosetting resin can be used as the overcoat liquid or adhesive, and the resin is used as a binder of the ink for firing. If so, first, it is performed at 400 ° C. in the atmosphere and then at 400 ° C. to 600 ° C. in an inert gas. Further, when a solvent is simply used as a binder of the ink without using a resin, baking in the air is not necessary and baking can be performed directly in an inert gas.

[0009]

The smoothness of the surface of the base material is the smoothness of the surface of the transparent conductive film obtained by the present invention. Therefore, it is preferable that the base material has a smooth surface. In the conventional printing method, since printing is performed with a film thickness of 2 μm to 5 μm, unevenness of 2 μm to 5 μm occurs between the printed portion and the base material, but in the method of the present invention, a smooth base material is used. Thus, the unevenness can be suppressed to 0.2 μm or less. The shape of the substrate may be a flat surface or a curved surface, for example, a film shape,
A plate shape, a roll shape, or the like can be used.

A screen printing method, a gravure printing method or the like is used for printing the transparent conductive ink on the substrate, and a wire bar coating method or a doctor blade coating method is used for coating the transparent conductive ink on the substrate. A roll coating method or the like is used.

The transparent conductive ink is a conductive ultrafine powder such as ITO or ATO having a particle diameter of 0.1 μm or less as a filler,
It is composed of a thermoplastic resin as a binder, a solvent, and an additive such as a dispersant, and is cured by drying after printing or coating. Since the binder resin is added to adjust the viscosity of the ink, it may be omitted depending on the coating method. In transparent conductive ink, a large amount of filler is added to reduce the surface resistance. Therefore, the conductive film formed by printing or coating tends to be porous, and the voids in the conductive film act as a light scattering factor, which adversely affects the optical characteristics of the conductive film.

For example, when ITO ultrafine powder is used as a filler, the ITO ultrafine powder is dispersed in a solvent or a solvent in which a resin such as acryl is dissolved to adjust the viscosity of the ink to obtain a transparent conductive ink. After printing or coating this conductive ink on a substrate and drying it, the conductive ink is heated to about 400 ° C. in the atmosphere to oxidize and burn the resin and a small amount of solvent remaining in the ink. Furthermore, this is 400 ° C in an inert gas atmosphere.
The film is heated at ˜600 ° C. to promote sintering between the ITO fine particles and simultaneously introduce oxygen vacancies into the ITO to lower the resistance of the film. The film characteristics of the transparent conductive film are determined by the film thickness. For example, when firing at 400 ° C., a film thickness of about 1 μm is about 100 Ω /
A film with a resistance value of about □ can be obtained. In this way, for example, a low-resistance ITO transparent conductive film can be formed on a polyimide film. However, the formed ITO film also has voids between particles to scatter light, so that the optical characteristics of the film However, it cannot be used as it is as a transparent conductive film.

Then, after printing or applying the transparent conductive ink on the substrate, and then overcoating it with an overcoat liquid comprising a resin and a solvent, the voids in the film are filled with the resin in the overcoat liquid. Light scattering is prevented,
The optical properties of the film are significantly improved. For example, with this overcoat, the light transmittance of 78% to 81% is increased to about 80% to 83%, and the haze value is 10% to
12% decreases to about 3% to 5%. Although a thermosetting resin or an ultraviolet curable resin is used as the overcoat liquid, it is preferable to mix the solvent with the resin to reduce the viscosity of the overcoat liquid so that the resin can be well penetrated into the film to fill the voids in the film.

As described above, the optical characteristics of the transparent conductive film are remarkably improved by the overcoat, but on the contrary, the surface resistance is sacrificed. Therefore, the problem is solved by the method described below. That is, after printing or applying ink on a substrate and drying, the transparent conductive film is formed by baking, and the overcoated transparent conductive film is applied to a substrate member with an overcoat liquid and / or an adhesive. After the matching, the overcoat layer and the adhesive layer are cured. A thermosetting resin or an ultraviolet curable resin is used for the adhesive, and a plastic such as polyester (PET) or polyether sulfone (PES) which transmits visible light or glass is used for the substrate member.

The substrate and the substrate member are bonded together by applying an adhesive or an overcoat liquid on the overcoat layer of the substrate or the substrate member, and then applying a steel roll or a rubber roll or the like at about 1 to 3 kgf / cm. Perform while applying linear pressure.
The curing of the adhesive layer and the overcoat layer after bonding the base material and the substrate member is performed by heating when a thermosetting resin is used, but when an ultraviolet curable resin is used, the base material or the substrate is used. Since UV irradiation is performed from the member side, either the base material or the substrate member must be made of a material that transmits UV light. The above is the case where the overcoat layer and the adhesive are cured together, but it goes without saying that they can be cured separately. That is, this is a method in which the overcoat layer is cured and then bonded using an adhesive to cure the adhesive.

In this way, after the base material and the substrate member are bonded and cured, the polyimide of the base material is removed by dissolution or swelling to form a transparent conductive film on the substrate member. When the base material is glass or a metal plate coated with polyimide, the base material and the substrate member are laminated and cured, and then peeled from the glass / metal plate / polyimide interface, and then the polyimide layer is dissolved and removed. By doing so, a transparent conductive film is formed on the substrate member. To dissolve the polyimide, hydrazine, hydrazine hydrate, or a mixture of them and a diamine can be used. These liquids are heated to room temperature to about 50 ° C. and immersed for several minutes to dissolve or swell the polyimide layer, and then washed with pure water and dried.

In order to improve the adhesion of the transparent conductive film to the substrate member, when the substrate member is plastic, corona discharge treatment, primer treatment, short wavelength ultraviolet ray irradiation treatment, etc. are performed to form the substrate member and the overcoat layer. It is desirable to carry out the adhesion improving treatment. Even when glass is used as the substrate member, it is preferable to similarly perform adhesion improving treatment such as silicon coupling treatment. Instead of performing the treatment for improving the adhesion between the substrate member and the overcoat layer, an adhesive that strongly bonds the substrate member and the overcoat layer can be used. For example, when glass is used as the substrate member and an ultraviolet curable resin is used as the adhesive, the adhesion to the glass can be improved by adding a small amount of a silicone-based monomer to the adhesive.

The transparent conductive film formed on the substrate member has its optical characteristics remarkably improved by the overcoating, and as a result of the removal by dissolution or swelling of the base material after laminating, the conductive surface of the conductive ultrafine particles is obtained. Appear on the surface, the surface resistance of the film can be reduced. Thus, a transparent conductive film satisfying both optical characteristics and resistance characteristics can be obtained.

[0019]

Example 1 A transparent conductive ink (X-101 manufactured by Tohoku Kako Co., Ltd.) using ITO ultrafine powder having a particle size of 0.03 μm as a filler and a thermoplastic resin as a binder was used as a substrate by a screen printing method. Polyimide film (Toray-Dupont Co., Ltd.)
Made Kapton KA-300, thickness 75μm) and thickness 3μ
After printing so as to have a thickness of m, drying, and baking in air at 400 ° C. for 30 minutes and in nitrogen gas at 400 ° C. for 25 minutes. Next, this transparent conductive film was overcoated with an overcoat liquid (see Table 1) using an ultraviolet curable resin with a wire bar having a wire diameter of 0.3 mm, and it was left at room temperature for 5 minutes at 50 ° C
Each was dried for 0 minutes. In this way, the transparent conductive film and the base material on which the overcoat layer was formed were laminated with another PET film (primer-treated product, Tetron HP-7 manufactured by Teijin Ltd., thickness 100 μm) as a substrate member.

The laminating is carried out by stacking the substrate member with the base material so that the overcoat layer is in face-to-face contact, and using a steel roll for 2 kg.
It was performed while applying a linear pressure of f / cm. The bonded base material and substrate member were UV-cured from the substrate member side with a metal halide lamp. The curing conditions were a curing time of 10 seconds and an ultraviolet illuminance of 150 mw / cm ² . About 4 after curing
After immersing in hydrazine hydrate heated to 0 ° C. for 10 minutes to dissolve the polyimide of the base material, washing with pure water and drying, a transparent conductive film and an overcoat layer were formed on the substrate member. . As an ultraviolet irradiation device, a metal halide lamp M01-L212 manufactured by Eye Graphic Co., Ltd.,
An irradiator (rolled mirror type) UE011-201C, a power supply device UB01.51-3A / BM-E2, and a heat ray cut filter were used.

The light transmittance, haze value and surface resistance of the obtained transparent conductive substrate were measured. The results are shown in Table 2.
Is shown in. Moreover, when the surface roughness of the transparent conductive substrate was measured, the unevenness on the surface was 0.2 μm or less. In performing these measurements, the light transmittance and the haze value of the transparent conductive substrate and the transparent conductive film were measured by the direct reading haze computer HGM- manufactured by Suga Test Machine Co., Ltd. together with the PET film as the base material or the substrate member. With ZDP, the surface resistance is Loresta MC manufactured by Mitsubishi Petrochemical Co., Ltd.
Each was measured by P-T400. In addition, the surface roughness of the transparent conductive substrate and the transparent conductive film was measured using a surface roughness measuring device Surfcom 900A manufactured by Tokyo Seimitsu Co., Ltd. The structures of the conventional transparent conductive substrates used in this example and the comparative example are shown in FIGS. 1 (a) and 1 (b).

Example 2 Transparent conductive ink in which ultrafine ITO powder having a particle size of 0.03 μm is dispersed in an organic solvent (DX-101 manufactured by Tohoku Kako Co., Ltd.)
A transparent conductive substrate was manufactured by the same method as in Example 1 except that was coated on a substrate with a wire bar having a wire diameter of 0.1 mm. The light transmittance, haze value, and surface resistance were measured using the same measuring device as in Example 1, and the results are shown in Table 2.

Example 3 The transparent conductive ink was fired in nitrogen gas at 500 ° C. for 15 hours.
The same procedure as in Example 2 was carried out except that the procedure was carried out for 1 minute. The light transmittance, haze value, and surface resistance were measured in Example 1.
The measurement results were as shown in Table 2.

Example 4 In the method of Example 1, after the transparent conductive film was printed and dried,
After baking and then drying the base material coated with the overcoat liquid, the overcoat layer was cured by irradiating with ultraviolet rays for 10 seconds in the atmosphere with a metal halide lamp at an illuminance of 150 mw / cm ² . After curing, a glass plate (soda lime A manufactured by Asahi Glass Co., Ltd.) was used as a substrate member.
S, thickness 1 mm), and the base material and the substrate member were bonded together with a thermosetting adhesive (see Table 1). In this bonding, an adhesive is applied on the substrate member by a doctor blade coating method so that the wet film thickness is 50 μm, and the base material is superposed on the substrate member so that the overcoat layer is in surface contact with the substrate member. Laminated at 2 kgf / cm.
After heat-curing the bonded base material and substrate member at 120 ° C. for 3 hours, the polyimide of the base material was dissolved and removed in the same manner as in Example 1 to manufacture a transparent conductive substrate. The light transmittance, haze value, and surface resistance were measured using the same measuring device as in Example 1, and the results are shown in Table 2.

Example 5 As a base material, a glass plate (soda lime A manufactured by Asahi Glass Co., Ltd.)
A polyimide varnish (litho coat PI manufactured by Ube Industries, Ltd.) was applied onto S (thickness: 1 mm) with a wire bar having a line length of 0.1 mm and dried at 200 ° C. After forming a transparent conductive film on this base material by the same method as in Example 3, the base material and the substrate member were bonded together, and then the overcoat layer was cured. After curing, the adhesion between the glass of the substrate and the polyimide layer is weak, so after peeling at the interface, soak in a 1: 1 mixture of hydrazine hydrate and ethylenediamine at a liquid temperature of 40 ° C. for 5 minutes, When swollen and then lightly rubbed with a cloth, the polyimide layer was completely peeled off. Then, it was washed with pure water and dried to manufacture a transparent conductive substrate. The light transmittance, haze value and surface resistance were measured using the same measuring device as in Example 1, and the results are shown in Table 2.
It was as shown in.

Comparative Example A transparent conductive ink using ITO ultrafine powder as a filler and a thermoplastic resin as a binder (X-manufactured by Tohoku Kako Co., Ltd.)
101) by a screen printing method using a glass plate (soda lime AS manufactured by Asahi Glass Co., Ltd., thickness 1 mm) as a substrate member.
Printed to a thickness of 3 μm and dried, then 40
The transparent conductive film was formed by baking at 0 ° C. for 30 minutes and then in nitrogen at 400 ° C. for 25 minutes. Further, the light transmittance, haze value, and surface resistance were measured using the same measuring device as in Example 1, and the results are shown in Table 2.

Table 1 (Composition of overcoat liquid and adhesive)

[Table 1]

Table 2 (Physical film properties of the transparent conductive film obtained in the present invention)

[Table 2]

[0029]

As described above, according to the present invention, it is possible to provide a transparent conductive substrate having significantly improved optical characteristics without impairing the surface resistance of the conventional transparent conductive film formed by the printing method. Further, since the smoothness of the transparent conductive film is remarkably improved, it is possible to obtain a transparent conductive substrate suitable for applications such as liquid crystal devices that require surface smoothness.

[Brief description of drawings]

FIG. 1A is a configuration diagram of an embodiment of a transparent conductive substrate according to the present invention. (B) is a block diagram of a conventional transparent conductive substrate.

Claims (8)

[Claims] 1. A transparent conductive film is formed by printing or coating a transparent conductive ink on a substrate, drying and baking, and then coating an overcoat liquid on the transparent conductive film. After forming the coating layer, the base material and the substrate member are bonded together in a state where the overcoat layer or the adhesive agent faces the substrate member that transmits visible light, and then the overcoat layer is formed. Production of a transparent conductive substrate, characterized in that the coating layer and / or the adhesive is cured, and after curing, the base material or a part thereof is removed by dissolution or swelling to form a transparent conductive film on a substrate member. Method 2. The method for producing a transparent conductive substrate according to claim 1, wherein the substrate is a polyimide film or a heat-resistant material such as heat-resistant glass or metal coated with polyimide. 3. The method for producing a transparent conductive substrate according to claim 1, wherein the transparent conductive ink is formed by dispersing ultrafine powder of indium-tin oxide or tin-antimony oxide in a solvent or a solvent in which a resin is dissolved. 4. The method for producing a transparent conductive substrate according to claim 1, wherein the firing is performed at 400 ° C. or higher in the air, and then at 400 ° C. to 600 ° C. in an inert gas atmosphere. 5. The firing is performed at 400 ° C. to 6 in an inert gas atmosphere.
The method for producing a transparent conductive substrate according to claim 1, which is performed at 00 ° C. 6. The method for producing a transparent conductive substrate according to claim 1, wherein the substrate member is a transparent material such as transparent plastic or glass. 7. The method for producing a transparent conductive substrate according to claim 1, wherein the overcoat liquid and the adhesive are a thermosetting resin solution or an ultraviolet curable resin solution. 8. The method for producing a transparent conductive substrate according to claim 1, wherein dissolution or swelling of the base material or a part thereof is performed with hydrazine, hydrazine hydrate or a mixture thereof with a diamine.