JPH0323229B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application of the Invention) The present invention relates to a method for forming a transparent conductive coating. (Conventional technology) In recent years, with the increase in semiconductor production, conductive paint has been applied to containers for transporting and storing semiconductor wafers, as well as flooring, wall materials, curtains, etc. in clean rooms and bio-clean rooms to provide antistatic properties. It can be applied to prevent semiconductors from being destroyed by static electricity, floors,
Measures are being taken to prevent dust from adhering to walls, curtains, etc. inside the clean room. For these purposes, conventionally carbon powder or fine metal powder was kneaded into synthetic resin film,
Alternatively, it is widely practiced to prevent non-conductors from being charged by applying a paint that has been made conductive by mixing these conductive substances to form a conductive coating. However, the film obtained by kneading carbon black and fine metal powder into synthetic resin has poor transparency, making it impossible to see the contents after packaging. There were problems such as it being impossible to view the situation on the other side through the curtains inside the clean room. On the other hand, the method of applying a conductive paint containing a conductive substance is not preferable because the color tone of the coating film becomes gray or blackish, which impairs the color tone of the object to be coated. Regarding conductive paints that improve the transparency of such films, for example, conductive fine powder with a particle size of 0.2 μm or less may be contained in an amount of 5 to 50% by weight relative to the resin, which is the main component of the coating film. Paint (Unexamined Japanese Patent Publication 1987-
85866), 50 to 90% by weight of conductive fine powder with a particle size of 0.4 μm or less, resin as the main component of the paint.
Paint containing 95 to 10% by weight (Japanese Patent Application Laid-open No. 1983
-91777 publication), a hydrocarbon linear polymer with one or more hydroxy groups in one molecule and a substantially saturated main chain, or a modified product thereof, is used as a coating resin, and this coating resin is coated with metal. 30~60 oxide fine powder
Paints containing % by weight (see JP-A-59-12256) are known, but the effect of improving transparency has not been sufficient. Therefore, it has been proposed to overcoat a paint that does not contain a conductive substance after applying a conductive paint in order to improve transparency or protect it. (Refer to JP-A-59-136167 and JP-A-5-198607.) However, although this method improves the transparency and strength of the coating film, it greatly reduces the conductivity of the coating film. The disadvantage was that it decreased. (Problems to be Solved by the Present Invention) An object of the present invention is to provide a method for forming a transparent conductive coating film that exhibits little change in surface resistance and excellent transparency even when coated over a transparent conductive coating layer. It is in. (Means for Solving the Problems) To summarize the present invention, a transparent conductive coating layer made of a conductive substance and a synthetic resin binder is formed on the surface of a transparent substrate, and then a polymeric layer having ionic crosslinking is applied on the transparent conductive coating layer. The present invention relates to a method for forming a transparent conductive coating film, which is characterized in that a surface treatment is performed by applying and drying an aqueous dispersion of a polymer (hereinafter referred to as an ionomer). To explain the present invention in more detail, the transparent conductive coating layer formed on the transparent substrate is a transparent conductive coating composition obtained by dispersing fine powder of a metal oxide, which is a conductive substance, in a synthetic resin binder. Obtained by applying a substance. Examples of the synthetic resin binder that can be used in the present invention include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, polyolefin resin, and the like. On the other hand, as the metal oxide used as the conductive substance, at least one fine powder selected from tin oxide, ammothine oxide, and indium oxide is used. Note that the smaller the particle size of the fine powder, the better the transparency of the coating layer, which is preferable. This transparent conductive coating composition consists of 15 to 35 parts by weight of a synthetic resin binder and 85 to 85 parts by weight of fine metal oxide powder.
It is blended in a proportion of 65 parts by weight and is used as a coating film forming component. This amount is necessary to maintain the surface resistivity of the transparent conductive coating layer in the range of 10 ⁶ Ω/R to 10 ⁸ Ω/R, and if the metal oxide is less than 65 parts by weight, the surface resistance On the other hand, if the amount exceeds 85 parts by weight, the transparency of the coating layer will deteriorate and the adhesion to the substrate and strength will deteriorate, which is not preferable. The transparent conductive coating composition is used in the form of an organic solvent solution adjusted to a suitable resin solid content concentration, usually 10 to 30% by weight. A gravure printer, roll coater, reversible roll coater, doctor knife coater, barcoder, spray, brush coating, etc. can be used to coat the transparent substrate, and a dry film thickness of 0.5 to 2.0 μm can be used on the surface of the substrate. Apply it so that it looks like this. After application, the coating film is dried at a temperature of room temperature to 60°C. The present invention is characterized in that the conductive coating layer thus formed is further coated with the following aqueous dispersion of an ionomer for surface treatment. Ionomers used for this surface treatment include polyethylene copolymer ionomers, polyurethane ionomers, acrylic ionomers, polyester ionomers, and the like. For example, as a polyethylene copolymer ionomer, ethylene is superimposed with α,β-ethylenically unsaturated carboxylic acid or/and other copolymer monomers, and some of the carboxyl groups of the copolymer are replaced with alkali metals. It is neutralized with hydroxide and dispersed in water. Examples of such an aqueous dispersion of ethylene copolymer include "Surlyn" manufactured by DuPont in the United States;
Products such as "Corpolene Latex" manufactured by Asahi Dow Co., Ltd. are commercially available. In addition, acrylic ionomers are available under the trade name "Neocryl" manufactured by Polyvinyl Corporation of the United States, urethane ionomers under the trade name "Hydran" manufactured by Dainippon Ink Co., Ltd., and polyester ionomers under the trade name "Faintex" manufactured by Dainippon Ink Co., Ltd. etc. are commercially available. In the present invention, the dried conductive coating layer is coated with an aqueous dispersion of the ionomer. Select a suitable method and perform coating. This is then heated and dried at 50 to 80°C for 0.5 to 1.0 minutes to complete the surface treatment. (Examples) Examples are shown below to specifically explain the present invention, but the present invention is not limited thereto. In addition, unless otherwise specified, the number of parts indicates parts by weight. Example 1 125 parts of polyurethane (product name: Honeytop, solid content 20% by weight, manufactured by Honey Kasei Co., Ltd.) and tin oxide (product name: T
Transparent conductive coating composition (trade name: EX-7220, solid content: 30
(wt% manufactured by Honey Kasei Co., Ltd.) was reduced to solid content with toluene.
It was adjusted to 20% by weight. This was applied to a polyethylene terephthalate film (thickness: 200 μm) using a barcoder (No. 6) and dried at 60° C. for 5 minutes. The dry film thickness was 1 μm, the surface resistivity of this coating layer was 1.5×10 ⁶ Ω/2, and the haze was 38%. Furthermore, this surface is coated with an acrylic ionomer (product name: Neocryl A602, manufactured by Polyvinyl Corporation in the United States).
An aqueous dispersion (solid content: 15% by weight) was coated with a bar coater (No. 6) to a dry film thickness of 1.0 μm and heated at 50°C.
and dried for 10 minutes. Surface-treated transparent conductive film at room temperature
The surface resistivity after standing for 24 hours is 3.0×
The haze was 10 ⁶ Ω/b and 8%. Examples 2 to 3 and Comparative Examples 1 to 3 The same method as in Example 1 was carried out except that the polymer shown in Table 1 was used instead of the acrylic ionomer, and a transparent conductive coating film was obtained. was formed. The surface resistivity value, haze value, and other properties of each transparent conductive coating film were as shown in Table 2. However, (1) Surface resistance is measured using the product name Digital Multimeter.
(manufactured by Takeda Riken). (2) Haze refers to the haze value, and is calculated as haze = diffuse transmittance / total light transmittance x 100 (diffuse transmittance = total light transmittance - parallel light transmittance).The value of haze is It was measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.).

【table】

[Table] (Effects of the invention) As is clear from the above explanation, the method of the present invention produces a transparent conductive coating film that has excellent transparency and shows little change in surface resistivity even after surface treatment. It is formed.

Claims (1)

[Claims] 1. A transparent conductive coating layer made of a conductive substance and a synthetic resin binder is formed on the surface of a transparent base material,
A method for forming a transparent conductive coating film, which comprises then applying a surface treatment by applying an aqueous dispersion of a high molecular weight polymer having ionic crosslinking bonds thereon and drying it. 2. The transparent conductive coating layer is formed by applying a conductive coating composition containing 65 to 85 parts by weight of a conductive substance and 35 to 15 parts by weight of a synthetic resin binder as film-forming components. The method for forming a transparent conductive coating according to item 1. 3. Formation of a transparent conductive coating film according to claims 1 to 2, wherein the conductive substance is a fine powder of at least one metal oxide selected from tin oxide, antimony oxide, and indium oxide. Method. 4. The transparent conductive material according to claim 1 or 2, wherein the synthetic resin binder is at least one selected from the group consisting of polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, polyolefin, etc. Method of forming a paint film. 5. The transparent conductive material according to claim 1, wherein the polymer having ionic crosslinking is at least one ionomer selected from the group consisting of polyethylene copolymer ionomers, polyurethane ionomers, and polyester ionomers. Method of forming a paint film.