JPS62114686A - Method for forming transparent conductive film - Google Patents

Abstract

PURPOSE:To obtain a coating layer having good transparency and reduced in the change of surface resistance, by coating the surface of a transparent base material with a transparent conductive coating composition prepared by dispersing a fine powder of metal oxide in a synthetic resin binder. CONSTITUTION:The surface of a transparent base material comprising polyethylene terephthalate is coated with a film forming component, wherein 85-65pts. wt. of a fine powder of metal oxide (e.g., tin oxide) is compounded with 15-35 pts.wt. of a synthetic resin binder such as polyester or polyurethane, in a form of an org. solvent solution of which the concn. is adjusted to 10-30wt% in a dry film thickness of 0.5-2.0mum by a gravure printer or a roll coater. After the formed film is dried at ambient temp. -60 deg.C, an aqueous dispersion of a polyurethane ionomer is applied to the film and dried at 50-10 deg.C. By this method, a film having good transparency and conductivity can be formed.

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, as the production of semiconductors has increased, conductive paints have been applied to containers for transporting and storing semiconductor wafers, flooring materials, wall materials, curtains, etc. in clean rooms and bio-clean rooms to provide antistatic properties. It is applied to prevent semiconductors from being destroyed by static electricity, and to prevent dust from adhering to floors, walls, curtains, and other surfaces within clean rooms.

For these purposes, conventionally, carbon powder or fine metal powder was kneaded into a synthetic resin film, or a conductive paint was applied by mixing these conductive substances to form a conductive coating film. It is widely used to prevent charging of nonconductors.
It has been implemented.

However, the film obtained by kneading carbon black and metal fine 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 in a 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 powders 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. 50% of conductive fine powder with a particle size of 0.4 μm or less
~90% by weight, a paint containing 95% to 10% by weight of resin, which is the main component of the paint (see Japanese Patent Application Laid-open No. 58-91777@), having one or more hydroxyl groups in one molecule,
A paint made by using a hydrocarbon linear polymer whose main chain is substantially saturated or a modified product thereof as a coating resin, and blending 30 to 60% by weight of fine metal oxide powder into this coating resin (JP-A-Show) 5
9-12256), but the effect of improving transparency was not yet 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. (Unexamined Japanese Patent Publication No. 59-136167,
(Refer to Japanese Patent Publication No. 9-198607) However, although this method improves the transparency and strength of the coating film, it has the disadvantage that the electrical conductivity of the coating film is significantly reduced.

(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. There is a particular thing.

(Means for solving the problem) 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 base material,
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 an aqueous dispersion of a high molecular weight polymer (hereinafter referred to as an ionomer) having an ionic cross-linking bond thereon and drying it.

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 a metal oxide used as a conductive material,
At least one type of fine powder selected from tin oxide, antimony 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 has a synthetic resin binder of 15
85 to 65 parts by weight of fine metal oxide powder is blended to 35 parts by weight, and this is used as a coating film forming component.

This amount increases the surface resistivity of the transparent conductive coating layer by 10
It is necessary to maintain the metal oxide in the range of 108 Ω/mm to 108 Ω/mm, and if the metal oxide is less than 65 parts by weight, the surface resistance increases and sufficient antistatic function is not exhibited.
If the amount exceeds the amount of water, the transparency of the coating layer will deteriorate, and the adhesion and strength to the base material will be deteriorated, 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@ffi%.

As a means of coating the transparent base material, a gravure printer,
A roll coater, a reverse roll coater, a doctor knife coater, a bar coater, a spray, a spade coater, etc. can be used, and the coating is applied to the surface of the substrate to a dry film thickness of 0.5 to 2.0 μm.

After coating, the coating film is dried under a temperature condition of room temperature to 60°C.

The present invention provides, on the conductive coating layer formed in this way,
Furthermore, it is characterized in that the surface is treated by coating with an aqueous dispersion of an ionomer as shown below.

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-edylenically unsaturated carboxylic acid or/and other copolymerizable monomers, and a part of the carboxyl groups of the copolymer is modified with an alkali metal. It is neutralized with hydroxide and dispersed in water. Such aqueous dispersions of ethylene copolymers are commercially available under the trade name of Pasarin, manufactured by DuPont, USA, and under the trade name of Copolene Latex, manufactured by Asahi Dow.

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 "Hytran" manufactured by Dainippon Ink, and polyester ionomers under the trade name "Finetex" manufactured by Dainippon Ink. Company-made products are commercially available.

In the present invention, the dried conductive coating layer is coated with an aqueous dispersion of the ionomer. Select appropriate methods for 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. Note that unless otherwise specified, the number of copies refers to the exclusive parts.

Example 1 Polyurethane (trade name Honeytop solid content 20%)
Manufactured by Honey Kasei > 125 parts and tin oxide (product name T-I
A transparent conductive coating composition containing 75 parts (manufactured by Mitsubishi Metals Co., Ltd.) as a film-forming component (trade name: EX-7220, solid content 30% by weight, manufactured by Honey Kasei Co., Ltd.) was reduced to a solid content of 20 f with toluene.
Adjusted to iffi%.

Add this to polyethylene terephthalate film (thickness 20
0 μm) with a bar coater (NO2O), and
It was dried at C for 5 minutes. The dry film thickness was 1 μm, the surface resistivity of this coating layer was 1.5×10 6 Ω/mouth, and the haze was 38%.

Furthermore, this surface is coated with acrylic ionomer (trade name).
An aqueous dispersion (solid content 15% by weight) of Neocryl A602 (manufactured by Polyvinyl, USA) was coated with a bar coater (No. 6>
Coat film rrL, 50'C so that the dry film thickness is 1.0μ surface.
and dried for 10 minutes.

The surface specific resistance of the surface-treated transparent conductive film after it was allowed to stand at room temperature for 24 hours was 3.0 x 106Ω/mouth,
The haze was at a value of 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, haze value, and other performances of each transparent conductive coating were as shown in Table 2.

However, (1) Surface resistance was measured using a digital multimeter (trade name) (manufactured by Kukegu Riken Co., Ltd.).

(2) Haze refers to the haze value, and is calculated as Diffuse Transmittance x 100 Total Light Transmittance (Diffuse Transmittance = Light Transmittance - Parallel Light Transmittance). (manufactured by Nippon Heavy Industries)
It was measured by

Margin below (effects of the invention) As is clear from the above explanation, according to the method of the present invention, a transparent conductive coating film is formed that has excellent transparency and shows little change in surface resistivity even after surface treatment. It is.

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, and then an aqueous dispersion of a high molecular weight polymer having ionic crosslinks is applied thereon. A method for forming a transparent conductive coating film, which comprises performing a surface treatment by coating and drying. 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. A method for forming a transparent conductive coating film according to item 1. 3. The 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. Formation method. 4. The transparent resin 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 for forming a conductive coating. 5. The polymer having ionic crosslinking is at least one ionomer selected from the group consisting of polyethylene copolymer ionomers, polyurethane ionomers, and polyester ionomers, according to claim 1. Method for forming transparent conductive coating.