JPH0246800A - Manufacture of conductive coating film - Google Patents

Abstract

PURPOSE:To obtain a uniform conductive film by providing a foundation coat layer on a supporting body and repeatedly applying a solution containing a compound semiconductor but no high polymer substance plural times at specific applying quantities in a laminated state, and then, drying the applied solution. CONSTITUTION:A foundation coat layer is formed on a supporting body. A resin which moderately swells when a solvent that dissolves a compound semiconductor is added to the resin is preferable as the resin for the foundation coat layer. Cuprous iodide and silver iodide are preferable as the compound semiconductor used for the conductive layer of a conductive coating film. Acetonitrile is used as the solvent for the cuprous iodide, since the acetonitrile reacts on the cuprous iodide and produces acetic acid. The viscosity of the compound semiconductor solution is not much different from that of the used solvent itself, with the viscosity of the applied solution at 25 deg.C being within a range of 0.5-10cp. Uniform application of the compound semiconductor solution can be obtained when the solution is repeatedly applied plural times at applying quantities of <=10ml/m<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a conductive film, particularly a method for manufacturing a coated conductive film.

(Prior Art) Imparting electrical conductivity to the surface of plastics has become a particularly important issue with the recent progress in electronics technology. The most familiar example is the prevention of various problems caused by static electricity, such as the adhesion of dirt and dust due to static electricity charging, and the prevention of various problems caused by discharge phenomena, and more recently, the prevention of electromagnetic interference in the case of electronic equipment. When using plastics such as these, technology to make the surface of the plastic conductive is particularly important. Transparent conductive films are also used as base materials for electrophotographic recording, base materials for electrostatic photographic recording, transparent electrodes for thin liquid crystal displays, transparent electrodes for distributed EL, transparent electrodes for touch panels, clean rooms, etc.
There has been a strong demand for the development of an inexpensive, high-performance transparent conductive film that has a wide range of applications, including meter windows, antistatic films for VTR tapes, and transparent heaters.

Among conventional transparent conductive films, a semiconductor thin film type is tin-doped indium oxide film (Indium T
in Oxide-ITO film), antimony-doped tin oxide film, cadmium tin oxide film (Cadmium tin oxide film)
um Tin Oxide-CTO film), copper iodide film,
Examples include titanium oxide film and zirconium oxide film. Among these, ITO film is the most excellent in both transparency and conductivity. Tin oxide film requires high substrate temperature for film formation;
Application to polymer films is difficult. The CTO film has a smaller energy gap than the indium oxide film (the absorption edge is on the long wavelength side), and as the film thickness increases, it becomes slightly yellowish. Copper iodide films, titanium oxide films, and zirconium oxide films are inferior in both transparency and conductivity compared to these films.

In addition, these semiconductor thin conductive films are created through vapor deposition and subsequent processing steps, but large-scale manufacturing equipment is required.
Therefore, it was expensive.

As a method for forming such semiconductor thin films at low cost,
A method is known in which a polymer film is pre-primed with an undercoat and a compound semiconductor is absorbed onto the surface of the layer.Furthermore, using this method, it is possible to improve the adhesion of the undercoat layer to the support and the upper layer. It is stated that. (Tokuko Akira≠r-
(Refer to Tata R≠ Publication) (Problems to be Solved by the Invention) This coating type compound semiconductor conductive film is usually formed by forming a solution of a compound semiconductor solubilized in a volatile solvent on a suitable support. It is formed by coating on the undercoat layer, absorbing the coating liquid into the undercoat layer, and evaporating the solvent.

However, unlike a resin solution, a compound semiconductor solution has a low viscosity and does not contain a binder resin, so no thickening effect is observed during the drying process.

Therefore, during the coating and drying process, uneven flow of the coating solution tends to occur due to various factors such as uneven drying air, making it difficult to form a uniform coating film.

Such uneven coating of the conductive film not only causes non-uniform conductivity, but also causes a decrease in transparency, induces crystal precipitation of compound semiconductors over time, and therefore deteriorates conductivity, which is extremely important in practical use. This was a hindrance and improvements were desired. Factors that can cause uneven coating due to the flow of the coating solution include uneven drying air, differences in the thickness of the support, irregularities such as curls, and the slope of the coating device from the coating section to the drying section. . By examining these factors individually, coating unevenness can be improved, but it is virtually impossible to establish conditions that do not cause stable liquid flow.

On the other hand, as a measure to improve coating unevenness caused by liquid flow, attempts are usually made to increase the viscosity of the coating liquid by adding a thickener such as a polymer.

However, if a thickening agent such as a polymer is added to a compound semiconductor solution in an amount necessary to suppress coating unevenness, the thickening agent will not act as a barrier to electrical conduction between compound semiconductors. Improvement by this method is not preferred since a significant decrease is observed.

Another common improvement is to increase the concentration of the compound semiconductor, reduce the amount applied, and dry quickly. In order to improve coating unevenness using this method, it is necessary to keep the coating amount below ioml/m2. but,
For example, in order to use it as a conductive film for electrophotography, it must have a surface resistance of 106 Ω/Ω or less, but in order to obtain a conductivity of 706 Ω/Ω or less, when using a compound semiconductor such as iodized steel, at least 0°20
g/m2 needs to be applied onto the support.

This is approximately 20 ml/m for a 1.3% solution by weight.
This corresponds to a coating amount of 2. As described above, the solubility of compound semiconductors in organic solvents is generally low, and the coating amount of 10 m is required to obtain a uniform coating surface condition with a uniform concentration of compound semiconductors.
It was almost impossible to increase the concentration to the level required to exhibit conductivity that can be used for normal electrophotography by applying the solution 7 times or less.

(Means for solving the problem) It was extremely difficult to apply the compound semiconductor solution uniformly as described above, but as a result of intensive research, we decided to apply this solution multiple times in a coating amount of 10 ml/m2 or less. The inventors have discovered that it is possible to obtain a uniform electrically conductive film having a surface resistance of zxio3Ω/hole by doing so, and have arrived at the present invention. As mentioned above, it is difficult to produce a conductive film that has both a conductivity of less than 105 Ω/hole in surface resistance and a uniform coated surface condition in one coating. The present invention was achieved by discovering that coating unevenness due to flow is less likely to occur by reducing the amount of coating per coat and repeating the coating multiple times. Furthermore, an advantage of the present invention is that even if coating unevenness occurs in the i/th coating, the coating unevenness is reduced as a result because that part is partially dissolved in the coating liquid in the second and subsequent coatings. It is.

That is, the present invention provides an undercoat layer on a support, and further coats a solution containing a compound semiconductor and substantially no polymer substance multiple times in a coating amount of 10 ml/rn2 or less, This invention relates to a method for manufacturing a conductive film that forms a conductive layer by drying, and the present invention has made it possible to create a coated conductive film of a compound semiconductor that can withstand practical use.

The conductive layer of the compound semiconductor obtained according to the present invention is transparent, and if the support is transparent, it will naturally become a transparent conductive film.

If the support is colored or opaque, the conductive film will be colored or opaque, so the support can be selected depending on the application.

In the present invention, conventionally known supports can be used, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, celluloses such as cellulose acetate, polymethyl methacrylates, and nylon T. Also usable are polyamides, polyimides, polycarbonates, polyvinyl alcohols, vinyl chloride-vinyl acetate copolymers, glass, and coated paper coated with the above-mentioned polyolefins and polyesters.

Further, in the present invention, an undercoat layer is provided on such a support,
The resin for the undercoat layer is preferably a resin that swells moderately in a solvent that dissolves the compound semiconductor. The degree of swelling of a resin in a solvent is measured by the following method. That is, a film of the resin to be used as the undercoat layer is formed on the support to a thickness of approximately 70 μm, and the film thickness is accurately measured. This film thickness is T
o. Next, this membrane is immersed in a solvent for 5 minutes, and the membrane thickness T1 after swelling is measured. The degree of swelling is expressed as T1/To, and for the resin effective in the present invention, this value is preferably /, O
! ~2. ! It is a resin in the range of , more preferably in the range of 7.03 to /.7. Specific undercoat layer resins that satisfy this value include vinylidene chloride/methyl acrylate,
Vinylidene chloride/methyl methacrylate, vinylidene chloride/acrylic acid, vinylidene chloride/acrylonitrile,
Vinylidene chloride/Itaconic acid, Vinylidene chloride/Methyl acrylate/Acrylic acid, Vinylidene chloride/Methyl methacrylate/Itaconic acid, Vinylidene chloride/Methyl acrylate/Itaconic acid, Vinylidene chloride/Acrylonitrile/Acrylic acid, Vinylidene chloride/Acrylonitrile/Itaconic acid, Chloride Examples include multi-component copolymer vinylidene chloride resins such as vinylidene/methyl acrylate/methyl methacrylate/acrylic acid, vinylidene chloride/acrylonitrile/itaconic acid/acrylic acid, and the like.

Furthermore, resins that form a network structure are also useful, but a network structure is a structure that is formed by forming chemical bonds between several specific atoms in a linear polymer. Since the resin is generally insoluble in solvents, it is preferable to form a network structure after coating. Resins formed include vinyl chloride resin, vinyl acetate resin,
Examples include polyvinyl acetal, polyacrylic acid ester, polymethacrylic acid ester, inbutylene polymer polyester, ketone resin, polyamides, polycarbonates, polythiocarbonates, copolymers of vinyl haloarylates, polyvinyl acetate, etc. It is not limited to these.

Patent application No. 1986-λλ71≠≠, Patent application No. 1982-30≠09
No. 0, Special Application No. 1982-30 Hiro 09/No., Special Application No. 1982-30
The resins described in ≠092 can also be used.

There is no particular limit to the thickness of the undercoat layer, but it is 0.0/~110
A range of 0p, preferably o, or-iopm gives good results.

The compound semiconductors used in the conductive layer of the conductive film of the present invention are preferably cuprous iodide and silver iodide, but other metal-containing compound semiconductors, such as other cuprous halides. Silver oxides; halides of bismuth, gold, indium, iridium, lead, nickel, radium, rhenium, tin, tellurium, and tungsten; cupric, cupric, and silver thiocyanate; or iodomerculate, etc. sell.

Metal-containing compound semiconductors are not readily soluble in most volatile solvents such as water and many organic solvents.

Therefore, by using a compound that forms a soluble complex salt with the semiconductor as a solubilizer for the semiconductor, it becomes possible to dissolve it in a volatile solvent.

Generally, alkali metal halides and ammonium halides are complexed with certain semiconducting metal halides such as silver halides, cuprous halides, tin halides, lead halides, and others. can be used as,
The generated complex compounds are often easily soluble in ketone solvents.

Although it is usually preferred to remove the complexing agent used herein, for example by washing with water, in some embodiments the complex salt itself provides sufficient electrical conductivity. In the case of ammonium no ride, the complex compound itself is a compound semiconductor.

Examples of volatile ketone solvents suitable for dissolving these complex compounds are acetone, methylethylketone, 2-pentanone, 3-pentanone, -monohexane, coheptanone, gouhezotanone, methylisopropylketone, ethylisopropylketone, diimpropylketone. , methyl isobutyl ketone, methyl-t-butyl ketone, diacetyl, acetylacetone, acetonylacetone, diacetone alcohol, mesityl oxide, chloroacetone, cyclotanone, cyclohexanone, and acetophenone. Mixtures of ketone solvents can also be used, and in some cases a single ketone solvent can be used. In some cases, some solvents other than ketones may be used to dissolve the iodide complex compound, particularly when lithium iodide, sodium iodide are used as complexing agents. Methyl acetate, ethyl acetate, n-propyl acetate, iso-amyl acetate isozorobyl acetate, n-butyl acetate, tetrahydrofuran, dimethylformamide, methyl cellosolve, methyl cellosol doacetate, ethyl acetate and others are iodide complex compounds It can be effectively used to dissolve.

As a solvent for cupric iodide, acetonitrile can be used because cupric iodide and acetonitrile form a complex salt. In addition, in this solution, a patent application filed in 1983-4 was added for the purpose of preventing crystal precipitation of compound semiconductor conductive films over time.
The isocyanate compounds described in 1377 can be used. In order to form a uniform conductive film, the compound semiconductor must be 0. /~jOins solution is preferably used, and the coating weight after drying is ≠0-2000mg/m
It is preferable to set the coating conditions so as to fall within the range of 2. Particularly preferred coating weight after drying is / 00 to / 00
omg/m2.

As mentioned above, the conductive layer according to the present invention is formed by applying a compound semiconductor solution onto the undercoat layer, absorbing the coating solution into the undercoat layer, and evaporating the solvent. Examples of methods for applying compound semiconductor solutions include spin coating, immersion coating, spray coating, bead coating using a continuous coating machine, continuously moving wick method, and coating method using a hopper. It is not limited.

The viscosity of the compound semiconductor solution is not much different from the solvent used itself, and the viscosity of the coating liquid at 2 to 0C is 09j to 10C.
within the range of p, preferably o, tcp~jc
p, particularly preferably 0, j cp~/cp. If the coating amount is 0.0 m2 or more, uneven coating will often occur due to flow during the coating or drying process. Furthermore, if the coating amount is less than 10 ml/m2 after seven coatings, it is difficult to obtain a conductivity of less than 106 Ω/m2 in terms of surface resistance.

(Effects of the Invention) The conductive film created by the method of the present invention not only has a uniform coated surface condition, but also suppresses crystallization of the compound semiconductor over time, and maintains high transparency and conductivity over a long period of time. It is a highly stable conductive film with

Furthermore, by the method of the present invention, a conductive film having a surface resistance of less than 1O6 Ω/2 can be obtained.

This conductive film is used as a base material for electrophotographic recording, a base material for electrostatic photographic recording, a transparent electrode for thin liquid crystal displays,
It can be used in a wide range of applications, including transparent electrodes for distributed EL, transparent electrodes for touch and ξ channels, antistatic films for clean rooms, meter windows, VTR tapes, transparent heaters, etc.

(Example) The present invention will be explained in more detail below based on examples.

Comparative Example 1-≠ Vinylidene chloride resin (Saran R2゜Co (trade name):
A solution prepared by dissolving Hiroshig (manufactured by Asahi Kasei ■) in a mixed solvent of 700 g of dichloromethane and '/clohexanone JOOfi was applied using an extrusion hopper and dried at θθ0C. The film thickness of this undercoat layer was Fio, 10 μm. Thereafter, a solution of 2 g of cuprous iodide dissolved in rg acetonitrile was applied onto this layer using an extrusion hopper in the coating amount shown in Table 1, and dried at 1000C.

The viscosity of this solution was 0, &cp at the liquid temperature λz'C. The condition and surface resistance of the coated surface are listed in Table/. Surface resistance i; i Loresta MCP-TEST
Measured with ER (manufactured by Mitsubishi Yuka@).

Table 7 When the coating amount is 10rnll/m2, the coated surface condition becomes better, and at tmml/m2, a uniform coated surface condition is obtained, but as the coating amount decreases, a decrease in conductivity is observed.
It was not possible to obtain a uniform conductive film with a surface resistance of io"07 or less.

Example 1 A solution of 2 g of cuprous iodide dissolved in rg of acetonitrile was extruded on top of the conductive film of Comparative Example 3 using an Om7! / m 2 coating amount and dried at /QO0C. As a result, the thin flow unevenness observed in the conductive film of Comparative Example 3 disappeared, and a transparent conductive film with a uniform coating surface was obtained, and the surface resistance of this film was /
×104Ω/mouth.

Example λ Comparative Example The copper 7 iodide solution used in Example 1 was further applied onto the conductive film of Hiro using an extrusion hopper in an amount of ml/m 2 and dried at 1000C. The coated surface condition was uniform as in Example 1, and the surface resistance was jX1
The resistance was 0.05Ω/mouth.

Further, the cuprous iodide solution used in Examples was applied onto this using an extrusion hopper in an amount of jml/m2, and dried at 100°C. The condition of the coated surface of this conductive film was uniform without any change, and the surface resistance was j×10 3 Ω/hole.

It has become clear that by repeating the coating several times in this manner, conductivity can be improved while maintaining a uniform coated surface condition.

Comparative Example j, A Polyisocyanate (Millionate MR-100 (product name): manufactured by Nippon Polyurethane ■) on a polyethylene terephthalate film of A H, Og, Tuboran 100 (product name) Nippon Polyurethane ■ on a polyester type polyol split) 2゜0g and polyester (Polyester Adhesive≠9ooo (product name): manufactured by DuPont)≠, Og with dichloromethane! A solution dissolved in 0.00 g was extruded and applied with a spatula, followed by drying at 1000C.

The film was left to cure at jo 0c for 2 days. The film thickness of this undercoat 1- was about 0.1 μm'. 7 on top of this layer
A solution of 2 g of cuprous iodide dissolved in 1 g of acetonitrile was mixed with a percoater to ml/m2 and λθnl/m.
It was applied to a coating amount of 2 and dried at ioo 0c to create a conductive film (Comparative Example!, Comparative Example 6). Comparative example!
The conductive film is uniform, but the conductivity is low, and the surface resistance is 2.
It was ×/ITΩ/mouth. In addition, the conductive film of Comparative Example B had significant coating unevenness on the coated surface due to flow, and was particularly cloudy in areas where the liquid was thought to have collected.

Example 3 On the conductive film of Comparative Example 3, the cupric iodide solution used in Comparative Example 3 was further applied with a percoater to a coating amount of 10m/m2, and dried at 1OOoC. The resulting conductive film has surface resistance! The electrical resistance was reduced by two digits compared to Comparative Example 3 at ×10 4 Ω/mouth, showing good conductivity, and the coated surface condition was uniform.

Example ≠ On the subbing layer used to make Comparative Example 3, silver iodide 7.
Using a hopper, extrude a solution of 74 g, potassium iodide λ, /4 g dissolved in 1/1 weight/weight method medium of acetone and cyclohexanone, and use a hopper / Oml / m
As a result of applying the product to a coating amount of 2 and drying at loo 0c, slight unevenness due to flow occurred. When the coating was repeated again in the same manner, the coating unevenness disappeared and a uniform coated surface was obtained. The surface resistance Fi7 of this conductive film
It was X/OsΩ/mouth.

(Reference) Comparative Example 3, Comparative Example B, Example/, To investigate the environmental stability of the conductive film of Example 3! It was left for 70 days in an environment of 0°CrO%RH. In the uneven coating areas of the conductive films of Comparative Example 3 and Comparative Example B, crystallization of cuprous iodide occurred, the film surface became cloudy, the surface resistance increased by λ~≠ orders of magnitude, and a decrease in conductivity was observed. .

On the other hand, in the conductive film of Example 1.3, no change was observed in either transparency or conductivity, indicating that the conductive film of the present invention has high stability over time.

From the above results, the method of the present invention not only makes it possible to create a uniform coating surface condition, but also suppresses the crystallization of compound semiconductors over time and creates a highly stable conductive film with good transparency. It is possible to obtain.

Patent Applicant: Fuji Photo Film Co., Ltd. Procedural Amendment

Claims (1)

[Claims] An undercoat layer is provided on the support, and 10 m of a solution containing a compound semiconductor and substantially free of polymeric substances is added on top of the undercoat layer.
A method for producing a conductive film, which comprises forming a conductive layer by laminating the coating multiple times at a coating amount of 1/m^2 or less and drying.