JPH0160141B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to conductive pigments used on the surface or inside of recording materials such as electrophotographic photosensitive paper, electrostatic recording paper, and electrochromic paper, as well as polymer films and the like. The present invention relates to a conductive pigment useful as an antistatic agent and a method for producing the same.

Normally, recording materials such as electrophotographic paper, electrostatic recording paper, and electrochromic paper are made by coating or impregnating a conductive substance on the surface or inside of an insulating support such as paper. However, they have been produced by providing a photoconductive layer, a dielectric layer, or an electrochromic layer on the support. In such manufacturing methods, ion conductive conductive materials such as polymer electrolytes and inorganic salts, or electronic conductive conductive materials such as conductive inorganic metal compounds have conventionally been used as the conductive substance.

Among these, the conductivity of those using ion-conducting conductive materials is greatly affected by changes in humidity.
That is, the conductivity is high under high humidity, and conversely, the conductivity is low under low humidity. Changes in conductivity due to humidity affect recording quality, for example in the recording materials mentioned above, and in particular, only extremely unclear images are recorded under low humidity of 20%RH or less or high humidity of 80%RH% or more. It was impossible to put it into practical use. Furthermore, in offset masters in which a photoconductive ZnO layer is provided on a conductive support using such an ion conductive conductive material, the ion conductive conductive material used on or inside the support is hydrophilic. Since the ZnO layer absorbs moisture from the bleaching water, it peels off from the support or breaks. In addition, when used as a support for an electrochromic recording material that utilizes color development due to heat generation during energization, color development due to injection or deelectronization of electrons due to energization, or color development due to electrolytic action,
It has low conductivity and is not practical.

On the other hand, when a conductive inorganic metal compound doped with impurities, such as Al-doped ZnO, is used as a conductive material that is relatively unaffected by humidity, it has a high electrical resistance, so Electrochromic recording materials have no practical use.
Furthermore, when used in electrophotographic photosensitive paper or electrostatic recording paper, it has low conductivity and must be used in large quantities (at least 10 g/m ² ) for the paper support, which may impair the naturalness of the paper. However, this method had the disadvantage of increasing the weight of the recording paper.

The present invention solves the above-mentioned conventional drawbacks, and
The object of the present invention is to provide an inexpensive conductive pigment that is useful for recording materials used in recording methods such as electrostatic recording paper, and also for preventing charging of polymer films, and a method for producing the same.

That is, the present invention solves the above-mentioned conventional drawbacks by using a conductive pigment whose surface is coated with a conductor mainly composed of copper iodide. It is produced by wetting an inorganic pigment with a solution of copper iodide and then drying it. The conductive pigments obtained by such a manufacturing method impart sufficient conductivity to the recording material or polymer film, etc. in which they are used, and the recording material, polymer film, etc. This has the effect that there is very little loss of quality.

Inorganic pigments used in the present invention include barite powder, precipitated barium sulfate, barium carbonate, carbonate lime powder, precipitated calcium carbonate, gypsum asbestos, clay, silica powder, finely divided silicic acid, diatomaceous earth, talc, and basic carbonate. Magnesium, alumina white, sachin white, zinc oxide, lead white, basic lead sulfate,
These include lead sulfate, lithopone, titanium oxide, antimony oxide, etc.

To produce conductive pigments by coating the surfaces of these inorganic pigments with copper iodide, the copper iodide is dissolved in an aqueous ammonia solution, the inorganic pigments are wetted with this solution, and then dried.

An organic solvent such as methanol, ethanol, acetone, or methyl ethyl ketone may be added to this aqueous solution to speed up drying.

The concentration of ammonia is preferably 2 to 10 wt%, and copper iodide is preferably dissolved in this aqueous solution to a concentration of 5 to 10 wt%. To wet the inorganic pigment with the solution obtained in this way, the above solution may be added dropwise to the inorganic pigment heated to around 100°C while stirring, or the pigment may be added to the solution and heated to evaporate. .

Ammonia water is used to make it alkaline, but if other alkaline agents are used, there will be problems with post-treatment such as disposal of the treatment solution, but ammonia water evaporates during drying. There is no such problem. Further, it does not remain on the surface of the conductive pigment and affect its properties.

For example, 100% of the conductive pigment thus obtained is
After molding with a pressure of Kg/cm ² , release the pressure, apply conductive paint (trade name: Dotite) to both ends, and measure the electrical resistance.
A resistance value as low as 10 ² Ω・cm can be obtained.

On the other hand, when the conventional conductive ZnO doped with Al was tested under the same conditions as described above, it showed a considerably larger resistance value than the present invention which showed an electrical resistance value of the order of 10 ⁵ Ω·cm or more.

Examples of the present invention will be shown below.

Example 1 7wt% ammonia aqueous solution 94g Cul 6g A mixture of the above composition was thoroughly stirred to obtain a dark blue solution, to which 30g of precipitated calcium carbonate was added,
The mixture is heated to a melting temperature of 80° C. with gentle stirring, and the liquid is evaporated to obtain a slightly grayish conductive pigment of the present invention.

The conductive pigment thus obtained was then coated with 100%
After molding with a pressure of Kg/ ^cm2 , the pressure was released, conductive paint (trade name: Dotite) was applied to both ends, and the electrical resistance was measured after leaving it for one week under the following temperature and humidity conditions. The following results were obtained.

20℃ 10%RH 6×10 ³ Ω・cm 20℃ 90%RH 3×10 ³ Ω・cm For comparison, the same test as above was conducted on conductive ZnO doped with Al, and the following results were obtained. Compared to the present invention, the resistance value was large and the change in resistance value due to humidity was also large.

20℃ 10%RH 1×10 ⁶ Ω・cm 20℃ 90%RH 5×10 ⁶ Ω・cm Example 2 Conductive pigments were prepared in the same manner as in Example 1 except that titanium oxide was used instead of precipitated calcium carbonate. obtained,
When we conducted a test, we obtained the following results.

20℃ 10%RH 1×10 ³ Ω・cm 20℃ 90%RH 6×10 ² Ω・cm Example 3 10wt% ammonia aqueous solution 60g Methanol 34g Cul 6g Example by dispersing 30g of clay in a solution with the above composition A test was conducted in the same manner as in Example 1, except that a conductive pigment was prepared in the same manner as in Example 1, and the following results were obtained.

20℃ 10%RH 8×10 ³ Ω・cm 20℃ 90%RH 5×10 ³ Ω・cm 20g of conductive pigment obtained as above, 25g of polyvinyl acetate latex (solid content 40%), 50g water
A conductive support was prepared by uniformly dispersing the mixture and coating it on high-quality paper to a solid content of 7 g/m ² to form a conductive layer.

The surface electrical resistance of the conductive support thus obtained was measured after being left for 24 hours under each of the following temperature and humidity conditions, and the following results were obtained.

20℃ 10%RH 5×10 ⁸ Ω・cm 20℃ 90%RH 1×10 ⁸ Ω・cm After forming the conductive layer, a photoconductive layer made of ZnO and resin is formed on the layer. Electrofax type photosensitive paper was created, and after forming an electrostatic latent image by charging and exposing it to light, it was developed with dry toner.
℃ and clear images with constant image quality were obtained in the range of 15%RH to 80%RH.

As is clear from the above results, the conductive pigment of the present invention has a low resistance value and extremely stable characteristics with little change in resistance value even when humidity changes.

Claims (1)

[Scope of Claims] 1. A conductive pigment characterized in that the surface of the inorganic pigment is coated with a conductor containing copper iodide as a main component. 2. A method for producing a conductive pigment, which comprises wetting an inorganic pigment with a solution of copper iodide dissolved in aqueous ammonia and then drying it.