JPH065393B2 - Coated carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated carrier for an electrophotographic developer.

Conventionally, as an electrophotographic method, US Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 (US Pat. No. 3,666,363), Japanese Patent Publication No. 43-24748 (US Pat. No. 4071361), etc. In these methods, the toner powder is uniformly charged on the photoconductive layer, and the latent image is formed by exposing the light image according to the original document to eliminate the charges outside the light image portion. It is developed, transferred to paper or cloth as required, and permanently fixed by heating and pressing.

As a method for developing the latent image, it is visualized by developing with a magnetic brush, cascade, far brush touchdown, powder cloud or the like.

In the magnetic brush development method used in the present invention, a mixture of carrier iron powder and toner is used as a developer. In the continuous copying of a large number of sheets, this developer exerts a change in carrier resistance and carrier particle size on the carrier iron powder due to mechanical impact, shearing force, etc. in the developing device, and further, the toner on the carrier surface is changed. Invite fusion.

The other is that the carrier surface is covered by fine toner accumulation during continuous copying.

Since such deterioration usually occurs around 10,000 to 20,000 sheets, it is not suitable for high-speed copying machines. Therefore, as a proposal for improving the above-mentioned drawbacks, there is a carrier coated with a resin.

These solve the above-mentioned deterioration, but when used as a developer because many of the resins used for coating have a low dielectric constant, the edge phenomenon may cause a decrease in image density or no image, which is not preferable. .

In order to prevent such development, it is necessary to adjust and increase the dielectric constant.

It is an object of the present invention to provide a coating carrier for electrophotographic development, in which the above drawbacks are improved.

That is, the present invention is a coated carrier for electrophotography, characterized in that the carrier is coated with a resin containing barium titanate fine powder or strontium titanate fine powder.

It has already been stated that the dielectric constant must be adjusted because the carrier coated with only the resin has a strong "edge phenomenon" and the image quality is extremely poor. The strontium fine powder has the following effects as a coating carrier dielectric constant adjustment.

1. Very good dispersibility in resin binder.

2. Does not hinder the adhesive strength to iron powder carriers.

Thus, the barium titanate fine powder or strontium titanate fine powder can be used in an amount of 0.1 to 10 parts by weight, preferably 0.3 to 10 parts by weight, based on 100 parts of the coating resin.
7 parts by weight is preferred.

As the coating resin used in the present invention, a large number of materials including known materials are used, and typical examples thereof include fluorine resin, various fluorine-containing polymers, melanin resin, xylene epoxy resin, polyphenylene. Oxide resin, silicone resin, polyester resin, polyamide resin, styrene-vinyl chloride copolymer resin, styrene-methyl methacrylate copolymer resin, styrene-butyl methacrylate copolymer resin, styrene-butadiene copolymer resin and the like are used.

The coating carrier in the present invention is produced by dispersing the coating resin and the above-mentioned barium titanate fine powder or strontium titanate fine powder in a solvent (toluene, xylene, MEK) or the like, and mixing the carrier with the spray dryer method. The carrier is coated with a fluidized bed method or the like, dried, granulated, sieved, and the passed portion is used as a coated carrier.

It is particularly preferable that the barium titanate fine powder or strontium titanate fine powder has a dielectric constant of 50 to 1,000.

Example 1 1 kg of spongy iron powder (EFV manufactured by Nippon Iron & Powder Co., Ltd.) having an average particle size of 40μ
In contrast, silicone varnish) Toray Silicone SP-24
06) Mix 100g with 5g barium titanate powder 10
% Toluene solution 200g was sprayed on the surface of iron powder in a Wurster type circulating fluidized bed at 85-90 ° C, then cured at 200 ° C for 20 minutes in the furnace, taken out of the furnace and cooled, and then sieved with 150 mesh. Aggregates were removed by passing through to obtain a low surface energy resin-coated carrier.

When an image was printed on the NP8500Super machine using a developer mixed with this carrier and 8wt% toner for NP-8500Super (Canon copier), the resulting image is a beautiful image without edge effect and the background No toner adhered to the area.

Example 2 Instead of the silicone varnish, 150 g of epoxy-modified Teflon enamel Teflon S954-101 (manufactured by Du Pont) was used, and an image-forming experiment was conducted in the same manner as in Example 1, as a result, the copy image was black. A beautiful image with no edge effect was obtained in which solid areas were uniformly developed.

Example 3 The same procedure as in Example 1 was carried out except that strontium titanate fine powder was used in place of barium titanate fine powder, and a good image having no solid portion removal edge effect was obtained.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-48-78932 (JP, A) JP-A-55-155363 (JP, A) JP-A-54-21730 (JP, A) JP-B-53- 6535 (JP, B1)

Claims (2)

[Claims] 1. A coated carrier for electrophotography, wherein the carrier is coated with a resin containing barium titanate fine powder or strontium titanate fine powder. 2. A fine powder of barium titanate or a fine powder of strontium titanate is added to 100 parts by weight of a resin.
The coated carrier for electrophotography according to claim 1, which contains 1 to 10 parts by weight.