JPH0470876A - developing device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a surface staining phenomenon, to obtain a high-definition image and to easily carry out a processing by constituting a toner carrier with conductive urethane rubber and adding silica into the rubber. CONSTITUTION:In a contact developing system developing device using nonmagnetic one component toner, the toner carrier where the silica 7 is added into the conductive urethane rubber 6, is used. It is desirable that toner has a negative triboelectrifying polarity and the value of volume resistivity of the carrier is set at 10<4> - 10<9>OMEGA.cm. On the other hand, the carrier can be formed in such a manner that the powder of the silica 7 is kneaded into the conductive rubber 6 in a liquid state, injected into a metal mold together with a core metal 8 to carry out molding, heated, and aged, and a surface is ground.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a contact development type electrophotographic developing device equipped with a carrier carrying a non-magnetic one-component developer used in electrophotographic copying machines, printers, etc. .

BACKGROUND OF THE INVENTION Electrophotography is a technique widely used in modern copiers and printers. In electrophotography, an electrostatic latent image is generally formed on a latent image carrier (image forming body), developed with toner, etc., and the resulting toner image (developed image) is transferred to paper. There is. Various developing methods have been proposed and put into practical use at this time, such as a cascade method, a magnetic brush method, and a contact developing method. In the contact development method, a thin layer of toner having a thickness of - is formed on a toner carrier and brought into contact with the latent image carrier, and toner powder is applied from the toner carrier side to the surface of the latent image carrier in accordance with one pattern. Developing is performed by moving the toner upward.In other words, in a developing device using a contact development method, non-magnetic monocomponent toner is tribo-electrified positively or negatively, and the toner is flown from the toner carrier to the latent image carrier by electrostatic force. things are done.

A bias is applied between the two in order to cause the toner to fly, but in order to apply the bias, the toner carrier itself must be electrically conductive.

Toner carriers used in conventional contact development methods include nitrile rubber (NBR) coated with resin and fine aluminum powder dispersed in the lower layer of the resin, silicone rubber with external addition of carphone, etc. was. Urethane rubber has also been used as a toner carrier.

On the other hand, the main component of the toner is a polyester resin, and a pulverized toner with a particle size of several μm to 30 μm is used. Hydrophobic silica to improve fluidity and carbon to impart conductivity are added to the toner as external additives.

The negatively triboelectrically charged toner is regulated by the toner thinning blade and forms one to two negative-like thin layers on the toner carrier. The formed thin toner layer on the toner carrier is conveyed to a development area where it comes into contact with the latent image carrier.

The toner that has entered the development area flies from the toner carrier to which a developing bias is applied to the latent image portion of the latent image carrier, which has a lower potential than the surrounding area due to exposure.

Problems to be Solved by the Invention However, the above conventional method had the following problems.

First, a case where urethane rubber is used for the toner carrier will be described. Since the main components of the toner, such as bonoester resin and styrene resin, are close to urethane in terms of triboelectric charging, they cannot sufficiently charge the toner negatively.

Therefore, toner of positive polarity is mixed in the unused toner, but this toner is conveyed to the developing section while maintaining its positive polarity, causing a so-called scumming phenomenon in the non-image area on the latent image carrier.

Furthermore, if the toner and toner carrier are close in terms of charging series,
When a high electric field is applied from the toner carrier to the toner,
It is also possible that positive charges are injected into the toner, which would increase the smearing phenomenon and deteriorate the image quality.

Furthermore, when a material other than urethane rubber is used for the toner carrier, the following problems occur.

(1) Toner carriers that use nitrile rubber (NBR) coated with resin and fine aluminum powder dispersed in the lower layer of the resin are expensive to manufacture, extremely difficult to manufacture, and have poor conductivity. The effect of aluminum powder dispersed in the resin to make it durable is small.

(2) Toner carriers made of silicone rubber with carbon externally added have poor processing precision due to the mechanical properties unique to silicone rubber, making it difficult to obtain uniform images, and the cost of non-containing materials is high.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an electrophotographic developing device that is less prone to background smearing, provides high-quality images, is easy to process, and is inexpensive.

Means for Solving the Problems In order to achieve the above object, the present invention comprises a toner carrier made of conductive urethane rubber, and silica is added internally to the urethane rubber.

Function: In the present invention, by providing the toner carrier with the above-mentioned structure, there is no need to disperse the fine aluminum powder using a special method, and therefore manufacturing costs are low, and processing accuracy is good due to the mechanical properties of urethane.

In addition, by adding glue force internally, the tendency of the charge to move in an undesirable direction when a bias is applied to the toner carrier is reduced, and the silica on the roller surface ensures that the toner is sufficiently negatively charged by friction. Become. Therefore, toner flying to areas other than the exposed areas on the latent image carrier is reduced, making it possible to provide an excellent developing device that produces good images.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

As shown in the figure, in the developing device of this embodiment, the toner carrier 2 is placed in contact with the latent image carrier 1, and the bias power source 3 is connected between the latent image carrier 1 and the toner carrier 2. .

A toner thinning blade (toner layer thickness measuring member) 4 is disposed near the toner carrier 2 and has a predetermined minute gap between it and the surface of the toner carrier 2, and further abuts on the toner carrier 2. Then, the toner supply roller 5 is arranged.

The toner carrier 2 used in this example has a structure as shown in FIG. 2, in which polyol is dehydrated, mixed with isocyanate, mixed with stirring, subjected to a primary reaction, and then a crosslinking agent is added and mixed with stirring. The conductive urethane rubber 6 is made into a liquid state by secondary reaction, and the particle size is 0.1 to 5 μm.
20% by weight or more of Soricaf powder was added and kneaded, poured into a mold together with a core metal 8, molded, heated and aged, and the surface was ground.

To explain the operation in the above configuration, the toner supplied by the toner supply roller 5 is negatively charged by friction between the toner supply roller 5 and the toner carrier 2 or between the toner thinning blade 4 and the toner carrier 2. . The negatively triboelectrically charged toner is regulated by the toner thinning plate 4 and forms about one to two negative-like thin layers on the toner carrier 2 . The thin toner layer formed on the toner carrier 2 is conveyed to a development area where it comes into contact with the latent image carrier 1 .

The thin layer of toner that has entered the development area flies from the toner carrier 2 to which a developing bias voltage is applied to the latent image area on the latent image carrier 1, which has a lower potential than the surrounding area due to exposure. .

Is there any toner accumulation at the contact area between the toner carrier 2 and the latent image carrier 1?
A high bias of about 0 to 1000 (1) is added.

Since the silica 7 added internally to the urethane rubber 6 tends to be positively charged, in order to reduce background smudges on the latent image carrier 1, the toner used is more likely to be negatively charged than the silica 7. Is it necessary to use materials with physical properties? Furthermore, in order to make it easier for the negative toner on the toner carrier 2 to fly onto the latent image carrier 1, is it necessary to set the potential of the latent image carrier 1 higher than the potential of the toner carrier 2? be. By setting the bias as described above, toner conveyance is improved and background smear on the latent image carrier 1 can be reduced.

When the toner carrier 2 of this embodiment is used, dielectric polarization occurs in the toner carrier 2 at the portion where the toner and the toner carrier 2 are in contact, but no exchange of charge occurs between the toner and the toner carrier 2. In addition, since Soricuff is added internally to the urethane rubber 6, dielectric breakdown is difficult to occur in the toner carrier 2, and the amount of charge of the toner does not change. Therefore, the toner does not fly to areas other than the exposed area of the latent image carrier 1, and
A good image can be obtained.

I tried investigating the development characteristics by varying the volume resistivity of the toner carrier (conductive urethane rubber 6).
When the volume resistivity value was 104 to 109 (Ω·an), a good image with little background staining was obtained.

Effects of the Invention As is clear from the above embodiments, according to the present invention, the toner carrier is made of conductive urethane rubber, and silica is added internally to the urethane rubber, thereby reducing manufacturing costs. Due to the mechanical properties of urethane rubber, processing accuracy is good.

In addition, by adding silica internally, when a bias is applied to the toner carrier, charge transfer to the toner does not occur, and the toner does not fly to areas other than the exposed areas on the latent image carrier, resulting in a good An excellent developing device for obtaining images can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of essential parts of a developing device according to an embodiment of the present invention, and FIG. 2 is a partial sectional view of a toner carrier in the developing device according to the present invention. 2... Toner carrier, 6... Conductive urethane rubber, 7... Silica.

Claims (3)

[Claims] (1) A developing device of a contact development type using non-magnetic one-component toner, characterized by having a toner carrier made of conductive urethane rubber with silica added therein. (2) The developing device according to claim (1), wherein the non-magnetic one-component toner has negative frictional charging polarity. (3) The volume resistivity value of the toner carrier is 10^4 to 10
Claim (1) characterized in that ＾9 (Ω・cm)
The developing device described.