JPS59127054A - Electrophotographic developing agent - Google Patents

Abstract

PURPOSE:To extend a life of a ferrite carrier for electrostatic development in electrophotography, etc. by forming a film of a specified thickness made of a fluororesin or epoxy resin high in electrical resistance and humidity resistance on the surface of a lithium type ferrite carrier of a specified particle diameter. CONSTITUTION:An electrostatic developing ferrite carrier is obtained by forming a 0.01-30mum thick film made of a fluororesin or epoxy resin having high electrical resistance and humidity resistance on the surface of a spinel type lithium ferrite carrier or that partially substd. by a di- or higher-valent metal having 10-1,000mum particle diameter. Triboelectrification of the magnetic carrier can be controlled by forming a single layer of the fluororesin alone or double layer films of the thin fluororesin stuck first and further the epoxy resin to optionally change electrical properties. Said film forms a tough film on the surface of the spinel type ferrite carrier and peeling of the film from the carrier during development and subsequent staining due to adhesion of the toner to the resin occur scarcely, and therefore, the life of the obtained magnetic carrier is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferrite carrier for a dry developer used for developing electrophotography and the like.

The commonly used two-component electrostatic developer mixes a magnetic carrier and a resin-based toner, is triboelectrically charged, and is then processed by a magnetic developer 7.

The fed t-toner contacts the photosensitive paper, and the latent image is fixed to form an image. However, when the magnetic carrier is used for a long time due to repeated latent image and fixing, frictional heat is generated inside the developing machine, and as the temperature rises, the toner melts and adheres to the surface of the magnetic chitria. The drawback is that the triboelectrification and electrical resistance of the magnetic carrier change significantly, resulting in image blurring and a decrease in print density, resulting in a significant deterioration of the image. This blurring of images and decrease in print density are directly related to the lifespan of the magnetic carrier.
? In order to extend the life of the rear (1) to prevent contamination due to toner fusing to the magnetic carrier, that is, toner spent, the surface of the magnetic carrier is coated with resin to prevent the reaction between the toner and the magnetic chitria. It is necessary to prevent this.

The present invention has been made to improve the above-mentioned drawbacks.
The main purpose of the present invention is to use a fluorine-based resin or epoxy-based resin that has high resistance and high moisture resistance, and to
1. To obtain a long-life ferrite carrier for electrostatic development such as electrophotography by forming a film with a thickness of 0.01 to 30 μm on the surface of 1,000 μm lithium-based ferrite Kyrelia.

The film-forming resin of the present invention is made by using a fluorine-based resin alone or by hardening a thin film on magnetic chitria using the fluorine-based resin, and then forming a double film with an EvoA xy-based resin to conduct electricity on a magnetic carrier. It is possible to maintain the mutual effect of triboelectrification control and long life by changing the physical properties arbitrarily. The resin film of the present invention forms a strong film on the surface of spinel-based lithium-based ferrite t-chitria. It has the advantage that it is less likely to adhere to soil and cause contamination, and therefore the magnetic carrier has a long lifespan.

Next, the effects of the present invention will be explained using examples.

Example 1 A solution obtained by melting a fluorine-based resin in a commonly used solvent was added with the following composition in molar ratio: 15 Zn, 120 Zn, and 10 Zn.
A film was formed on the surface of a spinel-based ferrite carrier of 0 75 Fe 203 by fusion using a fluidized bed to obtain a ferrite film having a strong film. A developer for image evaluation was prepared by mixing eboxy-based 1-ner (for Xerox 3500) into the ferrite carrier on which the film was formed so that the total amount was 3% by weight. The result of image desaturation using this developer was 1oo,,oo.

It was confirmed that the ferrite carrier is capable of making more than one image copy, and has a lifespan approximately three times longer than that of conventional iron powder carriers.

Example 2 Same conditions as Example 1 Te15Li 20 10Zn 07
After forming a fluorine-based resin film on the surface of a 5F820g ferrite carrier, a high-resistance double film was further formed with an epoxy-based resin, and a developer was prepared under the same conditions as in Example 1.
As a result, it was possible to make more than 10,000 copies. From the above, it was confirmed that this magnetic carrier has a lifespan approximately three times longer than that of conventional iron powder carriers.

In addition, the resin coating according to the present invention has a film thickness of
If the thickness is less than 0.01 μm, the film will deteriorate and the lifespan of chitria will be short; on the other hand, if the film thickness exceeds 1.000 μm, the electrical resistance and charging characteristics of the developer can be changed arbitrarily. On the other hand, there is a drawback that the magnetic R property is reduced, which adversely affects image characteristics and makes it impossible to obtain clear images. Therefore, the thickness of the film on the main 119 surface is o, oi -.

A range of 1.000 .mu.Ill is appropriate, but the optimum film range is preferably 0.1 .mu.m.~i, ooo.mu.n1. Further, as the starting material for forming the resin film, either a polymeric material or a polymer may be used.

As described above, the resin film according to the present invention firmly adheres to the main 1/rear surface, and toner does not easily stick to the surface of the film 1 during development, so it can be used as a two-component system for electronic copying machines. When used, the industrial value is extremely large due to its long life.

Claims (1)

[Claims] Spinel-based lithium noelite with a particle size of 10 to 1,000 am, or ferrite crystal in which a part of the metal is replaced with one or more divalent or higher metals, using a high-resistance, high-moisture-resistant fluororesin or epoxy resin. An electrophotographic developer characterized by forming a film with a thickness of 0.01 to 30 μm on the rear surface.