JPS6043667A - Carrier for electrostatic latent image developer - Google Patents

Abstract

PURPOSE:To obtain a long-life carrier which is highly resistant to wear and is not spent by providing a silicone resin coating layer contg. glass fibers on the surface of nucleous particles for the carrier. CONSTITUTION:A resin soln. prepd. by dispersing glass fibers of about 0.2-5mu fiber diameter and length pulverized to the size smaller than the film thickness of the coating layer into a silicone resin at 2-30pts.wt. by 100pts.wt. said resin is coated on the surfaces of pearticles consisting of a conventional material such as iron, glass or the like and having 10-1,000mu average grain size as nucleous particles for a carrier, thereby forming the coating layer. The coating layer is formed by using a fluidized bed type coating device, tec. The carrier which is highly resistant to wear, is not spent without sticking of a toner film on the carrier surface in the stage of developing at a high speed and maintains the initial electrifying characteristic for long time is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a carrier for a dry developer used for visualizing an electrostatic latent image formed by electrophotography, electrostatic recording, electrostatic printing, or the like.

BACKGROUND OF THE INVENTION So-called two-component dry developers comprising a mixture of carrier particles and toner particles are well known. In this two-component dry developer, minute toner particles are held on the surface of relatively large carrier particles by the electric force generated by the friction of rain particles, and when brought close to the electrostatic latent image, the electrostatic latent image The attraction force on the toner particles in the direction of the latent image due to the electric field formed by the toner particles overcomes the bonding force between the toner particles and carrier particles, and the toner particles are attracted and adhered to the electrostatic latent image, making the electrostatic latent image visible. It is something. The developer is used repeatedly while replenishing the toner consumed by development.

Therefore, during long-term use, the carrier particles must always triboelectrically charge the toner particles to a desired polarity and a sufficient amount of charge. However, in conventional developers, a toner film is formed on the surface of the carrier particles due to mechanical collisions between particles or with the inner wall of the developing section, or heat generated by these, resulting in so-called spent state, and the charging characteristics of the carrier particles deteriorate over time. However, it becomes necessary to replace the entire developer.

In order to prevent such spent formation, methods of coating the surface of carrier particles with various resins have been proposed, but no satisfactory method has been obtained yet. for example,
Carrier particles coated with resins such as styrene-methacrylate copolymers and styrene polymers have excellent charging properties, but the critical surface tension of their surfaces is relatively high, and they tend to become bent over time after repeated copying. The lifespan of the developer was not that long. In response to this problem, carrier particles coated with a silicone resin having low surface tension have been proposed. Silicone resin itself has low mechanical strength, so if it is strongly agitated for a long time in the developing section of a high-speed copying machine, carrier particles may collide with the inner wall of the developing section or the surface of the photoreceptor, or the particles may collide with each other. As the silicone resin coating wears away and peels off over time, the frictional charge changes from the charge between the toner and the silicone resin to the charge between the toner and the carrier core material, so the amount of charge on the developer remains constant. This resulted in deterioration of image quality.

1. An object of the present invention is to provide a carrier that increases mechanical strength and does not cause deterioration of developed image quality even after long-term use without impairing the effect of the silicone resin layer coated on the surface of carrier core particles against toner spent. It provides particles.

1. The present invention is a carrier particle for an electrostatic latent image developer, in which a coating layer made of a silicone resin containing glass fibers is provided on the surface of the core particle.

The glass fiber used in the present invention is 5i02,
A920g, Fe2O3, CuO1Mg○, Na2O,
Any material may be used as long as it contains components such as B20J and TiO2 and can be pulverized to a size equal to or less than the thickness of the coating layer made of silicone resin.

The silicone resin used in the present invention may be any conventionally known silicone resin, such as KR271 and KR2 manufactured by Shin-Etsu Chemical Co., Ltd., which are commercially available.
55, KR452 and SR2400 manufactured by Toshi Silicone Co., Ltd.
, 5H840, 5R2406, etc. are used.

In the present invention, carrier core particles to be coated with silicone resin include sand, cobalt, iron, copper, nickel, zinc, nonmetallic materials such as aluminium 11, brass, glass, etc., with an average particle size of 10 to 1000 μm, preferably 30 to 500 μm. or metal,
Conventionally used materials such as metal alloys can be used. The silicone resin layer may be formed by coating the coating layer composition onto the surface of the core particles by a conventionally known means such as a spraying method).

The coating layer composition is prepared by adding glass fibers to a silicone resin solution and dispersing the mixture using an appropriate mixer.

The glass fibers dispersed in the coating layer may be ones that have been pulverized using a milling machine, etc., and the size of the glass fibers may be as long as the diameter is less than or equal to the thickness of the coating layer, and the length of the glass fibers may be about the same. good. Considering the glass fiber as particulate, it is preferably about 0.2 to 5 μm.

The amount of glass fiber added is preferably 2 to 30 parts by weight, more preferably 5 to 20 parts by weight, per 100 parts by weight of the silicone resin.

Further, the coating layer composition may contain a conventionally known conductive agent such as carbon black or a triboelectric charge control agent.

The toner particles used together with the carrier particles of the present invention are those obtained by conventionally known methods, and specifically include a resin component and a colorant such as carbon black, which is usually necessary for forming a visible image. It is obtained by mixing well, kneading with a hot roll mill, cooling, assimilating, pulverizing, and classifying.

The amount of carrier particles and toner particles to be used is preferably such that the toner particles adhere to the resin surface of the carrier particles and occupy 30 to 90% of the surface area thereof.

Examples of the present invention are shown below.

Example 1 Silicone resin solution (Shin-Etsu Chemical Co., Ltd. 1KR250) 2.0
00 parts by weight Glass fiber (size Q, 77z) 12 parts by weight 1-luene 2,000 parts by weight The above formulation was dispersed in a homomixer for 30 minutes to prepare a coating layer forming liquid. This coating layer forming liquid was applied to the surface of 5,000 parts by weight of spherical iron oxide of 10071 using a fluidized bed coating device to form a coating layer and obtain carrier particles. The average thickness of the coating layer was 2.271 mm.

On the other hand, styrene-n-butyl methacrylate copolymer 87 h
A toner having an average particle size of 61 L was prepared, consisting of 10 parts by weight of carbon black and 3 parts by weight of a 2:1 type chromium complex dye of a monoazo dye.

100 parts by weight of the carrier and 2.5 parts by weight of the toner are mixed to form a developer, and the latent image on the selenium photoreceptor is developed at a rate of 30 times per minute. This was repeated 100,000 times while replenishing the developer.゛There was almost no change in copy image quality at that time. Further, when the carrier in the developer was separated and the average thickness of the coating layer was examined, it was found to be 2.08/j, showing almost no wear.

Comparative Example A silicone resin coated carrier having an average film thickness of 2.0μ was prepared in the same manner as in Example 1 except that glass fibers were removed from the carrier coating layer forming liquid formulation, and the same tests as in Example 1 were conducted. However, the copy image quality after 100,000 copies has deteriorated, and the average thickness of the carrier coating layer is also 1.2μ.
It was worn out.

Example 2 Silicone resin solution (manufactured by Toshi Silicone Co., Ltd. 5R2400
) 1,500 parts by weight Glass fiber (average particle size 0.8μ) 15 parts by weight Toluene 1.500 parts by weight The above formulation was dispersed in a homomixer for 30 minutes, and then this dispersion was mixed with 5,000 parts by weight of 10011 iron oxide powder. It is applied to the surface of the part using a fluidized bed type coating device, and the average thickness is t, o.
A carrier having a s7z coating layer was obtained. When the same test as in Example 1 was carried out and 100,000 copies were made, there was almost no change in image quality, and the thickness of the carrier coating layer was 0.99/j, showing almost no wear.

According to the above, the carrier particles of the present invention have a high mechanical strength Jσ of silicone resin 1, and
Near bit l→j The quality of the blood in the cursed image is poor (
It has a concentrated effect of not causing irritation.
Ru.

Claims (1)

[Claims] A carrier for an electrostatic latent image developer, characterized in that a coating layer made of a silicone resin containing glass fibers is provided on the surface of core particles.