JPS58123550A - Electrophotographic developing carrier - Google Patents

Abstract

PURPOSE:To obtain a carrier superior in image characteristics and long in service life, by specifying proportions of the components of ferrite consisting of MgO, MnO, Fe2O3, and ZnO, its electromagnetic characteristics, its particle diameter, and its surface state. CONSTITUTION:This ferrite consists of 1-40mol% MgO, 0.5-30mol% MnO, 45- 60mol% Fe2O3, and 0.1-30mol% ZnO, and it has 10<3>-10<12>ohm.cm, 15-80emu/ g saturation magnetization value, <=10Oe coercive force Hc, <=10 magnetic permeability mu, >=50 deg.C Curie temp. Tc, and 5-500 average particle diameter. It is spherical and the surface of each particle is oxidized or coated with a resin. As a result of copying test of this prepared sample of this carrier, 70,000-100,000 sharp copies were obtained as compared with 50,000 copies obtained with usual ferrite carrier in all its service life.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic toner carrier. Development methods for electrophotography include cascade development, magnetic brush development, and other methods, but the characteristics required for the carrier are appropriate triboelectric charging properties, and when the toner particles are attracted, they are dense and the strength of the particles increases. The particles must have sufficient fluidity and do not cause particle breakage, the particles must be uniform, the surface condition must be stable without changing various properties due to humidity, etc., and the tensile and compressive strength must be high. , and have appropriate saturation magnetization, magnetic permeability, or coercive force.

Conventionally, various materials have been used as toner carrier particles, but iron powder is the most commonly used material. Although the surface of iron powder is used after being appropriately treated, if it is used for a long time, the surface of the particles may change physically or chemically, causing toner to adhere to it or becoming sensitive to the humidity of the usage environment. The drawbacks are that the sharpness of the image may fade and the lifespan is short.

Furthermore, although the use of ferrite, which is an oxide magnetic material, as a gear carrier has been reported in Japanese Patent Laid-Open No. 52-56536, etc., conventional ferrite carriers are not necessarily satisfactory in terms of image characteristics or lifespan.

The present invention eliminates these drawbacks of conventional electrophotographic toner carriers and provides a carrier with improved image characteristics and a long life.

In the present invention, the electrical resistivity is 103Ωfi, lQl”Ω
α is good, but outside this range, the amount of friction zone "+M" cannot be controlled to an appropriate value, and it is easily affected by humidity etc., making it difficult to obtain the desired clear image. An appropriate value is 100 mw't<~80 θmVg; if it is smaller than this value, the adsorption force with the magnetic four is reduced and it is difficult to obtain a clear image as a target.

Moreover, if Hc is 100e or more, the particles themselves have magnetic properties and adhere to various parts, making it impossible to obtain good images.

Furthermore, if the magnetic permeability μ is less than 10, the response to the magnetic roll will be poor and the image quality will be affected.

This will be explained in detail below using examples.

Example 1 They were weighed and mixed in a molar ratio of 23% MgO, 23% Mn, 4% Zn, and 10350% lFe. As a mixer, a ball mill, a vibration mill, a mixer, etc. were used. The mixed powder was calcined at 800-12007. The calcined sample was pulverized using a pulverizer such as a ball mill, vibration mill, or attritor. The particle size after pulverization was measured using an air permeation method, and the average particle size was 0.3 to zOμ.

The pulverized sample was prepared using an aqueous solution of P, V, and k (borihinyl alcohol) as a binder (P, v, and h amounts are 0.0
5-5. C1wt%) and was granulated using a granulator such as a spray dryer, kneader, or mixer.

Next, the granulated powder was fired at a temperature of 1100 to 14007. Firing method: As a method, you can put the granulated powder in a container such as alumina and fire it, but if you put it in a multi-plate container and fire it, the grains will grow during firing and the grains will not stick together. 3 when joining.

Therefore, the sample may be fired while being rotated using a rotor gilt or the like. As a result of copying using the thus obtained spherical ferrite as a toner carrier,
By using the carrier of the present invention, it was possible to make clear copies of 7α,000 to 100,000 copies, compared to about 10,000 copies with the conventional iron carrier and 5α,000 copies with the ferrite carrier.

Example 2 Mg0. A sample was prepared in the same manner as in Example 1 by weighing AAgOa −, ZnO, and Fe+On into the following composition. The unit is mol%.

Next, the characteristics of these samples were measured and the results were as follows.

Next, these samples AB and 0 were spheroidized and fired,
As a result of a copy test using it as a toner carrier, the lifespan of lα000 sheets when using conventional iron powder and 5o and 00 sheets of a normal ferrite carrier,
It has been found that 70,000 to 100,000 clear copies can be made, and that dependence on the environment of the copying device is almost zero.

As described above, the ferrite carrier according to the present invention has a very long service life at which clear images can be obtained, and has very little dependence on the external environment, which has great industrial significance.

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Claims (1)

[Claims] L molar ratio MgO 1% to 40%, Mn00 5% to 30
%, Fe20545%~60%, znO01%~30%
It consists of electrical resistivity 101ΩcIILA1011IΩα
A spherical 7-element 7-carrier with a saturation magnetization value of 15 emu/g and 80 em $g, and an average particle size of 5 μm and 7% 7500 μm. 2. A ferrite carrier according to claim 1, characterized in that the coercive force is less than Ho1OOe. 3. A ferrite carrier according to claim 1, characterized in that it has a magnetic permeability of μm0 or more. A ferrite carrier according to claim 1, characterized in that the temperature TO is 50C or higher. 5. A ferrite carrier according to claims 1 to 4, characterized in that the surface of the particles is oxidized. 6. Claims 1 to 4. A ferrite carrier characterized in that the surface of the particles is coated with a resin or the like.