JPS58123554A - Electrophotographic developing carrier - Google Patents

Abstract

PURPOSE:To obtain a carrier superior in image characteristics and long in service life, by specifying components and contents of lithium and zinc oxides and their substd. oxides to be added to iron oxide, and their electrical resistivity, saturation magnetization value, particle diameter, etc. CONSTITUTION:A ferrite carrier consists of 5-15mol% Li2O, 5-17mol% ZnO, and 70-80mol%, and Li2O and /or ZnO in the fundamental composn. is partially substd. by >=2kinds of MbO, MgO, CuO, and Al2O3. It has characteristics of 10<5>-10<12>ohm.cm resistivity, and 45-70emu/g saturation magnetization value. It has <=10Oe coercive force Hc, >=50 magnetic permeability at 1MHz, >=300 deg.C Curie temp. Tc, and >=1,000kg/cm<2> particle strength, and its particles have spherical forms and 30-1,000mum average diameter, and the surface of each particles is oxidized or coated with resin or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner carrier for electrophotography. 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 toner particles are attracted, they are dense and the strength of the particles increases. is sufficient,
The particles must have high fluidity without causing grain breakage, the particles must be uniform, the surface condition must be stable without changing various properties due to humidity, etc., and the particles must have tensile and compressive strength. It has appropriate saturation magnetization, magnetic permeability, or coercive force.

Conventionally, various materials have been used as toner carrier particles.

It has been used, but it is the most commonly used.

There is iron filings. 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.

In addition, the use of ferrite, which is an oxide magnetic material, as a carrier has been reported in Japanese Patent Laid-Open No. 52-56536, etc., but the conventional 7-elite carrier is not necessarily satisfactory in terms of image characteristics or lifespan. isn't it.

The present invention eliminates these drawbacks of conventional toner carriers for photographic use and provides a carrier with vague image characteristics and a 14° longer life.

In the present invention, the electrical resistivity is 108ΩG to 1012Ωα
However, outside this range, it is impossible to control the friction charge to an appropriate value, and it is susceptible to the effects of humidity, etc., making it difficult to obtain the desired clear image. Also, the value of saturation magnetization is 45
emu@N70θmrg is the appropriate value.

If the magnetic roll is small, the adhesion force with the magnetic roll decreases, making it difficult to obtain the desired clear image.

Furthermore, when HO is greater than 1.00θ, the particles themselves have magnetic properties and adhere to various parts, making it impossible to obtain good images and affecting the image quality.

This will be explained in detail below using examples.

Example 1 Molar ratio: 1. i, 05 mol%, Zn010 mol%, Fe
A ball mill, a vibration mill, a mixer, etc. were used to prepare the mixture at 50% and 72 mol. The mixed powder was calcined at 800-11200 U. Calcined! 5 The 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 approximately LOμ.

The pulverized sample contained an aqueous solution of P, V, and A (borihinyl alcohol) as a binder (the amounts of P, v, and A were 0.
05-5.0wt%) using a spray dryer,
The mixture was granulated using a granulator such as a kneader or mixer. .

Next, the granulated powder was fired at 1150G. As for the firing method.

Then, you can put granulated powder in a container such as alumina and fire it, but if you put a large amount of powder in a container and fire it, the grains may grow during firing and curing, and the grains may join together, so rotor kiln is not recommended. The sample may be fired while rotating. The characteristics of the ferrite thus obtained are shown below.

Using this spherical ferrite as a toner carrier, the number of copies made using a conventional iron carrier is approximately 10,000 sheets.
By using the carrier of the present invention, clear copies of 7α000 to 100,000 sheets were possible compared to 50,000 sheets using the ferrite carrier.

Example 2 Li, 05 mol%, x1o5 mol%, Fa in molar ratio
Basic composition of lQ3'7'7 mol%, Zn07 mol%, A
It was weighed so that t1Oi was 3 mol%, and spherical ferrite was produced in the same manner as in the example. With this spherical ferrite toner carrier.

As a result, copying performance similar to that of Example 1 was obtained.

As described above, the ferrite carrier of the present invention has been found to have higher resistance and longer life than conventionally used iron powder carriers, and has shown outstanding effectiveness as a developing material for electronic copying machines, and has been found to be useful in industrial applications. It has great application value.

Claims (1)

[Claims] L molar ratio I, 1a05 mol% to 15 mol%, ZnO
3 mol% to 17 mol%, Fe10370 mol% to 80 mol% caranal basic composition of L120 and NiO or 2
Seed is MnO, job 01■0, At20. Electrical resistivity 10"ΩOI in a composition partially substituted with two or more of
The saturation magnetization value is 45emx/g at ~1012Ωσ, 70
emtl/g, with an average particle size of 30 μm to 10
00μm spherical ferrite carrier. 2. In the product described in claim 1, the coercive force Hc1. A ferrite carrier characterized by a QOe or lower. 3. A ferrite carrier according to claim 1, characterized in that it has a magnetic permeability of 850 or more. A ferrite carrier according to claim 1 EI, characterized in that it has a Curie temperature 'IQ of 300C or more. 5. The product described in claim 1 is characterized in that the strength of the particles is: coookg/i or more. Ferrite carrier. 6. A ferrite carrier according to claims 1 to 5, characterized in that the surface of the particles is oxidized. 7. A ferrite carrier according to claims 1 to 5, characterized in that the surface of the particles is coated with a resin or the like.