JPS59111162A - Electrophotographic ferrite carrier - Google Patents

Abstract

PURPOSE:To obtain a spherical electrophotographic ferrite carrier having long life and high electric resistance and forming an image superior in sharpness etc. by heat-treating a ferrite contg. Fe2O3 as an essential component and Li2O and ZnO in a specified molar ratio. CONSTITUTION:Starting materials are weighed and mixed to obtain a ferrite composed of 2-30mol% Li2O, 5-30mol% ZnO, and 50-90mol% Fe2O3, or a ferrite having a part of this compsn. substd. by a monovalent or higher valent metal, such as MgO. This powder mixture is calcined, pulverized, granulated, burned at 1,100-1,400 deg.C, and finally heat-treated at about 700 deg.C for about 2hr in a nitrogen atm. to obtain the intended electrophotographic ferrite carrier. The obtained ferrite carrier has 10<2>-10<13>OMEGA-cm resistivity, >=10emu/g saturation magnetization, >=10mu magnetic permeability, >=100 deg.C Curie. temp., and >=1,000g/ cm<2> particle strength.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an electrophotographic toner with improved electrical resistance and IQ.
It concerns the rear.

The development method for electrophotography is the cascade development method.

There are magnetic brush development methods and other methods, but the characteristics required for the carrier are appropriate triboelectric charging properties.
- Particles must be suctioned, the particle strength 1α is dense enough to not cause the destruction of C grains, the particles must be highly fluid, the particles must be uniform, and the surface condition varies depending on the degree of vigour, etc. The properties of the material must remain unchanged, have tensile and compressive strength, and have appropriate saturation magnetization, magnetic permeability, or coercive force. In particular, electrical resistance is closely related to triboelectrification and is known to greatly affect image characteristics.

Conventionally, various materials have been used for I/Narch 1z rear particles, but iron 1' is the most commonly used material.
f)). The surface of iron powder is used after being appropriately treated, but if used for a long time, the surface of the particles may change physically or chemically, causing adhesion of -ner or due to the environment in which it is used. They have the disadvantage that they are sensitive to humidity, which can distort the sharpness of the image, and that they have a short lifespan.

In addition, the use of ferrite, which is an oxide magnetic phase, as the key A/rear was published by JP-A-Sho! '+2-56536 etc. have been reported, but the conventional) Trai 1 ~ Ki 1? The rear camera is not always satisfactory in terms of image characteristics or lifespan.

The present invention aims to increase the printing temperature by arbitrarily changing the electric resistance, eliminate these drawbacks of conventional electrophotographic toners, and provide a toner with excellent image characteristics and a long service life.

In the present invention, it is preferable that the electrical resistivity is 102Ωcn+ or more; outside this range, the friction band Kaminari gate cannot be controlled to an appropriate value;
Furthermore, it is difficult to obtain a desired clear image because it is not affected by humidity or the like. Also, the value of saturation magnetism 1 is 108
m1J/(1 or more is appropriate; if the value is smaller than this value, the magnetic adsorption force will decrease and it will be difficult to obtain the desired clear image.

Furthermore, when the IC is 1000a 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 Molar ratio: 1i205%, 7nQ20%, Fe20
The mixture was weighed and mixed to give 375%.

A ball mill, a vibration mill, a mixer, etc. were used as the mixing mill. The mixed powder was calcined at 800 to 1200°C. Calcined samples are tested in ball mills and vibration mills.

It was pulverized using a pulverizer such as Attritor. The particle size after pulverization was measured using an air permeation method, and the average particle size was 0.3.
- It was ~2.0μ.

The crushed sample was mixed with an aqueous solution of P, V, A (polyvinyl alcohol) as a binder (in some cases P, V, A was 0).
．． 05 ・～5. %), and granulated using a granulator such as a spray dryer, Ni-Goo, or mixer.

Next, the Oni I'l powder was calcined at 1100-1300°C. As a firing method, granulated powder may be placed in a container such as Almiry and fired, but if a large amount is placed in a container and fired, the grains may grow during firing and the grains may join together. Therefore, the sample may be fired while rotating in a rotor kiln or the like.

Next, heat treatment was performed at 700° C. for 2 hours in a window element atmosphere. Table 1 shows the properties of the thus obtained ferrite.

Table 1 As a result of using and copying this spherical ferrite as ]・Naki I/Ria etc., the conventional iron powder Gt・Ria is approximately 10,
70,000 to 10 sheets by using the present invention Kiria for 50,000 sheets of ferrite carrier.
It was possible to make 0,000 clear copies.

Example 2 Molar ratio TeI-i 205%, ZnQ 15%, M(105
%1F820375%, and processed in the same manner as in Example 1 to obtain a spherical ferrite 1 having approximately the same characteristics.
~It was created. As a result of a copying test using this spherical ferrite [- as a ferrite carrier, copying performance similar to that of actual f1 color example 1 was obtained.

As described above, it has been found that the ferrite carrier of the present invention has a higher resistance than the conventionally used iron powder carrier, and is superior to C1 in developing materials for electrophotography. It has great industrial application value.

Claims (1)

[Claims] 1. Li2Q2%-30%, ZnO3%-3 in molar ratio
0%, l:e? 0350% to 90% or a part of the composition is replaced with one or more metals of 11iIIIi or more) By heat-treating T-light, the electrical resistance is improved to 102-1013 Ω-cm. A spherical electrophotographic flyray characterized by: 2. In the product described in claim 1, saturated [
1. Ferrite I-K1/Ria for electrophotography, characterized in that it has a monomerization of 10 emu/g or more. 3. A carrier for electrophotography according to claim 1, characterized in that it has a magnetic permeability of μm0 or more. 4. In the thing described in claim 1. Ferrite A/Ria for electrophotography, which is characterized by a temperature TC of 100°C or higher. 5. A ferrite chitria for electrophotography, characterized in that the strength of the particles is 1000 (1/0112 or more) according to claim 1. A ferrite crystal for electrophotography, which is different from the one described in item 5 (-), characterized in that the surface of the particles is oxidized. A ferrite carrier for electrophotography, characterized in that the surface of the particles is coated with a resin, etc.