JPS59111158A - 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 NiO in a specified molar ratio. CONSTITUTION:Starting materials are weighed and mixed to obtain a ferrite composed of 5-30mol% Li2O, 5-30mol% NiO, and 50-90mol% Fe2O3, or a ferrite having a part of this compsn. substd. by a monovalent or higher valent metal, such as CoO. 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 relates to a toner cartridge for electrophotography with improved electrical resistance.

The cascade development method is used as a development method for electrophotography.

There is an old method called magnetic brush development, but the characteristics required for the carrier are appropriate triboelectric charging properties, the ability to attract I.ner particles, dense particles with sufficient strength, and the characteristics required for the carrier. The particles must not cause breakage, have high fluidity, be uniform, have a stable surface condition that does not change various properties due to humidity, etc., have tensile and compressive strength, and have appropriate It has saturation magnetization, magnetic permeability, or coercive force. In particular, electrical resistance is closely related to triboelectric charging and is known to have a large effect on image quality.

Conventionally, various materials have been used as the 1-ner carrier particles, but the most commonly used materials are button and powder. 1. Particles whose surface has been appropriately treated (if used for a long time, the surface of the particles may change physically or IL-wise, and I-ner may adhere to them). Another disadvantage is that it becomes sensitive to the humidity of the environment in which it is used, resulting in poor image clarity and short lifespan.

In addition, the use of oxidized magnetodynamic 1 (1 material) T-lay 1- as chitria is disclosed in Japanese Patent Application Laid-Open No. 2003-120012-56536 etc.
However, it is not necessarily satisfactory in terms of conventional flight light chitria image characteristics or longevity ω.

The present invention increases the print density by arbitrarily changing the electric resistance, and provides a long-lasting print/rear of these conventional electrophotographic toners.

In the present invention, the electric resistance is preferably 1020 cm or more, and outside this range, the amount of frictional electrification can be controlled to an appropriate value, and the effect of humidity etc. can be eliminated, making it difficult to obtain the desired clear rain gap. It is rotation. Also, ili4 of saturation is 10
8ml or more is appropriate; if it is smaller than this value, the adsorption force with the magnetic roll will drop and it will be difficult to obtain the desired clear image.

If 1-10 is more than 10,000, the particles 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 in Example 1 below.

Example 1 L ratio -C1-i 20 5%, NIO 20%, Fe
2o.

They were weighed and mixed to give a total weight of 75%.

Mixing (ball mill, vibration mill, mixer, etc. was used in some cases. The mixed powder was calcined at 800-1200'C. Sample A61, which was calcined at 11 degrees, was mixed using a ball mill, vibration mill, etc.).

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.
It was 3-2.0μ.

The crushed sample was put in a binder and P. V. A (polyvinyl alcohol) aqueous solution (F), V. In the case of A, 0.05-5.0 wt%) was used, and granulation was performed using a one-piece granulator such as a spray shear, kneader, or mixer.

Next, the granulated powder was fired at 1100-1300°C. As a firing method, old grain powder may be placed in a container such as alumina and fired, but if the powder is placed in multiple towers 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 nitrogen atmosphere. The properties of the ferrite thus obtained are shown in Table 1.

Table 1 Using this spherical ferrite as toner chirelia, as a result of copying, the conventional iron powder chirelia is approximately 10,000
70,000-ioo by using the Ki-11 rear of the present invention compared to 50,000 Ki-1r rear
,.

00 clear copies were possible.

Example 2 L in molar ratio! 20'5%, Ni015%. V2051%
, COO5%, Fe2Q374%,
A spherical ferrite having almost the same characteristics as in Example 1 was prepared. As a result of a copy test using these spherical ferrites 1 to 11 as ferrite keys 11 rear, Example 1
The same copy performance was obtained.

As described above, the ferrite main/rear of the present invention has a higher resistance and longer tiQ than the conventionally used iron powder carrier.
It has been found that it has a great industrial application value as a developing material for electrophotography and shows excellent effects.

Claims (1)

[Claims] 1.'U:L ratio l i 2 0 5% ~ 30%,
Ni 05%・130%, “e2Q350%~90%
Alternatively, a part of the composition may be replaced with one or more of the following metals and the fly may be heat treated to reduce the electrical resistance to 102-1013 Ω-.
Spherical electrophotographic ferrite K1-Rear characterized by being improved to CIII. 2. The electrophotographic fly 1, key 1, and rear according to claim 1, characterized in that the saturation magnetization is 10 amu/'g or less. 3. In the product described in claim 1, C. Transparent Vk
Ferrite for electrophotography, which is characterized by a child having a rate of μ10 or more [one-ki-one-liter rear. 4. A carrier for electrophotography according to claim 1, characterized in that the temperature TO is 100° C. or higher. 5. Ferrays 1 to 17 for electrophotography according to claim 1, characterized in that the particles have a strength of 1000 g/cm2 or more. O. Claims 1 to 5. A Ferray 1 carrier for electrophotography as described in IQ, characterized in that the surface of the particles is oxidized. 7. An electrophotographic ferrite 1/ki 1/rear according to claims 1 to 5, characterized in that the surfaces of the particles are coated with a resin or the like.