JPS6045262A - Electrophotographic developing carrier and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a carrier small in density and mechanical load to be exerted on other materials and restraining a toner from attaching to it by using a hollow or porous fine spherical carrier composed essentially of magnetite and partially contg. alpha-hematite and having a specified apparent density. CONSTITUTION:The carrier to be used is hollow or porous fine spheres composed essentially of magnetite and partially contg. alpha-hematite, and having an apparent density of 0.5-3.5g/cc. Said carrier is manufactured by suspending iron powder in flames in the air, rapidly oxidizing it, melting it into grains, and further oxidizing iron oxide grains at <=700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carrier material for electrophotographic development that is incorporated into a dry developer used for electrophotography and electrostatic recording, and a method for producing the same.

(Prior art) When using the magnetic push method in the electrophotographic development process, the dry developer contains toner, which is an insulating fine powder made by dispersing pigments or dyes in resin, and the toner is charged by friction and applied to the photoreceptor. A mixture with a carrier material is used that has the function of attaching toner according to the charge on the electrostatic latent image formed on the surface, but conventional carrier materials are iron powders such as atomized iron powder and reduced iron powder. In particular, spherical iron powder is used because it prevents damage to the photoreceptor, makes it easy to adjust the particle size of the carrier, and makes it easy to always obtain a constant surface area in relation to the toner. However, when such iron powder is used as a carrier material, due to the high specific gravity of the carrier material, repeated collisions between the carrier materials and the mechanical parts of the developing machine or between the carrier materials cause wear, resulting in long-term edge 9-turning. When used) Vt eya 1. Ao, 6th class to wear. Disadvantages such as phenomenon, wrinkling, and deterioration of image quality were observed. .

(Object of the Invention) The present invention eliminates the above-mentioned drawbacks, provides a spherical carrier material for electrophotographic development that has a lower density and less mechanical load than conventional iron powder, and to which toner does not easily adhere, and a method thereof that can be mass-produced. It was completed for the purpose of construction.

(Structure of the Invention) The present invention is characterized in that it is a hollow or porous fine spherical body whose main component is magnetite and partly contains a-hematite, and whose apparent density is 03''3.3'/cc. The first invention is a carrier material for electrophotographic development, which includes a first step of suspending iron powder in a flame in the atmosphere and rapidly oxidizing and melting it into a spherical shape; 700
A second method for producing a carrier material for electrophotographic development is provided, which comprises a second step of oxidizing at a temperature below
This is an invention of the invention.

As the raw material iron powder in the present invention, various commercially available iron powders can be used.In addition to irregularly shaped iron powders such as reduced iron powder and crushed iron powder, iron powders of arbitrary shapes such as spherical iron powders such as cast steel shot can be used. Powder can be used.

In addition, in the first step, this iron powder is suspended in a flame in the atmosphere using a gas burner or a thermal spray gun, and is rapidly oxidized.
Melt and use the surface tension during rapid melting to spheroidize iron powder of any shape and expand it to an apparent density of 0.3~
It is a lightweight spherical body of 3.39/ca. Therefore, it is preferable to set the flame temperature in the first step to 1,000 or higher, as the apparent density will be lower if the iron powder is completely oxidized; Since it is possible to produce iron powder with a relatively high density by cooling with a cooling medium such as water during the process, the flame temperature may be lower than that. In this way, the iron oxide powder F spheroidized in the first step! As shown in the X-ray diffraction pattern shown in FIG. 1, the main component is magnetite (Fe3O4, triiron tetroxide), but if oxidation is incomplete, it may also contain iron. Next, the iron oxide powder spheroidized in the first step is oxidized by heat treatment at a temperature below 700'C, which is suitable for converting part of the magnetite into a-hematite, in an atmosphere with an appropriate oxygen concentration. If it deviates, a part of the magnetite, which is the main component of the iron oxide powder made into spherical iron powder through the first step, is converted into a-hematite (aFe203.iron sesquioxide) and becomes magnetite.7. ,: Tighter to increase electrical resistance.

The atmosphere in this case is generally air. Note that the apparent density of the carrier material of the present invention depends on the heating temperature of the iron powder or iron oxide powder in the first step and the second step and the oxygen concentration of the atmosphere. Furthermore, in the first step, the apparent density is greatly affected by the particle shape of the chemical composition of the raw material iron powder, and if raw materials containing components that generate gas during combustion, such as subelements and sulfur, are used, A carrier material for electrophotographic development with a low apparent density is obtained. Therefore, if these conditions are skillfully selected, the apparent density can be reduced to O3~3.
Carrier materials can be produced with apparent densities of 5'/cc.

The carrier material for electrophotographic development obtained in this way is a hollow or porous spherical body with a particle size of about 10-300 μm and an extremely small apparent density of θS ~ 3.3'/cc. , when mixing the developer, the stirring force may be smaller than that of conventional methods, and therefore the mechanical stress applied to the toner is weak.

As a result, the wear of the carrier material is small, so the amount of toner that adheres to the surface of the carrier material and does not come off is reduced, the quality of images is less likely to deteriorate, and it can be used repeatedly as a developer for a long time.

In addition, the electrical resistance of the carrier material required to triboelectrically charge the toner and carrier material by mixing and stirring is 1O7Ω・α
The above values are already / 0”~lO9Ω・ after the first process.
This was achieved by producing magnetite, which is a fungus, and the second
Since the electrical resistance is further increased during the process, it is possible to obtain images with unprecedented gradation.

(Example 1) A cast steel grid with a grain size of less than 11I9μm was heated to a flame temperature of 110μm.
It was dropped into the flame of a propane gas burner at 0°C and rapidly oxidized and melted into spheroids, which were then collected in the atmosphere.

This is sieved to produce hollow or porous spheroidized iron oxide powder with a particle size of about 80 μm and mainly composed of magnetite (
Sample /) was obtained. As shown in FIG. 1, the X-ray diffraction pattern showed that magnetite was the main component. A part of this iron oxide powder was heat-treated at about 380°C in the air to make a part of the magnetite into a-hematite (sample 2), and the rest was heated at about 3'O'C in the air. A carrier material (sample 3) in which part of the magnetite was converted into α-hematite by heat treatment was prepared as described above. The X-ray diffraction patterns of each sample obtained here are shown in FIGS. 2 and 3, respectively.

Further, the apparent density and electrical resistance of each sample were as shown in Table/.

Table 1 According to the results, it can be seen that those with a high proportion of α-hematite produced have high electrical resistance.

(Fire Example 2) Cast steel shot having a grain size of less than 749 μm was rapidly oxidized and melted into spheres using a thermal spray gun using oxygen and ethylene gas, and then captured in the atmosphere. This was sieved to obtain iron oxide powder (sample 1) having a particle size of about 20 ttm and containing magnetite as a main component.

A part of this iron oxide powder was heat-treated at about 380"C in the air to form a carrier material (sample S) in which part of the magnetite was turned into α-hematite, and the remaining part was heat-treated at about 670"C in the air.
A carrier material (sample 6) in which part of magnetite was converted into a-hematite was obtained.

The apparent density and electrical resistance of each sample obtained here are as shown in Table 2.

11. Figure 1 is the X-ray diffraction pattern of the sample in Example 1, Figure 2 is the X-ray diffraction pattern of Sample 2 in Dormitory Example 1, and Figure 3 is a brief explanation of the drawings. is the X-ray diffraction pattern of Sample 3 in Example 1.

Figure 1 three Figure 2

Claims (1)

[Claims] 1. The main component is magnetite, including a portion of a-hematite, and the apparent density is 03 to 1! A carrier material for electrophotographic development, characterized in that it is a hollow or porous fine spherical body of '/cc. 2. A first step in which iron powder is suspended in a flame in the atmosphere to rapidly oxidize and melt it into spheroids; a second step in which the spheroidized iron oxide powder is oxidized at a temperature of 700°C or less; A method for producing a carrier material for electrophotographic development, characterized by comprising: