JPS61117568A - Carrier for developer - Google Patents

Abstract

PURPOSE:To prevent moisture absorption and to obtain an image having high quality even under high humidity by packing the holes of carrier particles consisting of NiO, ZnO, etc. and Fe2O3 with a glass material. CONSTITUTION:The glass material is packed into the holes of the carrier particles consisting of a soft magnetic material which is a sintered body of the oxide of Ni, Zn, Mn, Mg, Cu Li, Ba, V, Cr, etc. and Fe2O3 and has spinel, perovskite, hexagonal, garnet or orthoferrite structure. The packing of the glass material into the holes of the carrier particles is executed, for example, by adding the glass materials to the carrier particles, kneading the particles while heating the same to the glass softening point or above, extruding the kneaded carriers through a fine hole, cutting the resulted yarn-like molding to a prescribed length and heating the cut molding to the softening point of the glass or above to spheroidize the same. The holes which are the hygroscopic point of the carrier particle surface are thus packed by the glass, by which the moisture absorption is prevented. The moisture absorption of the carrier is thus prevented even under high humidity and the image having high quality is obtd.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a carrier for two-component developers used in electrophotography, electrostatic recording, and electrostatic printing, and in particular to carriers that prevent moisture absorption of the carrier. It is.

``Conventional technology'' As developer carriers, iron powder-based carriers and saturation magnetization (
There are ferrite carriers with a small σS). When comparing the two, the ferrite carrier has superior fluidity and agitation properties, so the magnetic brush in the magnetic brush developing device becomes softer, and when copying, halftones are reduced. Good image quality can be obtained with no problems with reproducibility. Further, the ferrite carrier has an apparent density of about 273, which is smaller than that of iron powder, and requires a smaller conveyance torque.

A ferrite carrier like this 1 is published in Japanese Patent Application Laid-open No. 53-1
As disclosed in Japanese Patent Application Laid-open No. 5040 and Japanese Patent Application Laid-open No. 58-52305, an aqueous slurry of ferrite-forming metal oxide is prepared, a dispersant is added thereto, and the mixture is granulated and dried by a spray drying method, followed by sintering. It was formed as follows.

``Problems to be Solved by the Invention'' Ferrite carriers formed by spray drying as in the prior art have many pores in the carrier particles, and these pores are susceptible to moisture, especially in high humidity. There is a problem in that the carrier absorbs moisture and its resistance decreases, causing the characteristics (especially resistance) of the ferrite carrier to change, resulting in poor image quality of copies.

The present invention solves the above-mentioned problems.
n, Mn, Mg, Cu, Li, Ba, V
, sintering an oxide such as Cr and Fe2O3 to form carrier particles made of a soft magnetic material having a spinel, perovskite, hexagonal, garnet, or so-called orthoferrite structure. These carrier particles have pores on the surface, and a developer carrier is formed by filling the pores with a glass agent, so that good image quality can be obtained without the carrier absorbing moisture.

In order to obtain the developer carrier of the present invention, former, Zn+
Mn, Mg* Cur LL ”a+ V+ 1100-14 by mixing oxides such as Cr and trivalent iron oxide
By firing at 00°C for several hours, a sintered body is produced, and a soft magnetic material having a spinel, perovskite, hexagonal, garnet, or so-called orthoferrite structure is produced. This soft magnetic material is pulverized into particles smaller than a few liters to form carrier particles.

These carrier particles have pores on their surface, which tend to absorb moisture, so the pores can be filled with glassy additives (for example, old-5i-C).
Fill with a type (a). In this case, a glass agent is added to the carrier particles and kneaded while heating above the softening point of the glass.The mixed wire is extruded through a nozzle with a diameter of 20 to 200 ra to form a thread, and the thread-like molded body is formed into a predetermined length. Cut into pieces (for example, 1 to 5 times the length of the diameter). Thereafter, the glass is spheroidized in a heated atmosphere at a temperature higher than the softening point of the glass. Further, the spherical particles are classified to obtain a developer carrier whose pores are filled with a glass agent.

Here, the physical properties of the developer carrier will be explained.

The coercive force (He) of the developer carrier is 30 to 1500e
Desirably, if it is less than 300e, the fluidity will be poor;
If the value exceeds e, the conveyance torque increases.

Saturation magnetization (CRS) is 50-120 emu/g
Desirably, if it is less than 50, the carrier will separate from the sleeve of the developing roll and adhere to the photoreceptor, and if it exceeds 120, the magnetic brush will become hard.

The particle size is preferably from 20 to 200 ILIl, and the smaller the particle size, the larger the specific surface area, so the maximum toner concentration can be increased and the durability can be improved. However, if there is too much carrier of 20 Lm or less, the carrier will adhere to the photoreceptor, so the amount of carrier of 201 Lm or less is preferably 30% by weight or less, although it depends on the developing conditions.

The resistance can be adjusted, for example, by changing the firing conditions, but is preferably 10 5 to 10 12 Ωcm, and is set within that range depending on the developing conditions. When the resistance becomes less than tOSΩcm, carriers are attached, and when the resistance becomes more than 10I2ΩC1, the image density decreases.

"Example" 1st Example molar ratio: Ba015%, Zn015%, Nfo 10%
, Fe20360% was mixed in a ball mill and heated at 1300°C.
The sintered body is heated for 2 hours and sintered, and the particle size is 1IL.
It was pulverized as follows. Ha-Si-C in crushed grains
a Add 10% of glass agent, heat to 850°C and knead,
After extrusion from the nozzle, it was cut into lengths of 80-130 JL and spheroidized in a heated atmosphere. Rough particle size is 80~
125 JLtm was classified. “ The saturation magnetization of the developer carrier thus obtained (
crg) is 78 emu/g and the resistance is 3×1
It was 09ΩC■.

Second example molar ratio: old 015%, ZnO35%, Fe20350
% was mixed in a ball mill, sintered and pulverized in the same manner as in the first example, further kneaded with a glass agent to form spheroids, and then classified.

The saturation magnetization of the developer carrier thus obtained (
crg) is 85eWru/g and the resistance is 2×
It was 108ΩC■.

Third Example Molar ratio Te L1015%, Zn035%, Fe20350
% was mixed in a ball mill, sintered and pulverized in the same manner as in the first example, further kneaded with a glass agent to form spheroids, and then classified.

The saturation magnetism (σS) of the developer carrier thus obtained was 88 emu/g, and the resistance was 6.
The layer was ×10 7 ΩC.

In order to compare the above three examples with carriers that were granulated by a spray drying method without adding a glass agent in the conventional example, then sintered and classified, each carrier had a toner concentration of 5.
Toner is added and kneaded so as to give the same weight percentage, and the resulting developer is used in a commercial copying machine (F T-4 manufactured by Ricoh Co., Ltd.).
080).

As a result, good image quality was obtained for the first to third examples at a room temperature of 20° C. and a humidity of 50%. Also, the image quality of the conventional example was almost satisfactory. However, the room temperature is 30℃,
At a humidity of 80%, the first to third examples provided good image quality, but the conventional example had poor image quality.

"Effects of the Invention" The developing material carrier of the present invention contains old 0, ZnO, etc. and F.
[! Since the pores of the carrier particles consisting of 203 are filled with the glass material, moisture absorption is prevented, and even in high humidity, the carrier does not absorb moisture and a high quality image can be obtained.

Claims (1)

[Claims] Ni, Zn, Mn, Mg, Cu, Li, Ba, V, CT
In a developer carrier made of a soft magnetic material having a spinel, perovskite, hexagonal, garnet or orthoferrite structure, which is a sintered body of oxides such as Fe_2O_3 and Fe_2O_3, the pores of the carrier particles are filled with a glass agent. A developer carrier characterized by: