JPS6235369A - Ferrite carrier and developing method using said carrier - Google Patents

Abstract

PURPOSE:To have good reproducibility and to provide an image having high density and good half tone by consisting a ferrite carrier for a two-component type developer of spherical particles and irregular shaped particles. CONSTITUTION:The ferrite carrier for the two-component type developer consists of 90-10wt% spherical ferrite carrier particles and 10-90wt% irregular shaped ferrite carrier particles. The average particle size of the spherical ferrite carrier particles is 50-150mum and the characteristics of such carrier particles are preferably 40-804mu/g satd. magnetization, 1-30Oe coercive force and 1X10<5>-1X10<10>OMEGA.cm electric resistance. The preferable mixing ratio of the spherical carrier particles and irregular shaped carrier particles is 30:70-70:30. Since the ferrite carrier has good developability, the developing gap with a magnetic brush type developing machine can be made 1.5-3.5mm. The doctor gap may be made 1.0-3.0mm according thereto. Since the relatively large gap is possible in the above-mentioned manner, the design of the developing machine is easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a carrier for a two-component developer that has good developability and provides high-quality images.

[Prior Art and Problems] Ferrite carriers are widely used as carriers for two-component developers. Ferrite carrier is Ba
, Ni, Mn 1Cu , Mg, etc., and trivalent iron oxide are combined into one body by firing. The ferrite carrier has excellent magnetic properties (σ5=30-80eIIlu/g), development FM (7)la air)Li on: 81
Form a ki brush. The toner carried on the carrier in the magnetic brush comes into contact with a photosensitive drum having an electrostatic latent image and adheres thereto, forming a toner image corresponding to the latent image.

Ferrite carrier particles are usually spherical because they are produced by granulation and firing using a spray dryer or the like.

Spherical carriers give soft images with good halftones, but they have poor developability and require a development gap of about 1.5 mm or less. On the other hand, when the irregularly shaped carrier is made of iron powder, the development gap is 3 to 5 because the developability is good.
Although it can be obtained as wide as IIll+1, the image becomes hard-toned. Attempts were also made to make irregularly shaped carriers from ferrite, but the same tendency was observed.

Therefore, an object of the present invention is to provide a ferrite carrier that has good developability and provides a high quality image.

[Means for Solving the Problems] As a result of intensive research in view of the above objectives, the present inventor discovered that it is possible to produce spherical and irregularly shaped ferrite carrier particles and blend them, thereby completing the present invention. did.

The ferrite carrier for a two-component developer of the present invention is characterized by comprising 90 to 10% by weight of spherical ferrite carrier particles and 10 to 90% by weight of irregularly shaped ferrite carrier particles.

Spherical ferrite carrier particles can be produced by a conventional method.

First, the raw materials for Ferai are mixed in an appropriate mixing ratio.

Mixed raw materials at a temperature of 900℃ to 1000℃ from 0.5 to
Calcinate for 3.0 hours. Ba C03 in ferrite raw material
If carbonates such as carbonates are present, CO2 is removed by calcination. Calcining can be carried out either in a batch manner or in a continuous manner using a rotary kiln or the like.

The calcined ferrite powder is pulverized to have an average particle size of about 2.0 μm or less. For this purpose, a device such as a wet pulverizer using steel balls as the pulverizing medium is used.

The fine ferrite powder is granulated to a particle size of about 10 to 200 μm. Granulation methods include a spray dryer method, a method in which the powder is rolled and compressed with a binder in a kneader and then sized, an extrusion method, a method in which the binder is sprayed and aggregated in a vibrating or fluidized bed, and a method in which the powder is transferred on a rotating pan. etc.

The granulated powder is then fired. Firing at 1250℃~1350℃
for 3 to 5 hours at a temperature of In order to perform uniform firing at the above-mentioned temperature, it is appropriate to hold the sagger-packed granulated powder for a relatively long time.

The fired ferrite is crushed using a roll crusher or the like and classified to have an appropriate particle size distribution.

On the other hand, a deformed ferrite carrier can be produced by filtering and dehydrating the calcined and wet-pulverized ferrite in the above process, firing it as it is, and appropriately crushing and classifying the ferrite. In this method, filtration and dehydration can be performed while pressurizing and compressing as necessary. Firing at 1250℃
Carry out for 3-5 hours at a temperature of ~1350°C. Carrier particles obtained by pulverizing ferrite fired in the bulk state have irregular shapes with sharp corners. Note that the method for producing the irregularly shaped carrier is not limited to this, and elongated carrier particles can be obtained by extruding ferrite into a thin thread shape and cutting it, for example.

The spherical and irregularly shaped carrier particles are, for example, Ba-N
i-Zn-ferrite, Mn-Zn-ferrite, Ni
-Zn-ferrite, l-i -7n-ferrite,
It can be formed of Cu-Zn-ferrite, Cu-Zn-M(1-ferrite, M(+-Zn-ferrite, etc.).

The average particle diameter of the above-mentioned spherical carrier particles is 50 to 150 μm, and the characteristics of these carrier particles include a saturation magnetization of 40 to 150 μm.
Preferably, 80 emu/(J), coercive force 1 to 300 e1, and electrical resistance IX 105 to lX10+OΩ·am.

Spherical and irregularly shaped carriers can be coated with resin if necessary. Various resins can be used, but styrene-acrylic resins (for example, styrene-methyl methacrylate, styrene-butyl methacrylate, etc.), epoxy resins, styrene-butadiene resins, etc. are preferred from the viewpoint of charge amount and lifespan.

The weight of spherical carrier particles and irregularly shaped main particles is 90
: Mix at a ratio of 10:90 to 10:10. A preferred mixing ratio is 30:0 to 70:30. At a mixing ratio other than the above, the effect of mixing two types of carrier particles is insufficient.

Since the ferrite carrier of the present invention has good developability, the development gap is set to 1.5 to 1.5 in a magnetic brush type machine.
It can be 3.5 mm. Further, the doctor gap can be set to 1.0 to 3.0 mm accordingly. Since the gap can be made relatively large in this way, the design of the developing machine is facilitated.

[Example] The present invention will be further explained in detail by the following examples.

Example 1 BaO2,13-N i O0,17-Zn OO,3
[3a-Ni-Zn spherical trifluorite carrier particles having a composition of 3.FeQ3 were produced by a spray dry granulation method. This σs is 58emu /fJ 11HC
was 25 Qe, electrical resistance was 8×10 8 Ω·am, and particle size distribution was 74 to 149 μm. This is called carrier A.

Next, N i O0,3・Zn O0,7・Fe 20
Ni-Zn-based irregularly shaped ferrite carrier particles having the composition No. 3 were produced by the following method. That is, Ni03
0% by weight, 70% by weight of ZnO, and 100% by weight of Fe203 were mixed and calcined at 900° C. for 3 hours.

Next, after wet pulverization to an average particle size of 1 μm, 10k
It was filtered and dehydrated at a pressure of g/am2. The obtained green compact was calcined at 1300° C. for 3 hours, and then pulverized and classified.

The particle size distribution of the obtained irregularly shaped carrier particles is 74 to 149μ
It was m. Note that the characteristic of irregularly shaped carrier particles is that σs is 68.
emu/(1, ll-IC is 80e and electrical resistance is 5
x i08Ω・Cll1. This is called carrier B.

By blending carriers A and B in various proportions, Ricoh's F
Development tests were conducted on a T 4030 copier using a developer with a 0.8+nm development gap and a developer with a 3.3mm development gap, respectively. The results are shown in Table 1.

(margin below) Gai (2) wide diameter: n 3.3mm,
As is clear from the results of 2.9 mm or more, the ratio of carriers A and B is fi@te90:1o~1o
: In the case of 9o, good image quality can be obtained even with a wide-ft angle.

Example 2 Regarding carriers No. 3 and 3 of Example 1, the influence of the development gap on image quality was investigated. The results are shown in Table 2.

record (1 King Fu Doctor Gear V & Mari, immq.

"Effects of the Invention" Since the ferrite carrier for a two-component developer of the present invention is composed of spherical particles and irregularly shaped particles, it has good developability and provides images with high density and good halftone. In addition, since the developing property is good, the development gap of the developing machine can be made relatively wide.

Claims (3)

[Claims] (1) A carrier for a two-component developer characterized by comprising 90 to 10% by weight of spherical ferrite carrier particles and 10 to 90% by weight of irregularly shaped ferrite carrier particles. (2) In the carrier for a two-component developer according to claim 1, each of the spherical ferrite carrier particles and the irregularly shaped ferrite carrier particles is 40 to 8
Saturation magnetization (σs) of 0 emu/g, coercive force (_IHc) of 1 to 30 Oe and 1×10^5 to 1×10^1^0 Ω
- A carrier for a two-component developer characterized by having an electrical resistance of cm. (3) A two-component developer carrier consisting of 90 to 10% by weight of spherical ferrite carrier particles and 10 to 90% by weight of irregularly shaped ferrite carrier particles is used, and a development gap of 1
．． 5-3.5mm and doctor gap 1.0-3.0
A method of developing an electrostatic latent image using a magnetic brush type developing device.