JPS60229034A - Developer - Google Patents

Abstract

PURPOSE:To obtain a developer superior in reproducibility of wide areas and linear parts of characters or the like by using a developer composed of a carrier mixture obtained by mixing magnetic powders different in magnetic characteristics. CONSTITUTION:A ferrite carrier is small in true specific gravity and saturation magnetization, when a magnetic brush is rotated, it is liable to move on a sleeve, and stays in a developing zone for a short time. Since it is high in electric resistivity, the electric force lines of an electrostatic latent image diverge. On the other hand, since an iron powder carrier is high in true specific gravity and saturation magtization, when the magnetic brush is rotated, it is difficult to move on the sleeve, and it stays in the developing zone for a long time. Since it is small in resistivity, the magnetic force lines of the electrostatic latent image converge, and the difference between image reproducibilities is caused by the difference of the carriers. The advantages of both carriers are combined by mixing these different carriers and a developer superior in image reproducibility can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developer used in electronic copying machines and the like.

Conventional Structure and Problems The developer used in copying machines generally consists of a mixture of colored fine powder called toner and magnetic powder called carrier. These carriers include iron powder, iron powder with a resin coating on the surface, ferrite, and ferrite with a resin cordon on the surface. , carriers of the same type with fixed magnetic and electrical properties are used.

When using a developer using an iron powder carrier, images with large areas or image areas with gradation are faithfully reproduced, but reproducibility deteriorates in areas with low potential such as lines such as characters. . Furthermore, in areas where the line potential is high, such as characters, a phenomenon of thickening of the lines is observed, which deteriorates reproducibility such as characters being crushed. Furthermore, when using a developer using a ferrite carrier, for images with a large area,
There is a tendency for the image to appear as a white outline with only the periphery emphasized.

However, the reproducibility of line parts such as characters is good.

This is because ferrite has smaller magnetic properties and lighter specific gravity than iron powder carriers, so it stays in the developing area for a shorter time.
This is probably due to the short development time.

As described above, the above-mentioned conventional carriers have the drawback that any image cannot be faithfully reproduced.

OBJECTS OF THE INVENTION The present invention aims to eliminate the drawbacks of the above-mentioned conventional examples, and provides a developer that can faithfully reproduce images with wide areas and images with lines such as characters. be.

Structure of the Invention In order to achieve the above object, the present invention provides a mixture of a mixed carrier made of a mixture of two types of magnetic powder having the same particle size distribution and different true specific gravity, and a toner. Alternatively, two particles having the same particle size distribution and different magnetic properties may be used.
The toner is a mixture of a mixed carrier formed by mixing different kinds of magnetic powder and a toner.

Description of examples Examples of the present invention will be described in detail below.

The iron powder carrier used in the present invention is an iron powder carrier used in ordinary copying machines, and has a thick oxide film formed on its surface. Further, this surface may be coated with a polymer compound.

Further, the ferrite carrier used in the present invention is a ferrite carrier used in ordinary copying machines, and is classified as a soft ferrite and has low residual magnetism. As described above, the surfaces of these ferrite particles may also be coated with a polymer compound.

Comparing iron powder carriers and ferrite carriers, iron powder generally has higher magnetic properties (expressed by the magnitude of saturation magnetization in the present invention) and higher electrical resistance (in the present invention, the carrier forms a magnetic brush). When this happens, the current flowing through the magnetic brush is shown. Therefore, the larger the current, the smaller the electrical resistance.) is thicker for the ferrite carrier. Further, the true specific gravity of the ferrite carrier is smaller. Although the carrier particle size is not particularly limited, it is 20 to 500 microns, which is the size used in ordinary electronic copying machines.

With ferrite carriers, the reproducibility of images over large areas is poor, but the reproducibility of lines such as characters is good.On the other hand, with iron powder carriers, the reproducibility of images with large areas is good, but the reproducibility of lines such as characters is poor. The reason why it is bad is not clear, but it can be thought of as follows.

Ferrite carriers have a small true specific gravity and a small saturation magnetization. Therefore, when the magnetic brush is rotated, it moves easily on the sleeve and stays in the developing area for a short time. Furthermore, since the electrical resistance is large, the lines of electric force of the electrostatic latent image diverge.

On the other hand, since the iron powder carrier has a large true specific gravity and a large saturation magnetization, it is difficult to move on the sleeve when the magnetic brush is rotated, and it stays in the developing area for a long time. Furthermore, since the electrical resistance is small, the lines of electric force of the electrostatic latent image are concentrated.

Therefore, differences in image reproducibility occur due to differences in carriers.

It is believed that by mixing these different carriers, the advantages of each are combined, resulting in a developer with excellent reproducibility.

Next, the present invention will be explained in detail based on specific examples.

Example 1 Iron powder carrier (5TY-25T manufactured by Nippon Steel Powder) was heated to 450i
I-, ferrite carrier (1 Ferrous powder F-14'l)
-1535) and 450 toner (Matsushita Electric FP-13)
00 for copying machines) Mix 1ooy to make a developer.

The above iron powder carrier has the following characteristics.

Saturation magnetization 180e! Ilu/g Particle size distribution: about 30μ to about 150μ True specific gravity: about 7 Current flowing when forming a magnetic brush: 29μ The above ferrite carrier has the following characteristics.

Saturation magnetization esemu/g Particle size distribution Approximately 30μ to approximately 150μ True specific gravity approximately 5 Current flowing when forming magnetic brush 20μA460
? Characteristic saturation magnetization of carriers when mixed with 1106
mu/q Particle size distribution: Approx. 30 to approx. 150μ True specific gravity: Approx. 6 Current flowing when forming a magnetic brush: 14μm The developer made in this way can uniformly reproduce images over a wide area, and can even reproduce line drawings such as letters. faithfully reproduced. It was also found that image fidelity could be maintained even if the humidity during development was reduced.

Example 2 Iron powder carrier 900 and toner 10 used in Example 1
A developer was prepared by mixing 0f. Large areas were faithfully reproduced, but the text was poor.

Example 3 A developer was prepared by mixing 900 g of the ferrite carrier used in Example 1 and 10 g of toner.

The edge effect was large in large area areas, resulting in clear images in text areas.

Effects of the Invention As described in detail above, the present invention provides development that provides excellent reproducibility of large area areas and line areas such as characters by using a developer made of a mixed carrier made by mixing magnetic powders with different magnetic properties. You can get the drug.

Furthermore, by using a developer made of a mixed carrier made by mixing magnetic powders having different electrical resistances, it is possible to obtain a developer with excellent reproducibility in large area areas and line areas such as characters.

In addition, by using a developer produced from a mixed carrier made by mixing magnetic powders with different true specific gravity, it is possible to obtain a developer with excellent reproducibility of large areas and line parts such as characters. The effect of this can be obtained.

Claims (2)

[Claims] (1) 2 with the same particle size distribution and different magnetic properties
A developer characterized by a mixture of a mixed carrier formed by mixing magnetic powder of seeds and a toner. (2) A developer characterized in that a mixed carrier made of a mixture of two types of magnetic powder having the same particle size distribution and different true specific gravity and a toner are mixed.