JPH0143301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic development method, and more particularly to a magnetic brush development method using fine magnetic carrier particles in the 10μ to 40μ range.

Conventional two-component developers for electrophotography have had problems such as carrier deterioration and a narrow toner concentration range. As a means to overcome these drawbacks, it has been considered to reduce the particle size of the carrier. As the ultimate form of particle size reduction, there is a method in which a magnetic toner used in one-component development, that is, a resin in which magnetite is mixed and crushed, is used as a carrier. However, the problem with this method is that the carrier adheres to the photosensitive material during development. This development is explained by the fact that the carrier is minute and the magnetite is dispersed in the resin, so the magnetic attraction force to the mag roll is overwhelmingly weak. The carrier, which is charged oppositely to the toner, adheres to the periphery of the image and is developed by the action of the electric field at the edge of the image. As a measure to prevent the reduction of carriers in the developing machine due to carrier consumption, there is a method of collecting the transfer dirt carriers scraped off from the photosensitive material by the cleaning member (carriers are difficult to transfer because they have opposite polarity) back to the developing machine side. be.

However, the carriers that are recovered will gradually deteriorate and will eventually have to be replaced.

An object of the present invention is to take advantage of the fact that carriers tend to adhere to photosensitive materials during development, thereby preventing image quality deterioration due to changes in carriers over time.

According to the present invention, carrier is mixed in advance with the toner to be replenished, and the mixing rate is set to be the average ratio of carrier and toner consumed by development per copy.

Since some carrier is consumed and some new carrier is supplied, the developer in the developing device is always kept at a constant level.

That is, the present invention uses a developer in which a fine particle magnetic carrier having an average particle diameter of 10 to 40 μ, which is made by mixing magnetic powder in a resin, and a mixing ratio of the carrier and frictionally charged toner particles is 100:2 to 20. A recording material is magnetically held on the sleeve surface of a magnetic developing roll provided in a developing container, and the magnetic flux density on the sleeve surface of the magnetic developing roll is set to 1050 Gauss or more so that carrier consumption during development is 20% or less. This invention provides a developing method characterized by developing the above latent image and replenishing a carrier-containing replenishment toner having a carrier content of 20% by weight or less.

Generally, a drawback of using magnetic toner as a carrier is that the carrier adheres to the sensitive material much more often than in the past. However, since it is a magnetic toner, it does not cause any problems in processes other than development, which is a major difference from conventional carriers. Moreover, since the carrier has a different polarity from the toner, it has the advantage of being less likely to be transferred. Therefore, in the method of the present invention, the fact that the carrier adheres to the photosensitive material and is consumed is actively utilized to provide a carrier consumption type developing system. For this purpose, magnetic toner is mixed as a carrier in the replenishment toner at the proportion to be consumed, and the toner is replenished at the same time. If magnetic toner is used as a carrier, unlike conventional carriers, there is no risk of damaging the replenishing device.

However, if the replenishment toner is mixed with dispersed type micro magnetic carriers in advance, if the content ratio of the micro magnetic carriers exceeds 20%, it will have an adverse effect (the toner blocking phenomenon in the replenisher will become noticeable and replenishment will be affected). Furthermore, it has been found that when the amount of carrier consumed by development exceeds 20%, the sharpness of the copied image deteriorates and fog increases.

Therefore, we used a developer in which the mixing ratio (weight ratio) of dispersed type micromagnetic carrier particles and the carriers and frictionally charged toner particles was 100:2 to 100:20, and the amount of carrier consumption during development was 20%. % or less, the latent image on the recording medium is developed by setting the magnetic flux density on the sleeve surface of the magnetic developing roll to 1050 Gauss or more, and development using toner containing 20% or less of minute magnetic carriers as replenishment toner. The method obtained good results.

The present invention will be explained in more detail below.

100 parts by weight of styrene resin and fine ferrite powder
After cooling, the mixture was kneaded with 150 parts by weight, and after cooling, it was pulverized to obtain a magnetic carrier with an average particle size of 30 μm. Styrenic resin
100 parts by weight and 10 parts by weight of carbon black were kneaded, cooled, and finely divided to obtain a toner having an average particle size of 15 μm.

Using a developer formed by mixing 100 parts by weight of the magnetic carrier particles and 10 parts by weight of the toner particles,
The latent image on the Se-based photoreceptor was developed using a sleeve-rotating magnetic development roll and transferred onto plain paper to obtain a copy. At this time, the magnetic flux density on the sleeve surface of the magnetic development roll was changed to 1200 Gauss. Developing was performed using three types of magnetic developing rolls: , 1050 Gauss, and 900 Gauss.

When using a developing roll with a magnetic flux density of 1200 and 1050 Gauss on the sleeve surface, the carrier consumption rate due to development is 10% and 20%, respectively, and in that case, the copy image density is 1.2 and the fog density is 0.02. The image sharpness was also favorable.

However, when using a developing roll with a magnetic flux density of 900 Gauss on the sleeve surface, the carrier consumption rate is 30 Gauss.
%, the copy image density in that case was 1.2, the fog density was 0.15, and the image sharpness was not desirable.

At this time, in order to examine the variation in carrier consumption rate due to the latent image pattern on the photoreceptor, under each development condition, images with high line image density, images with average image density similar to those of ordinary printed books, and images with a wide area were analyzed. Carrier consumption was investigated for three types of image patterns with high density. As a result, variations in the carrier consumption rate due to changes in the image pattern were within a range of 3%. The present invention will be explained below with reference to Examples.

Example 100 parts by weight of styrene resin and fine ferrite powder
100 parts by weight of a magnetic carrier with an average particle diameter of 30μ obtained from 150 parts by weight, and an average particle size obtained from 100 parts by weight of styrene resin and 10 parts by weight of carbon black.
Using a developer made by mixing 10 parts by weight of 15μ toner, it was developed using a sleeve-rotating magnetic development roll.
The latent image on the Se-based photoreceptor was developed. When developing,
For a developer using a developer roll with a magnetic flux density of 1200 or 1050 Gauss, respectively, a carrier content of 10
A toner replenisher containing replenishment toner with a carrier content of 20% and a replenishment toner with a carrier content of 20% was attached, and copies were made up to 50,000 copies while replenishing the replenishment toner.

In all cases, good copies were obtained, and the carrier consumption rate at the time of 50,000 copies was almost the same as the value at the cut-off point. Further, toner blocking within the toner supply container did not occur.

According to the method of the present invention, the carrier is gradually consumed, and on the contrary, fresh carrier is gradually and smoothly replenished, so that although the entire developer undergoes some degree of aging in the initial stage, the aging stops after that. The copy quality is stable at a certain level, and troubles caused by deterioration can be permanently prevented.

Further, according to the developing system of the present invention, although it is a two-component development, it is possible to easily replenish the developer without the need for toner concentration detection, and it is possible to reproduce an excellent image without deterioration of the developer.

Claims (1)

[Claims] 1 The average particle size of magnetic powder mixed into resin is
The mixing ratio of the fine particle magnetic carrier of 10 to 40μ and the carrier and toner particles that are triboelectrically charged is 100:2 to 100:2.
20 is magnetically held on the sleeve surface of a magnetic developing roll provided in a developing container, and the magnetic flux density on the sleeve surface of the magnetic developing roll is adjusted so that carrier consumption during development is 20% or less. 1050
A developing method characterized by developing a latent image on a recording medium as Gaussian or higher, and replenishing a carrier-containing replenishment toner having a carrier content of 20% by weight or less.