JPS6326387B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry two-component reversal development method.

Conventionally, in electrostatography, there is a dry two-component reversal development method in which developer particles are attached to areas of an electrostatic latent image with little charge, but not to areas of maximum charge density. In this method, since the potential of the non-image area is higher than in the conventional normal rotation, ie, positive-positive development method, carrier adhesion occurs on the copy paper due to electrostatic induction, resulting in a poor image.

Therefore, in order to prevent such carrier adhesion, it is preferable to apply a bias voltage having the same polarity as the electrostatic latent image to the developing sleeve, but even this cannot completely prevent it. Moreover, the higher the bias voltage is, the more the background smear on the copy increases. On the other hand, when this bias voltage is low, although there is little background smudge, initial carrier adhesion occurs. In addition, the developing device has a means to measure the electrical characteristics of a certain amount of developer, convert it using the electrical characteristics values of the carrier and toner, and detect the toner concentration. This results in carrier adhesion to the bobbin or wall surface, resulting in unstable detection operation.

These points will be explained together with the measurement results. First, as shown in FIG. 1, the apparatus is provided with a photosensitive drum 1 which rotates in the direction of the arrow and on whose surface an electrostatic latent image is formed by charging and exposing means. A magnetic brush developing device 2 is disposed at the lower left of the photoreceptor drum 1, and the electrostatic latent image on the photoreceptor drum 1 is developed by the magnetic brush. Here, this magnetic brush developing device 2 has a developing sleeve 6 made up of a non-magnetic cylindrical sleeve 4 and a plurality of magnets 5 provided within the cylindrical sleeve 4 in a developing container 3.
A magnetic brush is formed on the surface of the cylindrical sleeve 4 which is rotated in the direction of the arrow by the magnet 5. Further, a scraping plate 7 is provided close to the surface of the cylindrical sleeve 4, and an opening 8 is formed approximately in the center of the scraping plate 7. A hopper 9 connected to the opening 8 is disposed below the scraping plate 7. The hopper 9 has a funnel shape, and an outlet 10 is provided at the bottom of the hopper 9, and a non-magnetic cylinder 11 is provided below the outlet 10. A coil 12 is wound around this cylinder 11, and this coil 12 forms an LC oscillation circuit with its inductance L and capacitor C, and is connected to a frequency detector 13 that detects the oscillation frequency. This frequency detector 13 and reference circuit 1
The comparison circuit 15 compares the output of the toner replenishing roller 17 provided at the bottom of the toner hopper 16 with a signal to the drive circuit 18 to control the rotation of the toner replenishing roller 17 provided at the lower part of the toner hopper 16.

Therefore, we used FT6400 manufactured by Ricoh Co., Ltd. as a positive polarity developer toner, and negative polarity as a carrier.
Using 2μ Teflon-coated spherical iron powder with a particle size of 100μ, a positively charged Se drum (approximately 800 V for dark areas and approximately 100 V for bright areas) was used as photoreceptor drum 1, and float development and earth development were performed. When a reversed image was created using bias development, the following results were obtained regarding image density (line), background, and carrier adhesion. First, in float development, although the image density was good, background smearing and carrier adhesion occurred, while in ground development, no background smearing occurred and the image density was fair, but considerable carrier adhesion occurred. In addition, in bias development, when the bias potential was set to 200V, good results were obtained in terms of image density and background, but carrier adhesion occurred, and when the bias potential was set to 400V, this carrier adhesion could be somewhat reduced, and when the bias potential was set to 600V, When the bias voltage was set to 800V, carrier adhesion remained the same as at 400V, but background staining occurred, and when the bias potential was set to 800V, good results were obtained in terms of image density and carrier adhesion.
The skin was considerably stained. In the end, neither case was a good copying condition. In addition, carriers adhered to the toner concentration sensor and bobbin, making it impossible to control the toner concentration properly.

In addition, iron powder flat carriers (particle size
Similar results were obtained when using a Teflon coat of approximately 2μ (150μ).

Furthermore, when non-coated Sayaria iron powder was used as a carrier, the following results were obtained. First, in the case of float development, only the image density was good, but background staining and carrier adhesion occurred considerably. In addition, in the case of ground development, only the background dirt is good, but the image density is bad.
Carrier adhesion was the worst. In 200V bias development, the image density in ground development,
The carrier adhesion was slightly improved, and the voltage was 400V.
In the case of , although the condition was slightly better, carrier adhesion still occurred and some background staining also occurred. And the bias potential is 400V
In the above case, the experiment was impossible due to bias leak. Therefore, even in this case, good copying conditions could not be obtained. However, the adhesion of the carrier to the sensor bobbin and mural is somewhat better than in the case of coated carriers.

The present invention was developed in view of the above points, and it is possible to obtain a reverse copy image without carrier adhesion and background stains, and has good reproducibility of fine lines. It is an object of the present invention to provide a dry two-component reversal development method that can also prevent adhesion.

The present invention focuses on the particle size and bias potential of the carrier in a dry two-component reversal developer, and by setting these to predetermined conditions, there is no carrier adhesion or background staining, and image density and fine line reproducibility are improved. This is how it was done.

An embodiment of the present invention will be described based on the drawings. First, an apparatus as shown in FIG. 1 is used to create a reverse developed image by bias development. Then, the relationship between the carrier particle size and carrier adhesion on copy paper was measured using the bias potential of the developing bias as a parameter while changing the carrier particle size under the conventional measurement conditions. The results shown in FIG. 6 were obtained.

First, Figure 2 shows the carrier particle size dependence of carrier adhesion on copy paper, and the results show that when the bias potential is 0V, the carrier particle size is 250μ or more, and when the bias potential is 200 to 400V, the carrier particle size is It can be seen that carrier adhesion cannot be prevented unless the particle size is 200μ or more.

FIG. 3 shows the dependence of image density on carrier particle size, and although there are differences in image density depending on the carrier particle size, no particularly poor results occur. In this case, it can be seen that sufficient image density can be obtained under the condition that the carrier particle size is 250 μm or more based on FIG.

Furthermore, FIG. 4 shows the dependence of the background stain on the carrier particle size, and it can be seen that the size of the carrier particle size does not particularly affect the background stain. However, the higher the bias potential is, the worse the degree of background staining becomes, and as a condition for preventing this background staining, it is necessary to lower the bias potential by 200 V or more than the non-image area potential. In this embodiment, the non-image area potential is 800V, so if the bias potential is 600V or less, background staining can be prevented.

Furthermore, Figure 5 shows the fine line reproducibility, that is, the dependence of line image rubbing on carrier particle size.
It can be seen that the fine line reproducibility decreases as the carrier particle size increases, and the carrier particle size needs to be 400 μm or less.

Furthermore, FIG. 6 shows the dependence of carrier particle size on the carrier particles on the sensor and bobbin, and it can be seen that the smaller the carrier particle size, the more likely this carrier particle size is to occur.

Therefore, according to these results, by setting the bias potential to 200 V or more lower than the non-image area potential of the electrostatic latent image and the carrier particle size to 250 to 400 μ, carrier adhesion on copy paper, background staining, and Image density and fine line reproducibility can be improved while preventing carrier adhesion to the sensor and bobbin.

As described above, the present invention lowers the bias potential of the developing bias by 200 V or more than the potential of the non-image area,
In addition, since development was carried out using a dry two-component reversal developer containing carrier particles with a particle size of 250 to 400μ, a reversal image with good image density and reproducibility of fine lines can be created while eliminating carrier adhesion to the copy paper and background stains. Furthermore, since carrier adhesion to the sensor and bobbin can be prevented, toner density control can be performed stably.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a side view of the vicinity of the developing device, FIG. 2 is a carrier adhesion-carrier particle size characteristic diagram, and FIG. 3 is an image density-carrier particle size characteristic diagram. FIG. 4 is a background stain-carrier particle size characteristic diagram, FIG. 5 is a thin line reproducibility-carrier particle size characteristic diagram, and FIG. 6 is a carrier adhesion-carrier particle size characteristic diagram.

Claims (1)

[Claims] 1. While setting the developing bias potential to be 200 V or more lower than the non-image area potential of the electrostatic latent image, the particle size is 250 V or more.
A dry two-component reversal developing method characterized in that development is carried out with a magnetic brush using a dry two-component reversal developer containing a carrier of ~400μ. 2. The dry two-component reversal developing method according to claim 1, characterized in that the bias potential of the developing bias is 0V.