JPS6231343B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a reversal development type transfer type electrophotographic copying method.

In the reversal development type electrophotographic copying method, for example, a uniformly charged photoreceptor is exposed to a negative image, and the areas (image areas) where the charges are discharged by this exposure are
A method of developing by adsorbing toner with a charge of the same polarity as the charge on the photoreceptor, in which the charged part of the photoreceptor surface is used as a background part to prevent toner from adhering to that part, and the uncharged part is used as a background part. This method is characterized in that the toner is attached to the image area.

By the way, when this reversal development method is adopted for transfer-type electrophotographic copying, the photoreceptor is used repeatedly, especially during continuous copying, so the same latent image from the same document is placed on the same location on the photoreceptor. As a result of repeated formation, a difference in photoreceptor fatigue occurs between the image portion (exposed portion) and the background portion (unexposed portion). Therefore, when a latent image from another document is formed on a photoreceptor with this fatigue difference, an afterimage occurs due to the fatigue difference. Even if copying is not continuous, a difference in fatigue occurs between the exposed area and the non-exposed area, and as copies are repeated, the fatigue difference increases and an afterimage occurs, even if it is not as noticeable as in continuous copying.

The purpose of the present invention is to prevent the occurrence of fatigue differences in the photoreceptor that cause the afterimage. This is characterized in that the entire surface of the photoreceptor is evenly exposed by exposing the bare background area to light.

Next, the present invention will be explained with reference to illustrated embodiments.
Reference numeral 1 denotes a photosensitive drum, which rotates in the direction of arrow A. The surface of the photosensitive drum 1 is charged to a potential of approximately +800 V in the charging section 2, and subjected to slit exposure with a negative image in the exposure section 3. By this exposure, the potential of the image portion is attenuated to about +200V, and an electrostatic latent image having a potential difference of about 600V with the background portion is formed on the surface of the photoreceptor drum 1. This electrostatic latent image undergoes reversal development in the developing section 4 and becomes a positive developed image. That is, approximately +
Magnetic brush 5 with 600V bias voltage applied
supplies the surface of the photoreceptor drum 1 with positively charged toner, which is attracted to the negatively charged carrier. As a result, toner is attracted only to the image portion, resulting in an inverted image.

As described above, the surface of the photosensitive drum 1 that has undergone reversal development is directed toward the transfer section 7, but prior to that, the entire surface is exposed by the light source 6 disposed between the development section 4 and the transfer section 7. . This exposure is the image part,
This is done regardless of the background area, but since toner is adsorbed to the image area, light is blocked by it, and the amount of light that actually reaches the surface of the photoreceptor drum 1 is inversely proportional to the amount of light received at the time of image light. The light source 6 is designed to provide the same wavelength distribution and light intensity as the light received by the surface of the photoreceptor drum 1 in the exposure part 3, so that the background part receives light under the same conditions as that received by the image part in the exposure part 3. 6, and the entire surface of the photoreceptor drum 1 is subject to the same fatigue.

The developed image on the surface of the photoreceptor drum 1 is transferred to copy paper fed as indicated by arrow B in the transfer section 7. Thereafter, the surface of the photosensitive drum 1 is neutralized by a static eliminating section 8 and cleaned by a cleaning section 9, and then reaches the charging section 2 again for repeated use.

As described above, the present invention includes a step of uniformly charging a photoreceptor, a step of exposing an image to the uniformly charged photoreceptor, and a step of charging the exposed photoreceptor with a charge having the same polarity as that of the photoreceptor. a step of developing with toner, a step of exposing the developed photoconductor to full-surface light with the same wavelength distribution and light intensity as during image exposure from the back side of the developed toner image, and transferring the toner image on the photoconductor that has been fully exposed to light; Since it involves a process of transferring the electrostatic latent image to the material, only the areas that were not (or were) exposed to light during the formation of the electrostatic latent image can be exposed in the same way as the image areas that have been exposed, reducing the fatigue of the photoreceptor. can be made uniform over the entire surface for each copy cycle, and as a result, it is possible to prevent afterimages from occurring due to fatigue differences.

[Brief explanation of the drawing]

The figure is a layout diagram showing an embodiment of the present invention. 1... Photosensitive drum, 3... Exposure section, 4... Development section,
6...Light source for full-surface exposure, 7...Transfer section.

Claims (1)

[Claims] 1. A step of uniformly charging a photoreceptor, a step of exposing an image to the uniformly charged photoreceptor, a step of developing the exposed photoreceptor with a toner having a charge of the same polarity as the photoreceptor, A step of exposing the developed photoreceptor to the same wavelength distribution and amount of light as during image exposure from the back side of the developed toner image, and a step of transferring the toner image on the photoreceptor that has been exposed to the entire surface to a transfer material. A reversal development type transfer type electrophotographic copying method characterized by the following.