JPS5865443A - Electrophotographic copying system - Google Patents

Abstract

PURPOSE:To improve the reproducibility of various colors by subjecting a photoreceptor to AC discharge after red developing then to uniform exposure followed by black developing. CONSTITUTION:A photoreceptor is provided with surface layer parts of 3 layers consisting of a conductive layer, a photoconductive layer and a transparent covering layer. Electrostatic latent images of two colors, black and red, are formed in said photoreceptor 1 by electrostatic chargers 2, 3 and filters 4, 5. After the electrostatic latent images are subjected to red developing by a red developing device 6, the entire part of the surface of the photoreceptor 1 is subjected to AC discharge by an AC charger 7. Thereafter the surface of the photoreceptor 1 is subjected to uniform exposure then to black developing by a black developing device 8. As a result, the sticking of the black toner on the red latent image is prevented in the stage of the black developing and the contrast potential of the black latent image is increased. In this way the reproducibility of each color is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic copying system that uses a photoreceptor to perform, for example, two-color development.

BACKGROUND ART Conventionally, the following method is known as a method for obtaining a two-color copy using a photoreceptor having a three-layer structure consisting of a conductive layer, a photoconductive layer, and an insulating transparent coating layer. When the 12 colors are red and black and the photoconductive layer is d'kpfli, when the surface of the photoreceptor is first charged with the first charger a shown in Fig. g1, the surface of the photoreceptor becomes the first one. As shown in FIG. 2, the surface of the coating layer C is charged to one charge, and the photoconductive layer d is charged to ten charges. In this state, if the second charging by the $II2 charger and the image exposure through the cyan filter/l are performed simultaneously, the third
As shown in the figure, in the white area, the photoconductive layer d becomes conductive, and ten charges are discharged to the conductive layer d, and from the photoconductive layer d in the black and red areas, where no light remains, from the second charger. The positive charge of the photoconductive layer d easily flows in, and the single charge of the photoconductive layer d is neutralized. On the other hand, in the black and red areas where there is no light or a small amount of light hits, the amount of 10 charges is larger than the white area, so the amount of + charge flowing in due to the second charging is small, and the - charge of the layered C The amount is retained larger than that of the white part. Next, when a second exposure is performed using a red filter h, the resistance of the photoconductive layer d in the red area decreases as shown in FIG.
A part of the ten charges held in K is discharged to the conductive layer, and since there is no light in the black area, the ten charges are held in the photoconductive layer d. Therefore, if the potentials of the black, white, and red areas are based on the white area (zero potential), black area 10 potential red area - potential white area zero potential, and two electrostatic charges of black and red are generated on the surface of the photoreceptor. A latent image is formed. The electrostatic latent image formed above first has a red potential of +
Polar toner tf! After developing a red color using my machine I, I uniformly exposed the entire surface of the photoreceptor with a light source to invert the black potential to -, and then developed it with a black developing machine T using raw polarity toner. Black'i! He was doing the 4 great things.

However, in the above method, after the red image is developed, one potential of the red area is not completely neutralized by the red toner, and when the next black development is performed, the + black toner also adheres to the red latent image area. This invention was made with the aim of improving this problem.14 Therefore, after red coloring, the entire surface of the photoreceptor was uniformly exposed to a dangerous light source that generated alternating current with an AC discharger, and then the entire surface of the photoreceptor was exposed to light. It is an attempt to improve the reproducibility of each color by providing an electrophotographic copying system capable of performing black printing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the following drawings. In the figure, 1 is the same conductive layer 1g as before;
A surface layer portion is formed of the three layers of the photoconductive layer 1b and the transparent coating layer IC, and when charged by the first charger 2), the surface of the coating layer IC as shown in FIG. When the second charging by the second charger 3 and the high exposure by the cyan filter 4 are performed at the same time, the photoconductive layer 1k is charged with one charge and the photoconductive layer 1k is charged with ten charges. ] A large amount of one charge is held in the covering layer IC in the black and red parts. In this situation, when second image exposure is performed using the red filter 5, ten charges in the red area are discharged to the conductive layer 1a as shown in FIG. 4, and the overall potential is set to zero in the white area. , black area 10 potential red area - As the potential increases, electrostatic latent images of two colors, black and red, are formed on the surface of the photoreceptor 10. This electrostatic latent image is then developed with a red developing machine 6 to form a red latent scratch, and then an AC Teiden machine 7 is used to develop a red latent scratch on the photoconductor 1.
An alternating current discharge is carried out over the entire surface. With this #I6
The potential of each part of MK shown in figure (a) changes to #! due to AC discharge. As shown in FIG. 6 (b), a large amount of 1 charge flows into the black portion of the photoconductive layer lh, which holds a large number of 10 charges. In this state, when the surface of the photoreceptor I is uniformly exposed by the light source 6, ten charges on the photoconductive layer 1 are discharged to the conductive layer 14 as shown in FIG. is reversed to one potential, and at this time, the potential difference (contrast) with the white portion becomes higher as shown in FIG. 7 by the inflow of one charge due to AC discharge. In this figure, V is the potential difference due to AC discharge, and ■4 is the potential difference due to full-surface exposure.

On the other hand, ten charges flow into the red developed area which is at the sea potential due to AC discharge and neutralize the one potential, so black toner is attached to the red latent scratches during the next black development by the black developing device 9. At the same time, a black latent image with increased contrast potential is developed by the black developing machine gK due to alternating current discharge and full-surface exposure.

The electrostatic latent image developed in red and black by the above process is transferred to a pre-transfer corotron II via a pre-transfer corotron 10t.
At this point, the two-color toner image is transferred to the paper 12.

The paper 12 onto which the toner has been transferred is transported to a transfer process (not shown), where the toner is fixed, and the untransferred toner remaining on the surface of the photoreceptor is removed by a static eliminating corotron 13.
After static electricity is removed by the cleaner 14, the surface of the photoreceptor 1 is removed by the cleaner 14, and the surface of the photoreceptor 1 from which the untransferred toner has been removed is irradiated with a static elimination lamp 15 to eliminate static electricity. Submitted to the process.

In the above embodiment, an AC discharge with zero DC component was explained, but a direct current bias or a negative DC bias may be superimposed on the AC discharge, and in that case, the potential level of the entire (black, white, red) becomes different from each other. Shift to the + side or one side. t
When a positive direct current is superimposed, a secondary effect can be obtained in that the white portion has a potential of 1000. A bias power source for the heat developing machine 9 is not necessary, and it is only necessary to connect it to the ground side. Furthermore, although the above embodiments have been described using black and red, it is of course possible to use other colors.

Since the present invention has been described in detail above, it is possible to easily obtain clear copies of predetermined colors without toners of other colors adhering to, for example, a red electrostatic latent image.

[Brief explanation of the drawing]

81 to 4 are explanatory diagrams of the conventional copying method, and FIGS. 5, 6, (a), (b), e→, and 7 are explanatory diagrams showing one embodiment of the copying method of the present invention. be. 1 is a photoreceptor, la is a conductive layer, IA is a photoconductive layer, jc is a transparent coating layer, and 4.5 is a filter. Applicant: Fuji Xerox Co., Ltd. Agent: Patent attorney: Masaaki Yonehara Patent attorney: Tadashi Hamamoto Figure 4 Me, fB O.

Claims (1)

[Claims] Surface layer part is conductive layer 1α, photoconductive layer 1b and transparent coating layer IC
2. A primary charging process in which the surface of the photoreceptor 10 is uniformly charged, and a carbon dioxide exposure is performed through a filter 4 that blocks a specific color to be reproduced, while at the same time charging is performed with the opposite polarity to the primary charging process. A secondary charging and primary exposure process, a secondary exposure process in which image exposure is performed through a filter 5 that transmits only a specific color, a primary development process in which only a specific color is developed, and a photoconductor 10 that has completed the first m. A tertiary charging process in which alternating current discharge is applied to the surface, and a 3 process in which the surface of the photoreceptor I is uniformly exposed to light after the tertiary charging process.
An electrophotographic copying method that is different from the next exposure step and the second development step in which development is performed with a toner of a different color from the first development step after the tertiary exposure step.