JPS60163074A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To prevent generation of a residual image by providing a voltage impressing stage of a positive polarity against a multi-layer structure selenium photosensitive body, between a transfer stage and an erasing stage. CONSTITUTION:A corona electrifier 17 for impressing a positive voltage is provided between a cleaner 15 and an eraser 16, by which a photosensitive drum 5 is charged electrostatically to positive. A residual toner is removed by the cleaner 15 of a blade type, and thereafter, charged electrostatically by an electrifier 17, and subsequently, this electrostatically charged charge is erased by the eraser 16. In this way, with regard to a part exposed by a light 9 in the previous process, it is prevented that the surface potential drops about 100V comparing with a part which is not exposed, in case of electrostatic charge by an electrifier 6, a drop quantity of the surface potential is set to about 30V, and generation of a residual image is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrophotographic method, and particularly to an electrophotographic method using a multilayer selenium photoreceptor sensitive to long wavelength light.

[Background of the invention]

Conventional so-called selenium photoreceptors using amorphous selenium are not sensitive to long wavelength light. Therefore, tellurium (T
This stone is designed to be sensitive to long wavelength light by adding sensitizers such as EL and arsenic (As).

Among these, the multilayered selenium photoreceptor F'i, which has a surface layer lower in sensitivity than the sensitized layer on top of the sensitized layer, has excellent electrical stability. However, this photoreceptor has a drawback in that carrier generated in the sensitized layer tends to remain as free carrier, and an afterimage of a previously printed image is likely to occur.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic method using a multilayered selenium photoreceptor in which no afterimage occurs.

[Summary of the invention]

In order to achieve this object, the present invention provides a charging process between transfer and erase in a general electrophotographic process for a photoreceptor, that is, charging, exposing, developing, transferring, cleaning, and erasing. It is characterized by preventing the generation of afterimages by causing the negative carriers generated in the surface layer and injected into the surface layer to quickly pass through the entire surface layer and suppressing them from remaining as free carriers in the surface layer.

[Embodiments of the invention]

Hereinafter, five aspects of the present invention will be explained with reference to the drawings. FIG. 1 shows an example of a multilayer selenium photoreceptor to which the electrophotographic process of the present invention is applied. FIG. 1(a) shows a selenium photoreceptor having a three-layer structure, and FIG. 1(b) shows a selenium photoreceptor having a two-layer structure. In other words, in Fig. 1(a) Vi, a carrier transport layer 2 with 50 μm of selenium deposited on an aluminum substrate 1 is provided, and a 3 μm thick layer of selenium/tellurium containing 35% tellurium as a sensitizer is deposited on top of the carrier transport layer 2. A sensitive layer 3 is provided, and 5 μb of selenium/tellurium containing 8% tellurium f is formed on the sensitive layer 3. 1(a) is a structure in which the carrier transport layer 2 in FIG. 1(a) is removed, and the aluminum substrate 1 is
A sensitizing layer 3 is formed by depositing 50 μm of selenium/tellurium containing 20% tellurium thereon, and a surface layer 4 is formed by depositing 5 μrn of selenium/tellurium containing 8% tellurium on top of the sensitizing layer 3. In this case, the sensitizing layer itself often serves as a carrier transport layer.

Figure 2 shows the spectral sensitivity characteristics (indicated by (1) in the figure) of the multilayer selenium photoreceptor shown in Figure 11(a).For comparison, only the surface layer 4 was prepared on an aluminum substrate. 50~60μ
Spectral sensitivity characteristics of the mq-1 photoreceptor (in the figure).

(2)) and the spectral sensitivity characteristics (indicated by (3) in the figure) of the photoreceptor with the surface layer 4 removed in FIG. 1(d). The multilayered selenium photoreceptor shown in Fig. 1 (a) and (1)) absorbs light with a wavelength shorter than 6Q Q n m in the surface layer 4, and absorbs light with a wavelength longer than 6001 m. As shown in FIGS. 1(a) and (1)), the sensitizing layer 3 absorbs light and generates positive and negative carriers, and the positive carriers (holes) are transferred to the aluminum substrate 1 side, and the negative carriers are transferred to the aluminum substrate 1 side. (electrons) move to the surface of the photoreceptor. Therefore, the spectral sensitivity 1 of (1)
The f curve is a composite of the spectral sensitivity curves 2 (2) and (3), and exhibits high sensitivity in the region of 770 to soon nm emitted by the semiconductor laser, as in the case without the surface layer 4. or,
The multilayer structure selenium photoreceptor shown in FIG. 1(b) is I-i e N
e Shows high sensitivity near the 6331m emitted by the laser. Generally, as the tellurium concentration on the surface of a photoreceptor increases, the photoreceptor has drawbacks such as a drop in surface potential, an increase in dark decay rate, and an increase in optical fatigue due to repeated use. However, the surface layer 4 of the photoreceptor shown in FIGS. 1(a) and 1(b) has relatively less tellurium compared to the sensitized layer 3 containing tellurium in each item, so it cannot be repeatedly used as described above. No problems will occur due to this. Generally, the tellurium concentration of the sensitized layer 3 is 15~
50 inches, and the tellurium concentration of the surface layer 4 is about .theta.~20 inches. In this way, the multilayered selenium photoreceptor in which the surface layer 4, which has low sensitivity due to the sensitizing layer 3, is provided has sufficient sensitivity to long wavelength light, and at the same time has stable characteristics even with repeated use. show.

However, problems arising from the layer structure itself tend to occur particularly in the case of the reversal development method. FIG. 3 shows a general printing process of a laser beam printer. The photosensitive drum 5 having the layered structure shown in FIG. 1(a), which rotates clockwise, is charged to about 700 cm by a charger 6, and then a semiconductor laser 8, which is horizontally scanned by a rotating polygon mirror 7, emits light. Exposure with 780 nm light 9 forms an electrostatic latent image. This electrostatic latent image is reversely developed with positively charged toner in the developing device 10 to form a toner image on the photoreceptor drum 5,
The transfer device 1 transfers this onto the paper 12 taken out from the cassette 11.
Electrostatic transfer due to the negative corona radiation of 3). The toner image transferred to the paper 12 is fixed by a fixing device 14.

Further, the residual toner remaining without being transferred to the photosensitive drum 5 is removed by a cleaner 15, and the residual charge is erased by an eraser 16, and the photosensitive drum 5 is used repeatedly. In this series of processes, the image printed in the previous process tends to appear as a tingling afterimage on the next print. This afterimage occurs when the tellurium concentration of the surface layer 4 is high, when the film thickness of the surface layer 4 is thick, and when the negative transfer voltage applied to the paper 12 by corona discharge during transfer is large.

If the amount of light 9 during exposure is large or the process speed is fast, this phenomenon tends to occur strongly. As shown in FIG. 1, this occurs in the sensitizing layer 3 during exposure with the light beam 9, and before the negative carriers injected into the surface layer 4 reach the surface of the photoreceptor, a negative transfer electric field causes them to move toward the inside of the photoreceptor. This shows that the carriers remain as free carriers inside the surface layer 4 due to the force of , which lowers the electrostatic pressure in the next process.

FIG. 4 shows a first embodiment of the present invention.

The difference from FIG. 3 is that a corona charger 17 is provided between the cleaner 15 and the eraser 16 to apply a positive voltage, thereby charging the photosensitive drum 5 in a positive direction.

That is, a 120φ photosensitive drum 5 having the configuration shown in FIG. was irradiated to form a complete electrostatic latent image, which was reversely developed with positively charged toner, and the resulting toner image was transferred onto paper 12 by negative corona discharge from transfer device 13.

The surface potential of the photosensitive drum 5 after the transfer was about -120 . After the residual toner on the photosensitive drum 5 is removed by a blade type cleaner 15, it is charged to 900 square meters by a charger 17. Next, this electrical charge is applied and erased by the r eraser 16. Photosensitive drum l by corona charger 17
When no voltage is applied to the electrifier 6, the part exposed to the light beam 9 in the previous process will be charged by the charger 6 in the next process.
The surface potential is about 80 to 100 compared to the unexposed area.
(2) The surface potential decreased by 1 μm as an afterimage during development, but by adding corona charging and a charging process using the device 17, the amount of decrease in surface potential was about 30 V, and the occurrence of afterimages was prevented.

FIG. 5 shows a second embodiment of the invention.

This is a case where development is performed using a regular image method. Therefore, I regret developing it.
ili', )ner is used, and the transfer device 13 is used with positive corona discharge. Since the transfer device 13 is used with positive corona radiation, the negative carriers generated by the light beam 9 and injected into the surface layer 4 are subjected to a positive electric field during transfer, so the amount of decrease in surface potential is smaller than in reverse development. However, if continuous printing is performed, carriers will gradually accumulate and an afterimage will occur.The difference between this embodiment and the first embodiment shown in FIG. 4 is as follows. In addition to the toner chargeability and transfer polarity described above, an eraser 18 process is provided between the cleaner 15 and the corona charger 170. By adding the charge erasing process by the eraser 18,
Nonuniformity in surface potential due to positive corona discharge during transfer due to the presence or absence of a toner image on the photoreceptor drum 5 is reduced, and at the same time, the next positive voltage application by the corona charger 17 is uniformly performed.

It also serves to prevent the non-paper portion through which the paper 12 does not pass during transfer from being overcharged by the corona charger 17. Therefore 1
During the next charging by the charger 6, non-uniformity in charging no longer occurs, and the image density becomes uniform, and at the same time, afterimage generation is prevented.

In the first embodiment of the present invention, the voltage was applied to the photosensitive drum 5 by corona charging, but the voltage may be applied to a conductive rubber roller or brush-like fibers in other ways. Further, the multilayer structure selenium photoreceptor of the present invention is made of tellurium (Te).
) Antimony (Sb), arsenic (As)-bismuth (Bi), which is sensitized but is used in general selenium-based photoreceptors.
, germanium (Ge), and the like.

〔Effect of the invention〕

As explained above, according to the present invention, there is an effect that the sensitizing layer can be stopped.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a selenium photoreceptor, FIG. 2 is a spectral sensitivity curve Wa diagram, and FIGS. 3, 4, and 5 are schematic diagrams of the printer. 3... Sensitized layer, 4... Surface layer, 5... Photosensitive drum, 17... Corona charger. Agent Patent attorney Akio Takahashi 0 [ 12 figures 3 eyes l otsu 569 ＼ entry, Tame 4 prisoners 5 figures

Claims (1)

[Claims] 1. A toner image transfer type electronic device using a multilayered selenium photoreceptor having a surface layer with lower sensitivity on a carrier generation layer sensitized to tellurium to have sensitivity to long wavelength light. An electrophotographic method, characterized in that a step of applying a positive voltage to the multilayered selenium photoreceptor is provided between the transfer and erase steps. 2. An electrophotographic method according to claim m1, wherein the electrophotographic method is a reversal development method.