JPS59195677A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To form an electrophotographic method removing or reducing the light fatigue of an amorphous silicon type photoconductive layer by exposing and electrostatically discharging a transferred photosensitive body in a spectral wavelength area less than a specific wavelength to remove residual toner from the surface of the photosensitive body. CONSTITUTION:A photoconductive layer 2 is electrostatically charged with fixed polarity by a corona charger 3, an original 13 to be copied is lighted up by a lamp 4 and the photoconductive layer 2 of the original 13 is exposed through an optical system 6 to form an electrostatic latent image corresponding to the picture on the original. The electrostatic latent image is developed with toner by a developing means 8. Transfer paper 14 is fed so as to be contacted with the drum surface at the position of a toner transferring charger 9 and corona charged with the same polarity as the electrostatic latent image from the back of the transfer paper 14 to transfer the toner image to the transfer paper 14. The toner-transferred photoconductive layer 2 is completely exposed by a destaticizing lamp 11 having a spectral wavelength area <=600mmu wavelength to erase the residuel charge and then the residual toner is removed by a cleaning means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method using an amorphous silicon-based photoconductor, and more specifically,
The present invention relates to an improvement in eliminating or reducing optical fatigue during high-speed repetitive copying using the photoconductive layer.

Amorphous silicon-based photoconductor layers have high surface hardness, are sensitive to light on the long wavelength side, and have good sensitivity, so they are attracting attention as photoreceptors for electrophotography.

However, according to research conducted by the present inventors, although amorphous silicon has the above-mentioned excellent properties, it has the problem of relatively high optical fatigue during high-speed copying. For example, when the various operations of charging, exposing, developing, transferring, and cleaning are repeated on a photosensitive layer in a normal copying cycle, in the case of a selenium photosensitive layer, the amount of charge after the second time is 0.5 of the amount of charge at the first time. However, in the case of amorphous silicon, the amount of charge after the second charge is 50% lower than the amount of charge after the first charge. There is a disadvantage that the density decreases by as much as 20%, and the second and subsequent images have a decrease in density that is noticeable to the naked eye compared to the first image.

Accordingly, an object of the present invention is to provide an electrophotographic method in which optical fatigue of an amorphous silicon-based photoconductor layer is eliminated or reduced.

Another object of the present invention is to
It is an object of the present invention to provide an electrophotographic method that suppresses the influence of optical fatigue to a negligible level and enables constant high-density image formation.

According to the present invention (C), an electrophotographic photoreceptor having an amorphous silicon-based photoconductor layer on a conductive substrate is charged, image exposed,
In electrophotography, which forms images by repeating development and transfer steps, the photoreceptor after transfer is exposed to wavelength 6
Provided is an electrophotographic method characterized in that static electricity is removed by exposure in a spectral wavelength region of 00 mμ or less, and residual toner is removed from the surface of a photoreceptor.

In FIG. 1 for explaining the electrophotographic method of the present invention,
B on the surface of the metal drum 1 that is driven and rotated.

An amorphous silicon based photoconductor layer 2 is provided.

Around this drum is a main charging corona charger 6:
An image exposure mechanism consisting of a lamp 4, a document support transparent plate 5, and an optical system 6: a developing mechanism 8 having toner 7; a corona charger 9 for toner transfer; a corona charger 101 for paper separation.
The i11t lamp 11; and the cleaning mechanism 12 are provided in this order. First, the photoconductor layer 2 is charged with a constant polarity using the corona charger 6. Next, the original 16 to be copied is illuminated by the lamp 4, and the photoconductor layer 2 is exposed to a light beam image of the original through the optical system 6, thereby forming an electrostatic latent image corresponding to the original image. This electrostatic latent image is developed with toner 7 by a developing mechanism 8. The transfer paper 14 is supplied so as to be in contact with the drum surface at the position of the toner transfer charger 9, and corona charging with the same polarity as the electrostatic image is performed from the back side of the transfer paper 14 to transfer the toner image onto the transfer paper 14. let The transfer paper 14 on which the toner image has been transferred is electrostatically peeled off from the drum by the separation corona charger 10, and is transferred to a fixing area (not shown).
etc. are sent to the processing area.

After the toner has been transferred, the photoconductor layer 2 is exposed to light from the entire surface by a discharge lamp 11 to erase residual charges, and then a cleaning mechanism 12 removes the residual toner.

As already mentioned, the amorphous silicon photosensitive layer 2 used in the present invention exhibits light fatigue of a non-negligible order, and the charged potential of the photosensitive layer after exposure is equal to the charged potential of the unexposed photosensitive layer. In comparison, there is a decrease of up to 20 inches, and the image densities of the first and subsequent copies are considerably different.

In the present invention, optical fatigue of an amorphous silicon-based photoconductor layer is greatly affected by the wavelength of the exposing light beam, and the wavelength 60
This is based on the new finding that by performing static neutralization by exposure in the spectral wavelength region of 0 mμ or less, the effects of optical fatigue described above are almost eliminated, making it possible to form images with constant high density.

Figure 2 is a diagram showing the wavelength dependence of photofatigue, where the horizontal axis shows the wavelength at the time of exposure of the photosensitive layer, and the vertical axis shows the amount or degree of decrease in surface potential5) (photofatigue rate %). ing. This second
Referring to the figure, the optical fatigue of amorphous silicon is highly dependent on the wavelength of light, showing maximum fatigue at a wavelength of 725 mμm, and almost no fatigue for light with a wavelength of 600 mμ or less. It turns out that there isn't.

Also, Figure 6 is the spectral sensitivity curve of amorphous silicon,
It can be seen that the sensitivity is extremely low at wavelengths of 850 mμ or more.

Furthermore, Figure 4 shows the rate of decrease in charged potential (C%) due to exposure time and optical fatigue when amorphous silicon is exposed to various light intensities (unit: μIV/crl) at a wavelength of 725 mμ. FIG. According to FIG. 4, it is clear that the degree of optical fatigue is greatly influenced by the light intensity, while the exposure time is saturated in a relatively short time and is hardly dependent on the amount of light. Still, the black circles in Figure 4 indicate exposure 1 to
The results show that light fatigue is less even at the same light intensity.

On the other hand, the recovery time of photofatigue of amorphous silicon photoconductor is
Although it also varies depending on the wavelength of the pre-exposed light,
It has been experimentally confirmed that the time is less than 1 second on the relatively short wavelength side, and about 2 to 6 seconds on the relatively long wavelength side.

In the present invention, in the electrophotographic method described above, the elapsed time from the static elimination exposure to the main charging is significantly shorter than the elapsed time from the end of the image exposure to the main charging, and thus the optical fatigue of the static elimination exposure is reduced. Since the effect of image exposure is significantly greater than that of image exposure, the above-mentioned trouble was solved by performing static elimination exposure in the spectral wavelength region of wavelength 6CJOmμ or less. , when copying A6 size copies at a speed of 18 pages per minute, the elapsed time from image exposure to the next main charge is approximately 2.2 to 6.1 seconds, while the time from static elimination exposure to main charge is approximately 2.2 to 6.1 seconds. The elapsed time is approximately 0.2 to 1
．． It will be 5 seconds. In this example, it is understood that the influence of optical fatigue due to image exposure hardly appears on the next main charge, and the influence of optical fatigue due to static elimination exposure occurs on the main charge. As shown in Figure 6, amorphous silicon has sufficient sensitivity for static elimination exposure at which the effects of optical fatigue are most likely to appear, but as shown in Figure 2, the wavelengths at which there is almost no optical fatigue are used. By carrying out the process in the spectral wavelength region of 600 mμ or less, it becomes possible to maintain the photoreceptor surface potential at a constant level of 1 to as high as possible during repeated copying.

In the present invention, the elapsed time after image exposure until the next main charging is longer than the photofatigue recovery time of the amorphous silicon photoconductor, and the image exposure is performed by using static eliminating light in the wavelength range mentioned above. In this case, it becomes possible to use white light that corresponds to the panchromatic sensitivity of the photoreceptor, achieving the remarkable advantage that there is no adverse effect on the quality or density of the image formed.

In the present invention, in order to satisfy the above-mentioned conditions,...
For a white light source containing infrared rays such as a rogen lamp, an interference filter is inserted to cut out light rays with a wavelength larger than 600 mμ and used as a light source for static elimination. Also,
Fluorescent lamps, especially green fluorescent lamps, are used as light sources that do not include infrared rays.
A blue fluorescent lamp, a grey-green neon lamp, a colorless light emitting diode, etc. are used as the static eliminating light source 7.

For the amorphous silicon-based photoconductor layer, any material known per se may be used, such as amorphous silicon deposited on the substrate by plasma decomposition of 7 run gas, etc. The material may be doped with hydrogen, halogen, or the like, and further doped with an element of Group 1 or Group 2 of the periodic table, such as boron or phosphorus.

The physical properties of a typical amorphous silicon photoreceptor include dark conductivity <io-"Ω-1・Cm', activation energy <0.85 eV, and photoconductivity>10-70-"071-'
, the optical bandgap is 1.7 to 1.9 eV, the amount of bonded hydrogen is 15 to 20 atomic units, and the dielectric constant of the film is in the range of 11.5 to 12.5.

This amorphous silicon photoconductive layer can be charged positively or negatively depending on the doping species, and the voltage applied to the corona charger is generally in the range of 1d5 to 8KV.

Light sources for image exposure include halogen lamps, fluorescent lamps,
Any light source can be used, such as helium-neon laser light, semiconductor laser light, etc., and it is generally desirable to have a light intensity on the photosensitive layer during imagewise exposure in the range of 50 to 250 microns/ci.

[Brief explanation of drawings]

FIG. 1 is a process diagram for explaining the electrophotographic method of the present invention, in which 2 represents an amorphous silicon photoconductive layer, 4 represents an exposure light source lamp, 8 represents a developing mechanism, and 11 represents a discharge lamp. Figure 2 shows the wavelength dependence of optical fatigue, Figure 6 shows the spectral sensitivity curve of the amorphous silicon photosensitive layer, and Figure 4 shows the exposure of the amorphous silicon photosensitive layer to various light intensities. FIG. 3 is a diagram showing the relationship between the exposure time and the rate of decrease in charging potential due to optical fatigue when performing the following steps. In Figure 2, -x-1-1-・--1 and -1110---- have an average light intensity of 28.0.95, respectively.
．． Corresponds to 2.6μF/c/l. Patent applicant Sanda Kogyo Co., Ltd. 1st factor 2nd liquid length (m/-1)

Claims (2)

[Claims] (1) In an electrophotographic method in which an image is formed on an electrophotographic photoreceptor having an amorphous silicon-based photoconductor layer on a conductive substrate by repeating the steps of main charging, image exposure, development, and transfer, An electrophotographic method characterized in that the photoreceptor after transfer is exposed to a spectral wavelength region of 600 mμ or less to remove static electricity, and residual toner is removed from the surface of the photoreceptor. (2) The method according to claim 1, wherein the elapsed time after image exposure until the next main charging is longer than the optical fatigue recovery time of the amorphous silicon photoconductor.