JPS59172671A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To adjust print density by varying the quantity of erasing light and controlling the surface potential of a photoconductor in a laser beam printer. CONSTITUTION:The photoconductor 1 is electrostatically charged by an electrostatic charger 2 and exposed to a light beam 3 containing picture information from a laser to form an electrostatic latent image, which is developed by a developing device 4 to form a toner image 6; and this toner image is transferred electrostatically to transfer paper 7. Residual toner 9 on the photoconductor 1 is removed by a cleaner 10 and residual charges on the photoconductor 1 are erased by the erasing light 11 to reuse the photoconductor 1. When the picture density of the transfer toner image 8 on transfer paper 7 is controlled, the surface potential at a development part 4 should be varied, but the surface potential varies in inverse proportion to the quantity of the erasing light, so the surface potential is controlled by the erasing light 11 to adjust the print density easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electrophotographic method, and more particularly to a method for controlling the surface potential of a photoconductor in a laser beam printer.

[Prior art]

In an electrophotographic method that basically repeats the process of charging, exposing, developing, transferring, cleaning, and erasing a photoconductor, photoconductor is generally used as a method to adjust the surface potential on the photoconductor. A method has been adopted in which the corona charging voltage applied to the body is varied, but this method has the drawback that adjustment is difficult because the corona discharge varies greatly depending on the voltage applied to the corona wire.

[Purpose of the invention]

The object of the present invention is, in particular, to provide a laser beam printer with a
An object of the present invention is to provide a method for controlling the surface potential of a photoconductor.

[Summary of the invention]

The present invention is based on the phenomenon that the surface potential of a photoconductor changes depending on the amount of erase light, and the present invention controls the surface potential of a photoconductor by changing the amount of erase light, thereby reducing adhesion to the photoconductor. This is to adjust the toner density and thus the print density.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

1 shows an outline of a laser beam printer to which the present invention is applied. In the figure, a drum-shaped photoconductor 1 rotating clockwise is uniformly charged, for example positively, by a charger 2. As shown in FIG. Next, an electrostatic latent image is formed by exposure with a light beam 3 containing image information emitted from a laser, and this is developed with toner 5 contained in a developing device 4 to form a toner image 6.
This is electrostatically transferred to transfer paper 7. The transferred toner image 8 on the transfer paper 7 is fixed by heat or pressure. The residual toner 9 on the photoconductor 1 is removed by a cleaner 10, and then the residual charge on the photoconductor 1 is erased by an erase light 11, and the photoconductor 1 is reused. In order to control the image density of the transferred toner image 8 on the transfer paper 7, it is necessary to change the surface potential in the developing section. In the case of a copy machine, ray 3
Since this is not laser light but reflected light from the object to be copied, all copying machines adjust the surface potential by adjusting the intensity of the amount of light irradiated onto the object to be copied. On the other hand, when the light beam 3 is a laser beam, an electrostatic latent image is formed by turning on and off the light beam 3, so the surface potential cannot be changed by the light beam 3.

The present invention adjusts the surface potential of a photoconductor having sufficient sensitivity to light with wavelengths longer than 5QQnm by adjusting the amount of erase light.

Next, a first embodiment of the present invention will be described based on FIG. As the photoconductor l in FIG. 1, an se-'f e alloy system is used which has a sensitivity defined by a half-light intensity of 5 μJ/m'' to a laser beam having a wavelength of 800 nm.

The surface movement speed of the drum-shaped photoconductor 1 with a diameter of 120 m (
The printing speed) was 1ocrn/s. A tungsten lamp is used as the light source of the erase light 11, and the photoconductor 1 is irradiated with light through a blue band pass filter ta that has maximum transmittance for light around 45 Q nm. When the amount of irradiation light is 100 mW/cm', the voltage applied to the corona wire of the charger 2 is set to a constant value so that the surface potential at the position of the developing device 4 is 600 cm.

In this state, if the amount of erase light is changed to 50 mW/cm2 by adjusting the power supply 12, the surface potential becomes 680 ■, and conversely, if the amount of erase light is increased to 200 mW/cm2,
cm", the surface potential decreases to 530 V. In other words, the surface potential changes in inverse proportion to the amount of erase light. This phenomenon is due to the recombination of carriers generated by the erase light irradiation, f4i] (C1 This is thought to be due to the fact that when the photoconductor is charged, part of the corona charge on the photoconductor is neutralized by the carriers.According to this example, the surface potential can be controlled by erasing light. This has the advantage that printing density can be easily adjusted in a laser beam printer.

Next, a second embodiment of the present invention will be explained with reference to FIG. The difference between FIG. 2 and FIG. 1 is that a temperature sensor 13 is provided near the photoconductor 1 to detect the ambient temperature of the photoconductor 1, and its signal is fed back to the power source 12 for the erase light 11. The point is that That is, generally Se
When the temperature of a -Te alloy-based photoconductor exceeds about 40° C., its corona charge retention property rapidly decreases, the surface potential decreases, and the image density becomes low. To prevent this, a temperature sensor 13 that detects the temperature of the photoconductor 1 is installed near the photoconductor 1, and when the temperature of the photoconductor 1 reaches 40'C, the power supply control circuit 14 turns on the power supply 12. The amount of the erase light 11 is reduced by controlling. Actually, erase light 1
When the light intensity of photoconductor 1 is constant at 100 mW/cm'', the surface potential is 600 V and 480 V when the temperature of photoconductor 1 is 30°C and 42°C, respectively, and the image density at 42'C is quite low. However, since the temperature sensor 13 sets the intensity of the erase light 11 to 30 mW/cm'' at 40'C, the surface potential at 42'C becomes 570V, and the image density is almost the same as at 30'C. Become.

The temperature sensor 13 may be installed anywhere as long as it corresponds to the temperature of the photoconductor 1, for example, in the developing device 4.
When the temperature difference between the side plate and the photoconductor 1 is constant,
The temperature of the side plate of the developing device 4 may be detected by the temperature sensor 13. According to this embodiment, there is an effect that the image density change due to the temperature of the photoconductor 1 is kept constant by the light guide at t11 (erasing).

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 shows only the vicinity of the erase light 11 in FIG. 1. In the figure, a side plate 16 of the lamp housing 15 on the charger 2 side for guiding the erase light 11 to the photoconductor 1 has a structure that rotates in place of the shaft 17. By rotating the side plate 16 from (a) to (b) while keeping the voltage of the power source 12 for the erase light 11 constant, the surface potential was reduced by about 30 degrees. This means that although the total amount of erase light 11 irradiated onto the photoconductor IK is constant, (1
When the 411 plate 16 is in (b), the erase light 11 is irradiated close to the charger 20, so the rate of recombination of generated carriers is lower than when the side plate 17 is in (a). This seems to be caused by. At the same time as changing the irradiation position of the erase light by rotating the side plate 16, the power source 12
By changing the amount of erase light, it is possible to further increase the amount of time the surface potential is being adjusted.

Next, a fourth embodiment will be described. As a photoconductor, a two-layer organic photoconductor with high sensitivity around 800 nm is used, in which a charge generation layer and a charge transport layer are stacked on a substrate.As an image light, 78
The present invention was applied to an apparatus similar to that shown in FIG. 1 using an optical system that selectively irradiates a copy optical image of a document using a 0 nm light guide laser beam and a tungsten or fluorescent lamp as a light source. In such an apparatus, since the wavelength of the image light is different during laser beam recording and copy optical image recording, the appropriate amount or wavelength of the erase light is different, making it impossible to record both images satisfactorily.

Therefore, in this embodiment, the light amount or wavelength of the erase light is set to an appropriate value during laser beam recording and copying light recording, and the light amount or wavelength is switched. To change the amount of light, the voltage applied to the lamp was changed, and to change the wavelength, the optical filter attached to the lamp was mechanically replaced. By doing this, it was possible to create an apparatus in which the image density changes slightly even when recording is performed alternately with laser light and Neri photographic images.

〔Effect of the invention〕

According to the present invention, in a laser beam printer using a photoconductor that is particularly sensitive to semiconductor laser light in the vicinity of 800 nm, the surface potential can be changed by controlling the erase light, so printing can be easily performed in a semiconductor laser beam printer. This has the effect of being able to control the concentration.

Feedback of the signal from the width sensor has the effect of reducing surface potential fluctuations due to /M degrees.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a laser beam printer using the present invention, and FIGS. 2 and 3 are explanatory diagrams of embodiments of the present invention. 1... Photoconductor, 2... Charger, 3... Light ray, 1
1... Erase light, 12... Source, 13... Temperature sensor. Agent Patent Attorney Akio Takahashi

Claims (1)

[Scope of Claims] 1. A uniformly charged photoconductor is exposed to light corresponding to an image to form an electrostatic latent image, and the electrostatic latent image is developed with toner.
In an electrophotographic method, in which a toner image is formed on the photoconductor, the toner image is transferred to a recording medium, and the photoconductor is reused by being irradiated with erase light. ' is a noodle method characterized in that the surface potential of the noodle is controlled by changing the light intensity wavelength of the erasing light or the irradiation part position. 2. The electrophotographic method according to claim 1, wherein the control is performed by detecting the temperature of the photoconductor. 3. An electrophotographic method according to claim 1 or 2, characterized in that the exposure is by laser light.