JPS5919331B2 - Electrostatic latent image formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrostatic latent image forming method that allows simple exposure without requiring a negative image when a first image exposure and a second image exposure are performed on a photoconductor in an overlapping manner. It is related to.

Recently, there has been a demand for recording a regular format such as ruled lines and an image such as characters overlappingly on a single sheet of paper, and two negative images are sequentially overlaid and exposed on a predetermined charged drum and then inverted. A method of developing and recording a normal positive image has been proposed.

However, since the negative images required for exposure can be obtained by reversing each of the positive images, for example, the configuration of a modulator for modulating laser light or the formation of an image on an optical fiber tube (OFT) is difficult. The disadvantage is that the circuit configuration for this is complicated. An object of the present invention is to provide an electrostatic latent image forming method that can easily perform exposure without requiring a negative image when first image exposure and second image exposure are overlapped on a photoconductor. It is.

In order to achieve the above object, the electrostatic latent image forming method of the present invention uses a photoreceptor consisting of three layers: a dielectric layer, a photoconductor layer, and a conductor layer, and first, the entire surface of the dielectric layer is exposed to light. After performing initial charging, charging with the opposite polarity to the initial charging and exposing a first image are performed simultaneously, then charging with the same polarity as the initial charging and exposing a second image are performed simultaneously, and then It is characterized in that electrostatic latent images of two images are formed on the photoreceptor in a superimposed manner by exposing the entire surface of the photoreceptor to light.

The present invention will be described in detail below with reference to examples.

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention.

In the figure, the exposure and development steps proceed as the photosensitive drum consisting of a conductive drum 1 and a photoconductor layer 2 and a dielectric layer 3 is rotated. First, an initial charging corotron 4 performs initial charging on the photoreceptor while exposing the entire surface to light 21, and then a simultaneous charging corotron 5 with a polarity opposite to the initial charging performs charging, and a copying optical system is passed through this. For example, a standard document 7 is exposed by the system 6. Next, the corotron 8 is simultaneously charged with the same polarity as the initial charge.
Characters and the like are written by scanning the laser beam 22 while being charged (g). Next, the entire surface is exposed to light 23, and the exposure process is completed. After this, according to a normal electrophotographic process, the electrostatic latent image 9 formed on the photoconductor layer 2 is developed by a magnetic brush developer 10, and the developed toner image 11 is brought into contact with a transfer paper 12. Then, voltage is applied from the transfer corotron 13 from the back side to perform transfer. The transfer paper 12 is then sent to a fixing device 14. On the other hand, since there is residual toner on the surface of the photoconductor layer 2 of the photosensitive drum after transfer, the toner is passed under the cleaner 15 to be cleaned and removed and returned to its original state. A feature of the present invention is that two images are superimposed by performing charging and simultaneous exposure twice using a photoreceptor having a dielectric layer.

In order to make this process easier to understand, Figures 2a to 2d show the charge distribution state 1 and surface potential 2 of the photoconductor layer during initial charging, first and second charging simultaneous exposure, and whole surface exposure, respectively. This is what is shown. In FIG. 3A, the surface of the dielectric layer 3 is initially charged.

At this time, when the photoreceptor is charged while being irradiated with light, an amount of opposite polarity charge corresponding to the charged charge is trapped at the interface between the dielectric layer 3 and the photoconductor layer 2. If the photoconductor layer 2 is charged without light irradiation, the charge with the opposite polarity to the charged charge is
Since this occurs only at the interface between the conductor layer 1 and the conductor layer 1, the amount of charge becomes smaller when the charging potential is the same. The surface potential of the dielectric layer 3 when irradiated with light is V. shall be. In FIG. 2B, the first image exposure, such as a regular image, is performed while being charged with a polarity opposite to the initial charging.

At this time, the trapped charges are released in the light image area, so that the charges on the dielectric layer 3 are easily neutralized and further charged to the opposite polarity. On the other hand, in the dark part of the optical image, the trapped charges are not released, resulting in a charge distribution as shown in FIG.

Next, in FIG. 3c, a second image of characters or the like is exposed while being charged with the same polarity as the initial charging. At this time, the trapped charges are released in the light image area, so that the dielectric layer 3 is charged with the same polarity as the initial charge. On the other hand, in the dark part of the optical image, the trapped charge is not released, so it is shown in the figure c.
The charge distribution becomes as follows.

In this case, the corotron 8 used preferably has a control electrode. The control electrode has been proposed by the present applicant in a separate application, and is intended to prevent the charging potential of the portion corresponding to the dark area from becoming excessive when two image exposures are performed overlappingly. between the corona discharge electrode and the photoreceptor.

A mesh or wire electrode to which a slightly higher voltage is applied is provided. In this way, the potential of the dark area in the first image exposure and the bright area in the second image exposure is determined.

or slightly larger. Further, in areas corresponding to bright areas in the first image exposure and dark areas in the second image exposure, it is necessary to adjust each charge amount so that the amount of charge on the dielectric layer 3 after the second image exposure becomes sufficiently small. Next, in d of the same figure, the entire surface of the photoreceptor is exposed.

This lowers the resistance of the photoconductor layer 2 and facilitates the movement of charges in this layer. Therefore, the latent image finally obtained is V in the portion corresponding to the dark portion in the first image exposure and the portion corresponding to the bright portion in the second image exposure. It has a surface potential of approximately 0, and almost O in other parts. In the copying optical system for the first image exposure, the image corresponds to the dark part of the optical image and the back corresponds to the bright part of the optical image, so in this case, it can be used as is without preparing a negative image, and the configuration is simplified. As explained above, according to the present invention, a photoreceptor consisting of three layers, a dielectric layer, a photoconductor layer, and a conductor layer, is used, and initial charging is performed while the entire surface of the dielectric layer is exposed to light. After that, charging with the opposite polarity to the initial charging and first image exposure are performed simultaneously, then charging with the same polarity as the initial charging and second image exposure are performed simultaneously, and further, the entire surface of the photoreceptor is exposed. It is.

This provides the advantage that electrostatic latent images of two images can be formed on the photoreceptor in a superimposed manner, and that the original can be applied as is without using a negative image for one of them.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention, Fig. 2a
-d is a process explanatory diagram of the operation of the embodiment, and in the figure, 1
is a conductive drum, 2 is a photoconductor layer, 3 is a dielectric layer, 4 is an initially charged corotron, 5 and 8 are simultaneously charged corotrons, 6
1 is a copying optical system, 7 is an original, 9 is an electrostatic latent image, 10 is a magnetic brush developer, 11 is a toner image, 12 is a transfer paper, 13 is a transfer corotron, 14 is a fixing device, 15 is a cleaner 21
, 23 indicates light, and 22 indicates laser light.

Claims (1)

[Scope of Claims] 1. Using a photoreceptor consisting of three layers: a dielectric layer, a photoconductor layer, and a conductor layer, first, the entire surface of the dielectric layer is exposed to light and an initial charge is applied, and then the initial charge is applied. Charging, charging with the opposite polarity and exposing the first image are performed simultaneously, then charging with the same polarity as the initial charging and exposing the second image are performed simultaneously, and furthermore, the entire surface of the photoreceptor is exposed to light. An electrostatic latent image forming method characterized by forming electrostatic latent images of two images in a superimposed manner on a photoreceptor. 2. A control electrode for controlling the amount of charge is provided between at least one of the corona discharge electrodes for performing the initial charging and charging simultaneously with the exposure of the first and second images and the photoreceptor. An electrostatic latent image forming method according to claim 1.