JPS5846360A - Formation of image - Google Patents

Abstract

PURPOSE:To make the high speed formation of two-color images possible with a simplified optical system by using a recording medium consisting of a conductive substrate, a photoconductive substrate and a transparent insulating layer, and subjecting the same to a specific electrostatic charging treatment then to the 1st developing after exposure of the 1st light image and the 2nd light image followed by the 2nd developing after uniform exposure. CONSTITUTION:The surface of a photoreceptor formed successively with a photoconductive layer 2 and a transparent insulating layer 3 on a conductive substrate 1 is electrostatically charged uniformly to form the electric charge reverse from that of the surface at the boundary of the layer 2 and the layer 3. Said surface is electrostatically charged reverse to decrease or invert the surface charge. After the 1st light image 1E is exposed thereon and the surface of the recording medium is charged uniformly in succession, the 2nd light image 2E is irradiated thereon. The area irradiated with the 2nd light image is reversally developed by using an electrostatically charged toner 4 of the same polarity as that of the 1st latent image and the recording medium is exposed uniformly; thereafter the 1st light image part is developed with the 2nd developer. The two-color images are transferred, whereby two-color images are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrophotography, and particularly to a method suitable for forming two-color images.

Conventional methods for forming two-color images using electrophotography include a method in which one drum is rotated twice to overlap one color at a time, and a method in which charging, first exposure, first development, second exposure, and second development steps are sequentially performed. There was a way to do it.

However, these methods have the drawbacks that the printing speed is low, the apparatus is complicated, and the apparatus is complicated and large in size.

The present invention eliminates the conventional drawbacks, and achieves high speed and easy device configuration.
An object of the present invention is to provide a color image forming method and apparatus.

In order to achieve the above object, the present invention uses a recording body basically consisting of a substrate, a plate, a photoconductor, and an insulating layer, and performs first development by exposing a first light image and exposing a second light image. By doing this first, the configuration of the optical system and the optical path for performing two types of exposure can be simplified.

FIG. 1 is a diagram showing an image forming process according to an embodiment of the present invention.

A recording body consisting of a conductive substrate 1, a photoconductor 2, and a transparent insulating layer is uniformly charged as shown in (a) to form charge pairs on the front and back sides of the insulator. In this charging step, it is preferable to charge the insulator surface positively when the photoconductor is an n-type photoconductor, and negatively when it is a p-type photoconductor, but it is not necessary to do so. Alternatively, light may be irradiated at the same time as this charging to facilitate the induction of charges at the interface between the insulating layer and the photoconductor.

Next, the insulator is charged in the opposite direction with a charger to reduce the electric charge on the surface of the insulator or to make it have a potential of opposite polarity. Reverse charging can be performed using a charger with a polarity opposite to that of the initial charging or with an AC corona discharge. FIG. 1(b) is an example of reverse charging, and shows when the charge on the surface of the insulator is removed.

Next, as shown in FIG. 1(C), exposure is performed with a first optical image IE. The charge on the photoconductor layer disappears at the location where the light is irradiated by exposure. Next, the surface of the recording medium is corona charged again to make the potential uniform. This situation is shown in FIG. 1(d). This charge is
Same as before the first light image exposure, reverse charging (DC or AC corona)
It is preferable to do this.

Next, as shown in FIG. 1(e), a second optical image 2E is irradiated. The charge in the photoconductor in the light irradiation area of the second exposure disappears, and the potential decreases. Next, as shown in Figure 1(f), the first
The recording medium is reversely developed with a developer containing toner charged to the same polarity as the latent image, and the first color toner 4 is attached to the light irradiated area of the first light image.

Next, when the recording medium is uniformly exposed to light as shown in FIG. 1(g), charges remain only in the first light image exposed portions where charges exist on the surface of the insulator. A regular image is applied to this area using a second developer, and a second color toner is attached as shown in FIG. 1(h).
A color image can be cast onto the recording surface.

In Figure 1 above, as shown in (b), the case is shown in which the charge on the surface of the insulator during reverse charging just disappears, but this is not necessarily the case, and the state in which the charge exists on the surface is also possible. , in this case, in (C) and below, the shape is biased by that amount.

FIG. 2 shows potential changes in the process shown in FIG. 1.

In FIG. 2, 6 is the first exposed bright area, 7 is the first exposed dark area,
8 is the second exposed bright area, 9 is the first exposed dark area, uniform exposure VE
10 is a curve showing the potential change after uniform exposure VE is irradiated at the first light exposure area.

FIG. 3 is a diagram showing potential changes when AC corona is used as reverse charging performed before and after the first exposure.

FIG. 4 shows an example of a recording apparatus using the image forming method of the present invention, which is a two-color laser beam printer.

The recording drum 11 is uniformly charged by a charger 12 and reversely charged by a reverse charger 13, and then exposed to a light-modulated first beam 14. Next, it is reversely charged again by the carrier camera 15, and then exposed with the optically modulated second beam 16. 1st. The second beam is scanned by a light source system consisting of a rotating mirror, a scanning mirror, and the like. Next, the charge latent image formed by exposure to the second beam light is developed by a first color developer. Next, the recording medium is exposed to light using the uniform exposure light source 2o. A latent image produced by the first beam exposure is developed by a second color developer.

The two-color toner image thus formed on the recording medium is uniformly charged by the charger 22, and the charging polarity of the toner is made uniform. Thereafter, a transfer corona is applied to the transfer paper 23 by the transfer charger 24 to transfer the two-color toner image. Eventually, the toner image is fused to the paper. The recording drum is cleaned by a cleaner 25 and used again.

In the above two-color image forming apparatus, the first. Selection and exchange of signals that change the second beam and the first beam. By selecting the operation of the second developing device, it is possible to change the colors in one-color printing and rearrange the colors in two-color printing.

As described above, in order to form two different toner images consisting of a substrate, a photoconductor, and an insulator, the first and second exposure steps are performed before the first development. After the exposure, a reheating 2 exposure with uniform charging is performed to make the surface potential of the recording medium uniform.
Since the two beams do not need to be placed before and after the developing device, there is no need to complicate the beam optical path and form an optical system, resulting in a compact and low-cost device, and optical system control based on toner scattering, etc. It has the advantage that the system is less dirty and maintenance is easy.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a cross section of a recording medium, charge latent image formation, and toner adhesion status in each step of the image forming method of the present invention, and FIGS. 2 and 3 are diagrams showing potential changes in each step. , FIG. 4 is a block diagram of a two-color image forming apparatus based on the image forming method of the present invention. 1...Substrate, 2...Photoconductor, 3...Transparent insulator, 4...No./l! 1 Figure 2

Claims (1)

[Claims] 1. Using a recording medium consisting of a substrate, a photoconductor, and an insulator,
In those that form two different toner images, there is a step of uniformly charging the surface of the recording material to generate a charge in the photoconductor layer or the photoconductor-insulator boundary region; a step of reverse charging in a direction to reduce the charge or reverse the polarity, then a step of exposing the first light image, followed by a step of uniformly charging the surface of the recording medium to make it uniform;
Next, a step of exposing a second light image, a step of developing a charge latent image formed by the second light image exposure with a first developer,
An image forming method comprising the steps of: successively exposing the recording medium uniformly to light; and developing a charge image of the first optical image developed by the uniform exposure with a second developer.