JPH0470871A - Image exposing method - Google Patents

Abstract

PURPOSE:To prevent the degradation of image quality caused by the fluctuation of a discharging gap by putting the potential of an image within a prescribed potential difference, with respect to the maximal value of the image potential changing characteristic of an unexposed part and/or an exposed part to the discharging gap. CONSTITUTION:A photosensitive body 10 where a transparent electrode 12 and a photoconductive layer 13 are formed on a supporting body 11, and a charge holding medium 20 where an electrode 22 and an insulating layer 23 are formed on a supporting body 21, are arranged so as to be opposed with each other, and a voltage is applied on the electrodes 12 and 22 to carry out an image exposure. For instance, an exposure is carried out by the discharging gap within the changing region G1 of the discharging gap with respect to a allowable potential fluctuation delta1 to the maximum potential of the characteristic B of the unexposed part, and a potential change in the unexposed part is put within the range delta1. Similarly, the exposure is carried out by the discharging gap within the discharging gap G2 put within the potential fluctuation delta2 with respect to the potential difference of one-gradation to the maximum potential of the characteristic A of the exposed part, and put within the potential fluctuation of the range delta2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image exposure method for recording an electrostatic image on an insulator.

[Conventional technology]

FIG. 6 is a diagram for explaining a conventional electrostatic image recording method.

A photoreceptor 10 having a transparent electrode 12 and a photoconductive layer 13 formed on a support 11 and a charge holding medium 20 having an electrode 22 and an insulating layer 23 formed on a support 21 are arranged facing each other, and electrodes 12.2
When image exposure is performed by applying a voltage of a predetermined polarity between the two from the power source 30, the exposed photoconductive layer portion exhibits conductivity,
A discharge occurs between the photoreceptor 10 and the charge holding medium 20 in that portion, and charges (〒), for example, are accumulated on the insulating layer 23 according to the amount of exposure. At this time, carriers are generated in the exposed portion of the photoconductive layer 13, and (-) charges are transferred to the transparent electrode I2.
The (+) charge moves to the surface of the photoconductive layer, and corresponding to this charge, the ionized (-
) charge is accumulated.

[Problem to be solved by the invention]

By the way, since the amount of static charge formed on the insulator changes when the discharge gap changes, it is necessary to maintain the discharge gap constant. However, it is difficult to maintain a constant discharge gap of several micrometers to several tens of micrometers. In addition, a predetermined potential is formed not only in the exposed area but also in the unexposed area due to dark current, and the potential of this area also changes when the discharge gear changes, changing the background condition and affecting the image quality. It turns out.

The present invention is intended to solve the above-mentioned problems, and the present invention performs image exposure using a discharge gap that minimizes fluctuations in potential on a charge holding medium in response to fluctuations in the discharge gap. The purpose is to prevent deterioration of image quality due to

Second Means for Solving the Problem The present invention provides an image exposure method in which a photoreceptor and an insulator are placed in an electric field, and an electrostatic latent image is formed on the insulator by discharge accompanying image exposure. Image exposure is performed using a discharge gap in which the image potential of the unexposed area and/or the exposed area falls within a predetermined potential difference with respect to the maximum value of the image potential change characteristic of the unexposed area and/or the exposed area with respect to the discharge gap. Features.

[Function] The present invention is characterized in that the change characteristics of the image potential with respect to the discharge gap in the exposed area and the unexposed area on the charge holding medium are
Focusing on the fact that it has at least one maximum value, the discharge gap is within an allowable potential difference with respect to the maximum potential of the unexposed area,
Further, image exposure is performed in a discharge gap within an allowable potential difference with respect to the maximum potential of the exposed portion.

By using such a discharge gap, even if the discharge gap changes somewhat, the image potential remains within an allowable range, and it is possible to prevent image quality from deteriorating due to a change in the discharge gap.

Mouth Example] Examples will be described below with reference to the drawings.

Fig. 1 is a diagram for explaining the image exposure method of the present invention, Fig. 2 is a diagram for explaining the configuration of the image exposure device, and Figs. 3, 4, and 5 are for explaining the image exposure method of the present invention. FIG. 4 is a diagram illustrating a potential change with respect to a discharge gap in an unexposed area at a time. Note that the same numbers as in FIG. 6 indicate the same contents.

First, as shown in FIG. 2, the photoconductive layer 13 of the photoreceptor 10
The film thickness of is Xp, the discharge gap is Xg, the film thickness of the charge retention layer 23 is Xd, and the voltage applied to the photoreceptor and charge retention medium is Vg.
If the surface potential of the exposed part is Vl and the surface potential of the unexposed part is Vd, then Cρ+Cd cp-
It is expressed as CdXp Xg Xd. Here, Cρ is the photoconductive layer capacitance, g is the void capacitance, Ctl is the charge retention layer capacitance, ε is the photoconductive layer dielectric constant, ε is the void permittivity, ε6 is the charge retention layer relative permittivity, and vb is the void. is the discharge starting voltage when is Xg.

Now, the photosensitive layer thickness and charge retention layer thickness are each 10 μm.
When the applied voltage is 750 V, in the case of an organic photoreceptor, the relative dielectric constant of the photosensitive layer and the relative dielectric constant of the charge storage layer are 3, and a change in image potential with respect to the discharge gap as shown in FIG. 3 can be obtained.

Further, in the case of a selenium photoreceptor under similar conditions, when the relative dielectric constant of the photoreceptor layer is 7 and the relative dielectric constant of the charge holding layer is 3, a change in image potential with respect to the discharge gap as shown in FIG. 4 can be obtained.

Further, in the case of a silicon photoreceptor under the same conditions, the photosensitive layer relative dielectric constant is 12, the charge retention soot layer relative dielectric constant is 3, and the image potential changes as shown in FIG. 5 are obtained.

As can be seen from Figures 3 to 5, both the unexposed area and the exposed area each have one maximum potential (however, in this example, the maximum potential), and the potential change is relatively gradual in that area. I understand. Therefore, it can be seen that near the maximum potential, even if the discharge gap changes somewhat, the image potential does not change much. Note that this maximum potential changes by changing the applied voltage. If the potential of the unexposed area changes, the background will change, so it is desirable that the potential of the unexposed area is as constant as possible with respect to the discharge gap, and the fluctuation of the maximum potential of the exposed area is In the case of gradation expression, it is necessary that the potential difference is within the range corresponding to one gradation.

Therefore, as shown in FIG. 1, for example, the allowable potential fluctuation with respect to the maximum potential, that is, the maximum potential with respect to the characteristic level of the unexposed area, is set to 61, and the discharge gap within the change range G1 of the discharge gap with respect to this potential fluctuation. If exposure is possible, the potential change in the unexposed area can be kept within the allowable range δ1. Similarly, if exposure can be performed at the discharge gap within the discharge gap G2 that falls within the potential fluctuation δ2 for a potential difference of one gradation with respect to the maximum potential, that is, the maximum potential, the potential fluctuation within the tolerance range δ2. It is possible to accommodate.

In this way, the present invention sets the discharge gap within 01 or within G2.
It was designed to be kept internally. Most preferably, if image exposure is performed in a discharge gap that satisfies both G1 and G2, potential fluctuations in both the unexposed and exposed areas can be kept within an acceptable range.

Although the image exposure has been explained with reference to the configuration shown in FIG. 2, the insulating layer 23 is laminated on the photoconductive layer 13, and the image is formed by causing discharge between the electrode 22 and the insulating layer. Even in such a case, the potentials of the unexposed area and the exposed area are determined in exactly the same way, so the present invention can be applied.

[Effect of Hathu]

As described above, according to the present invention, it is possible to keep the potential change in the unexposed area and/or the exposed area within the permissible range in response to fluctuations in the discharge gap, so it is possible to perform image exposure to obtain high image quality. becomes.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the image exposure method of the present invention, FIG. 2 is a diagram for explaining the configuration for performing image exposure,
Figures 3, 4, and 5 show the emission of unexposed areas when changing photoreceptors! FIG. 6 is a diagram showing a potential change with respect to a gap, and is a diagram for explaining a conventional static image recording method. IO: Photoreceptor, 13: Photoconductive layer, 2o: Charge retention medium, 23: Insulating layer. Applicant Dai Nippon Printing Co., Ltd. Agent Patent Attorney Masanobu Hirukawa (7 others) Figure 3 Figure 4

Claims (1)

[Claims] (1) In an image exposure method in which a photoreceptor and an insulator are placed in an electric field and an electrostatic latent image is formed on the insulator by discharge accompanying image exposure, the unexposed area and/or the exposed area in the discharge gap is 1. An image exposure method characterized by performing image exposure using a discharge gap in which the image potential of an unexposed area and/or an exposed area falls within a predetermined potential difference with respect to a maximum value of an image potential change characteristic of an area.