JPH03263062A - Color image forming device - Google Patents

Abstract

PURPOSE:To stably stick toner by equalizing the surface potential of the part exposing an image of an electrostatic latent image forming member to an arbitrary surface potential and then, carrying out developing. CONSTITUTION:A first electrification 11, an image-exposure 12, and a second electrification 13 are carried out in the moving direction of the electrostatic latent image forming member, at least following the above-mentioned order, on the surface of it. The multiple color electrifying grains 14-16 carrying out electrifying the same polarity as the electrostatic latent image forming member 111 are reversally developed and superimposed on the electrostatic latent image forming member. The surface potential of the part having the image-exposure 12 of the electrostatic latent image forming member 111 is equalized to the arbitrary surface potential, and then, the development is carried out. Thus, the dropping of the contrast potential in color-superimposing is eliminated and the image having a stable density is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application Field of the Invention First Friend of the Invention Regarding a color image forming method, in particular, electrostatic latent image formation and development are repeated multiple times on the surface of an electrostatic latent image forming member, and colored charged particles of different colors are electrostatically deposited on the surface of an electrostatic latent image forming member. The present invention relates to a method of forming a color image by stacking it on an electro-image forming member.

BACKGROUND OF THE INVENTION A well-known example of a color image forming method using the above-mentioned color image forming method is the apparatus described in Japanese Patent Application Laid-Open No. 60-95456. The following description is made with reference to the drawings.
The apparatus described in Publication No. 456 is explained in FIG. is a developer 50
9 is a pre-transfer charger; 510 is a pre-transfer exposure lamp; 51
1 is a transfer device, and 512 is a fixing device.Hereinafter, the electrostatic latent image forming member will be referred to as a photoreceptor, and the colored charged particles will be referred to as a toner. FIG. 6 is a flowchart of the operation of the apparatus shown below. First, the surface of the photoreceptor 501 is uniformly charged by the charger 502, and a first electrostatic latent image is formed by the image exposure device 504. The electrostatic latent image is developed and the first
A second toner image is formed. Furthermore, the photoconductor of Arashi 501 is charged, a second electrostatic latent image is formed by the image exposure device of 504, the electrostatic latent image is developed, and a second electrostatic latent image is formed.
A second toner image is formed.

In this way, repeated charging, image exposure, and development using a developing device each time are performed, and the spot positions of the previous image exposure and the spot positions of the subsequent image exposure are overlapped according to the color signal, thereby forming the image on the photoreceptor. However, the above structure has the following problems. Here, in the above configuration, a reversal development method is used in which toner is deposited at the image exposure position, and the potential difference between the development bias at that time and the surface potential on the photoreceptor in the area subjected to image exposure after charging is hereinafter referred to as contrast potential. 4 The problem here is that the contrast potential decreases when color overlapping is performed.This will be explained below. This is a diagram showing the amount of toner adhered per unit area.This diagram shows that the contrast potential fluctuates somewhat due to variations in the characteristics of materials such as the photoreceptor and toner, and environmental fluctuations such as temperature and humidity inside the copier. In order to obtain a stable amount of toner adhesion, the contrast potential must be at a certain level or higher (here, 500 V or higher). Changes in the surface potential of the photoconductor when toner is not attached to the photoconductor when changing the toner, and Charging, image exposure, and development are performed once to make the toner adhere to the photoconductor, and then the toner is further recharged. Changes in surface potential across the toner layer on the photoreceptor when the laser output is changed, and furthermore, charging, image exposure, and development are performed on the toner adhered to the photoreceptor to make the toner adhere, and the toner is removed. This figure shows the change in surface potential across the toner layer on the photoreceptor when the laser output is changed after further recharging.Here, yellow toner was used for the first development, and yellow toner was used for the second development Magenta toner was used for development. From this figure, it can be seen that the contrast potential decreases as the toner is charged, image exposed, and developed and stacked. This is true for the original toner with a constant development bias. This means that the more colors are overlapped, the worse the amount of adhesion becomes, which is different from the hue, saturation, and brightness of the image that should be obtained. It can be seen that the surface potential change across the toner layer when charged and the laser output is changed becomes saturated when the laser output is 1.5 mW or more, and the contrast potential at that time is 400 V or less. This means that sufficient image density is achieved. In order to obtain the contrast potential of 500
This means that the toner cannot be stably adhered to the photoconductor during the third development stage, whereas under these conditions, the hue, saturation, and brightness of the image may vary depending on the surrounding conditions. The above configuration had the above-mentioned problems.The present invention was developed in view of the above-mentioned problems.A color whose contrast potential does not change even when color overlap is performed. Means for Solving the Problems In order to solve the above problems, a color image forming method of the present invention is provided! The first charging, the image exposure, and the second charging are applied onto the surface of the electrostatic latent image forming member in the moving direction of the electrostatic latent image forming member.
A color image forming method in which multicolor charged particles charged to the same polarity as the electrostatic latent image forming member are superimposed on the electrostatic latent image forming member by performing reversal development in accordance with at least the above order, This method is characterized in that the surface potential of the image-exposed portion of the electrostatic latent image forming member is adjusted to a desired surface potential before development is performed.

Effect of the present invention With the above-described configuration, the surface of the photoreceptor whose potential has decreased due to image exposure is uniformly aligned by the second charging, thereby eliminating the decrease in contrast potential due to color overlapping, and as a result, the image has a stable density. It becomes an image.

EXAMPLE Hereinafter, one example of the color image forming method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. In FIG. 1, 11 is a first charging JR such as a corotron or scorotron, 12 is an image exposure means such as a semiconductor laser, and 13 is an image exposure means. a second charger 14 that adjusts the surface potential of the subsequent photoreceptor to an arbitrary potential;
15 and 16 are yellow (Y) and magenta (M), respectively.
Developer Sensei 1 with cyan (C) toner contained separately
8 is a transfer charger such as a corotron or scorotron for transferring the toner on the photoreceptor to the image receptor 19
110 is a conductive or dielectric transfer belt; 111
112 is a photoreceptor such as an organic photoconductor; 112 is a semi-immersed cleaning device such as a cleaning fur brush roll; and 113 is a photostatic eliminator, which is a developing means used in the present invention; non-contact type development in which the developer does not come into contact with the photoreceptor; The means are suitable.

Examples include powder cloud development and electric field development in which a voltage is applied between a toner carrier carrying a toner layer and a photoreceptor to cause the toner to fly. Among the above-mentioned electric field flying development, in particular, DC electric field flying where the voltage applied between the toner carrier and the photoreceptor is a DC voltage - The developed toner becomes difficult to fly back from the photoreceptor to the toner carrier. This is suitable because the developing means is not contaminated with different toners. Arrangement order of developing units (table) Taking into account the color mixing with other developing units due to toner spilling from the developing unit,
It is desirable that the toners be arranged in yellow, magenta, and cyan.Also, since the toners used in the present invention are stacked on the photoreceptor, at least the yellow and magenta toners have light transmittance to the light from the image exposure means. Is it suitable to have one? Q: The photoreceptor and toner used in the present invention are positive and
Since the present invention uses a reversal development method, the polarity of the two must be the same. Therefore, in one embodiment of the present invention, the photoreceptor is Since the organic photoreceptor is charged with a positive charge, the toner is positively charged. ) will be used to explain the present invention in detail. First, the surface of the photoconductor 111, which has been neutralized by a photostatic eliminator and cleaned by a cleaning device, has a neutralized potential.The first charger 11 uniformly applies a first charge to the surface of the photoconductor 111, thereby charging the photoconductor. As an example of the potential, it is set to 1200 V in advance in anticipation of the VE that takes into account the variation in the photoconductor charging potential due to color overlap (here, it can be arbitrarily set according to the round development conditions where the photoconductor charging potential is 1200 V). (2,1).

Thereafter, a first image exposure is performed by the image exposure means 12 to form an electrostatic latent image whose potential is lower than the charged potential of the photoreceptor (2.2). To the next number As shown in FIG. 4, taking into account the increase in the charged potential of the photoreceptor during color overlapping, the second charger 13 charges the photoreceptor after image exposure during two-color overlapping of yellow magenta toner. The exposure potential is adjusted to a potential VE higher than the highest image exposure potential (2.3). Next, the electrostatic latent image is subjected to first development using the first stage 14 of the yellow developer corresponding to the first image exposure among the developing means 14 to 16, and the toner is deposited on the photoreceptor 111. (2.
4). In the second rotation, the first charger 11 applies a second charge uniformly, and the surface potential of the photoconductor carrying the toner increases to 12
Set to 00V (2.5). Thereafter, a second image exposure is performed by the image exposure means 12 to form an electrostatic latent image whose potential is lower than the charged potential of the photoreceptor (2.6). A second charger 13 is connected to the electrostatic latent image so that the exposed potential portion of the photoreceptor after image exposure becomes VE in the same manner as after the first image exposure.
Align by (2.7). Next, the electrostatic latent image is subjected to a second development using the magenta developing means 15 of the developing means 14 to 16 corresponding to the second image exposure, and the toner is deposited on the photoreceptor 111 ( 2.8). In the same manner as the second rotation, the third rotation is again uniformly charged by the first charger 11, and the surface potential of the photoreceptor carrying the toner is set to 120[)V (2.9). Thereafter, a third image exposure is performed by the image exposure means 12 to form an electrostatic latent image whose potential is lower than the charged potential of the photoreceptor (2° 10).
. For the electrostatic latent image, the exposure potential of the photoreceptor after image exposure during color overlapping is adjusted to VE by the second charger 13 in the same manner as after the first and second image exposures (2.11) . Next, the electrostatic latent image is developed a third time using the cyan developing means 16 of the developing means 14 to 16 corresponding to the second image exposure, and the toner is deposited on the photoreceptor 111 ( 2.
12). By doing this, the photoconductor surface potential after the second charging of the photoconductor charged potential portion that has decreased due to image exposure can keep the above-mentioned contrast potential constant even when color overlapping is performed, and the toner can be stabilized. Finally, the toner adhering to the photoconductor is transferred all at once to the 19 image receptors conveyed by the 110 transfer belt using the 18 transfer chargers. According to this embodiment, first charging, image exposure, and second charging are performed on the surface of the electrostatic latent image forming member in at least the above order in the moving direction of the electrostatic latent image forming member (X In a color image forming method in which multicolored charged particles charged to the same polarity as the electrostatic latent image forming member are overlaid by performing reversal development on the electrostatic latent image forming member, imagewise exposure of the electrostatic latent image forming member is performed. The surface potential of the receiving area can be adjusted to a desired surface potential.As a result, the contrast potential does not change even when overlapping colors, and the toner can be stably attached. Using toner with the same polarity as the surface charge of the body, only the area where the image is to be formed is exposed, eliminating jitter in the background image outside of the image forming area, resulting in a beautiful background image.
When forming a character image with many non-image areas, the laser emission time is shortened, so the life of the photoreceptor and the image exposure means can be extended, making it efficient. When forming a character image using a charging device (Dai), the edge part of the character image can be formed in a shape that draws an arc outward, so the character image looks beautiful. Contact charging means are suitable. For example, when using a conductive bias roller, the background potential and the electrostatic latent image potential are made to be the same potential by the conductive bias roller. L% that adheres and makes it impossible to obtain a desirable copy image
For this reason, it is necessary to use a non-contact charging device such as a corona charger (especially a scorotron charger with high controllability of potential is preferable1). The first charging, image exposure, and second charging are carried out in at least the above order in the moving direction of the electrostatic latent image forming member (charging to the same polarity as the electrostatic latent image forming member) A color image forming method in which multicolored charged particles are superimposed by reversal development on the electrostatic latent image forming member, the surface potential of a portion of the electrostatic latent image forming member receiving image exposure being adjusted to an arbitrary surface. By performing development after aligning the potential, the contrast potential does not change when overlapping colors, and toner can be attached stably.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration of an embodiment of the present invention. FIG. 2 is an operational flowchart of an embodiment of the present invention. FIG.
Figure 4 shows the characteristics of the amount of toner deposited per unit area on the photoconductor with respect to the contrast potential. Characteristics 1 showing the surface potential of the photoreceptor when color overlapping is performed with respect to changes in . Figure 5 is a schematic diagram of the configuration of a conventional color image forming apparatus. Figure 6 is an operation flowchart of a conventional color image forming apparatus. 11... First charger 12... Image exposure means, 1
3...Second charger 14-16...Development half immersed 18
．． ,, Transfer charger 19. ,, image reception 110...
Transfer belt, 111...Photoreceptor 112...Cleaning semi-immersed 113...Optical static eliminator

Claims (1)

[Claims] First charging, image exposure, and second charging are performed on the surface of the electrostatic latent image forming member in at least the above order in the moving direction of the electrostatic latent image forming member, and the electrostatic latent image forming member A color image forming method in which multicolored charged particles charged to the same polarity are superimposed on the electrostatic latent image forming member by reversal development, the method comprising: A color image forming method characterized by performing development after adjusting the surface potential to a desired surface potential.