JPS60202456A - Color electrophotographic copying device - Google Patents

Abstract

PURPOSE:To prevent generation of ghost image and color shear by equalizing color quality of a destaticizing lamp to the light quality of the color separation and arranging three color developing devices in the order of Magenta, Yellow, and Cyan from the position of exposure. CONSTITUTION:A destaticizing device 7 consists of three chambers each housing a white fluorescent lamp 71, and each green, blue and red filter 81-83 is provided to each chamber. A sensitizing drum 3 is destaticized with green light, blue light, and red light after developing it in a first- third developing device contg. Magenta toner, Yellow toner, and Cyan toner, respectively. By this method, many numbers of color copy contg. no negative and positive ghost image nor color shear can be prepd. with high picture image density because of small light fatigue of the photosensitive body 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a color electrophotographic copying apparatus, and more particularly to an improvement in a static eliminating and developing device for a color electrophotographic copying apparatus.

PRIOR ART The process of making a color copy using a conventional color electrophotographic copying device will be explained with reference to FIG.
1) Irradiate the photoreceptor V ram (3) which is uniformly charged by K and is rotating in the direction of the arrow.

The electrostatic latent image thus formed on the photosensitive ram is transferred to the first developing device (4) containing cyan toner corresponding to the complementary color of red light.
1), and the obtained cyan toner image is transferred to copy paper wrapped around a transfer roll. The copy paper is taken out from the paper tray (9) in the direction of the chain line and wound around the transfer roll.

After the transfer, the photosensitive drum is cleaned by a cleaning device (6), and then the static electricity is removed by a static eliminator (7), and then the drum is subjected to a second color separation image creation process, for example, a green film.
After passing through the steps of color separation by a filter (22), image exposure, development by a second developing device containing magenta toner, transfer, cleaning, and charge removal, a third color separation image creation step, for example, color separation by a blue filter, and an image. Exposure, Yeo-)
After completing the development and transfer process by the third developer containing the toner, the copy paper is peeled off from the transfer roll, sent in the heeling direction, and fixed by the fixing device (10) to obtain a desired color copy.

The inventors of the present invention have confirmed the following fact in the static elimination process in the color copy making work as described above. First of all, it was found that the amount of space charge in the photoexcitation region of the photoreceptor largely depends on the absorption depth of the irradiated light by the photoreceptor, and that the absorption depth depends on the wavelength of the irradiated light. In other words, regarding the P-type photoconductor, when irradiating light that is strongly absorbed in shallow parts of the photoconductor surface, such as blue light, the positive space charge region inside the photoconductor increases, and ■ Penetrates from the surface of the photoconductor to the deep part. When irradiated with light such as red light, the negative space charge region inside the photoreceptor increases. This is the third
This will be explained with the help of figures: The upper part of Fig. 3 (A) is a diagram showing changes in the surface potential of the photoreceptor during the charging, exposing, and neutralizing steps and the next charging step when obtaining a yellow toner image using a blue filter. , the lower part is a diagram showing the charge distribution inside the photoreceptor corresponding to each process. In FIG. 3(A), when the surface of the photoreceptor is charged to a surface potential v0 and then imagewise exposed with blue light, an electrostatic latent image is formed on the surface of the photoreceptor and a large positive charge is generated inside the photoreceptor corresponding to the exposed area. A spatially charged area (Pl) is generated. This electrostatic latent image is developed with yellow toner, the resulting toner image is transferred to copy paper, and the surface of the photoconductor is cleaned. Then, when the static electricity is removed using a green light discharge lamp, the photoconductor The surface potential of the portion corresponding to the positively charged region is higher than the surface potential of the portion corresponding to the non-exposed portion.

Therefore, when charging is performed for the next image forming operation, the surface potential of the portion of the photoreceptor corresponding to the positive spatial charging area (P) is V. Since the potential becomes higher than that of ■H, if a toner image is created as it is, a so-called negative ghost will occur. ) in FIG. 3, the surface potential V. When a charged photoreceptor is imagewise exposed to red light, an electrostatic latent image is formed on the surface of the photoreceptor, and a large negative spatial charge region is generated inside the photoreceptor corresponding to the exposed area.

This electrostatic latent image is developed with cyan toner, and the resulting toner image is superimposed and transferred onto the previously obtained yellow toner image on the copy paper, and the surface of the photoreceptor is cleaned. When the charge is then removed using a green-light charge removal lamp, the surface potential of the portion of the photoreceptor corresponding to the negatively charged area becomes lower than the surface potential of the portion corresponding to the non-exposed area. Therefore, when performing the next charging,
The surface potential of the corresponding part between the negatively charged areas of the photoreceptor is ■
.

The photoreceptor in such a charged state exhibits the so-called positive J-st phenomenon.

For these reasons, when image exposure and charge removal are performed sequentially using blue, red, and green filters in a color electrophotographic copying machine, the light source for charge removal should have a light quality that includes at least the light quality of each image exposure ray, For example, it has been found that by using white light that includes all of blue light, red light, and green light, it is possible to prevent the occurrence of negative ghosts and positive ghosts.

The second fact confirmed by the present inventors is that when light that penetrates deeply into the photoreceptor, such as red light, is used as a light source for a static eliminator in the first color separation image forming step, optical fatigue of the photoreceptor occurs. occurs, which deteriorates the charge retention characteristics of the photoreceptor, resulting in an increase in the dark decay rate of the photoreceptor in the next color separation imaging process using a green filter, for example, and a decrease in the electrostatic contrast on the photoreceptor surface. The developed density of the image decreases, resulting in color shift in the final color copy obtained by superimposing three-color transfer. Furthermore, due to an increase in the dark decay rate of the photoreceptor, the image density of the copies gradually decreases when a large number of copies are made. That is, when light containing red light, for example, white light, is used as a static elimination light source, there is a drawback that light fatigue of the photoreceptor becomes noticeable.

Purpose of the Invention Based on the above-mentioned facts discovered by the present inventors, the purpose of the present invention is to provide a color copy that does not generate ghost images or color shift and does not reduce image density even when multiple copies are made. It is an object of the present invention to provide a color electrophotographic copying apparatus that can perform color electrophotographic copying.

Structure of the Invention The above-mentioned object of the present invention is to make the light quality of the static elimination lamp of the static elimination device equal to the light quality of exposure in each color separation process in each step of three-color separation image formation, and to This is achieved by a color electrophotographic copying apparatus characterized in that an i-zenta developer, a yellow developer, and a cyan developer are arranged in this order from the exposure position.

According to the present invention, in each step of the three-color separation operation, the light quality of the static elimination lamp is made equal to the light quality of exposure in each color separation step. That is, the first. When the respective exposures of the second and third color separation imaging steps are performed through green, blue and red filters, the light quality of the snow removal lamp after the respective imaging steps is changed to green light, blue light and red light. shall be.

By selecting the light quality of the static eliminating lamp in this way, it is possible to prevent the generation of negative d-st images and positive ghost images. In addition, static electricity removal using a red light source is only applied to static electricity removal after the completion of the red separation image formation process exposed to red light.
Since it is not used to remove static electricity after the color separation image forming process by green and blue exposure, the photoreceptor's capacity is reduced when making a single color copy, compared to conventional copying machines that always use white light containing red light. Light fatigue can be substantially suppressed.

In addition, the dark decay rate of the photoreceptor due to the light quality of the static elimination lamp is smaller in the order of red light, green light, and blue light, but the color separation static electricity immediately after static elimination has the highest dark decay rate. It is believed that sufficient electrostatic contrast can be obtained by developing the latent image at the position closest to the exposure position, and it is possible to avoid the effects of large dark decay of the photoreceptor. , green light, and blue light are used as light sources for static elimination in this order. On the other hand, as mentioned above, since it is required that the light quality of the exposure light source and the light quality of the static elimination light source in each color separation image formation process be made the same, the first color separation image formation process consists of green light exposure and magenta light exposure. Toner development/green light static elimination, the second color separation image forming process involves blue light exposure, yellow toner development, blue light static neutralization, and the third color separation image forming process involves red light exposure, cyan toner development, red light static neutralization. As a result, color copies with high image quality can be obtained.

An example of implementation of the present invention will be explained with reference to FIG.

Above the photosensitive drum (3), which is uniformly charged by the charging device (1) and rotating in the direction of the arrow, the green filter (21)
A color original image separated by color is exposed to green light, an electrostatic latent image formed on the photosensitive drum is developed with magenta toner by a first developer (41), and the obtained magenta toner image is transferred to a transfer roller (low) L/ (5) Transfer to the upper transfer paper.

After the transfer has been completed, the photosensitive drum is cleaned by a cleaning device (6), and then static electricity is removed by a static eliminator (7). The static eliminator contains white fluorescent light (71), and uses green light to eliminate static electricity using a green filter (81). Next, the photosensitive drum is uniformly charged by the charging device (1), and a blue filter (21) is used instead of the green filter (21).
22), the yellow toner image is created by the second developing device (42), transferred, and cleaned, and then reaches the static eliminator again. The static eliminator uses a green filter (81
) Instead, the photosensitive drum is neutralized with blue light using a blue filter (82). Similarly, red filter (23)
A third developing device (43) creates and transfers a cyan toner image, and then the transfer paper undergoes a fixing process to obtain a color copy. On the other hand, the photosensitive drum 9 undergoes a cleaning process and reaches the static eliminator (power), and the static electricity is removed by red light using a red filter (83) instead of the blue filter (82).

FIG. 4 shows another example of the static eliminator according to the present invention. (81), a blue filter (82) and a red filter (83), a first developer (41) containing magenta toner, and a second developer (41) containing yellow toner. 42) and a third developing device (43) containing cyan toner, the photoreceptor trim can be neutralized by green light, blue light, and red light.

Effects of the Invention According to the color electrophotographic copying apparatus of the present invention, negative and d-
This method has the advantage that a large number of color copies can be made with high image density because there is no generation of static images, positive ghost images, or color shift, and there is little optical fatigue of the photoreceptor.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional color electrophotographic copying device, Figure 2 is a diagram showing a conventional color electrophotographic copying device;
The figure shows a color electrophotographic copying apparatus according to the present invention, and FIG. A diagram showing the surface potential and internal charge distribution. Figure 3 (B) is a diagram showing the surface potential and internal charge distribution of the photoreceptor when a cyan toner image is obtained using a red filter. Figure 4 is a diagram showing the static elimination according to the present invention. It is a diagram showing another example of the device. Reference symbols in the figure: 1... Charging device, 21... Green filter, 22
... Blue filter, 23 ... Red filter, 3
...Photosensitive drum, 41...First developing device, 42...
- Second developing device, 43... Third developing device, 5... Transfer roll, 6... Cleaning device, 7... Static eliminator,
71... White fluorescent light, 81... Green filter,
82...Blue filter, 83...Red filter, 9...Paper tray, (3 other people)

Claims (1)

[Claims] In each process of three-color separation image creation, the light quality of the static elimination lamp of the static elimination device is made equal to the light quality of exposure in each color separation process, and the position of the three-color developer is changed from the exposure position to the magenta developer, yellow A color electrophotographic copying apparatus characterized in that a developing device and a cyan developing device are arranged in this order.