JPS62112168A - Color image forming method - Google Patents

Abstract

PURPOSE:To improve an intermediate gradation characteristic by forming a primary latent image forming stage of the 1st stage for making image exposing and electric discharge, 2nd stage for making image exposing and discharge weaker than in the 1st stage and 3rd stage for making discharge to maintain the uniform potential at which a toner does not stick to the surface of a photosensitive body. CONSTITUTION:The photosensitive body which has a color separating function member and of which the surface consists of an insulating layer is subjected to the primary electrostatic charging stage by the electric discharge and the primary latent image forming stage by image exposing and discharge and is then subjected repeatedly to the electrostatic image forming stage by uniform exposing of specific light and developing stage by color toners, by which the color image is formed thereon. The primary latent image forming stage in such a case is formed of the 1st stage to make image exposing and discharge, 2nd state to make the discharge weaker than in the 1st stage in succession of the 1st stage, and the 3rd stage for maintaining the uniform potential at which the toner does not stick to the surface of the photosensitive body. The color image is thus faithfully reproduced to medium densities without color deviation, color clouding and color tone deviation.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention relates to a color image forming method, and in particular, a color image forming method using a photoreceptor having a color separation function member and having an insulating layer on the surface. Regarding.

[Background of the invention]

The present inventors have previously described the above-mentioned color image forming method.
Figures 1 to 4 show examples of cross-sectional configurations, and Figures 5 to 7 show examples of the distribution shape of color separation filters in the filter layer, which is a color separation function member. We have invented a method for synthesizing color images on a photoreceptor without color shift by performing the steps shown in Table 1.

In FIGS. 1 to 4, l is a conductive member formed into an appropriate shape structure as required, such as a cylindrical shape or an endless belt shape, and 2 is a photoconductive layer made of an inorganic photoconductor or an organic photoconductor. ,
3 is an insulating layer including a layer 3a consisting of a distribution of minute color separation filters of red (8), green (CG), blue (B), etc. formed from various polymers, resins, etc. and colorants such as dyes. . The insulating layer 3 of the photoreceptor 4 in FIG. 1 is formed by attaching an insulating material such as a resin colored with a coloring agent onto the photoconductive layer 2 in a predetermined pattern by means such as printing. The insulating layer 3 of the photoreceptor 4 in FIG. 2 is the same as the insulating layer 3 in FIG.
The insulating layer 3 of the photoreceptor 4 in FIG. 3 has a transparent insulating layer under it, and the photoreceptor 4 in FIG. Insulating layer 3 of body 4
It has a transparent insulating layer on top of the insulating layer 3 shown in FIG.

The distribution shapes of the R2G, B filters, etc. in the filter layer 3a of the insulating layer 3 are not particularly limited, but the striped distribution shown in FIG. 5 is used for easy pattern formation, and the shapes shown in FIGS. The mosaic distribution shown in FIG. 3 is suitable for reproducing delicate multicolor images. And R,G
, B filter, etc., the length 1 shown by l in the figure.
A range of 0 to 200 μm is suitable from the viewpoint of image resolution, color reproducibility, and ease of forming a distribution pattern.

FIG. 8 shows the principle of forming a color image on the photoreceptor 4 as described above, and Table 1 shows the process by which colors in the original image are reproduced. Although FIG. 8 shows an example in which an n-type semiconductor photoconductor such as cadmium sulfide is used for the light guide W layer 2 of the photoreceptor 4, it is not possible to use a p-type semiconductor such as selenium. Even if there is, the basic color image forming process remains the same, only that the positive and negative signs of the charges in the following description are reversed.

In FIG. 8 (1), the photoreceptor 4 is uniformly discharged by the positive corona discharge from the charger 5? J[indicates a condition in which insulation ffl
A positive charge is generated on the surface of the photoreceptor 40, and a corresponding negative charge is induced at the interface between the photoconductive layer 2 and the insulating layer 3, and as a result, the surface of the photoreceptor 40 has a level as shown in the graph of the potential E. shows similar potentials. If it is difficult to inject charges into the photoreceptor 4 during charging, uniform irradiation with light may also be used.

FIG. 8 [2] shows, as an example, changes in the charged surface in a portion irradiated with the red image light IR in a state in which the above-mentioned charged surface is subjected to image exposure in the image exposure device flt6. The red image light IR passes through the R filter portion of the insulating layer 3 and reaches the photoconductive layer 2 below.
Since the 0 portion is made conductive, the negative charge at the interface between the light guide layer 1 and the insulating layer 3 disappears in that portion. On the other hand, G.

Since the B filter portion does not transmit the red image light IR, the negative charge of the photoconductive layer 2 remains in that portion. Other color component image lights of gJ exposure also give similar changes, although the corresponding filter portions are different. In this way, the insulating layer 3
A primary latent image is formed at the interface between the photoconductor #2 and the photoconductor #2, where each filter portion corresponds to the color component image light, resulting in a charge density. However, due to the action of the charger 61 of the image exposure device 6 which performs corona discharge of alternating current or direct current with the opposite sign to that of the charger 5, regardless of the amount of charge on the interface between the insulating layer 3 and the photoconductive layer 2,
That is, the surface potential of the photoreceptor remains constant, as seen in the graph of potential R, regardless of whether image exposure is applied or not. This is because the charge on the surface of the photoreceptor is distributed so as to be balanced with the charge on the interface. Changes due to the green and blue components of the image exposure give similar results, and the state in which they are integrated is the state in which the image light is applied by the image exposure device 6, and the next latent image is static in this direction. It does not function as an electronic image.

FIG. 8 [3] shows the above-mentioned image exposure surface being uniformly VC
It shows a state where N light is emitted. The blue light LB does not pass through the R and G filter parts, so it does not affect them much, but it passes through the B filter part and makes the photoconductive layer 2 below it conductive, thereby changing that part. Charges at the upper and lower interfaces of the photoconductive layer 2 are neutralized, and as a result, a potential pattern appears on the surface of the insulating layer 30 in the B filter portion, as shown in the graph, which gives a complementary color image of blue in the previous imagewise exposure.

FIG. 8 [4] shows a state in which a potential pattern formed by uniform exposure with blue light LB is imaged by a developing device fi8Y containing negatively charged yellow toner TY. The yellow toner TY only adheres to the B filter portions where the potential has changed due to the uniform exposure process, and does not adhere to the R and G filter portions where the potential has not changed. As a result, a color-separated one-color yellow toner image is formed on the surface of the photoreceptor 4. Although the potential of the part of the B filter to which the yellow toner TY is attached is somewhat lowered by development, the surface potential is not uniform as shown in the graph of the potential E.

FIG. 8 [5] shows that the charger 61 of the image exposure device 6 is applied to the surface of the photoreceptor 40 on which the yellow toner image is formed by the charger 9Y.
This shows a state where a corona discharge similar to that shown in the figure is performed. This discharge by the charger 9Y lowers the potential of the B filter portion to which the yellow toner TY is attached, and makes the surface potential uniform. The surface position of this photoreceptor 40 is shown in a graph.

Subsequently, this yellow toner image is formed in FIG.
] The surface of the photoreceptor 4 is uniformly exposed to green light obtained by a lamp and a green filter. As a result, the 8th
As described in FIG. 3, a potential pattern now appears in the G filter portion.

When this potential pattern is developed by a developing device containing magenta toner, the magenta toner adheres only to the G filter portion, forming a magenta toner image as shown in FIG. 8 [4]. As a result, two-color toner images are combined on the photoreceptor. Furthermore, a corona discharge is applied to this image forming surface using a charger in the same manner as in FIG. 8 [5] to make the surface potential uniform.

Subsequently, the surface of the photoreceptor 4 on which the two-color toner image has been formed is uniformly exposed to red light obtained from a lamp and a red filter, and the potential pattern appearing on the R filter portion is then exposed to cyan toner. By developing and forming a cyan toner image in the stored developing device, a color image without color shift or color staining is synthesized on the photoreceptor 4. For example, if the original image is a red image and the image exposure is red image light IR, In the case of R
Since no potential pattern appears on the filter portion and therefore no cyan toner image is formed even after development, the photoreceptor 4
The toner image formed above is a combination of the yellow toner image and the magenta toner image, resulting in a red toner image.

As is clear from the above, 1. Not only color images but also monochromatic images can be reproduced by the above-described process.

Table 1 shows the above color image forming process. In Table 1, the symbol "one" indicates an image pattern of charge density on the interface between the insulating layer 3 and the photoconductive layer 2 of the photoreceptor 4. what you can do,
The symbol "○" indicates that a potential pattern of an electrostatic image appears on the surface of the photoreceptor, and the symbol "■" indicates that a toner image is formed. The symbol "↓" indicates that the state in the upper column remains as it is. A blank field indicates that the image does not exist.

Also, "-" in the attached toner column means that no toner is attached, Y, )4. Cli indicates that yellow toner, magenta toner, and cyan toner are adhered to each other.

As already mentioned, a monochromatic image can also be formed by the steps shown in FIG. 8 and Table 1. However, the monochromatic image obtained by this method is caused by the fact that the reflectance of the color toner is higher than that of the black toner, or by the toner adhering to either one or two of the B, G, and R filter parts. Therefore, if the amount of toner adhered is small, the image density will be insufficient or the resolution will be even worse. Therefore, when forming a monochromatic image, uniform exposure is performed using white light, blue T green, or red light after image exposure to form a potential pattern on all of the B, G, and R filter portions, and the potential pattern Developed using one of the developing devices, or further developed using the method shown in FIG. 8 [4]K
As you can see, taking advantage of the fact that the surface of the photoreceptor 40 is not uniform, the images can be developed in a separate developing device.
A monochrome copying machine can form monochrome images with similar image density and resolution. This monochrome image forming step is
Shown in Table and Table 3. Table 2 shows the case where a developing device containing black toner is also provided.

On the other hand, Japanese Patent Publication No. 59-39740 and Japanese Patent Publication No. 39741 disclose a method of forming a monochromatic image with excellent intermediate gradation using a photoreceptor having a transparent insulating layer on the surface and no color separation function member.
It is known from various publications.

In this method, the surface of the photoreceptor is uniformly charged as shown in Fig. 8 [1], and the charged surface is exposed to imagewise light and the previous uniform charging has opposite polarity as shown in Fig. 8 [2]. This is carried out in three stages. In the second stage, the intermediate potential due to image exposure is increased, and in the third stage, only a part of this potential is removed, and then the image is In this method, an image is formed on the surface K of the photoreceptor by uniformly exposing the exposed surface, and this electrostatic image is developed with toner. This method is introduced in the Electrophotography Society Journal, Vol. 22, No. 1 (1983).
The present invention can also be applied to a color copying machine in which a toner image formed on a photoreceptor is transferred onto a transfer material and a multicolor image is synthesized on the transfer material.

However, when this method is used to form a color image on a photoreceptor having a color separation function member as described above,
In the step of forming the charge density image in FIG. 8 [2], a potential pattern is generated on the surface of the photoreceptor 4, and this potential pattern is superimposed on the potential pattern generated in the uniform exposure step in FIG. 8 [3]. However, in the developing process shown in FIG. 8 [4], the yellow toner TY adheres to the R and G filter areas other than the B filter area, which may cause color haze in the color image or transfer to the transfer material. The resulting color image will be biased toward the color of the toner used in the first development.

Therefore, in order to solve this problem, the present inventors formed a charge density image with excellent one-way gradation, and in addition, before uniform exposure, the potential pattern of toner adhering to the surface of the photoreceptor 40 was created. The present invention was achieved as a result of researching and discovering a method to achieve this state.

[Purpose of the invention]

The present invention provides a color image forming method in which a color image with excellent intermediate tonality is synthesized on a photoreceptor without color shift, color turbidity, or color tone bias.

(Structure of the Invention) The present invention provides: After performing a uniform charging step by discharge on a photoreceptor having a color separation function member and having a surface made of an insulating layer, and a step of forming a primary latent image by image exposure and discharge, In a method of forming a color image by repeating an electrostatic image forming step by uniform exposure to specific light and a developing step with color toner, the primary latent image forming step includes a first step of image exposure and discharge, and a first step of performing imagewise exposure and discharging. A second step of image exposure following the first step and a discharge weaker than the first step, and a third step of performing a discharge to bring the surface of the photoreceptor after the second step to a uniform potential to which toner does not adhere. A color image forming method is provided.

That is, in the image forming process explained in FIG. 8, the present invention includes a first step in which only the primary latent image step in FIG. By replacing the second step with image exposure and a discharge weaker than the first step, and the third step with a discharge that brings the surface of the photoreceptor after the second step to a uniform potential to which toner does not adhere, It is possible to reproduce a color image with excellent intermediate gradation quality, without any color shift, and without causing color distortion or tone bias.

(Example) The present invention will be described below with reference to the examples shown in FIGS. 9 to 15.

FIGS. 9 to 12 are schematic side views showing an example of an apparatus that performs the first to third steps instead of the primary latent image forming step of FIG. 8 [2]. Among these, the apparatus shown in FIG. 9 has a structure in which three scorotron corona dischargers are arranged in parallel, each of parts a to C, which perform discharge in the first to third steps, having an open back surface. The surface of the photoreceptor 40 facing the arc portion is charged more strongly than the surface of the photoreceptor 4 facing the portion b, for example, in the case of negative charging, a.

A high negative bias voltage is applied to the grid of the discharger in section C compared to the grid of the discharger in section B, and a.

The purpose is achieved by making the image exposure weight having the width of both slits enter the portion b and reach the surface of the photoreceptor 40. In this example, the same DC discharge voltage is applied to the discharge wires of the three dischargers, but different discharge voltages may be applied independently, or alternating current discharge voltages may be applied. The devices shown in Figures 10 and 11 are constructed by removing the adjacent partition walls of the three dischargers shown in Figure 9, and also removing the discharge wire of the middle discharger, making it a single discharger. . In the apparatus shown in FIG. 11, an alternating current discharge voltage is further applied to the discharge wire, the grid at 310 is grounded, and a positive bias voltage is applied to the grid at 5. Further, the device shown in FIG. 12 does not include the grid shown in FIG. 11, and instead applies a negative bias voltage to the casing outside the ape portion. In the apparatus shown in FIGS. 10 to 12, in addition to the bias voltage applied to the grid or the casing, the electric discharge wire is connected to the grid or the photoreceptor.
The fact that the distance on the 0 surface 1 is longer in the b part than in the 310 part also makes the discharge in the b part weaker than the discharge in the a part or even the C part.

The surface of the photoreceptor 40 is charged to a uniform potential by the charger 5 shown in FIG. 8 [1], and the charged surface is subjected to the incident light beam on the image side and discharge as described above by the devices shown in FIGS. 9 to 12. When this is performed, a primary latent image with excellent intermediate gradation is formed, and the surface of the photoreceptor 4 has no potential pattern, and specific light as shown in FIG. 8 [3] is applied to the surface. When uniform exposure is performed, a potential pattern with excellent intermediate gradation properties is generated in the corresponding filter portion of the surface of the photoreceptor.

@Figures 13 and 14 show potential changes on the surface of the photoreceptor in the above steps, and Figure 13 shows the image exposure and discharge in Step 9.1.
0.If the device shown in Fig. 12 is used, Fig. 14 will be the same as Fig. 11.
Each case is shown using the apparatus shown in the figure. 1st
3. In Figure 14, (:) indicates the original image density. -0,0,
(1) Acupuncture. -OJ, (Ilil beam, = 1.5
It is a potential change curve with respect to K. As can be seen from this figure, a potential pattern is generated on the surface of the photoreceptor due to the image exposure and discharge of part B to increase mesoscale brittleness, but this potential pattern is erased by the discharge of part C. , Only after uniform sawing using specific light is performed, an electrostatic image with excellent intermediate gradation properties as shown in the comparison of the curves (1) to (fil) will appear.

Here, the photosensitive light table r that appears due to uniform exposure of a specific light
It goes without saying that IfJt is the surface potential of the corresponding filter portion.

The rest is shown in Figure 8 [4] By carrying out the color image forming process in the same manner as described below, a color image with excellent intermediate gradation, without color shift, color unevenness, or tone bias is created. is formed.

For example, as shown in FIGS. 9 to 11, the voltage applied to the grid in the b section and the voltage applied to the grid in the a + 0 section can be adjusted in IN from the voltage applied to the grid in the a + 0 section to the ground.
If the discharge in the b part is made as strong as the discharge in the a part, a high-tone image can be obtained, and conversely, if the discharge in the b part is made weak, a soft-tone image can be obtained. A desired gradation can be obtained by changing the grid voltage of the b portion using the soft specifying member. It goes without saying that the gradation can be changed not only by adjusting the grid voltage, but also by adjusting the voltage applied to the discharge wire or the voltage applied to the side plates. Further, as shown in FIG. 15, the voltage can be adjusted automatically or manually depending on the document by operating a button or an operation panel, so that arbitrary gradation can be obtained.

FIG. 15 is a schematic configuration diagram showing an example of a copying machine that implements the color image forming method of the present invention. During one rotation in the direction, a multicolor image is formed by the following steps. That is, the charger 5 charges the surface of the photoreceptor 4 to a uniform potential, and the image exposure device 6 performs image exposure on the charged surface using self-irradiation light reflected from the document while exposing the surface of the photoreceptor 4 to an alternating current or charger 5.
Figures 9 to 14, which perform DC corona discharge with the opposite sign.
The action of the discharge device 620 as shown in the figure makes the surface level of the photoreceptor 40 approximately uniform as described above.

Next, this image-exposed surface is uniformly irradiated with blue light LB obtained by the lamp 7B, whereby a potential pattern that provides a complementary color image of blue appears on the image-exposed surface. This is developed by a developing device 8Y that stores yellow toner. Subsequently, the surface level of the photoreceptor 40 is made uniform by the action of the charger 9Y which performs corona discharge as described in FIG. 8 [5]. Next lamp 7G
Green glow obtained from K. is uniformly irradiated to form a potential pattern that provides a complementary color image of green, and a developing device 8M containing magenta toner develops the image, forming a two-color toner image on the surface of the photoreceptor 4. Similarly, the discharge of the charger 9M similar to the charger 9Y, and the red light LR obtained by the lamp 7R.
Uniform irradiation of cyan toner is carried out, and development is performed by a plastic forming device 8C containing cyan toner.

Through the above steps, a color image consisting of a composite of three-color toner images of yellow, magenta, and cyan is formed on the photoreceptor 4 with excellent gradation without color shift or color clouding. The color image formed as described above passes through the developing device 8 containing black toner, which is in an inactive state, without being developed, and is charged by the pre-transfer charger 14 and transferred. The image is easily transferred to the recording paper P fed from the paper feeder 15 by the transfer device 10. The recording paper P on which the color image has been transferred is separated from the photoreceptor 4 by a separator 11 (thereby, is sent to a fixing device 17 by a conveyance means 16, where the multicolor toner image is fixed, and is discharged outside the machine. After the color image is transferred, the surface of the photoreceptor 40 is deweighted by a static eliminator 12 that performs exposure and discharge, residual toner is removed by a cleaning device 13, and the state returns to the state where the next color image formation can be performed again.

In this copying machine, when the line drawing or gradation country designation button on the sweeping panel 20 is pressed depending on whether the original image is a line drawing such as text or a gradation drawing such as a landscape painting, the CPU 21 uses the information to select the line drawing or gradation country selection button. The voltage applied to the discharge device 62 of the image exposure device 6 is controlled so that a high contrast image or a soft contrast image is obtained.

In addition, in this copying machine, monochrome images of cyan and black are produced using photoreceptor 4.
At 0.01 rotation, the same density and resolution as in a conventional monochrome copying machine can be obtained, but other tables 2 and 3
The monochromatic image shown in the table is obtained by rotating the photoreceptor 402. In this regard, if the lamp 7B is configured to uniformly expose blue light using a filter, and the filter can be retracted,
All the monochrome images shown in Tables 2 and 3 can be formed by rotating the photoreceptor 401. The charger 9G and lamp 7 in FIG. 15 are used when further development is performed using the developing device 8K after the developing device 8GK is used for the purpose of enhancing the contrast of the color image, but these are omitted. It's okay. The lamp 7 is a lamp that performs uniform exposure with white light.

〔Effect of the invention〕

According to the method of the present invention, a color image can be faithfully reprinted at intermediate e-resizing without color shift, color staining, or color tone bias.

Note that a monochromatic image can also be formed using the present invention.

[Brief explanation of drawings]

1 to 4 are schematic partial sectional views showing examples of the R configuration of the photoreceptor used in the present invention, and FIGS. 5 to 7, respectively.
Each figure is a partial plan view showing an example of the distribution shape of color separation filters in the filter layer of a photoreceptor, and FIG. 8 shows a color image formed on the photoreceptor shown in FIGS. 1 to 7 without color shift. The process diagrams showing the filtering principle, Figures 9 to 12, are each in the middle? ! 1. Forms an excellent primary latent image of 1tK. Figures 13 and 14 are schematic side views showing an example of an apparatus for performing ζ-image exposure and discharge without creating a potential pattern on the surface of a photoreceptor; FIG. 15 is a schematic configuration diagram showing an example of a copying machine that implements the method of the present invention. l... Conductive member, 2... Photoconductive layer, 3...
...Insulating layer, 3a...Filter [hate, R
, G, B... Red-green, blue separation filter, 4... Photoreceptor, 5... Charger, 6... Image exposure device, 61... Charger, 62... Discharge device , 7B, 7G, 7R, 7K...Lamp, FB・
...filter, 8Y, 8M, 80, 8K...developing device, 9
Y, 9M, 9G...Obi'#L instrument, 20...
Operation panel, 21...CPU. 22... Drive circuit. '・Applicant Konishi Roku Photo Industry Co., Ltd. Agent Patent Attorney Haru Takashi '-゛, l, -/ 11M Figure 112 Figure 3 Figure 4 Figure 5! ! I Figure 6 Figure 7 Figure 1i9! I ■

Claims (3)

[Claims] (1) A photoreceptor having a color separation function member and having an insulating layer on the surface is subjected to a uniform charging process by electric discharge, and a primary latent image forming process by image exposure and electric discharge, and then uniformly exposed to specific light. In a method of forming a color image by repeating an electrostatic image forming step and a developing step using color toner, the primary latent image forming step includes a first step in which image exposure and discharge are carried out, and a step subsequent to the first step. A second step in which image exposure is carried out, a discharge weaker than that in the first step is carried out, and a third step is carried out in which a discharge is carried out to bring the surface of the photoreceptor after the second step to a uniform potential to which toner does not adhere. Color image forming method. (2) The color image forming method according to claim 1, wherein the discharge in the second step is controllable. (3) The color image forming method according to claim 2, wherein the discharge in the second step is made stronger when a high contrast image is designated by the designation information, and is weakened when a soft contrast image is designated.