JPS6032188B2 - Electrostatic latent image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a static latent image on a recording medium according to image information obtained by combining a plurality of pieces of image information.

In general, the subtractive color method is widely adopted in color electrophotography, in which a color document is separated into blue, green, and red images using a three-color separation filter, and corresponding toners, yellow toner, and
The image is developed using magenta toner and cyan toner, and images formed by each toner are substantially superimposed to obtain a copy image that reproduces the color original.

However, since the light absorption characteristics of each of the above toners are not unique as shown in FIG. 1, it is not possible to obtain a copy image that is faithfully reproduced from a color original by simply superimposing the toner images. I can't. For example, when reproducing a color original consisting of a yellow region Y, a red region R, and a reddish-purple region M, the yellow region Y is to be reproduced using yellow toner, the red region R is to be reproduced by a mixture of yellow toner and magenta toner, and the red region R is to be red toner. The purple region M is reproduced with magenta toner, but since the blue light that should be absorbed only by the yellow toner is also absorbed by the magenta toner, the reproduced image of the red region R becomes yellowish. In order to prevent this, the amount of yellow toner that should be deposited by the blue separation image must be
It is sufficient to deposit an amount of yellow toner that reduces the amount corresponding to the blue light absorption that occurs depending on the amount of magenta toner deposited, but in order to easily perform this color tone correction, it is necessary to The surface potential (absolute value) on the recording medium corresponding to the correction
It is necessary to form an electrostatic latent image with a controlled decrease. The same problem as described above also occurs when a blue region is reproduced by superimposing magenta toner and cyan toner. That is, since the cyan toner also absorbs green light that should be absorbed only by the magenta toner, the reproduced image in the blue region becomes tinged with reddish-purple (magenta color).
In order to prevent this, the amount of magenta toner that should be deposited based on the green color separation image should be reduced by the amount corresponding to the green light absorption that occurs according to the amount of cyan toner deposited. However, in order to easily perform this color tone correction, it is necessary to form a static latent image on the recording medium to be developed by the adhesion of magenta toner, the surface potential of which is controlled in accordance with the correction. . In the fields of silver halide photography and printing, masking is commonly performed to reduce the influence of this type of unauthorized absorption.

Masking is often performed by superimposing negative and positive images of the original based on the original to be reproduced, depending on the incorrect absorption of cyan and magenta, and as in printing, many identical images are obtained from one plate. Although this method is effective in some cases, it is extremely time consuming and inefficient when obtaining a small number of identical images. In order to obtain a multicolor image using electrophotography, there is a masking method in which two types of electrostatic latent images are combined on a recording medium to form a latent image including color tone correction. For example, a recording medium consisting of a light guide layer is uniformly charged and exposed to image light to form an electrostatic latent image for color tone correction on the recording medium, and then an ion flow control grid is used to form an electrostatic latent image on the grid. There is a method of forming a main electrostatic latent image on the surface of the recording medium in accordance with the electrostatic latent image of the formed filter-decomposed image so as to overlap with the electrostatic latent image for tone correction. However, the above method requires image exposure not only to the ion flow grid but also to the recording medium, making the process extremely complicated. The method of the present invention utilizes the filter effect of the toner image layer formed on the recording medium against light of a specific color, without any imagewise exposure of the photoconductive recording medium, to achieve uniform charging and uniform charging. This method is characterized in that a static latent image for color tone correction is formed by uniformly exposing the recording medium to light of a specific color. The electrostatic latent image forming method according to the present invention will be explained in detail below.

First, a photoconductive ion flow control grid (hereinafter referred to as "screen") used in the present invention.

) will be explained with reference to FIG. As shown in FIG. 2, one surface of a two-layer screen 4 formed by adhering a photoconductive layer 3 to the lower surface of a base 2 made of a conductive material having a large number of through holes 1 is shown in FIG. 2A. As shown in the figure, when the other side is positively charged and the other side is negatively charged, a peripheral electric field is generated in the space inside the through hole 1, and depending on the strength and direction of this electric field, the electric field will pass through the through hole 1. For example, when the screen 4 is irradiated with intestinal ions from one side of the screen 4, the ions can pass through the through-holes 1 and escape to the other side, but the negative ions In this case, the bond is lost due to the positive charge on one surface, and it cannot pass to the other surface.

On the contrary, if ions are irradiated from the other side of the screen 4 as shown in FIG. 2B, positive ions will be blocked and negative ions will be able to pass through. The amount of passing ions is determined by the strength of the peripheral electric field, that is, the amount of charge on the screen 4, and the electric field that promotes the ions to pass through the through hole 1, for example, between the ion irradiation source and the recording medium that face each other via the screen 4. It changes depending on the magnitude of the electric field. An example of a screen that controls ion flow based on the above principle and that can be suitably used in the present invention is shown partially enlarged in FIG.

This screen 4 has a photoconductive layer 6 provided on one side of a base 5 made of a silk-like metal grid, an insulating layer 7 on the other side, and a conductive layer for bias on the surface of this insulating layer 7. It is made up of Embodiments of the present invention will be described below with reference to FIGS. 4A to 40 of the accompanying drawings.

Embodiment 1 In the case of reproducing blue color using cyan toner and magenta toner A case will be described in which an electrostatic image including a tone correction amount to be developed with magenta toner is formed.

As shown in FIG. 4A, the photoconductive layer 6 of the screen 4 is uniformly charged with a positive charge, and the charged photoconductive layer 6 is made up of a reddish-purple area M, a blue area B, and a cyan area C. The image of the color original 9 is exposed through a red filter 10 by a white light source 11, and a first electrostatic latent image of a red separated image is formed on the photoconductive layer 6 by positive charges.

Next, the screen 4 on which the first electrostatic latent image has been formed in this way is
As shown in FIG. 48, the biasing conductive layer 8 is arranged so as to face the ion source 12, and the photoconductive layer 6 has a photoconductive insulating layer 14 on the conductor 13. It is arranged so as to face 15. A positive bias voltage is applied to the bias conductive layer 8 of the screen 4 by a power supply 16, and the conductor 13 is maintained at a positive potential higher than the base 5 of the screen 4 by a power supply 17.
8 activates the ion source 12 to generate anions 19.
is scanned while being radiated toward the screen 4. As mentioned above, a first electrostatic port image due to positive charges is formed on the photoconductive layer 6 of the screen 4, and the amount of anions 19 passing through a specific area of the screen 4 is as follows.
As already explained with reference to FIG. 2, the amount of positive charge on the photoconductive layer 6 in that area increases or decreases depending on the amount of positive charge. As a result, a second electrostatic latent image of the red color separation image due to negative charges is formed.

After developing this second electrostatic latent image with cyan toner, a fourth C latent image is developed.
As shown in the figure, the entire surface of the recording medium 15 is uniformly charged with a positive charge having a polarity opposite to that of the second electrostatic latent image using an ion source 20, and the filter 15 is charged simultaneously with or after the charging process. ' is selected so that the toner used for the next development, that is, the magenta toner, obtains the green light that should originally be absorbed, and uniform filter exposure is performed. At that time, due to illegal absorption of green light possessed by the cyan toner, the cyan toner layer 2
1 produces the effect of a green filter, and the green light reaching the photoconductive insulating layer 14 of the recording medium 15 is influenced by the amount of cyan toner that has developed and adhered. Therefore, the positive charge generates a positive potential on the surface of the recording medium 15 with a strength approximately proportional to the base of the cyan toner developed and deposited on the recording medium 15. This is because the positive charges remain on the recording medium in a state approximately proportional to the amount of cyan toner, or the negative charges remain on the photoconductive insulating layer of the recording medium 15 in a state approximately inversely proportional to the amount of cyan toner. This is thought to be because it occurred on 14th. On the other hand, the positive charges on the surface of the recording medium to which the cyan toner has not developed and adhered are rapidly reduced by the uniform filter exposure, or the negative charges approximately the same amount as the positive charges are generated on the surface of the recording medium. The positive potential on the surface of the recording medium rapidly decays to zero potential. FIG. 4D shows the potential distribution of positive charges on the recording medium 15 shown in FIG. 4C.

For the above potential distribution, the filter 10' in FIG. 4C is selected so as to obtain the red light that should be absorbed by the toner, that is, cyan toner, attached to the recording medium 15, and uniform filter exposure is performed. It can also be obtained by After being developed with cyan toner and further charged with a positive charge proportional to the amount of the cyan toner layer 21 deposited on the recording body 15 as shown in FIG. 4C, the recording body 15 is shaped as shown in FIG. 4E. Then, the photoconductive layer 6 of the screen 4 is uniformly charged with a positive charge, and the image of the color original 9 is transferred to the photoconductive layer 6 using the green filter 1 as shown in FIG. 4A.
A bias guiding fin layer 8 is disposed opposite the photoconductive layer 6 to the screen 4 which is exposed to light through 0 to form a first electrostatic latent image of a green color separation image due to positive charges.
An ion source 12 is disposed so as to face the base 5 of the screen 4, and a positive bias voltage is applied to the bias conductive layer 8 by a power supply 16, and the conductor 13 is maintained at a positive potential higher than the base 5 of the screen 4 by a power supply 17. In this state, the ion source 12 is operated by the power source 18 to emit and scan the anions 19 toward the screen 4. A first electrostatic latent image of a green color separation image due to positive charges is formed on the photoconductive layer 6 of the screen 4, and the negative ions 19
Since the amount of ions passing through the screen 4 increases or decreases depending on the amount of positive charge on the photoconductive layer 6, the recorded image on the recording medium 15 is caused by the negative ions 19 passing through the screen 4. It is negatively charged in accordance with the electrostatic port image.
However, since the cyan toner on the recording medium 15 holds a positively charged electrostatic image approximately proportional to the amount of cyan toner attached,
The anion 19 on the cyan toner will neutralize or coexist with the positive charge. Therefore, the second electrostatic latent image of the green separated image formed on the recording medium 15 is reduced on the cyan toner, as shown in FIG. 4F, and is reduced approximately in proportion to the amount of cyan toner adhered. It will be done. Therefore, when the recording medium 15 is developed with magenta toner, the problem that the reproduced image in the blue region takes on a reddish-purple (magenta) tinge caused by incorrect absorption of green light by the cyan toner can be solved by the second latent image. This does not occur and good blue color reproduction is possible. Embodiment 2 The same procedure as in Embodiment 1 is applied to the case where a static latent image containing a tone complementary component to be developed with yellow toner is formed.

That is, in FIG. 4A, yellow area Y and red area R
A green filter is used as the filter 10 for the image of the color original 9 consisting of the and magenta region M, and as in Example 1, the first electrostatic charge of the green separated image is applied to the photoconductive layer 6 of the screen 4 by positive charges. Form a latent image, then 4th B
As shown in the figure, a second electrostatic image of a green separated image is formed on the recording medium 15 in the same manner as in Example 1. After developing this second electrostatic latent image with magenta toner, the ion source 2
Using a uniform positive charge caused by a river and a blue filter or a green filter as the filter 10', Example 1
Similarly, uniform filter exposure was performed on the recording medium 15 to form an electrostatic image with a positive charge proportional to the amount of magenta toner developed and adhered to the recording medium 15, as shown in FIG. 4E. The recording medium 15 is provided opposite to the photoconductive layer 6 of the screen 4 on which the first electrostatic latent image of the blue-separated image is formed, and as in Example 1, negative charges corresponding to the blue-separated image are generated by the anions 19. to charge the recording medium 15-.
At this time, the negative charges on the magenta toner are partially neutralized or coexist with the positive charges charged on the toner, and a static dew image containing good color tone correction is formed on the recording medium 15 as in Example 1. It was done. Example 3 When creating a color image by developing and depositing cyan, magenta, and yellow toners on the recording medium 15 in the order of cyan, magenta, and yellow, performing Examples 1 and 2 will prevent incorrect green absorption of cyan toner and magenta toner. It is possible to correct the color tone of incorrect blue absorption.

That is, first of all, it is possible to create an electrostatic liquid image for magenta toner development that includes a tone correction amount for irregular green absorption of cyan toner by the same process as in Example 1, and then to create an electrostatic liquid image for developing magenta toner. According to Example 2, the developed recording medium is uniformly charged with positive charges and uniformly exposed to light using a blue or green filter 10, and then a second ant electromagnetic group is formed as a separated image using a blue filter. By forming on the recording medium, a static latent image for magenta toner containing a tone correction amount for incorrect green absorption of cyan toner and a yellow toner developing image containing a color tone correction amount for blue incorrect absorption of magenta toner. An electrostatic latent image is formed, making it possible to reproduce good color tones. Embodiment 4 FIG. 5 shows a specific example of the actual mechanization of the electrostatic port image forming method of the present invention. The ion flow control type screen 4, which is held and rotates on the electrostatic drum 25 and has a first electrostatic latent image, controls the negative ions generated in the ion source 12 according to the principle described above, and transfers them to the recording medium 15 as a second electrostatic latent image. Form an electrostatic image.

As in Example 3, when forming a color image on the recording medium 15, the photoconductive layer of the screen 4 is positively charged with the ion source 26, and then a red separated image is exposed on the photoconductive layer through a red filter. Then, a first electrostatic latent image of the decomposed image is formed on the screen 4. Thereafter, a recording medium 15 having a photoconductive insulating layer is fed from a recording medium roll 27 to a conductive drum 2 holding the recording medium 15 on the surface of a conductive substrate.
5 and each layer of the screen 4 as shown in FIG. A second electrostatic port image of a red separated image is formed at 15 and developed by a cyan toner developer 29-C. Thereafter, the recording medium 15 is dried with warm air in the drying section 28, and the remaining static and hazy latent image is removed by the lamp 30. Ion source 20
As shown in Example 1 (FIG. 4C), the entire surface of the recording medium 15 is positively charged from the two ion sources, and immediately after that, the filter 10' is charged with a green or red color. The entire surface of the recording medium 15 is exposed by a lamp 31 selected to obtain light, and the cyan toner layer is charged with an electrostatic image with a positive charge proportional to the amount of cyan toner deposited on the recording medium 15. Thereafter, a first electrostatic latent image of a green color separation image is formed on the screen 4 in the same manner, and the recording medium 1 is
5, an ion source 12 emits negative ions to form a second electrostatic latent image with negative charges. The second electrostatic latent image formed by the above method is a second electrostatic latent image for magenta toner development that includes a color tone correction for incorrect green absorption of cyan toner. As described in Example 3 below, magenta development is carried out in the developing unit 29-M, and after drying, removal, and uniform positive charging of the entire surface, the filter 10' is selected to obtain blue light or green light. Then, the lamp 31 illuminates the recording medium 15.
After exposing the entire surface to light, a second electrostatic latent image of the decomposed image is formed on the recording medium 15 from the first electrostatic latent image of the decomposed image formed on the screen 4 using the ion source 12. A latent image for yellow toner development is formed, which includes color tone correction for the irregular absorption of blue by the magenta toner. Thereafter, the recording medium is developed with yellow toner by the developing device 29-Y, thereby completing the creation of a color image that has undergone color tone correction by masking processing of cyan, magenta, and yellow. In this apparatus, the recording medium can further be subjected to a development process using black toner in order to correct image sharpness and black reproduction. The screen used in the present invention preferably has the configuration shown in FIG. 5, but screens with other configurations may also be used as long as they achieve the same effect.
For example, a screen without a conductive layer for bias or Japanese Patent Publication No. 45-3032, Japanese Patent Application Laid-Open No. 7504-1982, U.S. Pat. No. 3,220,324 or 368
The screen described in US Pat. No. 0,954 can be used.

[Brief explanation of the drawing]

Figure 1 of the attached drawings is a graph showing the relationship between wavelength and reflectance for the three primary colors, Figure 2 is an explanatory diagram showing the principle of ion flow control by a screen, Figure 3 is a partially enlarged sectional view of the screen, and Figure 3 is a graph showing the relationship between wavelength and reflectance for the three primary colors. 4A to 4F are schematic diagrams illustrating color correction according to the method of the present invention, and FIG. 5 is a schematic diagram of a copying machine to which the method of the present invention is applied. 1...Through hole, 2, 5...Base, 3
．． 6... Photoconductive layer, 4... Screen, 7... Insulating layer, 8... Conductive layer for bias, 9... Color original , 10, 10'... Filter, 11... White light source, 12, 20, 26...
...Ion source, 13... Guide body, 14...
... Photoconductive insulating layer, 15 ... Recording body, 16,
17, 18... Power supply, 19... Anion, 21... Cyan toner layer, 25...
- Conductive drum, 27...Recording roll, 28
...Drying section, 29...Developing device, 30,
31...Lamp. Figure ↑ Figure 2 Heron Figure 3 Figure 4A Figure 48 Figure 4C Figure 4D Book 5 Figure 4E Figure 4F

Claims (1)

[Scope of Claims] 1. Uniform charging is applied to the surface of a photoconductive insulating layer forming one side of a screen for controlling charged particles, and a light beam image of an original to be copied is passed through a predetermined filter to After forming a first electrostatic latent image by directing it to the charged surface, a corona discharge is applied from the opposite side to the photoconductive insulating layer of the screen, forming within the apertures of the screen. The charged particles that are allowed to pass through the screen under the control of the fringe electric field are brought into contact with the surface of the other photoconductive insulating layer of the recording medium, which is placed opposite the irradiation source of the corona charged particles with the screen sandwiched therebetween. A color image corresponding to the original can be reproduced on the recording medium by forming an electrostatic latent image and repeating a cycle of developing the electrostatic latent image with a predetermined colored toner a desired number of times. In the color image forming method, the surface of the recording medium after development is uniformly charged with a polarity opposite to that of the second electrostatic latent image, or at the same time, after the uniform charging, a specific color light is applied. After uniformly exposing the toner image to form an electrostatic latent image on the toner image consisting of a charge distribution approximately proportional to the density of the developed toner image as described above, the charge flowing through the screen in the next cycle is A method for forming an electrostatic latent image, characterized in that the particles are made to overlap with the electrostatic latent image on the toner image. 2.Specific colored light to be applied to the surface of the recording medium after development processing,
2. The electrostatic latent image forming method according to claim 1, wherein the toner used in the subsequent development process uses colored light that should originally be absorbed. 3.Specific colored light to be applied to the surface of the recording medium after development processing,
2. The electrostatic latent image forming method according to claim 1, wherein the color light is determined to be originally absorbed by the toner that accomplishes the development.