JPS6143709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to color electrophotography, and more particularly to a method for forming an electrostatic latent image on a recording medium that is corrected in accordance with color tone correction.

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

However, since the light absorption characteristics of each of the toners are not ideal, it is not possible to obtain a copy image in which a color original is faithfully reproduced by simply superimposing the toner images. For example, when reproducing a color original 1 consisting of a yellow area Y, a red area R, and a reddish-purple area M as shown in FIG. By mixing with the toner, the magenta toner reproduces the reddish-purple region M, but since the blue light that should be absorbed only by the yellow toner is also absorbed by the magenta toner, the red region R
The reproduced image becomes yellowish.

In order to prevent this, the amount of yellow toner to be deposited is the amount of yellow toner that should be deposited based on the blue separation image, minus the amount corresponding to the blue light absorption that occurs according to the amount of magenta toner deposited. However, in order to easily perform this color tone correction, an electrostatic latent image whose surface potential is controlled in accordance with the correction is formed on the recording medium to be developed by adhering yellow toner. It is necessary to encourage them. That is, as shown in FIG. 2, after the surface of the recording medium 2 having a photoconductive layer is uniformly charged, the yellow area Y and the red area R in FIG. However, as shown in FIG. 3, the electric potential V ₁ of the area corresponding to the red area R is higher than the electric potential V ₂ of the area corresponding to the yellow area Y, as shown in FIG. It is necessary to form an electrostatic latent image that is lower by a magnitude d that is inversely proportional to the amount of exposure. In the figure, the magnitude of the potential is conveniently indicated by + or - density.

However, it is theoretically very difficult to obtain an electrostatic latent image in which two pieces of image information are superimposed so as to cancel each other as shown in FIG. 3, but in practice it is very difficult. For example, in order to form an electrostatic latent image for forming a yellow toner image with the above-mentioned correction, theoretically, after charging the recording medium, the positive image of the blue separation image is exposed and the negative image of the green separation image is exposed. However, in practice, it is extremely difficult to expose negative images. Moreover, even if one directly converts the original into a negative image or uses reversal development to achieve substantially the same result as the exposure of the negative image, exposure of the positive image is also necessary. Since the image must have a negative-positive relationship, it is essential to perform reversal exposure in both cases. It is difficult to perform this reversal exposure using optical means.

It is an object of the present invention to produce an electrostatic latent image that is identical to that obtained when two three-color separation images of a color original are subtractively exposed onto the same photoconductive layer, and thus with no tonal correction. It is an object of the present invention to provide a method that can extremely easily form a copy image that has been made as it is. Next, an example will be described.

First, the ion flow control grid (hereinafter referred to as "screen") of the photoconductive layer used in the present invention will be explained. Generally, as shown in FIG. 4A, when one side of a mesh 4 having a large number of through holes 3 is charged positively and the other side is charged negatively, a peripheral electric field is generated in the space inside the through holes 3. Charged particles (ions) directed to pass through the through-holes 3 are affected by the strength and direction of this electric field, and for example, when cations are irradiated from one side of the network 4, the Ions pass through the through hole 3 and exit to the other surface, but in the case of anions, they are attracted to the positive charges on the one surface and their bonds disappear, and they cannot pass through to the other surface. On the contrary, the fourth
As shown in Figure B, if ions are irradiated from the other side, cations will be blocked and anions will pass through. The amount of ions that pass through varies depending on the strength of the peripheral electric field, that is, the amount of charge on the mesh body 4 and the magnitude of the electric field that promotes the ions to pass through the through holes 3.

FIG. 5 shows an example of a screen that controls ion flow based on the principle described above and can be suitably used in the present invention. This screen 5 has a photoconductive layer 7 provided on one side of a base 6 made of a metal grid having a large number of through holes, an insulating layer 8 on the other side, and a conductive layer 7 for bias on the surface of this insulating layer 8. A layer 9 is provided.

Hereinafter, a case where an electrostatic latent image including a color tone correction to be developed with yellow toner is formed will be described as an example.

In the present invention, as shown in FIG.
3, the photoconductive surface layer 12 is uniformly charged with a positive charge, and this charged photoconductive surface layer 1
2. The image of the color original is exposed through a blue filter. As a result, the photoconductive surface layer 12
A positive electrostatic image of a blue separated image due to positive charge is obtained, but of course this electrostatic image does not yet include the color tone correction, that is, it is in the potential state shown in FIG.

On the other hand, as shown in FIG. 7, the photoconductive layer of the screen 5 is uniformly charged with positive charges, and the image of the color original is exposed to the charged photoconductive layer 7 through a green filter. As a result, a positive electrostatic image of a green color separation image due to positive charges is obtained on the photoconductive layer 7. Next this screen 5
The ion source 1 is placed so as to face the conductive layer 9 for biasing.
0, the recording medium 13 is arranged so that its photoconductive surface layer 12 faces the photoconductive layer 7, and a positive bias voltage is applied to the biasing conductive layer 9 by the power source 14. While the conductor 11 of the recording body 13 is kept at a positive potential higher than the base 6 of the screen 5 by the power source 15, the power source 1
6, the ion source 10 is activated to emit negative ions 17 toward the screen 5 while scanning it. A positive image with positive charges is formed on the photoconductive layer 7 of the screen 5, and as described above, the amount of negative ions passing through a specific area of the screen 5 is determined by the amount of negative ions on the photoconductive layer 7 in that area. Since the amount of positive charge increases or decreases depending on the amount of positive charge, if an electrostatic image is not formed on the photoconductive surface layer 12 of the recording medium 13, it will be developed with a positive image of the green separated image due to negative charge, that is, with magenta toner. However, since a positive image of a blue separated image due to positive charges is formed on the photoconductive surface layer 12, an electrostatic latent image in which two electrostatic images are superimposed is formed. It is formed. Moreover, since the polarities of the charges on both electrostatic images are different, this is done in a destructive manner, and the potential distribution becomes the same pattern as shown in FIG.

Therefore, the electrostatic latent image obtained here is one in which the potential of the area where the magenta toner should adhere among the areas where the yellow toner should adhere is reduced, and by developing this electrostatic latent image with the yellow toner, , it is possible to obtain a yellow toner image in which the amount of blue light absorbed by the magenta toner is corrected.

Generally, when trying to subtractively superimpose the electrostatic image of the first image and the electrostatic image of the second image, a positive image and a negative image with charges of the same polarity are used as the husband's electrostatic image, or It is sufficient to use a positive image and a positive image or a negative image and a negative image using charges of mutually different polarities. However, in the present invention, as in the above-mentioned embodiments, the combination of the above-mentioned two types of electrostatic images can be achieved very easily without requiring reversal exposure.

That is, it is easy to form a positive electrostatic ^image of the first image on the photoconductive surface layer 12 of the recording medium 13 by exposure to light, which is a positive charge ^or a negative charge. Therefore, the electrostatic image of the second image to be combined with these images is a negative image + due to positive charges or a positive ^image due to negative charges for the electrostatic image ⁺ .
^- , and for an electrostatic image ^- , it is a negative ^image due to negative charges or a positive image ⁺ due to positive charges. In the present invention, the electrostatic image of the second image is formed by irradiating ions through the screen 5, and the polarity of the electrostatic image formed on the photoconductive layer 7 of the screen 5, that is, the exposure Since the charging polarity of the previous photoconductive layer 7 and the polarity of the ions from the ion source 10 are different, the positive electrostatic image is different from the electrostatic latent image of the photoconductive layer 7 on the photoconductive surface layer 12 of the recording medium 13. As a result, if the electrostatic image previously formed on the photoconductive surface layer 12 is ^positive , if the photoconductive layer 7 of the screen 5 is positively charged and exposed, if it is a negative ion, it becomes negative ^. began to form, and ^-
In this case, if the photoconductive layer 7 is negatively charged, ⁺ will be formed. In the end, only the photoconductive layer 7 is charged in accordance with the polarity of the electrostatic image of the first image, and other than that, an electrostatic latent image in which both electrostatic images are superimposed in a destructive manner is easily formed by normal operations. be able to.

The screen used in the present invention preferably has a structure as shown in FIG. 5, but it is also possible to use a four-layer screen as shown in, for example, Japanese Patent Publication No. 45-30320 FIG. 9B.

As detailed above, according to the electrostatic latent image forming method of the present invention, it is possible to easily obtain an electrostatic latent image that has been corrected in accordance with the color tone correction by an extremely simple method. There are extremely great benefits such as being able to obtain a copy image in which the original is faithfully reproduced.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a color original, Figure 2 A and B
3A and 3B are schematic explanatory diagrams and graphs showing potential states of electrostatic latent images without correction corresponding to color tone correction, respectively, corresponding to FIG. FIG. 4 is an explanatory diagram showing the operating principle of the screen used in the present invention; FIG. 5 is an explanatory sectional view showing an example of the screen that can be used in the present invention; 6 and 7 are explanatory diagrams of an embodiment of the electrostatic latent image forming method of the present invention. DESCRIPTION OF SYMBOLS 1... Color original, 2... Recording body, 4... Reticular body, 5... Screen, 6... Base, 7... Photoconductive layer, 8... Insulating layer, 9... Conductive layer for bias, 10 ...Ion source, 13...Recording body.

Claims (1)

[Claims] 1. Charging the photoconductive layer of a recording medium having a photoconductive layer, and exposing the charged photoconductive layer to one of the three color separation image information of the color original to correspond to a first color separation image. 4 layers having a large number of openings, each having a photoconductive layer on one side and a biasing conductive layer on the other side with a conductive layer in between. The photoconductive layer of the ion flow control screen of the configuration is positively charged when the electrostatic image formed on the photoconductive layer of the recording medium is a positively charged image, and negatively charged when it is a negatively charged image. 3. Coat the photoconductive layer on the color original.
A second electrostatic image corresponding to the second color separation image is formed by exposing the recording medium to another one of the color separation image information, and the recording medium is placed opposite to the photoconductive layer on which this electrostatic image is formed. the photoconductive layer of the recording medium through the ion flow control screen from the bias conductive layer side while applying a bias voltage that creates a deceleration electric field between the conductive layer and the bias conductive layer. A method for forming an electrostatic latent image, characterized in that the first electrostatic image and the second electrostatic image are superimposed on each other in a destructive manner by irradiating ions with a polarity opposite to that of the first electrostatic image. .