JPS5927903B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method that combines different images to form a desired image, and in particular, combines an original color separation image with a masking image to enable proper image reproduction. The present invention relates to an image forming method.

Conventionally, color reproduction used in the fields of printing, silver halide photography, and electrophotography is based on a subtractive color method.

Normally, for this color reproduction, cyan, magenta, yellow
These are the three primary colors, and dyes, pigments, etc. having each of these colors are used alone or in combination to reproduce the desired color. In order to achieve complete color reproduction using the three primary colors, the cyan, magenta, and yellow coloring materials are basically red light in visible light,
It is necessary to have ideal spectral reflection (or transmission) characteristics that completely absorb only green light and blue light in just the right amount.

However, for practical printing inks, color photographic materials, electrophotographic toners, and other coloring materials, their spectral reflection (or transmission) characteristics are as shown in Figure 1, and yellow absorbs unnecessary light. Although it is small, cyan absorbs a considerable amount of green light and a certain amount of blue light, and magenta absorbs a considerable amount of blue light.In other words, cyan is a mixture of ideal cyan, a considerable amount of magenta, and a certain amount of yellow. You can think of it as the same situation as you are. Furthermore, magenta can be considered to be the same as ideal magenta mixed with a considerable amount of yellow. Therefore, as long as a coloring material that absorbs unnecessary light is used as described above, accurate color reproduction cannot be obtained. A masking method has been put into practice in the printing field as a method for correcting errors due to color material characteristics.

A positive mask method used in color printing masking will be explained as an example. Color correction is performed by superimposing a light-density positive image (positive mask image) created from other color separation negative images onto a certain color separation negative image that requires correction at the stage of each color plate making process. . In such a method,
Two extra image forming steps are required to obtain a good one-color separated image.
It takes a process.

Moreover, the process is quite complicated and requires a certain amount of operator skill and time. Electrophotography is extremely effective for carrying out the above steps in that the image forming process can be completed in a short time and automatic processing is easy.

However, a process device capable of carrying out the above-mentioned masking step using electrophotography and achieving good image reproduction has not been realized.

Based on the research of the present inventors, one of the reasons why it has not been realized is that the image forming process requires both a negative image and a positive image, and it is difficult to reproduce both with good uniformity. It seems that attempts have been made to facilitate the reversal of negatives and positives through the development of new photosensitive materials and use them for image composition such as masking, but they are not yet at a stage where they can be put to practical use. In view of the above-mentioned points, the present invention aims to provide an image forming method in which different images are combined in a simple process to form a desired image.

To briefly describe the present invention, a step of forming a predetermined first electrostatic latent image on a first screen photoreceptor having multiple openings; a step of forming a predetermined electrostatic latent image on a second screen photoreceptor having multiple openings; This is an image forming method comprising: arranging a first screen photoreceptor and a second screen photoreceptor in a layered manner on a recording material, and applying an ion flow toward the recording material through these screen photoreceptors.

The details of the present invention will be explained below using specific examples with reference to the drawings.

First, a screen photoreceptor having multiple apertures to which the present invention is applied will be explained.

As will become clear from the following explanation, the screen photoreceptor in the present invention modulates a predetermined polarity charge flow (hereinafter referred to as ion flow) into an electrostatic image formed on the photoreceptor. Therefore, it goes without saying that the present invention is not limited to the specific example photoreceptor structure and process described below, and that various structures and processes can be used. The second illustrated screen photoreceptor 4 has a photoconductive layer 2 and an insulating layer 3 provided on a net-like base 1 made of a conductive material such as stainless steel or nickel.

The process of forming an electrostatic image on the screen photoreceptor 4 is illustrated in FIGS. 3a to 3c. First, the surface of the insulating layer 3 of the screen photoreceptor 4 is uniformly charged with a predetermined polarity (for example, negatively charged).

At this time, if a P-type photoreceptor is used for the photoconductive layer 2, positive charges can be injected and trapped at or near the interface between the insulating layer 3 and the photoconductive layer 2, even in a dark place, as shown in Figure 3a. obtain a state like this. Thereafter, when reverse polarity or AC charging is applied at the same time as image exposure, the charges trapped in the photoconductive layer 2 are released in the bright area L, as shown in FIG. 3b, and the charges are transferred to the surface. Negative charges are induced near the interface depending on the charged polarity.

On the other hand, in the dark area D, since the charges near the interface are trapped, the charge distribution remains approximately constant, although some of the charges on the surface of the insulating layer may be erased by reverse polarity charging. Next, by uniformly exposing the entire surface to light, the charges held on the surface or within the photoconductive layer are erased, as shown in FIG. is formed in the form of an image. Such an electrostatic image is caused by a flow of ions (meaning not only electrons but also gas ions and charged material particles) passing through the screen aperture.
) can be modulated and controlled well. FIG. 3d shows a mechanism for controlling the ion flow using an electrostatic image formed on the screen photoreceptor.

In the illustrated example, an electrostatic image corresponding to a positive image of the original image is formed on the recording material 7. In the figure, recording material 7
shows a recording material such as electrostatic recording paper comprising a chargeable layer 10 such as an insulating layer provided on a conductive support 9 which also functions as a counter electrode for the corona wire 8. The recording material 7 is arranged with the chargeable layer 6 facing the screen 4 side at an appropriate distance of 1 m 1 L to 10 m 1 L, while corona discharge serving as an ion flow source is performed by a corona wire 8, and at the same time the entire charged portion is give exposure to light. At this time, an electric field indicated by a solid line α is generated in the bright area of the photosensitive screen 4. This prevents corona ions from passing through the screen openings, and the corona ions flow into the exposed portion of the conductive screen 1. On the other hand, in the dark area of the photosensitive screen 4, the potential changes smoothly and continuously from the upper surface side to the lower surface side, and an electric field indicated by a solid line β is generated.

As a result, even though the corona ions have a polarity opposite to that of the electrostatic latent image on the photosensitive screen, they effectively reach the recording material 7 without canceling out the latent image. Then, if necessary, the electrostatic latent image created is visualized using a developer.
In order to obtain a positive original image in this manner, a voltage having a polarity opposite to the charge polarity on the surface of the insulating layer of the photosensitive screen is applied as shown in FIG. 3d. Conversely, to obtain a negative image,
The polarities of the power supplies 11 and 12 in FIG. 3d may be reversed. Further, as shown in FIG. 3d, when creating an electrostatic latent image on a photosensitive screen, when applying an AC voltage as a power source for the corona wire 8, it is necessary to apply a negative polarity voltage to the conductive support 9. A positive image can be obtained, whereas a negative image can be obtained by applying a positive polarity voltage. When the photoconductive layer 2 is an N-type photoconductive material, a positive image of the original image can still be obtained by performing all the charge polarities described in FIG. 3 with opposite polarities. Note that the dotted line in the figure indicates the flow of corona ions from the corona wire 8. Next, the method of the present invention will be explained in detail. To make the following easier to understand,
A case in which masking is performed during magenta development in color reproduction in which a color corrected image is obtained by combining an original color separated image and its masking image will be explained. Figure 4 shows an original manuscript with the following colors: green (G), yellow (7), red (8), magenta (goods), purple M, cyan (0, white (W), and black (BK)). 0 to green filter 1G.F
The first screen photoreceptor S1 is exposed to light through the color separation image, and a first electrostatic image corresponding to this color separation image is formed.

As explained in FIG. 3d, the electric field intensity is schematically shown by the number of arrows, with the direction of accelerating one ion, for example, of the electric field formed by the screen photoreceptor opening being in the direction of the arrow. Therefore, when an arrow is shown pointing toward one ion source, it means that it is acting as a blocking electric field.

In the figure, the insulating layer side of the screen photoreceptor is indicated by i,
The layout relationship has been clarified. The illustrated photoreceptor uses a P-type photoconductor, and after primary charging to O negative polarity, an electrostatic image is formed according to the process illustrated in the third figure.

The electric field formed in the dark area at this time later acts as an accelerating electric field. FIG. 5 shows a masking image formed using an N-type photoconductor for the photoconductive layer of the second screen photoreceptor S2, and a masking filter R. A second electrostatic image was formed by performing each process via F.

Therefore, the relationship between the electric field directions in the dark and bright areas of the screen is completely opposite. That is, in the screen photoreceptor S2,
An electric field is formed in the region where the light does not reach, which later acts as a blocking electric field. It is effective to appropriately adjust the electric field strength of the electrostatic image formed on each of these screens according to the amount of ion control. The screen photoreceptors Sl and S2, which have formed different color separation images of the original image in this way, are arranged with the insulating layer 1 side facing the recording material as shown in FIG. Emit 1 ion. The ions pass through the area indicated by the arrow on the screen photoreceptor S1 depending on the electric field strength. On the other hand, in the area indicated by the arrow on the screen photoreceptor S2, the passage of ions is blocked, so the original image of red (color), magenta (color),
Electrostatic charge images are formed in portions corresponding to purple (7) and black (BK). Of course, the amount of these ions passing through depends on the electric field strength of each screen. The voltages applied between the illustrated screen photoreceptors Sl and S2 and between the recording material are as follows:
It directs corona ions toward the recording material and also controls the amount of them passing through the screen. Therefore, the electrostatic charge image formed on the recording material has a considerable degree of freedom by adjusting the electric field formed on the screen photoreceptor and adjusting the voltage applied between the screen photoreceptors and between the recording material. Therefore, it is possible to fully and optimally adjust the spectral characteristics of the developer.

Furthermore, the screen photoreceptor used in the present invention allows image reproduction many times.

Examples will be described below to facilitate understanding of the present invention.

Example 1 In carrying out the above-described present invention, a screen photoreceptor S1 was produced as follows.

Se is vacuum-deposited onto a 250-mesh conductive screen made of stainless steel wire with a diameter of 30 μm so as not to cover the screen.

At this time, Se is attached to the conductive screen by vacuum evaporation so that the maximum thickness is approximately 70 μm. On the photoconductive layer of Se thus obtained, a solvent-type epoxy resin as an insulating material was further applied by spray coating to a thickness of about 10 μm and cured at 60° C. In this way, a screen photoreceptor having the cross-sectional configuration shown in the first figure is obtained. In addition to the above-mentioned materials, the insulating material may be formed by spraying polystyrene acrylic or the like with a thinner solution. The screen photoreceptor produced as described above is charged to -500V in a pre-charging process.

Next, using Color Patch (manufactured by Kodatsu) as the original image, a light image was irradiated through a green filter (Latten flat 58, manufactured by Kodatsu) at an exposure dose of 30 lux seconds, and at the same time, a negative current was A corona discharge is provided by an AC current through a 10 MΩ resistive member. Then, when the entire surface is exposed later, the surface of the insulating layer in the bright part of the image is +
An electrostatic latent image is obtained with a surface potential of 150V, 200V1 in dark areas, and -50V in halftone areas such as green. On the other hand, as the screen photoreceptor S2, a 200-mesh conductive screen made of stainless steel wire with a diameter of 40μ was mixed with CdS powder, which is generally used for electrophotographic photoreceptors, and a solvent-based epoxy resin as a binder at a ratio of 20% by weight. The solution is spray applied to the conductive screen without blocking the apertures.

Thereafter, it is dried and polymerized, and then the same resin as the binder is applied by spraying in the same manner so as not to block the openings to form an insulating layer. Next, an electrostatic latent image is formed with the polarity reversed from that of the screen photoreceptor S1. When the same original image as above is irradiated with a light image through a red filter (Ratsutenko 25, manufactured by Kodatsu) at an image exposure amount of 8 lux/sec, -100V is applied to the bright areas of the image, and +200V is applied to the dark areas. Obtain an electrostatic latent image consisting of the surface potential of . Next, the screen photoreceptor S1 was placed at an interval of 3 mm on a recording material formed by laminating 25 μm thick Mylar on an aluminum base.

This photoreceptor S1 was maintained at +2 KV with respect to the base. Next, a screen photoreceptor S2 is placed on this photoreceptor S, 3 m in the same manner.
They were placed at a distance of m. The photoreceptor S2 was maintained at +5 KV with respect to the photoreceptor S.

Further, a voltage of +7 KV was applied to a corona wire placed 15 mm above the photoreceptor S2 to generate a corona. As a result, each surface potential on recording material A is +5V at the edge, +400V at the red area, +390V at the magenta area, and -350V at the purple area.
The voltage was 0V in the cyan area, 0V in the white area, and +360V in the black area.

When the electrostatic image on this recording material was developed with a magenta wet developer, a good image was obtained. The above process was repeated 30 times, and the final image was also free of color loss.

As described above in detail using specific examples, the present invention is extremely effective because it can synthesize a plurality of different images through a simple process.

In particular, when the method of the present invention is applied to the masking of color separation images, it is possible to form a color corrected image in an extremely simple process and in a short time compared to the conventional color masking process, and is extremely superior. It is.

[Brief explanation of drawings]

Figure 1 shows the spectral characteristics of each color of practical color developers.
The figure is a sectional view showing a specific example structure of a screen photoreceptor applied to the method of the present invention. FIGS. 3a to 3d are process diagrams for forming an electrostatic image on a screen photoreceptor and recording an electrostatic image corresponding to the image on a recording material. Figures 4 to 6 explain the masking process of the original color separation image.
Each figure is an explanatory diagram of an electric field formed on a screen photoreceptor by separate image exposure of an original image. FIG. 6 is an explanatory diagram of the process of forming a composite image on recording material soil. In the figure, 1
2 is a conductive substrate, 2 is a photoconductive layer, 3 is an insulating layer, O is an original document, A is a recording material, Sl and S2 are screen photoreceptors, G. F is a green filter, R. F is a red filter.

Claims (1)

[Claims] 1 Step of forming a first electrostatic latent image on the first screen photoreceptor; Step of forming a second electrostatic latent image on the second screen photoreceptor; Recording the first screen photoreceptor and the second screen photoreceptor. modulating the ion flow by electrostatic latent images of the first and second screen photoreceptors;
An image forming method comprising forming an electrostatic charge image modulated by electrostatic latent images of first and second screen photoreceptors on the recording material.