JPS6013181B2 - Electrophotographic two-color copying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrophotographically copying two-color originals having images of black and specific colors other than black.

A document to be copied usually has characters, lines, etc. expressed in black. In such manuscripts, it is common practice to express parts that are particularly desired to be emphasized in red or underline them in red. Even if this is copied using an ordinary electrophotographic copying machine, the red part will be expressed almost identically to the black part, and the distinction by color coding cannot be reproduced. If a color copying machine is used, red parts can be expressed, but it is uneconomical to use a color copying machine for such originals. Under these circumstances, a copying machine capable of reproducing about two colors is expected to be a modern demand.

As an electrophotographic copying method capable of reproducing black and specific colors other than black, conventionally, as described in Tokusekki Publication No. 51-772, a high and low charge level difference is created between two colors, and a bias is applied. There are methods to obtain a two-color image by controlling development, methods to apply a general electrophotographic method such as that described in Tokukan Kai No. 48-102628, and to control dark color by a filter, A method is known in which latent images of two colors having different polarities are developed by a polarity reversal method as described in Japanese Patent No. 49-75332. However, in these two-color electrophotographic methods, even when developing a specific color, the latent image potential corresponding to the black image remains, so the specific color overlaps with the black, reducing the purity of the black color, and the toner This results in very dirty copies due to bleeding, misalignment of overlapping images, etc.

Particularly in those using color separation filters, since the black light absorption wavelength extends throughout the visible range, it is not possible to erase the latent image potential of a black image depending on the color separation filter. In addition, in the two-color development method using the so-called polarity reversal method, in which an insulating layer is provided on the surface of the photoreceptor, in the process of converting the two colors into positive and negative, the light intensity adjustment and charging conditions for the color signal of the original are extremely strict. Unless these conditions are satisfied, other specific colors will overlap with the black image. The two-color copying method according to the present invention uses two latent image carriers, forming a latent image corresponding to a black image on one and forming a latent image corresponding to a specific color image on the other, and developing these separately. After that, the developed images are aligned and transferred onto the same transfer paper in an overlapping manner. The two-color copying method according to the present invention is particularly characterized by the process of forming a bath image corresponding to a specific color image other than black.

This process forms a latent image corresponding to black on one latent image carrier, forms a latent image corresponding to black and a specific color on the other latent image carrier, and has a polarity opposite to that of the latent image. The surfaces of both latent image carriers on which latent images have been formed are aligned and brought into contact, thereby neutralizing and erasing the potential of the latent image corresponding to black, so that only the potential of the latent image corresponding to a specific color is retained. It consists of the process of leaving behind. According to this invention, a latent image corresponding to black and a latent image corresponding to another specific color are formed on separate latent image carriers and developed with toners of the respective colors. There is no loss of purity that makes it difficult to read, and there is no stain on the copy due to toner smearing or misalignment.

In general, a two-color original to be copied has mostly black parts, and therefore, a high purity of the reproduced black image is a condition for obtaining clear copies. Therefore, an object of the present invention is to provide an electrophotographic two-color copying method that can reproduce black images with high purity and clarity.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

For convenience of explanation, the specific color other than black is assumed to be red. First of all,
The red color development process will be explained step by step with reference to FIG.

'1} The first photoreceptor 1 is a conventional one in which a photoconductive insulating layer lb is provided on a conductive substrate la.

The surface of this photoconductive layer lb is uniformly charged to negative polarity by a corona discharger 2. This polarity may be positive depending on the physical properties of the photoconductive layer lb. (2) Next, a two-color original 3 having a white part 3a, a red part 3b, and a black part 3c, which are background parts, is illuminated by lamps 4 and 5, and a red filter 6 that passes red light through the regular twill of this original by known means. The surface of the photoreceptor is irradiated through the photoreceptor. Of the light reflected from the document, the light reflected from the white portion 3a and the red portion 3b passes through the filter 6 and is filtered onto the photoconductive layer l corresponding to these portions.
The region b is made conductive, and the negative charge held on the surface of the photoconductive layer is dissipated through the conductive substrate la. As a result, negative charges remain only in the surface area of the photoreceptor 1 corresponding to the black portion 3c. {3'Next, the surface of the second photoconductor 7, which is similar to the first photoconductor 1, is uniformly charged to a positive magnetism with a polarity opposite to the above-mentioned charging polarity using a corona discharger 8.

'4} A reverse image of the same original 3 is irradiated onto the surface of the photoreceptor 7 by lamps 4 and 5 through a cyan filter 9 that blocks red light. The positive charge on the surface of the photoreceptor 7 is dissipated in the area corresponding to the white part 3a of the document, and the positive charge is dissipated in the area corresponding to the white part 3a of the document, and the positive charge is
In the area corresponding to the black portion 3c, the reflected light from the original 3 does not act on the surface of the photoreceptor, so that it is held as it is on the surface of the photoreceptor. (5' Align the surface of the first photoreceptor 1 with the surface of the second photoreceptor 7 so that the black-corresponding port images are accurately overlapped, and bring them into contact with each other.

The respective black latent images formed on the surface of the second photoreceptor 7 and the first photoreceptor 1 are mirror images of each other and have opposite polarities, so the dews of both black latent images are neutralized and erased. be done. As a result, only the red latent image formed by the positive charges remains on the surface of the second photoreceptor 7. shelf
A negatively charged red toner 10 is supplied to the surface of the second photoreceptor 7 to develop a red latent image.

Next, the black developing process will be explained with reference to FIG.

'1} After the surface of the first photoreceptor 1 is de-exposed, it is uniformly charged to a positive polarity by a corona discharger 11.

This may be of negative polarity. ■ Photoreceptor 1 above
A reverse image of the same document 3 is irradiated onto the front surface through a red filter 6. As a result, a black latent image is formed on the surface of the photoreceptor 7. A negatively charged black toner 12 is supplied to the surface of the photoreceptor 1 to develop a black latent image.

The red toner image 10 on the second photoreceptor 7 and the black toner image 12 on the first photoreceptor 1 thus obtained are
As shown in the figure, the images are aligned and transferred onto the same transfer paper 13 in an overlapping manner.

Either toner image may be transferred first. Another red color development process will now be described with reference to FIG. 01
The surface of the photoreceptor 21 is uniformly charged to negative polarity by the corona discharger 22.

[2' Project the normal image of the two-color original 23 onto the surface of the photoreceptor 21 through the red filter 24 to obtain a black latent image on the surface of the photoreceptor 21.

{31 The black latent image is transferred onto the dielectric material 25 by a known static fin latent image transfer method.

[4' After removing the fins from the surface of the photoreceptor 21, it is uniformly charged to a positive polarity by a corona discharger 26.

'51 A reverse image of the original 23 is projected onto the surface of the photoreceptor 21 via the red light blocking filter 27, and the photoreceptor 21 is
1. Form red and black corresponding port images on one surface.

'61 The surface of the dielectric 25 is brought into contact with the surface of the photoreceptor 21 in such a way that both latent images corresponding to black are accurately overlapped, leaving only the latent image corresponding to red on the surface of the photoreceptor 21.

'71 A negatively charged red toner 28 is supplied to the surface of the photoreceptor 21 to develop a red latent image into red.

This step may include electrostatically transferring the red corresponding tank image to another dielectric, and then developing the red corresponding port image on this dielectric with a red toner. In order to perform two-color development using this red development process, the black development process may be performed using another photoconductor as shown in FIG.
Steps [1}, '21, and [31] in the figure may be performed first, and a static latent image for black development may be stored on another dielectric material.

Furthermore, in the red color development process, in order to erase the latent image potential corresponding to black color more effectively, various bias potentials may be applied to each photoreceptor or dielectric material.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing the red developing process in the two-color copying method of the present invention, FIG. 2 is a process diagram showing the black developing process, FIG. 3 is a process diagram showing the transfer process, and FIG. The figure is a step diagram showing another red color development process in the two-color copying method of the present invention. 1: First photoreceptor, 3: Two-color original, 6: Red filter,
9: cyan filter, 7: second photoreceptor, 10: red toner, 12: black toner. Rare 1st drawing, 2nd drawing, 1st drawing, 4th drawing

Claims (1)

[Scope of Claims] 1 The surface of a first photoreceptor is uniformly charged, and an erected image of a document having an image of black or a specific color other than black is passed through a filter that passes light of the specific color. , thereby obtaining an electrostatic latent image corresponding to a black image on the surface of the first photoreceptor, and irradiating the surface of the second photoreceptor, which is provided separately from the first photoreceptor, with the charging characteristics. is uniformly charged with opposite polarity, and a reverse image of the original is irradiated onto the surface of the second photoreceptor through a filter that blocks out the specific color, thereby creating electrostatic latent images corresponding to black and specific color images. The second statue above
the first and second photoreceptor surfaces are aligned and brought into contact with each other, thereby erasing the charge of the electrostatic latent image corresponding to a black image;
Electrophotography characterized in that only an electrostatic latent image corresponding to the specific color image is left on the surface of the photoconductor, and a toner of the specific color is supplied to the surface of the second photoconductor to reproduce the specific color image of the document. A method for reproducing specific colors other than black in a two-color copying method. 2 uniformly charging the surface of the first photoreceptor, irradiating the surface of the first photoreceptor with an erected image of a document having an image of black or a specific color other than black through a filter that passes light of the specific color; As a result, an electrostatic latent image corresponding to a black image is obtained on the surface of the first photoconductor, and the surface of the second photoconductor provided separately from the first photoconductor is uniformly charged with a polarity opposite to the charging characteristic. A reverse image of the document is irradiated onto the surface of the second photoconductor through a filter that blocks out the specific color, thereby creating an electrostatic latent image corresponding to black and specific color images on the second photoconductor.
the first and second photoreceptor surfaces are aligned and brought into contact with each other, thereby erasing the charge of the electrostatic latent image corresponding to a black image;
Leaving only an electrostatic latent image corresponding to the specific color image on the surface of the second photoconductor, toner of the specific color is supplied to the surface of the second photoconductor to reproduce the specific color image of the document, and After discharging the first photoreceptor, it is uniformly charged, and a reverse image of the original is irradiated onto the surface of the first photoreceptor through a filter that passes light of the specific color, thereby creating an electrostatic latent image corresponding to a black image on the first photoreceptor. 1
A black toner is supplied to the surface of the first photoconductor to reproduce a black image of the document, and a specific color image is transferred onto the first photoconductor and a black image is transferred onto the second photoconductor. A method for reproducing black and other specific colors in an electrophotographic two-color copying method characterized by reproducing black and other specific colors. 3. The surface of the photoreceptor is uniformly charged, and a reverse image of a document having an image of black or a specific color other than black is irradiated onto the surface of the photoreceptor through a filter that passes light of the specific color, thereby producing a black image. An electrostatic latent image corresponding to the above is obtained on the surface of the photoreceptor, and the electrostatic latent image on the surface of the photoreceptor is transferred to a dielectric surface provided separately from the photoreceptor, and the surface of the photoreceptor is
After the static electricity is removed, it is uniformly charged to a polarity opposite to the charged polarity, and a reverse image of the document is irradiated onto the surface of the photoreceptor through a filter that blocks the specific color, thereby producing black and specific color images. obtaining an electrostatic latent image on the photoreceptor surface corresponding to a black image, aligning the dielectric surface and the photoreceptor surface and bringing them into contact with each other, thereby erasing the charge of the electrostatic latent image corresponding to a black image; An electrophotographic two-color copying method characterized in that only an electrostatic latent image corresponding to the specific color image is left on the surface of the photoconductor, and toner of the specific color is supplied to the electrostatic latent image to reproduce the specific color image of the document. A method for reproducing specific colors other than black.