JPH04215673A - Dichromatic image forming method and device thereof - Google Patents

Abstract

PURPOSE:To improve the reproducibility of a black color and shorten the copy generating time when generating a dichromatic copy of red and black from a dichromatic document of red and black. CONSTITUTION:A latent image formed by exposing the reflected light from a document on a photoreceptor drum 7 not via a color separating filter is developed with a magenta developing device 10. A color toner image obtained by this development is transferred on the transfer paper on a transfer drum. A latent image formed by exposing the reflected light from the document on the photoreceptor drum 7 via the red filter 5 is developed with a black developing device 8. A black toner image obtained by this development is overlapped and transferred on the color toner image of the transfer paper on the transfer drum. Only a magenta color toner is stuck on the transfer paper corresponding to the red portion of the document, a black toner is overlapped on the color toner on the transfer paper corresponding to the black portion of the document to be seen as a black color, and a dichromatic copy can be obtained.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to multicolor image forming apparatuses such as copying machines, facsimile machines, printers, etc., and more particularly to a method and apparatus for forming two-color images.

0002

BACKGROUND OF THE INVENTION In recent years, full-color copying machines and the like have three color developing devices each equipped with yellow (Y), magenta (M), and cyan (C) developers so that black-and-white copies can be made as before. There is a tendency for black developing devices equipped with a black developer to be installed in most countries. Under these circumstances, when copying an original that consists of two colors (for example, black and red), if a digital optical system is used, it is difficult to separate the colors in the image processing of the reading system. , it is possible to develop the black part with a black developer and the red part with a red developer (or M developer, or a combination of M developer and Y developer), but in the analog method, the black color Since separation is not possible (image processing is impossible), for example, a latent image formed using a filter corresponding to complementary colors of Y, M, and C is developed using three color developers of Y, M, and C. , superimpose this image to create a black color (
Process black) etc. are obtained.

0003

[Problems to be Solved by the Invention] The current market trend is that there are few full-color originals, and especially in the business field, two-color originals such as black and red are the majority. When copying such a two-color original using a multicolor image forming device that uses a digital optical system, the black areas are developed with black developer during image processing using color separation as described above, so it is possible to produce clear black images. However, when copying with an image forming device that uses an analog optical system, it is necessary to reproduce black with process black, and when the color balance of Y, M, C, etc. is disrupted, etc. There was a problem in that it was not possible to obtain a clear black color.

[0004] Furthermore, in a multicolor image forming apparatus that employs an analog optical system, black must be reproduced using process black, so one color other than black (for example, red) of the original can be reproduced using one color developer. Even if it is set to be reproduced with one exposure and development using only M developer (for example, M developer), it is necessary to repeat exposure and development three times in order to reproduce black color with process black. However, there was also the problem that the image forming time was increased.

The present invention has been made in view of the above-mentioned problems of the prior art, and its first object is to
In forming a two-color image consisting of two colors,
The purpose is to provide a two-color image forming method and device capable of reproducing a clear black color.The second purpose is to reproduce a color other than black with one color developer, and to create a two-color image forming method and an apparatus therefor that can reproduce a clear black color. An object of the present invention is to provide a two-color image forming method that can shorten the image forming time compared to the conventional method when forming a two-color image consisting of two colors.

[0006]

[Means for Solving the Problems] In order to achieve the first object, the invention according to claim 1 provides a two-color image forming method in which light from an original is transferred onto an image carrier without passing through a color separation filter. a first latent image forming step in which a latent image is formed by image formation exposure; and a step in which the latent image formed in the first latent image forming step is developed using a developing device equipped with a developer other than black. a second latent image forming step of forming a latent image by exposing light from the document to an image carrier through a color separation filter; , and a step of developing using a developing device equipped with a black developer. An apparatus implementing this method is, for example, a two-color image forming apparatus equipped with a black developing device equipped with a black developer, a color developing device equipped with a color developer other than black, and a color separation filter. an instruction means for instructing a two-color image forming operation using the black developing device and the color developing device; and an instruction means for condensing light from the document onto the image carrier through the color separation filter according to instructions from the instruction means. The latent image formed by image exposure is developed in the black developing device, and the latent image formed by image-forming exposure of light from the original onto the image carrier without passing through the separation filter. The image forming apparatus is characterized in that it has a control means for executing development in the color developing device. Preferably, this control device causes the color developing device to perform development before the black developing device. In order to achieve the above second object, the invention according to claim 4:
In a two-color image forming method in which a two-color image consisting of black and one color is reproduced using one color developing device equipped with a color developer, light from an original is passed through a color separation filter. A first latent image forming step in which a latent image is formed by image formation exposure on an image bearing member without using a liquid, and a developing process using a non-black developer to develop the latent image formed in the first latent image forming step. a second latent image forming step of forming a latent image by exposing light from the original onto an image carrier through a color separation filter; and the second latent image forming step. The method is characterized by the step of developing the latent image formed by using a developing device equipped with a black developer.

[0007]

[Operation] A latent image is formed by exposing light from an original onto an image carrier without passing through a color separation filter. This latent image becomes a charge pattern that allows the area on the image carrier corresponding to the non-white portion of the document to be distinguished from the area on the image carrier corresponding to the white portion of the document. By developing this latent image with a developing device equipped with a developer other than black, a toner image is formed in which color toner adheres to areas corresponding to areas other than the white background of the document. In addition, a latent image is formed by exposing the image bearing member to light from the original through a color separation filter. This latent image distinguishes between areas on the image carrier corresponding to the white background portion of the document and portions of the document having color components that pass through this color separation filter, and areas on the image carrier corresponding to other portions of the document. This results in a charge pattern that can be created. The black portion of the document is included in the latter area. By developing this latent image with a developing device equipped with a black developer, an area on the image carrier corresponding to a portion of the document that is neither a white background portion of the document nor a portion of the document that has color components that pass through this color separation filter. A toner image is formed with black toner attached to the surface. These toner images are superimposed on an image carrier or a transfer material to obtain a two-color image. In this two-color image, the part corresponding to the white background part of the original remains the ground color of the transfer material without adhering either black toner or color toner, and corresponds to the part of the original that has color components that pass through the color separation filter. Some parts have only color toner attached and are reproduced in color toner colors, while black parts of the document and parts of the original that have color components that do not pass through the color separation filter have both color toner and black toner attached and are reproduced as black. It will be reproduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color copying machine which is an image forming apparatus will be described. First, the overall outline of a color copying machine will be explained using FIG. In FIG. 1, an original (not shown) on a contact glass 1 is irradiated with an illumination device 2, and the reflected light passes through a scanning mirror 3 and a lens 4, and is color-separated by a color separation filter 5. The photoreceptor drum (OPC photoreceptor drum) 7 which is an image carrier charged by the photoreceptor 6 is irradiated by
Forms a latent image on the surface. Around the photosensitive drum 7, there are a black developing device 8 equipped with a black developer, a yellow developing device 9 equipped with a Y developer, a magenta developing device 10 equipped with an M developer, and a cyan developer equipped with a C developer. A device 11, a transfer drum device 13 for transferring a toner image onto a transfer paper fed from a paper feed device 12, and a cleaning device 14 are arranged. In the full color mode, the latent image formed by the blue component light produced by the color separation filter Blue is transferred to the yellow developing device 9 equipped with a yellow developer, which is a complementary color of blue, and the green component light produced by the color separation filter Green. The latent image formed by
The latent images formed by the red component light from the color separation filter red are each developed in a cyan developing device 11 equipped with a cyan developer, which is a complementary color to red.
It is possible to form toner images of various colors. A pre-transfer exposure section 1 is provided between the cyan developing device 11 and the transfer drum device 13.
5 is provided to lower the latent image potential and facilitate transfer. A pre-cleaning charger 16 is provided between the transfer drum device 13 and the cleaning device 14 to uniformly charge the toner remaining on the photoreceptor without being transferred, and the residual toner is charged to the cleaning sleeve of the cleaning device 14. It is cleaned and removed by the upper mag brush. Reference numeral 17 denotes a static eliminator, which lowers the potential of the photoreceptor drum 7 to approximately zero V.
This is to prepare for the next image creation. Transfer drum device 1
3 uses a dielectric film transfer drum, and a paper feed device 12
The transfer paper fed from the transfer paper is aligned with the transfer drum by the registration rollers 18, attached to the clamper of the transfer drum, and moved to the transfer position. By the action of the transfer charger 19, the toner image on the photosensitive drum 7 is transferred to a transfer paper, the transfer paper is brought into close contact with the transfer drum, and the transfer is repeated the necessary number of times (three rotations). When the transfer is completed, the transfer paper is separated from the transfer drum by releasing the clamper, and sent to the fixing device 20 where it is fixed and a color copy is obtained. In addition to the full-color mode described above, this copying machine has a black-and-white mode using only a black developing device, and a two-color color mode in which two-color image formation, which will be described later, is performed.

Next, the two-color mode will be explained. In the two-color mode in this embodiment, any one of the yellow developing device 9, magenta developing device 10, and cyan developing device 11 and the black developing device 8 are used to create two colors according to the operator's selection. It forms a copy of the . A selection switch (not shown) is provided which serves both to select the two-color color mode and to select a developing device to be used together with the black developing device 8. For example, the selection key for two-color copying using black developing device 8 and magenta developing device 10 is "black/red", and the selection key for two-color copying using black developing device 8 and cyan developing device 11 is "black/red"; The selection key for color copying is "black/blue", and the selection key for two-color copying using black developing device 8 and yellow developing device 9 is "black/yellow". If none of these selection keys is selected, it means that either full color mode or black and white mode is selected.

[0010] The operation will be described below when the "black/red" selection key, which is a selection key for two-color copying using the black developing device 8 and magenta developing device 10, is selected. When the "black/red" selection key on the operation panel is turned on and the print switch is turned on with the original set on the contact glass 1, first, the magenta developing device 10, which is a color developing device, is used. Start the process. Exposure for forming a latent image is performed without using a color separation filter. However, it is also possible to use a filter that does not have a substantial color separation function, for example, for adjusting the amount of light. The latent image formed by this exposure is a latent image in which only the charges on the photosensitive drum 7 corresponding to the white portion of the document are erased. Therefore, charges remain on the photosensitive drum corresponding to not only the black portion of the document but also color portions such as the red portion of the document. This latent image is developed by a magenta developing device 10. As a result, a toner image in which magenta toner adheres is formed on the photoreceptor drum corresponding to color portions such as black and red portions of the document. This toner image is transferred to the transfer paper on the transfer drum by the action of the transfer charger 19. Subsequently, a process using the black developing device 8 is started. Exposure in this process is performed using a red filter. The latent image formed by this exposure is
A latent image is obtained by erasing the charges on the photosensitive drum 7 corresponding to the white background portion of the document and the color components of the document that pass through the red filter, that is, the red, yellow, and magenta portions. Therefore, the charges on the photosensitive drum corresponding to the black, green, blue, and cyan parts of the original remain. This latent image is developed by a black developing device 8. As a result, a toner image in which black toner adheres to the photosensitive drum corresponding to the black, green, blue, and cyan parts of the document is formed. This toner image is transferred by the action of the transfer charger 19 so as to be superimposed on the magenta toner image already transferred on the transfer paper on the transfer drum, thereby obtaining a two-color toner image. When the transfer of the black toner image is completed, the transfer paper is separated from the transfer drum by a separating claw, is conveyed, passes through a fixing section, and is discharged outside the machine as a two-color copy. In this two-color copy, the green, blue, cyan, and black parts of the original, which are the overlapped parts of magenta toner and black toner, are reproduced as black, and the red parts of the original, which are the parts to which only magenta toner has adhered, are reproduced as black. The yellow and magenta parts are reproduced as magenta, a purplish red. In this way, the color of the original and the reproduced color of the two-color copy will be different, but normally the original to be copied in two-color copy mode is a two-color original, especially black and other colors. (If there are three or more colors, the operator naturally plans for at least one color to be copied in a different color from the original), and this black developing device 8
The two-color copy mode using the and magenta developing device 10 is suitable for copying originals in black and red colors (red, magenta), and such originals are used as office originals. is also the most common.

Similarly, when the "black/blue" selection key is selected, a two-color copy is formed using the black developing device 8 and the cyan developing device 11, and the process using the black developing device 8 is performed. In the process using the cyan developing device 11, exposure is performed using a blue filter, and in the process using the cyan developing device 11, exposure is performed without using a color separation filter. Further, when the "black/yellow" selection key is selected, a two-color copy is formed using the black developing device 8 and the yellow developing device 9, and a green filter is applied in the process using the black developing device 8. In the process using the yellow developing device 9, the exposure is performed without using the yellow separation filter.

In the above embodiment, the process using the black developing device 8 is executed after the process using the color developing devices 9, 10, 11 is executed, so that the process using the black developing device 8 is executed.
), the color toner 31 adheres to the transfer paper 30, and the black toner 32 is stacked on top of the color toner 31, so that the black color when visually inspecting the copy is clear;
Instead of this, the black will be a slightly shifted color, but on the contrary, as shown in FIG. The process using the color developing devices 9, 10, and 11 may be executed after the process using the black developing device 8 is executed so that the color developing devices 9, 10, and 11 are stacked.

Further, in the above embodiment, the colors of the two-color copy are formed by a process using one color developing device 9, 10, 11, but instead of this, two colors can be formed as needed. Colors may be formed by superimposing toner images using a developing device. For example, when forming a two-color copy consisting of black and red, a yellow toner image is formed by executing a process using the yellow developing device 9 and a magenta toner image is formed by executing the process using the magenta developing device 10. A red color may be formed by overlapping with. In this case, exposure is performed without using a color separation filter in both the process using the yellow developing device 9 and the process using the magenta developing device 10. In this case, the number of processes is three in total, including one process using the black developing device 8, and the required copying time is the same as in the full color mode.

Further, in the above embodiment, the combination of the color developing device to be used and the color separation filter used in the process using the black developing device 8 is uniquely determined, but instead of this, The color developing device to be used and the color separation filter to be used in the process using the black developing device 8 may be independently selected using selection keys. Further, in the above embodiment, a single photoreceptor drum is used, but a plurality of photoreceptor drums may be used, and the toner may be directly transferred from each photoreceptor drum onto the transfer paper. Further, the shape of the photoreceptor is not limited to a drum shape, but may be a belt shape.

[0015]

As described above, according to the invention according to claim 1 or 2, only color toner is attached to the portion corresponding to the document portion having color components that pass through the color separation filter, and the color of the color toner is changed. Both the color toner and the black toner adhere to the black parts of the original and the parts that have color components that do not pass through the color separation filter and are reproduced as black, making it possible to clearly reproduce black. I can do it. According to the third aspect of the invention, since the black toner is superimposed on the color toner on the transfer material, black can be reproduced more clearly. According to the invention according to claim 4, since a two-color image of black and color can be formed by forming a latent image twice and developing it, the image forming time is shortened compared to the case of reproducing black with process black. I can do it. Furthermore, the number of times the toner images are superimposed on the transfer material etc. is one time, which is less than three times when reproducing black using process black, which is advantageous in terms of positioning.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a schematic configuration of a color electrophotographic copying machine according to an embodiment.

FIG. 2 is a diagram showing a state in which color toner is attached to a transfer paper and black toner is superimposed on the color toner.

FIG. 3 is a diagram showing a state in which black toner is attached to a transfer paper and color toner is superimposed on the black toner.

[Explanation of symbols]

5 Color separation filter 7 Photosensitive drum 8 Black developing device 9 Yellow developing device 10 Magenta developing device 11 Cyan developing device 13 Transfer drum device

Claims (4)

[Claims] 1. A two-color image forming method, comprising: a first latent image forming step of forming a latent image by exposing light from an original onto an image carrier without passing through a color separation filter; A step of developing the latent image formed in the latent image forming step using a developing device equipped with a developer other than black, and a step of exposing light from the document to form an image on an image carrier through a color separation filter. a second latent image forming step of forming a latent image using a second latent image forming step; and a step of developing the latent image formed by the second latent image forming step using a developing device equipped with a black developer. A two-color image forming method. 2. A two-color image forming apparatus comprising: a black developing device equipped with a black developer; a color developing device equipped with a color developer other than black; and a color separation filter; an instruction means for instructing a two-color image forming operation using the color developing device; and an instruction from the instruction means,
A latent image formed by image-forming exposure of light from the original document on the image carrier through the color separation filter is developed in the black developing device, and the light from the document is passed through the color separation filter. 1. A two-color image forming apparatus, comprising: a control means for causing the color developing device to develop a latent image formed by image forming exposure on an image carrier. 3. The two-color image forming apparatus according to claim 2, wherein said control means causes said color developing device to perform development before said black developing device. 4. A two-color image forming method in which a two-color image consisting of black and one color is reproduced using one color developing device equipped with a color developer, in which light from an original is reproduced. a first latent image forming step of forming a latent image by image-forming exposure on an image carrier without passing through a color separation filter;
A step of developing the latent image formed in the latent image forming step using a developing device equipped with a developer other than black, and a step of exposing light from the document to form an image on an image carrier through a color separation filter. a second latent image forming step of forming a latent image using a second latent image forming step; and a step of developing the latent image formed by the second latent image forming step using a developing device equipped with a black developer. A two-color image forming method.