JPS60186881A - Two-color image forming device - Google Patents

Abstract

PURPOSE:To obtain a latent image having high-contrast electrostatic potential and reduce color mixing, by performing electrostatic charge, exposure potential, and developing processes for forming images of each color under a condition where an original and photosensitive body stand still by one scanning. CONSTITUTION:An electrophotographic copying machine is composed of a bipolar photosensitive body 20, image forming mechanism A, polarity matching electrode 28, transferring electrode 29, separating electrode 30, feeding device, cleaner 36, destaticizing electrode 37, etc. The image forming mechanism A consists of a black image forming mechanism A-1 and red image forming mechanism A-2 and two colored images of an original 38 are simultaneously formed on the bipolar photosensitive body 20 by the image forming mechanism A-1 and A-2. The black image forming mechanism A-1 and red image forming mechanism A-2 make scanning in a body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer using electrophotographic technology, and particularly relates to a two-color image forming apparatus.

[Prior art]

Although it is rare that a full-color copying function is required for an office copying machine, it is possible to make a two-color copy of a document with black text and red underlining, for example, in its original color. The need for capable two-color image forming devices has increased in recent years.

An example of a conventional two-color image forming apparatus will be described with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram thereof, and FIG. 2 is a schematic diagram thereof.

This is a process diagram. A two-color image forming apparatus has one bipolar photoreceptor1. First developer 2. Second developer 3. Eraser 4 and first charged electrode 5. Second charged electrode6. Filter 7° polarity matching electrode 8.
Transfer pole 91 Separation pole 10. Standby roll 11. Paper feed cassette 12. Paper feed roller 13. Transport bell 1-14. Fixing roll 1
5. It is composed of a cleaner 16, a removing electrode 17, and the like. In addition.

Reference numeral 18 indicates a document, and reference numeral 19 indicates an optical path for image exposure.

The two-color image forming apparatus configured as described above is as follows.

The photoconductor is uniformly charged to negative polarity by primary charging.
1) A first electrostatic latent image is formed by exposing the light image of the original 18 in two colors, for example red and black, to the photoreceptor 1 through the red filter 7a (FIG. 2-2). This first color electrostatic latent image is developed by the first developing device 2 to form a black image (FIG. 2-3).

Next, after performing secondary charging with the opposite polarity to the primary charging (
Fig. 2-4), a second electrostatic latent image is formed by performing image exposure through the cyan filter 7b, Fig. 2-5),
A red image is obtained by developing with a second developing device 3, and two-color images, red and black, are formed on the photoreceptor 1. After the polarities of the two colors of toner with different polarities are matched to one polarity using the polarity matching electrode 8 (FIG. 2-7), the toners are transferred from the paper feed cassette 12 to the paper feed roller 13.
The image is transferred all at once by the transfer pole 9 onto the paper fed by the standby roll 11 at the timing (FIG. 2-8). The paper on which the two-color image has been transferred is separated from the photoreceptor 1 by one separation pole 10, and then transferred to II by a +1R conveyor belt 14.
The image is fed, fixed by the fixing roll 15, and then discharged to the outside of the machine.

[Problems with conventional technology] In the two-color image forming apparatus configured as described above.

There were the following problems.

(1) When copying a two-color image, the photoreceptor must be rotated at least once for each color, so the copying speed is slower than in one-color copying.

(2) If the first color image and the second color image do not overlap completely, the image that should be a single color will be distorted, resulting in a double image of two colors, which will be unsightly.

(3) Even when you want to copy only one color, the area developed with the toner in the first color developer passes through the area of the second color developer, so the developer from the second color developer will not adhere unnecessarily. or the second color developer may rub off and cause 1
In order not to disturb the color image,
It is necessary to scrape off the developer on the sleeve with a scraper or to move the developing device itself away from the photoreceptor, making the mechanism complicated and costly.

(4) Since it is necessary to superimpose the two colors with high accuracy, it is technically difficult and increases the cost.

(5) Since the circumferential length of the photoreceptor must be longer than the maximum original size, the size of the photoreceptor becomes large and the entire machine becomes large.

(6) When obtaining a two-color image, minimum return cannot be performed and the copy speed cannot be increased. In other words.

Even if the document is of short length, the leading edge of the image must be aligned, so the timing is the same as the maximum document copying time.

(7) Since there is a time between copying the first color and copying the second color, contrast cannot be obtained unless the photoreceptor has a high potential retention rate, resulting in mixing of the two colors or a decrease in the density of one of the colors. The image is bad.

[Purpose of the invention]

In view of the above-mentioned conventional drawbacks, the present invention provides a charging method for forming images of each color while a document and a photoreceptor are stationary.

By completing the exposure potential and development steps in one scan, two-color copies can be made at the same speed as making single-color copies.

Abolishing the developer conveyance control or contact/separation mechanism in the developing device,
Furthermore, it is an object of the present invention to provide a two-color image forming apparatus that can reduce the precision required for optical scanning and can perform a minimum return for two-color copying.

[Key points of the invention]

In order to achieve the above object, the present invention simultaneously forms two-color images on an image forming member by an image forming mechanism consisting of a first image forming section and a second image forming section that can integrally scan. It is characterized by

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to two drawings. FIGS. 3 and 4 are configuration diagrams showing an embodiment of the present invention.

The electrophotographic copying machine has 1 bipolar photoreceptor 201 image forming mechanism A
, polarity matching electrode 28. Transfer pole 291 Separation pole 30. It consists of a feeding device, a cleaner 36, a removing electrode 37, and the like.

The bipolar photoreceptor 20 includes rollers 23a and 23b.

A belt-shaped photoreceptor having a predetermined inner diameter is stretched over 23C and can rotate in the direction of the arrow after one image is formed.

The image forming mechanism A includes a black image forming mechanism A-1 and a red image forming mechanism A-2, and the black image forming mechanism A-1 includes a first charging electrode 25, a first developing device 21, and a light source 39a. , a red filter 27a, and a focusing light transmitter 40a. Further, the red image forming mechanism A-2 includes a first charging electrode 26, a second developing device 21, a light source 39b, a cyan filter 27b, and a convergent light transmitting body 40b. Both can be horizontally moved while maintaining the mutual positional relationship of each component.

The feeding device consists of a standby roll 31, a paper cassette 32, and a paper feed roller 33, and takes out a large number of sheets stored in the paper cassette 32 one by one with the paper feed roller 33.
The paper is re-fed using the standby roll 31 in synchronization with the movement of the photoreceptor.

A transfer pole 29 transfers the toner image to the paper.

Then, the paper onto which the toner image has been transferred is sent to the fixing roll 35 by the TA transport belt 34, and the toner image is fixed onto the paper.

On the other hand, the bipolar photoconductor 20 after the transfer is transferred to the removal electrode 37.
After the residual charge is erased by the cleaner 36 and the residual toner is removed by the cleaner 36, the surface potential is reduced to approximately zero volts by the eraser 24, and the surface potential is set to approximately zero volts in preparation for the first copying cycle.

Next, the operation of the present invention will be explained with reference to the accompanying drawings.

FIG. 4 fa) shows the operation when performing two-color copying of the maximum original size. The document 38 and the bipolar photoconductor 20 are stationary in the image forming mechanism A, and the black image forming mechanism A-1 and the red image forming mechanism A-2 are still connected to the left side of the copying machine. (Figure 4 (al-■)).

Image forming mechanism A=1 and A by copy start signal
-2 scans in the right direction between the document 38 and the bipolar photoreceptor 20, which are stationary in a connected state (FIG. 4 (al-■)).

At this time, processes 1 to 6 shown in FIG. 2 are performed simultaneously, and a two-color image of the document 38 is formed on the bipolar photoreceptor 20 as a toner image between each color.

In this case, since the converging light transmitters 40a and 40b move while the original 38 and the bipolar photoreceptor 20 remain stationary, the precision required to superimpose the two-color images is much lower than in the past. .

When the formation of the two-color toner image is completed, the bipolar photoreceptor 20
At the same time, the image forming mechanisms A-1 and 8-2 also move to the left at the same speed or slightly slower than the bipolar photoreceptor 20 and return to the Bauhm position (fourth Figure fal-■).

At this time, if the single image forming mechanisms A-1 and A-2 move at a faster speed than the bipolar photoreceptor 20, the toner image will be disturbed, which is not preferable. It was formed on a bipolar photoreceptor 20. The two-color toner images are polarized by a polarity matching band pole 28 and transferred to a sheet of paper (not shown) by a transfer pole 29 .

FIG. 4 (bl is the operation when performing the minimum return of the image forming mechanism. In the conventional method shown in FIG. 1,
Minimum return is possible when using a single color, but full return is required when using two colors because tip alignment is required to perform separate optical scanning for each color. But 9
In the wooden sword style.

In order to form black and red toner images at the same time, the image forming mechanisms A-1 and Δ- are moved from the start position shown in FIG.
2 to perform exposure and development (Fig. 4 (bl)
-■) By returning to the home position at the same speed as the two bipolar photoreceptors 20 or at the predetermined speed difference mentioned above (see Fig. 4 fbl
-■), minimum return is possible during two-color image formation, and two-color copies can be obtained at the same copying speed as when monochrome.

Figure 4 (C1) shows the operation when copying only a black image. In response to the copy start signal, only the black image forming mechanism A-1 starts scanning, leaving the red image forming mechanism A-2 at the home position.

Create a toner image (Fig. 4 (C1-■)).

When the toner image formation is completed, two bipolar photoreceptors 2
0 and black image forming mechanism A-1 move to the left at the same speed or with a predetermined speed difference.

The black image forming mechanism A-1 remains stationary at the home position (
Fig. 4fc)-■).

On the other hand, the toner image is sent to a transfer process with the polarity matcher not operating and is transferred onto a sheet of paper (not shown).

As a result, when copying only a black image as in the conventional example shown in Fig. 1, the red developer is scraped off from the top of the developing sleeve to prevent it from adhering to the black toner image on the bipolar photoreceptor l. There is no need for a scraper mechanism or a mechanism for avoiding the red developing device, which simplifies the developing device mechanism and reduces costs.

FIG. 4 Fdl shows the operation when copying only the red image. The image forming mechanisms A-1 and A-2 (Fig. 4 (dl-■) that were stationary on the left side of the main body are moved to the right side without the black image forming mechanism A-1 performing image forming operation due to the selection of red copy. It moves and waits (Fig. 4 (di-■)). In response to the copy start signal, the red image forming mechanism A-2 performs scanning while forming a red image, and the bipolar photoreceptor 2
A red toner image is formed on 0 (FIG. 4 Fdl-■).

The bipolar photoreceptor 20 and the red image forming mechanism A-2 move to the left at the same speed or with a predetermined speed difference, and the red image forming mechanism A-2 remains stationary at the home position as shown in FIG.
)-■), the toner image is sent to a transfer section and transferred onto a sheet of paper (not shown). In this case as well, the polarity matcher 28 remains inoperative.

Incidentally, after the above process is completed, the black image forming mechanism A-1 moves to the left side, docks with the red image forming mechanism A-2, and comes to rest at the home position, as shown in FIG. 4 (dl-■). When making a single-color copy of a red image using the above operations,
Produces brightly colored copies without smudges caused by black toner.

As described above, according to the two proposed inventions, it is possible to provide a copying machine that can perform two-color copying and single-color copying without causing any difference in copying performance.

〔Effect of the invention〕

According to the two-color image forming apparatus of the present invention configured as described above, since the document and the bipolar photoreceptor are stationary and the convergent light transmitter moves, it is possible to superimpose the black image and the red image. There is no discrepancy at all.

Even if there is some variation in the pre- or start-up during scanning, it does not have a major effect on the image, so the scanning mechanism can be rough, and it does not have the precision required for conventional two-color or multi-color color copying machines. No special mechanism is required. Further, unlike the conventional method, a separate scanning process for each color is not required, and an image can be formed in one scan, and the copying speed is the same for two-color copying as for li-color copying.

Furthermore, since there is little time lag between the formation of the first image (black) and the formation of the second image (red), the potential of the bipolar photoreceptor hardly drops, creating an electrostatic latent image with high potential contrast. As a result, it is possible to obtain a two-color image with a deep red color and less mixing of the two colors.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional two-color image forming apparatus. FIG. 2 is a process diagram, FIG. 3 is a configuration diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing (al, (bl, fcl, (d
1 is a process diagram showing the operation of the embodiment of the present invention. Δ-1...Black image forming mechanism, A-2...Red image forming mechanism, 20...Bipolar photoreceptor, 21...First
Developing device, 22...Second developing device, 23a, 23b, 23C...Roller, 24...Eraser. 25...First charging electrode, 26...Second charging electrode, 27
a..., red fill 9. 27b... Cyan filter, 28... Polarity matching electrode, 29... Transfer pole, 3
0... Separate digging, 31... Standby roll, 32...
・Paper feeding power cent, 33...m4 JE roller. 34Il! Feed Held, 35... Fixing Roll. 36... Cleaner, 37... Eliminating electrode. 38... Original, 39a, 39b---Light source. 40a... Focusing optical transmission body, 40b... Focusing optical transmission body. Patent Applicant Casio Computer Co., Ltd. Same as above ID Co., Ltd. Representative Patent Attorney Yoshiyuki Osuga Figure 1 Figure 2 Figure 4 (0) ■ ■ Figure 4 (b) ■ ■

Claims (2)

[Claims] (1) An image forming mechanism consisting of a first image forming section and a second image forming section that can integrally scan the image forming section
A two-color image forming apparatus characterized by forming color images simultaneously. (2) The two-color image forming apparatus according to claim 1, wherein the first image forming section and the second image forming section are capable of scanning independently.