JPS58211764A - Method and apparatus of two-color electrophotography - Google Patents

Abstract

PURPOSE:To provide 2-color electrophotography capable of executing 2-color copy faster than single color copy, by using 2 photoreceptors and raising movement speed of one of the photoreceptors and its exposure scan speed. CONSTITUTION:The first photoreceptor 1 used for a red image, the second photoreceptor 2 used for a black image, and the common optical system 13 are installed. When the 2-color image is formed, the photoreceptors 1, 2 are used, the system 13 is used to scan at V1 and 1/2 V1 speed. The photoreceptor 1 forms the red image, the photoreceptor 2 forms the black image on a transfer sheet 24 to form a 2-color image. When a single black image is formed, the second process alone is used. In that case, the first mirror and the second mirror are moved at V1, V2 speed, respectively, and a changeover mirror 20 is placed in the light path, and the second photoreceptor 2 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-color electrophotographic method and apparatus.

Methods and devices for reproducing or copying two-color images, such as red and black, using electrophotographic photoreceptors have been actively researched in recent years, and some have been put into practical use.

As an example of a two-color electrophotographic method, a method using a composite photoreceptor in which two photoconductive layers having different spectral sensitivities are laminated on a conductive substrate is disclosed in Japanese Patent Application Laid-Open Nos. 54-3537 and 1989-54- 1
43139, JP-A-54-147040, and the like. After these photoconductive layers are charged with substantially opposite polarities by primary charging and secondary charging with mutually increasing polarity, two-color light images are irradiated to charge the two-color reservoir electrostatically. A latent image is formed in each layer with opposite polarity, and these electrostatic latent images are developed with two-color toner charged with opposite polarity. Compared to other methods, it is simple and requires fewer steps. There are advantages. However, since a reverse electric field is generated around each electrostatic latent image, toners of different colors tend to adhere there, resulting in the formation of an edged toner image. Therefore, Japanese Patent Application Laid-Open No. 54-37746 discloses that two photoreceptors are used, two colors, for example, red, are formed using a composite photoreceptor, and black is formed using an ordinary photoreceptor. A method for forming a two-color copy by aligning and transferring both images onto a single sheet of transfer paper, and then fixing the two images has been shown. This has the advantage that good two-color copies without borders can be obtained.

By the way, in such a two-color electrophotographic method, unless development is performed with one color toner, a monochrome copy can be made, as a matter of course.

Furthermore, by forming a latent image using a normal black and white original and developing this with black toner, a black and white copy similar to that produced by a normal copying machine can be made. Since it would be expensive to have a normal black and white copying machine in addition to the two color copying machine, it is advantageous for the two color copying machine to also serve as a black and white copying machine. However, conventional two-color copying machines are mainly designed for two-color processes but also capable of monochrome processes, so the copying speed is limited by the two-color process. It's much slower than a copier.

Of course, it is possible to increase the copy speed in the case of monochrome copying, but this requires charging, exposure, development, transfer, static elimination,
The conditions for each process such as cleaning and fixing must be changed, which is not practical.

A primary object of the present invention is to provide a two-color electrophotographic method and an apparatus therefor, which allow monochrome copying to be performed faster than two-color copying without changing process conditions.

The purpose of this invention is to use a first photoreceptor for forming a chromatic image and a second photoreceptor for forming a black image, and to adjust the moving speed of the second photoreceptor to that of the first photoreceptor. This is achieved by making the scanning speed for image exposure on the second photoreceptor faster than that on the first photoreceptor.

Hereinafter, a major embodiment of the present invention will be described with reference to the accompanying drawings. In the figure, reference numeral 1 denotes a first photoreceptor for forming a chromatic color, for example, a red image, and reference numeral 2 represents a second photoreceptor for forming a black image. The first photoreceptor l is a composite photoreceptor in which two photoconductive layers with different spectral sensitivities are laminated on a conductive substrate, and rotates at a constant speed υ1, and around it,
Chargers 4, -jas 3 and 3', developing device 5, transfer charger 7, neutralizing charger 9, cleaning device 11
is located. The second photoreceptor 2 is a normal electrophotographic photoreceptor comprising a conductive substrate and one photoconductive layer sensitive to at least the chromatic color to be reproduced, and has a speed v2 higher than that of the first photoreceptor 1. It rotates at a constant speed, and around it,
A charging charger 4, a developing device 6, a transfer charger 8, a static eliminating charger IO, and a cleaning device 12 are arranged.

As a common device for these photoreceptor reservoirs, an image exposure optical system 1ψ is constructed above them. This optical system 1
Reference numeral 3 is a so-called mirror scanning type, which includes an original platen glass I5 on which the original 14 is placed, an exposure lamp 16 and a first mirror 17 arranged below it that move integrally at a speed υ1 or v2; velocity bvl or ]/2 in the direction
a second mirror 18 moving at a speed of v2, an imaging lens 19, an optical path switching mirror 20, and a right-angled third
Mirror 21. A third mirror 22 of the second photoconductor 2 and a filter 2 that transmits the chromatic light to be reproduced
Contains 3.

The first and second mirrors 17, 18 return to their original positions after moving in the direction of the arrows, although such reciprocating mechanisms and speed switching means are not specifically illustrated, as is usual for machines. It will be easily understood by those who have the knowledge.

The process of forming a red image using the first photoreceptor l is described in the above-mentioned Japanese Patent Laid-Open No. 54-3537 and Japanese Patent Laid-Open No. 54-1
Any of the techniques described in JP-A No. 43339, JP-A-54-147040, etc. can be used. First, the surface of the photoreceptor is charged to a predetermined polarity by the charger 3, and then charged to the opposite polarity by the charger 3', and the two photoconductive layers of the photoreceptor 1 are charged to substantially opposite polarities. Next, the two-color original 14 consisting of red and black on a white background placed on the original table glass 15↓ is illuminated by the exposure lamp 16 while the first mirror 17 moves at the same speed υ1 as the photoreceptor l and the /2τ1 is scanned by the second mirror (8), and its optical image is transmitted to the lens 1.
9 and the third mirror 2I onto the surface of the photoreceptor l. At this time, the switching mirror 20 is located outside the optical path as shown. By this light image irradiation, the electrical charge on the photoreceptor 1 is selectively erased, and an electrostatic latent image corresponding to the red image and an electrostatic latent image corresponding to the black image on the original 14 are formed with opposite polarity. be done.

Then, only this red latent image is developed by supplying red toner charged with the opposite polarity from the developing device 5.

In this invention, since the black latent image is not used at this time, it is preferable to control the charging voltage so that the potential of the latent image becomes approximately zero.

The red developed image thus formed is transferred to the transfer charger 7.
The toner image is stacked on the transfer paper 24 under , and is transferred onto the transfer paper 24 by being charged by the transfer charger 7 with the polarity on the side that attracts the toner image.

The scanning of the two-color original 14 at υ1 is completed. Then, the exposure lamp 16, the first mirror 17, and the second mirror returned to their original positions.
A second scan is performed by the mirror 18 at speeds υ2 and 1/2v2, and a black image is formed using the second photoreceptor 2. In this process, the usual Carlson method is used, and the switching mirror 20 enters the imaging optical path as shown by the chain line. When the surface of the second photoreceptor 20 rotating at a speed υ2 is charged to a predetermined polarity by the charging charger 4, the original platen glass 15 is moved by the first mirror 17 moving at a speed f2 and the second mirror 18 moving at a speed l/2v2. ''The second two-color original 14 is scanned. The imaging light flux that has passed through the lens 17 is reflected by the switching mirror 2o and the third mirror 22, and is irradiated onto the surface of the photoreceptor 2 through the red filter 23. As a result, only an electrostatic latent image corresponding to the black image on the two-color original 14 is substantially formed, and this is developed by supplying black toner charged to the opposite polarity to the latent image polarity from the developing device 6. . The black toner image obtained in this manner is transferred to a transfer paper 24 that is conveyed by a conveyance roller 25 and a timing roller 126.
Then, it is aligned with the red toner image already transferred thereon and transferred by the transfer charger 8. This alignment determines the time lag in both image formation by the distance from the light image irradiation position of the first photoconductor 1 to the transfer charger 7 and the transfer charger 8 of the second photoconductor 2, and the distance between the transfer charger 7 and the transfer charger 8 of the second photoconductor 2.
This can be done automatically by compensating for the distance from the light image irradiation position to the transfer charger 8 and the speed difference of the photoreceptors.

More preferably, in order to be able to sufficiently handle documents of different lengths or long documents such as B4 size and A3 size,
For example, the rotation and stopping of the timing roller 26 is controlled by a signal from a position detection sensor.

In this way, the transfer paper 24 on which both the red and black images have been transferred is separated from the second photoreceptor 2, enters the common fixing device 27, receives both images, and is discharged to the copy tray. be done. On the other hand, the photoreceptors 1 and 2, which have completed the transfer of their respective images, are each charged with a static elimination charger 9. After being neutralized by IO, residual toner is removed by cleaning devices 11 and 12.

When such a copying machine is used to obtain monochromatic black and white copies, only the latter process described above is performed. That is, the speed of the first mirror and the second mirror is υ2.
and 1//2v2, and the switching mirror 2o enters the optical path. If the original 14 is a two-color original of red and black on a white background and a black and white copy with the red image removed is to be obtained, a red filter 23 is interposed. If it is desired to reproduce both red and black images of a two-color original as black images, a 777-color filter is used instead of the red filter 23.

Furthermore, if it is desired to obtain a black-and-white copy using a normal black-and-white original instead of a two-color original, the red filter 23 is removed from the optical path. In either case, single-color copies can be obtained without significant changes in the conditions in the two-color process, and at a faster rate than in the two-color process.

The diameters of both photoreceptor drums 1 and 2 are both 80 mm, and the peripheral speed v1 of the first photoreceptor drum 1 is 150 mm/s.
ee.

The circumference and speed υ2 of the second photosensitive drum 2 are 300 mm/sec.
Then, υ1 and υ2 of the male optical system are set to the same values,
An experiment was conducted using an A4 size horizontally fed original. A 550 W halogen lamp is used as the exposure lamp 16, and the structure of the first photosensitive drum 1 and the process thereof are the same as those described in Japanese Patent Laid-Open No. 54-56445. In this case, since a black latent image is not used in this invention, the secondary charging voltage was controlled so that the surface potential at the end of secondary charging became zero. The first photoreceptor drum 2 was a normal Se-'f'e type photoreceptor having panchromatic spectral sensitivity, and a dichroic ink filter was used to improve the color sensitivity. When I made a two-color copy using such a device, the copy speed increased by 13.
．． 3 cpm was obtained. When red monochrome copying was performed using the first photosensitive drum 1, a copying speed of 20 cpm was obtained. Furthermore, when monochromatic black copying was performed using the second photosensitive drum 2, a copying speed of 40 cpm was obtained. First photoreceptor drum l
When monochromatic red copying was carried out at a speed of 3 oomm Aec using the following, sufficient potential contrast could not be obtained due to insufficient light intensity. Also, for comparison, a half mirror was provided at that position instead of the switching mirror 20, and the luminous flux from one exposure was transferred to 2/3 on the first photoreceptor drum 1 side and 1/3 on the second photoreceptor drum 2 side. The copy speed was similarly 13.3 cpm, but in this case, unless the process conditions were changed, monochromatic red and monochromatic black copies would also be (3,3 cpm). 3 cpm.Thus, according to the method and apparatus according to the invention:
For monochromatic black copies, copies can be made at a speed about three times faster than in the past.

As described above, according to the present invention, it is possible to achieve higher speed of monochrome copying without changing the main process conditions, but since two photoreceptors are used, it is also possible to combine images of two types of originals. . That is, a first original is used to form an image on the first photoreceptor drum, a second original is used to form another image on the second photoreceptor drum, and both images are combined into one sheet. Transfer the image to transfer paper and synthesize the image. It is preferable to use an automatic document feeder (ADF) to exchange both documents. In this method, in addition to the red and black two-color original, it is also possible to use a black and white original.
As described in Japanese Patent No. 56445, secondary charging in the red image process may be stopped. In addition, this invention can be modified in various ways using known techniques, for example, by replacing the mirror scanning type with a synchronous movement type optical system. All such modifications within the scope of God are intended to be included in this invention.

[Brief explanation of the drawing]

The figure is a schematic diagram showing an embodiment of the present invention. 1... 1st photoconductor, 2... 2nd photoconductor, 3.3',
4. Charger, 5, 6. Developing device, 7.
8... Transfer charger, 9.10... Static elimination charger, 11.12... Cleaning device, 13 - Image exposure optical system, 2o - Switching mirror, 27... Fixing device.

Claims (1)

[Scope of Claims] 1. On a first photoreceptor having two photoconductive layers having different spectral sensitivities on a conductive substrate-1-, two times of charging with mutually opposite polarities, one time of image exposure, and A process of performing development to form a chromatic image; and a process of performing a single charge, image exposure, and development to form a black image on a second photoreceptor having one photoconductive layer on a conductive substrate. In a two-color electrophotographic method for obtaining a two-color copy by transferring both formed images onto a single sheet of transfer paper and fixing them, the moving speed of the second photoreceptor is set lower than that of the first photoreceptor 2. A two-color electrophotographic method, characterized in that the scanning speed of the image exposure pool on the second photoreceptor is made faster than that of the first photoreceptor. 2. The two-color method according to claim 1, wherein the black image forming process and the chromatic image forming process are performed using different original documents, thereby obtaining a composite two-color copy. Electrophotography method. 3. A composite first photoconductor for forming a chromatic image and its charging, developing, transferring, neutralizing, and cleaning devices, and a conventional second photoconductor for forming a black image that moves at a faster speed than the first photoconductor. Photoreceptor and its charging, development, transfer,
a two-color electrophotographic device including static elimination and cleaning devices, an image exposure optical system equipped with a speed change means, and a common fixing device; 4. the image exposure optical system is a mirror scanning optical system; 4. A two-color electrophotographic apparatus according to claim 3, further comprising a switching mirror in a rear optical path for directing an imaging light beam to each photoreceptor in response to switching of said speed change means. 5. Claim 3, further comprising a timing roller in front of the transfer device of the second photoconductor, which aligns the transferred image by controlling the conveyance of the transfer paper.
The two-color electrophotographic device according to item 1 or 4.