JPH0728290A - Multicolor image recorder - Google Patents

Abstract

PURPOSE:To record the images of plural colors on one photosensitive body at a comparatively low potential by electrification by attaining the exposure/development of the first color after the electrification and then, the exposure of the second color with intensity higher than that of the first color, for the development of the second color. CONSTITUTION:The photosensitive body 1 is uniformly electrified by an electrifier 2. After that, an electrostatic latent image corresponding to the recording information of the first color is formed by the first exposure 3 and the image of the first color is formed on the photosensitive body 1 in the first development 4. Continuously, the electrostatic latent image corresponding to the recording information of the second color is formed on the photosensitive body 1 in the second exposure 5. The exposing intensity of the second color is set higher than that of the first color, so that the potential of the exposing part of the electrostatic latent image of the second color forms a potential well deeper than that of the first color and only at the exposing potential of the second color, the second development 6 is executed in developing bias conditions capable of developing, to form the image of the second color on the photosensitive body 1. An electrostatic transfer is performed on the paper carried from a paper feeding tray and the paper is carried to a fixing machine 11 after destaticization and peeling and heated/fixed by the fixing machine, to complete recording and ejected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for forming a multicolor image by superimposing a multicolor image on a photoconductor using an electrophotographic process.

[0002]

2. Description of the Related Art As a method for recording a multicolor image using an electrophotographic process, for example, a plurality of photoconductors described in Japanese Patent Application Laid-Open No. 1-179172 are used to form a plurality of color images independently. A method of superimposing on top of it, for example, Japanese Patent Laid-Open No. 2-186
A method of recording a multicolor image by rotating one photoconductor several times as described in Japanese Patent No. 371, forming an image of each color for each rotation, and transferring the image onto recording paper or an intermediate transfer member is known. Are known. The former method has a drawback that the device becomes large, and the latter method has a drawback that the recording speed is slow. As a method for compensating for these drawbacks, Japanese Patent Laid-Open No.
Japanese Patent Laid-Open No. 59-116763 discloses a method of forming an image of the first color by charging, exposing and developing, and then performing charging, exposing and developing again to form an image of two colors on one photoreceptor. . Further, USP 4,078,929 and the like disclose a method of forming a two-color image on one photoconductor by forming three potential levels with one exposure system and combining regular development and reversal development. . By using these methods, it is possible to realize a multicolor image recording apparatus that is relatively small and has a high recording speed.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In JP-A-59-116763, the number of photosensitive members is one, but around the photosensitive member, in addition to the charging device, the exposure system, the developing device, the transfer system, and the cleaning mechanism for one-color recording, Therefore, the charger, exposure system, and developing machine must be installed. In particular, the second color charger must be charged to a constant potential without disturbing the recorded image of the first color, and it is necessary to use a scorotron charger having a large size. Because many of these processes are located around the photoreceptor,
The diameter of the photoconductor becomes large. Therefore, the number of photoconductors is one, but the device cannot be downsized so much.

In the above-mentioned prior art USP 4,078,929, etc., a charger, an exposure system, and
In addition to the developing machine, the transfer system and the cleaning mechanism, only the developing machine for recording the second color may be arranged. In this system, three levels of potential are formed at a time. Each potential level has a high potential that provides sufficient image density in normal development, a low potential that provides sufficient image density in reversal development, and in both normal development and reversal development. It is necessary to set an intermediate potential that does not cause fogging, and it is necessary to increase the initial charging potential of the photoconductor. Particularly in the development of the second color, soft development with a wide development gap is required in order not to disturb the development of the first color, and generally the potential difference between the developing portion potential and the developing device potential must be increased. This has a problem that not only the power consumption used in the charger for the initial charging increases but also the damage to the photoconductor increases. Also,
In some cases, it may be difficult or impossible to stabilize the charging potential of a large photosensitive member that greatly exceeds 1 kV.

An object of the present invention is to solve these problems and provide a system capable of forming image recordings of a plurality of colors on a single photoconductor at a relatively low charging potential. A further object of the present invention is to provide a recording system that is compact and enables stable recording.

[0006]

To achieve the above object, after the exposure and development of the first color after charging, the second color is exposed to light more than the exposure amount of the first color without recharging. Strongly expose and develop the second color. As another means for achieving the above object, a potential of three levels or more is formed at the time of exposure after charging, and the first potential difference and the second potential difference become the difference between the second potential and the third potential. The exposure amount is adjusted so as to be smaller than that in comparison. In order to achieve the above object, in both recording processes, as a developing device for developing an image of the first color, a thin developer layer consisting of only colored resin powder is formed on a developer carrying member and brought into contact with the photoconductor. The developing method of developing by is used.

[0007]

In the above means, as a developing device for the first color, a thin developer layer consisting only of the colored resin powder is formed on the developer carrying member and is developed. The distance from the body can be made as close as the layer thickness of the developer, and thus a sufficient image density can be achieved with a low developing bias. At this time, the thickness of the toner layer formed on the developing roll can be reduced to a layer thickness corresponding to the amount of toner capable of obtaining a sufficient image density on the paper after printing. The photoconductor and the developing roll can be brought close to each other with the film sandwiched therebetween. In this case, a sufficient image density can be obtained even if the potential difference between the developing portion potential and the developing bias applied to the developing roll is about 50 to 200V. Further, in the above means, since the low bias development is used and the potential difference of the image portion of the first color can be reduced, the exposure amount of the first color is reduced and the exposure amount of the second color is reduced. By making it larger, it becomes possible to form the development potential difference required for the development of the second color on the same photoconductor without recharging. Further, in the above means, since the low bias development is used, the development potential difference of the first color can be made small even in the process of forming the three-level potential by exposure, so that the initial charging potential can be made small. This makes it possible to prevent an increase in power consumption of the charger and damage to the photoconductor.

[0008]

EXAMPLES Some examples of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a multicolor image recording apparatus which is an embodiment of the present invention, and FIG. 2 is each process position in the multicolor image recording apparatus which is an embodiment of the present invention shown in FIG. FIG. 3 is a diagram for explaining a potential relationship on the photoconductor in FIG. In FIG. 1, the photoconductor 1 is uniformly charged by the charger 2. After that, an electrostatic latent image according to the recording information of the first color is formed by the first exposure 3, and the image of the first color is formed on the photoconductor by the first development 4. In FIG. 2, V _E1 indicates the potential level formed by the first exposure 3, and V _D1 indicates the developing bias level of the first developing. Then, the second exposure 5 forms an electrostatic latent image on the photoconductor according to the recording information of the second color.
By making the exposure intensity of the second color stronger than that of the first color, the exposed portion potential of the electrostatic latent image of the second color forms a potential well deeper than that of the first color, so that only the exposure potential of the second color is formed. Is developed under a developing bias condition capable of developing, and a second color image is formed on the photoconductor. In FIG. 2, V _E2 represents the potential level formed by the second exposure, and V _D2 represents the developing bias level of the second developing. As an appropriate value of the developing bias capable of developing only the exposure potential of the second color, in general, there is often a potential that is slightly closer to the potential of the exposure portion of the first color than near the middle of the potential of the first exposure portion and the potential of the second exposure portion. . At the transfer position, the image on the photoconductor on which the two-color image is formed is electrostatically transferred 6 onto the 12 sheets conveyed from the paper feed tray, and the charge is removed 7
After that, the sheet is conveyed to the fixing device 11, heated and fixed by the fixing device 11, recording is completed, and the sheet is ejected.

At this time, the structure of the developing machine used as the first developing device is shown in FIG. In the figure, the toner storage container 1
The toner 17 in 8 is removed by the rotation of the scraping blades 15.
It is scraped out to the transport roll 14 side. The scraped-out toner is transported to the developing roll 13 by the transport roll 14 and rubbed against the surface of the developing roll 13 to form a toner layer on the developing roll. The toner layer on the developing roll is thinned by the regulation blade 19 and charged by friction with the regulation blade 19. The developing roll 13 on which the thin toner layer is formed is brought into contact with the photoconductor 1 to perform development. In this method, the distance between the developing roller 13 to which the developing bias is applied and the photoconductor 1 can be set to about several tens of μm which is the thickness of the toner layer, so that the electric field strength required for the development is relatively low. It can be obtained by the development potential difference, and the potential difference between the image portion and the non-image portion of the second color can be set small. FIG. 4 shows the relationship between the potential difference between the photosensitive member and the developing roll, which is obtained when an image is actually recorded by the developing machine shown in FIG. 3, and the image density obtained after the development. The three types of measurement results in the figure are the results of measurement in which the toner amount and the toner charge amount are different, but in all the results, the image potential changes from black to white due to the low potential difference of about 100V to 200V. You can see that you can get it.

The development of the second color does not disturb the image of the first color, so it is necessary to develop the image in the soft contact or non-contact state. Therefore, the distance between the developing roll and the photoconductor becomes relatively large, and in order to perform stable development, it is necessary to set the potential difference between the image portion and the non-image portion to a large value. Since the developing device as shown in FIG. 3 can perform development with a small potential difference of about 50 to 250 V, by using this as the developing device 5 for the first color, the charging potential of the photoconductor is 1 kV.
It is possible to achieve a development potential difference of 300 to 750 V capable of stably performing the development 6 by the soft contact or non-contact of the second color without increasing the voltage near or more. Increasing the charging potential of the photoconductor leads to an increase in the size of the apparatus and a reduction in the life of the photoconductor due to the necessity of using a large charger in addition to increasing the power consumption of the charger.

FIG. 5 is a diagram showing the structure of a multicolor image recording apparatus according to another embodiment of the present invention, and FIG. 6 is a schematic diagram of the multicolor image recording apparatus according to the embodiment of the present invention shown in FIG. It is a figure for explaining the electric potential relation on the photoconductor at each process position. In FIG. 5, the photoconductor 1 is uniformly charged by the charger 2. Then, the exposure device 3 forms a three-level electrostatic latent image according to the recording information of the first color and the recording information of the second color. Next, the regular development 4 develops the first color, and then the reversal development 6 develops the second color.
V _{E1 in} FIG. 6 represents the potential level formed by weak exposure as V
_E2 indicates a potential level formed by strong exposure. Also,
V _D1 indicates the development bias level of the first development which is the regular development, and V _D2 indicates the development bias level of the second development which is the reversal development. In this state, there are positively-charged toner and negatively-charged toner attached to the photoconductor, so that the polarity of the toner is unified to either positive or negative by the charger 21. At the transfer position 7, the image on the photoconductor is electrostatically transferred onto 12 sheets of paper conveyed from the paper feed tray, discharged by static elimination 8 and conveyed to a fixing device 11, heated and fixed, and recording is completed. To be done.

At this time, by using the developing device having the structure shown in FIG. 3 as the developing device for the first developing, the potential difference between the charging portion V ₀ and the weakly exposed portion potential V _E1 can be reduced. Further, as a result, the image part potential V _E2 and the non-image part potential V _E1 of the second development can be increased without increasing the charging part potential V ₀ so much, and stable soft development can be achieved. Alternatively, non-contact development can be achieved.

As described above, in the apparatus configuration shown in FIGS. 1 and 5, the developing system for forming a thin toner layer on the developing roll as shown in FIG. The potential difference V1 between the image part and the non-image part required for the color is 100 to
It can be set to about 250 V, which allows the initial charge potential to be set even if the potential difference between the image portion and the non-image portion required for the second color development is set to 400 to 750 V which is sufficient for soft development and non-contact development. , About 500 to 1000V.

FIG. 7 is a diagram for explaining an embodiment of the structure of a full-color recording apparatus using the recording system of the present invention. According to the configuration of the present invention, one stroke, that is, one rotation of the photosensitive member causes two rotations.
A color image can be formed. Therefore, as shown in FIG. 7, by mounting two types of recording methods of the present invention, recording of four colors becomes possible, and full color image recording can be achieved by using yellow, magenta, cyan and black. In FIG. 7, the two-color image formed by the first photoconductor 1-1 is transferred to the paper conveyed from the paper tray, and then the second paper is transferred.
After the two-color images of the photoconductor 1-2 are transferred in an overlapping manner, they are heated and fixed by the fixing device, and the paper on which the full-color image is recorded is discharged to the paper discharge tray. With this configuration, full-color image recording can be performed at the same process speed as the rotation speed of the photoconductor, which is suitable as a configuration of a high-speed full-color recording device. However, the use of two photoconductors has a drawback that the device becomes slightly large and complicated. FIG. 8 shows another embodiment of a full-color recording apparatus using the recording method of the present invention. In the configuration shown in the figure, four types of developing machines are arranged around one photoconductor, a two-color image is formed on the first rotation of the photoconductor, and the next two-color image is formed on the second rotation. A full-color image is obtained by forming a full-color image on a photoconductor and transferring it collectively onto a sheet conveyed from a sheet tray. With this configuration, it is necessary to control the printing process to achieve the two-rotation process such as retracting the cleaner 10 at the first rotation, but except for the developing machine, it is the same as the two-color process, and the number of parts is small. It is possible to achieve a full-color image recording device having a relatively small device size.

[0015]

As described above, in the multicolor image recording method of the present invention, a thin developer layer made of only colored resin powder is formed on the developer carrier as a developing device for developing the image of the first color. Since the developing method of developing by contacting the photoconductor is used, it is possible to reduce the potential difference between the image portion of the first color and the non-image portion. And the development of the second color by soft contact or non-contact development can be stably performed without disturbing the image of the first color. This makes it possible to achieve a stable two-color image recording process.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a device configuration of the present invention.

FIG. 2 is a diagram for explaining a potential relationship on a photoconductor in each printing process of the present invention shown in FIG.

FIG. 3 is a diagram showing an example of the configuration of a first developing device used in the apparatus of the present invention.

FIG. 4 is a diagram showing a result of actually measuring a relationship between a developing potential difference and an image density using the developing machine of FIG.

FIG. 5 is a diagram for explaining another embodiment of the device configuration of the present invention.

FIG. 6 is a diagram for explaining a potential relationship on a photoconductor in each printing process of the present invention shown in FIG.

FIG. 7 is a diagram for explaining an embodiment of a full-color image recording apparatus using the printing process of the present invention.

FIG. 8 is a diagram for explaining another embodiment of a full-color image recording apparatus using the printing process of the present invention.

[Explanation of Codes] 1 ... Photosensitive member, 2 ... Charging device, 3 ... First exposure, 4 ... First development, 5 ... Second exposure, 6 ... Second development, 7 ... Transfer device, 8 ... Eliminating stripper, 9 ... Erase lamp, 10 ... Cleaner, 11
... Fixing machine, 12 ... Paper entry path, 13 ... Developing roll, 1
4 ... Conveying roll, 15 ... Scraping blade, 16 ... Toner leakage return preventing member, 17 ... Toner, 18 ... Toner storage container, 19 ... Regulation blade, 20 ... Pressing spring, 21 ...
Charger with uniform polarity.

Claims (9)

[Claims] 1. An electrophotographic system in which a visible image is formed by developing an electrostatic latent image formed on a photoconductor by a charging / exposure process, and images of different colors are superposed on the photoconductor. In a multicolor image recording apparatus for forming a multicolor image, as a developing device for developing an image of the first color, a thin developer layer consisting of only colored resin powder is formed on a developer carrier, A multicolor image recording apparatus using a developing method of developing by contacting. 2. A multicolor image recording apparatus according to claim 1, wherein after exposing and developing the first color after charging, the second color is exposed and then the second color is developed. In the multicolor image recording apparatus, the exposure intensity of the first color is set to be smaller than the exposure intensity of the second color. 3. The multicolor image recording apparatus according to claim 1, wherein in the exposure after charging, a potential level of 3 levels or more is formed, the first color is developed, and then the coloring used for the first color development. A multicolor image recording apparatus, which develops a second color by using a colored resin powder having a charging polarity opposite to that of the resin powder. 4. The multicolor image recording apparatus according to claim 2, wherein the difference between the developing portion potential of the first color on the photoconductor and the developing bias of the first color is equal to the developing portion potential of the second color on the photoconductor. A multicolor image recording apparatus, wherein the exposure amount is set so as to be larger than the difference with the developing bias for the second color. 5. A multi-color image recording apparatus according to claim 1, wherein a developing method of forming a magnetic brush using a developer in which a colored resin powder and a magnetic powder are mixed is used as a developing method for the second color. A multicolor image recording apparatus characterized by using. 6. The multicolor image recording apparatus according to claim 1, wherein the developing method for the second color is configured such that the developer on the developer carrier roll and the photoreceptor are not in direct contact with each other. Multicolor image recording device. 7. A multicolor image recording apparatus according to claim 1, wherein as a second color developing method, a thin developer layer made of only colored resin powder is formed on a developer carrier and brought into contact with a photoreceptor. A multicolor image recording apparatus characterized in that a developing system for developing is used, and the peripheral speed of the photosensitive member and the surface peripheral speed of the developer carrier roll are set to be the same. 8. The multicolor image recording apparatus according to claim 4, wherein the difference between the developing portion potential of the first color and the developing bias is 50 to 3.
A multi-color image recording apparatus, wherein the multi-color image recording apparatus is 00 V, and the difference between the developing portion potential of the second color and the developing bias is 250 to 500 V. 9. The multicolor image recording apparatus according to claim 2, further comprising two sets of photoconductors, and a belt-shaped rotary member or a drum-shaped rotary member that conveys a sheet between transfer positions of the photoconductive members. A multicolor image recording apparatus characterized by the above.