JPH06208305A - Multicolor developing method and electrophotographic printer - Google Patents

Abstract

PURPOSE:To provide a multicolor developing method and an electro-photographic printer in which a distinct color image is obtained and image quality is made excellent. CONSTITUTION:This device is provided with a photosensitive drum 11 on which an electrostatic latent image is succesively formed based on information on a color-separated print, and a developing means 20 where developing units 21 to 24 having a developing roller and a squeeze roller and developing the electrostatic latent image formed on the drum 11 with toner having a hue corresponding to the information on the color-separated print are plurally arranged. By moving the developing means 20 in the tangent direction of the drum 11, the electrostatic latent image on the drum 11 is successively developed with the toner having the hue corresponding to the information on the color-separated print by each of plural developing units 21 to 24, thereby obtaining a toner image. Then, the developing means 20 is moved in the tangent direction by the number of times which is more than the number of the developing units 21 to 24 by one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor developing method and an electrophotographic printer using the method.

[0002]

2. Description of the Related Art An electrophotographic printer develops an electrostatic latent image formed on a photosensitive drum with toner, and heats and pressurizes the toner image onto a recording medium such as paper by a transfer means such as a heating roll. To do. Among such electrophotographic printers, the wet type electrophotographic printer using liquid toner can use fine toner particles of the submicron order, and therefore has a higher resolution and a sharper image than the dry type electrophotographic printer. It has the advantage of being obtained.

When a color image is formed in this electrophotographic printer, for example, an electrostatic latent image corresponding to a magenta hue is formed on a photosensitive drum, and this electrostatic latent image is developed with magenta liquid toner. After that, the magenta toner image is transferred to an intermediate transfer unit that is pressed against the photosensitive drum, for example, the intermediate transfer drum. Similarly, the cyan and yellow toner images are sequentially layered and transferred to the intermediate transfer drum to form a multicolor toner image. Then, the heating roll is pressed against the intermediate transfer drum, and the multicolor toner images laminated and transferred onto the intermediate transfer drum are transferred and fixed on a recording medium such as paper to form a color image.

[0004]

In the conventional electrophotographic printer, liquid toner is supplied from the developing drum to the photosensitive drum in each developing unit to develop the electrostatic latent image, and then the squeeze roller is used to develop the photosensitive drum. After the excess liquid toner above is squeezed, the developed toner image is sequentially transferred to the intermediate transfer drum. Therefore, the excess liquid toner that is not squeezed remains on the photosensitive drum on which the final color liquid toner has been developed.
Excess liquid toner of the final color not only adheres to the intermediate transfer drum and disturbs the toner image, but also stains the transfer paper, resulting in a lack of sharpness in the color image created, resulting in poor image quality. There was a problem that it would end up.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a multicolor developing method and an electrophotographic printer which have a clear color image and are excellent in image quality.

[0006]

To achieve the above object, according to the multicolor developing method of the present invention, electrostatic latent images based on color-separated print information are sequentially formed on a photosensitive drum, and the electrostatic latent image is formed. A latent image is developed by arranging a plurality of developing units each having a developing roller and a squeeze roller arranged in a tangential direction of the photosensitive drum, and toner is sequentially developed in each developing unit of the plurality of developing units to form a toner image. In the color developing method, the moving of the developing unit in the tangential direction is performed once more than the number of the developing units.

Preferably, the toner images on the photosensitive drum are sequentially transferred onto the intermediate transfer medium so as to be transferred to form a multicolor toner image, and the multicolor toner image is heated, pressure-fixed on the recording medium. Further, according to the electrophotographic printer of the present invention, a photosensitive drum on which an electrostatic latent image based on the color-separated print information is sequentially formed, and the electrostatic latent image formed on the photosensitive drum are color-separated. And a developing unit having a plurality of developing units each having a developing roller for developing with a toner having a hue corresponding to the print information and a squeeze roller,
The developing means is moved in the tangential direction of the photosensitive drum, and the electrostatic latent image on the photosensitive drum is sequentially tonered by a toner having a hue corresponding to the print information separated in each developing unit of the plurality of developing units. An electrophotographic printer that develops a toner image is provided with means for moving the developing means in the tangential direction more than once by the number of the developing units.

Preferably, in the electrophotographic printer, an exposing means for sequentially forming an electrostatic latent image based on the color-separated print information on the photosensitive drum, and a toner image on the photosensitive drum, which is brought into pressure contact with the photosensitive drum. Intermediate transfer medium on which a multicolor toner image is formed by sequentially superimposing images on the intermediate transfer medium, a transport means for loading and unloading a recording medium to which the multicolor toner image formed on the intermediate transfer medium is transferred, and the intermediate transfer medium. And a fixing unit which is brought into pressure contact with the recording medium.

Preferably, the developing means is a wet developing means for developing an electrostatic latent image with liquid toner.

[0010]

In the multicolor developing method and electrophotographic printer of the present invention, the tangential direction of the developing means is moved once more than the number of the developing units. As a result of being squeezed, it does not adhere to the intermediate transfer medium.

At this time, a multicolor toner image obtained by sequentially transferring the toner images on the photosensitive drum onto the intermediate transfer medium is heated and pressure-fixed on the recording medium to obtain a color print image excellent in image quality. . If the developing means is a wet developing means for developing an electrostatic latent image with liquid toner, a sharp color print image with high resolution can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the multicolor developing method and electrophotographic printer of the present invention will be described in detail below with reference to the accompanying drawings. First, the overall configuration of the electrophotographic printer according to the present invention will be described with reference to FIG. 1. The electrophotographic printer 1 includes a photosensitive unit 10, a developing unit 20, an intermediate transfer unit 30, a cleaning unit 40, a transfer unit 50, and an auxiliary squeeze. Roller 6
0, a sheet feeding device 70, and an exposure system (not shown) that emits exposure light from the direction of arrow A. Each arrow in the figure indicates the rotation direction of each member and the moving direction of the developing means. .

The photosensitive means 10 has a photosensitive drum 11, a static eliminator 12 for removing residual charges on the photosensitive drum 11, and a charger 13 for uniformly charging the photosensitive drum 11.
Prior to removing the residual charges, the surface is cleaned by the cleaning means 40. These cleaning means 40,
The static eliminator 12 and the charger 13 are arranged in this order between the intermediate transfer unit 30 and the developing unit 20 along the rotation direction of the photosensitive drum 11.

The photosensitive drum 11 has a photosensitive layer made of an organic photoelectric material (OPC) formed on the surface of a cylindrical drum. The material for the photosensitive layer is O
Other than PC, for example, selenium (Se) system, amorphous silicon (α-Si), or the like can be used. The static eliminator 12 is an LED
An array or a small incandescent lamp irradiates the surface of the photosensitive drum 11 with light to erase the residual latent image. The charger 13 uniformly charges the photosensitive drum 11 with the ions generated by the corona discharge.

Here, the exposure system forms an electrostatic latent image on the surface of the photosensitive drum 11, has a laser light source, a liquid crystal shutter, etc., and is color-separated corresponding to each hue of the color original. The photosensitive drum 11 is irradiated with laser light in the direction of arrow A based on the print information, and an electrostatic latent image corresponding to the color-separated print information is formed on the surface. Further, an LED array may be used as an exposure unit that irradiates the photosensitive drum 11 with print information.

The developing means 20 includes a first developing unit 21 to a fourth developing unit 24, which are horizontally arranged in an upper portion of the housing 210 in a direction orthogonal to the moving direction, and the developing units 21 to 24 as an integrated body. Is arranged in the driving unit 25 and each of the developing units 21 to 24 for horizontally moving in the left-right direction indicated by the arrow in the figure, which is the tangential direction of
Removable toner cartridge 26 in housing 210
Is equipped with. The drive means 25 has a ball screw 25a and a drive motor 25b. First developing unit 2
1 is a liquid toner tank 21 on the upper part of the housing 210.
1 is formed, and the toner cartridge 26 containing the liquid toner of each hue is housed in the lower part of the liquid tank 211.
To the developing roller 212 and the squeeze roller 2 respectively.
13 (see FIGS. 2 to 5) are arranged in parallel at a predetermined interval.

The developing means 20 includes each developing unit 21.
To 24 are provided with toner cartridges 26 containing yellow (Y), magenta (M), cyan (C) and black (Bk) liquid toners, respectively. It is arranged on the right side of the drum 11. When developing the toner image, the driving unit 25 drives the developing unit 21, the developing unit 22,
The developing unit 23 and the developing unit 24 are sequentially moved to the photosensitive unit 10 side, and the electrostatic latent images formed based on the color-separated print information are sequentially developed on the photosensitive drum 11. At this time, the developing means 20 is moved once more than the number of the developing units 21 to 24 in the tangential direction of the photosensitive drum 11, that is, in the leftward direction indicated by the thick arrow in the drawing, five times. As the liquid toner, a liquid carrier in which toner particles such as yellow, magenta, and cyan are dispersed is used.

Here, the details of the first developing unit 21 will be described later, but since the developing units 22 to 24 are respectively configured similarly to the first developing unit 21, the reference numerals corresponding to the corresponding portions in the drawings are used. And detailed description thereof will be omitted. The intermediate transfer unit 30 includes an intermediate transfer drum 31 and a charger 32 arranged along the rotation direction of the intermediate transfer drum 31, and the toner images sequentially developed by the developing unit 20 are transferred onto the intermediate transfer drum 31. Are sequentially transferred in layers.

The intermediate transfer drum 31 is formed by forming a thin silicone resin layer having an insulating property on the surface of a cylindrical metal drum, and is brought into pressure contact with the photosensitive drum 11 and the developing means 20.
Each time the toner image of each hue is developed, the toner images are sequentially layered and transferred from the photosensitive drum 11. As the intermediate transfer drum 31, a recording medium, for example, one having an appropriate diameter depending on the size of the transfer paper P can be used, and when the transfer paper P is large, as shown in FIG. Also has a larger diameter.

The charger 32 is the charger 13 of the photosensitive means 10.
The intermediate transfer drum 31 is charged according to the same principle as described above, and the influence of the previous toner image is canceled at the same time as the effect of the previous toner image is canceled so that the next toner image having a different hue transferred from the photosensitive drum 11 is easily transferred. The toner image transferred onto 31 is prevented from returning onto the photosensitive drum 11.

Then, in the intermediate transfer means 30, the toner images developed on the photosensitive drum 11 are sequentially transferred onto the intermediate transfer drum 31 while being charged by the charger 32. At the time of this transfer, a small amount of toner image or liquid toner not transferred to the intermediate transfer drum 31 remains on the photosensitive drum 11, but these are cleaned by the cleaning means 40.

At this time, among the liquid toners of yellow (Y), magenta (M), cyan (C) and black (Bk), yellow (Y) is first developed on the photosensitive drum 11. On the transfer paper P, a yellow toner image is fixed on the uppermost layer. Therefore, the yellow toner has a higher light transmittance than the toners of other hues, so that the obtained multicolor toner image becomes clear and the image quality is improved. Further, the yellow toner image is located in the lowermost layer on the intermediate transfer drum 31, and is most likely to remain on the intermediate transfer drum 31 without being transferred to the transfer paper P, but the yellow toner image has another hue. The toner image is less noticeable than the toner image of No. 1 and does not require cleaning.

The cleaning means 40 is the cartridge 4
A cleaning roller 42 is provided in the electrophotographic printer 1, and when mounted on the electrophotographic printer 1, the cleaning roller 42 contacts the photosensitive drum 11. This cleaning means 40 is
The cleaning roller 4 removes the toner image and the liquid toner residue remaining on the photosensitive drum 11 after the transfer to the intermediate transfer drum 31.
2 is electrostatically adsorbed and collected, and is scraped by a rubber blade made of urethane rubber or the like and collected in a toner collecting container.

The transfer means 50 has a heating roll 51 having a heater (not shown) built therein. The heating roll 51 is pressed against the intermediate transfer drum 31 by a pressing mechanism (not shown), and is laminated and transferred to the intermediate transfer drum 31. The multicolor toner image thus formed is heated and pressed to be fixed on the transfer paper P. Here, the pressing mechanism is used for the photosensitive drum 11 to the intermediate transfer drum 31.
When the toner image is transferred onto the intermediate transfer drum 31, the heating roll 51 is separated from the intermediate transfer drum 31. Then, the heating roll 51 is pressed against the intermediate transfer drum 31 with a predetermined pressing force by the pressing mechanism by the time the portion of the four types of toner images of the intermediate transfer drum 31 to which the last toner image is transferred arrives. As a result, the heating roll 51 pressurizes and heats the multicolor toner image laminated and transferred onto the intermediate transfer drum 31, and transfers and fixes the multicolor toner image onto the transfer paper P supplied from the paper feeding device 70.

The auxiliary squeeze roller 60 is the photosensitive drum 1
It is arranged between the developing unit 20 and the intermediate transfer unit 30 with a space of 30 μm, for example, and rotated so that the peripheral speed direction is opposite to the peripheral speed direction of the photosensitive drum 11. Then, the excess liquid toner exceeding this interval, especially the liquid carrier, is removed from the photosensitive drum 11 on which the toner image has been developed. The same effect can be obtained by using a squeeze corona using a charger instead of the auxiliary squeeze roller 60.

The paper feeding device 70 feeds the transfer paper P between the intermediate transfer drum 31 and the heating roll 50 when fixing the toner images formed on the intermediate transfer drum 31.
The electrophotographic printer 1 of the present invention is configured as described above and forms a color image as follows. First, residual charges are removed from the surface of the photosensitive drum 11 cleaned by the cleaning unit 40 by the static eliminator 12 and uniformly charged by the charger 13.

Next, as shown by arrow A in the figure, laser light is irradiated to sequentially form an electrostatic latent image based on the color-separated print information on the surface of the photosensitive drum 11. The electrostatic latent image by the irradiation of the laser light is formed four times in total corresponding to the hues of yellow, magenta, cyan and black. Before the electrostatic latent image of each color reaches the developing position, the ball screw 25
a is rotated by the drive motor 25b, the developing means 20 disposed on the right side of the photosensitive drum 11 in the figure is horizontally moved to the photosensitive drum 11 side, and the yellow toner image is transferred to the second developing unit 21 by the second developing unit 21. In the developing unit 22, the magenta toner image and the cyan and black toner images are sequentially developed in the same manner. In this way, the toner image developed by each developing unit is sequentially transferred to the intermediate transfer drum 31, and a multicolor toner image in which toner images of four colors are stacked is formed on the intermediate transfer drum 31.

In parallel with the transfer of the toner image developed by the fourth developing unit 24 to the intermediate transfer drum 31,
Alternatively, after the transfer is completed, the heating roll 51 is brought into pressure contact with the intermediate transfer drum 31 by the pressing mechanism, and the multicolor toner images formed on the intermediate transfer drum 31 are heated and pressed to collectively transfer onto the transfer paper P. After fixing, one step of forming a color image is completed.

Now, the first developing unit 21 of the developing means 20 will be described with reference to FIGS. 2 to 7. In the first developing unit 21, as shown in FIGS. 2, 3 and 5, the liquid tank 211 is divided into a developing tank B _D and a discharging tank B _E, and a supporting member 214 arranged in the central longitudinal direction, The partition plate 215, the side walls 211a, and 2 provided upright on the support member 214.
In the developing tank B _D defined by 11b and 211c, the developing roller 212 has side walls 211a, 211d, 211e,
Squeeze rollers 213 are arranged in the discharge tank B _E defined by 211f.

As shown in FIG. 5, the support member 214 is fixed to a concave portion 211g formed in the bottom wall of the liquid tank 211, and a plurality of small holes (not shown) communicating with the discharge tank B _E are provided at a plurality of positions. ing. Further, the support member 214 is provided with a plastic film F for scraping off the liquid toner on the rollers by attaching the upper end to the rollers 212, 213 on both sides. The film F may be made of metal. The liquid toner overflowing the partition plate 215 from the developing tank B _D flows into the discharging tank B _E through the small holes of the supporting member 214.

Further, as shown in FIGS. 2 to 4, the side walls 211e and 211f are each formed with a concave groove 211h having a narrow upper portion, and a bearing 216 is attached to each concave groove 211h. ing. Each bearing 216
The rotary shafts 212a and 213a of the rollers 212 and 213 are supported, and are held in the concave grooves 211h so as to be slightly movable up and down. And, between each bearing 216 and the liquid tank 211,
Torsion coil springs 217 are respectively interposed, and each bearing 2
16 is biased upward. Here, each bearing 216 is
Since the upper portion of the concave groove 211h is formed narrow, it does not come off.

On the other hand, concave grooves 211j having the same width are formed on the side walls 211b and 211c as shown in FIGS. 2 and 3, and bearings 218 are attached to the concave grooves 211j so as to be vertically movable. Has been. Each bearing 218
Supports the rotary shaft 212a of the developing roller 212 in a liquid-tight manner so that the liquid toner does not flow out from the developing tank B _D to the discharge tank B _E side.

Further, as shown in FIGS. 3 to 5, the liquid tank 211 is provided with a discharge port 211k for discharging the liquid toner to the toner cartridge 26 so as to project downward on the bottom surface of the discharge tank B _E. . Further, immediately below the rotary shaft 212a located on the side wall 211f side of the developing roller 212, an inlet 211n for liquid toner supplied from the toner cartridge 26 is provided.

As shown in FIGS. 2 and 3, the developing roller 212 and the squeeze roller 213 are provided with spacer rollers 219 at both ends of the rotary shaft 212a and the rotary shaft 213a, respectively. , 213b are attached. Each spacer roller 219 supports the rotary shaft 212a, 213a of each roller 212, 213 via a bearing 219a, and has an outer diameter slightly larger than the outer diameter of each roller 212, 213. As a result, the spacer roller 21
When the photosensitive drum 11 is in sliding contact with both ends of the photosensitive drum 11, the developing roller 212, the squeeze roller 213, and the photosensitive drum 1
A predetermined gap is formed between the two. In the electrophotographic printer 1 of the present embodiment, for example, the gap between the photosensitive drum 11 and the developing roller 212 is set to 100 μm, and the gap between the photosensitive drum 11 and the squeeze roller 213 is set to 50 μm.

Further, both rollers 212 and 213 are shown in FIG.
As shown in FIG. 4, the upper ends of the electrode plates E _P1 and E _P2 are pressed against the end faces of the rotary shafts 212a and 213a on the side wall 211e side, and the lower ends of the electrode plates E _P1 and E _P2 are respectively connected to a power source for voltage application. It is connected to the controller E _C. One of the electrode plates E _P1 applies a developing bias voltage to the developing roller 212 to increase the bias voltage from the white background area side to the printing area side when switching the developing unit for developing the electrostatic latent image on the photosensitive drum 11. Let That is, the developing roller 212
As shown in FIG. 6, normally, the developing bias voltage V _B
(About -300 ~-500 V) is applied, the surface potential of the photosensitive drum V _BW is about -500-700 V of white area A _W, the surface potential of the photosensitive drum V _BP of the printing area A _P of about -100 V Is set. At this time, when the developing unit is switched, the bias voltage applied to the developing roller 212 is increased in the positive direction from the white background area side to the printing area side. As a result, the excess liquid toner is removed from the surface of the photosensitive drum 11, the squeeze property of the liquid toner is improved, and the excess liquid toner is transferred to the intermediate transfer drum 31.
In particular, the liquid carrier is prevented from adhering.

Then, as shown in FIG.
Each of the gears 212b and 213b attached to
The rotation of the drive motor 20c is transmitted by a timing belt 20b wound around a plurality of transmission members 20a including an intermediate gear and a timing pulley together with the gears of the other developing units 22 to 24 provided on the back side of the electrophotographic printer 1. It As a result, in the developing units 21 to 24, the peripheral speed direction of the developing roller 212 is the same as the peripheral speed direction of the photosensitive drum 11, and the squeeze roller 213 is the peripheral speed direction thereof, as indicated by the arrow in FIG. The photosensitive drum 11 is rotationally driven in the direction opposite to the peripheral speed direction.

At this time, the peripheral velocities of the developing roller and the squeeze roller of each developing unit are determined by the plurality of transmitting members 20a.
By adjusting the number of teeth of, for example, the developing roller is set at the same speed as the photosensitive drum 11, and the squeeze roller is set to be 2.5 times the photosensitive drum 11. When the rotation speeds of the rollers are set in this way, the balance between the supply of the liquid toner to the photosensitive drum 11 and the squeeze of the liquid toner applied to the photosensitive drum 11 becomes good, and the optimal developing property of the electrostatic latent image is obtained. Is achieved.

The squeeze rollers 213 to 243 of the developing units 21 to 24 set the surface tension of the liquid toner to be larger than the surface tension of the photosensitive drum 11 to the liquid toner. As a result, the squeeze roller 213-
The effect that 243 removes the excess liquid toner on the photosensitive drum 11 is enhanced. Therefore, in the first developing unit 21, the electrostatic latent image formed on the photosensitive drum 11 is developed by the liquid toner supplied to the photosensitive drum 11 by the developing roller 212, and excessively attached to the photosensitive drum 11 by the squeeze roller 213. Liquid toner is squeezed,
The developed toner image is transferred to the intermediate transfer drum 31. This situation also applies to the other developing units 22-24. At this time, in the liquid tank 211, the liquid toner sent from the toner cartridge 26 is supplied to the inflow port 2
Liquid toner and squeeze roller 213 supplied from 11 n to developing tank B _D and overflowing partition plate 215.
The liquid toner flowing down the film F that is in contact with the sheet flows into the discharge tank B _E through the small holes provided in the support member 214, and flows back to the toner cartridge 26 from the discharge port 211k.

Next, the drive means 25 for integrally moving the developing units 21 to 24 in the left-right direction will be described with reference to FIG. The drive means 25 includes a ball screw 25a and a drive motor 25b for rotating the ball screw 25a.
The housing 210 is rotatably supported by 5c and 25c.
Support members 21 that also function as nuts provided at the bottom of the
It is screwed with 0a. The ball screw 25a is rotationally driven by a belt 28 wound around a pulley 25d attached to one end and a pulley 25e of a drive motor 25b. Thereby, the developing unit 2 of the developing means 20
1 to 24 are integrally moved in the left-right direction.

At this time, in the multicolor developing method of the present invention and the electrophotographic printer 1 using the method, the developing means 20 is moved to the tangential method once more than the number of the developing units 21 to 24, and the movement is completed. Sometimes the fourth developing unit 2
4 is located on the left side of the photosensitive drum 11. Here, when the developing units 21 to 24 move to the left from the initial position on the right side of the photosensitive drum 11 before the start of development, the first developing unit 21 first contacts the photosensitive drum 11. At this time, the developing roller 212 and the squeeze roller 213, as shown in FIGS.
Of the torsion coil spring 2 is supported by bearings 216 which are held in the respective concave grooves 211h so as to be slightly movable up and down.
17 is urged upward, and the spacer roller 2
19 is attached to the rotating shafts 212a and 213a.

Therefore, regarding the developing roller 212, first, the spacer rollers 219 attached to the rotary shaft 212a are brought into sliding contact with both ends of the photosensitive drum 11. When the first developing unit 21 moves further leftward from this state,
A pressing force that presses the developing roller 212 downward is exerted via each spacer roller 219. Then, the developing roller 2
The bearing 216 supporting the rotary shaft 212a of the 12 moves slightly downward in the concave groove 211h, and the developing roller 212
Passes the photosensitive drum 11 while maintaining a predetermined gap between the spacer roller 219 and the photosensitive drum 11. As a result, the first developing unit 21 causes the photosensitive drum 11 between the developing roller 212 and the squeeze roller 213.
Is moved to the developing position where is located.

When the developing unit is switched to another developing unit, the developing unit 2 is driven by the driving means 25.
1 to 24 are integrally moved to the left. With this configuration, when the developing unit 21 that has developed the electrostatic latent image on the photosensitive drum 11 is switched to the next developing unit 22, the liquid toner supplied to the photosensitive drum 11 is transferred to the developing roller 2
The squeeze roller 213, which comes closer to the squeeze roller 12, squeezes the squeeze roller 213 to prevent excess liquid toner from adhering to the photosensitive drum 11, and further improves the squeeze property for removing the liquid toner from the photosensitive drum 11. The excess liquid toner does not adhere to the developing units, and the liquid toner does not mix between adjacent developing units, so that the contamination between the liquid toners is prevented.

In particular, the multicolor developing method of the present invention and its method
In the electrophotographic printer 1 using the method, the developing means 20
One more time than the number of developing units 21-24
Then, even with the final liquid black toner,
Excess liquid toner adhered to the photosensitive drum 11 in the same manner as
Can squeeze enough. That is, the final
When developing a black toner image, which is a color,
At the bottom of the system 11, as shown in FIG.
Developing roller 242 and squeeze roller 243
Is being developed by the developing roller 242 during
Is not squeezed by the squeeze roller 243
Black liquid toner L _T Can be part of

Therefore, the developing means 20 is connected to the developing unit 2
When the number of movements is the same as the number 1 to 24, the development of the toner image in the developing unit 24 is completed, and the developing unit 2
When 0 moves to the left in the drawing with respect to the photosensitive drum 11, the black liquid toner L _T left unsqueezed below the photosensitive drum 11 adheres to the intermediate transfer drum 31 and disturbs the toner image. In addition, the transfer paper P is soiled.

At this time, in order to eliminate the unsqueezed portion of the liquid toner L _{T under} the photosensitive drum 11, for example, after developing the toner image in the developing unit 24, only the developing roller 242 is stopped from rotating, or , Liquid tank 24
This can be dealt with by stopping the supply of the liquid toner to No. 1. However, in the former case, it is necessary to change the operation timings of the developing roller 242 and the squeeze roller 243, and a complicated mechanism is required as is clear from the configuration shown in FIG. On the other hand, in the latter case, the liquid tank 24
It is necessary to stop the movement of the developing device 20 until the liquid toner runs out from 1 and it takes time to supply the liquid toner to the liquid tank 241 at the time of shifting to the next printing process. There is a problem in that

Therefore, as the simplest and rational means, after developing the toner image of the final color, the developing means 20 is moved once more in the tangential direction of the photosensitive drum 11. As a result, the unsqueezed portion of the liquid toner L _T under the photosensitive drum 11 shown in FIG. 9 is squeezed by the squeeze roller 243 of the developing unit 24, and the toner image on the intermediate transfer drum 31 is not disturbed. It does not stain the paper P.

As described above, in the developing means 20, when the developing units 21 to 24 are switched or returned to the initial position, the entire developing unit is simply moved in one direction in the left-right direction. There is an advantage that the structure of the driving means 25 can be simplified because it is not necessary to make a complicated movement such as moving the entire developing unit in the vertical direction in order to avoid.

In the electrophotographic printer of the present invention, if the print information is reflected light from a color original,
It goes without saying that it can be used as a color copying machine.

[0049]

As is apparent from the above description, according to the present invention, the developing means is moved in the tangential direction of the photosensitive drum by one more time than the number of developing units. The toner image on the intermediate transfer medium is not disturbed, the transfer paper is not stained, and a multicolor developing method and an electrophotographic printer having a clear color image and excellent image quality are provided. .

When a multicolor toner image obtained by sequentially superposing the toner images on the photosensitive drum on the intermediate transfer medium is transferred onto the recording medium by heating and pressure fixing, a color print image excellent in image quality can be obtained. Furthermore, when the developing means is a wet developing means for developing an electrostatic latent image with liquid toner, a sharp color print image having a high resolution can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an electrophotographic printer that creates a print image based on a multicolor developing method of the present invention.

FIG. 2 is a plan view showing a developing roller and a squeeze roller arranged in a developing unit.

3 is a sectional view of the developing means of FIG. 2 taken along line III-III.

FIG. 4 is a side view of the developing unit of FIG. 2 as viewed from the right side.

5 is a cross-sectional view of the developing means of FIG. 2 taken along line VV.

FIG. 6 is an explanatory diagram showing a relationship between photosensitive drum surface potentials.

FIG. 7 is a rear view of the electrophotographic printer of FIG. 1 viewed from the rear side.

8 is a front view showing a driving unit that integrally moves a developing unit of the electrophotographic printer of FIG.

FIG. 9 is a diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrophotographic printer 10 Photosensitive means 11 Photosensitive drum 12 Static eliminator 13 Charger 20 Developing means 21-24 Developing unit 25 Driving means 30 Intermediate transfer means 31 Intermediate transfer drum 40 Cleaning means 50 Transfer means 51 Heating roll 60 Auxiliary squeeze roller 70 Supply Paper equipment

Claims (5)

[Claims] 1. A developing means in which electrostatic latent images based on color-separated print information are sequentially formed on a photosensitive drum, and the electrostatic latent images are arranged in plural developing units each having a developing roller and a squeeze roller. In the multicolor developing method in which the photosensitive drum is moved in the tangential direction and the toner is sequentially developed in each developing unit of the plurality of developing units to form a toner image, the movement of the developing unit in the tangential direction is determined by the number of the developing units. A multicolor developing method characterized by being performed once more than 2. A multicolor toner image is formed by sequentially transferring the toner images on the photosensitive drum onto an intermediate transfer medium, and the multicolor toner image is heated, pressure-fixed on the recording medium. Item 1. The multicolor development method of Item 1. 3. A photosensitive drum on which an electrostatic latent image based on color-separated print information is sequentially formed, and a hue corresponding to the color-separated print information on the electrostatic latent image formed on the photosensitive drum. A developing unit having a plurality of developing units each having a developing roller for developing with the toner and a squeeze roller, and moving the developing unit in a tangential direction of the photosensitive drum to form an electrostatic latent image on the photosensitive drum. In an electrophotographic printer in which toner is sequentially developed with a toner having a hue corresponding to the color-separated print information in each of a plurality of developing units to form a toner image, the developing means is provided once more than the number of the developing units. Many electrophotographic printers are provided with means for moving them in the tangential direction. 4. An exposure unit that sequentially forms an electrostatic latent image based on the color-separated print information on the photosensitive drum, and is pressed against the photosensitive drum, and toner images on the photosensitive drum are sequentially transferred in an overlapping manner. An intermediate transfer medium on which a multicolor toner image is formed, a conveying unit that carries in and out a recording medium onto which the multicolor toner image formed on the intermediate transfer medium is transferred, and the intermediate transfer medium through the recording medium. The electrophotographic printer according to claim 3, further comprising a fixing unit that is pressed against the surface. 5. The electrophotographic printer according to claim 3, wherein the developing means is a wet developing means for developing an electrostatic latent image with liquid toner.