JPH07104546A - Color image electrophotographic device - Google Patents

Abstract

PURPOSE:To satisfactorily form a color image even on transparent plastic sheet by bringing the developing brush of a developing device already forming the final-color toner image into contact with the surface of the primary recording medium until the start of a process for transferring the color toner images on an intermediate transfer body to transparent sheet. CONSTITUTION:In the case of printing on the transparent sheet 14, during the period of time from the end of an intermediate transfer process to the start of the process for transferring the color toner images on the intermediate transfer medium 17 to the transparent sheet 14, the developing device 8 for forming the final-color toner image is operated, and the developing brush is brought into contact with the surface of the primary recording medium 1. Therefore, even when toner is caused to fall and stick to the surface of the medium 1 due to change in the rotating speed of the medium 1 and moves on the medium 1, it is formed by means of the developing device 8 before it reaches the medium 17 to which the color toner images have been transferred. The toner comes into contact with the electrified developing brush and is attracted by the developing brush by an electrostatic attracting force. Thus, the toner which has fallen and stuck to the surface of the medium 1 is prevented from being directly transferred onto the medium 17 and soiling the color toner images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image electrophotographic apparatus using an intermediate transfer medium, and more particularly to a color image electrophotographic apparatus capable of forming a good image on plain paper or a transparent plastic sheet.

[0002]

2. Description of the Related Art Generally, a color image electrophotographic apparatus uses yellow (Y) toner, magenta (M) toner, cyan (C) toner, and black (K) toner.

As an operation process of a color image electrophotographic apparatus using an intermediate transfer medium, a rotating primary recording medium is cleaned by a cleaning blade, and a residual charge on the surface is neutralized by a static eliminator and then uniformly charged by a charger. After that, a laser beam modulated with yellow (Y) data is irradiated to form an electrostatic latent image on the primary recording medium. Next, the electrostatic latent image is developed into a yellow (Y) toner image by a developing device for yellow (Y) which is one of developing devices of four colors. The yellow (Y) toner image formed on the primary recording medium is transferred to the intermediate transfer medium in contact with the primary recording medium. The yellow (Y) toner image remaining on the primary recording medium after transfer is 1
It is scraped off by a cleaning blade provided on the next recording medium and disappears. The above operation is sequentially performed for magenta (M), cyan (C), and black (K), and the toner images of the respective colors formed on the primary recording medium are sequentially transferred onto the intermediate transfer medium and transferred onto the intermediate transfer medium. A color toner image is created at. Next, each developing device on the primary recording medium is retracted, the color toner image on the intermediate transfer medium is transferred to the secondary recording medium (paper or transparent sheet), and finally the secondary recording medium (paper or The color toner image is fixed on the transparent sheet and discharged.

In a color image electrophotographic apparatus using this intermediate transfer medium, a method capable of forming a good image on a transparent plastic sheet has been proposed in Japanese Patent Laid-Open No. 53406/1993. In this proposal, in the process of transferring and fixing the color toner image on the intermediate transfer medium to the transparent sheet, the transport speed of the transparent sheet is made slower than the transport speed of plain paper, and fixing energy larger than that of plain paper is given in the fixing step. In order to obtain a good image even on a transparent sheet, the transparent sheet is formed on the primary recording medium in order to reduce the increase in the required printing time due to the slower conveyance speed and to match the operation speed of each part. Until the intermediate transfer process in which toner images of different colors are transferred from the primary recording medium to the intermediate transfer medium in an overlapping manner, the primary recording medium and the intermediate transfer medium are rotated at the same speed for both plain paper and transparent sheet. After the intermediate transfer process is completed, all the developing devices on the primary recording medium are retracted, and in the case of a transparent sheet, the intermediate transfer medium is rotated once or more and the rotation speed of the intermediate transfer medium is lowered. So that matching between the transparent sheet conveying speed of.

[0005]

In the case of printing on a transparent sheet in the color image electrophotographic apparatus using the above-mentioned intermediate transfer medium, the intermediate transfer medium which is in contact with the primary recording medium after completion of the intermediate transfer process is Since the number of rotations is decreased while rotating more than once, the contact angle of the cleaning blade in contact with the primary recording medium changes due to the change in the number of rotations of the primary recording medium, resulting in defective cleaning of residual toner, and
The floating toner adhering to the vicinity of the primary recording medium due to the change in the vibration of the apparatus due to the change in the number of revolutions drops onto the primary recording medium, and these are transferred from the primary recording medium to the intermediate transfer medium, so that the intermediate transfer medium There is a problem that the upper color toner image is stained and an image defect is caused.

An object of the present invention is to eliminate the above-mentioned problems so that a good color image can be formed even on a transparent plastic sheet.

[0007]

In order to achieve the above object, according to the present invention, in the case of printing on a transparent sheet, the color changing the rotational speed while rotating the intermediate transfer medium once or more after the intermediate transfer step is completed. In the image electrophotographic device,
When printing on a transparent sheet, from the end of the intermediate transfer step to the step before the step of transferring the color toner image on the intermediate transfer medium to the transparent sheet, operate the developing device that has formed the final color toner image, and The developing brush was brought into contact with the surface of the primary recording medium.

[0008]

As described above, when printing on a transparent sheet,
From the end of the intermediate transfer step to the step of transferring the color toner image on the intermediate transfer medium to the transparent sheet, the developing device for forming the toner image of the final color is operated and the developing brush is set to the primary recording medium. Since the toner is in contact with the surface, toner that adheres to and drops on the surface of the primary recording medium due to fluctuations in the number of revolutions of the primary recording medium, and moves on the primary recording medium, is transferred to the intermediate transfer medium onto which the color toner image has been transferred. Before reaching, the toner contacts the charged developing brush formed by the developing device that forms the toner image of the final color, and is attracted to the developing brush by the electrostatic attraction force. For this reason, there is an effect of preventing the toner attached and dropped on the surface of the primary recording medium from being directly transferred onto the intermediate transfer medium and contaminating the color toner image.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical side view of a laser beam printer which is a color image electrophotographic apparatus using an intermediate transfer medium.
FIG. 2 is an operation timing chart of the laser beam printer. The horizontal axis in the timing chart of FIG. 2 represents the rotation angle of the intermediate transfer belt 17, and 2π corresponds to one rotation of the intermediate transfer belt 17. The intermediate transfer belt 17
Both belt lengths are set so that the photosensitive belt 1 makes one rotation every two rotations (the rotation angle is 4π).

First, the operation of the laser beam printer of this embodiment will be described. The charge on the surface of the photosensitive belt 1 is neutralized by the static eliminator 2, and then the surface is uniformly charged by the charger 3. When the rotation angle of the intermediate transfer belt is 0, exposure is started by the exposure beam 4 modulated with Y data, and the electrostatic latent image formed by the exposure is transferred to the Y developing device 5.
To develop a Y-based toner image. The Y-based toner image on the photoconductor is intermediately transferred to the intermediate transfer belt 17 by the intermediate transfer device 18 when the rotation angle of the intermediate transfer belt 17 is 2π. Although the intermediate transfer belt 17 is provided with the cleaning device 12 for cleaning the residual toner on the intermediate transfer belt 17, the Y transferred onto the intermediate transfer belt 17 is used.
By the time the tip of the system toner image reaches the cleaning device 12 (the rotation angle of the intermediate transfer belt is 3π), the cleaning device 12 is retracted,
The respective color toner images formed on the intermediate transfer belt 17 are not removed by the subsequent steps. Further, a cleaning blade 13 is provided on the photosensitive belt 1 to always remove the toner remaining on the photosensitive belt 1 after the intermediate transfer of the toner image. Next, the intermediate transfer belt starts exposure with the exposure beam 4 modulated with the M data at the second rotation (rotation angle is 2π), and the latent image formed by the exposure is developed by the M developing device 6 and M System toner image is formed, and when the rotation angle of the intermediate transfer belt is 4π, the M system toner image is intermediately transferred to the intermediate transfer belt 17 by the intermediate transfer device 18 in a multiplex manner. Next, the exposure beam 4 modulated by the C data at the third rotation of the intermediate transfer belt (the rotation angle is 4π)
Exposure is started, the latent image formed by the exposure is developed by the C developing device 7 to form a C-based toner image, and the C-based toner image is transferred to the intermediate transfer device 18 when the rotation angle of the intermediate transfer belt is 6π. Thus, multiple intermediate transfer is performed on the intermediate transfer belt 17.
Finally, the intermediate transfer belt is in the fourth rotation (rotation angle is 6π)
Then, exposure is started with the exposure beam 4 modulated with K data, the latent image formed by the exposure is developed by the K developing device 8 to form a K-based toner image, and the rotation angle of the intermediate transfer belt is 8π.
At the point of time, the K-based toner image is transferred to the intermediate transfer belt 17 by the intermediate transfer device 18 in a multiplex manner. By the above steps, four color toner images are formed on the intermediate transfer belt 17. Next, the conveyance roller 15 performs synchronization control so that the conveyance timing of the secondary recording medium 14 in the recording medium conveyance path 9 matches the color toner images of the four colors. However, the control contents are different when the plain paper is used as the secondary recording medium and when the transparent sheet is used. When the plain paper is used, the transport timing of the plain paper is synchronized so that the rotation angle of the photosensitive belt 1 is 8.5π and the front ends of the color toner images of the four colors appear at the position of the transfer device 10. The transfer device 10 transfers the four color toner images onto the plain paper. Then, the fixing device 11 fixes the color toner images of the four colors on plain paper to obtain a color image printed matter. After that, the cleaning device 12 that has been retracted until then is operated to remove the toner remaining on the intermediate transfer belt 17 that has finished transferring the four color toner images to the plain paper.

On the other hand, when a transparent sheet is used, it is necessary for the transparent sheet to increase the transmittance of the non-scattered transmitted light of the toner image for projection, and the fixing energy in the fixing step is sufficiently larger than that of plain paper. Need to give.
For this reason, the corresponding control is performed by slowing the conveying speed of the transparent sheet. If the rotation speed of the intermediate transfer belt 17 is simply decreased to a desired speed at the time of rotation of 8.5π, the rotation speed of the photosensitive belt 1 is also decreased and affects the intermediate transfer process of the K toner image. After the intermediate transfer process of the K toner image is completed, the intermediate transfer belt 1 does not decrease in speed.
The rotation speed of 7 is reduced to the desired speed. At the same time as the end of the intermediate transfer process, the K developing device 8 for forming the K toner image of the final color is operated, the developing brush of the K developing device 8 is brought into contact with the surface of the photosensitive belt 1, and the speed of the intermediate transfer belt 17 is changed. The toner attached to or dropped on the surface of the photosensitive belt 1 is adsorbed by the developing brush of the K developing device 8. At this time, since the photosensitive belt 1 is not exposed, only the charge is removed by the charge eliminator 2 and the charge by the charger 3 is performed (charging by the charger 3 is also performed if necessary). A toner image is not formed on the photosensitive belt 1 even if the device 8 is operated. After the rotation speed of the intermediate transfer belt 17 is reduced to a desired speed, the next rotation is waited for the leading ends of the four color toner images to reach the position of the transfer device 10.
Since the intermediate transfer belt 17 is further rotated once in this manner, the restarting timing of the cleaning device 12 is also delayed by one rotation so that the four color toner images are not cleaned. The rotation angle of the intermediate transfer belt 17 is 10.5π.
Then, the conveyance of the transparent sheet is started synchronously so that the front ends of the four color toner images appear again at the position of the transfer device 10, and the transfer device 10 transfers the four color toner images to the transparent sheet. Transcribe. When the transfer is started, the operation of the K developing device 8 is stopped, and the developing brush of the K developing device 8 is retracted from the surface of the photosensitive belt 1. The transparent sheet on which the four color toner images are transferred fixes the four color toner images on the transparent sheet with the fixing device 11 at the lowered transport speed, so that the transmittance of non-scattered transmitted light is increased. Color images can be created on transparent sheets. After all the above steps (fixing step) are completed, the conveying speed is controlled to return to the normal speed.

FIG. 3 is a block diagram of a control circuit for controlling each process. As shown in the figure, a print command and image data for each color are input from the host computer 22 to the electrophotographic apparatus through the input / output unit 23. The control device in the electrophotographic apparatus is a microcomputer 19 and ROM 2
0, RAM 21, interrupt control unit 26, mechanism control unit 25,
The exposure control unit 24 and the like are connected via a bus. Here, based on a command from the microcomputer 19, the interrupt control unit 26 controls the motor control unit 2 according to the type of the recording medium.
7 sends a variable speed command to the motor 16 from the motor control unit 27.
To control. Further, the motor 16 is provided with a speed detector 28 such as an encoder, and the detected value is sent to the motor controller 27 to be feedback-controlled. The motor control unit 27 also controls the motors of other motors (for example, a sheet conveying device). Motor control unit 27
A signal from a mechanism control unit is also input to the drive control unit in cooperation with other devices.

As described above, according to the present embodiment, when printing is performed on the transparent sheet and the rotation speed is changed while rotating the intermediate transfer medium one or more times after the completion of the intermediate transfer step, the intermediate transfer medium It is possible to prevent a defect of the color image due to the speed change and form a good color image on the transparent plastic sheet.

[0014]

According to the present invention, an intermediate transfer medium is used in a color image electrophotographic apparatus in which the rotational speed is changed while rotating the intermediate transfer medium one or more times after the completion of the intermediate transfer step when printing on a transparent sheet. It is possible to prevent the toner attached and dropped on the surface of the primary recording medium from being transferred onto the intermediate transfer medium and contaminating the color toner image by changing the speed of the recording medium, which is good not only for general recording paper but also for transparent plastic sheets. There is an effect that a clear color image can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a laser beam printer using an intermediate transfer medium according to the present invention.

FIG. 2 is an operation timing chart of the laser beam printer shown in FIG.

FIG. 3 is a block diagram of a control device in the laser beam printer according to the present invention.

[Explanation of symbols]

1 ... Photosensitive belt, 2 ... Static eliminator, 3 ... Charging device, 4 ... Exposure beam, 5 ... Yellow developing device, 6 ... Magenta developing device, 7 ...
Cyan developing device, 8 ... Black developing device, 9 ... Recording medium conveying path, 1
0 ... Transfer device, 11 ... Fixing device, 12 ... Cleaning device, 13 ... Cleaning blade, 14 ... Secondary recording medium, 15 ... Conveying roller, 16 ... Motor, 17 ... Intermediate transfer belt, 18 ... Intermediate transfer device, 19 ... Microcomputer, 20 ... RO
M, 21 ... RAM, 22 ... Host computer, 23 ...
I / F circuit, 24 ... Exposure control section, 25 ... Mechanism control section, 2
6 ... Interrupt control unit, 27 ... Motor control unit, 28 ... Encoder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Kato 1-1-1 Higashitaga-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Information & Video Media Division

Claims (1)

[Claims] 1. A toner image forming means for forming toner images of different colors by a plurality of developing devices on a rotating primary recording medium, and an intermediate transfer of toner images of different colors formed on the primary recording medium. Color toner image forming means for forming a color toner image by superposing and transferring on a medium, transfer means for transferring the color toner image on the intermediate transfer medium to a secondary recording medium, and color toner on the secondary recording medium A fixing unit that fixes an image, a conveying unit that conveys the secondary recording medium, a recording medium supplying unit that selectively supplies a transparent sheet and plain paper as the secondary recording medium to the conveying unit, and controls these. Control means and an intermediate transfer step for transferring the toner image of the final color from the primary recording medium to the intermediate transfer medium in the transparent sheet mode in which the color toner image is transferred and fixed on the transparent sheet, and the color toner on the intermediate transfer medium. A control function for changing the speed of the intermediate transfer medium so that the intermediate transfer medium is rotated at least once during the process of transferring the image to the transparent sheet while rotating the intermediate transfer medium at a speed lower than that of plain paper. In the color image electrophotographic apparatus, in the transparent sheet mode, the color toner image on the intermediate transfer medium is transferred to the transparent sheet after the intermediate transfer step of transferring the final color toner image from the primary recording medium to the intermediate transfer medium. A color image electrophotographic apparatus characterized in that a developing device on which a toner image of the final color has been formed is operated until the step before the step of transferring to, and the developing brush of the developing device is brought into contact with the surface of the primary recording medium.