JPH02183276A - Fullcolor copying device - Google Patents

Abstract

PURPOSE:To improve image quality by making transfer potential at a final transfer stage larger than transfer potential at a transfer stage just before the final one and impressing specified voltage on a intermediate transfer medium during shifting to respective transfer stages. CONSTITUTION:An intermediate transfer belt 19 is electrostatically charged to be in a negative polarity by an intermediate transfer roller 22 on which 600V is impressed and it attracts and transfers a yellow toner image in a positive polarity on a photosensitive belt 8. The belt 19 still moves and is electrostatically charged to be in the negative polarity of 600V to attract and transfer a magenta toner image. Moreover, at the final stage of transfer, the belt 19 is electrostatically charged to be at 1,000V to attract and transfer a cyanogen toner image. When the belt 19 idly rotates during the respective transfer stages, high impressed voltage is impressed in the case that a processing speed is high and low one is impressed in the case that it is low. Thus, a phenomenon such as scattering, etc., which occurs by the mutual repulsion of toner in the case of the lowering of transfer efficiency and the idle rotation of the belt 19, is removed and an excellent color image is always obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention utilizes a method in which toner images of each color component formed on a photoreceptor are once superimposed on an intermediate transfer medium (intermediate transfer belt) and then transferred to paper. The present invention relates to a full-color copying device.

<Prior Art> Conventionally, in a color copying machine as an electrophotographic device, a belt-shaped photoreceptor is normally charged by a main charger using a direct current electric field such as a corona discharge, and an optical image of a color-separated original is generated. is projected onto the photoreceptor belt to form an electrostatic latent image, which is developed with a first color, eg, yellow, toner to form a toner image.

In this case, the yellow toner is charged in a manner opposite to that of the photoreceptor belt.

Next, a belt-shaped intermediate transfer medium, which is charged with a polarity opposite to that of the yellow toner, is brought into contact with the photoreceptor belt, and the yellow toner image formed on the photoreceptor belt is transferred.

After cleaning the remaining yellow toner, the photoreceptor belt is neutralized and the development and transfer of the first color is completed.

Below, the same operation as for the yellow toner is repeated for each color toner necessary to complete a color image, such as magenta and cyan. Through this series of operations, each color toner is sequentially superimposed on the intermediate transfer belt. After this superimposed toner image is transferred to a sheet of paper charged with the opposite polarity to that of the toner, the sheet is peeled off from the intermediate transfer belt by a peeling charger, and is ejected from the paper ejection port after being processed. It is configured so that the copying process is completed by

<Problems to be Solved by the Invention> By the way, in the above-mentioned copying process, the second and third color toner images on the photoreceptor belt are sequentially transferred to the intermediate transfer belt onto which the -th color toner image has been transferred. In the case of superimposed transfer, since these toners are all charged with the same polarity, they repel each other and cause image defects. In particular, in areas where toner overlaps, the potential increases each time the toner is transferred, so this phenomenon becomes remarkable. If the above image defects occur, toner may scatter (particularly around characters and lines, causing image bleeding),
Alternatively, the toner that has already been transferred may be reversely transferred, causing partial tones to be generated, resulting in a significant deterioration in image quality.

In addition, especially between the second transfer stage and the third transfer stage, the intermediate transfer medium rotates (medium rotation), and at this time, the toner image transferred to the intermediate transfer medium is returned to the surface of the photoreceptor. There was a problem in that the transferred toner image looked unsightly.

Therefore, an object of the present invention is to provide a color copying apparatus that can consistently produce images of excellent quality.

Means for Solving the Problems> The present invention provides a full-color copying device in which toner images of each color component formed on a photoconductor are once superimposed on an intermediate transfer medium and then transferred to paper. means for making the transfer potential at the final transfer stage higher than the potential at the immediately preceding transfer stage when transferring the toner image of each color component from 1 to the intermediate transfer medium; and means for applying a voltage of.

Since the transfer potential is increased at the final transfer stage, where the transfer efficiency is lowest, it is possible to compensate for the decrease in transfer efficiency, and also to apply a predetermined voltage to the intermediate transfer medium during idle rotation of the intermediate transfer medium. Therefore, it is possible to prevent the transferred toner from scattering onto the photoreceptor. In particular, the applied voltage during idle rotation is
Since the applied voltage is high when the process speed of the intermediate transfer medium is fast and is low when the process speed is slow, toner scattering can be effectively prevented.

<Example> An example of the present invention will be described below based on FIG.

As shown in FIG. 1, a full-color copying machine (hereinafter referred to as a copying machine) as an electrophotographic device is provided with a document table 3 on which a document 2 is placed at the top of a machine frame 1. 3
A copy lamp 4, a mirror 5..., a lens 6, and a filter device 7 having blue, Φ, red, and green filters are provided below the original 2, and a photoreceptor belt 8, which will be described later, scans the original 2 with exposure.
An optical system section 9 is provided for forming an electrostatic latent image.

A photoreceptor belt 8 made of, for example, an organic photoreceptor (OPc) is provided below the optical system section 9. The photoreceptor belt 8 is connected to driving rollers 10 arranged in parallel at regular intervals. A hook is provided between the driven roller 11 and the driven roller 11. Around the photoreceptor belt 8, a main charger 12, a developing device 13-14, a cleaner 16, and a static elimination lamp 17 are provided facing the photoreceptor belt 8. On 13th, 14th and 15th,
Yellow, magenta, and cyan developers are stored respectively.

An intermediate transfer device 18 is provided near the drive roller 10 mentioned above. This intermediate transfer device 18 includes an intermediate transfer belt 19 as an intermediate transfer medium, and rollers zO, 21, and 3.
5, an intermediate transfer roller 22, a paper transfer roller 23, a paper peeling plate 24, a cleaner 25, and the like.

The intermediate transfer belt 1 is attached to the rollers 20, 21, and 35 mentioned above.
The rollers 20-21 and 35 are in contact with the surface of the photoreceptor belt 8 located on the outer periphery of the drive roller 10. Around the intermediate transfer belt 19, an intermediate transfer roller 22, a paper transfer roller 23, a paper peeling plate 24, a cleaner 25, etc. are installed on the inner circumference of the intermediate transfer belt 19 and in the order of the transfer process from the contact position with the photoreceptor belt 8. It is provided facing the outer periphery.

On the paper feed side for the intermediate transfer device 18, a paper 26 is provided.
Paper cassettes 27-28 containing ... are installed above and below. Paper feed rollers 29-30 and timing rollers 31, 31 are provided between the upper part of each paper cassette 27φ28 and the intermediate transfer device 18. Also,
A conveyor belt 32 is provided on the paper ejection side with respect to the intermediate transfer device 18.
, a fixing device 33 and a paper discharge section 34 are provided.

FIG. 2 shows the control circuit. In the figure, a is a transfer stage detector, which detects all the states of the transfer stage to the intermediate transfer belt 18, and sends the information f: 110 to the CPU (d
). C is a process speed detector (C), which similarly outputs two pieces of information, slow and fast, to the CPU (d) via the I10 port (b). CPU (
d) outputs a voltage control signal to the voltage control circuit (e) according to information from the transfer stage detector (a) and the process speed detector (c).

The voltage control circuit (e) applies 600 V to the intermediate transfer roller (g) in response to the voltage control signal from the CPU (d).
600V.

1000 V+ P IV, P2 Vf selectively supply DC power supply (f) control.

In the above configuration, during a copying operation in this copying machine, the copy lamp 4 and mirror 5 of the optical system section 9 reciprocate on the lower surface of the document table 3 in the directions of arrows A and B to copy the document 2. scan. The reflected light of the light irradiated onto the original 2 from the copy lamp 4 passes through mirrors 5 .
The main charger 12 reaches the surface of the photoreceptor belt 8, which is uniformly charged to, for example, a negative polarity, and an electrostatic latent image corresponding to a third color, for example, yellow, is formed on the photoreceptor belt 8. This electrostatic latent image is developed by attracting positively charged yellow toner in the developing device 13 and reaches the intermediate transfer belt 19 of the intermediate transfer device 18 .

The intermediate transfer belt 19 is negatively charged by the intermediate transfer roller 22 to which 600 V'i is applied under the control of the voltage control circuit (e), and adsorbs and transfers the positive yellow toner image on the photoreceptor belt 8. . The intermediate transfer belt 19 continues to move, goes through the same process, is negatively charged by the intermediate transfer roller 22 to which 600 V is similarly applied, and absorbs and transfers the magenta toner image on the photoreceptor belt 8. Furthermore, in the final stage of transfer, the intermediate transfer belt 19
The intermediate transfer roller 22 to which OV is applied is negatively charged and adsorbs and transfers the cyan toner image on the photoreceptor belt 8 .

By the way, during idle rotation of the intermediate transfer belt 19 between each transfer stage, a high applied voltage PIv is applied depending on the process speed, for example, when the process speed is high,
Also, when the process speed is slow, the applied voltage p2 is low.
v is applied. In this way, it is possible to effectively suppress a decrease in transfer efficiency and prevent toner from scattering during idle rotation.

In the above embodiment, the transfer voltage is changed in the second and third transfer stages, but it may be changed in all the transfer stages. Furthermore, it is also effective to apply heavy application during idle rotation only at the second and third transfer stages.

Effects As described in detail above, according to the present invention, development such as scattering due to reduction in transfer efficiency and mutual repulsion of toner during idle rotation is eliminated, and good color images can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a full-color copying machine according to the present invention, and FIG. 2 is a control circuit diagram. a is a transfer stage detector, C is a process speed detector, e
is a voltage control circuit, f is a DC power supply, and g is an intermediate transfer roller.

Claims (1)

[Scope of Claims] 1. In a full-color copying device in which a toner image of each color component formed on a photoreceptor is once superimposed on an intermediate transfer medium and then transferred to paper, the toner image of each color component is transferred from the photoreceptor to a sheet of paper. means for making the transfer potential at the final transfer stage higher than the potential at the immediately preceding transfer stage when transferring the image to the intermediate transfer medium; and means for applying a predetermined voltage to the intermediate transfer medium during the transition to each of the transfer stages. A full-color copying device characterized by comprising: