JPS6252296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer method in a multicolor electrophotographic copying machine.

Multicolor electrophotographic copying machines use a system that separates the light image of the original into colors, forms toner images for each color on multiple photoreceptor drums, and transfers the toner images to paper, making it compact, inexpensive, and capable of high-speed copying. is possible. As such a conventional multicolor electrophotographic copying machine, a configuration as shown in FIG. 1 is known. In the figure, a charger 2 is placed around a photoreceptor drum 1 that forms an image of each color (the example in the figure shows a case where three colors are formed using three photoreceptor drums), and a photoreceptor 2 is used to transfer the color-separated optical image of the original to the photoreceptor. An optical device 3 for projecting images onto the photosensitive drum 1, a developing device 4, a transfer charger 5, and a static elimination charger 6 are arranged, and the paper 7 is transported to each photosensitive drum 1 by a conveyor belt 8 made of a dielectric belt.
The image is transported to one transfer position after another. Since similar members are arranged for each photoreceptor drum, corresponding members are given the same reference numerals, and each photoreceptor drum is distinguished by the addition of suffixes a, b, and c.

In such a copying machine, an optical device 3 is mounted on a photosensitive drum 1 which is charged by a charger 2.
The color-separated optical image is exposed for each color to form an electrostatic latent image, and the electrostatic latent image is developed into a predetermined color by the developing device 4 to form a toner image. The toner image is transferred to the paper that is attracted and conveyed under the action of the transfer charger 5.

Although the transfer on the first photoreceptor drum 1a is easily carried out, electric discharge occurs when the surface of the photoreceptor drum 1a and the paper 7 or the belt 8 are separated immediately after the transfer. Generates electrical charge. Since the belt is an insulator, charges cannot escape, and therefore the charging caused by peeling discharge affects the next transfer on the second photosensitive drum 1b. In other words, the electric charge remaining on the belt 8 cancels out the electric field by the second transfer charger 5b and makes transfer charging difficult, thereby inhibiting the transfer of the second photoreceptor drum 1b. The same thing occurs with respect to the third photosensitive drum 1c.

For example, if a conveyor belt made of 125 μ thick polyethylene terephthalate film is moved at a linear speed of 100 mm/sec and a +5.5 KV corona charge is applied from the back side of the belt while transferring, the surface of the polyethylene terephthalate will generate a potential of -1500 V after transfer. .

Second photoreceptor drum 1b, third photoreceptor drum 1c
In order to increase the transfer efficiency, a good transfer rate can be obtained by increasing the voltage applied to the second transfer charger 5b and the third transfer charger 5c, for example, to 6.5KV or 7.5KV. However, in this case, the transfer voltage must be changed for each transfer charger, making control complicated and inconvenient.Also, since the voltage is high, direct discharge may occur between the charge wire and the charge case in the case of a small charger. Abnormal discharge occurs, resulting in inconveniences such as a moon-shaped white spot on the transferred image and a resin-like pattern on the copy.

In order to eliminate the inconvenience caused by post-transfer peel-off discharge, there is a method of eliminating electricity immediately after transfer, as shown in FIG. That is, the paper 7 separated from the photoreceptor drum 1a and the conveyor belt 8 are transferred to a static elimination charger 9a to which a voltage of AC3.2KV RMS is applied, for example, and a counter electrode 10.
The static electricity is eliminated by passing between the Similarly, photoreceptor drum 1
After being separated from the charger 9b, the static electricity is eliminated between the static elimination charger 9b and the counter electrode 10b.

In this case, peeling discharge occurs between the conveyor belt 8 and the counter electrode 10a, so that the charge removal of the toner on the paper becomes uneven, and the toner has (+) portions and (-) portions. The same goes for the back side of the belt. Therefore, the toner is subjected to random forces. When the transfer position of the next photoreceptor drum is reached in this state, the toner with non-uniform charge is affected by the electric field caused by the transfer charger, and some of the toner moves from the paper toward the photoreceptor drum. This causes uneven transfer and reverse transcription. Such uneven transfer and reverse transfer are repeated on each photosensitive drum, resulting in poor image quality. In addition, the charger becomes seriously dirty due to toner scattering.

An object of the present invention is to provide a transfer method that eliminates the above-mentioned disadvantages.

This problem has been achieved by the present invention by creating a method for uniformly removing static electricity and preventing peeling discharge from occurring.

The details of the present invention will be explained with reference to embodiments shown in the figures.

In FIG. 3, each photoreceptor drum 1a, 1b, 1
After the transfer of image c, corona chargers 11 and 12 are provided on both sides of the belt 8 and the paper 7 and are disposed facing each other, and the belt 8 and the paper 7 are sandwiched from both sides by corona discharge to eliminate static electricity.

The chargers 11 and 12 are connected to an AC high voltage power supply 13.
can also be connected directly as shown in Figure 4.
As shown in FIG. 5, a capacitor 14 may be interposed between the chargers 11 and 12 so that one of the AC voltages is 90 degrees out of phase with the AC voltage power source 13. Furthermore, as shown in FIG. 6, if a transformer is interposed and the phase is shifted by 180 degrees, a good static elimination effect can be obtained.

Furthermore, as shown in FIG.
It is also possible to connect DC power supplies 15, 15' to the chargers 11, 12, respectively, so as to apply voltages of opposite polarity to the chargers 11, 12, respectively.

Each charger 11, 12 is installed so that a 0.06 mm diameter tungsten charge wire 17 stretched at the center of a 20 mm diameter charger case 16 is separated from the belt 8 or paper 7 by about 10 mm.
When a voltage of AC3.2KV RMS was applied with a phase shift of 90° to eliminate static electricity from the paper 7 and belt 8, uneven transfer and reverse transfer were reduced, and stains on the static elimination charger due to toner scattering were also reduced. I was able to obtain a copy with a beautiful color image.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional copying machine, FIG. 2 is an explanatory diagram of a conventional static elimination method, FIG. 3 is an explanatory diagram of a static elimination method according to the present invention, and FIGS. 4 to 7 are diagrams according to the present invention. It is a figure which shows the modification of the voltage application method of a static elimination charger. 1a, 1b, 1c...photosensitive drum, 5a, 5
b, 5c...Transfer charger, 7...Paper, 8...
... Conveyor belt, 11, 12 ... Static elimination charger, 13 ... AC power supply, 15 ... DC power supply.

Claims (1)

[Claims] 1. A plurality of photoconductor drums are exposed to color-separated optical images of the original to form electrostatic latent images, and the electrostatic latent images are developed toner images of different colors, which are conveyed by a conveyor belt made of a dielectric belt. In the transfer method of a multicolor electrophotographic copying machine, in which the toner image on the photoreceptor drum is sequentially transferred onto paper, the toner image on the photoreceptor drum is transferred to the paper under corona discharge by a transfer charger placed opposite the photoreceptor drum with a conveyor belt and the paper in between. A transfer method for a multicolor electrophotographic copying machine, characterized in that residual charges on the paper and belt are eliminated by transferring, and performing corona discharge using a static elimination charger that applies AC or DC voltage from both sides of the paper and belt after the transfer. .