JPS6134563A - Multicolor developing device - Google Patents

Abstract

PURPOSE:To obtain a flat single color image having no color mixing by changing over respectively separately the bias contributing to development and the bias prohibiting the development in each of plural pieces of developing devices. CONSTITUTION:The operator changes over a switch 6 belonging to the developing device having a cyan toner to the 1t bias power source 7 side in order to obtain a cyan image first in the case of a multi-color developing device using the three color toners; cyan, magenta and yellow. The operator changes over switches 13, 20 belonging to the other developing devices having the magenta toner and yellow toner to the 2nd bias power sources 15, 22 in this stage. The electrostatic latent image of an exposing body 1 is developed only by the cyan toner. The image having no color mixing is thus obtd. Such single color development is exectuted successively with the developing devices having the magenta and yellow toners, by which the flat multicolor image by the three-color toners is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact developing type developing device having a plurality of developing units arranged adjacent to a photoreceptor.

[Conventional technology]

Japanese Unexamined Patent Application Publication No. 4'1-13086 discloses a technique for multicolor development method. To explain this, a photoreceptor is uniformly charged by light reflected by an original containing distinguishable color information. The surface is exposed, and each color component of the document to be imaged is recorded at a separate charged potential on the photoreceptor surface. The photoreceptor is then passed to a development station that includes a number of developers equal to the number of distinguishable colors in the document.

A bias voltage is applied to each developer by electrical control means, and only color components recorded at or above a predetermined potential are developed in that developer. Development is performed sequentially starting from the color component recorded at the highest image potential.
Vias and voltages for each developer are set. For example, in a multicolor developing device consisting of a first developing device and a second developing device, as shown in FIG.
The image recorded on the toner is first developed with toner containing a first coloring agent in a first developing device. In this case, the bias potential Vbl in the first developing device is set between the high image potential v1 and the low image potential v2. Next, the image recorded at the lower image potential v2 is developed using toner containing the second colorant.

In this case, the bias potential vb2 in the second developing device is set lower than the low image potential v2.

[Problem that the invention seeks to solve]

According to the prior art, as described above, toner particles are attached to different potentials v1 and v2 of the same polarity. Therefore, when the bias voltage Vb2 is set lower than the low image potential v2 as shown in FIG. It also sticks. Therefore, in a portion with a high image potential V, color mixing occurs with the toner containing the first colorant that has already been developed. Further, in the conventional example described above, it is possible to develop not only two colors but also three or more colors, but there is a problem that sufficient image density cannot be obtained.

[Means and effects for solving the problem] The developing device of the present invention has a first bias power source that generates a voltage in which alternating current is superimposed on direct current, and a direct current potential having the same polarity as the surface potential of the photoreceptor. A second bias power supply is provided, and these two
The present invention is characterized in that a bias voltage switching means is provided between the two power supplies and the developing roller. A developing device that contributes to development is sequentially selected from among the plurality of developing devices, and the bias voltage switching means attached to the developing device is switched to connect the first bias power supply and the developing roller, and the bias voltage switching means attached to the developing device is switched to connect the first bias power supply and the developing roller. The bias voltage switching means is switched to connect the second bias power source and the developing roller. In this way, multicolor development is performed by sequentially switching each bias voltage switching means between the first degree bias power source and the second bias power source. There may be one or more developing devices that contribute to the development that should be selected simultaneously. Further, the bias voltage generated by the second bias power source is preferably 0.2 to 1.5 times the potential of the photoreceptor.

〔Example〕

FIG. 1 shows a developing device according to the present invention, in which three non-contact developing devices are provided adjacent to a photoreceptor 1. As shown in FIG.

Each developing device has the same configuration, and each developing roller 4
．． 11.18, and an equalizing roll 5.12.1 that contacts the developing roller and rotates due to frictional resistance with the developing roller.
9. Toner regulating member 2 that regulates toner on the developing roller
．． 9.16 and toner retaining member 3.10 on the equalizing member
．． It consists of 17. Further, toner containing different colorants is arranged in each developing device, and a bias voltage is applied to the core metal electrodes of the developing roller and the uniformizing roll. 7.
14.21 is a first developing bias power supply; 8.15.
22 is a second developing bias power supply. The first developing bias power source generates a voltage that is a combination of direct current and alternating current, and the toner attached to the developing roller is attracted to the photoreceptor by this developing bias voltage, thereby performing development. On the other hand, the second developing bias power supply generates a DC potential of the same polarity as the surface potential of the photoreceptor, and this generates an electric field between the developing roller and the surface of the photoreceptor that can attract toner to the photoreceptor. Since no development is carried out, it acts as a bias power source for preventing development.

Switches 6.13.20 are provided between the first and second bias power supplies and the developing roller, and these switches 6.13.20 switch between the first bias voltage and the second bias voltage. A bias voltage is selected. Here, when positively charged toner is used, the first bias voltage is a superposition of a DC voltage of 200 to 500V and an AC voltage of 500 to 1200V of 150 to 10007, and the second bias voltage is 600 to 500V. It has a DC voltage of 900μ.

Next, an example in which the present invention is applied to a multicolor developing device using toners of three colors, cyan, magenta, and yellow will be described. First, when obtaining a cyan image, a switch attached to a developing device having cyan toner is switched to the first bias power supply side. At this time, the switches attached to the developing devices containing the other magenta toner and yellow toner are switched to the second bias power supply side. As a result, the electrostatic latent image on the photoreceptor is developed only with cyan toner, and not with toner of the other two colors. Therefore, an image without color mixture can be obtained.

Thereafter, by sequentially carrying out such monochrome development in developing devices having magenta toner and yellow toner, a flat multicolor image using the three color toners can be obtained.

Furthermore, if the switch of the developing device containing cyan toner and magenta toner is set to the first developing bias power supply side, and the switch of the developing unit containing yellow toner is set to the second developing bias power supply side, the electrostatic latent image is formed by the cyan toner and magenta toner. Developed and not developed with yellow toner. In this case, since the toner layer and the photoreceptor are not in contact with each other, the first color toner image (cyan toner image) that has adhered to the photoreceptor first is not disturbed, and the second color toner image (magenta toner image) is formed.
is developed by the remaining developing electric field. As a result, a uniform blue image with sufficient density is obtained.

In the example above, the toner colors are cyan, magenta,
Although we used yellow toner, you may use a different color, for example, black toner, or you can add one more developer to create cyan, cyan,
It may be a four-color development system of magenta, yellow, and black, or a multicolor development system with more than four colors.

〔Effect of the invention〕

According to the present invention, a plurality of multicolor developments are sequentially performed by selectively switching the bias contributing to development and the bias preventing development in each of the plurality of developing devices, so that there is no color mixture. A flat monochrome image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a multicolor developing device according to the present invention, and FIG.
3 and 3 are graphs showing the basic principle of a multicolor developing device in the prior art. 1... Photoreceptor, 2.9.16... Toner regulation member,
3.10.17... Toner holding member, 4.11.18
...Developing roller, 5.12.19... Equalizing roll, 6.13.20... Changeover switch, 7.14.21
...First developing bar - Iasumi source, 8.15.22...
-Second development bias power supply.

Claims (1)

[Claims] (1) In a non-contact developing type developing device having a plurality of developing devices arranged adjacent to a photoreceptor, each developing device is
A developing roller, a first bias power source that generates a voltage that is a combination of direct current and alternating current, a second bias power source that generates a direct current voltage with the same polarity as the surface potential of the photoreceptor, and between these two power sources and the developing roller. 1. A multicolor developing device comprising: a bias voltage switching means disposed at a bias voltage switching means;