JPS59174860A - Dichroic electrophotographing device - Google Patents

Abstract

PURPOSE:To remove mixed toner effectively and obtain a clear dichroic toner image for a long period by making the bias voltage of a developing device for postdevelopment opposite in polarity to the electrostatic charge of a photoconductive recording body. CONSTITUTION:The position of the 1st toner 5 on a friction charge sequence is so selected that its polarity is negative when the toner is mixed with the developer in the 2nd developing machine 7 and rubbed. Consequently, when the 2nd latent image is developed by the 2nd developing machine 7, the mixed toner 5 sticks to a no-image part of the recording body 1 which is charged positively. Then, the toner image on the recording body 1 is transferred to recording paper. The toner 5 sticking to the no-image part is not transferred by being repulsed by coronas for transfer which have the same polarity and removed at a cleaner part. When the 2nd developing machine 7 is applied with a negative bias by a bias power source 11, the mixed toner 5 sticks to the no-image part of the recording body 1 effectively and a clear dichroic toner image is obtained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a two-color electrophotographic apparatus, and particularly to a developing device thereof.

[Hatsu, a background of my friend]

As an apparatus for obtaining toner images of 92 colors by electrophotography, the surface of a uniformly charged photoconductive recording drum is imagewise exposed to form an electrostatic latent image, and this is used to form an electrostatic latent image containing toner of a first color. The component developer is subjected to reversal development by a first developing device using a magnetic brush, and then a second electrostatic latent image is created by a second image exposure, and this is converted into a two-component developer containing a second color toner. It has been proposed to carry out reversal development using a second developing device that utilizes a magnetic brush for developer. However, in this device,
Before the first color toner image is fixed, a second electrostatic latent image is created and developed again in the second developing machine, so the first color toner is rubbed by the second color magnetic brush. Mixed into the second developing machine. If this operation is repeated, the amount of the first color toner in the second developing machine increases, causing the second color toner image to mix, making it impossible to obtain a clear two-color toner image. .

[Object of the Invention] Therefore, the object of the present invention is to provide a clear two-dimensional image during long-term operation.
An object of the present invention is to provide a two-color electrophotographic device capable of obtaining color toner images.

[Summary of the invention]

In order to achieve the above object, the present invention performs reversal development with a first toner and then performs reversal development with a second toner.
It is designed to develop by applying a bias voltage with the opposite polarity to the potential of the latent image to the second developing device, so that the first toner becomes the potential of the latent image and the opposite polarity due to friction with the second developer. By selecting a toner that is electrically charged, when developing the second latent image, the first toner mixed in the second developing machine can be applied to the non-image area of the second electrostatic latent image. It is characterized in that color mixing is prevented by allowing the toner to adhere and removing it from the second developing device.

[Embodiments of the Invention] Hereinafter, embodiments of the F1 invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a non-impact printer that performs two-color printing 9 using electrostatic recording technology using electrophotography to which the present invention is applied.

In the figure, the surface of a photoconductive recording medium 1 rotating clockwise is uniformly charged by a charger 2 in a dark place. For example, when selenium is used as the photoconductive recording material 1, it is positively charged. Next, a first electrostatic latent image is created using the first light beam 3, and this is reversely developed by the first developing device 4. Here, a laser beam is used as the first light beam 3, and this light is changed intermittently or in intensity by mapping converted into an electric signal, and the surface of the photoconductive recording medium 10 is exposed to form an electrostatic latent image. It will be done. Further, since reversal development is performed in the first developing device 4, the first toner 5 having a positive charge is used as a developer. As a result, the first
The area covered by the light beam 3 is developed to form a toner image. A second light beam 6 is then applied to create a second electrostatic latent image on the photoconductive record 1, which is then reversibly developed by a second color toner 8 placed in a second developer 7. be done.

It goes without saying that the second toner 8 also has a positive charge. Thereafter, the two-color toner image formed on the surface of the photoconductive recording medium 10 is electrostatically transferred to the recording paper 9. However, conventionally, when performing the second development, when the toner image formed in the first development is rubbed during the second development, a portion of the toner image is peeled off and mixed into the second developer. Repeated use not only causes color mixing in the toner image formed by the second developing device, but also has the serious drawback of degrading the developing characteristics of the second developing device 7.

As a method for preventing this color mixture, the toner 8 in the second developing machine is replaced with the first toner 5 mixed in the second developing machine 7.
A toner whose charged polarity is reversed from positive to negative due to friction with the toner is selected, and when developing the second latent image, the image area is developed with the second toner 8, and the second developing An effective method is to remove the toner 5 that has entered the machine 7 by allowing it to adhere to the non-image area.

The present invention relates to a two-color electrophotographic apparatus that makes the method for preventing color mixture more effective.

An embodiment of the present invention will be explained with reference to FIG. Normally, in non-impact printers, reversal development is used to prevent background smudges on recordings.

In other words, the area corresponding to the image is exposed to light to eliminate the surface potential, and toner is attached to the area where the electric charge has disappeared. For example, taking the case of a selenium photoreceptor, in FIG. 2, selenium 1 is uniformly charged to a positive polarity of 700 V by charger 2, and is exposed to light beam 3, which corresponds to the image area. The charge disappears at the location, resulting in a residual potential of 0 to 300V. This residual potential area is developed using a developing device 4 containing a developer composed of a carrier charged to a negative polarity and a toner 5 charged to a positive polarity, and the latent image area of 0 to 300 cm is charged to a positive polarity. The applied toner is applied to create a toner image. In this case, applying a positive bias of 0 to 300 to 600 V to the developing device 4 in contrast to the bias power supply 10 is effective in improving the developing effect.

Next, the second latent image formed by the irradiation with the second light beam 6 is reversely developed by a second developing device 7. The development using the toner 8 used for the second development is also a two-component magnetic brush development, and the second toner 8 is also positively charged. During development with the second toner 8, since the surface of the photoconductive recording medium 1 is rubbed with a magnetic brush, a part of the first toner 5 adhering to the surface of the recording medium 1 is peeled off, and the first toner 5 is removed. mixed into the developing machine 7 of No. 2. If this is repeated, the concentration of the mixed toner 5 in the second developing device 7 becomes high, and when developing the second latent image, the printed image is developed by developing with a mixture of toner 5 and toner 8. The colors will be mixed. put it here,
By selecting the position of the first toner 5 on the triboelectrification series so that it has negative polarity when mixed and rubbed into the developer in the second developing machine 7, the first toner 5 is charged with negative polarity. The mixed toner 5 has negative polarity. As a result, when the second developing device 7 develops the second latent image, the mixed toner 5 is transferred to the recording medium 1.
It adheres to non-image areas of the image, that is, areas where charges remain.

After this, the toner image on the recording medium 1 is transferred to a recording paper 9 (not shown).
transferred by negative corona transfer. Here, the toner 5 adhering to the non-image area is repelled by the transfer corona of the same polarity and is not transferred, but reaches a cleaner section (not shown) and is removed.

Here, applying a negative polarity bias of 0 to 300 μ by the bias power supply 11 to the second developing device 7 is effective in making the mixed toner 5 adhere to the non-latent image area of the recording medium 1, and the negative polarity When the bias exceeds 300 square meters, it begins to adhere to the latent image area. From this, it can be understood that in order to effectively remove the toner 5 mixed into the second developing device 7, it is effective to apply a bias voltage opposite to the charging characteristics of the photoconductive recording medium 1.

As for the developer used in this example, both toners were mainly composed of styrene-butyl methacrylate copolymer resin, the first toner was mixed with carbon black and nigrosine dye, and the second toner was mixed with carbon black and nigrosine dye. A toner containing watching red as a coloring agent was used, and an iron oxide powder carrier was used as a carrier. When selecting these toners and carriers, as mentioned above, when the first toner 5 enters the second developing device 7, the charged polarity may be opposite to that of the second toner 8 due to friction. is necessary. Therefore, it is necessary to select and adjust in advance the carrier material, the type of toner resin, the pigment, dye, charge control agent, etc. to be added thereto.

In addition, as the bias voltage during development in the example, θ ~
Although 300V has been explained, the optimum value varies depending on the resistance value of the developer, and these voltage widths should be changed depending on the developer.

In the above explanation, an example was explained in which black was used as the first color toner 5. However, when black toner is used as the first color, this toner gets mixed into the second developing machine, and this toner is used in the present invention. It was explained that if the device effectively adheres to the non-image area, that is, the white area, and removes it, it will not be electrostatically adhered when transferred to the recording paper, but some of it will be recorded due to mechanical pressure or other factors. There is a transition to paper, and it becomes a black dot on a blank sheet of paper. This result degrades the quality of the recording paper. On the other hand, if a light colored toner is used as the first color, it is advantageous because the dirt on the recording paper will not be noticeable.

Furthermore, another advantage of using the present invention is that it is possible to prevent a phenomenon in which a toner image of a second color is developed overlapping a toner image of a first color. In other words, the reverse bias allows the second toner to adhere only to the latent image of the second color. Therefore, when adjusting in this way, even if a chromatic color is used as the first color and a black toner is used as the second color, it is effective to prevent the second color toner from adhering to the first color toner image and color clouding. be. Therefore, if the present invention is used, there is no restriction on the color order and it is easy to set it arbitrarily.

〔Effect of the invention〕

As explained above, according to the present invention, the bias voltage of the developing device for later development is set to 1 to effectively remove the mixed toner by setting the polarity opposite to the charging polarity of the recording medium. It is possible to obtain clear two-color images without color mixture over a long period of time without deteriorating the developing characteristics of the second developing machine.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a general two-color printing Jinon impact printer to which the present invention is applied, and FIG. 2 is a schematic configuration diagram of a two-color printing Jinon impact printer showing an embodiment of the present invention. 1... Photoconductive recording medium, 2... Charger, 3... First
4... First developing machine, 5... First toner, 6... Second light ray, 7... Second developing machine, 8...
・Second color toner, 9. Recording paper, 10. Bias power supply for the first developing machine, Fig. 1, Fig. 2 Threshold

Claims (1)

[Scope of Claims] 1. A first developing device that reversely develops a first charge latent image formed on a photoconductive recording medium, and a photoconductive device in which the first charge latent image is developed. A two-color electrophotographic apparatus comprising a second developing device for reversing developing a second charge latent image formed on the recording medium, wherein the second developing device is configured to control the polarity of the charged charge on the photoconductive recording medium. A two-color electrophotographic apparatus characterized by being provided with a bias power supply that provides a bias voltage of opposite polarity. 2. In claim 1, the first developing device uses a toner with a higher color brightness, and the second developing device uses a toner with a lower brightness. A two-color electrophotographic device characterized by: