JPS584101Y2 - liquid developer - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a developing device for wet electrophotography.

In plain paper copying machines using wet electrophotography, an aluminum drum coated with selenium is commonly used as a photoreceptor.

This drum is not coated with a selenium vapor-deposited coating over its entire surface, and the aluminum surface is usually exposed at both ends. It is designed to push down rollers, etc.

Naturally, the aluminum surface portions at both ends of the drum are at ground potential, so in a normal development method where the image forming area is a portion with a higher potential than the other portions, toner does not adhere to the aluminum surface portion. There is no -1 in the developing process.

However, in an apparatus that functions as a terminal such as a computer, that is, an apparatus in which image exposure is performed using a cathode ray tube or an optical fiber tube, reversal development is performed.

That is, when a charged selenium photoreceptor layer is subjected to negative image exposure and developed with toner having the same polarity as the charging polarity, the toner adheres to the portions where the potential has dropped due to exposure, and a positive image is obtained.

When a liquid developer is used, as shown in FIG. 1, in order to uniformly supply the developer to the photoreceptor surface A, the charging electrode 1 needs to be wider than the photoreceptor part, and both ends of the electrode are This extends to the aluminum background portion B, and this background portion B, which is at ground potential, also attracts toner.

As a result, the aluminum background portion B is stained with toner, and the transfer paper is further contaminated via the above-mentioned L/sist roller or pick-off belt that comes into contact with this portion.

In view of the above-mentioned problems, the present invention aims to prevent the bias effect of the developing electrode from reaching the aluminum background portion, eliminate the toner suction effect, and thereby obtain high-quality images.

The present invention will be explained below with reference to illustrated embodiments.

In the first embodiment shown in FIG. 2, a side edge electrode 2 that is on the same plane as the developing electrode 1 is electrically insulated from the developing electrode 1 via an insulator 3, and the side edge electrode 2 is grounded. Therefore, the potential is the same as that of the aluminum background portion B.

According to this, the side edge electrode 2 merely has the function of uniformly flowing the developer, so even if a bias voltage that is equal to or slightly lower than the charged level of the photoreceptor surface A is applied to the developing electrode 1, , unnecessary bias is not applied to the side edge portions, and toner is prevented from adhering to the aluminum background portion B.

FIG. 3 shows another embodiment.

In this case, the developing electrode 1 has a sufficient width and is covered with ground electrodes 4 above both sides facing the aluminum background part BE via an insulator 3' to shield the bias seedlings.

This embodiment is an improvement over the structure shown in FIG. 2, in which the side edge portion 2 and the developing electrode 1 are integrated through an insulator, so that the structure is M, which makes it difficult to hold.

However, if the ground electrodes 2 and 4 as shown in FIGS. 2 and 3 are provided on both sides of the developing electrode 1, toner will not adhere to the aluminum background part B, but between the ground electrode 2 and the bias electrode. Since a high electric field is applied to the ground electrode 4, toner adheres to the ground electrode 4 and makes it dirty.

The embodiment shown in FIG.
4, a voltage lower than the bias voltage is applied, and according to this embodiment, the above-mentioned problems can be solved.

The one shown in FIG. 5 has been further developed, and the developing electrode 1
The side edge portion 1 of is made of an insulating material.

In the figure, reference numeral 8 indicates a developer tank, and 9 indicates a pump.

As described above, according to the present invention, since the bias voltage of the developing electrode does not act on the aluminum background portions at both ends of the drum, it is possible to completely prevent the drum of an apparatus for obtaining a reverse developed image by a wet development method from becoming dirty. It is.

Moreover, the fact that toner does not adhere to the aluminum surface also eliminates contamination of the equipment around the drum that comes in contact with it, which has the excellent effect of making it possible to obtain high-quality images.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing a conventional example of a liquid developing device, and FIGS. 2 to 5 are explanatory views showing embodiments of the present invention. A: Photoreceptor surface, B: Aluminum background portion, 1: Developing electrode, 2, 4: Ground electrode, 3. Please...insulator.

Claims (1)

[Scope of utility model registration request] In a wet electrophotographic transfer device having a developing electrode disposed opposite to a photoreceptor drum, a portion of the developing electrode facing the exposed metal portion of the photoreceptor drum,
A liquid developing device characterized in that it is provided directly or indirectly with means for shielding bias voltage effects.