JPS5911906B2 - Development bias application control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wet type developing device that uses a bias developing method.

As is well known, there are two types of developing methods for electrostatic latent images: dry and wet. In the wet method, the developing toner is suspended in a solvent such as kerosene, so the particle size is fine, about 1 μm at most. Be made into powder.

Therefore, it has the advantage of being rich in gradation and resolution, but on the other hand, it is prone to fogging. That is, in the case of dry development, development is performed only when the surface potential of the recording medium reaches approximately 20V or more, whereas in wet development, development is performed even if the surface potential is close to OV, so that the surface potential on the recording medium is For example, toner also adheres to charged potential areas due to slight friction, etc., resulting in fog. In order to eliminate the above-mentioned drawbacks of the wet development method, a bias development method was devised.

For example, if the toner is a positive toner, a positive potential of about 30 V is applied to the recording medium by the i pair of developing electrodes to repel the toner, and the toner adheres only to the electrostatic latent image area, and the toner remains to the surrounding white area. This prevents it from adhering to the surface. Although fog can be effectively removed by this method, there is a drawback that the surface of one of the developing electrodes becomes black and stained during use. Therefore, a cleaning tool called a drainer is provided to keep the surface of the developing electrode clean, but the present invention minimizes the contamination of the developing electrode itself, eliminates the need for cleaning, and eliminates fogging. The aim is to obtain beautiful images that are not possible. The present invention includes a developer tank containing a developer;
A roller-shaped electrode is provided so that the lower part of its circumference is in contact with the developer, and an electrostatic latent electrode is provided at the entrance side of the developer tank and passes over the roller-shaped electrode into the developer tank. A feed roller that feeds the electrostatic recording paper holding an image, a squeezing roller that is provided on the exit side of the developer tank and that squeezes out the developer that has adhered to the electrostatic recording paper that has been developed, and the roller-shaped electrode. , means for applying a reverse bias to the recording paper to a feed roller and a squeeze roller, the wet type developing device scooping up a developer with the roller-shaped electrode to develop the electrostatic latent image on the electrostatic recording paper, Detectors for detecting the ingress and ejection of the electrostatic recording paper are provided at the entrance and exit of the developer tank, and during the period when any of the detectors is detecting the electrostatic recording paper, the reverse bias is applied. The present invention is characterized in that the application means is operated and the roller-shaped electrode is rotated only during the period, which will be described in detail below with reference to the drawings.

FIG. 1 shows a conventional wet-type developing device, in which numeral 1 is an electrostatic recording paper having a charge retention layer for holding a electrostatic latent image on its surface and a low-resistance base layer on its back surface.

2a, 2b are feeding rollers, 3a, 3b are developing rollers, 4
Reference numerals a and 4b denote squeezing rollers, 5 a developing solution tank, and 6 a developing solution in which plastron toner is suspended.

The upper feed roller and squeeze rollers 2a, 4a are grounded, and the developing rollers 3a, 3b are applied with a negative bias voltage -V of about 20 to 30 V, and rotate at high speed in the opposite direction to the direction in which the recording paper 1 travels. To explain the operation, the recording paper 1 is placed on the feed rollers 2a and 2b with its charge retention layer facing down.
It is inserted in between and moves in the direction of the arrow.

The developing rollers 3a and 3b rotate in the direction of the arrow to scoop up the developer 6 and apply it to the charge retention layer of the recording paper 1. Therefore, the positive toner in the developer is attracted to the negative electrostatic latent image formed on the charge retention layer, and development is performed. At this time, the developing rollers 3a and 3b are negatively biased with respect to the recording paper 1, and therefore the recording paper 1 is positively biased with respect to the developing rollers 3a and 3b and the developer 6, so that the positive The toner is subjected to a repulsive force by this positive bias voltage, and the positive toner is attracted only to the electrostatic latent image area having a high negative voltage, thereby removing fog. However, in such an apparatus, since a negative voltage is constantly applied to the developing rollers 3a and 3b and the toner in the developer is of a positive type, this toner and various foreign substances in the developer are transferred to the drum 3a.
, 3b.

As a result, the surface of the developing roller, which was initially a beautiful surface with a metallic luster, becomes contaminated with pitch black as time passes. In such a state, the black adhesive layers of the developing rollers 3a and 3b rub against the recording paper 1, and the surface of the recording paper becomes stained black. Therefore, in the conventional apparatus, a blade-shaped drainer 8 is applied to the developing rollers 3a and 3b to constantly peel off the black adhesive layer and prevent staining, but it is still not possible to ensure completeness. FIG. 2 shows a developing device according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the apparatus shown in FIG. 2, recording paper detectors Sl and S2 are arranged at the input and exit of the recording paper 1 to the developing section, and their outputs are input to the amplifier A through the OR circuit 0R. This amplifier A functions as a switching circuit, and when there is an input, it outputs a negative voltage -V and applies this to the developing rollers 3a and 3b, and when there is no input, it is in a zero voltage output state. Detector Sl,
As S2, a photoelectric type or other appropriate object detector can be used. The installation position of the detector S1 is between the developing roller groups 3a and 3.
The detector S2 is installed at an appropriate position before the first roller 3a in b and after the last roller 3b for development. In the apparatus shown in FIG. 2, when a recording paper on which an electrostatic latent image has been recorded enters the developing section, the detector 1 immediately detects this and generates an ON output as shown in FIG. As a result, amplifier A produces an output of 1 V and applies a reverse bias to developing rollers 3a and 3b. Although not shown, the output of the detector S1 is input to the drive motor control circuit for the developing rollers 3a and 3b, and when the recording paper 1 comes onto the developing roller 3a, this motor is activated to start the rotation of the developing rollers 3a and 3b. let Recording paper 1 is fed by feed rollers 2a and 2b and then delivered to developing rollers 3a and 3.
3b, these developing rollers come into contact with the scooped up developer to perform development, and then squeeze rollers 4a,
The adhering developer is squeezed out through 4b and discharged from the developing section. Detector S2 detects the recording paper 1 coming out from the developing section.
is detected and produces an ON output as shown in FIG. 3, which is applied to amplifier A through OR circuit 0R. Therefore, when the tail end of the recording paper 1 passes through the detector S1 and further passes through the detector S2, the outputs of both these detectors become zero, and -V in FIG.
As shown in , the amplifier A loses its output and the developing roller 3a
, 3b is stopped. By rotating the developing roller 3a after the recording paper 1 comes onto the developing roller 3a, it is possible to avoid the developer scooped up by the developing roller 3a flowing onto the upper surface of the recording paper 1 and contaminating it.

When the recording paper comes to the surface of the developing roller 3b, the roller is already rotating, but since it has not been rotating for a while, the amount of developer scooped up is small (in a steady state of rotation, a layer with a thickness of about 1 to 2 U is formed). ) There is little risk of contamination of the recording paper. As is clear from the above description, according to the present invention, the developing roller 3a
, 3b is applied only during development, and is in a no-voltage state during the standby state where no development is performed. This makes the development process faster compared to conventional devices in which a bias voltage is constantly applied. The amount of toner etc. adhering to the roller surface can be considerably reduced, thereby making it possible to minimize contamination of the recording paper.

Detectors Sl and S2 detect that the recording paper 1 is present in the developing section.If the recording paper 1 has a constant size and a constant speed, only the detector S1 may be used, but if the recording paper has different dimensions. Considering this fact and the fact that the developing section may be temporarily stopped in a state where the developing section is entered, it is preferable to provide the detectors Sl and S2 at both the entrance and the exit as in this embodiment.

Also, to reverse bias the recording paper to prevent fogging, apply a positive voltage to the feed and aperture rollers 2a, 4a, and apply a positive voltage to the developing roller 3a.
, 3b may be grounded.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the bias developing system, FIG. 2 is an explanatory diagram of the control system of the present invention, and FIG. 3 is a time chart for explaining the operation. In the drawing, 3a and 3b are developing rollers, 1 is recording paper, Sl and S
2 is a recording paper detector.

Claims (1)

[Claims] 1. A developer tank containing a developer, a roller-shaped electrode provided so that a lower part of the circumference is in contact with the developer, and a roller-shaped electrode provided on the entrance side of the developer tank, and the roller in the developer tank. A feed roller that feeds the electrostatic recording paper carrying the electrostatic latent image so as to pass over the shaped electrode, and a developer that is provided on the exit side of the developer tank and that adheres to the electrostatic recording paper that has been developed. and means for applying a recording paper reverse bias to the roller-shaped electrode, the feed roller, and the squeeze roller, and the developer is scooped up by the roller-shaped electrode to form an electrostatic latent image on the electrostatic recording paper. A wet-type developing device for developing an image, wherein detectors are provided at the inlet and outlet of the developer tank to detect the entry and ejection of the electrostatic recording paper, and one of the detectors detects when the electrostatic recording paper is detected. A wet type developing device characterized in that the reverse bias applying means is operated during the detection period, and the roller-shaped electrode is rotated only during the period.