JPH0326524Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a two-color image forming apparatus, and particularly to an improvement of a corona discharger for secondary charging.

[Prior art]

The conventional two-color image forming process will be explained with reference to FIG. 2. Perform image exposure of the black area A, red area B, and white background area C).

By this image exposure, an electrostatic latent image corresponding to the A section of the original OR is formed on the photoreceptor P, and the electrostatic latent image is developed with A color toner a corresponding to the A section of the original OR. . In this state, the polarity is opposite to that of A,
That is, the surface of the photoreceptor P is positively charged, and then the image of the original OR is exposed again through a cyan filter to form an electrostatic latent image corresponding to part B of the original OR on the photoreceptor P, and then the original is removed. B corresponding to part B of OR
Develop with color toner B.

In this way, the A color toner a is deposited on the photoreceptor P.
A two-color toner image is formed using the B-color toner b and B color toner b, and when this is transferred and fixed onto a transfer paper (not shown), a two-color image is formed.

By the way, positive polarity charging is performed by secondary charging, but since the electrostatic latent image on the photoreceptor P has a negative potential at this point, if secondary charging is performed without taking any measures, secondary charging will occur. Positive corona discharge current due to charging tends to flow into areas with high negative potential, and especially in thin lines and edges, because the electric field contrast with the surrounding area is high, it tends to concentrate and flow, even to areas that should be suppressed to approximately zero potential by secondary charging. is charged to the opposite polarity, and when developing the second color, the B color toner b also adheres to the photoreceptor P portion corresponding to the A portion of the original OR.

In order to prevent this phenomenon, it has been proposed to perform secondary charging using a corona discharger as shown in FIG. That is, an insulating slit member 3 is provided at a right angle to the side surface of the shield at the opening for corona ion irradiation of a corona discharger consisting of a corona discharge electrode 1 and a conductive shield 2, and this insulating slit member 3 irradiates corona ions. This is intended to narrow the width of the current and increase the straightness and speed of the corona discharge current to prevent it from flowing concentratedly into high potential areas of opposite polarity on the photoreceptor P. Incidentally, the photoreceptor P in FIG. 2 consists of a photoconductor layer 4 and a conductive substrate 5.

[Problems with conventional technology]

However, if the insulating slit member 3 is provided perpendicular to the side surface of the shield, the insulating slit member 3 charged by the corona discharge current will control the flow of the corona discharge current to the charged surface. Most of the discharge current is absorbed by the shield 2, reducing charging efficiency. In addition, if a large amount of discharge is performed at a very high voltage in order to obtain a sufficient amount of charge, the lines of electric force inside the slit will act strongly as shown in Figure 3, causing the corona discharge current to be significantly bent, and instead This hinders the convergence effect. Also,
Compared to a normal full-opening device, the charging width is inevitably narrower and the amount of charging is smaller, so it has the disadvantage of uneven charging. Therefore, good secondary charging is not performed.

[Purpose of invention]

In view of the above-mentioned conventional drawbacks, the present invention improves the linearity and speed of the corona discharge current during secondary charging, improves the charging efficiency, and performs good secondary charging.
It is an object of the present invention to provide a two-color image forming apparatus that can obtain clear two-color images.

[Key points of the idea]

In order to achieve the above object, the present invention performs primary charging with a predetermined polarity, and performs primary charging on a photoreceptor on which a first latent image or a first developed image is still formed by image exposure, development, etc. In a two-color image forming apparatus using a corona discharge current, which is provided with a slit member having an opening for controlling a corona ion flow in the vicinity of an opening for corona ion irradiation when performing secondary charging of opposite polarity, The slit member includes a first conductor layer to which a bias voltage having the same polarity as the voltage applied to the corona wire of the corona discharger, an insulator layer, and a bias voltage having the same polarity as the bias voltage and lower thereby. It is composed of two slit members, a conductive slit member and an insulating slit member, which are laminated in the order of the second conductor layer to which a voltage is applied, and the two slit members are arranged to extend the conductive layer from the opening side toward the photoreceptor side. A slit member and an insulating slit member are disposed in this order, and the conductive slit member is disposed with the first conductive layer side facing the opening side.

[Example of idea]

An embodiment of the present invention will be described in detail below with reference to the drawings.

2 image formed by the two-color image forming apparatus of the present invention.
The color image formation process is similar to that shown in FIG.
Next, a first developed image (for example, a black toner image) is formed through image exposure and development, and then a second developed image (for example, a black toner image) is charged on the photoreceptor with the opposite polarity to the primary charge. A second developed image (for example, a red toner image) is formed by image exposure and development, and then the first developed image and second developed image on the photoreceptor are transferred to transfer paper and fixed, resulting in a two-color image. However, in performing the above-mentioned secondary charging, the present invention uses a corona discharger shown in FIG.

FIG. 4 is a configuration diagram of a corona discharge current used for secondary charging in the present invention. Note that the same parts as in FIG. 2 are denoted by the same reference numerals, and redundant explanation will be omitted.

In FIG. 4, two slit members are provided near the opening for corona ion irradiation of the corona discharger. First, an electrode slit member 7 is provided as the first slit member, and an opening is provided in the center of the electrode slit member 7. 11 is formed. The electrode slit member 7 is composed of three layers, conductor layers 7a and 7c and an insulator layer 7b, and a predetermined bias is applied to the conductor layers 7a and 7c by a bias power supply 9. Further, an insulating spacer 8 is interposed between the conductor layer 7a and the conductive shield 2. Furthermore, an insulating slit member 6 is provided as a second slit member on the outside of the electrode slit member 7, that is, on the side closer to the surface of the photoreceptor P, and an opening 10 is formed in the center of the insulating slit member 6.

With the above configuration, the photoreceptor P of the electrode slit member 7
By applying a bias of the same polarity as the bias applied to the corona discharge electrode 1 to the conductor layer 7c on the surface side, and applying a potential higher than the bias potential to the other conductor layer 7a, the electrode slit member 7
As shown in FIG.
An electric field as shown by a solid line is generated from a to the conductor layer 7c. Therefore, the flowing corona ion stream as shown by the dotted line is accelerated by this electric field and can easily pass through the opening 11 of the electrode slit member 7. That is, as shown in FIG. 4, the corona ion flow passing through the opening 11 is constricted, but its speed is increased, so that the flow of corona ions passing through the opening 11 is
The number of ions that can pass through the opening 11 is increased compared to the case where a slit member is simply provided, and it is as if the area of the opening 11 has been increased, so that the utilization efficiency of the corona discharge current is significantly improved. In addition, the opening 11
The corona ion flow that has passed through is attracted by the electric field formed between the conductor layer 7c and the conductive substrate 5 serving as a back electrode, reaches the photoconductor layer 4, and charges it. A portion of the corona ions whose traveling direction is bent by the electric field of the electrode slit member 7 is blocked by the insulating slit 6, and the corona ions as a whole that have passed through the opening 10 of the insulating slit member 6 continue to travel straight. Becomes superior in quality. In this way, the straightness of the corona discharge current increases, so corona ions of opposite polarity are no longer attracted to the high potential area of the photoreceptor P after the primary charging, and there is no longer a problem where the potential difference immediately before the secondary charging occurs. Secondary electrification is performed while relatively maintaining . Furthermore, since the charging efficiency is improved, the potential of the black corresponding area on the photoreceptor P can be suppressed sufficiently low, and the potential of the red corresponding area can be made high enough to enable development. This causes phenomena such as color mixing that occurs during red development due to the uneven flow of positive charges into the black latent image area due to secondary charging, and black-red reversal due to the concentrated flow of positive charges into thin lines or edge areas. is eliminated, and a clear two-color image is obtained.

As another modification process, after the surface of the photoreceptor is uniformly and negatively charged, it is exposed to image light through a red filter to form a first electrostatic latent image, and then the first electrostatic latent image on the surface of the photoreceptor is After positively charging other parts than the forming part, image exposure is performed again through a cyan filter to form a second electrostatic latent image, and the first electrostatic latent image and the second electrostatic latent image are In a two-color image forming apparatus that sequentially develops and visualizes images using two types of toners of different colors each charged with opposite polarity, performing secondary charging according to the present invention has a similar effect.

[Effect of idea]

As explained in detail above, the two-color image forming apparatus of the present invention improves the linearity and speed of the corona discharge current during secondary charging, and also improves the charging efficiency, so that the corona discharge current changes depending on the potential of the photoreceptor. Regardless of the color, the particles flow uniformly throughout the entire surface, resulting in good secondary charging and a clear two-color image.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the two-color image forming process;
2 and 3 are configuration diagrams of a conventional corona discharger used for secondary charging, and FIG. 4 is a configuration diagram of a corona discharger used for secondary charging in the present invention. 1... Corona discharge electrode, 2... Conductive shield, 6
... Insulating slit member, 7... Electrode slit member,
8... Insulating spacer, 9... Bias power supply, 10,
11...Aperture, OR...Original, P...Photoconductor.

Claims (1)

[Claims for Utility Model Registration] Primary charging of a predetermined polarity is performed, and a first latent image or a first developed image is formed on the photoreceptor by image exposure, development, etc. In a two-color image forming apparatus using a corona discharger equipped with a slit member having an opening for controlling corona ion flow near an opening for corona ion irradiation when performing secondary charging, the slit member is , a first conductor layer and an insulator layer to which a bias voltage having the same polarity as the voltage applied to the corona wire of the corona discharger is applied;
It is composed of two slit parts: a conductive slit member laminated in the order of a second conductive layer to which a bias voltage of the same polarity as the bias voltage and lower than the bias voltage is applied, and an insulating slit member, and the two slit members are The conductive slit member and the insulating slit member are disposed in this order from the opening side toward the photoreceptor side, and the conductive slit member is disposed with the first conductive layer side facing the opening side. A two-color image forming apparatus.