JPS6370871A - Image forming method - Google Patents

Abstract

PURPOSE:To almost completely prevent a toner from being splashed, by forming an electric field in which a toner of a photodetecting part of an image exposure which has been carried on a photosensitive body receives an electric force in the direction of a photosensitive body surface by a process before an image exposure process, at the time of the image exposure process. CONSTITUTION:At the time of an image exposure process for forming at least a second image, an electric field in which a toner image of a first image receives an electric force in the direction of a photosensitive body surface is formed. The electric field is formed by providing a toner splash preventive electrode, and applying a voltage of the same polarity as that of a toner to said electrode. The toner splash preventive electrode 4 is provided on a necessary part, and installed at an exposing part where the toner splash is apt to be generated most, and also, at a position opposed to a photosensitive body 1. This toner splash preventive electrode 4 is a plate-shaped conductive member having an opening part for exposure, and by applying a voltage of the same polarity as that of the toner, to the toner splash preventive electrode 4 by a power source 5, the toner splash is prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an image forming method in which multiple toner images are obtained on a photoreceptor surface by repeating the processes of charging, image exposure, and development multiple times using electrophotography. The present invention relates to an image forming method.

[Background of the Invention ftl] In the image forming method in which charging, image exposure, and development are repeated multiple times on the surface of a photoconductor to obtain a toner image,
- When performing exposure by recharging the photoreceptor surface containing the toner image formed in the second process, if exposure is performed near the toner image, the electric field distribution near the toner image changes rapidly, so the toner image is Disturbed. Because toner particles are charged to the same polarity and repel each other, toner scatters, and even if there is a slight potential difference, toner adheres to areas where Coulomb force is applied, contaminating the inside of the device, and even causing uneven exposure. In addition to causing problems such as this, the image quality is degraded by causing fog on the image. This phenomenon is particularly noticeable in the case of reversal development. In the image forming method, an exposure system using a laser, LED, etc. as a light source performs image exposure to form an electrostatic latent image, and develops it with toner, which is a charged particle. This is done by scanning the body surface, but in a normal image, the area of the background is overwhelmingly larger than the colored area, so the area of the background is much larger than the colored area.
When exposed in such a way as to irradiate the area with light, (i) the life of the light source is shortened (ii) the life of the image forming body is shortened (iii)
The scanning unevenness of the optical system appears as lines on the background. There are other problems. For this reason, the skin is not exposed to light,
It is widely practiced to form a latent image by irradiating a colored portion. In this case, unlike a normal copying machine, a latent image is formed with a low potential in the colored part and a high potential in the background part, and development is performed by reversal development in which toner is attached to the low potential part of this latent image. Become. FIG. 4 is an explanatory diagram showing that when reversal development is performed, the adhesion of toner to the image area is weak and toner scattering is likely to occur. FIG. 4(a) shows the state after the first image exposure and development. By developing under a preset development bias, the toner adheres to the image area on the photoreceptor 1 that is close to the ground potential. . FIG. 4(b) shows a state where the second image exposure is performed near the image area where toner has adhered, and the electric field near the toner adhered to the image area is disturbed by the laser beam. The toner is in a state where it is about to move or scatter. Pt54 diagram (c) shows the state of the exposed area immediately after the second image exposure, where some of the toner scattered by the laser beam is on the ground and the writing unit 3 is located opposite the image area. It shows the state where it adheres to. In order to prevent this toner from staining, conventional methods have been to create an i-prone air flow to suction and collect the toner, to install a brush-like or sheet-like screen, or to block the toner with a cover in the necessary place. Methods such as doing this were used. [Problems to be Solved by the Invention] The above method of preventing toner adhesion by forming an air flow requires a fan, a duct, a filter to collect toner powder, etc. to form the air flow, and the equipment is complicated. There were problems such as large size, high price, and high noise level. Furthermore, the method of installing a screen has the problem that it cannot be installed in a structurally effective manner in the exposed area where the problem is most likely to occur. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method for forming a multicolor image in which a simple and effective means for preventing toner scattering is provided in the exposure area.

[Means to solve the problem]

The above purpose is achieved by repeating the charging, image exposure, and development processes multiple times to form multiple toner images on the surface of the photoreceptor, and then transferring the multiple toner images onto transfer paper. At least in the second and subsequent image exposure processes, the toner in the light-receiving portion of the image exposure carried on the photoreceptor surface by the process prior to the image exposure process is directed toward the photoreceptor surface. This is achieved by a method of forming an image, which is characterized by forming an electric field that receives an electric force.

【Example】

FIG. 1(a) is a schematic diagram showing the configuration of one embodiment of the present invention, fjSi diagram (b) is a schematic diagram showing the configuration of another embodiment of the present invention, and FIG. 2(,) is a schematic diagram showing the configuration of another embodiment of the invention. 70 of the process
-It is a chart. FIG. 2(b) is a timing chart of the embodiment shown in FIG. 1(b). The embodiment shown in FIG. 1(,) is a two-color multicolor image forming apparatus, but the basic principle remains the same even if the multicolor image forming apparatus uses three or more colors, except that the number of developing units increases. Although the embodiment shown in FIG. 1(b) is a multiple image forming apparatus using two developing devices, the present invention is not limited to the number of developing devices as described above, nor is it limited to the number of toner colors. Needless to say, ν1 is also useful when stacking toners of the same color. 5 is a power supply for supplying voltage to the toner scattering prevention electrode 4; 6^, 6B is a developing device; 7 is a paper feeding means for supplying the transfer paper P; 8 is a toner image on the photoreceptor 1. a transfer device equipped with a transfer electrode for transferring the image onto the transfer paper P;
9 is a separator equipped with a separation electrode for separating the transfer paper P to which the toner image has been transferred from the photoreceptor 1; 10 is the transfer paper P;
A fixing device 11 fixes the upper toner image, a cleaning device 11 cleans residual toner on the photoreceptor 1, and L an exposure laser beam projected onto the photoreceptor 1 from a writing unit. Next, prior to explaining the toner scattering prevention means newly provided according to the present invention, an image forming method using this toner scattering prevention means will be explained with reference to FIGS. 2(a) and 2(b). (1) When the photoreceptor 1 begins to rotate for image formation, the surface of the photoreceptor 1 is uniformly charged by the charger 2 (in this case, an example in which the photoreceptor 1 is negatively charged is shown). (2) When the charged photoreceptor 1 is illuminated and an image corresponding to the first image is exposed to laser light at the timing shown in FIG. 2 (1), the charge on the image area hit by the laser light disappears and the static Form a latent image. (3) The first color reversal development is performed on this electrostatic latent image by the developer 6.
A toner T1 having a negative polarity adheres to the portion where the charge disappears due to friction with the carrier. Photoreceptor 1
continues to rotate, but the developing device 6B, transfer device 8, separator 9, and cleaning device W111 do not operate. (4) The developed image is transferred to the first charger 2 again by the charger 2.
The toner image of the image is formed on the photoreceptor 1, which is ν, is recharged, and the toner image and a portion of the toner image become approximately at the same potential. (5) Exposure corresponding to the second image is performed, and the charge in the exposed portion disappears. In this state, a toner image and an electrostatic latent image coexist on the photoreceptor. In addition, when the toner image and the electrostatic latent image overlap and ν, a state exists in which the toner image and the electrostatic latent image are close to each other. (6) Reversal development of the second image is performed by the developing device 6B, and the second color toner T2 is attracted to the charge disappearing portion. (7) Here, the transfer paper P is conveyed to the transfer section by a paper feeding means, and the toner images of the first and second images are transferred onto the transfer paper P by the transfer device 8. (8) Transfer paper P to which the toner images of the first and second images have been transferred
is separated from the photoreceptor 1 by a separator 9. (9) The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 10, fixed, and discharged from the apparatus. (10) The photoreceptor 1 from which the transfer paper P has been separated is cleaned by the cleaning device fill and prepared for the next image creation. The charger 2 is suitably one with potential controllability, such as a Sufrotron discharger, and the developer 6A, especially the developer 6B, is capable of performing development without the developer coming into contact with the photoreceptor 1. A non-contact developing device is suitable, which is equipped with a magnetic roller and a developing sleeve around its outer periphery, and to which a voltage equal to one DC voltage is applied as a developing bias voltage. According to the present invention, in the multicolor image forming method described above, at least during the image exposure process for forming the second image, an electric field is formed so that the toner image of the first image receives an electric force in the direction of the surface of the photoreceptor. It is. The electric field is formed by providing a toner scattering prevention electrode and applying a voltage having the same polarity as the toner to the electrode. The toner scattering prevention electrode 4 is provided at a necessary location, and in this embodiment, an example is shown in which it is provided at a position facing the photoreceptor 1 in an exposed area where toner scattering is most likely to occur. The toner scattering prevention electrode 4 is a plate-shaped conductive member having an opening for exposure.
j'ig applies a voltage of the same polarity as the toner to prevent toner scattering. In the case of reversal development, as shown in FIG. 3, a voltage is applied which has the same polarity as the surface potential of the photoreceptor 1 uniformly charged by the charger 2 and is the same as that potential but slightly higher. Toner scattering occurs when the first toner image is exposed to light after being recharged, so it is necessary to apply it simultaneously with exposure as shown in FIG. 2(b). Naturally, there is no problem as long as the voltage is applied for a longer period including this timing. By providing such a toner scattering prevention means, toner scattering is prevented, image quality is improved, and toner adhesion to the mirror, lens, etc. of the exposure section is significantly reduced, making maintenance easier. occured. In order to confirm this effect, the present inventor actually created an image under the conditions shown in Table 1 and conducted an experiment regarding toner scattering. Table 1 First, when 2000 copies were made under the condition that the toner scattering prevention electrode was grounded without applying any particular voltage, toner adhesion of 1 wg/cx2 was observed. The toner scatter prevention electrode on the dog has a potential slightly higher than the photoreceptor potential.
When a voltage of 00■ is applied, the amount of toner adhesion is approximately Oy.
g/cm".Also, when the photoreceptor potential is changed, toner scattering can be prevented by applying a voltage with the same polarity as that potential and whose absolute value is slightly larger than the photoreceptor potential to the toner scattering prevention electrode. Furthermore, a similar effect was obtained when AC voltage was used in addition to DC voltage as the power source.

Effects of the Invention As explained above, in the electrophotographic multiple image forming method, a toner scattering prevention electrode to which a voltage of the same polarity as that of the toner is applied is installed at least during the second image exposure process. Toner scattering can be almost completely prevented by creating an electric field in which the toner in the image-exposed light-receiving area, which is carried on the photoreceptor in a process prior to the exposure process, receives an electric force in the direction of the photoreceptor surface. Since the contamination of the optical system is also significantly reduced, it is possible to provide a multicolor image forming apparatus that is inexpensive, easy to maintain, and has excellent image quality.

[Brief explanation of the drawing]

! l'LJi Figure (a) is a schematic diagram showing the configuration of one embodiment of this invention, Figure 1 (b) is a schematic diagram showing the configuration of another embodiment of this invention, and Figure 2 (a) is a schematic diagram showing the configuration of another embodiment of this invention. 70-chart of the process of the example, FIG. 2(b) is a timing chart of the example shown in FIG. 1(b), FIG. 3 is an explanatory diagram of the toner scattering prevention means, and FIG. 4 is the toner in reversal development. An explanatory diagram of the state. In the figure, 1...Photoconductor 2...Charger 3...Writing unit 4...Toner scattering prevention'WLm5...
Power supply 6^, 6B...Developer 7...Paper feeding means 8...Transfer device 9...Separator
10... Fixing device 11... Cleaning device L... Laser light P... Transfer paper. Applicant Roku Konishi Photo Industry Co., Ltd. Figure 2 (a) Figure 2 (b) ime Figure 3 Figure 4 1st time! jI) Beg/Oumii LIL 2nd time scale 2nd time round Naoki, Rusu P

Claims (4)

[Claims] (1) In an image forming method in which a multiple toner image is formed on a photoreceptor surface by repeating each process of charging, image exposure, and development multiple times, and then the multiple toner image is transferred onto a transfer member, the multiple process At least during the second and subsequent image exposure processes, the toner in the light-receiving portion of the image exposure, carried on the photoreceptor surface by a process prior to the image exposure process, receives an electric force in the direction of the photoreceptor surface. An image forming method characterized by forming an electric field. (2) The image forming method according to claim 1, wherein the developing process is reversal development. (3) The image forming method according to claim 1, wherein the image exposure process is performed by scanning a light spot. (4) The image forming method according to claim 1, wherein the electric field is formed by applying a voltage having the same polarity as that of the toner.