JPH02297575A - Electrophotographic copying method - Google Patents

Abstract

PURPOSE:To prevent a repeated fluctuation in an electrified potential without installing a sensitizing charger, etc., and to form a copy free from color variation by carrying out destaticization through at least one pre-electrification and pre-exposure prior to an image zone electrifying stage. CONSTITUTION:After the switch of a copying machine is turned on, a photosensitive drum 3 is pre-processed. In other words, an electrifying part 11 applies pre-processing to the photosensitive drum 3, a transfer part 8 applies pre-transfer thereto, and a light destaticizing part 14 applies pre-exposure thereto. Namely, prior to image zone electrification, the photosensitive drum 3 is not only destaticized through pre-exposure, but also the electrification charger of the electrifying part 11 and the transfer charger of the transfer part 8 electrify the photosensitive drum 3 by as much as one rotation of the photosensitive body 3. Consequently, a repeated fluctuation in the electrified potential is prevented, a monochromic or full-color copy free from density fluctuation and color variation can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic copying method particularly suitable for forming full-color images using a laminated organic photoreceptor drum.

[Prior art]

Basically, electrophotographic copying methods using a laminated organic photoreceptor drum (a charge generation layer and a charge transfer layer are provided directly on a conductive support or indirectly through a low resistance layer) are as follows: The photoreceptor drum is subjected to the following steps: image area charging, image exposure, development, and electrostatic transfer using a transfer film. However, with this method, the 4th place charge in the image area is the 1st and 2nd.
There is a problem that it is different depending on the number and subsequent sheets. In the case of monochromatic black and white copies, this repeat variation in charge 4 appears as a variation in image density between the first and second copy, and also appears in yellow (Y) toner images, magenta (M) toner images, and cyan toner images. (C) In the case of full-color copying with overlapping colors of toner images, the amount of toner adhering to the first color (Y in this case) on the first sheet is smaller than on the second and subsequent sheets, so as shown in Figure 1, The color changes from the second and subsequent copies and is cursed. In particular, the latter color variation is more noticeable than the former density variation, and is therefore a serious problem.

Therefore, conventionally, light irradiation (pre-exposure) was performed before the image area charging process, or similarly, before the charging process, pre-charging was performed using a separately provided charger (called a sensitizing charger), and then light irradiation was performed. was being carried out. However, as will be explained later, the former pre-exposure method is insufficiently effective (the electrical charge between the first and second sheets may reach several tens of volts), and it is especially difficult to solve the fundamental problem of color variation. It is not. On the other hand, although the latter method using a sensitizing charger does not have the same problems as the former method, it requires a new sensitizing charger, which is problematic in terms of space and cost.

[Problem to be solved by the invention]

The purpose of the present invention is to provide an electrophotographic copying method that can form copies without density fluctuations or single color fluctuations by preventing repeat fluctuations in the 4th charge without installing an intensifying charger or the like that poses problems in terms of space and cost. The goal is to provide the following.

[Structure and operation of the invention]

The electrophotographic copying method of the present invention is basically an electrophotographic copying method in which each step of image area charging, image exposure, development, and electrostatic transfer using a transfer film is performed on a laminated organic photoreceptor drum. This method is characterized by performing at least one pre-charging process and a static elimination process by pre-exposure before the area charging process.

In the present invention, in order to further improve the effect of preventing repeat fluctuations in the fourth charge, a pre-transfer step is performed in which a transfer electric field is applied for at least one revolution of the photoreceptor drum in addition to the pre-charging step, before the image area charging step. is preferred.

A method for forming a full-color image by the preferred electrophotographic method of the present invention is shown in a full-color copying machine as shown in FIG. Optical system with filter F, 5 is a document table, 6 is a fixing section, 7 is a paper discharge section, 8 is a transfer section, 9 is a charger for paper separation, 10 is a cleaning section, 11 is a charging section, 12 is a charger before cleaning , 13 is a transfer film static eliminator, 14 is an optical static eliminator, and Y, M, C, and 8 represent a Y developing section, an M developing section, a C developing section, and a black developing section, respectively. First, turn on the copy machine
After that, the photoreceptor drum 3 is subjected to a pretreatment process that is a feature of the present invention, that is, a precharging process by the charging section 11, and a transfer section 8.
After performing the pre-transfer step by the optical charge eliminating (pre-exposure) section 14 and the charge eliminating step by the optical charge eliminating (pre-exposure) section 14, for example, first, for Y color, a Y charging step is carried out by the charging section 11.

Seven images are formed on the transfer paper on the transfer drum 2 through a Y exposure process by an optical system (having a color separation filter F) 4, a Y development process, and a Y transfer process by a transfer section (transfer charger) 8.

Next, the photosensitive drum after transfer is charged by a pre-cleaning charger (PCC) 12 (hereinafter referred to as FCC process).
After that, cleaning is performed in the cleaning section 10, and after static electricity is removed, Y
As in the case of color, M images are superimposed and transferred onto the same paper through a pre-charging process (pre-treatment process is unnecessary, the same applies hereafter), a 1M exposure process, an M development process, and an M transfer process.

After the transfer, the photoreceptor drum 3 is again subjected to the PCC process, the cleaning process, and the static elimination process, and then subjected to the C color process in the same manner as in the case of Y color.
Charging process, C exposure process.

C images are superimposed and transferred onto the same paper through a C development process and a C transfer process. The transfer paper on which the full-color image has been formed is then separated from the transfer film on the transfer drum 2 by the transfer film static eliminator 13, fixed in the fixing section 6, and then taken out from the paper discharge section 7 as a full-color copy. On the other hand, the photosensitive drum 3 is subjected to the FCC process, cleaning process, and static elimination process as described above in preparation for the next copy.

Further, the transfer film on the transfer drum 2 is similarly subjected to a static elimination process in preparation for the next copy.If continuous copying is to be performed, a pretreatment process for the second and subsequent sheets is not necessary.

The positional relationship of each member in the full-color image forming method as described above is shown in a timing chart as shown in FIG. 3. As can be seen from this figure, the feature of the preferred method of the present invention is that before charging the image area, the photoreceptor drum is not only charged by pre-exposure as in the conventional method, but also charged for at least one rotation of the photoreceptor. Charging is performed by a charging charger in the transfer section and a transfer charger in the transfer section. This pretreatment step makes it possible to more effectively prevent repeat fluctuations in the 4th charged position.

By the way, if we consider the charging process when forming the first color image (Y in this example) after the second copy of a full-color copy, we find that unlike the first copy, the photoreceptor drum is not always charged just before the first color image is formed. It can be seen that the image is influenced by charging at the charging section, exposure at the optical system, and electric field application at the transfer section.

Regarding exposure, the amount of exposure before transfer is significantly larger than the amount of image exposure, so if pre-transfer exposure (PTL) is performed before charging the image area of the first sheet, it will be possible to It is thought that the difference in the 4th place charge between the two will be almost eliminated. However, as described in the prior art, this alone is insufficient as a measure against repeat fluctuations. Therefore, as in the present invention, in addition to PTL, charging is performed in addition to PTL before charging the image area of the first sheet, or preferably charging and a transfer electric field are applied, as shown by the solid line in FIG. Potential fluctuations between the first and subsequent sheets are suppressed to below IOV, and therefore density fluctuations or color fluctuations between the first sheet and the second sheet and subsequent sheets due to fluctuations in the fourth charged state are almost eliminated.

Note that the dotted line indicates the case where the pretreatment step is only PTL as in the conventional case. Further, as shown in FIG. 3, the pre-cleaning charger (FCC) is turned on when the switch is turned on, but no particular difference between the ON and OFF states of this FCC has been confirmed regarding repeat fluctuations.

[Operations and effects of the invention]

According to the method of the present invention, the pretreatment process consists of two steps: precharging and preexposure.
Although the effect of preventing repeat fluctuations in the 4th-position charge is remarkable in the process alone, if a pre-transfer process is further added to these processes, this effect is further improved. Moreover, these steps can be carried out by using the parts that come with the copying machine as they are.
It is also advantageous in terms of space and cost. Therefore, according to the method of the present invention, monochromatic or full-color copies without density or color variations can be provided at low cost.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of color variations appearing in a full-color image obtained by the conventional method, Fig. 2 is an example of a full-color copying machine for carrying out the method of the present invention, and Fig. 3 is an illustration of a full-color copying machine as shown in Fig. 2. FIG. 4 is an explanatory diagram showing the effect of the method of the present invention on preventing fluctuations in the fourth position of charging. 1...Paper feed section 2...Transfer film covered transfer drum 3...Photoconductor drum 4...Optical system having color separation filter F 6...Fixing section 8...Transfer section 9...・Paper separation charger 10...Cleaning section 11...Charging section 12...
・Pre-cleaning charger 13...Static eliminator 14 for transfer film...Optical static eliminator Solid line in FIG. 4...Method of the present invention Dotted line in FIG. 4...Conventional method

Claims (1)

[Scope of Claims] 1. In an electrophotographic copying method in which image area charging, image exposure, development, and electrostatic transfer using a transfer film are performed on a laminated organic photoreceptor drum, the image area charging step 1. An electrophotographic copying method characterized by performing at least one pre-charging step and a pre-exposure static elimination step. 2. The method according to claim 1, further comprising performing a pre-transfer step in which a transfer electric field is applied for at least one rotation of the photoreceptor dom in addition to the pre-charging step.