JPS58106575A - Exposing method of electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent occurrence of contamination in a machine due to a remaining toner, by executing the exposure by effective image size corresponding to width and length of smaller one of an original or recording paper. CONSTITUTION:A toner stored in a developing device is charged to positive polarity to the same polarity as charge polarity of a photoconductive drum 12 in advance, therefore, development is executed as reverse development, by which a toner image being a positive picture is obtained. This toner image is overlapped on transfer paper 5 which is fed to the photoconductive drum 12 as shown with an arrow D, and after that, is transferred on the transfer paper. On the other hand, in the reverse development, the toner adheres onto the part to which light on the photoconductive drum 12 has been irradiated, but this part is always contained in the exposure range, and also its exposure range is limited to size of smaller one of an original 1 or transfer paper 5, therefore, a toner does not adhere onto the drum 12 outside of the effective image-size, and after transfer has ended, no toner is left on the drum 12.

Description

Detailed Description of the Invention Therefore, an electrostatic latent image corresponding to the original image is formed on the photoconductor, and the electrostatic latent image is reversely developed with toner to obtain a toner image, and the toner image is transferred to the recording paper. The present invention relates to an exposure method for an electrophotographic apparatus that transfers images onto images.

It is well known that a reversal development method is used when attempting to obtain a positive image on recording paper based on a negative original. In this reversal development method, a photoconductor is charged to a certain polarity, for example, a positive polarity, and the charged photoconductor is exposed to light based on a negative original image, so that a static image corresponding to the negative original image is formed on the photoconductor. A toner that forms a positive image is formed by applying toner charged to the same polarity as the photoconductor (positive polarity in this case) to the photoconductor that has formed the latent image and thus carries the latent image. An image is obtained, and the entire recording paper is superimposed on the toner image formed on the photoconductive tree, and the toner image is transferred onto the recording paper J:.

In this way, in reversal development, toner is attached to the uncharged area on the photoconductor, so if the area C of the photoconductor 2 is not the area where the recording paper is to be overlapped. If you try to expose the unnecessary areas (hereinafter referred to as unnecessary areas), toner may also adhere to those unnecessary areas. In that case, after the transfer is completed, the toner attached to the unnecessary areas will still remain on the photoconductor. It will remain. Normally, the entire surface of the photoconductor that has undergone the transfer process is cleaned with an IJ-ring, but at this time,
If toner remains in unnecessary areas as described in item 2, the remaining toner will be scraped off from the photoconductor by the cleaner and scattered inside the machine, resulting in the problem of staining various parts of the machine. .

By the way, in the conventional reversal development method, no particular attention is paid to the exposure range in the exposure step in which the entire electrostatic latent image is formed on the photoconductor, and in general, the recording paper is overlapped. Exposure is performed over a considerably wider area than the actual area. Therefore, in this conventional method, the internal contamination due to the above-mentioned residual toner cannot be avoided.

The present invention aims to solve the above-mentioned problems in conventional exposure methods.

Hereinafter, the method of the present invention will be explained based on drawings showing an embodiment in which the method of the present invention is applied to an all-laser recording apparatus.

The accompanying drawing is a perspective view schematically showing the laser recording device. In the figure, a document 1 having a negative image is read by a photoelectric sensor 3 disposed below through a lens 2 while being fed in the direction of the arrow. in this case,
The photoelectric sensor 8 is designed to detect not only the original image but also the size of the original, that is, the width and length.
and is sent to the control section 4 as a document size signal Sm8.

On the other hand, the control unit 4 receives a transfer paper size signal s indicating the width and length of the transfer paper 5 from a paper size detection unit 7 provided in the paper feed tray 6 holding the transfer paper 5.

is sent.・The above document sent to control unit 4 is also 15m long.
5 and the transfer paper size signal S□ are compared in the width direction and the length direction in the control unit 4, and as a result, the effective image size defined by the smaller of the width and length is determined.

The image signal S sent to the control section 4 is a modulated signal S'
p from the control unit 4 to the modulator 8, and the laser light source 9
The laser light (double-dashed line) from is subjected to a modulation effect based on its modulation signal 4, and therefore on the image signal sp. At this time, the effective image size determined in the control unit 4 as described above is determined by the effective image size signal S8. is sent to a modulator 8 along with a modulation signal 4 as an effective image size signal se
Based on p, it is possible to pass or block the laser light.

The laser light emitted from the light source 9 and passed through the modulator 8 is reflected by the reflective surface of a rotating polygon mirror 11 which has reflective surfaces on its side surfaces and rotates in the direction of arrow B, and is directed toward the photoconductor drum 12. The laser beam directed toward the photoconductor drum 12 is detected by the synchronization detection sensor 18.
When detected by the sensor 13, a synchronizing signal sy is sent from the sensor 13 to the control unit 4, and using this as a signal, the modulator 8 modulates the laser beam based on the modulation signal 4.

The modulated laser light is scanned in the axial direction on the photoconductor drum 12 according to the rotation of the rotating polygon mirror 11, thereby performing exposure in the width direction. On the other hand, the photoconductor drum 12 rotates in the direction of arrow C at a constant speed or intermittently as necessary, thereby performing exposure in the longitudinal direction. In this exposure work in the width direction and length direction, the laser light passing through the modulator 8 is controlled to be cut off according to the effective image size signal S from the control section 4, so that the photoconductor drum 12 Exposure is performed at an effective image size, that is, a size determined by the smaller of the width and length of the original 1 and the transfer paper 5, respectively.

Before the photoconductor drum 12 rotating in the C direction is scanned by laser light, its entire surface is charged in advance to a certain polarity, for example, a positive polarity, by a charging device (not shown), and therefore the effective image size is The exposure forms an electrostatic latent image on photoconductor drum 12 corresponding to the original image. This electrostatic latent image is developed by a developing device (not shown) while moving as the drum 12 rotates in the C direction.

In that case, the I/toner held in the developing device is charged in advance to the same polarity as the photoconductor drum 12, that is, to a positive polarity, and therefore the above development is performed as a reversal development. Therefore, a toner image as a positive image is obtained here. This toner image is superimposed on the transfer paper 5 sent to the photoconductor drum 12 as shown by the arrow, and then transferred onto the transfer paper by a transfer device (not shown).

By the way, in the above-mentioned reversal development, the toner adheres to the portion of the photoconductor drum 12 that is irradiated with light, but the portion that is irradiated with light is always included within the exposed range; Moreover, as described above, the exposure range is limited to the four-effect image size, that is, the smaller of the original 1 or the transfer paper 5. Therefore, toner does not adhere to the drum 12 outside the effective image size, and therefore, there is no toner remaining on the drum 12 after the transfer is completed.

After the transfer is completed, the photoconductor drum 12 is cleaned by a cleaning device (not shown), but as described in the second series, no toner remains on the drum 12.
Unlike in the past, toner does not scatter during cleaning, and therefore does not stain the inside of the machine.

Incidentally, in the above embodiment, the effective image size signal S from the control section 4. μ×, the modulator 8 adjusts the passage/blocking of the laser beam to achieve exposure of the effective image size.
The present invention is not limited to this, but if a semiconductor laser or the like is used as the laser light source 9, the exposure can be achieved by turning the light source on and off.

[Brief explanation of the drawing]

The accompanying drawing is a schematic perspective view of a laser recording device used to carry out the method of the invention. 12... Photoconductor (photoconductor drum) l... Original
5... Recording paper (transfer paper) 9... Optical system (light source) 8... Optical system (modulator) 11... Optical system (
Rotating polygon mirror) 13... Optical system (synchronization detection sensor) 4... Control unit, '・φ

Claims (2)

[Claims] (1) By charging and exposing the photoconductor,
An electrostatic latent image corresponding to the original image is formed on the photoconductor, and the electrostatic latent image is reversely developed behind the toner to obtain a toner image, and the toner image is transferred to the entire recording paper. An exposure method for an electrophotographic apparatus as described above, characterized in that exposure is performed at an effective image size corresponding to the width and length of whichever is smaller of a document or recording paper. (2) An electronic photograph according to claim 1, comprising a light beam scanning optical system and a control unit that modulates light by sending an image signal based on an original image to the optical system. In the exposure method of the device, information indicating the size of the document and information indicating the size of the recording paper are sent to the control unit, which compares the image information to determine the total effective image size, and then determines the effective image size. An exposure method characterized by performing exposure by modulating light based on size.