JPS61138266A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent the execution of unnecessary development in areas except and image area by scanning the image area of an image carrying body including the boundary between the image area and non-image area with a modulated light beam and subjecting the non-image area to blank exposing by another lamp. CONSTITUTION:The modulated laser light emitted from a semiconductor laser 91 is made into a laser beam I by a polygonal mirror 92, an ftheta lens 93 and a mirror 94 and a photosensitive drum 1 including the boundary between the image area and the non-image area is scanned by said beam. Reflecting mirrors not shown are provided at both ends of a scanning line as beam detectors. The standard output timing of an image signal is controlled from the output thereof. On the other hand, the non-image area is subjected to bland exposing by an exposing lamp 7 to erase preliminarily the electric charge applied by a corona discharger 2, in the stage of the laser beam scanning. A control device 12 feeds the control signal corresponding to the size of paper by the signals from cassettes 10, 11 to the laser 91 and the lamp 7 to set the timing for blank exposing.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides blank exposure to an image bearing member such as a photosensitive drum or a photosensitive belt so as to prevent unnecessary development outside the image forming area on the image bearing member. The present invention relates to an image forming method.

[Background of the Invention] - Conventionally, an image forming apparatus using the I-photography method charges a photosensitive drum 1 having an electrophotographic photoreceptor with a corona discharger 2, for example, as shown in FIG. After that, a light beam modulated according to the recorded information is applied to a radar or LED array, etc. to form an electrostatic latent image on the photosensitive drum 1, and this latent image is developed by the developing device 3, and then the developed image is transferred. The image is transferred to a transfer material P on a transfer drum 5 by a corona discharger 4, and further fixed by a fixing device 6 to obtain a recorded image or a copied image.

The development methods used in this type of image forming apparatus include the so-called image scanning method in which a light beam is applied to the background area and the unexposed area is exposed to regular There is a so-called packground scanning method in which toner is attached by development.

In any of the above methods, it is necessary to apply a light beam so that toner does not adhere to a non-image area outside the image area.

Note that in this specification, the image area refers to an area where a transfer material comes into contact with an image carrier such as a photosensitive drum.

One method is to constantly apply a light beam in a non-image area, but this is undesirable because it degrades an expensive light source such as a laser light source or an LED array light source.

Another method is to use a bean rung or L as shown in Figure 3.
The photosensitive drum 1 is exposed by a blank exposure rung 7 such as an ED element.
There is a method of irradiating the non-image area of the image. This method spreads to blank exposure, but it is difficult to sharply irradiate only the non-image area, and some parts of the non-image area near the leading or trailing edge of the image area are not exposed to blank exposure. As a result, toner adheres to the non-image area, staining the transfer corona discharger 4, transfer material P, paper feed guide, etc., and toner scattering within the apparatus. Of course, the amount of toner consumed also increases. especially,
In a color image forming method having a transfer device that carries a transfer material on a transfer material carrying sheet 8 having multiple openings such as a mesh screen and corona transfers a toner image as shown in FIG. 4, a photosensitive drum is used. Even if toner adhesion in the non-image area on 1 is limited to an area slightly exceeding the size of the transfer material, toner adhesion will occur on the transfer corona discharger 4, resulting in uneven transfer and, in severe cases, spark discharge. This may have caused the equipment to malfunction.

In addition, stains may occur on the back side of the transfer material and on the edges of the transfer material due to toner adhesion.

The above problem will be explained with reference to FIG. The toner image T on the photosensitive drum 1 exists up to the area beyond the edge of the transfer material P, and the transfer material P is charged by the discharge wire W of the transfer charger during transfer.
A glass charge is applied to the back surface of the screen 8, and the toner image T on the photosensitive drum is transferred onto the transfer material. At the same time, the toner image outside the transfer material area is attracted by the positive charges of corona ions generated from the discharge wire W through the openings of the screen 8. Most of the attracted toner receives corona charge in the process of approaching the discharge wire W, reverses to glass polarity, is repelled near the discharge wire W, and adheres to the transfer charger shield member. Further, a portion of the sucked toner directly adheres to the discharge wire.

When toner adhesion to the shield member or the discharge wire W increases, local dielectric breakdown occurs and spark discharge occurs.

Furthermore, some of the attracted toner is directly attracted to and adheres to the edge of the back of the transfer material, the wooden edge of the transfer material, and the glass charge on the back of the screen near them, and the toner that has become opposite in polarity due to corona charging. It sticks because it is pushed away by the corona wind. As a result, stains occur on the back side of the transfer material around 10 m from the edge and on the wood edge.

[Purpose of the invention]

The present invention has been made in view of these conventional problems, and by combining a blank exposure lamp and a light beam to provide blank exposure to the entire non-image area, excessive burden is placed on the light source of the light beam. It is an object of the present invention to provide an image forming method that can perform sharp blank exposure on the entire non-image area without applying any image.

[Summary of the invention]

The gist of the present invention is to provide an image forming method in which an electrostatic latent image is formed by scanning a light beam modulated by recorded information on a carrier.
The boundary portion between the image area of the image carrier and a non-image area outside the image area is scanned by the light beam to perform blank exposure, and the non-image area is exposed by an exposure lamp whose lighting is controlled so as to expose the non-image area. The present invention provides an image forming method characterized by subjecting an area to blank exposure.

[Embodiments of the invention]

The present invention will be explained in detail below based on the embodiments shown in FIGS. 1 and 2.

FIG. 1 is a schematic diagram of a color radar printer using a two-round scanning method according to the present invention, in which a photosensitive drum sensitive to radar beams is first charged to, for example, a positive polarity by a corona discharger 2. . Next, the photosensitive drum 1 is scanned and exposed by a Lede beam camera to form an electrostatic latent image.

Here, the radar beam I is a semiconductor radar 91 that is modulated by a recorded information signal by a computer or the like, and the modulated radar beam is transmitted to a polygon mirror 92, an fθ lens 93,
The light is imaged as a spot light onto the photosensitive drum 1 via the optical system 9 including a mirror 94 and the like.

In addition, during the Rade beam scanning, the light is reflected by a mirror (not shown) provided at the tip of one line scanning of the Rade beam and the scanning end, and is guided to a beam detector (not shown). The detection signal from this detector is used as a standard output timing control signal for image signals. On the other hand, blank exposure is performed during this radar beam scanning, and the outside of the image area and the boundary between the image area and the non-image area are exposed, thereby preventing development from occurring in the next developing step.

FIG. 2 is a timing chart showing the exposure timing, and the horizontal axis shows the image area in the traveling direction of the photosensitive drum 1.

In other words, the blank exposure rung 7 blankly exposes most of the non-image area before and after forming the latent image to the extent that no light enters the image area, and the Rede light beam Blank exposure is performed only on the border area.

Therefore, the boundary portion is sharply exposed to blank light, and the non-image area is also sufficiently exposed to blank light.

In addition, blank exposure with a laser beam is applied to the image area from 1 to
If they overlap by about 2 vm, it is effective to prevent toner from scattering from the wood end portion of the transfer paper P.

Further, the exposure control of the exposure rung 7 and the Rede light beam
A signal specified by is input to the control circuit 12,
According to the size of the transfer paper P, the blank exposure lamp lighting signal and the radar beam lighting signal are outputted at the timing shown in FIG. 2 (5).

The latent image formed on the photosensitive drum 1 is developed by the developing device 3 and made visible. This developing device 3 is controlled so that developing devices 31, 32, 33, and 34 for each color of cyan, magenta, yellow, and dull are rotated and sequentially brought into contact with the photosensitive drum IK, and record information on which a latent image has been formed. A developing device of a color designated by the type of color contacts the photosensitive drum 1 and develops the image.

The prescription transfer paper P is delivered to the paper feed cassette 10 by the paper feed device 13.
Alternatively, the paper is fed from 11, the leading end is held by the glyph /4'-51 by the transfer drum 5, and the rear part is held by the screen 8.
is supported and transported to the transfer section. There, the transfer paper P passes through the screen 8 and is subjected to corona discharge from the back side by the transfer charger 4, and the developed image on the photosensitive drum 1 is transferred.The transfer paper P is electrostatically attracted to the screen 8 by this transfer corona charge, and the transfer paper P is transferred. The visualized image transferred to the drum 5 is held in a non-contact manner. If you want to get a multicolor print, use 2 sheets of transfer paper P.
The photosensitive drum 1 is brought into contact with the photosensitive drum 1 for 4 times to transfer the visible images in layers.

Further, the transfer paper P holding the visible image is separated from the transfer drum 5 and sent to a fixing device 6 to obtain a fixed toner image.

[Effects of embodiments of the invention]

As described above, according to the present embodiment, the boundary between the image area and the non-image area is blank-exposed in a strip-like manner by the Radhebeam, and the non-image area is further blank-exposed as a whole by the exposure lamp 7. , the edge of the transfer paper, which allows blank exposure to sharpen the border area,
This provides the effect of preventing stains on the transfer charger and the like.

Furthermore, since the blank exposure of the Rade beam is used in spots, it does not affect the life of the Rade light source.

In this embodiment, the exposure timing was explained with respect to the traveling direction of the photosensitive drum, that is, the sub-scanning direction.
Exposure timing in the main scanning direction is performed in the same manner.

In addition, if a detection means for detecting the size of the transfer paper is provided in the transfer paper feeding path, accurate blank exposure can be achieved even when feeding paper when the size of the transfer paper is uncertain, such as when manually feeding. can.

Further, in this embodiment, a laser beam is used as a light beam for writing information, but the same applies to a light beam for writing information such as an LED array or a liquid crystal shutter.

Further, although this embodiment has been described based on a color radar printer, the present invention may be applied to a black and white electrophotographic printer that does not require a transfer drum, and in that case, the tip of the paper feed guide and the electrophotographic It is possible to prevent dirt from forming inside the printer.

〔Effect of the invention〕

As described above, according to the present invention, since the outside of the image area and the boundary between the image area and the non-image area can be sufficiently blank exposed, it is possible to prevent toner from adhering to the edges of the transfer paper. If applied to an image forming apparatus having a transfer drum, the effect of preventing staining of the transfer charger etc. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a color laser printer used to carry out the image forming method according to the present invention, FIG. 2 is a timing chart showing the timing of blank exposure according to the present invention, and FIG. 3 is a conventional laser printer. FIG. 4 is a perspective view of the transfer drum, and FIG. 5 is a diagram illustrating the transfer state. 2: Corona discharger 3: Developing device
4: Transfer corona discharger 5: Transfer drum
6: Fixing device 7: Blank exposure lamp 8 Screen 9: Optical system
10.11: Cassette 12: Control circuit
13: Paper feed device 31.3233.34: Developing device 51: Grid 7/4 9 Semiconductor radar 92: Polygon mirror 93: fθ lens 94: Mirror Fig. 2 Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] In an image forming method in which an electrostatic latent image is formed by scanning a light beam modulated by recorded information on an image carrier, the boundary portion between an image area of the image carrier and a non-image area outside the image area is An image forming method characterized by performing blank exposure by scanning with a light beam, and blankly exposing the non-image area using an exposure lamp whose lighting is controlled so as to expose the non-image area.