JPS59149375A - Eliminating device of electric charge in non-image area - Google Patents

Abstract

PURPOSE:To destatisize the electric charge in the area other than an optional required area without limiting the range to reduction copy, by providing a light transmission controller consisting of a light transmission control panel and a lamp. CONSTITUTION:A photosensitive body 1 which is electrostatically charged uniformly by a corona electrifier 2 has the image of an original exposed through an optical system 4 to attain an electrostatic latent image. If a voltage is not impressed to a liquid crystal part 55 which faces a non-image formation area of the photosensitive body 1, of a light transmission control panel 51 of a light transmission controller 5, which covers the overall width of the photosensitive body 1 in the axial direction, while interlocking with original size detection or reduction power, the light of a lamp 52 is irradiated to the photosensitive body, and the electric charge of the non-image formation area is discharged. At this time, the voltage is impressed to the liquid crystal part 55 facing an image area of the photosensitive body to intercept the light to the image area, and the latent image is not erased. Thus, the voltage impression to fractionized liquid crystal parts 55 is controlled to distatisize the electric charge in an optional non-image area.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an apparatus for eliminating charges in a non-image area other than the area where an electrostatic latent image is formed by image exposure on a photoreceptor in an electrophotographic copying machine.

<Prior Art> An electrophotographic copying machine uniformly charges a photoreceptor and then exposes the original image to light to form an electrostatic latent image on the photoreceptor. Toner is attached to the surface and visualized. This toner image is transferred onto paper as necessary, and the paper onto which the toner image has been transferred is sent to a fixing section where the toner is fixed and used as a copy.

Therefore, the entire area of the photoreceptor is uniformly charged by a charger, and if the document is smaller than the photoreceptor, an image area where a latent image is formed by image exposure and other non-image areas are formed. Since this non-image area is uniformly charged, toner is fed to the developing device. If this is transferred to paper larger than the original size, the image of the original will not be covered, and the black solid image in the non-image area will also be transferred, resulting in an extremely unsightly copy. Therefore, by pressing the entire surface of the placing table using a blank document presser that covers the area on which the original is placed, charges in the non-image area are discharged during exposure.

However, although the original presser is effective when pushing a sheet-shaped original from the top onto the mounting table, a book-shaped original will float above the mounting table.

Therefore, in non-image areas other than those corresponding to the original, charges cannot be completely removed during image exposure, and toner adheres to L1.

Furthermore, even in the case of sheet originals, there are times when it is only possible to discharge the charges in non-image areas.

For example, if the document holder becomes black and dirty.

Further, when making a reduced copy, there inevitably arises a non-image area that is not exposed to light in addition to the image area formed on the photoreceptor, making it impossible to prevent toner adhesion.

Conventionally, when performing reduction copying, two methods have been used to prevent toner transfer from the non-image area of the photoreceptor: one is to feed and copy paper that corresponds to the reduction ratio, and the other is to feed and copy paper that corresponds to the reduction ratio. A static elimination light source is placed correspondingly.
There are methods of discharging electrical charges in areas that are not exposed to light. These methods not only limit the size of the paper that can be used and require highly accurate transport, but also make it impossible to remove static electricity from the non-exposed area of the photoreceptor only at a preset reduction ratio. It was not possible to form an electrostatic image only in a necessary area corresponding to an arbitrary reduction magnification.

<Objective of the Invention> An object of the present invention is to provide an apparatus for eliminating electric charge in any area other than necessary areas, not only in reduction copying.
It is white.

<Example> FIG. 1 is a diagram showing the copying process in the present invention.

In the figure, 1 is a drum-shaped photoreceptor, 2 is a corona charger for uniformly charging the photoreceptor, and 3 is an image that forms an image of a document onto the photoreceptor via an optical system 4. 5 is a light transmission control device, which will be described in detail later, and 6 is a photoreceptor 1.
2, a developing device for feeding toner on the electrostatic latent image; 7, a corona discharger for electrostatically transferring the toner image onto a sheet of paper being conveyed; 8; The device 9 is a cleaning device for removing residual toner on the photoreceptor.

2. The light transmission control device 1π5 is composed of a light transmission control panel 51 and a lamp 52, as shown in FIG. 2, in order to discharge the electric charges in the non-image forming area of the photoreceptor 1 which is not image exposed. As shown in FIG. 3, the light transmission control panel 51 includes a panel 53 provided with a large number of subdivided light transmission sections 54, and a member for controlling light transmission, such as a liquid crystal section 55, installed in the light transmission section 54. A mask 56 for blocking light is formed around the segmented liquid crystal section 55. 2. The liquid crystal section 55 transmits or does not transmit light by controlling the voltage applied thereto. For example, by applying a voltage, the liquid crystal section 55 blocks light. The light transmission control panel 51 is formed by forming segmented voltage application electrodes on a transparent plate such as a glass plate, sealing the transparent plate via a spacer, and filling the space formed by the spacer with liquid crystal. However, it can be easily created by forming a light-transmitting mask around the further subdivided electrodes. The light transmission control panel 51 has a length that can cover the entire rlj of the photoreceptor 1 in the axial direction.

The light transmission control device 5 is configured as described above, and unless a voltage is applied to the liquid crystal section 55 corresponding to the non-image forming area of the photoreceptor of the light transmission control panel 51, the light from the lamp 52 will not illuminate the photoreceptor. The charge in the non-image forming area is discharged. At this time, light is blocked from the image area of the photoreceptor by applying a voltage to the liquid crystal section 55 corresponding to this area, so that the latent image is not erased. In this way, the subdivided liquid crystal section 5
By controlling the voltage application in step 5, charges in any non-image area can be removed.

Here, the voltage application control of the liquid crystal section 55 may be performed in conjunction with document size detection or in conjunction with reduction magnification, for example. In other words, if the document size is A4, it is sufficient to control the voltage application so that the liquid crystal portion 55 corresponding to the width of A4 blocks light from the lamp 52 and the light is transmitted through the other liquid crystal portions 55. In the case of reduction, the application of voltage to the liquid crystal section 55 is controlled so that light from the lamp 52 is irradiated onto a non-image area other than the area where the reduced image is formed on the photosensitive unit 1.

In this embodiment, the light transmission control device 5 is provided between the exposure section 3 and the developing device 6, but it is sufficient to arrange it before the developing device 6. Of course, light irradiation may be performed simultaneously with step 3. Further, although an example is shown in which liquid crystal is used for the segmented light transmitting portions, the present invention is not limited to this, and any material that can control light transmission may be used.

<Effects of the Invention> According to the device of the present invention, the segmented light transmitting member is appropriately controlled to allow light to pass through only the necessary portions, so that it is possible not only to eliminate charges only in a predetermined area, but also to eliminate charges only in a predetermined area. Charges in any unnecessary area can be easily removed. Therefore, charges in the non-image area can be easily removed according to an arbitrary reduction ratio.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a copying process in which the apparatus of the present invention is arranged, FIG. 2 is a side view showing -(a) of the light transmission control device of the present invention, and FIG. 3 is the structure of the control panel of the light transmission control device. 1: photoreceptor, 2: corona charger, 3: image exposure section, 5: light transmission control device, 6: developing device, 51: light transmission control device,
52: Lamp, 53: Spring/U. 54: Light transmission section, 55: Liquid crystal section, 56: Mask.

Claims (1)

[Claims] 1. After uniformly charging the photoreceptor, an electrostatic latent image corresponding to the image is formed on the photoreceptor by exposing the image to light, and this electrostatic latent image is visualized by a developing device. In an apparatus for optically eliminating charges in a non-image area other than an area where an electrostatic latent image is formed on a photoreceptor, there is provided a panel in which an area for transmitting light from a light source is subdivided, and the subdivision. 1. A charge removal device for a non-image area, characterized in that a light transmission control device comprising a member for controlling light transmission in a non-image area is disposed in front of the developing device. 2. The device for removing charges in a non-image area according to claim 1, wherein a liquid crystal is used as the light transmission control member.