JPH0424659A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent attraction of polarized unexposed toner on a base body to a transfer sheet by providing a destaticizing means which destaticizes the transfer sheet surface between a transfer position and a separating position of the transfer sheet against the base body. CONSTITUTION:The destaticizing brush 9 destaticizing the surface of the transfer sheet 8 is provided between the transfer position and the separating position of the transfer sheet 8 against the base body. Then, the destaticizing brush 9 is brought to a sliding contact with the transfer sheet 8 immediately after the transfer position, and is activated to have the negative charge on the transfer sheet 8 escape to a grounding point. Because of this, the transfer sheet 8 loses the force to sunction the toner 1, and the toner 1 is carried to a toner container 2 side still attracted on the surface of the drum 3. Furthermore, a cleaning blade is provided on the toner container 2 side, and the unnecessary toner on the drum 3 is recovered in the toner container 2. Thus, the undesired charge on the transfer sheet is eliminated before the transfer sheet 8 is separated from the base body, and the attraction of the unexposed toner on the base body to the transfer sheet 8 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus such as an electronic copying machine or a printer.

Eh Todo technique! In these image forming apparatuses, it is generally necessary to arrange at least a charger, an exposure means, a transfer means, and a cleaning means around a base such as a photoreceptor drum in order from the upstream side in the direction of movement of the base. The disadvantage is that the entire structure becomes large and the cost is high.

Therefore, recently, an image forming apparatus has been proposed that uses a conductor instead of a photoreceptor as a base and eliminates the need for a surrounding charger. This device includes the steps of: charging a photosensitive toner to a predetermined polarity and applying it onto a substrate; A step of exposing a light image to the toner to form an electrostatic latent image; While the toner in the light irradiated area remains conductive, the toner area on which the electrostatic latent image has been formed is transferred to a transfer sheet. Applying a bias voltage of the same polarity as the initial charge polarity of the toner to the transfer sheet facing the toner to reverse the polarity of the toner that maintains conductivity and at the same time transferring the toner to the transfer sheet. The image forming apparatus is configured to form an image on the transfer sheet by the following steps.

In this device, as can be seen from the above description, toner that is not exposed by the exposure device is not transferred to the transfer sheet. However, this unexposed toner 1 is dielectrically polarized by the transfer voltage as shown in FIG. ) may attract each other, resulting in a thin layer of toner on the non-image area of the transfer sheet 8.

An object of the present invention is to provide an image forming apparatus that is designed to prevent such problems from occurring.

In order to achieve the above object, in the present invention, a photosensitive toner that becomes conductive when irradiated with light and then maintains conductivity for an appropriate period of time is charged to a predetermined polarity to form a substrate. a step of exposing the toner on the substrate with a light image to form an electrostatic latent image; The toner portion on which the toner is formed is opposed to a transfer sheet, and a bias voltage having the same polarity as the initial charged polarity of the toner is applied to the transfer sheet to reverse the polarity of the toner that maintains conductivity and at the same time reverse the polarity of the toner. In an image forming apparatus that forms an image on a transfer sheet by a step of transferring toner to the transfer sheet, a charge eliminating means for eliminating charge on the surface of the transfer sheet is provided between a transfer position and a separation position of the transfer sheet with respect to the substrate. It is structured as follows.

In this case, the static eliminating means can be constituted by a static eliminating brush that is connected to a predetermined potential point and has one end in contact with the transfer sheet.

With this configuration, the surface charge of the transfer sheet in contact with the substrate is removed by the static eliminating means on the downstream side of the transfer position with respect to the moving direction of the substrate, and the unexposed toner on the substrate is no longer removed. loses the ability to suck the bow. Therefore, polarized unexposed toner will no longer adhere to the transfer sheet.

EXAMPLE 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a printer using photosensitive toner 1. As shown in FIG. Photosensitive toner 1 used here
The particles are formed by integrating a photoconductive agent such as zinc oxide, a dye sensitizer, and a pigment with a binder resin, and when oxygen is adsorbed on the surface, they become insulating, and when oxygen is released, they become conductive. becomes. The removal of oxygen is performed using, for example, semiconductor laser light, as will be described later. The dye sensitizer plays the role of bringing the sensitivity of the toner 1 into the infrared light region (semiconductor laser light).

In FIG. 1, photosensitive toner 1 is contained in a toner container 2 together with a magnetic carrier.

A sleeve 4 facing an electrically conductive rotating drum 3 is provided within the toner container 2 . This sleeve 4 is adapted to be rotated in the direction shown by arrow A. On the other hand, the drum 3 facing the sleeve 4 is rotated in the direction shown by arrow B, and their opposing peripheral surfaces move in the same direction. Sleeve 4 is negatively biased while drum 3 is held at ground potential.

5 is an exposure device that exposes an optical image using a semiconductor laser. 6 is a transfer roller, which is negatively biased by a DC power source 7. Reference numeral 9 denotes a static elimination brush, one end of which is grounded and the other end is in close contact with the transfer sheet. 10 is a separation claw that separates the transfer sheet 8 from the drum 3.

Next, the operation of the apparatus shown in FIG. 1 will be explained. First, a negative bias voltage having the same polarity as the polarity (unipolarity in this embodiment) with which the photosensitive toner 1 is triboelectrically charged is applied to the sleeve 4 . On the other hand, the drum 3 is grounded. A magnet 12 is fixedly disposed within the sleeve 4 at a position facing the drum 3 with the sleeve 4 in between. The photosensitive toner 1 contained in the toner container 2 is mixed with a magnetic carrier by the rotation of the stirring roller 11 and triboelectrically charged to a negative polarity. The frictionally charged photosensitive toner 1 is conveyed on a rotating sleeve 4 and transferred to a drum 3 by a magnet 12.
A magnetic brush 13 is formed at a position opposite to. and,
When the magnetic brush 13 comes into sliding contact with the drum 3, the negatively charged photosensitive toner 1 is sequentially deposited over the entire length of the drum surface.

In this way, the toner 1 formed on the drum 3 is conveyed to the exposure position by the exposure device 5 as the drum 3 rotates. At the exposure position, the toner layer on the drum 3 is exposed to a light image, irradiated with semiconductor laser light, and the toner whose electrical resistance decreases and becomes conductive passes through the grounded drum 3, where its charge is reduced. (This toner is represented by a white circle 1a in FIG. 1). On the other hand, the charged toner 1 that is not irradiated with light does not become conductive and maintains a negatively charged state. As a result, an electrostatic latent image is formed on the photosensitive toner layer on the drum 3 that has passed through the exposure position of the exposure device 5 based on the amount of negative charge held.

The toner layer on which the electrostatic latent image has been formed after passing through the exposure position by the exposure device 5 is conveyed to an area facing the transfer roller 6 as the drum 3 rotates. A negative voltage having the same polarity as the charged polarity of the photosensitive toner is applied to the transfer roller 6 by a DC power source 7, and the transfer sheet 8 is conveyed between the transfer roller 6 and the drum 3. The photosensitive toner 1a, which has lost its charge on the drum 3, maintains conductivity with its electrical resistance value decreasing until it reaches the area facing the transfer roller 6. Then, the transfer sheet 8 is conveyed between the transfer roller 6 and the drum 3 at the timing when the toner layer on the drum 3 reaches the area facing the transfer roller 6.

At this time, the transfer sheet 8 and the toner layer on the drum 3 are brought into contact with each other while a negative bias voltage is applied to the transfer roller 6.

As a result, ten charges of opposite polarity are injected from the drum 3 into the low-charge negative polarity toner 1a which has been made conductive by being irradiated with light. As a result, the toner 1a on the drum 3 irradiated with the laser beam becomes fertile and is transferred onto the transfer sheet 8. The negatively charged toner 1a on the drum 3 that is not irradiated with the laser beam is not in a conductive state and thus maintains its negative polarity and is not transferred onto the transfer sheet 8.

As mentioned above, a negative charge is applied to the surface of the transfer sheet 8 by the transfer voltage of the transfer roller as shown in FIG. 2, and this negative charge attracts the dielectric polarization charge of the unexposed toner 1 to form a However, in this embodiment, the static elimination brush 9 comes into sliding contact with the transfer sheet 8 immediately after the transfer position, and acts to release the negative charges on the transfer sheet 8 to the ground point. Therefore, the transfer sheet 8 loses its ability to attract the toner 1, and the toner 1 is conveyed to the toner container 2 while remaining attached to the surface of the drum 3. Toner container 2
A cleaning blade (not shown) is provided on the side to collect unnecessary toner on the drum 3 into the toner container 2 (more specifically, into a toner hopper (not shown)).

As explained above, according to the present invention, the undesired charge on the transfer sheet is removed by the charge eliminating means provided after the transfer position.
Since the transfer sheet is removed before separation from the substrate,
Unexposed toner on the substrate will not be adsorbed to the transfer sheet.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of main parts of an image forming apparatus embodying the present invention, and FIG. 2 is an explanatory diagram. 1... Photosensitive toner 2... Toner container, 3...
... Drum, 4... Sleeve, 5... Exposure device, 6... Transfer roller, 8... Transfer sheet, 9... Static elimination brush, lO... Separation claw, 11...
...Agitating roller.

Claims (2)

[Claims] (1) A step of charging a photosensitive toner to a predetermined polarity and applying it onto a substrate, which becomes conductive when irradiated with light and then maintains conductivity for an appropriate period of time; The process of exposing a light image to the upper toner to form an electrostatic latent image; Transferring the toner area on which the electrostatic latent image was formed while the toner in the area irradiated with light maintains conductivity. Applying a bias voltage of the same polarity as the initial charged polarity of the toner to the transfer sheet facing the sheet to reverse the polarity of the toner that maintains conductivity and at the same time transfer the toner to the transfer sheet. An image forming apparatus that forms an image on a transfer sheet through a step of forming an image on a transfer sheet, the image forming apparatus comprising: a charge eliminating means for eliminating charge on the surface of the transfer sheet between a transfer position of the transfer sheet with respect to the substrate and a separation position. . (2) The image forming apparatus according to claim 1, wherein the static eliminating means is a static eliminating brush connected to a predetermined potential point and having one end in contact with the transfer sheet.