JPS63291080A - Visible image before-transfer electrostatic eliminator - Google Patents

Abstract

PURPOSE:To improve the transfer efficiency of a visible image and the image quality of a copy image by performing corona discharging and electric charging prior to the transfer of the visible image, and then performing optical discharging. CONSTITUTION:The electric discharging is carried out prior to the transfer of the visible image to increase charges of toner constituting the visible image more and decreases the potential of a photosensitive body. Then charges on a photosensitive body are further removed by the optical discharging. Namely, a before-transfer corona discharging device 4 carries out electric discharging by DC corona discharging to the same polarity with toner charges or AC corona discharging by DC biasing for the photosensitive body 1 where the visible image is formed. An optical discharging device 5 is provided between this before- transfer corona discharging device 4 and a transfer part 6 to irradiate the photosensitive body 1 uniformly with light after the electric discharging and before visible image transfer, thereby performing optical discharging. Consequently, stable, excellent visible image transfer is performed and the image quality of a copy image is improved.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a static eliminator before visible image transfer.

(Prior Art) In a transfer method in which a transfer sheet is superimposed on a visible image formed by toner on a photoreceptor, and a corona discharge is applied from the back side of the transfer sheet to transfer the visible image onto the transfer sheet, In order to improve the efficiency of visible image transfer, static elimination is usually performed before visible image transfer. As this visible image transfer static elimination,
BACKGROUND ART Conventionally, there are known a photostatic charge removal method in which charge is removed only by light, a corona charge removal method in which charge is removed only by corona discharge, and a photocorona simultaneous charge removal method in which light charge removal and corona charge removal are performed simultaneously.

However, in the optical static elimination method, if the amount of toner constituting the visible image is large, the irradiation light is blocked by the visible image, and the photoreceptor is not sufficiently irradiated, making it impossible to obtain a sufficient static elimination effect. If an attempt is made to improve the static elimination effect by increasing the intensity of the irradiated light, optical fatigue may occur on the photoreceptor and an afterimage may occur.

With the corona static elimination method, it is difficult to optimize the corona static elimination electric field.
If the neutralizing electric field is too strong, the separation property when separating the transfer sheet to which the visible image has been transferred from the photoreceptor may be deteriorated.

The simultaneous optical corona static elimination method also has the same problems as the corona static elimination method and the optical static elimination method.

(Purpose) The present invention has been made in view of the above-mentioned circumstances, and its purpose is to effectively improve the transfer efficiency of visible images and improve the image quality of copied images. can make
A new static elimination device before visible image transfer is developed.

(composition) The present invention will be explained below.

The visible image pre-transfer static eliminator of the present invention superimposes a transfer sheet on a visible image formed by toner on a photoreceptor, and applies corona discharge from the back side of the transfer sheet to transfer the visible image onto the transfer sheet. This is a pre-transfer static eliminator for a transfer method in which the transfer sheet is transferred to a photoreceptor, and then a static eliminator field is applied to the transfer sheet to separate the transfer sheet from the photoreceptor, and the device has the following features.

That is, the visible image pre-transfer static eliminator of the present invention includes a pre-transfer corona static eliminator and an optical static eliminator. The pre-transfer corona static eliminator is used prior to the transfer of the visible image.

The photoreceptor on which the visible image is formed is electrically neutralized by direct current corona discharge having the same polarity as the toner charge, or by alternating current corona discharge biased with a direct current having the same polarity as the toner charge.

The optical static eliminator is provided between the pre-transfer corona static eliminator and the transfer section, and after the pre-transfer corona static eliminator electrically eliminates the static electricity and before the visible image is transferred, the photoreceptor is uniformly irradiated with light. , perform optical static elimination.

As described above, in the static eliminator before visible image transfer of the present invention, prior to the transfer of the visible image, electrical static elimination is first performed by corona discharge, and then optical static elimination is performed.

Electrical charge removal is performed by direct current corona discharge or alternating current corona discharge, but in either case, it is performed with the same polarity as the toner charge, that is, the charge that charges the toner. That is, during DC corona discharge, a corona discharge having the same polarity as the toner charge is performed, and during AC corona discharge, bias is performed with DC having the same polarity as the toner charge.

Therefore, in the present invention, before the visible image is transferred, electrical charge is first removed, the toner constituting the visible image is further charged, and the potential of the photoreceptor is lowered.

Subsequently, in photostatic discharge, the charges on the photoreceptor are further dissipated.

As the optical static eliminator, in addition to a normal lamp, it is possible to use an array of various light emitting elements, such as an array of light emitting diodes or a cold cathode tube.

(Example) Hereinafter, description will be given based on specific examples.

FIG. 1 is an explanatory diagram schematically showing only the parts necessary for explanation of an example of a copying apparatus to which the present invention is applied.

The photoreceptor 1 is formed in the shape of a drum, rotates in the direction of the arrow during copying, is uniformly charged by a charger 2, and then exposed to an image by a beam of image exposure light to form an electrostatic latent image. Note that the charging polarity of the photoreceptor 1 by the charger 2 is as follows:
In this example, it is assumed that the polarity is positive.

The electrostatic latent image formed on the photoreceptor 1 is then developed by a developing device 3 using a magnetic brush development method using negatively charged toner, and is visualized.

The visible image thus obtained is charge-eliminated by the visible image pre-transfer charge eliminator according to the present invention prior to transfer.

That is, the pre-transfer corona static eliminator 4 and the optical static eliminator 5 constitute a visible image pre-transfer static eliminator. The pre-transfer corona static eliminator is provided on the developing device side between the developing device 3 and the transfer section, and the optical static eliminator 5 has the following functions:
It is provided downstream of the pre-transfer corona static eliminator 5 and upstream of the transfer section.

The visible image that has received the p# voltage before transfer is then superimposed on a transfer sheet S, which is a transfer sheet, in a transfer section. At this time, a corona discharge having a polarity opposite to that of the toner charge, that is, a positive polarity, is applied to the back side of the transfer paper S by the transfer device 6, and the visible image is transferred onto the transfer paper S.

Subsequently, the static eliminating separator 7 applies a DC biased AC corona discharge to the transfer paper S to reduce the electrostatic adhesion force of the transfer paper S to the photoreceptor 1 due to the corona discharge during transfer,
Separating the transfer paper S from the photoreceptor 1, at this time the separation claw 8
promotes separation of the transfer paper S. The transfer paper S, on which the visible image has been transferred and separated from the photoreceptor 1, is sent to a fixing device (not shown), where the visible image is fixed, and then discharged from the apparatus.

After the visible image has been transferred, the photoreceptor 1 is cleaned of residual toner by a cleaning device 9 and subjected to a new copying process.

Now, in the static elimination before visible image transfer according to the present invention, electrical static elimination is first performed by the pre-transfer corona static elimination device 4, and then optical static elimination is performed by the optical static elimination device 5.

In this embodiment, electrical static elimination is performed by direct current corona discharge having the same polarity as the toner charge, that is, negative polarity.

In FIG. 2 (III), the portion designated by the symbol A represents the unexposed portion, and the portion designated by the symbol B represents the exposed portion. The potential distribution in the exposed and unexposed areas is as shown in Figure 2 (before the pre-transfer static elimination is performed).
This is similar to (a) in III).

FIG. 2(I) shows the appearance of a visible image on the photoreceptor 1. FIG. The negatively charged toner T constituting the visible image is attached to the positive latent image charge on the photoreceptor 1 . When a negative polarity corona discharge is performed on the photoreceptor on which a visible image has been formed by the pre-transfer corona static eliminator 4, the potential distribution of the photoreceptor changes as shown in Figure 2 (
It will be something like (0) in III). In other words, the potential of the photoreceptor decreases as a whole due to the action of negative corona discharge.

The effect of this negative corona discharge further increases the negative charge held by the toner.

Subsequently, when optical static elimination is performed by the optical static elimination device 5, the charge on the photoreceptor is optically attenuated as shown in FIG. becomes something like (c) in FIG. 2 (III).

During this optical neutralization, there is no effect on the charge on the toner, so that during the transfer of the visible image, the charge on the toner remains in the state increased during the electrical neutralization.

Therefore, when the pre-transfer static elimination of the present invention is performed, the transfer efficiency is
Firstly, it is improved due to the static elimination effect of the photoreceptor, and secondly, it is further improved due to the effect of increasing the charge on the toner.

Furthermore, if optical static elimination is performed following electrical static elimination, separation of the transfer paper during transfer will be performed stably.

This will be explained with reference to FIG.

FIG. 3 shows the separation performance when electrical static elimination and optical static elimination are used together as in the present invention.

In the figure, the shaded area indicates the appropriate range of transfer separation performance. The wider the area of the shaded area, the greater the margin of transfer separation performance, and the greater the margin of transfer separation performance, and the greater the ability to respond to environmental conditions, types of transfer paper, etc.

In FIG. 3, PTC represents the static elimination current of the pre-transfer corona discharge, and IDC represents the DC component (DC bias component) of the corona current of the static elimination separator 7.

FIG. 1(I) shows the case where optical charge removal is not performed, but as shown, the area of the shaded area indicating the appropriate range of transfer separation performance is small, which causes a moderate inconvenience in practical use.

(II), (III), and (IV) in FIG. 3 are cases in which photostatic charge removal is performed. .5.2.10mA. Increasing the amount of light in optical charge removal in this way increases the margin of transfer separation performance.

In addition, when performing only optical static neutralization without electrical static neutralization,
Even if the amount of light for optical static elimination is increased, there is almost no improvement in separation performance. Furthermore, when using electrical static elimination and optical static elimination in combination, the effect will be small if the order is reversed to that of the present invention or at the same time. This is because when the potential (positive polarity) of the unexposed area decreases due to optical static elimination, the efficiency of toner charging (negative polarity) by the corona static eliminator decreases (the higher the positive potential, the easier it is to attract negative charges). Conceivable.

(Effects) As described above, according to the present invention, a novel static elimination device before visible image transfer can be provided. Since this device has the above-described configuration, stable and good visible image transfer is possible, and the quality of the copied image is accordingly improved. In the embodiment, electrical charge elimination by the pre-transfer corona charge removal device is performed by direct current corona discharge, but electrical charge removal may also be performed by alternating current corona discharge biased with direct current. can be made uniform. Of course, the present invention is also applicable to color copying apparatuses.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one example of a copying apparatus to which the present invention is applied, FIG. 2 is a diagram for explaining static elimination before visible image transfer according to the present invention, and FIG. 3 is a diagram for explaining the present invention in detail. This is a diagram for

Claims (1)

[Claims] A transfer sheet is superimposed on the visible image formed by toner on the photoconductor, and a corona discharge is applied from the back side of the transfer sheet to transfer the visible image onto the transfer sheet, and then the visible image is transferred onto the transfer sheet. A pre-transfer static eliminator for a transfer method in which a static neutralizing electric field is applied to a transfer sheet to separate the transfer sheet from a photoreceptor; a pre-transfer corona static eliminator that performs electrical static neutralization by DC corona discharge with the same polarity as the toner charge or AC corona discharge biased with a DC bias with the same polarity as the toner charge; the pre-transfer corona static eliminator and the transfer section; established between
A visible image characterized by having a photostatic charge eliminating device that uniformly irradiates a photoreceptor with light to perform photostatic discharge after electrical charge elimination by a pre-transfer corona static eliminating device and before visible image transfer. Pre-transfer static eliminator.