JPS6249387A - Transfer type image forming device - Google Patents

Abstract

PURPOSE:To easily separate a transfer material from a photosensitive body by irradiating the surface of the photosensitive body through the transfer material from the back of the transfer material superposed to the surface of the photosensitive body and photo-destaticizing the residual electric charge on the surface of the photosensitive body. CONSTITUTION:A light source 8 irradiates light to the surface 1a of the photosensitive body through the transfer material 5. Although negative charge is applied to the transfer material 5 by a transfer device 6, the charge can not be removed by said light irradiation. Therefore, the negative charge of the transfer material 5 is neutralized with the positive charge of the photosensitive body by a corona discharger 11. The charge left on the photosensitive body without being removed by the corona discharger 11 is completely removed by the light source 8. Consequently, the transfer material can be easily separated from the photosensitive body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image forming apparatus such as an electrophotographic apparatus, a recording machine, etc. using a reversal development method, and particularly to an image forming apparatus such as an electrophotographic apparatus, a recording machine, etc. that uses a reversal development method. The present invention relates to an image forming apparatus equipped with an image forming apparatus.

A conventional electrophotographic apparatus generally includes a photoreceptor 1 rotating in the direction of an arrow and a charger 2 disposed around the photoreceptor, as shown in FIG.
, a developing device 3, a conveyance device (not shown) that supplies the transfer material 5 so as to overlap the photoreceptor 1, a transfer device 6, a conveyance device 10 that sends out the transfer material 6 after transfer, and the like. The surface of the rotating photoreceptor 1 is charged by a charger 2, exposed to light according to image information by an exposure device (not shown) to form an electrostatic latent image, and the latent image is developed by a developer 3. A toner image is formed by the transfer device 6, and the toner image is transferred by the transfer device 6 onto the transfer material 6, which is transported in the direction of the arrow by a transport device (not shown). It is separated by its rigidity and its own weight, and then transferred to a fixing device (not shown) using the τ conveying device 10.
to obtain recorded images. In such an electrophotographic apparatus, it is important to separate the transfer material 5 after transfer from the surface of the photoreceptor 10. For this reason, conventionally, the transfer material 5 is separated from the surface of the photoreceptor 10 downstream (hereinafter simply referred to as "downstream") of the transfer device 6 as viewed from the transfer path of the transfer material 6. )
A separating corona discharger 11 is arranged to remove the electric charge from the transfer material 5.

Also, a separating claw 1 is provided for peeling off the transfer material 6 that could not be separated from the surface of the photoreceptor 1 depending on the corona discharger 11.
2 is also known.

Furthermore, other examples include a method in which a separation belt is interposed between the non-image forming part of the surface of the photoreceptor and the transfer material, a method in which the transfer material is attracted by a roller or belt charged with the opposite polarity to the transfer material, and There are methods that utilize airflow, and methods that use a combination of these methods.

Problems to be Solved by the Invention However, in any of the above configurations, the surface charge of the photoreceptor is left as is, so the transfer material is attracted to the photoreceptor by Coulomb force and is difficult to separate. There was a problem.

The above-mentioned problem becomes noticeable when development is performed using a reversal development method. Generally, in the reversal development method, as shown in Figure 6, the photoreceptor is uniformly charged (positive charge in this example).
is mostly erased in the image area by exposure according to the image information, forming an electrostatic latent image, and toner particles 4 of the same polarity as the charge on the photoreceptor adhere to the portion of this electrostatic latent image that has almost no charge. I am made to do so. By the way, in general image recording mainly containing text information, there are areas that are not developed with toner (
(non-image area), that is, the area of the electrostatic latent image where the charged charges remain even after exposure occupies a large area. This means that
This means that the above-mentioned Coulomb force is large, which makes it more difficult to separate the transfer material from the surface of the photoreceptor when development is performed using a reversal development method.

Therefore, as a means for removing the surface charge on the photoreceptor after the developing process, there is a device that has an optical charge eliminating means between the developing process and the transfer process (for example, Japanese Utility Model Application No. 59-149152), or a device that has an optical charge eliminating means installed at the same position. A device equipped with a corona discharger (for example, Japanese Patent Laid-Open No. 69-214868) has been proposed. However, these devices remove the surface charge on the photoreceptor and
Although it is possible to make the separation easier, a new problem has arisen in that the transferred image is likely to become ``blur'' or ``bleed.'' The reason for this is thought to be as follows. In FIG. 6, toner particles 4 that have adhered to the photoreceptor surface 1& due to reversal development induce charges of opposite polarity in the vicinity of the photoreceptor surface to which the toner particles have adhered, and adhere to the surrounding photoreceptor surface. It is thought that the particles are restrained from moving by the charges of the same polarity that remain in them. If no static eliminating means is provided between the development process and the transfer process, the toner particles 4 are thus restrained on the surface of the photoreceptor 1! It is carried toward the transfer device 6 while remaining attached to L. However, if a static eliminating means for removing residual charges is provided before the transfer process to remove the residual charges on the surface of the photoreceptor, there is no force to prevent the toner particles 4 from moving on the surface of the photoreceptor, and on the other hand, the transfer Device 6
has a potential opposite to that of the toner particles 4, so as the photoreceptor moves and the τ toner particles 4 approach the transfer device 6, an electric force acts on the toner particles 4 in the direction of the arrow. This causes toner particles to scatter.

For this reason, toner tends to scatter during the transfer process, resulting in a transferred image with a lot of so-called ``blur'' or ``bleeding''.

The present invention has been developed in view of the above-mentioned problems, and it is possible to easily separate the photoreceptor and transfer material by removing the surface charge of the photoreceptor after the development process without causing toner scattering during the transfer process. An object of the present invention is to provide a transfer type image forming apparatus that can be separated into two parts.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method for transferring the photoreceptor to the photoreceptor by passing through the transfer material from the back side of the transfer material that overlaps the surface of the photoreceptor downstream of the transfer means. A light irradiation means for irradiating the surface with light is provided, and a transmitted light amount detection means for detecting the light transmittance of the transfer material is provided upstream of the transfer means, and the light irradiation means is determined based on information from the transmitted light amount detection means. This device is equipped with a control circuit that controls the amount of light.

Effect of the present invention With the above-described configuration, after the transfer process, the io-light irradiation means passes through the transfer material from the back side of the transfer material and irradiates the surface of the photoreceptor with light, thereby illuminating the surface of the photoreceptor in the portion overlapping with the transfer material. It removes the residual charge and eliminates the Coulomb force that attracts the transfer material to the photoreceptor, thereby facilitating separation of the photoreceptor and the transfer material. At this time, the amount of light irradiated to remove static electricity from the surface of the photoconductor is controlled based on the light transmittance of the transfer material, so regardless of the type of transfer material, the amount of light irradiated is always the minimum amount required to eliminate static electricity from the surface of the photoconductor. The amount of light can be set to a limited amount, and the life of the photoreceptor will not be shortened due to excessive exposure.

In addition, since the residual charge on the non-image area of the photoconductor is left as is before the transfer process, the toner particles of the toner image on the photoconductor surface are prevented from moving on the photoconductor surface, and the toner scatters during the transfer process. does not occur much.

Example Hereinafter, preferred embodiments of the present invention will be described.

FIG. 1 shows a schematic configuration of a transfer type electrophotographic apparatus according to an embodiment of the present invention. In the figure, 1 is a photoreceptor, 2 is a charger that charges the surface of the photoreceptor 1, 3 is a developer, 4 is toner particles attached to the surface of the photoreceptor, 6 is a transfer material, and e is a transfer device. A light source 8 is provided downstream of the transfer devices as a light irradiation means for transmitting light from the back side of the transfer material 6 and irradiating the surface of the photoreceptor 1 with light. Furthermore, the transfer device 6
A transmitted light amount detecting means comprising a light emitting section 7& and a light receiving section 7b arranged to sandwich the transfer material 6 is provided on the transport path of the transfer material 6 upstream of the transfer material 6, and the light receiving section of this transmitted light amount detecting means A light amount control circuit 9 is also provided that controls the amount of light from the light source 8 based on the information.

Reference numeral 10 denotes a conveying device for the transfer material 5 separated from the photoreceptor 1.

Next, the operation of the above device will be explained.

The surface of the photoreceptor 1 rotating in the direction of the arrow is charged with a charger 2 to, for example, a positive polarity, and then an exposure device (not shown) exposes it to light according to image information to form an electrostatic latent image. .

This electrostatic latent image is formed by erasing the charges in the image area. The electrostatic latent image is formed by toner particles 4 charged to the same polarity (positive polarity in this example) as the surface charge of the photoreceptor by the developing device 3.
It is developed with The toner particles 4 adhering to the surface of the photoreceptor are carried while remaining attached to the surface of the photoreceptor, are overlapped with a transfer material 5 that is transported in the direction of the arrow by a transport device (not shown), and are transferred onto the transfer material 6 by a transfer device 6. Ru. on the other hand,
Before the transfer material 6 is superimposed on the surface of the photoreceptor 1, the transfer material 5 passes between the light emitting section 7 & of the transmitted light amount detection means and the light receiving section 7b, and during this time, the light emitting section 71 emits light and the transfer material The light transmitted through the light receiving section 5 reaches the light receiving section 7b, and the amount of transmitted light is detected by the light receiving section 7b. The light amount of the light source 8 is determined by the τ light amount control circuit 9 based on information from the light receiving section 7b. The surface charge on the photoreceptor after the previous transfer is removed by light energy transmitted from the back side of the transfer material 5 by the light source 8 and transmitted through the transfer material 5. As a result, the Coulomb force that had been attracting the transfer material 6 to the photoreceptor 1 disappears, so that the transfer material 5 is separated from the photoreceptor 1 due to its own weight and rigidity, and is sent to a fixing device (not shown) by the conveyance device 10 to form a recorded image. is obtained.

The process of separating the transfer material 5 from the photoreceptor 1 will be described in detail below.

FIG. 2 is a diagram illustrating this separation step in the present invention. In this figure, 1a represents the surface of the photoreceptor that moves in the direction of the arrow. Charges having a polarity opposite to the residual charge on the photoreceptor are induced in the transfer material 5 fed and superimposed on the photoreceptor surface 1& in the vicinity of the contact with the photoreceptor surface. As a result, a Coulomb force acts between the photoreceptor 1 and the transfer material 6, which acts to prevent separation. A light source 8 downstream of the transfer device 6 irradiates the back surface of the transfer material 6 with light. A portion of this light passes through the transfer material 6 and irradiates the surface of the photoreceptor, and residual charges on the surface of the photoreceptor are removed by this light irradiation. As a result, the above-mentioned Coulomb force disappears, and the transfer material 6 and the photoreceptor 1 can be easily separated. Incidentally, the amount of light required from the light source 8 to transmit through the transfer material 5 and remove residual charges on the surface of the photoreceptor naturally varies depending on the light transmittance of the transfer material.
If the light intensity of the light source 8 is set according to the transfer material with the lowest light transmittance among the expected transfer materials, the light transmittance will be large for other thin transfer materials, etc., and the photoreceptor 1
will be irradiated with an amount of light greater than that required for optical static elimination. Exposing the photoreceptor to more light than necessary shortens the life of the photoreceptor. Therefore, in the present invention, the amount of light from the light source 8 is adjusted based on the light transmittance of the transfer material 6 so that irradiation is always performed with the minimum amount of light necessary to eliminate static electricity on the surface of the photoreceptor.
It's in control. More specifically, when the light transmittance of the transfer material is high, the light amount of the light source 8 is decreased, and when the light transmittance is low, the light amount is increased. This prevents the life of the photoreceptor from becoming short. In addition,
By making the wavelength of the light emitted from the light emitting section 7a the same as the wavelength of the light source 8, the above-mentioned effect can be further enhanced.

FIG. 3 illustrates changes in the surface potential of the photoreceptor from charging to separation. In the case of an electrophotographic apparatus using a reversal development method, the surface of the photoreceptor is charged to a predetermined potential by a charger, and only the image area is neutralized in an exposure process. The non-image area is not neutralized in the exposure step, and the potential is lowered for the time being during the dark decay phase B::,' until the transfer step. In the transfer process, under the influence of the potential applied to the transfer device,
A decrease in the surface potential of the photoreceptor is observed. Thereafter, the separation process begins, and according to the present invention, residual charges can be almost completely erased, as shown by "optical charge removal" in FIG. The line labeled "MuC corona charge removal" in FIG. 3 shows the residual charge when the conventional AC corona discharger 10 shown in FIG. 6 is used, and in this case, the photoreceptor surface potential remains at a high level.

Further, according to the separation device of the present invention, unlike the case where a residual charge eliminating means is provided between the development process and the transfer process (for example, Japanese Utility Model Application Publication No. 59-149152), even in the transfer process, non-static charge is removed. Since the image area is kept at a high potential, toner particles of the same polarity hardly move on the photoreceptor surface, which prevents toner scattering and eliminates transferred images with a lot of so-called 'blurring' and 'bleeding'. There is no risk of obtaining.

Incidentally, a potential having a polarity opposite to that of the toner particles 4 (negative polarity in this embodiment) is applied to the transfer device 6, but depending on how much this potential is applied, the transfer material may be charged. FIG. 4 shows another embodiment of the present invention suitable for such a case.

In FIG. 4, 11 is a corona discharger, and 8 is a photoreceptor surface 1a that passes through the transfer material 6 from behind the corona discharger 11.
This is a light source constituting a light irradiation means that irradiates light to. Although the transfer material 6 is given a negative charge by the transfer device 6,
This charge cannot be removed by light irradiation.

Therefore, the negative charge on the transfer material 6 is removed by the corona discharger 11.
Neutralize the positive charge on the photoreceptor. The light source 8 can almost completely remove the charge on the photoreceptor that has not been removed by the corona discharger 11. Although not shown, the light amount of this light source 8 is also controlled by the light transmittance of the transfer material 5, similar to the embodiment shown in FIG. In this way, also in this embodiment, the photoreceptor and the transfer material can be easily separated.

In the embodiment shown in FIG. 4, the light source 8 is placed behind the corona discharger 11, but this means that if it is located downstream of the transfer device from the conveyance path of the transfer material, the light source 8 is located behind the corona discharger 11. The same effect as this embodiment can be obtained whether it is upstream or downstream. Further, the separation device used in combination with the light source 8 is not limited to a corona discharger, and similar effects can be expected even if other known separation devices such as separation claws or separation belts are used. .

In each of the above embodiments, the light irradiation means for transmitting light from the back side of the transfer material and irradiating the surface of the photoreceptor includes:
It is clear that the present invention is not limited to direct light sources such as those illustrated in FIGS. 1, 2, and 4. Further, the transfer means is not limited to the corona discharger as shown in the drawings, but may be a roller transfer method, for example.

Effects of the Invention As is clear from the above description, the present invention is capable of irradiating the surface of the photoreceptor with light that passes through the transfer material from the back side of the transfer material that overlaps the surface of the photoreceptor after the transfer process. Since the residual charge is photo-eliminated, the Coulomb force that attracts the transfer material to the photoreceptor is eliminated, making it possible to easily separate the photoreceptor and transfer material. Since the amount of light is controlled based on the light transmittance of the transfer material, the life of the photoreceptor will not be shortened due to excessive exposure, and any residual charge on the non-image area of the photoreceptor surface will be removed before the transfer process. This has the effect of preventing the toner particles of the toner image formed on the surface of the photoconductor from moving on the surface of the photoconductor, and preventing toner scattering during the transfer process. be.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a transfer type electrostatic photographic apparatus showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the main parts thereof, and Fig. 3 shows the photosensitive process from charging to separation. 4 is a diagram illustrating a main part of another embodiment of the present invention. FIG. 6 is a schematic configuration diagram showing a conventional electrostatic photographic apparatus. FIG. 3 is a diagram for explaining how toner scatters in a transfer process. 1...Photoconductor, 1T...Photoconductor surface, 2
...Charger, 3...Developer, 4...
... Toner particles, 5 ... Transfer material, 6 ...
. . . Transfer device, 711 . . . Light emitting part of the transmitted light amount detection means, END b . . . Light receiving part of the same, 8 . . . Light source (light irradiation means), 9... ...Light amount control circuit, 10
...Transfer device, 11...Corona discharger, 12...Separation claw. Name of agent: Patent attorney Toshio Nakao and one other person■
9 small wanderings and glances

Claims (1)

[Claims] A means for transferring the toner image on the photoconductor to a transfer material superimposed thereon is arranged downstream from the conveyance path of the transfer material, and transfers the toner image from the back side of the transfer material overlapping the surface of the photoconductor to the transfer material. a light emitting unit that irradiates the surface of the photoconductor with light, and a light emitting unit and a light receiving unit that are arranged to sandwich a transfer material conveyance path located upstream from a position where the transfer material is overlapped on the surface of the photoconductor. A transfer device comprising: a transmitted light amount detection means for detecting the light transmittance of the transfer material; and a control circuit for controlling the light amount of the light irradiation means based on information from the transmitted light amount detection means. type image forming device.