JPH0418311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus capable of multiple-transferring developed images formed on an image carrier onto a transfer material.

Conventionally, in a device such as a color copying device that sequentially forms different color images on an image carrier such as a photoreceptor drum and multiple-transfers each color image onto a transfer material, the transfer material is a sheet having a dielectric surface. Alternatively, the image on the image carrier is transferred to the transfer material by the action of corona discharge while being held by a mesh-like transfer material carrying means. However, in such an apparatus, the electrostatic adsorption force between the transfer material and the transfer material carrying means may be overcome by the curvature of the transfer material film and the transfer material carrying means, and the conveyance force may become weak. As a result, color misregistration or conveyance failure occurs.

In addition, under low humidity conditions, charges may accumulate on the transfer material and the transfer material carrying means, and when the transfer material is separated from the image bearing member and circulated, there is a risk of air discharge occurring. Once an air discharge occurs, the discharge energy is large, which disturbs the development on the transfer material.

The present invention has been made in view of the above points, and relates to a new and excellent image forming apparatus.

The present invention provides an image forming apparatus capable of multiple-transferring a developed image formed on an image carrier onto a transfer material, including a transfer charging means for transferring an image on the image carrier to the transfer material at a transfer position, and A transfer material carrying means having a dielectric surface carrying a material and circulating in the transfer position; and a transfer material carrying means provided in a gap separating the image carrier and the transfer material carried by the transfer material carrying means, The device is characterized in that it includes a wire electrode that generates a discharge induced by the transferred charge by the charging means.

Hereinafter, details of the present invention will be explained using specific examples with reference to the drawings. The illustrated embodiment is one in which the transfer device according to the present invention is applied to a copying device, in which a photosensitive drum is used as an image bearing member, and the transfer drum is used as a transfer material carrying means that moves in circulation. An example of a transfer device is shown in which a developed image is multiple-transferred onto a transfer material held by a transfer drum.

In FIG. 1, 1 is a photosensitive drum that carries an image, 2 is a transfer drum that carries a transfer material, 3 is a charger, 4 is an image exposure optical system, 5 is a developing device, and 6 is a transfer device facing the photosensitive drum. A corona discharger, 7 a gripper, and 8 a linear conductive member (hereinafter referred to as a static elimination wire). The photosensitive drum 1 described above is a conductive cylinder whose surface is coated with a photoconductive substance such as Se, CdS, ZnO, or the like. The transfer drum 2 is, for example, as shown in FIG. 2, a cylinder 21 with a cutout in the center, and a dielectric material 22 made of a sheet of polyester, nylon, polypropylene, etc. or a perforated mesh stretched over the cutout part of the cylinder 21. It is.

Further, in an apparatus that sequentially forms different color images on a photosensitive drum and multiple-transfers each color image onto a transfer material, a plurality of color developing devices can be provided as the developing device 5.

In the above-mentioned apparatus, the surface of the photosensitive drum 1 is charged by the charger 3, and then the image of the document is exposed by the optical system 4, thereby producing an electrostatic latent image.
This is developed and visualized by the developing device 5. For transfer materials made of paper or transparent film, grip the tip 7.
The transfer corona discharger 6 and the photoreceptor 1 are held on a transfer drum 2 whose surface is made of a dielectric material 22, and wrapped around the surface of the transfer drum 2.
move between. The transfer material is a transfer corona discharger 6.
The toner image on the photosensitive drum 1 is transferred by
Here, the transfer drum 2 obtains an electrostatic adhesion force and is conveyed. A static elimination wire 8 is placed in the gap at the transfer material separation position.
is stretched by insulating support arms 9. Wire 8 is grounded. The separated transfer material is conveyed by the grounded static elimination wire 8 with increased electrostatic adsorption force. Thereafter, the transfer material is separated from the transfer drum 2 and discharged. If necessary, multiple transfer is performed by further rotating without separation and performing the next transfer.

3a and 3b show a situation in which a toner image is transferred to a transfer material and separated from the photosensitive drum 1. FIG. In the figure, 10 is a transfer material, 11 is a charge charged by a transfer corona discharger, 12 is a toner, 13 is a charge due to air discharge, and 14 is a charge due to discharge from a static elimination wire.

FIG. 3a shows the case where there is no static elimination wire.

In FIG. 3a, toner 12 is attached to the photosensitive drum 1 in correspondence with the latent image charge (for convenience, it is assumed to be positive).

A transfer material 10 is superimposed on the transfer material carrier 2 on this surface, and the transfer material 10 is supported by a transfer corona discharger 6. By transferring by corona, there is no transfer defect in the character part, which occurs when transferring by roller. As a result, positive charges 11 are attached to the back surface of the transfer material carrier 2 . When the transfer material 10 and the transfer material carrier 2 are separated from the photosensitive drum 1, the toner 12 on the photosensitive drum 12 due to the positive charge 11 and the charge 13 due to air discharge at the time of separation adhere to the surface of the transfer material 10. At this time, the total charge density of the toner 12 attached to the transfer material and the charge 13 due to the air discharge is smaller than the charge density of the charge 11 from the transfer corona discharger 6.

In the above transfer device, the electrostatic adsorption force between the transfer material 10 and the transfer material carrier 2 is generated by the interaction of these positive and negative charges. Furthermore, the electrostatic attraction force can be increased. Further, the surface potential of the transfer material is 3000 V or more due to the influence of the positive charges 11. Although the transfer material alone does not have such a high potential, the transfer material carrier maintains a high potential because it is a dielectric material. Since this high potential (and electric charge) does not decay for a relatively long time, the transfer material remains electrostatically attracted to the transfer material carrier.

However, when the humidity is low, the surface potential of the transfer material becomes higher than 4000V, and the energy of air discharge increases. Therefore, the toner image on the transfer material is disturbed, and a discharge pattern is generated on the image.

The present invention is characterized in that the above-mentioned aerial discharge is performed immediately after transfer before the distance between the image carrier and the transfer material is too great, and the discharge between the transfer material and the static elimination wire is uniformly performed. .

In FIG. 3b, the transfer material 10 is attached to the photosensitive drum 1.
By providing the static elimination wire 8 immediately after separation from the transfer material, since the surface of the transfer material is at a high potential, discharge occurs between the static elimination wire 8 and the transfer material, and negative charges are deposited on the transfer material. Since this discharge is performed while the distance between the photosensitive drum and the transfer material is extremely short, the energy is small and the discharge is uniform, so there is no problem of creating a discharge pattern on the image.

The setting position of the static eliminating wire may be in the vicinity of the separation position of the transfer material, preferably between the photosensitive drum and the transfer material carrier, or slightly closer to the photosensitive drum.

Furthermore, if the diameter of the static eliminating wire exceeds 200μ, the self-discharge effect will deteriorate, so a diameter of 200μ or less, preferably 100μ or less is effective.

FIG. 4 shows a case where two static elimination wires 8 are used, which further increases the negative charge injected onto the transfer material and increases the adsorption force.

When a plurality of static eliminating wires 8 are used, color shift becomes less likely to occur by placing them close enough to each other so as not to impede discharge efficiency.

In FIG. 5, the static eliminating wire 8 is connected to the dielectric support member 25.
(for example, a 200 μm thick polyester film), the static eliminating wire 8 is reinforced by this, and there is no fear that the static eliminating wire 8 will be cut when the transfer material jam is taken out. Moreover, the static elimination effect is maintained as it is. In addition, since it is possible to use a wire with a small diameter (for example, 80μ) with low strength, the discharge efficiency can be increased and effective static elimination can be expected. As the dielectric support member, a dielectric film plate or round bar made of polyester polycarbonate, acrylic, etc. can be used.

As described above in detail using specific examples, the present invention includes:
This is extremely good as it prevents the transfer material from being disturbed.
Moreover, it exhibits a remarkable effect of obtaining a good transferred image without color shift in color multiple transfer in which the transfer material is repeatedly circulated.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a specific example transfer device of the present invention, FIG.
Figures a and b are explanatory diagrams showing the state when the transfer material is separated;
FIG. 4 and FIG. 5 are explanatory diagrams of a modified example of a static elimination wire based on the present invention. In the figure, 1...image carrier, 2...transfer drum, 3
... Charger, 8 ... Static elimination (self-discharge type) wire.

Claims (1)

[Scope of Claims] 1. In an image forming apparatus capable of multiple-transferring a developed image formed on an image carrier onto a transfer material, the image forming apparatus includes a transfer charging means for transferring the image on the image carrier onto the transfer material at a transfer position. a transfer material carrying means having a dielectric surface carrying a transfer material and circulating in the transfer position; and a transfer material carrying means provided in a gap separating the image carrier and the transfer material carried by the transfer material carrying means. An image forming apparatus comprising: a Y electrode that generates discharge due to being induced by the transfer charge by the transfer charging means.