JPH04208969A - Transfer device - Google Patents

Abstract

PURPOSE:To sufficiently secure a transfer area and to maintain stable transfer performance which is excellent in durability and receives little effect of environmental variation by forming a conductive member in a belt shape and making an opposed part to an image carrier have specified area. CONSTITUTION:A transfer device is disposed on the downstream side of a developing device in the moving direction of the surface of a photosensitive body and provided with a conductive belt 6 being the conductive member. A metallic sheet such as an aluminum sheet or a conductive rubber belt may be used as the belt 6. The belt 6 is spanned between a conductive roller 7 pair being a bias roller, and one are spanned over the roller 7 pair is positioned to wind around and contact with the surface of the photosensitive body through a transfer sheet. By winding the belt 6 around the conductive surface of the photosensitive body 1, the sufficient transfer area is formed. Thus, the excellent transfer performance is maintained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transfer device employed in an image forming apparatus such as an electrophotographic or electrostatic recording type copying machine, facsimile machine, or printer. , using a conductive member that is disposed opposite to an image carrier carrying a toner image and to which a transfer bias is applied from a power source, and on a transfer material that passes through the opposing portion of the image carrier and the conductive member. The present invention relates to a transfer device for transferring a toner image to a transfer device.

[Conventional technology]

Conventionally, this type of transfer device is an image forming device that forms an electrostatic latent image on a photoreceptor as an image carrier and visualizes it with charged toner. It can be directly transferred to the final transfer material, transfer paper, under a transfer electric field, or it can be transferred to an intermediate transfer material, which is an intermediate transfer material, under a transfer electric field, and then transferred to the final transfer material, transfer paper. It is known that it transfers.

The method for forming the transfer electric field in the former case is as follows.

As shown in FIG. 3(a), a corona charger 2 placed opposite the photoreceptor drum 1, which is an image carrier, applies an electric charge to the back surface of the transfer paper 3 that is in contact with the surface of the photoreceptor. As shown in FIG. 3(b), one bias roller 4 is arranged opposite to the photoreceptor drum 1, and the transfer paper 3 is held between the bias roller 4 and the surface of the photoreceptor. Generally, a method is adopted in which a transfer electric field is created by

However, in those using the corona charger 2, ozone is generated during corona charging. - On the other hand, in the case of using the bias roller 4, high-speed transfer is possible in principle with very high transfer efficiency, but since a predetermined transfer pressure due to contact with the photoreceptor is required, When both the drum 1 and the bias roller 4 are rigid bodies, the life of the photoreceptor is shortened, and it is difficult to secure a transfer area (considered as the transfer nip width, which influences the transfer time).

In addition, in the case where the toner image on the photoconductor is once transferred to the intermediate transfer body, as shown in FIG. There is also known a method in which a predetermined transfer area is formed by contacting the intermediate transfer belt 5, and a transfer electric field is formed by holding charges in the area of the intermediate transfer belt 5 located between the plurality of bias rollers 4.

However, according to this configuration, since the charge injected from the bias roller 4 is held by the intermediate transfer belt 5,
There are strict restrictions on the electrical characteristics of the intermediate transfer belt 5 (for example, in the invention disclosed in Japanese Unexamined Patent Publication No. 63-264778, the specific resistance value of the intermediate transfer member must be set to 10" to 10"8 Ω-). ), intermediate transfer belt 5
There was a problem in that it was not possible to select a material that had good durability and was not easily affected by environmental changes.

[Problem to be solved by the invention]

The present invention has been developed in view of the above-mentioned problems of the prior art, and its purpose is to secure a sufficient transfer area, have excellent durability, and be resistant to environmental changes. It is an object of the present invention to provide a transfer device capable of maintaining stable transfer performance with little influence.

[Means to solve the problem]

In order to achieve the above object, a transfer device according to the present invention includes:
Using a conductive member that is arranged opposite to an image carrier carrying a toner image and to which a transfer bias is applied from a power source,
In a transfer device that forms a transfer electric field at a facing portion of the image carrier and the conductive member and transfers a toner image onto a transfer material passing through the facing portion, the conductive member is formed into a belt shape, The device is characterized in that the portion facing the carrier has a predetermined area.

The invention according to claim 2 is the invention according to claim 1,
The present invention is characterized in that the electrically conductive member used is one whose resistance is equal to or less than the resistance value of the transfer material. In addition, this resistance value means the surface resistance value, and its measurement method is JIS
According to C6484.

[Effect]

A belt-shaped conductive member is opposed to the image carrier with a predetermined width to form a transfer area. A transfer bias is applied from a power source to this conductive member, thereby forming a transfer electric field in the transfer area. A transfer material is conveyed to a transfer area where this transfer electric field is formed, and while the transfer material is on a transfer photoreceptor drum, a toner image in the form of an image carrier is transferred onto the transfer material by the transfer electric field.

〔Example〕

An embodiment of the present invention will be described based on FIG.

FIG. 1 is a front view showing a configuration in which a transfer device according to this embodiment is applied to an electrophotographic copying machine using a photosensitive drum.

The photoreceptor drum 1 is a drum-shaped base on which a photoreceptor layer is formed, and in addition to a transfer device, a charging device (not shown) for uniformly charging the surface of the photoreceptor is installed around the photoreceptor drum 1. , an optical system for irradiating reflected light from the original to form an image, a developing device for supplying toner to the electrostatic latent image and making it visible, a cleaning device for removing residual toner on the photoreceptor after transfer; A static eliminator and the like are provided to remove residual charges on the surface of the photoreceptor. In this example, development is performed using negatively charged toner.

The transfer device is disposed downstream of the developing device in the direction of movement of the surface of the photoreceptor, and includes a conductive belt 6 that is a conductive member. This conductive belt 6 may be made of a metal sheet such as an aluminum sheet, or may be a conductive rubber belt. Examples of this conductive rubber include nitrile rubber (
NBR) and epichlorohydrin rubber (ECO) are preferred.

This conductive belt 6 is stretched around 7 pairs of conductive rollers that are bias rollers, and one region that is stretched between the 7 pairs of rollers wraps around and contacts the surface of the photoreceptor through the transfer paper. Positioned. At least one of the 7 pairs of rollers is a drive roller, and the surface of the conductive belt 6 is rotated by a drive source (not shown) in a direction in which the surface of the conductive belt 6 moves in the same direction as the surface of the photoreceptor at the portion facing the photoreceptor drum 1. Driven. One roller of this pair of rollers is connected to a transfer electric field power source 8 of, for example, plus 100 OV. The transfer paper 3, which is the final transfer material, is conveyed to a portion where the surface of the photoreceptor and the conductive belt 6 face each other by a paper feed conveyance device (not shown).

In the above configuration, the conductive belt 6 is connected to the conductive roller 7.
Since it is connected to the transfer electric field power supply through the transfer electric field and has a predetermined potential, a potential difference is generated between the photoconductor drum 1 base and the photoconductor surface in the area facing the photoconductor surface, and this makes the negative polarity toner conductive. A transfer electric field is formed in a direction that attracts the transfer belt 6 side.

At the same time as the toner image formed on the surface of the photoreceptor by the developing device is carried into the area where the transfer electric field is formed as the photoreceptor drum 1 rotates,
Transfer paper 3 is conveyed from the paper feed conveyance means, and toner on the photoreceptor is transferred onto this transfer paper 3.

According to this embodiment, since the conductive belt 6 is used, a sufficient transfer area can be formed by wrapping the conductive belt 6 around the surface of the photosensitive drum 1.

Also, when charges are injected into the transfer paper 3 from the conductive belt 6 and the transfer paper 3 itself, which retains the injected charges, is used as a pseudo electrode opposite to the base of the photoreceptor drum 1, the conductive Since a sufficient contact area between the transfer belt 6 and the transfer paper 3 can be ensured, sufficient charge can be injected even into the transfer paper 3 having a relatively high resistance. Therefore, it is possible to use a relatively high-resistance transfer paper 3 that is not easily affected by environmental fluctuations such as temperature and humidity, and it is possible to maintain stable transferability.

Next, a second example will be described in which the present invention is applied to a copying machine that once transfers a toner image on a photoreceptor drum 1 to an intermediate roller.
This will be explained using figures.

In FIG. 2, an intermediate transfer belt 5 serving as an intermediate transfer body is stretched between a ground roller 9 and a pair of conductive rollers 7 via a conductive belt 6. As shown in FIG. Then, the area passed through the conductive belt 6 to the pair of conductive rollers wraps around and comes into contact with the surface of the photoreceptor, and the toner image on the surface of the photoreceptor is transferred onto the intermediate transfer belt 5 along with the surface of the photoreceptor. A first transfer area is formed for this purpose. As the intermediate transfer belt 5, a dielectric belt may be used, or a belt with reduced resistance may be used as required. The conductive belt 6 and the pair of conductive rollers 7 can be the same as those in the above embodiment and can be used as they are. The grounding roller 9 is grounded via a bearing or the like, and together with a bias roller that comes into contact with it from below, the toner image on the intermediate transfer belt 5 is transferred to the transfer paper 3 on the opposing part of both rollers.
A second transfer portion is formed for transferring the image. The bias roller 10 is connected to a power source (not shown) so as to generate a predetermined potential difference between the bias roller 10 and the ground roller 9 to form a transfer electric field. The transfer paper 3, which is the final transfer material, is conveyed to the second transfer area by a paper feeding and conveying device (not shown) to a portion where the surface of the photoreceptor and the conductive belt 6 face each other.

In the above configuration, as in the above embodiment, the conductive belt 6 is connected to the transfer electric field power supply via the conductive roller 7 and has a predetermined potential. A potential difference is generated between the photosensitive drum 1 and the substrate, thereby forming a transfer electric field that attracts the negative polarity toner toward the conductive belt 6 side. As a result, the toner on the surface of the photoreceptor is transferred to the surface of the intermediate transfer belt 5.

The toner image attached to the surface of the intermediate transfer belt 5 is conveyed to the second transfer area by the rotation of the intermediate transfer belt 5, and here, the toner image is transferred onto the transfer paper 3 conveyed from the paper feed conveyance means at the same timing. be done.

On the other hand, the intermediate transfer belt 5 applied from the conductive roller 7
The electric charge is removed when passing through the grounding roller 9.

According to this embodiment, since the conductive belt 6 is used in the same way as in the above embodiment, by wrapping the conductive belt 6 around the surface of the photosensitive drum 1, sufficient first
A transfer area can be formed.

Further, a conductive belt 6 having a predetermined potential comes into contact with the area of the intermediate transfer belt 5 in the transfer area from the side opposite to the surface of the photoreceptor, and a transfer electric field is generated by the potential difference between the conductive belt 6 and the base of the photoreceptor. Therefore, even if the charge injected into the intermediate transfer belt 5 contributes little to the formation of the transfer electric field, a sufficient transfer electric field can be formed. Further, since a sufficient contact area between the intermediate transfer belt 5 and the conductive belt 6 is ensured, charges can be efficiently injected even if the intermediate transfer belt 5 has a relatively high resistance. Therefore, compared to the conventional transfer device, in which charges are injected into the intermediate transfer belt 5 by the bias roller 10 that partially contacts the intermediate transfer pair in a relatively narrow area, and a transfer electric field is mainly formed by the injected charges. There are few restrictions on the material of the intermediate transfer belt 5, and it has excellent durability.
Materials that are less susceptible to environmental changes can be used.

In this embodiment, the bias roller 10 is used as a member that forms the second transfer area together with the intermediate transfer belt 5, but instead of this, a conductive belt stretched between the pair of rollers is used as the conductive belt surface. It may be used in such a manner that the surface of the intermediate transfer belt 5 and the surface of the intermediate transfer belt 5 are in contact with each other over a sufficient area.

In addition, in a device that forms an image using toner of multiple colors, such as a full-color image, a transfer device using this intermediate transfer belt 5 performs transfer after overlapping toner images of each color on the intermediate transfer belt 5. It is effective as a transfer device for transferring to paper 3, but it can be used for full color images and single color images (
(including solid black), the transfer paper 3 is conveyed to the above-mentioned second transfer area when forming a full color image, and the transfer paper 3 is conveyed to the first transfer area when forming a single color image. It may also be used together with a paper feed conveyance means having a switching function so as to convey the paper.

Further, in each of the above embodiments, the present invention is applied to a transfer device in an image forming apparatus using a drum-shaped image bearing member. It can also be applied to

〔Effect of the invention〕

As described above, according to the present invention, the conductive member that is disposed opposite to the image carrier that carries the toner image and forms the transfer electric field in the portion facing the image carrier is shaped like a belt, and Since the facing portion is configured to have a predetermined area, a sufficient transfer area can be secured.

Also, when a transfer electric field is formed by charges injected into the transfer material, the conductive member and the transfer material are in contact over a relatively large area, resulting in good charge injection efficiency and a relatively small field that is not easily affected by environmental changes. Since a high-resistance transfer material can be used, stable transfer performance can be maintained with less influence from environmental fluctuations. Furthermore, by using a relatively high-resistance transfer material, leakage of charge to the image bearing member in the transfer area can be minimized, and good transfer performance can also be maintained from this point of view.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the configuration of a transfer device according to an embodiment of the present invention. FIG. 2 is a front view showing the configuration of a transfer device according to another embodiment of the present invention. Figure 3 shows a conventional transfer device, and (a)
1 shows a transfer device using a corona charger, and (b) shows a transfer device using a bias roller. FIG. 2C is a diagram showing a transfer device using an intermediate transfer member and a plurality of bias rollers. 1... Photosensitive drum, 3... Transfer paper, 5... Intermediate transfer belt, 6... Conductive belt, 7... Conductive roller, 8... Power source for transfer electric field.

Claims (2)

[Claims] (1) Using a conductive member that is placed opposite to an image carrier carrying a toner image and to which a transfer bias is applied from a power source, a transfer electric field is applied to the opposing portion of the image carrier and the conductive member. In a transfer device that transfers a toner image onto a transfer material that forms a toner image and passes through the facing portion, the conductive member is formed into a belt shape, and the portion facing the image carrier is configured to have a predetermined area. A transcription device featuring: (2) The transfer device according to claim 1, wherein the electrically conductive member is a member whose resistance is equal to or lower than the resistance value of the transfer material.