JPH0488385A - Transferring device - Google Patents

Abstract

PURPOSE:To obtain an image having enough density, no irregularity and high quality by making the photosensitive surface of an image carrier contact with an intermediate transferring belt at all area where the transferring electric field of a transferring part executing the transferring of the toner image on the image carrier to the intermediate transferring belt is actuated so that the toner image is transferred to the intermediate transferring belt. CONSTITUTION:A tension roller 12 adds tension to the intermediate transferring belt 14 in order to make the intermediate transferring belt 14 turn while the intermediate transferring belt 14 is guided by a contact starting roller 8 and a contact ending roller 10. By the rotation of a photosensitive body 5, the toner image reaches a contact S (an interval between the contacts S and E is an electric field action area, and the contact S is an electric field action starting point) where the transferring electric field starts actions through a transferring roller 6. And the toner image is made to contact with the intermediate transfer ring belt 14 simultaneously as it reaches the contact S, and the toner image is transferred to the intermediate transferring belt 14. Thus, a transferring efficiency is improved, and the image having enough density, no image irregular ity and high quality is obtained on the transferring material.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention is an image forming apparatus using electrophotography or the like, in which a toner image formed on an image carrier is transferred and carried on an intermediate transfer member, and this intermediate transfer The present invention relates to a transfer device used to retransfer a toner image carried on a body onto a transfer material to obtain an image on the transfer material.

In an image forming apparatus using an electrophotographic method or the like, a transfer device equipped with an intermediate transfer member is used to transfer and carry a toner image formed on an image carrier onto the intermediate transfer member. , retransfer the toner image carried on this intermediate transfer member onto a transfer material,
It is known to obtain images on transfer materials.

FIG. 2 shows an example of a portion where a toner image is transferred to an intermediate transfer member in a conventional transfer device using an intermediate transfer member. The transfer section shown in FIG. 2 is related to a transfer device used in an image forming apparatus such as an electrophotographic copying device.

As shown in FIG. 2, an electrostatic latent image of an image formed on the photoreceptor 1 as an image carrier is transferred to a toner 2 in a developing section (not shown).
is developed and visualized as a toner image, and the toner image faces the intermediate transfer member 3 as the photoreceptor 1 rotates.
The toner image is transferred to the intermediate transfer body 3 at a transfer section (-next transfer section). In this transfer section, the toner image on the photoconductor 1 is brought into close contact with the intermediate transfer body 3, and a voltage of opposite polarity to the toner 2 constituting the toner image is applied from the back side of the intermediate transfer body 3 using the transfer roller 4 or a corona discharger. By applying a transfer electric field,
Toner 2 is transferred from photoreceptor 1 onto intermediate transfer member 3 by electrostatic force, and a toner image is transferred onto intermediate transfer member 3 .

In this case, in terms of transfer efficiency only, the higher the applied voltage of the transfer electric field within an appropriate range, the better the result. However, as a result, a part of the toner image on the photoreceptor 1 is inevitably transferred before it comes into close contact with the intermediate transfer member 3, so that the transfer position of the toner image on the intermediate transfer member 3 is not the original position. Image distortion occurs when the image is shifted from the position of .

The image disturbance during transfer including the above positional deviation is
This will be explained in detail below using figures. The photoreceptor 1 facing the rotating intermediate transfer member 3 rotates, the toner image on the photoreceptor 1 approaches and contacts the intermediate transfer member 3, and the toner image after being transferred onto the intermediate transfer member 3 is transferred to the photoreceptor. The process of separating from 1 is 5.
If we break it down into stages, we get the following:

First, the first stage is when the toner image on the photoreceptor 1 is located in an area A that is sufficiently far away from the intermediate transfer member 3, and at this stage, the toner image is not affected by the transfer electric field by the transfer roller 4. Therefore, the toner 2 constituting the toner image is not transferred onto the intermediate transfer member 3, and the toner image is not completely transferred to the intermediate transfer member 3.

Next, at the second stage where the toner image on the photoreceptor 1 is located in the area B close to the intermediate transfer member 3, the toner image is affected by the transfer electric field by the transfer roller 4, so that the toner 2 is slightly The toner image is transferred and transferred from the photoreceptor 1 onto the intermediate transfer member 3, and as a result, as described above, some image disturbance occurs in which the transfer position of the toner image onto the intermediate transfer member 3 is shifted from its original position.

In the next third stage, the toner image on the photoreceptor 1 is transferred to the transfer roller 4.
This is the stage when the toner image is substantially transferred to the intermediate transfer body 3 when the toner image is located in the transfer area C, which is the transfer area where the toner image is placed. At this stage, the toner image comes into contact with the intermediate transfer member 3, and a transfer electric field having a voltage with a polarity opposite to that of the toner 2 by the transfer roller 4 is applied from the back surface of the intermediate transfer member 3, and as a result, a toner image is formed. The toner 2 is transferred onto the intermediate transfer member 3 by electrostatic force caused by the transfer electric field, and the toner image is transferred onto the intermediate transfer member 3, thereby substantially transferring the toner image.

The next fourth stage is a stage in which the toner image transferred onto the intermediate transfer member 3 begins to separate from the photoreceptor 1, but is still located in the region D, which is close to the photoreceptor 1. Image disturbance occurs in the toner image mainly in these four stages.

This is because electric charges are charged between the photoreceptor 1 and the intermediate transfer member 3 in the third stage. Since the behavior of the image disturbance varies depending on the volume resistivity of the intermediate transfer member 3, it is necessary to consider the volume resistivity of the intermediate transfer member 3 separately.

Now, in the fourth stage, the corresponding portions of the photoreceptor 1 and the intermediate transfer member 3 to which the toner image has been transferred are separated from the close contact state to the close state. At this time, the volume resistivity of the intermediate transfer body 3 is 10'1Ωc
If it is a relatively large value greater than or equal to m, the third
The electric charges charged between the photoconductor 1 and the intermediate transfer body 3 at this stage mainly pass through the intermediate transfer body 3 and are difficult to escape, so that an electric field due to the charged charges is generated between the photoconductor 1 and the intermediate transfer body 3. The photoreceptor 1 and intermediate body 3 are formed and are therefore spaced apart.
This means that the distance between the photoreceptor 1 and the intermediate transfer member 3 increases with respect to a constant charge under the electric field caused by the charged charges.
A voltage rise occurs between the

Therefore, spark discharge occurs due to dielectric breakdown in the gap between the photoreceptor 1 and the intermediate transfer member 3, causing image disturbance of the toner image on the intermediate transfer member 3 and deterioration of the surface of the photoreceptor 1.

On the other hand, if the volume resistivity of the intermediate transfer body 3 is a relatively small value of 1080 cm or less, the electric charge accumulated between the photoreceptor 1 and the intermediate transfer body 3 in the third stage is transferred from the intermediate transfer body 3 to the surrounding area. It is easy to escape through structural members and moisture in the air, and this also causes image disturbance in the toner image on the intermediate transfer member 3.

The final fifth stage is a stage in which the toner image on the intermediate transfer member 3 is located in an area E that is sufficiently far away from the photoreceptor 1, and the toner image from the photoreceptor 1 is transferred onto the intermediate transfer member 3. It's finished. The toner 2 constituting the toner image on the intermediate transfer member 3 is not affected by the transfer electric field generated by the transfer roller 4, nor is it affected by the potential of the photoreceptor 1.

As described above, the photoreceptor 1 and the intermediate transfer member 3 are transferred before and after the third stage in which substantial transfer is performed with the photoreceptor 1 and the intermediate transfer member 3 in contact with each other.
In the second and fourth stages in which the toner image and the intermediate transfer body 3 are in close proximity, image disturbance occurs in the toner image.

As an application of the above transfer method using an intermediate transfer body, toner images of each color are formed on the intermediate transfer body,
There is a color copying machine that then transfers the image all at once from the intermediate transfer member to the transfer paper. The advantages of this type of transcription are:
Examples include reducing color shift in images, expanding the types of transfer paper, and expanding transfer conditions.

However, if the toner image on the photoconductor is not properly transferred onto the intermediate transfer member, the above advantages cannot be achieved; rather, the toner image on the photoreceptor must be transferred to the intermediate transfer member and transferred from there to the transfer paper. Since there are two transfer steps, the disadvantage is that the problems that occur during transfer are increased compared to systems that require only one transfer step.

The conventional technology described above has the disadvantage that the toner image is disturbed in the process of transferring the toner on the photoreceptor onto the intermediate transfer member. has adopted a method to reduce the disturbance in the above image. For this reason, it has been difficult to obtain high-quality images with sufficient density and no image disturbance by copying.

Therefore, an object of the present invention is to improve the transfer efficiency by transferring the toner image on the image carrier onto the intermediate transfer member without disturbing it, and as a result, to improve the transfer efficiency of the toner image from the intermediate transfer member onto the transfer material. It is an object of the present invention to provide a transfer device capable of obtaining a high-quality image with sufficient density and no image disturbance on a transfer material by transfer.

The above-mentioned object is achieved by the transfer device according to the present invention. In summary, the present invention provides a transfer device that transfers and carries a toner image formed on an image carrier onto an intermediate transfer member, and retransfers the toner image carried on the intermediate transfer member onto a transfer material. , the photosensitive surface of the image carrier and the intermediate transfer body in the entire region of the transfer area of the toner image onto the intermediate transfer body, where the transfer electric field used for transferring the toner image onto the intermediate transfer body acts. The transfer device is characterized in that the toner image is transferred onto the intermediate transfer member by bringing the toner image into contact with the intermediate transfer member. According to a preferred embodiment of the present invention, the intermediate transfer body has a volume resistivity of 10
It is a flexible endless belt with a resistance of 6 to 1013 Ωcm.

K Godan Examples of the present invention will be described in detail below.

FIG. 1 is an explanatory diagram showing a portion where a toner image is transferred to an intermediate transfer belt in an embodiment of a transfer device of the present invention.

In FIG. 1, reference numeral 14 indicates an intermediate transfer belt, and a major feature of the present invention is that the transfer device is constructed using the intermediate transfer belt 14 as an intermediate transfer body.

The intermediate transfer belt 14 has a volume resistivity of 108 to 10.
It consists of a flexible endless belt of 12 Ωcm, and a transfer roller 6 is provided inside the orbit of the intermediate transfer belt 14 at a position close to the photoreceptor 5 as an image carrier rotating in the direction of the arrow. A contact start roller 8 having a shaft 9 and a contact end roller 10 having a shaft 11 are provided at positions close to the photoreceptor 5 with the roller 6 in between, and a tension roller 12 having a shaft 13 at a position opposite to the transfer roller 6. is provided.

The voltage applied to the transfer roller 6 is applied to the shaft 7 of the transfer roller 6 in the absence of the photoreceptor 5 and the intermediate transfer belt 14.
A concentric equipotential surface is formed with the transfer roller 6 with the transfer roller 6 in the center, and lines of electric force spread radially in a direction perpendicular to the outer peripheral surface of the transfer roller 6. At this time, the area where the transfer electric field acts on the toner image on the photoreceptor 5 is between two tangent lines drawn to the outer peripheral surface of the photoreceptor 5 through the shaft 7 of the transfer roller 6. In other words, the area between the contact points S and E of the two tangent lines of the photoreceptor 5 passing through the shaft 7 of the transfer roller 6 with the photoreceptor 5 is an electric field action area, where the contact point S is the start point of the electric field action, and E is the end point of the electric field action. becomes.

The above-mentioned contact start roller 8 is provided with the shaft 9 positioned on the normal line of the photoreceptor 5 passing through this contact point S, and the contact start roller 8
The intermediate transfer belt 14 is attached to the photoreceptor 5 by the guide and do.
The trajectory is reversed in this direction, and the contact point S starts contacting the outer circumferential surface of the photoreceptor 5. Similarly, the above-mentioned contact end roller 10 is provided with the shaft 11 positioned on the normal line of the photoreceptor 5 passing through the contact point E, and the intermediate transfer belt 14 is moved in the opposite direction to the photoreceptor 5 by being guided by the contact end roller 10. The trajectory is reversed, and contact with the outer peripheral surface of the photoreceptor 5 is released at the contact point E.

The tension roller 12 applies tension to the intermediate transfer belt 14 so that the intermediate transfer belt 14 rotates while being guided by the contact start roller 8 and the contact end roller 10.

According to the transfer device configured as described above, before the toner image formed on the photoreceptor 5 reaches the transfer area where the transfer roller 7 is disposed, the toner image is sufficiently separated from the intermediate transfer belt 14. Therefore, no toner image is transferred onto the intermediate transfer belt 14.

Next, as the photoreceptor 5 rotates, the toner image is transferred to the transfer roller 6.
reaches a contact point S where the transfer electric field starts acting. This contact point S corresponds to area B shown in FIG. 2 above, and some of the toner constituting the toner image is transferred onto the intermediate transfer belt 14 and transfer occurs. At this time, in the conventional case, the toner image is not in close contact with the intermediate transfer body 3, so the transfer position of the toner image to the intermediate transfer body 3 is shifted from the original position, causing image disturbance, but in the present invention, the toner image Since the image contacts the intermediate transfer belt 14 at the same time as it reaches the contact point S, even if some toner image transfer occurs, the toner image is not transferred to the intermediate transfer belt 14.
The transfer position on the soil will not shift, and image disturbance will not occur due to this.

Further, since the photoreceptor 5 and the intermediate transfer belt 14 are in contact with each other to eliminate the gap, there is no possibility of dielectric breakdown occurring in the gap between them and generating electric discharge, as in the conventional case.

Furthermore, since the intermediate transfer belt 14 has a volume resistivity of 108 to 1080 cm, when the photoreceptor 5 and the corresponding part of the intermediate transfer belt 14 to which the toner image has been transferred are separated, the substantial There is no dielectric breakdown caused by the charged charges between the photoreceptor 5 and the intermediate transfer belt 14 that are charged during transfer, and therefore the discharge causes the intermediate transfer belt 1 to
There is no possibility that image disturbance occurs in the toner image on the toner image 4 or deterioration of the surface of the photoreceptor 5 occurs. Charges do not escape from the intermediate transfer belt 14 through surrounding components or moisture in the air, and this does not cause disturbances in the toner image.

Furthermore, since the intermediate transfer belt 14 on which the toner image has been transferred is sufficiently isolated from the photoreceptor 5 by the tension roller 12, the toner image is prevented from being disturbed by the influence of the potential of the photoreceptor 5 outside the transfer area. .

As explained above, in the transfer device of the present invention, an intermediate transfer belt is used as an intermediate transfer member to transfer the toner image on the image carrier, and the toner image on the image carrier is transferred. In the entire area where the transfer electric field of the transfer section that performs transfer onto the intermediate transfer body acts,
Since the toner image is transferred onto the intermediate transfer belt by bringing the photosensitive surface of the image carrier into contact with the intermediate transfer belt, the toner image can be transferred onto the intermediate transfer belt without disturbing it.
Therefore, the transfer efficiency of the toner image from the image carrier onto the intermediate transfer member is improved, and as a result, the toner image is transferred from the intermediate transfer member onto the transfer material, and the density is sufficient and High quality images without image distortion can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a portion where a toner image is transferred to an intermediate transfer belt in an embodiment of a transfer device of the present invention. FIG. 2 is an explanatory diagram showing a transfer section of a toner image onto an intermediate transfer body in a conventional transfer device. 5: Photoreceptor 6: Transfer roller 8: Contact start roller 10: Contact end roller 12: Tension roller 14: Intermediate transfer belt S, E: Contact point

Claims (1)

[Scope of Claims] 1) A transfer device that transfers and carries a toner image formed on an image carrier onto an intermediate transfer member, and retransfers the toner image carried on the intermediate transfer member onto a transfer material. , the photosensitive surface of the image bearing member and the intermediate transfer member are connected to each other in the entire area of the transfer portion of the toner image onto the intermediate transfer member, where the transfer electric field used for transferring the toner image onto the intermediate transfer member acts. A transfer device, characterized in that the toner image is transferred onto an intermediate transfer member by bringing the toner image into contact with the intermediate transfer member. 2) The intermediate transfer body has a volume resistivity of 10^8 to 10^1^
The transfer device according to claim 1, which is a flexible endless belt of 2 Ωcm.