JPH02213884A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To obtain a satisfactory picture on an overhead projector (OHP) sheet by providing a transfer electric field imparting means, which imparts an electric field to a toner picture on an intermediate transfer body, in the vicinity of a transfer roller in a toner picture transfer position but on the side of the place where a transfer paper is fed into the transfer roller. CONSTITUTION:An electrophotographic device is provided with a paper guide 30, a corona transfer device 31, a second transfer roller 32, a peeling plate 33, and a cleaner 34 along the surface of the intermediate transfer body 25. When the transfer paper 18 is an OHP sheet, an electric field required for transfer is given to the toner picture of the intermediate transfer body 25 from the corona transfer device 31; the toner picture on the intermediate transfer body 25 is transferred to a transfer paper 18 by bringing the transfer paper 18 into press-contact with the toner picture of the intermediate transfer body 25 by means of the second transfer roller 32. In this case, the toner picture on the intermediate transfer body 25 is given a sufficient intensity of electric field by the corona transfer device 31, and consequently it is ready to be peeled from the intermediate transfer body 25. Thus, the toner picture is securely transferred onto the transfer paper 18 by the second transfer roller 32.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic device such as an electrostatic transfer copying machine or a laser printer, and in particular, to an electrophotographic device such as an electrostatic transfer copying machine or a laser printer, and in particular, to a method for transferring an image developed on a photoreceptor to an intermediate transfer member. Furthermore, the present invention relates to an electrophotographic apparatus that obtains a desired image on transfer paper by transferring the image from an intermediate transfer member to transfer paper.

[Conventional technology]

For example, an electrostatic transfer copying machine as an electrophotographic device has
There is a full-color copying machine that uses developers of three primary colors, yellow, magenta, and cyan, and is capable of reproducing and copying the colors of an original image. This full-color copying machine forms toner images of the three primary colors individually on a belt-shaped photoreceptor, transfers these toner images in a superimposed state onto a belt-shaped intermediate transfer member, and then transfers these toner images onto a belt-shaped intermediate transfer member. A full-color copy image is obtained by further transferring the layered toner image to a transfer paper.

At the position where the toner image is transferred from the intermediate transfer body to the transfer paper, a metal transfer roller is provided on the front side of the intermediate transfer body, and an insulating bank up roller made of rubber is provided on the back side of the intermediate transfer body. A back electrode is provided. and,
To transfer the toner image from the intermediate transfer body to the transfer paper, the transfer paper is fed along the intermediate transfer body and the transfer roller is pressed against the back roller, so that the toner on the transfer paper and the intermediate transfer body between both rollers is transferred. This is performed by bringing the image into pressure contact with the image and applying a transfer voltage between the transfer roller and the back electrode.

[Problem to be solved by the invention]

However, the conventional structure described above has the problem that, for example, when an OHP (OHP) sheet is used as the transfer paper, the toner image cannot be properly transferred from the intermediate transfer member to the OHP sheet. are doing.

That is, a strong electric field is required to transfer the toner image from the intermediate transfer member to the OHP sheets 1 to 1. Therefore, if the transfer voltage between the transfer roller and the back electrode is increased in order to obtain such an electric field, bin poles will occur in the toner image. Alternatively, near the line of the three-layer toner image, discharge occurs in a gap created by the difference in thickness between the three-layer tree image and the single-layer toner image, resulting in transfer failure. As a result, a good copy image cannot be obtained.

[Means to solve the problem]

In order to solve the above problems, an electrophotographic apparatus of the present invention includes an intermediate transfer member that is provided in contact with the surface of a photoreceptor and that transfers a toner image transferred from the photoreceptor to a transfer paper. In an electrophotographic apparatus in which a transfer roller that presses the transfer paper against the toner image on the intermediate transfer body is provided at the toner image transfer position from the intermediate transfer body to the transfer paper, the area near the transfer roller at the above-mentioned toner image transfer position The apparatus is characterized in that a transfer electric field applying means for applying an electric field to the 1-toner image on the intermediate transfer member is provided on the side where the transfer paper enters the transfer roller.

[For production]

According to Mihara's configuration, when a toner image on an intermediate transfer member is transferred to an OHP sheet as a transfer paper, a 0)-(P sheet is supplied between the intermediate transfer member and the transfer roller. At this time, an electric field of a predetermined intensity is applied from the transfer electric field applying means to the toner image on the intermediate transfer body through the OHP sheet, and the OI (P sheet is pressed against the toner image on the intermediate transfer body by the transfer roller). As a result, it is possible to obtain an electric field of the strength required for transferring the l/toner image to the OHP sheet at the toner image transfer position of the intermediate transfer member, and this electric field is not applied to the OHP sheet, for example, as in the conventional case. This does not occur between the transfer roller that presses the toner image on the intermediate transfer member and the back electrode, so pinholes occur in the toner image, or discharge occurs in the gaps in the three-layer toner image. Therefore, it is possible to properly transfer the toner image on the intermediate transfer member to the ○HP sheet.Thus, even when OHP sheet 1- is used as the transfer paper, the toner image on the intermediate transfer member can be transferred to the OHP sheet Good images can be obtained at the top.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1, a full-color copying machine (hereinafter referred to as a copying machine) as an electrophotographic device has a transparent document table 3 on which a document 2 is placed in the -L section of a machine frame 1. ing. An optical system section 4 is provided below the document table 3 to scan the document 2 and form an electrostatic latent image on a photoreceptor 9, which will be described later.

The optical system section 4 includes a copy lamp 5 that irradiates light onto the original 2 on the original platen 3, and a plurality of mirrors 6 that guide reflected light from the original 2 onto a photoreceptor 9 as shown by a dashed line.・・・
. . , an imaging lens 7 disposed on the optical path, and a filter device 8 having color filters for the three primary colors of red, green, and blue.

A belt-shaped photoreceptor 9 made of an organic photoreceptor (OPC photoreceptor) is provided below the optical system section 4 . This photoreceptor 9 is connected to drive rollers 1 arranged in parallel at regular intervals.
A hook is passed between the roller 0 and the driven roller 11. Around the photoreceptor 9, there is a charger 12 and a developing device 13.
4 and 15, a cleaner 16 and a static elimination lamp 17 are arranged facing the photoreceptor 9. The above developing devices 13 to 15
contains yellow, magenta and cyan color developers separately.

Below the driven roller 11 side of the photoreceptor 9, there are paper feed cassettes 19 and 2 for each size that accommodate transfer paper 18...
0 are placed above and below. Paper feed rollers 21 and 22 are provided at the paper output portion of each paper feed cassette 19 and 20, and further,
A timing roller 23 is provided in the paper feeding direction of the paper feeding cassettes 19 and 20.

On the other hand, an intermediate transfer device 24 is provided on the drive roller 10 side. The intermediate transfer device 24 includes a belt-shaped intermediate transfer body 25, first to 31st colas 26 to 28 for rotationally driving the intermediate transfer body 25, a back electrode roller 29, a paper guide 30, and a corona serving as a transfer electric field applying means. A transfer device 31, a second transfer roller 32 as a transfer roller,
Peeling plate 33, cleaner 34, and first transfer roller 3
It is composed of 5th grade. The intermediate transfer body 25 described in -1- is pressed against the drive roller 10 of the photoreceptor 9, and a first transfer roller 35 is provided on the back surface of the intermediate transfer body 25 at this location. The back electrode roller 29 is provided between the second and thirtieth rollers 27 and 28 on the back side of the intermediate transfer member 25 . Further, the paper guide 30, the corona transfer device 31, the second transfer roller 32, the peeling plate 33, and the cleaner 34 are provided along the surface of the intermediate transfer body 25. The second transfer roller 32 mentioned above is the intermediate transfer body 2
It is in pressure contact with the 30th-ra 28 via the 30th-ra. Further, the corona transfer device 31 is arranged between the second transfer roller 32 and the paper guide 30, that is, on the paper input side of the second transfer roller 32. A known corona transfer device 31 can be used.

In the paper output direction of the intermediate transfer body 25 and the second transfer roller 32, a conveyance heald 36, a fixing device 37, and a paper discharge section 3B are provided in this order.

In the above configuration, during a copying operation in this copying machine, the copy lamp 5 and mirror 6 of the optical system section 4 reciprocate in the direction of arrow C-D, and the original 2 is placed on the original platen 3-. to scan. The reflected light from the original 2 reaches the surface of the photoreceptor 9 via the mirrors 6 . As a result, the photoreceptor 9 is exposed and an electrostatic latent image is formed. Furthermore, if this copy is a full-color copy, the scan of original 2 will be 3
the filter device 8 is scanned 3 times during each scan.
Insert colored filters one by one into the optical path. Therefore, electrostatic latent images of three colors are sequentially formed on the photoreceptor 9.

The three electrostatic latent images formed on the photoreceptor 9 are transferred to the developing device 13.
15, the image is sequentially developed with yellow, magenta and cyan developers to form a toner image. Next, these toner images are sequentially transferred by the first transfer roller 35 from the surface of the photoreceptor 9 to the same position on the intermediate transfer member 25 so as to overlap, thereby forming a completed full-color toner image.

On the other hand, the transfer paper 18 housed in the paper feed cassette 19 or 20 is fed to the timing roller 23 by the paper feed roller 21 or 22. The timing roller 23 transfers the transfer paper 18 to the intermediate transfer body 25 in synchronization with the intermediate transfer body 25.
and the corona transfer device 31. When the transfer paper 18 is an OHP sheet, the corona transfer device 31
An electric field required for transfer is applied to the toner image on the intermediate transfer body 25 from the 2nd transfer roller 32, and the second transfer roller 32 presses the transfer paper 18 against the toner image on the intermediate transfer body 25, so that the toner image on the intermediate transfer body 25 is The image is transferred onto transfer paper 18. At this time, the toner image on the intermediate transfer body 25 is transferred to the corona transfer device 3.
Since a sufficiently strong electric field is applied from 1 to the intermediate transfer body 25, the second transfer roller 32 reliably transfers the toner to the transfer paper 18-A.

The transfer paper 18 on which the 1-toner image has been transferred is transported by the conveyor belt I.3.
6, the sheet is sent to the fixing device 37, where the I/toner image is fixed, and then discharged from the paper discharge section 38 to the outside of the machine.

〔Effect of the invention〕

As described above, the electrophotographic apparatus of the present invention includes an intermediate transfer member that is provided in contact with the surface of a photoreceptor and that transfers a toner image transferred from the photoreceptor to a transfer paper, and also includes a In an electrophotographic apparatus in which a transfer roller that presses the transfer paper against the toner image on the intermediate transfer body is provided at the toner image transfer position to the transfer paper, a portion near the transfer roller at the above-mentioned toner image transfer position is used. , a transfer electric field current applying means for applying an electric field to the toner image on the intermediate transfer member is provided on the side where the transfer paper enters the transfer roller.

Therefore, even when using 01 (P Sheet 1-) as a transfer paper, the OHP sheet can be printed without causing problems such as bin poles in the toner image or discharge in the gaps in the toner image. Good images can be obtained at the top.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and is an overall configuration diagram of a full-color copying machine. 2 is a document, 414 is an optical system section, 9 is a photoreceptor, 13 to 15 are developing devices, 24 is an intermediate transfer device, 25 is an intermediate transfer body, 2
6 to 28 are first to 30th rollers, 29 is a back electrode roller,
31 is a corona transfer device (transfer electric field applying means), and 32 is a second transfer roller (transfer 11-ra).

Claims (1)

[Scope of Claims] 1. An intermediate transfer member is provided in contact with the surface of the photoreceptor and transfers the toner image transferred from the photoreceptor to the transfer paper, and the toner is transferred from the intermediate transfer member to the transfer paper. In an electrophotographic apparatus in which the image transfer position is provided with a transfer roller that presses the transfer paper against the toner image on the intermediate transfer body, a portion near the transfer roller at the above-mentioned toner image transfer position that is connected to the transfer roller. An electrophotographic apparatus characterized in that a transfer electric field applying means for applying an electric field to a toner image on an intermediate transfer member is provided on the input side of the transfer paper.