JPH0750358B2 - Full color copier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a full-color copying machine including a transfer intermediate applied to, for example, an electrostatic transfer copying machine or a laser printer.

[Conventional technology]

In a conventional full-color copying machine using electrophotography,
There is known a copying machine of a type in which a transfer paper is fixed to a transfer drum and three color toner images of yellow, magenta, and cyan are directly transferred onto a transfer paper from a photoconductor in order.

As an alternative transfer method, a copying machine is provided with a transfer intermediate, and the toner image on the photoconductor is temporarily transferred to the transfer intermediate, and yellow, magenta, and cyan color images are transferred onto the transfer intermediate. Form a full-color image by superimposing, and then create a full-color image with three colors superimposed.
A system in which transfer is performed on a transfer paper every time is also known from the past.

Among such transfer methods, the above-mentioned transfer intermediate, which is provided in a full-color copying machine in which an electrostatic transfer method is adopted as a toner image transfer method, is obtained by impregnating resin such as polycarbonate or polyimide with carbon dispersed therein. The material is used, the entire shape is formed into a belt shape, and the surface resistance of the transfer intermediate is set to about 10 ⁸ to 10 ¹² Ω.

Then, the photoconductor and the first transfer charger for transferring the toner image on the photoconductor to the transfer intermediate are arranged to face each other so as to sandwich the transfer intermediate, and further, the full color image is sandwiched so as to sandwich the transfer intermediate. A second transfer charger for transferring an image onto a transfer sheet and a grounded back electrode plate for the second transfer charger are arranged opposite to each other.

In this case, first, charges are applied from the back side of the transfer intermediate by the first transfer charger, the toner images of the respective colors on the photoconductor are superposed and transferred onto the transfer intermediate, and then the toner images on the transfer intermediate are transferred. Transfer the toner image from the transfer intermediate to the transfer paper by superposing the transfer paper on the surface on which the (full-color image) is formed and applying an electric charge from the back side of the transfer paper with the second transfer charger. Has become.

[Problems to be Solved by the Invention]

By the way, in the above configuration, when the full-color image formed on the transfer intermediate is transferred to the transfer paper by the second transfer charger, good adhesion is always provided between the transfer intermediate and the back electrode plate. Is required. This is because when the adhesion between the transfer intermediate and the back electrode plate is insufficient, electric charges are accumulated in the inadequate portion, and the transfer from the transfer intermediate to the transfer paper is not performed well, This is because a transfer failure will occur.

However, in the above-described configuration of the full-color copying machine, when the transfer intermediate is passed between the second transfer charger and the back electrode plate, a partial floating state is present between the transfer intermediate and the back electrode plate. Therefore, it is difficult to say that good adhesion is provided between the transfer intermediate and the back electrode plate. Therefore, electric charges are accumulated in the floating portion and the gap portion, and a remarkable transfer failure from the transfer intermediate to the transfer paper occurs.

The present invention has been made in view of the above problems, and even if the adhesion between the transfer intermediate and the back electrode plate is insufficient, the transfer from the transfer intermediate to the transfer paper is good. It is to provide a full-color copying machine that can perform the above.

[Means for Solving the Problems]

In the full-color copying machine of the present invention, in order to solve the above problems, a plurality of toner images formed on the surface of the photoconductor are firstly formed.
A transfer intermediate that is superposed on the surface by a transfer charger, a second transfer charger that electrostatically transfers the toner image that is superposed on the transfer intermediate to a transfer paper, and a toner image on the transfer intermediate is transferred. A back electrode plate of a second transfer charger arranged so as to contact the surface opposite to the surface of the transfer intermediate, the surface of the transfer intermediate on the side contacting the back electrode plate. A conductive layer is formed on the back electrode plate, and the back electrode plate is provided with switching means for switching the back electrode plate to a grounded or non-grounded state.

[Action]

According to the above configuration, since the conductive layer is formed on the surface of the transfer intermediate which is in contact with the back electrode plate, the transfer intermediate is provided between the second transfer charger and the back electrode plate. When passing, for example, even if a good adhesion is not obtained between the transfer intermediate and the back electrode plate, and even if a partial floating state or a gap is generated, the charges pass through the conductive layer in the transfer intermediate. Since the conductive layer and the back electrode plate escape from the contacting portion, no charge is accumulated in the transfer intermediate unlike the conventional case. Therefore, stable transferability from the transfer intermediate to the transfer paper can be obtained.

Further, when the toner image is transferred from the photoconductor to the transfer intermediate by the first transfer charger, the back electrode plate is switched to the non-grounded state by the switching means, so that the transfer from the photoconductor is performed without any trouble. It is possible to transfer the toner image to the intermediate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

First, the overall structure of the full-color copying machine will be described. As shown in FIG. 3, an endless belt-shaped photoconductor 2 is hung in the copying machine body 1 so as to be movable in a fixed direction. There is.

Around the periphery of the photoconductor 2, a charging charger 21 for forming a charged region on the surface of the photoconductor 2, a blank lamp 22 for forming a blank on the charged region on the photoconductor 2,
Developing devices 23a, 23b, and 23c in which yellow, magenta, and cyan developers are stored for each color, and the toner images after development formed on the photoconductor 2 are transferred and sequentially superposed to form one full-color image. An endless belt-shaped transfer intermediate body 24 that is movable in a fixed direction for forming, and a cleaning unit 25 for removing the developer remaining on the surface of the photoconductor 2 after being transferred to the transfer intermediate body 24. And a discharging lamp 26 for discharging the photoconductor 2 are arranged in order along the moving direction of the photoconductor 2.

The above-mentioned transfer intermediate body 24 is arranged so as to come into contact with the surface of the photoconductor 2, and the toner image formed on the photoconductor 2 is transferred to the back surface side of the transfer intermediate body 24 at the contact portion. There is provided a first transfer charger 24a for transferring to.

In addition, the first of the transfer intermediates 24 that can move in a fixed direction
A second transfer charger 24b for transferring the full-color image formed on the transfer intermediate 24 onto the transfer paper 7 is provided downstream of the transfer charger 24a, and a second transfer charger 24b for separating the transfer paper 7 from the transfer intermediate 24. The peeling charger 24c, the charge removing charger 24d for removing charge from the transfer intermediate 24, and the cleaning means 24e for removing the developer remaining on the transfer intermediate 24 after transfer are They are arranged in order along the moving direction.

On the other hand, on the upstream side of the transfer path of the transfer paper 7, a paper feed unit 3 in which a paper feed cassette or the like can be mounted is provided, and the second transfer charger 24b disposed in the middle of the transfer paper 7 transfer path.
The fixing device 4 is provided on the downstream side of the peeling charger 24c, and the paper discharge section 5 is formed on the downstream end thereof.

A transparent document table 69 is arranged on the upper surface of the copying machine main body 1. Below the document table 69, a light source 61 for irradiating light toward the document surface on the document table 69 and an optical image reflected from the document surface are provided. A plurality of mirrors 62 to 66 for further reflecting and guiding to the exposure point P on the photoconductor 2, and an imaging lens 6 provided on the optical path thereof.
7 and a color separation filter 68 for separating an optical image for each color component, and the exposure optical system 6 is configured by these.

Next, the full-color copying process will be described. When the exposure optical system 6 scans the surface of a color original, only the blue light of the color separation filter 68 is transmitted through the color separation filter 68,
At the exposure point P, the surface of the photoconductor 2 is exposed. This allows
A latent image having blue information is formed on the photoconductor 2, and by moving the photoconductor 2, yellow toner is attached by the developing device 23a. This yellow toner image is
Further, when the photoconductor 2 moves, it is transferred onto the transfer intermediate 24 by the first transfer charger 24a.

Similarly to the above, when the exposure optical system 6 scans the color original surface again, only the green light is transmitted by the color separation filter 68 to form a latent image on the photoconductor 2 and the latent image having the green information is formed. On the other hand, the developing device 23b attaches magenta toner to form a toner image. The magenta toner image formed on the photoconductor 2 is transferred so that the image positions of the magenta toner image and the previous yellow toner image formed on the transfer intermediate 24 coincide with each other.

Further, when the exposure optical system 6 scans the surface of the color original, only red light of the original reflected light obtained by this scanning passes through the color separation filter 68 and a latent image is formed on the photoconductor 2. . Cyan toner adheres to the latent image on the photoconductor 2 by the developing device 23c, and this cyan toner image is also formed on the previous yellow and magenta toner images formed on the transfer intermediate 24. The images are transferred so as to overlap each other so that the image positions match.

A full-color image is formed by the toner images of the three colors superimposed as described above. The full-color image formed on the transfer intermediate 24 is transferred onto the transfer paper 7 supplied from the paper feeding unit 3 by the second transfer charger 24b, and then the transfer paper 7 is separated from the transfer intermediate 7 by the peeling charger 24c. Then, the full-color image is fixed on the transfer paper 7 by the fixing device 4 and then transferred to the paper discharge unit 5. In this way, a full-color image is formed on the transfer paper 7.

As shown in FIG. 1 (a), the transfer intermediate body 24 has a belt body 24 'in which carbon is dispersed and impregnated in a polycarbonate resin or a polyimide resin, and its surface (toner adhering surface) resistance Is about 10 ⁹ Ω, thickness is 100
It has a size of about μm and is formed into a belt shape as a whole.

On the back surface of the belt member 24 ', that is, the surface opposite to the surface on which the toner image is transferred, as shown in FIG. 1 (b),
A conductive layer 24 ″ having a thickness of about 30 μm is formed. The conductive layer 24 ″ is formed, for example, by depositing aluminum on the back surface of the belt body 24 ′. There is no limitation on the forming method.

In addition, as shown in FIG. 2, the second transfer charger 24b for transferring the toner image (full color image) formed on the surface of the transfer intermediate 24 onto the transfer paper 7 is provided with the second transfer charger 24b. A back electrode plate 24f is arranged so as to face the charger 24b with the transfer intermediate 24 interposed therebetween.

In the above configuration, the belt body that constitutes the transfer intermediate body 24
When the conductive layer 24 ″ is formed on the back surface of 24 ′, the transfer intermediate 24 becomes the second transfer charger 24b and its back electrode plate 24f.
When passing between the transfer intermediate 24 and the back electrode plate 24f, the charge passes through the conductive layer 24 ″ of the transfer intermediate 24 even if a partial floating state or a gap is generated between the transfer intermediate 24 and the back electrode plate 24f. And escapes from the portion where the conductive layer 24 ″ and the back electrode plate 24f are in contact with each other. Therefore, unlike the conventional case, the electric charge is not accumulated in the partially floated portion or the gap portion, and the situation where the electric charge is accumulated in the floating portion or the gap portion between the two and the transfer failure is not caused, The toner image (full-color image) formed on the transfer intermediate 24 is reliably and satisfactorily transferred to the transfer paper 7 in a stable state.

When the transfer intermediate 24 having the conductive layer 24 ″ formed on the back surface of the belt body 24 ′ is used, the transfer intermediate from the photoconductor 2 is transferred.
The toner image is set to be floated from the ground during the primary transfer of the toner image to 24, and is set to be grounded at the secondary transfer of the toner image (full color image) from the transfer intermediate 24 to the transfer paper 7. It is necessary to have a switching mechanism that can do this. With such a switching mechanism, when the toner image is transferred from the photoconductor 2 to the transfer intermediate 24, the back electrode plate 24f is set to a non-grounded state so that the transfer from the photoconductor 2 is performed without any trouble. The toner image can be transferred to the intermediate body 24.

〔The invention's effect〕

In the full-color copying machine of the present invention, as described above, a plurality of toner images formed on the surface of the photoconductor are superposed on the surface by the first transfer charger and the transfer intermediate is superposed on the transfer intermediate. A second transfer charger for transferring the formed toner image to a transfer sheet, and a back surface of the second transfer charger arranged so as to come into contact with the surface of the transfer intermediate opposite to the surface on which the toner image is transferred. In a full-color copying machine equipped with an electrode plate, a conductive layer is formed on the surface of the transfer intermediate that contacts the back electrode plate, and the back electrode plate is grounded. Alternatively, a switching means for switching to a non-grounded state is provided.

As a result, when this transfer intermediate passes between the second transfer charger and its back electrode plate, good adhesion cannot be obtained between the transfer intermediate and the back electrode plate. Even if a floating state or a gap is generated, the charge passes through the conductive layer of the transfer intermediate and escapes from the part where the conductive layer and the back electrode plate are in contact with each other. There is no accumulation. Therefore, it becomes possible to obtain stable transferability from the transfer intermediate to the transfer paper, and it is possible to obtain a stable and high-quality copy image.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, and FIG. 1 (a) is a longitudinal sectional view of a main part of a transfer intermediate showing a state before a conductive layer is formed on a belt body. FIG. 1 (b) is a longitudinal sectional view of a main part of a transfer intermediate showing a state where a conductive layer is formed on the back surface of the belt body, and FIG. 2 is a main part of a full-color copying machine equipped with the transfer intermediate. FIG. 3 is a schematic diagram showing the structure of a full-color copying machine to which the present invention is applied. 2 is a photoconductor, 7 is a transfer paper, 24 is a transfer intermediate, 24 'is a belt body, 24 "is a conductive layer, 24a is a first transfer charger, 24b is a second transfer charger, 24c is a peeling charger, and 24f is a spine. It is a counter electrode plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taisuke Uemura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Yukihiko Ueno 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Incorporated (72) Inventor Hideyuki Nishimura 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture Incorporated (56) Reference JP-A-57-23975 (JP, A) JP-A-59-154475 ( JP, A) Actual development Sho 59-186852 (JP, U)

Claims (1)

[Claims] 1. A transfer intermediate on which a plurality of toner images formed on the surface of a photoconductor are superposed on the surface by a first transfer charger, and a toner image superposed on the transfer intermediate is transferred onto a transfer paper. A full-color copy including a second transfer charger that transfers the toner image and a back electrode plate of the second transfer charger that is arranged so as to be in contact with the surface of the transfer intermediate opposite to the surface on which the toner image is transferred. In the machine, a conductive layer is formed on the surface of the transfer intermediate which is in contact with the back electrode plate, and the back electrode plate is
A full-color copying machine comprising switching means for switching the back electrode plate to a grounded or non-grounded state.