JPH06130829A - Image forming device - Google Patents

Abstract

PURPOSE:To improve transferring efficiency, to prevent an intermediate transfer medium from being contaminated, and to obtain a transferred image having high anchor effect by making the hardness of an elastic roller for pressing a printing medium to a heated part within a range specified by a JIS standard A measuring method. CONSTITUTION:The intermediate transfer medium 1 is a film made of polyimide resin coated with polytetrafluoroethylene whose surface resistance is <=10<4>OMEGA, and its surface is conductively processed. The pressure mechanism of a transfer fixing part is a fixing backup roll 7 made of elastic silicone rubber, and its volume electric resistance is about 10<6>OMEGA.cm, and its hardness of >=25 degrees and <=60 degrees by the JIS standard A measuring method. The shaft of the roll 7 and the medium 1 are connected to a high voltage power source and turned on/off by a switching means at any time. When, the paper 16 enters between the roll 7 and the medium 1, voltage having a polarity reverse to a toner image 21 is impressed on the roll 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an intermediate transfer medium, and more particularly to a laser printer used in electrophotographic printers, plain paper facsimiles, etc., and a fixing section of electrophotographic copying machines.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a visualized toner image on an electrostatic latent image carrier is directly transferred onto a sheet which is a printing medium, and then heated by means such as a fixing roller and a backup roll. And a mechanism for fixing the toner on the paper by applying pressure.

Further, in an image forming apparatus using an intermediate transfer medium, the toner image on the electrostatic latent image carrier is once transferred to the intermediate transfer medium, and the transferred image (toner image) on the intermediate transfer medium is heated and applied. It is equipped with a mechanism to fix it on paper by pressure.

[0004]

In the image forming apparatus using the above-mentioned conventional intermediate transfer medium, the transfer efficiency at the time of transferring the toner image from the intermediate transfer medium to the print medium is not perfect,
The problem is that a slight amount of toner remains on the intermediate transfer medium. For example, even if the transfer efficiency is 99%,
If the remaining 1% of the toner is not transferred, it becomes a stain on the intermediate transfer medium, and the toner is melted in the heating part, and these are accumulated and cause a stain on the print medium and the image forming apparatus. A problem arises.

Further, when the toner, which is a powder, is transferred from the intermediate transfer medium to the printing medium, the toner is first heated and melted on the intermediate transfer medium to become a highly viscous liquid. The toner adheres to the surface, but at this time, the toner merely adheres to the surface, and the so-called anchor effect is small, so the fixing strength is weak and the transfer efficiency is 1
It has not reached 00%.

An object of the present invention is to solve these problems, thereby improving the transfer efficiency to 100% in an image forming apparatus using an intermediate transfer medium, and preventing the intermediate transfer medium from getting dirty and having a large anchoring effect. An object is to provide an image forming apparatus capable of obtaining an image.

[0007]

An image forming apparatus according to the present invention has an electrostatic latent image carrier, an intermediate transfer medium contacting the electrostatic latent image carrier, and a mechanism for heating the intermediate transfer medium. In the image forming apparatus, the print medium abutting on the heating portion is run at the same speed as the intermediate transfer medium to simultaneously transfer and fix the image on the intermediate transfer medium to the print medium. The means for pressing is an elastic roller, and the hardness of this elastic roller is 25 degrees or more and 60 degrees or less according to the JIS standard A measurement method. Further, the elastic roller is not less than 10 ⁴ Ω · cm 1
0 ⁸ Ω · cm may have the following conductive.

Further, an electric field generating means for generating an electric field of 300 V or more and 3000 V or less may be provided between the intermediate transfer medium and the elastic roller. The electric field may be generated only when it exists between the medium and the elastic roller,
Further, an electric field of opposite polarity may be generated only when the print medium is not present between the intermediate transfer medium and the elastic roller.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view of a main portion of the image forming apparatus of the present invention. As shown in FIG. 1, the image forming apparatus of the present invention includes an electrostatic latent image carrier 8 that rotates in the direction of the arrow.
First, the charging device 11 charges the electrostatic charge to impart photosensitivity, and subsequently, an electrostatic latent image is formed by the laser light 20 irradiated from a light irradiation device (not shown). Further, the toner 5 supplied from the supply roll 4 is transferred to the developing blade 18
Then, the toner is regulated to a constant amount and sent to the developing roll 3. Then, the electrostatic latent image on the electrostatic latent image carrier 8 is visualized by the adhesion of the toner 5 and becomes a toner image 21.

On the other hand, the belt-shaped intermediate transfer medium 1 is engaged with the drive roll 2, the transfer roll 22, the tension roll 22 and the fixing heating element 24, and is driven by the drive roll 2. Then, the toner image 21 on the electrostatic latent image carrier 8 is transferred to the intermediate transfer medium 1 by the pressing of the transfer roll 22, and is sent to the position of the fixing heating element 24. The tension roll 22 holds the tension of the driven intermediate transfer medium 1 constant.

Here, the fixing heating element 24 is constructed so that the toner image 21 on the intermediate transfer medium 1 is pressed by the fixing backup roll 7 and heated and fixed to the paper 16 which is a printing medium. .

The intermediate transfer medium 1 used in the image forming apparatus of the present invention is a polyimide resin film coated with polytetrafluoroethylene (PTFE) having a surface resistance of 10 ⁴ Ω or less, and the surface thereof is subjected to a conductive treatment. Has been done. The pressing mechanism of the transfer and fixing unit is a fixing backup roll 7 made of elastic silicone rubber, and its volume electric resistance is approximately 10 ⁶ Ω · cm.

The shaft of the fixing backup roll 7 and the intermediate transfer medium 1 are connected to a high voltage power source. Then, a switching means that can be turned on and off at any time is provided.
As a result, an electric field of 300 V or more and 3000 V or less can be applied between the fixing backup roll 7 and the intermediate transfer medium 1.

Here, when the paper 16 enters between the fixing backup roll 7 and the intermediate transfer medium 1, a voltage having a polarity opposite to that of the toner image 21 is applied to the fixing backup roll 7. That is, in this case, if the polarity of the toner image 21 is negative, a positive voltage is applied to the fixing backup roll 7.

At the break between the sheets, a voltage of opposite polarity is applied to the intermediate transfer medium 1 and the fixing backup roll 7. That is, a negative voltage is applied to the fixing backup roll 7.

[0017]

As described above, in the image forming apparatus of the present invention, the toner, which is a powder, enters the fibers of the print medium by the electrostatic force and is then heated and melted. Acts as an anchor, and as a result, strong fixing to the print medium is obtained, so that the transfer efficiency from the intermediate transfer medium to the print medium can be improved to almost 100%. As a result, there is an effect that the contamination of the intermediate transfer medium and the melting of the toner in the heating portion do not occur, and the contamination of the print medium and the contamination of the image forming apparatus are eliminated.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a main part of an image forming apparatus of the present invention.

[Explanation of symbols]

 1 Intermediate Transfer Medium 2 Driving Roll 3 Developing Roll 4 Supplying Roll 5 Toner 7 Fixing Backup Roll 8 Electrostatic Latent Image Carrier 11 Charger 16 Paper 18 Developing Blade 20 Laser Light 21 Toner Image 22 Transfer Roll 23 Tension Roll 24 Heat Generation for Fixing body

Claims (5)

[Claims] 1. An electrostatic latent image carrier, an intermediate transfer medium that contacts the electrostatic latent image carrier, and a mechanism that heats the intermediate transfer medium. In an image forming apparatus that runs at the same speed as the transfer medium and simultaneously transfers and fixes the image on the intermediate transfer medium to the print medium, the means for pressing the print medium against the heated portion is an elastic roller. An image forming apparatus in which the hardness of the body roller is 25 degrees or more and 60 degrees or less according to the JIS standard A measurement method. 2. The image forming apparatus according to claim 1, wherein the elastic roller has a conductivity of 10 ⁴ Ω · cm or more and 10 ⁸ Ω · cm or less. 3. The image forming apparatus according to claim 2,
An image forming apparatus comprising: an electric field generating unit that generates an electric field of 300 V or more and 3000 V or less between the intermediate transfer medium and the elastic roller. 4. The image forming apparatus according to claim 3, wherein the electric field generating means generates an electric field only when the print medium exists between the intermediate transfer medium and the elastic roller. 5. The image according to claim 3, wherein the electric field generating means generates an electric field of opposite polarity only when the print medium is not present between the intermediate transfer medium and the elastic roller. Forming equipment.