Wet type electrophotography apparatus to heat toner on intermediate transfer medium

• US 6,173,147 B1
• Filed: 06/24/1999
• Issued: 01/09/2001
• Est. Priority Date: 08/27/1997
• Status: Expired due to Fees

• Current Assignee: PFU Limited (Fujitsu Limited)
• Original Assignee: PFU Limited (Fujitsu Limited)
• Inventors: Uesugi, Shigrki, Takabatake, Masanari, Nakashima, Yutaka, Takeda, Seiichi, Ichida, Motoharu, Okano, Shigeharu, Moto, Satoru, Inamoto, Akihiko
• Primary Examiner(s): Braun, Fred L.
• Application Number:
  US09/284,136
• Time in Patent Office: 565 Days
• Field of Search: 399/302, 399/308, 399/233, 399/237
• US Class Current: 399/308
• CPC Class Codes: G03G 15/161 with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent
• CPC Class Codes: G03G 2215/0187 Multicoloured toner image formed on the recording member
• CPC Class Codes: G03G 2215/0629 liquid at room temperature

Abstract

A wet type electrophotography apparatus according using a non-volatile, high-viscosity, high-concentration liquid toner as a developing solution, and including a photoconductive medium on which an electrostatic latent image is formed, a prewetting device for coating the surface of the photoconductive medium with a film of prewetting solution, a developing device, an intermediate transfer medium for transferring the toner particles deposited on the photoconductive medium, a pressure roller rotating in contact with the intermediate transfer medium for transferring a printing medium while forcing the printing medium onto the intermediate transfer medium, and a heating device for heating locally the surface of the intermediate transfer medium at a location immediately before the intermediate transfer medium comes in contact with the pressure roller. The wet-type electrophotography apparatus can efficiently heat and fuse the toner transferred on the intermediate transfer medium without causing thermal effects on the photoconductive medium.

Claims

1. A wet type electrophotography apparatus using as a liquid developer a non-volatile, high-viscosity, high-concentration liquid toner, comprising:

an image carrier on which an electrostatic latent image is formed;

a prewetting solution applicator to apply a prewetting liquid film on said image carrier;

a developing device to supply a liquid toner as a liquid developing solution to said image carrier by making contact with said image carrier, and causing toner particles to deposit on said image carrier in accordance with an electrical field formed between said developing device and said image carrier;

an intermediate transfer medium on which said toner particles deposited on said image carrier are transferred in accordance with said electrical field formed between said intermediate transfer medium and said image carrier;

a pressure roller to transport a printing medium while forcing said printing medium onto said intermediate transfer medium as said pressure roller rotates in contact with said intermediate transfer medium; and

a mechanism to cause a preheated heating device to make contact with said intermediate transfer medium only when needed to locally heat the surface of said intermediate transfer medium at a location before said intermediate transfer medium comes in contact with said pressure roller.

2. A wet type electrophotography apparatus as set forth in claim 1, wherein said heating device comprises a heating roller having a heat source therein,

wherein a voltage is applied to said heating roller having the same polarity as the polarity of a static charged to said toner particles with respect to said intermediate transfer medium to prevent said toner particles from migrating to said heating roller.

3. A wet type electrophotography apparatus as set forth in claim 2, wherein the surface of said heating roller is coated with a semi-conductive coating material, said coating material having a thickness of 10-100 μ

m and a volume resistivity of 10⁸˜

10¹² Ω

·

cm.

4. A wet type electrophotography apparatus as set forth in claim 2, wherein a solution comprising silicone oil as a carrier solution containing 5-30% of solid matter is used as said liquid toner, the thickness of said toner image electrostatically transferred onto said intermediate transfer medium is 1-20 μ

m, and said voltage applied to said heating roller is several to several hundred kilovolts with respect to said intermediate transfer medium.

5. A wet type electrophotography apparatus as set forth in claim 4, wherein a material having an intimacy with said carrier solution is used as said coating material to improve the effect of eliminating the carrier during heating.

6. A wet type electrophotography apparatus as set forth in claim 4, further comprising:

a heat-resistant blade to recover said carrier solution by making contact with said heating roller; and

a roller comprising a non-woven fabric member that contacts said heating roller at a location before said heat-resistant blade in the direction of the rotation of said heating roller.

7. A wet type electrophotography apparatus as set forth in claim 1, wherein said heating device comprises a plurality of rollers in a non-contact state with said intermediate transfer medium, at least one of which is heated from inside, and a belt driven by said rollers to rotate while making contact with said intermediate transfer medium.

8. A wet type electrophotography apparatus as set forth in claim 7, wherein said belt comprises a base material, and at least the base material of said belt comprises a metal.

9. A wet type electrophotography apparatus as set forth in claim 7, wherein said belt comprises a highly heat-resistant elastic layer on the surface thereof.

10. A wet type electrophotography apparatus as set forth in claim 7, further comprising a drive unit to drive said intermediate transfer medium, wherein said belt is driven by the drive unit which drives said intermediate transfer medium, and said belt is adapted to eliminate slips due to differences in peripheral speed between both.

11. A wet type electrophotography apparatus as set forth in claim 7, wherein said belt is driven by three rollers, one roller of which is disposed close to said pressure roller in a proximity of the surface of said intermediate transfer medium and has a smaller diameter than the diameter of the other rollers.

12. A wet type electrophotography apparatus as set forth in claim 7, wherein said belt is brought in contact with said intermediate transfer medium at the same speed, and

further comprising an internal heat source on a rear side of said belt to replenish thermal energy to said heating belt, the temperature of which falls due to heat conduction by contact with said toner.

13. A wet type electrophotography apparatus as set forth in claim 12, wherein said internal heat source comprises a stationary heater block in sliding contact with the rear side of said heating belt.

14. A wet type electrophotography apparatus as set forth in claim 13, wherein a portion of said stationary heater block at which said stationary heater block comes in contact with said heating belt is formed into a concave curved surface having a curvature equal to or slightly larger than a diameter of said intermediate transfer medium.

15. A wet type electrophotography apparatus as set forth in claim 12, wherein said internal heat source comprises a heating roller that is rotated as said heating roller is driven in contact with the rear side of said heating belt.

16. A wet type electrophotography apparatus as set forth in claim 12, wherein said internal heat source comprises a radiation heat source to supply thermal energy to said heating belt in a non-contact state.

17. A wet type electrophotography apparatus as recited in claim 16, wherein the radiation heat source is a halogen lamp.

18. A wet type electrophotography apparatus as set forth in claim 16, further comprising a reflector to concentrate radiation heat, and a black heat resistant material provided on the rear surface of said heating belt to facilitate energy absorption.

19. A wet type electrophotography apparatus as recited in claim 18, wherein the black heat resistant material is paint.

20. A wet type electrophotography apparatus as set forth in claim 7, further comprising:

belt tension rollers to drive said belt, the belt tension rollers being forced onto said intermediate transfer medium by a pressure that is as soft as not to collapse an image, and

wherein a tension roller on the toner fusing and transfer side at the final part of the contact area of said heating belt is forced onto said heating belt with a slightly stronger force.

21. A wet type electrophotography apparatus as set forth in claim 20, wherein each of said tension rollers exerts a pressure to said intermediate transfer medium independently via a pressure exerting arrangement independent from a belt contact/retract mechanism.

22. A wet type electrophotography apparatus as set forth in claim 20, wherein said heating belt, which is driven by a belt tension roller on the toner fusing and transfer side, has a tight side on the belt surface on which said heating belt comes in contact with said intermediate transfer medium.

23. A wet type electrophotography apparatus as set forth in claim 1, wherein said intermediate transfer medium comprises a belt driven by a plurality of rollers, and the surface of said intermediate transfer medium is locally heated by a heating roller making contact with the rear side of said belt only when toner is transferred to a printing medium.

24. A wet type electrophotography apparatus as set forth in claim 23, wherein said belt comprises a material having a high thermal conductivity.

25. A wet type electrophotography apparatus as set forth in claim 23, further comprising a printing medium transfer section, wherein said heating roller is provided on said printing medium transfer section to serve as a backup roller.

26. A wet type electrophotography apparatus as set forth in claim 1, wherein said heating device includes a device to preheat the toner to such an extent as not to fuse the toner prior to a toner heating and fusing process.

27. A wet type electrophotography apparatus as set forth in claim 1, further comprising a control device to control a heating amount of said heating device in accordance with information about the amount of toner deposited on said intermediate transfer medium.

28. A wet type electrophotography apparatus as set forth in claim 1, wherein said intermediate transfer medium comprises a metallic drum, an electrically conductive, heat-resistant elastic material layer, and a surface layer having electrical conductivity, heat resistance and releasability on the surface of said metallic drum.

29. A wet type electrophotography apparatus as set forth in claim 28, wherein said elastic material layer comprises low-elasticity solid rubber.

30. A wet type electrophotography apparatus as set forth in claim 28, wherein said elastic material layer comprises an electrically conductive porous material.

31. A wet type electrophotography apparatus as set forth in claim 28, wherein said surface layer comprises an electrically conductive fluorine resin or fluoro-silicone rubber.

32. A wet type electrophotography apparatus as set forth in claim 31, wherein said electrically conductive fluorine resin or fluoro-silicone rubber is applied on said elastic material layer by spraying a liquefied form thereof.

33. A wet type electrophotography apparatus as set forth in claim 31, wherein the film form of said electrically conductive fluorine resin or fluoro-silicone rubber is wound on said elastic material layer.

34. A wet type electrophotography apparatus as set forth in claim 28, wherein said elastic material layer comprises an electrically conductive silicone sponge, and said surface layer is formed by coating an electrically conductive polyimide film with fluorosilicone rubber.

35. A wet type electrophotography apparatus as set forth in claim 28, further comprising butt flanges to limit the relative movement of said intermediate transfer medium with said photoconductive medium provided on both sides of said intermediate transfer medium.

36. A wet type electrophotography apparatus using as a liquid developer a non-volatile, high-viscosity, high-concentration liquid toner, comprising:

an image carrier on which an electrostatic latent image is formed;

a prewetting solution application device to apply a prewetting liquid film on said image carrier;

a developing device to supply a liquid toner as a liquid developing solution to said image carrier by making contact with said image carrier, and causing toner particles to deposit on said image carrier in accordance with an electrical field formed between said developing device and said image carrier;

an intermediate transfer medium on which said toner particles deposited on said image carrier are transferred in accordance with an electrical field formed between said intermediate transfer medium and said image carrier;

a pressure roller to transport a printing medium while forcing said printing medium onto said intermediate transfer medium as said pressure roller rotates in contact with said intermediate transfer medium; and

an infrared-ray heating device to locally heat the surface of said intermediate transfer medium at a location before said intermediate transfer medium comes in contact with said pressure roller,

wherein said intermediate transfer medium comprises an infrared-ray reflective surface.

37. A wet type electrophotography apparatus using as a liquid developer a non-volatile, high-viscosity, high-concentration liquid toner, comprising:

an image carrier on which an electrostatic latent image is formed;

a prewetting solution applicator to apply a prewetting liquid film on said image carrier;

a developing device to supply a liquid toner as a liquid developing solution to said image carrier by making contact with said image carrier, and causing toner particles to deposit on said image carrier in accordance with an electrical field formed between said developing device and said image carrier;

an intermediate transfer medium on which said toner particles deposited on said image carrier are transferred in accordance with said electrical field formed between said intermediate transfer medium and said image carrier;

a pressure roller to transport a printing medium while forcing said printing medium onto said intermediate transfer medium as said pressure roller rotates in contact with said intermediate transfer medium; and

an infrared-rave heating device to locally heat the surface of said intermediate transfer medium at a location before said intermediate transfer medium comes in contact with said pressure roller,

wherein said intermediate transfer medium comprises an infrared-ray absorbing surface.