Print method and apparatus for re-writable medium

• US 5,866,284 A
• Filed: 05/28/1997
• Issued: 02/02/1999
• Est. Priority Date: 05/28/1997
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Vincent, Kent D.
• Primary Examiner(s): GOODROW, JOHN L
• Application Number:
  US08/864,604
• Time in Patent Office: 615 Days
• Field of Search: 345/84, 345/85, 345/107, 355/404, 355/400, 430/31, 430/37, 359/296
• US Class Current: 430/37
• CPC Class Codes: B41J 2/471 using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror
• CPC Class Codes: B41J 3/4076 printing on rewritable, bistable "electronic paper" by a focused electric or magnetic field
• CPC Class Codes: G03G 15/04072 by laser
• CPC Class Codes: G03G 15/18 of a charge pattern
• CPC Class Codes: G03G 15/221 Machines other than electrographic copiers, e.g. electrophotographic cameras, electrostatic typewriters
• CPC Class Codes: G03G 15/6597 the imaging being conformed directly on the copy material, e.g. using photosensitive copy material, dielectric copy material for electrostatic printing
• CPC Class Codes: G03G 2215/00447 Plural types handled
• CPC Class Codes: G03G 2215/00518 Recording medium, e.g. photosensitive

Abstract

A low cost, high speed, high resolution laser printer method and apparatus for re-writable media is presented. Three aspects are presented: 1) a bi-stable, microencapsulated dichroic sphere colorant and surface coating therefore for producing an electric field writable and erasable medium--such as paper or a paper-like display, 2) an electrophotographic printer that is capable of conventional toner-based printing and re-writable "paper" printing and 3) a greatly simplified electrophotographic printer that is dedicated to printing re-writable media. The printer embodiments are based on conventional low cost laser printer designs, and have significant advantages in product cost, printing resolution and speed over the electrode array printer. A laser scanner is used to writably erase the uniform, high voltage charge deposited on the surface of a photoconductor drum or belt. When the re-writable paper is brought in contact with the charge written photoconductor through a biased back electrode roller, fields generated between the photoconductor and back electrode cause color rotation of the dichroic spheres to develop the desired print image.

Claims

1. A printer for a re-writable medium, the medium having a first recording layer that includes a plurality of polarized dichroic spheres, the printer comprising:

photoconductor means for storing a high voltage charge deposited thereon;

writing means for writably erasing the charge deposited on the photoconductor means; and

support means for holding the re-writable medium proximate to the photoconductor means in a nip contact area such that, when the re-writable medium passes the charge written photoconductor means, fields generated from the photoconductor means cause color rotation of the dichroic spheres to develop a print image on the re-writable medium.

2. The printer as set forth in 1, wherein the support means is biased such that the fields are generated between the photoconductor means and the support means and cause color rotation of the dichroic spheres.

3. The printer as set forth in 1, wherein the first recording layer of the re-writable medium is disposed on a substrate including a conductive layer and the conductive layer is biased such that the fields are generated between the photoconductor means and the conductive layer and cause color rotation of the dichroic spheres.

4. The printer as set forth in 3, wherein the re-writable medium includes a second recording layer disposed on the substrate and opposing the first recording layer, wherein the support means and the conductive layer are biased such that the fields are generated between the photoconductor means and the conductive layer and cause color rotation of the dichroic spheres in the first recording layer but not in the second recording layer.

5. The printer as set forth in 1, comprising medium type detection means for detecting presence of the re-writable medium for printing.

6. The printer as set forth in 1, comprising medium orientation detection means for detecting proper orientation of the re-writable medium for printing.

7. The printer as set forth in 6, wherein if the medium orientation detection means detects improper orientation of the re-writable medium for printing, the writing means writably erases the charge deposited on the photoconductor means according to a mirror of the print image such that, when the re-writable medium passes the charge written photoconductor means, fields generated from the photoconductor means cause color rotation of the dichroic spheres to develop the print image properly on the re-writable medium.

8. The printer as set forth in 1, comprising medium erasure means for erasing the re-writable medium prior to printing.

9. The printer as set forth in 8, wherein the medium erasure means and the photoconductor means are biased so as to apply approximately equal magnitude but opposite direction fields to the re-writable medium when respectively erasing and writing.

10. The printer as set forth in 1, wherein the support means is biased so as to erase prior orientation of the dichroic spheres of the re-writable medium while printing.

11. The printer as set forth in 10, wherein the support means and the photoconductor means are biased so as to apply approximately equal magnitude but opposite direction fields to the re-writable medium when the photoconductor is respectively charged and discharged.

12. The printer as set forth in 1, wherein the printer can enter a toner print mode, such that when in the toner print mode, the photoconductor means and the support means are biased to make charged toner particles deposited on the photoconductor means be transferred to the writable medium, in accordance with the writable erasing of the charge deposited on the photoconductor means.

13. The printer as set forth in 12, comprising fuser means for fusing toner onto the writable medium after printing in the toner print mode.

14. The printer as set forth in 12, comprising medium type detection means for detecting presence of the re-writable medium for printing, and if re-writable medium presence is not detected, causing the printer to enter the toner print mode.

15. A printing process, the process comprising the steps of:

depositing a high voltage charge on a photoconductor;

writably erasing the charge deposited on the photoconductor; and

holding a re-writable medium proximate to the photoconductor in a nip contact area, the re-writable medium having a first recording layer that includes a plurality of polarized dichroic spheres such that, when the re-writable medium passes the charge written photoconductor, fields generated from the photoconductor cause color rotation of the dichroic spheres to develop a print image on the re-writable medium.

16. The process as set forth in 15, comprising the step of biasing a support holding the re-writable medium proximate to the photoconductor such that the fields are generated between the photoconductor and the support and cause color rotation of the dichroic spheres.

17. The process as set forth in 15, wherein the first recording layer of the re-writable medium is disposed on a substrate including a conductive layer, the process comprising the step of biasing the conductive layer such that the fields are generated between the photoconductor and the conductive layer and cause color rotation of the dichroic spheres.

18. The process as set forth in 17, wherein the re-writable medium includes a second recording layer disposed on the substrate and opposing the first recording layer, the process comprising the step of biasing the support and the conductive layer such that the fields are generated between the photoconductor and the conductive layer and cause color rotation of the dichroic spheres in the first recording layer but not in the second recording layer.

19. The process as set forth in 15, comprising the step of detecting presence of the re-writable medium for printing.

20. The process as set forth in 15, comprising the step of detecting proper orientation of the re-writable medium for printing.

21. The process as set forth in 20, comprising the step of:

if improper orientation of the re-writable medium for printing is detected, the writably erasing the charge deposited on the photoconductor according to a mirror of the print image such that, when the re-writable medium passes the charge written photoconductor, fields generated from the photoconductor cause color rotation of the dichroic spheres to develop the print image properly on the re-writable medium.

22. The process as set forth in 15, comprising the step of erasing the re-writable medium prior to printing.

23. The process as set forth in 22, wherein a medium eraser and the photoconductor are biased so as to apply approximately equal magnitude but opposite direction fields to the re-writable medium when respectively erasing and writing.

24. The process as set forth in 15, comprising the step of biasing a support, holding the re-writable medium proximate to the photoconductor, so as to erase prior orientation of the dichroic spheres of the re-writable medium while printing.

25. The process as set forth in 24, wherein the support and the photoconductor are biased so as to apply approximately equal magnitude but opposite direction fields to the re-writable medium when the photoconductor is respectively charged and discharged.

26. The process as set forth in 15, comprising the step of entering a toner print mode, such that when in the toner print mode, the photoconductor and a support, holding the re-writable medium proximate to the photoconductor, are biased to make charged toner particles deposited on the photoconductor be transferred to the writable medium, in accordance with the writable erasing of the charge deposited on the photoconductor.

27. The process as set forth in 26, comprising the step of fusing toner onto the writable medium after printing in the toner print mode.

28. The process as set forth in 26, comprising the step of detecting presence of the re-writable medium for printing, and if re-writable medium presence is not detected, causing the printer to enter the toner print mode.

29. A re-writable medium, comprising:

a substrate; and

a first recording layer on the substrate, the first recording layer including a first plurality of polarized microencapsulated dichroic spheres.

31. The re-writable medium as set forth in claim 29, wherein the substrate includes a conductive layer, and the re-writable medium comprises:

a second recording layer on an opposing side of the substrate from the first recording layer, the second recording layer including a second plurality of polarized microencapsulated dichroic spheres.

33. The re-writable medium as set forth in claim 29, wherein the substrate is polymer impregnated.

34. The re-writable medium as set forth in claim 29, wherein the substrate includes polymer fibers.

30. The re-writable medium as set forth in 29, comprising a protective layer, the first recording layer being disposed between the protective layer and the substrate.

32. The re-writable medium as set forth in 31, comprising a protective layer, the first recording layer being disposed between the protective layer and the substrate.