Display device

• US 20030141807A1
• Filed: 11/19/2002
• Published: 07/31/2003
• Est. Priority Date: 01/31/2001
• Status: Active Grant

• Current Assignee: 138 East LCD Advancements Limited (Vector Capital Corporation)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kawase, Takeo
• Granted Patent: US 7,068,418 B2
• Time in Patent Office: Days
• US Class Current: 313/498
• CPC Class Codes: G02F 1/13336 Combining plural substrates to produce large-area displays, e.g. tiled displays
• CPC Class Codes: H10K 10/46 Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/125 including organic TFTs [OTFT]
• CPC Class Codes: H10K 59/129 Chiplets
• CPC Class Codes: H10K 59/17 Passive-matrix OLED displays
• CPC Class Codes: H10K 59/18 Tiled displays

Abstract

The invention provides a display device (26) including a plurality of discrete display segments (2). Each display segment (2) is provided with a drive circuit for driving the display elements arranged within the display area. The display device may be provided either as a passive, active or direct pixel addressed array. By interconnecting a number of display segments, a large area display can be achieved without the requirement for long electrodes. This reduces the electrical resistance and parasitic capacitance of the addressing electrodes, enabling the display to provide improved luminance in a displayed image and to operate at higher speeds, providing improved resolution. An active matrix addressing scheme can also be implemented using relatively low mobility organic thin film transistors.

Claims

1. A display device comprising a plurality of display segments arranged on a substrate, each display segment having a display area of pixels defined by an array of display elements, and a drive circuit for driving the display elements and arranged within the display area.

2. A display device as claimed in claim 1, wherein the display elements comprise organic light emitting diodes.

3. A display device as claimed in claim 2, wherein the organic light emitting diodes comprise organic polymer material.

4. A display device as claimed in claim 3, wherein the organic polymer comprises a conjugated polymer.

5. A display device as claimed in claim 4, wherein the conjugated polymer comprises a fluorene group.

6. A display device as claimed in claim 2, wherein the organic light emitting diodes comprise small molecule material.

7. A display device as claimed in any one of the preceding claims wherein the display elements are arranged between a passive array of cathode electrodes and a passive array of anode electrodes, and the drive circuit comprises a first drive circuit for providing signals to the array of anode electrodes and a further drive circuit for providing signals to the array of cathode electrodes.

8. A display device as claimed in claim 7, wherein the first and/or further drive circuits are arranged in wells provided on a first surface of the substrate.

9. A display device as claimed in claim 7, wherein the first and/or further drive circuits are arranged between the anode electrodes and the substrate.

10. A display device as claimed in claim 7, wherein the first and/or further drive circuits are arranged in overlying relationship with the cathode electrodes.

11. A display device as claimed in any one of claims 8 to 10, wherein the drive circuit for providing signals to the electrodes disposed on an opposite side of the array of display elements is provided with conductive tracks arranged to connect to the said electrodes on the opposite side in spaces between the pixels defined by the display elements and the arrays of anode and cathode electrodes.

12. A display device as claimed in any one of claims 8 to 10 when appendant to claim 7 when appendant to claims 2 to 6, wherein the drive circuit for providing signals to the electrodes disposed on an opposite side of the array of active display elements comprises a plurality of pins arranged to connect to the said electrodes on the opposite side through the organic light emitting diode display elements.

13. A display device as claimed in any one of claims 7 to 12, wherein the first and/or further drive circuits comprise unencapsulated integrated circuit devices.

14. A display device as claimed in claim 13, when appendant to claim 10, comprising an encapsulation layer for encapsulating the first and further drive circuits.

15. A display device as claimed in any one of claims 1 to 6 wherein each of said display elements includes a respective drive circuit comprising a, thin film switching transistor and a thin film current driver transistor, thereby to provide active matrix display segments.

16. A display device as claimed in claim 15 wherein the switching transistors and the current driver transistors comprise organic or polymer material transistors.

17. A display device as claimed in claim 16 wherein the organic or polymer material has a band gap such that the transistors are substantially transparent to visible light.

18. A display device as claimed in claim 17 wherein the current driver transistor comprises a source and a drain region each region formed as a plurality of longitudinally extending sections joined at one end by a plurality of transversely extending sections and wherein the longitudinally extending sections of the source region are interdigitated with and spaced from the longitudinally extending sections of the drain region, thereby to provide a spacing between the interdigitated longitudinally extending sections of serpentine shape whereby the thin film transistor is provided with a channel region having a channel length equal to the width of the spacing and a channel width extending the length of the serpentine shape spacing.

19. A display device as claimed in claim 18 wherein the thin film transistor has a channel length in the range of 2-30 microns and a channel width in excess of 1000 microns.

20. A display device as claimed in any one of claims 17 to 19 wherein the switching transistor and the current driver transistor are arranged between the substrate and a light emitting layer.

21. A display device as claimed in any one of claims 15 to 20 wherein each display segment comprises gate lines and data lines for affording control signals to the driver circuits, the gate lines and data lines comprising a conductive organic material.

22. A display device as claimed in claim 21 wherein the gate lines and data lines each comprises a bi-layer structure having a first layer comprising the conductive organic material and a further layer comprising a metal.

23. A display device as claimed in claim 21 or 22 wherein the conductive organic material is substantially transparent to visible radiation.

24. A display device as claimed in any one of claims 1 to 6 wherein each display segment comprises a cathode electrode and an anode electrode one of the electrodes being common to all pixels of the display segment and the other of the electrodes having an electrode pattern so as to provide a respective electrode area for each pixel of the display segment and wherein the driver circuit is coupled to the anode and cathode electrodes and arranged on the opposite side of the display elements to the substrate.

25. A display device as claimed in claim 24 wherein the common electrode comprises the anode electrode arranged between the display elements and the substrate.

26. A display device as claimed in any one of the preceding claims, wherein the substrate comprises a rigid substrate of glass, plastics or silicon.

27. A display device as claimed in any one of claims 1 to 26, wherein the substrate comprises a spoolable plastic material.

48. An electronic apparatus comprising a display device as claimed in any one of claims 1 to 27.

52. A transistor as claimed in any one of claims 48 to 51 comprising source gate and drain electrodes of a conducting organic material.

53. A transistor as claimed in claim 52 wherein the conducting organic material is substantially transparent to visible radiation.

28. A method for fabricating a display device comprising providing a plurality of display segments on a substrate, each having a display area of pixels defined by an array of display elements and arranging a drive circuit for driving the display elements within the display area.

29. A method as claimed in claim 28, comprising the step of fabricating the active display elements from an organic material.

30. A method as claimed in claim 29, comprising the step of fabricating the display elements from an organic polymer material.

31. A method as claimed in claim 30, comprising the step of fabricating the display elements from an organic small molecule material.

32. A method as claimed in claim 29, comprising the step of forming the organic material from a conjugated polymer.

33. A method as claimed in claim 32, wherein the conjugated polymer is selected to comprise a fluorene group.

34. A method as claimed in any one of claims 28 to 33 comprising arranging the display elements between a passive array of cathode electrodes and a passive array of anode electrodes, and providing the drive circuit as a first drive circuit for providing signals to the array of anode electrodes and a further drive circuit for providing signals to the array of cathode electrodes.

35. A method as claimed in claim 34, comprising the step of arranging the first and further drive circuits in wells provided on a first surface of the substrate.

36. A method as claimed in claim 34, comprising the step of arranging the first and further drive circuits between the anode electrodes and the substrate.

37. A method as claimed in claim 35, comprising the steps of arranging the first and further drive circuits in overlying relationship with the cathode electrodes.

38. A method as claimed in any one of claims 28 to 33 wherein each of said display elements is arranged to comprise a respective drive circuit comprising a thin film switching transistor and a thin film current driver transistor, thereby to provide active matrix display segments.

39. A method as claimed in claim 38 wherein the switching transistors and the current driver transistors are selected to comprise organic or polymer material transistors.

40. A method as claimed in claim 39 wherein the organic or polymer material is selected to have a band gap such that the transistors are substantially transparent to visible light.

41. A method as claimed in claim 40 wherein the current driver transistor is provided to have a source region and a drain region each formed as a plurality of longitudinally extending sections joined at one end by a plurality of transversely extending sections, and arranging the longitudinally extending sections of the source region in an interdigitated manner with and spaced from the longitudinally extending regions of the base region, thereby to provide a spacing of serpentine shape between the interdigitated longitudinally extending sections to provide a channel region having a channel length equal to the width of the spacing and a channel width extending the length of the serpentine shape spacing.

42. A method as claimed in any one of claims 38 to 41 comprising providing each display segment with gate lines and data lines for affording control signals to the driver circuits fabricated from a conductive polymer material.

43. A method as claimed in claim 42 wherein the gate lines and data lines are each provided as a bi-layer structure having a first layer comprising the conductive organic polymer material and a further layer comprising a metal.

44. A method as claimed in claim 42 or 43 wherein the conductive organic polymer material is selected to be substantially transparent to visible light.

45. A method as claimed in any one of claims 28 to 33 comprising arranging each display segment to comprise a cathode electrode and an anode electrode and arranging one of the electrodes common to all pixels of the display segment and the other of the pixels as an electrode pattern so as to provide a respective electrode area for each pixel of the display segment, coupling to driver circuit to the anode and cathode electrodes, and arranging the driver circuit on the opposite side of the display elements to the substrate.

46. A method as claimed in claim 45 comprising arranging the common electrode as the anode electrode between the display elements and the substrate.

47. A method as claimed in any one of claims 29 to 31 or 39 to 44 wherein the organic material is deposited using ink jet printing, or micro contact printing, or screen printing or photo patterning.

49. A thin film transistor comprising a substrate, organic or polymer material source and drain regions each formed as a plurality of longitudinally extending sections joined at one end by a plurality of transversely extending sections and wherein the longitudinally extending sections of the source region are interdigitated with and spaced from the longitudinally extending sections of the drain region thereby to provide a serpentine shaped spacing between the source and the drain regions and the thin film transistor with a channel region having a channel length equal to the width of the spacing and a channel width extending the length of the serpentine shape spacing.

50. A transistor as claimed in claim 49 wherein the thin film transistor has a channel length in the range of 2 to 30 microns and a channel width in excess of 1000 microns.

51. A transistor as claimed in claim 49 or 50 wherein the organic or polymer material is substantially transparent to visible radiation.

54. A method of fabricating a transistor as claimed in any one of claims 49 to 53 using ink jet printing, micro contact printing, screen printing or photo patterning.