Liquid crystal display

• US 20060072047A1
• Filed: 09/23/2003
• Published: 04/06/2006
• Est. Priority Date: 12/06/2002
• Status: Abandoned Application

• Current Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Inventors: Sekiguchi, Kanetaka
• Application Number:
  US10/537,780
• Publication Number:
  US 20060072047A1
• Time in Patent Office: Days
• US Class Current: 349/25
• CPC Class Codes: G02F 1/133342 for double-sided displays
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors
• CPC Class Codes: G09G 2300/046 with an emissive area and a light-modulating area combined in one pixel
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An EL element (33) is provided on a first substrate (1) to make it possible to perform both light emission display according to the EL element (33) and reflective display according to a liquid crystal display element. An EL control switching element (17) and a liquid crystal layer switching element (18) are provided on a face of the first substrate (1) positioned on the side of a liquid crystal layer (51). The EL control switching element (17) is connected to an anode electrode (21) or a cathode electrode (24) constituting the EL element (33). By connecting the liquid crystal layer switching element (18) to a display electrode (31) and a reflective electrode (28) constituting a liquid crystal display element, a liquid crystal display element and a light emitting element are integrated in a liquid crystal display device incorporated with the liquid crystal display element therein, so that thinning and weight reduction are achieved considering electrical connection therebetween and both reflective display and transmissive display are made possible.

Claims

1. A liquid crystal display device where a first substrate having a display electrode and a second substrate having an opposite electrode are disposed so as to be opposed to each other via a predetermined clearance, and a liquid crystal display element having a liquid crystal layer is provided in the clearance, wherein

an electroluminescent element is provided between the first substrate and the second substrate,

the liquid crystal display element includes a first reflection film that reflects light from an external light source, and

the electroluminescent element includes a second reflection film different form the first reflection film.

2. The liquid crystal display device according to claim 1, wherein an EL control switching element for controlling the electroluminescent element is formed on a liquid crystal layer side of the first substrate, and the electroluminescent element is formed on a liquid crystal side of the EL control switching element via an insulating film.

3. The liquid crystal display device according to claim 1, wherein the electroluminescent element is formed on a liquid crystal layer side of the first substrate, and an EL control switching element for controlling the electroluminescent element is formed on a liquid crystal layer side of the electroluminescent element via an insulating film.

4. The liquid crystal display device according to claim 3, wherein the electroluminescent element allows light to transmit the first substrate to go out to a side of the first substrate.

5. The liquid crystal display device according to claim 2, wherein an EL connecting opening is formed in the insulating film, and the electroluminescent element and the EL control switching element are electrically connected to each other via the EL connecting opening.

6. The liquid crystal display device according to claim 1, wherein the electroluminescent element comprises plural kinds of electroluminescent elements that emit different color lights, respectively.

7. The liquid crystal display device according to claim 6, wherein a protective film that prevents moisture from permeating the electroluminescent element is provided on the electroluminescent element.

8. The liquid crystal display device according to claim 7, wherein an insulating planarizing film for planarizing a step is formed on the electroluminescent element or the EL control switching element, and a display electrode for the liquid crystal display element is formed on the planarizing film.

9. The liquid crystal display device according to claim 8, wherein the planarizing film is provided with a diffusing member that diffuses light.

10. The liquid crystal display device according to claim 8, wherein the display electrode is a reflective electrode and has an opening in its region overlapping with the electroluminescent element.

11. The liquid crystal display device according to claim 10, wherein a surface of the reflective electrode is formed in an undulated shape.

12. The liquid crystal display device according to claim 11, wherein a surface of the planarizing film is formed in an undulated shape.

13. The liquid crystal display device according to claim 1, further comprising a liquid crystal layer switching element for supplying a signal for display to the liquid crystal layer between the first substrate and the second substrate to be connected to the display electrode.

14. The liquid crystal display device according to claim 13, wherein a display electrode is formed on a liquid crystal layer side of the liquid crystal layer switching element, and the display electrode and the switching element for liquid crystal display layer control are electrically connected to each other via an LC connecting opening formed in the insulating film.

15. The liquid crystal display device according to claim 13, wherein

the display electrode is formed on a region that approximately covers a set of two switching elements comprising the liquid crystal layer switching element and the EL control switching element.

16. The liquid crystal display device according to claim 1, wherein

the switching element comprises a thin film transistor having a source electrode, a drain electrode, and a gate electrode.

17. The liquid crystal display device according to claim 16, wherein

the gate electrodes of the EL control switching element and the switching element for liquid crystal display element included in the same display pixel region are connected to each other and the source electrodes thereof are independent from each other.

18. The liquid crystal display device according to claim 16, wherein gate electrodes of the EL control switching elements included in two display pixel regions adjacent to each other, respectively, are connected to each other, gate electrodes of the liquid crystal layer switching elements included in two display pixel regions adjacent to each other, respectively, are connected to each other, and a source electrode of the EL control switching element is connected to a source electrode of the liquid crystal layer switching element included in an adjacent display pixel region.

19. The liquid crystal display device according to claim 16, wherein

gate electrodes of the EL control switching elements included in two display pixel regions adjacent to each other, respectively, are connected to each other, gate electrodes of the liquid crystal layer switching elements included in two display pixel regions adjacent to each other, respectively, are independent from the gate electrodes of the EL control switching elements and are connected to each other, and source electrodes of the EL control switching element and the liquid crystal layer switching element are independent from each other.

20. The liquid crystal display device according to claim 16, wherein the switching element is a thin film transistor having a semiconductor layer made of a poly-silicon thin film.

21. The liquid crystal display device according to claim 20, wherein the EL control switching element is a thin film transistor having a semiconductor layer made of a poly-silicon thin film, and the liquid crystal layer switching element is a thin film transistor having a semiconductor layer made of an amorphous silicon film.

22. The liquid crystal display device according to claim 1, comprising a color filter disposed between the first substrate and the second substrate.

23. The liquid crystal display device according to claim 1, wherein the liquid crystal layer is a mixture of liquid crystal and transparent solid material, and is a scattering type liquid crystal layer that controls scattering and transmission according to magnitude of a voltage applied to the liquid crystal layer.

24. The liquid crystal display device according to claim 1, comprising an organic insulating film mixed with a member that absorbs moisture and disposed between the first substrate and the display electrode.

25. The liquid crystal display device according to claim 1, comprising at least a polarizing film on a side of the second substrate side opposite to the side on which the liquid crystal layer is provided.

26. The liquid crystal display device according to claim 1, comprising at least one optical compensator and a polarizing film disposed on a side of the second substrate opposed from the liquid crystal layer in this order from the second substrate side.

27. The liquid crystal display device according to claim 25, comprising a light diffusing layer positioned between the electroluminescent element and the polarizing film.

28. The liquid crystal display device according to claim 1, comprising a light diffusing layer positioned between the electroluminescent element and the second substrate.

29. The liquid crystal display device according to claim 26, wherein arrangement of an orientation direction of the liquid crystal layer, and the polarizing film and the optical compensator provided on a side of the second substrate opposed from the liquid crystal layer meets arrangement where a transmissivity of the liquid crystal layer becomes approximately maximum during non-application of a voltage to the liquid crystal layer.

30. The liquid crystal display device according to claim 29, wherein a voltage where the transmissivity of the liquid crystal layer becomes approximately maximum is applied to the liquid crystal layer via the liquid crystal layer switching element during light emission from the electroluminescent element.

31. The liquid crystal display device according to claim 1, wherein a display face of the liquid crystal display element is positioned on the side of the second substrate, and a light emitting face of the electroluminescent element is positioned on the side of the first substrate.

32. The liquid crystal display device according to claim 1, wherein the first reflection film is a reflection film or a reflecting electrode for performing reflective display according to the liquid crystal display element.

33. The liquid crystal display device according to claim 1, wherein the second reflection film is a reflecting electrode constituting the electroluminescent element.

34. The liquid crystal display device according to claim 1, wherein at least one of a plurality of electrodes constituting the electroluminescent element is a transparent electric conductive film.

35. The liquid crystal display device according to claim 1, wherein an EL control switching element for controlling the electroluminescent element is formed between the first substrate and the second substrate.

36. The liquid crystal display device according to claim 1, further comprising a liquid crystal layer switching element for supplying a signal for display to the liquid crystal layer between the first substrate and the second substrate, being connected to the display electrode.

37. The liquid crystal display device according to claim 35, wherein the electroluminescent element is formed on a liquid crystal layer side of the first substrate, the EL control switching element or the liquid crystal switching element is formed on a liquid crystal layer side of the electroluminescent element via an insulating film, and the liquid crystal display element is formed on a liquid crystal layer side of the EL control switching element or the liquid crystal switching element via an insulating film.

38. The liquid crystal display device according to claim 8, wherein the display electrode is a reflective electrode, and the reflection film included in the liquid crystal display element has an opening in a region overlapped with the electroluminescent element.

39. The liquid crystal display device according to claim 1, wherein a substrate that emits reflective light for reflective display according to the liquid crystal display element is different from a substrate that emits emission light according to the electroluminescent element, from among the first substrate and the second substrate.