Display device and driving method thereof

• US 20030201960A1
• Filed: 04/29/2003
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Abandoned Application

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Fujieda, Ichiro
• Application Number:
  US10/424,925
• Publication Number:
  US 20030201960A1
• Time in Patent Office: Days
• US Class Current: 345/87
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 2201/44 Arrangements combining different electro-active layers, e.g. electrochromic, liquid crystal or electroluminescent layers
• CPC Class Codes: G02F 2203/09 transflective
• CPC Class Codes: G09G 2300/046 with an emissive area and a light-modulating area combined in one pixel
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

The invention provides a thin type display device provided with a simplified constitution and driving circuit, which offers an excellent visibility both in a light place and in a dark place.

Liquid crystal 70 is placed between a substrate 10 on which a plurality of light emitting devices 20 including a reflecting electrode 21 is disposed and a transparent substrate 60 provided with a transparent electrode 63 and a color filter 61. A driving circuit switches to either a reflection display mode of displaying an image by reflection of ambient light from the reflecting electrode 21 of the light emitting device 20, or a self-emission display mode of displaying an image by self light emission from the light emitting device 20.

Claims

1. A display device comprising a first substrate on which a plurality of light emitting devices including a reflecting electrode is disposed;

a second substrate made of a transparent material provided with a color filter and a transparent electrode;

a liquid crystal layer placed between said first substrate and said second substrate disposed in such a manner that a face of said light emitting devices and a face of said transparent electrode confront each other; and

a driving circuit for controlling a voltage to be applied to said liquid crystal layer, and selecting either a reflection display mode of displaying an image by reflecting ambient light with said reflecting electrode of said light emitting device or a self-emission display mode of displaying an image by light emission of said light emitting device.

3. The display device as set forth in claim 1, wherein said light emitting device further comprise a light emitting material formed on said reflecting electrode and a transparent electrode formed on said light emitting material.

5. The display device as set forth in claim 3, wherein said driving circuit further controls optical characteristic of said liquid crystal through control of a voltage applied between said transparent electrode of said light emitting device and said transparent electrode of said second substrate, and controls light emission by said light emitting device through control of a voltage applied between said transparent electrode of said light emitting device and said reflecting electrode.

7. The display device as set forth in claim 5, wherein each of said light emitting devices and said color filter corresponding to each light emitting device constitute a pixel, and said driving circuit comprises a switching transistor for selecting each of such pixels, light emission amount control circuit for controlling a current amount of said light emitting device and a switching control circuit for switching to either said reflection display mode or said self-emission display mode.

9. The display device as set forth in claim 7, wherein said switching control circuit electrically connects said reflecting electrode of said light emitting device with said transparent electrode of light emitting device as well as said switching transistor with said reflecting electrode of said light emitting device, in said reflection display mode.

11. The display device as set forth in claim 7, wherein said switching control circuit connects said light emitting device with said light emission amount control circuit as well as said switching transistor with said light emission amount control circuit, in said self-emission display mode.

13. The display device as set forth in claim 9, wherein said switching control circuit connects said light emitting device with said light emission amount control circuit as well as said switching transistor with said light emission amount control circuit, in said self-emission display mode.

15. The display device as set forth in claim 1, further comprising a circular polarizing plate on a surface of said second substrate on a face not confronting said liquid crystal layer, so that said driving circuit adjusts a reflection factor of ambient light by switching a polarization status of light passing through said liquid crystal layer, in said reflection display mode.

17. The display device as set forth in claim 1, further comprising a circular polarizing plate on a surface of said second substrate on a face not confronting said liquid crystal layer, so that said driving circuit maintains a constant polarization status of light passing through said liquid crystal layer, in said self-emission display mode.

19. The display device as set forth in claim 1, wherein said first substrate further comprises a protection layer covering said light emitting device and a first alignment layer formed on said protection layer, and said second substrate further comprises a second alignment layer formed on said transparent electrode.

21. The display device as set forth in claim 19, wherein said protection layer comprises a projection or a strut that reaches said second substrate, between said first substrate and said second substrate and in a region where said light emitting devices are not located.

2. A display device comprising a first substrate on which a plurality of light emitting devices including a reflecting electrode is disposed and a color filter is provided over them;

a second substrate made of a transparent material provided with a transparent electrode;

a liquid crystal layer provided between said first substrate and said second substrate disposed in such a manner that a face of said color filter and a face of said transparent electrode confront each other; and

a driving circuit for controlling a voltage to be applied to said liquid crystal layer, and selecting either a reflection display mode of displaying an image by reflecting ambient light with said reflecting electrode of said light emitting device or a self-emission display mode of displaying an image by light emission of said light emitting device.

4. The display device as set forth in claim 2, wherein said light emitting device further comprise a light emitting material formed on said reflecting electrode and a transparent electrode formed on said light emitting material.

6. The display device as set forth in claim 4, wherein said driving circuit further controls optical characteristic of said liquid crystal through control of a voltage applied between said transparent electrode of said light emitting device and said transparent electrode of said second substrate, and controls light emission by said light emitting device through control of a voltage applied between said transparent electrode of said light emitting device and said reflecting electrode.

8. The display device as set forth in claim 6, wherein each of said light emitting devices and said color filter corresponding to each light emitting device constitute a pixel, and said driving circuit comprises a switching transistor for selecting each of such pixels, light emission amount control circuit for controlling a current amount of said light emitting device and a switching control circuit for switching to either said reflection display mode or said self-emission display mode.

10. The display device as set forth in claim 8, wherein said switching control circuit electrically connects said reflecting electrode of said light emitting device with said transparent electrode of light emitting device as well as said switching transistor with said reflecting electrode of said light emitting device, in said reflection display mode.

12. The display device as set forth in claim 8, wherein said switching control circuit connects said light emitting device with said light emission amount control circuit as well as said switching transistor with said light emission amount control circuit, in said self-emission display mode.

14. The display device as set forth in claim 10, wherein said switching control circuit connects said light emitting device with said light emission amount control circuit as well as said switching transistor with said light emission amount control circuit, in said self-emission display mode.

16. The display device as set forth in claim 2, further comprising a circular polarizing plate on a surface of said second substrate on a face not confronting said liquid crystal layer, so that said driving circuit adjusts a reflection factor of ambient light by switching a polarization status of light passing through said liquid crystal layer, in said reflection display mode.

18. The display device as set forth in claim 2, further comprising a circular polarizing plate on a surface of said second substrate on a face not confronting said liquid crystal layer, so that said driving circuit maintains a constant polarization status of light passing through said liquid crystal layer, in said self-emission display mode.

20. The display device as set forth in claim 2, wherein said first substrate further comprises a protection layer formed between said color filter and said light emitting device so as to cover said light emitting device and a first alignment layer formed on said color filter, and said second substrate further comprises a second alignment layer formed on said transparent electrode.

22. Driving method of a display device comprising a first substrate on which a plurality of light emitting devices including a reflecting electrode is disposed;

a second substrate made of a transparent material provided with a color filter and a transparent electrode;

a liquid crystal layer provided between said first substrate and said second substrate disposed in such a manner that a face of said light emitting devices and a face of said transparent electrode confront each other;

comprising the steps of controlling a voltage to be applied to said liquid crystal layer, and selecting either a reflection display mode of displaying an image by reflecting ambient light with said reflecting electrode of said light emitting device or a self-emission display mode of displaying an image by light emission of said light emitting device.

24. Driving method of a display device as set forth in claim 22, wherein said reflecting electrode and said transparent electrode of said light emitting device formed with said light emitting material disposed therebetween are electrically connected in said reflection display mode.

26. Driving method of a display device as set forth in claim 22, wherein a light emission amount control circuit for controlling a light emission amount of said light emitting device is connected with said light emitting device, in said self-emission display mode.

23. Driving method of a display device comprising a first substrate on which a plurality of light emitting devices including a reflecting electrode is disposed and a color filter is provided over them;

a second substrate made of a transparent material provided with a transparent electrode;

a liquid crystal layer provided between said first substrate and said second substrate disposed in such a manner that a face of said color filter and a face of said transparent electrode confront each other;

comprising the steps of controlling a voltage to be applied to said liquid crystal layer, and selecting either a reflection display mode of displaying an image by reflecting ambient light with said reflecting electrode of said light emitting device or a self-emission display mode of displaying an image by light emission of said light emitting device.

25. Driving method of a display device as set forth in claim 23, wherein said reflecting electrode and said transparent electrode of said light emitting device formed with said light emitting material disposed therebetween are electrically connected in said reflection display mode.

27. Driving method of a display device as set forth in claim 23, wherein a light emission amount control circuit for controlling a light emission amount of said light emitting device is connected with said light emitting device, in said self-emission display mode.