Liquid crystal display device having switchable reflective layer

• US 6,842,209 B2
• Filed: 07/09/2001
• Issued: 01/11/2005
• Est. Priority Date: 07/11/2000
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Sumiyoshi, Ken, Hayama, Hiroshi
• Primary Examiner(s): Chowdhury, Tarifur R.
• Assistant Examiner(s): SCHECHTER, ANDREW M
• Application Number:
  US10/332,472
• Publication Number:
  US 20040021809A1
• Time in Patent Office: 1,282 Days
• Field of Search: 349/114, 349/115
• US Class Current: 349/115
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters

Abstract

A liquid crystal display device comprising a first polarizing sheet (16a), a color filter layer (6) formed on glass sheet (18), a second polarizing sheet (16b), three-layered HPDLC (17) formed below the liquid crystal layer (1) and acting as a reflective structural layer having a reflectivity changed electrically, and a backlight unit as the lowermost layer. Each layer of the three-layered HPDLC (17) is composed of a liquid crystal droplet layer polymer layer and reflects blue, green, red by Bragg reflection. When voltage is applied to the three-layered HPDLC (17), the reflectivity of liquid crystal droplet layer of each layer change, so that the HPDLC can be made transparent by equalizing the reflectivities of the liquid crystal liquid droplet layer to those of polymer layers.

Claims

1. A liquid crystal display device comprising:

a liquid crystal layer;

a reflective structural layer that is arranged below said liquid crystal layer and that includes a plurality of reflectors for reflecting only light of specific frequency bands by means of Bragg reflection, wherein reflectance of each of said reflectors can be electrically switched;

a backlight unit that is arranged at the lowermost layer for irradiating light from the backside of the liquid crystal layer;

a first color filter layer that is arranged above said liquid crystal layer; and

a second color filter layer that is arranged below said reflective structural layer.

2. A liquid crystal display device according to claim 1, wherein said liquid crystal layer is on a substrate that is a thin-film glass.

3. A liquid crystal display device according to claim 1, wherein said liquid crystal layer is on a substrate that is a film substrate.

4. A liquid crystal display device according to claim 1, wherein each of said reflectors is formed by stacking in the direction of stacking of said liquid crystal layer and said backlight unit with respect to said reflective structural layer.

5. A liquid crystal display device according to claim 1, wherein each of said reflectors contains liquid crystal.

6. A liquid crystal display device according to claim 5, wherein each of said reflectors contains cholesteric liquid crystal.

7. A liquid crystal display device according to claim 5, wherein each of said reflectors is a construction in which one or more liquid crystal drop layers that contain drops of liquid crystal are alternately stacked with one or more polymer layers.

8. A liquid crystal display device according to claim 5, wherein each of said reflectors is composed of a polymer layer containing drops of cholesteric liquid crystal.

9. A liquid crystal display device according to claim 1, further comprising a first polarizer that is arranged above said liquid crystal layer.

10. A liquid crystal display device according to claim 9, further comprising a second polarizer that is arranged below said liquid crystal layer.

11. A liquid crystal display device according to claim 10, further comprising a compensator for compensating phase difference that is arranged below said first polarizer and above said second polarizer.

12. A liquid crystal display device according to claim 11, wherein said compensator is arranged above said reflective structural layer.

13. A liquid crystal display device according to claim 1, wherein said liquid crystal layer is driven by an active matrix.

14. A liquid crystal display device comprising

a liquid crystal layer;

a reflective structural layer that is arranged below said liquid crystal layer and that includes a plurality of reflectors for reflecting only light of specific frequency bands by means of Bragg reflection, wherein reflectance of each of said reflectors can be electrically switched; and

a backlight unit that is arranged at the lowermost layer for irradiating light from the backside of the liquid crystal layer,

wherein each of said reflectors is arranged parallel to a direction that is substantially orthogonal to the direction of stacking of said liquid crystal layer and said backlight unit with respect to said reflective structural layer.

15. A liquid crystal display device according to claim 14, further comprising a first color filter layer that is arranged above said liquid crystal layer.

16. A liquid crystal display device according to claim 14, wherein each of said reflectors contains liquid crystal.

17. A liquid crystal display device according to claim 14, further comprising a first polarizer that is arranged above said liquid crystal layer.