Liquid display

• US 6,567,060 B1
• Filed: 04/13/2000
• Issued: 05/20/2003
• Est. Priority Date: 10/16/1997
• Status: Expired due to Fees

• Current Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Sekiguchi, Kanetaka
• Primary Examiner(s): Chow, Dennis-Doon
• Application Number:
  US09/529,477
• Time in Patent Office: 1,132 Days
• Field of Search: 345/89, 345/87, 345/102, 349/114, 349/113, 349/106, 349/96, 349/110, 349/61, 359/485
• US Class Current: 345/87
• CPC Class Codes: G02F 1/133509 Filters, e.g. light shielding masks
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G02F 2201/343 cholesteric liquid crystal reflector

Abstract

A printed layer having opening portions is provided at a position opposite to an observer of a liquid crystal display device, a display is performed by use of absorption or chromaticity of the printed layer when an external light source is utilized, and a display is performed by transmitting light through the opening portions of the printed layer when an auxiliary light source is turned on, and further different voltages between when the external light source is utilized and when the auxiliary light source is used are applied to a liquid crystal layer by a gradation reversal circuit. Moreover, reversal of brightness and darkness of a display by the use of the external light source and the auxiliary light source is eliminated by a polarizing film or a cholesteric liquid crystal polymer film disposed on the rear face of the liquid crystal display device, thereby enabling a liquid crystal display device with excellent visibility.

Claims

1. A liquid crystal display device, comprising:

a liquid crystal cell made by disposing a first substrate provided with scanning electrodes and a second substrate provided with data electrodes in such a manner that the scanning electrodes and the data electrodes are oppositely disposed to each other with a predetermined space therebetween, and a liquid crystal layer being filled between the first substrate and the second substrate,

wherein the second substrate of said liquid crystal cell is disposed on the visible side, a polarizing film is disposed on the side of each face of the first substrate and second substrate opposite the face contacting the liquid crystal layer,

wherein the polarizing film disposed on the first substrate side is a reflection-type polarizing film which transmits light linearly polarized in a direction parallel to a transmission axis thereof and reflects light linearly polarized in a direction parallel to a reflection axis thereof orthogonal to the transmission axis, an auxiliary light source is provided on the side of the reflection-type polarizing film opposite the face on the first substrate side, and

wherein means for reversing a magnitude relation of a voltage applied to the liquid crystal layer between the auxiliary light source being turned on and being turned off is provided.

2. The liquid crystal display device according to claim 1, wherein a gradation signal is applied to the liquid crystal layer for displaying half tone and the means for reversing a magnitude relation of a voltage applied to the liquid crystal layer between the auxiliary light source being turned on and being turned off is a circuit for reversing a magnitude relation of a gradation signal applied to the liquid crystal layer.

3. The liquid crystal display device according to claim 2, wherein the gradation signal is set such that the halftone is deviated in a direction where the reflectance is large when the auxiliary light source is turned off, and the halftone is deviated in a direction where the transmittance is small when the auxiliary light source is turned on.

4. The liquid crystal display device according to claim 1, wherein a scattering film having light scattering properties is provided between the first substrate and the reflection-type polarizing film.

5. The liquid crystal display device according to claim 4, wherein the scattering film adheres to the reflection-type polarizing film.

6. The liquid crystal display device according to claim 1, wherein a light absorbing layer for transmitting part of light is provided between the reflection-type polarizing film and the auxiliary light source.

7. The liquid crystal display device according to claim 6, wherein a scattering film having light scattering properties is provided between the reflection-type polarizing film and the light absorbing layer.

8. The liquid crystal display device according to claim 7, wherein the scattering film adheres to the reflection-type polarizing film.

9. The liquid crystal display device according to claim 7, wherein the scattering film is a plastic film in which asperities are formed on the front face thereof or a plastic film in which beads with different refractive indexes are dispersed and is bonded to the rear face of the reflection-type polarizing film with an adhesive.

10. The liquid crystal display device according to claim 7, wherein a gap is provided between the scattering film and the light absorbing layer.

11. The liquid crystal display device according to claim 6, wherein the light absorbing layer is made of a printed layer having opening portions with a large transmittance and absorbing portions with a small transmittance.

12. The liquid crystal display device according to claim 11, wherein the light absorbing layer having the opening portions forms a grid form in which the opening portions and the absorbing portions are arranged regularly and the printed layer forming the absorbing portions is made of a thick film for absorbing external light by the thickness thereof when an incident angle of the external light becomes large.

13. The liquid crystal display device according to claim 6, wherein the light absorbing layer has a plurality of opening portions or portions having a transmission characteristic at a pixel portion.

16. The liquid crystal display device according to claim 5, wherein the gradation signal is set such that the halftone is deviated in a direction where the reflectance is large when the auxiliary light source is turned off and the halftone is deviated in a direction where the transmittance is small when the auxiliary light source is turned on.

14. A liquid crystal display device, comprising:

a liquid crystal cell made by disposing a first substrate provided with scanning electrodes and a second substrate provided with data electrodes in such a manner that the scanning electrodes and the data electrodes are oppositely disposed to each other with a predetermined gap therebetween, and a liquid crystal layer being filled between the first substrate and the second substrate,

wherein the second substrate of said liquid crystal cell is disposed on the visible side,

wherein an absorption-type polarizing film is disposed on the side of a face of the second substrate opposite the face contacting the liquid crystal layer, and a cholesteric liquid crystal polymer film is disposed on the side of a face of the first substrate opposite to the face contacting the liquid crystal layer respectively,

wherein an auxiliary light source is disposed on the side of a face of the cholesteric liquid crystal polymer film opposite the face on the first substrate side, and

wherein means for reversing a magnitude relation of a voltage applied to the liquid crystal layer between the auxiliary light source being turned on and being turned off is provided.

15. The liquid crystal display device according to claim 14, wherein a gradation signal is applied to the liquid crystal layer for displaying halftone, and the means for reversing a magnitude relation of a voltage applied to the liquid crystal layer between the auxiliary light source being turned on and being turned off is a circuit for reversing a magnitude relation of a gradation signal applied to the liquid crystal layer.

17. The liquid crystal display device according to claim 14, wherein a retardation film is disposed between the second substrate and the absorption-type polarizing film, and a quarter-wavelength film is disposed between the first substrate and the cholesteric liquid crystal polymer film respectively.

18. The liquid crystal display device according to claim 14, wherein a light absorbing layer for transmitting part of light is provided between the cholesteric liquid crystal polymer film and the auxiliary light source.

19. The liquid crystal display device according to claim 18, wherein the light absorbing layer is a printed layer having transparency so that the light absorbing layer as a whole transmits part of light.

20. A liquid crystal display device, comprising:

a liquid crystal cell made by disposing a first substrate provided with scanning electrodes and a second substrate provided with data electrodes in such a manner that the scanning electrodes and the data electrodes are opposed to each other with a predetermined gap therebetween, a liquid crystal layer being filled between the first substrate and the second substrate, and a first color filter being provided on the first substrate,

wherein the second substrate of said liquid crystal cell is disposed on the visible side,

wherein an absorption-type polarizing film is disposed on the side of a face of the second substrate opposite the face contacting the liquid crystal layer, and a reflection-type polarizing film is disposed on the side of a face of the first substrate opposite to the face contacting the liquid crystal layer respectively,

wherein an auxiliary light source is disposed on the side of a face of the reflection-type polarizing film opposite to the face on the first substrate side with a second color filter therebetween, and

wherein means for reversing magnitude relation of a voltage applied to the liquid crystal layer between the auxiliary light source being turned on and being turned off is provided.

21. The liquid crystal display device according to claim 20, wherein a scattering film having light scattering properties is provided between the first substrate and the second color filter.

22. The liquid crystal display device according to claim 21, wherein the scattering film is a plastic film in which asperities are formed on the front face thereof or a plastic film in which beads with different refractive indexes are dispersed.

23. The liquid crystal display device according to claim 21, wherein each of the first color filter and the second color filter is made of red, green, and blue color filters.

24. The liquid crystal display device according to claim 23, wherein the first color filter and the second color filter are provided on one face side of the first substrate and on the other face side respectively and disposed in such a manner that the color filters of the same color overlap one another with the first substrate therebetween in almost the same areas.

25. The liquid crystal display device according to claim 20, wherein means for controlling a voltage applied to the liquid crystal layer is provided to vary brightness of a display of a halftone in accordance with brightness of an external environment.