Liquid crystal display device with pixels having stripe-shaped projections with equal heights

• US 5,604,613 A
• Filed: 05/26/1995
• Issued: 02/18/1997
• Est. Priority Date: 07/30/1992
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tsukamoto, Takeo, Kaneko, Tetsuya, Shinjo, Katsuhiko, Kaneko, Shuzo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MILLER, CHARLES LELAND
• Application Number:
  US08/452,019
• Time in Patent Office: 634 Days
• Field of Search: 359/56, 359/54, 359/74, 359/87, 359/100
• US Class Current: 349/147
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 2203/30 Gray scale

Abstract

A liquid crystal display device is constituted by a pair of oppositely disposed substrates each having a plurality of opposing electrodes, and a ferroelectric liquid crystal disposed between the substrates so as to form a plurality of pixels each composed by a combination of a pair of the opposing electrodes and the ferroelectric liquid crystal disposed therebetween. Each pixel is provided with regions of different polarity inversion threshold voltages, and at least one of the pair of opposing electrodes is provided with a plurality of regions having unevennesses at different densities including a region with a higher density of unevennesses corresponding to a region of a lower polarity inversion threshold voltage and a region with a lower density of unevennesses corresponding to a region of a higher polarity inversion threshold voltage.

Claims

1. A liquid crystal device, comprising a plurality of pixels each comprising a pair of opposing electrodes, and a ferroelectric smectic liquid crystal disposed between the opposing electrodes so as to develop bistable states,

the liquid crystal device being equipped with a halftone signal application means for applying a halftone signal between the opposing electrodes,

each pixel being provided with stripe-shaped projections having substantially equal heights and being disposed with a prescribed spacing therebetween, such that each pixel is provided with locally different threshold voltages so as to develop at least one inverted region corresponding to the halftone signal in a stripe pattern substantially parallel to smectic layers of the liquid crystal.

2. A device according to claim 1, wherein the polarity-inverted region is caused to have a varying size and/or density so as to display a varying halftone.

3. A device according to claim 1, wherein said halftone signal comprises plural signals having different waveheights and/or pulse widths.

4. A liquid crystal device, comprising a plurality of pixels, each comprising a pair of opposing electrodes and a smectic liquid crystal disposed between the opposing electrodes,

the liquid crystal device being electrically connected with a halftone signal application means for applying a halftone signal between the opposing electrodes,

at least one of the pair of opposing electrodes having stripe-shaped projections thereon having substantially equal heights, each pixel including plural regions wherein the projections are disposed at different spacings so as to selectively switch liquid crystal molecules in a region depending on the spacing of projections in a region depending on a supplied halftone signal.

5. A device according to claim 4, wherein the stripe-shaped projections are covered with a film.

6. A device according to claim 4 wherein the projections are disposed at a spacing which gradually increases in a prescribed direction.

7. A device according to claim 4, wherein the other one of the opposing electrodes has a substantially flat surface.

8. A device according to claim 4, wherein each pixel is provided with nine regions having mutually different spacings for projections.

9. A device according to claim 4, wherein said one of the opposing electrodes is an elongated transparent electrode and the stripe-shaped projections are disposed thereon in parallel with a direction of the elongation.

10. A liquid crystal device, comprising a plurality of pixels, each comprising a pair of opposing electrodes and a liquid crystal assuming either one of two orientation states depending on a voltage applied thereto disposed between the opposing electrodes,

the liquid crystal device being electrically connected with a halftone signal application means for applying a halftone signal between the opposing electrodes,

at least one of the pair of opposing electrodes having stripe-shaped projections thereon having substantially equal heights, each pixel including plural regions wherein the projections are disposed at different spacings so as to selectively switch liquid crystal molecules in a region depending on the spacing of projections in a region depending on a supplied halftone signal.

11. A device according to claim 10, wherein the stripe-shaped projections are covered with a film.

12. A device according to claim 10, wherein the projections are disposed at a spacing which gradually increases in a prescribed direction.

13. A device according to claim 10, wherein the other one of the pair of opposing electrodes has a substantially flat surface.

14. A device according to claim 10, wherein each pixel is provided with nine regions having mutually different spacings for projections.

15. A device according to claim 10, wherein said one of the opposing electrodes is an elongated transparent electrode and the stripe-shape projections are disposed thereon in parallel with the direction of the elongation.

16. A device according to claim 4 or 10, wherein said stripe-shaped projections comprise a conductor.

17. A device according to claim 4 or 10, wherein said stripe-shaped projections comprise an insulating material.

22. A device according to any one of claims 4, 18 or 10, where each said pixel includes a first region wherein a plurality of said stripe-shaped projections are disposed at a first uniform spacing, and a second region wherein a plurality of said stripe-shaped projections are disposed at a second uniform spacing different from the first uniform spacing.

23. A device according to any one of claims 4, 18 or 10, wherein each said pixel is divided into a plurality of regions such that the stripe-shaped projections are disposed at a uniform spacing in each region and the spacings indifferent different regions are different from each other.

18. A liquid crystal device comprising:

a plurality of pixels each comprising a pair of opposing electrodes and a liquid crystal disposed therebetween assuming either one of two orientation states depending on a voltage applied thereto, each pixel further comprising a plurality of regions wherein strip-shaped projections having substantially equal heights are disposed at mutually different spacings, so that liquid crystal molecules in at least one of said regions are selectively switched in response to a halftone signal applied to one of the pair of opposing electrodes.

19. A device according to claim 18, wherein said liquid crystal is a chiral liquid crystal.

20. A device according to claim 18, wherein said liquid crystal is a chiral smectic liquid crystal.

21. A device according to claim 18, wherein said liquid crystal is a ferroelectric liquid crystal.