Liquid crystal display device having protrusions on the electrodes

• US 5,644,372 A
• Filed: 05/22/1995
• Issued: 07/01/1997
• 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:
  US08/446,991
• Time in Patent Office: 771 Days
• Field of Search: 359/54, 359/56, 359/74, 359/87, 359/100
• US Class Current: 349/139
• 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 display device, comprising:

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;

wherein each pixel is provided with regions of different polarity inversion threshold voltages, and at least one of said pair of opposing electrodes is provided with a plurality of regions having island-shaped 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.

2. A device according to claim 1, wherein the unevennesses comprise a part of the opposing electrode.

3. A device according to claim 1, wherein the unevennesses comprise a conductor formed on the opposing electrode.

4. A device according to claim 1, wherein the unevennesses comprise an insulating member formed on the opposing electrode.

5. A liquid crystal display device, comprising a pair of opposing electrodes and a ferroelectric liquid crystal disposed between the opposing electrodes;

wherein at least one of the opposing electrodes is provided with a means for causing a lowering in polarity inversion threshold voltage of the ferroelectric liquid crystal in the form of a line, and at least one of the opposing electrodes is provided with island-shaped unevenesses disposed in a line as a means for causing a change in shape of a polarity-inverted region in direction of the line of lowered polarity inversion threshold voltage.

6. A liquid crystal display device, comprising:

a pair of oppositely disposed substrates each having a plurality of opposing electrodes, and a chiral smectic 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 chiral smectic liquid crystal disposed therebetween;

wherein each pixel is provided with regions of different polarity inversion threshold voltages, and at least one of said 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, and the unevennesses comprise projections having substantially equal heights.

7. A device according to claim 6, wherein the unevennesses are island-shaped.

8. A device according to claim 6, wherein the unevennesses are stripe-shaped.

9. A device according to claim 7 or 8, wherein the unevennesses comprise a part of the opposing electrode.

10. A device according to claim 7 or 8, wherein the unevennesses comprise a conductor formed on the opposing electrode.

11. A device according to claim 7 or 8, wherein the unevennesses comprise an insulating member formed on the opposing electrode.

12. A liquid crystal display device, comprising a pair of opposing electrodes and a chiral smectic liquid crystal disposed between the opposing electrodes, wherein at least one of the opposing electrodes is provided with a means for causing a lowering in polarity inversion threshold voltage of the chiral smectic liquid crystal in the form of a line, and at least one of the opposing electrodes is provided with a means for causing a change in shape of a polarity-inverted region in direction of the line of lowered polarity inversion threshold voltage, wherein said means for causing a lowering in polarity inversion threshold voltage comprises a plurality of projections having substantially equal heights.

13. A device according to claim 12, wherein said means for causing a lowering in polarity inversion threshold voltage comprises stripe-shaped unevennesses disposed in parallel.

14. A device according to claim 12, wherein said means for causing a change in shape of a polarity-inverted region comprises island-shaped or stripe-shaped unevennesses disposed in alignment with the line of polarity inversion threshold voltage.

15. A device according to claim 12, wherein said means for causing a change in shape of a polarity-inverted region comprises a means for causing an electric field applied to the chiral smectic liquid crystal to gradually increase or decrease in a direction along the line of lowered polarity inversion threshold voltage.

16. A device according to claim 15, wherein said means for causing an electric field applied to the chiral smectic liquid crystal to gradually increase or decrease in a direction along the line of lowered polarity inversion threshold voltage comprises island-shaped or stripe-shaped unevennesses arranged at a varying density which increases or decreases in a direction of the line of lowered polarity inversion threshold voltage.

17. A device according to claim 15, wherein said means for causing an electric field applied to the chiral smectic liquid crystal to gradually increase or decrease in a direction along the line of lowered polarity inversion threshold voltage comprises a gradient formed in a direction along the line of lowered polarity inversion threshold voltage.

18. A device according to claim 15, wherein said means for causing an electric field applied to the chiral smectic liquid crystal to gradually increase or decrease in a direction along the line of lowered polarity inversion threshold voltage comprises a means for applying a bias voltage across one of the opposing electrode in a direction along the line of lowered polarity inversion threshold voltage.