Liquid crystal display device with stripe-shaped unevennesses on the electrodes

• US 5,495,352 A
• Filed: 07/29/1993
• Issued: 02/27/1996
• 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): Gross, Anita Pellman
• Assistant Examiner(s): MILLER, CHARLES LELAND
• Application Number:
  US08/099,054
• Time in Patent Office: 943 Days
• Field of Search: 359/56, 359/54, 359/74, 359/87, 359/100
• US Class Current: 349/143
• 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,

wherein at least one of the opposing electrodes is provided with stripe-shaped unevennesses extending in a direction such that said direction forms acute angles with two molecular orientation directions in the bistable states of the liquid crystal, the smallest one of the acute angles in terms of absolute value not exceeding a cone angle of the ferroelectric liquid crystal in chiral smectic phase.

2. A device according to claim 1, wherein said ferroelectric liquid crystal is disposed to form smectic layers providing a layer normal direction which forms an acute angle with said direction of the stripe-shaped unevennesses not exceeding the cone angle.

3. A device according to claim 1, wherein a rubbing direction associated with the opposing electrode provided with the stripe-shaped unevennesses and said direction of the stripe-shaped unevennesses form an acute angle therebetween giving an absolute value which is at most the cone angle, and said rubbing direction and a rubbing direction associated with the other opposing electrode form an acute angle therebetween giving an absolute value which is at most two times the cone angle.

4. A device according to claim 1, wherein a side of the opposing electrode opposite to the opposing electrode provided with the stripe-shaped unevennesses is subjected to rubbing.

5. A device according to claim 1, wherein both sides of said pair of opposing electrodes are subjected to rubbing in directions which are substantially parallel or anti-parallel.

6. A device according to claim 1, wherein each pixel comprises plural regions respectively having stripe-shaped unevennesses disposed at different pitches.

7. A device according to claim 1, wherein the ferroelectric liquid crystal is reset to one of the two molecular orientation directions in the bistable states which is closer to the direction of the stripe-shaped unevennesses, and the stripe-shaped unevennesses are disposed in plural regions including a region of a relatively small disposition density of the stripe-shaped unevennesses which provides a relatively large inversion threshold voltage.

8. A device according to claim 1, wherein the ferroelectric liquid crystal is reset to one of the two molecular orientation directions in the bistable states which is remoter from the direction of the stripe-shaped unevennesses, and the stripe-shaped unevennesses are disposed in plural regions including a region of a relatively small disposition density of the stripe-shaped unevennesses which provides a relatively small inversion threshold voltage.

9. A liquid crystal device, comprising a plurality of pixels each 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 stripe-shaped unevennesses extending in a direction such that said direction forms acute angles with two molecular orientation directions of the chiral smectic liquid crystal, the smallest one of the acute angles in terms of absolute value not exceeding a cone angle of the chiral smectic liquid crystal, and a normal to a chiral smectic layer of the liquid crystal intersects with said direction of extension of the stripe-shaped unevennesses.

10. A device according to claim 9, wherein said chiral smectic liquid crystal is disposed to form smectic layers providing a layer normal direction which forms an acute angle with said direction of extension of the stripe-shaped unevennesses not exceeding the cone angle.

11. A device according to claim 9, wherein a rubbing direction associated with the opposing electrode provided with the stripe-shaped unevennesses form an acute angle therebetween giving an absolute value which is at most the cone angle, and said rubbing direction and a rubbing direction associated with the other opposing electrode form an acute angle therebetween giving an absolute value which is at most two times the cone angle.

12. A device according no claim 9, wherein a side of the opposing electrode opposite to the opposing electrode provided with the stripe-shaped unevennesses is subjected to rubbing.

13. A device according to claim 9, wherein both sides of said pair of opposing electrodes are subjected to rubbing in directions which are substantially parallel or anti-parallel.

14. A device according to claim 9, wherein each pixel comprises plural regions respectively having stripe-shaped unevennesses disposed at different pitches.