Driving method for liquid crystal device

• US 4,738,515 A
• Filed: 08/01/1986
• Issued: 04/19/1988
• Est. Priority Date: 08/05/1985
• Status: Expired due to Term

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Okada, Shinjiro, Inaba, Yutaka, Taniguchi, Osamu
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Mai, Huy V.
• Application Number:
  US06/891,584
• Time in Patent Office: 627 Days
• Field of Search: 350/350 S, 350/332, 350/339 R, 340/784, 340/805, 340/811
• US Class Current: 349/133
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A driving method for a liquid crystal device of the type comprising arranged picture elements each comprising oppositely spaced electrodes, and a ferroelectric liquid crystal layer and a dielectric layer disposed between the electrodes, the ferroelectric liquid crystal layer having a resistance R(Ω) and a capacitance C₁ (F), the dielectric layer having a capacitance C₂ (F); wherein a driving voltage having a pulse duration ΔT(sec) set to satisfy the following formula (1) is applied to the picture elements: ##EQU1## wherein a is a coefficient satisfying the relationship of a<|-Va|/|V_ON |, V_ON is a value of voltage (volt) applied to a picture element at the time of writing, -Va is a value of voltage (volt) of a reverse polarity applied to the picture element after the application of the writing voltage V_ON, b is a coefficient defined by the equation of b=|V₁ |/|V_ON |, and V₁ is the inversion initiation voltage (volts) of the liquid crystal layer.

Claims

1. A driving method for a liquid crystal device of the type comprising arranged picture elements each comprising oppositely spaced electrodes, and a ferroelectric liquid crystal layer and a dielectric layer disposed between the electrodes, said ferroelectric liquid crystal layer having a resistance R(Ω

) and a capacitance C₁ (F), said dielectric layer having a capacitance C₂ (F);

wherein a driving voltage having a pulse duration Δ

T(sec) set to satisfy the following formula (1) is applied to the picture elements;

##EQU7## wherein a is a coefficient satisfying the relationship of a<

|-Va|/|V_ON |, V_ON is a value of voltage (volt) applied to a picture element at the time of writing, -Va is a value of voltage (volt) of a reverse polarity applied to the picture element after the application of the writing voltage V_ON, b is a coefficient defined by the equation of b=|V₁ |/|V_ON |, and V₁ is the inversion initiation voltage (volts) of the liquid crystal layer.

2. A driving method according to claim 1, wherein said ferroelectric liquid crystal is formed in a bistability condition.

3. A driving method according to claim 1, wherein said ferroelectric liquid crystal has a resistance in the range of 10⁸ to 10₁₄ Ω

.

4. A driving method according to claim 1, wherein said dielectric layer has a capacitance of 5.5×

10³ pF/cm₂ or above.

5. A driving method according to claim 1, wherein said dielectric layer has a capacitance in the range of 5.5×

10³ pF/cm² to 3.0×

10⁵ pF/cm².

6. A driving method according to claim 1, wherein said dielectric layer has a capacitance of 9×

10³ pb/cm² to 5.5×

10⁴ pF/cm².

7. A driving method according to claim 1, wherein said picture elements are arranged in a plurality of rows and columns, a driving voltage for providing a first display state based on a first orientation state of the ferroelectric liquid crystal is applied row by row and sequentially to all or a part of the picture elements on a row in a first phase, and a driving voltage for providing a second display state based on a second orientation state of the ferroelectric liquid crystal is applied to selected picture elements on the row in a second phase.

8. A driving method according to claim 7, which includes a third phase for applying an auxiliary signal.

9. A driving method according to claim 1, wherein said picture elements are arranged in a plurality of rows and columns, a driving voltage for providing a first display state based on a first orientation state of the ferroelectric liquid crystal is applied row by row and sequentially to selected picture elements on a row in a first phase, and a driving voltage for providing a second display state based on a second orientation state of the ferroelectric liquid crystal is applied to other selected picture elements on the row in a second phase.

10. A driving method according to claim 9, which includes a third phase for applying an auxiliary signal.

11. A driving method according to claim 1, wherein said ferroelectric liquid crystal is placed under a bistability condition.

12. A driving method according to claim 1, wherein said ferroelectric liquid crystal is a chiral smectic liquid crystal.

13. A driving method according to claim 12, wherein said chiral smectic liquid crystal is in chiral smectic C phase, H phase, I phase, J phase, K phase, G phase or F phase.

14. A driving method according to claim 1, wherein said coefficient a is 1/2 or less.

15. A driving method according to claim 1, wherein said coefficient a is 1/3 or less.

16. A driving method according to claim 1, wherein said coefficient b is in the range of 5/6 to 1.

17. A driving method according to claim 1, wherein said dielectric layer has been subjected to a uniaxial orientation treatment.

18. A driving method according to claim 17, wherein said uniaxial orientation treatment is rubbing.

19. A driving method according to claim 1, wherein said dielectric layer is a laminate of at least two dielectric layers, the upper one of which has been subjected to a uniaxial orientation treatment.

20. A driving method according to claim 19, wherein said uniaxial orientation treatment is rubbing.

21. A driving method according to claim 1, wherein said dielectric layer is a color filter layer.

22. A driving method according to claim 1, wherein said dielectric layer is a laminate of at least two dielectric layers, of which a lower dielectric layer is a color filter layer and the upper layer has been subjected to a uniaxial orientation treatment.

23. A driving method according to claim 22, wherein said uniaxial orientation treatment is rubbing.

24. A driving method according to claim 1, wherein said dielectric layer is a film of an inorganic insulating material or an organic insulating material.