Liquid crystal device with the retardation of the liquid crystal layer greater than .lambda./2 and a method for driving the same

• US 5,640,259 A
• Filed: 12/19/1994
• Issued: 06/17/1997
• Est. Priority Date: 12/20/1993
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ishii, Yutaka, Yamamoto, Yoshitaka, Sawayama, Yutaka, Kimura, Naofumi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MILLER, CHARLES LELAND
• Application Number:
  US08/358,953
• Time in Patent Office: 911 Days
• Field of Search: 359/55, 359/93
• US Class Current: 349/33
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2203/62 Switchable arrangements whereby the element being usually not switchable
• CPC Class Codes: G02F 2413/01 Number of plates being 1
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

A liquid crystal device includes a pair of substrates, a liquid crystal layer interposed between the pair of substrates, at least one polarizing element, and a plurality of pixels. A retardation (d×Δn) of the liquid crystal layer satisfies the relation:

d×Δn>λ/2

when incident light is output after passing through the liquid crystal layer once. The retardation satisfies the relation:

2d×Δn>λ/2

when the incident light is output after passing through the liquid crystal layer twice. In these relations, d a thickness of the liquid crystal layer, Δn is a birefringence, and λ is a wavelength of the light incident on the liquid crystal layer. A driving voltage supplier applies a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels. Such application of the driving voltage allows utilization of a relaxation process of liquid crystal molecules in the liquid crystal layer to obtain a predetermined light output density.

Claims

1. A liquid crystal device comprising:

a pair of substrates;

a liquid crystal layer interposed between the pair of substrates;

at least one polarizing element;

a plurality of pixels;

a retardation (d×

Δ

n) of the liquid crystal layer satisfying one of a relation;

space="preserve" listing-type="equation">d×

Δ

n>

λ

/2

in a case where an incident light is output after passing through the liquid crystal layer once, and a relation;

space="preserve" listing-type="equation">2d×

Δ

n>

λ

/2

in a case where the incident light is output after passing through the liquid crystal layer twice, where d is a thickness of the liquid crystal layer, Δ

n is a birefringence, and λ

is a wavelength of the light incident on the liquid crystal layer; and

driving voltage applying means for applying a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels thereby utilizing a relaxation process of liquid crystal molecules in the liquid crystal layer to obtain a predetermined output light intensity.

2. A liquid crystal device according to claim 1, wherein the driving voltage applying means applies the driving voltage to the pixels by a field sequential addressing method.

3. A liquid crystal device according to claim 2, includes retardation compensation means between the liquid crystal layer and the polarizing element.

4. A liquid crystal device according to claim 3, wherein the retardation compensation means has at least a pair of substrates and a second liquid crystal layer interposed therebetween, and an electro-optical characteristic of the second liquid crystal layer is substantially identical with that of the liquid crystal layer.

5. A liquid crystal device according to claim 3, wherein the retardation compensation means is selected from a phase plate and a phase film.

6. A liquid crystal device according to claim 5, wherein the retardation compensation means is selected from a uniaxially oriented polymer film and a biaxially oriented film.

7. A liquid crystal device according to claim 1, wherein the driving voltage applying means applies a voltage higher than the maximum voltage providing the extremum of the output light intensity in the voltage-output light intensity characteristic and a voltage between the voltage higher than the maximum voltage and the maximum voltage, thereby controlling the output light intensity of the pixels.

8. A liquid crystal device according to claim 1, wherein the driving voltage applying means reverses a polarity of the driving voltage in each frame.

9. A liquid crystal device according to claim 1, wherein the driving voltage applying means applies a first preliminary voltage having an absolute value larger than that of a signal voltage corresponding to a predetermined output light intensity before applying the signal voltage to the pixels.

10. A liquid crystal device according to claim 9, wherein the driving voltage applying means further applies a second preliminary voltage having an absolute value smaller than that of the signal voltage before applying the signal voltage corresponding to the predetermined output light intensity and after applying the first preliminary voltage.

11. A liquid crystal device according to claim 10, wherein the absolute value of the second preliminary voltage is smaller than that of the maximum voltage providing the extremum in the voltage-output light intensity characteristic of the pixels.

12. A liquid crystal device according to claim 10, wherein a sum of the time period for applying the first preliminary voltage and the time period for applying the second preliminary voltage is one-fifth or less than a time period for applying the signal voltage.

13. A liquid crystal device according to claim 10, wherein the driving voltage applying means applies the first preliminary voltage and the second preliminary voltage to the pixels connected to at least one scanning line for display.

14. A liquid crystal device according to claim 10, wherein at least one of the first preliminary voltage and the second preliminary voltage has an identical value for all the pixels.

15. A liquid crystal device according to claim 9, wherein the output light intensity at a maximum value of the signal voltage is equal to or less than 10% of a maximum in the voltage-output light intensity characteristic of the pixels.

16. A liquid crystal device according to claim 9, wherein a time period for applying the first preliminary voltage is one-fifth or less than that for applying the signal voltage.

17. A liquid crystal device according to claim 9, wherein the driving voltage applying means applies the first preliminary voltage to the pixels connected to at least one scanning line.

18. A liquid crystal device according to claim 9, wherein the driving voltage applying means applied the first preliminary voltage to the pixels connected to each of a plurality of scanning lines at the same time.

19. A liquid crystal device according to claim 9, wherein a value of the first preliminary voltage is identical for all the pixels.

20. A liquid crystal device according to claim 1, wherein one of the pair of substrates is a silicon single crystalline substrate, and the silicon single crystalline substrate has a transistor switching a voltage applied from the driving voltage applying means to each of the plurality of pixels.

21. A projection-type liquid crystal display device including a liquid crystal element, wherein the liquid crystal element comprises:

a pair of substrates;

a liquid crystal layer interposed between the pair of substrates;

at least one polarizing element;

a plurality of pixels;

a retardation (d×

Δ

n) of the liquid crystal layer satisfying one of a relation;

space="preserve" listing-type="equation">d×

Δ

n>

λ

/2

in case where an incident light is output after passing through the liquid crystal layer once, and a relation;

space="preserve" listing-type="equation">2d×

Δ

n>

λ

/2

in a case where the incident light is output after passing through the liquid crystal layer twice, where d is a thickness of the liquid crystal layer Δ

n is a birefringence, and λ

is a wavelength of the light incident on the liquid crystal layer; and

driving voltage applying means for applying a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels thereby utilizing a relaxation process of liquid crystal molecules in the liquid crystal layer to obtain a predetermined output light intensity.

22. A method for improving a contrast ratio of a liquid crystal device including:

a pair of substrates;

a liquid crystal layer interposed between the pair of substrates;

at least one polarizing element; and

a plurality of pixels said method comprising the steps of;

providing a retardation (d×

Δ

n) of the liquid crystal layer satisfying one of a relation;

space="preserve" listing-type="equation">d×

Δ

n>

λ

/2

in a case where an incident light is output after passing through the liquid crystal layer once, and a relation;

space="preserve" listing-type="equation">2d×

Δ

n>

λ

/2

in a case where the incident light is outputted after passing through the liquid crystal layer twice, where d is a thickness of the liquid crystal layer, Δ

n is a birefringence, and λ

is a wavelength of the light incident on the liquid crystal layer; and

utilizing a relaxation process of liquid crystal molecules in the liquid crystal layer to obtain a predetermined output light intensity applying a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels.

23. A method according to claim 22, wherein the driving voltage applying step includes applying a first preliminary voltage having an absolute value larger than that of a signal voltage corresponding to a predetermined output light intensity before applying the signal voltage to the pixels.

24. A method according to claim 23, wherein a time period for applying the first preliminary voltage is one-fifth or less than that for applying the signal voltage.

25. A method according to claim 23, wherein the driving voltage applying step includes applying the first preliminary voltage to the pixels connected to each of a plurality of scanning lines at the same time.

26. A method according to claim 23, wherein a value of the first preliminary voltage is identical for all the pixels.

27. A method according to claim 23, wherein the driving voltage applying step includes applying the first preliminary voltage to the pixels connected to at least one scanning line.

28. A method according to claim 23, wherein the driving voltage applying step further includes applying a second preliminary voltage having an absolute value smaller than that of the signal voltage before applying the signal voltage corresponding to the predetermined output light intensity and after applying the first preliminary voltage.

29. A method according to claim 28, wherein the absolute value of the second preliminary voltage is smaller than that of the maximum voltage providing the extremum in the voltage-output light intensity characteristic of the pixels.

30. A method according to claim 28, wherein a sum of the time period for applying the first preliminary voltage and the time period for applying the second preliminary voltage is one-fifth or less than a time period for applying the signal voltage.

31. A method according to claim 28, wherein the driving voltage applying step includes applying the first preliminary voltage and the second preliminary voltage to the pixels connected to at least one scanning line for display.

32. A method according to claim 28, wherein at least one of the first preliminary voltage and the second preliminary voltage has an identical value for all the pixels.

33. A method according to claim 22, wherein the driving voltage applying step includes applying the driving voltage to the pixels by a field sequential addressing method.

34. A method according to claim 22, wherein the driving voltage applying step includes applying a voltage higher than the maximum voltage providing the extremum of the output light intensity in the voltage-output light intensity characteristic and a voltage between the voltage higher than the maximum voltage and the maximum voltage, thereby controlling the output light intensity of the pixels.

35. A method according to claim 22, wherein a polarity of the driving voltage is reversed in each frame.

36. A liquid crystal device comprising:

a pair of substrates;

a liquid crystal layer interposed between the pair of substrates;

at least one polarizing element;

a plurality of pixels;

a retardation (d×

Δ

n) of the liquid crystal layer satisfying one of a relation;

space="preserve" listing-type="equation">d×

Δ

n>

λ

/2

in a case where an incident light is output after passing through the liquid crystal layer once, and a relation;

space="preserve" listing-type="equation">2d×

Δ

n>

λ

/2

in a case where the incident light is output after passing through the liquid crystal layer twice, were d is a thickness of the liquid crystal layer, Δ

n is a birefringence, and λ

is a wavelength of the light incident on the liquid crystal layer; and

driving voltage applying means for applying a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels thereby utilizing a relaxation process of liquid crystal molecules in the liquid crystal layer to obtain a predetermined output light intensity,

wherein the driving voltage applying means applies a first preliminary voltage having an absolute value larger than that of a signal voltage corresponding to a predetermined output light intensity before applying the signal voltage to the pixels, and a second preliminary voltage having an absolute value smaller than that of the signal voltage before applying the signal voltage and after applying the first preliminary voltage.

37. A liquid crystal device according to claim 36, wherein the absolute value of the second preliminary voltage is smaller than that of the maximum voltage providing the extremum in the voltage-output light intensity characteristic of the pixels.

38. A liquid crystal device according to claim 36, wherein a sum of the time period for applying the first preliminary voltage and the time period for applying the second preliminary voltage is one-fifth or less than a time period for applying the signal voltage.

39. A liquid crystal device according to claim 36, wherein the driving voltage applying means applies the first preliminary voltage and the second preliminary voltage to the pixels connected to at least one scanning line for display.

40. A liquid crystal device according to claim 36, wherein at least one of the first preliminary voltage and the second preliminary voltage has an identical value for all the pixels.

41. A liquid crystal device according to claim 36, further including retardation compensation means between the liquid crystal layer and the polarizing element thereby reducing the driving voltage.

42. A liquid crystal device according to claim 36, wherein the driving voltage supplying means applies the driving voltage to the pixels by a field sequential addressing method.

43. A liquid crystal device according to claim 42, wherein one of the pair of substrates is a silicon single crystalline substrate, and the silicon single crystalline substrate has a transistor switching a voltage applied from the driving voltage applying means to each of the plurality of pixels.

44. A method for improving a contrast ratio of a liquid crystal device including:

a pair of substrates;

a liquid crystal layer interposed between the pair of substrates;

at least one polarizing element; and

a plurality of pixels, said method comprising the steps of;

providing a retardation (d×

Δ

n) of the liquid crystal layer satisfying one of a relation;

space="preserve" listing-type="equation">d×

Δ

n>

λ

/2

in a case where an incident light is output after passing through the liquid crystal layer once, and a relation;

space="preserve" listing-type="equation">2d×

Δ

n>

λ

/2

in a case where an incident light is outputted after passing through the liquid crystal layer twice, where d is a thickness of the liquid crystal layer, Δ

n is a birefringence and λ

is a wavelength of the light incident on the liquid crystal layer; and

applying a driving voltage including a voltage higher than a maximum voltage providing an extremum of the output light intensity in a voltage-output light intensity characteristic of the pixels to the plurality of pixels,

wherein the driving voltage applying step includes applying a first preliminary voltage having an absolute value larger than that of a single voltage corresponding to a predetermined output light intensity before applying the signal voltage to the pixels and a second preliminary voltage having an absolute value smaller than that of the signal voltage before applying the signal voltage corresponding to the predetermined output light intensity and after applying the first preliminary voltage.

45. A method according to claim 44, wherein the absolute value of the second preliminary voltage is smaller than that of the maximum voltage providing the extremum in the voltage-output light intensity characteristic of the pixels.

46. A method according to claim 44, wherein a sum of the time period for applying the first preliminary voltage and the time period for applying the second preliminary voltage is one-fifth or less than a time period for applying the signal voltage.

47. A method according to claim 44, wherein the driving voltage applying step includes applying the first preliminary voltage and the second preliminary voltage to the pixels connected to at least one scanning line for display.

48. A method according to claim 44, wherein at least one of the first preliminary voltage has an identical value for all the pixels.

49. A method according to claim 44, wherein the driving voltage applying step includes applying the driving voltage to the pixels by a field sequential addressing method.

50. A method according to claim 44, wherein the driving voltage applying step includes applying the first preliminary voltage to the pixels connected to each of a plurality of scanning lines at the same time.