Liquid crystal device

• US 5,666,217 A
• Filed: 08/01/1995
• Issued: 09/09/1997
• Est. Priority Date: 08/04/1994
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kishi, Etsur o, Kojima, Makoto, Gofuku, Ihachiro, Nakamura, Katsutoshi, Kaneko, Shuzo
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Dudek, James A.
• Application Number:
  US08/509,929
• Time in Patent Office: 770 Days
• Field of Search: 359/74, 359/79, 359/100
• US Class Current: 349/122
• CPC Class Codes: G02F 1/133397 for suppressing after-image or image-sticking
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/133711 by organic films, e.g. polymeric films
• CPC Class Codes: G02F 1/133719 with coupling agent molecules, e.g. silane
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

A liquid crystal device is constituted by a pair of oppositely disposed substrates including a first substrate having a uniaxial alignment characteristic and a second substrate having a non-uniaxial alignment characteristic and a liquid crystal disposed between the first and second substrates. The first and second substrates are controlled to have surface potentials providing a difference therebetween of less than 50 mV in terms of an absolute value at their liquid crystal-contacting surfaces. As a result, the liquid crystal device is provided with an improved symmetry of switching threshold while retaining a good liquid crystal alignment characteristic.

Claims

1. A liquid crystal device, comprising a pair of oppositely disposed substrates including a first substrate-having a uniaxial alignment characteristic and a second substrate having a non-uniaxial alignment characteristic and a liquid crystal disposed between the first and second substrates, wherein

said first and second substrates have surface potentials of an identical polarity and providing a difference therebetween of less than 50 mV in terms of an absolute value at their liquid crystal-contacting surfaces.

2. A liquid crystal device according to claim 1, said difference between the surface potentials of the first and second substrates is at most 30 mV.

3. A liquid crystal device according to claim 1, wherein the surface potentials of the first and second substrates are substantially identical to each other.

4. A liquid crystal device according to claim 1, wherein said second substrate having a non-uniaxial alignment characteristic is provided with a film for adjusting the surface potential.

5. A liquid crystal device according to claim 1 wherein said first substrate having a uniaxial. alignment characteristic is provided with a film having a volume resistivity in the range of 10⁴ -10⁸ ohm.cm.

6. A liquid crystal device according to claim 4, wherein said second substrate having a non-uniaxial alignment characteristic is provided with a coating film with fine particles dispersed therein.

7. A liquid crystal device according to claim 6, wherein the fine particles have a particle size of 30-150 Å

.

8. A liquid crystal device according to claim 6, wherein the fine particles comprise an oxide which is doped with an electroconductivity-controlling impurity.

9. A liquid crystal device according to claim 8, wherein the fine particles comprise SnO_x doped with antimony.

10. A liquid crystal device according to claim 1, wherein said first substrate having a uniaxial alignment characteristic is provided with an alignment control film comprising a polymer film subjected to a uniaxial aligning treatment.

11. A liquid crystal device according to claim 1, wherein each of said first and second substrate has a surface potential of at most 100 mV in terms of an absolute value.

12. A liquid crystal device according to claim 1 wherein said second substrate having a non-uniaxial alignment characteristic has a surface energy of at most 30 dynes/cm at its liquid crystal-contacting boundary.

13. A liquid crystal device according to claim 1, wherein said second substrate having a non-uniaxial alignment characteristic has a surface energy larger than that of said first substrate having a uniaxial alignment characteristic at their liquid crystal-contacting boundaries.

14. A liquid crystal device according to claim 1 wherein said second substrate having a non-uniaxial alignment characteristic has a surface energy of at least 40 dynes/cm at its liquid crystal-contacting boundary.

15. A liquid crystal device according to claim 4, wherein said film for adjusting the surface potential on the second substrate having a non-uniaxial alignment characteristic is a laminate film including a plurality of element films.

16. A liquid crystal device according to claim 15, wherein said plurality of element films in the laminate film provide mutually different surface potentials, and the laminate film shows a surface potential which is intermediate said different surface potentials.

17. A liquid crystal device according to claim 15, wherein an element film closest to the substrate among the plurality of element films is a film comprising a polycrystalline metal oxide or a polycrystalline semiconductor, each doped with an electroconductivity-controlling impurity.

18. A liquid crystal device according to claim 17, wherein said film comprising a polycrystalline metal oxide or a polycrystalline semiconductor has a volume resistivity of 10⁴ -10⁸ ohm.cm in its thickness direction and a volume resistivity of 10⁶ -10⁹ ohm.cm in its film extension direction.

19. A liquid crystal device according to claim 15, wherein an element film closest to the substrate among the plurality of element films is a film comprising a matrix containing dispersed therein fine particles doped with an electroconductivity-controlling impurity.

20. A liquid crystal device according to claim 19, wherein said film comprising a matrix containing therein fine particles has a volume resistivity of 10⁴ -10⁸ ohm.cm.

21. A liquid crystal device according to claim 4, wherein said film for adjusting the surface potential on the second substrate having a non-uniaxial alignment characteristic comprises a mixture of plural different materials.

22. A liquid crystal device according to claim 21, wherein said film has a volume resistivity of 10⁴ -10⁸ ohm.cm.

23. A liquid crystal device according to claim 21, wherein said film comprises a matrix and fine particles having a particle size of 30-300 Å

dispersed in the matrix.

24. A liquid crystal device according to claim 23, wherein said fine particles have a particle size of 30-150 Å

.

25. A liquid crystal device according to claim 23, wherein said matrix comprises silica or siloxane polymer.

26. A liquid crystal device according to claim 21, wherein said film has a thickness of 300-5000 Å

.

27. A liquid crystal device according to claim 21 wherein said substrate having a uniaxial alignment characteristic has thereon an alignment film subjected to a uniaxial alignment treatment, said alignment film comprising a mixture of plural organic polymer materials.

28. A liquid crystal device according to claim 1, wherein said substrate having a uniaxial alignment characteristic is provided with an alignment film providing the uniaxial alignment characteristic, said alignment film comprising a mixture of plural organic polymer materials each capable of forming an alignment film showing a uniaxial alignment characteristic.

29. A liquid crystal device according to claim 1, wherein said liquid crystal is a liquid crystal showing a chiral smectic phase.

30. A liquid crystal device according to claim 29, wherein said liquid crystal is free from cholesteric phase.

31. A liquid crystal device according to claim 1, wherein said liquid crystal comprises a composition containing a fluorine-containing mesomorphic compound having a central core to which a fluorocarbon terminal portion and a hydrocarbon terminal portion are connected, and showing a smectic phase or a latent smectic phase.

32. A liquid crystal device according to claim 1, wherein said liquid crystal is a ferroelectric liquid crystal.

33. A liquid crystal device according to claim 1, wherein said liquid crystal is an anti-ferroelectric liquid crystal.

34. A liquid crystal device according to claim 1, showing a switching threshold difference of at most 1.0 volt.

35. A liquid crystal device, comprising a pair of oppositely disposed substrates including a first substrate having a uniaxial alignment characteristic and a second substrate having a non-uniaxial alignment characteristic and a liquid crystal disposed between tie first and second substrates, wherein

said first and second substrates have surface potentials of an identical polarity at their liquid crystal, contacting surfaces.

36. A liquid crystal device according to claim 35, wherein said second substrate having a non-uniaxial alignment characteristic is provided with a film for adjusting the surface potential.

37. A liquid crystal device according to claim 36, wherein said film provided to the second substrate has a volume resistivity in the range of 10⁴ -10⁸ ohm.cm.

39. A liquid crystal device according to claim 36, wherein said film provided to the second substrate is a laminate film including a plurality of element films.

40. A liquid crystal device according to claim 39, wherein said plurality of element films in the laminate film provide mutually different surface potentials, and the laminate film shows a surface potential which is intermediate said different surface potentials.

41. A liquid crystal device according to claim 39, wherein an element film closest to the substrate among the plurality of element films is a film comprising a polycrystalline metal oxide or a polycrystalline semiconductor, each doped with an electroconductivity-controlling impurity.

42. A liquid crystal device according to claim 35, herein said liquid crystal is a chiral smectic liquid crystal.

43. A liquid crystal device according to claim 42, wherein said liquid crystal causes a successive phase transition in the order of isotropic phase, smectic A phase and chiral smectic phase on temperature decrease.

44. A liquid crystal device according to claim 35, wherein said first substrate having a uniaxial alignment characteristic is provided with an alignment control film comprising a polymer film subjected to a uniaxial aligning treatment.

45. A liquid crystal device according to claim 35, wherein the surface potentials of the first and second substrates provide a difference therebetween of at most 100 mV in terms of an absolute value.

46. A liquid crystal device according to claim 35, wherein each of the surface potentials of the first and second substrates is at most 100 mV in terms of an absolute value.

47. A liquid crystal device according to claim 35, showing a switching threshold difference of at most 1.0 volt.

38. A wherein said film provided to the second substrate 36, where said film provided to the second substrate comprises a matrix and fine particles dispersed within the matrix.

48. A liquid crystal device, comprising a pair of oppositely disposed substrates including a first substrate having a uniaxial alignment characteristic and a second substrate having a non-uniaxial alignment characteristic and a liquid crystal disposed between the first and second substrates, wherein

said second substrate having a non-uniaxial alignment characteristic is provided with a film having a volume resistivity in the range of 10⁴ -10⁸ ohm.cm.

49. A liquid crystal device according to claim 48, wherein said second substrate having a non-uniaxial alignment characteristic has a surface energy larger than that of said first substrate having a uniaxial alignment characteristic respectively as measured according to the liquid droplet contact angle measurement method at their liquid crystal-contacting boundaries.

50. A liquid crystal device according to claim 48, wherein said film provided to the second substrate is a coating film.

51. A liquid crystal device according to claim 48, wherein said coating film has an a surface unevenness of at least 200 Å

.

52. A liquid crystal device according to claim 51, wherein said coating film comprises a matrix and electroconductive particles having a particle size 30-300 Å

dispersed in the matrix.

53. A liquid crystal device according to claim 52, wherein said matrix comprises a siloxane polymer.

54. A liquid crystal device according to claim 48, wherein said second substrate having a non-uniaxial alignment characteristic is further provided with an inorganic film having a volume resistivity of 10⁴ -10⁸ ohm.cm in its thickness direction directly below said film having a volume resistivity in the range of 10⁴ -10⁸ ohm.cm.

55. A liquid crystal device according to claim 48, wherein said first substrate having a uniaxial alignment characteristic is provided with an alignment control layer having a volume resistivity in the range of 10⁴ -10⁸ ohm.cm.

56. A liquid crystal device according to claim 48, wherein said liquid crystal is a chiral smectic liquid crystal.

57. A liquid crystal device according to claim 56, wherein said liquid crystal causes a successive phase transition in the order of isotropic phase, smectic A phase and chiral smectic phase on temperature decrease.