Method of plasma beam bombardment of aligning films for liquid crystals

• US 7,714,965 B2
• Filed: 05/17/2004
• Issued: 05/11/2010
• Est. Priority Date: 05/19/2003
• Status: Expired due to Fees

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Dobrovolskyy, Andriy, Yaroshchuk, Oleg, Chien, Liang-Chy, Lavrentovich, Oleg
• Primary Examiner(s): Nguyen; Dung
• Assistant Examiner(s): DUONG, TAI V
• Application Number:
  US10/553,326
• Publication Number:
  US 20060209241A1
• Time in Patent Office: 2,185 Days
• Field of Search: 349/123, 349/124, 349/125, 349/187, 349/130, 349/136, 428/1.2, 430/321, 250/423.F, 250/426, 313/362.1, 315/111.21, 315/111.91
• US Class Current: 349/124
• CPC Class Codes: G02F 1/132 Thermal activation of liquid crystals exhibiting a thermo-optic effect
• CPC Class Codes: G02F 1/133711 by organic films, e.g. polymeric films
• CPC Class Codes: G02F 1/13378 by treatment of the surface, e.g. embossing, rubbing or light irradiation G02F1/133711, G02F1/133734, G02F1/133753 take precedence

Abstract

Methods for treating aligning substrates produces uniform alignment of liquid crystals in at least two modes. The method is based on the treatment of liquid crystal aligning substrates with a collimated or partially collimated plasma beam. In one embodiment, the method comprises a step of bombarding an aligning substrate with at least one plasma beam from a plasma beam source at a designated incident angle to align the atomic/molecular structure or the surface profile of the aligning substrate in at least one aligned direction.

Claims

1. A process for preparing an aligning substrate for liquid crystals, comprising the steps of:

providing an aligning substrate comprising an aligning film; and

bombarding at least a portion of the substrate with a plasma beam from a plasma beam source at an incident angle of greater than 0°

to about 85°

thereby inducing a surface anisotropy and producing an alignment direction on the bombarded portion of the aligning substrate, wherein 0°

is a position of the beam normal to the substrate, wherein an azimuth angle has a reference axis that is a projection of the plasma beam on the aligning substrate in the first bombarding step and a zenithal angle is an angle between the alignment direction and the aligning substrate, wherein

i) the plasma beam bombarded portion of the aligning substrate imparts to a liquid crystal the alignment direction having an azimuth angle φ

of 70°

to 110° and

a zenithal angle θ

of about 0°

; and

ii) the plasma beam bombardment includes a second bombarding step and after the first bombarding step wherein the substrate or plasma source is rotated so that in the second bombarding step, the direction of plasma irradiation is perpendicular to irradiation of the first bombarding step, wherein the bombarded portion of the alignment substrate imparts to a liquid crystal the alignment direction having an azimuth angle φ

of 90° and

a zenithal angle θ

of 0°

to 5°

.

2. The process according to claim 1, wherein the plasma beam source is a closed drift thruster.

3. The process according to claim 2, wherein current density of the plasma beam is about 0.1 to about 1000 μ

A/cm², and wherein the ion energy is from about 100 to about 5000 eV.

4. The process according to claim 3, wherein said closed drift thruster is an anode layer thruster.

5. The process according to claim 3, wherein the aligning film comprises polyvinyl cinnamate, unsaturated polyester, polyimide, poly(meth)acrylate, polyvinyl acetate, glass, quartz, gold, indium tin oxide, silicon, silicon oxide, hydrogenated diamond-like carbon, or hydrogenated amorphous silicon.

6. The process according to claim 5, wherein in the i) alignment direction the azimuth angle φ

is about 90°

.

7. The process according to claim 5, wherein current density of the plasma beam is about 0.5 to about 30 μ

A/cm², and wherein the ion energy is from about 200 to about 700 eV.

8. The process according to claim 3, wherein the incident angle is about 20°

to about 85°

.

9. The process according to claim 8, wherein the incident angle is about 50°

to about 75°

.

10. The process according to claim 2, further including a step of forming a liquid crystal cell comprising the aligning substrate and thermotropic or lyotropic liquid crystals.

11. The process according to claim 3, further including a step of forming a liquid crystal cell comprising the aligning substrate and thermotropic or lyotropic liquid crystals.

12. The process according to claim 2, further including a step of placing a mask onto the substrate prior to said bombarding to prevent the plasma beam from reaching a predetermined portion of the aligning substrate.

13. The process according to claim 5, further including a step of placing a mask onto the substrate prior to said bombarding to prevent the plasma beam from reaching a predetermined portion of the aligning substrate.

14. The process according to claim 2, wherein the plasma beam is in the form of a sheet.

15. The process according to claim 5, wherein the plasma beam is in the form of a sheet.

16. The process according to claim 2, further including the step of moving the aligning substrate through a path of the plasma beam.

17. The process according to claim 3, further including the step of moving the aligning substrate through a path of the plasma beam.

18. The process according to claim 5, further including the step of moving the aligning substrate through a path of the plasma beam.

19. The process according to claim 1, wherein the aligning substrate is positioned at a distance of about 5 to about 50 cm from the plasma beam source.

20. The process according to claim 3, wherein the aligning substrate is positioned at a distance of about 5 to about 50 cm from the plasma beam source.

21. The process according to claim 5, wherein the aligning substrate is positioned at a distance of about 5 to about 50 cm from the plasma beam source.

32. The process according to claim 1, wherein the plasma beam bombarding provides the alignment direction i), and wherein the liquid crystals are thermotropic or lyotropic liquid crystals.

33. The process according to claim 1, wherein the plasma beam bombarding provides the alignment direction ii), and wherein the liquid crystals are thermotropic or lyotropic liquid crystals.

22. A process for preparing an aligning substrate for liquid crystals, comprising the steps of:

providing an aligning substrate comprising an aligning film; and

bombarding at least a portion of the substrate with a plasma beam from a plasma beam source at an incident angle of greater than 0°

to about 85°

thereby inducing a surface anisotropy and an alignment direction on the aligning substrate on the area of the aligning substrate bombarded by the plasma beam, wherein 0°

is a position normal to the substrate, wherein current density of the plasma beam is about 0.5 to about 30 μ

A/cm², wherein the ion energy is from about 200 to about 700 eV, wherein the aligning film comprises polyvinyl cinnamate, unsaturated polyester, polyimide, poly(meth)acrylate, polyvinyl acetate, glass, quartz, gold, indium tin oxide, silicon, silicon oxide, hydrogenated diamondlike carbon, or hydrogenated amorphous silicon, wherein the plasma beam source is a closed drift thruster, wherein an azimuth angle has a reference axis that is a projection of the plasma beam on the aligning substrate in the first bombarding step and a zenithal angle is an angle between the alignment direction and the aligning substrate, wherein

i) the plasma beam bombarded portion of the aligning substrate imparts to a liquid crystal the alignment direction having an azimuth angle φ

of 70 to 110° and

a zenithal angle θ

of about 0°

; and

ii) the plasma beam bombardment includes a second bombarding step and after the first bombarding step, wherein the substrate or plasma source is rotated so that in the second bombarding step, the direction of plasma irradiation is perpendicular to the irradiation of the first bombarding step, wherein the bombarded portion of the alignment substrate imparts to a liquid crystal the alignment direction having an azimuth angle φ

of 90° and

a zenithal angle θ

of 0°

to 5°

.

23. The process according to claim 22, wherein said closed drift thruster is an anode layer thruster.

24. The process according to claim 22, wherein in the i) alignment direction the azimuth angle φ

is about 90°

.

25. The process according to claim 22, wherein the incident angle is about 20°

to about 85°

.

26. The process according to claim 25, wherein the incident angle is about 50°

to about 75°

.

27. The process according to claim 22, further including a step of forming a liquid crystal cell comprising the aligning substrate and thermotropic or lyotripic liquid crystals.

28. The process according to claim 22, further including a step of placing a mask onto the substrate prior to said bombarding to prevent the plasma beam from reaching a predetermined portion of the aligning substrate.

29. The process according to claim 22, wherein the plasma beam is in the form of a sheet.

30. The process according to claim 22, further including the step of moving the aligning substrate through a path of the plasma beam.

31. The process according to claim 22, wherein the aligning substrate is positioned at a distance of about 5 to about 50 cm from the plasma beam source.

34. The process according to claim 22, wherein the plasma beam bombarding provides the alignment direction i), and wherein the liquid crystals are thermotropic or lyotropic liquid crystals.

35. The process according to claim 22, wherein the plasma beam bombarding provides the alignment direction ii), and wherein the liquid crystals are thermotropic or lyotropic liquid crystals.