Liquid crystal device comprising alignment posts having a random or pseudorandom spacing therebetween
View Patent ↗A liquid crystal device has a surface alignment structure comprising an array of alignment features ( 10 ) which are shaped and/or orientated to produce a desired alignment. Depending on the geometry and spacing of the features ( 10 ), the liquid crystal may be induced to adopt a planar, tilted, or homeotropic alignment.
1. A liquid crystal device comprising:
a first cell wall and a second cell wall enclosing a layer of liquid crystal material;
electrodes for applying an electric field across at least some of said liquid crystal material; and
a surface alignment structure on an inner surface of at least said first cell wall, providing a single desired uniform alignment to a liquid crystal director,
wherein said alignment is selected from the group consisting of planar, tilted and homeotropic,
wherein said surface alignment structure comprises a two-dimensional array of alignment posts having a random or pseudorandom spacing therebetween, and
wherein said alignment posts are formed from a material selected from the group consisting of a photoresist material and a plastics material, and are shaped and oriented to produce the desired alignment.
2. A device as claimed in claim 1 , wherein said posts have a height in the range of about 0.5 to 5 μm.
3. A device as claimed in claim 1 , wherein said posts have a height in the range of about 1.0 to 1.2 μm.
4. A device as claimed in claim 1 , wherein at least part of a side wall of said posts is tilted with respect to the normal to the plane of the first cell wall.
5. A device as claimed in claim 1 , wherein each post has a width in the range of about 0.2 to 3 μm.
6. A device as claimed in claim 1 , wherein said posts are spaced from about 0.1 to 5 μm apart from each other.
7. A device as claimed in claim 1 , wherein the liquid crystal material contains a surfactant.
8. A device as claimed in claim 1 ,
wherein said two-dimensional array of alignment posts includes a first alignment post and a second alignment post, and
wherein said first and second alignment posts are of at least one of a different height from one another, a different shape from one another, a different tilt from one another and a different orientation from one another.
9. A device as claimed in claim 1 , wherein said liquid crystal material is a nematic liquid crystal.
10. A device as claimed in claim 1 , further comprising one or more spacer posts, said one or more spacer posts spanning the entire cell.
11. A device as claimed in claim 1 , wherein said posts are not treated with or formed from a material which will induce local homeotropic alignment in the liquid crystal material.
12. The liquid crystal device of claim 1 , wherein said alignment posts are produced by casting.
13. The liquid crystal device of claim 1 , wherein said alignment posts are produced by a technique selected from the group consisting of embossing and injection moulding.
14. The liquid crystal device of claim 1 , wherein said two-dimensional array of alignment posts includes a first alignment post that when viewed from above, has a cross-sectional shape selected from the group consisting of a triangle, a square, a circle, an oval, an ellipse and a polygon.
15. The liquid crystal device of claim 1 , wherein said two-dimensional array of alignment posts includes a first alignment post that is pyramid-shaped.
16. The liquid crystal device of claim 1 , wherein said two-dimensional array of alignment posts includes a first alignment post that has an irregular surface.
17. The liquid crystal device of claim 1 , wherein said two-dimensional array of alignment posts includes a first alignment post that has a curved length-wise face.
18. The liquid crystal device of claim 1 , wherein said two-dimensional array of alignment posts includes a first alignment post that has less than two planes of reflection symmetry that are normal to said surface of said first cell wall.
19. A cell wall for use in manufacturing a liquid crystal device, comprising:
a wall structure having a surface alignment structure on a surface thereof, for providing a single desired uniform alignment to a liquid crystal director,
wherein said alignment is selected from the group consisting of planar, tilted and homeotropic,
wherein said surface alignment structure comprises a two-dimensional array of alignment posts having a random or pseudorandom spacing therebetween, and
wherein said alignment posts are formed from a material selected from the group consisting of a photoresist material and a plastics material, and are shaped and oriented to produce the desired alignment.
20. The cell wall of claim 19 , wherein said alignment posts are produced by casting.
21. The cell wall of claim 19 , wherein said alignment posts are produced by a technique selected from the group consisting of embossing and injection moulding.
22. The cell wall of claim 19 , wherein said two-dimensional array of alignment posts includes a first alignment post that when viewed from above, has a cross-sectional shape selected from the group consisting of a triangle, a square, a circle, an oval, an ellipse and a polygon.
23. The cell wall of claim 19 , wherein said two-dimensional array of alignment posts includes a first alignment post that is pyramid-shaped.
24. The cell wall of claim 19 , wherein said two-dimensional array of alignment posts includes a first alignment post that has an irregular surface.
25. The cell wall of claim 19 , wherein said two-dimensional array of alignment posts includes a first alignment post that has a curved length-wise face.
26. The cell wall of claim 19 , wherein said two-dimensional array of alignment posts includes a first alignment post that has less than two planes of reflection symmetry that are normal to said surface of said cell wall.
27. The cell wall of claim 19 ,
wherein said two-dimensional array of alignment posts includes a first alignment post and a second alignment post, and
wherein said first and second alignment posts at least one of a different height from one another, a different shape from one another, a different tilt from one another and a different orientation from one another.
28. A liquid crystal device comprising:
a first cell wall and a second cell wall enclosing a layer of liquid crystal material;
electrodes for applying an electric field across at least some of said liquid crystal material; and
a surface alignment structure on an inner surface of at least said first cell wall, providing a single desired uniform alignment to a liquid crystal director,
wherein said alignment is selected from the group consisting of planar, tilted and homeotropic,
wherein said surface alignment structure comprises a two-dimensional array of alignment posts having a random or pseudorandom spacing therebetween, and
wherein said alignment posts are shaped and oriented to produce the desired alignment, and have a height in a range of about 0.5 to 5 μm.
29. A device as claimed in claim 28 , wherein said posts have a height in the range of about 1.0 to 1.2 μm.
30. A device as claimed in claim 28 , wherein at least part of a side wall of said posts is tilted with respect to the normal to the plane of the first cell wall.
31. A device as claimed in claim 28 , wherein each post has a width in the range of about 0.2 to 3 μm.
32. A device as claimed in claim 28 , wherein said posts are spaced from about 0.1 to 5 μm apart from each other.
33. A device as claimed in claim 28 , wherein said posts are formed from a photoresist or a plastics material.
34. A device as claimed in claim 28 , wherein the liquid crystal material contains a surfactant.
35. A device as claimed in claim 28 ,
wherein said two-dimensional array of alignment posts includes a first alignment post and a second alignment post, and
wherein said first and second alignment posts are of at least one of a different height from one another, a different shape from one another, a different tilt from one another and a different orientation from one another.
36. A device as claimed in claim 28 , wherein said liquid crystal material is a nematic liquid crystal.
37. A device as claimed in claim 28 , further comprising one or more spacer posts, said one or more spacer posts spanning the entire cell.
38. The liquid crystal device of claim 28 , wherein said alignment posts are produced by casting.
39. The liquid crystal device of claim 28 , wherein said alignment posts are produced by a technique selected from the group consisting of embossing and injection moulding.
40. The liquid crystal device of claim 28 , wherein said two-dimensional array of alignment posts includes a first alignment post that when viewed from above, has a cross-sectional shape selected from the group consisting of a triangle, a square, a circle, an oval, an ellipse and a polygon.
41. The liquid crystal device of claim 28 , wherein said two-dimensional array of alignment posts includes a first alignment post that is pyramid-shaped.
42. The liquid crystal device of claim 28 , wherein said two-dimensional array of alignment posts includes a first alignment post that has an irregular surface.
43. The liquid crystal device of claim 28 , wherein said two-dimensional array of alignment posts includes a first alignment post that has a curved length-wise face.
44. The liquid crystal device of claim 28 , wherein said two-dimensional array of alignment posts includes a first alignment post that has less than two planes of reflection symmetry that are normal to said surface of said first cell wall.