Display device with uniform off-axis luminance reduction
A display device comprising a spatial light modulator having a display polariser arranged on one side of the spatial light modulator is provided with an additional polariser arranged on the same side as the display polariser and polar control retarders between the additional polariser and the display polariser. The polar control retarders include a liquid crystal retarder having two surface alignment layers disposed adjacent to a layer of liquid crystal material on opposite sides. The surface alignment layers provide alignment in the adjacent liquid crystal material with an in-plane component, wherein the angle of said in-plane component changes monotonically along a predetermined axis across the display device, providing reduction of luminance in directions that are offset from a viewing axis, increasing uniformity in the reduction of luminance in directions that are offset from a viewing axis.
1. A method of manufacturing a surface alignment layer for aligning liquid crystal molecules, the method comprising:
generating a beam of light that is linearly polarised with a controllable polarisation direction;
directing the beam of light to illuminate a portion of a layer of photoalignment material so as to provide alignment of the portion of the layer of photoalignment material based on the polarisation direction; and
providing relative movement between the beam of light and the layer of photoalignment material while the beam of light illuminates the portion of the layer of photoalignment material such that different portions of the layer of photoalignment material are illuminated with linearly polarised light and changing the polarisation direction of the beam of light continuously during the relative movement so that the polarisation direction is different and changes continuously between the different portions of the layer of photoalignment material.
2. The method according to claim 1 , further comprising providing a mask in the optical path of the beam of light, wherein the mask allows the beam of light to be incident on a portion of the layer of photoalignment material.
3. The method according to claim 1 , further comprising supporting the layer of photoalignment material on a support arrangement.
4. The method according to claim 1 , further comprising simultaneously changing the polarisation direction of the beam of light and changing the illuminated portion of the layer of photoalignment material.
5. The method according to claim 1 , further comprising moving the layer of photoalignment material to provide the relative movement.
6. The method according to claim 1 , further comprising moving a light source that generates the beam of light to provide the relative movement.
7. The method according to claim 1 , wherein the layer of photoalignment material is provided on a substrate.
8. The method according to claim 1 , wherein changing the polarisation direction of the beam of light comprises physically rotating a polariser of the beam of light.
9. The method according to claim 1 , wherein changing the polarisation direction of the beam of light comprises polarising the beam of light with a fixed linear polariser and using a controllable retarder to change the polarisation direction of light polarised by the fixed linear polariser.
10. The method according to claim 1 , further comprising monotonically changing the polarisation direction of the beam of light during the relative movement so that the polarisation direction changes monotonically across the layer of photoalignment material.
11. The method according to claim 1 , wherein the beam of light is ultraviolet light.
12. The method according to claim 1 , further comprising using the beam of light to cure the different portions of the layer of photoalignment material.
13. The method according to claim 1 , further comprising directing the beam of light at an angle to the plane of the layer of photoalignment material in order to achieve a pre-tilt in the layer of photoalignment material.
14. An apparatus for manufacturing a surface alignment layer for aligning liquid crystal molecules, the apparatus comprising:
a light source arranged to provide a beam of light;
a polariser configured to linearly polarise the beam of light with a controllable polarisation direction;
a support arrangement configured to support a layer of photoalignment material; and
a mask configured to allow the beam of light to be incident on a portion of the layer of photoalignment material, the light source being configured so that the beam of light provides alignment of the portion of the layer of photoalignment material based on the polarisation direction,
wherein the apparatus is configured to provide relative movement between the beam of light and the layer of photoalignment material while the beam of light illuminates the portion of the layer of photoalignment material such that different portions of the layer of photoalignment material are illuminated with linearly polarised light and to change the polarisation direction of the beam of light continuously during the relative movement so that the polarisation direction is different and changes continuously between the different portions of the layer of photoalignment material that are illuminated.
15. The apparatus according to claim 14 , wherein the apparatus is configured to move the layer of photoalignment material to provide the relative movement between the beam of light and the layer of photoalignment material.
16. The apparatus according to claim 14 , wherein the light source is movably mounted and the apparatus is configured to change the illuminated portion of the layer of photoalignment material by moving the light source to provide the relative movement between the beam of light and the layer of photoalignment material.
17. The apparatus according to claim 14 , wherein the support arrangement is arranged to support a substrate having the layer of photoalignment material provided thereon.
18. The apparatus according to claim 14 , wherein the apparatus is configured to physically rotate the polariser so as to change the polarisation direction of the beam of light.
19. The apparatus according to claim 14 , wherein the polariser comprises a fixed linear polariser and a controllable retarder, and wherein the controllable retarder is configured to change the polarisation direction of light polarised by the fixed linear polariser.
20. The apparatus according to claim 14 , wherein the apparatus is configured to change the polarisation direction of the beam of light during the relative movement so that the polarisation direction changes monotonically across the layer of photoalignment material.
21. The apparatus according to claim 14 , wherein the controller is configured to change the polarisation direction of the light across the plurality of different illuminated portions by at least 40 degrees.
22. The apparatus according to claim 14 , wherein the light source is an ultraviolet light source.
23. The apparatus according to claim 14 , wherein the light source is further configured so that the beam of light cures the portion of the layer of photoalignment material that is illuminated.
24. The apparatus according to claim 14 , wherein the apparatus is configured such that, when a layer of photoalignment material is supported by the support arrangement, the beam of light is directed at an angle to the plane of the layer of photoalignment material in order to achieve a pre-tilt in the layer of photoalignment material.