Method of aligning negative dielectric anisotropic liquid crystals
A method for alignment of a homeotropic liquid crystal cell by doping a percentage of a positive Δε (dielectric anisotropy), neutral (Δε approximately 0), or negative Δε liquid crystal material, a high contrast ratio homeotropic alignment of difluoro compounds or mixtures is achieved, independent of operating temperature. Without special requirement on alignment layers, rubbing methods or pretilt angles, the uniform aligned homeotropic liquid crystal cell results even at high temperature and the physical properties, such as the birefringence and viscosity, of the liquid crystal mixtures are improved. In an embodiment the method the homeotropic vertically aligned nematic liquid crystal cells are used in the production of high contrast microdisplays.
1 . A method of producing stable aligned homeotropic liquid crystal cells comprising the steps of:
providing a first negative dielectric anisotropic liquid crystal material; and
mixing at least one of a positive, a neutral and a second negative dielectric anisotropic liquid crystal material into said first negative dielectric anisotropic liquid crystal material to produce an improved molecular alignment for a higher contrast ratio and a larger figure-of-merit than said first negative dielectric anisotropic liquid crystal material.
2 . The method of claim 1 , wherein said mixing step comprises the steps of:
providing said positive dielectric anisotropic liquid crystal material; and
mixing said positive dielectric anisotropic liquid crystal material with said first negative dielectric anisotropic liquid crystal material to form a mixture having a concentration of said positive dielectric anisotropic liquid crystal material within the range from approximately 0.1 percent by weight to approximately 99.9 percent by weight.
3 . The method of claim 2 , wherein said concentration of said positive dielectric anisotropic liquid crystal material is within a range from approximately 3 percent by weight to approximately 60 percent by weight.
4 . The method of claim 1 , wherein said mixing step comprises the steps of:
providing said neutral dielectric anisotropic liquid crystal material; and
mixing said neutral dielectric anisotropic liquid crystal material with said first negative dielectric anisotropic liquid crystal material to form a mixture having a concentration of said neutral dielectric anisotropic liquid crystal material within the range from approximately 0.1 percent by weight to approximately 99.9 percent by weight.
5 . The method of claim 4 , wherein said concentration of said neutral dielectric anisotropic liquid crystal material is within a range from approximately 3 percent by weight to approximately 60 percent by weight.
6 . The method of claim 1 , wherein said mixing step comprises the steps of:
providing said second negative dielectric anisotropic liquid crystal material; and
mixing said second negative dielectric anisotropic liquid crystal material with said first negative dielectric anisotropic liquid crystal material to form a mixture having a concentration of said second negative dielectric anisotropic liquid crystal material within the range from approximately 0.1 percent by weight to approximately 99.9 percent by weight.
7 . The method of claim 6 , wherein said concentration of said second negative dielectric anisotropic liquid crystal material is within a range from approximately 10 percent by weight to approximately 90 percent by weight.
8 . The method for producing a liquid crystal media comprising the steps of:
providing a negative dielectric anisotropic liquid crystal material;
providing a positive dielectric anisotropic liquid crystal material;
providing a neutral dielectric anisotropic liquid crystal material; and
mixing said positive dielectric anisotropic liquid crystal material and said neutral dielectric anisotropic liquid crystal material with said first negative dielectric anisotropic liquid crystal material to produce a higher contrast ratio and a larger figure-of-merit than said first negative dielectric anisotropic liquid crystal material.
9 . The method of claim 8 , wherein a concentration of said positive dielectric anisotropic liquid crystal material and said neutral dielectric anisotropic liquid crystal is within a range from approximately 0.1 percent by weight to approximately 99.9 percent by weight.
10 . The method of claim 3 , wherein said concentration of said positive dielectric anisotropic liquid crystal material is within a range from approximately 5 percent by weight to approximately 15 percent by weight.
11 . The method of claim 5 , wherein said concentration of said neutral dielectric anisotropic liquid crystal material is within a range from approximately 5 percent by weight to approximately 15 percent by weight.
12 . The method of claim 6 , wherein said concentration of said second negative dielectric anisotropic liquid crystal material is approximately 30 percent by weight.