The liquid crystal alignment is mainly defined by azimuthal angle and pretilt angle. The patterned alignment can have spatially variable azimuthal angles or pretilt angles. The general application of the patterned alignment layer is to spatially modulate light properties like phase, polarization and intensity. Photoalignment technology is today, one of the most promising technologies for use in the preparation of the patterned alignment structure.

In order to prepare a patterned photoalignment layer in the azimuthal direction, polarized light is normally used. When different areas of the photoalignment layer are exposed to light with different polarizations, the patterned photoalignment layer is formed. In order to provide methods that are easy and simple for photo-patterning, fou...[ Read more ]

The liquid crystal alignment is mainly defined by azimuthal angle and pretilt angle. The patterned alignment can have spatially variable azimuthal angles or pretilt angles. The general application of the patterned alignment layer is to spatially modulate light properties like phase, polarization and intensity. Photoalignment technology is today, one of the most promising technologies for use in the preparation of the patterned alignment structure.

In order to prepare a patterned photoalignment layer in the azimuthal direction, polarized light is normally used. When different areas of the photoalignment layer are exposed to light with different polarizations, the patterned photoalignment layer is formed. In order to provide methods that are easy and simple for photo-patterning, four methods are studied in this thesis. These four methods will design different photo masks for generation light with spatially varying polarization using patterned quarter-wave plate, patterned half-wave plate, twisted nematic liquid crystal cell and a multi-retarder system, respectively. To verify the properties of these four methods, a series of optical elements are made and tested.

By combining the patterned photoalignment technology with the nematic or ferroelectric liquid crystals, electrically tunable liquid crystal devices can be produced. To evaluate the performance of these tunable devices, tunable Dammann gratings have been made and tested, using both nematic and ferroelectric liquid crystals. The results show that the tunable Dammann gratings can be switched between diffractive and non-diffractive states.

The technology of patterned photoalignment in the pretilt direction is also studied in this thesis. A new photoalignment material called CPL024 is used in the research. The photoalignment material has the property whereby the aligned pretilt angle can be tuned in the range of 10 to 890 under different light exposure energies. Using this material, circular and cylindrical tunable liquid crystal lenses are fabricated and tested.