Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-07-08
2001-08-07
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S126000, C349S129000
Reexamination Certificate
active
06271906
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to liquid crystal cells with fine structures made up of regions having defined different orientations. The invention also relates to optical conductors made up of the aforementioned fine structures, and to a method of manufacturing such structures.
BACKGROUND OF THE INVENTION
For the purpose of this description, fine structures are defined as two-dimensional or three-dimensional extensions of the order of 0.1 to 100 &mgr;m.
It is known to produce the aforementioned fine structures in liquid crystal layers by applying an electric field to suitably segmented electrodes. In the region exposed to the electric field, the orientation of the liquid crystal is changed relative to the surrounding field-free regions. This usually results in a change in the optical properties of the effected region, and is therefore the basis of the electro-optical display effects of liquid crystal cells.
It is also known to produce fine structures in liquid crystal cells which have formed in a field-free state. To this end, the wall orientation of the liquid-crystal molecules is brought about by oriented photopolymers. The molecules can be variously aligned to produce orientation patterns in the liquid crystal (see Swiss Patent Application 2244/91 and 2246/91 dated Jul. 26, 1991).
These orientation patterns can be used, for example, for producing liquid crystal cells containing patterns made up of regions having different preferred orientation, patterns of regions with and without preferred orientations, or patterns of regions of varying twist, i.e. patterns of TN and STN regions.
SUMMARY OF THE INVENTION
An unexpected discovery has now been made. Fine structures of the aforementioned kind can be produced by micromechanical surface treatment of the plates bounding the liquid crystal. According to the invention, the initially-mentioned liquid crystal cells are characterized in that the plates bounding and orienting the liquid crystal have micromechanically produced regions with different defined preferential directions.
It has also been found that these fine structures can be used in relatively simple manner to produce optical conductors. As is known, the precondition for optical conduction is total reflection at the boundary surfaces of the optical conductor, i.e. the boundary surfaces must have a change in refractive index from a higher value inside the optical conductor to a lower value outside.
According to the invention, optical conducting regions in a liquid crystal can be produced in that the region is given a fine structure to produce a molecular orientation having a higher refractive index than the surrounding regions for guiding and polarizing irradiated light.
Another aim of the invention is to provide a method of producing the aforementioned fine structures. A method for this purpose according to the invention comprises micromechanical structuring of the orientation layers on the plates bounding the liquid crystal. Preferably in this method, a given two-dimensional region is mechanically structured in a uniform direction by a stylus moved by piezoelectric means.
Liquid crystals have properties which are important for manufacture of optically conducting structures. They have high optical anisotropy, their orientation can be controlled by boundary conditions, and they have very powerful electro-optical effects in quasi-static operation. Some newly-developed ferroelectric liquid crystals also have high optical non-linearity. Also, liquid crystals can be used in simple manner to produce thin layers.
Accordingly, conventional (nematic) liquid crystals can be used to produce slow (static) switching networks. If however ferroelectric liquid crystals are used, extremely short switching times <<<1 ns via the Pockels effect) are also attainable.
In light-conducting structures also, the light energy is concentrated in a very small volume, so that efficient frequency doubling and mixing are possible.
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Funfschilling Jurg
Grutter Peter
Hug Hans-Josef
Jung Thomas A.
Schwarz Udo
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Ngo Julie
Rolic AG
Sikes William L.
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