Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1997-04-21
2000-12-12
Kelly, C. H.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229966, 25229961, 570128, 570144, C09K 1930, C09K 1912, C07C 1908
Patent
active
061593931
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to benzene derivatives and to a liquid-crystalline medium, to the use of the latter for electrooptical purposes, and to displays containing this medium.
Liquid crystals are used, in particular, as dielectrics in display devices since the optical properties of such substances can be affected by an applied voltage. Electrooptical devices based on liquid crystals are extremely well known to those skilled in the art and may be based on various effects. Devices of this type are, for example, cells having dynamic scattering, DAP (deformation of aligned phases) cells, guest/host cells, TN cells having a twisted nematic structure, STN (super-twisted nematic) cells, SBE (super-birefringence effect) cells and OMI (optical mode interference) cells. The most common display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.
The liquid-crystal materials must have good chemical and thermal stability and good stability toward electrical fields and electromagnetic radiation. Furthermore, the liquid-crystal materials should have low viscosity and give short addressing times, low threshold voltages and high contrast in the cells.
Furthermore, they should have a suitable mesophase, for example, for the abovementioned cells, a nematic or cholesteric mesophase, at customary operating temperatures, i.e. in the broadest possible range above and below room temperature. Since liquid crystals are generally used as mixtures of a plurality of components, it is important that the components are readily miscible with one another. Further properties, such as electrical conductivity, dielectric anisotropy and optical anisotropy, must meet various requirements depending on the cell type and the area of application. For example, materials for cells having a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity.
For example, the media desired for matrix liquid-crystal displays containing integrated nonlinear elements for switching individual image points (MLC displays) are those having high positive dielectric anisotropy, broad nematic phases, relatively low birefringence, very high specific resistance, good UV and temperature stability and a low vapour pressure.
Matrix liquid-crystal displays of this type are known. Examples of nonlinear elements which can be used to switch the individual image points individually are active elements (i.e. transistors). This is then referred to as an "active matrix", and a differentiation can be made between two types:
1. MOS (Metal Oxide Semiconductor) or other diodes on a silicon wafer as substrate.
2. Thin-film transistors (TFTs) on a glass plate as substrate.
The use of monocrystalline silicon as the substrate material limits the display size since even the modular assembly of the various part displays results in problems at the joints.
In the case of the more promising type 2, which is preferred, the electrooptical effect used is usually the TN effect. A differentiation is made between two technologies: TFTs comprising compound semiconductors, such as, for example, CdSe, or TFTs based on polycrystalline or amorphous silicon. Intensive research efforts are being made worldwide in the latter technology.
The TFT matrix is applied to the inside of one glass plate of the display, while the inside of the other glass plate carries the transparent counter-electrode. Compared with the size of the image point electrode, the TFT is very small and hardly affects the image at all. This technology can also be extended to fully colour-compatible image displays, where a mosaic of red, green and blue filters is arranged in such a manner that each filter element is located opposite a switchable image element.
The TFT displays usually operate as TN cells with crossed polarizers in transmission and are illuminated from the back.
The term MLC display here covers any matrix display containing integrated nonlinear elements, i.e. in addition to the active matrix, also displays containing passive elements such as var
REFERENCES:
patent: 5308542 (1994-05-01), Poetsch et al.
patent: 5520846 (1996-05-01), Plach et al.
patent: 5523127 (1996-06-01), Ohnishi et al.
patent: 5536442 (1996-07-01), Reiffenrath et al.
patent: 5565140 (1996-10-01), Hittich et al.
Bartmann Ekkehard
Pauluth Detlef
Poetsch Eike
Reiffenrath Volker
Schoen Sabine
Kelly C. H.
Merck Patent Gesellschaft mit beschrankter Haftung
LandOfFree
Benzene derivatives and liquid-crystalline medium does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Benzene derivatives and liquid-crystalline medium, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Benzene derivatives and liquid-crystalline medium will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-213039