Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2000-04-10
2002-07-02
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299610, C252S299660
Reexamination Certificate
active
06413593
ABSTRACT:
The present invention relates to a liquid crystal composition and a liquid crystal shutter arrangement containing such a composition, for example a liquid crystal display device including a multiplicity of liquid crystal shutters.
BACKGROUND OF THE INVENTION
Liquid crystal devices having liquid crystal layers including ferroelectric liquid crystal compositions are the subject of active research interest. In the production of such devices, the liquid crystal layer is formed by introducing the liquid crystal composition at an elevated temperature so as to cause it to be in the isotropic (or nematic), free flowing phase into a narrow gap (the cell gap) between a pair of substrates. At this stage, the liquid crystal composition is at a temperature somewhat higher than its operating temperature. The liquid crystal composition is then cooled in a controlled manner until an optically active tilted smectic phase is achieved, typically the smectic C phase, SmC*, (the * denotes chirality or optical activity). In order for the liquid crystal composition to have the required advantageous properties, it is desired for it to pass from the isotropic phase (I) through chiral nematic (N*) and smectic A (SmA) phases before reaching the operative smectic C* phase. This is referred to as an I-N*-SmA-SmC* phase sequence. The temperature (T
A-C
) at which the transition from the SmA phase to the SmC* phase affects the working temperature range over which the device can operate. Thus, a low T
A-C
. effectively reduces the working temperature range of the device.
Liquid crystal compositions commonly comprise a host material such as those based on mixtures of two or more phenylpyrimidinyl compounds exhibiting or capable of exhibiting a smectic C phase, and optionally other materials which may be included to modify the properties of the host material, for example a chiral dopant to impart chirality if the host material is not inherently chiral, or to enhance or induce formation of certain phases in the phase sequence.
A liquid crystal composition has been proposed in which the host material is based on a 1:2 by weight mixture of the compounds [Ia] and [Ib]) below:
Such a host material is formulated to have a low dielectric biaxiality and a low switching viscosity so that, in compositions containing a chiral dopant, a high value of Ps/&dgr;&egr; (spontaneous polarisation/dielectric biaxiality can be obtained. However, this material has a low T
A-C
, 54° C., even before mixing with chiral dopant (which can suppress T
A-C
).
It is an object of the present Invention to provide a liquid crystal composition having an improved T
A-C
.
REFERENCES:
patent: 5507975 (1996-04-01), Koden et al.
patent: 5820786 (1998-10-01), Sage et al.
patent: 6251301 (2001-06-01), Sage et al.
patent: 6280653 (2001-08-01), Jones et al.
patent: 0 360 043 (1990-03-01), None
patent: 0 414 230 (1991-02-01), None
patent: 0 414 230 (1991-02-01), None
patent: 89/02425 (1989-03-01), None
patent: 95/16760 (1995-06-01), None
Jones John C
Minter Victoria
Slaney Andrew J
Nixon & Vanderhye
Qinetiq Limited
Wu Shean C.
LandOfFree
Liquid crystal composition and liquid crystal shutter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal composition and liquid crystal shutter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal composition and liquid crystal shutter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2822401