Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-03-28
2003-04-22
Barts, Samuel (Department: 1621)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C558S418000, C560S045000, C560S046000, C564S442000, C428S001400, C428S473500
Reexamination Certificate
active
06552161
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compositions useful for inducing alignment of a liquid crystal medium with polarized light and liquid crystal display elements.
Most liquid crystal devices, including displays, have a finite pre-tilt angle, controlled, for instance, by the mechanical buffing of selected polymeric alignment layers. Liquid crystal. molecules in contact with such a layer align parallel to the buffing direction, but not exactly parallel to the substrate. The liquid crystal molecules are slightly tilted from the substrate, for instance, by about 0.5-15°. For most display applications, a finite and uniform pre-tilt angle of the liquid crystal is desirable. For other display applications requiring predominately homeotropic alignment of liquid crystals, a much higher pre-tilt angle is desired, for instance, 85-89.9°. In these cases, controlling the pre-tilt by a mechanical rubbing process is very difficult.
A new process for aligning liquid crystals with polarized light was disclosed in U.S. Pat. No. 4,974,941 entitled “Process of Aligning and Realigning Liquid Crystal Media”. Controlling the pre-tilt angle of liquid crystals in contact with optical alignment layers. while maintaining high uniformity of alignment, is an important requirement for optical alignment materials. Continuing effort has been directed to the development of compositions for optical alignment of liquid crystals and liquid crystal displays.
SUMMARY OF THE INVENTION
The present invention provides polarizable fluorinated amines of the general formula I
P—L
f
—A—(NH
2
)
q
I
wherein A is a divalent or trivalent organic moiety, L
f
is a divalent organic radical comprising at least four fluorinated carbon atoms; P is a polar group comprising a Pi electron system containing at least one heteroatom selected from the group N, O and S; and q is 1 to 2.
The invention also provides a polyamic acid composition which is the reaction product of an amine component and a tetracarboxylic dianhydride component which comprises at least one structural element of each of formulas IV and V
wherein X
4
is an electron withdrawing group having a positive &sgr;, A is a trivalent organic moiety, P is a polar group comprising a Pi electron system containing at least one heteroatom selected from the group N, O, and S, and L
f
consists essentially of:
—X—(CH
2
)
n
—(CF
2
)
p
—(CH
2
)
n
—X—
wherein —(CF
2
)
p
— is a straight chain or branched chain perfluoroalkyl radical, p is 4 to 20, X is selected from the group consisting of —CH
2
O—, —CH
2
S—, —CH
2
NR—, —O—, —S—, —NR— and a covalent bond, wherein R is a C
1
-C
4
hydrocarbon, n is up to 4 and M is a tetravalent organic radical derived from said tetracarboxylic dianhydride containing at least two carbon atoms, no more than two carbonyl groups of the dianhydride being attached to any one carbon atom of the tetravalent radical.
The invention further provides polyimides derived from the polyamic acids and liquid crystal display elements made with the polyimide compositions.
REFERENCES:
Zuev et al(Chem Abstract 1990:36946, CRN 124741-18-0), 1990.
Gibbons Wayne M.
Shannon Paul J.
Zheng Hanxing
Barts Samuel
Elsicon Inc.
Huntley & Associates
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