Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2001-01-03
2004-05-18
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299610, C252S299630, C252S299660, C544S229000, C544S303000, C549S380000, C549S214000, C556S430000, C556S431000, C570S162000
Reexamination Certificate
active
06737124
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compounds useful as components in liquid crystal (LC) compositions, particularly as components of LC compositions that exhibit smectic phases and more particularly as components of LC compositions that exhibit smectic A and/or smectic C phases. LC compositions of this invention may also exhibit nematic phases. LC compositions of this invention can be ferroelectric liquid crystals (FLCs). The invention also relates to optical devices employing LC compositions of the invention in optical switching and display elements.
Several types of smectic liquid crystal materials (LCs) have been investigated for rapid switching, view-angle enhancement and higher contrast, including surface-stabilized ferroelectric LCs (FLCs), deformed helix ferroelectric LCs (DHFLCs), and antiferroelectric LCs (AFLCs). Recently, smectic material exhibiting thresholdless or more properly V-shaped switching LCs (VLCs) have been described (Inui, S. et al. (1996) J. Mater. Chem. 6(4):671-673; Seomun, S. S. et al. (1997) Jpn. J. Appl. Phys. 36:3580-3590). Ferroelectric LCs when a ligned parallel to the substrate surfaces using the surface stabilized effect (in an surface-stabilized ferroelectric liquid crystal (SSFLC) device) exhibit two stable state switching on a microsecond time scale. Antiferroelectric LCs exhibit three stable-state switching, which by application of a bias field can be converted for use in a bistable switching mode LC devices. Two of the AFLC states have the same transmittance, so that alternate symmetrical switching can be used in AFLC devices. VLCs, in contrast, exhibit very rapid, analog electro-optic response, allow symmetrical driving, and no dc balance is required. VLCs are particularly attractive for applications requiring generation of multiple levels of gray scale.
Liquid crystal (LC) compositions exhibit one or more LC phases. LC compositions may be composed of one or more components. Components of LC compositions may exhibit liquid crystal phases, have latent liquid crystal phases or be compatible with (not suppress) liquid crystal phases in the LC composition. LC compounds and components of LC mixtures of this invention are rod-like molecules most typically having a generally linear mesogenic core with one or more directly or indirectly linked alicylic or aromatic rings (which may be fused aromatic rings) and linear or branched tail groups distributed on either side of the mesogenic core, e.g.:
LC components which do not themselves exhibit liquid crystal phases, but which exhibit LC phases on combination with one or more other components are described as having “latent” liquid crystal phases. Chiral nonracemic LCs useful in FLCS, DHFLCS, AFLC and VLCS compositions have at least one component that has a chiral non-racemic tail group. FLCS, DHFLCS, AFLC and VLCS compositions may be composed entirely of chiral non-racemic components, but are typically composed of a mixture of chiral nonracemic and achiral or racemic components.
SUMMARY OF THE INVENTION
The invention relates to liquid crystal compounds having silane tails having a perfluoroalkyl terminal portion which are useful as components in liquid crystal compositions, particularly those compositions exhibiting smectic liquid crystal compositions and more particularly those exhibiting chiral smectic phases, such as smectic C phases. Silanes of this invention can be chiral nonracemic, chiral racemic or achiral molecules. Chiral racemic and achiral silanes of this invention are useful alone or in combination as liquid crystal host materials. The materials of this invention can also be combined with known liquid crystal host materials to impart improved properties. Chiral nonracemic silanes of this invention can function as additives or dopants in host materials to impart chirality into an LC material. When introduced into host materials the silanes of this invention tend to broaden the smectic C phase of the material and to improve alignment of the material in a liquid crystal cell. Of particular interest are compound which are disilanes.
The invention relates to liquid crystal materials comprising liquid crystal compounds having a silane tail with a terminal perfluoroalkyl portion attached to a linear rod-like liquid crystal core. LC compounds of this invention include compounds having the formula:
where:
a and b can be 1 or 0 to indicate the presence or absence of a structural element; k is 0 or an integer ranging from 1-10; preferably k is 0 or 1;
m and n are integers ranging from 1 to about 20; j is 0 or an integer ranging from 1 to 20, n+m+k(j) ranges from about 5 to about 20;
one or more non-neighboring carbons in the —(CH
2
)m— group or the —(CH
2
)n— group of the silane tail can be replaced with a double bond, a triple bond or an oxygen, preferably only one carbon of these groups is replaced, more preferably no carbons of the groups are replaced;
A and B, independently are linker groups selected from the group consisting of a single bond, —COO—, —OOC—. —CH
2
—CH
2
—, —OCH
2
—, —CH
2
—O—, —CH═CH— (cis or trans), —CH═CH—CH═CH— (cis or trans) and —C≡C—;
Z is —O— or a single bond;
X is —O—, —COO— or —OCO—, or a single bond;
Y indicates optional substitution on the core ring and can represent up to four substituents when the rings are aromatic and up to 10 substituents when the rings are alicyclic, substituents include halides, CN, NO
2
, alkyl (lower alkyl having 1-6 carbon atoms), alkoxy (lower alkoxy having 1-6 carbon atoms), preferred core ring substituents are fluorine;
R is an alkyl or alkenyl group having from 3 to about 20 carbons atoms in which one or more of the non-neighboring carbons can be replaced with —O—, or in which one or more of the carbons is substituted with one or more halogens, particularly one or more fluorines, or R is R*, a chiral non-racemic group, which can be a chiral nonracemic alkyl or alkenyl group, a chiral nonracemic halogen (particularly fluorine) substituted alkyl or alkenyl group, a group containing a cyclic lactone ring (as illustrated in Scheme 3) or a chiral nonracemic epoxide (as illustrated in Scheme 3).
R
1
, R
1′
, R
2
and R
2′
are alkyl groups or perfluorinated alkyl groups, typically having from 1 to 6 carbon atoms, and particularly —CH
3
groups;
R
F
is a perfluorinated alkyl group having from 1 to about 10 carbon atoms;
Core rings A, B and C can be aromatic or alicyclic and preferably are 5- or 6-membered rings.
One of the rings in the core can be replaced with a single fused ring aromatic, such as a naphthalene ring, or a partially aromatic ring, such as a dehydronaphthalene ring. for aromatic rings one or two ring carbons can be replaced with O, S, or N, preferably N. Alicyclic rings can have from 3 to about 10 carbon atoms in the ring, but cyclohexane and cyclohexene rings are preferred. In alicyclic rings one or two of the CH2 groups of the ring can be replaced with a NH, O, S or C═O group. The core can contain one, two or three rings. R can be R
F
or a partially fluorinated tail. R can have a terminal portion that is perfluorinated, such as in the formula: —X(CH2)p CqFq+1, where p is an integer ranging from 1 to 20 and q is an integer ranging from 1 to 20 (preferably p and q range from 1 to 10). Preferred one ring cores are aromatic (phenyl, pyrimidinyl, pyridinyl). Preferably two or three of the A, B and C rings are aromatic. Preferred cores include: phenylpyrimidines, phenylbenzoates, biphenyls, and terphenyls. Preferably one or two of the rings A, B or C is alicyclic. Scheme 4 illustrates a number of exemplary cores of the compounds of this invention.
In a specific embodiment, compounds of this invention have the formula:
where B, Ring B and Ring C can take values as noted above and each D, independent of other D's, can be CH or CH
2
, a nitrogen atom, CY or CHY, where Y is a CN, NO
2
, an alkyl, a perhaloalkyl (e.g., perfluoroalkyl), or a halide, particularly a fluorine. Rings B and C can be alicyclic or aromatic and B and C that are aromatic can
Chen Xin-Hua
Gough Neil
Thurmes William N.
Wand Michael
Displaytech, Inc.
Greenlee Winner and Sullivan P.C.
Wu Shean C.
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