Naphthyl organic compounds

Details Naphthyl organic compounds Naphthyl organic compounds

1998-09-10

2001-09-18

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299620, C349S086000, C349S088000, C349S092000, C349S182000

Reexamination Certificate

active

06291034

ABSTRACT:

This invention relates to compounds containing a naphthyl group and which have liquid crystalline properties and/or which are suitable for use as constituents of liquid crystal materials. The invention also relates to use of such compounds in liquid crystal materials.
Liquid crystal materials and devices exploit the electro-optical properties of nematic and cholesteric (N or N*), or smectic (S) with particularly useful smectic phases being chiral smectic C (S
C
*) or smectic A.
Liquid crystal materials which show ferroelectric S
C
* phase are useful in fast switching displays such as television or VDU screens as the S
C
* phase can be switched in a few milliseconds or even microseconds. The principle of S
C
* switching is described inter alia by N A Clark and S T Lagerwall in App Phys Lett 36 (1980) p899.
Materials which show an S
A
liquid crystal phase may be used in display devices which exploit the electroclinic effect.
The use of liquid crystal materials to exhibit electro-optical effects in displays and other optical devices such as digital calculators, watches, meters and alphanumeric laptop computers is now well known. However, known liquid crystal materials are not ideal in all respects and a considerable amount of work is currently being carried out in the art to improve their properties.
Liquid crystal materials normally consist of specially selected mixture compositions and improved materials are often obtained by forming new mixtures having an improved combination of properties.
The composition of a liquid crystal mixture is generally selected so that the mixture shows desirable properties. In particular such properties include:
(1) a liquid crystalline temperature range—including room temperature (20° C.)—which is as wide as possible;
(2) a melting point (solid-to-liquid crystal transition temperature) which is as low as possible;
(3) a clearing point (liquid crystalline to isotropic liquid transition temperature) which is as high as possible;
(4) a positive or negative (as appropriate) dielectric anisotropy (permittivity measured parallel to the molecular axis less that measured perpendicular to the molecular axis) which is as great as possible in order to minimise the display voltage;
(5) a viscosity which is as low as possible in order to minimise the display switching speeds;
(6) an electro-optical response which varies as little as possible with temperatures;
(7) a good chemical and photochemical stability;
Examples of further particular properties useful in specific applications include:
(8) a good multiplexability;
(9) an ability to switch dielectric anisotropy with frequency;
(10) a birefringence of selected magnitude;
(11) specific elastic constants which can be tailored to meet specific device requirements; and
(12) high electrical resistivity for certain applications.
Liquid crystal materials and devices exploit the electro-optical properties of nematic or cholesteric (N and N* respectively), or smectic (S) in particular chiral smectic C (S
C
*) or smectic A (S
a
) phase. The most common type of liquid crystal materials in use are those which show a nematic phase and these are extensively used in, for example, watches, clocks, calculators, electronic displays etc.
For some applications of liquid crystal materials a high birefringence is sought, eg in so called “electrically controlled birefringence” (ECB) effect devices (see, for example, M F Schieckel and K Fahrensohn Applied Physics Letters 19 p2912 1971), in thin film transistors and supertwisted nematic devices. It is rare for the requisite desirable properties to be found in a single liquid crystalline compound and generally liquid crystalline materials consist of mixtures of component compounds. Very many liquid crystalline compounds suitable for such uses are known and will be apparent to those in the art.
Some liquid crystalline compounds based on the phenyl-naphthalene system are known eg
For example, Bull Soc Chim Fr 11-12(2) p2521-2426 (1975) describes compounds where A is alkoxy and B is alkyl or alkoxy, and Helv Chim Acta 68(5) p1406-1426 describes those in which a is alkyl or alkoxy and B is cyano or trifluoromethyl.
It is the aim of this invention to provide novel compounds which provide improved or alternative liquid crystalline and/or monotropic characteristics.
According to this invention, liquid crystal naphthyl compounds of formula I are provided;
R
1
—A—(X)
m
—(B)
n
—R
2
  Formula I
where A is selected from naphthyl, fluorinated naphthyl, brominated naphthyl, B is selected from phenyl, methylated phenyl, brominated phenyl, fluorinated phenyl, thiophene, pyrimidine and pyridine, R
1
and R
2
are independently selected from alkyl, alkoxy, alkynyl, thioalkyl, Br, CN, SCN, NCS, perfluoroalkyl, perfluoroalkoxy and hydrogen, X is selected from C≡C, COO and C═C, m is 0 or 1, n is 0 or 1 where m is 1 and n is 0 where m is 0;
provided that
where A is naphthyl, n is land m is O then B is selected from methylated phenyl, brominated phenyl, thiophene, pyrimidine and pyridine;
and further provided that
where A is naphthyl, X is C≡C, m is 1 and n is 1, then B is selected from thiophene, pyrimidine and pyridine.
The preferred embodiments of the invention discussed below are inter alia chosen with respect to their liquid crystalline properties, particularly with respect to suitability for use in high birefringence nematic or ferro-electric Sc* liquid crystal materials. Preferably for use in nematic materials alkyl, alkoxyl, thioalkyl and alkynyl substituents R
1
and R
2
contain 1-15 carbon atoms, and more preferably contain 1-5 carbon atoms for use as nematic materials and 3-9 carbon atoms for use as smectic materials. Preferably for smectic C materials R
1
and R
2
are selected from n-alkyl or n-alkoxy.
According to a further aspect of this invention compounds suitable for inclusion in devices utilising pretransitional characterisitcs of liquid crystalline materials in the isotropic phase are provided, of general Formula II
R
3
—J—(Y)
p
—(Z)
q
—R
4
  Formula II
where J is selected from naphthyl, fluorinated naphthyl, brominated naphthyl, Z is selected from phenyl, methylated phenyl, brominated phenyl, fluorinated phenyl, thiophene, pyrimidine and pyridine, R
1
and R
2
are independently selected from alkyl, alkoxy, alkynyl, thioalkyl, Br, CN, SCN, NCS, perfluoroalkyl, perfluoroalkoxy and hydrogen, Y is selected from C═C, COO and C≡C, p is 0 or 1, q is 0 or 1 where p is 1 and q is 0 where p is 0.
Typically such compounds can be utilised in devices such as Optical Kerr Effect devices. Such devices are often used as optical shutters or optical modulators, and rely on the the fact that birefringence (&Dgr;n) of a medium being proportional to the square of an applied electric field. Such an effect is often termed the quadratic electro-optic effect and can be investigated using degenerate four wave mixing (P Madden et al IEEE J of Quantum Electronics QE22 No 8 August 1986 p1287).
Preferably where R
3
and R
4
are selected from C
1-15
alkyl, alkoxy, thioalkyl and alkynyl; more preferably C
1-9
and even more preferably C
3-9
.
Preferred overall structures of formula I and formula II are now listed:
Naphthyl materials of formula I and formula II may be generally prepared by various routes which will be apparent to those in the art. Typical routes which can be used include reaction of an appropriate phenyl (or equivalent eg thiophene, pyrimidine etc) boronic acid with an appropriate naphthol triflate. Alternatively, an appropriate boronic acid can be reacted with such appropriate compounds as bromonitro—eg acid can be reacted with such appropriate compounds as bromonitro—eg appropriate benzene, thiophene residues etc, for CN and NCS terminal groups. Terminal groups of alkyls, alkoxys, alkynyls and thioalkyls can be achieved by well known alkylation, O-alkylation, alkylation (via appropriate triflate) and thioalkylation routes respectively. Naphthyl materials of where m and n are 0 can be prepared from bromonaphthol by using eg alkylation, thioalkyl

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