CA1110352A - Azine liquid crystal compounds for use in light- control devices - Google Patents
Azine liquid crystal compounds for use in light- control devicesInfo
- Publication number
- CA1110352A CA1110352A CA314,105A CA314105A CA1110352A CA 1110352 A CA1110352 A CA 1110352A CA 314105 A CA314105 A CA 314105A CA 1110352 A CA1110352 A CA 1110352A
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- Canada
- Prior art keywords
- liquid crystal
- crystal material
- light
- cyano
- group
- Prior art date
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C251/00—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton
- C07C251/72—Hydrazones
- C07C251/88—Hydrazones having also the other nitrogen atom doubly-bound to a carbon atom, e.g. azines
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C255/00—Carboxylic acid nitriles
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/06—Non-steroidal liquid crystal compounds
- C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
- C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
- C09K19/24—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a chain containing nitrogen-to-nitrogen bonds
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Liquid Crystal Substances (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Abstract of the Disclosed Embodiments A light-control device includes a liquid crys-tal material sandwiched between a pair of planar, light-transmitting members. The liquid crystal material particu-larly includes an asymmetrical azine compound having the general formula:
Description
3~:
Background of the Invention This invention relates generally to the art of visual displays and similar light-control devices and relates more par-ticularly to liquid crystal displays which incorporate an azine compound as part of the system for selective transmission of visible light.
Organic substances which exhibit a mesophase have been known for many years, but it has been only more recently that the technology of liquid crystal materials has been deve~oped suffi-10 ciently to achieve commercial application in such devices aswrist watches and digital readouts.
The substances which exhibit a liquid crystal phase, as postulated by Gray and Harrison in U.S. Patent No. 3,947,374 for example, comprise a molecule with a central linkage group and a pair of distal chemical groups of varying character. These paten-tees recognize the prior utility of Schiff Bases and ~hemselves disclose commercially useful liquid crystal properties for cer-tain biphenyl compounds. Gray and Harrison also teach that the presence of an unsaturated group in the linkage unit is asso-20 ciated with undesirable, chemical and/or photochemical instability.In addition, Kmetz and Willisen in "Nonemissive Electrooptic Displays", Plenum Press, New York and London (1976), have suggested possible display performance for azine compounds with identical distal groups, although the authors admit that almost nothing is known about the properties of liquid ~g 35~
crystal azine compounds.
Summary of the Invention Contrary to the teachings and sugges~ions of the prior art, appl.icants have discovered that certain azine compounds 9 despite the presence of two doubLe bonds in the central linkage group, are ade~uately stahle and have other useful proper~.ies for display devices. In particular, the ~
azine compounds of the present invention have dissimilar -distal groups, i.e. the azine molecule is asymmetric.
Accordingly, a general object of the presen~
invention has been to provide a new class of liquid crystal compounds which have unexpected utility in a variety of light-control devices.
Another object of the present invention is to provide a new class o~ liquid crystal compounds which are stable and which are easily and economically synthesized. ~;~
Applicants have established that a liquid crys-tal compound which is usëful for visual display purposes possesses a melting point of no higher than about 75C, 20 has a comparatively low viscosity in order to exhibit a short turn-off time, is chemically stable and non-toxic, and shows a high transition temperature from the mesomorphic phase to the isotropic liquid state of at least about 50 C. ;
In order to formulate a material that is acceptable for a given display application, it is sometimes necessary to mix a particular asymmetrical azine compound of the present in-vention with another like compound oe with some other "., 35;;~
substance, especially to obtain ~ desired melting point, it having been found that mixtures of some liquid crystal materials have melting points which are depressed to a con-siderably greater extent than is predictable from simple thermodynamics. On the other hand, the temperatures of ~ransition to isotropic liquid ordinarily vary linearly with molar average composition, between the respective temperatures or the pure components of the mixture.
Description of the Preferred Embodiments The particular azine compounds of the present - invention have the general formula:
X y Rl - ~ _ C = N _ N = C _ ~ _ R2 wherein Rl and R2 are different para-substituents whereby to produce an asymmetrical molecular structure, wherein Rl and R2 are selected from the group comprising cyano, halogen, alkyl; and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydro-gen and methyl radicals. The transition temperatures for specific compounds answering this definLtion and comprising examples of asymmetrical azines which we have specifically synthesized, are set forth in Table I below.
... . , , I
3~iiZ
:
TABLE I
TR~NSITION TEMPERATURES FOR
SELECTED, AS ~ETRICAL AZINE COMPOUNDS ~ -Crystal (or Smectic) Nematic to to Nematic Isotropic Liquid ~;
Rl R2 X YTransition Transition , F n-C3H7 CH3 H (Sm) 69C . 75 CN n-C4Hg c~3 H (Sm) 56 117 10 CN n-C5Hll H CH3 71 131 CH3 n-C4Hg H H - 58 87 CH3 n-C5HLl H H 60 100 CH3 n~C7HlS H H~Sm) 56 89 C2H5 n-C4H9 H H 39 82 C~H5 n-C5Hll H 32 92 C2H5 n-C6H13 H H 37 82 C2H5 ~-C6Hl3 CH3 H 32 62 20 C2Hs n-C8H17 H H 33 75 n-C3H7 n-C4Hg H H 37 95 n-C3H7 n-C4H9 CH3 H 39 76 n-C3~7 n-C4H9 H CH3 44 77 n-C3H7 n-C5Hll H H (Sm) 34 105 n-C3H7 n-C5Hll H CH3 43 83 n-C3H7 n-C6H13 H H . 23 92 n-C3H7 n-C7H15 H H 37 95 3~
TABLE I
CONT'D.
' 1 .. _ . . .. _ .
Crystal (o~ Smectic) ~ematic to to Nematic Isotropis Liquid Rl R2 X Y Transition Transition n-C3H7 n-C8H17 H H (Sm) 28 89 `
n-C3H7 n-CgHl9 H H ~Sm) 42 93 n-C4Hgn~C6HI3 H H (Sm) 38 86 ;~
~ 9 7 15 H 34 91 ~:
n-C4Hg n-C8H17 H H (Sm) 33 84 n-CsHlln-C7EI15 H H ~ 48 98 n-C5Hlln-C8H17 H H 43 9~ :~
CH~CH~CN n-C4Hg H H 71 105 n-C5Hll n-C9Hl9 H H 54 94 n C6H13 n-C7H15 H H 47 86 ~-n-C6~13 n-C8H17 H H 37 84 n-C6H13 ~-C9Hl9 H H 59 87 It will be noted tha~ all of the compounds in Table I have melting points (crystalline to smetic or to nematic transition point~ below the desired temperature of 75C; and in fact, many of them are below 30 C. More-over the clearing points (nematic to isotropic liquid transition points) are in excess of 5Q C and, ln many cases, above 80 C. By comparison; a symmetrical azine .:
. : , ~ .. .. .
35~
composition in which both Rl and R2 are alkyl radicals containing eight carbon atoms, the smectic to nematic -~
transition temperature has been observed to be 68 C
with a nematic range of only 20 C.
The as~mmetrical azine compounds of the present invention are also characterized by desirably low viscosity, especially when formulated in mixtures for optical display purposes. Fast response or turn-off times result, as much as twice as fast as mixtures of ester liquid crystal 10 compounds. For example, a display with an ester liquid crystal mixture showed a turn-off time of about 140 micro-seconds, whereas a corresponding display employing a mixture of asymmetrical azine compounds according to the present invention exhibited a turn-off time of about 60 microseconds.
Thus, the asymmetrical azine compounds of the present invention exhibit viscosities and turn-off times equivalent to commercial biphenyl liquid crystal compounds while, at the same time, possessing higher and more desirable isotropic transition temperatures. In addition5 the asymmetrical azine compounds 20 o~ the present invention exhibit improved chemical and photochemcial stability over Schi~f Base liquid crystal compounds, although not as great as biphenyl or ester liquid crystal compound 8 ~
The asymmetrical azine compounds of the present ~r invention can be combined in mixtures with other liquid crystal compounds as well as with other asymmetrical azine compounds .
5~
' 1 using conventional methods such that the resulting oomposition exhibits a greater mesomorphic range than that of the indivi-dual compounds~ In addition, asymmetrical ~zine compounds of the present invention, especially those having melting polnts -of 60 C or higher, can be usefully combined with biphenyl liquid crystal compounds or with Schiff Base liquid crystal compounds or with ester liquid crystal compounds to elevate the ~ransition temperature from thenematic phase to the isotropic liquid phase of the resultant mi~ture. The compo- ;
10 sition of one eminently useful mixture, according to the the present invention is set forth in Table II below.
TABLE II
M~XTURE #1 .. . ... _ .... . .. _ Compound % by Weight R Rl X
C3H7 C6H13 H . H 14.3 :~:
C3H7 C5Hll H H 19 C~Hg -C6H13 H H 14.3 ClH3 C4H9 H H 9.5 20 ClH3 C8H17 H H 9.5 C3H7 C8H17 H H 14.3 F C3~7 CH3 H 14.3 CN C4H9 CH3 H 4.8 The nem~tic range of Mixture #1 is from -10 C to 85 C.
~ 8 , ~, . . .
35~
A twisted nematic display requires the use of a liquid crystal mixture having a positive dielectric -anisotropy; and for prior art liquid crystal compounds, this is ordinarily accomplished by utili~ing a cyano (CN) group as one of the substituents, thus introducing a dipole along the long axis of the molecuIe. However, the asymmetrical azine compounds of the present invention inherently possess a mildly positive dielectric anisotropy without need to resort to synthesis so as to incorporate a cyano group. However, 10 when a display device with a low voltage threshold is to be ~
fabricated, a cyano group is advantageously employed as one of ;;
the para-substituents in the azine compounds of the present Lnvention; and as will be noted, Mixture`#l contains such a `~
compound. A twisted nematic display using Mixture ~1 has dis-played a threshold voltage of 2.8 volts. In addition to com-positions employing two or more asymmetrical azine compounds, ;
~.',;
:~
:
:
- 8a -. .
~93 3~
other compositions can be formulated using other types of liquid ~rystal material. For example, ten percent by weight of a cyano ester, specifically cyano-phenly-pentyl benzoate, may be added to Mixture #l; and this latter composition has exhibited a nematic range of from -22~C to 83 C. In a twisted nematic display, it exhibits a threshold voltage of 1.60.
The asymmetrical azine liquid crystal compo~mds of the present invention also show a very low order of bire-10 fringence; and thus, digital and other displays can be fabri- ;
cated which are thin and possessed of fast response times without undesirable color variations such as mottling.
Although the classical preparation o~ a sym-metrical azine compound typically involves reaction of a hydrazine with an excess of an aldehyde, the asymmetrical azines of the present in~ention are advantageously synthesized by first preparing the hydrazone of one of the components by use of the procedure of G.R. Newkome and D.L Fishel (J. Org.
Chem., 31? 677 [1966]). The reaction then proceeds as i~ the 20 following typical equation:
tl H MeoH H ,H r~
7 3 ~ C_N- NH2 ~ O=C ~ CsHll~ H7C3 ~ C--N-N-C ~ CSHll ( ) ; ..
In the foregoing reaction, the hyd~azone (A~
which has been s~eci~ically prepared from n-propylbenzaldehyde, is mechanically mixed with the molecular equivalent weight or (B), n-pentylbenzaldehyde, in a suitable solvent such as _ g _ :
3~:
,~ .
methanol, for a period of about 15-30 minutes. The resulting azine product is then separated from the reaction mixture and purified by recrystallization.
In order that the principles of the present invention may be more readily understood5 a physical em-bodiment ther~o~applied to a light-control device or display, is shown in the accompanying drawing wherein Fig. 1 is a schematic, cross-sectional view showing an electrooptical display incorporating an asymmetrical azine liquid crystal composition according to the present invention.
Referring in detail to the drawing, a light- ~
control device or shutter indicated generally by the refer- ~ -ence numeral 10 is shown to comprise a first and a second planar light-transmitting member, 12 and 14. A thin film of liquid crystal material 16 is ~onfined between the planar members 12 and 14; and in order to retain the liquid cr~stal ;
material 16 in place3 a continuous liquid-stop ring 18 en-compasses the liquid crystal material between the planar members 12 and 1~. As will~be appreciated, the ring 18 may 20 be configurated to define the perimeter of a numerical dig;t or other symbol which it is desired to illuminate selectively.
In order to provide external electrical con-nection to the liquid crystal material 16, the planar members 12 and 14, which are advantageously fabricated from a suitable glass, are coated on their confronting surfa~es with thin conductive films 20 and 22 respectively. These films are 35~
advantageously fabricated of tin oxide and form respective electrsdes for suitable attachment to an external electrical circuit 24. Circuit 24 comprises a direct current source 26, such as a battery, and a manual or other switching device 28.
As will be appreciated, the planar members 12 and 14 are out-wardly offset from the liquid stop ring 18 in order to facili-tate connections with the circuit 24.
According to conventional practice, a polariz-ing filter 30 is applied to the outer planar surface o~
member 14. Similarly, a coating 32 is applied to the outer planar surface of member 12; and the coating 32 may be a cooperating polarizing filter with a reflective material such as me~allic silver depending on whether it is desired that ~he device be transmissive or reflective. In addition, a light source 34 is focused on the polarizing filter 30; and in the case where the dQvice 10 is reflective in nature, a viewing element 36, such~as a photocell or the human eye, is disposed to observe the device 10 from the same aspect as~' light source 34.
In accordance with the present invention, the liquid crystal material 16 includes a compound which has a transition temperature of at least about 70 C, which has a melting point of no higher that about 60 C, and which comprises an asymmetrical azine liquid crystal compound as -~
described hereinabove. Advantageously, the liquid crystal material 16 may take the ~orm of Mixture ~1 which has been described hereinabove.
In operation, when the switching device 28 is directed into a circuit-opening condition, the viewing element 36 will contemplate a bright background surrounding an opaque image of the indicia or other pattern created by the liquid crystal material 16. Contrariwise, when the switching device 28 is directed into a condition completing the circuit 24, the liquid crystal material 16 becomes light-transmissive, and the entire format of the device 10 10 appears reflective.
Various arrangements of light and dark areas may, of course, be created as circumstances make desirable.
The term "light-control device" as used herein is intended to mean an optical gate for permitting or obstructing the passage of light.
The drawing and the foregoing disclosures are not intended to represent the only forms of our invention in regard to the details of fabrication and manner of ap-plication. Changes in the construction of display devices and in the formulation of liquid crystal compositions, as weIl as the substitution of equivalents, are contemplated as circumstances may suggest or render expediènt; and al-though specific terms have been employed, they are intended in a generic and descrip~ive sense only and not for the purposes of limitation, the scope of the invention being delineated in the following claims.
..
Background of the Invention This invention relates generally to the art of visual displays and similar light-control devices and relates more par-ticularly to liquid crystal displays which incorporate an azine compound as part of the system for selective transmission of visible light.
Organic substances which exhibit a mesophase have been known for many years, but it has been only more recently that the technology of liquid crystal materials has been deve~oped suffi-10 ciently to achieve commercial application in such devices aswrist watches and digital readouts.
The substances which exhibit a liquid crystal phase, as postulated by Gray and Harrison in U.S. Patent No. 3,947,374 for example, comprise a molecule with a central linkage group and a pair of distal chemical groups of varying character. These paten-tees recognize the prior utility of Schiff Bases and ~hemselves disclose commercially useful liquid crystal properties for cer-tain biphenyl compounds. Gray and Harrison also teach that the presence of an unsaturated group in the linkage unit is asso-20 ciated with undesirable, chemical and/or photochemical instability.In addition, Kmetz and Willisen in "Nonemissive Electrooptic Displays", Plenum Press, New York and London (1976), have suggested possible display performance for azine compounds with identical distal groups, although the authors admit that almost nothing is known about the properties of liquid ~g 35~
crystal azine compounds.
Summary of the Invention Contrary to the teachings and sugges~ions of the prior art, appl.icants have discovered that certain azine compounds 9 despite the presence of two doubLe bonds in the central linkage group, are ade~uately stahle and have other useful proper~.ies for display devices. In particular, the ~
azine compounds of the present invention have dissimilar -distal groups, i.e. the azine molecule is asymmetric.
Accordingly, a general object of the presen~
invention has been to provide a new class of liquid crystal compounds which have unexpected utility in a variety of light-control devices.
Another object of the present invention is to provide a new class o~ liquid crystal compounds which are stable and which are easily and economically synthesized. ~;~
Applicants have established that a liquid crys-tal compound which is usëful for visual display purposes possesses a melting point of no higher than about 75C, 20 has a comparatively low viscosity in order to exhibit a short turn-off time, is chemically stable and non-toxic, and shows a high transition temperature from the mesomorphic phase to the isotropic liquid state of at least about 50 C. ;
In order to formulate a material that is acceptable for a given display application, it is sometimes necessary to mix a particular asymmetrical azine compound of the present in-vention with another like compound oe with some other "., 35;;~
substance, especially to obtain ~ desired melting point, it having been found that mixtures of some liquid crystal materials have melting points which are depressed to a con-siderably greater extent than is predictable from simple thermodynamics. On the other hand, the temperatures of ~ransition to isotropic liquid ordinarily vary linearly with molar average composition, between the respective temperatures or the pure components of the mixture.
Description of the Preferred Embodiments The particular azine compounds of the present - invention have the general formula:
X y Rl - ~ _ C = N _ N = C _ ~ _ R2 wherein Rl and R2 are different para-substituents whereby to produce an asymmetrical molecular structure, wherein Rl and R2 are selected from the group comprising cyano, halogen, alkyl; and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydro-gen and methyl radicals. The transition temperatures for specific compounds answering this definLtion and comprising examples of asymmetrical azines which we have specifically synthesized, are set forth in Table I below.
... . , , I
3~iiZ
:
TABLE I
TR~NSITION TEMPERATURES FOR
SELECTED, AS ~ETRICAL AZINE COMPOUNDS ~ -Crystal (or Smectic) Nematic to to Nematic Isotropic Liquid ~;
Rl R2 X YTransition Transition , F n-C3H7 CH3 H (Sm) 69C . 75 CN n-C4Hg c~3 H (Sm) 56 117 10 CN n-C5Hll H CH3 71 131 CH3 n-C4Hg H H - 58 87 CH3 n-C5HLl H H 60 100 CH3 n~C7HlS H H~Sm) 56 89 C2H5 n-C4H9 H H 39 82 C~H5 n-C5Hll H 32 92 C2H5 n-C6H13 H H 37 82 C2H5 ~-C6Hl3 CH3 H 32 62 20 C2Hs n-C8H17 H H 33 75 n-C3H7 n-C4Hg H H 37 95 n-C3H7 n-C4H9 CH3 H 39 76 n-C3~7 n-C4H9 H CH3 44 77 n-C3H7 n-C5Hll H H (Sm) 34 105 n-C3H7 n-C5Hll H CH3 43 83 n-C3H7 n-C6H13 H H . 23 92 n-C3H7 n-C7H15 H H 37 95 3~
TABLE I
CONT'D.
' 1 .. _ . . .. _ .
Crystal (o~ Smectic) ~ematic to to Nematic Isotropis Liquid Rl R2 X Y Transition Transition n-C3H7 n-C8H17 H H (Sm) 28 89 `
n-C3H7 n-CgHl9 H H ~Sm) 42 93 n-C4Hgn~C6HI3 H H (Sm) 38 86 ;~
~ 9 7 15 H 34 91 ~:
n-C4Hg n-C8H17 H H (Sm) 33 84 n-CsHlln-C7EI15 H H ~ 48 98 n-C5Hlln-C8H17 H H 43 9~ :~
CH~CH~CN n-C4Hg H H 71 105 n-C5Hll n-C9Hl9 H H 54 94 n C6H13 n-C7H15 H H 47 86 ~-n-C6~13 n-C8H17 H H 37 84 n-C6H13 ~-C9Hl9 H H 59 87 It will be noted tha~ all of the compounds in Table I have melting points (crystalline to smetic or to nematic transition point~ below the desired temperature of 75C; and in fact, many of them are below 30 C. More-over the clearing points (nematic to isotropic liquid transition points) are in excess of 5Q C and, ln many cases, above 80 C. By comparison; a symmetrical azine .:
. : , ~ .. .. .
35~
composition in which both Rl and R2 are alkyl radicals containing eight carbon atoms, the smectic to nematic -~
transition temperature has been observed to be 68 C
with a nematic range of only 20 C.
The as~mmetrical azine compounds of the present invention are also characterized by desirably low viscosity, especially when formulated in mixtures for optical display purposes. Fast response or turn-off times result, as much as twice as fast as mixtures of ester liquid crystal 10 compounds. For example, a display with an ester liquid crystal mixture showed a turn-off time of about 140 micro-seconds, whereas a corresponding display employing a mixture of asymmetrical azine compounds according to the present invention exhibited a turn-off time of about 60 microseconds.
Thus, the asymmetrical azine compounds of the present invention exhibit viscosities and turn-off times equivalent to commercial biphenyl liquid crystal compounds while, at the same time, possessing higher and more desirable isotropic transition temperatures. In addition5 the asymmetrical azine compounds 20 o~ the present invention exhibit improved chemical and photochemcial stability over Schi~f Base liquid crystal compounds, although not as great as biphenyl or ester liquid crystal compound 8 ~
The asymmetrical azine compounds of the present ~r invention can be combined in mixtures with other liquid crystal compounds as well as with other asymmetrical azine compounds .
5~
' 1 using conventional methods such that the resulting oomposition exhibits a greater mesomorphic range than that of the indivi-dual compounds~ In addition, asymmetrical ~zine compounds of the present invention, especially those having melting polnts -of 60 C or higher, can be usefully combined with biphenyl liquid crystal compounds or with Schiff Base liquid crystal compounds or with ester liquid crystal compounds to elevate the ~ransition temperature from thenematic phase to the isotropic liquid phase of the resultant mi~ture. The compo- ;
10 sition of one eminently useful mixture, according to the the present invention is set forth in Table II below.
TABLE II
M~XTURE #1 .. . ... _ .... . .. _ Compound % by Weight R Rl X
C3H7 C6H13 H . H 14.3 :~:
C3H7 C5Hll H H 19 C~Hg -C6H13 H H 14.3 ClH3 C4H9 H H 9.5 20 ClH3 C8H17 H H 9.5 C3H7 C8H17 H H 14.3 F C3~7 CH3 H 14.3 CN C4H9 CH3 H 4.8 The nem~tic range of Mixture #1 is from -10 C to 85 C.
~ 8 , ~, . . .
35~
A twisted nematic display requires the use of a liquid crystal mixture having a positive dielectric -anisotropy; and for prior art liquid crystal compounds, this is ordinarily accomplished by utili~ing a cyano (CN) group as one of the substituents, thus introducing a dipole along the long axis of the molecuIe. However, the asymmetrical azine compounds of the present invention inherently possess a mildly positive dielectric anisotropy without need to resort to synthesis so as to incorporate a cyano group. However, 10 when a display device with a low voltage threshold is to be ~
fabricated, a cyano group is advantageously employed as one of ;;
the para-substituents in the azine compounds of the present Lnvention; and as will be noted, Mixture`#l contains such a `~
compound. A twisted nematic display using Mixture ~1 has dis-played a threshold voltage of 2.8 volts. In addition to com-positions employing two or more asymmetrical azine compounds, ;
~.',;
:~
:
:
- 8a -. .
~93 3~
other compositions can be formulated using other types of liquid ~rystal material. For example, ten percent by weight of a cyano ester, specifically cyano-phenly-pentyl benzoate, may be added to Mixture #l; and this latter composition has exhibited a nematic range of from -22~C to 83 C. In a twisted nematic display, it exhibits a threshold voltage of 1.60.
The asymmetrical azine liquid crystal compo~mds of the present invention also show a very low order of bire-10 fringence; and thus, digital and other displays can be fabri- ;
cated which are thin and possessed of fast response times without undesirable color variations such as mottling.
Although the classical preparation o~ a sym-metrical azine compound typically involves reaction of a hydrazine with an excess of an aldehyde, the asymmetrical azines of the present in~ention are advantageously synthesized by first preparing the hydrazone of one of the components by use of the procedure of G.R. Newkome and D.L Fishel (J. Org.
Chem., 31? 677 [1966]). The reaction then proceeds as i~ the 20 following typical equation:
tl H MeoH H ,H r~
7 3 ~ C_N- NH2 ~ O=C ~ CsHll~ H7C3 ~ C--N-N-C ~ CSHll ( ) ; ..
In the foregoing reaction, the hyd~azone (A~
which has been s~eci~ically prepared from n-propylbenzaldehyde, is mechanically mixed with the molecular equivalent weight or (B), n-pentylbenzaldehyde, in a suitable solvent such as _ g _ :
3~:
,~ .
methanol, for a period of about 15-30 minutes. The resulting azine product is then separated from the reaction mixture and purified by recrystallization.
In order that the principles of the present invention may be more readily understood5 a physical em-bodiment ther~o~applied to a light-control device or display, is shown in the accompanying drawing wherein Fig. 1 is a schematic, cross-sectional view showing an electrooptical display incorporating an asymmetrical azine liquid crystal composition according to the present invention.
Referring in detail to the drawing, a light- ~
control device or shutter indicated generally by the refer- ~ -ence numeral 10 is shown to comprise a first and a second planar light-transmitting member, 12 and 14. A thin film of liquid crystal material 16 is ~onfined between the planar members 12 and 14; and in order to retain the liquid cr~stal ;
material 16 in place3 a continuous liquid-stop ring 18 en-compasses the liquid crystal material between the planar members 12 and 1~. As will~be appreciated, the ring 18 may 20 be configurated to define the perimeter of a numerical dig;t or other symbol which it is desired to illuminate selectively.
In order to provide external electrical con-nection to the liquid crystal material 16, the planar members 12 and 14, which are advantageously fabricated from a suitable glass, are coated on their confronting surfa~es with thin conductive films 20 and 22 respectively. These films are 35~
advantageously fabricated of tin oxide and form respective electrsdes for suitable attachment to an external electrical circuit 24. Circuit 24 comprises a direct current source 26, such as a battery, and a manual or other switching device 28.
As will be appreciated, the planar members 12 and 14 are out-wardly offset from the liquid stop ring 18 in order to facili-tate connections with the circuit 24.
According to conventional practice, a polariz-ing filter 30 is applied to the outer planar surface o~
member 14. Similarly, a coating 32 is applied to the outer planar surface of member 12; and the coating 32 may be a cooperating polarizing filter with a reflective material such as me~allic silver depending on whether it is desired that ~he device be transmissive or reflective. In addition, a light source 34 is focused on the polarizing filter 30; and in the case where the dQvice 10 is reflective in nature, a viewing element 36, such~as a photocell or the human eye, is disposed to observe the device 10 from the same aspect as~' light source 34.
In accordance with the present invention, the liquid crystal material 16 includes a compound which has a transition temperature of at least about 70 C, which has a melting point of no higher that about 60 C, and which comprises an asymmetrical azine liquid crystal compound as -~
described hereinabove. Advantageously, the liquid crystal material 16 may take the ~orm of Mixture ~1 which has been described hereinabove.
In operation, when the switching device 28 is directed into a circuit-opening condition, the viewing element 36 will contemplate a bright background surrounding an opaque image of the indicia or other pattern created by the liquid crystal material 16. Contrariwise, when the switching device 28 is directed into a condition completing the circuit 24, the liquid crystal material 16 becomes light-transmissive, and the entire format of the device 10 10 appears reflective.
Various arrangements of light and dark areas may, of course, be created as circumstances make desirable.
The term "light-control device" as used herein is intended to mean an optical gate for permitting or obstructing the passage of light.
The drawing and the foregoing disclosures are not intended to represent the only forms of our invention in regard to the details of fabrication and manner of ap-plication. Changes in the construction of display devices and in the formulation of liquid crystal compositions, as weIl as the substitution of equivalents, are contemplated as circumstances may suggest or render expediènt; and al-though specific terms have been employed, they are intended in a generic and descrip~ive sense only and not for the purposes of limitation, the scope of the invention being delineated in the following claims.
..
Claims (10)
1. A light-control device comprising: first and second planar light-transmitting members; liquid crystal material having a nematic temperature range of from about -20° C to about 80° C, said liquid crystal material being confined between said members and including a compound which has a transition temperature from the nematic phase to the isotropic liquid phase of at least about 50° C, which has a melting point from the crystalline phase to a liquid crystal phase of no higher than about 75° C, and which has the general formula:
wherein R1 and R2 are different para-substituents whereby to pro-duce an asymmetrical molecular structure, wherein R1 and R2 are selected from the group comprising cyano, halogen, alkyl, and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydrogen and methyl radicals; and electrode means disposed in contact with said liquid crystal material for connecting said liquid crystal material externally of said planar members.
wherein R1 and R2 are different para-substituents whereby to pro-duce an asymmetrical molecular structure, wherein R1 and R2 are selected from the group comprising cyano, halogen, alkyl, and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydrogen and methyl radicals; and electrode means disposed in contact with said liquid crystal material for connecting said liquid crystal material externally of said planar members.
2. A light-control device according to Claim 1 wherein said liquid crystal material further includes a second azine compound having an asymmetrical molecular structure.
3. A light-control device according to Claim 1 wherein one of R1 and R2 is a cyano group.
4. A light-control device according to Claim 1 wherein said liquid crystal material further includes a cyano ester.
5. A light-control device according to Claim 4 wherein said cyano ester is cyano-phenyl-pentyl benzoate.
6. A liquid crystal material comprising an azine having the general formula:
wherein R1 and R2 are different para-substituents whereby to pro-duce an asymmetrical molecular structure, wherein R1 and R2 are selected from the group comprising cyano, halogen, alkyl, and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydrogen and methyl radicals.
wherein R1 and R2 are different para-substituents whereby to pro-duce an asymmetrical molecular structure, wherein R1 and R2 are selected from the group comprising cyano, halogen, alkyl, and substituted alkyl radicals in which the alkyl radical has from one to nine carbon atoms, and wherein X and Y are selected from the group comprising hydrogen and methyl radicals.
7. A liquid crystal material according to Claim 6 wherein said material further includes a second azine compound having an asymmetrical molecular structure.
8. A liquid crystal material according to Claim 6 wherein one of R1 and R2 is a cyano group.
9. A liquid crystal material according to Claim 6 wherein said material further includes a cyano ester.
10. A liquid crystal material according to Claim 9 wherein said cyano ester is cyano-phenyl-pentyl benzoate.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86195477A | 1977-12-19 | 1977-12-19 | |
| US93750778A | 1978-08-28 | 1978-08-28 | |
| US937,507 | 1978-08-28 | ||
| US861,954 | 1986-05-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110352A true CA1110352A (en) | 1981-10-06 |
Family
ID=27127655
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA314,105A Expired CA1110352A (en) | 1977-12-19 | 1978-10-24 | Azine liquid crystal compounds for use in light- control devices |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5487688A (en) |
| CA (1) | CA1110352A (en) |
| CH (1) | CH642103A5 (en) |
| DE (1) | DE2852851A1 (en) |
| FR (1) | FR2411873A1 (en) |
| GB (1) | GB2010274B (en) |
| PH (1) | PH14293A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69708231T2 (en) * | 1996-08-22 | 2002-07-11 | Dainippon Ink & Chemicals | Azine derivative, process for its preparation, nematic liquid crystalline composition containing the same and liquid crystalline display device containing the same |
| JP4918734B2 (en) * | 2001-02-27 | 2012-04-18 | Ｄｉｃ株式会社 | Liquid crystal composition and liquid crystal display element |
| JP4934899B2 (en) * | 2001-03-30 | 2012-05-23 | Ｄｉｃ株式会社 | Liquid crystal composition and liquid crystal display element |
| EP2305638B1 (en) | 2008-06-30 | 2014-11-12 | Zeon Corporation | Asymmetric azine compound and method for producing the same |
| JP5845655B2 (en) * | 2011-06-24 | 2016-01-20 | Dic株式会社 | Liquid crystal composition having negative dielectric anisotropy, and liquid crystal display device using the liquid crystal composition |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2418703C3 (en) * | 1973-04-24 | 1978-06-29 | Dai Nippon Toryo K.K., Osaka (Japan) | Nematic liquid crystal mass and its use in electro-optical elements |
-
1978
- 1978-10-24 CA CA314,105A patent/CA1110352A/en not_active Expired
- 1978-10-26 GB GB7842082A patent/GB2010274B/en not_active Expired
- 1978-11-14 FR FR7832077A patent/FR2411873A1/en active Granted
- 1978-11-15 CH CH1175478A patent/CH642103A5/en not_active IP Right Cessation
- 1978-11-17 PH PH21821A patent/PH14293A/en unknown
- 1978-11-24 JP JP14595678A patent/JPS5487688A/en active Pending
- 1978-12-07 DE DE19782852851 patent/DE2852851A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| FR2411873B1 (en) | 1984-12-28 |
| GB2010274A (en) | 1979-06-27 |
| FR2411873A1 (en) | 1979-07-13 |
| DE2852851A1 (en) | 1979-06-21 |
| PH14293A (en) | 1981-05-04 |
| CH642103A5 (en) | 1984-03-30 |
| JPS5487688A (en) | 1979-07-12 |
| GB2010274B (en) | 1982-05-06 |
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