CA2069936A1 - Complex ligands for ions in ferroelectric liquidcrystal mixtures - Google Patents
Complex ligands for ions in ferroelectric liquidcrystal mixturesInfo
- Publication number
- CA2069936A1 CA2069936A1 CA002069936A CA2069936A CA2069936A1 CA 2069936 A1 CA2069936 A1 CA 2069936A1 CA 002069936 A CA002069936 A CA 002069936A CA 2069936 A CA2069936 A CA 2069936A CA 2069936 A1 CA2069936 A1 CA 2069936A1
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- flc
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- flc mixture
- complex ligands
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- 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
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3491—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom
- C09K19/3497—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom the heterocyclic ring containing sulfur and nitrogen atoms
-
- 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
- C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
- C09K19/0225—Ferroelectric
-
- 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
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3441—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having nitrogen as hetero atom
- C09K19/3488—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having nitrogen as hetero atom the heterocyclic ring having more than 6 members, e.g. macrocycles, phthalocyanines
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- 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
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3491—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having sulfur as hetero atom
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- 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
- C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
- C09K19/58—Dopants or charge transfer agents
- C09K19/582—Electrically active dopants, e.g. charge transfer agents
- C09K19/584—Electrically active dopants, e.g. charge transfer agents having a condensed ring system; macrocyclic compounds
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- 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
- C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
- C09K19/3402—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom
- C09K2019/3438—Crown ethers
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- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Liquid Crystal Substances (AREA)
- Liquid Crystal (AREA)
- Inorganic Insulating Materials (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Compounds Of Iron (AREA)
Abstract
(57) Abstract A ferroelectric liquid crystal mixture containing two or more components. at least one of which is a complex ligand for ions in particular for cations, is particularly suitable for use in ferroelectric liquid crystal displays.
Description
HOECHST AKTIENGESELLSC~AFT ~OE 89/F 377K Dr. JA/AP
Description Use of complex ligand~ for ions in ferroelectric liquid-crystal mixture~
Switching and display elements containing ferroelectric liquid-cxystal mixtures ~"FLC light valves") are known, ~ -for example from ~P-B 0 032 362. Liquid-crystal light valves are devices which, for example as a consequence of electrical actuation~ modify their optical transmission properties in such a manner that incident light which may be reflected again is modulated in intensity. Examples are conventional watch and calculator displays or liquid cry~tal displays in the office automation and television ~iectors. However, the6e al80 include light shutters as are employed in photocopiers, printers, welding goggles, polarized spectacles for 3D viewing, etc. Spatial light modulators are also applications for liquid-crystalline light valves (see Liquid Crystal Device Handbook, Nikkan ;~
Kogyo Shim~un, Tokyo, 1989; ISBN 4-526-02590-9Ç 3054 and the paperq cited therein). `
Electrooptical swit~hing and display elements generally contain at lea~it one alignment layer, electrode~, outer .
plates (for example made of gla89~, and one polarizer if they are operated in gue~t-hogt or reflective mode or two ;-~
polarizers if transmiesive bire~ringçnce mode i5 used.
~he ewitching and display elements may, if desired, !;, ~ ~
contain further auxiliary layers, ~uch as, for example, i~ -diffusion barrier or insulation layers~
: ' The alignment layers, which comprise an organic (for example polyimide, polyamide or polyvinyl alcohol) or ~ r~
inorganic (for example SiO) material, together with a spacing between the outer plates which i~ chiosen to be su~ficiently emall, bring the FLC molecule~ into a configuration in which their longitudinal axes are ., r ~ 3 ~
Description Use of complex ligand~ for ions in ferroelectric liquid-crystal mixture~
Switching and display elements containing ferroelectric liquid-cxystal mixtures ~"FLC light valves") are known, ~ -for example from ~P-B 0 032 362. Liquid-crystal light valves are devices which, for example as a consequence of electrical actuation~ modify their optical transmission properties in such a manner that incident light which may be reflected again is modulated in intensity. Examples are conventional watch and calculator displays or liquid cry~tal displays in the office automation and television ~iectors. However, the6e al80 include light shutters as are employed in photocopiers, printers, welding goggles, polarized spectacles for 3D viewing, etc. Spatial light modulators are also applications for liquid-crystalline light valves (see Liquid Crystal Device Handbook, Nikkan ;~
Kogyo Shim~un, Tokyo, 1989; ISBN 4-526-02590-9Ç 3054 and the paperq cited therein). `
Electrooptical swit~hing and display elements generally contain at lea~it one alignment layer, electrode~, outer .
plates (for example made of gla89~, and one polarizer if they are operated in gue~t-hogt or reflective mode or two ;-~
polarizers if transmiesive bire~ringçnce mode i5 used.
~he ewitching and display elements may, if desired, !;, ~ ~
contain further auxiliary layers, ~uch as, for example, i~ -diffusion barrier or insulation layers~
: ' The alignment layers, which comprise an organic (for example polyimide, polyamide or polyvinyl alcohol) or ~ r~
inorganic (for example SiO) material, together with a spacing between the outer plates which i~ chiosen to be su~ficiently emall, bring the FLC molecule~ into a configuration in which their longitudinal axes are ., r ~ 3 ~
parallel to one another and in which the smectic planes are perpendicular or inclined to the alignment layer. In this arrang~ment, the molecules, as is known, have two equivalent orientations between which they ean be switched by applying a pulsed electrical field, i.e. FLC
displays are capable of bistable switching. The ~witch-ing times are inv rsely proportional to the spontaneous polarization of the FLC mixture and are in the range of micro~econds.
The principal advantage of ~uch FLC displays over the LC
displays which are still the ones predominantly encoun-tered hitherto in industry i~ regarded as being the multiplex ratio which can be achieved, i.e. the maximum numher of lines which can be addressed in time-sequential mode ("multiplex mode"), which, in contrast to LC dis-play~ is virtually unlimited in the case of FLC di~plays.
This electrical addres~iny is e~sentially based on the pulse addressing mentioned above and described in illus-trative terms in SID 85 Dige~t p. 131 (1985).
However, during further development of FLC displays in recent years, a disadvantage has b~come apparent in that said pulse addre~sing frequently only results in repro-ducible switchiny between the two stable states in the case of sufficiently low values for the spontaneous polarization. For ex~mple, it can be observed that an FLC display which has been in one of the two stable states for a relatively long time ("stationary image") can be switched into the other state only with great difficulty, i.e~ only with a high amplitude, very long pul~e duration of the applied voltage or after repeated application of the pulses. ~hi optical hysteresis behavior results, in picture dicplay~, in an image which has been inscribed over a relatively long period being visible in the subsequent image as a ~hadowy ghost image.
This observation of optical hysteresi~ is more pronounced the higher the spontaneous polarization of the FLC
mixture, and depends, in addition, on the nature and ~ 3 ~ 3 ~ ~
thickness of the alignment layer.
This effect i8 apparent and interfering even at only low spontaneous polarization. At particularly high values (Ps > 35 nC cm~2), switching i8 generally no longer pos-sible at all via pulse addressing. Since, as is known, very short ~witching times can only be achieved through high polarization, this prevents, in particular, the use of very rapid FLC mixtures. One of the hypotheses on the cause of the phenomenon of optical hysteresis is that ionic impurities in the FLC mixture are responsible (cf.
for example B.J. Dijon et al., SID conference, San Diego 1988, pages 2 - 249). The solutions known hitherto of a) direct contact between the FLC mixture and the electrodes and b) complex cleaning have not yet re~ulted in complete success; the first method is very complex due to the necessity for involving specific measures to avoid electrical shortcircuits, and the second requires a specific type of cleaning for each component of a mixture and complex and expensive handling of the FLC mixture.
A further ~olution has been propo~ed by M. Nitta et al.
(Japanese Jo~1rnal of Applied Physics 27 (198~) 1447), in which charge-transfer complexes (CTCs) are employed to improve the optical switching behavior.
A further serious disadvantage of FLC displays is, in addition, that they have, in the non-addressed tate, (u~ually) unde~ired non-uniformity of the director (i.e.
the preferential direction of the molecule) and one or mor~ so-called twist ~tate~ ~see M.A. Handschy, N.A. Clark, S.T. Lagerwall; Phys. Rev. Lett. Vol. 51, 471 (1983): M. Glogarova, J. Pavel; J.Phys~ (France) Vol. 45, 143 (1984): N. Higi, T. Ouchi, ~. Takezoe, A. Fukuda; Jap.
J. Appl. Phy Vol. 27, 8 (1988)). In the memory state and in multiplexed mode thi~ non-uniformity results in a considerable reduction in contrast in the display, in particular because the opaque ~tate becomes considerably les~ dark ~gray dark state). The contrast is the ratio betweenthe transmis~ionsin the bright and dark switching ~ . .
' '' -,'' , ~$~3~
states. The appearance of twist states i5, in addition, frequently associated with wavelength dispersion, which can result in false colors in the display. Currently, maximum contrast values of from 5 to 10 are given for FLC
displays. An exception is displays in which the align-ment layer used is SiO vapor-deposited at an angle and which have higher values for the contrast, but are rarely encountered due to the considerable costs for applying the SiO layer.
It has already been attempted to suppress the appearance of interfering twist states through a suitable choice of alignment layers, but hitherto only with unsatisfactory results. The virtually uniform states which sometimes occur (for example when SiO vapor-deposited at an angle is used) very frequently proved to be unstable and dropped back into twist state. The occurrence of twist states appears to be favored by high spontaneous polari-zation, in particular when ferxoelectric-crystal mixtures are used (in this respect, cf. M.A. Handschy and N.A.
Clark; Ferroelectrics 59, 69 (1984)). However, such mixtures are particularly suitable since they reiult in short switching times.
The object of the present invent;on i9 to provide FLC
mixtures, compri~ing at lea6t two components, which exhi~it only negligibly small optical hysteresis, and associated ghost imagei~, or none at all, and do not orm twist states, but instead uniform ~tates and thus result in high optical contrast.
Surprisingly, it has been found that addition of complex ligands for ~ons to FLC mixtures can suppr ss the above-described ghost image~ and the twist states. It i~ even possible to cause switching of FLC mixtures having par-ticularlyhigh value~for spontaneouspolarization ~Ps~35/
in particular > 50 nC cm~2), which are otherwise incapable of ~witching in multiplex mods A further advantage of the invention is the sudden improvement in contrast.
2 ~
A further essential advantage is that FLC displays, which frequently become inoperable after relatively long stor-age, remain switchable even after a relatively long period by mean~ of the FLC mixtures employed according to the invention. Since ionic impurities are responsible for thP appearance of gho~t images, and since these can be eliminate~ by addition of an excess of complex ligands, even ionic impurities introduced subsequently and arising, for example, through diffusion from the alignment layer have no adver~e consequence~.
The FLC light valve~ according to the invention contain a ferroelectric liquid-crystalline mixture (FLC mixture) which contains at least one compound which is a complex ligand for ions.
. ~ .
The switching and di~play devices have the following components: a liquid~cry6talline mixture according to the invention, outer plate~ (for example made of gla~s or plastic) coated with tran~parent electrodes (two elec~
trodes), at least one alignment layer~ spacers, ~ sealing frame, polarizers and, for color displays, thin colored filter shee~. Other possible components are anti-reflection, passivation, leveling and barrier layers and electrically non-linear elements, such as, f or example, thin-film tran istors (~FT) and metal-insulator-metal ~MIM~ elements. ~he ge~eral construction of liquid-crystal displays has already been described in detail in the relevant monographs (for example E. Kaneko, "Liquid Cry3tal TV Di~plays: Principles and Applications of Liquid Cry~tal Display~", KTK Scientific Publishers, 1987, pages 12 to 30 and 163 to 172).
: . . ~ . - ...
Of FLC light valve~, witching devices which are ad-dressed in multiplex mode are preferred. Particular preference i9 given to liquid-crystal cells which operate in SSFLC ("sur~ace ~tabilized ferroelectric liquid crystal") mode and in which the c211 thickness (i.e. the di~tance between the outer plate~) i3 from 1 to 20 ~m.
`; '.";' .
r~ 2 ~ 3 ~
Particular preference is given to a cell thickness of from 1 to 10 ~m, and, in birefringence mode, in partic-ular of 1.2 to 3 ~m.
In addition, the compounds according to the invention can advantageously be employed during operation of an SSF~C
display in guest-ho~t mode, where the optical e~fect is not attributed to birefringence phenomena but to aniso-tropic absorption by dichroic dyes dis~olved in an FLC
matrix.
The compounds according to the invention suppre~ the occurrence of optical hysteresis and/or twist ~tates for various geometries of the Ymectic layers in the SSFLC
cell (~ee, for example, H.R. DUbal et al., Proc. 6th Intl~ Symp. on Electrets, Oxford, E~gland 1988). In particular, this applies to the virgin liquid-crystal texture, in which the smectic layers have a chevron geometry, and for the bookshelf or quasi-bookshelf geometry, in which the ~mectic layer~ are perpendicular or virtually perpendicular to the glass plates (see Y.
Sato et al., Jap. ~. Appl. Phys., Vol. 28, 483 (1989)).
The use of the FLC mixtures accordi.ng to the invention in this bookshelf geometry i8 particularly advantageous ~ince this results not only in good dark states, but also in high tran~mi sion of the bright state due to the large effective ~witching ~ngle.
In addition, it has been shown that the complex ligands according to the invention facilitate field-induced production of a homogeneous qua3i-bookshelf ~eometry in the FLC mixtures (Y. Sato et al., Jap. J. Appl. Phys.
Vol~ 28, 483 (19~9)).
The liquid-crystal mixtures generally comprise 2 to 20, preferably 2 to 15, components, including at least one complex ligand for ions. The other constituents are preferably selected from known compound~ having nemat;.c and/or cholesteric and/or tilted smectic phases. These . ' ^' ~ ~ $ ~
include, for example, Schiff's bases, biphenyl~, ter- :
phenyls, phenylcyclohexanes, cyclohexylbiphenyls, pyrimi-dines, difluorophenyls and esters of p-alkylbsnzoic acids. Particular preference i~ given here to mixtures which contain derivatives of phenylpyrimidine, phenyl-pyridine, or phenylthiadiazol~. In general, the commer-cially available liquid-crystal mixtures, even before addition of the compound(s) according to the invention, ::.; .
are in the form of mixtures of various components, of which at least one ie m~sogenic, i~e. a compound which, in derivatised form or in a mixture with certain com- ~
ponPnts, exhibits a liguid-crystal phase. ~: .
The FLC mixture preferably has an Sc phase in the service temperature range and the phase sequence of the mixture~ -on cooling i~ N ~SA ~SC or IIN ~Sc. ::
The complex ligands employed to reduce optical hysteresis -and to eliminate twist state~ are preferably electrically :::
neutral compounds. :~
These compounds preferably contain at least two nitrogen ~
and~or oxygen and/or sulphur and/or phosphorus donor ` ~-centers and are preferably complex ligands for cationsO :-:, These compounds are particularly preferably medio- or macrocycles (8 to 12 ring members = mediocycles, >13 ~
macrocycles according to Rompps Chemie Lexikon [Rompp'si:.
Lexicon of Ch0mi~try] 8th Edition, Franksche Verlagsbuch~
handlung, Stuttgart, 1989).
';~'' ':.: . ' The compounds used in FLC mixtures according to the invention are, in particular, cryptandQ, coronands and.~ ;
podands, preferably in concentration~ of from 0.01 to 10 :;
mol-%, based on the total mixture. Very particular preference is given to cyclic compounds aontaining 16 or more ring member~. Bicyclic ligands of the cryptand type are preferred.
'' ' ~
r~ 8 ~ 3 ~
For a classification of said complex ligands, reference is made to E. Weber and F. V~gtle, Inorganica Chimica Acta, Vol. 45, (1989) L65-L67. The ligand topologies listed therein are reproduced below:
open-chain cyclic spherical ~ , D~/3~C
~,. ~ ., pod~nd coron~nd cryp~nd D: donor D Y o: crown ~tbor D: brldg~h~d ~torl -.. ...
~~ ;
A D
E G
(~ (O ~ ¢~
c r H K :
A-C: erdlc (p~: 9-F: n~on~ercllc ~c~ron~xl)~
G-H: ~Icrdic ~ort~, ~ypw~ orrp~
Typical examples of coronands are:
'~
o ~ ~~,Jo~
'~:
.
9 2 ~ 3 ~ -~o o) ,~ o~ ~, o~o o ~
. o o ~o o ~ o ~C~ o~ . ~
~oJ \~oJ ~ ,o~
~o~ ~~~ o o~ .. '~.
~~J~ v~ 11~_o ~
r~O ~ o~ o~
~o o~3 ""'"
o~ o ~_oJ ~oJ ,~
C~`t, 1~ ,._ R
~o o~ ~ ~ 3 ~
~ .... ......
~ 0 0 ~ ~ s s ~ ~ ~ Ht~
~o~ oJ ~oJ
~`-~ ' ~o ';
~ ~ oJ~
)1~ ~0 0~ :
o P~f~jh ~0~0~
D _~ )lrh V )'h o~ ~ ~
,O ~';'~' '' 0 - ~ 3 ~3 ç~ç3 f~
~o o~ ~o O ' b`b ~ ~
~) ~~ (5 5) ~
~oJ ~J
~o~
~fS ~J ~N
o~ D
r--OR f~ ~3 ~3 ~o o3 ~''J
~ ~
~? o~'o s s ~o~
~ OXO~JO~ ~5 5~~,o~
V
A ~
-- 1 1 2 ~
.. :
~ o~
n ~
rl ~ ~ ' ~
~2 ". , , ,::
1. 3 I~,N
~5~ SS~
SJ
~;
- 12 ~ 3 5~5 ~ X- CO
~ X 0~ S~ CI
r O r~
¢~0 0~ ¢~0 o~ ¢~ c~-o~
f~o~
¢~~~ ~ ~-f~ o ~ `^~
_oJ ~ o~ ~o~
, or~'~o @~o ~ (~0 o~J
.'~ ~;' "' " ` - ''"' - 1 3 - ~ :
--S--~ f"S_~ D--} -~O
~o~J ~-J ~-~
~fS'~ 5~5~ ~,~ ~s~`~~s~
~,sJ ~o~ o~~o~
~s~s~ ~o~3 ~o~o~
~o ~i ~, ~5 ~
~ ~O~ A~ ~~
; ;'~ , ' ,; ,' .
~r~X~
displays are capable of bistable switching. The ~witch-ing times are inv rsely proportional to the spontaneous polarization of the FLC mixture and are in the range of micro~econds.
The principal advantage of ~uch FLC displays over the LC
displays which are still the ones predominantly encoun-tered hitherto in industry i~ regarded as being the multiplex ratio which can be achieved, i.e. the maximum numher of lines which can be addressed in time-sequential mode ("multiplex mode"), which, in contrast to LC dis-play~ is virtually unlimited in the case of FLC di~plays.
This electrical addres~iny is e~sentially based on the pulse addressing mentioned above and described in illus-trative terms in SID 85 Dige~t p. 131 (1985).
However, during further development of FLC displays in recent years, a disadvantage has b~come apparent in that said pulse addre~sing frequently only results in repro-ducible switchiny between the two stable states in the case of sufficiently low values for the spontaneous polarization. For ex~mple, it can be observed that an FLC display which has been in one of the two stable states for a relatively long time ("stationary image") can be switched into the other state only with great difficulty, i.e~ only with a high amplitude, very long pul~e duration of the applied voltage or after repeated application of the pulses. ~hi optical hysteresis behavior results, in picture dicplay~, in an image which has been inscribed over a relatively long period being visible in the subsequent image as a ~hadowy ghost image.
This observation of optical hysteresi~ is more pronounced the higher the spontaneous polarization of the FLC
mixture, and depends, in addition, on the nature and ~ 3 ~ 3 ~ ~
thickness of the alignment layer.
This effect i8 apparent and interfering even at only low spontaneous polarization. At particularly high values (Ps > 35 nC cm~2), switching i8 generally no longer pos-sible at all via pulse addressing. Since, as is known, very short ~witching times can only be achieved through high polarization, this prevents, in particular, the use of very rapid FLC mixtures. One of the hypotheses on the cause of the phenomenon of optical hysteresis is that ionic impurities in the FLC mixture are responsible (cf.
for example B.J. Dijon et al., SID conference, San Diego 1988, pages 2 - 249). The solutions known hitherto of a) direct contact between the FLC mixture and the electrodes and b) complex cleaning have not yet re~ulted in complete success; the first method is very complex due to the necessity for involving specific measures to avoid electrical shortcircuits, and the second requires a specific type of cleaning for each component of a mixture and complex and expensive handling of the FLC mixture.
A further ~olution has been propo~ed by M. Nitta et al.
(Japanese Jo~1rnal of Applied Physics 27 (198~) 1447), in which charge-transfer complexes (CTCs) are employed to improve the optical switching behavior.
A further serious disadvantage of FLC displays is, in addition, that they have, in the non-addressed tate, (u~ually) unde~ired non-uniformity of the director (i.e.
the preferential direction of the molecule) and one or mor~ so-called twist ~tate~ ~see M.A. Handschy, N.A. Clark, S.T. Lagerwall; Phys. Rev. Lett. Vol. 51, 471 (1983): M. Glogarova, J. Pavel; J.Phys~ (France) Vol. 45, 143 (1984): N. Higi, T. Ouchi, ~. Takezoe, A. Fukuda; Jap.
J. Appl. Phy Vol. 27, 8 (1988)). In the memory state and in multiplexed mode thi~ non-uniformity results in a considerable reduction in contrast in the display, in particular because the opaque ~tate becomes considerably les~ dark ~gray dark state). The contrast is the ratio betweenthe transmis~ionsin the bright and dark switching ~ . .
' '' -,'' , ~$~3~
states. The appearance of twist states i5, in addition, frequently associated with wavelength dispersion, which can result in false colors in the display. Currently, maximum contrast values of from 5 to 10 are given for FLC
displays. An exception is displays in which the align-ment layer used is SiO vapor-deposited at an angle and which have higher values for the contrast, but are rarely encountered due to the considerable costs for applying the SiO layer.
It has already been attempted to suppress the appearance of interfering twist states through a suitable choice of alignment layers, but hitherto only with unsatisfactory results. The virtually uniform states which sometimes occur (for example when SiO vapor-deposited at an angle is used) very frequently proved to be unstable and dropped back into twist state. The occurrence of twist states appears to be favored by high spontaneous polari-zation, in particular when ferxoelectric-crystal mixtures are used (in this respect, cf. M.A. Handschy and N.A.
Clark; Ferroelectrics 59, 69 (1984)). However, such mixtures are particularly suitable since they reiult in short switching times.
The object of the present invent;on i9 to provide FLC
mixtures, compri~ing at lea6t two components, which exhi~it only negligibly small optical hysteresis, and associated ghost imagei~, or none at all, and do not orm twist states, but instead uniform ~tates and thus result in high optical contrast.
Surprisingly, it has been found that addition of complex ligands for ~ons to FLC mixtures can suppr ss the above-described ghost image~ and the twist states. It i~ even possible to cause switching of FLC mixtures having par-ticularlyhigh value~for spontaneouspolarization ~Ps~35/
in particular > 50 nC cm~2), which are otherwise incapable of ~witching in multiplex mods A further advantage of the invention is the sudden improvement in contrast.
2 ~
A further essential advantage is that FLC displays, which frequently become inoperable after relatively long stor-age, remain switchable even after a relatively long period by mean~ of the FLC mixtures employed according to the invention. Since ionic impurities are responsible for thP appearance of gho~t images, and since these can be eliminate~ by addition of an excess of complex ligands, even ionic impurities introduced subsequently and arising, for example, through diffusion from the alignment layer have no adver~e consequence~.
The FLC light valve~ according to the invention contain a ferroelectric liquid-crystalline mixture (FLC mixture) which contains at least one compound which is a complex ligand for ions.
. ~ .
The switching and di~play devices have the following components: a liquid~cry6talline mixture according to the invention, outer plate~ (for example made of gla~s or plastic) coated with tran~parent electrodes (two elec~
trodes), at least one alignment layer~ spacers, ~ sealing frame, polarizers and, for color displays, thin colored filter shee~. Other possible components are anti-reflection, passivation, leveling and barrier layers and electrically non-linear elements, such as, f or example, thin-film tran istors (~FT) and metal-insulator-metal ~MIM~ elements. ~he ge~eral construction of liquid-crystal displays has already been described in detail in the relevant monographs (for example E. Kaneko, "Liquid Cry3tal TV Di~plays: Principles and Applications of Liquid Cry~tal Display~", KTK Scientific Publishers, 1987, pages 12 to 30 and 163 to 172).
: . . ~ . - ...
Of FLC light valve~, witching devices which are ad-dressed in multiplex mode are preferred. Particular preference i9 given to liquid-crystal cells which operate in SSFLC ("sur~ace ~tabilized ferroelectric liquid crystal") mode and in which the c211 thickness (i.e. the di~tance between the outer plate~) i3 from 1 to 20 ~m.
`; '.";' .
r~ 2 ~ 3 ~
Particular preference is given to a cell thickness of from 1 to 10 ~m, and, in birefringence mode, in partic-ular of 1.2 to 3 ~m.
In addition, the compounds according to the invention can advantageously be employed during operation of an SSF~C
display in guest-ho~t mode, where the optical e~fect is not attributed to birefringence phenomena but to aniso-tropic absorption by dichroic dyes dis~olved in an FLC
matrix.
The compounds according to the invention suppre~ the occurrence of optical hysteresis and/or twist ~tates for various geometries of the Ymectic layers in the SSFLC
cell (~ee, for example, H.R. DUbal et al., Proc. 6th Intl~ Symp. on Electrets, Oxford, E~gland 1988). In particular, this applies to the virgin liquid-crystal texture, in which the smectic layers have a chevron geometry, and for the bookshelf or quasi-bookshelf geometry, in which the ~mectic layer~ are perpendicular or virtually perpendicular to the glass plates (see Y.
Sato et al., Jap. ~. Appl. Phys., Vol. 28, 483 (1989)).
The use of the FLC mixtures accordi.ng to the invention in this bookshelf geometry i8 particularly advantageous ~ince this results not only in good dark states, but also in high tran~mi sion of the bright state due to the large effective ~witching ~ngle.
In addition, it has been shown that the complex ligands according to the invention facilitate field-induced production of a homogeneous qua3i-bookshelf ~eometry in the FLC mixtures (Y. Sato et al., Jap. J. Appl. Phys.
Vol~ 28, 483 (19~9)).
The liquid-crystal mixtures generally comprise 2 to 20, preferably 2 to 15, components, including at least one complex ligand for ions. The other constituents are preferably selected from known compound~ having nemat;.c and/or cholesteric and/or tilted smectic phases. These . ' ^' ~ ~ $ ~
include, for example, Schiff's bases, biphenyl~, ter- :
phenyls, phenylcyclohexanes, cyclohexylbiphenyls, pyrimi-dines, difluorophenyls and esters of p-alkylbsnzoic acids. Particular preference i~ given here to mixtures which contain derivatives of phenylpyrimidine, phenyl-pyridine, or phenylthiadiazol~. In general, the commer-cially available liquid-crystal mixtures, even before addition of the compound(s) according to the invention, ::.; .
are in the form of mixtures of various components, of which at least one ie m~sogenic, i~e. a compound which, in derivatised form or in a mixture with certain com- ~
ponPnts, exhibits a liguid-crystal phase. ~: .
The FLC mixture preferably has an Sc phase in the service temperature range and the phase sequence of the mixture~ -on cooling i~ N ~SA ~SC or IIN ~Sc. ::
The complex ligands employed to reduce optical hysteresis -and to eliminate twist state~ are preferably electrically :::
neutral compounds. :~
These compounds preferably contain at least two nitrogen ~
and~or oxygen and/or sulphur and/or phosphorus donor ` ~-centers and are preferably complex ligands for cationsO :-:, These compounds are particularly preferably medio- or macrocycles (8 to 12 ring members = mediocycles, >13 ~
macrocycles according to Rompps Chemie Lexikon [Rompp'si:.
Lexicon of Ch0mi~try] 8th Edition, Franksche Verlagsbuch~
handlung, Stuttgart, 1989).
';~'' ':.: . ' The compounds used in FLC mixtures according to the invention are, in particular, cryptandQ, coronands and.~ ;
podands, preferably in concentration~ of from 0.01 to 10 :;
mol-%, based on the total mixture. Very particular preference is given to cyclic compounds aontaining 16 or more ring member~. Bicyclic ligands of the cryptand type are preferred.
'' ' ~
r~ 8 ~ 3 ~
For a classification of said complex ligands, reference is made to E. Weber and F. V~gtle, Inorganica Chimica Acta, Vol. 45, (1989) L65-L67. The ligand topologies listed therein are reproduced below:
open-chain cyclic spherical ~ , D~/3~C
~,. ~ ., pod~nd coron~nd cryp~nd D: donor D Y o: crown ~tbor D: brldg~h~d ~torl -.. ...
~~ ;
A D
E G
(~ (O ~ ¢~
c r H K :
A-C: erdlc (p~: 9-F: n~on~ercllc ~c~ron~xl)~
G-H: ~Icrdic ~ort~, ~ypw~ orrp~
Typical examples of coronands are:
'~
o ~ ~~,Jo~
'~:
.
9 2 ~ 3 ~ -~o o) ,~ o~ ~, o~o o ~
. o o ~o o ~ o ~C~ o~ . ~
~oJ \~oJ ~ ,o~
~o~ ~~~ o o~ .. '~.
~~J~ v~ 11~_o ~
r~O ~ o~ o~
~o o~3 ""'"
o~ o ~_oJ ~oJ ,~
C~`t, 1~ ,._ R
~o o~ ~ ~ 3 ~
~ .... ......
~ 0 0 ~ ~ s s ~ ~ ~ Ht~
~o~ oJ ~oJ
~`-~ ' ~o ';
~ ~ oJ~
)1~ ~0 0~ :
o P~f~jh ~0~0~
D _~ )lrh V )'h o~ ~ ~
,O ~';'~' '' 0 - ~ 3 ~3 ç~ç3 f~
~o o~ ~o O ' b`b ~ ~
~) ~~ (5 5) ~
~oJ ~J
~o~
~fS ~J ~N
o~ D
r--OR f~ ~3 ~3 ~o o3 ~''J
~ ~
~? o~'o s s ~o~
~ OXO~JO~ ~5 5~~,o~
V
A ~
-- 1 1 2 ~
.. :
~ o~
n ~
rl ~ ~ ' ~
~2 ". , , ,::
1. 3 I~,N
~5~ SS~
SJ
~;
- 12 ~ 3 5~5 ~ X- CO
~ X 0~ S~ CI
r O r~
¢~0 0~ ¢~0 o~ ¢~ c~-o~
f~o~
¢~~~ ~ ~-f~ o ~ `^~
_oJ ~ o~ ~o~
, or~'~o @~o ~ (~0 o~J
.'~ ~;' "' " ` - ''"' - 1 3 - ~ :
--S--~ f"S_~ D--} -~O
~o~J ~-J ~-~
~fS'~ 5~5~ ~,~ ~s~`~~s~
~,sJ ~o~ o~~o~
~s~s~ ~o~3 ~o~o~
~o ~i ~, ~5 ~
~ ~O~ A~ ~~
; ;'~ , ' ,; ,' .
~r~X~
3 ~
Typical examples of cryptands are.
o ~ ; $
~N--1 ?~0~,0~ J
~ x~ .
~ ~o~
::
~ ~ ~
0 ~ ~ ~, 2 ~ 3 ~ ~
- 1 5 - ~
:- ~ .. ..
O O . . .
~ o ?
o~Jo . ~
.. ~, ., Q ~
~o o~ ~s s~ ~ ~
,o~,oJ~ "O~,o~
o~o 5~ 5 ~_~
.. . :
,' . "~ .
.;, ;"':~ , .
f Or~o~ N~ : -N N ) r O ~ O -~
o ~_~ O ~ ~ ~ O
: ~ ~, J ` ~ :
~, r~
N
~ ~r~ ~ ".' N NJ ~ ~
> .' " ' ` .
: :~ .;: '~ ' ' ~ " '' ' ~ 16 - ~ 3~
r~s~ r'~ ,, N S S N~ ~NrS S--N) N N N O~N X~ O
~o ~~ o~ ~x d--o x~ X~CH
~ ~~ 3 x~ phenylene N o ~ N~-~o~ tl X-~H
Characteristic representatives of podands are ~o ~
'N ~0 o o o~
SJ s fl ~ n-~,H
t 0~ o~ ~ 7 ' . .:
~o O ~--~r~A~ :, - . .~.
,05~ X: O O O S~
O ~.C~ 0~ ~ ~ ~ O--R
R~ C~
0~ ~., .' C~O O 0 ~ H ~ ~(C~ OCOOC;~ H~
A.C~ a~ 4~~ inter alia :::
~~ ~ r-C~ 7LC~ In~
:"'.~ . :.' .. . .
.. .~ ' .
,, ' ,' ~ "
' '~''" '' ` ' ' .
' ' ' ' ' ' ' ~ ''''.', ,;:! ;. . ~ ," , . ,, .',; . !' t~ ~
~-0~ ~ ": ' "
o o ~l`N~ ~--~ o D O ~ O-CI~
~-~\o~o~o~or~\ 0~o~o~o "'.' ;~
0 o/~
'.''' ' f~~ ~:
0~cc)~ ~ ~C~13 (-o~o-3) ' ~o o'C~ ~ ":`~
~, o J ~ R f~ ~ ~
n ~ 0-2 ~J R ~ H, OCtl~, NO2, c~ ~0 COOH. COOEt.
CO~HR, IcHCOR ~:
~ ' .'.',; ,,, "
cf`t~
,,~ '~ ~ a H, a~
~_O O) ~_~
~_ ''; ;'~ ' '' 3 jr~
Particular preference is given to complex ligands which complex alkali metal and alkaline ear~h metal ions.
Macrocycles, preferably having a ring size of 1~, which contain at least two nitrogen atoms and optionally 5 or 5 oxygen atoms as donor centers and have bicyclic or tricyclic structure have proven particularly uitable.
The complex ligands are preferably employed in F~C
mixtures which contain, as chiral components, oxirane ether and/or oxirane ester and/or dioxolane derivatives.
Of chiral dopes having two centers of chirality, both the cis- and trans-configured compounds are suitable (see DE-A 36 33 968 and DE-A 37 18 174). Other dopes which are ~uitable for use with the complex ligands employed according to the invention are described in DE-A
39 07 601, DE-A 38 32 502t DE-A 38 32 503, DE-A
38 27 599, DE-A 37 13 273, DE-A 37 03 228l DE-A
36 30 933, DE-A 36 18 213, DE-A 36 17 826 and DE-A
36 20 049.
:- ~ .;.
Since the complex ligands used according to the inv ntion make it possible to use ferroelectric liquid-crystal mixtures of high spontaneous polarization, and since these are distinguished by particularly short switching time~, the complex ligands are preferably u~ied in FLC
mixtures having a spon~aneous polarization ~ 30 ~C cm~2, a~i described, for example, in DE-A 39 09 354.
. . . .
It has be~n ~ihown that ~he complex ligand according to the invention alway~ re~ult in an increa~e in the elec-trical conductivity. This is particularly pronounced if the complex ligands employed are cryptands. In thi~
case, the optical hy~tereRiis and the twist ~tates are eliminated particularly efficiently.
If the FLC light valves are addressed in multiplex mode, the ratio (~ bias) betwsen the line voltage and the gap voltage (data pulse level) i~ an important parameter with a crucial effect on the contra~t in operation (see ;' .~ ' 3 ~ ~ :
-- 19 -- :
T. Harada et al., Japan Display ConferPnce 1986). High bias values prove to be particularly favorable here. Of the complex ligands accordiny to the inventiOn, the cryptands, in particular, result in extraordinarily high bias values.
In a further embodiment, the mixtures according to the invention contain a plurality of different complex ligands, each of the various complex ligands beinq able to preferentially complex certain cations (on the ques-tion of seleativity, see, for example, N. Hiraoka, Crown Compounds - Their characteristics and applications, Kodansha Ltd , Tokyo, 1982, p. 67 ff.). The FLC mixture here again contains a total of from 0.01 to 10 mol-% of complex ligands. Since the introduc~ion of complex ligands is frequently associated with problems of solubi-lity in the FLC mixture or effects on the liquicl-crystal-line phases, it may be advantageou~, for problem-free use of the complex ligands, to preferably use mixtures of coronands and cryptands. In this case, too, a total of from 0.01 to 10 mol-% are employed.
. :.'' For the alignment of the liquid crystal, organic materi-als containinq a polyimide or polyamide as the base component are generally employed (in this reipect, cf.
Mol. Cryet. Liq. Cryst. 109, I (1984)). However, it has been shown that an alignment layer comprising SiO2 is particularly suitable for the FLC mixtures according to the invention. The SiO2 filmæ are preferably obtained by spin-coating or 3praying or by dipping into or~anosilicon compounds, with ~ub~equent thermal treatment at from 100 to 400C. The alignment capacity of the SiO2 films is achieved in a conventional manner by rubbing the film (in this respect, cf. DE-A-28 52 395, EP-A 0 046 401, DE-A
27 22 900). A further advantage of the rubbed Si02 filmR
is the significantly improved insulation capacity com-pared with polyimides and the high transparency, even forthick cells.
:
, , ; ,, , " , , , : " ~ : "~
2 ~
The mixtures describ2d are particularly suitable as ,.
components ~or liquid-crystal, switching and display devices, as described at the outset.
The invention is illustrated in greater detail by the examples below~
Exzmples In the examples below, the cr~ptands and coro~ands are -: :
employed in concentrations of from 0.5 mol-% to 1.5 : :
mol-~. Examples of coronands and cryptands are the : .~
compounds Kl to K12 below. : . ~.
~C~) ''';''~"'''`''"' ~ 0~_~ ~ Rl .;;. .:
'~''' ' ' ' .":
1,7,10,16-Tetraoxa-4,13-diazacyclooctadecane :-~
(Kryptofix~ 22) `~
;''~'.;:- ' ,:
21 lO ~ N C10~21 . -.
K2 :: -.'::' '.. " ' 4,13-Didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (~rYptofix~ 22 DD) 10~21 ~ ,,.
~vO~ R3 ~;-5-Decyl-4,7,13,16,21-pentaoxa-1,10-diazabiCyclo[8.8.5]-tricosane (Kryptofix~ 221D) .~
N ~v~_ N ~ :
~ ~ O ~ X4 :.
,' ,':,~:, 4,7,13,16,21-Pentaoxa-l,10-diazabicyclo[8.8.5]-tricosane (Kryptofix~ 221) ' "'' '',, ' ;", ',' ' ' '" ',"''' , '~' ','" " ' ., ' '';,''; ,,," '''' ' ' ''. ' " ,'' `' '"
/~
~ ~ O ~ O ~ ~5 2,5,8,15,18,21-Hexaoxatricvclo[20.4Ø 09 14 ] hexacosane ~ ;
J'~o/~
r~f O
~ ~ O J K6 1,4,7,10,13-Pentaoxa[13)orthocyclophane o~ J-\ o . ~ ~ ~
C O ~ K7 1,4,7,10,13,16-Hexaoxa~16]orthocyclophane N ~ ~ ~ ~ K8 ~/ ~, , .4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexaco- : :
~ane (~ryptofi~ 222) 10 K9 ::
0 ~0~0\~0 ' ', ''~
2~5~8~ 8~2~24~27-octaoxatricyclo~26.4.o.ol2~7]dotria contane ~ CX2-N ~ ~ ~ C 2 ~ ~10 4,13~Dibenzyl-1,7,10,16-tetxaoxa-4,13-diazabicyclo-octadecane N N ~ 2 ~ -COOR
Kll \~/
~ 2 ~ 3 ~
1-[4-Carboxybenzyl]-1,4,7,11-tetrazacyclotetradecane ~:
~_ O~ '-~ O ~~
1,4,7,10,13,16-Hexaoxacyclooctadecane (18-crown-6) In the examples, three liquid-crystal base mixtures A, B ~
and C, various chiral dopes and an FLC mixture containing :- .
a dye (guest-host system) are employed.
LC mixture A contains the following three components (in ;~
mol-%):
-" :~,' ' 33~7 ~21ClO-e~ LOL 0 ~6 ~13 ~A 1) 4~25 ~17C8'D' ~ .CO-O~ C6~3 (A 2) ~ -~
' '' ' ~' 2~ 00 ~17C8-Ob ~ ~ (A 3) The mixture exhibits the following phase sequences ~ :
Sc 72 5~ 74 N 88 I
LC mixture B contains the following eight components (in mol~
17C8~ ~ C8R17 11.67 ~17Ca'~ -OC4X9 ':' '' " ' '' ' ' 2~3~ ~3 9.26 N1~6-o~ ~-ocloN2l 1 7 50 1-25C~2~ ~~QC~CS~11 17.70 N17C6- ~ ~ ~ -C6N13 11.80 N17C8- ~ - ~ 'C10N21.
15.88 N17c8- ~ ~ -C3N~7 1_.06 ~17~8~- ~ ^ ~ e6H13 '''"," .' The mixture exhibits the following phase sequence~
S' 69 SA 76 N 92 I
LC mixtur~ C contains the following eight components (in :~
~ol-%)~
13.39 N~7C9-- ~ ~ '-C~513 4~49 H1~C8' ~ '~8 ~ :
~ 3 ~ ~:
7;~ R17C~ ~ OC4X~
8.14 ~1~C8-O ~ ~ -C10~2' h~ '~"''"
8.16 H17C8_O. ~ ~ '~12~Z5 19.04 N~1C10 ~ ~ ~ ~'~' ~ C5N~
12,~0 N17~8~ C1ZN25 20.GO ~C~ ~C6~13 The miXtUr2 eXhibit5 the fO11OWing PhaSe SeqUenCe:
SC 71 SA 78 N ~3 I .
Examples of the dopes employed are the following com~
psunds: .
C~H17--~ ~ e--P ~. . .
5Dope D1 2 . .
~S) ,.
Dope D2 C8~17- -~ O~ CO ~ 3X7 O~,~50~
2 ~ 3 ~ - :
, ~, . ...
: 25 .
D~e D3 C~17- ~ tS)~
Dope D4 9 19 ~ ~ 0-C0-C~- ~ (25,3S) : Dope D5 C~3 ~CH3 C8~Y 7-0(X~o. ~CB2)2-C*X' t~2)2^~c~3 "' ' , (S) ',. ,', ~ ' The following examples according to the invention are - ~
produced from said LC base mixtures, dopes and additiYes r X1 to K12, taking into account ~he above data: :
Example 1 ' :~
As described at the outset, twist states result in a -~
considerable reduction in contrast, in particular because -.
the opaque state becomes consider:ably less dark. Com- `
pared with uniform states, twist states additionally have a smaller angle ~2 o~s~) between the two switching states.
Since the transmission in the bright switching state is :
proportional to sin2 ~4 9.rs) and 2 ~.~s should ideally be 45, the brightness of a display also decreases if 2 ~r~
is small. In the chevron texture, compared with the ~:.
bookshelf geometry, a reduction in the switchiny angle is ~:~
also obtained, as a conseguence of the specific layer structure.
The formation o~ twist states results in small angles .
between the memory states and gray dark states not only in FLC mixtures, but also in LC mixtures having achiral, ~; 2 ~
tilted smectic phases.
In order to suppress twist states, 2 mol-% of coronand K5 are added to the achiral LC mixture A (Sc pha~e), and the mixture is introduced into a commercially available, 2 ~m ;.~
thick test cell provided with electrodes and having a :~ -rubbed polyimide at the alignment layer (manufacturer E.H.C. Inc., Tokyo). ~he alignment of the liquid ~rystal is achieved by slowly cooling the test cell, the phase sequence described in the introduction occurring. The effect is characterized using the angle (2 ~ofS~ between :~
the two memory states in the chevron te~ture. The angles .. :
are measured by examining the filled test cell under a polarizing microscope equipped with a rotary stag~ with angle scale. The corresponding angle~ of the mixture with and without coronand are shown in Table 1. This angle increases from 20 to 2~ on addition of coronand X5. .
Example 2 FLC mixture M1 ha~ the following composition (in mol-%~: -' ' ~
LC mixture B 78.3 % ::-Dope Dl 4.7 % .
Dope D2 9.0 % ~ ~;.
Dope D3 8.0 ~
and the phase sequence Sc 60 SA 70 N~ 89 I and a spon-taneous polarization of 55 nC cm~2. .;
The effective switching angle (2 ~afr), the transmiasion in the dark and bright 3tates and the optical contrast are mea~ured for various cryptand~ and coronands added to the FLC mixture ~1, in each ca~e in an amount of 1 mol-%. To this end, the measurement cell provided with elec-trodes (manufacturer E.H.C. Inc., Tokyo) containi~g the corre~ponding FLC mixture i8 examined under a polarizing microscope equipped with a rotary ~tage. When the cell . ~ .:
:"
2 ~
is driven, the effective switching angle can be deter-mined by rotatlng the micro cope stage between the two switching states. -The transmi~sion in the bright and dark states is S measured using a photodiode under the polarizing micro-scope. The optical contrast i9 calculated from the ratio between the transmissions in the bright and dark stat~s.
The results are shown in Table 2. After addition of the corresponding cryptands or coronands, FLC mixture M1 exhibits considerably better properties, which is reflec ted in the corresponding measurement results.
Example 3 FLC mixture M2 has the following composition (in mol-%):
LC mixture B 84.0 % ~ -Dope D1 7~7 %
Dope D2 8.3 %
and the phase sequence Sc 63 SA 73 N a1 I and a spon-taneous polarization of 37 nC cm~2. In order to uppress optical hysteresi~, 1 mol-% of the complex ligand R8 was added to the FLC mixture M2. Addition of the cryptand K8 gave the phase ~equence Sc 5 8 SA 7 1 N 7 8 I and a spon-taneous polarization of 36 nC cm~2. Fig, 1 shows the optical switching re~pon~es of the FLC mixture M2 with and without cryptand in teqt cell~ 2.1 ~m thick (manu~
25 facturer E.H.C. Inc., Tokyo), under a polarizing micro-scope. The switching of fhe test cells was recorded using a fast photodiode. Fig. 1 shows pulse addressing (CH1) and the optical tran~mission (CH2) of a test cell filled with FLC mixture M2 at a temperature of 25C and variable pulse intervals. The left-hand side shows the pure mixture M2, while the result~ with 1 mol-% of cryptand K8 are ~hown on the right-hand side.
: . . ., . : , , . ,, , . : , ,. , : . . .
3 ~
- 28 ~
For pulse addressing at a temperature of 25C, bipolar pulses having an overall width of 200 ~s and a height of 4 V/~m were used. The intervals between the pulses were a) 1000 ms, b) 100 ms and c) 20 ms. It can clearly be 5 seen that the FLC mixture containing the cryptand K8 (right-hand side of Fig. 1) exhibits improved switching behavior and is al~o witchable for longer pul~e inter-vals (a). Corresponding photo micrographs of the test cells (Fig. 2) show, for the F~C mixture M2, non-~witch-able region~, which only occur to a consid~rably reducedextent after ~8 has been added. Fig. 2 3how~ photo micrographs of the test cells filled with FLC mixture M2 (left-hand side) and FLC mixture M2 additionally contain-ing 1 mol-~ of cryptand K8 (right-hand side). a) shows the ~table dark state and b) the stable bright state.
The co~stant parameters are field 3trength 4 V/~m, pulse width 200 ~, and pul e interval 50 ms at a temperature o~ 25C.
The following test method wa~ u~edL to obtain a mea~ured quantity for the appearance of gh~ t images in the FLC
displays with the test cell~ used^
Bipolar pul~es of the same polarity sequence and an overall width of 200 ~6 and a height of 4 V/~m are used.
The pul8e interval i5 20 ms. The polarity sequence change~ every 5 ~econds. Fig9 3 shows the wikching behavior on u~e of bipolar pul~ec of the same polarity sequence, which chanqe6 after 5 ~econd~. Even for this pulse addressing, the advantage of the FLC mixture according to the invention can be ~een from the very rapid switching from bright to dark and vice-versa without the annoying appearance of o-called ~mearing effects. Here too the optical transmi~ion at a tempera-ture of 25C of a te~t cell filled with the FLC mixture is plotted against time. a) FLC mixture M2, b) FLC
mixture M2 containing 1 mol-% of cryptand K8.
~$~$
- 29 - . .
Example 4 FLC mixtura M3 ha~ the following composition (in mol~
.. : .
LC mixture C 31.7 Dope D4 7.0 ,:;.
Dope D5 1~3 and the phase sequence Sc 69 SA 75 N~ 82 I. It has a :~ .
pontaneous polarization of -9.6 nC-cm~2.
In this example too, the test scheme described above for characterizing ghost image~ clearly showed the advantages of the use according to the invention of complex ligands for ions, shown in Fig. 4 in analogous manner to that in Fig. 3.
The optical transmis6ion of a test cell filled with FLC
mixture M3 at a temperature of 25C i~ plotted against time. Bipolar pulses of the same polarity 3equence and an overall width of 200 ~s and a .height of 12 V/~m are used. The pulse interval i9 20 m The polarity sequence changes every 5 seconds. a) FLC mixture M3, b) --:
FLC mixture ~3 containing 1 mol-~ of complex ligand K8.
~ere too, the switching ~rom dark to bright takes place instantly and without smearing effects, in contrast to FhC mixture M3 containing no complex ligands.
Example 5 FLC mixture M4 ha~ the following composition tin mol %):
LC mixture C 87.67 %
Dope Dl 4.53 %
Dope D2 2.70 %
Dope D3 5.10 %
and the phase ~equencs Sc 61 SA 69 N 85 I and a spon-taneous polarization of 30 nC cm~2.
2 ~
The cryptands or coronands K8 (0.5 mol-%) and K5 (1.5 ~
mol-%) are added to FLC mixture M4 to give mixture M4'. ; -The test cells used (our own cell construction) are coated both with a conventional polyimide and with a partially fluorinated polyimide a8 the aliynment material.
. : , The mixtures according to the invention are assessed using the effective switching angle, the transmis~ions in the bright and dark states and the op~ical contrast. ~-, '; ' ..
Table 3 shows a comparison between FhC mixture M4 with the modified FLC mixture (M4~). The effective tilt angle and the aseoci~ted transmission in the bright state ,;;~
increase con~iderably. However, the transmission in the `~
dark state al~o drops ~ignificantly, causing an overall drastic increase in the optical contrast. If FLC cells are treated with alternating electrical fields o~ certain field strength and freguency (for example 10 Hz, 15 V/ym)l a change in the smectic layer structure can be ~-;
achieved (book3helf geometry, see Dubal et al. in "Proceedings of the 6th International Symposium on Elektrets", Oxford, England 1988 ~ds. D.K. Das-Gypta and A.W. Pattullo), which are di~tingui~hed by a switching angle close to 45. U~ing this texture, a transmission in the bright state of virtually 100% can thus be ~S achieved. The result~ for the F~C mixture M4 with and `~
without coronands or cryptands are shown in Table 4.
Here too, a considerable improvement in the dark state and thus in the optical contrast are apparent.
FLC mixture M4 and the modified FLC mixture M4' are introduced into two identical, commercially available FLC
cells provided with electrodes tfrom E.H.C.) with align-ment layer~ on both sides comprising SiO~ (vapor-deposition at an angle o~ 83).
,",:' :~.
The cells are subjected at room temperature to alternat-ing bipolar electrical pul~es with an overall duration of ,:~ ' . ' , ~ 3 1 msO From a certain critical pulse amplitude (field strength), the cell filled with the mixture accordiny to the invention switches to and fro between the known bistable and uniform switching states. In the aase of the comparison cell (only M4), by contrast, two twist states occur at these amplitude~, which hardly differ in their optical kransmission capacity and therefore do not give good contrast.
Only at very much higher amplitude~ doe~ the comparison cell (FLC mixture M4 without additive~) also ~witch with high contrast between two unifor~ state~; even here, however, the contrast does not reach the value for the mixture according to the invention. The compari~on is ;
~hown diagrammatically in Fig. 5. The contrast (CR) is plotted against the field strength E 5in V/m). Curve (a) corresponds to the FLC mixture according to the inven-tion, and curve (b) to the FLC mixture M4 without addi-tion of cryptands or coronand~.
. ' ':
Example 6 In separate experiments, 1 mol-% of each of the complex Iigands K5 (FLC mixture 6A), K8 (FLC mixture 6B) and K12 (FLC mixture 6C) are added to FLC mixture M4. ~he ghost image behavior is characterized using the test 3cheme described in Example 3O The ~witching from bright to dark (in chevron geometry) should take place very quickly and without ~mearing effects. The time con~tant with which the bright ~torage state i~ produced on ~witching from dark to bright can be employed as a characteri~tic quantity for assessing a complex ligand. Table 5 ~hows the relative effectivenes~ of complex ligands K5, K8 and K12 in test mixture M4, ~tting the action of K8 (time con~tant of switching) at one.
.
3 l~j - 32 - :
Table 5 FLC mixture Effectiveness ~ ;
6A 0.18 6B 1.00 5C 0 60 :
,, .: , ~ "
The table clearly shows that the cryptands are parti cularly suitable for avoiding optical hystereæis.
Example 7 (guest-host cell) ~dye cell) : 10 A ferroelec~ric mixture M5 according to the invention compri e~ the following 14 components (in % by weight): ~
`.'~, .
`'~;"'' '' ' '":''. ~'' ', ',, :.
:' ': : '' ' ' ~ ;".
8H17~ O- C6~13 11. 8 8~17~ )'CloH21 9. 1 8H17~ ) ' - e~Hl 711 . 4 C3H~ O~ O~C6H13 C~7H17''~-'C3H17 3'3 C8H17~ ~~ ~ O~ C4~g 7 . 6 C2H17''~''CLOH21 7~4 ClOH21 ~ ).C0-(~)-CSN:L:~24 .6 ; 8H17-~) 2 ~ S~,l S .i5 ~3 C3H7~C0-0-~ O CO~C5HLL 2.0 S~;CH~C~I CO-O. ~'O'C6N171,2 J 3 ~ :
- 34 - ~ :
Compound X8 1.5 .; .
Compound K5 1.5 blue, dichroic dye 4.8 which iR ~ioluble in the LC material ;~.
and has the following pha e~i (in ~C): .
..:
X -4.5 Sc 66~3 SA 69.6 N 94 I
This mixture is introduced into a cell (internal plate separation 3.4 ~im~ with polyimide alignment layer~i rubbed parallel and subjected ~or about 3 minutes to field treatment with rectangular pulses of a frequency of 10 Hz and a field strength ~f ~ 10 V/~m~l:
Under a tran~imi~ted light microscope, a polarizing foil i8 oriented at an angle to the temperature-controlled cell BO that light tran~mi~ision is at a minimum (pola~
rizer and preferential alignmient of the molecule~i are crossed. After a eiwitching pulse (8 V/~m~1; 500 ~iS), the molecules adopt a position rotated by 47 relative to this po~ition, and the light is abE~iorbed less ~trongly.
In order to match the illumlnation to the dye, a filter i~ uied during the contra~t meaiurement (manufacturer:
Schott, 75760/632 nm)~ The contrast, i.e. the ratio between the transmis~ion~ in the bright state and dark state i8 measured using a photodiodP and iB 24:1 for thi6 cell.
Aia comparative example, a polyimide-coated cell (inter-nal plate ~eparation of 3.0 ~im) was filled with a mixture which differed from the mixtuire according to the inven-tion only in that it contained no coronands or cryptands.
~he contrait of thi~ mixture, detenmined a~ de~cxibed above, iei 11:1. The u~e of complexing agents accordingly results in a significant improvement in contra~t.
~ ~3 ~ ~ eJ 3 6 This example confirms that coronands and cryptands re~ult in a significant improvement in LC mixtures containing dyes for u~e in guest-host displays.
Example 8 To demonstrate the advantageous properties of the FLC
mixture according to the invention together with SiO
alignment layerR, we have produced our own test cellsO
To this end, gla~s plates coated with a 4 x 4 mm2 elec-trode area comprising indium tin oxide (ITO) were cleaned using an aqueous surfactant olution and 6ubsequently with alcohol and then coated with a dilute organosilicon compound. The application was effected using a spin coater, but other methods, for example printing or dipping, can also be used. The layer, approximately 20 nm thick, was conditioned at a temperature of about ~50C and ~ub~equently rubbed with a velour-like material. The glass plateR obtained in this way were stuck together to form test cell~;. The starting com-pound~ ~or the alignment layers wlere an SiO2-containing material ~uch as, for example, ~Liquicoat (manufacturer:
Merck, Darmstadt) and ~Silan-TPN ~manufacturer: Wacker Chemie, Munich). The test cell~ produced by us were compared with conventional test cells (manufacturer:
E.H.C. In~., Tokyo) ha~ing a polyimide alignment layer.
This was done using FLC te~t mixture M4 to which 1.5 mol--~ K8 had been added. The mixtures according to the invention in combination with an SiO2 alignment layer were assessed using the transmissions in the bright and dark states, the optical contrast, the switching angle 2 ~ U~f and the maximum possible bias ~ratio between l~ne and data voltage). The re~ult~ for chevron and bookshelf qeometries are shown in Table 6. Compared with conven-tional polyimide, SiO2 alignment layers and the FLC
mixtures acaording to the invention give considerably better contrast. A further advantage is the better insulation capacity of SiO2 layers, since electrical shortcircuits are a problem which mu t be taken , ,,,, , . ~,.. ,.. , . ' , J' .!, . ' ,. ' , ' ' ' , ' : .. 'i ., , 3~ 3 ~
Typical examples of cryptands are.
o ~ ; $
~N--1 ?~0~,0~ J
~ x~ .
~ ~o~
::
~ ~ ~
0 ~ ~ ~, 2 ~ 3 ~ ~
- 1 5 - ~
:- ~ .. ..
O O . . .
~ o ?
o~Jo . ~
.. ~, ., Q ~
~o o~ ~s s~ ~ ~
,o~,oJ~ "O~,o~
o~o 5~ 5 ~_~
.. . :
,' . "~ .
.;, ;"':~ , .
f Or~o~ N~ : -N N ) r O ~ O -~
o ~_~ O ~ ~ ~ O
: ~ ~, J ` ~ :
~, r~
N
~ ~r~ ~ ".' N NJ ~ ~
> .' " ' ` .
: :~ .;: '~ ' ' ~ " '' ' ~ 16 - ~ 3~
r~s~ r'~ ,, N S S N~ ~NrS S--N) N N N O~N X~ O
~o ~~ o~ ~x d--o x~ X~CH
~ ~~ 3 x~ phenylene N o ~ N~-~o~ tl X-~H
Characteristic representatives of podands are ~o ~
'N ~0 o o o~
SJ s fl ~ n-~,H
t 0~ o~ ~ 7 ' . .:
~o O ~--~r~A~ :, - . .~.
,05~ X: O O O S~
O ~.C~ 0~ ~ ~ ~ O--R
R~ C~
0~ ~., .' C~O O 0 ~ H ~ ~(C~ OCOOC;~ H~
A.C~ a~ 4~~ inter alia :::
~~ ~ r-C~ 7LC~ In~
:"'.~ . :.' .. . .
.. .~ ' .
,, ' ,' ~ "
' '~''" '' ` ' ' .
' ' ' ' ' ' ' ~ ''''.', ,;:! ;. . ~ ," , . ,, .',; . !' t~ ~
~-0~ ~ ": ' "
o o ~l`N~ ~--~ o D O ~ O-CI~
~-~\o~o~o~or~\ 0~o~o~o "'.' ;~
0 o/~
'.''' ' f~~ ~:
0~cc)~ ~ ~C~13 (-o~o-3) ' ~o o'C~ ~ ":`~
~, o J ~ R f~ ~ ~
n ~ 0-2 ~J R ~ H, OCtl~, NO2, c~ ~0 COOH. COOEt.
CO~HR, IcHCOR ~:
~ ' .'.',; ,,, "
cf`t~
,,~ '~ ~ a H, a~
~_O O) ~_~
~_ ''; ;'~ ' '' 3 jr~
Particular preference is given to complex ligands which complex alkali metal and alkaline ear~h metal ions.
Macrocycles, preferably having a ring size of 1~, which contain at least two nitrogen atoms and optionally 5 or 5 oxygen atoms as donor centers and have bicyclic or tricyclic structure have proven particularly uitable.
The complex ligands are preferably employed in F~C
mixtures which contain, as chiral components, oxirane ether and/or oxirane ester and/or dioxolane derivatives.
Of chiral dopes having two centers of chirality, both the cis- and trans-configured compounds are suitable (see DE-A 36 33 968 and DE-A 37 18 174). Other dopes which are ~uitable for use with the complex ligands employed according to the invention are described in DE-A
39 07 601, DE-A 38 32 502t DE-A 38 32 503, DE-A
38 27 599, DE-A 37 13 273, DE-A 37 03 228l DE-A
36 30 933, DE-A 36 18 213, DE-A 36 17 826 and DE-A
36 20 049.
:- ~ .;.
Since the complex ligands used according to the inv ntion make it possible to use ferroelectric liquid-crystal mixtures of high spontaneous polarization, and since these are distinguished by particularly short switching time~, the complex ligands are preferably u~ied in FLC
mixtures having a spon~aneous polarization ~ 30 ~C cm~2, a~i described, for example, in DE-A 39 09 354.
. . . .
It has be~n ~ihown that ~he complex ligand according to the invention alway~ re~ult in an increa~e in the elec-trical conductivity. This is particularly pronounced if the complex ligands employed are cryptands. In thi~
case, the optical hy~tereRiis and the twist ~tates are eliminated particularly efficiently.
If the FLC light valves are addressed in multiplex mode, the ratio (~ bias) betwsen the line voltage and the gap voltage (data pulse level) i~ an important parameter with a crucial effect on the contra~t in operation (see ;' .~ ' 3 ~ ~ :
-- 19 -- :
T. Harada et al., Japan Display ConferPnce 1986). High bias values prove to be particularly favorable here. Of the complex ligands accordiny to the inventiOn, the cryptands, in particular, result in extraordinarily high bias values.
In a further embodiment, the mixtures according to the invention contain a plurality of different complex ligands, each of the various complex ligands beinq able to preferentially complex certain cations (on the ques-tion of seleativity, see, for example, N. Hiraoka, Crown Compounds - Their characteristics and applications, Kodansha Ltd , Tokyo, 1982, p. 67 ff.). The FLC mixture here again contains a total of from 0.01 to 10 mol-% of complex ligands. Since the introduc~ion of complex ligands is frequently associated with problems of solubi-lity in the FLC mixture or effects on the liquicl-crystal-line phases, it may be advantageou~, for problem-free use of the complex ligands, to preferably use mixtures of coronands and cryptands. In this case, too, a total of from 0.01 to 10 mol-% are employed.
. :.'' For the alignment of the liquid crystal, organic materi-als containinq a polyimide or polyamide as the base component are generally employed (in this reipect, cf.
Mol. Cryet. Liq. Cryst. 109, I (1984)). However, it has been shown that an alignment layer comprising SiO2 is particularly suitable for the FLC mixtures according to the invention. The SiO2 filmæ are preferably obtained by spin-coating or 3praying or by dipping into or~anosilicon compounds, with ~ub~equent thermal treatment at from 100 to 400C. The alignment capacity of the SiO2 films is achieved in a conventional manner by rubbing the film (in this respect, cf. DE-A-28 52 395, EP-A 0 046 401, DE-A
27 22 900). A further advantage of the rubbed Si02 filmR
is the significantly improved insulation capacity com-pared with polyimides and the high transparency, even forthick cells.
:
, , ; ,, , " , , , : " ~ : "~
2 ~
The mixtures describ2d are particularly suitable as ,.
components ~or liquid-crystal, switching and display devices, as described at the outset.
The invention is illustrated in greater detail by the examples below~
Exzmples In the examples below, the cr~ptands and coro~ands are -: :
employed in concentrations of from 0.5 mol-% to 1.5 : :
mol-~. Examples of coronands and cryptands are the : .~
compounds Kl to K12 below. : . ~.
~C~) ''';''~"'''`''"' ~ 0~_~ ~ Rl .;;. .:
'~''' ' ' ' .":
1,7,10,16-Tetraoxa-4,13-diazacyclooctadecane :-~
(Kryptofix~ 22) `~
;''~'.;:- ' ,:
21 lO ~ N C10~21 . -.
K2 :: -.'::' '.. " ' 4,13-Didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (~rYptofix~ 22 DD) 10~21 ~ ,,.
~vO~ R3 ~;-5-Decyl-4,7,13,16,21-pentaoxa-1,10-diazabiCyclo[8.8.5]-tricosane (Kryptofix~ 221D) .~
N ~v~_ N ~ :
~ ~ O ~ X4 :.
,' ,':,~:, 4,7,13,16,21-Pentaoxa-l,10-diazabicyclo[8.8.5]-tricosane (Kryptofix~ 221) ' "'' '',, ' ;", ',' ' ' '" ',"''' , '~' ','" " ' ., ' '';,''; ,,," '''' ' ' ''. ' " ,'' `' '"
/~
~ ~ O ~ O ~ ~5 2,5,8,15,18,21-Hexaoxatricvclo[20.4Ø 09 14 ] hexacosane ~ ;
J'~o/~
r~f O
~ ~ O J K6 1,4,7,10,13-Pentaoxa[13)orthocyclophane o~ J-\ o . ~ ~ ~
C O ~ K7 1,4,7,10,13,16-Hexaoxa~16]orthocyclophane N ~ ~ ~ ~ K8 ~/ ~, , .4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexaco- : :
~ane (~ryptofi~ 222) 10 K9 ::
0 ~0~0\~0 ' ', ''~
2~5~8~ 8~2~24~27-octaoxatricyclo~26.4.o.ol2~7]dotria contane ~ CX2-N ~ ~ ~ C 2 ~ ~10 4,13~Dibenzyl-1,7,10,16-tetxaoxa-4,13-diazabicyclo-octadecane N N ~ 2 ~ -COOR
Kll \~/
~ 2 ~ 3 ~
1-[4-Carboxybenzyl]-1,4,7,11-tetrazacyclotetradecane ~:
~_ O~ '-~ O ~~
1,4,7,10,13,16-Hexaoxacyclooctadecane (18-crown-6) In the examples, three liquid-crystal base mixtures A, B ~
and C, various chiral dopes and an FLC mixture containing :- .
a dye (guest-host system) are employed.
LC mixture A contains the following three components (in ;~
mol-%):
-" :~,' ' 33~7 ~21ClO-e~ LOL 0 ~6 ~13 ~A 1) 4~25 ~17C8'D' ~ .CO-O~ C6~3 (A 2) ~ -~
' '' ' ~' 2~ 00 ~17C8-Ob ~ ~ (A 3) The mixture exhibits the following phase sequences ~ :
Sc 72 5~ 74 N 88 I
LC mixture B contains the following eight components (in mol~
17C8~ ~ C8R17 11.67 ~17Ca'~ -OC4X9 ':' '' " ' '' ' ' 2~3~ ~3 9.26 N1~6-o~ ~-ocloN2l 1 7 50 1-25C~2~ ~~QC~CS~11 17.70 N17C6- ~ ~ ~ -C6N13 11.80 N17C8- ~ - ~ 'C10N21.
15.88 N17c8- ~ ~ -C3N~7 1_.06 ~17~8~- ~ ^ ~ e6H13 '''"," .' The mixture exhibits the following phase sequence~
S' 69 SA 76 N 92 I
LC mixtur~ C contains the following eight components (in :~
~ol-%)~
13.39 N~7C9-- ~ ~ '-C~513 4~49 H1~C8' ~ '~8 ~ :
~ 3 ~ ~:
7;~ R17C~ ~ OC4X~
8.14 ~1~C8-O ~ ~ -C10~2' h~ '~"''"
8.16 H17C8_O. ~ ~ '~12~Z5 19.04 N~1C10 ~ ~ ~ ~'~' ~ C5N~
12,~0 N17~8~ C1ZN25 20.GO ~C~ ~C6~13 The miXtUr2 eXhibit5 the fO11OWing PhaSe SeqUenCe:
SC 71 SA 78 N ~3 I .
Examples of the dopes employed are the following com~
psunds: .
C~H17--~ ~ e--P ~. . .
5Dope D1 2 . .
~S) ,.
Dope D2 C8~17- -~ O~ CO ~ 3X7 O~,~50~
2 ~ 3 ~ - :
, ~, . ...
: 25 .
D~e D3 C~17- ~ tS)~
Dope D4 9 19 ~ ~ 0-C0-C~- ~ (25,3S) : Dope D5 C~3 ~CH3 C8~Y 7-0(X~o. ~CB2)2-C*X' t~2)2^~c~3 "' ' , (S) ',. ,', ~ ' The following examples according to the invention are - ~
produced from said LC base mixtures, dopes and additiYes r X1 to K12, taking into account ~he above data: :
Example 1 ' :~
As described at the outset, twist states result in a -~
considerable reduction in contrast, in particular because -.
the opaque state becomes consider:ably less dark. Com- `
pared with uniform states, twist states additionally have a smaller angle ~2 o~s~) between the two switching states.
Since the transmission in the bright switching state is :
proportional to sin2 ~4 9.rs) and 2 ~.~s should ideally be 45, the brightness of a display also decreases if 2 ~r~
is small. In the chevron texture, compared with the ~:.
bookshelf geometry, a reduction in the switchiny angle is ~:~
also obtained, as a conseguence of the specific layer structure.
The formation o~ twist states results in small angles .
between the memory states and gray dark states not only in FLC mixtures, but also in LC mixtures having achiral, ~; 2 ~
tilted smectic phases.
In order to suppress twist states, 2 mol-% of coronand K5 are added to the achiral LC mixture A (Sc pha~e), and the mixture is introduced into a commercially available, 2 ~m ;.~
thick test cell provided with electrodes and having a :~ -rubbed polyimide at the alignment layer (manufacturer E.H.C. Inc., Tokyo). ~he alignment of the liquid ~rystal is achieved by slowly cooling the test cell, the phase sequence described in the introduction occurring. The effect is characterized using the angle (2 ~ofS~ between :~
the two memory states in the chevron te~ture. The angles .. :
are measured by examining the filled test cell under a polarizing microscope equipped with a rotary stag~ with angle scale. The corresponding angle~ of the mixture with and without coronand are shown in Table 1. This angle increases from 20 to 2~ on addition of coronand X5. .
Example 2 FLC mixture M1 ha~ the following composition (in mol-%~: -' ' ~
LC mixture B 78.3 % ::-Dope Dl 4.7 % .
Dope D2 9.0 % ~ ~;.
Dope D3 8.0 ~
and the phase sequence Sc 60 SA 70 N~ 89 I and a spon-taneous polarization of 55 nC cm~2. .;
The effective switching angle (2 ~afr), the transmiasion in the dark and bright 3tates and the optical contrast are mea~ured for various cryptand~ and coronands added to the FLC mixture ~1, in each ca~e in an amount of 1 mol-%. To this end, the measurement cell provided with elec-trodes (manufacturer E.H.C. Inc., Tokyo) containi~g the corre~ponding FLC mixture i8 examined under a polarizing microscope equipped with a rotary ~tage. When the cell . ~ .:
:"
2 ~
is driven, the effective switching angle can be deter-mined by rotatlng the micro cope stage between the two switching states. -The transmi~sion in the bright and dark states is S measured using a photodiode under the polarizing micro-scope. The optical contrast i9 calculated from the ratio between the transmissions in the bright and dark stat~s.
The results are shown in Table 2. After addition of the corresponding cryptands or coronands, FLC mixture M1 exhibits considerably better properties, which is reflec ted in the corresponding measurement results.
Example 3 FLC mixture M2 has the following composition (in mol-%):
LC mixture B 84.0 % ~ -Dope D1 7~7 %
Dope D2 8.3 %
and the phase sequence Sc 63 SA 73 N a1 I and a spon-taneous polarization of 37 nC cm~2. In order to uppress optical hysteresi~, 1 mol-% of the complex ligand R8 was added to the FLC mixture M2. Addition of the cryptand K8 gave the phase ~equence Sc 5 8 SA 7 1 N 7 8 I and a spon-taneous polarization of 36 nC cm~2. Fig, 1 shows the optical switching re~pon~es of the FLC mixture M2 with and without cryptand in teqt cell~ 2.1 ~m thick (manu~
25 facturer E.H.C. Inc., Tokyo), under a polarizing micro-scope. The switching of fhe test cells was recorded using a fast photodiode. Fig. 1 shows pulse addressing (CH1) and the optical tran~mission (CH2) of a test cell filled with FLC mixture M2 at a temperature of 25C and variable pulse intervals. The left-hand side shows the pure mixture M2, while the result~ with 1 mol-% of cryptand K8 are ~hown on the right-hand side.
: . . ., . : , , . ,, , . : , ,. , : . . .
3 ~
- 28 ~
For pulse addressing at a temperature of 25C, bipolar pulses having an overall width of 200 ~s and a height of 4 V/~m were used. The intervals between the pulses were a) 1000 ms, b) 100 ms and c) 20 ms. It can clearly be 5 seen that the FLC mixture containing the cryptand K8 (right-hand side of Fig. 1) exhibits improved switching behavior and is al~o witchable for longer pul~e inter-vals (a). Corresponding photo micrographs of the test cells (Fig. 2) show, for the F~C mixture M2, non-~witch-able region~, which only occur to a consid~rably reducedextent after ~8 has been added. Fig. 2 3how~ photo micrographs of the test cells filled with FLC mixture M2 (left-hand side) and FLC mixture M2 additionally contain-ing 1 mol-~ of cryptand K8 (right-hand side). a) shows the ~table dark state and b) the stable bright state.
The co~stant parameters are field 3trength 4 V/~m, pulse width 200 ~, and pul e interval 50 ms at a temperature o~ 25C.
The following test method wa~ u~edL to obtain a mea~ured quantity for the appearance of gh~ t images in the FLC
displays with the test cell~ used^
Bipolar pul~es of the same polarity sequence and an overall width of 200 ~6 and a height of 4 V/~m are used.
The pul8e interval i5 20 ms. The polarity sequence change~ every 5 ~econds. Fig9 3 shows the wikching behavior on u~e of bipolar pul~ec of the same polarity sequence, which chanqe6 after 5 ~econd~. Even for this pulse addressing, the advantage of the FLC mixture according to the invention can be ~een from the very rapid switching from bright to dark and vice-versa without the annoying appearance of o-called ~mearing effects. Here too the optical transmi~ion at a tempera-ture of 25C of a te~t cell filled with the FLC mixture is plotted against time. a) FLC mixture M2, b) FLC
mixture M2 containing 1 mol-% of cryptand K8.
~$~$
- 29 - . .
Example 4 FLC mixtura M3 ha~ the following composition (in mol~
.. : .
LC mixture C 31.7 Dope D4 7.0 ,:;.
Dope D5 1~3 and the phase sequence Sc 69 SA 75 N~ 82 I. It has a :~ .
pontaneous polarization of -9.6 nC-cm~2.
In this example too, the test scheme described above for characterizing ghost image~ clearly showed the advantages of the use according to the invention of complex ligands for ions, shown in Fig. 4 in analogous manner to that in Fig. 3.
The optical transmis6ion of a test cell filled with FLC
mixture M3 at a temperature of 25C i~ plotted against time. Bipolar pulses of the same polarity 3equence and an overall width of 200 ~s and a .height of 12 V/~m are used. The pulse interval i9 20 m The polarity sequence changes every 5 seconds. a) FLC mixture M3, b) --:
FLC mixture ~3 containing 1 mol-~ of complex ligand K8.
~ere too, the switching ~rom dark to bright takes place instantly and without smearing effects, in contrast to FhC mixture M3 containing no complex ligands.
Example 5 FLC mixture M4 ha~ the following composition tin mol %):
LC mixture C 87.67 %
Dope Dl 4.53 %
Dope D2 2.70 %
Dope D3 5.10 %
and the phase ~equencs Sc 61 SA 69 N 85 I and a spon-taneous polarization of 30 nC cm~2.
2 ~
The cryptands or coronands K8 (0.5 mol-%) and K5 (1.5 ~
mol-%) are added to FLC mixture M4 to give mixture M4'. ; -The test cells used (our own cell construction) are coated both with a conventional polyimide and with a partially fluorinated polyimide a8 the aliynment material.
. : , The mixtures according to the invention are assessed using the effective switching angle, the transmis~ions in the bright and dark states and the op~ical contrast. ~-, '; ' ..
Table 3 shows a comparison between FhC mixture M4 with the modified FLC mixture (M4~). The effective tilt angle and the aseoci~ted transmission in the bright state ,;;~
increase con~iderably. However, the transmission in the `~
dark state al~o drops ~ignificantly, causing an overall drastic increase in the optical contrast. If FLC cells are treated with alternating electrical fields o~ certain field strength and freguency (for example 10 Hz, 15 V/ym)l a change in the smectic layer structure can be ~-;
achieved (book3helf geometry, see Dubal et al. in "Proceedings of the 6th International Symposium on Elektrets", Oxford, England 1988 ~ds. D.K. Das-Gypta and A.W. Pattullo), which are di~tingui~hed by a switching angle close to 45. U~ing this texture, a transmission in the bright state of virtually 100% can thus be ~S achieved. The result~ for the F~C mixture M4 with and `~
without coronands or cryptands are shown in Table 4.
Here too, a considerable improvement in the dark state and thus in the optical contrast are apparent.
FLC mixture M4 and the modified FLC mixture M4' are introduced into two identical, commercially available FLC
cells provided with electrodes tfrom E.H.C.) with align-ment layer~ on both sides comprising SiO~ (vapor-deposition at an angle o~ 83).
,",:' :~.
The cells are subjected at room temperature to alternat-ing bipolar electrical pul~es with an overall duration of ,:~ ' . ' , ~ 3 1 msO From a certain critical pulse amplitude (field strength), the cell filled with the mixture accordiny to the invention switches to and fro between the known bistable and uniform switching states. In the aase of the comparison cell (only M4), by contrast, two twist states occur at these amplitude~, which hardly differ in their optical kransmission capacity and therefore do not give good contrast.
Only at very much higher amplitude~ doe~ the comparison cell (FLC mixture M4 without additive~) also ~witch with high contrast between two unifor~ state~; even here, however, the contrast does not reach the value for the mixture according to the invention. The compari~on is ;
~hown diagrammatically in Fig. 5. The contrast (CR) is plotted against the field strength E 5in V/m). Curve (a) corresponds to the FLC mixture according to the inven-tion, and curve (b) to the FLC mixture M4 without addi-tion of cryptands or coronand~.
. ' ':
Example 6 In separate experiments, 1 mol-% of each of the complex Iigands K5 (FLC mixture 6A), K8 (FLC mixture 6B) and K12 (FLC mixture 6C) are added to FLC mixture M4. ~he ghost image behavior is characterized using the test 3cheme described in Example 3O The ~witching from bright to dark (in chevron geometry) should take place very quickly and without ~mearing effects. The time con~tant with which the bright ~torage state i~ produced on ~witching from dark to bright can be employed as a characteri~tic quantity for assessing a complex ligand. Table 5 ~hows the relative effectivenes~ of complex ligands K5, K8 and K12 in test mixture M4, ~tting the action of K8 (time con~tant of switching) at one.
.
3 l~j - 32 - :
Table 5 FLC mixture Effectiveness ~ ;
6A 0.18 6B 1.00 5C 0 60 :
,, .: , ~ "
The table clearly shows that the cryptands are parti cularly suitable for avoiding optical hystereæis.
Example 7 (guest-host cell) ~dye cell) : 10 A ferroelec~ric mixture M5 according to the invention compri e~ the following 14 components (in % by weight): ~
`.'~, .
`'~;"'' '' ' '":''. ~'' ', ',, :.
:' ': : '' ' ' ~ ;".
8H17~ O- C6~13 11. 8 8~17~ )'CloH21 9. 1 8H17~ ) ' - e~Hl 711 . 4 C3H~ O~ O~C6H13 C~7H17''~-'C3H17 3'3 C8H17~ ~~ ~ O~ C4~g 7 . 6 C2H17''~''CLOH21 7~4 ClOH21 ~ ).C0-(~)-CSN:L:~24 .6 ; 8H17-~) 2 ~ S~,l S .i5 ~3 C3H7~C0-0-~ O CO~C5HLL 2.0 S~;CH~C~I CO-O. ~'O'C6N171,2 J 3 ~ :
- 34 - ~ :
Compound X8 1.5 .; .
Compound K5 1.5 blue, dichroic dye 4.8 which iR ~ioluble in the LC material ;~.
and has the following pha e~i (in ~C): .
..:
X -4.5 Sc 66~3 SA 69.6 N 94 I
This mixture is introduced into a cell (internal plate separation 3.4 ~im~ with polyimide alignment layer~i rubbed parallel and subjected ~or about 3 minutes to field treatment with rectangular pulses of a frequency of 10 Hz and a field strength ~f ~ 10 V/~m~l:
Under a tran~imi~ted light microscope, a polarizing foil i8 oriented at an angle to the temperature-controlled cell BO that light tran~mi~ision is at a minimum (pola~
rizer and preferential alignmient of the molecule~i are crossed. After a eiwitching pulse (8 V/~m~1; 500 ~iS), the molecules adopt a position rotated by 47 relative to this po~ition, and the light is abE~iorbed less ~trongly.
In order to match the illumlnation to the dye, a filter i~ uied during the contra~t meaiurement (manufacturer:
Schott, 75760/632 nm)~ The contrast, i.e. the ratio between the transmis~ion~ in the bright state and dark state i8 measured using a photodiodP and iB 24:1 for thi6 cell.
Aia comparative example, a polyimide-coated cell (inter-nal plate ~eparation of 3.0 ~im) was filled with a mixture which differed from the mixtuire according to the inven-tion only in that it contained no coronands or cryptands.
~he contrait of thi~ mixture, detenmined a~ de~cxibed above, iei 11:1. The u~e of complexing agents accordingly results in a significant improvement in contra~t.
~ ~3 ~ ~ eJ 3 6 This example confirms that coronands and cryptands re~ult in a significant improvement in LC mixtures containing dyes for u~e in guest-host displays.
Example 8 To demonstrate the advantageous properties of the FLC
mixture according to the invention together with SiO
alignment layerR, we have produced our own test cellsO
To this end, gla~s plates coated with a 4 x 4 mm2 elec-trode area comprising indium tin oxide (ITO) were cleaned using an aqueous surfactant olution and 6ubsequently with alcohol and then coated with a dilute organosilicon compound. The application was effected using a spin coater, but other methods, for example printing or dipping, can also be used. The layer, approximately 20 nm thick, was conditioned at a temperature of about ~50C and ~ub~equently rubbed with a velour-like material. The glass plateR obtained in this way were stuck together to form test cell~;. The starting com-pound~ ~or the alignment layers wlere an SiO2-containing material ~uch as, for example, ~Liquicoat (manufacturer:
Merck, Darmstadt) and ~Silan-TPN ~manufacturer: Wacker Chemie, Munich). The test cell~ produced by us were compared with conventional test cells (manufacturer:
E.H.C. In~., Tokyo) ha~ing a polyimide alignment layer.
This was done using FLC te~t mixture M4 to which 1.5 mol--~ K8 had been added. The mixtures according to the invention in combination with an SiO2 alignment layer were assessed using the transmissions in the bright and dark states, the optical contrast, the switching angle 2 ~ U~f and the maximum possible bias ~ratio between l~ne and data voltage). The re~ult~ for chevron and bookshelf qeometries are shown in Table 6. Compared with conven-tional polyimide, SiO2 alignment layers and the FLC
mixtures acaording to the invention give considerably better contrast. A further advantage is the better insulation capacity of SiO2 layers, since electrical shortcircuits are a problem which mu t be taken , ,,,, , . ~,.. ,.. , . ' , J' .!, . ' ,. ' , ' ' ' , ' : .. 'i ., , 3~ 3 ~
6 -; :
seriously .
Table 1 Comparison of the e~f~ctive switching angle for LC base mixture A and mixture ( A + coronand ) according to the invention LC mixture A LC mixture A +
2 mol % of X5 2 ~e~20 2a ~ o c ~
.
- 37 ~ 3~
~ ~ o ~ ~ o U ~; N O~ ~
h o U~
_~
_ILr r~
h C~ ~ O U~ ~
4~
O O
~~t~
C~ ~; ~ ,~ ~ er ' ' In U~ O
~1 : .
er '.
~ ' ~ ~ O
.~ . ~ .
~ ~4 O o U~
~C
t~
_~
h . , X
~ .C ,.-U ~ o ~3 u~
~a n~
tJ~ o o .~ ~
~l ~
_~ E -- E ~ ~ ~ ;
o h f~ s~ h o E~ U ~ U . ~,~.", . .
~, - ' .
~ 3 ~
_ 38 --, '.; '' U~
~ o -:'' d : .:
U~ .. :
. :
a) -1 8 ~ ~
. .
. .
a~ o U ~ h ~
a) u~ C~- ~ o .
S ~ I ~ 0 o~
~ O ~ a ~, N O ~D ~1 .~ oC~` S .,' .~ .
~:: O ~ ~t ~.- . . .
U~
~ ~ U~ : .
U n~ U E! ;~
h a~ ~ ~ ; ~ .
O ~
O :. , E~ Q. ~ '."
~: ~ ':: ' O O ., O S .~ .
U ~
~r . .'', aJ ....
U ~ .. , .,1 . ~ .-.
::~ .;-, -., ~ ':' .
~ ~ ;, 4~ ~ ~ _~
~ ~ o . - :
:E ~ O
a~ ` cr x ~ ~ ~
~, u x u~
~ ::
:,..- ' .
o o :~
.
o u~
h ~ d C: .. ...
~d 1~ o . .
E-l ~ El ~ E~ .q U .
$J~ 3 U ~ ~
~ o ~
~ U~ o h ~a e ~ h O ~ ^
cn ~
~ ~ 3 ~
O In O O~
~ _I ~ q~ O
o ~ ~ ~ .n C~ ~ ~
c ~ ~ ~ ~
. .
o ~ ~ ~C
.-1 rl .~ o ~ ~
-1 h ~ : .
q .:
_~
U ~
h la .,1 U S ~ ~ ~ ~:
~ ~ 4) 0 h h E~ Q ~ ~
': :
h S
Q~'t 3 ~ ~ ~a '~
u ~ o ~ ~ ::`
O h h E3 h ~; ~
>1 ~ . ..
.,1 0 ~ O C ' -:
~ h hC4 --l . ~. .
,C ~1 3 C3'~
~ 1 Ql ~ O I` o ' 3 ~ ~ ~ m o o~
71 ' ~, .
h ~ ~ 1 . ,/ ` '.
o t:a ~ ", x a~ .,- . ,.
.C .: :, C) X ~ . ~
0 ., .
h E~ h 1~1 ~;
~ 3 3~ ~
o~q ~ _ ~ :
S ~, i~'. .
d h h ~ h 1~ 0 E~ ~ U
... :
~. .
.. : ~', ,.
3 ~ ::
f'~
40 ~
, . :, Table 6 :
Chevron geometry~
Test cell having an alignment ~ :.
layer of :
Polyimide ~Liquicoat Silan-TPN ::
. .
Transmission 24 25 ~5 bright ~
Transmission 0~6 0.4 0.5 dark (%) ~ ' Contra~t 40 62.5 50 maximum bias 2 90~ 20 23 24 Bookshelf geometry: :~
Test cell having an alignment layer of : -.
: Polyimide ~Li~uicoat Silan-TPN ~:
Transmission 92 94 96 ~;
~0 bright (%) Tran~mi~ion 2.5 0.8 0.6 ;
dark (~) Contrast 37 117 160 ~. !
maximum bian 4 3.5 5 ;
2 ~ff 53 52 52 ;
;'','~ ' 3 ~ ~3 Re. Figure 5 (a) The contrast tCR) of an E.H.C. cell with SiOX vapor- -deposited at an angle as the alignment layer and filled with mixture M4' according to the invention is shown as a function of the ~mplitude (field strength ~) of the bipolar switching pul es used for switching.
(b) The contrast (CR) of a cell filled with comparative mixture M4 is shown under the same conditions as ~ :
(a)- ~
~ i `'",~
,'., '': .
,"','.
'","' ' ~''' :., ~'''.
~'''' ''~' '~ '. ~'
seriously .
Table 1 Comparison of the e~f~ctive switching angle for LC base mixture A and mixture ( A + coronand ) according to the invention LC mixture A LC mixture A +
2 mol % of X5 2 ~e~20 2a ~ o c ~
.
- 37 ~ 3~
~ ~ o ~ ~ o U ~; N O~ ~
h o U~
_~
_ILr r~
h C~ ~ O U~ ~
4~
O O
~~t~
C~ ~; ~ ,~ ~ er ' ' In U~ O
~1 : .
er '.
~ ' ~ ~ O
.~ . ~ .
~ ~4 O o U~
~C
t~
_~
h . , X
~ .C ,.-U ~ o ~3 u~
~a n~
tJ~ o o .~ ~
~l ~
_~ E -- E ~ ~ ~ ;
o h f~ s~ h o E~ U ~ U . ~,~.", . .
~, - ' .
~ 3 ~
_ 38 --, '.; '' U~
~ o -:'' d : .:
U~ .. :
. :
a) -1 8 ~ ~
. .
. .
a~ o U ~ h ~
a) u~ C~- ~ o .
S ~ I ~ 0 o~
~ O ~ a ~, N O ~D ~1 .~ oC~` S .,' .~ .
~:: O ~ ~t ~.- . . .
U~
~ ~ U~ : .
U n~ U E! ;~
h a~ ~ ~ ; ~ .
O ~
O :. , E~ Q. ~ '."
~: ~ ':: ' O O ., O S .~ .
U ~
~r . .'', aJ ....
U ~ .. , .,1 . ~ .-.
::~ .;-, -., ~ ':' .
~ ~ ;, 4~ ~ ~ _~
~ ~ o . - :
:E ~ O
a~ ` cr x ~ ~ ~
~, u x u~
~ ::
:,..- ' .
o o :~
.
o u~
h ~ d C: .. ...
~d 1~ o . .
E-l ~ El ~ E~ .q U .
$J~ 3 U ~ ~
~ o ~
~ U~ o h ~a e ~ h O ~ ^
cn ~
~ ~ 3 ~
O In O O~
~ _I ~ q~ O
o ~ ~ ~ .n C~ ~ ~
c ~ ~ ~ ~
. .
o ~ ~ ~C
.-1 rl .~ o ~ ~
-1 h ~ : .
q .:
_~
U ~
h la .,1 U S ~ ~ ~ ~:
~ ~ 4) 0 h h E~ Q ~ ~
': :
h S
Q~'t 3 ~ ~ ~a '~
u ~ o ~ ~ ::`
O h h E3 h ~; ~
>1 ~ . ..
.,1 0 ~ O C ' -:
~ h hC4 --l . ~. .
,C ~1 3 C3'~
~ 1 Ql ~ O I` o ' 3 ~ ~ ~ m o o~
71 ' ~, .
h ~ ~ 1 . ,/ ` '.
o t:a ~ ", x a~ .,- . ,.
.C .: :, C) X ~ . ~
0 ., .
h E~ h 1~1 ~;
~ 3 3~ ~
o~q ~ _ ~ :
S ~, i~'. .
d h h ~ h 1~ 0 E~ ~ U
... :
~. .
.. : ~', ,.
3 ~ ::
f'~
40 ~
, . :, Table 6 :
Chevron geometry~
Test cell having an alignment ~ :.
layer of :
Polyimide ~Liquicoat Silan-TPN ::
. .
Transmission 24 25 ~5 bright ~
Transmission 0~6 0.4 0.5 dark (%) ~ ' Contra~t 40 62.5 50 maximum bias 2 90~ 20 23 24 Bookshelf geometry: :~
Test cell having an alignment layer of : -.
: Polyimide ~Li~uicoat Silan-TPN ~:
Transmission 92 94 96 ~;
~0 bright (%) Tran~mi~ion 2.5 0.8 0.6 ;
dark (~) Contrast 37 117 160 ~. !
maximum bian 4 3.5 5 ;
2 ~ff 53 52 52 ;
;'','~ ' 3 ~ ~3 Re. Figure 5 (a) The contrast tCR) of an E.H.C. cell with SiOX vapor- -deposited at an angle as the alignment layer and filled with mixture M4' according to the invention is shown as a function of the ~mplitude (field strength ~) of the bipolar switching pul es used for switching.
(b) The contrast (CR) of a cell filled with comparative mixture M4 is shown under the same conditions as ~ :
(a)- ~
~ i `'",~
,'., '': .
,"','.
'","' ' ~''' :., ~'''.
~'''' ''~' '~ '. ~'
Claims (24)
1. A ferroelectric liquid-crystal mixture comprising at least two components, wherein one component is at least one complex ligand for ions.
2. An FLC mixture as claimed in claim 1, containing at least one complex ligand for cations.
3. An FLC mixture as claimed in claim 1, wherein the complex ligands are electrically neutral compounds.
4. An FLC mixture as claimed in claim 1, wherein the complex ligands complex cations and contain at least two nitrogen and/or oxygen and/or sulfur and/or phosphorus donor centers.
5. An FLC mixture as claimed in claim 1, wherein the complex ligands are mediocyclic or macrocyclic compounds.
6. An FLC mixture as claimed in claim 1, wherein the complex ligands are cryptands.
7. An FLC mixture as claimed in claim 1, wherein the complex ligands are coronands.
8. An FLC mixture as claimed in claim 1, wherein the complex ligands are podands.
9. An FLC mixture as claimed in claim 1, wherein the complex ligands are bicyclic compounds which contain at least two nitrogen atoms.
10. An FLC mixture as claimed in claim 1, wherein the complex ligands are bicyclic or tricyclic compounds.
11. An FLC mixture as claimed in claim 1, wherein the complex ligands are bicyclic or tricyclic compounds which contain at least two nitrogen atoms and at least four oxygen atoms.
12. An FLC mixture as claimed in claim 1, containing at least two different complex ligands for ions.
13. An FLC mixture as claimed in claim 1, containing at least one complex ligand for alkali metal and/or alkaline earth metal ions.
14. An FLC mixture as claimed in claim 1, containing at least two different complex ligands for different cations.
15. An FLC mixture as claimed in claim 1, wherein the complex ligand is a compound of the general formula (I), (I) in which -Z- is -O- or -S-, m and n are integers greater than zero, where m+n = 2 to 6, -X1- and -X2- are identical or different and are or -X1- and -X2- together are N-CH2(-CH2-z-CH2)1-CH2-N or N-CO(-CH2-Z-CH2)1-CO-N or H-C-CH2(CH2-z-CH2)2-CH2-C-H, where R is alkyl or alkoxy having from 1 to 15 carbon atoms, phenyl, benzyl or benzoyl and 1 is 1 or 2.
16. An FLC mixture as claimed in claim 1, wherein the complex ligand is a compound of the general formula (II) (II) where R1, R2, R3 and R4, independently of one another, are -H, -(C1-C12)alkyl, , or and p, q, r and s, independently of one another, are an integer from 2 to 4, and where p+q+r+s = 8 to 16.
17. An FLC mixture as claimed in claim 1, containing from 0.01 to 10 mol-% of at least one complex ligand.
18. An FLC mixture as claimed in claim 1, which has a spontaneous polarization of at least 35 nC-cm-2.
19. The use of a ferroelectric liquid-crystal mixture as claimed in claim 1 in electrooptical switching and display devices.
20. The use of a ferroelectric liquid-crystal mixture as claimed in claim 1 in SSFLC cells having a cell thickness of from 1 to 10 µm.
21. A liquid-crystal stitching or display device con-taining a ferroelectric liquid-crystalline medium, outer plates, electrodes, at least one alignment layer and, if desired, additional auxiliary layers, wherein the ferroelectric liquid-crystalline medium is an FLC mixture which contains at least one com-pound which is a complex ligand for ions.
22, A liquid-crystal switching or display device as claimed in claim 20, which is an SSFLC cell having an FLC layer thickness of from 1 to 20 µm and wherein the FLC mixture contains, as complex ligand, at least one mediocyclic or macrocyclic compound.
23. A liquid-crystal switching or display device as claimed in claim 20, which is an SSFLC cell having an FLC layer thickness of from 1 to 10 µm and wherein the FLC mixture contains, as complex ligand, at least one cryptand and/or coronand.
24. A liquid-crystal switching or display device as claimed in claim 20, wherein the alignment layer comprises an SiO2-containing material.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3939697A DE3939697A1 (en) | 1989-12-01 | 1989-12-01 | Ferroelectric liq. crystalline mixts. - contg. complex ligand for ions are used in electro=optical components |
| DEP3939697.5 | 1989-12-01 | ||
| DE4011803A DE4011803A1 (en) | 1990-04-12 | 1990-04-12 | Ferroelectric liq. crystal mixts. - contain at least 2 components, at least one of which is a complex ligand for ions, esp. cations |
| DEP4011803.7 | 1990-04-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2069936A1 true CA2069936A1 (en) | 1991-06-02 |
Family
ID=25887543
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002069936A Abandoned CA2069936A1 (en) | 1989-12-01 | 1990-11-26 | Complex ligands for ions in ferroelectric liquidcrystal mixtures |
Country Status (18)
| Country | Link |
|---|---|
| EP (1) | EP0502964B1 (en) |
| KR (1) | KR100189050B1 (en) |
| CN (1) | CN1034220C (en) |
| AT (1) | ATE118808T1 (en) |
| AU (1) | AU640440B2 (en) |
| CA (1) | CA2069936A1 (en) |
| DE (1) | DE59008550D1 (en) |
| ES (1) | ES2071289T3 (en) |
| FI (1) | FI922407A0 (en) |
| HU (1) | HUT60758A (en) |
| IE (1) | IE904328A1 (en) |
| IL (1) | IL96508A0 (en) |
| NO (1) | NO922135L (en) |
| NZ (1) | NZ236274A (en) |
| PL (1) | PL165258B1 (en) |
| PT (1) | PT96055A (en) |
| WO (1) | WO1991008272A1 (en) |
| YU (1) | YU226790A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4011804A1 (en) * | 1990-04-12 | 1991-10-24 | Hoechst Ag | USE OF MACROCYCLIC COMPOUNDS AS A COMPONENT FOR FERROELECTRIC LIQUID MIXTURES |
| DE4011805A1 (en) * | 1990-04-12 | 1991-10-17 | Hoechst Ag | METHOD FOR PRODUCING A SHOCK-STABILIZED LIQUID CRYSTAL CIRCUIT AND DISPLAY DEVICE |
| TW226994B (en) * | 1991-08-21 | 1994-07-21 | Hoechst Ag | |
| DE4133719A1 (en) * | 1991-10-11 | 1993-04-15 | Hoechst Ag | New chiral macrocyclic cpds. - useful as ferroelectric liq. crystal additives |
| JPH05297375A (en) * | 1992-04-20 | 1993-11-12 | Hoechst Japan Ltd | Ferroelectric liquid crystal mixture and display element constituted by using this mixture |
| US5695683A (en) * | 1993-09-30 | 1997-12-09 | Hoechst Aktiengesellschaft | Ferroelectric liquid crystal mixture |
| DE69526636D1 (en) * | 1994-07-29 | 2002-06-13 | Innogenetics Nv | CLEANED HEPATITIS-C-VIRUS ENVELOPE PROTEINS FOR DIAGNOSTIC AND THERAPEUTIC USE |
| TW434310B (en) * | 1995-07-13 | 2001-05-16 | Merck Patent Gmbh | Liquid crystal composition |
| EP1367114A1 (en) * | 2002-04-11 | 2003-12-03 | Clariant International Ltd. | Active matrix liquid crystal device and smectic liquid crystal mixture |
| US6824707B2 (en) | 2001-10-23 | 2004-11-30 | Clariant International Ltd. | Active matrix liquid crystal device and smectic liquid crystal mixture |
| EP1306419A1 (en) * | 2001-10-23 | 2003-05-02 | Clariant International Ltd. | Active matrix liquid crystal device and smectic liquid crystal mixture |
| US10759996B2 (en) * | 2015-10-30 | 2020-09-01 | Merck Patent Gmbh | Liquid-crystal medium |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3814700A (en) * | 1972-08-03 | 1974-06-04 | Ibm | Method for controllably varying the electrical properties of nematic liquids and dopants therefor |
| JPS52114482A (en) * | 1976-03-18 | 1977-09-26 | Merck Patent Gmbh | Liquid cryatal dielectric substance and manufacture |
| DE2637430A1 (en) * | 1976-08-20 | 1978-02-23 | Merck Patent Gmbh | Heterocyclic diaza cpd. in liquid crystalline dielectric - for electrooptical registration devices, giving stable orientation parallel to electrode surfaces |
| JPS5412534A (en) * | 1977-06-29 | 1979-01-30 | Takeda Riken Ind Co Ltd | Strobe generator for ic tester |
| JPS54106084A (en) * | 1978-02-08 | 1979-08-20 | Mitsubishi Electric Corp | Liquid crystal composition |
| JP2636035B2 (en) * | 1989-02-27 | 1997-07-30 | 松下電器産業株式会社 | Ferroelectric liquid crystal composition and ferroelectric liquid crystal display |
| DE3908580A1 (en) * | 1989-03-16 | 1990-09-20 | Nokia Unterhaltungselektronik | LIQUID CRYSTAL MIXTURE AND LIQUID CRYSTAL CELL |
-
1990
- 1990-11-26 EP EP91900771A patent/EP0502964B1/en not_active Expired - Lifetime
- 1990-11-26 AU AU69545/91A patent/AU640440B2/en not_active Ceased
- 1990-11-26 KR KR1019920701291A patent/KR100189050B1/en not_active IP Right Cessation
- 1990-11-26 AT AT91900771T patent/ATE118808T1/en not_active IP Right Cessation
- 1990-11-26 HU HU921418A patent/HUT60758A/en unknown
- 1990-11-26 WO PCT/EP1990/002018 patent/WO1991008272A1/en active IP Right Grant
- 1990-11-26 CA CA002069936A patent/CA2069936A1/en not_active Abandoned
- 1990-11-26 DE DE59008550T patent/DE59008550D1/en not_active Expired - Lifetime
- 1990-11-26 ES ES91900771T patent/ES2071289T3/en not_active Expired - Lifetime
- 1990-11-27 YU YU226790A patent/YU226790A/en unknown
- 1990-11-29 NZ NZ236274A patent/NZ236274A/en unknown
- 1990-11-29 IL IL96508A patent/IL96508A0/en unknown
- 1990-11-30 IE IE432890A patent/IE904328A1/en unknown
- 1990-11-30 PT PT96055A patent/PT96055A/en not_active Application Discontinuation
- 1990-11-30 PL PL90288038A patent/PL165258B1/en unknown
- 1990-12-01 CN CN90109853A patent/CN1034220C/en not_active Expired - Fee Related
-
1992
- 1992-05-26 FI FI922407A patent/FI922407A0/en unknown
- 1992-05-29 NO NO92922135A patent/NO922135L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| AU6954591A (en) | 1991-06-26 |
| PT96055A (en) | 1991-09-30 |
| HU9201418D0 (en) | 1992-09-28 |
| IE904328A1 (en) | 1991-06-05 |
| NO922135D0 (en) | 1992-05-29 |
| DE59008550D1 (en) | 1995-03-30 |
| NZ236274A (en) | 1993-02-25 |
| KR100189050B1 (en) | 1999-06-01 |
| CN1053633A (en) | 1991-08-07 |
| FI922407A (en) | 1992-05-26 |
| FI922407A0 (en) | 1992-05-26 |
| WO1991008272A1 (en) | 1991-06-13 |
| PL288038A1 (en) | 1992-06-15 |
| CN1034220C (en) | 1997-03-12 |
| ATE118808T1 (en) | 1995-03-15 |
| YU226790A (en) | 1992-07-20 |
| EP0502964A1 (en) | 1992-09-16 |
| IL96508A0 (en) | 1991-08-16 |
| ES2071289T3 (en) | 1995-06-16 |
| AU640440B2 (en) | 1993-08-26 |
| NO922135L (en) | 1992-07-17 |
| HUT60758A (en) | 1992-10-28 |
| PL165258B1 (en) | 1994-12-30 |
| EP0502964B1 (en) | 1995-02-22 |
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| EEER | Examination request | ||
| FZDE | Discontinued |