GB2393966A - High-twist liquid-crystalline medium and liquid-crystal display - Google Patents
High-twist liquid-crystalline medium and liquid-crystal display Download PDFInfo
- Publication number
- GB2393966A GB2393966A GB0318087A GB0318087A GB2393966A GB 2393966 A GB2393966 A GB 2393966A GB 0318087 A GB0318087 A GB 0318087A GB 0318087 A GB0318087 A GB 0318087A GB 2393966 A GB2393966 A GB 2393966A
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- 239000004973 liquid crystal related substance Substances 0.000 title abstract description 6
- 150000001875 compounds Chemical class 0.000 claims abstract description 94
- -1 naphthalene-2,6-diyl Chemical group 0.000 claims description 100
- 125000004432 carbon atom Chemical group C* 0.000 claims description 53
- 125000000217 alkyl group Chemical group 0.000 claims description 46
- 230000003098 cholesteric effect Effects 0.000 claims description 35
- 229910052731 fluorine Inorganic materials 0.000 claims description 29
- 239000000203 mixture Substances 0.000 claims description 26
- 125000003545 alkoxy group Chemical group 0.000 claims description 25
- 229910052801 chlorine Inorganic materials 0.000 claims description 15
- 229910052739 hydrogen Inorganic materials 0.000 claims description 14
- 229910052736 halogen Inorganic materials 0.000 claims description 13
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 12
- 125000003342 alkenyl group Chemical group 0.000 claims description 10
- 150000002367 halogens Chemical class 0.000 claims description 9
- 125000001140 1,4-phenylene group Chemical group [H]C1=C([H])C([*:2])=C([H])C([H])=C1[*:1] 0.000 claims description 8
- 229910052794 bromium Inorganic materials 0.000 claims description 8
- 229910052740 iodine Inorganic materials 0.000 claims description 8
- 125000003118 aryl group Chemical group 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 125000004434 sulfur atom Chemical group 0.000 claims description 6
- 125000004955 1,4-cyclohexylene group Chemical group [H]C1([H])C([H])([H])C([H])([*:1])C([H])([H])C([H])([H])C1([H])[*:2] 0.000 claims description 5
- 125000004453 alkoxycarbonyl group Chemical group 0.000 claims description 5
- 125000004448 alkyl carbonyl group Chemical group 0.000 claims description 5
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 125000001931 aliphatic group Chemical group 0.000 claims description 2
- 125000004093 cyano group Chemical group *C#N 0.000 claims description 2
- 125000000753 cycloalkyl group Chemical group 0.000 claims description 2
- 125000004971 nitroalkyl group Chemical group 0.000 claims description 2
- 125000005843 halogen group Chemical group 0.000 claims 3
- 125000005725 cyclohexenylene group Chemical group 0.000 claims 1
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- 150000003254 radicals Chemical class 0.000 description 34
- 239000002019 doping agent Substances 0.000 description 21
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- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 11
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- 229910052799 carbon Inorganic materials 0.000 description 5
- QUPDWYMUPZLYJZ-UHFFFAOYSA-N ethyl Chemical compound C[CH2] QUPDWYMUPZLYJZ-UHFFFAOYSA-N 0.000 description 5
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- 239000000654 additive Substances 0.000 description 3
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- 125000006850 spacer group Chemical group 0.000 description 3
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- 125000004975 3-butenyl group Chemical group C(CC=C)* 0.000 description 2
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- RGHNJXZEOKUKBD-SQOUGZDYSA-N D-gluconic acid Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C(O)=O RGHNJXZEOKUKBD-SQOUGZDYSA-N 0.000 description 2
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- 125000001309 chloro group Chemical group Cl* 0.000 description 2
- HVYWMOMLDIMFJA-DPAQBDIFSA-N cholesterol group Chemical class [C@@H]1(CC[C@H]2[C@@H]3CC=C4C[C@@H](O)CC[C@]4(C)[C@H]3CC[C@]12C)[C@H](C)CCCC(C)C HVYWMOMLDIMFJA-DPAQBDIFSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
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- 125000001301 ethoxy group Chemical group [H]C([H])([H])C([H])([H])O* 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- VUWZPRWSIVNGKG-UHFFFAOYSA-N fluoromethane Chemical compound F[CH2] VUWZPRWSIVNGKG-UHFFFAOYSA-N 0.000 description 2
- 125000004785 fluoromethoxy group Chemical group [H]C([H])(F)O* 0.000 description 2
- 150000002334 glycols Chemical class 0.000 description 2
- 125000003187 heptyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 125000004051 hexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 2
- 125000000959 isobutyl group Chemical group [H]C([H])([H])C([H])(C([H])([H])[H])C([H])([H])* 0.000 description 2
- 125000001972 isopentyl group Chemical group [H]C([H])([H])C([H])(C([H])([H])[H])C([H])([H])C([H])([H])* 0.000 description 2
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 2
- 125000001147 pentyl group Chemical group C(CCCC)* 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
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- BHQCQFFYRZLCQQ-UHFFFAOYSA-N (3alpha,5alpha,7alpha,12alpha)-3,7,12-trihydroxy-cholan-24-oic acid Natural products OC1CC2CC(O)CCC2(C)C2C1C1CCC(C(CCC(O)=O)C)C1(C)C(O)C2 BHQCQFFYRZLCQQ-UHFFFAOYSA-N 0.000 description 1
- ZKJNETINGMOHJG-GGWOSOGESA-N (e)-1-[(e)-prop-1-enoxy]prop-1-ene Chemical compound C\C=C\O\C=C\C ZKJNETINGMOHJG-GGWOSOGESA-N 0.000 description 1
- 125000005739 1,1,2,2-tetrafluoroethanediyl group Chemical group FC(F)([*:1])C(F)(F)[*:2] 0.000 description 1
- MYWOJODOMFBVCB-UHFFFAOYSA-N 1,2,6-trimethylphenanthrene Chemical compound CC1=CC=C2C3=CC(C)=CC=C3C=CC2=C1C MYWOJODOMFBVCB-UHFFFAOYSA-N 0.000 description 1
- HNEGJTWNOOWEMH-UHFFFAOYSA-N 1-fluoropropane Chemical group [CH2]CCF HNEGJTWNOOWEMH-UHFFFAOYSA-N 0.000 description 1
- UUFQTNFCRMXOAE-UHFFFAOYSA-N 1-methylmethylene Chemical compound C[CH] UUFQTNFCRMXOAE-UHFFFAOYSA-N 0.000 description 1
- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical group CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 description 1
- 125000004793 2,2,2-trifluoroethoxy group Chemical group FC(CO*)(F)F 0.000 description 1
- 125000004206 2,2,2-trifluoroethyl group Chemical group [H]C([H])(*)C(F)(F)F 0.000 description 1
- 125000004777 2-fluoroethyl group Chemical group [H]C([H])(F)C([H])([H])* 0.000 description 1
- 125000004200 2-methoxyethyl group Chemical group [H]C([H])([H])OC([H])([H])C([H])([H])* 0.000 description 1
- 125000004493 2-methylbut-1-yl group Chemical group CC(C*)CC 0.000 description 1
- 125000005916 2-methylpentyl group Chemical group 0.000 description 1
- 125000005917 3-methylpentyl group Chemical group 0.000 description 1
- 125000006043 5-hexenyl group Chemical group 0.000 description 1
- 101100129500 Caenorhabditis elegans max-2 gene Proteins 0.000 description 1
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- 125000004123 n-propyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 1
- 125000001400 nonyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 125000002347 octyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000012788 optical film Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 150000002924 oxiranes Chemical class 0.000 description 1
- 125000005740 oxycarbonyl group Chemical group [*:1]OC([*:2])=O 0.000 description 1
- 125000002958 pentadecyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 125000001148 pentyloxycarbonyl group Chemical group 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- COLNVLDHVKWLRT-UHFFFAOYSA-N phenylalanine Natural products OC(=O)C(N)CC1=CC=CC=C1 COLNVLDHVKWLRT-UHFFFAOYSA-N 0.000 description 1
- 125000004351 phenylcyclohexyl group Chemical group C1(=CC=CC=C1)C1(CCCCC1)* 0.000 description 1
- 125000006410 propenylene group Chemical group 0.000 description 1
- 125000004742 propyloxycarbonyl group Chemical group 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000600 sorbitol Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 125000005407 trans-1,4-cyclohexylene group Chemical group [H]C1([H])C([H])([H])[C@]([H])([*:2])C([H])([H])C([H])([H])[C@@]1([H])[*:1] 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 125000002889 tridecyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 125000002948 undecyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000004474 valine Substances 0.000 description 1
- 238000001429 visible spectrum Methods 0.000 description 1
Classifications
-
- 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
- C09K19/586—Optically active dopants; chiral dopants
-
- 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
- C09K19/0208—Twisted Nematic (T.N.); Super Twisted Nematic (S.T.N.); Optical Mode Interference (O.M.I.)
-
- 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
- C09K19/42—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40
-
- 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
- C09K19/42—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40
- C09K19/44—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40 containing compounds with benzene rings directly linked
-
- 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
- C09K19/586—Optically active dopants; chiral dopants
- C09K19/588—Heterocyclic compounds
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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)
Abstract
A liquid crystal medium with a helically twisted phase comprising a nematic component and an optically active component wherein the optically active component comprises one or more chiral compounds at least one of which is a chiral derivative of formula I. Also shown is its use for LC displays, SSCT and PCST displays, or for lasing or fluorescence applications.
Description
- 1 2393966
High-twist liquid-crystalline medium and liquid-crystal display Field of the Invention
5 The present invention relates to a high-twist liquid-crystalline (LC) medium, to its use for LC displays and lasing or fluorescence phenomena, and to LC displays and lasing devices containing the LC medium. 10 Background and Prior Art
Cholesteric liquid crystals (CLCs) exhibit selective reflection of circularly polarized light, wherein the direction of rotation of the light vector corresponds to the handedness of the cholesteric helix.
The terms "chiral nematic" LCs and "cholesteric" LCs are used simultaneously in the prior art. "Chiral nematic" often refers to LC
materials consisting of a nematic host mixture doped with an optically active component which induces a helically twisted superstructure, 20 whereas "cholesteric" often refers to chiral LC materials, for example cholesterol derivatives, which have a "natural" helically twisted cholesteric phase. Both terms are also used in parallel to mean the same thing. In the present application, both of the abovementioned types of LC materials are referred to as "cholesteric", and this term is 25 meant to encompass the broadest meaning of both "chiral nematic" and "cholesteric".
In CLC materials the bandwidth of the reflection spectrum AX, centered at climax' is given by: AX = \x- (1) n Where An is the birefringence and n is the average refractive index, 35 both associated with the director plane (i.e. not in the bulk).
The wavelength climax is defined as
- 2 k'',X = nPO (2) Where PO is the pitch of the cholesteric helix.
Substituting equation (2) into equation (1) leads to: \ = Po- (3) A chiral nematic phase can for example be induced by adding a few percent of chiral additive to a nematic LC host mixture, which is characterized by the extraordinary and ordinary refractive indices ne and nO. In this case, the parameters of equation (1) become n=ne-nO and n=(ne+nO)/2.
The helical pitch of the induced cholesteric phase is given by 20 PO = (HTP c)4 (4) wherein c is the concentration c and HTP the helical twisting power of the chiral additive.
25 It has been suggested in prior art to use CLCs for methods and
devices utilizing the lasing and fluorescence phenomenon. US 3,771,065 for example describes the principle of lasing in chiral nematic LCs.
30 Dielectric materials with a periodic modulation of the refractive index exhibit a photonic bandgap. The presence of a photonic bandgap affects the emission of fluorescent guest molecules: inside the gap emission is reduced, at the band edges it is enhanced due to the high photonic density of states. Hence, at the band edges laser emission 35 may be observed. CLC colour filters act as optical resonators for circularly polarised light, with two resonance frequencies located at the
- 3 edges of the reflection band. Laser emission of dye-doped CLC films has been repeatedly demonstrated. The lasing performance of low molar mass systems has been found to be limited by distortions of the cholesteric structure due to the heat dissipated in the lasing process.
To induce absorption in the dye incorporated in the LO, a laser pulse with a suitable wavelength is required. In theory, this induced absorption can be stimulated through photons generated in electron-hole recombination process. As most dyes have an absorption spectrum in 10 the UV regions, new ways of pumping up the system are sought.
The follow-up emission of the excited dye atoms is conditioned by the fluorescence spectrum of the dye and the CLC's photonic band gap.
For increased lasing efficiency, the fluorescence spectrum needs to 15 overlap the selective reflection band gap of the LO. Irrespective of the way the dye atoms are excited, the lasing effect is determined by combining the selective reflection band of the cholesteric with the maximum fluorescence region of the dye dissolved in it.
20 However, the lasing performance in low molar mass CLCs has been found to be limited by distortions of the cholesteric structure due to the heat dissipated in the lasing process. Temperature variation of the cholesteric pitch induces disturbance in the cholesteric arrangement and affects unfavorably the lasing performance.
More recent publications, like E. Yablanovitch, Phys. Rev. Lett.
58(20),2059 (1987); J. Dowling, M. Scalora, M. Bloemer, M. Bowden, J. Appl. Phys. 75(4),1896 (1994); V. Kopp, B. Fan, H. Vithana, A. Genack, Optics Letters 23(21),1707 (1998) and P. Palffy-Muhoray, 30 A. Munoz, B. Taheri, R. Twieg, SID Digest, 1170 (2000) describe dye fluorescence spectrum, dye shape and orientation in the cholesteric host and tenability of the selective reflection gap with the maximum of the dye's fluorescence spectrum. However, the influence of the physical parameters of the CLC host has hitherto not been 35 investigated.
- 4 CLC materials have further been suggested in prior art for a broad
variety of applications, like for example liquid crystal displays (LCD), optical films like polarisers and colour filters, or reflective films for decorative applications and security uses.
For example, LCDs are known which contain LC media having a chiral nematic or cholesteric structure. A cholesteric display contains a CLC medium with a considerably higher twist than for example displays of the TN (twisted nematic) or STN (super-twisted nematic) 10 mode which have a twist angles of 90 to 270 , and utilizes the property of the CLC medium to selectively reflect circular polarized light within or close to the visible wavelength range.
Examples of CLC displays are SSCT (surface stabilized cholesteric 15 texture) and PSCT (polymer stabilized cholesteric texture) displays.
In these displays the CLC medium can be switched from a planar, lightreflecting state into a focal conic, light-scattering state or into a homeotropic, transparent state by applying an electric alternating current pulse. CLC displays generally require no backlighting and are 20 bistable, i.e. the respective state is retained after the electrical field is
switched off, and is transferred back into the initial state only by re applying a field. Therefore they consume considerably less power
than e.g. TN or STN displays. Also, they exhibit a low viewing-angle dependence, if any, in the scattering state. In addition, they do not 25 require active-matrix addressing like TN displays, but can be operated in the simpler multiplex or passive matrix mode. SSCT and PSCT displays are described for example in WO 92/19695, US 5,384,067 and US 5,453,863.
30 Furthermore, displays are known using CLC materials having a flexoelectric effect. The flexoelectric effect is described for example by Patel and Meyer, Phys. Rev. Lett. 58 (15),1538-1540 (1987) and Rudquist et al., Liq. Cryst. 22 (4), 445-449 (1997). In a flexoelectric CLC material, application of an electric field perpendicular to the helix
35 axis causes distortion to the molecular LC directors, whereas the direction of the helical axis remains unchanged. This leads to a tilt of
r _;, _ the optical axis of the CLC material relative to the helical axis in the plane perpendicular to the direction of the applied field.
Flexoelectric displays are typically operated in the so-called uniformly 5 lying helix (ULH) mode, which is described for example by P. Rudquist et al., Liq. Cryst. 23 (4), 503 (1997). The uniform lying helix (ULH) texture is realized using a CLC with a short pitch which is unidirectionally aligned with its helical axis parallel to the substrates, e.g. glass plates, of an LC cell. If an electrical field is applied to this
10 configuration normal to the helical axis, the optical axis is rotated in the plane of the cell. When the cell is placed between crossed polarizers, the tilt of the optical axis of the CLC material causes a change in transmission which can be exploited in electrooptical applications. Flexoelectric displays have fast switching times and 15 excellent grey scale capability. They can be used as transmissive or reflective displays, and can be operated by active matrix addressing or as multiplex or passive matrix displays. CLC materials for use in flexoelectric devices are described for example in EP 0 971 016 and GB 2 356 629.
However, the CLC materials known from prior art for use in
flexoelectric and CLC displays often do not exhibit suffciently broad LC phase ranges, sufficiently low viscosities and sufficiently high values of the dielectric anisotropy. Furthermore they often require 25 high voltages and do not show a birefringence that is well adapted to the required cell thickness.
Therefore, there is a need for improved CLC media which are suitable for the above mentioned uses and which do not have the 30 disadvantages of the media of the prior art, or at least do so to a
significantly reduced extent.
Generally, the CLC media should have a good chemical and thermal stability and a good stability towards electric fields and
35 electromagnetic radiation. Furthermore, they should have a broad cholesteric LC phase exhibiting a high clearing point, a sufficiently
- 6 high birefringence, a high positive dielectric anisotropy and a low rotational viscosity. The CLC should also allow to realize different reflection wavelengths, in particular in the visible range, by simple and controlled variation. They should furthermore exhibit a low 5 temperature dependence of the reflection wavelength.
For use in displays, the CLC media should have a high twist, a broad operating temperature range, short response times, a low threshold voltage and a low temperature dependence of the reflection 1 0 wavelength.
The chiral dopants used in the CLC media should exhibit a high twisting power with low temperature dependence, a high stability and a good solubility in the LO host. Moreover they should ideally not 15 have an adverse effect on the liquid-crystalline and electro-optical properties of the LO host. A high twisting power of the dopants is desired, inter alla, to achieve small pitches but also to be able to lower the concentration of the dopant. As a result, on the one hand the risk of impairment of the properties of the CLC medium by the 20 dopant is lowered, and on the other hand the scope with regard to the solubility of the dopant is extended, so that it is possible, for example, to use dopants of relatively low Volubility.
One aim of the invention is to provide a CLC medium which has the 25 above mentioned required properties.
A further aim of this invention is to provide an advantageous use of a CLC medium according to this invention.
30 Further aims of this invention relate to LCDs and lasing and fluorescence applications comprising a CLC medium according to the present invention with improved properties.
Other aims of the present invention are immediately evident to the 35 person skilled in the art from the following detailed description.
It has now been found that the above aims can be achieved by using CLC media according to the present invention.
Summarv of the Invention The invention relates to a liquid-crystalline (LC) medium with a helically twisted phase comprising a nematic component and an optically active component, characterized in that the optically active component comprises one or more chiral compounds at least one of 10 which is selected of formula I (Y4)y4S(X)x' 15 MU-VxW' (Y2)y2uz V2 W2 wherein X4, X2, y, and y2 are independently of each other H. F. Cl, Br, I, ON, SON, SF5, straight chain or branched alkyl with up to 25 C 25 atoms which may be unsubstituted, mono- or poly substituted by F. Cl, Br, I or ON, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by -O-, -S-, N H-, -N R -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO
30 S-, -CH=CH- or -C-C- in such a manner that O and/or S atoms are not linked directly to one another, a polymerizable group, or cycloalkyl or aryl with up to 20 C atoms that is optionally mono- or polysubstituted by L or by a polymerizable group, R is H or alkyl with 1 to 4 C atoms,
- 8 x, and x2 are independently of each other 0, 1 or 2, y' and y2 are independently of each other 0, 1, 2, 3 or 4, B and C are independently of each other an aromatic or partially or fully saturated aliphatic sixmembered ring, wherein one or more CH groups may be replaced by N and one or more CH2 groups may be replaced by O and/or S. one of W. and w2 is -Z4A4-(Z2-A2)m-R and the other is R* or A*, or both of W. and w2 are -Z4-A'(Z2-A2)m-R, with We and w2 not being at the same time H. or 15 W' >A Z'A'-(Z2-A2)m-R / - or >Z' A1-(Z2 A2)m R U' and u2 are independently of each other CH2, O. S. CO or CS, V' and v2 are independently of each other (CH2)n, wherein up to four non-adjacent CH2-groups may be replaced by O 25 and/or S. and one of V, and V2, or, in case W. ≥0 Z'-A'-(Z2-A2)m-R one or both of V, and v2 may also denote a single bond, n is an integer from 1 to 7, Z' and z2 are independently of each other -O-, -S-, -CO-, - COO-, OCO-, -O-COO-, -CO-NR -, -NR -CO-, -OCH2-, -CH2O-,
35 -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-,
CH2CH2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-,
- 9 - N=CH-,-N=N-,-CH=CH-,-CF=CH-,-CH=CF-,-CF=CF-,
-C_C-,-CH=CH-COO-,-OCO-CH=CH- or a single bond, At, A2 and A* are independently of each other 1,4-phenylene in which, 5 in addition, one or more CH groups may be replaced by N. 1,4-cyclohexylene in which, in addition, one or two non adjacent CH2 groups may be replaced by O and/or S. 1,3 dioxolane-4,5-diyl, 1,4-cyclohexenylene, 1,4-bicyclo (2,2,2)octylene, piperidine-1,4-dlyl, naphthalene-2,6-dlyl, 10 decahydronaphthalene-2,6-dlyl, or 1,2,3,4 tetrahydronaphthalene-2,6- dlyl, it being possible for all these groups to be unsubstituted, mono- or polysubstituted with L, and A, may also be a single bond, 15 L is halogen or a cyano, nitro alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl, m is in each case independently 0, 1, 2 or 3, and R and R* are independently of each other H,F,CI, Br, I, ON, SON, OH,SF5, straight chain or branched alkyl with up to 25 C atoms which may be unsubstituted, monoor polysubstituted by F,CI, Br, I or ON, it being also 25 possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by -O-, -S-, -N H-,-N Rig-, - CO-, -COO-, -OCO-, -OCO-O-, -S-CO-,-CO-S-,-CH=CH- or-C_C- in such a manner that O and/or S atoms are not linked directly to one 30 another, or a polymerizable group.
The invention further relates to the use of LO media according to the present invention in LC displays, in particular bistable displays such as flexoelectric or cholesteric displays like SSCT and PSCT displays, for 35 lasing and fluorescence applications such as telecommunication applications like waveguides and high resolution filters, photonic
- 10 crystal lasers, switches, backlights and LED type applications, for diagnostics, temperature indicators, decorative or security applications like security markings or security threads for authentification of objects or documents of value.
The invention further relates to an LC display, in particular a bistable display such as a flexoelectric, cholesteric, SSCT or PSCT display, comprising a CLC medium as described above and below.
10 The invention further relates to a lasing or fluorescence device, a temperature indicator or security or identification marking comprising a CLC medium as described above and below.
Brief Description of the Drawinns
Figure 1 shows Climax as a function of temperature for CLC media according to example 1.
Figure 2 shows the red edge of the reflection band against 20 temperature for CLC media according to example 1.
Figure 3 shows the blue edge of the reflection band against temperature for CLC media according to example 1.
25 Figure 4 shows values of Climax, bred and Sue for a CLC medium according to example 2.
Figure 5 shows values of Relax' Fred and Ague for a CLC medium according to example 3.
Detailed Description of the Invention
Especially preferred are LO media wherein the nematic component comprises one or more compounds of formula 11
- 11 R1 IN wherein R' is H. alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms 10 which is unsubstituted, monosubstituted by ON or CF3 or mono- or polysubstituted by halogen, where one or more CH2 groups in these radicals may also, in each case independently of one another, be replaced by -O-, -S-, CO-, -CO-O-, -O-CO-, -O-CO-O- or -C_C- in such a way 15 that oxygen atoms are not linked directly to one another, L1 to L6 are each independently of one another H or F. and a isOor1. The compounds of formula 11 are preferably selected from the following formulae L4 25 R1 IN ha L4 L' R1 4, O >_ _CN fib
- 12 F L3 R1 CN no R1 9 CN lid R CN He 15 wherein R' is as defined in formula I and L, to L6 are each, independently of one another, H or F. In these compounds, R. is particularly preferably alkyl or alkoxy having 1 to 8 carbon atoms.
Particular preferred are compounds of formula Ha and lib, in 20 particular those in which L, to L4 are H. Further preferred are compounds of formula llc, in particular those in which L3 is H. Further preferred are LC media wherein the nematic component comprises one or more compounds of formula lil R1 Z3{: NCS lil wherein R. is H. alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or mono- or polysubstituted by halogen, where one or more CH2 groups in these radicals may also, in each case
- 13 independently of one another, be replaced by -O-, -S-, CO-, -CO-O-, O-CO-, -O-CO-O- or -C--C- in such a way that oxygen atoms are not linked directly to one another, Ls is {> or {a 10 L1 to L6 are each independently of one another H or F. Z3 iS -CH=CH- or a single bond, and b isOor1. The compounds of formula 11 are preferably selected from the following formulae L R1 NCS Illa L' R1{}CH=CHNCS Illb L2 30 L5 L3 L1
R1 _ j =;- NCS Illc
- 14 wherein R, and L, to L6 are as defined above. In these compounds, R. is particularly preferably straight-chain alkyl or alkoxy with 1 to 8 Catoms. 5 Particular preferred are compounds of formula Illa wherein L' and L2 are F. and compounds of formula Illb wherein L, is F and L2 is H or F. Further preferred are compounds of formula Illc wherein L, and L2 are H and L5 and L6 are F. Further preferred are compounds of formula Illa and Illc wherein R. is straight-chain alkyl with 1 to 8 C 10 atoms, and compounds of formula lilb wherein R. is straight-chain alkoxy with 1 to 5 C-atoms.
The chiral compounds of formula I enable a high twist in the LC media according to the present invention even when used in small amounts, 15 and furthermore result in a low temperature dependence of the helical pitch and the reflection wavelength of the LC media. Furthermore, due to the use of compounds of formula I the position of the reflection band that does not or only slightly change with temperature.
20 The use of the compounds of formula 11 and lil in the LC media according to the invention results in a high polarity and a high An value.
Furthermore, the LC media according to the present invention have the following advantages: 25 - they have a broad cholesteric phase range, in particular at low temperatures, and a high clearing point, - they have a high UV stability, - they have a low temperature dependence of the reflection 30 wavelength, - they have a low temperature dependence of the position of the reflection spectrum, - they have high birefringence.
- 15 The compounds of the formulae 11 and lil have a broad range of application. Depending on the choice of substituents, these compounds can serve as base materials of which the LC media are predominantly composed; however, it is also possible to add 5 compounds of the formulae 11 and lil to LC base materials from other classes of compounds in order, for example, to modify the dielectric and/or optical anisotropy of a medium of this type and/or to optimize its viscosity. In the pure state, the compounds of the formulae 11 and lil are colourless and form LC mesophases in a temperature range 10 which is favourably located for the desired use. They are stable chemically, thermally and to light.
Preferred LC media comprise, in addition to the compounds of the formulae 1, II and lil, one or more compounds selected from the group 15 consisting of the bicyclic compounds of the following formulae R4R2 IV1
R'{ R2 IV2
RiCH2CH2{R2 IV3 R'}R2 IV4
R'} Q R2 IV5
R'{R2 IV6
- 16 R1 CH2CH2 R2 IV7
5 R'COO}R2 IV8
R1CH=CH R2 IV9
R1 COO R2 IV34
and/or one or more compounds selected from the group consisting of 15 the tricyclic compounds of the following formulae R'(R2 IV1 0
R'CH2CH2{: - R2 IV11
R1{( R2 IV12
R}R2 IV13
R'{>CH2CH2{R2 IV14
R'{} CH2cH2} R2 IV15
- 17 R1{:}R2 IV16
5 R1{CH2CH2 R2 IV17
R1CH2CH2 R2 IV18
R'{ - CH2CH2CH2CH2{} R2 IV19
15 A'{}} R2 IV20
R13R2 IV21
R {3 R2 IV22
R1 CH2CH2 R2 IV23
R' CH=CH R2 IV24
30 L1 R1 COO R2 IV32
R1 COO R2 IV33
- 18 and/or one or more compounds selected from the group consisting of the tetracyclic compounds of the following formulae R' R2 IV25
10 R1{: CH2CH2 3 R2 IV26
R (A R2 IV27
R13CH2CH2}R2 IV28
20 R ( 3 R2 IV29
R1{{3coo {R2 IV30 R' R2 IV31
30 in which Rat and R2 have one of the meanings given for R' above, and are preferably each, independently of one another, an alkyl, alkoxy or alkenyl group having 1 to 12 carbon atoms, where one or two non adjacent CH2 groups may also be replaced by -O-, -CH=CH-, -C-C-, -CO-, -OCO- or COO- in such a way that oxygen atoms are not 35 linked directly to one another, and L, is H or F. R' and R2 are
- 19 particularly preferably straight-chain alkyl or alkoxy having 1 to 12 carbon atoms.
The 1,4-phenylene groups in IV10 to IV19 and IV23 to IV 32 may also 5 each, independently of one another, be monosubstituted or polysubstituted by fluorine.
Particular preference is given to compounds of the formulae IV 25 to IV 34 in which R. is alkyl and R2 is alkyl or alkoxy, in particular alokxy, 10 in each case having 1 to 7 carbon atoms. Preference is furthermore given to compounds of the formulae IV 25 and IV 31 in wich L, is F. Very particular preference is given to compounds of the formulae IV25 and IV34.
15 Further preferred are LC media wherein the nematic component additionally comprises one or more compounds selected of formula V L 20 R' Z4- ON V
wherein R. has one of the meanings given above, and are independently of each other 30 {> or L, to L6 are each, independently of one another, H or F. Z4 iS -COO- or a single bond, and
- 20 c isO, 1 or2.
The compounds of formula V are preferably selected from the 5 following formulae L1 RAN Va 10 L 5 i:: Vb R. A} COO IN Vc R1 COOCN Vd R COO 3 5} CN Ve wherein R. is as defined above and is preferably straight-chain alkyl or alkoxy having 1 to 8 carbon atoms, and L' and L2 are H or F. Particular preferred are compounds of formula Va, Vb and Vc, in particular those wherein L' and L2 are H. Particularly preferred compounds of formula I are those wherein
- 21 - at least one, preferably both, of the radicals B and C are an aromatic ring, - at least one, preferably both, of the radicals B and C contain two saturated carbon atoms, - at least one, preferably both, of the radicals B and C contain four saturated carbon atoms, - at least one, preferably both, of the radicals U. and u2 are O. - V' and v2 are (CH2)n in which n is 1, 2, 3 or 4, and preferably one 10 of the radicals V, and v2 is CH2 and the other is CH2 or (CH2)2, - one of the radicals V, and v2 is CH2 and the other is a single bond, - at least one of the radicals Z. and Z2 iS -CF2O-, -OCF2- or 1 5 CF2CF2-,
- Z' is a single bond, - at least one of the radicals Z' and Z2 iS -CF2O-, -OCF2-, -CF2CF2- or -CF=CF- and the others are -COO-, -OCO-, -CH2-CH2- or a single 20 bond, - at least one of the radicals Z. and Z2 iS -C_C-, 25 W' >I Z'-A'-(Z2-A2)m-R' or Z'-A'-(Z2-A2)m-R' and m is O or 1, in particular 0, preferably m is 0 and A, is a single 30 bond, - W' is R* or A*, in particular H or F. and w2 is Z'-A'-(Z2-A2)m-R', in which m is 1 or 2, - x, and x2 are 1, 35 - y' and y2 are 1, - x',x2,yandy2areO,
- 22 - at least one, preferably one or two, of the radicals X,, X2, Y' and y2 are a polymerizable group or contain a polymerizable group, - R' is a polymerizable group, 5 - R' is straight-chain alkyl having 1 to 12 carbon atoms, where one or more hydrogen atoms may also be replaced by F or CN and where one or more non-adjacent CH2 groups may also, in each case independently of one another, be replaced by -O-, -S-, -NH-, N(CH3)-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -CH=CH
10 or -C-C- in such a way that oxygen atoms and/or sulfur atoms are not linked directly to one another, particularly preferably alkyl or alkoxy having 1 to 12 carbon atoms, - X], X2, y4, y2 and R* are selected from H. F and straight-chain alkyl having 1 to 12 carbon atoms, where one or more hydrogen atoms 15 may also be replaced by F or CN and where one or more non adjacent CH2 groups may also, in each case independently of one another, be replaced by-O-, -S-, -NH-, -N(CH3)-, -CO-, -COO-, OCO-, -OCOO-, -S-CO-, -CO-S-, -CH=CH- or -C=C- in such a way that oxygen atoms and/or sulfur atoms are not linked directly to one 20 another, and are particularly preferably H. F or alkyl or alkoxy having 1 to 12 carbon atoms, - X', X2, y, and y2 are selected from aryl, preferably phenyl which may be unsubstituted or mono- or polysubstituted by L, preferably monosubstituted in 4 position, - L is F. Cl, CN or optionally fluorinated alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl having 1 to 7 carbon atoms, - L is F. Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F or OC2F5, 30 A* is 1,4-phenylene or 1,4cyclohexylene which may also be substituted by up to 5, preferably by 1, 2 or 3 F or Cl atoms, CN or NO2 groups or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups having 1 to 4 carbon atoms, where one or more hydrogen atoms may also be replaced by F or Cl,
- 23 - A' and A2 are selected from 1,4-phenylene and trans-1,4 cyclohexylene which groups may be unsubstituted or substituted by up to 4 L radicals, - the mesogenic group Z'-A'-(Z2-A2)m contains one, two or three 5 five- or six-membered rings, - the mesogenic group Z,-A4-(Z2-A2)m is bicyclohexyl, biphenyl, phenylcyclohexyl, cyclohexylphenyl or biphenylcyclohexyl, where the phenyl rings may also be substituted by one or two fluorine 1 0 atoms, The mesogenic group -Z'-A4-(Z2-A2)m in formula I is preferably selected from the following subformulae or their mirror images. Here Phe is 1,4-phenylene which may be substituted by one or more L 15 groups, and Cyc is 1,4-cyclohexylene. Z is, independently at each occurrence, as defined above for Z'.
-Phe -Cyc 20 -Phe-Z-Phe -Phe-Z-Cyc -Cyc-Z-Cyc -Phe-Z-Phe-Z-Phe -Phe-Z-PheZ-Cyc 25 -Phe-Z-Cyc-Z-Phe -Cyc-Z-Phe-Z-Cyc -Cyc-Z-Cyc-Z-Phe -Cyc-Z-Cyc-ZCyc 30 L is preferably F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, CF3, CHF2, CH2F, OCF3 OCHF2, OCH2F, OC2F5, in particular F. Cl, ON, CH3, CHF2, C2H5, OCH3, OCHF2, CF3 or OCF3, very particularly preferably F. CH3, CF3, OCH3, OCHF2 or OCF3.
35 The polymerizable group is preferably selected from the formula P-Sp X, in which
- 24 o P is CH2=CW4-COO-, W HO-CH-, W242(CH2)k, 0 CH2=CW2-(0)k1-, CH3CH=CH-O-, Ho-CW2W3-, HS-CW2W3-, 5 HW2N-, Ho-CW2W3-NH-, CH2=CW1-CO-NH-, CH2=CH-(COO)k1 Phe-(O)k2-, Phe-CH=CH-, HOOC-, OCN- or W4W5W6Si, Sp is a spacer group having 1 to 25 carbon atoms or a single bond, 1 0 X is -O-, S-, -OCH2-, -CH2O-, -CO-, -COO-, -OCO-, -OCO-O-, -CO-N(R )-, -N(R )-CO-, -OCH2-, -CH2O-, -SCH2-, -CH2S-,
-CH=CH-COO-, -OOC-CH=CH- or a single bond, and W. is H. Cl, ON, phenyl oralkyl having 1 to 5 carbon atoms, in 15 particular H. Cl or CH3, W2 and W3 are each, independently of one another, H or alkyl having 1 to 5 carbon atoms, in particular methyl, ethyl or n-propyl, 20 W4, W5 and w6 are each, independently of one another, Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 carbon atoms, Phe is 1,4-phenylene, 25 k1 and k2 are each, independently of one another, 0 or 1, and R is H or alkyl having 1 to 4 carbon atoms.
P is preferably a vinyl, acrylate, methacrylate, propenylether or epoxy 30 group, in particular an acrylate or methacrylate group.
Sp is preferably chiral or achiral, straight-chain or branched alkylene having 1 to 20, preferably 1 to 12, carbon atoms, where one or more nonadjacent CH2 groups may also be prefaced by -O-, -S-, -NH-, 35 N(CH3)-,CO-,-O-CO-,-S-CO-,-O-COO-,-CO-S-,-CO-O-,
- 25 CH(halogen)-, -CH(CN)-, -CH=CH- or -C-C- in such a way that oxygen atoms are not linked directly to one another.
Typical spacer groups are for example -(CH2)p-, -(CH2CH2O)r-CH2CH2-, 5 CH2CH2-S-CH2CH2- or-CH2CH2-NH-CH2CH2-, where p is an integer from 2 to 12 and r is an integer from 1 to 3.
Preferred spacer groups are for example ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, 10 decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
15 Particularly preferred compounds of formula I are the following }R la 20 To 25 jR.R lb jR.ZR lo
- 26 OR Id 10 R*}R le 5 OCFZCFzR If to OR 19 R*Z R Ih
- 27 z1- R 1i 10 R*Z,_ R Ik R^ZocF2{}R Im 20 it; R*Z OCF2{){R In lo 30 = 0 R
- 28 5 o lip 10 j R*R Iq 15 \ 25 4 0-\ R Is R" / - LO: tLo: it LO;
- 29 R*R to {}A Iv in which R. R* and Z. are as defined in formula 1, R' and R" have one of the meanings of R in formula 1, and L' and L2 are H or have one of the meanings of L in formula 1.
In these preferred formulae, Lo and L2 are preferably H or F. R* is preferably H or F. R' and R" are preferably H. F. alkyl or alkoxy having 1 to 12 carbon atoms or P-Sp-X-. R" is particularly preferably CH3. Particular preference is given to compounds of the following formulae 30 PAR lb]
- - 30 }OR Ic1 5 [A wherein R is alkyl with 1 to 8 C-atoms and Z. is -COO, -OCO- or a single bond, preferably a single bond.
10 The optically active component comprises one or more chiral compounds, preferably selected of formula 1, whose twisting power and concentration are selected such that the helical pitch of the LC medium is smaller than 1 m.
15 The proportion of the optically active component in the LC medium according to the invention is preferably < 20%, in particular < 10%, particularly preferably from 0.01 to 7%, very particularly preferably from 0.5 to 5%. The optically active component preferably comprises from 1 to 6, in particular 1, 2, 3 or 4 chiral compounds.
The helical pitch of the LC medium according to the present invention is preferably from 130 nm to 1000 nm, in particular from 200 nm to 750 nm, particularly preferably from 250 nm to 500 nm.
25 The helical pitch is preferably chosen such that the medium reflects light in the visible wavelength range. The term "visible wavelength range" or "visible spectrum" typically comprises the range of wavelengths from 400 to 800 nm. Above and below, this term is also meant to encompass the wavelength range from 200 to 1200 nm including the UV and infrared (JR) range and the far UV and far IR range. The reflection wavelength of the LC medium according to the present invention is preferably in the range from 200 to 1500 nm, in particular 35 from 300 to 1200 nm, particularly preferably from 350 to 900 nm, very particularly preferably from 400 to 800 nm. Preference is furthermore
- 31 given to LC media having a reflection wavelength of from 400 to 700 nm, in particular from 400 to 600 nm.
Especially preferred are LC media according to the present invention 5 that have a cholesteric phase (CLC media), preferably with a cholesteric phase range of at least 90 C, in particular at least 100 C.
The cholesteric phase range preferably extends at least from -20 to + 80 C. While maintaining the cholesteric phase down to -20 C, preferably down to -30 C, particularly preferably down to -40 C, the 10 LC media according to the invention preferably have clearing points above 70 C, preferably above 90 C, particularly preferably above 1 1 0 C.
The LC media preferably have dielectric anisotropy values As 2 5, 15 preferably 210, in particular > 15, and birefringence values An > 0.15, preferably > 0.22, very preferably > 0.26.
Particular preference is given to LC media according to the invention wherein the temperature dependence of the reflection wavelength 20 (d\/dT) /\maX is 5 % or less, in particular 2 % or less, very particularly preferably 1 % or less, preferably in the range between 0 and 50 C, in particular between -10 and 60 C, particularly preferably between 20 and 70 C, very particularly preferably in the range from - 20 C to a temperature 10 C, in particular 5 C, below the clearing point.
For many applications like e.g. Iasing phenomena, it is important that the position of the whole reflection spectrum of the CLC medium does not change with temperature. The "red" and "blue" edges of this band Fred and Able can be determined from the following expressions: \=d = \X + 2 = \x (1 + 2n) (4) 35 blue max 2 max(l- 2n) (5)
- 32 In LC media according to the present invention the temperature dependence of the red edge of the reflected waveband (dred/dT)/\red is preferably 5 % or less, in particular 2 % or less, very particularly preferably 1 % or less. The temperature dependence of the blue edge 5 of the reflected waveband (db'UeIdT)Ilbue is preferably 5 % or less, in particular 2 % or less, very particularly preferably 1 % or less. The above values of (dred/dT)/7red and (db'UeIdT)I\bue preferably refer to the temperture range between O and 50 C, in particular between -10 and 60 C, particularly preferably between - 20 and 70 C, very 10 particularly preferably in the range from - 20 C to a temperature 10 C, in particular 5 C, below the clearing point.
Unless otherwise indicated, d\X/dT is the local slope of the function \(T) , where a nonlinear function x(T) is described approximately by a 15 2nd or 3rd order polynomial. The value of Climax as given above and below refers to the half-width half-maximum (HWHM) of the reflection band. The chiral dopants should preferably have a high helical twisting 20 power (HTP) with low temperature dependence. They should furthermore have a good solubility in the nematic component and not impair the liquid- crystalline properties of the LC medium, or impair them only to a small extent. They can have the same or the opposite orientation of rotation and the same or the opposite temperature 25 dependence of the twist.
Particular preference is given to dopants having an HTP of 20 m' or more, in particular of 40 m4 or more, particularly preferably of 70 um' or more.
In LC media according to the present invention especially the chiral dopants of formula I exhibit a good solubility in the nematic component and induce a cholesteric structure having a high twist and a low temperature dependence of the helical pitch and the reflection 35 wavelength. For this reason, it is possible to obtain novel LC media which have reflection colours in the visible wavelength range having a
- 33 high brilliancy and a low temperature dependence and which are especially suitable for use in SSCT and PSCT displays or for lasing devices, even when only one of these dopants is used in low amounts. This is a significant advantage over CLC media of the prior art which
usually require at least two dopants having opposite temperature dependence of the twist (for example one dopant having a positive temperature dependence, i.e. increasing twist with increasing 10 temperature, and one dopant having a negative temperature dependence) to achieve a temperature compensation of the reflection wavelength. Moreover, the known CLC media often require large amounts of dopants to achieve reflection in the visible range.
15 A particularly preferred embodiment of the invention therefore relates to a LC medium as described hereinbefore and hereinafter, in which the chiral component consists of one chiral compound of formula 1, preferably in an amount of 15 % or less, in particular 10 % or less, particularly preferably 5 % or less. An LC medium of this preferred 20 embodiment has a low temperature dependence of the reflection wavelength over a broad temperature range.
In addition to the compounds of formula 1, the optically active component may also comprise one or more further chiral dopants, 25 which should preferably have a high twist. Particularly suitable dopants are those having one or more chiral radicals and one or more mesogenic groups, or one or more aromatic or alicyclic groups which form a mesogenic group with the chiral radical.
30 Suitable chiral radicals are for example chiral branched hydrocarbon radicals, chiral ethanediols, binaphthols or dioxolanes, furthermore monovalent or multivalent chiral radicals selected from the group comprising sugar derivatives, sugar alcohols, sugar acids, lactic acids, chiral substituted glycols, steroid derivatives, terpene 35 derivatives, amino acids or sequences of a few, preferably 1-5, amino acids.
- 34 Preferred chiral radicals are sugar derivatives such as glucose, mannose, galactose, fructose, arabinose, dextrose; sugar alcohols such as sorbitol, mannitol, iditol, galactitol or their anhydro 5 derivatives, in particular dianhydrohexites such as dianhydrosorbide (1,4:3,6-dianhydro-Dsorbide, isosorbide), dianhydromannitol (isosorbitol) or dianhydroiditol (isoiditol); sugar acids such as gluconic acid, gulonic acid, ketogulonic acid; chiral substituted glycol radicals such as mono- or oligoethylene or mono- or oligopropylene glycols in 10 which one or more CH2 groups are substituted by alkyl or alkoxy; amino acids such as alanine, valine, phenylglycine or phenylalanine, or sequences of from 1 to 5 of these amino acids; steroid derivatives such as cholesteryl or cholic acid radicals; terpene derivatives such as menthyl, neomenthyl, campheyl, pineyl, terpineyl, isolongifolyl, 15 fenchyl, carreyl, myrthenyl, nopyl, geranlyl, linaloyl, neryl, citronellyl or dihydrocitronellyl. Suitable chiral radicals and mesogenic chiral compounds are described, for example, in DE 34 25 503, DE 35 34 777, DE 35 34 20 778, DE 35 34 779 and DE 35 34 780, DE-A-43 42 280, EP-A-1 038 941 and DE-A-195 41 820.
In particularly preferred embodiments the LC medium comprises: 25 - one or more, preferably 1 or 2 chiral compounds of formula la, lb or Ic, very preferably of formula Ib1, - 0.1 to 10 %, preferably 1 to 8 %, very preferably 2 to 5 % of chiral compounds of formula 1, 20 % or less, preferably 10% or less, very preferably 0.01 to 7%, of the optically active component, - one or more, preferably 2 to 6 compounds of formula lla, in 35 particular wherein L' to L4 are H.
- 35 - one or more, preferably 1, 2 or 3 compounds of formula lib, in particular wherein L, to L4 are H. one or more, preferably 1,2 or 3 compounds of formula llc, in 5 particular wherein L3 is H. - 1 to 10, preferably 3 to 8 compounds of formula 11, - a nematic component comprising 25 to 95 %, preferably 35 to 75 10 % of one or more compounds of formula 11, a nematic component comprising 15 to 80 %, preferably 30 to 70 % of one or more compounds of formula lla, 15 - one or more, preferably 2 to 5 compounds of formula lila, in particular wherein L, to L4 are H. one or more, preferably 2 to 6 compounds of formula lilb, in particular wherein L' and L2 are F. 1 to 9, preferably 2 to 7 compounds of formula lil, - a nematic component comprising 5 to 65 %, preferably 15 to 55 % of one or more compounds of formula lil, a nematic component comprising 5 to 35 %, preferably 10 to 25 % of one or more compounds of formula Illa, - 5 to 35 %, preferably 10 to 25 % of one or more compounds of 30 formula lilb, - one or more compounds of formula V, preferably of Va, Vb and Vc, in particular wherein L' and L2 are H. The amount of these compounds in the nematic component is preferably 2 to 35 %, 35 very preferably 3 to 30 %,
- 36 a nematic component comprising in total 65 to 99 % of compounds of the formulae 11, III, IV and V, - a nematic component essentially consisting of compounds 5 selected from formulae 11, IV and V. - a nematic component essentially consisting of compounds selected from formulae lil, IV and V. 10 The optimum weight ratio of compounds of the formulae I to V largely depends on the desired properties, on the choice of the components of the formulae I to V and on the choice of any other components which may be present. Suitable weight ratios within the range given above can easily be determined from case to case.
Another preferred embodiment relates to a twisted CLC medium according to the present invention which comprises one or more compounds having at least one polymerizable group. Such CLC media are particularly suitable for use e.g. in polymer gel displays or 20 PSCT displays. The polymerizable compounds can be part of the nematic and/or chiral component or form an additional component of the medium.
Suitable polymerizable compounds are known to the person skilled in 25 the art and have been described in the prior art. Examples of
particularly suitable compounds are compounds having a group P as described for formula Xll, in particular alkyl or aryl acrylates, methacrylates and epoxides. The polymerizable compounds may additionally be mesogenic or liquid-crystalline. They can contain one 30 or more, preferably two, polymerizable groups. Typical examples of non-mesogenic compounds having two polymerizable groups are alkyl diacrylates or alkyl dimethacrylates having alkyl groups of 1 to 20 carbon atoms. Typical examples of non-mesogenic compounds having more than two polymerizable groups are trimethylolpropane 35 trimethacrylate or pentaerythritol tetraacrylate.
- 37 Preferred chiral polymerizable mesogenic compunds are compounds of the formulae Xll to XVI containing one or more radicals containg a group P as defined for formula All.
5 Further suitable polymerizable compounds are described, for example, in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586 and WO 97/00600. Typical examples for suitable polymerizable mesogenic compounds are shown in the following list which is intended to illustrate the subject-matter of the present 10 invention without limiting it: P-(CH2)XO COO 3 Ye (Vl la) P-(CH2)XO Coo Y (Vl 1 b) 20 P-(CH2)xO COO R5 (VIIC) P-(CH2)XO COO R5 (Vl Id) P-(CH2)XO CH=CH-COO R5
(Vile) 30 CH2=CHCOO(CH2)x O R5 v (Vllf) P-(CH2)XO COO 3t CH2CH(CH3) C2H5 (Vl19)
- 38 P-(cH2)xo COO COO CH2CH(CH3)c2H5 (Vl I h) P-(cH2)xo COO-Ter (Vlli) P(CH2)xO /3 COO-Chol 10 (Vlik) P-(CH2)XO COO
(Vllm) P(CH2)x coo oco O(CH2)yP (Vl I n) L1 L2 P(CH2)x CH2CH2 CH2CH2 o(CH2)yP (Vl 1O) P O CO2 O2C O P
25 <3 <3 \ (Vllp) /=\ H P(CH2)x CH=CHCOO>, O 30 OOCCH=CH O(CH2)yP (Vl Iq)
- 39 P(CH2)0 o:H VO(CH2)yP (Vllr) In these compounds, P is a polymerizable group as defined in formula 1, x and y are identical or different integers from 1 to 12, C 10 and D are 1,4-phenylene or 1,4- cyclohexylene, v is 0 or 1, Y is a polar group, R5 is a nonpolar alkyl or alkoxy group, Ter is a terpenoid radical such as menthyl, Chol is a cholesterol radical, L, and L2 are each, independently of one another, H. F. Cl, CN, OH, NO2 or optionally halogenated alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl 15 having 1 to 7 carbon atoms.
The polar group Y is preferably CN, NO2, halogen, OCH3, OCN, SON, COR6, COOR6 or mono-, oligo- or polyfluorinated alkyl or alkoxy having 1 to 4 carbon atoms. R6 is optionally fluorinated alkyl 20 having 1 to 4, preferably 1, 2 or 3 carbon atoms. Y is particularly preferably F. Cl, CN, NO2, OCH3, COCH3, COC2H5, COOCH3, COOC2H5, CF3, C2F5, OCF3, OCHF2 or OC2F5, in particular F. Cl, CN, OCH3 or OCF3.
25 The nonpolar group R5 is preferably alkyl having 1 or more, in particular 1 to 15, carbon atoms or alkoxy having 2 or more, in particular 2 to 15, carbon atoms.
The abovementioned polymerizable compounds can be prepared by 30 methods which are known per se and which are described in standard works of organic chemistry, for example Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.
In the abovementioned formulae I to Vll, the term "fluorinated alkyl or 35 alkoxy having 1 to 3 carbon atoms" preferably means CF3, OCF3, CFH2, OCFH2, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H,
- 40 CFHCFH2, CH2CF3, CH2CF2H, CH2CFH2, CF2CF2H, CF2CFH2,
OCFHCF3, OCFHCF2H, OCFHCFH2, OCH2CF3, OCH2CF2H,
OCH2CFH2, OCF2CF2H, OCF2CFH2, C3F7 or OC3F7, in particular CF3, OCF3, CF2H, OCF2H, C2F5, OC2F5, CFHCF3, CFHCF2H, CFHCFH2,
5 CF2CF2H, CF2CFH2, OCFHCF3, OCFHCF2H, OCFHCFH2,
OCF2CF2H, OCF2CFH2, C3F7 or OC3F7, particularly preferably OCF3 or OCF2H.
The term "alkyl" encompasses straight-chain and branched alkyl 10 groups having 1-7 carbon atoms, particularly the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups having 2-5 carbon atoms are generally preferred.
The term "alkenyl" encompasses straight-chain and branched alkenyl 15 groups having 2-7 carbon atoms, in particular the straight-chain groups. Particularly preferred alkenyl groups are C2-C7-1 E-alkenyl, C4C7-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, in particular C2-C7-1 E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4-alkenyl.
Examples of preferred alkenyl groups are vinyl, 1 E-propenyl, 20 1 Ebutenyl, 1 E-pentenyl, 1 E-hexenyl, 1 E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 carbon atoms are generally preferred.
25 The term "fluoroalkyl" preferably encompasses straight-chain groups with terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. Other positions of fluorine are not precluded, however.
30 The term "oxaalkyl" preferably encompasses straight-chain radicals of the formula CnH2n±O-(CH2)m, where n and m are each, independently of one another, from 1 to 6. Preferably, n = 1 and m is 1 to6.
35 Halogen is preferably F or Cl, in particular F.
-41 If one of the abovementioned radicals is an alkyl radical and/or an alkoxy radical, this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, 5 butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy. 10 Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.
If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by -CH=CH-, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it is in particular vinyl, prop-1- or prop-2-enyl, 20 but-1-, -2- or but-3-enyl, pent-1-, -2-, -3- or pent-4-enyl, hex-1-, -2-, 3-, -4or hex-5-enyl, inept-1-, -2-, -3-, -4-, -5- or hept-6-enyl, oct-1-, 2-, 3-, -4-, -5-, -6- or oct-7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or non-8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or dec-9-enyl.
25 If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by -O- and one has been replaced by -CO-, these are preferably adjacent. These thus contain an acyloxy group -CO-Oor an oxycarbonyl group -O-CO-. These are preferably straight-chain and have 2 to 6 carbon atoms.
They are accordingly in particular acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyl oxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 35 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy
- 42 carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy carbonyl) ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl or 4(methoxycarbonyl)butyl.
If one of the abovementioned radicals is an alkyl radical in which one CH2 group has been replaced by unsubstituted or substituted -CH=CH- and an adjacent CH2 group has been replaced by CO or CO-O or O-CO, this can be straight-chain or branched. It is preferably 10 straight-chain and has 4 to 13 carbon atoms. Accordingly, it is in particular acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8acryloyloxyoctyl, 9-acryloyloxynonyl, 1 O-acryloyloxydecyl, methacryloyloxymethyl, 2-methacryloyloxyethyl, 15 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxy pentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9methacryloyloxynonyl.
If one of the abovementioned radicals is an alkyl or alkenyl radical 20 which is monosubstituted by ON or CF3, this radical is preferably straight-chain. The substitution by ON or CF3 is in any position.
If one of the abovementioned radicals is an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is 25 preferably straight-chain and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resulting radicals also include perfluorinated radicals. In the case of monosubstitution, the fluoro or chloro substituent can be in any desired position, but is preferably in the co-position.
Compounds containing branched pendent groups may occasionally be of importance owing to better solubility in the conventional liquid crystalline base materials. However, they are particularly suitable as chiral dopants if they are optically active.
- 43 Branched groups of this type generally contain not more than one chain branch. Preferred branched radicals are isopropyl, 2-butyl (= 1methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3methylbutyl), 2-methylpentyl, 3-methylpentyl, 5 2-ethylhexyl,2propylpentyl, isopropoxy,2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy,1-methylhexoxy or 1methylheptoxy.
If one of the abovementioned radicals is an alkyl radical in which two 10 or more CH2 groups have been replaced by -O- and/or-CO-O-, this can be straight-chain or branched. It is preferably branched and has 3 to 12 carbon atoms. Accordingly, it is in particular biscarboxymethyl, 2,2biscarboxyethyl, 3,3-biscarboxypropyl,4,4-biscarboxybutyl, 5,5biscarboxypentyl, 6,6-biscarboxyhexyl, 7,7-biscarboxyheptyl, 15 8,8biscarboxyoctyl, 9,9-biscarboxynonyl,10,10-biscarboxydecyl, bis (methoxycarbonyl)methyl,2,2-bis(methoxycarbonyl)ethyl, 3,3-bis (methoxycarbonyl)propyl,4,4-bis(methoxycarbonyl)butyl, 5,5-bis (methoxycarbonyl)pentyl, 6,6-bis(methoxycarbonyl)hexyl, 7,7-bis (methoxycarbonyl)heptyl, 8,8-bis(methoxycarbonyl)octyl, bis(ethoxy 20 carbonyl)methyl, 2,2-bis(ethoxycarbonyl)ethyl, 3,3-bis(ethoxy carbonyl) propyl,4,4-bis(ethoxycarbonyl)butyl or 5,5-bis(ethoxy carbonyl)hexyl. The invention furthermore relates to electro-optical displays 25 containing LO media according to the invention, in particular SSCT and PSCT displays having two plane-parallel outer plates which, together with a frame, form a cell, and a cholesteric liquid-crystal mixture which is located in the cell. The structure of bistable SSCT and PSCT cells is described, for example, in WO 92/19695, WO 30 93/23496, US 5,453,863 or US 5,493,430.
The ratio d/p between the layer thickness of the liquid crystal cell d (separation of the outer plates) in a display according to the invention and the natural helical pitch p of the LC medium is preferably greater 35 than 1, in particular in the range from 2 to 20, particularly preferably from 3 to 15, very particularly preferably from 4 to 10.
- 44 The individual compounds which can be used in the media according to the invention are either known or can be prepared analogously to the known compounds.
The LO media which can be used in accordance with the invention are prepared in a manner conventional per se. In general, the desired amount of the components used in a lesser amount is dissolved in the components making up the principal constituent, expediently at 10 elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again after thorough mixing, for example by distillation.
15 The LO media mixtures according to the invention may also comprise further additives such as one or more stabilizers or antioxidants.
In the present application and in the following examples, the structures of the liquid-crystal compounds are specified by acronyms, which are 20 transformed into chemical formulae according to the following Tables A and B. All radicals CnH2n+, and CmH2m+, are straight-chain alkyl radicals having n or m C atoms. The coding according to Table B is self-evident.
Table A specifies the acronym for the parent body only. In individual cases, the acronym for the parent body is followed, separated 25 therefrom by a hyphen, by a code for the substituents R4, R2, L', L2 and L3 Code for R', R' R2 L, L2 L3 R2, L', L2, L3
nm CnH2n+1 CmH2m+1 H H H nOm CnH2n+10 CmH2m+1 H H H nO.m CnH2n+1 OCmH2m+ 1 H H H n CnH2n+1 CN H H H 35 n-N CnH2n+1 CN H H H nN.F CnH2n+1 CN F H H
- 45 nN.F.F CnH2n+4 CN F F H nF CnH2n+1 F H H H nOF OCnH2n+, F H H H 5 nF. F CnH2n+1 F F H H nmF CnH2n+1 CmH2m+1 H H F nOCF3/ nOT CnH2n+' OCF3 H H H n-Vm CnH2n+1 CH=CHCmH2m+1 H H H nV-Vm CnH2n+,CH=CH CH=CHCmH2m+4 H H H 10 nO-S CnH2n+0 NCS H H H nS.F.F CnH2n+4 NCS F F H Preferred mixture components are shown in Tables A, B and C. 15 Table A: (L,, L2, L3 = H or F) L1 R' 3 _ R2 R1{43,_ R2
20 L2 BCH CCH
R1{R2 R1{R2
CCP PCH
L1 L
30 R C2H4{>R2 R1{}C2H4
L2 r2 ECCP CECP
- 46 R' {I-CON R R {I COO R2
CH CP L1 L' R {}COO {I R R' > COO{R2
1n V ME HP
L1 R1{}COO{ R2 R' {it>-Coo{3 R2 15 L2 D OS L1 L1 20 { NO R2 {I> R2
PYP POX
25 R1 {I COO {I R R {I COO { 3 R2
CE HD 30 R1} R2 R{R2
CCPC CBC
L1 L2 L' L2
35 R'C_CR2 R1{}C-CR2
- 47 CPTP PTP
R1 {it} C2H4{ R R1 R2 EPCH B
1 o R1 {I} C2H4 {I R2 R {> C2H4 R2 EBCH BECH
5 R1 {)_ R2 R1 {C} C2H4 <} R2
F CPC PET
R1{3 C2H4{} C-C R2
CEPTP Table B:
CnH2n+1 ON CnH2n+1 COO {IN K3n BB3n 35 CnH2n+1 {I ON CnH2n+1 CN
- 48 M3n Tan / C H {)COO{}CN
CnH2n+1 {) CH=CH ZINCS 2 5 PVG-nO-S CHE CnH2n+1 IN PGIP-n-N 15 The following examples should illustrate the invention without limiting it.
Hereinbefore and hereinafter, percentages are given in per cent by weight. All temperatures are specified in degrees Celsius. m.p. denotes melting point, cl.p. = clearing point. Furthermore, C = 20 crystalline state, S = smectic phase, N = nematic phase, Ch = cholesteric phase and I = isotropic phase. The data between these symbols represent the transition temperatures. Furthermore, the following abbreviations are used (unless indicated otherwise the values refer to a temperature of 20 C) 25 An optical anisotropy at 589 nm ne extraordinary refractive index at 589 nm Ac dielectric anisotropy all dielectric constant parallel to thelongitudinal axes of the molecules 30, rotational viscosity [mPa À see] Max maximum reflection wavelength [nary] The helical twisting power HTP of a chiral compound which produces a helically twisted superstructure in a liquid-crystalline mixture is given by the equation HTP = (pc)' [,um] in which p is the helical pitch of the helically twisted phase, given in m, and c the concentration of the
- 49 chiral compound (for example, a c value of 0.01 corresponds to a concentration of 1 % by weight). Unless otherwise indicated, HTP values hereinbefore and hereinafter refer to a temperature of 20 C and the commercially available neutral nematic TN host mixture MLC 5 6260 (Merck KGaA, Darmstadt).
Example 1
The nematic host mixture M1 is formulated as follows K15 29.0 % cl.p. 109. 0 M9 12.0 % An 0.2820 M15 13.0 % ne 1.8080 M24 5.0 % As +16.9 15 T15 8.0 % all 22.6 BCH-5 11.0 %
PGIP-3-N 22.0 %
Mixture M1 is doped with the chiral compound of formula Ib1a in 20 different concentrations to give cholesteric mixtures C11 and C12.
C3H7 Ib1 a 25 To Furthermore, mixture M1 is doped with the chiral dopant D known from prior art and disclosed e.g. in WO 98/00428, to give cholesteric
mixture C13 as comparative example.
CH3O {: COO {a} co:? D 35 H OOC {: OOC {}OCH3
* - 50 The compositions of C11-C13 are shown in the table below M1 Ib1 a D 5 C11 97.31 % 2.69 %
C12 97.01 % 2.99 %
C13 (comparative) 96.07 % 3.93 % The resulting cholesteric mixtures have a maximum of the reflection 10 band climax in the visible range.
The values of climax for the chiral mixtures C11, C12 and C13 are shown in Figure 1 as a function of temperature. As can be seen, climax decreases by about 5% in the case of C13 containing a prior art
15 dopant, while it remains almost constant for C11 and C12 (less than 1 % change).
In Figures 2 and 3, Fred and Rue are plotted versus temperature for the same chiral mixtures as for figure 1. The value of Fred for the 20 samples C11 and C12 containing the dopant of formula Ib1a is only reduced by 2% as the temperature increases from -10 C to 60 C, whereas in the case of the mixture C13 doped with prior art dopant D,
Fred changes by at least 5% for the same temperature range. Rue iS independent of temperature for C11 and C12 (less than 0.5% 25 change) while it decreases by about 4% for C13.
Example 2
The nematic host mixture M2 is formulated as follows K6 10.0 % cl.p. 96.0 K9 5.0 % An 0.2456 K15 42.0 % ne 1.7697 M15 11.0 % As +16.2 35 T15 5.0 % ú11 21.5
BCH-5 14.0 %
- 51 BB21 3.0 %
CHE 10.0 %
Mixture M2 is doped with 2.57 % of the chiral compound of formula 5 Ib1a to give cholesteric mixture C21.
Figure 4 illustrates the values of Timex' Fred and Sue as a function of temperature, obtained for mixture C21. In this case, the wavelength corresponding to the red edge does not depend on temperature (less 10 than 1% variation) while the change in climax and Ague iS about 2% for a temperature range of-10 to 60 C.
Example 3
15 The nematic host mixture M3 is formulated as follows K6 5.0 % cl.p. 103.5 K9 4.0 % An 0.3242 K15 25.0 % ne 1.862 20 M9 8.0 % Ac 19.4 T15 6. 0 % 611 24.8
PGIP-3-N 12.0 %
PVG-20-S 10.0 %
PVG-40-S 11.0 %
25 BCH-2S.F.F 7.0 %
BCH-3S.F.F 6.0 %
BCH-5S.F.F 6.0 %
Mixture M3 is doped with 2.99 % of the chiral compound of formula 30 Ib1a to give cholesteric mixture C31.
In Figure 5, Oman Fred and Sue measured for mixture C31are represented as a function of temperature. For a temperature interval ranging from -20 C to 60 C, Ague remains almost constant with 35 temperature (about 0.7% change) while Bred decreases by only 2.5%.
Claims (16)
1. A liquid-crystalline (LC) medium with a helically twisted phase comprising a nematic component and an optically active component, 5 wherein the optically active component comprises one or more chiral compounds, at least one of which is selected of formula I 10 (Y)y4:S(X)x, MU' V' W'
15 (Y)y2(Rx) 1 wherein X', X2, Y. and y2 are independently of each other H. F. Cl, Br, I, ON, SON, SF5, straight chain or branched alkyl with up to 25 C atoms which may be unsubstituted, mono- or poly-substituted by F. Cl, Br, I or ON, it being also 25 possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by-O-,-S-,-NH-,-NR -,-CO-,-COO-,-OCO -OCO-O-, -S-CO-, -CO-S-, -CH=CH- orC_C- in such a manner that O and/or S atoms are not linked 30 directly to one another, a polymerizable group, or cycloalkyl or aryl with up to 20 C atoms that is optionally mono- or polysubstituted by L or by a polymerizable group, 35 R is H or alkyl with 1 to 4 C atoms,
- 53 x, and x2 are independently of each other 0, 1 or 2, y' and y2 are independently of each other 0, 1, 2, 3 or 4, 5B and C are independently of each other an aromatic or partially or fully saturated aliphatic sixmembered ring, wherein one or more CH groups may be replaced by N and one or more CH2 groups may be replaced by O and/or S. one of W' and w2 is -Z4A'-(Z2-A2)m-R and the other is R* or A*, or both of W' and w2 are -Z4-A'(Z2-A2)m-R, with W' and w2 not being at the same time H. or 15W' >0 Z'-A'(Z2-A2)m-R or >Z'-A'-(Z2-A2)m-R U' and u2 are independently of each other CH2, O. S. CO or CS, V' and v2 are independently of each other (CH2)n, wherein up to four non-adjacent CH2-groups may be replaced 25 by O and/or S. and one of V' and V2, or, in case W' ≥0 Zi-A'-(Z2-A2)m-R one or both of V' and v2 may also denote a single 30 bond, n is an integer from 1 to 7, Z. and Z2 are independently of each other -O-, -S-, -CO-, 35 -COO-, OCO-, -O-COO-, -CO-N R -, -N R -CO-,
-OCH2-, -CH2O-, -SCH2-' -CH2S-, -CF2O-' -oCF2-,
-54 -CF2S-,-SCF2-,-CH2CH2-,-CF2CH2-,-CH2CF2-,
-CF2CF2-,-CH=N-,-N=CH-,-N=N-,-CH=CH-,-CF=CH-,
-CH=CF-,-CF=CF-,-C_C-,-CH=CH-COO-,-OCO
CH=CH- or a single bond, A', A2 and A are independently of each other 1,4phenylene in which, in addition, one or more CH groups may be replaced by N. 1,4-cyclohexylene in which, in addition, one or two non-adjacent CH2 groups may be 10 replaced by O and/or S. 1,3-dioxolane-4,5-dlyl, 1,4 cyclohexenylene, 1,4-bicyclo-(2,2,2)-octylene, piperidine-1,4-dlyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, or 1,2,3,4 tetrahydronaphthalene-2,6-diyl, it being possible for 15 all these groups to be unsubstituted, mono- or polysubstituted with L, and A' may also be a single bond, L is halogen or a cyano, nitro alkyl, alkoxy, 20 alkylcarbonyl or alkoxycarbonyl group with 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl, m is in each case independently 0, 1, 2 or 3, and R and R* are independently of each other H,F,CI, Br, I, ON, SCN,OH,SF5, straight chain or branched alkyl with up to 25 C atoms which may be unsubstituted, mono- or polysubstituted by F, CI, Br, I or ON, it 30 being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by -O-, -S-, -NH-, NR -,-CO-,-COO-,-OCO-,-OCO-O-,-S-CO-,-CO
S-,-CH=CH- or -C_C- in such a manner that O 35 and/or S atoms are not linked directly to one another, or a polymerizable group.
2. A liquid-crystalline medium as claimed in claim 1, wherein the nematic component comprises one or more compounds of formula 11 L6 L5 L4 L3 L'
R' CN
wherein R' is H. alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by ON or CF3 or mono- or polysubstituted by halogen, where one or more CH2 groups in these radicals may also, in each case independently of one another, be replaced by-O-, -S-, -CO-, -CO-O-,-O-CO-, -O-CO O- or -C-C- in such a way that oxygen atoms are not linked directly to one another, L, to L6 are each independently of one another H or F. and a isOor1.
3. A liquidcrystalline medium as claimed in claim 1 or 2, wherein the nematic component comprises one or more compounds of formula 25 111
L3 L1 R' Z3{NCS l l l wherein
R' is H. alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or mono- or polysubstituted by halogen, where one or more CH2 groups in these radicals may also, in each case independently of one another, be s replaced by -O-, -S-, -CO-, CO-O-, -O-CO-, -O-CO O- or -C-C- in such a way that oxygen atoms are not linked directly to one another, to is {> or {I L' to L6 are each independently of one another H or F. Z3 is -CH=CH- or a single bond, and b isOor1.
4. A liquid-crystalline medium as claimed in any of the preceding claims, wherein the nematic component comprises one or more 20 compounds of formula V R' z4: CN V wherein R' is H. alkyl, alkenyl or alkoxy having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by 30 CN or CF3 or mono- or polysubstituted by halogen, where one or more CH2 groups in these radicals may also, in each case independently of one another, be
replaced by-O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-
O- or -C-C- in such a way that oxygen atoms are not linked directly to one another, and are independently of each other { - or {I, L' to L6 are each, independently of one another, H or F. Z4 iS -COO- or a single bond, and 75 C iS 0, 1 or2.
5. A liquid-crystalline medium as claimed in any of the preceding claims, which comprises 0.1 to 10 % of chiral compounds of formula 1.
6. A liquidcrystalline medium as claimed in any of the preceding claims, wherein the optically active component consists of one chiral compound of formula 1.
as
7. A liquid-crystalline medium as claimed in any of claims 2 to 6, wherein the nematic component comprises 25 to 95 % of one or more compounds of formula 11.
8. A liquid-crystalline medium as claimed in any of claims 3 to 6, do wherein the nematic component comprises 5 to 65 % of one or more compounds of formula lilt
9. A liquid-crystalline medium as claimed in any of claims 4 to 6, wherein the nematic component comprises 2 to 35 % of one or more compounds of formula V. s
10. A liquid-crystalline medium as claimed in any of the preceding claims, wherein it has a reflection wavelength in the range from 400 to 800 nm.
11. A liquid-crystalline medium as claimed in any of the preceding to claims, wherein it has a temperature dependence of the reflection wavelength (d\/dT)/\max of 5 % or less in the temperature range between O and 50 C.
12. A liquid-crystalline medium as claimed in any of the preceding Is claims, wherein the temperature dependence of the red edge (dred/dT) /\red and the temperature dependence of the blue edge (dbueIdT)Ilbue of the reflected waveband are each 5 % or less in the temperature range between O and 50 C.
20
13. A liquid-crystalline medium substantially as hereinbefore described with reference to compositions C11, C12, C21 or C31 in the Examples
14. Use of an LC medium as claimed in any of claims 1 to 13 for LC Is displays, bistable displays, flexoelectric or cholesteric displays, SSCT and PSCT displays, or for lasing or fluorescence applications.
15. A LC display, bistable display, flexoelectric, cholesteric, SSCT or PSCT display comprising an LC medium as claimed in any of claims 30 1 to 13.
16. A lasing or fluorescence device, temperature indicator or security or identification marking comprising an LC medium as claimed in any of claims 1 to 13.
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|---|---|---|---|---|
| CN103468272A (en) * | 2013-09-06 | 2013-12-25 | 华映视讯（吴江）有限公司 | Liquid crystal composite |
| CN107636116A (en) * | 2015-05-23 | 2018-01-26 | 默克专利股份有限公司 | Liquid crystal media and the high frequency assembly for including it |
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|---|---|---|---|---|
| WO2002034739A1 (en) * | 2000-10-20 | 2002-05-02 | Merck Patent Gmbh | Chiral binaphthol derivatives |
| WO2002094805A1 (en) * | 2001-05-21 | 2002-11-28 | Merck Patent Gmbh | Chiral compounds |
| WO2002100979A1 (en) * | 2001-06-13 | 2002-12-19 | Merck Patent Gmbh | Fluid crystalline medium and high-torsion liquid crystalline display device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2002034739A1 (en) * | 2000-10-20 | 2002-05-02 | Merck Patent Gmbh | Chiral binaphthol derivatives |
| WO2002094805A1 (en) * | 2001-05-21 | 2002-11-28 | Merck Patent Gmbh | Chiral compounds |
| WO2002100979A1 (en) * | 2001-06-13 | 2002-12-19 | Merck Patent Gmbh | Fluid crystalline medium and high-torsion liquid crystalline display device |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103468272A (en) * | 2013-09-06 | 2013-12-25 | 华映视讯（吴江）有限公司 | Liquid crystal composite |
| CN103468272B (en) * | 2013-09-06 | 2015-04-22 | 华映视讯（吴江）有限公司 | Liquid crystal composite |
| CN107636116A (en) * | 2015-05-23 | 2018-01-26 | 默克专利股份有限公司 | Liquid crystal media and the high frequency assembly for including it |
| JP2018523006A (en) * | 2015-05-23 | 2018-08-16 | メルク パテント ゲゼルシャフト ミット ベシュレンクテル ハフツングＭｅｒｃｋ Ｐａｔｅｎｔ Ｇｅｓｅｌｌｓｃｈａｆｔ ｍｉｔ ｂｅｓｃｈｒａｅｎｋｔｅｒ Ｈａｆｔｕｎｇ | Liquid crystal medium and high frequency device including the same |
| CN107636116B (en) * | 2015-05-23 | 2021-12-10 | 默克专利股份有限公司 | Liquid-crystalline medium and high-frequency module comprising same |
| US11254874B2 (en) | 2015-05-23 | 2022-02-22 | Merck Patent Gmbh | Liquid-crystalline medium and high-frequency components comprising same |
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| GB0318087D0 (en) | 2003-09-03 |
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