GB2398569A

GB2398569A - Chiral compounds comprising Group IV element with two 1,1'-binaphth-2,2'-diyl-containing or related substituents

Info

Publication number: GB2398569A
Application number: GB0403135A
Authority: GB
Inventors: Elvira Montenegro; Peer Kirsch; Michael Heckmeier
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2003-02-19
Filing date: 2004-02-12
Publication date: 2004-08-25
Anticipated expiration: 2024-02-12
Also published as: JP4744809B2; GB2398569B; GB0403135D0; JP2004339192A

Abstract

A chiral compound of formula 1 <EMI ID=1.1 HE=36 WI=74 LX=230 LY=132 TI=CF> <PC>[wherein <DL TSIZE=11> <DT>K<1-4><DD>are independently of each other anellated benzene, cyclohexane or cyclohexene, wherein one or more CH groups are optionally replaced by N and one or more CH2 groups are optionally replaced by O and/or S such that O and/or S atoms are not linked directly to one another, <DT>U<1-4><DD>are independently of each other CH2, O, S, CO, NH or CF2, <DT>V<1-4><DD>have independently of each other one of the meanings of U<1-4>, with the proviso that O, S and NH are not directly adjacent to each other, or independently of each other may denote a single bond, <DT>Z<DD>is C, Si, Ge, Sn or Ti, <DT>X<1-12><DD>are independently of each other R, P-Sp or -W<1>-A<1>-(W<2>-A<2>)m-R, <DT>R<DD>is in each occurrence independently H, F, Cl, Br, I, CN, NO2, OH, NCS, SF5, straight chain or branched alkyl which has 1 to 40 C-atoms, is unsubstituted, mono- or polysubstituted by F, Cl, Br, I or CN, and in which one or more CH2 groups are optionally replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR<0>-, -SIR<0>R<00>-, -CO-, - COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SO2-, - CG<1>=CG<2>- or -C I C-, in such a manner that two O or two S atoms are not linked directly to one another, or denotes P-Sp, <DT>R<0> and R<00><DD>are independently of each other H or alkyl with 1 to 12 C-atoms, <DT>G<1> and G<2><DD>are independently of each other H, F, Cl or CN, <DT>P<DD>is a polymerizable or reactive group, <DT>Sp<DD>is a spacer group or a single bond, <DT>A<1> and A<2><DD>are in each occurrence independently a substituted or unsubstituted aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N, O and S, <DT>W<1> and W<2><DD>are in each occurrence independently -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-NR<0>-, -NR<0>-CO-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, - CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH2CH2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, - CH=CH-, -CH=CR<0>-, -CR<0>=CR<00>-, -CG<1>=CG<2>-, -C I C-,-CH=CH-COO-, -OCO-CH=CH- or a single bond, <DT>m<DD>is in each occurrence independently 0, 1, 2 or 3] </DL> have large helical twisting power and maybe used in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor, electrophotographic and lasing application, and to liquid crystal media, polymers, optical components, displays and decorative or security markings.

Description

Chiral Compounds

Field of the Invention

The invention relates to chiral compounds and to their use in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor, electrophotographic and lasing applications. The invention further relates to liquid crystal media, polymers, optical components, displays and decorative or security markings comprising the chiral compounds.

Background and Prior Art

Chiral compounds can be used as dopants to induce or enhance a helical twist in a liquid crystal mixture that is used for example in liquid crystal displays. The pitch p of the molecular helix in the first approximation, which is sufficient for most practical applications, is inversely proportional to the concentration c of the chiral dopant in the liquid crystal host mixture according to equation (1): p.HTP= c (1) The proportionality factor is the helical twisting power (HTPtof the chiral dopant.

For many applications it is desirable to have LC mixtures with a twisted phase. Among these are e.g. phase-change displays, guest-host displays, passive and active matrix TN and STN displays like,AMD-TN, ferroelectric displays and cholesteric displays like SSCT (surface stabilized cholesteric texture), PSCT (polymer stabilized cholesteric texture) displays or displays based on "blue phases", including displays with temperature compensated characteristics, e.g. by appropriate selection of the cholesteric compounds according to the invention either alone or in combination with further chiral dopants. For these - 2 applications it is advantageous to have available a chiral dopant with a high HTP in order to reduce the amount of dopant needed to induce the desired pitch For some applications it is desired to have LC mixtures that exhibit a strong helical twist and thereby a short pitch length. For example in liquid crystal mixtures that are used in selectively reflecting cholesteric displays like SSCT or PSCT, the pitch has to be selected such that the maximum of the wavelength reflected by the cholesteric helix is in the range of visible light. Another possible application are polymer films with a chiral liquid crystal phase for optical elements, such as cholesteric broadband polarizers or retardation films.

As can be seen from equation (1), a short pitch can be achieved by using high amounts of dopant or by using a dopant with a high HTP.

Chiral compounds are disclosed for example in WO 95/16007, WO 98/00428 and GB 2 328 207 A. However, the chiral dopants of prior art often exhibit low values of the HTP, so that high amounts of dopant are needed. This is a disadvantage because chiral dopants can be used only as pure enantiomers and are therefore expensive and difficult to synthesize.

Furthermore, when using chiral dopants of prior art in high amounts, they often negatively affect the properties of the liquid crystal host mixture, such as e.g. the clearing point, the dielectric anisotropy 6ú, the viscosity, the driving voltage or the switching times.

Another disadvantage of prior art chiral compounds is that they often show low solubility in the liquid crystal host mixture, which leads to undesired crystallization at low temperatures. To overcome this disadvantage, typically two or more different chiral dopants have to be added to the host mixture. This implies higher costs and also requires additional effort for temperature compensation of the He - 3 mixture, as the different dopants have to be selected such that their temperature coefficients of the twist compensate each other.

Consequently, there is a considerable demand for chiral compounds with a high HTP which are easy to synthesize, can be used in low amounts, show improved temperature stability of the cholesteric pitch e.g. for utilizing a constant reflection wavelength, do not affect the properties of the liquid crystal host mixture and show good solubility in the host mixture.

The invention has the aim of providing chiral compounds having these properties, but which do not have the disadvantages of the chiral dopants of the state of the art as discussed above.

Another aim of the invention is to extend the pool of chiral compounds that can be used as dopants available to the expert.

It has been found that these aims can be achieved by providing chiral compounds as described below.

Summary of the Invention

The present invention relates to chiral compounds of formula I X3 X2 X2 X3 4,, X,X4 >-U] V\ /v3 u3-x5.

"U-V V-U_X,, X,o/\X7 X7x,o Xg X8 X8 Xg wherein K'-4 are independently of each other anellated benzene, cyciohexane or cyclohexene, wherein one or more CH groups are optionally replaced by N and one or more CH2 groups are optionally replaced by O and/or S such that O and/or S atoms are not linked directly to one another, U'- are independently of each other CH2, O. S. CO, NH or CF2, V'-4 have independently of each other one of the meanings of U4, with the proviso that O. S and NH are not directly adjacent to each other, or denote a single bond, Z isC,Si,Ge,SnorTi, x- 2 are independently of each other R. P-Sp or -W4-A'-(W2 A)n,-R, R is in each occurrence independently H. F. Cl, Br, I, CN, NO2, OH, NCS, SF5, straight chain or branched alkyl which has 1 to 40 C-atoms, is unsubstituted, monoor polysubstituted by F. Cl, Br, I or CN, and in which one or more CH2 groups are optionally replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR -SiR R -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, CO-S-, -SO2-, -CG'=CG2- or-C-C-, in such a manner that two O or two S atoms are not linked directly to one another, or denotes P-Sp, R and R are independently of each other H or alkyl with 1 to 12 C-atoms, G' and G2 are independently of each other H. F. Cl or CN, P is a polymerizable or reactive group, - 5 Sp is a spacer group or a single bond, A' and A2 are in each occurrence independently a substituted or unsubstituted aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N. O and S. W' and w2 are in each occurrence independently-Or, -S-, - CO-, COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-N R -, NR -CO-, -OCH2-, - CH2O-, -SCH2-, -CH2S-, -CF2O-, OCF2-, -CF2S-, -SCF2-, -CH2CH2-, -CF2CH2-, -CH2CF2-, CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CH-, -CH=CR -, CR =CR00-,CG'=CG2-,-C-C-,-CH=CH-COO-,-OCO CH=CH- or a single bond, m is in each occurrence independently 0, 1, 2 or 3.

The invention further relates to an optically active material or chiral dopant material, in particular for doping liquid crystal mixtures, comprising one or more chiral compounds of formula I and optionally one or more additional chiral compounds.

The invention further relates to a liquid crystal mixture comprising at least one compound of formula I or comprising a chiral dopant material as described above.

The invention further relates to a polymerizable liquid crystal material comprising at least one compound of formula I or comprising a chiral dopant material as described above.

The invention further relates to a polymerizable liquid crystal mixture comprising at least one compound of formula I and at least one polymerizable mesogenic compound, which can be said compound of formula I and/or an additional compound. - l pi - - 6

The invention further relates to a linear or crosslinked polymer obtained by polymerizing a polymerizable compound of formula I or a polymerizable liquid crystal mixture comprising one or more compounds of formula 1.

The invention further relates to an anisotropic polymer with twisted structure obtained by polymerizing a polymerizable compound of formula I or a polymerizable liquid crystal mixture comprising one or more compounds of formula I in its oriented state, preferably an anisotropic polymer film obtained from a layer of said polymerizable material.

The invention further relates to the use of compounds of formula I as chiral dopants in liquid crystal materials or optical, electrooptical, electrical, semiconducting or electronic components or devices.

The invention further relates to the use of a compound of formula 1, a liquid crystal mixture, polymer or polymer film as described above and below in electrooptical displays, liquid crystal displays, optical films, polarizers, compensators, beam splitters, reflective films, alignment layers, colour filters, holographic elements, hot stamping foils, coloured images, decorative or security markings e.g. for consumer objects or documents of value, LC pigments, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, nonlinear optics, optical information storage, as chiral dopants, in electronic devices like for example field effect transistors (FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications, electroluminescent displays or backlights of LCDs, for photovoltaic or sensor devices, in lasing applications and devices, as electrode or electrolyte materials in batteries, as photoconductors, for electrophotographic applications or electrophotographic recording.

The invention further relates to a liquid crystal device comprising a compound of formula 1, a liquid crystal mixture, polymer or polymer film as described above and below.

Definition of Terms The terms 'liquid crystal or mesogenic material' or'liquid crystal or mesogenic compound' means materials or compounds comprising one or more rod-shaped, lath-shaped or disk-shaped mesogenic groups, i.e., groups with the ability to induce LC phase behaviour.

The compounds or materials comprising mesogenic groups do not necessarily have to exhibit an LC phase themselves. It is also possible that they show LC phase behaviour only in mixtures with other compounds, or when the mesogenic compounds or materials, or the mixtures thereof, are polymerized.

The terms 'polymerizablet and 'reactive' include compounds or groups that are capable of participating in a polymerization reaction, like radicalic or ionic chain polymerization, polyaddition or polycondensation, and reactive compounds or reactive groups that are capable of being grafted for example by condensation or addition to a polymer backbone in a polymeranaloguous reaction.

The term 'film' includes self-supporting, i.e., free-standing, films that show more or less pronounced mechanical stability and flexibility, as well as coatings or layers on a supporting substrate or between two substrates.

The term 'director' means the preferred orientation direction of the long molecular axes in case of calamitic compounds, or of the short molecular axis in case of discotic compounds, of the mesogens in a liquid crystal material.

The term 'planar structure' or 'planer orientation' refers to a layer of optically anisotropic material wherein the optical axis is substantially parallel to the plane of the layer. - 8

The term 'helically twisted structure' refers to a film comprising one or more layers of liquid crystal material wherein the mesogens are oriented with their main molecular axis in a preferred direction within molecular sublayers, said preferred orientation direction in different sublayers being twisted at an angle around a helix axis. The term helically twisted structure with planar orientation' means a film with helically twisted structure as described above, wherein the helix axis is substantially perpendicular to the film plane, i.e. substantially parallel to the film normal.

Detailed Description of the Invention

The present invention relates to both enantiomeric forms of the chiral compounds of formula 1. Either of the enantiomeric R- and S-form of the compounds of formula I can be used as optically active material or chiral dopant to induce a helical twist e.g. in a liquid crystal material.

The chiral compounds of formula I have several advantages À they exhibit a high HTP with low temperature dependence, À they exhibit high solubility in liquid crystal mixtures, À they can exhibit liquid crystalline phases, À they exhibit high thermal and chemical stability, À when they are used as chiral dopant in a liquid crystal mixture, due to their high solubility higher amounts of dopant can be used to produce a high twist (= a low pitch), À in case high amounts of dopants are needed, due to the broad liquid crystalline phases of the inventive dopants the liquid crystal phase of the host mixture is less negatively influenced, À due to their high HTP, lower amounts of inventive dopants are needed to achieve a high pitch, and thereby the liquid crystalline properties of the mixture are less negatively affected, - 9 - À both the R- and S-enantiomer of the chiral compounds of formula I are easy to prepare with high enantiomeric purity, À they can easily be synthesized from commercailly available and cheap chiral starting materials, À they can easily be modified for specific applications, À the availability of both helices is a considerable advantage, e.g. for the use in security applications, as it enables the production of chiral films or coatings reflecting circularly polarized light of a single handedness.

The chiral compounds of formula I can be mesogenic or even liquid crystalline, i.e. they can induce or enhance mesophase behaviour for example in admixture with other compounds, or even exhibit one or more mesophases themselves. It is also possible that the inventive compounds show mesophase behaviour only in mixtures with other compounds, or, in case of polymerizable compounds, when being (co)polymerized. Mesogenic inventive chiral compounds are especially preferred.

The compounds of formula I are especially suitable for use in mixtures for LCD applications, in particular for applications using LC mixtures in the nematic or isotropic phase where high birefringence, high polarity and high dielectric anisotropy are required.

Furthermore, the compounds of formula I can be used as reactive mesogens and can be used to make polymers or polymer films for use as optical films, in particular optical retardation or compensation films, alignment layers, colour filters or polarizers in an LCD.

Another field of use of polymerizable compounds of formula I is as semiconductors or charge transport materials. These materials can be used in electronic devices like for example field effect transistors (FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light - 10 emitting diode (OLED) applications, electroluminescent displays or backlights of LCDs, for photovoltaic or sensor devices.

It is also possible to copolymerize compounds of formula I via a group P with other polymerizable mesogenic monomers, as well as with other compounds of formula 1, in order to induce or enhance LO phase behaviour.

The LCDs according to the present invention are for example conventional LCDs, in particular those of the DAP (deformation of aligned phases) or VA (vertically aligned) mode, like e.g. ECB (electrically controlled birefringence), CSH (colour super homeotropic), VA or VAC (vertically aligned cholesteric) displays, MVA (multi-domain vertically aligned) or PVA (patterned vertically aligned) displays, in displays of the bend mode or hybrid type displays, like e.g. OCB (optically compensated bend cell or optically compensated birefringence), R-OCB (reflective OCB), HAN (hybrid aligned nematic) or pi-cell (-cell) displays, furthermore in displays of the TN (twisted nematic), HTN (highly twisted nematic) or STN (super twisted nematic), in AMD-TN (active matrix driven TN) displays, in displays of the IPS (in plane switching) mode which are also known as 'super TFT' displays, or in displays using liquid crystals in the isotropic state, hereinafter shortly referred to as "isotropic mode display", as described for example in DE 102 172 73 and WO 02/93244 A1, furthermore in phase-change, guest-host, ferroelectric, flexoelectric or cholesteric displays like SSCT 7surface stabilized cholesteric texture), PSCT (polymer stabilized cholesteric texture) or displays based on "blue phases".

Especially preferred are TN, STN, AMD-TN, cholesteric, ferroelectric and isotropic mode displays.

Formula I covers, inter alia, the following compounds - compounds of formula 11 wherein K', K2, K3 and K4 are benzene - 11 X4: 'X1 X1 X4 X5 X' U] V\ V3-U3:Xs 11 X11\U-V V4 4X, Xg X8 X8 Xg - compounds of formula 12 wherein K1, K2, K3 and K4 are anellated cyclohexane X3 X2 X2 X3 X4'X, X3X4 Xs \Z\ X5 12 X14U-V2 V4-U4: ,X11 Xg X8 X8 Xg - compounds wherein K1, K2, K3 and K4 are anellated cyclohexene, like for example those of the following formulae X3 X2 X2 X3 4.X X1x4 X5U' V\ jV3 U3;:Xs 13 X10U-V V-UX,o Xg X8 X8 Xg - 12 X4 \,X1 X1 X4 Xsu1 V\ /v3 u3JXs 14 X11 <U-V2 V4 U44X11 8 X8 X9 - compounds wherein K' and K2 are benzene and K3 and K4 are anellated cyclohexane or cyclohexene, or wherein K3 and K4 are benzene and K1 and K2 are anellated cyclohexene or cyclohexadiene, - compounds wherein one or more of K1-4 are benzene, anellated cyclohexane or cyclohexene, like for example shown in formula 11 14, but wherein, in addition, one or more CH groups are replaced by N and/or one or more CH2 groups are replaced by O and/or S such that O and/or S atoms are not linked directly to one another, like for example those of the following formulae X4\l'NX, X, N:,X4 Xs X,2 MU-V\ /V-U - X' 1 U-V2 V4-U4x, X,O \X7 X7 NJ\xo x8 x8 c 13 x2 x2 X4\l\lx, X1N:'X4 NO \Z\ X>,N 16 N:U-V V4-U4N X NX7 X7 N X1O x8 x8 1 2 2/Z\ X5 17 X..u-v V4-Ux,, Xg X8 X8 Xg X4oX, X'OX4 X1 2 2/Z\ J x,2 18 oU-V V4-U4 x8 x8 Especially preferred are compounds of formula 11-18, most preferred those of formulae 11, 12, 17 and 18.

Further preferred are compounds of formula I wherein - the compound is optically active, - the compound has at least 90 % enantiomeric purity, 14 - if Z is Si or Ti and each of U'-V4, U2-V2, U3-V3 and U4-V4 is O then at least one of K' to K4 is different from unsubstituted phenylene and/or at least one of X' to x42 is different from H. - if Z is C and each of U1-V1, U2-V2, U3-V3 and U4-V4 is O. O-CH2 or C2H4, then at least one of K' to K4 is different from unsubstituted phenylene and/or at least one of X' to x'2 is different from H. - V' and v2 are a single bond and V3 and V4 are not a single bond, - V' and v2 are not a single bond and V3 and V4 are a single bond, - V', V2, V3 and V4 are a single bond, - V4, V2, V3 and V4 are not a single bond, - U'-4 are selected from CH2, O and CO, - V'- are selected from CH2, O and CO and a single bond, - U] = U2 = U3 = U4 - U' = U2it U3 = U4, - V'=V2=V3=V4, - V'=v2=v3=v4 - Z is a carbon atom, Ki=K2=K3=K4 - W' is a single bond, - at least one of x'-42 is different from H. - X', X2, X4, X7, X and X' are different from H and X3, X5, X6, X9, X and x42 are H. - X], X2, X7 and X are different from H and X3, X4, X5, X6, X9, X] , X'' and x'2 are H. - one or more of x'-'2 denote R that is different from H. - R or x'-42 are selected from F. Cl, Br, I, CN, OH, NO2, NCS, SF5 or straight chain or branched alkyl which has 1 to 40 C-atoms, is unsubstituted, mono- or polysubstituted by F. Cl, Br, I or CN, and in which one or more CH2 groups are optionally replaced, in each case independently from one another, by -O-, -S-, -NH-, -NR -, - 15 Si RARE-, CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SO2-, CG'=CG2- or -C_C-, in such a manner that oxygen atoms are not linked directly to one another, R or x4-42 are selected from F. Cl, ON, NO2, straight chain or branched alkyl, alkenyl, alkinyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonlyoxy, thioether, alkylsulfonyl, alkylsulfanyl, alkylsulfanylcarbonyl, aminoalkyl or aminodialkyl with 1 to 20 C atoms, wherein one or more H atoms are optionally substituted by F or Cl, very preferably from F. Cl, ON and alkyl or alkoxy with 1 to 12 C atoms, - at least one, preferably one or two of x'-'2 denote or comprise a polymerizable group, - at least one, preferably one or two groups R are P-Sp-, - at least one, preferably two, four or six Of x'-42 are -W'-A4-(W2-A2)m R, - -A4-(W2-A2)m- incorporates one, two or three five- or six-membered rings, - -A4-(W2-A2)m- is bicyclohexyl, biphenyl, phenylcyclohexyl, cyclohexylphenyl or biphenylcyclohexyl, wherein the phenyl rings are optionally substituted with one or two F atoms, - W' and w2 are selected from -COO-, -OCO-, -CH2-CH2- and a single bond, - at least one of W. and w2 is -CF2O-, -OCF2-, -CF2CF2- or -CF=CF and the other are -COO-, -OCO-, -CH2-CH2- or a single bond, - at least one of W' and w2 is -C_C-, - misOor1.

A' and A2 are independently of each other an aromatic or alicyclic ring, preferably a 5-, 6- or 7-membered ring, or a group comprising two or more, preferably two or three, fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N. O and S. and are optionally mono- or polysubstituted by L, wherein L has one of the meanings of R. - 16 Preferred groups A' and A2 are for example furan, pyrrol, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, cyclohexenylene, pyran, all-or tetrahydropyran, dioxane, dithiane, pyridine, pyrimidine, pyrazine, azulene, indane, naphthalene, tetra or decahydronaphthalene, anthracene and phenanthrene.

Very preferably A' and A2 are selected from 1,4-phenylene 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 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-dlyl, or 1,2,3,4 tetraNydronaphthalene-2,6-dlyl, it being possible for all these groups to be unsubstituted, mono- or polysubstituted with L. Especially preferred groups A' and A2 are 1,4phenylene which is optionally substituted in 2-, 3-, 5- and/or 6-position by L, trans-1,4 cyclohexylene, 2,6-dioxane-1,4-dlyl, 3,5-dioxane-1,4-diyl, 2 0 t e t r a h y d r o p y r a n e - 2, 5 - d i y I a n d t e t r a h y d r o p y r a n e - 3, 6 - d i y I. L is preferably F. Cl, Br, I, CN, OH, NO2, NCS, SFs or straight chain or branched alkyl, alkenyl, alkinyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonlyoxy, thioether, alkylsulfonyl, alkylsulfanyl, alkylsulfanylcarbonyl, aminoalkyl or aminodialkyl with 1 to 8 C atoms, wherein one or more H atoms are optionally L is very preferably F. Cl, CN, OH, NO2, CH3, C2H5, OCH3, OC2H5, OC3H7, COCH3, COC2H5, COOCH3, COOC2H5, SO2CF3, CF3, OCF OCHF2 or OC2F5, in particular F. Cl, CN, CH3, C2H5, OCH3, COCH3 or OCF3, most preferably F. Cl, CH3, OCH3 or COCH3.

Preferably the group -A'-(W2-A2)m- contains only monocyclic groups Ai and A2. Very preferably the group -A'-(W2-A2)m- is a group with one or two 5or 6-membered rings. - 17

Especially preferred groups -A'-(W2-A2)m-R are shown in table 1 below

5Table 1

4Yz 0 0OO 00 10Y3 R R R R R 0 0 00 00 I w I w I at w w R R: R R R R R R Y44Y2;4Y2Y4Y2 ó Y Y2y y7 y yz

R R R R R R

Y4Y2 Y4Y2 0 Y4Y2 00 0 YsY1 it Ys - Y1 Ys - Y1 Y4Y2:0 y4 2 Y4Y2

R R R R R R - 18

2 y4Y2 YY2;Y2 YóY7Y4óY2Y:Y,YóY7 me, Y4:Y, W2 W2 l2 9óY6Y13óY1 onto R R R 8 R R YUMMY, Ys<Y' Ys'Y1 Ys'Y, YUMMY, y4)Y2 Y4/Y2 Y4/Y2 Y4/ - Y2 Y4J?Y2 Iw, w, w, w, w, Ye - Y6 Y8SY6 y8SY6 o 97 Y9Y7 00 :0 )' to

R R R R R

Y5Y1 YSY1 Y5Y1 YsY1 Y5Y1 Y5Y1 Y4Y2 Y4//Y2 Y4 Y2 Y4 Y2 Y4 Y2 Y4 Y2 0 0 ONTO ma; To wherein R has one of the meanings of formula 1, Y]-43 have independently of each other one of the meanings of L given above, and W. W' and w2 have independently of each other one of the meanings of W' in formula 1. - 19

R in these groups is preferably straight chain alkyl or alkoxy with 1 to 12, preferably 1 to 8 C-atoms or alkenyl with 2 to 12, preferably 2 to 7 C-atoms, or P-Sp.

Y]-43 in these groups denote preferably H. F. Cl, straight chain or branched alkyl, alkenyl, alkinyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonlyoxy, sulfanylalkyl or sulfonylalkyl with 1 to 8, preferably 1 to 4 C atoms, wherein one or more H atoms are optionally substituted by F or Cl, in particular CF3, OCF3, SO2CF3, or SCF3.

W. W' and w2 in these groups denote preferably a single bond, CH=CH, C-C, OCF2,CF2O, CH2CH2, CF2CH2, CH2CF2, CF2CF2, COO, OOC, CH2O or OCH2.

Especially preferred are the following compounds X4,::X, X,.-X4 \z' la U2V2/ \v4-u4 4 X,oX7 x7JX,o x8 X8 - C \Z' 1 lb ] U2 V2' \V4-U4 T,: - 20 " X2 x2 X4\<x1 X, 'X4 \ / 1,z 1 Ic U2 \U4 1 0 x8 x8 x2 x2 <X1 X1 U1 U3:J\J I \z/ I Id t u2 \U4 t x8 x8 x2 x2 X4'x1 X1 X4 /z le 9 U2-V2 \U4 r X8 x8 x2 x2 US V\z/U3JLJ If it, U2-V2 U4 x8 x8 wherein Us, V]-4, X4-42 and Z have one of the meanings of formula I or of the preferred meanings given above and below.

Especially preferred are compounds of formula la-if wherein X', X2, X3, X7, X8 and X, are selected from the groups shown in table 1.

Further preferred are compounds of formula la-if wherein Z is a C atom.

U V\ /V U /Z\ in formula la and lb is preferably selected from U2_V2 -U4 H2 H2 CH2- C>:CH2 CH2-OxO-CH2 O-CO o-oc,co- CH2 CH ACHE CH2 O O-CH2 O-CO OOC CO-O 2 H2 H2 H2 CH2-C,wO CH2-CXCO-O CO-O O-OC CH2-C-o CH2 C CO-O CO OXO OC H2 2 U\ MU U2/ \U4 in formula Ic and Id is preferably selected from - 22 O C CH2 CH2 CH2 0 X and O O CH2 CH2 CH2 0 U' V' US /Z\ in formula le and If is preferably selected from u2 v2 U4 H. H2 O- CxO O-CXCH2 o-ocxo O-OCXCH2

O-C O O-C CH O-OC O O-OC CH

LO 2 2 n2 1 l2 If one of R. L or x'-'2 is an alkyl or alkoxy radical, i.e. where the terminal CH2 group is replaced by-O-, this may be straightchain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.

Oxaalkyl, i.e. where one CH2 group is replaced by -O-, 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 7oxaoctyl, 2-,3-,4-,5-,6-,7-or8-oxanonylor2-,3-,4-,5-,6-,7-,8-or9 oxadecyl, for example.

If one of R. L or x'-42 is an alkyl group wherein one or more CH2 groups are replaced by -CH=CH-, this may be straight-chain or branched. It is preferably straight-chain, has 2 to 10 C atoms and accordingly is preferably vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent1-, 2-, 3- or pent-4-enyl, hex-1-, 2-, 3-, 4- or hex - 23 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-i-, 2-, 3-, 4- 5-, 6-, 7-, 8- or dec-9-enyl.

Especially preferred alkenyl groups are C2 C7-1 E-alkenyl, C4-C7-3E 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-alkenyl.

Examples for particularly preferred alkenyl groups are vinyl, 1 E-propenyl, 1 E-butenyl, 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 C atoms are generally preferred.

If one of R. L or x'-'2 is an alkyl group, wherein one CH2 group is replaced by -O- and one by -CO-, these radicals are preferably neighboured. Accordingly these radicals together form a carbonyloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably this group is straightchain and has 2 to 6 C atoms.

It is accordingly preferably acetyloxy, propionyloxy, butyryloxy,pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl?ethyl, 2-(propoxy carbonyl) ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.

If one of R. L or x4-42 is an alkyl group, wherein two or more CH2 groups are replaced by-O- and/or-COO-, it can be straight-chain or branched. It is preferably straight-chain and has 3 to 12 C atoms.

Accordingly it is preferably bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 13,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy - 24 pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis carboxyoctyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, 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 (ethoxycarbonyl)-methyl, 2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis (ethoxycarbonyl)-propyl, 4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis (ethoxycarbonyl)-hexyl.

If one of R. L or x'-'2 is an alkyl or alkenyl group that is monosubstituted by CN or CF3, it is preferably straight-chain. The substitution by CN or CF3 can be in any desired position.

If one of R. L or x'-42 is an alkyl or alkenyl group that is at least monosubstituted by halogen, it is preferably straight-chain. Halogen is preferably F or Cl, in case of multiple substitution preferably F. The resulting groups include also perfluorinated groups. In case of monosubstitution the F or Cl substituent can be in any desired position, but is preferably in c-position. Examples for especially preferred straight-chain groups with a terminal F substituent are fluormethyl, 2fluorethyl, 3-fluorpropyl, 4-fluorbutyl, 5-fluorpentyl, 6-fluorhexyl and 7-fluorheptyl. Other positions of F are, however, not excluded.

Halogen is preferably F or Cl.

R. L or x,-42 can be a polar or a non-polar group. In case of a polar group, it is selected from CN, SF5, halogen, OCH3, SON, COR', COOR' or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R' is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferred polar groups are selected of F. Cl, CN, OCH3, COCH3, COC2H5, COOCH3, COOC2H5, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, C2F5 and OC2F5, in particular F. Cl, CN, CF3, OCHF2 and OCF3. In case of a non-polar - 25 group, it is preferably alkyl with up to 15 C atoms or alkoxy with 2 to C atoms.

R. L or x'-42 can be an achiral or a chiral group. In case of a chiral group it is preferably selected of formula lil: -Q] CH Q2 wherein Q' is an alkylene or alkylene-oxy group with 1 to 9 C atoms or a single bond, Q2 is an alkyl or alkoxy group with 1 to 10 C atoms which may be unsubstituted, mono- or polysubstituted by F. Cl, Br 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 -C_C-, -O-, -S-, -NH-, -N(CH3)-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO- or -CO-S- in such a manner that oxygen atoms are not linked directly to one another, Q3 is F. Cl, Br, ON or an alkyl or alkoxy group as defined for o2 but being different from Q2.

In case Q' in formula lil is an alkylene-oxy group, the O atom is preferably adjacent to the chiral C atom.

Preferred chiral groups of formula lil are 2-alkyl, 2-alkoxy, 2methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy, 2-(2-ethin)-alkyl, 2-(2 ethin)-alkoxy, 1,1,1-trifluoro-2-alkyl and 1,1,1-trifluoro-2-alkoxy.

Particularly preferred chiral groups are 2-butyl (=1-methylpropyl), 2 methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2 propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2 - 26 methylpentoxy, 3methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2 octyloxy, 2-oxa-3methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6 methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2 methyl butyryl oxy, 3-methylva le royloxy, 4-m ethyl hexanoyloxy, 2 chlorpropionyloxy, 2-chloro-3-methylbutyryloxy, 2-chloro- methylvaleryloxy, 2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2 fluorodecyloxy, 1,1,1-trifluoro-2-octyloxy, 1,1,1-trifluoro-2-octyl, 2 fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl, 2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-trifluoro-2-octyl and 1,1,1 trifluoro-2-octyloxy.

In addition, compounds containing an achiral branched group R. L or X4-'2 may occasionally be of importance, for example, due to a reduction in the tendency towards crystallization. Branched groups of this type generally do not contain more than one chain branch.

Preferred achiral branched groups are isopropyl, isobutyl (=methylpropyl), isopentyl (=3-methylbutyl), isopropoxy, 2-methyl propoxy and 3-methylbutoxy.

The polymerizable or reactive group P is preferably selected from CH2=CW4COO-, W2HC-CH- W2(CH2)k'-O- CH CW2 ( )k,-' CH3-CH=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH- OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, Ho-CW2W3-, HSCW2W3-, HW2N-, Ho-CW2W3-NH-, CH2=CW4-CO-NH-, CH2=CH (COO)k,-Phe-(O)k2-, Phe-CH=CH-, HOOC-, OCN-, and W4W5W6Si-, with W' being H. Cl, CN, phenyl or alkyl with 1 to 5 C-atoms, in particular H. Cl or CH3, w2 and W3 being independently of each other H or alkyl with 1 to 5 C- atoms, in particular methyl, ethyl or n propyl, W4, W5 and w6 being independently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phe being 1,4 phenylene and k' and k2 being independently of each other 0 or 1. - 27

Especiaily preferably P is a vinyl group, an acrylate group, a methacrylate group, an oxetane group or an epoxy group, especially preferably an acrylate or methacrylate group.

As for the spacer group Sp all groups can be used that are known for this purpose to the skilled in the art. The spacer group Sp is preferably of formula Sp'-X, such that P-Sp- is P-Sp'-X-, wherein Sp' is alkylene with up to 20 C 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- -NH-, -NR -, -SiR R -, -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 another, X is-O-,-S-,-CO-,-COO-,-OCO-,-O-COO-,-CO-NR -,- NR -CO -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, SCF2-,-CF2CH2-,CH2CF2-,-CF2CF2-,-CH=N-,-N=CH-,-N=N-, -CH=CR -, -CG'=CG2-, -C-C-, -CH=CH-COO-, -OCO-CH=CH or a single bond, and R , R , G' and G2 have one of the meanings given in formula 1.

X is preferably-Or, -S-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, OCF2-, CF2S-, -SCF2- -CH2CH2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, CH=N-, -N=CH-, -N=N, -CH=CR -, -CX'=CX2-, -C3C- or a single bond, in particular -O-, -S-, -C-C-, -CX'=CX2- or a single bond, very preferably a group that is able to from a conjugated system, such as -C_C- or -CX'=CX2-, or a single bond.

Typical groups Sp' are, for example, -(CH2)p-, -(CH2CH2O)q-CH2CH2-, CH2CH2-S-CH2CH2- or -CH2CH2-NH-CH2CH2- or -(SiR R -O)p-, with p being an integer from 2 to 12, q being an integer from 1 to 3 and R and R having the meanings given above. - 28

Preferred groups Sp' are ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyl iminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene for example.

Further preferred are compounds with one or two groups P-Sp wherein Sp is a single bond. In case of compounds with two groups P-Sp, each of the two polymerizable groups P and the two spacer groups Sp can be identical or different.

In another preferred embodiment the group Sp'is a chiral group of formula IV: * -Q'-CH-Q4 03 IV wherein Q' and Q3 have the meanings given in formula lil, and Q4 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, being different from Qua, with Q' being linked to the polymerizable group P. Another preferred embodiment relates to chiral compounds of formula I comprising a photoisomerizable group, for example a group with a C=C, C=N or N=N double bond. These compounds change their shape, for example by E-Z- or cis-trans isomerization, upon photoirradiation e.g. with UV light. - 29

Particularly preferred are photoisomerizable compounds of formula I comprising one or more groups -W'-A'-(W2-A2)m-R wherein W' or w2 is a photoisomerizable group, in particular -CH=GH-COO- or -OCO CH=CH-. Very particularly preferred are photoisomerizable compounds of formula I comprising one or more groups -W4-A'-(W2 A2)m-R wherein W' is -OCO-CH=CHand A1 is optionally substituted phenylene.

The compounds of formula I can be synthesized according to or in analogy to methods that are known and described in the literature. In particular, they can be prepared according to or in analogy to the reaction schemes shown below. Further methods for preparing the inventive compounds can be taken from the examples.

Starting materials like for example (1)-(5) as shown below can be synthesized using procedures described for example in a) D. S. Lingenfelter, R.C. Helgeson, D. J. Cram, J. Org. Chem. 1981, 46, 393-406; b) P. Wipf, J.K. Jung, J. Org. Chem. 2000, 65, 6319-6337; c) P.J. Cox, W. Wang, V. Snieckus, Tet. Letters 1992, 33, 2253 2256; d) L. Pu, Chem. Rev. 1998, 98, 2405-2494; e) Y. Tian, Q. C. Yang, T. C. W. Mak, Tetrahedron 2002, 58, 3951-3961; Al H. F. Chow, M. K. Ng, Tet. Asymmetry 1996, 7, 2251-2262 and g) M. Hatsuda, H. Hiramatsu, M. Seki, J. Org. Chem.2001, 66, 4437-4439.

O. TO Br, I, B(OH)2. 41: Or, 1, B(oH)2,;7( ^ OH, COOH, CH2OH OH, COOH, CH2OH H. COOH, CHzOH OH, COOH, CH2OH BOr;, B(OH)2.B, 0 p Br, 1, B(OH)2. .B (1) /7\ (2) \1( - 30 -(, 8r, I, B(OH)2 LOH, COOH, CH2OH OH, COOH, CH2OH O.sO, Br, I, B(OH) (3) 1 1 o.Bo Br, I, B(OH)2, o B'o < Br, I, B(OH)2,;- ; OH, COOH, CH2OH LOH, COOH, CH2OH (OH, COOH, CH2OH OH, COOH, CH2OH Br, I, B(OH)2' I O.B (4) Br, I, B(OH)2,; - o The synthesis of compounds of formula I from the starting materials can be achieved as shown in Scheme 1-3 below, according or in analogy to procedures as described for example in a) D. Yang, M.-K.

Wong, J. Am. Chem. Soc. 1998, 120, 5943-5952; b) J. Jamrozik, S. Schab, K. Nagraba, Monatsh. fur Chemie 1994, 125, 451 -456; c) I. Shibuya, Y. Gama, M. Shimizu, Heterocycles 1998, 48, 461_464; d) A. Gaucher, Y. Zuliani, J. -P. Mazaleyrat, Tet. Asymm. 2001, 12, 2571-2580 and e) D. Xiao, Z. Zhang, X. Zhang, Org. Leff. 1999, 1, 1679- 1681.

Scheme 1 - 31 2 OH Br:Br KOH, DMSO 1_0X [=OH Br Br 5h, 120 C = 2 + CS: + Ag. to>,

OH _O O_

Scheme 2 1) Cs2cO3 1Loco + IW!_OH _OH Cl C1 2) RuC13, NalO4 TO OH 1_o:<o-= Scheme 3 CH2Br COOEt K2CO3. DMF COOEt CH2Br COOEt = \COOEt | NaOH, MeOH 32 0 (3 all LOH SCOOT -i0 OH POOH The compounds of formula I can be used in a liquid crystal mixture for displays exhibiting a helically twisted molecular structure of the liquid crystal matrix like, for example, TN displays of the active or passive matrix type, STN, phase-change, guest-host, ferroelectric or cholesteric displays like SSCT (surface stabilized cholesteric texture) PSCT (polymer stabilized cholesteric texture) or displays based on "blue phases".

Thus, another object of the invention is a liquid crystal mixture, in particular a chiral smectic or cholesteric liquid crystal mixture, comprising at least one chiral compound of formula 1.

Another object of the invention is a liquid crystal display comprising a liquid crystal medium containing at least one chiral compound of formula 1.

The chiral compounds of formula I are characterized by high values of the HTP. This enables the preparation of liquid crystal mixtures with a high helical twist, i.e. a low pitch, by using only low amounts of chiral compounds of formula 1. This is a considerable advantage, as it is often observed that the addition of high amounts of chiral dopants to a liquid crystal mixture negatively affects its liquid crystal phase behaviour and electrooptical properties, such as the dielectric anisotropy, the viscosity or the clearing point. Thus, by using chiral compounds of formula I in a liquid crystal mixture or display its properties are altered only to a minor extent, compared to prior art dopants, resulting for example in a lower threshold voltage and faster switching times of the display.

The chiral compounds of formula I are further characterized by a high solubility in a liquid crystal host mixture. Undesired spontaneous - 33 crystallization at low temperatures is reduced, and the operating temperature range of the mixture can be broadened. The use of a second dopant, which is often added to avoid crystallization, can thus be avoided.

A particularly preferred embodiment of the present invention therefore relates to a liquid crystal mixture comprising only one chiral compound, which is a compound of formula 1, and to a display comprising such a mixture.

The chiral compounds of formula I also show a low temperature dependence of the HTP when added to a liquid crystal host mixture.

They are thus useful as chiral dopants for liquid crystal mixtures and displays with a low temperature dependence of the pitch.

A liquid crystal mixture according to the invention comprises preferably 0.1 to 30 %, in particular 1 to 25 % and very particularly preferably 2 to 15 % by weight of chiral compounds of formula 1. It preferably comprises 1, 2 or 3 chiral compounds of formula 1.

The compounds of formula I are especially suitable for use in cholesteric liquid crystal mixtures for cholesteric displays, in particular SSCT or PSCT displays. Cholesteric displays are described for example in WO 92/19695, WO 93/23496, US 5,453,863 or US 5,493,430, the entire disclosure of these documents being introduced into this application by way of reference.

It was found that when using chiral compounds of formula I as dopants in cholesteric liquid crystal media, for SSCT or PSCT display, they exhibit good solubility in the nematic host mixture and induce a high helical twist with low temperature dependence of the helical pitch and the reflection wavelength. Cholesteric mixtures with high brightness of the reflection colour and low temperature dependence can be achieved even by using only one chiral dopant according to formula 1, preferably in low amounts. This is a considerable advantage over prior art, where high amounts of - 34 dopants are needed, and where it is often necessary to use two or more dopants with opposite temperature dependence of the helical twist (e.g. one with positive temperature dependence and one with negative temperature dependence) to achieve good temperature compensation of the reflection wavelength.

Thus, a particularly preferred embodiment of the present invention relates to a cholesteric liquid crystal medium, in particular for use in SECT and PSCT displays, comprising one chiral dopant, which is a compound of formula 1, preferably in an amount of 15 % or less, in particular 10 % or less, very preferably 5 % or less.

For the applications described above the liquid crystal mixture preferably contains a chiral component which contains at least one chiral compound of formula 1, and a nematic component comprising one or more nematic or nematogenic compounds.

Preferably the liquid crystal mixture consists of 2 to 25, preferably 3 to 15 compounds, at least one of which is a chiral compound of formula 1. The other compounds, forming the nematic component, are preferably low molecular weight liquid crystal compounds selected from nematic or nematogenic substances, for example from the known classes of the azoxybenzenes, benzylidene-anilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohehexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclohexanecarboxylic acid and of cyclo hexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexyl biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 1,4-bis cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclo hexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclo hexylpyridazines, phenyl- or cyclohexyidioxanes, phenyl- or cyclo hexyl-1, 3-dithianes, 1,2-diphenyl-ethanes, 1,2-dicyclohexylethanes, 1-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2-(4-phenylcyclohexyl) toe ethanes, 1-cyclohexyl-2-biphenyl-ethanes, 1-phenyl2-cyclohexyl phenylethanes, optionally halogenated stilbenes, benzyl phenyl ether, tolanes, substituted cinnamic acids and further classes of nematic or nematogenic substances. The 1,4-phenylene groups in these compounds may also be laterally mono- or difluorinated.

The liquid crystal mixture of this preferred embodiment is based on the achiral compounds of this type.

The most important compounds that are possible as components of these liquid crystal mixtures can be characterized by the following formula R'L'-G'-E-R" wherein L' and E, which may be identical or different, are in each case, independently from one another, a bivalent radical from the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -B-Phe- and -B-Cyc- and their mirror images, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans 1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-dlyl, Dio is 1,3-dioxane-2,5-diyl abd B is 2-(trans-1,4 cyclohexyl)ethyl, pyrimidine-2,5-dlyl, pyridine-2,5-dlyl or 1,3-dioxane 2, 5-dlyl.

G' in these compounds is selected from the following bivalent groups -CH=CH-, -N(0)N-, -CH=CY-, -CH=N(0)-, -C-C-, -CH2-CH2-, -CO-O-, -CH2-O-, -CO-S-, -CH2-S-, -CH=N-, -COO-Phe-COO- or a single bond, with Y being halogen, preferably chlorine, or -CN.

R' and R" are, in each case, independently of one another, alkyl, alkenyl, alkoxy, alkenyloxy, alkanoyloxy, alkoxycarbonyl or alkoxycarbonyloxy with 1 to 18, preferably 3 to 12 C atoms, or alternatively one of R' and R" is F. CF3, OCF3, Cl, NCS or CN. - 36

In most of these compounds R' and R" are, in each case, independently of each another, alkyl, alkenyl or alkoxy with different chain length, wherein the sum of C atoms in nematic media generally is between 2 and 9, preferably between 2 and 7.

Many of these compounds or mixtures thereof are commercially available. All of these compounds are either known or can be prepared by methods which are known per se, as described in the literature (for example in the standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for said reactions. Use may also be made here of variants which are known per se, but are not mentioned here.

A preferred use of the compounds of formula I is the preparation of polymerizable liquid crystal mixtures, anisotropic polymer gels and anisotropic polymer films, in particular polymer films that exhibit a helically twisted molecular structure with uniform planar orientation, i. e. wherein the helical axis is oriented perpendicular to the plane of the film, like oriented cholesteric films.

Anisotropic polymer gels and displays comprising them are disclosed for example in DE 195 04 224 and GB 2 279 659.

Oriented cholesteric polymer films can be used for example as broadband reflective polarizers, colour filters, security markings, or for the preparation of liquid crystal pigments.

Broadband cholesteric reflective polarizers are described for example in EP 0 606 940, WO 97/35219 or EP 0 982 605. Colour filters are described for example in EP 0 720 041 or EP 0 685 749 and R. Maureretal., SID 1990 Digest,110-113. Liquid crystal pigments are described for example in EP 0 601 483, WO 97/27251, WO 97/27252, WO 97/30136 or WO 99/11719. - 37

For the preparation of anisotropic polymer gels or oriented polymer films, the liquid crystal mixture should comprise at least one polymerizable compound, preferably a polymerizable mesogenic compound.

Thus, another object of the invention is a polymerizable liquid crystal mixture comprising at least two compounds, at least one of which is a chiral compound of formula I and at least one of which is a polymerizable compound. The polymerizable compound can be said at least one compound of formula I or an additional compound.

Preferably the polymerizable liquid crystal mixture comprises at least one polymerizable mesogenic compound having one polymerizable functional group and at least one polymerizable mesogenic compound having two or more polymerizable functional groups.

Polymerisable mesogenic mono-, di- and multireactive compounds used for the present invention can be prepared by methods which are known per se and which are described, for example, in standard works of organic chemistry such as, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.

Examples of suitable polymerizable mesogenic compounds that can be used as monomers or comonomers together with the compounds according to the present invention in a polymerizable LC mixture, are disclosed for example in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586, WO 97/00600 and GB 2 351 734. The compounds disclosed in these documents, however, are to be regarded merely as examples that shall not limit the scope of this invention.

Examples of especially useful chiral and achiral polymerizable mesogenic compounds (reactive mesogens) are shown in the following lists which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention: - 38 P-(CH2)XO COO R (R1) P-(CH2)XO COO 3R (R2) P-(CH2)XO COO I} R (R3) P(CH2)XO COO OCO R (R4) P-(cH2)xo COO ( R (R5) P-(CH2)xo (3 I} R (R6) P(CH2)x-o _4_- ' r R (R7) P-(CH2)XO CH=CH-COO R (R8) P(CH2)XO:Z =Ro (R9) lL)r {L)r P(CH2)X {: Z R (R10) - 39 P-(CH2)xo R (R1 1) (F) (F) (F) P-(CH2)XO (C )U 3+ CH2CH(CH3)C2H5 (R12) L1 1 0 P-(CH2)XO coo coo CH2CH(CH3)c2H5 (R 1 3) P(CH2)xO COO-Ter (R14) P(CH2) xO COO-Chol (R15) P-(cH2)xocoo - (R16) P(CH2)x O-CO J3 R (R17) L1 L2 _ P(CH2)x coo oco o(CH2)yp (R 1 8) L1 L2 P(CH2)XO <3 CH2CH2 CH2CH2 O(CH2)yP (R 1 9) L' L2 P -OóCO26O2CóO (R20) - 40 P(CH2) XOZ óCH=CHCOC: (R21) OOCCH=CH {Z {)VO(CH,)yP P(CH2)Xo}z ócoq (R22) H {VO(CH2)yP P(CH,)xOZ : Z:O(CH2)yP In the above formulae, P is a polymerisable group, preferably an acryl, methacryl, vinyl, vinyloxy, propenyl ether, epoxy, oxetane or styryl group, x and y are identical or different integers from 1 to 12, A is 1,4 phenylene that is optionally mono-, di- or trisubstituted by L', or 1,4 cyclohexylene, u and v are independently of each other 0 or 1, Z is COO-, -OCO-, -CH2CH2-, -CH=CH-, -C-C- or a single bond, R is a polar group or an unpolar group, Ter is a terpenoid radical like e.g. menthyl, Chol is a cholesterol group, L, L' and L2 are independently of each other H. F. Cl, CN or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl or alkoxycarbonyloxy group with 1 to 7 C atoms, and r is 0, 1, 2, 3 or 4. The phenyl rings in the above formulae are optionally substituted by 1, 2, 3 or 4 groups L. The term 'polar group' in this connection means a group selected from F. Cl, CN, NO2, OH, OCH3, OCN, SCN, an optionally fluorinated alkycarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group with up to 4 C atoms or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. The term 'unpolar group' means an optionally halogenated alkyl, alkoxy, alkycarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy group with 1 or more, preferably 1 to 12 C atoms which is not covered by the above definition of 'polar group'.

A polymerizable liquid crystal mixture for the preparation of anisotropic polymer films or poylmer gels comprises preferably 0.1 to 35 %, in particular 0.5 to 15 % and very particularly preferably 0.5 to 5 % by weight of one or more polymerizable chiral compounds of formula 1.

Polymerizable liquid crystal mixtures are preferred that comprise 1 to 3 chiral compounds of formula 1.

Further preferred are polymerizable liquid crystal mixtures comprising at least one chiral compound of formula I having at least one polymerizable group P. To prepare anisotropic polymer films, the polymerizable LC mixture is preferably coated onto a substrate, aligned and polymerized in situ, for example by exposure to heat or actinic radiation, to fix the orientation of the LC molecules. Alignment and curing are carried out in the LC phase of the mixture. This technique is well-known in the art and is generally described for example in D.J. Broer, et al., Angew. Makromol. Chem. 183, (1990), 45-66.

Alignment of the LC material can be achieved for example by treatment of the substrate onto which the material is coated, by shearing the material during or after coating, by application of a magnetic or electric field to the coated material, or by the addition of surface-active compounds to the LC material. Reviews of alignment techniques are given for example by 1. Sage in "Thermotropic Liquid Crystals", edited by G. W. Gray, John Wiley & Sons, 1987, pages 75 77, and by T. Uchida and H. Seki in "Liquid Crystals - Applications and Uses Vol. 3", edited by B. Bahadur, World Scientific Publishing, Singapore 1992, pages 1-63. A review of alignment materials and techniques is given by J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 1-77. - 42

Polymerization takes place by exposure to heat or actinic radiation.

Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays or irradiation with high energy particles, such as ions or electrons. Preferably polymerization is carried out by UV irradiation at a non-absorbing wavelength. As a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced. Another possible source for actinic radiation is a laser, like e.g. a UV laser, an IR laser or a visible laser.

Polymerization is preferably carried out in the presence of an initiator absorbing at the wavelength of the actinic radiation. For example, when polymerizing by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or ions that start the polymerization reaction. When curing polymerizable materials with acrylate or methacrylate groups, preferably a radical photoinitiator is used, when curing polymerizable materials with vinyl, epoxide and oxetane groups, preferably a cationic photoinitiator is used. It is also possible to use a polymerization initiator that decomposes when heated to produce free radicals or ions that start the polymerization. As a photoinitiator for radical polymerization for example the commercially available Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (all from Ciba Geigy AG) can be used, whereas in case of cationic photopolymerization the commercially available UVI 6974 (Union Carbide) can be used.

Preferably polymerization is carried out under an atmosphere of inert gas, preferably under a nitrogen atmosphere.

As a substrate for example a glass or quarz sheet as well as a plasticfilm or sheet can be used. It is also possible to put a second substrate on top of the coated mixture prior to, during and/or after polymerization. The substrates can be removed after polymerization or not. When using two substrates in case of curing by actinic - 43 radiation, at least one substrate has to be transmissive for the actinic radiation used for the polymerization. Isotropic or birefringent substrates can be used. In case the substrate is not removed from the polymerized film after polymerization, preferably isotropic substrates are used.Preferably at least one substrate is a plastic substrate such as for example a film of polyester such as polyethyleneterephthalate (PET) or polyethylenenaphthalate (PEN), of polyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC), especially preferably a PET film or a TAC film. As a birefringent substrate for example an uniaxially stretched plastic film can be used. For example PET films are commercially available from ICI Corp. under the trade name Melinex.

The polymerizable mixture is preferably coated as a thin layer on a substrate or between substrate, and aligned in its chiral mesophase, e.g. the cholesteric or chiral smectic phase, to give a planar orientation, i. e. wherein the axis of the molecular helix extends transversely to the layer. Planar orientation can be achieved for example by shearing the mixture, e.g. by means of a doctor blade. It is also possible to apply an alignment layer, for example a layer of rubbed polyimide or sputtered SiOX, on top of at least one of the substrates. Alternatively, a second substrate is put on top of the coated material. In this case, the shearing caused by putting together the two substrates is sufficient to give good alignment. It is also possible to apply an electric or magnetic field to the coated mixture.

In some cases it is of advantage to apply a second substrate not only to aid alignment of the polymerizable mixture but also to exclude oxygen that may inhibit the polymerization. Alternatively curing can be carried out under an atmosphere of inert gas. However, curing in air is also possible using suitable photoinitiators and high lamp power. When using a cationic photoinitiator oxygen exclusion most often is not needed, but water should be excluded.

An inventive polymerizable liquid crystal mixture for the preparation of anisotropic polymer films comprises preferably 0.1 to 35 %, in particular - 44 0.5 to 15 % and very particularly preferably 0.5 to 5 % by weight of one or more polymerizable chiral compounds of formula 1. Polymerizable liquid crystal mixtures are preferred that comprise 1 to 3 chiral compounds of formula 1.

The polymerizable material can additionally comprise one or more other suitable components such as, for example, catalysts, sensitizers, stabilizers, inhibitors, chain-transfer agents, co-reacting monomers, surface-active compounds, lubricating agents, wetting agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes or pigments.

Preferably the inventive polymerizable mixture comprises a stabilizer that is used to prevent undesired spontaneous polymerization for example during storage of the composition. As stabilizers in principal all compounds can be used that are known to the skilled in the art for this purpose. These compounds are commercially available in a broad variety. Typical examples for stabilizers are 4-ethoxyphenol or butylated hydroxytoluene (BHT).

It is also possible, in order to increase crosslinking of the polymers, to add a non mesogenic compound with two or more polymerizable functional groups, preferably in an amount of up to 20% by weight, to the polymerizable mixture alternatively or additionally to multifunctional mesogenic polymerizable compounds. Typical examples for difunctional non mesogenic monomers are alkyidiacrylates or alkyidimethacrylates with alkyl groups of 1 to 20 C atoms. Typical examples for non mesogenic monomers with more than two polymerizable groups are trimethylpropanetrimethacrylate or pentaerythritoltetraacrylate.

Polymerization of inventive compositions comprising compounds with only one polymerizable functional group leads to linear polymers, whereas in the presence of compounds with more than - 45 one polymerizable functional group crosslinked polymers are obtained.

For the preparation of anisotropic polymer gels, the liquid crystal mixtures can be polymerized in situ as described above, however, in this case alignment of the polymerizable mixture is not always necessary.

The chiral dopant material or optically active material according to the present invention may also comprise one or more further chiral dopants in addition the chiral compounds of formula 1. Typically used chiral dopants are e.g. the commercially available R or S 811, R or S 1011, R or S 2011, R or S 3011, R or S 4011 or CB 15 (from Merck KGaA, Darmstadt, Germany). Very preferred are chiral dopants with a high helical twisting power (HTP), in particular dopants comprising a sorbitol group as described in WO 98/00428, dopants comprising a hydrobenzoin group as described in GB 2,328,207, chiral binaphthyl derivatives as described in WO 02/94805, chiral binaphthol acetal derivatives as described in WO 02/34739, chiral TADDOL derivatives as described in WO 02/06265, and chiral dopants with at least one fluorinated linkage group and a terminal or central chiral group as described in WO 02/06196 and WO 02/06195.

The liquid crystal mixtures or polymerizable liquid crystal mixtures as described above may comprise one or more optically active compounds of formula I or a dopant material comprising one or more compounds of formula I and one or more additional dopants, for example selected from those listed above.

The chiral compounds of formula I and liquid crystal mixtures, liquid crystal polymers or liquid crystal pigments comprising them are also suitable for use in cosmetic and pharmaceutical compositions, for example for coloured make-up as described in EP 815 826 or as UV filters for the protection of human skin or hair, in particular protection against UV-A and UV-B-radiation, as described for example in DE 196 29 761 or EP 1 038 941. The inventive dopants have a high - 46 HTP, therefore only small amounts are needed to yield a short pitch, resulting in a material that shows reflection in the UV range and is suitable as UV- filter.

A liquid crystal mixture, liquid crystal polymer or liquid crystal pigment comprising a chiral compound of formula I and reflecting UV light, in particular of a wavelength of 200 to 400 nm, is another object of the invention. Another object is a cosmetic composition, in particular a cosmetic or pharmaceutical composition for protection of human skin or hair, comprising as UV-filter a liquid crystal mixture, liquid crystal polymer or liquid crystal pigment comprising a chiral compound of formula I and reflecting UV light, in particular in a wavelength range of 200-440 nm, especially 280-400 nm, 200-230 nm (UV-C) and 280 330 nm (UV-B).

The chiral compounds of formula I are particularly suitable for the preparation of cholesteric liquid crystal films or layers with planar orientation, i.e. with a helically twisted structure wherein the helix axis is substantially perpendicular to the film plane. Such layers or films show selective reflection of visible light that is circularly polarized, caused by interaction of incident light with the helically twisted structure of the cholesteric material. The central wavelength of reflection depends on the pitch p and average refractive index n of the cholesteric material according to equation (2) \=n p (2) The bandwidth AX of the reflected wavelength band depends on the pitch and the birefringence An of the cholesteric material according to equation (3) = An p (3) - 47 The reflection wavelength of a cholesteric layer with planar orientation depends on the viewing angle in first approximation according to equation (4) \(a) = \(0) cos[arcsin((sina)/n)] (4) wherein \(0) is the reflection wavelength at normal observation and \(o) is the reflection wavelength at viewing angle or (see Eberle et al., Liq. Cryst. 1989, 5(3), 907-916). Thus, the reflection colour at larger viewing angles is shifted towards shorter wavelengths. This phenomenon is also known to the expert as "colour flop", and is exploited in decorative or security applications.

Thus, the invention further relates to a chiral anisotropic polymer film, in particular a cholesteric film, obtained by polymerizing a compound of formula I or a polymerizable LC mixture as described above and below in its oriented state.

It is also possible to prepare a cholesteric reflective film wherein the optical properties, like the pitch, or the reflection wavelength, its viewing angle or temperature dependence, the reflection bandwidth or the handedness of the reflected light can be varied easily. For example, by using different cholesteric materials and/or photomasking techniques a reflective film can be prepared that has a pattern of at least two regions with different orientation and/or different optical properties. Preferably, such a film exhibits a pattern of at least two regions that differ in at least one property selected from helical pitch, reflection wavelength, handedeness of reflected light, and viewing angle dependence of reflected light (colour flop).

Such a film is another object of the invention.

For example, cholesteric reflective films with a horizontal pattern comprising regions of different reflection wavelength X, or broadband reflective films with a broad bandwidth of the reflected wavelength band can be prepared. The preparation of such films is described for example in WO 00/34808 and in P. van de Witte et al., J. Mater. - 48

Chem. 9 (1999), 2087-2094, the entire disclosure of which is incorporated into this application by way of reference.

Such a film can also be prepared for example by using liquid crystal mixtures according to the invention comprising a chiral compound having a photoisomerizable group. The chiral photoisomerizable compound can be a compound of formula I as described above or an additional compound. As described above, the photoisomerizable compound changes its shape, for example by E-Z- or cis-trans isomerization, upon photoirradiation e.g. with UV light, thus completely changing the shape of the molecule and hence the physical molecular properties like the helical twisting power. For example, if photoisomerization reduces the HTP of the compound, this in turn increases the pitch and thus the reflection wavelength of the liquid crystal mixture.

Photoirradiation can be achieved for example with irradiation by UV light or other high energy sources such as lasers. By using photomasking techniques it is possible to change the chirality only in selected regions of the material, which is then fixed for example by polymerization. In this way, a pattern in the shape of the photomask is obtained, where different regions of the layer show different reflection wavelength. As the change of the HTP of the chiral photoisomerizable compound usually depends on the intensity of photoradiation, the change of the twist in the liquid crystal mixture can also be controlled by local variation of the radiation intensity, for example by the use of grey filters alternatively or in addition to a photomask.

It is also possible to use liquid crystal mixtures comprising a chiral isomerizable and a chiral non-isomerizable compound with different concentration and/or HTP and/or handedness, to prepare films wherein the pitch and/or the handedness of the reflected light can be easily varied. A change of the twist sense in such a film, or selected parts thereof, can be achieved by appropriately selecting the amount and HTP of the two chiral compounds. For example, a liquid crystal - 49 mixture contains a chiral isomerizable and a chiral non-isomerizable compound, one of which is levorotatory and the other is dextrorotatory. The isomerizable compound has a larger HTP and/or is present in an excess amount compared to the non-isomerizable compound, so that the net twist sense of the liquid crystal mixture corresponds to that of the isomerizable compound. Upon photoradiation the HTP of the isomerizable compound is reduced, whereas the non-isomerizable chiral compound does not change its HTP. As a result, the net twist sense of the chiral liquid crystal mixture is reversed.

It is also possible to achieve a change of the twist in a direction vertical to the plane of a cholesteric film or layer by adding a dye to the liquid crystal mixture that has an absorption maximum at the wavelength where the isomerizable compound shows photoisomerization, for example a UV dye. The dye will create a gradient in intensity of photoradiation throughout the thickness of the layer, so that the isomerization and thus the change of twist is faster at the top of the layer than at the bottom. In this way a pitch gradient is created, leading to a broadening of the reflected wavelength band.

This method is especially useful for the preparation of broadband reflective polarizers.

The LO films according to the present invention are useful as optical elements like polarizers, compensators, circular polarizers or colour filters in liquid crystal displays or projection systems, as decorative image, for the preparation of liquid crystal or effect pigments, in nonlinear optics, for optical recording or information storage, for reflective films with spatially varying reflection colours, patterned or multicolour films or images for decorative, information storage or security uses, such as product labels or security markings for identification, verification or authentification of objects or prevention of counterfeiting of ID cards, banknotes, credit cards tickets or other documents of value. - 50

The LC films according to the present invention can be used in displays of the transmissive or reflective type. They can be used in conventional LCDs, in particular those of the DAP (deformation of aligned phases) or VA (vertically aligned) mode, like e.g. ECB (electrically controlled birefringence), CSH (colour super homeotropic), VAN or VAC (vertically aligned nematic or cholesteric) displays, MVA (multi-domain vertically aligned) or PVA (patterned vertically aligned) displays, in displays of the bend mode or hybrid type displays, like e.g. OCB (optically compensated bend cell or optically compensated birefringence), R-OCB (reflective OCB), HAN (hybrid aligned nematic) or pi-cell (-cell) displays, furthermore in displays of the TN (twisted nematic), HTN (highly twisted nematic) or STN (super twisted nematic) mode, in AMD-TN (active matrix driven TN) displays, or in displays of the IPS (in plane switching) mode which are also known as 'super TFT' displays.

In the foregoing and in the following examples, unless otherwise indicated, all temperatures are set forth uncorrected in degrees Celsius and all parts and percentages are by weight.

The values of the helical twisting power HTP of a chiral compound in a liquid crystalline host are given according to the equation HTP = (pc)' in Imp', wherein p is the pitch of the molecular helix, given in m, and c is the concentration by weight of the chiral compound in the host given in relative values (thus, e.g. a concentration of 1 % by weight is corresponding to a value of c of 0.01). Unless stated otherwise, the HTP values were determined in the commercially available liquid crystal host mixture MLC-6260 (Merck KGaA, Darmstadt, Germany) at a concentration of 0. 5 % and a temperature of 20 C.

The following abbreviations are used to illustrate the liquid crystalline phase behaviour of the compounds: G = glassy, C = crystalline; N = nematic; S = smectic; N*, Ch = chiral nematic or cholesteric; I = isotropic. The numbers between these symbols indicate the phase transition temperatures in degree Celsius. - 51

ExampIe 1 Compound (1) is prepared as follows OH lo o: iOH + CS2 + Ag:_oX03 (1) To a solution of carbon disulfide(O.4 mL,7 mmol), R-(+)-1,1'bi-2 naphtol (5 9,17 mmol) and triethylamine (7 mL, 51 mmol) in acetonitrile (35 mL), silver trifluoroacetate (7.7 9, 35 mmol) was bit by bit added over 3 min with stirring on an ice-water bath. The reaction mixture was continuously stirred for 5 h at room temperature. After evaporation of the solvent under reduced pressure, ethyl acetate was added to the residue, and silver sulfide was removed by filtration.

The resulting organic solution was passed through a silica gel column to obtain a colorless solid (3 g, 30%).

MS (El): 580 (M+), 295, 268, 239.

[a]25D = -16,6 (CH2CI2, c= 1.08) Fluorescence: Xemis(CH2CI2, nary)= 400, 388 kexc= 280, 340 CD (CH2CI2, nary): 346 HTP: 33.9.

In a similar way the following compounds were obtained OogoJ ciao 0 (2) C 278 1 HTP 5 P03025 De.doc - 52 Br: X Br 0 0] G 180 1 HTP 45.5 - 53

Claims

- Claims 1. A chiral compound of formula 1 X4:,' :X4 X5z LAZY/\ 4X5.

MU- u 1 wherein K, are independently of each other anellated benzene, cyclohexane or cyclohexene, wherein one or more CH groups are optionally replaced by N and one or more CH2 groups are optionally replaced by O and/or S such that O and/or S atoms are not linked directly to one another, USA are independently of each other CH2, O. S. CO, NH or CF2, Vat have independently of each other one of the meanings of U'-, with the proviso that 0, S and NH are not directly adjacent to each other, or independently of each other may denote a single bond, Z isC,Si,Ge,SnorTi, X'-42 are independently of each other R. P-Sp or-VV'-Ai (1N2-A2) -R - 54 R is in each occurrence independently H. F. Cl, Br, I, CN, NO2, OH, NCS, SF5, straight chain or branched alkyl which has 1 to 40 C-atoms, is unsubstituted, mono- or polysubstituted by F. Cl, Br, I or CN, and in which one or more CH2 groups are optionally replaced, in each case independently from one another, by-O-,-S-, -NH-, -NR -, -SiR R -, -CO-, COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SO2-, CG4=CG2- or -C-C-, in such a manner that two O or two S atoms are not linked directly to one another, or denotes P-Sp, R and R are independently of each other H or alkyl with 1 to 12 C-atoms, G' and G2 are independently of each other H. F. Cl or CN, P is a polymerizable or reactive group, Sp is a spacer group or a single bond, A' and A2 are in each occurrence independently a substituted or unsubstituted aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N. O and So W' and w2 are in each occurrence independently-Or, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-N R -NR -CO-, -OCH2-, -CH2O-, -SCH2-, -CH28-, CF2O-, -OCF2-, -CF2S-' -SCF2-' - CH2CH2-' -CF2CH2-' -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, CH=CH-, -CH=CR -, -CR =CR -, - CG'=CG2-, -C-C -CH=CH-COO-, -OCO-CH=CH- or a single bond, m is in each occurrence independently 0, 1, 2 or 3. .= - 55

2. A chiral compound as claimed in claim 1, wherein the two groups V' and v2 or the two groups V3 and V4 or all of V'-4 are a single bond.

3 A chiral compound as claimed in claim 1, wherein V', V2, V3 and V4 are not a single bond.

4 A chiral compound as claimed in any of the preceding claims, wherein Z is a carbon atom.

5. A chiral compound as claimed in any of the preceding claims, which is selected from the following formulae X4'X' X4 -U, V: V3-U3 - jet la <U2 V2 V4-U4 ii CIV: TV-US lb CóU2V2 \VL43 - 56 x2 x2 X4\ x1 X1 X4 : /U35) . 1C 2 \u4::q X10-1>J-X7. X7Xio X2 \z\ -J Id 0, X8 x8 X4 x,x4 MU V:zU le rSU2-V2 \u4 i X1Ox7 X7o À X8 - 57 \ . X1 U-V\zU If ^ 2 i' \ 4 wherein 1U At, V'-, X À-12 and Z are as defined in claim 1.

6. A chiral compound as claimed in any of the preceding claims, wherein at least one of X '-42 is different from H. 7 A chiral compound as claimed in any of the preceding claims, wherein at least one of R and X À-42 denotes or comprises a polymerizable group. v

3 A chiral compound as claimed in any of the preceding claims, wherein R and X À-42 are selected from F. Cl, ON, NO2, straight chain or branched alkyl, alkenyl, alkynyl, alkoxy, alkycarbonyl, alkoxycarbonyl, alkylcarbonlyoxy, thioether, alkylsulfonyl, alkylsulfanyl, alkylsulfanylcarbonyl, aminoalkyl or aminodialkyl with 1 to 20 C atoms, wherein one or more H atoms are optionally substituted by F or Cl.

9 A chiral compound as claimed in any of the preceding claims, wherein at least one of X À-42 is W'A'(W2A2)mR.

A chiral compound as claimed in any of the preceding claims, wherein A' and A2 are selected from 1,4-phenylene 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 replaced by O and/or S. 1,3dioxolane-4,5-dlyl, 1,4-cyclohexenylene, 1,4-bicyclo-(2,2,2/ - 58 octylene, piperidine-1,4-dlyl, naphthalene-2i6-dlyl, decahydronaphthalene-2,6-diyl, or 1,2,3,4- tetrahydronaphthalene-2,6-diyl, it being possible for all these groups to be unsubstituted, mono- or polysubstituted with L, wherein L has one of the meanings of R in formula 1.

11 A chiral compound substantially as hereinbefore described with reference to compounds 1-3 in example 1.

12 An optically active material or chirp dopant matinal rmh' one or more choral compounds of formula I as claimed in any of the preceding claims and optionally one or more additional chiral compounds.

13 A liquid crystal mixture comprising at least one chiral compound or material as claimed in any of the preceding claims.

14 A polymerizble liquid crystal material comprising at least one chiral compound or material as claimed in any of claims 1 to 12 A polymerizable liquid crystal mixture comprising at least one compound of formula I or material as claimed in any of claims 1 to 12 and at least one polymerizable mesogenic compound, which can be said compound of formula I or an additional compound.

16 A linear or crosslinked polymer obtained by polymerising a compound, material or mixture as claimed in any of the preceding claims.

17 An anisotropic polymer film with twisted structure obtained by polymerising a-layer of a compound, material or mixture as claimed in any of claims 1 to in its oriented state.

18 Use of a compound or material as claimed in any of claims 1 to 12 as chiral dopants in liquid crystal materials or optical, electrooptical, electrical, semiconducting or electronic components or devices. - 59

19 Use of a compound, material, mixture, poisoner or polymer film as claim-cd in any of claims 1 to 17 in electroopticaLdisplays, liquid crystal displays, optical films, polarizers, compensators, beam splitters, reflective films, alignment layers, colour filters, holographic elements, hot stamping foils, coloured images, À decorative or security markings for consumer objects or documents of value, LC pigments, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, nonlinear optics, optical information storage, as chiral dopants, in electronic devices like for example field effect transistors (FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications, electroluminescent displays or backlights of LCDs, for photovoltaic or sensor devices, in lasing applications and devices, as electrode or electrolyte materials in banerles'as photoconductors, for electrophotographic applications or electrophotographic recording.

20. A liquid crystal display comprising a compound, material,.mi.xture, polymer or.polymer film as claimed in any of claims 1 to 17.

21. An optical film, retardation or compensation film, alignment layer, colour filter, polarizer, liquid crystal pigment, decorative7mage, reflective film with spatially varying reflection colours, patterned or multicolour film or images for decorative, information storage or security uses, product label or security marking for identification, verification or authentification of objects or prevention of counterfeiting of ID cards, banknotes, credit cards tickets or other documents of value, which comprises a compound, material, mixture, polymer or polymer film as claimed in any of claims 1 to 17. -

22. Semiconductor or charge transport material, electronic device, field effect transistor (PET), component of integrated circuitry, thin film transistor, Radio Frequency Identification (RFID) tag, semiconducting component of an organic light emitting diode (OLED), electroluminescent display or backlight of a display, photovoltaic or sensor device, which comprises a compound, material, mixture, polymer or polymer film as claimed in any of claims 1 to 17.