GB2356399A - Polymerizable chiral dopants containing a chiral 4-[(1-phenylethyl)iminomethyl](phenyl/cyclohexyl) terminus for use in liquid crystalline mixtures - Google Patents

Abstract

There are provided chiral (ie both R- and S-) polymerizable compounds of formula I <EMI ID=1.1 HE=14 WI=81 LX=1016 LY=88 TI=CF> <PC>wherein <DL TSIZE=3> <DT>P<DD>is a polymerizable group; <DT>X<DD>is -O-, -S-, -CH=CH-, -C I C-, -CO-, -COO-, -OCO-, -OCO-O-, -CO-NH-, -NH-CO-, -OCH<SB>2</SB>-, -CH<SB>2</SB>O-, -SCH<SB>2</SB>-, -CH<SB>2</SB>S-, -CH=CH-COO-, -OOC-CH=CH- or a single bond; <DT>Sp<DD>is a spacer group with 1 to 25 C atoms; <DT>n<DD>is 0 or 1; <DT>Z<DD>is independently -O-, -S-, -CO-, -COO-, -OCO-, -CO-NH-, -NH-CO-, -CH<SB>2</SB>CH<SB>2</SB>-, -OCH<SB>2</SB>-, -CH<SB>2</SB>O-, -SCH<SB>2</SB>-, -CH<SB>2</SB>S-, -CH=CH, -C I C--CH=CH-COO-, -OCO-CH=CH- or a single bond; <DT>A<DD>is independently 1,4-phenylene (in which one or more CH groups may optionally be replaced by N), 1,4-cyclohexylene (in which one or two non-adjacent CH<SB>2</SB> groups may optionally 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-diyl, naphthalene-2,6-diyl, 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 halogen, cyano or nitro groups or with alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups having 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl; <DT>m<DD>is 0, 1 or 2; and <DT>B<DD>is 1,4-cyclohexylene or 1,4 phenylene that may also be substituted by halogen, cyano or nitro groups or by alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups having 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl. </DL> Such compounds exhibit high twisting power (HTP). There are also provided liquid crystalline mixtures comprising at least one such chiral compound, chiral linear or crosslinked liquid crystalline polymers obtainable by polymerizing such mixtures, and the use of the above in liquid crystal displays, active and passive optical elements, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, liquid crystal pigments, for decorative and security applications, nonlinear optics, optical information storage or as chiral dopants.

Description

PhELAmin 2356399 Chiral Polymerizable Compounds The invention relates to

chiral polymerizable compounds, to liquid crystalline mixtures containing one or more of these chiral polymerizable compounds, to polymers obtained from these liquid crystalline mixtures, and to the use of these chiral polymerizable compounds, liquid crystalline mixtures and polymers obtained thereof in liquid crystal displays, active and passive optical elements like polarizers, compensators, alignment layers, colour filters or holographic elements, in adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, liquid crystal pigments, for decorative and security applications, in nonlinear optics, optical information storage or as chiral dopants.

Chiral compounds can be used as dopants to induce or enhance a helical twist of the molecules of a liquid crystalline mixture that can be 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 The proportionality factor is the helical twisting power (HTP) of the chiral dopant. For many applications it is desirable to have LC mixtures that exhibit a twist. Among these are e.g. phase-change displays, guest- host 30 displays, passive and active matrix TN and STN displays like AMDTN, including such 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 applications it is advantageous 35 to have available a chiral dopant with a high HTP in order to reduce the amount of dopant needed to induce the desired pitch.

PhEtAmin 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 crystalline mixtures that are used in selectively reflecting -cholesteric displays, 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 crystalline phase for optical elements, such as cholesteric broadband polarizers or chiral liquid crystalline 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.

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 crystalline host mixture, such as e.g. the dielectric anisotropy As, the viscosity, the driving voltage or the switching times.

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

PhEtAmin It has been found that these aims can be achieved by providing chiral compounds according to formula 1.

The inventive chiral compounds bear -several advantages, 0 they exhibit a good solubility in liquid crystalline mixtures, they exhibit a high twisting power HTP, when the inventive compounds are used as chiral dopant in a liquid crystalline mixture, due to their high HTP a lower amount of dopant is needed to produce a high twist (= a low pitch), since lower amounts of inventive dopants are needed, the liquid crystalline properties of the mixture are less negatively affected, the inventive compounds have a mesogenic structure, therefore, when used in a liquid crystalline mixture the liquid crystal properties of the mixture are less negatively affected, enantiornerically pure chiral compounds are easy to prepare from cheap, readily available starting materials, both the R and S enantiomers can be prepared, which allows the formation of a cholesteric phase with either a right or left handed cholesteric helix, 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.

A. Kutuly et al., Kristallografiya 38, 183 (1993) disclose chiral Narylidene S-1-phenylethyl amines of the formula R coo CH=N-CH 3 PhEtAmin wherein R is H, CnH2n+l or CmH2m+l, n is 1-4 and rn is 1-3 or 10, for use as dopants, in cholesteric liquid crystalline mixtures. However, there is no disclosure of polymerizable compounds in this reference.

One object of the the present invention are chiral polymerizable compounds of formula I CH=N-CH P-(SP-X)n-(A-Z) -(D- 1-0 M UM3 wherein P is a polymerizable group, X is -0-, -S-, -CH=CH-, -C-=C-, -CO-, -COO-, -OCO-, -OCO-O-, -CO-NH-, -NH-CO-, -OCH2-, -CH20-, -SCH2-, -CH2S-, -CH=CH-COO-, -OOC-CH=CH- or a single bond, Sp is a spacer group with 1 to 25 C atoms, n is 0 or 1, Z is in each case independently from one another -0-, -S-, -CO-, -COO-, -OCO-, -CO-NH-, -NH-CO-, -CH2CH2-, -OCH2-, -CH20-, -SCH2-, -CH2S-, -CH=CH-, -CH=CH-COO-, -OCO-CH=CH-, -C=-C- or a single bond, A is in each case independently from one another 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 0 and/or S, 1,3 dioxolane-4,5-diyi, 1,4-cyclohexenylene, 1,4-bicyclo-(2,2,2) octylene, piperidine-1,4-diyl, naphthaiene-2,6-diyl, decahydronaphthalene-2,6-diyl, or 1,2,3,4 tetrahydronaphthalene-2,6-diyl, it being possibie for all these groups to be unsubstituted, mono- or polysubstituted with PhEtAmin halogen, cyano or nitro groups or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups with 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl, m is 0, 1 or 2, and B is 1,4-cyclohexylene or 1,4 phenylene that may also be substituted by halogen, cyano or nitro groups or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups with I to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl Another object of the invention is a liquid crystalline mixture containing at least one compound of formula 1.

Another object of the present invention is a polymerizable liquid crystalline mixture comprising at least one compound of formula I and at least one polymerizable mesogenic compound having at least one polymerizabie functional group. 20 Another object of the invention is a chiral linear or crosslinked liquid crystalline polymer obtainable by polymerizing a polymerizable liquid crystalline mixture comprising one or more compounds of formula 1. A further object of the invention is the use of a chiral compound, 25 mixture or polymer as described above in liquid crystal displays, such as STN, TN, AMD-TN, temperature compensation, guest-host, phase change or surface stabilized or polymer stabilized cholesteric texture (SSCT, PSCT) displays, in active and passive optical elements like polarizers, compensators, alignment layers, colour filters or 30 holographic elements, in adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, liquid crystal pigments, for decorative and security applications, in nonlinear optics, optical information storage or as chiral dopants. 35 PhEtAmin Yet another object of the invention is a liquid crystal display comprising a liquid crystalline mixture or a polymerizable liquid crystalline mixture comprising at least one chiral compound of formula 1.

The inventive chiral compounds can additionally 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.

Especially preferably B is unsubstituted 1,4-phenylene or trans- 1,4 cyclohexylene, in particular 1,4-phenylene.

Of the inventive compounds especially preferred are those wherein the group -(A-Z),- incorporates one or two five- or six-membered rings. Further preferred compounds are wherein Z is -COO-, -OCO-, -CH2-CH2-or a single bond.

Another preferred embodiment relates to compounds wherein at least one radical Z denotes -C-=C-. These compounds are especially suitable for uses where highly birefringent materials are needed.

X is preferably -0-, -CO-, -COO-, -OCO-, -CH20-, -OCH2-or a single bond, in particular -0-, -COO-, -OCO- or a single bond.

Particularly preferred compounds are those wherein rn is 1 or 2 and A is selected of 1,4-phenylene and trans- 1,4-cyclohexylene, these rings being unsubstituted or substituted in 1 to 4 positions with F, Cl, CN or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl with 1 to 4 C atoms. From these preferred compounds, especially preferred are those comprising a biphenyl or cyclohexylphenyl group.

PhELAmin A smaller group of preferred groups -(A-Z),,- is listed below. For reasons of simplicity, Phe in these groups is 1,4-phenylene, Phe L is a 1,4-phenylene group which is substituted by at least one group L, with L being F, Cl,,CN or an optionally fluorinated alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 4 C atoms, and Cyc is 1,4-cyciohextylene. The list of preferred mesogenic groups comprise the following formulae as well as their mirror images -Phe-Z- 11-1 -CYC-Z11-2 -PheL-Z- 11-3 -Phe-Z-Phe-Z- 11-4 -Phe-Z-Cyc-Z- 11-5 -CYC-Z-CYC-Z11-6 -PheL-Z-Phe-Z- 11-7 -PheL-Z-Cyc-Z- 11-8 -PheL-Z-PheL-Z- 11-9 Bicyclic groups -(A-Z)n- are preferred. Further preferred are compounds wherein -(A-Z)n- is selected of formula 11-7,11-8 or 11-9 and L is F; Cl, CH3, OCH3, OCF3 or CN.

In the above list of preferred groups Z has the meaning given in formula I described above. Preferably Z is -COO-, -OCO-, -CH2CH2-, -C=-C-, -CH=CH-COO- or a single bond.

L is preferably F, Cl, CN, N02, CH3, C21-15, OCH3, OC21-15, COCH3, COC2115, CF3, OCF3, OCHF2, OC2F5, in particular F, Cl, CN, CH3, C2H5, OCH3, COCH3 and OCF3, most preferably F, CH3, OCH3 and COCH3.

Particularly preferred are chiral compounds wherein -(A-Z),,- is -M-Z-, with M selected from the following formulae or their mirror images (L)r __( 0 - Ila PhEtAmin Ilb (L)r (L)r 0 0 11C (L)r Ild Ile (L)r (L)r --(0 -COO--(O Ilf (L)r (L)r -CH 2 CH 2 llg (L)r (L)r IIh In these formulae L has the meaning given above and r is 0, 1 or 2.

The group in these preferred formulae is very preferably L L L L L denoting I I or I furthermore -(k.

PhEtAmin with L having each independently one of the meanings given above.

Especially preferred are compounds of formula I wherein n is 1.

/ 0 The polymerizable group P is preferably selected from WHC CHCH2=CW-COO-, WCH=CH-O-, and CH2=CH-Phenyl-(O)k-, with W being H, CH3or Cl and k being 0 or 1.

P is preferably a vinyl group, an acrylate group, a methacrylate group, a propenyl ether group or an epoxy group, especially preferably an acrylate or a methacrylate group.

As for the spacer group Sp in formula I all groups can be used that are known for this purpose to the skilled in the art. The spacer group Sp is preferably a linear or branched alkylene group having 1 to 20 C atoms, in particular 1 to 12 C atoms, in which, in addition, one or more non-adjacent CH2groups may be replaced by -0-, -S-, -NH-, -N(CH3)-, -CO-, -0-CO-, -S-CO-, -0-COO-, -CO-S-, -CO-O-, -CH(halogen)-, -CH(CN)-, -CH=CHor -C-=C-.

Typical spacer groups are for example -(CH2)1)-, -(CH2CH20)r-CH2CH2-, -CH2CH2-S-CH2CH2-or -CH2CH2-NH-CH2CH2-,with o being an integer from 2 to 12 and r being an integer from 1 to 3.

Preferred spacer groups are ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethyl ene-th i oethyle n e, ethylene- N-methyl 30' iminoethylene, 1-methyl-alkylene, ethenylene, propenylene and butenylene for example.

Especially preferred are inventive chiral compounds of formula I wherein Sp is denoting an alkyl or alkoxy group with 2 to 6 C atoms.

Straight-chain alkyl or alkoxy groups are especially preferred.

PhEtAmin In another preferred embodiment of the invention the chiral compounds of formula I comprise at least one spacer group Sp that is a chiral group of the formula III:

1- 2_ -Q CH-Q I Q 3 111 wherein Q1 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, Q2 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, being different from Q1, and Q3 is halogen, a cyano group or an alkyl or alkoxy group with 1 to 4 C atoms different from Q2.

In case Q1 in formula III is an alkylene-oxy group, the 0 atom is preferably adjacent to the chiral C atom.

The inventive chiral compounds can be synthesized according to or in analogy to reaction scheme 1.

Scheme I CICH 2 CH 2 CO 2 (CH 2)XO-&CO 2 H SOCI 21 DCM y CICH 2 CH 2 CO 2 (CH 2)xO-&COCI + HO--O-CHO (1 a) PhELAmin NEt,, DCM H CH =CHCO CO H N" C 2(CH2)xo-& -0-CHO + 2 CH3 2 2 (1 b) EtOH Y H CH2=CHC02(CH2)xO-&CO 2 &CH-NWI-Cl CH3 wherein x is an integer from 1 to 12.

The inventive chiral compounds can be used in a liquid crystal mixture for displays exhibiting a twisted molecular structure of the liquid crystal matrix like, for example, supertwisted or active matrix liquid crystal displays, or in displays comprising a liquid crystal mixture with a chiral liquid crystalline phase, like for example chiral smectic or chiral nernatic (cholesteric) mixtures for ferroelectric displays or cholesteric displays.

Thus, another object of the invention is a liquid crystalline mixture comprising at least one chiral compound of formula 1.

Yet another object of the invention are cholesteric liquid crystal displays comprising cholesteric liquid crystalline media containing at least one chiral compound of formula 1. The inventive chiral compounds of formula I exhibit high values of the 35 HTP. Thus liquid crystalline mixtures with a high helical twist, i.e. a short cholesteric pitch, can be prepared by using the inventive PhEtAmin compounds, or otherwise a liquid crystalline mixture with a moderate helical twist can be achieved already when using the inventive compounds as dopants in low amounts.

in a preferred embodiment of the invention the chiral compounds show a strong temperature dependence of the HTIP in nematic liquid crystal mixtures. Such mixtures are useful as thermochromic media. The high HTP values of the inventive compounds makes them also 10 suitable to be used in combination with other compounds for the temperature compensation of the properties of liquid crystal mixtures, such as the cholesteric pitch, and of the properties of displays, e.g. such as the threshold voltage. 15 The inventive compounds are furthermore advantageous because they are affecting the physical properties of the liquid crystalline mixture only to a minor extent. Thus, when admixing the chiral compounds of formula I for example 20 to a liquid crystalline mixture with positive dielectric anisotropy that is used in a liquid crystal display, AF, is being only slightly reduced and the viscosity of the liquid crystalline mixture is increased only to a small extent. This leads to lower voltages and improved switching times of the display when compared to a display comprising 25 conventional dopants.

In a particularly preferred embodiment of the invention the chiral compounds show a low temperature dependence of the HTIP in nernatic liquid crystal mixtures.

The liquid crystalline mixture according to the invention comprises preferably 0.1 to 15 %, in particular 1 to 12 % and very particularly preferably 4 to 10 % by weight of chiral compounds of formula 1.

The liquid crystalline mixture according to the invention preferably comprises 1 to 3 chiral compounds of formula 1.

PhEukmin For temperature compensation applications as described above the liquid crystalline mixture preferably contains a chiral component which contains at least one chiral compound of formula 1.

in a preferred embodiment of the invention the liquid crystalline mixture is consisting of 2 to 25, preferably 3 to 15 compounds, at least one of which is a chiral compound of formula 1. The other compounds are preferably low molecular weight liquid crystalline 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, cyciohexylphenyl 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 cyclohexyldioxanes, phenyl- or cyclo hexyl-1,3-dithianes, 1,2-diphenyl-ethanes, 1,2-dicyclohexylethanes, 1 phenyl-2-cyclohexylethanes, 1 -cyclohexyl-2-(4-phenyicyclohexyl)- 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 nernatogenic substances. The 1,4-phenylene groups in these compounds may also be laterally mono- or difluorinated.

The liquid crystalline mixture of this preferred embodiment is based on the achiral compounds of this type The most important compounds that are posssible as components of these liquid crystalline mixtures can be characterized by the following formula PhELAniin 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-Pheand -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-diyl, Dio is 1,3-dioxane-2,5-diyl abd B is 2-(trans-1,4 cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane 2,5-diyl.

G' in these compounds is selected from the following bivalent groups -CH=CH-, -N(O)N-, -CH=CY-, -CH=N(O)-, -C-=C-, -CH2-CH2-, -CO-O-, -CH2-0-, -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.

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 Chernie [Methods of Organic Chemistry], Georg-Thieme-Veriag, Stuttgart), to be precise under reaction conditions which are known and suitable for said reactions. Use may PhEtAmin also be made here of variants which are known per se, but are not mentioned here.

The inventive compounds are in particular useful for anisotropic- polymer gels and for low molar mass or polymerizable or polymerized cholesteric: liquid crystalline mixtures for cholesteric displays, such as for example phase change displays or surface stabilized or polymer stabilized cholesteric texture displays (SSCT, PSCT).

A further advantage of the chiral compounds according to the invention is that cholesteric liquid crystalline mixtures or materials comprising these compounds exhibit a low temperature dependence of the reflection wavelength dX/dT (T = temperature, X = reflection wavelength maximum).

Cholesteric displays are described for example in WO 92/19695, WO 93/23496, US 5,453,863 or US 5,493,430, with the entire disclosure of these documents being introduced into this application by way of reference.

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

It has been found that PSCT displays comprising the inventive compounds have reduced response times, lower voltages and improved contrast compared to displays comprising conventional dopants, like e.g. R 811 or CB 15, that are commercially available by Merck KGaA (Darmstadt, Germany). For example, PSCT displays in which the conventional dopants are replaced by chiral compounds of according to the present invention can show reduced switching time.

Cholesteric films made by using the inventive compounds instead of prior art dopants show improved brightness, leading to a better contrast between the coloured planar texture and the almost clear focal conic state which is made black using a black backpiate.

PhEtAmin -16 The inventive chiral compounds and polymerizabie liquid crystalline mixtures comprising these compounds are also particularly useful for the preparation of anisotropic polymer films with a chiral liquid crystalline phase, such as cholesteric or chiral smectic polymer films, in particular films that exhibit helically twisted molecular structure with uniform planar orientation, i.e. wherein the helical axis is oriented perpendicular to the plane of the film.

For example, oriented cholesteric polymer films can be used as broad waveband reflective polarizers, as described e.g. in EP 0 606 940, as colour filters, for security markings, or for the preparation of liquid crystal pigments. 1. Heynderickx and D.J. Broer in Mol.Cryst.Liq.Cryst. 203, 113-126 (1991) describe crosslinked cholesteric polymer films that are made of liquid crystalline diacrylates and contain a low molecular weight chiral dopant.

It has been found that cholesteric polymer films made by using the inventive chiral compounds are brighter compared to films comprising dopants of prior art like e.g. R 811 or CB 15 as mentioned above.

For the preparation of anisotropic polymer gels or oriented polymer films, the liquid crystalline mixture should comprise at least one polymerizable compound, preferably a polymerizable mesogenic compound, in additon to chiral compounds of formula 1.

Thus, another object of the invention are poiymerizable liquid crystalline mixtures comprising at least one chiral compound of formula I and at least one polymerizable mesogenic compound.

Examples of suitable polymerizable mesogenic compounds that can be used as components of the polymerizable CLC material, are disclosed for example in WO 93/22397; EP 0,261,712; DE 195,04,224; WO 95/22586 and WO 97/00600. The compounds disclosed in these documents, however, are to be regarded merely as examples that shall not limit the scope of this invention.

PhEtAmin Preferably the polymerizable CLC 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. 5 Examples of especially useful monoreactive chiral and achiral polymerizable mesogenic compounds are shown in the following list of compounds, which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention:

P-(CH 2)X0 -Cq coo pva Y (Va) P-(CH2)xo _C>-COO -0-0-Y (Vb) P-(CH2)xo -C coo +V & R 0 (Vc) P-(CH2)xo -C COO+04v&R 0 (Vd) P-(CH2)xo -& CH=CH-COO RO (Ve) CH2=CHCOO(CH2).o R 0 P-(CH2).o --C coo CHiH(CHOCA (Vg) PhEtAmin P-(CH2).o __C coo CH2CH(CH3)C2H. (Vg) L CH(CH H5 P-(CH2)xo -a COO 16 COO --& CH2 X2 (Vh) P-(CH2)xo --& COO-Ter P-(CH2)xo -a COO-Choi (Vk) P-(CH2)xo _C_ coo (Vm) wherein, P has one of the meanings of formula I and its preferred meanings as mentioned above, x is an integer from I to 12, A and D is 1,4-phenylene or 1,4-cyclohexylene, v is 0 or 1, Y is a polar group, Ro is an unpolar alkyl or alkoxy group, Ter is a terpenoid radical like e. g. menthyl, Choi is a cholesteryl group, and Ll and L 2 are each independently H, F, Cl, CN, OH, N02or an optionally halogenated alkyl, alkoxy or carbonyl group with 1 to 7 C atoms.

The polar group Y is preferably CN, N02, halogen, OCH3, OCN, SCN, COR', COOR' or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. R1 is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferably the polar group Y is are selected of F, Cl, CN, N02, OCH3, COCH3, COC2H5, COOCH3, COOC2H5, C173, C2F5, OCF3, OCHF2, andOC2175, in particular of F, Cl, CN, OCH3and OCF3- The unpolar group Ro is preferably an alkyl group with 1 or more, preferably 1 to 15 C atoms or an alkoxy group with 2 or more, preferably 2 to 15 C atoms.

Examples of useful direactive chiral and achiral polymerizable mesogenic compounds are shown in the following list of compounds, which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention 5 Li P(CH2).O -a coo 000 -a O(CH2)YP (Via) L 1 L 2 P(CHO.O -aCH2CH2 GH2CH2 --& O(CH2)YP (VIb) L P O-aCO2 502c-o-O-"'P (VIC) H P(CHAP O-CH=CF(GOO OOCCH=CHO(CH2)YP (Vid) H 0 MHOP D 0 D O(CH2)yp 0 V 0 H (Vie) wherein P, X, D, L' and 1-2have one of the meanings given above and y is an integer from I to 12 the same as or different from x.

A polymerizable CLC material according to the first preferred embodiment as described above comprises one or more chiral dopants which themselves do not necessarily have to show a liquid crystalline phase and give good planar alignment themselves, in particular non-polymerizable chiral dopants.

PhEtAmin The mono- and difunctional polymerizable mesogenic compounds of above formulae V and VI can be prepared by methods which are known per se and which are described in the documents cited above and, for example, in standard works of organic chemistry such as, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.

In a preferred embodiment of the invention the polymerizable liquid crystalline mixtures comprise at least one inventive chiral compound, at least one monofunctional compound of formulae Va-Vrn and at least one bifunctional polymerizable compound of formulae Vla-Vle.

In another preferred embodiment the polymerizable liquid crystalline mixtures comprise at least one inventive chiral compound and at least two monofunctional compounds of formulae Va-Vm.

Another object of the invention is an anisotropic polymer film with an oriented chiral liquid crystalline phase obtainable by (co)polymerizing a liquid crystalline mixture comprising at least one chiral compound offormula I and at least one polymerizable mesogenic compound preferably selected of formula Va-Vrn and Vla-Vle and/or at least one polymerizable chiral compound of formula 1.

To prepare anisotropic polymer film with a chiral liquid crystalline phase with uniform orientation the inventive liquid crystalline mixtures, for example, are coated onto a substrate, aligned and polymerized in situ by exposing them to heat or actinic radiation.

Alignment and curing are preferably carried out in the liquid crystalline phase of the liquid crystalline mixtures.

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. As a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. Another possible source for actinic radiation is a laser, like e.g. a UV laser, an IR laser or a visible laser.

PhEtAmin 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.

it is also possible to use a cationic photoinitiator, when curing reactive mesogens with for example vinyl and epoxide reactive groups, that photocures with cations instead of free radicals.

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. 15 Preferably the polymerizable liquid crystalline mixtures comprising polymerizable chiral compounds of formula I and/or polymerizable mesogenic compounds of formulae V1-V17 additionally comprise 0.01 to 10 %, in particular 0.05 to 8 %, very preferably 0.1 to 5 % by weight of a photoinitiator, especially preferably a UV-photoinitiator. In a preferred embodiment of the invention the polymerization of the polymerizable mesogenic material is carried out under an atmosphere of inert gas, preferably under a nitrogen atmosphere. 25 As a substrate for example a glass or quarz sheet as well as a plastic film 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 30 or not. When using two substrates in case of curing by actinic 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 35 substrate is not removed from the polymerized film after polymerization, preferably isotropic substrates are used.

PhEtAmin Preferably at least one substrate is a plastic substrate such as for example a film of polyester such as polyethyleneterephthalate (PET), of polyvinylalcohol (PVA), polycarbonate (PC) or triacetylcel I u lose JAC), 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.

in a preferred embodiment of the present invention, the inventive mixture of the polymerizable liquid crystalline mixture comprising a chiral compound of formula I is coated as a thin layer on a substrate or between substrate, and is preferably aligned in its chiral mesophase, eg. the cholesteric or chiral smectic phase, to give a planar orientation, i.e. an orientation so that the axis of the molecular helix extends transversely to the layer.

A 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 SiO,,, on top of at least one of the substrates.

In another preferred embodiment, a second substrate is put on top of the coated material. In this case, the shearing caused by puft-ing 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 the curing can be carried out under an atmosphere of inert gas. However, curing in air is also possible using suitable photoinitiators and high 35 lamp power. When using a cationic photoinitiator oxygen exclusion most often is not needed, but water should be excluded.

% PhEttkniin A detailed description of the in situ polymerization of polymerizable mesogenic compounds can be found in D.J.Broer et al., Makromolekulare Chemie 190, 2255 (1989).

A polymerizable liquid crystalline mixture for the preparation of anisotropic polymer films 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 crystalline mixtures are preferred that comprise I to 3 chiral compounds of formula 1.

The inventive polymerizable liquid crystalline mixtures can additionally comprise one or more other suitable components, such as, for example, catalysts, sensitizers, stabilizers, co-reacting monomers or surface-active compounds.

in a preferred embodiment of the invention, the inventive polymerizable liquid crystalline 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 up to 20% of a non mesogenic compound with two or more polymerizable functional groups to the polymerizable composition alternatively or additionally to the multifunctional polymerizable mesogenic compounds.

Typical examples for difunctional non mesogenic monomers are alky1diacrylates or alky1dimethacrylates with alkyl groups of 1 to 20 C atoms. Typical examples for non mesogenic monomers with more PhELAmin -24 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 one polymerizable functional group crosslinked polymers are obtained.

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

The inventive chiral compounds of formula I can also be used for the prepration of thermochromic liquid crystalline mixtures. Such mixtures are characterized in that they exhibit a chiral liquid crystalline phase or chiral mesophase, like e.g. a chiral smectic phase or a chiral nematic (= cholesteric) phase, with a helically twisted molecular structure that shows selective reflection of a specific waveband of light, wherein the pitch of the molecular helix and thereby the reflected wavelengths are depending on the temperature.

Especially preferred are inventive liquid crystalline mixtures with thermochromic behaviour that exhibit a cholesteric phase. Of these preferred compositions, further preferred are compositions that exhibit a cholesteric phase and a smectic phase, most preferably a chiral smectic phase, at temperatures below the temperature range of the cholesteric phase. The inventive liquid crystalline mixtures exhibiting thermochromic behaviour can be polymerizable or non polymerizable.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various PhEtAmin -25 changes and modifications of the invention to adapt it to various usages and conditions.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to ist fullest extent. The following examples are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.

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 = (p-c)-' in 4m-1, 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).

The following abbreviations are used to illustrate the liquid crystalline phase behaviour of the compounds: K = crystalline; N = nematic; S = smectic; Ch = cholesteric; I = isotropic. The numbers between these symbols indicate the phase transition temperatures in degree Celsius. Furthermore, An is the birefringence at 589 nm and 20 OC and AE: is the dielectric anisotropy at 20 OC.

PhEtAmin Example 1 Compound (1) was prepared according to reaction scheme 1 5 H CH 2=CHCO 2(CH 2)60-&co 20-CH=N-'-C-CH 3 (R) Acid chloride (11 a) 4-[6-(3-Chicro-propionyloxy)-hexyloxy]-benzoic acid (15.0 g, 45.6 15 mmol) was stirred with thionyl chloride (4.4 rril, 60.3 mmol, 1.3 equivalents) and a catalytic amount of 1-methyl-2-pyrrolidinone under reflux in DCM for 16 hours. The mixture was cooled and evaporated to dryness to leave an oily residue. Yield = 16.2 g, 100 %. The product was used without further purification in the next step. 20 Preparation of ester (1 b) The acid chloride (1 a) (15.5 g, 45.6 mmol), 4- hydroxybenzaidehyde (5.6 g, 45.6 mmol) and triethylamine (25.4 ml, 183 mmol) were stirred 25 in DCM at 35 "C overnight. The mixture was cooled to room temperature, the DCM layer was washed with water, then with dilute hydrochloride acid, and then dried (Na2SO4). Evaporation of the solvent left a pale pink solid residue. This was used without further purification. 30 Preparation of chiral Phenylethylamine (1) The aldehyde (1 b) (2.5 g, 6.3 mmol) and R-(+)-methylbenzylamine (1.8 g, 14.9 mmol) were stirred under reflux in ethanol. On cooling the 35 solution, crystals precipitated. Further recrystallization from ethanol I'llEtAmin gave a crystalline solid. 1H NIVIR spectroscopy showed expected signals.

The HTP of (1) was 44 tm-', measured in the commercially available nernatic host mixture BL 087 (from Merck Ltd., Poole, UK) at a concentration of 7 % by weight.

The host mixture BL 087 has the following properties N 89.5 1, As = 20.6, An = 0.2363 Example 2

Compound (2) was prepared as described in example 1, but with using S-(-)-methylbenzylamine in the final step.

H CH 2 =CHCO 2 (CH 2)60-&CO2 O-CH=NW,-C11 CH 3 (S) (2) Compound (2) has a HTP of 43 Lrn-' (7,6 % in nernatic host BL 087).

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding 30 examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various conditions and usages.

28

Claims (14)

Claims

1 A chiral polymerizable compound of formula I P-(Sp-X),-(A-Z) CH=N-CH _& 1-0 M UH3 wherein P is a polymerizable group, X is -0-, -S-, -CH=CH-, -C=-C-, -CO-, -COO-, -OCO-, -OCO-O-, -CO-NH-, -NH-CO-, -OCH2-, -CH20-, -SCH2-, -CH2S-, -CH=CH-COO-, -OOC-CH=CH- or a single bond, Sp is a spacer group with I to 25 C atoms, n is 0 or 1, Z is in each case independently from one another -0-, -S-, -CO-, -COO-, -OCO-, -CO-NH-, -NH-CO-, -CH2CH2-, -OCH2-, -CH20-, -SCH2-, -CH2S-, -CH=CH-, -C-=C -CH=CH-COO-, -OCO-CH=CH- or a single bond, A is in each case independently from one another 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 0 and/or S, 1,3-dioxoiane-4,5-diyl, 1,4 cyclohexenylene, 1,4-bicyclo-(2,2,2)-octylene, pipericline 1,4-diyl, naphthalene-2,6-diyl, 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 halogen, cyano or nitro groups or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups with 1 to 7 29 C atoms, wherein one or more H atoms may be substituted by F or Cl, m is 0, 1 or 2, and B is 1,4-cyclohexylene or 1,4 phenylene that may also be substituted by halogen, cyano or nitro groups or alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl groups with 1 to 7 C atoms, wherein one or more H atoms may be substituted by F or Cl.

io

2. A chiral compound as claimed in claim 1, wherein B is 1,4phenylene.

3. A chiral compound as claimed in claim 1 or claim 2, wherein -(A- Z)mis -M-Z-, with M selected from the following formulae or their mirror images (L)r 0 Ila Ilb (L)r (L)r -(0 0 11C (L)r Ile (L)r -COO--(O (L)r (L)r CH2CH2 llg (L)r M, 11h wherein L is F, Cl, CN or an optionally fluorinated alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 4 C atoms and r is 0, 1 or 2.

4. A chiral compound as claimed in any of claims 1 to 3, wherein P is a vinyl group, an acrylate group, a methacrylate group, a propenyl ether group or an epoxy group.

5. A chiral compound substantially as hereinbefore described in the foregoing examples.

6. A liquid crystalline mixture comprising at least one chiral compound as claimed in any of claims 1 to 5.

7. Use of at least one chiral compound as claimed in any of claims 1 to in a liquid crystalline mixture.

8. A liquid crystalline mixture as claimed in claim 6, further comprising at least one polymerizable mesogenic compound having at least one polymerizable functional group.

9. Use of at least one chiral compound as claimed in claim 6 and at least one polymerizable mesogenic compound having at least one polymerizable functional group in a liquid crystalline mixture.

10. A chiral linear or crosslinked liquid crystalline polymer obtainable by polymerizing a mixture as claimed in claim 6 or B.

11. A chiral linear or crosslinked liquid crystalline polymer obtained by polymerizing a mixture as claimed in claim 6 or 8.

12. Use of a chiral compound, mixture or polymer as claimed in any of claims 1 to 6, 8, 10 or 11 in a liquid crystal display, preferably, STN, TN, AMD-TN, temperature compensator, guest-host, phase change or surface stabilized or polymer stabilized cholesteric texture (SSCT, PSCT) display, an active or passive optical element like a polarizer, compensator, alignment layer, colour filter or holographic element, an adhesive, synthetic resin with anisotropic mechanical properties, cosmetic, diagnostic, liquid crystal pigment, for decorative and security applications, nonlinear optic, an optical information storage or as a chiral dopant.

13. A liquid crystal display, preferably, STN, TN, AMD-TN, temperature compensator, guest-host, phase change or surface stabilized or 32 polymer stabilized cholesteric texture (SSCT, PSCT) display, an active or passive optical element like a polarizer, compensator, alignment layer, colour filter or holographic element, an adhesive, synthetic resin with anisotropic mechanical properties, cosmetic, diagnsotic, liquid crystal pigment, for decorative and security applications, nonlinear optic, an optical information storage or chiral dopant comprising a chiral compound, mixture or polymer as claimed in any of claims 1 to 6, 8, 10 or 11.

io

14. A liquid crystal display comprising a liquid crystalline mixture as claimed in claim 6 or claim 7.