BIMESOGENIC COMPOUNDS AND MESOGENIC MEDIA

Abstract

The invention relates to bimesogenic compounds of formula I

##STR00001##

to the use of bimesogenic compounds of formula I in liquid crystal media and particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.

Claims

1. Bimesogenic compounds of formula I ##STR00160## R.sup.11 and R.sup.12 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms, which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each occurrence independently from one another, by —O—, —S—, —NH—, —N(CH.sub.3)—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, preferably F, Cl, CN, a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN more preferably a polar group, most preferably F, Cl, CN, OCF.sub.3, CF.sub.3, and at least one of R.sup.11 and R.sup.12 is an alkyl group, i.e. a straight-chain or branched alkyl group with 1 to 25 C atoms, which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each occurrence independently from one another, by —O—, —S—, —NH—, —N(CH.sub.3)—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, preferably a polar group, in which one CH.sub.2 groups is replaced by —CH═CH—, —CH═CF—, —CF═CF—, but from which OCF.sub.3 and CF.sub.3, are excluded, preferably a non-polar group, more preferably unsubstituted alkyl, alkenyl or alkinyl, most preferably a straight-chain or branched alkyl group with 1 to 25 C atoms, MG.sup.11 and MG.sup.12 are each independently a mesogenic group, at least one of MG.sup.11 and MG.sup.12 comprises one, two or more 5-atomic and/or 6-atomic rings, in case of comprising two or more 5- and/or 6-atomic rings at least two of these may be linked by a 2-atomic linking group, preferably selected from the group of linking groups —CO—O—, —O—CO—, —CH.sub.2—O—, —O—CH.sub.2—, —CF.sub.2—O— and —O—CF.sub.2—, Sp.sup.1 is a spacer group comprising 1, 3 or 5 to 40 C atoms, wherein one or more non-adjacent and non-terminal CH.sub.2 groups may also be replaced by —O—, —S—, —NH—, —N(CH.sub.3)—, —CO—, —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O—, —CH(halogen)-, —CH(CN)—, —CH═CH— or ≡C≡C—, however in such a way that no two O-atoms are adjacent to one another, now two —CH═CH— groups are adjacent to each other and no two groups selected from —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O— and —CH═CH— are adjacent to each other, preferably —CH.sub.2).sub.n— (i.e. 1,n-alkylene with n C atoms), with n an integer, preferably from 3 to 19, more preferably from 3 to 11, most preferably an odd integer (i.e. 3, 5, 7, 9 or 11), X.sup.11 and X.sup.12 are independently from one another a linking group selected from —CO—O—, —O—CO—, —O—, —CH═CH—, —C≡C—, —CF.sub.2—O—, —O—CF.sub.2—, —CF.sub.2—CF.sub.2, —CH.sub.2—O—, —O—CH.sub.2—, —CO—S—, —S—CO—, —CS—S—, —S—, and a single bond, preferably —CO—O—, —O—CO— or a single bond, most preferably a single bond, however under the condition that in —X.sup.11-Sp.sup.1-X.sup.12— no two O atoms are adjacent to one another, no two —CH═CH— groups are adjacent to each other and no two groups selected from —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O— and —CH═CH— are adjacent to each other.

2. Bimesogenic compounds according to claim 1, characterized in that at least one of MG.sup.11 and MG.sup.12 comprises one or two 5-atomic rings, and one or more 6-atomic rings, and at least two of these are optionally linked by a 2-atomic group.

3. Bimesogenic compounds according to claim 1, characterized in that both MG.sup.11 and MG.sup.12 comprise one or two 5-atomic rings.

4. Bimesogenic compounds according to claim 1, characterized in that R.sup.12 is selected from OCF.sub.3, CF.sub.3, F, Cl and CN.

5. Bimesogenic compounds according to claim 1, characterized in that Sp.sup.1 is —(CH.sub.2).sub.o— and o is 1, 3 or an integer from 5 to 15.

6. (canceled)

7. Liquid-crystalline medium, characterised in that it comprises one or more bimesogenic compounds according to claim 1.

8. Liquid-crystalline medium according to claim 7, characterised in that it additionally comprises one or more compounds selected from the group of the compounds of the formulae III
R.sup.31-MG.sup.31-X.sup.31-Sp.sup.3-X.sup.32-MG.sup.32-R.sup.32  III wherein R.sup.31 and R.sup.32 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each case independently from one another, by —O—, —S—, —NH—, —N(CH.sub.3)—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, MG.sup.31 and MG.sup.32 are each independently a mesogenic group, Sp.sup.3 is a spacer group comprising 5 to 40 C atoms, wherein one or more non-adjacent CH.sub.2 groups may also be replaced by —O—, —S—, —NH—, —N(CH.sub.3)—, —CO—, —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O—, —CH(halogen)-, —CH(CN)—, —CH═CH— or ≡C≡C—, and X.sup.31 and X.sup.32 are each independently —O—, —S—, —CO—, —COO—, —OCO—, —O—CO—O—, —CO—NH—, —NH—CO—, —CH.sub.2CH.sub.2—, —OCH.sub.2—, —CH.sub.2O—, —SCH.sub.2—, —CH.sub.2S—, —CH═CH—, —CH═CH—COO—, —OCO—CH═CH—, —C≡C— or a single bond, and with the condition that compounds of formula I are excluded.

9. (canceled)

10. Liquid crystal device comprising a liquid crystalline medium comprising two or more components, one or more of which is a bimesogenic compound of formula I according to claim 1.

11. Liquid crystal device according to claim 10, characterized in that it is a flexoelectric device.

Description

COMPOUND AND SYNTHESIS EXAMPLES

Synthesis Example 1: Preparation of

[0228] ##STR00131##

[0229] The compound of interest is prepared according to the following scheme.

##STR00132##

Stage 1.1

[0230] ##STR00133##

[0231] 4-Cyano-4′-hydroxybiphenyl (20.0 g, 102.45 mmol) is added into a flask containing 300 mL acetone. Then potassium carbonate (29.74 g, 215.15 mmol) is added. The mixture is heated to gentle reflux for one hour before being cooled to ambient temperature (also called room temperature), which is 20° C. in this application, unless explicitly specified otherwise. Then it is added dropwise to a flask containing 1,7-dibromoheptane (100 mL, 593.04 mmol). After the addition is completed, the flask is heated to gentle reflux for 20 hours. The reaction mixture is cooled to room temperature and the solid material is separated by filtration in vacuo. The filter pad is washed with acetone (100 mL). The filtrate is concentrated in vacuo before a portion of petroleum ether 40-60° C. (50 mL) is added. The solid formed is separated by filtration in vacuo and purified by column chromatography over silica gel, eluted with 10% ethyl acetate in petroleum ether 40-60° C. The pure product is obtained as a white powder.

Stage 1.2

[0232] ##STR00134##

[0233] To a solution of 4′-(7-bromo-heptyloxy)-biphenyl-4-carbonitrile (2.17 g, 5.83 mmol,) in butan-2-one (75.00 mL), which is stirred under a nitrogen atmosphere, 4-pentyl-phenol (0.96 g, 5.83 mmol,) and potassium carbonate (1.07 g, 7.58 mmol,). The reaction mixture is heated to 80° C. for 48 hours. The reaction mixture is cooled and the solid material is removed by filtration in vacuo. The filter pad is well washed with butan-2-one (100 mL). The filtrate is then concentrated in vacuo to give a pale orange solid. The solid is purified by column chromatography over silica gel, eluting with dichloromethane: petroleum ether (1:5 ratio). The fractions containing product are collected and concentrated in vacuo. The solid is then recrystallised from acetonitrile (30 mL) to give the pure product as a white powder.

Synthesis Example 2: Preparation of

[0234] ##STR00135##

[0235] The compound of interest is prepared according to the following scheme.

##STR00136##

Stage 2.1

[0236] ##STR00137##

[0237] 3-Fluoro-4-bromo phenol (15.0 g, 78.54 mmol,) and 4-cyano-bezene boronic acid (11.6 g, 78.9 mmol,) are added into a reaction flask containing 1,4-dioxane (300 mL). Then sodium carbonate (15.9 g, 150.0 mmol) and water (150 mL) are added. The reaction vessel is purged with nitrogen before addition of palladium (dppf) dichloride (550.0 mg, 0.75 mmol). The system is heated for 16 hours at 80° C. The reaction mixture is cooled to ambient temperature before being gravity filtered and neutralized by addition of dilute hydrochloric acid. Then dichloromethane (50 mL) is added. The organic phase is separated and washed with brine, water and dried over magnesium sulphate, filtered and concentrated in vacuo to dryness. The crude product is purified by column chromatography over silica gel, eluting with 1% methanol in dichloromethane.

Stage 2.2

[0238] ##STR00138##

[0239] Heptanedioic acid (8.00 g, 49.95 mmol), dicyclohexylcarbodiimide (10.31 g, 49.95 mmol) and dimethylaminopyridine (609.86 mg, 4.99 mmol) are charged into a flask containing 80 mL dichloromethane at ambient temperature. After stirring for 30 minutes 4′-hydroxy-biphenyl-4-carbonitrile (9.75 g, 49.95 mmol) is added and the reaction mixture is stirred at ambient temperature for 100 hours. Then water (20 mL) is added, the organic phase is separated, dried over magnesium sulphate and concentrated in vacuo to dryness. The crude product is purified by column chromatography over silica gel, eluted with a mixture of ethyl acetate:petroleum ether (1:1 ratio).

Stage 2.3

[0240] ##STR00139##

[0241] Heptanedioic acid mono-(4′-cyano-2-fluoro-biphenyl-4-yl) ester (10.0 g, 28.14 mmol), dicyclohexylcarbodiimide (5.81 g, 28.14 mmol) and dimethylaminopyridine (343.60 mg, 2.81 mmol) are charged into a flask containing dichloromethane (80 mL) and stirred for 30 min before 4-pentyl-phenol (4.81 mL, 28.14 mmol) are added. The reaction mixture is stirred at ambient temperature for 18 hours. Then water (20 ml) is added. The organic phase is separated, dried over magnesium sulphate and evaporated in vacuo. The crude product is purified by column chromatography over silica gel, eluting with dichloromethane:petroleum ether (with increasing ratio up to 9:1 ratio). The product is isolated as a white solid.

Synthesis Example 3: Preparation of

[0242] ##STR00140##

[0243] The compound of interest is prepared according to the following scheme.

##STR00141##

Stage 3.1

[0244] ##STR00142##

[0245] To a 3 necked round bottom flask under nitrogen hex-5-ynoic acid methyl ester (3.84 g; 30.47 mmol), 1-iodo-4-(4-propyl-cyclohexyl)-benzene (10.0 g; 30.47 mmol), diisopropylamine (12.85 ml; 91.40 mmol) and toluene (38 mL) are added. The flask is purged with nitrogen, and bis(triphenylphosphin)-palladium(II)-chlorid (320.77 mg; 0.46 mmol) and copper(I) iodide (162.46 mg; 0.85 mmol) are added. The reaction mixture is warmed to 30° C. for 20 minutes and then 40° C. for 1 hour. The mixture is cooled to room temperature and the solids filtered off and is washed throughly with ethyl acetate. The volatiles are removed under reduced pressure. Pure product is obtained after column chromatography over silica gel using petroleum ether:ethyl acetate as an eluent.

Stage 3.2

[0246] ##STR00143##

[0247] 6-[4-(4-Propyl-cyclohexyl)-phenyl]-hex-5-ynoic acid methyl ester (5.7 g, 17.0 mmol) and platinum on carbon (1 g, 5% on carbon) was charged in a Buchi autoclave containing 17 mL toluene. The hydrogenation was performed at 2 bar and 20° C. for overnight. The mixture is filtered through celite to give a clear solution. This is concentrated under reduced pressure to give the product.

Stage 3.3

[0248] ##STR00144##

[0249] 6-[4-(4-Propyl-cyclohexyl)-phenyl]-hexanoic acid methyl ester (12.00 g, 36.31 mmol) is added to flask containing tetrahydrofuran (100 mL), then lithium hydroxide (2.61 g, 108.92 mmol) in 100 mL water is added and stirred overnight at room temperature. The reaction mixture is acidified with concentrated hydrochloric acid. The organic phase is separated and aqueous phase is extracted with dichloromethane (two times 30 mL). The organic layers are combined, dried over magnesium sulphate and evaporated. The crude is passed through a pad of silica gel by washing with dichloromethane:ethyl acetate (6:4 ratio). The volatiles are removed in vacuo to yield the desired product.

Stage 3.4

[0250] ##STR00145##

[0251] 6-[4-(4-Propyl-cyclohexyl)-phenyl]-hexanoic acid (2.0 g, 6.32 mmol), dicyclohexylcarbodiimide (1.30 g, 6.32 mmol) and dimethylaminopyridine (77.16 mg, 0.63 mmol) are charged into a flask containing 50.00 mL dichloromethane at room temperature, The reaction mixture is stirred for 30 min. Then 4-hydroxy-benzonitrile (828.07 mg, 6.95 mmol) is added and stirred at room temperature for 16 hours. Water (20 mL) is added, and the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel using petrolum ether:dichloromethane (3:7 ratio) as an eluent gives pure product.

Compound Examples 4 and Following

[0252] The following compounds of formula I are prepared analogously.

Compound Example 4

[0253] ##STR00146##

Compound Example 5

[0254] ##STR00147##

[0255] Phase sequence: K 97.4 N100.4 I, e/K=1.65 Cm.sup.−1N.sup.−1=1.65 V.sup.−1.

Compound Example 6

[0256] ##STR00148##

Compound Example 7

[0257] ##STR00149##

[0258] Phase sequence: K 67.2 I, e/K=1.82 V.sup.−1.

Compound Example 8

[0259] ##STR00150##

[0260] Phase sequence: K (73.8 N) 85.1 I, e/K=2.15 V.sup.−1.

Compound Example 9

[0261] ##STR00151##

[0262] Phase sequence: K 33.9 I, e/K=1.99 V.sup.−1.

Compound Example 10

[0263] ##STR00152##

[0264] Phase sequence: K (54 SmA 63 N) 90 I, e/K=2.04 V.sup.−1.

Compound Example 11

[0265] ##STR00153##

[0266] Phase sequence: K 97 I, e/K=1.79 V.sup.−1.

Compound Example 12

[0267] ##STR00154##

[0268] Phase sequence: K 88 N 98 I, e/K=2.11 V.sup.−1.

Compound Example 13

[0269] ##STR00155##

[0270] Phase sequence: K (118 N) 135 I, e/K=2.22 V.sup.−1.

Compound Example 14

[0271] ##STR00156##

[0272] Phase sequence: K 113 N 198 I, e/K=1.96 V.sup.−1.

Compound Example 15

[0273] ##STR00157##

[0274] Phase sequence: K 92 N 114 I, e/K=2.04 V.sup.−1.

Compound Example 16

[0275] ##STR00158##

[0276] Phase sequence: K I, e/K=1.75 V.sup.−1.

[0277] The materials in the above table generally show increased performance in the screening mixtures, as compared to known, more conventional bimesogenic compounds as e.g. those shown in the table below.

Comparative Compound Example 1

[0278] ##STR00159##

[0279] Phase sequence: K 98 (N 83) I, e/K=2.25 V.sup.−1.

Use Examples, Mixture Examples

[0280] Typically a 5.6 m thick cell, having an anti-parallel rubbed PI alignment layer, is filled on a hotplate at a temperature at which the flexoelectric mixture in the isotropic phase.

[0281] After the cell has been filled phase, transitions, including clearing point, are measured using Differential Scanning Calorimetry (DSC) and verified by optical inspection. For optical phase transition measurements, a Mettler FP90 hot-stage controller connected to a FP82 hot-stage is used to control the temperature of the cell. The temperature is increased from ambient temperature at a rate of 5 degrees C. per minute, until the onset of the isotropic phase is observed. The texture change is observed through crossed polarizers using an Olympus BX51 microscope and the respective temperature noted.

[0282] Wires are then attached to the ITO electrodes of the cell using indium metal. The cell is secured in a Linkam THMS600 hot-stage connected to a Linkam TMS93 hot-stage controller. The hot-stage is secured to a rotation stage in an Olympus BX51 microscope.

[0283] The cell is heated until the liquid crystal is completely isotropic. The cell is then cooled under an applied electric field until the sample is completely nematic. The driving waveform is supplied by a Tektronix AFG3021B arbitrary function generator, which is sent through a Newtons4th LPA400 power amplifier before being applied to the cell. The cell response is monitored with a Thorlabs PDA55 photodiode. Both input waveforms and optical response are measured using a Tektronix TDS 2024B digital oscilloscope.

[0284] In order to measure the flexoelastic response of the material, the change in the size of the tilt of the optic axis is measured as a function of increasing voltage. This is achieved by using the equation:

[00001]$\tan .Math..Math.\varphi =\frac{P_0}{2.Math.\pi }.Math.\frac{e}{K}.Math.\underset{\_}{E}$

wherein φ is the tilt in the optic axis from the original position (i.e. when E=0), E is the applied field, K is the elastic constant (average of K.sub.1 and K.sub.3) and e is the flexoelectric coefficient (where e=e.sub.1+e.sub.3). The applied field is monitored using a HP 34401A multimeter. The tilt angle is measured using the aforementioned microscope and oscilloscope. The undisturbed cholesteric pitch, P.sub.0, is measured using an Ocean Optics USB4000 spectrometer attached to a computer. The selective reflection band is obtained and the pitch determined from the spectral data.

[0285] The mixtures shown in the following examples are well suitable for use in USH-displays. To that end an appropriate concentration of the chiral dopant or dopants used has to be applied in order to achieve a cholesteric pitch of 200 nm or less.

Comparative Mixture Example 1.0

Host Mixture H-0

[0286] The host mixture H-0 is prepared and investigated in particular studying its properties for being aligned.

TABLE-US-00006 Composition Compound No. Abbreviation Conc./% 1 F—PGI—O-9-O—GP—F 25.0 2 F—PGI—O-9-O—PP—N 25.0 3 F—PGI—ZI-9-Z—GP—F 25.0 4 F—PGI—ZI-9-Z—PP—N 25.0 Σ 100.0

[0287] The alignment of the mixtures, like mixture H-0, is determined in a test cell with anti-parallel rubbed PI orientation layers, for planar alignment, having a cell gap of 10 μm at a wavelength of 550 nm. The optical retardation of the samples is determined using an elipsometer instrument for various angles of incidence ranging from −60° to +40°. The results are compiled in the following table.

[0288] The sample of H-0 shows an optical retardation of 25 nm under perpendicular observation (i.e. at an angle of incidence of 00). This already indicates the presence of a homogeneous alignment. For various angles of incidence, the values of the retardation range from 2 nm to 55 nm. Though they scatter quite significantly as a function of the angle of incidence, there seems to be a trend of the retardation increasing with increasing angle of incidence. However, the significant scatter of the retardation values indicate a rather poor quality of the homeotropic alignment.

TABLE-US-00007 Angle/° −60 −40 −20 0 20 40 Example Mixt. d .Math. Δn/nm C H-0 2 33 42 25 55 44 1 M-1.0 67 33 9 1 7 23 2 M-2.0 120 61 18 0 18 62 3 M-3.0 70 57 35 33 58 104

[0289] 2% of the chiral dopant R-5011 are added to the mixture H-0 leading to the mixture H-1, which is investigated for its properties.

TABLE-US-00008 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F—PGI—O-9-O—GP—F 24.5 3 F—PGI—O-9-O—PP—N 24.5 4 F—PGI—ZI-9-Z—GP—F 24.5 5 F—PGI—ZI-9-Z—PP—N 24.5 Σ 100.0

[0290] The mixture H-1 may be used for the USH-mode. It has a clearing point of 82° C. and a lower transition temperature [T(N2,N)] of 33° C. It has a cholesteric pitch of 301 nm at 35° C. The e/K of this mixture is 1.9 Cm.sup.−1N.sup.−1 at a temperature of 34.8° C.

Mixture Examples 1.0 and 1.1

[0291] 25% of the compound of synthesis example 1 are added to the mixture H-0 leading to Mixture M-1.0, which is also investigated for its alignment.

Mixture Example 1.0: Mixture M-1.0

[0292]

TABLE-US-00009 Composition Compound No. Abbreviation Conc./% 1 F—PGI—O-9-O—GP—F 18.75 2 F—PGI—O-9-O—PP—N 18.75 3 F—PGI—ZI-9-Z—GP—F 18.75 4 F—PGI—ZI-9-Z—PP—N 18.75 5 Compound 1* 25.0 Σ 100.0 Remark: *Compound of Synthesis Example 1.

[0293] This mixture (M-1.0) is prepared and investigated.

[0294] The data for its orientation behaviour are compiled in the table above. The mixture shows very good homeotropic alignment. This is indicated by the retardation at normal incidence being close to zero and further the retardation increasing almost symmetrically for positive and negative angles of incidence with increasing absolute value of the angle of incidence.

[0295] Compare this to the mixture H-0, where clearly homogeneous alignment is indicated by the completely different dependence of retardation on the angle of incidence.

[0296] 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 1 are added to the mixture H-0 leading to the mixture M-1.1, which is investigated for its properties.

Mixture Example 1.1: Mixture M-1.1

[0297]

TABLE-US-00010 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F—PGI—O-9-O—GP—F 22.0 3 F—PGI—O-9-O—PP—N 22.0 4 F—PGI—ZI-9-Z—GP—F 22.0 5 F—PGI—ZI-9-Z—PP—N 22.0 6 Compound 1* 10.0 Σ 100.0 Remark: *Compound of Synthesis Example 1.

[0298] This mixture (M-1.1) is prepared and investigated. It is well suitable for the ULH-mode. It has a transition from the nematic phase to the isotropic phase [T(N,I)] at 77.0° C. This mixture (M-1.1) is well suitable for the USH-mode. It has a cholesteric pitch of 313.7 nm at 43° C. The e/K of this mixture is 2.03 Cm.sup.−1N.sup.−1 at a temperature of 42.6° C.

Mixture Examples 2.0 to 2.2

Mixture Example 2.0: Mixture M-2.0

[0299] 25% of the compound of synthesis example 2 are added to the mixture H-0 leading to Mixture M-2.0, which is also investigated for its alignment.

TABLE-US-00011 Composition Compound No. Abbreviation Conc./% 1 F—PGI—O-9-O—GP—F 18.75 2 F—PGI—O-9-O—PP—N 18.75 3 F—PGI—ZI-9-Z—GP—F 18.75 4 F—PGI—ZI-9-Z—PP—N 18.75 5 Compound 2* 25.0 Σ 100.0 Remark: *Compound of Synthesis Example 2.

[0300] This mixture (M-2.0) is prepared and investigated.

[0301] The data for its orientation behaviour are compiled in the table above. The mixture shows extremely good, almost perfect homeotropic alignment, as indicated by the retardation at normal incidence being very close to zero and the retardation increasing symmetrically with increasing absolute value of the angle of incidence.

Mixture Example 2.1: Mixture M-2.1

[0302] 10% of the compound of synthesis example 2 are added to the mixture H-0 leading to Mixture M-2.1, which is also investigated for its alignment.

Mixture Example 2.1: Mixture M-2.1

[0303]

TABLE-US-00012 Composition Compound No. Abbreviation Conc./% 1 F—PGI—O-9-O—GP—F 22.5 2 F—PGI—O-9-O—PP—N 22.5 3 F—PGI—ZI-9-Z—GP—F 22.5 4 F—PGI—ZI-9-Z—PP—N 22.5 5 Compound 2* 10.0 Σ 100.0 Remark: *Compound of Synthesis Example 2.

[0304] This mixture (M-2.1) is prepared and investigated.

[0305] The data for its orientation behaviour are compiled in the table above. The mixture shows similarly good, only slightly inferior homeotropic alignment, compared to mixture M-2-0 as described above.

Mixture Example 2.2: Mixture M-2.2

[0306] 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 2 are added to the mixture H-0 leading to the mixture M-2.1, which is investigated for its properties.

TABLE-US-00013 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F—PGI—O-9-O—GP—F 22.0 3 F—PGI—O-9-O—PP—N 22.0 4 F—PGI—ZI-9-Z—GP—F 22.0 5 F—PGI—ZI-9-Z—PP—N 22.0 6 Compound 2* 10.0 Σ 100.0 Remark: *Compound of Synthesis Example 2.

[0307] This mixture (M-2.1) is prepared and investigated. It is well suitable for the ULH-mode. It has a transition from the nematic phase to the isotropic phase [T(N,I)] at 76° C. This mixture (M-2.1) is well suitable for the USH-mode. It has a cholesteric pitch of 299 nm at 41° C. The e/K of this mixture is 2.04 Cm.sup.−1N.sup.−1 at a temperature of 41.1° C.

Mixture Examples 3.0 and 3.1

[0308] 25% of the compound of synthesis example 1 are added to the mixture H-0 leading to Mixture M-3.0, which is also investigated for its alignment.

Mixture Example 3.0: Mixture M-3.0

[0309]

TABLE-US-00014 Composition Compound No. Abbreviation Conc./% 1 F—PGI—O-9-O—GP—F 18.75 2 F—PGI—O-9-O—PP—N 18.75 3 F—PGI—ZI-9-Z—GP—F 18.75 4 F—PGI—ZI-9-Z—PP—N 18.75 5 Compound 3* 25.0 Σ 100.0 Remark: *Compound of Synthesis Example 3.

[0310] This mixture (M-3.0) is prepared and investigated. The data for its orientation behaviour are compiled in the table above. The mixture shows good homeotropic alignment.

Mixture Example 3.1: Mixture M-3.1

[0311] 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 1 are added to the mixture M-1.0 leading to the mixture M-1.1, which is investigated for its properties.

Mixture M-3.1

[0312]

TABLE-US-00015 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F—PGI—O-9-O—GP—F 22.0 3 F—PGI—O-9-O—PP—N 22.0 4 F—PGI—ZI-9-Z—GP—F 22.0 5 F—PGI—ZI-9-Z—PP—N 22.0 6 Compound 3* 10.0 Σ 100.0 Remark: *Compound of Synthesis Example 3.

[0313] This mixture (M-3.1) is prepared and investigated. It is well suitable for the ULH-mode. It has a transition from the nematic phase to the isotropic phase [T(N,I)] at 73.2° C. This mixture (M-3.1) is well suitable for the USH-mode. It has a cholesteric pitch of 310 nm at 38° C. The e/K of this mixture is 2.14 Cm.sup.−1N.sup.−1 at a temperature of 38.6° C.

[0314] The investigation described above is performed with 10% each of several compounds of formula I instead of that of synthesis example 1 used in host mixture H-0, together with 2% R-5011. The results are shown in the following table.

TABLE-US-00016 T(N, I)/ T.sub.low/ P/ e/K/ Ex. Mixt. Compound ° C. ° C. nm V.sup.−1 C1.1 H-1.0 None  82 33 301 1.9  C1.2 H-1.1 N-PGI-9-GP-N t.b.d. t.b.d. 298 2.22 C1.3 H-1.21 N-PP-9-PP-N t.b.d. 42 t.b.d. t.b.d. C1.4 H-1.3 F-PGI-O-7-O-GP-F 108   26.5 332 1.70 E1.1 M-1.1 Compound 1* t.b.d. t.b.d. 314 2.03 E1.2 M-1.2 Compound 2* t.b.d. t.b.d. 299 2.04 E1.3 M-1.3 Compound 3* t.b.d. t.b.d. 310 2.14 E1.4 M-1.4 Compound 4* t.b.d. t.b.d. 295 n/a E1.5 M-1.5 Compound 5* t.b.d. t.b.d. 333 1.65 E1.6 M-1.6 Compound 6* t.b.d. t.b.d. t.b.d. t.b.d. E1.7 M-1.7 Compound 7* t.b.d. t.b.d. 315 1.82 E1.8 M-1.8 Compound 8* t.b.d. t.b.d. 337 2.15 E1.9 M-1.5 Compound 9* t.b.d. t.b.d. 337 1.99 E1.10 M-1.10 Compound 10* t.b.d. t.b.d. 302 2.04 E1.11 M-1.11 Compound 11* t.b.d. t.b.d. 341 1.79 E1.12 M-1.12 Compound 12* t.b.d. t.b.d. 304 2.11 E1.13 M-1.13 Compound 13* t.b.d. t.b.d. 292 2.22 E1.14 M-1.14 Compound 14* t.b.d. t.b.d. 311 1.97 E1.15 M-1.15 Compound 15* t.b.d. t.b.d. 310 1.87 E1.16 M-1.16 Compound 16* t.b.d. t.b.d. 302 1.75 Remarks: *compound n: of Synthesis Example No. n, t.b.d.: to be determined the cholesteric pitch (P) is given at 0.9T(N, I) and e/K is given in V.sup.−1 (i.e. Cm.sup.−1N.sup.−1) at 0.9T(N, I).