Liquid crystal system and liquid crystal display

Abstract

The instant invention relates to mesogenic systems comprising a) a polymeric component, component A, obtained or obtainable from polymerisation of a precursor comprising one or more mesogenic mono-reactive compounds, one or more di-reactive compounds, which optionally are also mesogenic compounds and optionally a photo-initiator and a low molecular weight component, component B, comprising one or more mono-reactive, mesogenic compounds, one or more mesogenic compounds and one or more chiral dopants, exhibiting a Blue Phase, as well as to the use of these systems in deices and to these devices.

Claims

1. A mesogenic system comprising a) a polymeric component, component A, obtained from polymerization of a precursor comprising one or more mesogenic mono-reactive compounds of formula IA ##STR00175## wherein R.sup.11 is H, F, Cl, Br, I, CN, NO.sub.2, NCS, SF.sub.5 , SO.sub.2CF.sub.3 or alkyl which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl, Br, I or CN, and in which one or more non-adjacent CH.sub.2 groups are optionally replaced, in each case independently from one another, by O, S, NH, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.1CY.sup.2or CCin such a manner that O and/or S atoms are not linked directly to one another, R.sup.01 and R.sup.02 are, independently of each other, H or alkyl with 1 to 12 C atoms, ##STR00176## is a mesogenic moiety, PG.sup.11 is a polymerizable or reactive group, Sp.sup.11 is a spacer group or a single bond, and X.sup.11 is O, S, CO, COO, OCO, SCO, COS, OCOO, CONR.sup.01, NR.sup.01CO, OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CF.sub.2O, OCF.sub.2, CF.sub.2S, SCF, CH.sub.2CH.sub.2, CF.sub.2CH.sub.2, CH.sub.2CF.sub.2, CF.sub.2CF.sub.2, CHN, NCH, NN, CHCR.sup.01, CY.sup.01CY.sup.02, CC, (CH.sub.2).sub.4, CHCHCOO, OCOCHCH or a single bond, and Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl or CN, and alternatively one of them may be H, one or more di-reactive compounds, which optionally are also mesogenic compounds and optionally a photo-initiator and b) a low molecular weight component, component B, comprising one or more mesogenic compounds and one or more chiral dopants, exhibiting a Blue Phase.

2. The system according to claim 1, wherein the precursor of component A comprises one or more mesogenic di-reactive compounds.

3. The system according to claim 1, wherein the precursor of component A comprises one or more non-mesogenic (isotropic) mono-reactive compounds.

4. The system according to claim 1, wherein the precursor of component A comprises one or more compounds, which lead to an increase of the characteristic temperatures during and/or upon its polymerization and one or more compounds which on their own lead or would lead to a decrease of the characteristic temperatures during and/or upon its polymerization.

5. The system according to claim 1, having a Blue Phase extending at least over a temperature range from 10 C. or below to +50 C. or above.

6. A light modulation element, comprising a system according to claim 1.

7. In a light modulation medium comprising a mesogenic system, the improvement wherein the system is one according to claim 1.

8. An electro-optical display, comprising a system according to claim 1.

9. They system according to claim 2, wherein the mesogenic di-reactive compound is ##STR00177## wherein ##STR00178## has the meaning given for ##STR00179## under formula I above, PG.sup.12 and PG.sup.13 independently of each other, have one of the meanings given for PG.sup.11 in formula I, SP.sup.12 and SP.sup.13 independently of each other, have one of the meanings given for SP.sup.11 in formula I, and X.sup.12 and X.sup.13 independently of each other, have one of the meanings given for X.sup.11 in formula I.

Description

EXAMPLES

(1) The examples given in the following are illustrating the present invention without limiting it in any way.

(2) However, the physical data especially of the compositions both of the polymer precursors and of the mesogenic host mixtures illustrate to the expert which properties can be achieved in which ranges. The combination of the various properties which can be preferably achieved is thus well defined.

(3) In the following set of examples (examples 1-1 to 1-6 and 2-1 to 2-7) the influence of monomers and of cross-linkers is investigated for mixtures containing a combination of monoacrylated reactive mesogen (MRM) and diacrylated reactive mesogen (DRM).

Examples 1-1 to 1-7 and Comparative Example 1

(4) In this first set of examples (examples 1-1 to 1-7) the influence of the mono-reactive monomers is investigated.

(5) A small amount of photoinitiator 2,2-dimethoxy-1,2-diphenyl-ethanone

(6) (commercially known as Irgacure-651, here also short IRG-651) is added to the mixture. A chiral dopant with a high value of the helical twisting power (HTP), R-5011, obtainable from Merck KGaA, is added to the mixture in concentrations from 2.8% to 3.8%. The HTP of the chiral dopant R-5011 is measured as 130 m.sup.1 in the polar host mixture A-0 with the composition given in the table below,

(7) TABLE-US-00008 TABLE 1 Composition and Properties of Host Mixture A-0 Compound Concentration/ Abbreviation mass-% Physical Properties GZU-3A-N 15.0 T(N, I) = 56.5 C. GZU-4A-N 15.0 GZU-4O-N 15.0 n (20 C., 589 nm) = 0.164 UZU-3A-N 8.0 CUZU-2-N 9.0 CUZU-3-N 9.0 CUZU-4-N 9.0 HP-3N.F 6.0 HP-4N.F 6.0 HP-5N.F 8.0 100.0

(8) The types of cells used are typically either 10 m thick cells without any alignment layers or 50 m thick SSCT cells with planar alignment as thicker samples are occasionally required to allow for the optical observation of the Blue Phases. The cells have a size of approximately 2.0 cm2.5 cm. The electrode area is about 1.0 cm1.0 cm. They are filled by capillary action in an oven at a temperature of typically 100 C. Before polymerisation, the mixtures are characterised by polarising microscopy and their transition temperatures are measured on heating at 1 C./min. The experimental set-up consists of an Olympus BX51 polarising microscope equipped with a Linkam temperature programmer and hot-stage.

(9) Polymerisation experiments are carried out using an EFOS UV lamp at 1.5 mW/cm.sup.2 supplied with a broadband filter (320 nm to 500 nm). Initially, the sample is maintained at a temperature in the Blue Phase regime. After each increment of 15 s of UV irradiation, the texture of the cell is checked under polarising microscope to assess any changes. If a phase transition has occurred, the temperature for the next step of UV irradiation is changed accordingly. Total exposure times are typically 120 s at which stage, the final texture is stabilised.

(10) As host mixture the mixture A-0 described above is used.

(11) The compounds of formula IA are investigated in mixtures with the composition (in weight-%) given in the following table, table 5.

(12) TABLE-US-00009 TABLE 2 Composition of the mixtures investigated in examples 1-1 to 1-6 Compound/Mixture Concentration/ Abbreviation mass-% Respective comp. of formula IA 7.0 Comp. of formula IB-6 5.0 R-5011 2.8 Irgacure-651 0.6 A-0 84.6 100.0

(13) The phase behaviour of the systems before and after polymerisation is given in the following table, table 3.

(14) TABLE-US-00010 TABLE 3 Phase behaviour of examples 1-1o 1-6 and of comparative example 1 Com- Expl. pound of Phases # formula Phases before curing BP after curing C.E. 1 none N* 47.1 BPI 47.6 BPII 51.4 I not applicable 1-1 IA-1 N* 49.9 BPI 51.1 I 20 C. to 47 C. 1-2 IA-2 N* 30.9 BPI 32.5 BPIII .sup. 20 C. to 35 C. 1-3 IA-3 N* 30.3 BPI 31.7 BPIII 33.5 I 20 C. to 40 C. 1-4 IA-4 N* 42.6 BP .sup. 20 C. to 40 C. .sup. 1-5 IA-5 N* 47.8 BPI 49.5 BPIII .sup. 20 C. to 37 C. 1-6 IA-6 N* 47.3 BPI 48.5 BPII 49.1 20 C. to 46 C. BPIII 51.5 Iso 1-7 IA-7 n.d. 20 C. to 46.5 C. Remarks: n.d. not deternined, .sup. no transition to isotropic phase observed and .sup. small areas of cholesteric (N*) present in the cells besides the Blue Phase (BP).

(15) The best results obviously are obtained for examples 1-1, 1-6 and 1-7.

Examples 2-1 to 2-7

(16) In this second set of examples (examples 2-1 to 2-7) the influence of the direactive monomers, the cross-linkers is investigated.

(17) Here again the host mixture A-0 is used.

(18) The compounds of formula IB are investigated in mixtures with the composition (in weight-%) given in the following table, table 4.

(19) TABLE-US-00011 TABLE 4 Composition of the mixtures investigated in examples 2-1 to 2-7 Compound/Mixture Concentration/ Abbreviation mass-% Comp. of formula IA-1 7.0 Respective comp. of formula IB 5.0 R-5011 3.8 Irgacure-651 0.6 A-0 84.6 100.0

(20) The phase behaviour of the systems before and after polymerisation is investigated as described under example 1 and the results are given in the following table, table 5.

(21) TABLE-US-00012 TABLE 5 Phase behaviour of examples 2-1o 2-7 Com- Expl. pound of Phases # formula Phases before curing BP after curing 2-1 IB-1 N* 48.4 BPI 49.5 BPIII 50.9 I 20 C. to +37 C. .sup. 2-2 IB-2 N* 41 BPI 41.5 BPIII 42 I 20 C. to +40 C. .sup.$ 2-3 IB-3 N* 48.3 BPI 49 Iso 20 C. to +42 C. 2-4 IB-4 N* 40.5 BPI 41.8 BPIII 42.5 I 20 C. to +39 C. 2-5 IB-5 N* 37.9 BPI 38.3 BPIII 38.4 I 20 C. to +38 C. .sup. 2-6 IB-6 N* 43 BPI 45 I 20 C. to +36 C. 2-7 IB-7 N* 47 BPI 48 BPIII 50 I 32 C. to 44 C. Remarks: .sup. dark BP, probably BPIII and .sup. small areas of cholesteric (N*) present in the cells besides the Blue Phase (BP).

(22) The best results obviously are obtained for examples 2-2, 2-3 and 2-6.

Comparative Example 2

(23) A combination of a 2-ethylhexylacrylate (abbreviated as EHA), a non-mesogenic mono-reactive monomer and the compound of formula IB-6 were added to highly polar host mixture A-0 in the concentration given in the following table, table 6.

(24) TABLE-US-00013 TABLE 6 Composition of the mixtures investigated in example 1 Compound/Mixture Concentration/ Abbreviation mass-% EHA 2.5 Comp. of formula IB-6 5.0 R-5011 2.8 Irgacure-651 0.4 A-0 89.3 100.0

(25) This precursor is investigated as described under example 1. Phase separation between the non-mesogenic monomer EHA and the LC host occurs in the host mixture filled in the cell with a thickness of 10 m and without alignment layer after 2 mins polymerisation by exposure to 1.5 mW/cm.sup.2 UV light leading to the darker domains under the microscope, being polymer-rich regions and to nucleation of dendritic chiral nematic defects.

Examples 3.1 to 3.4 and Comparative Example 3

(26) To host mixture A-0 the compound of formula IA-1, as mono-reactive mesogenic compound, and the compound of formula IB-6, as di-reactive mesogenic compound are added in various concentrations, together with 2.8% of the chiral dopant R-5011 and a small concentration (typically 0.6%) of the photo-intiator Irgacure-651 (short IRG-651). The compositions are given in the following table, table 7. The ratio of the concentration of mono-reactive mesogenic compound to that of the di-reactive mesogenic compound is kept constant at 1.4, whereas the total concentration of the reactive mesogens is varied in steps of 3% from 6% to 18%.

(27) TABLE-US-00014 TABLE 7 Composition and results of examples 3.1 to 3.4 and of comparative example 3 Example No. C.E. 3 3.1 3.2 3.3a 3.3b 3.4 Composition c(R-5011)/% 2.8 c(IRG-651)/% 0.6 1.06 0.6 c(IA-1)/% 3.5 5.25 7.0 8.75 10.5 c(IB-6)/% 2.5 3.75 5.0 6.25 7.5 c(IA-1) + c(IB-6)/% 6.0 9.0 12.0 15.0 18.0 Characteristic Temperatures T.sub.2/ C. none 38.0 39.0 34.0 33.0 31.0 T.sub.3/ C. none 38.0 30.0 25.0 25.0 25 T.sub.1/ C. none 38.0 1.0 3.5 1.0 1.0 T(BP)/ none 0.0 40.0 37.5 34 30.0 T(FR)/ none 0.0 9.0 9.0 8.0 6.0 Characteristic Voltages T.sub.op./ C. none 38 10.0 10.0 10.0 10.0 V.sub.10, min/V none 17 17.0 n.d. 20.0 31.0 V.sub.90, min/V none 34 36.0 n.d. 47.0 64.0 V.sub.100, min/V none 38 41.0 52.0 55.0 74.0

(28) The resulting mixtures are filled into test cells and cured by illumination with UV and investigated. In this example and in the following examples test cells with an approximate size of 1.0 cm1.0 cm are used. They have interdigital electrodes in a striped (comb-shaped) pattern on the inside of one substrate. The cells are filled on a hot plate having a temperature of about 80 C. to 100 C., while laying in a horizontal position. The characteristic temperatures and the minimum values of the characteristic voltages are determined. The results are also summarised in the preceeding table, table 8.

(29) Obviously the total concentration of the polymer precursor of 6% used in comparative example 3 is too small to stabilise a blue phase, whereas that of 9% used in the example 3.1 is just sufficient for this purpose under the applied conditions.

(30) The temperature dependence of the characteristic voltages of the cell of example 3.2 is given in table 8, below.

(31) TABLE-US-00015 TABLE 8 Temperature dependence of characteristic voltages of example 3.2 T/ C. V.sub.10/V V.sub.90/V 10.0 34.0 78.0 5.1 22.0 48.0 0.3 18.0 38.0 4.9 17.0 36.0 9.6 17.0 36.0 15.0 17.0 37.0 20.0 19.0 39.0 25.0 21.0 41.0 30.1 22.0 44.0 34.9 25.0 47.0 39.8 28.0 54.0 40.1 29.0 55.0 45.1 44.0 82.0 50.1 61.0 116.0

(32) The temperature range, over which the response times .sub.on and ..sub.off, both are below 5 ms and at the same time the characterisic voltage are still sufficiently low, for this example (3.2) extends from 30.1 C. to 40.1 C.

Example 4

(33) Similar to example 3, 12% of the reactive mesogens and 0.6% of the photoinitiator Irgacure-651 are added together with the chiral dopant R-5011 to host mixture A-0. Now, however 4.0%, of R-5011 are used, as summarised in the following table, table 10. The resulting mixture is filled into test a cell and cured by illumination with UV and investigated. The characteristic temperatures and the minimum values of the characteristic voltages are determined. The results are also summarised in the following table, table 9. The data for examples 3.2 to 3.4 are included in this table for comparison.

(34) TABLE-US-00016 TABLE 9 Composition and results of examples 4 and 5 Example No. 3.2 3.3a 3.4 4 5 Composition c(IRG-651)/% 0.6 c(R-5011)/% 2.8 4.0 2.7 c(IA-1)/% 7.0 8.75 10.5 7.0 6.8 c(IB-6)/% 5.0 6.25 7.5 5.0 4.85 [c(IA-1) + 12.0 15.0 18.0 12.0 11.65 c(IB-6))/% c(TRI)/% none 3.0 Characteristic Temperatures T.sub.2/ C. 39.0 34.0 31.0 30.0 29.0 T.sub.3/ C. 30.0 25.0 25 30.0 25.0 T.sub.1/ C. 1.0 3.5 1.0 0.0 0.0 T(BP)/ 40.0 37.5 30.0 30.0 29.0 T(FR)/ 9.0 9.0 6.0 0.0 4.0 Characteristic Voltages T.sub.op./ C. 10.0 10.0 10.0 5.0 5.0 V.sub.100, min/V 41.0 52.0 74.0 57.0 40.0

Example 5

(35) Again similar to example 3, totally 11.65% of the reactive mesogens and 0.6% of the phitoinitiator Irgacure-651 are added together with 2.7% of the chiral dopant R-5011 to host mixture A-0. Now, however, additionally 3.0% of the trialkoxy-compound (short TRI) of the formula

(36) ##STR00174##
are added to the host mixture A-0, as summarised in the preceeding table, table 10. The resulting mixture is filled into a test cell and cured by illumination with UV and investigated. The characteristic temperatures and the minimum values of the characteristic voltages are determined. The results are also summarised in the preceeding table, table 10.

Examples 6.1 to 6.4

(37) In these examples, besides 12% of the reactive mesogens, 0.6% of the phitoinitiator Irgacure-651 and 2.8% of the chiral dopant R-5011 to host mixture A-0, used in example 3, various amounts of compounds of the type AUUQU-n-F are added, as summarised in the following table, table 10. The resulting mixtures are filled into test cells and cured by illumination with UV and investigated. The characteristic temperatures and the minimum values of the characteristic voltages are determined. The results are also summarised in the following table, table 11. The data for example 3.2 are included in this table for comparison.

(38) TABLE-US-00017 TABLE 10 Composition and results of examples 6.1 to 6.4 Example No. 3.2 6.1 6.2 6.3 6.4 Composition c(IRG-651)/% 0.6 c(R-5011)/% 2.8 c(IA-1)/% 7.0 c(IB-6)/% 5.0 c(IA-1) + c(IB-6)/% 12.0 c(AUUQU-1-F)/% none none none 8.0 9.0 c(AUUQU-2-F)/% 10.0 c(AUUQU-3-F)/% 15.0 10.0 11.0 c(AUUQU-4-F)/% none 10.0 7.0 9.0 c(AUUQU-5-F)/% none 5.0 7.0 c(AUUQU-6-F)/% none 7.0 c(AUUQU-7-F)/% 7.0 c(AUUQU-n-F)/% 0.0 15.0 30.0 40.0 60.0 Characteristic Temperatures T.sub.2/ C. 39.0 45.0 45.0 n.d. n.d. T.sub.3/ C. 30.0 25.0 25.0 n.d. n.d. T.sub.1/ C. 1.0 0.0 <15.0 n.d. n.d. T(BP)/ 40.0 45.0 >30.0 n.d. n.d. T(FR)/ 9.0 20.0 20.0 n.d. n.d. Characteristic Voltages T.sub.op./ C. 10.0 6.0 15.0 n.d. n.d. V.sub.100, min/V 41.0 36.0 35.0 n.d. n.d. Remarks: n.d.: not determined.

Examples 7 and 8

(39) In these examples, like in examples 6.1 to 6.4, additional mesogenic compounds are added to the host mixture A-0, besides the polymer precursor, the chiral dopant and the photo-initiator. Now, however, the compounds added are terminally CN-substituted. The compound used in example 7 is AUZU-3-N and the compound used in example 8 is AUUQU-3-N. The concentration used is 15% in each case, as shown in the following table, table 12. The results are also shown in the following table, table 11.

(40) TABLE-US-00018 TABLE 11 Composition and results of examples 7 and 8 Example No. 3.2 6.1 7 8 Composition c(IRG-651)/% 0.6 c(R-5011)/% 2.8 c(IA-1)/% 7.0 c(IB-6)/% 5.0 c(IA-1) + c(IB-6)/% 12.0 Compound none AUUQU-3-F AUZU-3-N AUUQU-3-N c(Compound)/% 0.0 15.0 Characteristic Temperatures T.sub.2/ C. 39.0 45.0 45.0 55.0 T.sub.3/ C. 30.0 25.0 35.0 35.0 T.sub.1/ C. 1.0 0.0 0.0 5.0 T(BP)/ 40.0 45.0 45.0 50.0 T(FR)/ 9.0 20.0 20.0 20.0 Characteristic Voltages T.sub.op./ C. 10.0 6.0 10.0 10.0 V.sub.100, min/V 41.0 36.0 39.0 32.0 Remarks: n.d.: not determined.

(41) The temperature dependence of the characteristic voltages of the cell of example 8 is given in table 12 below.

(42) TABLE-US-00019 TABLE 12 Temperature dependence of characteristic voltages of example 8 T/ C. V.sub.10/V V.sub.90/V 10.0 56 126.0 5.0 28 60.0 0.0 18 38.0 10.0 14.0 28.0 20.1 15.0 29.0 29.9 16.0 31.0 30.2 16.0 31.0 35.2 17.0 32.0 40.0 18.0 33.0 45.0 18.0 35.0 50.0 20.0 38.0 55.0 21.0 44.0 60.0 37.0 70.0

(43) The temperature range over which the response times .sub.on and ..sub.off, both are below 5 ms and at the same time the characteristic voltage are still sufficiently low for this example (3.2) extends from 35.2 C. to 55.0 C.

Examples 9.1 to 9.3 and Comparative Examples 9.1 and 9.2

(44) In comparative example 9.1 the total amount of 7% by weight of the mono-reactive mesogenic compound IA-1 used in example 3.2 is replaced by an equal percentage (7% by weight) of the non-mesogenic mono-reactive compound EHA used in comparative example 2. Otherwise the composition is kept unchanged. The resulting system does not show a stabilised BP-texture under the microscope.

(45) In comparative example 9.24% by weight of the non-mesogenic mono-reactive compound EHA used in comparative example 2 is used together with 8% of the di-reactive mesogenic compound IB-6. The results obtained are shown in the following table, table 13.

(46) In examples 9.1 to 9.3 the mono-reactive mesogenic compound IA-1 is used simultaneously with the non-mesogenic mono-reactive compound EHA. The concentration of the polymer precursors is kept constant at 12%, whereas the relative concentrations of the mono-reactive compounds are changed systematically, as shown in the following table, table 13.

(47) TABLE-US-00020 TABLE 13 Composition and results of examples 9.1 to 9.4 and comparative example 9.2 Example No. 3.2 9.1 9.2 9.3 9.4 C.E. 9.2 Composition c(IRG-651)/% 0.6 0.61 0.62 0.64 c(R-5011)/% 2.8 2.84 2.86 2.90 2.92 3.0 c(IA-1)/% 7.0 5.6 4.9 3.5 2.8 0.0 c(EHA)% 0.0 0.8 1.2 2.0 2.4 4.0 c(IB-6)/% 5.0 5.6 5.0 6.5 6.8 8.0 [c(IA-1) + c(EHA) + 12.0 c(IB-6)]/% Characteristic Temperatures T.sub.2/ C. 39.0 n.d. n.d. n.d. 36.0 55.0 T.sub.3/ C. 30.0 n.d. n.d. n.d. 24.0 35.0 T.sub.1/ C. 1.0 n.d. n.d. n.d. 5.0 0.0 T(BP)/ 40.0 n.d. n.d. n.d. 41.0 55.0 T(FR)/ 9.0 n.d. n.d. n.d. 12.0 30.0 Characteristic Voltages T.sub.op./ C. 10.0 n.d. n.d. n.d. 0.0 5.0 V.sub.100, min/V 41.0 n.d. n.d. n.d. 44.0 54.0 Remarks: n.d.: not determined.

(48) For the systems of examples 3.2 and 9.1 to 9.3, as well as for comparative examples 09.1 and 9.2 the characterisic temperature(s) is/are monitored during the polymerisation process at appropriate regular time intervals until no further change is observed.

(49) The results are compiled in the following table, table 14.

(50) TABLE-US-00021 TABLE 14 Composition and charactristic temperatures during polymerisation of examples 9.1 to 9.3 and comparative example 9.2 Example No. 3-2 9-1 9-2 9-3 9.4 C.E. 9-2 C.E. 9-1 c(IRG-651)/% 0.6 0.61 0.62 0.64 0.6 c(R-5011)/% 2.8 2.84 2.90 2.90 2.92 3.0 2.8 c(IA-1)/% 7.0 5.6 3.5 3.5 2.8 0.0 c(EHA)% 0.0 0.8 2.0 2.0 2.4 4.0 7.0 c(IB-6)/% 5.0 5.6 6.5 6.5 6.8 8.0 5.0 [c(IA-1) + 12.0 c(EHA) + c(IB-6)]/% Characteristic Temperatures During Curing Time(curing)/S T.sub.2/ C. 0 48.3 43.5 39.9 35.8 31.0 17.0 0.0 5 n.d. n.d. n.d. n.d. 31.0 17.0 0.0 10 n.d. 42.8 39.9 35.8 31.0 18.0 3.0 15 46.2 n.d. n.d. n.d. 31.0 19.0 3.0 20 n.d. 41.0 38.6 34.9 31.0 20.0 n.d. 25 n.d. n.d. n.d. 34.9 31.0 21.0 n.d. 30 43.6 39.2 37.4 n.d. 31.0 22.0 10.0 40 n.d. 39.2 n.d. 34.3 31.0 23.0 n.d. 45 42.0 n.d. n.d. n.d. 31.0 n.d. n.d. 50 n.d. n.d. n.d. n.d. n.d. 24.0 n.d. 60 41.2 39.2 n.d. 34.3 n.d. 25.0 20.0 75 n.d. n.d. n.d. n.d. 31.0 26.0 n.d. 90 40.0 39.2 37.4 n.d. n.d. 27.0 24.2 105 n.d. n.d. n.d. n.d. n.d. 28.0 n.d. 120 40.0 39.2 n.d. n.d. 31.0 29.0 27.8 135 n.d. n.d. 37.4 34.3 n.d. n.d. n.d. 140 n.d. n.d. n.d. n.d. n.d. 29.5 n.d. 150 n.d. 39.2 n.d. n.d. n.d. n.d. 30.2 160 n.d. n.d. n.d. n.d. n.d. 30.0 n.d. 180 40.0 39.2 37.4 34.3 31.0 31.0 32.2 210 n.d. 39.2 n.d. n.d. n.d. 31.5 n.d. 240 n.d. 39.2 n.d. n.d. n.d. 32.0 34.9 300 n.d. n.d. n.d. n.d. n.d. 32.0 36.5 360 n.d. n.d. n.d. n.d. n.d. 32.0 37.7 420 n.d. n.d. n.d. n.d. n.d. n.d. 38.6 540 n.d. n.d. n.d. n.d. n.d. n.d. 40.0 Remarks: n.d.: not determined.

(51) As can be seen from the results in table 14 appropriate selection both of mono-reactive compounds being mesogenic and of mono-reactive compounds being non-mesogenic, as well as selecting their appropriate mixing ratio in the polymer precursor allows to minimise the change of the transition temperature during the process of polymerisation, in order to keep the system in the preferred phase, preferably the Blue Phase, and thus makes a control and adjustment of the temperature during the process of polymerisation obsolete.

(52) Especially the results for example 9.2, which are almost completely compensated for temperature change during the process, and for example 9.3 clearly illustrate this effect.

(53) In particular, example 9.4 shows almost no temperature change of T.sub.2 after polymerisation. Thus, example 9.4a, with stepwise polymerisatoin, as described above, is repeated, but with 180 mS exposure to UV in one single application as additional example 9.4b. The result of the previous example (9.4a) is well repruduced also this way.

(54) In contrast example 3.2 shows a marked decrease of the transition temperature during polymerisartion, whereas comparative examples 9.1 and 9.2 both show the opposite change of the transition temperature upon polymerisation, both of which are undesired.