LIQUID-CRYSTALLINE MEDIUM FOR USE IN A SWITCHING ELEMENT

Abstract

The present invention relates to liquid-crystalline media comprising one or more mesogenic compounds, one or more chiral compounds, and one or more polymerisable mesogenic compounds, wherein the media exhibit a pitch of 0.55 μm or more and a clearing point of 80° C. or more and wherein the one or more polymerisable mesogenic compounds are contained in an amount, based on the overall contents of the media, of 5% by weight or less. The present invention further relates to modulation materials obtainable from the media and to switching layers and window elements containing the materials.

Claims

1. A window element, which is operable in and electrically switchable between an optically transparent state and a scattering state and which comprises a switching layer containing a material which comprises a liquid-crystalline medium comprising one or more mesogenic compounds and one or more chiral compounds, wherein the liquid-crystalline medium has a clearing point of 80° C. or more, and a polymeric component comprising one or more polymeric structures obtained by or respectively obtainable from polymerisation of one or more polymerisable mesogenic compounds, wherein the polymeric component is contained in the material in an amount, based on the overall contents of the material, of 5% by weight or less.

2. The window element according to claim 1, wherein the liquid-crystalline medium as set forth in claim 1 contains, based on the overall contents of the medium, at least 15% by weight of one or more mesogenic compounds of formula I ##STR00370## wherein R.sup.1 and R.sup.2 denote, independently of one another, a group selected from F, Cl, CF.sub.3, OCF.sub.3, and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, A.sup.11 denotes ##STR00371## n denotes 0 or 1, and A.sup.21, A.sup.31 and A.sup.41 denote, independently of one another, ##STR00372## wherein L is on each occurrence, identically or differently, halogen selected from F, Cl and Br.

3. The window element according to claim 1, wherein the liquid-crystalline medium further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III ##STR00373## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 denote, independently of one another, a group selected from F, CF.sub.3, OCF.sub.3, CN, and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, and L.sup.1, L.sup.2, L.sup.3, L.sup.4 and L.sup.5 denote, independently of one another, H or F.

4. The window element according to claim 1, wherein the liquid-crystalline medium exhibits a positive dielectric anisotropy Δε and an optical anisotropy Δn, determined at 20° C. and 589 nm, of 0.13 or more, and wherein the one or more chiral compounds contained in the liquid-crystalline medium have an absolute value of the helical twisting power of 5 μm.sup.−1 or more.

5. A method for preparing a window element of claim 1, comprising (i) providing a liquid-crystalline medium which comprises one or more mesogenic compounds, one or more chiral compounds and one or more polymerisable mesogenic compounds as a layer between two opposing transparent substrates which are each provided with an electrode, wherein the liquid-crystalline medium has a clearing point of 80° C. or more and exhibits a pitch of 0.55 μm or more, and wherein the one or more polymerisable mesogenic compounds are contained in the medium in an amount, based on the overall contents of the medium, of 5% by weight or less, and (ii) polymerising the one or more polymerisable mesogenic compounds in the presence of an applied electric field in the layer.

6. The method according to claim 5, wherein the electrodes are arranged as conductive layers above the inner surface of each substrate, wherein preferably the conductive layers are respectively arranged on a passivation layer, more preferably arranged between passivation layers, and wherein optionally alignment layers are further provided which are in direct contact with the liquid-crystalline medium.

7. The method according to claim 5, wherein polymerising as set forth in step (ii) is carried out by photopolymerisation and wherein the applied electric field induces a homeotropic alignment.

8. The method according to claim 5, wherein subsequent to step (ii) a thermal treatment is carried out in the presence or absence of an electric field.

9. A window element for the modulation of the passage of light, wherein the window element is obtained by or respectively obtainable from carrying out the method according to claim 5.

10. The window element according to claim 1, which is switchable into an optically transparent state by applying an AC voltage V1 and which is switchable into a scattering state by applying an AC voltage V2, wherein V1>V2.

11. The window element according to claim 1, wherein the liquid-crystalline medium exhibits a pitch of 0.55 μm or more in the scattering state.

12. A liquid-crystalline medium, comprising one or more mesogenic compounds, one or more chiral compounds, one or more polymerisable mesogenic compounds in an amount, based on the overall contents of the medium, of 5% by weight or less, wherein the medium exhibits a pitch of 0.55 μm or more and a clearing point of 80° C. or more.

13. The medium according to claim 12, which contains, based on the overall contents of the medium, at least 15% by weight of one or more mesogenic compounds of formula I, ##STR00374## wherein R.sup.1 and R.sup.2 denote, independently of one another, a group selected from F, Cl, CF.sub.3, OCF.sub.3, and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO—, or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, A.sup.11 denotes ##STR00375## n denotes 0 or 1, and A.sup.21, A.sup.31 and A.sup.41 denote, independently of one another, ##STR00376## wherein L is one each occurrence, identically or differently, halogen selected from F, Cl and Br, which optionally further comprises one or more photoinitiators, and which optionally further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III ##STR00377## wherein R.sup.3, R.sup.4, R.sup.5 and R.sup.6 denote, independently of one another, a group selected from F, CF.sub.3, OCF.sub.3, CN, and straight-chain or branched alkyl or alkoxy having 1 to 15 carbon atoms or straight-chain or branched alkenyl having 2 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or mono- or polysubstituted by halogen and wherein one or more CH.sub.2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, and L.sup.1, L.sup.2, L.sup.3, L.sup.4 and L.sup.5 denote, independently of one another, H or F.

14. The medium according to claim 12, wherein one or more of the one or more polymerisable mesogenic compounds comprise one, two or more acrylate and/or methacrylate groups.

15. The medium according to claim 12, which comprises a compound having the formula ##STR00378##

16. A liquid-crystalline medium, comprising a compound having the formula ##STR00379##

17. The liquid-crystalline medium according to claim 16, which further comprises a compound having the formula ##STR00380##

18. A modulation material, comprising a liquid-crystalline medium comprising one or more mesogenic compounds and one or more chiral compounds, wherein the liquid-crystalline medium has a clearing point of 80° C. or more and exhibits a pitch of 0.55 μm or more, and a polymeric component comprising one or more polymeric structures obtained by or respectively obtainable from polymerisation of one or more polymerisable mesogenic compounds, wherein the polymeric component is contained in the material in an amount, based on the overall contents of the material, of 5% by weight or less.

19. A switching layer, comprising the medium according to claim 12.

20. A switching layer, comprising the medium according to claim 13.

Description

EXAMPLES

[0348] Liquid crystal mixtures and composite systems are realized with the compositions and properties as given in the following. Their properties and optical performance are investigated.

Reference Example 1

[0349] A liquid-crystal base mixture B-1 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00008 GGP-5-Cl  17.00% Clearing point: 101.0° C. PGIGI-3-F  7.00% Δn [589 nm, 20° C.]: 0.181 CPG-2-F  8.00% n.sub.e [589 nm, 20° C.]: 1.693 CPG-3-F  8.00% Δϵ [1 kHz, 20° C.]: 13.2 CPG-5-F  5.00% ϵ.sub.∥ [1 kHz, 20° C.]: 18.0 CGU-2-F  7.00% CGU-3-F  7.00% CGU-5-F  4.00% PGU-2-F  8.00% PGU-3-F  8.00% CPGU-3-F  10.00% CPP-3-2  5.00% CGPC-3-3  3.00% CGPC-5-3  3.00% Σ 100.00%

Reference Example 2

[0350] A liquid-crystal base mixture B-2 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00009   PP-1-2V1  8.00% Clearing point: 98.0° C. CP-3-O1  7.00% Δn [589 nm, 20° C.]: 0.231 CP-3-Cl  3.00% n.sub.e [589 nm, 20° C.]: 1.755 PGP-2-2V  9.00% Δε [1 kHz, 20° C.]: 7.0 PGP-3-2V  6.00% ε.sub.∥ [1 kHz, 20° C.]: 11.0 PGU-3-F  4.00% GGP-3-Cl  9.00% GGP-5-Cl  20.00% GPEP-2-Cl  8.00% GPEP-5-Cl  12.00% PGIGI-3-F  5.00% CPGP-4-3  3.00% CPGP-5-2  3.00% DPGU-4-F  3.00% Σ 100.00%

Reference Example 3

[0351] A liquid-crystal base mixture B-3 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00010   PGIGI-3-F  12.00% Clearing point: 104.0° C. CPG-2-F  8.00% Δn [589 nm, 20° C.]: 0.161 CPG-3-F  8.00% Δε [1 kHz, 20° C.]: 10.9 CPG-5-F  5.00% ε.sub.∥ [1 kHz, 20° C.]: 15.2 CPU-5-F  10.00% CPU-7-F  10.00% PGU-3-F  4.00% PGU-5-F  9.00% CCGU-3-F  8.00% CPP-3-2  4.00% CGPC-3-3  3.00% CGPC-5-3  3.00% CGPC-5-5  3.00% CPGU-3-OT  3.00% CP-5-N  10.00% Σ 100.00%

Reference Example 4

[0352] A liquid-crystal base mixture B-4 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00011   PGIGI-3-F  10.00% Clearing point: 105.0° C. CPG-2-F  6.00% Δn [589 nm, 20° C.]: 0.160 CPG-3-F  7.00% n.sub.e [589 nm, 20° C.]: 1.663 CPG-5-F  5.00% Δε [1 kHz, 20° C.]: 10.0 CPU-5-F  10.00% CPU-7-F  10.00% PGU-3-F  4.00% PGU-5-F  7.00% CCGU-3-F  8.00% CPP-3-2  4.00% CGPC-3-3  3.00% CGPC-5-3  3.00% CGPC-5-5  3.00% CPGU-3-OT  5.00% CP-5-N  15.00% Σ 100.00%

Reference Example 5

[0353] A liquid-crystal base mixture B-5 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00012   CP-5-N  15.00% Clearing point: 101.0° C PGIGI-3-F  10.00% Δn [589 nm, 20° C.]: 0.173 CPG-2-F  6.00% n.sub.e [589 nm, 20° C.]: 1.680 CPG-3-F  7.00% Δε [1 kHz, 20° C.]: 11.0 CPG-5-F  5.00% ε.sub.∥ [1 kHz, 20° C.]: 15.2 CPU-5-F  10.00% CPU-7-F  10.00% PGU-3-F  4.00% PGU-5-F  3.00% PGP-2-3  4.00% PGP-2-4  5.00% PGP-2-5  4.00% CCGU-3-F  8.00% CPGP-3-OT  5.00% CPGP-5-2  4.00% Σ 100.00%

Reference Example 6

[0354] A liquid-crystal base mixture B-6 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00013   APUQU-3-F  8.00% Clearing point: 127.8° C. CPU-3-F  15.00% Δn [589 nm, 20° C.]: 0.206 CCGU-3-F  8.00% n.sub.e [589 nm, 20° C.]: 1.711 CPGP-5-2  4.00% Δε [1 kHz, 20° C.]: 42.7 CPGP-5-3  4.00% ε.sub.∥ [1 kHz, 20° C.]: 48.2 CPGU-3-OT  8.00% DPGU-4-F  4.00% PGU-2-F  10.00% PGU-3-F  11.00% PGUQU-3-F  8.00% PGUQU-4-F  10.00% PGUQU-5-F  10.00% Σ 100.00%

Reference Example 7

[0355] A liquid-crystal base mixture B-7 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00014   CP-3-N  14.00% Clearing point: 119.3° C. PTP-1-O2  8.00% Δn [589 nm, 20° C.]: 0.236 PTP-3-O1  6.00% n.sub.e [589 nm, 20° C.]: 1.752 CP-3-O1  8.50% Δε [1 kHz, 20° C.]: 7.2 PGP-2-2V  8.00% ε.sub.∥ [1 kHz, 20° C.]: 11.0 CPGP-4-3  5.00% CPGP-5-2  5.00% PGP-2-3  5.00% PGP-2-4  5.00% PGP-2-5  10.00% CPTP-3-O1  6.00% CPTP-3-O2  6.00% PGUQU-3-F  7.50% PGUQU-4-F  2.00% PP-1-2V1  4.00% Σ 100.00%

Reference Example 8

[0356] A liquid-crystal base mixture B-8 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00015   CP-1V-N  16.00% Clearing point: 110.1° C. PP-2-N  7.00% Δn [589 nm, 20° C.]: 0.218 PGUQU-3-F  10.00% n.sub.e [589 nm, 20° C.]: 1.737 CPG-2-F  10.00% Δε [1 kHz, 20° C.]: 11.1 PP-1-2V1  10.00% ε.sub.∥ [1 kHz, 20° C.]: 15.3 PGIGI-3-F  12.00% CPGP-5-2  8.00% CPGP-5-3  8.00% PGP-2-3  7.00% PGP-2-4  6.00% PGP-2-5  6.00% Σ 100.00%

Reference Example 9

[0357] A liquid-crystal base mixture B-9 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00016   PUQU-2-F  6.00% Clearing point: 98.1° C. PUQU-3-F  12.00% Δn [589 nm, 20° C.]: 0.166 PGU-2-F  5.00% n.sub.e [589 nm, 20° C.]: 1.668 PGU-3-F  11.00% Δε [1 kHz, 20° C.]: 11.4 PPGU-3-F  4.00% ε.sub.∥ [1 kHz, 20° C.]: 15.2 CPGP-5-2  7.00% CPGP-5-3  6.00% CPGP-4-3  7.00% CC-3-V  25.00% PGP-2-3  4.00% PGP-2-4  4.00% CPU-3-F  9.00% Σ 100.00%

Reference Example 10

[0358] A liquid-crystal base mixture B-10 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00017   PGUQU-3-F  6.00% Clearing point: 101.0° C. PGUQU-4-F  10.00% Δn [589 nm, 20° C.]: 0.194 PGUCU-5-F  10.00% n.sub.e [589 nm, 20° C.]: 1.699 PUQU-3-F  17.00% Δε [1 kHz, 20° C.]: 37.0 PGU-2-F  10.00% ε.sub.∥ [1 kHz, 20° C.]: 42.9 PGU-3-F  11.00% CPGU-3-OT  8.00% CCGU-3-F  8.00% CPU-3-F  12.00% CPGP-5-2  4.00% CPGP-5-3  4.00% Σ 100.00%

Reference Example 11

[0359] A liquid-crystal base mixture B-11 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00018   CP-3-O1  8.00% Clearing point: 111.5° C. CC-3-V  12.00% Δn [589 nm, 20° C.]: 0.213 CPGP-5-2  6.00% n.sub.e [589 nm, 20° C.].sub.: 1.729 CPGP-5-3  6.00% Δε [1 kHz, 20° C.]: 3.1 PGP-2-2V  14.00% ε.sub.∥ [1 kHz, 20° C.]: 6.3 PGP-1-2V  13.00% PGP-3-2V  13.00% PGP-2-5  6.00% PP-1-2V1  12.00% PUQU-3-F  6.00% PGUQU-3-F  4.00% Σ 100.00%

Reference Example 12

[0360] A liquid-crystal base mixture B-12 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00019   PGIGI-3-F  8.00% Clearing point: 102.0° C. GGP-3-F  8.00% Δn [589 nm, 20° C.]: 0.169 GGP-5-F  7.00% n.sub.e [589 nm, 20° C.]: 1.675 CPG-2-F  7.00% Δε [1 kHz, 20° C.]: 12.2 CPG-3-F  7.00% ε.sub.∥ [1 kHz, 20° C.]: 16.9 CPG-5-F  5.00% CPU-5-F  10.00% PGU-3-F  4.00% PGU-5-F  7.00% CCGU-3-F  8.00% CGPC-3-3  3.00% CGPC-5-3  3.00% CGPC-5-5  3.00% CPGU-3-OT  5.00% CP-5-N  15.00% Σ 100.00%

Reference Example 13

[0361] A liquid-crystal base mixture B-13 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00020   PGIGI-3-F  7.00% Clearing point: 99.9° C. GGP-3-F  8.00% Δn [589 nm, 20° C.]: 0.179 GGP-5-F  7.00% n.sub.e [589 nm, 20° C.]: 1.681 CPG-3-F  7.00% Δε [1 kHz, 20° C.]: 13.9 CPG-5-F  5.00% ε.sub.∥ [1 kHz, 20° C.]: 18.7 CPU-5-F  10.00% PGU-2-F  6.00% PGU-3-F  6.00% PGU-5-F  7.00% CCGU-3-F  8.00% CGPC-3-3  3.00% CGPC-5-3  3.00% CGPC-5-5  3.00% CPGU-3-OT  5.00% CP-5-N  15.00% Σ 100.00%

Reference Example 14

[0362] A liquid-crystal base mixture B-14 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00021   PGIGI-3-F  6.00% Clearing point: 101.0° C. GGP-3-F  7.00% Δn [589 nm, 20° C.]: 0.174 GGP-5-F  8.00% n.sub.e [589 nm, 20° C.]: 1.684 CPG-2-F  9.00% Δε [1 kHz, 20° C.]: 12.6 CPG-3-F  8.00% ε.sub.∥ [1 kHz, 20° C.]: 17.4 CPG-5-F  8.00% PGU-2-F  7.00% PGU-3-F  7.00% PGU-5-F  7.00% CCGU-3-F  8.00% CGPC-3-3  4.00% CGPC-5-3  4.00% CGPC-5-5  4.00% CP-5-N  13.00% Σ 100.00%

Reference Example 15

[0363] A liquid-crystal base mixture B-15 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00022   CCGU-3-F  8.00% Clearing point: 105.0° C. BCH-5F.F.F  10.00% Δn [589 nm, 20° C.]: 0.160 PGU-5-F  7.00% n.sub.e [589 nm, 20° C.]: 1.663 PGIGI-3-F  10.00% Δε [1 kHz, 20° C.]: 11.4 BCH-2F.F  6.00% ε.sub.∥ [1 kHz, 20° C.]: 15.7 BCH-7F.F.F  10.00% BCH-3F.F  7.00% CBC-53F  3.00% BCH-5F.F  5.00% CBC-55F  3.00% BCH-32  4.00% PCH-5  15.00% PGU-3-F  4.00% CPGU-3-OT  5.00% CBC-33F  3.00% Σ 100.00%

Reference Example 16

[0364] A liquid-crystal base mixture B-16 is prepared and characterized with respect to its general physical properties, having the composition and properties as indicated in the following table.

TABLE-US-00023   PGU-5-F  9.00% Clearing point: 92.0° C. PGIGI-3-F  7.00% Δn [589 nm, 20° C.]: 0.163 BCH-2F.F  6.00% n.sub.e [589 nm, 20° C.]: 1.670 PGU-2-F  9.00% BCH-3F.F  6.00% CBC-53F  3.00% BCH-5F.F  5.00% CBC-55F  3.00% BCH-32  7.00% PCH-7  14.00% PCH-5  15.00% PGU-3-F  9.00% CBC-33  4.00% CBC-33F  3.00% Σ 100.00%

Example 1

[0365] A cholesteric mixture C-1 is prepared by mixing 97.01% of mixture B-1 as described in Reference Example 1 above with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 1.25% of compound of formula RM-A

##STR00360##

0.62% of compound of formula RM-B

##STR00361##

0.62% of compound of formula RM-C

##STR00362##

and 0.08% of the photoinitiator Irgacure® 651 (abbreviated as IRG-651 in the following)

##STR00363##

available from Ciba, Switzerland.

[0366] The obtained pitch of mixture C-1 is 1.84 μm.

[0367] The pitch is confirmed by measuring the wavelength of the selective reflection maximum λ.sub.max at 20° C. using the NIR spectroscopic method described above.

[0368] The mixture C-1 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0369] Subsequently polymerisation is carried out by irradiating the test cell with UV light (UVA and UVB, 3.5 mW/cm.sup.2 light intensity) while a square-wave voltage (70V, 60 Hz) is applied.

[0370] After the polymerisation the haze is determined according to ASTM 1003-92 using a spectrophotometer (Lambda 1050, Perkin Elmer) and a 150 mm Ulbricht's sphere.

[0371] The obtained cell has a clear state which at 63V has 6% haze and 100% clarity. Furthermore, at 0V the cell has a privacy (scattering) state with 100% haze and 13% clarity.

[0372] Clarity herein is determined using haze-gard i from BYK-Gardner.

[0373] No undesirable off-axis colour effects are observed.

Example 2

[0374] A cholesteric mixture C-2 is prepared by mixing 98.28% of mixture B-1 as described in Reference Example 1 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D

##STR00364##

0.63% of compound of formula RM-E

##STR00365##

and 0.04% of IRG-651.

[0375] The obtained pitch of mixture C-2 is 1.84 μm.

[0376] The mixture C-2 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 20 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0377] The filled test cell is further treated and measured as described in Example 1.

[0378] The obtained cell after polymerisation has a clear state which at 50V has 4% haze and 100% clarity. Furthermore, at 0V the cell has a privacy (scattering) state with 100% haze and 18% clarity.

[0379] No undesirable off-axis colour effects are observed.

Comparative Example 1

[0380] A cholesteric mixture CC-1 is prepared by mixing 99.58% of mixture B-1 as described in Reference Example 1 above with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt.

[0381] The mixture CC-1 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 35 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0382] The obtained cell has a clear state which at 63V has 3% haze and 100% clarity. Furthermore, at 3V the cell has a privacy (scattering) state with 79% haze and 25% clarity.

[0383] The cell exhibits an undesirable colour effect resembling a rainbow-like appearance with angular dependence when observed off-axis.

Comparative Example 2

[0384] A cholesteric mixture CC-2 is prepared by mixing 98.70% of mixture B-1 as described in Reference Example 1 above with 0.63% of compound of formula RM-D as shown in Example 2 above, 0.63% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG 651.

[0385] The mixture CC-2 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar alignment), wherein the cell gap is 25 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0386] The filled test cell is further treated and measured as described in Example 1.

[0387] The obtained cell after polymerisation has a privacy (scattering) state which at 70V has 54% haze. However, the cell exhibits no clear state, where at 3V the haze is still 21%.

Example 3

[0388] A cholesteric mixture C-3 is prepared by mixing 98.28% of mixture B-1 as described in Reference Example 1 above with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D as shown in Example 2 above, 0.58% of compound of formula RM-E as shown in Example 2 above, 0.05% of compound of formula RM-F

##STR00366##

and 0.04% of IRG 651.

[0389] The mixture C-3 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar alignment), wherein the cell gap is 25 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0390] The filled test cell is further treated as described in Example 1.

[0391] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0392] No undesirable off-axis colour effects are observed.

Example 4

[0393] A cholesteric mixture C-4 is prepared by mixing 98.64% of mixture B-1 as described in Reference Example 1 above with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.45% of compound of formula RM-D as shown in Example 2 above, 0.45% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG 651.

[0394] The mixture C-4 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar alignment), wherein the cell gap is 20 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0395] The filled test cell is further treated as described in Example 1.

[0396] The obtained cell after polymerisation has a clear state which at 50V has 3% haze and 100% clarity. Furthermore, at 0V the cell has a privacy (scattering) state with 100% haze and 10% clarity.

[0397] No undesirable off-axis colour effects are observed.

Example 5

[0398] A cholesteric mixture C-5 is prepared by mixing 98.58% of mixture B-1 as described in Reference Example 1 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and 1.00% of compound of formula RM-G

##STR00367##

[0399] The mixture C-5 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (vertical alignment), wherein the cell gap is 20 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0400] The filled test cell is further treated and measured as described in Example 1.

[0401] The obtained cell after polymerisation has a clear state which at 50V has 5% haze and 100% clarity. Furthermore, at 0V the cell has a privacy (scattering) state with 100% haze and 15% clarity.

[0402] No undesirable off-axis colour effects are observed.

Example 6

[0403] A cholesteric mixture C-6 is prepared by mixing 98.61% of mixture B-1 as described in Reference Example 1 with 0.64% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and 0.75% of compound of formula RM-G as shown in Example 5 above.

[0404] The mixture C-6 is filled by vacuum filling into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 15 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0405] Subsequently polymerisation is carried out by irradiating the test cell with UV light (UVA and UVB, 3.5 mW/cm.sup.2 light intensity) while a square-wave voltage (50V, 60 Hz) is applied.

[0406] The obtained cell after polymerisation has a clear state which at 50V has 2% haze and 100% clarity. Furthermore, at 0V the cell has a privacy (scattering) state with 100% haze and 35% clarity.

[0407] No undesirable off-axis colour effects are observed.

Example 7

[0408] A cholesteric mixture C-7 is prepared by mixing 98.28% of mixture B-12 as described in Reference Example 12 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D as shown in Example 2 above, 0.63% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG-651.

[0409] The obtained pitch of mixture C-7 is 1.84 μm.

[0410] The mixture C-7 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm.

[0411] Subsequently polymerisation is carried out by irradiating the test cell with UV light (UVACUBE 2000, Hönle, 9 mW/cm.sup.2 light intensity) for 10 minutes while a square-wave voltage (70V, 60 Hz) is applied.

[0412] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 94.4% is obtained. In the clear state a haze value of 2.3% is obtained.

Example 8

[0413] A cholesteric mixture C-8 is prepared by mixing 98.28% of mixture B-4 as described in Reference Example 4 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D as shown in Example 2 above, 0.63% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG-651.

[0414] The obtained pitch of mixture C-8 is 1.84 μm.

[0415] The mixture C-8 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm.

[0416] Subsequently polymerisation is carried out as described in Example 7.

[0417] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 95.7% is obtained. In the clear state a haze value of 2.6% is obtained.

Example 9

[0418] A cholesteric mixture C-9 is prepared by mixing 98.28% of mixture B-14 as described in Reference Example 14 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D as shown in Example 2 above, 0.63% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG-651.

[0419] The obtained pitch of mixture C-9 is 1.84 μm.

[0420] The mixture C-9 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm.

[0421] Subsequently polymerisation is carried out as described in Example 7.

[0422] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 96.7% is obtained. In the clear state a haze value of 3.3% is obtained.

Example 10

[0423] A cholesteric mixture C-10 is prepared by mixing 98.28% of mixture B-13 as described in Reference Example 13 with 0.42% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.63% of compound of formula RM-D as shown in Example 2 above, 0.63% of compound of formula RM-E as shown in Example 2 above and 0.04% of IRG-651.

[0424] The obtained pitch of mixture C-10 is 1.84 μm.

[0425] The mixture C-10 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm.

[0426] Subsequently polymerisation is carried out as described in Example 7.

[0427] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 96.7% is obtained. In the clear state a haze value of 2.5% is obtained.

Comparative Example 3

[0428] A cholesteric mixture CC-3 is prepared by mixing 91.12% of mixture B-1 as described in Reference Example 1 above with 6.49% of chiral dopant CB 15 available from Merck KGaA, Darmstadt, Germany, 2.37% of ethyleneglycol dimethacrylate and 0.02% of IRG-651.

[0429] The mixture CC-3 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 25 μm.

[0430] Subsequently polymerisation is carried out as described in Example 7.

[0431] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 95.1% is obtained. In the clear state a haze value of 4.3% is obtained.

Example 11

[0432] A cholesteric mixture C-11 is prepared by mixing 98.61% of mixture B-4 as described in Reference Example 4 above with 0.64% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, and 0.75% of compound of formula RM-G as shown in Example 5 above.

[0433] No photoinitiator is added. The obtained pitch of mixture C-11 is 1.1 μm.

[0434] The mixture C-11 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 15 μm.

[0435] Subsequently polymerisation is carried out as described in Example 7.

[0436] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 95% is obtained. In the clear state a haze value of 2.1% is obtained.

Example 12

[0437] A cholesteric mixture C-12 is prepared by mixing 98.68% of mixture B-4 as described in Reference Example 4 above with 0.57% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, and 0.75% of compound of formula RM-G as shown in Example 5 above.

[0438] No photoinitiator is added. The obtained pitch of mixture C-12 is 1.24 μm.

[0439] The mixture C-12 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 18 μm.

[0440] Subsequently polymerisation is carried out as described in Example 7.

[0441] After the polymerisation the haze is determined. In the scattering (hazy) state a haze value of 97% is obtained. In the clear state a haze value of 3.5% is obtained.

Example 13

[0442] A cholesteric mixture C-13 is prepared by mixing 98.61% of mixture B-15 as described in Reference Example 15 above with 0.64% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, and 0.75% of compound of formula RM-G as shown in Example 5 above.

[0443] The mixture C-13 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 20 μm.

[0444] Subsequently polymerisation is carried out as described in Example 7.

[0445] After the polymerisation the haze is determined.

[0446] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0447] No undesirable off-axis colour effects are observed.

Example 14

[0448] A cholesteric mixture C-14 is prepared by mixing 98.78% of mixture B-15 as described in Reference Example 15 above with 0.44% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.75% of compound of formula RM-G as shown in Example 5 above, and 0.03% of compound of formula A-1

##STR00368##

[0449] The mixture C-14 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 20 μm.

[0450] Subsequently polymerisation is carried out as described in Example 7.

[0451] After the polymerisation the haze is determined.

[0452] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0453] No undesirable off-axis colour effects are observed.

Example 15

[0454] A cholesteric mixture C-15 is prepared by mixing 98.75% of mixture B-15 as described in Reference Example 15 above with 0.44% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.75% of compound of formula RM-G as shown in Example 5 above, 0.03% of compound of formula A-1 as shown in Example 14 above, and 0.03% of compound of formula A-2

##STR00369##

[0455] The mixture C-15 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 20 μm.

[0456] Subsequently polymerisation is carried out as described in Example 7.

[0457] After the polymerisation the haze is determined.

[0458] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0459] No undesirable off-axis colour effects are observed.

Example 16

[0460] A cholesteric mixture C-16 is prepared by mixing 98.82% of mixture B-16 as described in Reference Example 16 above with 0.40% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.75% of compound of formula RM-G as shown in Example 5 above, and 0.03% of compound of formula A-1 as shown in Example 14 above.

[0461] The mixture C-16 is filled into a test cell having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap is 20 μm.

[0462] Subsequently polymerisation is carried out as described in Example 7.

[0463] After the polymerisation the haze is determined.

[0464] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0465] No undesirable off-axis colour effects are observed.

Example 17

[0466] A cholesteric mixture C-17 is prepared by mixing mixture B-15 as described in Reference Example 15 above with chiral dopant S-1011 available from Merck KGaA, Darmstadt, Germany such that a pitch of 2 μm is obtained, wherein 99.25% of this mixture is further mixed with 0.75% of compound of formula RM-G as shown in Example 5 above to obtain mixture C-17.

[0467] The mixture C-17 is further treated as described in Example 1.

[0468] The cell exhibits favourable clear and scattering states and favourable switching and electro-optical performance.

[0469] No undesirable off-axis colour effects are observed.

Examples 18 to 26

[0470] Cholesteric mixtures C-18, C-19, C-20, C-21, C-22, C-23, C-24, C-25 and C-26 are prepared and further treated according to Example 2, wherein however instead of the chiral dopant R-5011 the chiral dopant S-1011 is used and wherein instead of mixture B-1 respectively the mixtures B-2, B-3, B-5, B-6, B-7, B-8, B-9, B-10 and B-11 as described respectively in Reference Examples 2, 3 and 5 to 11 are used.

[0471] The cells exhibit favourable clear and scattering states and favourable switching and electro-optical performance.

[0472] No undesirable off-axis colour effects are observed.