SWITCHING LAYERS FOR USE IN A SWITCHING ELEMENT

Abstract

The present invention relates to an assembly of switching layers for dimming and scattering of light and to window elements comprising the arrangement of switching layers.

Claims

1. A multilayer arrangement for regulating the passage of light, which comprises a first switching layer which is switchable between an optically clear state and a light scattering state and which contains a material which comprises a liquid-crystalline medium comprising one or more mesogenic compounds and one or more chiral compounds, and a polymeric component, 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, and a switching element comprising a second switching layer, wherein the switching element is switchable between a bright state and a dark state and wherein the second switching layer is a liquid-crystalline layer.

2. The multilayer arrangement according to claim 1, wherein the first switching layer and the second switching layer are each interposed between two transparent substrates each respectively supporting an electrode which is arranged as a transparent conductive layer, wherein optionally alignment layers are further provided which are in direct contact with the switching layers.

3. The multilayer arrangement according to claim 1, wherein the second switching layer comprises one or more dichroic dyes and optionally one or more chiral compounds.

4. The multilayer arrangement according to claim 1, wherein the switching element comprises another switching layer which is a liquid crystalline layer and which contains at least one dichroic dye and optionally one or more chiral compounds.

5. The multilayer arrangement according to claim 1, wherein the switching element further comprises at least one polarization layer and optionally at least one retardation layer.

6. The multilayer arrangement according to claim 1, wherein, relative to the outer face which is facing the light source, the first switching layer is placed in front of the switching element.

7. The multilayer arrangement according to claim 1, wherein the liquid-crystalline medium comprised in the first switching layer has a clearing point of 80° C. or more and exhibits a pitch of 0.55 μm or more in the scattering state, and wherein the polymeric component comprised in the first switching layer contains one or more polymeric structures obtained by or respectively obtainable from polymerization of one or more polymerizable mesogenic compounds.

8. The multilayer arrangement according to claim 1, wherein the liquid-crystalline medium comprised in the first switching layer contains, based on the overall contents of the medium, at least 15% by weight of one or more mesogenic compounds of formula I ##STR00408## 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—, —C≡C—, ##STR00409## in such a manner that oxygen atoms are not linked directly to one another, A.sup.11 denotes ##STR00410## n denotes 0 or 1, and A.sup.21, A.sup.31 and A.sup.41 denote, independently of one another, ##STR00411## wherein L is on each occurrence, identically or differently, halogen selected from F, Cl and Br.

9. The multilayer arrangement according to claim 1, wherein the liquid-crystalline medium comprised in the first switching layer further comprises one or more mesogenic compounds selected from the group of compounds of formulae II and III ##STR00412## 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—, —C≡C—, ##STR00413## 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.

10. The multilayer arrangement according to claim 1, wherein the liquid-crystalline medium comprised in the first switching layer exhibits 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 comprised in the first switching layer have an absolute value of the helical twisting power of 5 μm.sup.−1 or more.

11. An insulating glazing unit comprising a multilayer arrangement according to claim 1.

12. A window element comprising a multilayer arrangement according to claim 1 and which is electrically switchable between a state which is optically clear and bright and a state which is light scattering and dark.

13. The window element according to claim 12, which is switchable into the optically clear and bright state by applying an AC voltage V1 and which is switchable into the light scattering and dark state by applying an AC voltage V2, wherein V1>V2.

14. The window element according to claim 12, which is further operable in and electrically switchable to a state which is optically clear and dark and a state which is light scattering and bright.

15. The window element according to claim 12, which in the state which is light scattering and dark exhibits a transmittance of visible light of less than 40%, and/or for a normally incident collimated light beam from a white light source, a ratio of the averaged intensity of light transmitted into radiation angles from −3° to +3° to the averaged intensity of light transmitted into radiation angles from −60° to +60° of 5 or less.

16. A method of reducing glare from sunlight radiation comprising using a multilayer arrangement according to claim 1, to reduce glare from sunlight radiation.

17. The multilayer arrangement according to claim 1, wherein the first switching layer and the second switching layer are each interposed between two transparent substrates each respectively supporting an electrode which is arranged as a transparent conductive layer, wherein the transparent conductive layers are respectively embedded between two transparent dielectric layers, and wherein optionally alignment layers are further provided which are in direct contact with the switching layers.

18. A method of reducing glare from sunlight radiation comprising using a window element according to claim 12 to reduce glare from sunlight radiation.

Description

EXAMPLES

[0469] In the Examples, [0470] V.sub.o denotes threshold voltage, capacitive [V] at 20° C., [0471] n.sub.e denotes extraordinary refractive index at 20° C. and 589 nm, [0472] n.sub.o denotes ordinary refractive index at 20° C. and 589 nm, [0473] Δn denotes optical anisotropy at 20° C. and 589 nm, [0474] ε∥ denotes dielectric permittivity parallel to the director at 20° C. and 1 kHz, [0475] ε⊥denotes dielectric permittivity perpendicular to the director at 20° C. and 1 kHz, [0476] Δε denotes dielectric anisotropy at 20° C. and 1 kHz, [0477] cl.p., T(N,l) denotes clearing point [° C.], [0478] γ.sub.1 denotes rotational viscosity measured at 20° C. [mPa.Math.s], [0479] determined by the rotation method in a magnetic field, [0480] K.sub.1 denotes elastic constant, “splay” deformation at 20° C. [pN], [0481] K.sub.2 denotes elastic constant, “twist” deformation at 20° C. [pN], [0482] K.sub.3 denotes elastic constant, “bend” deformation at 20° C. [pN],

[0483] The term “threshold voltage” for the present invention relates to the capacitive threshold (V.sub.0), unless explicitly indicated otherwise. In the Examples, as is generally usual, the optical threshold can also be indicated for 10% relative contrast (V.sub.10).

[0484] 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

[0485] 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-CI 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.]: 1.69 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% CCGU-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

[0486] 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 PGIGI-3-F 10.00%  clearing point [° C.]: 105 CPG-2-F 6.00% Δn [589 nm, 20° C.]: 0.160 CPG-3-F 7.00% n.sub.e [589 nm, 20° C.]: 1.66 CPG-5-F 5.00% Δε [1 kHz, 20° C.]: 11.4 CPU-5-F 10.00%  ε.sub.⊥ [1 kHz, 20° C.]: 4.3 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% CBC-33F 3.00% CBC-53F 3.00% CBC-55F 3.00% CPGU-3-OT 5.00% CP-5-N 15.00%  Σ 100.00%   

Reference Example 3

[0487] 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 CPG-3-F 5.00% clearing point [° C.]: 114.5 CPG-5-F 5.00% Δn [589 nm, 20° C.]: 0.135 CPU-3-F 15.00%  n.sub.e [589 nm, 20° C.]: 1.63 CPU-5-F 15.00%  Δε [1 kHz, 20° C.]: 11.3 CP-3-N 16.00%  ε.sub.⊥ [1 kHz, 20° C.]: 4.2 CP-5-N 16.00%  K.sub.1 [pN, 20° C.]: 13.4 CCGU-3-F 7.00% K.sub.3 [pN, 20° C.]: 18.5 CBC-33F 4.00% V.sub.0 [V, 20° C.]: 1.15 CBC-53F 4.00% CBC-55F 4.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CCZPC-3-5 3.00% Σ 100.00%   

[0488] A host mixture H-3 is prepared by mixing 99.97% of mixture B-3 with 0.03% of the compound of formula

##STR00394##

which in the following will be referred to ST-1.

Reference Example 4

[0489] 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 CY-3-O2 9.00% clearing point [° C.]: 110.5 CY-3-O4 9.00% Δn [589 nm, 20° C.]: 0.132 CY-5-O2 12.00%  n.sub.e [589 nm, 20° C.]: 1.62 CY-5-O4 8.00% Δε [1 kHz, 20° C.]: −4.9 CCY-3-O2 5.00% ε.sub.⊥ [1 kHz, 20° C.]: 8.8 CCY-3-O3 5.00% K.sub.1 [pN, 20° C.]: 16.8 CCY-4-O2 5.00% K.sub.3 [pN, 20° C.]: 20.4 CPY-2-O2 7.00% V.sub.0 [V, 20° C.]: 2.14 CPY-3-O2 6.00% PYP-2-3 12.00%  CCP-V-1 6.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CBC-33F 5.00% CBC-53F 5.00% Σ 100.00%   

[0490] A host mixture H-4 is prepared by mixing 99.97% of mixture B-4 with 0.03% of the compound ST-1 as shown in Reference Example 3 above.

Reference Example 5

[0491] 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 CPG-3-F 8.00% clearing point [° C.]: 114 CPG-5-F 8.00% Δn [589 nm, 20° C.]: 0.130 CPU-5-F 14.00%  n.sub.e [589 nm, 20° C.]: 1.62 CPU-7-F 11.00%  Δε [1 kHz, 20° C.]: 10.0 CP-5-N 18.00%  ε.sub.⊥ [1 kHz, 20° C.]: 4.0 CP-7-N 13.00%  CCGU-3-F 7.00% CC-3-O3 2.00% CBC-33F 4.00% CBC-53F 4.00% CBC-55F 3.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CCZPC-3-5 2.00% Σ 100.00%   

Reference Example 6

[0492] 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 CC(CN)-4-7 14.00%  clearing point [° C.]: 114.6 CC(CN)-5-5 14.00%  Δn [589 nm, 20° C.]: 0.045 CC(CN)-3-3 6.00% n.sub.e [589 nm, 20° C.]: 1.52 CCZC-3-3 3.00% Δε [1 kHz, 20° C.]: −5.2 CCZC-3-5 3.00% ε.sub.⊥ [1 kHz, 20° C.]: 8.5 CCZC-4-3 3.00% CCZC-4-5 3.00% CC-3-O1 11.00%  CC-5-O1 4.00% CC-5-O2 4.00% CC(CN)C-3-5 10.00%  CC(CN)C-5-5 12.00%  CC(CN)C-5-3 10.00%  CCZPC-3-3 3.00% Σ 100.00%   

Reference Example 7

[0493] 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 CPG-3-F 8.00% CPG-5-F 8.00% CPU-5-F 14.00%  CPU-7-F 11.00%  CP-3-N 18.00%  CP-7-N 13.00%  CCGU-3-F 7.00% CC-3-O3 2.00% CBC-33F 4.00% CBC-53F 4.00% CBC-55F 3.00% CCZPC-3-3 3.00% CCZPC-3-4 3.00% CCZPC-3-5 2.00% Σ 100.00%   

Reference Example 8

[0494] 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-5-N 15.00%  clearing point [° C.]: 92 CP-7-N 14.00%  Δn [589 nm, 20° C.]: 0.163 CPG-2-F 6.00% n.sub.e [589 nm, 20° C.]: 1.67 CPG-3-F 6.00% CPG-5-F 5.00% PGU-2-F 9.00% PGU-3-F 9.00% PGU-5-F 9.00% CPP-3-2 7.00% CBC-33F 3.00% CBC-53F 3.00% CBC-55F 3.00% CBC-33 4.00% PGIGI-3-F 7.00% Σ 100.00%   

Comparative Example 1

[0495] A mixture M-1 is prepared by mixing 98.877% of mixture B-1 as described in Reference Example 1 with 0.470% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.129% of compound of formula DD-1

##STR00395##

[0496] 0.244% of compound of formula DD-2

##STR00396##

[0497] and 0.280% of compound of formula DD-3

##STR00397##

[0498] The mixture M-1 is filled by vacuum filling into a 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.

[0499] The obtained cell has a clear state which at 48 V has 3% haze and 64.5% transmission. Furthermore, at 5 V the cell has a dark privacy state with 83% haze and 22% transmission.

[0500] Unwanted off-axis colour effects are observed when viewed from the side. A bidirectional transmittance distribution function (BTDF) measurement is performed with an EZLite 120R instrument from Eldim using a white light source and normal incidence of the light.

[0501] The ratio of the averaged intensity of light transmitted into radiation angles from −3° to +3° to the averaged intensity of light transmitted into radiation angles from −60° to +60°, <I.sub.−3°<θ<3°>/<I.sub.−60°<θ<60°>, is 15.7.

[0502] Although the cell effectively dims the overall light intensity, the light is not sufficiently diffused. The cell does not sufficiently reduce the contrast of a bright light source and thus does not reliably prevent glare from e.g. sunlight.

Comparative Example 2

[0503] A mixture M-2 is prepared by mixing 98.72% of mixture H-3 as described in Reference Example 3 with 0.05% of chiral dopant S-811 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.24% of compound of formula DD-1 as shown in Comparative Example 1 above, 0.46% of compound of formula DD-2 as shown in Comparative Example 1 above and 0.53% of compound of formula DD-3 as shown in Comparative Example 1 above.

[0504] The mixture M-2 is filled by vacuum filling into a 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.

[0505] The obtained cell has a clear state which at 12 V has 49% transmission. Furthermore, at 0 V the cell has a dark state with 25% transmission.

[0506] A bidirectional transmittance distribution function (BTDF) measurement is performed with an EZLite 120R instrument from Eldim using a white light source and normal incidence of the light.

[0507] The ratio of the averaged intensity of light transmitted into radiation angles from −3° to +3° to the averaged intensity of light transmitted into radiation angles from −60° to +60°, <I.sub.−3°<θ<3°>/<I.sub.−60°<θ<60°>, is 18.7.

[0508] Although the cell effectively dims the overall light intensity, the light is not sufficiently diffused. The cell does not sufficiently reduce the contrast of a bright light source and thus does not reliably prevent glare from e.g. sunlight.

Comparative Example 3

[0509] A cholesteric mixture C-1 is prepared by mixing 98.61% of mixture B-2 as described in Reference Example 2 with 0.64% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above and 0.75% of compound of formula RM-A

##STR00398##

[0510] The mixture C-1 is filled by vacuum filling into a 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.

[0511] Subsequently polymerisation is carried out by irradiating the 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 for 30 minutes.

[0512] The obtained cell after polymerisation has a clear state which at 60 V has 6.6% haze and 88% transmission. Furthermore, at 0 V the cell has a privacy (scattering) state with 99% haze and 72% transmission.

[0513] The transmission in the privacy state is still too high to reliably eliminate glare from sunlight experienced by a user.

Example 1

[0514] A stack of cells is arranged combining a cell prepared according to Comparative Example 3 together with a cell prepared according to Comparative Example 1.

[0515] This assembly of the combined cells has a transparent state which at 63 V has 7.7% haze and 57% transmission. Furthermore, at 5 V the assembly of the cells has an anti-glare state with 100% haze and 12% transmission. Besides, in a privacy state, where the scattering cell according to Comparative Example 3 is operated at 5 V and the dye-doped cell according to Comparative Example 1 is operated at 63 V, the assembly has 99% haze and 46% transmission.

[0516] A bidirectional transmittance distribution function (BTDF) measurement is performed for the combined cells in the anti-glare state with an EZLite 120R instrument from Eldim using a white light source and normal incidence of the light.

[0517] In the anti-glare state the ratio of the averaged intensity of light transmitted into radiation angles from −3° to +3° to the averaged intensity of light transmitted into radiation angles from −60° to +60°, <I.sub.−3°<θ<3°>/<I.sub.−60°<θ<60°>, is 3.0.

[0518] The combination of cells effectively reduces the overall transmission of light, while furthermore distributing the transmitted light also into wider angles more evenly. The combination of the cells gives excellent anti-glare performance, in particular for sunlight.

[0519] In addition, no undesirable off-axis colour effects are observed.

Example 2

[0520] A cholesteric mixture C-2 is prepared by mixing 98.640% of mixture B-1 as described in Reference Example 1 with 0.423% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany, 0.450% of compound of formula RM-B

##STR00399##

[0521] 0.450% of compound of formula RM-C

##STR00400##

[0522] and 0.037% of the photoinitiator Irgacure® 651, abbreviated as IRG-651 in the following,

##STR00401##

available from Ciba, Switzerland.

[0523] The mixture C-2 is filled by vacuum filling into a 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.

[0524] Subsequently polymerisation is carried out by irradiating the 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.

[0525] The obtained cell is arranged in a stack together with a cell prepared according to Comparative Example 2.

[0526] This assembly of the combined cells has a transparent state which at 48 V has 17.6% haze and 46.3% transmission. Furthermore, at 0 V the assembly of the cells has an anti-glare state with 100% haze and 18% transmission. Besides, in a privacy state, where the scattering cell as prepared herein is operated at 0 V and the dye-doped cell according to Comparative Example 2 is operated at 12 V, the assembly has 100% haze and 26% transmission, and in a solar intensity control state, where the scattering cell as prepared herein is operated at 48 V and the dye-doped cell according to Comparative Example 2 is operated at 0 V, the assembly has 24% haze and 22% transmission. Also, grey scale switching is possible by varying the voltage for the dye-doped cell.

[0527] A bidirectional transmittance distribution function (BTDF) measurement is performed for the combined cells in the anti-glare state with an EZLite 120R instrument from Eldim using a white light source and normal incidence of the light.

[0528] In the anti-glare state the ratio of the averaged intensity of light transmitted into radiation angles from −3° to +3° to the averaged intensity of light transmitted into radiation angles from −60° to +60°, <I.sub.−3°<θ<3°>/<I.sub.−60°<θ<60°>, is 1.6.

[0529] The combination of cells effectively reduces the overall transmission of light, while furthermore distributing the transmitted light also into wider angles more evenly. The combination of the cells gives excellent anti-glare performance, in particular for sunlight.

[0530] In addition, no undesirable off-axis colour effects are observed.

Example 3

[0531] A cholesteric mixture C-3 is prepared by mixing 98.764% of mixture B-2 as described in Reference Example 2 with 0.486% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above and 0.750% of compound of formula RM-A as shown in Comparative Example 3.

[0532] The mixture C-3 is filled by vacuum filling into a 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.

[0533] Subsequently polymerisation is carried out by irradiating the 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.

[0534] A mixture M-3 is prepared by mixing 99.559% of mixture H-3 as described in Reference Example 3 with 0.050% of chiral dopant S-811 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.077% of compound of formula DD-1 as shown in Comparative Example 1 above, 0.146% of compound of formula DD-2 as shown in Comparative Example 1 above and 0.168% of compound of formula DD-3 as shown in Comparative Example 1 above.

[0535] The mixture M-3 is respectively filled by vacuum filling into two test cells each having glass substrates with ITO electrodes as well as polyimide alignment layers (AL-1054 from Japan Synthetic Rubber, planar, TN), wherein the cell gap for each cell is 25 μm, and the filling ports are sealed. The two dye-doped cells are arranged into a double cell, wherein the first dye-doped cell is oriented to have its main axis of absorption normal to the main axis of absorption of the second dye-doped cell. Electrical wiring is applied to the cells by soldering.

[0536] A stack of cells is arranged by combining the polymer-stabilized cholesteric scattering cell with the dye-doped double cell arrangement. This assembly of the combined cells has a transparent state, where the scattering cell is operated at 48 V and the two dye-doped cells are operated at 12 V, with 9.5% haze and 46% transmission. Furthermore, at 0 V the assembly of the cells has an anti-glare state with 99% haze and 8.5% transmission. Besides, in a privacy state, where the scattering cell is operated at 0 V and the dye-doped cells are operated at 12 V, the assembly has 99% haze and 38.5% transmission, and in a solar intensity control state, where the scattering cell is operated at 48 V and the dye-doped cells are operated at 0 V, the assembly has 11% haze and 10% transmission.

[0537] The combination of the cells gives excellent anti-glare performance, in particular for sunlight. In addition, no undesirable off-axis colour effects are observed.

Example 4

[0538] The mixture M-3 as shown in Example 3 above is filled into an electrically switchable cell having the Heilmeier configuration, using an ITOS XP-40HT polariser, antiparallel polyimide planar alignment layers and a switching layer thickness of 12 μm.

[0539] A cholesteric mixture C-4 is prepared by mixing 98.89% of mixture B-2 as described in Reference Example 2 with 0.33% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.75% of compound of formula RM-A as shown in Comparative Example 3 and 0.03% of compound of formula ST-1 as shown in Reference Example 3.

[0540] The mixture C-4 is filled by vacuum filling into a cell having glass substrates with ITO electrodes and no alignment layers, wherein the cell gap is 25 μm, and the filling ports are sealed. Electrical wiring is applied to the cell by soldering.

[0541] Subsequently polymerisation is carried out by irradiating the 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.

[0542] A stack is arranged by combining both cells. The combination gives excellent anti-glare performance, in particular for sunlight. In addition, no undesirable off-axis colour effects are observed.

Example 5

[0543] The procedure as described in Example 4 is repeated, wherein however instead of the mixture C-4 a mixture C-5 is prepared and used which has the following composition:

[0544] 98.78% of mixture B-2 as described in Reference Example 2, 0.44% of chiral dopant R-5011 available from Merck KGaA, Darmstadt, Germany and shown in Table F above, 0.75% of compound of formula RM-A as shown in Comparative Example 3 and 0.03% of compound of formula ST-1 as shown in Reference Example 3.

Example 6

[0545] The procedure as described in Example 4 is repeated, wherein however instead of the mixture M-3 a mixture M-6 is prepared and used which has the following composition:

[0546] 97.77% of mixture H-3 as described in Reference Example 3, 0.34% of compound of formula DD-1 as shown in Comparative Example 1 above, 0.72% of compound of formula DD-2 as shown in Comparative Example 1 above, 0.87% of compound of formula DD-3 as shown in Comparative Example 1 above, 0.15% of compound of formula ST-1 as shown in Reference Example 3 and 0.15% of compound of formula ST-2

##STR00402##

Example 7

[0547] The procedure as described in Example 4 is repeated, wherein however instead of the mixture M-3 a mixture M-7 is prepared and used which has the following composition:

[0548] 95.55% of mixture H-3 as described in Reference Example 3, 1.20% of compound of formula DD-4

##STR00403##

[0549] 0.35% of compound of formula DD-5

##STR00404##

[0550] 0.50% of compound of formula DD-6

##STR00405##

[0551] 1.20% of compound of formula DD-7

##STR00406##

[0552] and 1.20% of compound of formula DD-8

##STR00407##

Example 8

[0553] A mixture M-8 is prepared by mixing 99.95% of mixture H-4 as described in Reference Example 4 with 0.05% of chiral dopant S-811 available from Merck KGaA, Darmstadt, Germany and shown in Table F above.

[0554] Two VA cells, VA-1 and VA-2, are prepared using glass substrates with ITO electrodes and rubbed polyimide homeotropic alignment layers with a pretilt of 3°, wherein the cell gap is 25 μm, applying a thin film polarizer on the first substrate of each cell and a thin film polarizer with retarder, for optical compensation for improving viewing angle dependence, on the other substrate of each cell, both from Polatechno. For VA-1 the two polarizers are arranged at 0° with respect to each other, and for VA-2 the two polarizers are arranged at 90° with respect to each other.

[0555] The mixture M-8 is respectively filled into the cells VA-1 and VA-2.

[0556] A scattering cell, SC, is prepared using mixture the C-3 and the conditions as described in Example 3 above.

[0557] Two stacks are arranged combining VA-1 and SC and respectively VA-2 and SC. Using the following operating voltages, different useful optical modes of the stacks are obtainable as follows

[0558] Stack 1

TABLE-US-00016 VA-1 SC mode  0 V 48 V transparent bright  0 V  0 V scattering bright 12 V 48 V transparent dark 12 V  0 V anti-glare (scattering dark)

[0559] Stack 2

TABLE-US-00017 VA-2 SC mode 12 V 48 V transparent bright 12 V  0 V scattering bright  0 V 48 V transparent dark  0 V  0 V anti-glare (scattering dark)

Examples 9 to 11

[0560] The procedure as described in Example 3 is repeated, wherein however instead of using the dye-doped mixture M-3 respectively mixtures M-9, M-10 and M-11 are prepared and used, where M-9, M-10 and M-11 have the following compositions.

TABLE-US-00018 M-9 M-10 M-11 base mixture B-5 99.552%  99.746%  99.620%  (Ref. Example 5) DD-1 0.071% 0.037% — DD-2 0.132% 0.062% — DD-3 0.165% 0.075% 0.300% S-811 0.050% 0.050% 0.050% ST-1 0.030% 0.030% 0.030%

Example 12

[0561] The procedure as described in Example 1 is repeated, wherein however instead of the mixture B-1 the base mixture B-6 as shown in Reference Example 6 is used to prepare a mixture M-12 and a dye-doped cell based on this mixture M-12.

Examples 13 and 14

[0562] The procedure as described in Example 1 is repeated, wherein a cell is prepared according to Comparative Example 2, however instead of using mixture H-3 respectively base mixture B-7 as described in Reference Example 7 and base mixture B-8 as described in Reference Example 8 are used to prepare the respective mixtures M-13 and M-14.