LIQUID CRYSTAL MEDIUM

Abstract

The present invention relates to a liquid crystal (LC) medium comprising a compound of formula I

##STR00001## and one or more compounds selected from the group of compounds of the formulae IIA, IIB, IIC and IID,

##STR00002## as defined in claim 1, and to the use thereof for optical, electro-optical and electronic purposes, in particular in LC displays, especially in IPS, FFS, VA or PS-VA displays.

Claims

1. A liquid crystal medium comprising one or more compounds of formula I ##STR00541## in which R.sup.1 denotes H, a straight chain or branched alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by ##STR00542##  C≡C—, —CF.sub.2O—, —OCF.sub.2—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, ##STR00543##  denotes ##STR00544## Y.sup.1 denotes H or CH.sub.3, n is 0 or 1, v is 1, 2, 3, 4, 5, or 6; and one or more compounds selected from the group of compounds of the formulae IIA, IIB, IIC and IID, ##STR00545## in which R.sup.2A, R.sup.2B, R.sup.2C and R.sup.2D each, independently of one another, denote H, an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF.sub.3 or at least monosubstituted by halogen, where, in addition, one or more CH.sub.2 groups in these radicals may be replaced by —O—, —S—, ##STR00546##  —C≡C—, —CF.sub.2O—, —OCF.sub.2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another, L.sup.1 to L.sup.4 each, independently of one another, denote F, Cl, CF.sub.3 or CHF.sub.2, Y denotes H, F, Cl, CF.sub.3, CHF.sub.2 or CH.sub.3, Z.sup.2, Z.sup.2B and Z.sup.2D each, independently of one another, denote a single bond, —CH.sub.2CH.sub.2—, —CH═CH—, —CF.sub.2O—, —OCF.sub.2—, —CH.sub.2O—, —OCH.sub.2—, —COO—, —OCO—, —C.sub.2F.sub.4—, —CF═CF— or —CH═CHCH.sub.2O—, p denotes 0, 1 or 2, q denotes 0 or 1, and v denotes an integer from 1 to 6, wherein the compounds of formula I are excluded from formula IID.

2. The medium according to claim 1, wherein in formula I ##STR00547##  denotes ##STR00548##  and n is 1.

3. The medium according to claim 1, wherein the medium comprises one or more compounds of formula III ##STR00549## in which R.sup.11 and R.sup.12 each, independently of one another, denote H, an alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by ##STR00550##  —C≡C—, —CF.sub.2O—, —OCF.sub.2—, —CH═CH—, by —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, A.sup.1 on each occurrence, independently of one another, denotes a) 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH.sub.2 groups may be replaced by —O— or —S—, b) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, or c) a radical from the group spiro[3.3]heptane-2,6-diyl, 1,4-bicyclo-[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl, where the radicals a), b) and c) may be mono- or polysubstituted by halogen atoms, n is 0, 1 or 2, Z.sup.1 on each occurrence independently of one another denotes —CO—O—, —O—CO—, —CF.sub.2O—, —OCF.sub.2—, —CH.sub.2O—, —OCH.sub.2—, —CH.sub.2—, —CH.sub.2CH.sub.2—, —(CH.sub.2).sub.4—, —CH═CH—CH.sub.2O—, —C.sub.2F.sub.4—, —CH.sub.2CF.sub.2—, —CF.sub.2CH.sub.2—, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—, —C≡C— or a single bond, and L.sup.11 and L.sup.12 each, independently of one another, denote F, Cl, CF.sub.3 or CHF.sub.2, and W denotes O or S.

4. The medium according to claim 3, wherein W in formula III denotes S.

5. The medium according to claim 1, wherein the medium comprises one or more compounds of formula III-3 ##STR00551## in which R.sup.11, R.sup.12 identically or differently, denote H, an alkyl or alkoxy radical having 1 to 15 C atoms, in which one or more CH.sub.2 groups in these radicals are optionally replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —OCF.sub.2—, —CH═CH—, ##STR00552##  —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen.

6. The medium according to claim 1, wherein the medium has an average elastic constant K.sub.avg of greater than 15 pN at 20° C., where K.sub.avg is defined as: $K_{\mathrm{avg}}=\frac{1}{3}\left(1.5.Math.K_1+K_3\right)$ in which K.sub.1 and K.sub.3 are the splay and bend elastic constants, respectively.

7. The medium according to claim 1, wherein the medium comprises one or more compounds of formula ##STR00553## in which R.sup.41 denotes alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms, and R.sup.42 denotes alkyl having 1 to 7 C atoms or alkoxy having 1 to 6 C atoms or alkenyl having 2 to 7 C atoms.

8. The medium according to claim 1, wherein the medium comprises one or more compounds selected from the group of compounds of the following formulae: ##STR00554##

9. The medium according to claim 1, wherein the medium comprises one or more compounds of formula V ##STR00555## in which R.sup.51, R.sup.52, identically or differently, denote alkyl having 1 to 7 C atoms, alkoxy having 1 to 7 C atoms, or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, ##STR00556##  identically or differently, denote ##STR00557## Z.sup.51, Z.sup.52 each, independently of one another, denote —CH.sub.2—CH.sub.2—, —CH.sub.2—O—, —CH═CH—, —C≡C—, —COO— or a single bond, and n is 1 or 2.

10. The medium according to claim 1, wherein the medium comprises a chiral dopant.

11. The medium according to claim 1, wherein the medium comprises one or more polymerisable compounds of formula P
P-Sp-A.sup.1-(Z.sup.1-A.sup.2).sub.z-R  P in which P denotes a polymerisable group, Sp denotes a spacer group or a single bond, A.sup.1, A.sup.2 identically or differently, denote an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L, L denotes F, Cl, —CN, P-Sp- or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH.sub.2-groups are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl, Z.sup.1 denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —OCH.sub.2—, —CH.sub.2O—, —SCH.sub.2—, —CH.sub.2S—, —CF.sub.2O—, —OCF.sub.2—, —CF.sub.2S—, —SCF.sub.2—, —(CH.sub.2).sub.n1—, —CF.sub.2CH.sub.2—, —CH.sub.2CF.sub.2—, —(CF.sub.2).sub.n1—, —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH—, —CH.sub.2—CH.sub.2—CO—O—, —O—CO—CH.sub.2—CH.sub.2—, —CR.sup.0R.sup.00—, or a single bond, R.sup.0, R.sup.00 identically or differently, denote H or alkyl having 1 to 12 C atoms, R denotes H, L, or P-Sp-, z is 0, 1, 2 or 3, n1 is 1, 2, 3 or 4.

12. The medium according to claim 11, wherein the polymerisable compounds of formula P are polymerised.

13. A process of preparing an LC medium according to claim 1, comprising mixing one or more compounds of formula I with one or more compounds selected from the group consisting of formula IIA, IIB, IIC and ID of claim 1 and optionally with one or more mesogenic or liquid-crystalline compounds and/or with a polymerisable compound of formula P
P-Sp-A.sup.1-(Z.sup.1-A.sup.2).sub.z-R  P in which P denotes a polymerisable group, Sp denotes a spacer group or a single bond, A.sup.1, A.sup.2 identically or differently, denote an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L, L denotes F, Cl, —CN, P-Sp- or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH.sub.2-groups are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl, Z.sup.1 denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —OCH.sub.2—, —CH.sub.2O—, —SCH.sub.2—, —CH.sub.2S—, —CF.sub.2O—, —OCF.sub.2—, —CF.sub.2S—, —SCF.sub.2—, —(CH.sub.2).sup.n1—, —CF.sub.2CH.sub.2—, —CH.sub.2CF.sub.2—, —(CF.sub.2).sub.n1—, —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH—, —CH.sub.2—CH.sub.2—CO—O—, —O—CO—CH.sub.2—CH.sub.2—, —CR.sup.0R.sup.00—, or a single bond, R.sup.0, R.sup.00 identically or differently, denote H or alkyl having 1 to 12 C atoms, R denotes H, L, or P-Sp-, z is 0, 1, 2 or 3, n1 is 1, 2, 3 or 4, and/or with one or more additives.

14. An LC display comprising the medium according to claim 1.

15. The display according to claim 14, wherein the display is a PSA display.

16. The display according to claim 15, wherein the display is a PS-VA, PS-IPS, PS-FFS, PS-UB-FFS, polymer stabilised SA-VA or polymer stabilised SA-FFS display.

17. The display according to claim 14, wherein the display is a VA, IPS, U-IPS, FFS, UB-FFS, SA-FFS or SA-VA display.

18. in the display according to claim 14, which is an electro-optical displays.

Description

WORKING EXAMPLES

[0529] The following examples are intended to explain the invention without limiting it. In the examples, m.p. denotes the melting point and C denotes the clearing point of a liquid-crystalline substance in degrees Celsius; boiling temperatures are denoted by m.p. Furthermore: C denotes crystalline solid state, S denotes smectic phase (the index denotes the phase type), N denotes nematic state, Ch denotes cholesteric phase, I denotes isotropic phase, T.sub.g denotes glass-transition temperature. The number between two symbols indicates the conversion temperature in degrees Celsius.

[0530] The host mixture used for determination of the optical anisotropy Δn of single compounds is the commercial mixture ZLI-4792 (Merck KGaA). The dielectric anisotropy Δε is determined using commercial mixture ZLI-2857. The physical data of the compound to be investigated are obtained from the change in the dielectric constants of the host mixture after addition of the compound to be investigated and extrapolation to 100% of the compound employed. In general, 10% of the compound to be investigated are dissolved in the host mixture, depending on the solubility.

[0531] Unless indicated otherwise, parts or percent data denote parts by weight or percent by weight.

[0532] Above and below: [0533] V.sub.o denotes threshold voltage, capacitive [V] at 20° C., [0534] n.sub.e denotes extraordinary refractive index at 20° C. and 589 nm, [0535] n.sub.o denotes ordinary refractive index at 20° C. and 589 nm, [0536] Δn denotes optical anisotropy at 20° C. and 589 nm, [0537] ε.sub.⊥ denotes dielectric permittivity perpendicular to the director at 20° C. and 1 kHz, [0538] ε∥ denotes dielectric permittivity parallel to the director at 20° C. and 1 kHz, [0539] Δε denotes dielectric anisotropy at 20° C. and 1 kHz, [0540] cl.p., T(N,I) denotes clearing point [° C.], [0541] γ.sub.1 denotes rotational viscosity measured at 20° C. [mPa.Math.s], [0542] K.sub.1 denotes elastic constant, “splay” deformation at 20° C. [pN], [0543] K.sub.2 denotes elastic constant, “twist” deformation at 20° C. [pN], [0544] K.sub.3 denotes elastic constant, “bend” deformation at 20° C. [pN], [0545] K.sub.avg. denotes the average elastic constant defined as

[00001]$K_{\mathrm{avg}.=}\frac{1}{3}\left(1.5K_1+K_3\right)$  at 20° C. [pN], and [0546] LTS denotes low-temperature stability (nematic phase), determined in test cells or in the bulk, as specified.

[0547] Unless explicitly noted otherwise, all values indicated in the present application for temperatures, such as, for example, the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I) or cl.p., are indicated in degrees Celsius (° C.). M.p. denotes melting point. Furthermore, Tg=glass state, C=crystalline state, N=nematic phase, S=smectic phase and I=isotropic phase. The numbers between these symbols represent the transition temperatures.

[0548] The term “threshold voltage” for the present invention relates to the capacitive threshold (V.sub.0), also called the Freedericksz threshold, 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).

[0549] The display used for measurement of the capacitive threshold voltage consists of two plane-parallel glass outer plates at a separation of 20 μm, which each have on the insides an electrode layer and an unrubbed polyimide alignment layer on top, which cause a homeotropic edge alignment of the liquid-crystal molecules.

[0550] The display or test cell used for measurement of the tilt angle consists of two plane-parallel glass outer plates at a separation of 4 μm, which each have on the insides an electrode layer and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to one another and cause a homeotropic edge alignment of the liquid-crystal molecules.

[0551] Unless indicated otherwise, the VHR is determined at 20° C. (VHR.sub.20) and after 5 minutes in an oven at 100° C. (VHR.sub.100) in a commercially available instrument Model LCM-1 (00004) from TOYO Corporation, Japan. The voltage used has a frequency of in a range from 1 Hz to 60 Hz, unless indicated more precisely.

[0552] The stability to UV irradiation is investigated in a “Suntest CPS+”, a commercial instrument from Heraeus, Germany, using a Xenon lamp NXE1500B. The sealed test cells are irradiated for 2.0 h, unless explicitly indicated, without additional heating. The irradiation power in the wavelength range from 300 nm to 800 nm is 765 W/m.sup.2 V. A UV “cut-off” filter having an edge wavelength of 310 nm is used in order to simulate the so-called window glass mode. In each series of experiments, at least four test cells are investigated for each condition, and the respective results are indicated as averages of the corresponding individual measurements.

[0553] The decrease in the voltage holding ratio (AVHR) usually caused by the exposure, for example by UV irradiation or by LCD backlighting, is determined in accordance with the following equation (1):

ΔVHR(t)=VHR(t)−VHR(t=0)  (1).

[0554] In order to investigate the low-temperature stability, also known as “LTS”, i.e. the stability of the LC mixture in the bulk against spontaneous crystallisation of individual components at low temperatures or the occurrence of smectic phases, as the case may be, several sealed bottles, each containing about 1 g of the material, are stored at one or more given temperatures, typically of −10° C., −20° C., −30° C. and/or −40° C. and it is inspected at regular intervals visually, whether a phase transition is observed or not. As soon as the first one of the samples at a given temperature shows a change time is noted. The time until the last inspection, at which no change has been observed, is noted as the respective LTS.

[0555] The ion density from which the resistivity is calculated is measured using the commercially available LC Material Characteristics Measurement System Model 6254 from Toyo Corporation, Japan, using VHR test cells with AL16301 Polyimide (JSR Corp., Japan) having a 3.2 μm cell gap. The measurement is performed after 5 min of storage in an oven at 60° C. or 100° C.

[0556] The so-called “HTP” denotes the helical twisting power of an optically active or chiral substance in an LC medium (in μm). Unless indicated otherwise, the HTP is measured in the commercially available nematic LC host mixture MLD-6260 (Merck KGaA) at a temperature of 20° C.

[0557] The Clearing point is measured using the Mettler Thermosystem FP900. The optical anisotropy (Δn) is measured using an Abbe Refractometer H005 (Natrium-spectral lamp Na10 at 589 nm, 20° C.). The dielectric anisotropy (Δε) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1). The turn on voltage (V.sub.0) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1). The rotational viscosity (γ.sub.1) is measured using a TOYO LCM-2 (0002) at 20° C. (gamma 1 negative cells with JALS-2096-R 1). The elastic constant (K.sub.1, splay) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε parallel-cells with JALS 2096-R1). K.sub.3: The elastic constant (K.sub.3, bend) is measured using an LCR-Meter E4980A/Agilent (G005) at 20° C. (ε-parallel-cells with JALS 2096-R1). The measurement of the elastic constants is known to the skilled person and described on page 147 of the article M. J. Bradshaw and E. P. Raynes, Mol. Cryst. Liq. Cryst., 1983, Vol. 91, pages 145-155.

[0558] Unless explicitly noted otherwise, all concentrations in the present application are indicated in percent by weight and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents. All physical properties are determined in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status November 1997, Merck KGaA, Germany, and apply for a temperature of 20° C., unless explicitly indicated otherwise.

[0559] The following mixture examples having negative dielectric anisotropy are suitable, in particular, for liquid-crystal displays which have at least one planar alignment layer, such as, for example, IPS and FFS displays, in particular UB-FFS (=ultra-bright FFS), and for VA displays.

MIXTURE EXAMPLES AND COMPARATIVE EXAMPLES

[0560] Comparative mixture C-1 and mixture examples N-1 to N-64 have the compositions and properties given in the following tables.

Comparative Mixture C1

[0561]

TABLE-US-00008 B(S)-2O-O5 3.0% T(N, I) [° C.]: 98.5 CC-3-V 29.5% Δn [589 nm, 20° C.]: 0.0926 CC-3-V1 8.0% n.sub.e [589 nm, 20° C.]: 1.5731 CC-3-5 5.5% n.sub.o [589 nm, 20° C.]: 1.4805 CCY-3-O1 6.0% Δε [1 kHz, 20° C.]: −3.9 CCY-3-O2 8.0% ε.sub.∥ [1 kHz, 20° C.]: 3.4 CLY-3-O2 9.0% ε.sub.⊥ [1 kHz, 20° C.]: 7.3 CLY-3-O3 6.0% γ.sub.1 [mPa s, 20° C.]: 133 CLY-4-O2 5.0% K.sub.1 [pN, 20° C.]: 18.4 CLY-5-O2 5.0% K.sub.3 [PN, 20° C.]: 19.3 COB(S)-2-O4 5.0% LTS bulk [h, −20° C.]: 432 CY-3-O2 10.0% Σ 100.0%

Mixture Example N-1

[0562]

TABLE-US-00009 B(S)-2O-O4 2.0% T(N, I) [° C.]: 99.2 B(S)-2O-O5 2.5% Δn [589 nm, 20° C.]: 0.0926 CC-3-V 47.5% n.sub.e [589 nm, 20° C.]: 1.5748 CC-3-V1 2.5% n.sub.o [589 nm, 20° C.]: 1.4822 CCOY-2-O2 5.0% Δε [1 kHz, 20° C.]: −3.9 CCOY-3-O2 5.0% ε.sub.∥ [1 kHz, 20° C.]: 3.3 CCY-3-O2 11.0% ε.sub.⊥ [1 kHz, 20° C.]: 7.2 CLY-3-O2 9.0% γ.sub.1 [mPa s, 20° C.]: 118 CLY-5-O2 5.0% K.sub.1 [pN, 20° C.]: 18.2 COB(S)-2-O4 10.0% K.sub.3 [PN, 20° C.]: 19.0 CPY-3-O2 0.5% LTS bulk [h, −20° C.]: 240 Σ 100.0%

Mixture Example N-2

[0563]

TABLE-US-00010 B(S)-2O-O4 4.0% T(N, I) [° C.]: 96.4 B(S)-2O-O5 5.0% Δn [589 nm, 20° C.]: 0.0932 CC-3-V 43.5% n.sub.e [589 nm, 20° C.]: 1.5742 CC-3-V1 8.0% n.sub.o [589 nm, 20° C.]: 1.4810 CCOY-2-O2 5.0% Δε [1 kHz, 20° C.]: −3.8 CCOY-3-O2 5.0% ε.sub.∥ [1 kHz, 20° C.]: 3.3 CCY-3-O2 10.5% ε.sub.⊥ [1 kHz, 20° C.]: 7.1 CLY-3-O2 9.0% γ.sub.1 [mPa s, 20° C.]: 111 CLY-5-O2 5.0% K.sub.1 [pN, 20° C.]: 18.3 COB(S)-2-O4 5.0% K.sub.3 [PN, 20° C.]: 19.3 Σ 100.0% LTS bulk [h, −20° C.]: 240

TABLE-US-00011 TABLE 1 Mixture γ.sub.1/K.sub.1 K.sub.avg C-1 7.2 15.6 N-1 6.5 15.4 N-2 6.1 15.6

[0564] Comparative example C-1 is very similar to mixtures N-1 and N-2 in terms of composition, clearing temperature, dielectric anisotropy and birefringence but does not contain a compound of formula I. The comparison of mixture examples N-1 and N-2 with C-1 unexpectedly shows significantly improved (lower) γ.sub.1/K.sub.1 values of the liquid crystalline media according to the invention due to the use of a compound of formula I, which results in faster switching of a display comprising the medium (Table 1). In addition, the value of K.sub.avg is practically unchanged or even improved which corresponds to an unchanged high or even improved contrast.

Mixture N-3

[0565]

TABLE-US-00012 CCP-3-1 7.0% T(N, I) [° C.]: 92.5 CCP-V-1 11.0% Δn [589 nm, 20° C.]: 0.1007 CCP-V2-1 6.0% n.sub.e [589 nm, 20° C.]: 1.5863 CCOY-3-O2 6.0% n.sub.o [589 nm, 20° C.]: 4.4856 CLY-3-O2 4.0% Δε [1 kHz, 20° C.]: −3.8 CLY-4-O2 5.0% ε.sub.∥ [1 kHz, 20° C.]: 3.6 CLY-5-O2 4.0% ε.sub.⊥ [1 kHz, 20° C.]: 7.4 PGIY-2-O4 3.0% γ.sub.1 [mPa s, 20° C.]: 124 B(S)-2O-O4 4.0% K.sub.1 [pN, 20° C.]: 18.4 B(S)-2O-O5 4.0% K.sub.3 [PN, 20° C.]: 17.1 B(S)-2O-O6 4.0% CC-3-V1 6.2% CC-2-3 18.0% CC-3-4 5.0% CY-3-O2 9.0% Y-4O-O4 3.5% CCQU-3-F 0.3% Σ 100.0%

Mixture N-4

[0566]

TABLE-US-00013 B(S)-2O-O5 4.0% T(N, I) [° C.]: 74.5 CPP-3-2 5.0% Δn [589 nm, 20° C.]: 0.1031 CC-3-V1 7.0% n.sub.e [589 nm, 20° C.]: 1.5907 CC-3-4 7.0% n.sub.o [589 nm, 20° C.]: 1.4876 CC-3-5 9.0% Δε [1 kHz, 20° C.]: −3.2 CCP-3-1 8.0% ε.sub.∥ [1 kHz, 20° C.]: 3.6 CCY-3-O1 6.0% ε.sub.⊥ [1 kHz, 20° C.]: 6.8 CCY-3-O2 8.0% γ.sub.1 [mPa s, 20° C.]: 109 CLY-3-O2 1.0% K.sub.1 [pN, 20° C.]: 14.5 CY-3-O2 10.5% K.sub.3 [PN, 20° C.]: 16.8 CP-3-O1 14.5% LTS bulk [h, −20° C.]: 1000 PY-1-O2 8.0% PY-2-O2 2.0% CCOY-3-O2 7.0% PP-1-3 3.0% Σ 100.0%

Mixture N-5

[0567]

TABLE-US-00014 B(S)-2O-O5 4.0% T(N, I) [° C.]: 75.5 CC-4-V1 10.5% Δn [589 nm, 20° C.]: 0.1029 CC-3-V1 8.0% n.sub.e [589 nm, 20° C.]: 1.5875 CC-3-4 7.5% n.sub.o [589 nm, 20° C.]: 1.4846 CC-3-5 8.0% Δε [1 kHz, 20° C.]: −3.2 CCP-3-1 7.0% ε.sub.∥ [1 kHz, 20° C.]: 3.6 CCY-3-O1 6.0% ε.sub.⊥ [1 kHz, 20° C.]: 6.7 CCY-3-O2 6.0% γ.sub.1 [mPa s, 20° C.]: 107 CLY-3-O2 1.0% K.sub.1 [pN, 20° C.]: 16.4 CY-3-O2 9.5% K.sub.3 [PN, 20° C.]: 16.9 CP-3-O2 10.0% LTS bulk [h, −20° C.]: 1000 PY-1-O2 8.0% PY-2-O2 4.0% CCOY-3-O2 5.0% PYP-2-3 5.5% Σ 100.0%

Mixture N-6

[0568]

TABLE-US-00015 CP-3-O2 16.0% T(N, I) [° C.]: 75.5 CC-3-4 11.0% Δn [589 nm, 20° C.]: 0.1125 CC-2-5 5.0% n.sub.e [589 nm, 20° C.]: 1.6017 COY-3-O2 11.0% n.sub.o [589 nm, 20° C.]: 1.4892 CCOY-2-O2 5.0% Δε [1 kHz, 20° C.]: −3.8 CCOY-3-O2 5.0% ε.sub.∥ [1 kHz, 20° C.]: 3.7 CCOY-4-O2 4.0% ε.sub.⊥ [1 kHz, 20° C.]: 7.5 PP-1-5 8.0% γ.sub.1 [mPa s, 20° C.]: 137 CPP-3-2 5.0% K.sub.1 [pN, 20° C.]: 15.7 CPP-5-2 3.0% K.sub.3 [PN, 20° C.]: 16.5 CCP-3-1 6.0% LTS bulk [h, −20° C.]: 1000 CPY-3-O2 10.0% B(S)-2O-O5 4.0% B(S)-2O-O4 3.0% CY-3-O2 4.0% Σ 100.0%

Mixture N-7

[0569]

TABLE-US-00016 CP-3-O2 17.0% T(N, I) [° C.]: 75.5 CC-3-4 11.0% Δn [589 nm, 20° C.]: 0.1126 CC-2-5 7.0% n.sub.e [589 nm, 20° C.]: 1.5996 COY-3-O2 4.0% n.sub.o [589 nm, 20° C.]: 1.4870 CCOY-2-O2 4.0% Δε [1 kHz, 20° C.]: −4.0 CCOY-3-O2 3.0% ε.sub.∥ [1 kHz, 20° C.]: 4.1 CCOY-4-O2 6.5% ε.sub.⊥ [1 kHz, 20° C.]: 8.1 PP-1-5 5.0% γ.sub.1 [mPa s, 20° C.]: 146 CPP-3-2 3.0% K.sub.1 [pN, 20° C.]: 15.6 CPY-2-O2 7.0% K.sub.3 [PN, 20° C.]: 15.6 CPY-3-O2 12.0% LTS bulk [h, −20° C.]: 1000 B(S)-2O-O4 3.0% B(S)-2O-O5 4.0% CLP-3-T 3.0% CY-3-O2 10.5% Σ 100.0%

Mixture N-8

[0570]

TABLE-US-00017 CP-3-O2 17.0% T(N, I) [° C.]: 74.0 CC-3-4 11.0% Δn [589 nm, 20° C.]: 0.1143 CC-2-5 7.0% Δε [1 kHz, 20° C.]: −4.3 COY-3-O2 4.0% γ.sub.1 [mPa s, 20° C.]: 150 CCOY-2-O2 4.0% CCOY-3-O2 3.0% CCOY-4-O2 6.5% PP-1-5 5.0% CPP-3-2 3.0% CPY-2-O2 7.0% CPY-3-O2 12.0% B(S)-2O-O4 4.0% B(S)-(c5)1O-O2 3.0% CLP-3-T 3.0% CY-3-O2 10.5% Σ 100.0%

Mixture N-9

[0571]

TABLE-US-00018 B(S)-2O-O4 2.0% T(N, I) [° C.]: 96.0 B(S)-2O-O5 2.5% Δn [589 nm, 20° C.]: 0.0957 CC-3-V 47.5% Δε [1 kHz, 20° C.]: −3.8 CC-3-V1 2.5% CCOY-2-O2 6.0% CCOY-(c3)1-O2 4.0% CCY-3-O2 11.0% CLY-3-O2 9.0% CLY-5-O2 5.0% COB(S)-2-O4 10.0% CPY-3-O2 0.5% Σ 100.0%

Mixture N-10

[0572]

TABLE-US-00019 B(S)-2O-O4 2.5% T(N, I) [° C.]: 104.1 B(S)-2O-O5 5.0% Δn [589 nm, 20° C.]: 0.0936 B(S)-2O-O6 4.0% n.sub.e [589 nm, 20° C.]: 1.5737 CC-3-V 31.0% n.sub.o [589 nm, 20° C.]: 1.4801 CC-3-V1 8.0% Δε [1 kHz, 20° C.]: −4.1 CCH-35 8.0% ε.sub.∥ [1 kHz, 20° C.]: 3.4 CCOY-3-O2 10.0% ε.sub.⊥ [1 kHz, 20° C.]: 7.4 CCY-3-O1 8.0% γ.sub.1 [mPa s, 20° C.]: 145 CCY-3-O2 11.0% K.sub.1 [pN, 20° C.]: 19.5 CLY-3-O2 9.0% K.sub.3 [PN, 20° C.]: 21.6 CLY-5-O2 3.5% Σ 100.0%

Mixture N-11

[0573]

TABLE-US-00020 B(S)-2O-O4 3.0% T(N, I) [° C.]: 91.5 B(S)-2O-O5 4.0% Δn [589 nm, 20° C.]: 0.0940 B(S)-2O-O6 3.0% n.sub.e [589 nm, 20° C.]: 1.5764 CC-3-V 31.5% n.sub.o [589 nm, 20° C.]: 1.4824 CC-3-V1 7.0% Δε [1 kHz, 20° C.]: −3.9 CCH-35 5.0% ε.sub.∥ [1 kHz, 20° C.]: 3.4 CCP-31 13.5% ε.sub.⊥ [1 kHz, 20° C.]: 7.4 CCY-3-O2 2.0% γ.sub.1 [mPa s, 20° C.]: 111 CLY-3-O2 6.0% K.sub.1 [pN, 20° C.]: 18.4 COB(S)-2-O4 5.0% K.sub.3 [PN, 20° C.]: 19.2 COY-3-O2 10.0% LTS bulk [h, −20° C.]: 696 CCOY-3-O2 10.0% Σ 100.0%

[0574] The following mixtures N-11 to N-40 additionally contain the stabilisers indicated above. The amount of host mixture and the amount of stabiliser given in the table add up to give 100% by weight.

TABLE-US-00021 TABLE 1 Mixtures comprising stabilisers. Mixture Host-Mixture Stabiliser (percentage in the mixture) N-11 N-1 0.03% of ST-3a-1 N-12 N-2 0.02% of ST-12 N-13 N-3 0.01% of ST-3b-1 N-14 N-4 0.03% of ST-2a-1 and 0.02% of ST-3a-1 N-15 N-5 0.03% of ST-2a-1 N-16 N-6 0.015% of ST-9-1 N-17 N-7 0.015% of ST-8-1 N-18 N-8 0.03% of ST-12 N-19 N-9 0.03% of ST-8-1 N-20 N-10 0.25% of ST-3a-1 N-21 N-11 0.02% of ST-8-1 and 0.01% of ST-3a-1 N-22 N-1 0.02% of ST-8-1 and 0.1% of ST-3a-1 N-23 N-2 0.01% of ST-3a-1 N-24 N-3 0.025% of ST-8-1 N-25 N-4 0.025% of ST-12 N-26 N-5 0.02% of ST-9-1 and 0.02% of ST-3b-1 N-27 N-6 0.04% of ST-3b-1 and 0.01% of ST-9-1 N-28 N-7 0.02% of ST-3a-1 and 0.05% of ST-3b-1 N-29 N-8 0.02% of ST-3a-1 and 0.01% of ST-8-1 N-30 N-9 0.02% of ST-3a-1 and 0.3% of the compound of the formula [00539] N-31 N-10 0.01% of ST-17 N-32 N-11 0.05% of ST-3b-1 and 0.15% of ST-12 N-33 N-1 0.02% of ST-8-1 N-34 N-1 0.02% of ST-12 N-35 N-2 0.01% of ST-3b-1 N-36 N-3 0.03% of ST-2a-1 and 0.02% of ST-3a-1 N-37 N-4 0.03% of ST-2a-1 N-38 N-5 0.015% of ST-9-1 N-39 N-6 0.015% of ST-8-1 N-40 N-7 0.03% of ST-12 N-41 N-8 0.03% of ST-8-1 N-42 N-9 0.25% of ST-3a-1 N-43 N-10 0.02% of ST-8-1 and 0.01% of ST-3a-1 N-44 N-11 0.02% of ST-8-1 and 0.1% of ST-3a-1 The chiral nematic mixture N-45 consists of 99.20% of Mixture N-11 and 0.80% of chiral dopant S-2011: [00540] Mixture N-45 is distinguished by very high stability under UV load and shows improved switching times.