LIQUID-CRYSTAL MEDIUM

Abstract

The present invention relates to a liquid-crystalline medium having a clearing point of 120° C. or more, comprising one or more compounds selected from the group of the compounds of the formulae IA, IB, IC, ID and II

##STR00001##

in which the groups and parameters occurring have the meanings indicated in Claim 1, in a total concentration of 65% or more, and to the use thereof for electro-optical purposes, in particular for liquid-crystal light valves for use in lighting devices for motor vehicles, to liquid-crystal light valves containing this medium, and to lighting devices based on liquid-crystal light valves of this type.

Claims

1. Liquid-crystalline medium, characterised in that it comprises one or more compounds, in a total concentration of 65% or more, selected from the group of the compounds of the formulae IA, IB, IC, ID and II ##STR00255## in which R.sup.1A, R.sup.1B, R.sup.1C and R.sup.2 in each case, 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 ##STR00256## —C≡C—, —O—, —S—, —CF.sub.2O—, —OCF.sub.2—, —OC— or —O—CO— in such a way that O atoms are not linked directly to one another, R.sup.1 and R.sup.1′ in each case, independently of one another, denote H or alkyl having 1 to 4 C atoms, A.sup.2 denotes a) 1,4-cyclohexylene or 1,4-cyclohexenylene, in which one or two non-adjacent CH.sub.2 groups may be replaced by —O— or —S—, b) 1,4-phenylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by F or Cl, L.sup.1 to L.sup.12 in each case, independently of one another, denote F, CF.sub.3, CHF.sub.2 or Cl, Z.sup.1, Z.sup.1′ and Z.sup.2 in each case, 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—, —C≡C—, —CH═CHCH.sub.2O—, a denotes 0 or 1, p denotes 0, 1 or 2, q denotes 0 or 1, v denotes an integer from 1 to 7, t denotes an integer from 1 to 7, and (O) denotes a single bond or —O—, and furthermore characterised in that the clearing point of the medium is 120° C. or more.

2. Medium according to claim 1, where the medium comprises one or more compounds selected from the group of the compounds of the formulae ##STR00257## ##STR00258## in which alkyl and alkyl* in each case, independently of one another, denote a straight-chain alkyl radical having 1-7 C atoms, in which one CH.sub.2 group may be replaced by ##STR00259## and (O) stands for —O— or a single bond.

3. Medium according to claim 1, where the medium comprises one or more compounds selected from the group of the compounds of the formulae ##STR00260## in which L.sup.11 and L.sup.12 have the meanings indicated in claim 1, and alkyl and alkyl* in each case, independently of one another, denote a straight-chain alkyl radical having 1-7 C atoms, in which one CH.sub.2 group may be replaced by ##STR00261## and alkoxy and alkoxy* in each case, independently of one another, denote a straight-chain alkoxy radical having 1-7 C atoms, in which one CH.sub.2 group may be replaced by ##STR00262##

4. Medium according to claim 1, where the medium additionally comprises one or more compounds of the formula ##STR00263## in which R.sup.41 and R.sup.42 in each case, independently of one another, denote straight-chain alkyl or alkenyl having 1 to 7 C atoms, alternatively R.sup.42 also denotes alkoxy having 1 to 7 C atoms, in a total concentration of 20% or less.

5. Medium according to claim 1, where the medium additionally comprises one or more compounds of the formulae ##STR00264## in which R.sup.51 and R.sup.52 in each case, independently of one another, denote straight-chain alkyl or alkenyl having up to 7 C atoms, R.sup.52 alternatively denotes alkoxy having 1 to 7 C atoms.

6. (canceled)

7. (canceled)

8. Process for the preparation of a medium according to claim 1, characterised in that one or more compounds selected from the group of the compounds of the formulae IA, IB, IC, ID and II are mixed with one another, where one or more additives are optionally added.

9. Electro-optical component containing a liquid-crystalline medium according to claim 1.

10. Electro-optical component according to claim 9, where the component is a transmissive liquid-crystal light valve.

11. Electro-optical component according to claim 9, where the component is a reflective liquid-crystal light valve.

12. Electro-optical component according to claim 11 of the LCoS type.

13. Lighting device for vehicles comprising an electro-optical component according to claim 9.

14. Liquid-crystal display comprising an electro-optical component according to claim 9.

15. The lighting device of claim 13, which comprises a liquid-crystal light valve comprising the liquid-crystalline medium.

Description

WORKING EXAMPLES

[0134] 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 an.

[0135] The host mixture used for determination of the optical anisotropy Δn of the compounds of the formula IA 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.

[0136] Unless indicated otherwise, parts or percent data denote parts by weight or percent by weight.

[0137] Above and below: [0138] V.sub.o denotes threshold voltage, capacitive [V] at 20° C., [0139] n.sub.e denotes extraordinary refractive index at 20° C. and 589 nm, [0140] n.sub.o denotes ordinary refractive index at 20° C. and 589 nm, [0141] Δn denotes optical anisotropy at 20° C. and 589 nm, [0142] ε.sub.⊥ denotes dielectric permittivity perpendicular to the director at 20° C. and 1 kHz, [0143] ε.sub.∥ denotes dielectric permittivity parallel to the director at 20° C. and 1 kHz, [0144] Δε denotes dielectric anisotropy at 20° C. and 1 kHz, [0145] cl.p., T(N,I) denotes clearing point [° C.], [0146] γ.sub.1 denotes rotational viscosity measured at 20° C. [mPa.Math.s], determined by the rotation method in a magnetic field, [0147] K.sub.1 denotes elastic constant, “splay” deformation at 20° C. [pN], [0148] K.sub.2 denotes elastic constant, “twist” deformation at 20° C. [pN], [0149] K.sub.3 denotes elastic constant, “bend” deformation at 20° C. [pN], [0150] LTS denotes low-temperature stability (nematic phase), determined in test cells.

[0151] 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), are indicated in degrees Celsius (° C.). M.p. denotes melting point, cl.p.=clearing 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.

[0152] 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).

[0153] 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.

[0154] 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.

[0155] The polymerisable compounds are polymerised in the display or test cell by irradiation with UVA light (usually 365 nm) of a defined intensity for a pre-specified time, with a voltage simultaneously being applied to the display (usually 10 V to 30 V alternating current, 1 kHz). In the examples, unless indicated otherwise, a 50 mW/cm.sup.2 mercury vapour lamp is used, and the intensity is measured using a standard UV meter (make Ushio UNI meter) fitted with a 365 nm band-pass filter.

[0156] The tilt angle is determined by a rotational crystal experiment (Autronic-Melchers TBA-105). A low value (i.e. a large deviation from the 90° angle) corresponds to a large tilt here.

[0157] The VHR value is measured as follows: 0.3% of a polymerisable monomeric compound are added to the LC host mixture, and the resultant mixture is introduced into TN-VHR test cells (rubbed at 90°, alignment layer TN polyimide, layer thickness d≈6 μm). The HR value is determined after 5 min at 100° C. before and after UV exposure for 2 h (sun test) at 1 V, 60 Hz, 64 μs pulse (measuring instrument: Autronic-Melchers VHRM-105).

[0158] In order to investigate the low-temperature stability, also known as “LTS”, i.e. the stability of the LC mixture to spontaneous crystallisation-out of individual components at low temperatures, bottles containing 1 g of liquid-crystal mixture are stored at the temperature indicated, for example −20° C., and it is regularly checked whether the mixtures have crystallised out.

[0159] 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.

[0160] Owing to the surprisingly high clearing points and excellent LTS, the following mixture examples having negative dielectric anisotropy are suitable, in particular, for light valves for lighting devices for motor vehicles which have at least one homeotropic alignment layer and for VA displays.

[0161] In addition, they are suitable for light valves and liquid-crystal displays having a planar alignment which are based on the IPS or FFS effect.

MIXTURE EXAMPLES

Example M1

[0162]

TABLE-US-00007 CCY-3-O2 6.0% T.sub.(N, I) [° C.]: 124.5 CCY-3-O3 6.0% Δn (20° C., 589.3 nm): 0.1595 CCY-4-O2 6.0% Δε (20° C., 1 kHz): −5.3 CPY-2-O2 12.0% CPY-3-O2 12.0% K.sub.1 (20° C.) [pN]: 30.8 PYP-2-3 10.0% K.sub.3 (20° C.) [pN]: 39.6 PYP-2-4 10.0% CCH-34 10.0% V.sub.0 (20° C.) [V] 2.89 CCH-35 6.0% CCP-3-1 8.0% B(S)-2O-O4 7.0% B(S)-2O-O5 7.0%

Example M2

[0163]

TABLE-US-00008 CCY-3-O2 6.0% CCY-3-O3 6.0% CCY-4-O2 6.0% CPY-2-O2 14.0% CPY-3-O2 14.0% CCH-34 10.0% CCH-35 6.0% CCP-3-1 8.0% BCH-32 8.0% BCH-52 8.0% B(S)-2O-O4 7.0% B(S)-2O-O5 7.0%

Example M3

[0164]

TABLE-US-00009 CY-3-O4 16.0% T.sub.(N, I) [° C.]: 137.2 CY-5-O4 7.0% Δn (20° C., 589.3 nm): 0.1480 CCY-3-O2 6.0% CCY-3-O3 6.0% CCY-4-O2 6.0% K.sub.1 (20° C.) [pN]: 22.1 CPY-2-O2 12.0% K.sub.3 (20° C.) [pN]: 24.3 CPY-3-O2 12.0% CCP-3-1 8.0% V.sub.0 (20° C.) [V] 2.08 CBC-33F 3.0% CBC-53F 6.0% CPGP-5-2 4.0% CPGP-5-3 4.0% B(S)-2O-O4 5.0% B(S)-2O-O5 5.0%

Example M4

[0165]

TABLE-US-00010 CY-3-O4 20.0% T.sub.(N, I) [° C.]: 143.2 CCY-3-O2 6.0% Δn (20° C., 589.3 nm): 0.1524 CCY-3-O3 6.0% Δε (20° C., 1 kHz): −4.6 CCY-4-O2 6.0% CPY-2-O2 12.0% K.sub.1 (20° C.) [pN]: 21.9 CPY-3-O2 12.0% K.sub.3 (20° C.) [pN]: 24.2 CCH-34 5.0% CCP-3-1 8.0% V.sub.0 (20° C.) [V] 2.43 CBC-33F 3.0% CBC-53F 6.0% CPGP-5-2 5.0% CPGP-5-3 5.0% PGIY-2-O4 6.0%

Example M5

[0166]

TABLE-US-00011 CY-3-O2 4.0% T.sub.(N, I) [° C.]: 122.0 CY-3-O4 8.0% Δn (20° C., 589.3 nm): 0.1778 CCY-3-O2 6.0% Δε (20° C., 1 kHz): −4.1 CCY-3-O3 6.0% CCY-4-O2 6.0% K.sub.1 (20° C.) [pN]: 19.1 CPY-2-O2 12.0% K.sub.3 (20° C.) [pN]: 21.1 CPY-3-O2 12.0% PYP-2-3 12.0% V.sub.0 (20° C.) [V] 2.08 PYP-2-4 12.0% CC-4-V 3.0% LTS (−30° C.) [h] 1000 CCP-V-1 9.0% LTS (−40° C.) [h] 600 CPTP-301 5.0% PTP-102 5.0%

Example M6

[0167]

TABLE-US-00012 CY-3-O2 20.0% T.sub.(N, I) [° C.]: 137.3 CY-5-O4 9.0% Δn (20° C., 589.3 nm): 0.1382 CCY-3-O2 6.0% Δε (20° C., 1 kHz): −4.8 CCY-3-O3 6.0% CCY-4-O2 6.0% K.sub.1 (20° C.) [pN]: 21.0 CPY-2-O2 12.0% K.sub.3 (20° C.) [pN]: 24.2 CPY-3-O2 12.0% CCP-3-1 8.0% V.sub.0 (20° C.) [V] 2.37 CBC-33F 4.0% CBC-53F 7.0% LTS (−30° C.) [h] 1008 CPGP-5-2 5.0% CPGP-5-3 5.0%

Example M7

[0168]

TABLE-US-00013 CY-3-O2 8.0% T.sub.(N, I) [° C.]: 134.7 CY-5-O4 8.0% Δn (20° C., 589.3 nm): 0.1623 CCY-3-O2 6.0% Δε (20° C., 1 kHz): −4.5 CCY-3-O3 6.0% CCY-4-O2 6.0% K.sub.1 (20° C.) [pN]: 20.9 CPY-2-O2 12.0% K.sub.3 (20° C.) [pN]: 22.9 CPY-3-O2 12.0% PYP-2-3 12.0% V.sub.0 (20° C.) [V] 2.39 PYP-2-4 12.0% CCP-3-1 8.0% LTS (−20° C.) [h] 744 CBC-33F 4.0% LTS(−40° C.) [h] 600 CBC-53F 6.0%

Example M8

[0169]

TABLE-US-00014 CY-3-O4 8.0% T.sub.(N, I) [° C.]: 138.0 CY-5-O4 8.0% Δn (20° C., 589.3 nm): 0.1610 CCY-3-O2 6.0% Δε (20° C., 1 kHz): −4.4 CCY-3-O3 6.0% CCY-4-O2 6.0% K.sub.1 (20° C.) [pN]: 21.0 CPY-2-O2 12.0% K.sub.3 (20° C.) [pN]: 23.8 CPY-3-O2 12.0% PYP-2-3 10.0% V.sub.0 (20° C.) [V] 2.45 PYP-2-4 12.0% CCP-3-1 8.0% LTS(−30° C.) [h] 528 CBC-33F 5.0% LTS(−40° C.) [h] 384 CBC-53F 7.0%

Example M9

[0170]

TABLE-US-00015 CY-3-O4 7.0% T.sub.(N, I) [°C.]: 149.5 CCY-3-O2 6.0% Δn (20° C., 589.3 nm): 0.1754 CCY-3-O3 6.0% Δε (20° C., 1 kHz): −3.6 CCY-4-O2 6.0% CPY-2-O2 12.0% K.sub.1 (20° C.) [pN]: 22.2 CPY-3-O2 12.0% K.sub.3 (20° C.) [pN]: 25.5 PYP-2-3 10.0% PYP-2-4 10.0% V.sub.0 (20° C.) [V] 2.81 CC-4-V 3.0% CCP-V-1 9.0% LTS (−30° C.) [h] 1450 CPTP-301 5.0% LTS (−40° C.) [h] 240 PTP-102 3.0% CBC-33F 4.0% CBC-53F 7.0%

Example M10

[0171]

TABLE-US-00016 BCH-32 9.0% T.sub.(N, I) [° C.]: 132.2 CBC-33 1.5% Δn (20° C., 589.3 nm): 0.1674 CBC-33F 3.0% CBC-53F 1.5% CCP-3-1 3.5% CCY-3-O1 2.0% CCY-3-O2 6.0% CCY-3-O3 5.5% CCY-4-O2 6.0% CCY-5-O2 6.0% CPY-2-O2 9.0% CPY-3-O2 9.0% CY-3-O4 3.0% CY-5-O4 5.0% PY-1-O4 3.5% PY-4-O2 3.5% PYP-2-3 11.5% PYP-2-4 11.5%

Example M11

[0172] Example M11 consists of 91.84% of the medium from Example M10, 8.0% of the reactive mesogen RM-1 and 0.16% of the photoinitiator Irgacure 907®. This medium is suitable, in particular, for the production of light valves of the PDLC type.

##STR00254##