Liquid-crystalline medium

Abstract

The present invention relates to liquid-crystalline media comprising a) one or more compounds of the formula ST-1, as defined herein, and b) one or more compounds of the formula ST-2, as defined herein, and c) one or more compounds of the formula RV, as defined herein, and d) one or more compounds selected from formula IA and IB, as defined herein, and to liquid-crystal displays containing these media, especially to displays addressed by an active matrix and in particular to displays of the in-plane switching (IPS) or fringe-field switching (FFS) type.

Claims

1. A liquid-crystalline medium, comprising: a) one or more compounds of formula ST-1a ##STR00265## in which R.sup.S3 denotes alkyl having 1 to 6 C atoms; t is 1, and q is 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9; and b) one or more compounds of formula ST-2 ##STR00266## in which ##STR00267## denotes ##STR00268## R.sup.S1 denotes H, or an alkyl, alkenyl or alkoxy radical in each case having up to 15 C atoms, and in which one or more H atoms may each be replaced by halogen, R.sup.S2 denotes H, or alkyl, alkenyl or alkoxy radical in each case having up to 7 C atoms, and in which one or more H atoms may each be replaced by halogen, r is 0 or 1; and c) one or more compounds of formula RV ##STR00269## in which R.sup.21 denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, and R.sup.22 denotes an unsubstituted alkenyl radical having 2 to 7 C atoms, and d) one or more compounds selected from formulae IA and IB, ##STR00270## in which R.sup.A and R.sup.B each, independently of one another, denotes a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by CC, CF.sub.2O, CHCH, ##STR00271## O, COO or OCO in such a way that O atoms are not linked directly to one another, X.sup.A and X.sup.B each, independently of one another, denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 C atoms, and Y.sup.1-13 each, independently of one another, denote H or F; wherein the medium comprises one or more compounds of formula ST-1a in a total concentration of 1500 ppm to 3000 ppm, and comprises one or more compounds of formula ST-2 in a total concentration of 300 ppm or more.

2. The liquid-crystalline medium according to claim 1, wherein the medium comprises a compound of formula ST-1a in which q is 7, t is 1 and R.sup.S3 denotes ethyl.

3. The liquid-crystalline medium according to claim 1, wherein said one or more compounds of formula ST-2 is/are one or more compounds of formula ST-2a ##STR00272## in which R.sup.1A denotes alkyl having 1 to 7 C atoms.

4. The liquid-crystalline medium according to claim 1, wherein said one or more compounds selected from formulae IA are selected from formulae IA-a to IA-f, ##STR00273## wherein groups R.sup.A and X.sup.A are as defined in claim 1.

5. The liquid-crystalline according to claim 1, wherein said one or more compounds selected from formulae IB are selected from formulae IB-a to IB-h ##STR00274## wherein groups R.sup.B and X.sup.B are as defined in claim 1.

6. The liquid-crystalline medium according to claim 1, wherein said medium additionally comprises one or more compounds selected from formulae II and/or III, ##STR00275## in which R.sup.0 denotes a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by CC, CF.sub.2O, CHCH, ##STR00276## O, COO or OCO in such a way that O atoms are not linked directly to one another, X.sup.0 denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 C atoms, Y.sup.1-5 each, independently of one another, denote H or F, and ##STR00277## each, independently of one another, denote ##STR00278##

7. The liquid-crystalline medium according to claim 1, wherein said medium additionally comprises one or more compounds selected from formulae IV to VIII, ##STR00279## in which R.sup.0 denotes a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by CC, CF.sub.2O, CHCH, ##STR00280## O, COO or OCO in such a way that O atoms are not linked directly to one another, X.sup.0 denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 C atoms, Y.sup.1-4 each, independently of one another, denote H or F, Z.sup.0 denotes C.sub.2H.sub.4, (CH.sub.2).sub.4, CHCH, CFCF, C.sub.2F.sub.4, CH.sub.2CF.sub.2, CF.sub.2CH.sub.2, CH.sub.2O, OCH.sub.2, COO or OCF.sub.2, and, in formulae V and VI, Z can also be a single bond, and, in formulae V and VIII, Z can also be CF.sub.2O, r denotes 0 or 1, and s denotes 0 or 1.

8. The liquid-crystalline medium according to claim 1, wherein said medium additionally comprises one or more compounds selected from formulae IX to XII, ##STR00281## in which X.sup.0 denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 C atoms, L denotes H or F, alkyl denotes C.sub.1-6-alkyl, R denotes C.sub.1-6-alkyl or C.sub.1-6-alkoxy R denotes C.sub.1-6-alkyl, C.sub.1-6-alkoxy or C.sub.2-6-alkenyl, and alkenyl and alkenyl* each, independently of one another, denote C.sub.2-6-alkenyl.

9. The liquid-crystalline medium according to claim 1, wherein said medium additionally comprises one or more compounds of formula XVII, ##STR00282## in which R.sup.1 and R.sup.2 each, independently of one another, denote n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 8 C atoms, and L denotes H or F.

10. The liquid-crystalline medium according to claim 1, wherein said medium further comprises one or more compounds selected from formulae XXVII, XXVIII and XXIX, ##STR00283## in which R.sup.1 denotes n-alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 8 C atoms, and X.sup.0 denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 C atoms.

11. The liquid-crystalline medium according to claim 1, wherein said medium further comprises one or more compounds selected from formulae XIX, XX, XXI, XXII, XXIII and XXIV, ##STR00284## in which R.sup.0 denotes a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by CC, CF.sub.2O, CHCH, ##STR00285## O, COO or OCO in such a way that O atoms are not linked directly to one another, X.sup.0 denotes F, Cl, CN, SF.sub.5, SCN, NCS, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 C atoms, and Y.sup.1-4 each, independently of one another, denote H or F.

12. The liquid-crystalline medium according to claim 1, wherein said medium further comprises 20% by weight of a compound of formula IXb, ##STR00286## in which alkyl denotes C.sub.1-6-alkyl.

13. The liquid-crystalline medium according to claim 1, wherein said medium additionally comprises one or more compounds selected from formulae IIIA, IIB and IIC ##STR00287## in which R.sup.2A, R.sup.2B and R.sup.2C 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 each be replaced by O, S, ##STR00288## CC, CF.sub.2O, OCF.sub.2, OCO or OCO in such a way that O atoms are not linked directly to one another, L.sup.1-4 each, independently of one another, denote F, Cl, CF.sub.3 or CHF.sub.2, Z.sup.2 and Z.sup.2 each, independently of one another, denote a single bond, CH.sub.2CH.sub.2, CHCH, CF.sub.2O, OCF.sub.2, CH.sub.2O, OCH.sub.2, COO, OCO, C.sub.2F.sub.4, CFCF, or CHCHCH.sub.2O, (O) denotes O or a single bond, P denotes 0, 1 or 2, q denotes 0 or 1, and v denotes 1 to 6.

14. A process for the preparation of a liquid-crystalline medium according to claim 1, said process comprising: mixing one or more compounds of the formula IA and one or more compounds of the formula IB and one or more compounds of formula RV, with one or more further liquid-crystalline compounds and one or more additives of formula ST-1a and one or more additives of formula ST 2.

15. A method of generating an electro-optical effect comprising applying a voltage to a liquid-crystalline medium according to claim 1.

16. The method according to claim 15, wherein said liquid-crystalline medium is in a shutter glass, a 3D application, or in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, PS-FFS or PS-VA-IPS display.

17. An electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 1.

18. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-1a in a total concentration of 2000 ppm to 3000 ppm.

19. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-2 in a total concentration 400 ppm or more.

20. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-2 in a total concentration 500 ppm or more.

21. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-2 in a total concentration of from 300 ppm to 1000 ppm.

22. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-2 in a total concentration of from 300 to 800 ppm.

23. The liquid-crystalline medium according to claim 1, wherein the medium comprises one or more compounds of formula ST-2 in a total concentration of from 400 to 600 ppm.

24. The liquid-crystalline medium according to claim 1, wherein the compound of formula ST-2 is a compound of the following formula: ##STR00289##

Description

EXAMPLES

(1) The nematic host mixtures N1 to N6 are prepared as follows:

(2) TABLE-US-00006 Mixture N1 CC-3-V 48.0% Clearing point [ C.]: 85.0 CC-3-V1 8.5% n (589 nm, 20 C.): 0.1122 CCP-V2-1 6.0% n.sub.e (589 nm, 20 C.): 1.6012 CCGU-3-F 4.5% n.sub.o (589 nm, 20 C.): 1.4890 CCQU-5-F 3.0% (1 kHz, 20 C.): 3.4 CPGU-3-OT 3.0% .sub.|| (1 kHz, 20 C.): 6.2 PGP-2-2V 6.5% .sub. (1 kHz, 20 C.): 2.8 PGP-2-3 5.0% .sub.1 [mPa .Math. s], (20 C.): 58 PGP-2-4 3.0% K.sub.1 [pN]: 13.9 PGP-2-5 4.0% K.sub.3 [pN]: 15.1 PUQU-3-F 7.5% PGUQU-4-F 1.0% Mixture N2 CC-3-V 24.5% Clearing point [ C.]: 94.0 CC-3-V1 9.5% n (589 nm, 20 C.): 0.1038 CC-3-2V1 10.0% n.sub.e (589 nm, 20 C.): 1.5776 CCP-3OCF.sub.3 4.0% n.sub.o (589 nm, 20 C.): 1.4738 CCQU-3-F 9.0% (1 kHz, 20 C.): 17.3 CDUQU-5-F 10.0% .sub.|| (1 kHz, 20 C.): 21.1 APUQU-2-F 6.0% .sub. (1 kHz, 20 C.): 3.8 APUQU-3-F 8.0% .sub.1 [mPa .Math. s], (20 C.): 111 PGUQU-3-F 3.0% K.sub.1 [pN]: 15.9 PGUQU-4-F 7.0% K.sub.3 [pN]: 16.1 DPGU-4-F 5.0% DGUQU-4-F 4.0% Mixture N3 CC-3-V 42.0% Clearing point [ C.]: 79.5 CC-3-V1 5.5% n (589 nm, 20 C.): 0.1054 CCP-V-1 4.0% n.sub.e (589 nm, 20 C.): 1.5864 CCP-3OCF.sub.3 4.0% n.sub.o (589 nm, 20 C.): 1.4810 PGP-2-2V 5.0% (1 kHz, 20 C.): 4.5 APUQU-2-F 5.0% .sub.|| (1 kHz, 20 C.): 8.4 APUQU-3-F 12.0% .sub. (1 kHz, 20 C.): 3.9 CPGU-3-OT 3.0% .sub.1 [mPa .Math. s], (20 C.): 62 PGUQU-3-F 5.0% K.sub.1 [pN]: 13.1 CPY-3-O2 3.0% K.sub.3 [pN]: 14.4 CY-5-O2 9.0% PYP-2-3 3.0% Mixture N4 CC-3-V 39.5% Clearing point [ C.]: 95.5 CC-3-V1 10.0% n (589 nm, 20 C.): 0.1042 CCP-V-1 12.0% n.sub.e (589 nm, 20 C.): 1.5892 CCP-V2-1 6.0% n.sub.o (589 nm, 20 C.): 1.4850 CCQU-3-F 4.5% (1 kHz, 20 C.): 5.0 PGP-2-2V 4.5% .sub.|| (1 kHz, 20 C.): 7.8 PGP-3-2V 5.0% .sub. (1 kHz, 20 C.): 2.8 APUQU-2-F 6.0% .sub.1 [mPa .Math. s], (20 C.): 69 APUQU-3-F 6.0% K.sub.1 [pN]: 15.4 CPGU-3-OT 4.5% K.sub.3 [pN]: 17.6 PGUQU-3-F 2.0% Mixture N5 CDUQU-3-F 8.0% Clearing point [ C.]: 106.5 CPGP-5-2 2.5% n (589 nm, 20 C.): 0.1107 DGUQU-4-F 6.5% n.sub.e (589 nm, 20 C.): 1.5965 DPGU-4-F 4.0% n.sub.o (589 nm, 20 C.): 1.4858 PGUQU-3-F 2.5% (1 kHz, 20 C.): 6.6 CCP-3OCF.sub.3 5.0% .sub.|| (1 kHz, 20 C.): 9.6 CCP-V-1 11.0% .sub. (1 kHz, 20 C.): 3.0 CCP-V2-1 9.0% .sub.1 [mPa .Math. s], (20 C.): 95 PGP-2-2V 6.0% K.sub.1 [pN]: 18.8 CC-3-2V1 8.0% K.sub.3 [pN]: 19.9 CC-3-V 23.5% CC-3-V1 10.0% PP-1-2V1 4.0% Mixture N6 CC-3-V 32.5% Clearing point [ C.]: 79.5 CC-3-V1 12.0% n (589 nm, 20 C.): 0.0992 CC-3-2V1 10.5% n.sub.e (589 nm, 20 C.): 1.5827 CCP-V-1 10.5% n.sub.o (589 nm, 20 C.): 1.4835 CCP-V2-1 2.0% (1 kHz, 20 C.): 3.0 PGP-2-2V 7.0% .sub.|| (1 kHz, 20 C.): 6.5 APUQU-2-F 6.0% .sub. (1 kHz, 20 C.): 3.5 APUQU-3-F 7.5% .sub.1 [mPa .Math. s], (20 C.): 58 CY-5-O2 5.5% B-2O-O5 3.5% PP-1-2V1 2.5% PPGU-3-F 0.5%

Mixture Examples

(3) From the host mixtures N1 to N6, the following mixture examples are prepared by addition of stabilizers of the formulae ST-1a-2-1 and ST-2a-3 in the amounts given in the table below.

(4) ##STR00264##

(5) TABLE-US-00007 concentration of component [%] Host Host Example Mixture Mixture ST-1a-2-1 ST-2a-3 C1 N1 100.0 M1 N1 99.97 0.03 M2 N1 99.95 0.05 M3 N1 99.90 0.10 M4 N1 99.85 0.15 M5 N1 99.80 0.20 M6 N1 99.92 0.03 0.05 M7 N1 99.90 0.05 0.05 M8 N1 99.85 0.10 0.05 M9 N1 99.80 0.15 0.05 M10 N1 99.75 0.20 0.05 M11 N2 99.92 0.03 0.05 M12 N2 99.90 0.05 0.05 M13 N2 99.85 0.10 0.05 M14 N2 99.80 0.15 0.05 M15 N2 99.75 0.20 0.05 M16 N3 99.92 0.03 0.05 M17 N3 99.90 0.05 0.05 M18 N3 99.85 0.10 0.05 M19 N3 99.80 0.15 0.05 M20 N3 99.75 0.20 0.05 M21 N4 99.92 0.03 0.05 M22 N4 99.90 0.05 0.05 M23 N4 99.85 0.10 0.05 M24 N4 99.80 0.15 0.05 M25 N4 99.75 0.20 0.05 M26 N5 99.85 0.10 0.05 M27 N6 99.85 0.10 0.05
Stress Tests

(6) Test cells having the alignment layer AL-16301 (Japan Synthetic Rubber (JSR), Japan) with a layer thickness of 3.2 m (electrodes: ECB layout) are filled with the corresponding mixtures and their voltage holding ratio is measured.

(7) Measurement Conditions

(8) 1. UV-Load

(9) The initial value and the value after UV exposure with a high-pressure mercury vapor lamp from Hoya (Execure 3000) with an edge filter (T=50% at 340 nm), with an exposure intensity of 3 J/cm.sup.2, are determined at a temperature of 25 C. The exposure intensity is measured using an Ushio UIT-101+UVD-365PD sensor at a wavelength of 365 nm. The VHR is measured at a temperature of 100 C. after 5 minutes in the oven. The voltage is 1 V at 60 Hz. The results are summarized in the following table 1.

(10) 2. Heat Load

(11) For the heat load experiments the test cells are kept at 100 C. in an oven for the given period of time.

(12) 3. Backlight Load

(13) Corresponding investigations of the mixtures were then carried out in sealed test cells with exposure to commercial LCD TV backlighting (CCFL). The temperature of the test cells here was about 40 C. due to the heat evolution by the backlighting.

(14) The results of the stress tests are summarized in tables 1 to 3.

(15) TABLE-US-00008 TABLE 1 VHR values after UV load.sup.[1] Mixture C1 M1 M2 M3 M4 M5 initial 98.10 98.95 98.93 98.98 99.00 99.00 after UV 97.72 99.14 99.01 99.08 99.06 99.08 .sup.[1]measured at 60 Hz, 100 C.

(16) TABLE-US-00009 TABLE 2 VHR values afterheat load.sup.[1] Mixture t [h] C1 M1 M2 M3 M4 M5 0 97.56 98.80 99.08 99.07 99.13 99.27 24 97.74 99.49 99.59 99.59 99.61 99.62 48 97.26 99.53 99.56 99.63 99.62 99.59 120 96.92 99.56 99.66 99.62 99.63 99.65 .sup.[1]measured at 60 Hz, 100 C.

(17) TABLE-US-00010 TABLE 3 VHR values after backlight load.sup.[1] Mixture t [h] C1 M1 M2 M3 M4 M5 0 98.29 99.27 99.24 99.33 99.22 99.13 24 95.62 99.52 99.51 99.55 99.50 99.50 168 88.87 99.33 99.32 99.37 99.33 99.28 336 80.72 98.99 98.97 99.12 99.11 99.10 504 76.39 98.77 98.72 98.86 98.90 98.91 .sup.[1]measured at 60 Hz, 100 C.

(18) The values given in the tables 1 to 3 show, that even in a small concentration of only 0.03%, the VHR of the mixtures comprising the compound of the formula ST-1a-2-1 is significantly improved in comparison to the unstabilized host mixture (comparative example C1) before UV, backlight or heat stress and in particular thereafter. An increase in the concentration does not lead to a further improvement of the VHR after stress.

(19) LTS Measurements

(20) A nematic mixture N7 is prepared from 99.95% of mixture N1 and 0.05% of additive ST-2a-3. Mixtures M28 to M32 are prepared by addition of additive ST-1a-2-1 in the amounts given in the following table 4.

(21) TABLE-US-00011 TABLE 4 LTS tests (in bulk) concentration of component [%] Host Host Example Mixture Mixture ST-1a-2-1 LTS [h] at 20 C. M28 N7 99.97 0.03 >1000 M29 N7 99.95 0.05 >1000 M30 N7 99.90 0.10 >1000 M31 N7 99.85 0.15 >1000 M32 N7 99.80 0.20 768 < Cr < 792

(22) As can be seen from table 4, for concentrations of 0.03 to 0.15% of additive ST-1a-2-1, no crystallization occurs for at least 1000 h. In case of mixture M32 having a concentration of 0.020% of ST-1a-2-1, crystallization did only occur after a period of between 768 and 792 h which is still sufficient for practical applications.

(23) Hence, the additive ST-1a-2-1 is surprisingly well soluble in a very high concentration of at least 0.20%.

(24) The VHR values obtained by investigation of the mixtures M6 to M27, additionally comprising the additive ST-2a-3, are, within the measuring accuracy, the same as observed for the mixtures M1 to M5.

(25) Surprisingly, the mixtures M5, M10, M15, M20 and M25, comprising 0.2% of additive ST-1a-2-1 and in combination with 0.05% of additive ST-2a-3 show a very advantageous combination of low image sticking, very good LTS and in particular no or for applications sufficiently low degree of edge mura in display panels. This is particularly unexpected because there was no further improvement of the VHR when using concentrations of ST-1a-2-1 higher than 0.03% as shown above.

(26) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(27) In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

(28) The entire disclosure[s] of all applications, patents and publications, cited herein and of corresponding EP application No. 17161384.7, filed Mar. 16, 2017, is [are] incorporated by reference herein.

(29) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(30) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.