LIQUID-CRYSTALLINE MEDIUM

Abstract

Liquid-crystalline media containing a) one or more compounds of formula IA,

##STR00001## and b) one or more compounds of formula II

##STR00002## and c) one or more compounds of formulae III-1 to III-4,

##STR00003##

their use in electro-optical displays, particularly in active-matrix displays based on the VA, ECB, FFS or IPS effect.

Claims

1. A liquid-crystalline medium, comprising a) one or more compounds of formula IA, ##STR00161## in which ##STR00162## denotes ##STR00163## R.sup.1A denotes H, an alkyl, alkenyl or alkoxy radical having up to 15 C atoms, in which one or more H atoms are optionally replaced by halogen, R.sup.2A denotes H, alkyl or alkenyl or alkoxy having up to 7 C atoms, in which one or more H atoms are optionally replaced by halogen, r is 0 or 1; and b) one or more compounds of the formula II ##STR00164## 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 c) one or more compounds of formulae III-1 to III-4, ##STR00165## in which R.sup.31 on each occurrence, identically or differently, denotes an unsubstituted alkyl radical having 1 to 7 C atoms, R.sup.32 on each occurrence, identically or differently, denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkoxy radical having 1 to 6 C atoms, and m, n and o each, identically or differently, denote 0 or 1.

2. The medium according to claim 1, wherein the one or more compounds of formula IA are of formulae IA-1 to IA-2 ##STR00166## in which R.sup.1A denotes alkyl having 1 to 7 C atoms.

3. The medium according to claim 1, further comprising one or more compounds of formula IB ##STR00167## in which G denotes a divalent aliphatic or cycloaliphatic radical having 1 to 20 C atoms.

4. The medium according to claim 3, wherein the one or more compounds of formula IB are of formula IB-1 ##STR00168## in which R.sup.1B denotes H or alkyl having 1 to 6 C atoms, t is 0 or 1, and q is 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

5. The medium according to claim 4, comprising one or more compounds of formula IA-1 ##STR00169## in which R.sup.1A denotes methyl, ethyl, n-propyl, n-butyl or n-pentyl, and one or more compounds of formula IB-1 ##STR00170## in which R.sup.1B denotes ethyl t is 1, and q is 0, 1, 2, 3, 4, 5, 6, 7, 8, or 9.

6. The medium according to claim 1, wherein the total concentration of the compounds of formula IA in the medium is 1 ppm to 2000 ppm.

7. The medium according to claim 3, wherein the total concentration of the compounds of formula IB in the medium is 10 ppm to 3000 ppm.

8. The medium according to claim 1, wherein in the compound of formula II, R.sup.21 denotes n-propyl and R.sup.22 denotes vinyl.

9. The medium according to claim 1, wherein the total concentration of the compounds of the formula II in the medium as a whole is 20% to 60%.

10. The medium according to claim 1, comprising one or more compounds of formula III-2-2 ##STR00171## in which R.sup.31 and R.sup.32 have the respective meanings indicated for the compound of formula III-2.

11. An electro-optical display or electro-optical component, which contains a liquid-crystalline medium according to claim 1.

12. The display according to claim 11, which is an IPS or FFS display.

13. The display according to claim 11, which contains an active-matrix addressing device.

14. A process for preparing the liquid-crystalline medium according to claim 1, comprising mixing together one or more compounds of formula IA with one or more compounds of formula II and/or one or more compounds of formulae III-1 to III-4.

Description

EXAMPLES

[0228] The following examples explain the present invention without restricting it in any way. However, the physical properties make it clear to the person skilled in the art what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

[0229] The nematic host mixture N1 is prepared as follows:

Host Mixture N1

[0230]

TABLE-US-00008 CCY-3-O1 7.0% T.sub.(N, I) [ C.]: 85.0 CCY-3-O2 4.0% n (589 nm, 20 C.): 0.1047 CLY-3-O1 8.0% n.sub.e (589 nm, 20 C.): 1.5876 CPY-2-O2 10.0% : (1 kHz, 20 C.): 3.4 CPY-3-O2 10.0% : (1 kHz, 20 C.): 3.5 PYP-2-3 6.0% .sub.1 [mPa .Math. s], (20 C.): 112 CC-3-V 30.0% K.sub.1 [pN], (20 C.): 14.3 CC-3-V1 9.0% K.sub.3[pN], (20 C.): 17.5 CY-3-O2 12.0% CY-5-O2 4.0%

[0231] Using the following stabilisers ST, IA-1c, IB-1a-1 and IB-1b-1

##STR00160##

[0232] The comparative mixture C1 and the mixture examples M1 to M7 are prepared as follows:

TABLE-US-00009 concentration of component [%] Mixture N1 ST IA-1a IB-1a IB-2a C1 99.97 0.03 M1 99.95 0.05 M2 99.92 0.03 0.05 M3 99.85 0.05 0.1 M4 99.85 0.05 0.1

[0233] The mixtures C1 and M1 to M4 are exposed to thermal or UV stress and their VHR and conductivities are measured following the procedures described above.

[0234] The results are summarised in tables 1 to 3.

TABLE-US-00010 TABLE 1 VHR after heat load (measured at 60 Hz, 100 C.) Mixture time [h] VHR C1 0 72.1 48 61.3 120 59.1 M1 0 72.7 48 63.7 120 64.3 M2 0 71.6 48 60.4 120 59.9 M3 0 86.8 48 94.1 120 93.8 M4 0 87.4 48 93.0 120 93.6

TABLE-US-00011 TABLE 2 VHR after UV load (measured at 3 Hz, 60 C.) VHR of mixture [%] C1 M1 M2 M3 M4 initial 79.7 78.3 76.8 91.4 90.1 after UV load 75.3 75.6 74.4 92.2 90.7

TABLE-US-00012 TABLE 3 Resistivity after UV load (measured at 10 V, 1 Hz, 60 C.) Resistivity of mixture [G] C1 M1 M2 M3 M4 initial 2.65 2.03 2.01 1.26 1.06 after UV load 2.71 2.14 2.20 1.43 1.15

[0235] As can be seen from table 1, replacement of the stabiliser ST from the state of the art in comparative mixture C1 by the stabiliser IA-1a-1 (mixture M1) or the use of a combination of the stabilisers IA-1a-1 and ST (mixture M2) result in a very similar or slightly improved VHR after heat load.

[0236] Likewise, the VHR before and after UV load of the mixtures M1 and M2 is on a similarly high level as the comparative mixture C1 (table 2).

[0237] The mixtures M1 and M2 show a significantly lower resistivity before and after UV load (table 3) compared to comparative mixture C1.

[0238] Unexpectedly, the VHR both after heat load (table 1) and after UV load (table 2) of the mixture M1 is significantly improved by the addition of a stabiliser of formula IB-1a-1 (mixture M3) or IB-1b-1 (mixture M4). Surprisingly, also the resistivity both before and after UV load is significantly lower (table 3) compared to mixture C1 and even to M1, resulting in a reduction of more than 50% of the resistivity value of mixtures M3 and M4 in comparison to comparative mixture C1.

[0239] It is understood that although the resistivity of the mixtures M1 to M4, in particular M3 and M4, is lower than the resisitvity of mixture C1, all resistivity values are still on an extremely high level and the mixtures are very well suitable for practical use, e.g. in LC displays.

[0240] The results show that the stabiliser of formula IA has a beneficial effect for the reliability of the host mixture N1 either used alone or in combination with a stabilisers of formula IB.

[0241] Further, it can be shown that all mixtures show very high long term reliability in panel tests. In addition, very low or no image sticking is observed in panel tests using media according to the invention.

[0242] Without wishing to be bound by theory, and although this has not yet been fully evaluated, it is assumed and believed that the combination of [0243] 1) a VHR value that is on a similar high level or higher than the VHR of a corresponding medium without a stabiliser according to the invention, with [0244] 2) a resistivity value that is lower than the resistivity value of a corresponding medium without a stabiliser according to the invention, leads to an improvement (lower degree) of image sticking or even to the total absence of image sticking.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] The entire disclosures of all applications, patents and publications, cited herein and of corresponding European application No. EP 17161354.0, filed Mar. 16, 2017, are incorporated by reference herein.