LIQUID-CRYSTAL MEDIUM

Abstract

The invention relates to a liquid-crystalline medium, in particular based on a mixture of polar compounds, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PA-VA, PALC, FFS, PS-FFS, IPS or PS-IPS effect.

Claims

1. A liquid crystal (LC) medium comprising one or more compounds of formula Q, one or more compounds of formula AN and one or more compounds of formula S ##STR00347## in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meanings: ##STR00348## or ##STR00349## or ##STR00350## R.sup.Q alkyl, alkoxy, or oxaalkyl having 1 to 9 C atoms or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated, X.sup.Q F, Cl, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, L.sup.Q1 to L.sup.Q6 H or F, with at least one of L.sup.Q1 to L.sup.Q6 being F, R.sup.A1 alkenyl having 2 to 9 C atoms or, if at least one of the rings X and Y denotes cyclohexenyl, also one of the meanings of R.sup.A2, R.sup.A2 alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH.sub.2 groups may each be replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are not linked directly to one another, x 1 or 2, R.sup.a-d are independently of each other straight chain or branched alkyl with 1 to 10 C atoms, X is H, CH.sub.3, OH or O., A is straight-chain, branched or cyclic alkylene with 1 to 20 C-atoms which is optionally substituted.

2. The LC medium of claim 1, wherein the compounds of formula AN are selected from the following formulae: ##STR00351## in which m denotes 1, 2, 3, 4, 5 or 6, i denotes 0, 1, 2 or 3, and R.sup.b1 denotes H, CH.sub.3 or C.sub.2H.sub.5.

3. The LC medium of claim 1, wherein the compounds of formula AN are selected from the following formulae: ##STR00352##

4. The LC medium according to claim 1, wherein the compounds of formula Q are selected from the following subformulae ##STR00353## wherein R.sup.Q has one of the meanings of claim 1.

5. The LC medium according to claim 1, wherein the compounds of formula Q are selected from formula Q1 ##STR00354## wherein R.sup.Q is n-propyl.

6. The LC medium according to claim 1, wherein the compounds of formula S are selected from the following subformulae ##STR00355## wherein X is H, CH.sub.3, OH or O., R.sup.A is methyl, ethyl, propyl, butyl, pentyl or hexyl, n1 is an integer from 2 to 12, n2 is 0 or an integer from 1 to 12, preferably 0, n3 is or an integer from 1 to 12, and in formulae S1-S4 one or more H-atoms in the radical (CH.sub.2).sub.n1 are optionally replaced by a methyl, ethyl, propyl, butyl, pentyl or hexyl group.

7. The LC medium according to claim 1, wherein the compounds of formula S are selected from the following subformulae ##STR00356## ##STR00357##

8. The LC medium according to claim 1, wherein said medium comprises one or more compounds selected from formulae CY and PY: ##STR00358## wherein a denotes 1 or 2, b denotes 0 or 1, ##STR00359## denotes ##STR00360## or ##STR00361## R.sup.1 and R.sup.2 each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH.sub.2 groups may each be replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are not linked directly to one another, Z.sup.x and Z.sup.y each, independently of one another, denote —CH.sub.2CH.sub.2—, —CH═CH—, —CF.sub.2O—, —OCF.sub.2—, —CH.sub.2O—, —OCH.sub.2—, —CO—O—, —O—CO—, —C.sub.2F.sub.4—, —CF═CF—, —CH═CH—CH.sub.2O— or a single bond, L.sup.1-4 each, independently of one another, denote F, Cl, OCF.sub.3, CF.sub.3, CH.sub.3, CH.sub.2F, CHF.sub.2.

9. The LC medium according to claim 1, wherein said medium further comprises one or more compounds of the following formula: ##STR00362## in which the individual radicals have the following meanings: ##STR00363## denotes ##STR00364## or ##STR00365## denotes ##STR00366## or ##STR00367## R.sup.3 and R.sup.4 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH.sub.2 groups may each be replaced by —O—, —CH═CH—, —CO—, —O—CO— or —CO—O— in such a way that O atoms are not linked directly to one another, Z.sup.y denotes —CH.sub.2CH.sub.2—, —CH═CH—, —CF.sub.2O—, —OCF.sub.2—, —CH.sub.2O—, —OCH.sub.2—, —CO—O—, —O—CO—, —C.sub.2F.sub.4—, —CF═CF—, —CH═CH—CH.sub.2O— or a single bond.

10. The LC medium according to claim 1, wherein R.sup.a-d are independently of each other straight chain or branched alkyl with 1 to 10 C atoms.

11. The LC medium according to claim 1, wherein R.sup.a-d are each methyl.

12. The LC medium according to claim 1, wherein A is optionally substituted by one or more groups L.sup.A.

13. The LC medium according to claim 1, wherein substituents L.sup.A are selected from F, and straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy, each having up to 12 C atoms and in which one or more H atoms may each optionally be replaced by F or Cl.

14. The LC medium of claim 8, wherein R.sup.1 and R.sup.2 each, independently of one another, denote alkyl or alkoxy having 1 to 6 C atoms.

15. The LC medium of claim 8, wherein Z.sup.x and Z.sup.y are each a single bond.

16. An LC display comprising an LC medium as defined in claim 1.

17. The LC display of claim 16, wherein said display is a VA, PSA, PS-VA, PA-VA, PALC, FFS, PS-FFS, IPS or PS-IPS display.

Description

EXAMPLES

Comparison Example 1

[0290] The nematic LC mixture N1 is formulated as follows.

TABLE-US-00005 PY-3-O2 16.50%  cl.p. 75.2° C. CY-3-O2 5.00% Δn 0.1079 CCY-3-O1 5.00% Δε −3.2 CCY-3-O2 2.50% ε.sub.|| 3.6 CCY-4-O2 8.00% K.sub.3/K.sub.1 1.10 CPY-2-O2 10.00%  V.sub.0 2.25 V CPY-3-O2 10.00%  γ.sub.1 93 mPa s CC-3-V 37.50%  BCH-32 5.50%

[0291] The mixture does not contain a quaterphenyl compound of formula Q.

Comparison Example 2

[0292] The nematic LC mixture N2 is formulated as follows.

TABLE-US-00006 PY-3-O2 13.50%  cl.p. 74.6° C. CY-3-O2 9.00% Δn 0.1082 CCY-3-O1 8.00% Δε −3.2 CCY-3-O2 3.00% ε.sub.|| 3.7 CCY-4-O2 3.00% K.sub.3/K.sub.1 1.12 CPY-2-O2 10.00%  V.sub.0 2.29 V CPY-3-O2 10.00%  γ.sub.1 94 mPa s CC-3-V 36.50%  BCH-32 6.50% PPGU-3-F 0.50%

Example 1

[0293] To 100% of the LC mixture N2 are added 0.005% (50 ppm) of a stabilizer of formula S2a to form mixture M1.

##STR00345##

Example 2

[0294] To 99.99% of the LC mixture N2 are added 0.01% (100 ppm) of a stabilizer of formula S2a to form mixture M2.

Example 3

[0295] To 99.975% of the LC mixture N2 are added 0.025% (250 ppm) of a stabilizer of formula S1a to form mixture M3.

##STR00346##

[0296] The LC mixture compositions are shown in Table 1.

TABLE-US-00007 TABLE 1 LC Mixture Composition PPGU-3-F Stabilizer S2a Stabilizer S1a Example LC Host (%) (ppm) (ppm) C1 N1 0 0 0 C2 N2 0.5 0 0 M1 N2 0.5 50 0 M2 N2 0.5 100 0 M3 N2 0.5 0 250

[0297] The mixture of example C1 is a comparison mixture which does not contain a quaterphenyl compound of formula Q1, and does not contain a stabilizer.

[0298] The mixture of example C2 is a comparison mixture which contains a quaterphenyl compound PPGU-3-F of formula Q1, but does not contain a stabilizer.

[0299] The mixtures of examples M1, M2 and M3 according to the invention contain both a quaterphenyl compound PPGU-3-F of formula Q1, and a stabilizer of formula S2a or S1a, respectively.

[0300] The mixtures were filled into test VA-VHR cells as described above, and the VHR values were measured before and after UV load, suntest and backlight load test, respectively, as follows:

[0301] For the UV load the test cells were exposed to a high pressure Hg lamp (300 nm ˜400 nm) with 50 mW/cm.sup.2 for 120 s (6J) and 600 s (30J).

[0302] For the suntest the test cells were exposed to a Xenon lamp (300 nm˜800 nm) with 765W/m.sup.2 for 1 hr.

[0303] For the backlight load test the test cells were exposed to an LED backlight unit as used in an LCD TV panel for 24 hrs, 168 hrs, 336 hrs, 500 hrs and 1000 hrs.

[0304] Table 2 shows the results of the UV load test for the mixtures of examples C1 and C2.

TABLE-US-00008 TABLE 2 VHR values after UV load C1 C2 VHR at 60° C. (%) VHR (%) Initial 99.3 99.3 After UV load (6J) 98.7 98.8 After UV load (30J) 96.7 97.1

[0305] From Table 2 it can be seen that mixture of example C2 with a quaterphenyl compound shows a slightly higher VHR value after UV load than the mixture of example C1 without a quaterphenyl compound.

[0306] This shows that the addition of the quaterphenyl to the mixture leads to an improved VHR.

[0307] Table 3 shows the results of the UV load test for the mixtures of examples C2, M1 and M2.

TABLE-US-00009 TABLE 3 VHR values after UV load C2 M1 M2 VHR at 60° C. (%) VHR (%) Initial 98.8 98.8 98.8 After UV load (6J) 97.6 98.5 98.3 After UV load (30J) 94.0 97.2 97.5

[0308] Table 4 shows the results of the suntest for the mixtures of examples C2, M1 and M2.

TABLE-US-00010 TABLE 4 VHR values after suntest C2 M1 M2 VHR at 60° C. (%) VHR (%) After suntest 91.8 96.2 96.8

[0309] Table 5 shows the results of the backlight load test for the mixtures of examples C2, M1 and M2.

TABLE-US-00011 TABLE 5 VHR values after backlight load C2 M1 M2 VHR at 60° C. (%) VHR (%) Initial 99.3 99.3 99.2 After 24 h 98.4 99.2 99.1 backlight load After 168 h 94.5 97.6 97.8 backlight load After 336 h 85.2 94.5 95.7 backlight load After 500 h 77.7 91.5 93.5 backlight load After 1000 h 64.1 81.7 87.7 backlight load

[0310] From Tables 3-5 it can be seen that the mixtures of examples M1 and M2 with a quaterphenyl compound of formula Q1 and a stabilizer of formula S2a show a significantly higher VHR value after UV load, suntest and backlight load, compared to the mixture of example C2 with a quaterphenyl compound of formula Q1, but without a stabilizer.

[0311] This shows that the addition of both a quaterphenyl of formula Q and a stabilizer of formula S to the mixture lead to an significantly improved VHR after UV load, suntest and backlight load.

[0312] Table 6 shows the results of the UV load test for the mixtures of examples C2 and M3.

TABLE-US-00012 TABLE 6 VHR values after UV load C2 M3 VHR at 60° C. (%) VHR (%) Initial 98.8 98.8 After UV load (6J) 97.3 98.4 After UV load (30J) 93.6 97.5

[0313] Table 7 shows the results of the suntest for the mixtures of examples C2 and M3.

TABLE-US-00013 TABLE 7 VHR values after suntest C2 M3 VHR at 60° C. (%) VHR (%) After suntest 92.6 97.2

[0314] From Tables 6 and 7 it can be seen that the mixture of example M3 with a quaterphenyl compound of formula Q1 and a stabilizer of formula S1 shows a significantly higher VHR value after UV load and suntest than the mixture of example C2 with a quaterphenyl compound of formula Q1, but without a stabilizer.

[0315] This shows that the addition of both a quaterphenyl of formula Q and a stabilizer of formula S to the mixture lead to an significantly improved VHR after UV load and suntest.

[0316] The entire disclosures of all applications, patents and publications, cited herein and of corresponding European Application No. EP 16170155.2, filed May 18, 2016 are incorporated by reference herein.

[0317] 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.

[0318] 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.

[0319] 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.