Liquid Crystal Medium

Abstract

The present invention relates to a liquid crystalline medium comprising a polymerizable compound, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in liquid crystalline displays, especially in a liquid crystalline display of the polymer sustained alignment (PSA) type, and to a liquid crystalline display, especially a PSA display, comprising it.

Claims

1. A liquid crystalline medium comprising a polymerizable component A) comprising one or more polymerizable compounds, and a liquid-crystalline component B), hereinafter referred to as LC host mixture, comprising one or more mesogenic or liquid-crystalline compounds, wherein component B) comprises from 0.01 to 3% of one or more compounds of formula A ##STR00338## in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: R.sup.1, R.sup.2 are alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated, L.sup.1, L.sup.2, L.sup.3 are F or Cl.

2. The liquid crystalline medium of claim 1, wherein the compounds of formula A are of the formula: ##STR00339## wherein alkyl denotes a straight-chain alkyl radical having 1-6 C atoms, and n is 0 or 1.

3. The liquid crystalline medium of claim 1, wherein component B) comprises from 0.05 to 2% of compounds of formula A or A1.

4. The liquid crystalline medium according to claim 1, wherein component A) comprises one or more polymerizable compounds of formula I
R.sup.a-B.sup.1-(Z.sup.b-B.sup.2).sub.m-R.sup.bI in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: R.sup.a and R.sup.b are P, P-Sp-, H, F, Cl, Br, I, CN, NO.sub.2, NCO, NCS, OCN, SCN, SF.sub.5 or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH.sub.2 groups may each be replaced, independently of one another, by C(R.sup.0)C(R.sup.00), CC, N(R.sup.00), O, S, CO, COO, OCO, OCOO in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I, CN, P or P-Sp-, where, if B.sup.1 and/or B.sup.2 contain a saturated C atom, R.sup.a and/or R.sup.b may also denote a radical which is spiro-linked to this saturated C atom, wherein at least one of the radicals R.sup.a and R.sup.b denotes or contains a group P or P-Sp-, P is a polymerizable group, Sp is a spacer group or a single bond, B.sup.1 and B.sup.2 are an aromatic, heteroaromatic, alicyclic or heterocyclic group, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L, Z.sup.b is O, S, CO, COO, OCO, OCOO, 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, CHCH, CFCF, CC, CHCHOCO, OCOCHCH, CR.sup.0R.sup.00 or a single bond, R.sup.0 and R.sup.00 is H or alkyl having 1 to 12 C atoms, m is 0, 1, 2, 3 or 4, n1 is 1, 2, 3 or 4, L is P, P-Sp-, OH, CH.sub.2OH, F, Cl, Br, I, CN, NO.sub.2, NCO, NCS, OCN, SCN, C(O)N(R.sup.x).sub.2, C(O)Y.sup.1, C(O)R.sup.x, N(R.sup.x).sub.2, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, Y.sup.1 is halogen, and R.sup.x is P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by O, S, CO, COO, OCO, OCOO in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, P or P-Sp-, an optionally substituted aryl or aryloxy group having 6 to 40 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms.

5. The liquid crystalline medium according to claim 4, wherein the polymerizable compounds of formula I B.sup.1 and B.sup.2 each, independently of one another, are 1,4-phenylene, 1,3-phenylene, naphthalene-1,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7-diyl, 9,10-dihydro-phenanthrene-2,7-diyl, anthracene-2,7-diyl, fluorene-2,7-diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1,4-diyl, in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by 0 and/or S, 1,4-cyclohexenylene, bicycle[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, piperidine-1,4-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, where all these groups may be unsubstituted or mono- or polysubstituted by L.

6. The liquid crystalline medium according to claim 4, wherein the polymerizable compounds of formula I are: ##STR00340## ##STR00341## ##STR00342## ##STR00343## in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: P.sup.1, P.sup.2, P.sup.3 are a vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane or epoxy group, Sp.sup.1, Sp.sup.2, Sp.sup.3 are a single bond or a spacer group where, in addition, one or more of the radicals P.sup.1-Sp.sup.1-, P.sup.1-Sp.sup.2- and P.sup.3-Sp.sup.3- may also denote R.sup.aa, with the proviso that at least one of the radicals P.sup.1-Sp.sup.1-, P.sup.2-Sp.sup.2 and P.sup.3-Sp.sup.3- present is different from R.sup.aa, R.sup.aa is H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH.sub.2 groups may each be replaced, independently of one another, by C(R.sup.0)C(R.sup.00), CC, N(R.sup.0), O, S, CO, COO, OCO, OCOO in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, CN or P.sup.1-Sp.sup.1-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms), R.sup.0, R.sup.00 H or alkyl having 1 to 12 C atoms, R.sup.y and R.sup.z H, F, CH.sub.3 or CF.sub.3, X.sup.1, X.sup.2, X.sup.3 COO, OCO or a single bond, Z.sup.1 O, CO, C(R.sup.yR.sup.z) or CF.sub.2CF.sub.2, Z.sup.2, Z.sup.3 OCO, CH.sub.2O, OCH.sub.2, OCF.sub.2 or (CH.sub.2).sub.n, where n is 2, 3 or 4, L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, L, L H, F or Cl, r 0, 1, 2, 3 or 4, s 0, 1, 2 or 3, t 0, 1 or 2, x 0 or 1.

7. The liquid crystalline medium according to claim 4, wherein the polymerizable compounds of formula I are of the formulae M2, M13, M17, M22, M23, M24 or M30.

8. The liquid crystalline medium according to claim 1, wherein the component B) comprises one or more compounds of formulae AN or AY which are different from formula A: ##STR00344## in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: ##STR00345## R.sup.A1 is alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z denotes cyclohexenyl, also can have one of the meanings of R.sup.A2, R.sup.A2 is alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH.sub.2 groups may be replaced by O, CHCH, CO, OCO or COO in such a way that O atoms are not linked directly to one another, Z.sup.x is 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, CHCHCH.sub.2O, or a single bond, L.sup.1-4 is H, F, Cl, OCF.sub.3, CF.sub.3, CH.sub.3, CH.sub.2F or CHF.sub.2H, x is 1 or 2, and z is 0 or 1.

9. The liquid crystalline medium according to claim 1, wherein the component B) comprises one or more compounds of the formulae CY or PY: ##STR00346## in which the individual radicals have the following meanings: a denotes 1 or 2, b denotes 0 or 1, ##STR00347## denotes ##STR00348## 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 be replaced by O, CHCH, CO, OCO or COO in such a way that O atoms are not linked directly to one another, Z.sup.x denotes CHCH, CH.sub.2O, OCH.sub.2, CF.sub.2O, OCF.sub.2, O, CH.sub.2, CH.sub.2CH.sub.2 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.

10. The liquid crystalline medium according to claim 1, wherein component B) comprises one or more compounds of formulae ZK or DK: ##STR00349## in which the individual radicals on each occurrence, identically or differently, have the following meanings: ##STR00350## denotes ##STR00351## denotes ##STR00352## denotes ##STR00353## and 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 be replaced by O, CHCH, CO, OCO or COO in such a way that O atoms are not linked directly to one another, Z.sup.y denotes 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 a single bond, R.sup.5 and R.sup.6 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 be replaced by O, CHCH, CO, OCO or COO in such a way that O atoms are not linked directly to one another, and e denotes 1 or 2.

11. The liquid crystalline medium according to claim 1, wherein component B) comprises one or more compounds of formula PY2: ##STR00354## in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms.

12. The liquid crystalline medium according claim 1, wherein component B) comprises one or more compounds of formula BF1: ##STR00355## in which R and R each, independently of one another, denote a straight-chain alkyl or alkoxy radical having 1-7 C atoms.

13. The liquid crystalline medium according to claim 1, wherein the polymerizable compounds are polymerized.

14. An liquid crystalline display comprising a liquid crystalline medium as defined in claim 1.

15. The liquid crystalline display of claim 14, which is a PSA display.

16. The liquid crystalline display of claim 15, which is a PS-VA, PS-IPS, PS-FFS or PS-UB-FFS display.

17. The liquid crystalline display of claim 15, comprising two substrates, at least one which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and located between the substrates a layer of the liquid crystalline medium wherein the polymerizable compounds are polymerized between the substrates of the display.

18. A process for the production of a liquid crystalline display according to claim 17, comprising providing the liquid crystalline medium between the substrates of the display, and polymerizing the polymerizable compounds.

19. A process of preparing an LC medium according to claim 1, comprising mixing one or more compounds of formula A or an LC component B), with one or more of the polymerizable compounds and optionally with further liquid crystalline compounds and/or additives.

Description

LC Host Mixtures

COMPARISON EXAMPLE 1

[0418] The nematic LC host mixture NC1 is formulated as follows.

TABLE-US-00005 CY-3-O2 15.00% cl.p. 75.5 C. CCY-4-O2 9.50% n 0.1075 CCY-5-O2 5.00% 3.0 CPY-2-O2 9.00% .sub. 3.5 CPY-3-O2 9.00% K.sub.11 12.9 CCH-34 9.00% K.sub.33 13.0 CCH-23 22.00% .sub.1 115 mPa s PYP-2-3 7.00% .sub.1/K.sub.33 8.85 PYP-2-4 7.50% PCH-301 7.00%

[0419] The mixture does not contain a compound of formula A.

COMPARISON EXAMPLE 2

[0420] The nematic LC host mixture NC2 is formulated as follows.

TABLE-US-00006 B-2O-O5 4.00% cl.p. 75.0 C. BCH-32 3.00% n 0.1096 CC-3-V1 9.00% 3.09 CCH-301 2.00% .sub. 3.5 CCH-34 8.00% K.sub.11 13.6 CCH-35 8.00% K.sub.33 16.3 CCP-V2-1 5.00% .sub.1 109 mPa s CCY-3-O2 1.50% .sub.1/K.sub.33 6.69 CPY-2-O2 8.00% CPY-3-O2 8.00% CY-3-O2 6.50% PCH-301 17.50% PY-3-O2 9.50% CLY-3-O2 10.00%

[0421] The mixture contains 10% of compound CLY-3-O2 of formula A.

COMPARISON EXAMPLE 3

[0422] The nematic LC host mixture NC3 is formulated as follows.

TABLE-US-00007 B-2O-O5 4.00% cl.p. 74.4 C. BCH-32 8.00% n 0.1087 CC-3-V1 9.00% 3.08 CCH-301 2.00% .sub. 3.6 CCH-34 8.00% K.sub.11 14.3 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.00% .sub.1 107 mPa s CCY-3-O2 4.00% .sub.1/K.sub.33 6.48 CCY-4-O2 2.50% CPY-3-O2 2.00% CY-3-O2 8.50% PCH-301 11.00% PY-3-O2 16.00% CLY-3-O2 10.00%

[0423] The mixture contains 10% of compound CLY-3-O2 of formula A.

COMPARISON EXAMPLE 4

[0424] The nematic LC host mixture NC4 is formulated as follows.

TABLE-US-00008 B-2O-O5 4.00% cl.p. 74.1 C. BCH-32 8.00% n 0.1090 CC-3-V1 9.00% 3.09 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.2 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 109 mPa s CCY-3-O2 11.00% .sub.1/K.sub.33 6.61 CPY-3-O2 7.00% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50%

[0425] The mixture does not contain a compound of formula A.

COMPARISON EXAMPLE 5

[0426] The nematic LC host mixture NC5 is formulated as follows.

TABLE-US-00009 CC-3-V 15.00% cl.p. 74.4 C. CC-3-V1 9.00% n 0.1086 CCH-23 8.00% 3.2 CCH-34 7.50% .sub. 3.5 CCY-3-O2 10.00% K.sub.11 14.3 CCY-5-O2 8.00% K.sub.33 15.7 CPY-2-O2 3.00% .sub.1 102 mPa s CPY-3-O2 8.50% .sub.1/K.sub.33 6.50 CY-3-O2 7.00% PY-3-O2 16.00% PYP-2-3 8.00%

[0427] The mixture does not contain a compound of formula A.

EXAMPLE 1

[0428] The nematic LC host mixture N1 is formulated as follows.

TABLE-US-00010 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1088 CC-3-V1 9.00% 3.10 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.1 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 109 mPa s CCY-3-O2 11.49% .sub.1/K.sub.33 6.61 CPY-3-O2 6.50% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50% CLY-3-O2 0.01%

[0429] The mixture contains 0.01% of compound CLY-3-O2 of formula A.

EXAMPLE 2

[0430] The nematic LC host mixture N2 is formulated as follows.

TABLE-US-00011 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1085 CC-3-V1 9.00% 3.09 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.2 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 109 mPa s CCY-3-O2 11.45% .sub.1/K.sub.33 6.61 CPY-3-O2 6.50% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50% CLY-3-O2 0.05%

[0431] The mixture contains 0.05% of compound CLY-3-O2 of formula A.

EXAMPLE 3

[0432] The nematic LC host mixture N3 is formulated as follows.

TABLE-US-00012 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1088 CC-3-V1 9.00% 3.10 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.2 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 109 mPa s CCY-3-O2 11.40% .sub.1/K.sub.33 6.61 CPY-3-O2 6.50% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50% CLY-3-O2 0.10%

[0433] The mixture contains 0.10% of compound CLY-3-O2 of formula A.

EXAMPLE 4

[0434] The nematic LC host mixture N4 is formulated as follows.

TABLE-US-00013 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1089 CC-3-V1 9.00% 3.10 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.1 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 109 mPa s CCY-3-O2 11.00% .sub.1/K.sub.33 6.61 CPY-3-O2 6.50% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50% CLY-3-O2 0.50%

[0435] The mixture contains 0.5% of compound CLY-3-O2 of formula A.

EXAMPLE 5

[0436] The nematic LC host mixture N5 is formulated as follows.

TABLE-US-00014 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1094 CC-3-V1 9.00% 3.08 CCH-301 2.00% .sub. 3.6 CCH-34 9.00% K.sub.11 14.2 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.50% .sub.1 108 mPa s CCY-3-O2 10.50% .sub.1/K.sub.33 6.55 CPY-3-O2 6.50% CY-3-O2 10.00% PCH-301 9.00% PY-3-O2 15.50% CLY-3-O2 1.00%

[0437] The mixture contains 1.00% of compound CLY-3-O2 of formula A.

EXAMPLE 6

[0438] The nematic LC host mixture N6 is formulated as follows.

TABLE-US-00015 B-2O-O5 4.00% cl.p. 74.2 C. BCH-32 8.00% n 0.1091 CC-3-V1 9.00% 3.09 CCH-301 2.00% .sub. 3.6 CCH-34 8.00% K.sub.11 14.5 CCH-35 7.00% K.sub.33 16.5 CCP-3-1 8.00% .sub.1 108 mPa s CCP-V2-1 5.00% .sub.1/K.sub.33 6.55 CCY-3-O2 10.50% CPY-3-O2 2.50% CY-3-O2 11.50% PCH-301 5.50% PY-3-O2 18.00% CLY-3-O2 1.00%

[0439] The mixture contains 1.00% of compound CLY-3-O2 of formula A.

Polymerizable Mixtures

[0440] Polymerizable mixtures are prepared by adding reactive mesogen M1 to each of nematic LC host mixtures NC1-NC5 and N1-N6, respectively, at a concentration of 0.2-0.35% by weight.

##STR00337##

[0441] The compositions of the polymerizable mixtures are shown in Table 1 below.

TABLE-US-00016 TABLE 1 Polymerizable Mixture Compositions Concentration of Concentration CLY-3-O2 (%) in of Mixture No. LC Host LC Host* M1 (%)** C1 NC1 0 0.20 C2 NC2 10.00 0.30 C2a NC2 10.00 0.35 C3 NC3 10.00 0.30 C3a NC3 10.00 0.35 C4 NC4 0 0.30 C5 NC5 0 0.30 P1 N1 0.01 0.30 P2 N2 0.05 0.30 P3 N3 0.1 0.30 P3a N3 0.1 0.35 P4 N4 0.5 0.30 P5 N5 1.0 0.30 P5a N5 1.0 0.35 P6 N6 1.0 0.35 *The % values of CLY-3-O2 refer to the host mixture without reactive mesogen M1. The concentration in % of CLY-3-O2 in the final polymerizable mixture, which additionally contains 0.20-0.35% of M1, is therefore slightly lower (for example as in mixture P7 below). **The % values of M1 refer to the final polymerizable mixture.

EXAMPLE P7

[0442] The polymerizable mixture P7 is formulated as follows.

TABLE-US-00017 B-2O-O5 3.97% cl.p. 74.5 C. BCH-32 7.95% n 0.1104 CC-3-V1 8.94% 3.07 CCH-301 1.99% .sub. 3.6 CCH-34 7.95% K.sub.33 16.4 CCH-35 6.95% .sub.1 111 mPa s CCP-3-1 7.95% CCP-V2-1 4.98% CCY-3-O2 10.43% CPY-3-O2 2.48% CY-3-O2 11.43% PCH-301 5.46% PY-3-O2 17.88% CLY-3-O2 0.99% PPGU-3-F 0.30% M1 0.35%

USE EXAMPLES

VHR, Reliability

[0443] The VHR values of the polymerizable LC media are measured with and without contact with a black matrix (BM) material. The experiment is carried out as follows:

[0444] The polymerizable LC medium is contacted with BM powder material extracted from a BM coated substrate at the rate of 100 to 0.8. The resultant sample is heated at 100 C. for 2 hours. The sample is filtered through a membrane filter and is introduced into VA-VHR test cells which comprise an unrubbed VA-polyimide alignment layer. The VHR value is determined before and after UV exposure at 1 V, 60 Hz, 64 s pulse (measuring instrument: Autronic-Melchers VHRM-105).

[0445] The VHR values are shown in Table 2.

TABLE-US-00018 TABLE 2 VHR values VHR (%) C1 C2 C3 C4 P1 P2 P3 P4 P5 No BM UV 0 min 98.8 98.3 98.5 98.4 98.3 98.4 98.4 98.4 98.7 contact UV 20 min 98.1 95.6 95.1 97.8 97.8 97.9 98.0 97.9 98.0 UV 40 min 98.1 94.7 93.8 97.9 97.9 97.8 97.9 97.8 97.8 Contact UV 0 min 98.5 97.3 97.4 97.6 97.5 97.4 97.8 97.8 98.0 with BM UV 20 min 92.2 95.1 94.7 95.4 95.9 96.8 96.9 97.3 97.2 UV 40 min 83.8 93.8 93.1 73.6 77.9 86.9 90.8 96.6 96.7 VHR (%) C1 C2a C5 P6 No BM UV 0 min 98.2 97.2 97.9 97.1 contact UV 20 min 98.3 96.1 97.7 97.4 UV 40 min 98.3 95.7 96.8 97.5 Contact UV 0 min 97.7 92.7 96.2 94.2 with BM UV 20 min 90.7 94.7 74.0 95.8 UV 40 min 83.2 93.8 53.1 93.0

[0446] From Table 2 it can be seen that the mixtures P1-P6 according to the present invention, which contain a small amount of the compound CLY-3-O2 of formula A, maintain a relatively high VHR value after UV exposure, either with or without being in contact with the BM material.

[0447] Compared thereto, mixtures C1, C4 and C5 without compound CLY-3-O2 of formula A show a stronger decrease of the VHR after UV exposure when being in contact with the BM material, while mixtures C2, C2a and C3, which contain approx. 10% of compound CLY-3-O2 of formula A, show a stronger decrease of the VHR after UV exposure without contact with the BM material.

[0448] Therefore, mixtures P1-P6 are best suitable for maintaining a high VHR after UV exposure either with or without contact with the BM material.

Pretilt Angle

[0449] Polymerizable mixtures according to the invention and polymerizable comparison mixtures are each inserted into a VA e/o test cell. The test cells comprise a VA-polyimide alignment layer (JALS-2096-R1) which is rubbed antiparallel. The LC-layer thickness d is approx. 4 m.

[0450] The pretilt angle is determined after UV irradiation with 50 mW/cm.sup.2 for 120s (6J) by a crystal rotation experiment (Autronic-Melchers TBA-105).

[0451] The pretilt angles are shown in Table 3.

TABLE-US-00019 TABLE 3 Pretilt angles C1 C2 C2a C3a C4 C5 P3 P3a P5 P5a pretilt () 86.2 87.6 86.8 87.1 86.6 84.6 86.7 86.1 87.2 86.7 C5 C2a P6 pretilt () 84.6 87.2 86.6

[0452] From Table 3 it can be seen that, independently of the RM concentration, the mixtures P3, P5 and P6 according to the present invention, which contain a small amount of the compound CLY-3-O2 of formula A, show a tilt angle which is better than that of comparative mixtures C2 and C3 with approx. 10% of compound CLY-3-O2, and similar to comparative mixtures C1, C4 and C5 without compound CLY-3-O2.

Residual RM

[0453] In order to determine the polymerization rate, the residual content of unpolymerized RM (in % by weight) in the test cells is measured by HPLC after polymerization in the test cell by UV exposure for 80 min at 60 C. using a fluorescent UV lamp type C (305 nm355 nm). For this purpose the polymerized mixture is then rinsed out of the test cell using MEK (methyl ethyl ketone) and measured.

[0454] The residual concentration of the RM in the mixture after 40 min and 80 min UV irradiation is shown in Table 4.

TABLE-US-00020 TABLE 4 Residual RM content RM (%) C1 C2 C2a C3a C4 C5 P3 P3a P5 P5a UV 40 min 0.0000 0.0433 0.0479 0.0541 0.0088 0.0044 0.0155 0.0121 0.0267 0.0240 UV 80 min 0.0000 0.0140 0.0134 0.0130 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 RM (%) C5 C2a P6 UV 40 min 0.0015 0.0444 0.0322 UV 80 min 0.0000 0.0160 0.0084

[0455] From Table 4 it can be seen that, independently of the RM concentration, the mixtures P3, P5 and P6 according to the present invention, which contain a small amount of the compound CLY-3-O2 of formula A, show a complete polymerization with low amount of residual RM, which is lower than that of comparative mixtures C2 and C3 with approx. 10% of compound CLY-3-O2, and similar to comparative mixtures C1, C4 and C5 without compound CLY-3-O2.

[0456] 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.

[0457] 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.