Method of reducing ODF mura in polymer stabilised liquid crystal displays
The present invention relates to a method of reducing ODF mura in liquid crystal (LC) displays of the polymer sustained alignment (PSA) type and to PSA LC displays made by this method.
1. A method of reducing the One Drop Filling (ODF) mura in a liquid crystal display (LCD) of the polymer stabilised alignment (PSA) mode, comprising providing or using in the PSA display an LC medium, comprising
a polymerisable component A) comprising 0.005 to 0.02% of a first polymerisable compound and 0.2 to 0.3% of a second polymerisable compound, wherein the first polymerisable compound has faster polymerisation speed than the second polymerisable compound, the first polymerisable compound is one or more compounds of formulae F1-F6, and the second polymerisable compound is one or more compounds of formulae S1-S3, and
a liquid-crystalline component B), comprising one or more mesogenic or liquid-crystalline compounds
in which
P each, independently, is a polymerisable group,
Sp each, independently, is a spacer group or a single bond,
Sp′ is a spacer group,
L each, independently, is 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,
R a , R b each, independently, is -Sp-P, -Sp′(P) 2 , H or one of the meanings given for L,
r is 0, 1, 2, 3 or 4,
s is 0, 1, 2 or 3, and
t is 0, 1 or 2.
2. The method of claim 1 , wherein in the one or more compounds of formulae F1-F6 and S1-S3 the group P denotes CH 2 ═CW 1 —CO—O—, wherein W 1 is H, F, CF 3 or alkyl having 1 to 5 C atoms.
3. The method of claim 1 , wherein the one or more compounds of formulae F1-F6 are selected from compounds of the following formulae
wherein
P each, independently, is a polymerisable group,
Sp each, independently, is a spacer group or a single bond,
Sp′ is a spacer group,
L, L′ each, independently, is 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,
r is 0, 1, 2, 3 or 4,
s is 0, 1, 2 or 3, and
t is 0, 1 or 2.
4. The method according to claim 1 , wherein the one or more compounds of formulae S1-S3 are selected from compounds of the following formulae
wherein
P each, independently, is a polymerisable group,
Sp′ is a spacer group,
L′ is F, Cl, CN or straight-chain or branched, optionally mono- or poly-fluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms.
5. The method according to claim 1 , wherein in the one or more compounds of formulae F1-F6 and S1-S3 the group Sp′, and those groups Sp that are not a single bond, each independently, denote —(CH 2 ) p1 —, —(CH 2 ) p1 —O—, —(CH 2 ) p1 —O—CO—, —(CH 2 ) p1 —CO—O—, or —(CH 2 ) p1 —O—CO—O—, in which p1 denotes an integer from 1 to 6, and wherein these groups Sp′ and Sp that are not a single bond are linked to the polymerisable group P such that two O-atoms are not directly adjacent to each other.
6. The method according to claim 1 , wherein in the one or more compounds of formula F1-F6 and S1-S3 the group L′ denotes F.
7. The method according to claim 1 , wherein the LC method comprises 0.3% of the second polymerisable compound.
8. The method according to claim 1 , wherein component B) comprises one or more compounds of formulae AN and/or AY:
in which
each, independently, is
R A1 is alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z denotes cyclohexenyl, also one of the meanings of R A2 ,
R A2 is alkyl having 1 to 12 C atoms, in which one or two non-adjacent CH 2 groups may 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 x is —CH 2 CH 2 —, —CH═CH—, —CF 2 O—, —OCF 2 —, —CH 2 O—, —OCH 2 —, —CO—O—, —O—CO—, —C 2 F 4 —, —CF═CF—, —CH═CH—CH 2 O—, or a single bond,
L 1-4 each, independently, is H, F, Cl, OCF 3 , CF 3 , CH 3 , CH 2 F or CHF 2 H,
x 1 or 2, and
z 0 or 1.
9. The method according to claim 1 , wherein component B) comprises one or more compounds of formulae CY and/or PY:
in which
a denotes 1 or 2,
b denotes 0 or 1,
R 1 and R 2 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which one or two non-adjacent CH 2 groups may 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 x denotes —CH═CH—, —CH 2 O—, —OCH 2 —, —CF 2 O—, —OCF 2 —, —O—, —CH 2 —, —CH 2 CH 2 — or a single bond,
L 1-4 each, independently of one another, denote F, Cl, OCF 3 , CF 3 , CH 3 , CH 2 F, or CHF 2 .
10. The method according to claim 1 , wherein component B) comprises one or more compounds of formulae ZK and/or DK:
in which
each, independently, denotes
and
R 3 and R 4 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which one or two non-adjacent CH 2 groups may 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 y denotes —CH 2 CH 2 —, —CH═CH—, —CF 2 O—, —OCF 2 —, —CH 2 O—, —OCH 2 —, —COO—, —OCO—, —C 2 F 4 —, —CF═CF— or a single bond,
R 5 and R 6 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which one or two non-adjacent CH 2 groups may be replaced by —O—, —CH═CH—, —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 method according to claim 1 , wherein the polymerisable compounds of component A) are polymerised.
12. A method of manufacturing an LCD of the PSA mode, comprising
a) dispensing an array of droplets ( 2 ) of an LC medium comprising components A) and B) on a first substrate ( 1 ),
wherein component A) is polymerisable and comprises 0.005 to 0.02% of a first polymerisable compound and 0.2 to 0.3% of a second polymerisable compound, wherein the first polymerisable compound has faster polymerisation speed than the second polymerisable compound, the first polymerisable compound is one or more compounds of formulae F 1 -F 6 , and the second polymerisable compound is one or more compounds of formulae S1-S3, and
component B) is liquid-crystalline and comprises one or more mesogenic or liquid-crystalline compounds
in which
P each, independently, is a polymerisable group,
Sp each, independently, is a spacer group or a single bond,
Sp′ is a spacer group,
L each, independently, is 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,
R a , R b each, independently, is -Sp-P, -Sp′(P) 2 , H or one of the meanings given for L,
r is 0, 1, 2, 3 or 4,
s is 0, 1, 2 or 3, and
t is 0, 1 or 2;
b) providing a second substrate ( 4 ) on top of the surface of the first substrate ( 1 ) that is covered by the LC medium, optionally under vacuum condition, causing the droplets ( 2 ) of the LC medium to spread and form a continuous layer between the first substrate ( 1 ) and the second substrate ( 4 ), and
c) exposing the LC medium to UV radiation that causes photopolymerisation of the polymerisable compounds of component A).
13. The method according to claim 12 , wherein the first and second substrates ( 1 , 4 ) are glass substrates.
14. The method according to claim 12 , wherein the first substrate ( 1 ) is equipped with a first electrode structure and the second substrate ( 4 ) is equipped with a second electrode structure.
15. The method according to claim 12 , wherein one of the two substrates ( 1 , 4 ) is equipped with a first and a second electrode structure, and the other of the two substrates ( 1 , 4 ) is not equipped with an electrode structure.
16. The method according to claim 12 , wherein the first substrate ( 1 ) and the second substrate ( 4 ) are each equipped with an alignment layer that is in contact with the LC medium ( 2 ).
17. The method according to claim 12 , wherein a sealant material ( 3 ) is provided between the first substrate ( 1 ) and the second substrate ( 4 ), and the first substrate ( 1 ) and second substrate ( 4 ) are glued together by curing the sealant material ( 3 ).
18. The method according to claim 17 , wherein the sealant material ( 3 ) is cured by exposure to photoradiation, wherein the photoradiation is such that it does not cause polymerisation of the polymerisable component A) of the LC medium, and/or the LC medium is protected from the photoradiation for curing the sealant material ( 3 ).
19. The method according to claim 18 , wherein the LC medium is protected from the photoradiation for curing the sealant material ( 3 ) by a photomask.
20. The method according to claim 12 , wherein in step c) a voltage is applied to the first and second electrode.
21. An LC display prepared by a method according to claim 12 .
22. The LC display of claim 21 , which is a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-posi-VA or PS-TN display.
23. An LC medium comprising components A) and B), wherein
component A) is polymerizable and comprises 0.005 to 0.02% of a first polymerisable compound and 0.2 to 0.3% of a second polymerisable compound, wherein the first polymerisable compound has faster polymerisation speed than the second polymerisable compound, the first polymerisable compound is one or more compounds of formulae F1-F6, and the second polymerisable compound is one or more compounds of formulae S1-S3, and
component B) is a liquid-crystalline and comprises one or more mesogenic or liquid-crystalline compounds
in which
P each, independently, is a polymerisable group,
Sp each, independently, is a spacer group or a single bond,
Sp′ is a spacer group,
L each, independently, is 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,
R a , R b each, independently, is -Sp-P, -Sp′(P) 2 , H or one of the meanings given for L,
r is 0, 1, 2, 3 or 4,
s is 0, 1, 2 or 3, and
t is 0, 1 or 2.
24. A process of preparing an LC medium comprising components A) and B) according to claim 23 , comprising mixing component B) with the one or more first and second polymerisable compounds or with polymerisable component A), and optionally with further LC compounds and/or additives.
25. The method of claim 1 , wherein component A) comprises either one or more compounds of formulae F2-F6 and/or one or more compounds of formulae S2-S3.