Low molecular weight polar compound for homogeneously aligning liquid crystal medium, and liquid crystal medium containing same

1. A liquid crystal medium-sealed between a pair of substrates subjected to neither alignment treatment nor an alignment film and having a transparent electrode formed on at least one of the substrates, wherein the liquid crystal medium contains a low molecular weight polar compound for homogeneously aligning the liquid crystal medium relative to the substrate, so that the homogeneous alignment of the liquid crystal medium relative to the substrate occurs spontaneously,

wherein the low molecular weight polar compound is represented by formula (2) or (3):

wherein, in formulas (2) and (3),

R 4 is hydrogen, halogen or alkyl having 1 to 20 carbons, and in R 4 , at least one —CH 2 — may be independently replaced by —O— or —S—, and at least one —(CH 2 ) 2 — may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by halogen,

P 1 , P 2 , P 3 and P 4 are independently a group represented by formula (Q-0) or straight-chain, branched-chain or cyclic alkyl having 1 to 25 carbons, and in P 1 , P 2 , P 3 and P 4 , at least one —CH 2 — nonadjacent to each other may be independently replaced by —N(—P 0 )—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a manner that N, O and/or S atoms are not directly connected to each other, at least one tertiary carbon (CH group) may be replaced by N, at least one hydrogen may be independently replaced by F or Cl, and at least one —(CH 2 ) 2 — may be independently replaced by —CH═CH— in which P 1 , P 2 , P 3 and P 4 contain one or more heteroatoms selected from N, S and/or O, and

P 0 is independently straight-chain, branched-chain or cyclic alkyl having 1 to 25 carbons, and in P 0 , at least one —CH 2 — nonadjacent to each other may be independently replaced by —N(—P 0 )—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a manner that N, O and/or S atoms are not directly connected to each other, at least one tertiary carbon (CH group) may be replaced by N, at least one hydrogen may be independently replaced by F or Cl, and at least one —(CH 2 ) 2 — may be independently replaced by —CH═CH— or —C≡C—, in which P 0 contains one or more heteroatoms selected from N, S and/or O, and

in formula (Q-0), R 1 , R 2 and R 3 are independently hydrogen, halogen or alkyl having 1 to 20 carbons, and in R 1 , R 2 and R 3 , at least one —CH 2 — may be independently replaced by —O— or —S—, and at least one —(CH 2 ) 2 — may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by halogen.

2. The liquid crystal medium according to claim 1 , wherein the low molecular weight compound has having a positive-phase negative-phase CV product of 1.3 or more.

3. A liquid crystal composition containing at least one low molecular weight polar compound represented by formula (2) or (3):

wherein, in formulas (2) and (3),

R 4 is hydrogen, halogen or alkyl having 1 to 20 carbons, and in R 4 , at least one —CH 2 — may be independently replaced by —O— or —S—, and at least one —(CH 2 ) 2 — may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by halogen,

P 1 , P 2 , P 3 and P 4 are independently a group represented by formula (Q-0) or straight-chain, branched-chain or cyclic alkyl having 1 to 25 carbons, and in P 1 , P 2 , P 3 and P 4 , at least one —CH 2 — nonadjacent to each other may be independently replaced by —N(—P 0 )—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a manner that N, O and/or S atoms are not directly connected to each other, at least one tertiary carbon (CH group) may be replaced by N, at least one hydrogen may be independently replaced by F or Cl, and at least one —(CH 2 ) 2 — may be independently replaced by —CH═CH— or —C≡C—, in which P 1 , P 2 , P 3 and P 4 contain one or more heteroatoms selected from N, S and/or O, and

P 3 is independently straight-chain, branched-chain or cyclic alkyl having 1 to 25 carbons, and in P 0 , at least one —CH 2 — nonadjacent to each other may be independently replaced by —N(—P 0 )—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a manner that N, O and of S atoms are not directly connected to each other, at least one tertiary carbon (CH group) may be replaced by N, at least one hydrogen may be independently replaced by F or Cl, and at least one —(CH 2 ) 2 — may be independently replaced by —CH═CH— or —C≡C—, in which P 0 contains one or more heteroatoms selected from N, S and/or O, and

in formula (Q-0), R 1 , R 2 and R 3 are independently hydrogen, halogen or alkyl having 1 to 20 carbons, and in R 1 , R 2 and R 3 , at least one —CH 2 — may be independently replaced by —O— or —S—, and at least one —(CH 2 ) 2 — may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by halogen.

4. The liquid crystal composition according to claim 3 , wherein a total positive-phase negative-phase CV product, which is a product of a positive-phase negative-phase CV product and a content of the low molecular weight polar compound, is 0.01 or more.

5. The liquid crystal composition according to claim 4 , wherein a ratio of the total positive-phase negative-phase CV product to a surface free energy of the substrate is 0.025 to 1.

6. The liquid crystal composition according to claim 3 , further containing at least one liquid crystal compound represented by any one of formulas (5) to (7):

wherein, in formulas (5) to (7),

R 13 is alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in R 13 , at least one —CH 2 — may be replaced by —O—, and at least one hydrogen may be replaced by fluorine;

X 11 is fluorine, chlorine, —OCF 3 , —OCHF 2 , —CF 3 , —CHF 2 , —CH 2 F, —OCF 2 CHF 2 or —OCF 2 CHFCF 3 ;

ring C 1 , ring C 2 and ring C 3 are independently 1,4-cyclohexylene, 1,4-phenylene in which at least one hydrogen may be replaced by fluorine, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl;

Z 14 , and Z 16 are independently a single bond, —(CH 2 ) 2 —, —CH═CH—, —C≡C—, —COO—, —CF 2 O—, —OCF 2 —, —CH 2 O— or —(CH 2 ) 4 —; and

L 11 and L 12 are independently hydrogen or fluorine.

7. The liquid crystal composition according to claim 3 , further containing a liquid crystal compound represented by formula (8):

wherein, in formula (8),

R 14 is alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in R 14 , at least one —CH 2 — may be replaced by —O—, and at least one hydrogen may be replaced by fluorine;

X 12 is —C≡N or —C≡C—C≡N;

ring D 1 is 1,4-cyclohexylene, 1,4-phenylene in which at least one hydrogen may be replaced by fluorine, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl;

Z 17 is a single bond, —(CH 2 ) 2 —, —C≡C—, —COO—, —CF 2 O—, —OCF 2 — or —CH 2 O—;

L 13 and L 14 are independently hydrogen or fluorine; and

i is 1, 2, 3 or 4.

8. The liquid crystal composition according to claim 3 , further containing at least one liquid crystal compound represented by any one of formulas (16) to (18):

wherein, in formulas (16) to (18),

R 11 and R 12 are independently alkyl having 1 to 10 carbons, alkoxy having 1 to 10 carbons, alkoxyalkyl having 2 to 10 carbons, alkenyl having 2 to 10 carbons or difluorovinyl;

ring B 1 , ring B 2 , ring B 3 and ring B 4 are independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; and

Z 11 , Z 12 and Z 13 are independently a single bond, —(CH 2 ) 2 —, —CH═CH—, —C≡C— or —COO—.

9. The liquid crystal composition according to claim 3 , further containing a polymerizable compound represented by formula (19):

wherein, in formula (19),

ring F and ring I are independently cyclohexyl, cyclohexenyl, phenyl, 1-naphthyl, 2-naphthyl, tetrahydropyran-2-yl, 1,3-dioxane-2-yl, pyrimidine-2-yl or pyridine-2-yl, and in the rings, at least one hydrogen may be independently replaced by halogen, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, or alkyl having 1 to 12 carbons in which at least one hydrogen is replaced by halogen;

ring G is 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, naphthalene-1,2-diyl, naphthalene-1,3-diyl, naphthalene-1,4-diyl, naphthalene-1,5-diyl, naphthalene-1,6-diyl, naphthalene-1,7-diyl, naphthalene-1,8-diyl, naphthalene-2,3-diyl, naphthalene-2,6-diyl, naphthalene-2,7-diyl, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyrimidine-2,5-diyl or pyridine-2,5-diyl, and in the rings, at least one hydrogen may be independently replaced by halogen, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, or alkyl having 1 to 12 carbons in which at least one hydrogen is replaced by halogen;

Z 22 and Z 23 are independently a single bond or alkylene having 1 to 10 carbons, and in Z 22 and Z 23 , at least one —CH 2 — may be independently replaced by —O—, —CO— or —COO—, and at least one —CH 2 CH 2 — may be independently replaced by —CH═CH—, —C(CH 3 )═CH— or —C(CH 3 )═C(CH 3 )—, and in the groups, at least one hydrogen may be replaced by fluorine or chlorine;

Q 1 , Q 2 and Q 3 are independently a polymerizable group;

Sp 1 , Sp 2 and Sp 3 are independently a single bond or alkylene having 1 to 10 carbons, and in Sp 1 , Sp 2 and Sp 3 , at least one —CH 2 — may be independently replaced by —O—, —COO—, —OCO— or —OCOO—, and at least one —CH 2 CH 2 — may be independently replaced by —CH═CH— or —C≡C—, and in the groups, at least one hydrogen may be independently replaced by fluorine or chlorine;

d is 0, 1 or 2; and

e, f and g are independently 0, 1, 2, 3 or 4, and a sum of e, f and g is 1 or more.

10. The liquid crystal composition according to claim 9 , wherein, in formula (19), Q 1 , Q 2 and Q 3 are independently a polymerizable group represented by any one of formulas (Q-1) to (Q-5):

wherein, in formulas (Q-1) to (Q-5),

M 1 , M 2 and M 3 are independently hydrogen, fluorine, alkyl having 1 to 5 carbons, or alkyl having 1 to 5 carbons in which at least one hydrogen is replaced by halogen.

11. The liquid crystal composition according to claim 9 , wherein the polymerizable compound represented by formula (19) is a polymerizable compound represented by any one of formulas (19-1) to (19-7):

wherein, in formulas (19-1) to (19-7),

L 21 , L 22 , L 23 , L 24 , L 25 , L 26 , L 27 and L 28 are independently hydrogen, fluorine or methyl;

Sp 1 , Sp 2 and Sp 3 are independently a single bond or alkylene having 1 to 10 carbons, and in Sp 1 , Sp 2 and Sp 3 , at least one —CH 2 — may be independently replaced by —O—, —COO—, —OCO— or —OCOO—, and at least one —(CH 2 ) 2 — may be independently replaced by —CH═CH— or —C≡C—, and in the groups, at least one hydrogen may be independently replaced by fluorine or chlorine; and

Q 4 , Q 5 and Q 6 are independently a polymerizable group represented by any one of formulas (Q-1) to (Q-3), in which M 1 , M 2 and M 3 are independently hydrogen, fluorine, alkyl having 1 to 5 carbons, or alkyl having 1 to 5 carbons in which at least one hydrogen is replaced by halogen:

12. The liquid crystal composition according to claim 3 , further containing at least one selected from a polymerization initiator, a polymerization inhibitor, an optically active compound, an antioxidant, an ultraviolet light absorber, a light stabilizer, a heat stabilizer and an antifoaming agent.