Polymerizable compound, polymerizable composition and liquid crystal display device

A polymerizable compound, represented by formula (1):

• wherein in formula (1),
• P1, P2, P3 and P4 are a polymerizable group;
• S1, S2, S3 and S4 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene, at least one —CH2— may be replaced by —O—, —COO—, —OCO— or —OCOO—, at least one —CH2—CH2— may be replaced by —CH═CH— or —C≡C—, and at least one hydrogen may be replaced by fluorine or chlorine;
• a1, a3, and a4 are independently 0, 1, 2, 3 or 4, a2 is 1, 2, 3 or 4, and a sum of a1, a2, a3 and a4 is 3 to 10;
• ring A1 and ring A4 are independently phenyl, pyrimidyl, pyridyl, naphthyl, cyclohexyl, cyclohexenyl, tetrahydropyranyl or 1,3-dioxanyl, and in the rings, at least one hydrogen may be replaced by halogen, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkyl having 1 to 12 carbons in which at least one hydrogen is replaced by halogen, or alkoxy having 1 to 12 carbons in which at least one hydrogen is replaced by halogen;
• ring A2 and ring A3 are independently 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 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, 1,4-cyclohexylene, 1,4-cyclohexenylene, tetrahydropyran-2,5-diyl or 1,3-dioxane-2,5-diyl, and in the rings, at least one hydrogen may be replaced by halogen, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkyl having 1 to 12 carbons in which at least one hydrogen is replaced by halogen, or alkoxy having 1 to 12 carbons in which at least one hydrogen is replaced by halogen;
• Z1, Z2 and Z3 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene, at least one —CH2— may be replaced by —O—, —CO—, —COO— or —OCO—, with a proviso that a total number of —COO— and —OCO— in Z1, Z2 and Z3 is 0 or 1, at least one —CH2—CH2— may be replaced by —CH═CH—, —C(CH3)═CH—, —CH═C(CH3)— or —C(CH3)═C(CH3)—, and at least one hydrogen may be replaced by fluorine or chlorine;
• and
• b1 is 0 or 1.