Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element having thereof

A liquid crystal alignment, comprising:

• a polymer composition (A), synthesized by reacting a mixture that includes a tetracarboxylic dianhydride component (a) and a diamine component (b);
• and
• a solvent (B);
• and
• wherein the diamine component (b) includes at least one diamine compound (b-1) having a structure of formula (I), at least one diamine compound (b-2) having a group consisting of a structure of formula (II) to (III) to and an other diamine compound (b-3):
• in the formula (I), B1 is an alkylene group of 1 to 6 carbons;
• B2 is
• B3 is an alkyl group of 1 to 6 carbons, an alkoxy group of 1 to 6 carbons, an alkenyl group of 1 to 6 carbons, an aryl group of 6 to 20 carbons or an aralkyl group of 7 to 20 carbons;
• in the formula (II), B2 is the same as above;
• B4 is an alkylene group, a haloalkylene group of 1 to 12 carbons;
• B5 is a steroid-containing group, a structure of formula (II-1) or —B51—B2—B52, wherein B51 is an alkylene group of 1 to 10 carbons and B52 is a steroid-containing group or has a structure of formula (II-1):
• in the formula (II-1), B6 is a hydrogen atom, a fluoro atom or a methyl group;
• B7, B8 and B9 respectively are a single bond,
• or an alkylene group of 1 to 3 carbons;
• B10 is
• wherein B12 and B13 respectively are a hydrogen atom, a fluoro atom or a methyl group;
• B11 is a hydrogen atom, a fluoro atom, an alkyl group of 1 to 12 carbons, a fluoroalkyl group of 1 to 12, an alkoxyl group of 1 to 12 carbons, —OCH2F, —OCHF2 or —OCF3;
• a is 1 or 2;
• b, c and d respectively are an integer of 0 to 4;
• e, f and g respectively are an integer of 0 to 3, and e+f+g≧1;
• i and j respectively are 1 or 2;
• when B6, B7, B8, B9, B10, B11, B12 or B13 are pluralities, B6, B7, B8, B9, B10, B11, B12 or B13 respectively are the same or different;
• in the formula (III), B2 is the same as above, and B14 has a structure of formula (III-1):
• in the formula (III-1), k, p and q respectively are an integer of 0 to 3, and k+p+q≧3.