Varnish for photo alignment film and liquid crystal display device
According to one embodiment, a varnish for a photo alignment film includes an imidization promotor and a first polyamic acid-based compound in an organic solvent. The first polyamic acid-based compound is a polyamic acid or a polyamic acid ester. The imidization promotor has skeleton containing no primary amino group and no secondary amino group. The first polyamic acid-based compound has terminal skeletons containing no primary amino group.
1. A varnish for a photo alignment film which is provided by imidizing and radiating the varnish applied on a substrate of a lateral electric field type liquid crystal display device with UV light, comprising an organic solvent, a first polyamic acid-based compound, and an imidization promotor for promoting dehydration and cyclization reaction to the first polyamic acid-based compound, the first polyamic acid-based compound being a polyamic acid or a polyamic acid ester,
wherein
the imidization promotor has skeleton containing neither a primary amino group nor a secondary amino group,
the imidization promotor is a pyridine-based compound, a quinoline-based compound, an isoquinoline-based compound, an imidazole-based compound, a benzimidazole-based compound or a tertiary amine, and
the first polyamic acid-based compound has terminal skeletons containing no primary amino group.
2. The varnish according to claim 1 , wherein the imidization promotor comprises an amine-reactive skeleton.
3. The varnish according to claim 2 , wherein the amine-reactive skeleton comprises a halogen group, a diazo group, a carboxyl group, a hydroxyl group, an isocyanate group or an acid anhydride skeleton.
4. The varnish according to claim 1 , wherein the imidization promotor has a molecular weight of 130 or more.
5. The varnish according to claim 1 , wherein the first polyamic acid-based compound has a structural unit represented by Formula (1) below:
where X is a cyclic group, each of R 1 and R 2 is independently —COOH or —COOR where R is an alkyl group, and Y 1 is an organic group.
6. The varnish according to claim 1 , wherein the terminal skeletons comprise an imide skeleton, an amide skeleton, a urea skeleton, a tertiary amino skeleton, an azo bond or a carboxyl group.
7. The varnish according to claim 1 , further comprising a second polyamic acid-based compound, which is a polyamic acid or a polyamic acid ester, and the first polyamic acid-based compound has a polarity higher than that of the second polyamic acid-based compound.
8. A liquid crystal display device comprising an alignment film comprising an imidized product of the varnish according to claim 1 .