Composition for forming a liquid crystal alignment film, and liquid crystal display device

1. A composition for forming a liquid crystal alignment film, wherein the composition comprises:

a material for forming a liquid crystal alignment film; diethylene glycol diethyl ether;

diisobutyl ketone; and

at least one of y-butyrolactone and N-methyl-2-pyrrolidone.

2. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition comprises at least one of the y-butyrolactone and the N-methyl-2-pyrrolidone as a good solvent for the material for forming a liquid crystal alignment film.

3. The composition for forming a liquid crystal alignment film according to claim 1

wherein the composition comprises the diethylene glycol diethyl ether and the diisobutyl ketone as poor solvents for the material for forming a liquid crystal alignment film.

4. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the material comprises a copolymer formed by polymerizing two diamines with an acid anhydride.

5. The composition for forming a liquid crystal alignment film according to claim 4 ,

wherein the two diamines includes:

diamine having a side chain including a photofunctional group and fluorine; and

diamine having a side chain including a vertical alignment functional group.

6. The composition for forming a liquid crystal alignment film according to claim 4 ,

wherein the material for forming a liquid crystal alignment film is a polyamic acid or a polyimide which comprises:

an acid anhydride unit derived from an acid anhydride; a photo-alignment

diamine unit derived from a diamine having a side chain including a photofunctional group and fluorine; and

a vertical alignment diamine unit derived from a diamine having a side chain including a vertical alignment functional group,

and has the acid anhydride unit and any of the photo-alignment diamine unit and the vertical alignment diamine unit alternately arranged in the polyamic acid or the polyimide.

7. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film has a solid content of 2% to 5% by weight.

8. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film has a surface tension of 28 to 32 mN/in at 24° C.

9. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film has a viscosity of 5 to 10 mPa·s at 24° C.

10. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film has the boiling point of 160 to 220° C. at atmospheric pressure.

11. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film spreads not less than 13 mm in a liquid spreading test and shrinks 100 nm or less in a liquid shrinkage test.

12. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film starts exhibiting a property of controlling alignment of liquid crystal molecules by photoirradiation.

13. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film further comprises dipentyl ether.

14. The composition for forming a liquid crystal alignment film according to claim 1 ,

wherein the composition for forming a liquid crystal alignment film is discharged to a substrate for liquid crystal display device by inkjet printing.

15. A liquid crystal display device comprising

a liquid crystal alignment film formed from the composition for forming a liquid crystal alignment film according to claim 1 and provided with an alignment treatment by photoirradiation.

16. The liquid crystal display device according to claim 15 ,

wherein the thickness of the liquid crystal alignment film after pre-baking is 40 to 150 nm.

17. The liquid crystal display device according to claim 15 ,

wherein the composition for forming a liquid crystal alignment film comprises a copolymer including as essential constitutional units:

a first constitutional unit starting exhibiting a property of controlling alignment of liquid crystal molecules by photoirradiation; and

a second constitutional unit exhibiting the property of controlling alignment of liquid crystal molecules regardless of the photoirradiation, and

the liquid crystal alignment film is a film formed from the composition for forming a liquid crystal alignment film and provided with an alignment treatment by photoirradiation.