Liquid crystal display device and manufacturing method thereof
View Patent ↗The present invention prevents the shaving of an alignment film caused by a columnar spacer in a liquid crystal display device of an IPS method using photo-alignment. A plinth higher than a pixel electrode is formed at a part where a columnar spacer formed over a counter substrate touches a TFT substrate. When an alignment film of a double-layered structure is applied over the pixel electrode and the plinth, the thickness of the alignment film over the plinth reduces by a leveling effect. When photo-alignment is applied in the state, a photodegraded upper alignment film over the plinth disappears and a lower alignment film having a high mechanical strength remains. As a result, it is possible to prevent the shaving of the alignment film.
1. A liquid crystal display device comprising:
pixels formed in regions surrounded by scanning lines extending in a first direction and arrayed in a second direction and picture signal lines extending in the second direction and arrayed in the first direction;
a pixel electrode formed at each of the pixels over an insulation film and a passivation film;
a TFT substrate supplying a picture signal to each of the pixel electrodes through a TFT;
a counter substrate formed opposite the TFT substrate; and
a liquid crystal layer interposed between the TFT substrate and the counter substrate,
wherein a columnar spacer to retain a space from the TFT substrate is formed over the counter substrate;
a plinth facing a tip of the columnar spacer is formed over the TFT substrate and an alignment film is formed so as to cover the plinth, the pixel electrodes, the insulation film, and the passivation film;
photo-alignment treatment is applied to the alignment film;
a top end of the plinth is higher than top ends of the pixel electrodes;
the alignment film includes a lower alignment film formed by using polyamide acid as a precursor and an upper alignment film formed by using polyamide acid ester as a precursor;
when the thickness of the lower alignment film is defined as p1 and the thickness of the upper alignment film is defined as p2, p2/p1 over the plinth is smaller than p2/p1 over the insulation film; and
wherein p2/(p1+p2) is 0.3 or less over the plinth.
2. The liquid crystal display device according to claim 1 , wherein p2/(p1+p2) is 0.2 or less over the plinth.
3. The liquid crystal display device according to claim 1 , wherein p2/(p1+p2) is 0.1 or less over the plinth.
4. The liquid crystal display device according to claim 1 , wherein p2 is 30 nm or less over the plinth.
5. The liquid crystal display device according to claim 1 , wherein p2 is 20 nm or less over the plinth.
6. The liquid crystal display device according to claim 1 , wherein p2 is 10 nm or less over the plinth.
7. The liquid crystal display device according to claim 1 , wherein the plinth: is formed over the scanning lines; and, as a constituent component, includes a material identical to the pixel electrodes, a material identical to the semiconductor layer of the TFT, or a material identical to the picture signal lines.
8. The liquid crystal display device according to claim 1 , wherein the plinth: is formed over the picture signal lines; and, as a constituent component, includes a material identical to the pixel electrodes or a material identical to the semiconductor layer of the TFT.