Liquid crystal display device and manufacturing method thereof
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:
a TFT substrate,
a pixel electrode, a thin film transistor and a common electrode formed on the TFT substrate,
a counter substrate opposed to the TFT substrate,
a spacer formed on the counter substrate to determine a distance between the TFT substrate and the counter substrate, and
a liquid crystal layer between the TFT substrate and the counter substrate,
wherein
a projection is formed on the TFT substrate and opposed to the spacer,
a top of the projection is closer to the counter substrate than a top of the pixel electrode,
the common electrode has an opening corresponding to the thin film transistor,
an alignment film is a photo-alignment film and formed on the projection and the pixel electrode,
the alignment film is formed with a material having at least polyamide acid, and has a first layer and a second layer formed on the first layer,
a thickness of the first layer on the projection is less than a thickness of the first layer on the pixel electrode,
a thickness of the second layer on the projection is less than a thickness of the second layer on the pixel electrode,
a top of the spacer is in contact with the first layer on the projection,
the first layer contains a first material, the second layer contains a second material,
provided a thickness of the first layer is p1 and a thickness of the second layer is p2, a value of p1/p2 is larger on the pixel electrode than on the projection, and
in a plan view, the projection overlaps a layer formed from a same material and formed on a same layer as the common electrode and a layer formed from a same material and formed on a same layer as the pixel electrode.
2. The liquid crystal display device according to claim 1 , further comprising a signal line electrically connected to the pixel electrode through the thin film transistor,
wherein the projection overlaps the signal line in a plan view.
3. The liquid crystal display device according to claim 2 , wherein
the projection is a stacked structure and includes at least one of a same material, a same material as a semiconductor layer for the thin film transistor, and a same material as the signal line.
4. The liquid crystal display device according to claim 2 , wherein
the spacer overlaps the signal line in a plan view.
5. The liquid crystal display device according to claim 1 , wherein
one of the first material and the second material is polyamide acid.
6. The liquid crystal display device according to claim 5 , wherein
the second material is polyamide acid and does not contain cyclobutane.
7. The liquid crystal display device according to claim 6 , wherein
the first material contains cyclobutane.
8. The liquid crystal display device according to claim 1 , further comprising a gate line formed on the TFT substrate,
wherein a first semiconductor layer and a second semiconductor layer overlap the gate line in a plan view,
the thin film transistor includes one of the first semiconductor layer and the second semiconductor layer, and
one of the first semiconductor layer and the second semiconductor layer overlaps with the spacer in a plan view.
9. The liquid crystal display device according to claim 8 , wherein
the first semiconductor layer and the second semiconductor layer are located next to each other with a space in an extending direction of the gate line.
10. The liquid crystal display device according to claim 8 , wherein
one of the first semiconductor layer and the second semiconductor layer electrically connects to the pixel electrode.
11. The liquid crystal display device according to claim 8 , wherein
the projection is formed from one of the first semiconductor layer and the second semiconductor layer.