Active-matrix color LCD device having a polished color filter substrate
View Patent ↗A color filter substrate in an active-matrix LCD device has a glass substrate, and a black matrix, coloring layers and an orientation film which are consecutively formed on the glass substrate. The projected surfaces of the coloring layers due to overlapping with the black matrix are polished to reduce the width of the slope surfaces of the projected surface of the coloring layers. The polishing of the coloring layers prevents a disclination caused by the slope surface.
1. A liquid crystal display device (LCD) comprising a TFT substrate, a color filter substrate, and a twisted nematic liquid crystal (LC) layer sandwiched between said TFT substrate and said color filter substrate, said color filter substrate comprising:
a transparent substrate;
a light shield layer formed on said transparent substrate and having a substantially lattice pattern;
a coloring layer formed on a portion of said transparent substrate within each space of said light shield layer and on an edge portion of a stripe of said light shield layer; and
an orientation film overlying said coloring layers and the other portions of said stripes of said light shield layer,
said coloring layer having a substantially flat surface overlying said space of said light shield layer, a slope surface having a width of not more than 2.575 μm extending and rising from said flat surface and overlying said edge portion of said stripe of said light shield layer, a polished flat surface extending from said slope surface, and a rear edge surface extending between said polished flat surface and said other portion of said stripe of said light shield layer, wherein the following relational expression holds:
D
=
2
ϕ
-
(
0.25
θ
+
1
+
L
1
/
4
-
1.034
0.03724
)
>
0
,
where the θ, L and φ represent an angle of said slope surface with respect to a surface of said transparent substrate, a width of said slope surface, and a pre-tilt angle of LC molecules in said LC layer, respectively.
2. The LCD device according to claim 1 , wherein said angle of said slope surface is between 5 degrees and 10 degrees inclusive of both.
3. The LCD device according to claim 1 , wherein said LC layer is driven with a driving voltage between 3 volts and 5 volts inclusive of both.
4. The LCD device according to claim 1 , wherein said LCD device has a contrast ratio of not less than 200:1.
5. A method for fabricating a color filter substrate in a liquid crystal display (LCD) device comprising a TFT substrate, said color filter substrate, and a twisted nematic liquid crystal (LC) layer sandwiched between said TFT substrate and said color filter substrate, said method comprising the consecutive steps of:
forming a light shield layer having a substantially lattice pattern on a transparent substrate;
forming a coloring layer on a portion of said transparent substrate within each space of said light shield layer and on an edge portion of a stripe of said light shield layer, said coloring layer having a substantially flat surface overlying said space of said light shield layer, a slope surface having a width of not more than 2.575 μm extending and rising from said flat surface and overlying said edge portion of said stripe of said light shield layer, and a rear edge surface extending between said slope surface and the other portion of said stripe of said light shield layer;
polishing a surface portion of said coloring layer so that a polished surface formed between said slope surface and said rear edge surface satisfies the following relational expression:
D
=
2
ϕ
-
(
0.25
θ
+
1
+
L
1
/
4
-
1.034
0.03724
)
>
0
,
where the θ, L and φ represent an angle of said slope surface with respect to a surface of said transparent substrate, width of a remaining portion of said slope surface after said polishing, and a pre-tilt angle of LC molecules in said LC layer, respectively; and
forming an orientation film overlying said coloring layer and the other portion of said light shield layer.
6. A liquid crystal display device (LCD) comprising a TFT substrate, a color filter substrate, and a twisted nematic liquid crystal (LC) layer sandwiched between said TFT substrate and said color filter substrate, said color filter substrate comprising:
a transparent substrate;
a light shield layer formed on said transparent substrate and having a substantially lattice pattern;
a coloring layer formed on a portion of said transparent substrate within each space of said light shield layer and on an edge portion of a stripe of said light shield layer; and
an orientation film overlying said coloring layers and the other portions of said stripes of said light shield layer,
said coloring layer having a substantially flat surface overlying said space of said light shield layer, a slope surface having a width of not more than 2.575 μm extending and rising from said flat surface and overlying said edge portion of said stripe of said light shield layer, a polished flat surface extending from said slope surface, and a rear edge surface extending between said polished flat surface and said other portion of said stripe of said light shield layer, wherein the following relational expression holds:
D
=
2
ϕ
-
(
0.25
θ
+
1
+
L
1
/
4
-
1.034
0.03724
)
>
0
,
where the θ, L and φ represent an angle of said slope surface with respect to a surface of said transparent substrate, a width of said slope surface, and a pre-tilt angle of LC molecules in said LC layer, respectively, and wherein said pre-tilt angle is not more than 3 degrees.
7. The LCD device according to claim 6 , wherein said angle of said slope surface is between 5 degrees and 10 degrees inclusive of both.
8. The LCD device according to claim 6 , wherein said LC layer is driven with a driving voltage between 3 volts and 5 volts inclusive of both.
9. The LCD device according to claim 6 , wherein said LCD device has a contrast ratio of not less than 200:1.
10. A method for fabricating a color filter substrate in a liquid crystal display (LCD) device comprising a TFT substrate, said color filter substrate, and a twisted nematic liquid crystal (LC) layer sandwiched between said TFT substrate and said color filter substrate, said method comprising the consecutive steps of:
forming a light shield layer having a substantially lattice pattern on a transparent substrate;
forming a coloring layer on a portion of said transparent substrate within each space of said light shield layer and on an edge portion of a stripe of said light shield layer, said coloring layer having a substantially flat surface overlying said space of said light shield layer, a slope surface having a width of not more than 2.575 μm extending and rising from said flat surface and overlying said edge portion of said stripe of said light shield layer, and a rear edge surface extending between said slope surface and the other portion of said stripe of said light shield layer;
polishing a surface portion of said coloring layer so that a polished surface formed between said slope surface and said rear edge surface satisfies the following relational expression:
D
=
2
ϕ
-
(
0.25
θ
+
1
+
L
1
/
4
-
1.034
0.03724
)
>
0
,
where the θ, L and φ represent an angle of said slope surface with respect to a surface of said transparent substrate, width of a remaining portion of said slope surface after said polishing, and a pre-tilt angle of LC molecules in said LC layer, respectively, and wherein said pre-tilt angle is not more than 3 degrees; and
forming an orientation film overlying said coloring layer and the other portion of said light shield layer.