High quality and ultra large screen liquid crystal display device and production method thereof
A large screen liquid crystal display device using a transverse electric field system which is capable of dramatically improving an aperture ratio, a transmittance ratio, brightness, and contrast with low cost and high production yield. For example, the width of the common electrodes that shield the electric fields of the video signal lines can be decreased dramatically and the aperture ratio can be improved dramatically. Especially, the bumps covering the video signal lines can be used along with the spacers, and with the use of halftone exposure method, the bumps covering the video signal lines and the spacers can be constructed at the same time, which dramatically shortens the time required for the production process.
1. A liquid crystal display device having a transverse electric field type active matrix substrate, comprising:
a thin and long bump made of insulation material for covering a video signal line formed on the active matrix substrate;
a spacer to define a liquid crystal cell gap, the spacer and the thin and long bump being formed at the same time through a halftone exposure process; and
a common electrode formed on the thin and long insulation bump in a manner to cover the video signal line;
thereby shielding an electric field generated by the video signal line by the common a electrode; and
wherein a height difference h 2 between a height of the thin and long insulation bump and a height of the spacer that defines the gap of the liquid crystal cell is within a range between 0.2 micrometers and 2.0 micrometers.
2. A liquid crystal display device as defined in claim 1 , wherein the spacer that is constructed at the same time as the thin and long insulation bump through the halftone exposure process is not covered by the common electrode at an area around the top thereof so as to expose dielectric material that forming the spacer.
3. A liquid crystal display device as defined in claim 1 , wherein a density of the spacers that are constructed at the same time with the thin and long insulation bumps through the halftone exposure process is in a range between one and seventy five per square millimeter and the spacers are distributed evenly throughout the substrate.
4. A liquid crystal display device as defined in claim 1 , wherein an area of the spacer that is constructed at the same time with the thin and long insulation bump through the halftone exposure process is in a range between 200 square micrometers and 2000 square micrometers per one square millimeter.
5. A liquid crystal display device having a transverse electric field type active matrix substrate, comprising:
a thin and long bump made of insulation material for covering a video signal line on the active matrix substrate;
a spacer to define a liquid crystal cell gap: the spacer and the thin and long bump being formed at the same time through a halftone exposure process;
a common electrode formed on the thin and long insulation bump in a manner to cover the video signal line, thereby shielding an electric field generated by the video signal line;
a thin and long insulation bump formed on a scanning line through a halftone exposure process in a manner to cover the scanning line; and
a common electrode formed on both side walls of the insulation bump in a manner to sandwich the scanning line, thereby shielding an electric field generated by the scanning line;
wherein a height difference h 2 between a height of the thin and long insulation bump and a height of the spacer that defines the gap of the liquid crystal cell is within a range between 0.2 micrometers and 2.0 micrometers.
6. A liquid crystal display device as defined in claim 5 , wherein the spacer that is constructed at the same time with the thin and long insulation bump through the halftone exposure process is not covered by the common electrode at an area around the top thereof so that dielectric material that forming the spacer is exposed.
7. A liquid crystal display device as defined in claim 5 , wherein a density of the spacers that are constructed at the same time with the thin and long insulation bump through the halftone exposure process is in a range between one and seventy five per square millimeter and the spacers are distributed evenly throughout the substrate.
8. A liquid crystal display device as defined in claim 5 , wherein an area of the spacer that is constructed at the same time with the thin and long insulation bump through the halftone exposure process is in a range between 200 square micrometers and 2000 square micrometer per one square millimeter.
9. A liquid crystal display device as defined in claim 1 , wherein an electrode for one pixel for driving the liquid crystal molecule is configured by three different electrodes including a single electrode connected to a thin film transistor for driving a liquid crystal, a lower layer common electrode formed both right and left sides of a pixel for shielding the video signal line, and an upper layer shielding common electrode formed along the thin and long insulation bump surrounding the video signal line, thereby excluding common electrodes from the pixel.
10. A liquid crystal display device as defined in claim 1 , wherein a process for leveling the active matrix substrate and construction of photolithography spacers are conducted at the same time by applying negative photoresist with a thickness which is a sum of a liquid crystal cell gap and the largest thickness among a common electrode within a pixel made of non-transparent metal material or metal silicide or metal nitride, a lower layer common electrode for shielding the video signal line, and a liquid crystal drive electrode, and then exposing the ultraviolet light to an entire effective pixel area from a back surface of the active matrix substrate, then completely exposing an ultraviolet light to the portions where spacers are formed using a photomask for the photolithography spacers, and developing the active matrix substrate.
11. A liquid crystal display device as defined in claim 1 , wherein the video signal line, the thin and long insulation bump formed in the manner to cover the video signal line, an upper layer common electrodes for shielding an electric field caused by the video signal line, a lower layer common electrode for shielding, and a liquid crystal drive electrode within a pixel are bent within the pixel at least once at an angle within a range between 0-30 degrees (except 0 degree) relative to an alignment direction of a liquid crystal molecule, and a color filter layer and a light shielding film (black mask) are bent within the pixel at least once, in a manner similar to the video signal line, at an angle within a range between 0-30 degrees (except 0 degree) relative to the alignment direction of the liquid crystal molecule, wherein an electrode for driving the liquid crystal molecules within the pixel is configured by three electrodes including the liquid crystal electrode connected to the thin film transistor element, the lower layer common electrode for shielding the video signal line provided at both sides of the pixel, and the upper layer common electrode formed along the thin and long insulation bump, thereby excluding a common electrode from the pixel.
12. A liquid crystal display device as defined in claim 1 , wherein the video signal line, the thin and long insulation bump formed in the manner to cover the video signal line, an upper layer common electrode for shielding an electric field caused by the video signal line, a lower layer common electrode for shielding, and a liquid crystal drive electrode within a pixel are bent within the pixel at least once at an angle within a range between 60-120 degrees (except 90 degrees) relative to an alignment direction of a liquid crystal molecule, and a color filter layer and a light shielding film (black mask) are bent within the pixel at least once, in a manner similar to the video signal line, at an angle within a range between 60-120 degrees (except 90 degrees) relative to the alignment direction of the liquid crystal molecule, wherein an electrode for driving the liquid crystal molecules within the pixel is configured by three electrodes including the liquid crystal electrode connected to the thin film transistor element, the lower layer common electrode for shielding the video signal line provided at both sides of the pixel, and the upper layer common electrode formed along the thin and long insulation bump, thereby excluding a common electrode from the pixel.