Active matrix liquid crystal display

• US 5,459,595 A
• Filed: 02/04/1993
• Issued: 10/17/1995
• Est. Priority Date: 02/07/1992
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Tanaka, Hirohisa, Ishiguro, Kenichi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US08/013,642
• Time in Patent Office: 985 Days
• Field of Search: 359/59, 359/67, 359/54
• US Class Current: 349/111
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/136218 Shield electrodes

Abstract

A parasitic capacitance is not caused between a shielding film and a gate line and between a pixel electrode and the gate line in a liquid crystal display of the present invention because the shielding film and the pixel electrode do not overlap the gate lines. The display characteristics are thus improved. Furthermore, since the counter shielding film is formed so as to cover a smaller gap of one between the shielding film and the gate line and one between the gate line and pixel electrode, light leak through the gap can be blocked. The shielding film can be small because it only covers the gap, thereby preventing a degradation of an aperture ratio. Moreover, a degradation of yield caused by increasing a number of production steps is also prevented because the production steps are not complicated. In another aspect of the liquid crystal display of the present invention, since the gate line is electrically connected to a counter electrode, a part of the parasitic capacitance caused between the pixel electrode and the shielding film end between the pixel electrode and the gate line is connected in parallel to a capacitance of liquid crystal and used as a storage capacitance. As a result, the parasitic capacitance less influences on the display characteristics, which is thus further improved. Further, since storage capacitance lines are not required, the aperture rate is not degraded and a degradation of yield caused by increasing a number of the production steps is prevented.

Claims

1. An active matrix liquid crystal display comprising:

an active matrix substrate having;

a plurality of parallel scanning lines extending in a first direction, each scanning lines having two sides which are parallel to the first direction;

a plurality of parallel signal lines crossing the scanning lines;

pixel electrodes respectively formed in substrate portions defined by two adjacent scanning lines and two adjacent signal lines;

switching elements each of which is connected to a corresponding pixel electrode, a corresponding scanning line and a corresponding signal line; and

pairs of first shielding films provided in the active matrix substrate, a film of each pair being provided in light leakage-blocking relation to a respective one of the two sides of each scanning line;

a counter substrate opposed to the active matrix substrate having;

a counter electrode; and

second shielding films extending in the first direction and above the scanning lines for blocking light leakage which is not blocked by the first shielding films; and

a liquid crystal layer between the active matrix substrate and the counter substrate.

2. An active matrix liquid crystal display according to claim 1, wherein none of the first shielding films overlay the scanning lines.

3. An active matrix liquid crystal display according to claim 2, wherein the second shielding films covers at least the smaller one of:

(1) a gap between the first shielding film and the scanning line; and

(2) a gap between the pixel electrode and the scanning line.

4. An active matrix liquid crystal display according to claim 1, wherein the switching elements are thin film transistors, and a drain in each thin film transistor also serves as one of the pair of first shielding films.

5. An active matrix liquid crystal display according to claim 1, wherein the signal lines are made from a type of material as used for the first shielding films.