Active-matrix liquid crystal display device and method for compensating for defective display lines

• US 6,462,792 B1
• Filed: 11/24/2000
• Issued: 10/08/2002
• Est. Priority Date: 09/28/1995
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ban, Atsushi, Shimada, Takayuki, Katayama, Mikio
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Ngo, Julie
• Application Number:
  US09/718,412
• Time in Patent Office: 683 Days
• Field of Search: 349/39, 349/38, 349/40-43, 349/54
• US Class Current: 349/39
• CPC Class Codes: G02F 1/136272 Auxiliary lines
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line

Abstract

In a liquid crystal display device, auxiliary lines are formed under pixel electrodes so as to be parallel to signal or scanning lines. The auxiliary lines are connected to the signal or scanning lines at one point for each pixel. This permits a voltage to be applied to a signal or scanning line if a disconnection defect occurs in the signal or scanning line. The auxiliary line is connected to the signal or scanning line at opposite sides of the defect to form a circuit around the defect. Moreover, if a leakage defect occurs at a crossing point between the scanning line and the signal line, the signal or scanning line may be cut off at both sides of the scanning or signal line, and the auxiliary line forms a circuit that avoids the line leak. Thus, a voltage may be applied to the signal or scanning line by the auxiliary line.

Claims

1. The active-matrix type liquid crystal display device comprising:

a substrate;

pixel electrodes disposed in a matrix form on said substrate;

a plurality of scanning lines in a layer of said substrate, for applying a scanning line voltage to each pixel electrode, said plurality of scanning lines being aligned in parallel so as to pass between pixel electrodes;

a plurality of signal lines crossing said plurality of scanning lines at a right angle, said signal lines applying a signal voltage to each pixel electrode, and said plurality of signal lines being aligned in parallel so as to pass between pixel electrodes;

each pixel electrode is disposed in a region adjacent scanning lines and adjacent signal lines;

a switching element for switching ON/OFF an application of a signal voltage to each pixel electrode through each signal line by a scanning voltage to be applied to each scanning line, and

auxiliary lines formed in the same layer as said scanning lines, each auxiliary line short-circuiting two regions of one of said plurality of scanning lines and applying the scanning voltage respectively to two pixel electrodes which are adjacent to each other along the scanning line.

2. An active-matrix type liquid crystal display device, comprising;

a substrate;

a plurality of scanning lines formed on said substrate;

a plurality of signal lines formed so as to cross said plurality of scanning lines at right angles;

pixel electrodes each disposed in a region adjacent scanning lines and adjacent signal lines; and

switching elements for switching ON/OFF application of signal voltages to said pixel electrodes through said plurality of signal lines by means of scanning voltages to be applied to said plurality of scanning lines, wherein;

said plurality of signal lines includes auxiliary lines formed in a same layer as said plurality of signal lines and electrically connected to said plurality of signal lines;

said pixel electrodes are insulated from said plurality of signal lines and said auxiliary lines to form a separate layer, and

each of said pixel electrodes has a first overlapping portion which overlaps at least one of a first signal line and an auxiliary line which short-circuits the first signal line,

each of said pixel electrodes has a second overlapping portion which overlaps at least one of a second signal line, and an auxiliary line which short-circuits the second signal line; and

the two overlapping portions have equal capacitances.

3. The active-matrix type liquid crystal display device as set forth in claim 2 wherein:

a signal voltage whose polarity reverses at every signal line is applied to each signal line; and

a voltage applied to one of the two overlapping portions has an opposite polarity from that applied to another of the overlapping portions.

4. A method of compensating for a defective pixel designed for an active-matrix type liquid crystal display device including:

a substrate;

a plurality of scanning lines formed on said substrate;

a plurality of signal lines formed so as to cross said plurality of scanning lines at right angles;

pixel electrodes each disposed in a region adjacent scanning lines and adjacent signal lines; and

switching elements for switching ON/OFF application of signal voltages to said pixel electrodes through said plurality of signal lines by means of scanning voltages to be applied to said plurality of scanning lines, wherein

said plurality of signal lines includes auxiliary lines formed in a same layer as said plurality of signal lines and electrically connected to said plurality of signal lines;

said pixel electrodes are insulated from said plurality of signal lines and said auxiliary lines to form a separate layer, and

each of said pixel electrodes has a first overlapping portion which overlaps at least one of a first signal line and an auxiliary line, which short-circuits the first signal line,

each of said pixel electrodes has a second overlapping portion which overlaps at least one of a second signal line, and an auxiliary line which short-circuits the second signal line; and

the two overlapping portions have equal capacitances, wherein;

said method is such that when a leakage defect occurs at a crossing point between a scanning line and a signal line, the signal line is cut off on both sides of the scanning line.

5. An active-matrix type liquid crystal display device, comprising

a substrate;

a plurality of scanning lines formed on said substrate;

a plurality of signal lines formed so as to cross said plurality of scanning lines at right angles;

pixel electrodes each disposed in a region adjacent scanning lines and adjacent signal lines;

switching elements for switching ON/OFF application of signal voltages to said pixel electrodes through said plurality of signal lines by means of scanning voltages to be applied to said plurality of scanning lines, wherein;

said plurality of signal lines includes auxiliary lines formed in a same layer as said plurality of signal lines and electrically connected to said plurality of signal lines;

said pixel electrodes are insulated from said plurality of signal lines and said auxiliary lines to form a separate layer, and

each of said pixel electrodes has a first overlapping portion which overlaps at least one of a first signal line and an auxiliary line which short-circuits the first signal line,

each of said pixel electrodes has a second overlapping portion which overlaps at least one of a second signal line and an auxiliary line which short-circuits the second signal line; and

a voltage applied to one of the two overlapping portions has an opposite polarity from that applied to another of the overlapping portion.

6. A method of compensating for a defective pixel designed for an active-matrix type liquid crystal display device including:

a substrate;

a plurality of scanning lines formed on said substrate;

a plurality of signal lines formed so as to cross said plurality of scanning lines at right angles;

pixel electrodes each disposed in a region adjacent scanning lines and adjacent signal lines; and

switching elements for switching ON/OFF application of signal voltages to said pixel electrodes through said plurality of signal lines by means of scanning voltages to be applied to said plurality of scanning lines, wherein;

said plurality of signal lines includes auxiliary lines formed in a same layer as said plurality of signal lines and electrically connected to said plurality of signal lines;

said pixel electrodes are insulated from said plurality of signal lines and said auxiliary lines to form a separate layer, and

each of said pixel electrodes has a first overlapping portion which overlaps at least one of a first signal line and an auxiliary line which short-circuits the first signal line,

each of said pixel electrodes has a second overlapping portion overlaps at least one of a second signal line and an auxiliary line which short-circuits the second signal line; and

a signal voltage whose polarity reverses at every signal line when applied to each signal line, and

a voltage applied to one of the two overlapping portions has an opposite polarity from that applied to another of the overlapping portions, wherein;

said method is such that when a leakage defect occurs at a crossing point between a scanning line and a signal line, the signal line is cut off on both sides of the scanning line.