LIQUID CRYSTAL DISPLAY DEVICE

• US 20090256816A1
• Filed: 10/30/2008
• Published: 10/15/2009
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kim, Cheol Se
• Granted Patent: US 8,232,974 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

The liquid crystal display device is for recognizing a variation in liquid crystal capacitance according to a touch to be capable of sensing whether or not the device is touched and the position of a touched region and includes a first substrate and a second substrate being opposite to each other; a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define pixel regions; pixel transistors respectively disposed at the intersections of the plurality of gate lines and the plurality of data lines, and pixel electrodes respectively disposed in the pixel regions; a common electrode disposed on the entire surface of the second substrate; a liquid crystal layer filling a gap between the first and second substrates; liquid crystal capacitors between the pixel electrodes and the common electrode; first storage capacitors disposed between the pixel electrodes and first storage electrodes on the first substrate; second storage capacitors and sensing capacitors in series between the gate lines and the common electrode; a read out line being parallel with the data lines; and switching transistors, each of which is provided with a gate electrode connected to a node between the second storage capacitor and the sensing capacitor, a drain electrode connected to the read out line, and a source electrode connected to a power voltage line.

Claims

1. A liquid crystal display device comprising:

a first substrate and a second substrate being opposite to each other;

a plurality of gate lines and a plurality of data lines crossing each other on the first substrate to define pixel regions;

pixel transistors respectively disposed at the intersections of the plurality of gate lines and the plurality of data lines, and pixel electrodes respectively disposed in the pixel regions;

a common electrode disposed on the entire surface of the second substrate;

a liquid crystal layer filling a gap between the first and second substrates;

liquid crystal capacitors between the pixel electrodes and the common electrode;

first storage capacitors disposed between the pixel electrodes and first storage electrodes on the first substrate;

second storage capacitors and sensing capacitors disposed in series between the gate lines and the common electrode;

a read out line being parallel with the data lines; and

switching transistors, each of which is provided with a gate electrode connected to a node between the second storage capacitor and the sensing capacitor, a drain electrode connected to the read out line, and a source electrode connected to a power voltage line.

2. The liquid crystal display device according to claim 1, wherein the sensing capacitors have a capacitance value varied according to a variation in the thickness of the liquid crystal layer at a touched region.

3. The liquid crystal display device according to claim 1, further comprising resistances respectively connected to the second storage capacitors in parallel and respectively disposed between the gate lines and the gate electrodes of the switching transistors.

4. The liquid crystal display device according to claim 3, wherein a time constant defined by a resistance value of the resistance and capacitance values of the second storage capacitors, the sensing capacitors, and the switching capacitors is smaller than a 1 frame time and is larger than a turn-on time of a gate high signal applied to the gate lines.

5. The liquid crystal display device according to claim 1, wherein each of the second storage capacitors is defined by the gate line, the second storage electrode overlapping the gate line, and an insulating film between the gate line and the second storage electrode.

6. The liquid crystal display device according to claim 5, wherein each of the sensing capacitors is defined by the second storage electrode, the common electrode, and the liquid crystal layer between the second storage electrode and the common electrode.

7. The liquid crystal display device according to claim 1, wherein each of the first storage electrodes includes a common line separated from each of the gate lines and disposed in the peripheral part of each of the pixel regions being parallel with the respective gate lines.

8. The liquid crystal display device according to claim 7, wherein the power voltage line, to which the source electrode of each of the switching transistors, is the common line.

9. The liquid crystal display device according to claim 1, wherein an auxiliary sensing pattern is further disposed at a position under the common electrode corresponding to the sensing capacitor.

10. The liquid crystal display device according to claim 9, wherein the thickness of the auxiliary sensing pattern is smaller than a value obtained by subtracting a variation in the thickness between the first and second substrate, which is maximally changed when touched, from the cell gap of the liquid crystal layer.