Liquid crystal display device integrated with capacitive touch panel

• US 8,907,917 B2
• Filed: 07/14/2010
• Issued: 12/09/2014
• Est. Priority Date: 09/29/2009
• Status: Expired due to Fees

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kim, Cheol-Se
• Primary Examiner(s): Nguyen, Chanh
• Assistant Examiner(s): SEYOUM, TSEGAYE H
• Application Number:
  US12/836,408
• Publication Number:
  US 20110074727A1
• Time in Patent Office: 1,609 Days
• Field of Search: 345/174, 345/98, 345/173, 345/104, 178/18.05, 178/18.03
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells

Abstract

Disclosed is a liquid crystal display device which can sense a change of static capacitance of liquid crystals caused by a touch to detect the touch and a position of the touch, the liquid crystal display device includes, a pixel transistor on each of crossed portions of gate lines and data lines and a pixel electrode at each of the pixel regions, a liquid crystal capacitor between the pixel electrode and a common electrode, a storage line formed on the first substrate, a switching line formed in parallel to the gate line, a read out line parallel to the data line, a first storage capacitor between the storage line and the pixel transistor, a second storage capacitor and a sensing capacitor in series between the switching line and the common electrode, a switching transistor having a gate electrode connected to a contact point of the second storage capacitor and the sensing capacitor, and a drain electrode connected to the read out line.

Claims

1. A liquid crystal display device comprising:

a first substrate and a second substrate formed to face each other;

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

a pixel transistor formed on each of crossed portions of the gate lines and data lines data and a pixel electrode formed at each of the pixel regions;

a common electrode formed on an entire surface of the second substrate;

a liquid crystal layer filled between the first and second substrates;

a liquid crystal capacitor formed between the pixel electrode and the common electrode;

a storage line formed on the first substrate;

a switching line formed in parallel to the gate line;

a read out line parallel to the data line;

a first storage capacitor formed between the storage line and the pixel transistor;

a second storage capacitor and a sensing capacitor formed in series between the switching line and the common electrode;

a switching transistor having a gate electrode connected to a contact point of the second storage capacitor and the sensing capacitor, and a drain electrode connected to the read out line; and

a resistor formed between the switching line and the gate electrode of the switching transistor in parallel to the second storage capacitor,

wherein a time constant is defined with a resistance value of the resistor and capacitance values of the second storage capacitor, the sensing capacitor and the switching transistor, the time constant is smaller than one frame time period and greater than an on-time period of a high signal applied to the switching line.

2. The liquid crystal display device according to claim 1, wherein the switching transistor includes a source electrode connected to the storage line.

3. The liquid crystal display device according to claim 1, wherein the switching transistor includes a source electrode connected to a separate power source voltage line.

4. The liquid crystal display device according to claim 1, further comprising a sensing spacer formed on the common electrode spaced from an uppermost surface on the first substrate, the sensing spacer is formed at a portion where the sensing capacitor is defined.

5. A liquid crystal display device comprising:

a first substrate and a second substrate formed to face each other;

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

a pixel transistor formed on each of crossed portions of the gate lines and data lines and a pixel electrode formed at each of the pixel regions;

a common electrode formed on an entire surface of the second substrate;

a liquid crystal layer filled between the first and second substrates;

a liquid crystal capacitor formed between the pixel electrode and the common electrode;

a storage line formed on the first substrate;

a read out line parallel to the data line;

a first storage capacitor formed between the storage line and the pixel transistor;

a second storage capacitor and a sensing capacitor formed in series between the gate line and the common electrode;

a switching transistor having a gate electrode connected to a contact point of the second storage capacitor and the sensing capacitor, and a drain electrode connected to the read out line; and

a resistor formed between the gate line and the gate electrode of the switching transistor, in parallel to the second storage capacitor,

wherein a time constant is defined with a resistance value of the resistor and capacitance values of the second storage capacitor, the sensing capacitor and the switching transistor, the time constant is smaller than one frame time period and greater than an on-time period of a gate high signal applied to the gate line.

6. The liquid crystal display device according to claim 5, wherein the switching transistor includes a source electrode connected to the storage line.