Liquid crystal display device

• US 9,076,402 B2
• Filed: 02/02/2010
• Issued: 07/07/2015
• Est. Priority Date: 02/24/2009
• Status: Active Grant

• Current Assignee: Japan Display Incorporated, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Japan Display Incorporated, Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yamanaka, Satoru, Hirota, Shinichi, Arima, Kazuya
• Primary Examiner(s): Elahi, Towfiq
• Application Number:
  US12/698,209
• Publication Number:
  US 20100214261A1
• Time in Patent Office: 1,981 Days
• Field of Search: 345/174
• US Class Current: 1/1
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

A liquid crystal display device includes a pixel array substrate having signal lines and scan lines arranged in a matrix, and pixel circuits arranged at intersections of the signal and scan lines. A touch panel is attached on the counter substrate to draw pictures or characters on a display panel. A first voltage generation circuit generates an analog pixel voltage applied to the signal lines and a second voltage generation circuit generates a counter electrode voltage applied to the counter electrode. A settling adjustment circuit adjusts a settling time of at least one of the analog pixel voltage and the counter electrode voltage.

Claims

1. A liquid crystal display device, comprising:

a pixel array portion including signal lines and scan lines arranged in a matrix and pixel circuits arranged in cross areas of the signal and scan lines;

signal drivers connected to the signal lines to drive the signal lines;

scan drivers connected to the scan lines to drive the scan lines; and

a touch panel attached on the pixel array portion;

wherein the pixel circuit includes

switching element formed in each of the pixel circuits;

a liquid crystal capacitance formed between a pixel electrode connected to the switching element and a counter electrode; and

an auxiliary capacitance formed between the pixel electrode and an auxiliary capacitance line;

wherein the signal drivers include

a first voltage generation circuit to generate an analog pixel voltage applied to the signal lines;

a second voltage generation circuit to generate a polarity inverted counter electrode voltage applied to the counter electrode;

a precharge circuit to apply a precharge voltage to all the signal lines generated in circumference of the pixel array portion during a horizontal blanking time prior to start a next driving of the signal lines at a time of performing a polarity inversion driving to avoid malfunction of the touch panel caused by electric magnetic noises; and

a settling adjustment circuit to adjust a settling time of the voltage generated by the second voltage generation circuit to eliminate malfunction of the touch panel caused by electric magnetic noises generated in circumference of the pixel array portion,

wherein the signal drivers generate a rise wave form and a fall wave form of the counter electrode voltage in a curved shape having gradually increasing or decreasing slope as a function of time,

such that the decreasing slope of the rise wave form has a rate of decrease that is higher than a corresponding rate of increase of the increasing slope of the fall wave form, or

such that the decreasing slope of the rise wave form has a rate of decrease that is lower than a corresponding rate of increase of the increasing slope of the fall wave form.

2. The liquid crystal display device according to claim 1, wherein the settling adjustment circuit comprises:

a plurality of buffer circuits with different input signal delay time each other, and a buffer selection circuit to select one of the buffer circuits and adjust the settling time of the voltage generated by the second voltage generation circuit.

3. The liquid crystal display device according to claim 1, wherein the signal driver circuit comprises:

an analog switch circuit to apply the analog pixel voltage to selected signal lines; and

a timing adjustment circuit to control the switching time of the analog switch so as to match to the settling time adjusted by the settling adjustment circuit.

4. The liquid crystal display device according to claim 1, wherein the liquid crystal display device comprises:

a reference voltage generation circuit to generate a reference voltage used to generate an auxiliary capacitance line voltage applied to the auxiliary capacitance line and a counter electrode voltage applied to a counter electrode;

a first buffer circuit to generate an auxiliary capacitance voltage applied to the auxiliary capacitance line based on the reference voltage; and

a second buffer circuit to generate the counter electrode voltage based on the reference voltage.

5. The liquid crystal display device according to claim 1, wherein a voltage setting of the precharge voltage and the adjustment of the settling time by the settling adjustment circuit are made in a manufacturing step of the display device and are not made after that.