Liquid crystal display device and method for driving same

Patent metadata

Field	Value
Publication number	US-9761187-B2
Application number	US-201314432766-A
Country	US
Kind code	B2
Filing date	Jul 26, 2013
Priority date	Oct 2, 2012
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Grayscale values for previous and current frames are different, and therefore, an overshoot voltage, which has a higher absolute value than a signal voltage, are applied to a data signal line. Next, in a second drive frame, normal drive is performed, so that a signal voltage of the same polarity as the overshoot voltage is written to the data signal line. Moreover, in a first drive frame of a third pause drive period, the grayscale values for the previous and current frames are equal, and also greater than or equal to a boundary value, and therefore, undershoot drive is performed. An undershoot voltage, which has a lower absolute value than a signal voltage, is applied to the data signal line. Next, in a second drive frame, normal drive is performed, so that a signal voltage of the same polarity as the undershoot voltage is written to the data signal line.

First claim

The invention claimed is:

1. A liquid crystal display device formed on an insulating substrate and performing pause drive in an alternating-voltage drive mode, the device comprising:
a plurality of scanning signal lines;
a plurality of data signal lines crossing each of the scanning signal lines;
pixel forming portions at intersections of the scanning signal lines and the data signal lines;
a correction circuit that outputs a corrected image signal which is corrected with a correction value for correcting a grayscale value of the input image signal when the correction value is provided with the correction circuit and the input image signal which is not corrected when the correction value is not provided with the correction circuit;
a scanning signal line driver circuit that sequentially selects and scans the scanning signal lines;
a data signal line driver circuit that writes either correction voltages in accordance with the corrected image signal or signal voltages in accordance with the input image signal to the data signal lines; and
a timing control circuit that controls the scanning signal line driver circuit and the data signal line driver circuit, wherein,
the pause drive alternatingly repeats a drive period consisting of a plurality of drive frames and a pause period following the drive period and lasting until the start of the next drive period,
the correction value is determined only by the grayscale value for a current frame,
the correction circuit includes an adder circuit that outputs either the corrected image signal or the image signal to the data signal line driver circuit,
the adder circuit outputs a first correction image signal by adding the correction value to the grayscale value of the input image for the current frame, a second correction image signal by subtracting the correction value from the grayscale value of the input image for the current frame or the input image signal to the data signal line driver circuit at least during the first drive frame of the drive period and also outputs the input image signal to the data signal line driver circuit during the last drive frame,
the data signal line driver circuit generates the signal voltage, a first correction voltage having a higher absolute value than that of the input image signal or a second correction voltage having a lower absolute value than that of the input image signal based on the input image signal, the first correction image signal or the second correction image signal, and writes the signal voltage, the first correction voltage, or the second correction voltage at least once to the data signal line, and further, writes the signal voltage having the same polarity as the written first or second correction voltage, once to the data signal line, and
a voltage written by the data signal line driver circuit to the data signal line during the first drive frame of the drive period includes the first correction voltage, the second correction voltage, and the signal voltage.

2. The liquid crystal display device according to claim 1 , wherein,
the correction circuit includes:
a table storing the correction values; and

the table provides the adder circuit with the correction value correlated with the grayscale value for the current frame for the input image signal every time the adder circuit is provided with the grayscale value for the current frame, and
the adder circuit outputs the first correction image signal when the grayscale value for the current frame for the input image signal is smaller than a boundary value which is predetermined, outputs the second correction image signal when the grayscale value for the current frame for the input image signal is larger than the boundary value, and outputs the image signal when the grayscale value for the current frame for the input image signal is the same as the boundary value.

3. The liquid crystal display device according to claim 2 , further comprising a temperature sensor for measuring an ambient temperature around the liquid crystal display device, wherein,
the table includes a plurality of sub-tables having stored different correction values for predetermined temperature ranges, such that one of the sub-tables is selected in accordance with temperature information provided by the temperature sensor.

4. The liquid crystal display device according to claim 2 , further comprising a temperature sensor for measuring an ambient temperature around the liquid crystal display device, wherein,
the correction circuit further includes nonvolatile memory for storing a plurality of data items for different correction values for predetermined temperature ranges, and
the nonvolatile memory selects one of the data items in accordance with temperature information provided by the temperature sensor and provides the selected data item to the table.

5. The liquid crystal display device according to claim 3 , wherein,
the temperature sensor is provided on the insulating substrate, and
the temperature sensor provides the temperature information to the timing control circuit via serial communication.

6. The liquid crystal display device according to claim 3 , wherein the temperature sensor is provided in the timing control circuit.

7. The liquid crystal display device according to claim 1 , wherein the pixel forming portion includes a thin-film transistor having a control terminal connected to the scanning signal line, a first conductive terminal connected to the data signal line, a second conductive terminal connected to a pixel electrode to which the first correction voltage, the second correction voltage, or the signal voltage is to be applied, and a channel layer formed of an oxide semiconductor.

8. The liquid crystal display device according to claim 7 , wherein the oxide semiconductor is InGaZnO mainly composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O).

9. The liquid crystal display device according to claim 1 , wherein the pixel forming portion includes a thin-film transistor having a control terminal connected to the scanning signal line, a first conductive terminal connected to the data signal line, a second conductive terminal connected to a pixel electrode to which the first correction voltage, the second correction voltage, or the signal voltage is to be applied, and a channel layer formed of either an amorphous semiconductor or a polycrystalline semiconductor.

10. The liquid crystal display device according to claim 1 , wherein the liquid crystal display device is driven by dot-by-dot inversion drive, line-by-line inversion drive, column-by-column inversion drive, or frame-by-frame inversion drive in the alternating-voltage drive mode.

11. A method for driving a liquid crystal display device performing pause drive in an alternating-voltage drive mode and including a plurality of scanning signal lines, a plurality of data signal lines crossing each of the scanning signal lines, pixel forming portions at intersections of the scanning signal lines and the data signal lines, a correction circuit that outputs a corrected image signal which is corrected with a correction value to correct a grayscale value of an input image signal when the correction value is provided by the correction circuit and an input image signal which is not corrected when the correction value is not provided by the correction circuit, a scanning signal line driver circuit that sequentially selects and scans the scanning signal lines, and a data signal line driver circuit that writes to the data signal lines correction voltages in accordance with the corrected image signal or signal voltages in accordance with the input image signal, the method comprising the steps of:
outputting

Assignees

• Sharp Kk

Inventors

• Inada Ken
• Nakano Taketoshi
• Fujioka Akizumi
• Yamato Asahi

Classifications

• G09G2340/16

  Determination of a pixel data signal depending on the signal applied in the previous frame · CPC title

• G09G2320/041

  Temperature compensation · CPC title

• G09G2320/0285

  using tables for spatial correction of display data · CPC title

• G09G2320/10

  Special adaptations of display systems for operation with variable images · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title