Liquid crystal display device and driving control method thereof

• US 7,221,344 B2
• Filed: 11/07/2001
• Issued: 05/22/2007
• Est. Priority Date: 11/10/2000
• Status: Expired due to Fees

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Shimomaki, Shinichi
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Shapiro, Leonid
• Application Number:
  US10/007,468
• Publication Number:
  US 20020057243A1
• Time in Patent Office: 2,022 Days
• Field of Search: 345 94- 96, 345209-215, 345/87, 345/92, 349 42- 47
• US Class Current: 345/87
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

In a liquid crystal display device of an active matrix type, at first, an initialization signal voltage having a voltage value equal to or higher than the maximum voltage value of a display signal is applied to display pixels in a signal application period in a field period. The display signal is thereafter applied. As a result, the change amount of the voltage applied to liquid crystal due to the field-through voltage in relation to a gate pulse can be arranged to be substantially constant, and can always be cancelled by a common electrode voltage. Occurrence of flicker and seizure phenomena can be thereby restricted so that the display quality can be improved.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display panel having a plurality of signal lines, a plurality of scanning lines, and a plurality of display pixels arrayed in a matrix and provided respectively near cross-points between the signal lines and the scanning lines through switching elements; and

a driver which supplies the plurality of signal lines with a display signal in a field period, and which supplies the plurality of scanning lines with a scanning signal, to apply the display signal to the plurality of display pixels, wherein

the driver includes means which supplies an initialization signal including a constant single pulse voltage to the plurality of signal lines and supplies a first gate pulse as the scanning signal to the display pixels,

and after completing the supply of the initialization signal to the plurality of signal lines and completion of the supply of the first gate pulse to the plurality of scanning lines, and after a predetermined hold time, supplying the display signal to the plurality of signal lines and supplying a second gate pulse as the scanning signal to the plurality of scanning lines, thereby applying the display signal to the display pixel, at least one signal application period set within the field period,

the liquid crystal display panel includes, a plurality of pixel electrodes arrayed in a matrix through the switching elements, common electrodes opposed to the pixel electrodes, and liquid crystal sandwiched between the pixel electrodes and the common electrode, and

the hold time is set to a time equal to or longer than a voltage-write response time of the liquid crystal in the display pixels,

wherein the initialization signal in the driver has a value equal to or higher than a maximum voltage value of the display signal.

2. The liquid crystal display device accordinq to claim 1, wherein the liquid crystal display panel is a non-auxiliary capacitance type.

3. The liquid crystal display device according to claim 1, wherein each of the switching elements of the liquid crystal display panel includes a thin film transistor.

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

the driver applies the initialization signal and the display signal to the display pixels connected to the scanning lines of the liquid crystal display panel, at a predetermined time interval, sequentially for every one of the scanning lines, in the signal application period in the field period, and

the time interval is set to a value at which timings of applying the initialization signal voltage and the display signal to every one of the display pixels connected to each of the scanning lines do not overlap with each other.

5. The liquid crystal display device according to claim 1, wherein

application timing is set such that the driver applies the initialization signal simultaneously to all of the display pixels of the liquid crystal display panel, and thereafter applies the display signal to the display pixels connected to the scanning lines of the liquid crystal display panel, at a predetermined time interval, sequentially for every one of the scanning lines, in the signal application period in the field period.

6. The liquid crystal display device according to claim 1, wherein

the driver provides three signal application periods in one field period.

7. The liquid crystal display device according to claim 6, wherein

the display signal comprises first, second, and third color component signals, and

the driver applies the initialization signal and thereafter applies any one of the first, second, and third color component signals, to the display pixels connected to the scanning lines of the liquid crystal display panel, sequentially for every one of the scanning lines, in each of the signal application periods of the field period.

8. The liquid crystal display device according to claim 7, further comprising an illumination light source capable of controlling light emission color,

the illumination light source being controlled to have light emission color corresponding to any one of the first, second, and third color component signals that is applied by the driver in each signal application period.

9. The liquid crystal display device according to claim 6, wherein of the display signal, the first color component signal is a red component signal, the second color component signal is a green component signal, and the third color component signal is a blue component signal.

10. A drive control method for a liquid crystal display device which has a plurality of signal lines, a plurality of scanning lines, and a plurality of display pixels arrayed in a matrix and provided respectively near cross-points between the signal lines and the scanning lines through switching elements, the plurality of display pixels including a plurality of pixel electrodes arrayed in a matrix through the switching elements, common electrodes opposed to the pixel electrodes, and liquid crystal sandwiched between the pixel electrodes and the common electrode, wherein the plurality of signal lines are supplied with a display signal in a field period and scanning signals are supplied to the plurality of scanning lines, to apply the display signal to the plurality of display pixels, comprising:

providing at least one signal application period in the field period;

applying an initialization signal including a constant single pulse to the display pixels, by supplying the initialization signal to the plurality of signal lines and supplying a first gate pulse as the scanning signal to the scanning lines; and

applying the display signal to the display pixels by supplying the display signal to the plurality of signal lines and supplying a second gate pulse as the scanning signal to the plurality of scanning lines after a predetermined voltage hold time has passed after completion of applying the initialization signal to the display pixels and the first gate pulse to the plurality of scanning lines,

wherein the hold time is set to a time equal to or longer than a voltage-write response time of the crystal liquid in the display pixels,

wherein the initialization signal has a value equal to or higher than a maximum voltage value of the display signal.

11. The drive control method according to claim 10, wherein applying the initialization signal includes applying the initialization signal to the display pixels connected to the scanning lines, sequentially for every one of the scanning lines,

applying the display signal includes applying the display signal to the display pixels connected to the scanning lines, sequentially for every one of the scanning lines, and

application timings of applying the initialization signal and the display signal for every one of the scanning lines are set so as not to overlap with each other.

12. The drive control method according to claim 10, wherein

applying the initialization signal includes applying the initialization signal simultaneously to all display pixels connected to the scanning lines.

13. The drive control method according to claim 10, wherein

providing the signal application period in the field period includes providing three signal application periods in one field period.

14. The drive control method according to claim 13, wherein

the display signal comprises first, second, and third color component signals, and

applying the initialization signal includes applying the initialization signal simultaneously to the plurality of display pixels connected to the scanning lines, in each of the signal application periods, and

applying the display signal includes applying any of the first, second, and third color component signals, to the display pixels connected to the scanning lines, sequentially for every one of the scanning lines, in each of the signal application periods.

15. The drive control method according to claim 14, further comprising controlling light emission color of an illumination light source, wherein

controlling of light emission color includes controlling the light emission color of the light source so as to correspond to any of the first, second, and third color component signals that is applied to the display pixels in applying the display signal.