Driving method for a display device

• US 5,398,043 A
• Filed: 10/08/1992
• Issued: 03/14/1995
• Est. Priority Date: 10/09/1991
• Status: Expired due to Term

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yamashita, Ichiro, Tsukada, Takashi, Adachi, Katsumi, Takeda, Etsuya
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): NGUYEN, CHANH DUY
• Application Number:
  US07/958,268
• Time in Patent Office: 887 Days
• Field of Search: 340/784, 340/805, 340/765, 340/811, 340/812, 340/813, 340/718, 340/719, 359/54, 359/59, 345/87, 345/92, 345/94, 345/96, 345/97
• US Class Current: 345/94
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• 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

A plurality of ON signal voltages are applied to a thin film transistor (TFT) within one field period, thereby transmitting an image signal voltage to a pixel electrode, two types of modulation signals are alternately supplied to a first wiring (17) at every field during an OFF period of the thin film transistor so that the potential of the pixel electrode is changed, and the change of the potential is superimposed on and/or offset by an image signal voltage so as to apply a resultant voltage to a display material to be driven. Before the termination of a first ON period of the plurality of ON signal voltages applied to the thin film transistor, a part of the potential of the modulation signal is varied.

Claims

1. A driving method for a display device in which pixel electrodes each connected through a capacitance Cs to a first wiring for modulation signals are arranged in a form of a matrix, each of said pixel electrodes having transistor switching means the drain of which is electrically connected thereto, the source of which is electrically connected to an image signal wiring and the gate of which is electrically connected to a scan signal wiring, and said each of said pixel electrodes also being connected through a display material to a counter electrode for a counter voltage signal thereby to drive said display material with alternating current supply, said method comprising the steps of:

applying a plurality of ON signal voltages consisting of one or more preliminary ON signals and a substantial ON signal to said switching means for each row of said matrix, said plurality of ON signal voltages being applied within a horizontal scanning period for each row of said matrix, all of said rows of said matrix being scanned via said scan signal wirings within a period of one field so as to transmit an image signal voltage via said image signal wirings to said pixel electrodes by way of said turned on switching means;

supplying two types of modulation signals having different polarities alternately at every field to said first wirings during an OFF-period of said switching means;

varying a part of the potential of said modulation signals before termination of the preliminary ON period for precharge of said plurality of ON signal voltages applied to said switching means, thereby varying the potential of said pixel electrodes; and

superimposing the change of the potential of said pixel electrodes onto said image signal voltage thereby to apply a resultant voltage to said display material to be driven.

2. The driving method according to claim 1, wherein the part of the potential of said modulation signals is varied after termination of the last ON period of said plurality of ON signal voltages applied to said switching means.

3. The driving method according to claim 1 or 2, wherein the potential of said modulation signals upon termination of the preliminary ON period for precharge of said plurality of ON signal voltages applied to said switching means is made equal to that upon starting of the last ON period thereof.

4. The driving method according to claim 1, wherein each of said first wirings has such an electrical structure serving as the scan signal wiring, and wherein the modulation signal is applied to said scan signal wiring while being superimposed on the scan signal.

5. The driving method according to claim 2, wherein each of said first wirings has such an electrical structure serving as the scan signal wiring, and wherein the modulation signal is applied to said scan signal wiring while being superimposed on the scan signal.

6. The driving method according to claim 3, wherein each of said first wirings has such an electrical structure serving as the scan signal wiring, and wherein the modulation signal is applied to said scan signal wiring while being superimposed on the scan signal.

7. The driving method according to claim 4, wherein the scan signal voltage during the middle period between the preliminary ON period and the substantial ON period of said plurality of ON signal voltages is set to the modulation voltage.

8. The driving method according to claim 4, wherein the image signal voltage transmitted during an ON period of said switching means inverts the polarity of the image signal voltage at every scan line on a display screen, and the polarity of said modulation signal applied to said first wiring during an OFF period of said switching means is inverted at every scan line.