Method for driving liquid crystal display unit

• US 5,666,133 A
• Filed: 04/10/1996
• Issued: 09/09/1997
• Est. Priority Date: 12/13/1991
• Status: Expired due to Fees

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Nagata, Seiichi, Matsuo, Shigeki
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US08/630,565
• Time in Patent Office: 517 Days
• Field of Search: 345/94, 345/95, 345/96, 345/98, 345/100, 345/92, 345/93, 345/99, 345/208, 345/209, 345/210, 345/213
• US Class Current: 345/100
• 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 3/2011 by amplitude modulation
• 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
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
• CPC Class Codes: G09G 3/3677 suitable for active matrices only

Abstract

Disclosed is a method for driving a liquid crystal display unit, in particular, a method for driving an active matrix type liquid crystal display unit using a thin-film transistor as a switching element. According to the drive method, a plurality of scanning signal power voltages of which levels vary in synchronization with inversion in polarity of an image signal are input to a scanning signal supply circuit, and any of the plural scanning signal power voltages is selected to serve as a scanning signal. Otherwise, some scanning signal power voltages of which levels vary in synchronization with inversion in polarity of the image signal and some scanning signal power voltages of which levels are invariable are input to the scanning signal supply circuit, and any of the plural scanning signal power voltages is selected to serve as a scanning signal.

Claims

1. A method for driving an active matrix liquid crystal display unit comprising:

interposing a liquid crystal material between a plurality of pixel electrodes and an electrode, the liquid crystal material exhibiting dielectric anisotropy;

connecting a switching transistor to each of the plurality of pixel electrodes;

supplying a scanning signal for turning on and off the switching transistor from a scanning signal supply circuit to the switching transistor via a scanning signal line;

supplying an image signal from an image signal supply circuit to each of the pixel electrodes via an image signal line and the switching transistor, the image signal comprising two kinds of voltage level signals;

supplying a counter electrode signal to the electrode, the counter electrode signal comprising two kinds of voltage level signals;

inputting to the scanning signal supply circuit a plurality of scanning signal power voltages having levels that vary in synchronization with an inversion in polarity of the image signal; and

combining the plurality of scanning signal power voltages to serve as the scanning signal for turning on and off the switching transistor connected to each of the plurality of pixel electrodes,

whereby variance of the application voltage attributable to the dielectric anisotropy of the liquid crystal material is eliminated and whereby the image signal and the counter electrode signal form an alternating voltage and are impressed on the liquid crystal material.

2. A method for driving a liquid crystal display unit as claimed in claim 1, comprising:

forming an additional capacitance by capacitively connecting each of the pixel electrodes with the scanning signal line adjacent to each of the pixel electrodes, and

supplying the scanning signal of the adjacent scanning signal line to the pixel electrode via the additional capacitance to eliminate a direct current component of a voltage applied to the liquid crystal material.

3. A method for driving a liquid crystal display unit as claimed in claim 1, wherein, among the scanning signal power voltages, a scanning signal power voltage for turning on the switching transistor is varied in synchronization with the image signal so that the power voltage is in phase with the image signal.

4. A method for driving an active matrix liquid crystal display unit comprising:

interposing a liquid crystal material between a plurality of pixel electrodes and an electrode, the liquid crystal material exhibiting dielectric anisotropy;

connecting a switching transistor to each of the plurality of pixel electrodes;

supplying a scanning signal for turning on and off the switching transistor from a scanning signal supply circuit to the switching transistor via a scanning signal line;

supplying an image signal from an image signal supply circuit to each of the pixel electrodes via an image signal line and the switching transistor, the image signal comprising two kinds of voltage level signals;

supplying a counter electrode signal to each of the counter electrode, the counter electrode siqnal comprising two kinds of voltage level signals;

inputting to the scanning signal supply circuit scanning signal power voltages having levels that vary in synchronization with an inversion in polarity of the image signal and scanning signal power voltages having levels that are invariable; and

combining the plurality of scanning signal power voltages to serve as the scanning signal for turninq on and off the switching transistor connected to each of the plurality of pixel electrodes,

whereby variance of the application voltage attributable to the dielectric anisotropy of the liquid crystal material is eliminated and whereby the image signal and the counter electrode siqnal form an alternating voltage and are impressed on the liquid crystal material.

5. A method for driving a liquid crystal display unit as claimed in claim 4, comprising:

forming an additional capacitance by capacitively connecting each of the pixel electrodes with the scanning signal line adjacent to each of the pixel electrodes, and

supplying the scanning signal of the adjacent scanning signal line to the pixel electrode via the additional capacitance to eliminate a direct current component of a voltage applied to the liquid crystal material.

6. A method for driving a liquid crystal display unit as claimed in claim 4, wherein one of the plurality of scanning signal power voltages is a scanning signal power voltage of which level is invariable to turn on the switching transistor.