Liquid crystal display device and its driving method

A liquid crystal display device comprising:

• a display part comprising:
• a plurality of scanning lines arranged in rows, the rows being numbered from the top consecutively starting with 1 and ending with m,
• a plurality of signal lines arranged in columns, the columns being numbered from the left consecutively staring with 1 and ending with n,
• switching elements disposed at respective intersections of said scanning lines and said signal lines,
• a pixel electrode connected to an output end of the respective switching element,
• counter electrodes capacitively coupled with the respective pixel electrodes,
• liquid crystal cells disposed between said pixel electrodes and said counter electrodes, thereby defining a matrix of m rows and n columns of pixels,
• an auxiliary capacitance whose one end is connected to an output end of each of said switching elements, and
• a plurality of auxiliary capacitance lines arranged in rows, each of the auxiliary capacitance lines being connected to a corresponding row of the auxiliary capacitances;
• a scanning line driving circuit for providing each row of said scanning lines with a scanning line driving signal having an on time and a holding time in which the switching element in each row can be turned on and off, respectively;
• a signal line driving circuit for providing a signal line driving signal for each column of said signal lines;
• a counter electrode driving circuit for providing said counter electrodes with a counter electrode driving signal having a set frequency and a set cycle;
• and
• an auxiliary capacitance line driving circuit for providing an auxiliary capacitance line driving signal for each row of said auxiliary capacitance lines, wherein
• said auxiliary capacitance line driving circuit comprises a first driving transistor and a second driving transistor connected to each of said auxiliary capacitance lines,
• said first driving transistor has a first main electrode connected to the other end of said auxiliary capacitance,
• said first driving transistor has a second main electrode connected to a counter electrode wiring (COM1) as a first common electrode,
• said first driving transistor has a control electrode connected to an i th row scanning line (Gi),
• said second driving transistor has a first main electrode connected to the first main electrode of said first driving transistor,
• said second driving transistor has a second main electrode connected to a second common electrode wiring (COM2), and
• said second driving transistor has a control electrode connected to an (i+2) th scanning line (Gi+2), and wherein
• said auxiliary capacitance line driving circuit is adapted to apply a first voltage to the auxiliary capacitance lines in a first half cycle of said counter electrode driving signal during the on time of said scanning line driving signal and apply a second voltage in a (p+½)th cycle after said first half cycle of said counter electrode driving signal where p is 0 or a natural number said auxiliary capacitance line making the auxiliary capacitance line in a floating condition after said (p+½)th cycle during the remaining holding time.

A method of driving a liquid crystal display device, said liquid crystal device comprising a display part that includes:

• a plurality of scanning lines arranged in rows, the rows being numbered from the top consecutively starting with 1 and ending with m,
• a plurality of signal lines arranged in columns, the columns being numbered from the left consecutively staring with 1 and ending with n,
• switching elements disposed at respective intersections of said scanning lines and said signal lines,
• a pixel electrode connected to an output end of the respective switching element,
• counter electrodes capacitively coupled with the respective pixel electrodes,
• liquid crystal cells disposed between said pixel electrodes and said counter electrodes, thereby defining a matrix of m rows and n columns of pixels,
• an auxiliary capacitance whose one end is connected to an output end of each of said switching elements, and
• a plurality of auxiliary capacitance lines arranged in rows, each of the auxiliary capacitance lines being connected to a corresponding row of the auxiliary capacitances,
• the method comprising the steps of:
• providing each row of said scanning lines a scanning line driving signal having an on time and a holding time in which the switching element in each row can be turned on and off, respectively;
• providing a signal line driving signal for each column of said signal lines;
• providing said counter electrode with a counter electrode driving signal having a set frequency and a set cycle;
• applying a first voltage to the other end of said auxiliary capacitance for a first half cycle of said counter electrode driving signal during the on time of said scanning line driving signal and applying a second voltage for a (p+½)th cycle after said first half cycle of said counter electrode driving signal where p is 0 or a natural number;
• and
• making said auxiliary capacitance line in a floating condition after said (p+½)th cycle during the remaining holding time to thereby increase the absolute value in potential difference between said pixel electrode and said counter electrode.

A liquid crystal display device comprising:

• a display part comprising:
• a plurality of scanning lines arranged in rows, the rows being numbered from the top consecutively starting with 1 and ending with m,
• a plurality of signal lines arranged in columns, the columns being numbered from the left consecutively staring with 1 and ending with n,
• switching elements disposed at respective intersections of said scanning lines and said signal lines,
• a pixel electrode connected to an output end of the respective switching element,
• counter electrodes capacitively coupled with the respective pixel electrodes,
• liquid crystal cells disposed between said pixel electrodes and said counter electrodes, thereby defining a matrix of m rows and n columns of pixels,
• an auxiliary capacitance whose one end is connected to an output end of each of said switching elements,
• a plurality of auxiliary capacitance lines arranged in rows, each of the auxiliary capacitance lines being connected to a corresponding row of the auxiliary capacitances, and
• a parasitic capacitance shield wiring arranged to be interposed between the signal line and the auxiliary capacitance line at every intersection of the signal line the auxiliary capacitance line;
• a scanning line driving circuit for providing each row of said scanning lines with a scanning line driving signal having an on time and a holding time in which the switching element in each row can be turned on and off, respectively;
• a signal line driving circuit for providing a signal line driving signal for each column of said signal lines;
• a counter electrode driving circuit for providing said counter electrodes with a counter electrode driving signal;
• and
• an auxiliary capacitance line driving circuit for providing an auxiliary capacitance line driving signal for each row of said auxiliary capacitance lines, wherein
• said auxiliary capacitance line driving circuit comprises a first and a second driving transistor connected to each of said auxiliary capacitance lines,
• said first driving transistor has a first main electrode connected to the other end of said auxiliary capacitance,
• said first driving transistor has a second main electrode connected to a counter electrode wiring (COM1) as a first common electrode,
• said first driving transistor has a control electrode connected to an i th row scanning line (Gi),
• said second driving transistor has a first main electrode connected to the first main electrode of said first driving transistor,
• said second driving transistor has a second main electrode connected to a second common electrode wiring (COM2), and
• said second driving transistor has a control electrode connected to an (i+2) th scanning line (Gi+2), and wherein
• said auxiliary capacitance line driving circuit is adapted to apply a first voltage to the auxiliary capacitance lines in a first half cycle of said counter electrode driving signal and apply a second voltage thereto in a (p+½) the cycle after said first period of said counter electrode driving signal where p is 0 or a natural number, said auxiliary capacitance line driving circuit making the auxiliary capacitance line in a floating condition after said (p+½)th cycle.

A method for driving a liquid crystal display, the liquid crystal display comprising a plurality of scanning lines disposed in rows and a plurality of signal lines disposed in columns, the plurality of scanning lines and the plurality of signal lines defining a m by n matrix of pixels, each of said pixels comprising:

• a transistor having a gate, a source and a drain, the gate being connected to the adjacent scanning line, the source being connected to the adjacent signal line;
• a pixel electrode connected to the drain of the transistor;
• a liquid crystal layer over the pixel electrode;
• a counter electrode forming a liquid crystal cell together with the liquid crystal layer and the pixel electrode;
• and
• an auxiliary capacitance electrode capacitively coupled to the pixel electrode, the auxiliary capacitance electrode forming an auxiliary capacitance together with the pixel electrode;
• the method comprising the steps of:
• applying scanning pulse signals of a set frame frequency to the plurality of scanning lines to turn on the transistors in rows, thereby successively selecting the rows of pixels from the top, wherein a period during which the transistor at a pixel is turned on defines a selection period for the pixel, and a period during which the transistor at the pixel is turned off defines a holding period for the pixel,
• providing display signals on the signal lines in synchronization with said scanning pulse signal to charge the corresponding pixel electrodes to respective desired potentials;
• applying a rectangular wave signal that alternately exhibits a HIGH level and a LOW level at a set frequency to said counter electrodes, the rectangular wave signal assuming one of the HIGH and LOW levels during the selection period for each pixel;
• for each of the plurality of pixels, applying a first voltage to the auxiliary capacitance electrode during the selection period, and applying a second voltage that differs from the first voltage to the auxiliary capacitance electrode when the rectangular wave signal assumes said one of the HIGH and LOW levels during the holding period that follows the selection period, the auxiliary capacitance electrode being made in a floating condition immediately thereafter during the remaining holding time until the next selection period arrives for the pixel, a value of the second voltage being selected such that an absolute value of a voltage across the liquid crystal cell is raised when the second voltage is applied.

A liquid crystal display device comprising:

• a plurality of scanning lines disposed in rows and a plurality of signal lines disposed in columns, the plurality of scanning lines and the plurality of signal lines defining a m by n matrix of pixels, each of said pixels comprising:
• a transistor having a gate, a source and a drain, the gate being connected to the adjacent scanning line, the source being connected to the adjacent signal line;
• a pixel electrode connected to the drain of the transistor;
• a liquid crystal layer over the pixel electrode;
• a counter electrode forming a liquid crystal cell together with the liquid crystal layer and the pixel electrode;
• and
• an auxiliary capacitance electrode capacitively coupled to the pixel electrode, the auxiliary capacitance electrode forming an auxiliary capacitance together with the pixel electrode;
• a scanning line driver configured to apply scanning pulse signals of a set frame frequency to the plurality of scanning lines to turn on the transistors in rows, thereby successively selecting the rows of pixels from the top, wherein a period during which the transistor at a pixel is turned on defines a selection period for the pixel, and a period during which the transistor at the pixel is turned off defines a holding period for the pixel,
• a signal driver configured to provide display signals on the signal lines in synchronization with said scanning pulse signal to charge the corresponding pixel electrodes to respective desired potentials;
• a counter electrode driver configured to apply a rectangular wave signal that alternately exhibits a HIGH level and a LOW level at a set frequency to said counter electrodes, the rectangular wave signal assuming one of the HIGH and LOW levels during the selection period for each pixel;
• an auxiliary capacitance electrode driver configured to apply, for each of the plurality of pixels, a first voltage to the auxiliary capacitance electrode during the selection period, and applying a second voltage that differs from the first voltage to the auxiliary capacitance electrode when the rectangular wave signal assumes said one of the HIGH and LOW levels during the holding period that follows the selection period, the auxiliary capacitance electrode being made in a floating condition immediately thereafter during the remaining holding time until the next selection period arrives for the pixel, a value of the second voltage being selected such that an absolute value of a voltage across the liquid crystal cell is raised when the second voltage is applied.