JP2010026393A - Driving method of liquid crystal display device and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device with a satisfactory display quality by suppressing the occurrence of a flicker, and also to provide the driving method of the liquid crystal display device. <P>SOLUTION: The liquid crystal display device comprises: a battery power supply PS; a plurality of pixel electrodes PE; a common electrode CE disposed in correspondence to the pixel electrodes PE; a liquid crystal display panel PNL having a display pixel PX having a liquid crystal layer responding on the basis of the potential difference between the pixel electrodes PE and the common electrode CE; driving means GD, SD, COM driving the display pixel PX ; and a driving control means CTR for controlling the driving means GD, SD, COM, the driving means GD, SD, COM have a first voltage supply means COM for supplying the first voltage to the common electrode CE. The driving control means CTR has a correction means 10 for correcting the value of a first voltage Vcom according to the value of the voltage signal outputted from a battery power supply PS. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and a driving method of the liquid crystal display device, and more particularly to an active matrix liquid crystal display device and a driving method thereof.

  Liquid crystal display devices are widely used as display devices for personal computers, portable information terminals, televisions, car navigation systems, and the like by taking advantage of features such as light weight, thinness, and low power consumption.

  The liquid crystal display device includes a liquid crystal display panel and a control circuit that controls the liquid crystal display panel. The liquid crystal display panel includes a pair of substrates facing each other, a liquid crystal layer sandwiched between the pair of substrates, and a display unit including a plurality of display pixels arranged in a matrix.

  In the display portion, gate lines extending along rows where display pixels are arranged and source lines extending along columns where display pixels are arranged are arranged. In each display pixel, a pixel switch is disposed in the vicinity of the position where the gate line and the source line intersect.

  In general, when an image is displayed using a liquid crystal, it is driven by an AC signal in order to improve the reliability and life of the liquid crystal. That is, the video signal is periodically inverted in polarity with respect to the common voltage and supplied to each display pixel.

  For example, when frame inversion driving is employed, the video signal is set to reverse polarity for each frame, and when line inversion driving is employed, the video signal is set to reverse polarity for each line. At this time, if the common voltage deviates from an appropriate value, flicker may occur.

Conventionally, in order to prevent the occurrence of flicker, the common voltage is adjusted so that the adjuster adjusts the contrast to the best while looking at the gray scale or projects an image with easy flicker recognition. There has been proposed a method of adjusting an image so that there is no unevenness on the screen (see Patent Document 1).
Japanese Patent Laid-Open No. 10-62748

  However, when a battery power source is used as the power source, the value of the voltage signal output from the power source may change with the passage of time since the start of use. When the voltage output from the power supply changes, the value of the gate voltage generated by the voltage signal supplied from the battery power supply changes accordingly.

  When the value of the gate voltage changes, the drop in the liquid crystal voltage at the end of the pixel switch selection period, that is, the punch-through voltage that is generated changes. This punch-through voltage is scanned at the moment when the gate voltage applied to the scanning line changes from the voltage level at which the pixel switch is turned on (on voltage level) to the voltage level at which the pixel switch is turned off (off voltage level). This is caused by the coupling capacitance between the line and the liquid crystal capacitance.

  Even if the common voltage value is set to the optimum value in advance, if the punch-through voltage value changes as described above, the pre-adjusted common voltage value will deviate from the optimum value, causing flicker and display. In some cases, the quality deteriorated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a liquid crystal display device and a driving method of the liquid crystal display device that suppress the occurrence of flicker and have good display quality.

  The liquid crystal display device according to the first aspect of the present invention includes a battery power source, a plurality of pixel electrodes arranged in a matrix, a common electrode arranged corresponding to the pixel electrode, and the pixel electrode and the common electrode. A liquid crystal display panel having a display pixel having a liquid crystal layer that responds based on a potential difference; a drive unit that drives the display pixel; and a drive control unit that controls the drive unit. A first voltage supply unit configured to supply a first voltage to the electrode; and the drive control unit includes a correction unit configured to correct the value of the first voltage according to a value of a voltage signal output from the battery power source. Have.

  A driving method of a liquid crystal display device according to a second aspect of the present invention includes a battery power source, a plurality of pixel electrodes arranged in a matrix, a common electrode arranged corresponding to the pixel electrode, the pixel electrode, and the common A liquid crystal display panel having a display pixel having a liquid crystal layer that responds based on a potential difference with respect to an electrode, and a driving method for the liquid crystal display device, which controls on / off of a switching element connected to the pixel electrode A scanning signal supply step for supplying a scanning signal; a first voltage supply step for supplying a first voltage to the common electrode; and a correction step for correcting the value of the first voltage. A measurement step of measuring a value of the voltage signal output from the battery power supply, and calculating an amplitude of the scanning signal from a measurement result in the measurement step, A scanning signal calculation step of calculating the value of the penetration voltage from the width, and a first voltage calculating step of calculating the first voltage after the correction from the calculation results of the scanning signal calculation step.

  According to the present invention, it is possible to provide a liquid crystal display device and a driving method of the liquid crystal display device that suppress the occurrence of flicker and have good display quality.

  Hereinafter, a liquid crystal display device according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the liquid crystal display device according to the present embodiment is driven by a battery power source PS, a liquid crystal display panel PNL, a drive unit that drives the liquid crystal display panel PNL, and power supplied from the battery power source. A drive control unit CTR for controlling the unit.

  The liquid crystal display panel PNL includes an array substrate (not shown), a counter substrate (not shown), and a liquid crystal layer sandwiched between the array substrate and the counter substrate. This liquid crystal layer includes, for example, an OCB mode liquid crystal that is previously transitioned from a splay alignment to a bend alignment as a liquid crystal material for a normally white display operation. In this embodiment, the reverse transition from the bend alignment to the splay alignment of the liquid crystal is prevented by periodically applying a high voltage, for example, a drive voltage corresponding to black display as a non-video signal to the liquid crystal layer.

  The liquid crystal display panel PNL includes a display unit DYP including display pixels PX arranged in a matrix. The liquid crystal display panel PNL has a pair of substrates facing each other, that is, an array substrate and a counter substrate.

  On the array substrate of the liquid crystal display panel PNL, pixel electrodes PE are arranged for the respective display pixels PX. A common electrode CE is disposed on the counter substrate so as to face the plurality of pixel electrodes PE in correspondence with the pixel electrodes. The liquid crystal layer responds based on the potential difference between the pixel electrode PE and the common electrode CE.

  Each of the plurality of display pixels PX has a liquid crystal capacitance Clc constituted by a liquid crystal layer held between the pixel electrode PE and the common electrode CE. The liquid crystal capacitance Clc is determined by the relative dielectric constant of the liquid crystal material, the pixel electrode area, and the liquid crystal cell gap.

  Further, a storage capacitor Cst is configured by a part of the pixel electrode PE and a common electrode Cs that is stacked with an insulating film and a part of the pixel electrode PE and extends substantially parallel to the scanning line G. Is done.

  Further, on the array substrate, a plurality of scanning lines GL extending along a row where the display pixels PX are arranged and a plurality of signal lines SL extending along a column where the display pixels PX are arranged are arranged in the display unit DYP. ing.

  As shown in FIG. 2, a pixel switch SW is arranged in the vicinity of the intersection between the scanning line GL and the signal line SL. The pixel switch SW has a thin film transistor (TFT) as a switching element, for example.

  The gate electrode of the pixel switch SW is electrically connected to the corresponding scanning line GL. The source electrode of the pixel switch SW is electrically connected to the corresponding signal line SL. The drain electrode of the pixel switch SW is electrically connected to the pixel electrode PE disposed in each display pixel PX. As shown in FIG. 2, a gate-drain capacitance Cgd is generated between the gate electrode and the drain electrode of the pixel switch W.

  Due to the generation of the gate-drain capacitance Cgd, the liquid crystal voltage decreases at the timing when the selection period of the pixel switch SW ends. That is, the punch-through voltage ΔV is generated at the timing when the selection period of the pixel switch SW ends. The punch-through voltage ΔV is generated by coupling capacitance between the scanning line G and the liquid crystal capacitance at the moment when the gate voltage Vg applied to the scanning line G changes from the on voltage level to the off voltage level.

  In the case of the liquid crystal display device according to the present embodiment, the value of the punch-through voltage ΔV is (Cgd / (CLC + Cs + Cgd)) × gate voltage amplitude. The gate voltage amplitude is a difference between the on voltage level and the off voltage level of the gate voltage Vg.

  The drive unit includes a gate driver GD, a source driver SD, and a common voltage generation unit COM. The plurality of scanning lines GL are electrically connected to the gate driver GD. The plurality of signal lines SL are electrically connected to the source driver SD. The gate driver GD and the source driver SD are controlled by the drive control unit CTR to write video signals corresponding to the display pixels PX.

  The drive control unit CTR includes a gate voltage generation unit GV that generates a gate voltage signal from the voltage signal supplied from the battery power source PS, and a source voltage generation unit SV that generates a source voltage signal from the voltage signal supplied from the battery power source PS. A signal control unit SC that converts a video signal supplied from the external signal source SS into data that can be supplied to the source driver SD, and a common voltage correction unit 10.

  The common voltage correction unit 10 includes a measurement unit 12 to which a voltage signal output from the battery power source PS is input, a gate voltage calculation unit 14 to which an output signal of the measurement unit 12 is input, and an output signal of the gate voltage calculation unit 14 Is input to the common voltage calculation unit 16.

  Next, the operation of the liquid crystal display device will be described below. A voltage signal is supplied from the battery power source PS to the gate voltage generation unit GV. The signal control unit SC controls the gate voltage generation unit GV to generate the gate voltage Vg based on the voltage signal from the battery power source PS. The gate voltage Vg is output to the gate driver GD, and is supplied from the gate driver GD to the display pixel PX via the scanning line GL.

  A voltage signal is supplied from the battery power source PS to the source voltage generator SV. The source voltage generation unit SV generates a predetermined number of gradation reference voltages based on a voltage signal from the battery power source PS. A video signal is input from the external signal source SS to the signal controller SC. The signal controller SC converts the input video signal into video data that can be supplied to the source driver SD and outputs the video data.

  The source driver SD generates a source voltage from the gradation reference voltage supplied from the source voltage generation unit SV and the video data supplied from the signal control unit SC. The source voltage is supplied from the source driver SD to the display pixel PX via the signal line S. That is, the source voltage is applied from the signal line SL to the pixel electrode PE of the corresponding display pixel PX through the pixel switch SW that is turned on when the gate voltage Vg is turned on.

  The voltage signal output from the battery power supply is supplied to the voltage regulator VR. The voltage regulator VR outputs a predetermined voltage signal to the common voltage generator COM based on the supplied voltage signal. The common voltage generator COM generates a preset common voltage Vcom from the voltage signal supplied from the voltage regulator VR, and outputs it to the liquid crystal display panel PNL. The common voltage Vcom supplied to the liquid crystal display panel PNL is applied to the common electrode CE.

  As described above, the source voltage applied to the pixel electrode PE and the common voltage Vcom applied to the common electrode CE are applied to the liquid crystal capacitor Clc, and a desired display is made in response thereto.

  Here, when correcting the common voltage Vcom, first, the measurement unit 12 measures and monitors the output voltage value of the battery power source PS (step ST1). Subsequently, the gate voltage calculation unit 14 calculates the amplitude of the gate voltage generated by the gate voltage generation unit GV from the voltage value measured by the measurement unit 12 (step ST2), and from the calculated amplitude of the gate voltage. Then, a new value of the penetration voltage ΔV ′ is calculated (step ST3). Next, the common voltage calculation unit 16 newly calculates an optimum value Vcom ′ of the common voltage from the value of the penetration voltage ΔV ′ calculated by the gate voltage calculation unit 14 (step ST4).

  The new optimum value Vcom ′ of the common voltage output from the common voltage calculation unit 16 is input to the common voltage generation unit COM. The common voltage generator COM outputs the value of the input optimum value Vcom ′ of the common voltage to the liquid crystal display panel PNL as the common voltage Vcom. The common voltage Vcom input to the liquid crystal display panel PNL is supplied to the common electrode CE.

  Therefore, when the value of the voltage signal supplied from the battery power source PS to the drive control unit CTR changes and, as a result, the punch-through voltage ΔV changes, the value of the common voltage Vcom adjusted in advance deviates from the optimum value. Even so, the drive control unit CTR includes the common voltage correction unit 10 as described above, and flickers are generated by supplying a new common voltage optimum value Vcom ′ to the liquid crystal display panel PNL as the common voltage Vcom. Can be suppressed.

  That is, according to the liquid crystal display device and the driving method of the liquid crystal display device according to the present embodiment, the occurrence of flicker is suppressed without depending on the state of the battery power supply, and the liquid crystal display device and the liquid crystal with good display quality are suppressed. A driving method of a display device can be provided.

  Further, by combining the driving method of the liquid crystal display device according to the present embodiment with the OCB mode liquid crystal display device, for example, as the value of the voltage signal output from the battery power source starts to be used with the passage of time. Even when the voltage is reduced, the common voltage Vcom can be set to an optimum value, so that reverse transition can be more effectively prevented.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, the liquid crystal display device according to the above embodiment is an OCB mode liquid crystal display device, but the present invention can be applied to all liquid crystal mode liquid crystal display devices.

  Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine the component covering different embodiment suitably.

The figure which shows schematically the structural example of the liquid crystal display device of the liquid crystal display device which concerns on one Embodiment of this invention. FIG. 2 is a diagram schematically showing a configuration example of display pixels of the liquid crystal display device shown in FIG. 1. FIG. 3 is a diagram for explaining an example of a driving method of the liquid crystal display device illustrated in FIG. 1. 4 is a flowchart for explaining a driving method of the liquid crystal display device shown in FIG. 1.

Explanation of symbols

  PS ... battery power supply, PNL ... liquid crystal display panel, CTR ... drive control unit, PX ... display pixel, PE ... pixel electrode, CE ... common electrode, GD ... gate driver, SD ... source driver, COM ... common voltage generation unit.

Claims (3)

Battery power,
A liquid crystal display panel having a plurality of pixel electrodes arranged in a matrix, a common electrode arranged corresponding to the pixel electrode, and a display pixel having a liquid crystal layer that responds based on a potential difference between the pixel electrode and the common electrode When,
Driving means for driving the display pixels;
Drive control means for controlling the drive means,
The driving means includes first voltage supply means for supplying a first voltage to the common electrode,
The liquid crystal display device, wherein the drive control unit includes a correction unit that corrects the value of the first voltage in accordance with a value of a voltage signal output from the battery power source. The driving unit further includes scanning signal supply means for supplying a scanning signal for controlling on / off of a switching element connected to the pixel electrode,
The correction means measures the value of the voltage signal output from the battery power source, calculates the amplitude of the scanning signal from the measurement result of the measuring means, and calculates the value of the punch-through voltage from the amplitude of the scanning signal. The liquid crystal display device according to claim 1, further comprising: a scanning signal calculating unit that calculates, and a first voltage calculating unit that calculates the corrected first voltage from a calculation result of the scanning signal calculating unit. A display having a battery power source, a plurality of pixel electrodes arranged in a matrix, a common electrode arranged corresponding to the pixel electrode, and a liquid crystal layer that responds based on a potential difference between the pixel electrode and the common electrode A liquid crystal display panel having pixels and a method for driving a liquid crystal display device having pixels,
A scanning signal supply step for supplying a scanning signal for controlling on / off of a switching element connected to the pixel electrode;
Supplying a first voltage to the common electrode;
A correction step of correcting the value of the first voltage,
The correcting step includes a measuring step of measuring a value of a voltage signal output from the battery power source,
A scanning signal calculating step of calculating an amplitude of a scanning signal from a measurement result in the measuring step, and calculating a value of a penetration voltage from the amplitude of the scanning signal;
And a first voltage calculation step of calculating the corrected first voltage from the calculation result in the scanning signal calculation step.

Images