JP2009139649A - Liquid crystal display and method of driving liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display suppressing deterioration in display quality, and a method of driving the liquid crystal display. <P>SOLUTION: There is provided the method of driving the liquid crystal display having a first display unit and a second display unit differing in number of scan lines from each other, and a driving unit which supplies driving signals to the first display unit and the second display unit. When a display unit having a smaller number of scan lines between the first display unit and the second display unit is driven, the driving unit divides a one-frame period into a plurality of field periods and inverts the polarity of an opposite voltage for every plurality of field periods, and a blank period is provided in each field period after scan lines are driven. <P>COPYRIGHT: (C)2009,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 type liquid crystal display device and a driving method thereof.

  A liquid crystal display device has features such as thinness, light weight, and low power consumption, and is applied to various uses such as an OA device information terminal, a clock, and a television. In particular, a liquid crystal display device having a thin film transistor (hereinafter referred to as TFT) is used as a monitor for displaying a large amount of information, such as a portable television or a computer, because of its high responsiveness.

  In general, a liquid crystal display device includes a pair of substrates arranged to face 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. ing.

  In the display portion, scanning lines arranged along rows in which a plurality of display pixels are arranged and signal lines arranged along columns in which the plurality of display pixels are arranged are arranged. A pixel switch is disposed in the vicinity of the position where the scanning line and the signal line intersect.

  On one substrate, pixel electrodes are arranged corresponding to the respective display pixels. On the other substrate, a counter electrode facing a plurality of pixel electrodes is disposed. By applying a voltage to the pixel electrode and the counter electrode, a liquid crystal voltage is applied to the liquid crystal sandwiched between these electrodes.

  In recent years, devices having a plurality of display units have been proposed (see Patent Document 1). For example, in a device having a main screen with a large display capacity and a sub-screen with a small display capacity, when one of these screens is in a video display state, the other screen may be driven to be in a non-display state. .

On the other hand, an interlace driving method has been proposed in which one or more scanning lines are thinned out and driven.
JP 2000-250064 A

  Depending on the state of the input signal, interlaced driving may be applied to a liquid crystal display device having a plurality of display units, for example, a main screen and a sub screen as described above. In this case, when the main screen is in the non-display state and the sub screen is in the display state, the sub display section has a smaller number of display lines than the main display section, so the last field period in one frame period is the other. This is longer than the field period.

  In this case, the period during which the counter potential is applied in the last field period becomes longer, and there is a difference in luminance between the line where signal writing is performed in another field period and the line where signal writing is performed in the last field period. As a result, horizontal streaks appear on the display screen and display quality may be degraded.

  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 that suppresses display quality deterioration and a driving method thereof.

  A liquid crystal display device according to a first aspect of the present invention is a display pixel comprising a plurality of display pixels in which a liquid crystal layer is held between a pixel electrode connected to a scanning line and a signal line via a switch element and a counter electrode. A driving method of a liquid crystal display device having a display panel having a plurality of lines and a driving unit that drives the scanning lines, signal lines, and counter electrodes, and divides one frame period into at least three field periods In addition, a blanking period is set so that each field period becomes equal, a first voltage is applied to the counter electrode in the first field period, and the pixel electrodes of the display pixel lines of the first group are sequentially applied to the pixel electrodes. A video signal is applied, a second voltage is applied to the counter electrode in a second field period, and a video is sequentially applied to the pixel electrodes of the display pixel lines of a second group. Was applied items, the third field period, and applies a first voltage to the counter electrode, sequentially applies the video signal to the pixel electrode of the display pixel line of the third group.

  The driving method of the liquid crystal display device according to the second aspect of the present invention includes a first display unit and a second display unit having different numbers of scanning lines, and a driving unit that supplies a drive signal to the first display unit and the second display unit When driving a display unit having a small number of scanning lines of the first display unit and the second display unit, the driving unit includes a plurality of frame periods. In each field period, the polarity of the counter voltage is inverted, and in each field period, a different scanning line is driven and then a blank period is provided so that each field period is equalized. .

  According to the present invention, it is possible to provide a liquid crystal display device that suppresses display quality deterioration and a driving method thereof.

  The liquid crystal display device according to the first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the liquid crystal display device according to this embodiment includes a first liquid crystal display panel PNL1 and a second liquid crystal display panel PNL2. The first liquid crystal display panel PNL1 and the second liquid crystal display panel PNL2 are electrically connected by a flexible substrate 305.

  Each of the first liquid crystal display panel PNL1 and the second liquid crystal display panel PNL2 includes a first display unit DYP1 and a second display unit DYP2 each including a plurality of display pixels (not shown) arranged in a matrix. Yes.

  In the first display unit DYP1, scanning lines 201 extending along rows in which display pixels are arranged, and signal lines 304 extending in columns in which display pixels are arranged are arranged. A pixel switch (not shown) is disposed in the vicinity of the position where the scanning line 201 and the signal line 304 intersect.

  In the second display unit DYP2, scanning lines 202 extending along rows where display pixels are arranged and signal lines 304 extending along columns where display pixels are arranged are arranged. A pixel switch (not shown) is disposed in the vicinity of the position where the scanning line 202 and the signal line 304 intersect.

  In the liquid crystal display device according to the present embodiment, a part of the signal line 304 arranged in the second display unit DYP2 extends to the first display unit DYP1. That is, a part of the signal line 304 is shared by the first liquid crystal display panel PNL1 and the second liquid crystal display panel PNL2.

  The liquid crystal display device according to the present embodiment includes a drive unit that drives the first display unit DYP1 and the second display unit DYP2. The driving unit includes a scanning line driving circuit 211 and a signal line driving circuit 303.

  The scanning line driving circuit 211 is connected to a first scanning signal supply wiring W <b> 1 that supplies scanning signals to the scanning lines 201 and 202. The signal line driver circuit 303 is connected to a supply wiring W <b> 2 that supplies a video signal to the signal line 304.

  As shown in FIG. 1, a first switch 203 is connected to one end of the scanning line 201. The first switch 203 switches the connection between the scanning line 201 and the first scanning signal supply wiring W1. That is, the scanning line 201 is connected to the first scanning signal supply wiring W <b> 1 through the first switch 203.

  A second switch 204 is connected to one end of the scanning line 202. The second switch 204 switches the connection between the scanning line 202 and the first scanning signal supply wiring W1. That is, the scanning line 202 is connected to the first scanning signal supply wiring W <b> 1 through the second switch 204.

  The first switch 203 and the second switch 204 are controlled to be turned on / off by the scanning line driving circuit 211, and as a result, the connection between the scanning line driving circuit 211 and one end of the scanning lines 201 and 202 is switched. The scanning line driving circuit 211 sequentially supplies a scanning signal to the first scanning signal supply wiring W1, and sequentially drives the scanning line 201 or the scanning line 202.

  The scanning line driving circuit 211 has interlace driving means 211A for interlace driving the scanning lines 201 and 202. The interlace driving unit 211A divides one frame period into a plurality of field periods, and scans the scanning lines 201 and 202 by thinning out one or more scanning lines in each field period.

  For example, in the liquid crystal display device according to the present embodiment, one frame period is divided into a first field period, a second field period, and a third field period. In each field period, after the driving of the scanning line is finished, it is a blank period.

  That is, in the first field period, the first, fourth, seventh,... Scanning lines are driven. In the first field period, it is a blank period after the scanning line is driven.

  In the second field period, the second, fifth, eighth,... Scanning lines are driven. In the second field period, after the scanning line is driven, it is a blank period.

  In the third field period, the third, sixth, ninth,... Scanning lines are driven. In the third field period, after the scanning line is driven, it is a blank period.

  Next, the operation of the liquid crystal display device according to this embodiment will be described below. Hereinafter, a case where the first liquid crystal display panel is in the video display state and the second liquid crystal display panel is in the non-video display state will be described. As shown in FIG. 2, in the liquid crystal display device according to the present embodiment, the display unit DYP2 of the first liquid crystal display panel has 96 scanning lines, and one vertical period is 288 horizontal periods (field periods). ).

  In other words, in the present embodiment, one frame period is divided into a first field period, a second field period, and a third field period so as to be substantially equal to each other. The scanning line driving circuit 211 drives the first line, the fourth line, the seventh line,... Of the scanning line 201 in the first field period. In the first field period, after the scanning line 201 is driven, it is a blank period in which no signal is written to the display pixel.

  The scanning line driving circuit 211 drives the second line, the fifth line, the eighth line,... Of the scanning line 201 in the second field period. In the second field period, after the scanning line 201 is driven, it is a blank period in which no signal is written to the display pixel.

  The scanning line driving circuit 211 drives the third line, the sixth line, the ninth line,... Of the scanning line 201 in the third field period. In the third field period, after the scanning line 201 is driven, it is a blank period in which no signal is written to the display pixel.

  Further, in the liquid crystal display device according to the present embodiment, the counter voltage is inverted every field period.

  Conventionally, as shown in FIG. 3, the third field period is longer than the other field periods.

  The counter potential applied in the third field period is held until the next frame period. For this reason, depending on the scanning line, there may occur a case where the period of the counter potential having the opposite polarity to the counter potential at the time of writing is greatly different.

  That is, in the case of the present embodiment, the scanning line (second line, fifth line, eighth line,...) Driven in the second field period is a period in which the opposite voltage having the opposite polarity to the opposite potential at the time of writing is held. Becomes longer.

  At this time, the voltage applied to the liquid crystal changes by (1− (Cst + Clc) / Ctot) × ΔVcom due to a change in the counter potential. Here, Cst is the auxiliary capacity of each display pixel, Clc is the liquid crystal capacity of each display pixel, Ctot is the total capacity of each display pixel, and ΔVcom is the amount of change in the counter voltage.

  That is, if the third field period is longer than the other field periods, the counter potential having the opposite polarity than the first line, the fourth line, the seventh line,. In the second line, the fifth line, the eighth line,.

  Therefore, the voltage applied to the liquid crystal corresponding to the second, fifth, and eighth scanning lines 201 may have a value different from the originally held potential. In this case, a luminance difference is generated between lines having different execution voltages applied to the liquid crystal, and the display quality may be lowered.

  On the other hand, in the liquid crystal display device according to the present embodiment, a blank period is provided in each field period, and each field period is controlled to be substantially equal. For example, in this embodiment, the first field period is 96 horizontal periods, the second field period is 96 horizontal periods, the third field period is also 96 horizontal periods, and each field period has substantially the same length. become.

  For this reason, in the liquid crystal display device according to the present embodiment, the execution voltage applied to each liquid crystal corresponding to the scanning line scanned in each field period becomes substantially equal, so that the display quality is not lowered.

  That is, according to the liquid crystal display device according to the present embodiment, it is possible to provide a liquid crystal display device that suppresses display quality deterioration and a driving method thereof.

  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 present invention can be applied to devices other than a liquid crystal display device as long as the display device has a display period and a non-display period.

  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 suitably the component covering different embodiment.

1 is a diagram schematically showing a configuration example of a liquid crystal display device according to an embodiment of the present invention. FIG. 3 is a diagram for explaining an example of a driving method of the liquid crystal display device illustrated in FIG. 1. The figure for demonstrating an example of the driving method of the conventional liquid crystal display device.

Explanation of symbols

  DYP1 ... first display unit, DYP2 ... second display unit, 211 ... drive unit

Claims (4)

A display panel including a plurality of display pixel lines each composed of a plurality of display pixels in which a liquid crystal layer is held between a pixel electrode connected to a scanning line and a signal line via a switch element and a counter electrode;
A driving unit for driving the scanning line, the signal line, and the counter electrode, and a driving method of a liquid crystal display device,
Each frame period is divided into at least three field periods, and blanking periods are set so that each field period becomes equal,
In the first field period, a first voltage is applied to the counter electrode, and a video signal is sequentially applied to the pixel electrodes of the display pixel lines of the first group,
In the second field period, a second voltage is applied to the counter electrode, and a video signal is sequentially applied to the pixel electrodes of the display pixel lines of a second group,
In the third field period, a first voltage is applied to the counter electrode, and a video signal is sequentially applied to the pixel electrodes of the display pixel lines of a third group. A driving method of a liquid crystal display device, comprising: a first display unit and a second display unit having different numbers of scanning lines; and a driving unit that supplies a driving signal to the first display unit and the second display unit,
When driving a display unit having a small number of scanning lines of the first display unit and the second display unit, the driving unit divides one frame period into a plurality of field periods,
Inverting the polarity of the counter voltage for each of the plurality of field periods,
A driving method of a liquid crystal display device in which a blank period is provided after driving different scanning lines in each field period, thereby making each field period equal.   The driving unit is a driving method of a liquid crystal display device in which one or more scanning lines are thinned and sequentially driven in each of the plurality of field periods. A driving method of a liquid crystal display device further comprising switching means for switching display between the first display unit and the second display unit,
The driving unit drives the liquid crystal display device to control the switching unit.

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