TW201312540A - Display device and drive method for same - Google Patents

Abstract

Provided is a display device in which a reduction in display quality is suppressed while power consumption is reduced more than conventional configurations. A liquid crystal display device performs so-called low-frequency refresh driving for providing an idle period after a scan period, and drives a gate line in two types of drive modes, a video display mode and a still image display mode. The liquid crystal display device performs two operations in still image display mode, a rewrite operation and a normal operation. The rewrite operation is performed during a still image rewrite period including two video scan periods (T11). Normal operation is performed by alternately repeating the video scan period (T11) and the still image rest period (T12) using a single still image frame period as a unit.

Description

Display device and driving method thereof

The present invention relates to a display device and a driving method thereof, and more particularly to a display device suitable for display of a still image and a driving method thereof.

Since the prior art, display devices such as liquid crystal display devices have required a reduction in power consumption. For this reason, Patent Document 1 discloses a method of driving a display device in which a gate period T1 in which all gate lines are in a non-scan state is provided after a scan period T1 in which a gate line of a liquid crystal display device is scanned. During the rest period T2, no clock signal or the like is supplied to the gate driver. Therefore, since the driving frequency of the gate line as a whole is reduced, it is possible to achieve low power consumption. In the following, as in the driving method described in Patent Document 1, the driving by the idle period T2 after the scanning period T1 is referred to as "low frequency update driving". This low frequency update driver is mainly used for still image display.

The above-described low frequency update driving system shortens the scanning period T1 earlier than the previous one, and sets a longer rest period T2. Therefore, when the low-frequency update driving is performed, the time for writing the video signal to each pixel forming portion is shortened, so that the image (after-image) of the previous frame period is displayed.

Therefore, Patent Document 2 discloses a driving method of a display device in which the above-described rest period T2 is set after the scanning period T1 (two scanning of the gate line) is provided twice as shown in FIG. According to the low frequency update drive disclosed in Patent Document 2, the time for writing a video signal to each pixel formation portion is approximately twice as large as that of the low frequency update drive described in Patent Document 1. Therefore, the display of the afterimage can be eliminated.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-312253

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2002-278523

In the case of the low frequency update driving described in the above Patent Document 2, when the same image is displayed in the continuous frame period, the gate line is also scanned twice in each frame period. However, in this case, it is not necessary to scan the gate line twice. Therefore, when the same image is displayed during the continuous frame period, the power consumption is increased by performing unnecessary scanning on the gate line.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a display device and a method of driving the same that suppress a reduction in display quality and reduce power consumption earlier.

A first aspect of the present invention is a display device, comprising: a display portion including a plurality of scanning signal lines; a plurality of image signal lines crossing the plurality of scanning signal lines; and respectively corresponding to the plurality of scanning signals a plurality of pixel forming portions of the switching elements arranged in a matrix in which the scanning signal lines and the plurality of image signal lines are arranged; and the scanning signal line driving circuit capable of being driven in two driving modes of the first driving mode and the second driving mode The plurality of scanning signal lines; the image signal line driving circuit driving the plurality of image signal lines; And a display control circuit for controlling the scanning signal line driving circuit and the image signal line driving circuit; and the scanning signal line driving circuit: in the first driving mode, scanning for selecting the plurality of scanning signal lines in sequence The first frame period of the period is a period, and the plurality of scanning signal lines are driven, and in the second driving mode, the scanning period and the plurality of scanning signal lines are in a non-selected state. The plural number is driven in such a manner that the scanning period and the rest period alternately occur in a period including the scanning period and the second frame period of the rest period, except for a specific period immediately after the change of the image to be displayed. Scanning the signal line, and causing the length of the scanning period in the second frame period to be the same as the length of the scanning period in the first frame period, and making the ratio of the scanning period in the specific period larger than the above The ratio of the above scanning periods in the second frame period.

According to a second aspect of the present invention, in the first aspect of the present invention, the first frame period further includes the rest period, and The scanning signal line drive circuit drives the plurality of scanning signal lines such that the scanning period and the rest period alternately appear in a cycle of the first frame period.

According to a second aspect of the present invention, in the scanning signal line drive circuit, the sleep period in the second frame period is longer than the rest period in the first frame period.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the pixel forming portion includes a liquid crystal layer, and the scanning period included in the specific period includes two of the above-described first frame periods The scanning signal period drive circuit performs the polarity inversion driving during the scanning period of the same length, and causes the signals applied to the respective image signal lines to have the same polarity in the two scanning periods in the specific period.

According to a fifth aspect of the present invention, in the third aspect of the present invention, the pixel forming portion includes a liquid crystal layer, and the scanning period included in the specific period includes two of the above-described first frame periods The scanning signal period drive circuit performs the polarity inversion driving during the scanning period of the same length, and causes the signals applied to the respective image signal lines to have mutually different polarities in the two scanning periods in the specific period.

A sixth aspect of the present invention is the fourth aspect or the fifth aspect of the present invention, wherein the specific period sequentially includes: a scanning period of the same length as the scanning period in the first frame period; The rest period in the first frame period is a rest period of the same length; a scan period having the same length as the scan period in the first frame period; and the rest period in the second frame period For the rest period of the same length.

According to a seventh aspect of the present invention, in the fourth aspect or the fifth aspect of the present invention, the specific period includes two scan periods having the same length as the scan period in the first frame period, And a rest period of the same length as the above-described rest period in the second frame period.

According to a third aspect of the present invention, in the third aspect of the present invention, the scanning period included in the specific period includes the scanning period of the same length as the first frame period, and the specific period is sequentially The scanning period that is the same length as the first frame period and the rest period that is the same length as the rest period in the second frame period are included.

According to a ninth aspect of the invention, the pixel forming portion includes a liquid crystal layer, and the image signal line driving circuit performs polarity inversion driving.

According to a tenth aspect of the present invention, in the first aspect of the present invention, the pixel forming portion includes a liquid crystal layer, wherein the one frame period includes the scanning period, and the scanning period included in the specific period includes two The scan period in the first frame period is a scan period of the same length, and the specific period includes two scan periods having the same length as the scan period in the first frame period and the second scan. In the above-described rest period in the frame period, the video signal line drive circuit performs polarity inversion driving, and causes the signals applied to the respective video signal lines to have the same polarity in the two scanning periods in the specific period.

According to a first aspect of the present invention, in the first aspect of the present invention, the pixel forming portion includes a liquid crystal layer, and the one frame period includes the scanning period, and the scanning period included in the specific period includes two Above 1st The scan period in the frame period is a scan period of the same length, and the specific period includes two scan periods of the same length as the scan period in the first frame period and the second frame. In the above-described rest period of the period, the video signal line drive circuit performs polarity inversion driving, and causes signals to be supplied to the respective video signal lines to have mutually different polarities in the two scanning periods in the specific period.

According to a twelfth aspect of the present invention, the display control circuit is configured to perform a moving image display in the display unit, so that The scanning signal line driving circuit drives the scanning signal line driving circuit in a first driving mode to control the scanning signal line driving circuit, and when the display unit performs a still image display, the scanning is performed. The signal line drive circuit controls the scanning signal line drive circuit by driving the plurality of scanning signal lines in the second driving mode.

According to a thirteenth aspect of the present invention, in the first aspect to the twelfth aspect, the switching element is a thin film transistor in which a semiconductor layer is formed by an oxide semiconductor.

A fourteenth aspect of the present invention is a driving method of a display device, comprising: a display portion including a plurality of scanning signal lines; and a first driving mode and a second driving The two driving modes of the mode drive the scanning signal line driving circuit of the plurality of scanning signal lines; and the driving method includes the following steps: in the first driving mode, the plurality of scannings are sequentially selected The first frame period of the scanning period of the scanning signal line is a period, and the plurality of scanning signal lines are driven; and in the second driving mode, the scanning period and the plurality of scanning signal lines are included In addition to the specific period immediately after the change of the image to be displayed in the non-selected state, the scanning period and the rest period are alternately cycled with the second frame period including the scanning period and the rest period. And causing the plurality of scanning signal lines to be driven, and causing the length of the scanning period in the second frame period to be the same as the length of the scanning period in the first frame period, and causing the above-mentioned specific period The ratio of the scanning period is greater than the ratio of the above scanning period in the second frame period.

According to the first aspect of the present invention, the image is displayed in two driving modes of the first driving mode and the second driving mode. In the second driving mode, since the so-called low-frequency update driving is performed after the scanning period is set, the power consumption can be reduced. Further, in the specific period in the second driving mode, a scanning period longer than the scanning period in the second frame period is set. Therefore, the writing of the potential corresponding to the image to be displayed to each pixel forming portion can be sufficiently performed, so that the display of the afterimage is eliminated. Thereby, the deterioration of the display quality can be suppressed. On the other hand, in the period other than the above-described specific period in the second driving mode, only the scanning period which is the same as the scanning period in the first frame period is set once for each second frame period, so that it can be further reduced. The power consumption required to drive the signal line.

According to the second aspect of the present invention, in the first driving mode, since Since the so-called low-frequency update driving during the rest period is set after the scanning period, further low power consumption can be realized.

According to the third aspect of the present invention, since the rest period in the second frame period is longer than the rest period in the first frame period, further low power consumption can be realized in the second driving mode.

According to the fourth aspect or the fifth aspect of the present invention, in the liquid crystal display device that performs the polarity inversion driving, the scanning period in the two first frame periods is included in the specific period in the second driving mode. Therefore, the writing of the potential corresponding to the image to be displayed to each pixel forming portion can be sufficiently performed, so that the display of the afterimage is eliminated. Thereby, the deterioration of the display quality can be sufficiently suppressed.

According to the sixth aspect or the seventh aspect of the present invention, the low frequency update drive can be performed even in the specific period described above, and the same effects as those of the fourth aspect or the fifth aspect of the present invention can be exhibited. Further, according to the seventh aspect of the present invention, since the number of times of switching between the operation during the scanning period and the operation during the rest period is lower than that of the sixth aspect of the present invention, it is possible to further reduce the power consumption.

According to the eighth aspect of the present invention, in the specific period in the second driving mode, one scanning period having the same length as the first frame period is included. Therefore, since the writing of the potential corresponding to the image to be displayed is sufficiently performed on each pixel forming portion, the display of the afterimage can be eliminated. Thereby, the deterioration of the display quality can be sufficiently suppressed. Further, since the driving frequency of the scanning signal line at the time of changing the image to be displayed is lowered, further low power consumption can be realized.

According to the ninth aspect of the present invention, the liquid crystal display device that performs the polarity inversion driving can exhibit the same effects as the eighth aspect of the present invention.

According to the tenth aspect or the eleventh aspect of the present invention, in the liquid crystal display device that performs the polarity inversion driving, the scanning period in the two first frame periods is included in the specific period in the second driving mode. Therefore, the writing to the respective pixel forming portions of the potential corresponding to the image to be displayed is sufficiently performed, so that the display of the afterimage is eliminated. Thereby, the deterioration of the display quality can be sufficiently suppressed.

According to the twelfth aspect of the present invention, the first driving mode can be used for moving image display, and the second driving mode can be used for still image display.

According to the thirteenth aspect of the invention, the thin film transistor in which the semiconductor layer is formed by the oxide semiconductor is used as the switching element in the pixel formation portion. Therefore, the potential written to the pixel formation portion can be maintained for a long period of time, so that the rest period can be sufficiently set. Therefore, the driving frequency of the gate line is lower than that of the previous low frequency update driving, so that further low power consumption can be realized. Further, the writing of the potential corresponding to the image to be displayed can be accelerated to the pixel forming portion, that is, since the scanning period can be shortened, the amplitude of the luminance waveform of the display portion becomes small. As a result, it becomes difficult to recognize the flicker.

According to the fourteenth aspect of the present invention, the driving method of the display device can exhibit the same effects as those of the first aspect of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the "same length" in this specification also includes "actually the same length."

<1. First embodiment> <1.1 Overall composition and operation>

1 is a block diagram showing the overall configuration of an active matrix type liquid crystal display device according to a first embodiment of the present invention. As shown in FIG. 1 , the liquid crystal display device includes a power supply 100, a DC/DC (Direct Current/Direct Current) converter 110, a display control circuit 200, and a source driver (video signal line driver circuit) 300. A gate driver (scanning signal line driver circuit) 400, a common electrode driving circuit 500, and a display portion 600. The source driver 300 and/or the gate driver 400 may be implemented as an IC (Integrated Circuit), or may be formed on the display unit 600 using an IGZO (Indium Gallium Zinc Oxide) or the like. On the LCD panel.

On the display unit 600, n source lines (video signal lines) SL1 to SLn, m gate lines (scanning signal lines) GL1 to GLm, and gate lines SL1 to SLn and gate lines are respectively formed. m × n pixel forming portions provided at the intersection of GL1 and GLm. The m×n pixel formation units are arranged in a matrix to form a pixel array. Each pixel forming portion includes: a thin film transistor 80 as a switching element, a gate terminal connected to a gate line passing through a corresponding intersection, and a source terminal connected to a source line passing through the intersection; a pixel electrode a common electrode Ec connected to the plurality of pixel forming portions as a counter electrode; and a liquid crystal layer collectively disposed in the plurality of pixel forming portions and sandwiched Hold between the pixel electrode and the common electrode Ec. Further, the pixel capacitance Cp is constituted by a liquid crystal capacitor formed by the pixel electrode and the common electrode Ec. Furthermore, in order to reliably maintain the voltage in the pixel capacitor Cp, and the liquid crystal capacitor The auxiliary capacitor is provided in parallel, and since the auxiliary capacitor is not directly related to the present invention, the description and illustration thereof are omitted.

The semiconductor layer of the thin film transistor 80 is formed, for example, by an oxide semiconductor (for example, IGZO). Furthermore, a specific implementation example using the IGZO will be described below.

The power supply 100 supplies a specific power supply voltage to the DC/DC converter 110, the display control circuit 200, and the common electrode drive circuit 500. The DC/DC converter 110 generates a specific DC voltage for operating the source driver 300 and the gate driver 400 from the power source voltage, and supplies the DC voltage to the source driver 300 and the gate driver 400. The common electrode driving circuit 500 supplies a specific potential Vcom to the common electrode Ec.

The display control circuit 200 receives the image signal DAT transmitted from the outside and the timing signal group TG such as a horizontal synchronization signal or a vertical synchronization signal, and outputs the digital image signal DV to control the source of the image display in the display unit 600. The pulse signal SSP, the source clock signal SCK, the latch strobe signal LS, the gate start pulse signal GSP, and the gate clock signal GCK. The display control circuit 200 performs control for switching between the moving image display mode and the still image display mode described below.

The source driver 300 receives the digital image signal DV, the source start pulse signal SSP, the source clock signal SCK, and the latch strobe signal LS output from the display control circuit 200, and applies images to the source lines SL1 to SLn, respectively. Signals SS(1)~SS(n).

The gate driver 400 is based on the gate start pulse signal GSP and the gate clock signal GCK outputted from the display control circuit 200. The application of the scanning signals GS(1) to GS(m) to the gate lines GL1 to GLm is repeated. The gate driver 400 can drive the gate lines GL1 to GLm in two driving modes of the moving image display mode (first driving mode) and the still image display mode (second driving mode). The moving image display mode is a mode for displaying the moving image on the display unit 600. The still image display mode is a mode for displaying a still image in the display unit 600. Hereinafter, not only the moving image display mode and the still image display mode are used as the mode of the gate driver 400, but also the mode of the display control circuit 200 and the liquid crystal display device will be described.

<1.2 Dynamic image display mode and still image display mode>

A frame memory (not shown) is provided in the display control circuit 200. The display control circuit 200 is pre-stored in the frame memory with the image signal DAT corresponding to the 1 frame before the 1 frame, and the image signal DAT corresponding to the 1 frame of the current frame. Compare. Furthermore, if the image signal DAT corresponding to the 1-frame before the frame is substantially inconsistent with the image signal DAT of the current frame corresponding to the 1-frame, the control circuit 200 is displayed to enable the gate driver 400. The gate start pulse signal GSP and the gate clock signal GCK are output in a moving image display mode operation, and the source driver 300 outputs the desired image signal SS(1) in the moving image display mode. The ~SS(n) mode outputs the source start pulse signal SSP, the source clock signal SCK, and the latch strobe signal LS. Moreover, if the image signal DAT before the first frame coincides with the image signal DAT of the current frame, the display control circuit 200 outputs the gate start pulse signal in such a manner that the gate driver 400 operates in the still image display mode. GSP, and gate clock signal GCK, and The source driver 300 outputs the desired image signals SS(1) to SS(n) in the moving image display mode to output the source start pulse signal SSP, the source clock signal SCK, and the latch selection communication. No. LS.

In addition, it is necessary to distinguish between the case where the image (still image) to be displayed in the still image display mode is changed and the case where the image is switched from the still image display mode to the moving image display mode. Therefore, in more detail, the display control circuit 200 is connected to the image signal DAT corresponding to the 1 frame and the image signal corresponding to the 1 frame of the current frame before the 1 frame in the still image display mode. When the DAT is inconsistent and the specific frame is continued, the driving mode of the gate driver 400 is shifted to the moving image display mode. On the other hand, in the still image display mode, the image signal DAT corresponding to the 1 frame before the 1 frame is inconsistent with the image signal DAT of the current frame corresponding to the 1 frame, and the phenomenon continues. Less than the above-described specific number of times, the gate driver 400 is caused to perform an operation for overwriting a still image in the still image display mode.

Furthermore, the display control circuit 200 is in a state in which the image signal DAT corresponding to the 1-frame before the 1 frame in the moving image display mode is identical to the image signal DAT of the current frame corresponding to the 1-frame. The transition from the moving image display mode to the still image display mode is performed for a certain number of times.

In the above description, it is assumed that the image signal DAT corresponding to the 1 frame and the image signal DAT corresponding to the 1 frame of the current frame are compared by comparing the image signal DAT in front of the 1 frame stored in the frame memory. It is determined whether the image is a moving image or a still image, but the present invention is not limited thereto. For example, the image signal DAT itself may be added to the control data indicating that the image signal DAT is a moving image data or a still image data, and the image to be displayed may be determined. Which of the dynamic images or still images is the one.

<1.3 Action of Liquid Crystal Display Device>

Fig. 2 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the embodiment. More specifically, FIG. 2(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 2(B) is a signal waveform diagram for explaining the operation in the still image display mode. 2(A) and 2(B), the scanning signal GS(1) supplied to the gate line GL(1) of the first column and any source line to the source lines SL1 to SLn are shown. The image signal to be provided and the average brightness of the entire liquid crystal display panel including the display unit 600 (hereinafter referred to as "panel brightness"). Here, it is assumed that the liquid crystal display panel is a panel of a normally black mode. Hereinafter, the so-called polarity inversion driving will be described in the present embodiment. Further, in order to simplify the description of the operation of the liquid crystal display device, in the still image display mode, the m×n pixel forming portions in the display unit 600 write images of the same polarity in one frame period. The signals are written to mutually different polar image signals for each pixel forming portion during any two consecutive frames.

<1.3.1 Action in dynamic image display mode>

In the present embodiment, so-called low frequency update driving is performed. That is, as shown in FIG. 2(A), the frame period (the first frame period) in the moving image display mode in the present embodiment includes the scanning period and the scanning period. The period of rest after the period. During this scanning period, the scanning signals GS(1) to GS(m) sequentially change to the high level potential according to the gate clock signal GCK. On the other hand, in the rest period, any of the m gate lines GL1 to GLm (scan signals GS(1) to GS(m)) becomes a low level potential. Hereinafter, the above-described scanning period in the moving image display mode will be referred to as a "moving image scanning period", and will be represented by a symbol T11. The above-described rest period in the moving image display mode is referred to as a "moving image pause period" and is represented by a symbol T12. During the dynamic image scanning, the gate lines GL1 GL GLm are driven at a higher speed than 60 Hz (16.7 msec), for example.

In the moving image scanning period T11, each image signal becomes positive. The gate lines GL1 to GLm are sequentially selected in accordance with the scanning signals GS(1) to GS(m), and a positive image signal is written in each pixel forming portion. Therefore, as shown in Fig. 2(A), the panel brightness is increased.

In the moving image rest period T12, each image signal is fixed to the Vcom potential. Thereby, the fluctuation of the pixel potential (the potential of the pixel electrode) caused by the off leak current of the thin film transistor 80 in each pixel formation portion can be reduced. Furthermore, each image signal may be fixed to a potential other than the Vcom potential (for example, an average luminance value of each image signal in the 1-frame period, etc.). Further, after the Vcom potential or the like is supplied to each of the video signal lines, the video signal line may be in a high impedance state. Here, the off leakage current does not completely disappear. As described above, by fixing each video signal to the Vcom potential, the pixel potential of each pixel formation portion can be made close to the Vcom potential. Therefore, as shown in FIG. 2(A), the panel luminance is lowered during the moving image rest period T12.

In the liquid crystal display device of the present embodiment, the moving image scanning period T11 and the moving image rest period T12 shown above are alternately repeated in units of one moving image frame period in the moving image display mode. .

Furthermore, in the above example, a dynamic image frame period is used as a package. The one moving picture scanning period T11 and the moving image rest period T12 are described, and the configuration of the one moving picture frame period (the operation during the moving picture frame period) may be corresponding to the required one. Various changes are made in display quality and the like. For example, each of the moving image frame periods may include two moving image scanning periods T11 and a moving image rest period T12 provided thereto. For example, a moving image frame period including one moving image scanning period T11 and moving image rest period T12, and a moving image including two moving image scanning periods T11 and moving image rest periods T12 may be used. Repeatedly during the frame.

<1.3.2 Action in still image display mode>

As shown in FIG. 2(B), in the still image display mode, an action for overwriting the above-described still image (hereinafter referred to as "overwrite operation") and an action for displaying the same still image are performed. (hereinafter referred to as "normal movement"). In the example shown in FIG. 2(B), an overwrite operation from the display image A to the display image B is performed.

The still image frame period during the frame period (the second frame period) in the still image display mode includes the scanning period of the same length as the above-described moving image scanning period T11 (hereinafter simply referred to as "the moving image scanning period" T11") and a rest period (hereinafter referred to as "still image rest period") longer than the moving image rest period T12 after the moving image scanning period T11. Hereinafter, the still image rest period is indicated by a symbol T2. Further, the operations during the scanning period and the rest period are the same in the moving image display mode and the still image display mode except for the length of the period.

<1.3.2.1 Overwrite Action>

As shown in FIG. 2(B), the overwriting operation is performed during the still image overwriting period which is a specific period immediately after the image to be displayed changes. The still image overwriting period in the embodiment includes the one-time moving image frame period and the one-time still image frame period set after the one moving picture frame period. That is, the still image overwriting period includes a moving image scanning period T11, a moving image rest period T12, a moving image scanning period T11, and a still image rest period T12, and includes a moving image scanning period T11 and static. The ratio of each of the still image frames during the image rest period T12 is larger than that during the scanning period. In order to perform overwriting of the self-display image A to the display image B, first, the gate lines GL1 to GLm are scanned once and displayed in the moving image scanning period T11 during the first moving image frame period. The video signal corresponding to the image B (positive polarity) is written in each pixel forming portion. However, as described above, the gate lines GL1 to GLm are driven at a high speed in the moving image scanning period T11 during the moving picture frame period as described above, so that the image signals corresponding to the display image B cannot be sufficiently performed. The writing of the pixel forming portion. Furthermore, after the moving image scanning period T11, a moving image rest period T12 for low frequency update driving is set.

Therefore, in the present embodiment, the gate lines GL1 to GLm are scanned again in the moving image scanning period T11 in the still image frame period after the one of the moving picture frame periods, which corresponds to The video signal of the display image B of the same polarity (positive polarity) in the first moving image scanning period T11 is written again to each pixel forming portion. Therefore, the writing to the respective pixel forming portions of the image signal corresponding to the display image B is sufficiently performed. By this, Eliminate the afterimage caused by insufficient write time of the image signal. After the dynamic image scanning period T11, a still image rest period T2 for low frequency update driving is set.

Furthermore, during the still image frame period during the still image overwriting period in the present embodiment, during the moving image scanning period, as in the case of the moving picture frame period in the moving image display mode. After the brightness of the panel in T11 is increased, the brightness of the panel is lowered during the moving image rest period T12. Next, during the still image frame during the still image overwriting period, after the panel brightness is increased in the moving image scanning period T11, the panel brightness is lowered during the still image rest period T12.

<1.3.2.2 General Action>

The normal operation in the present embodiment is performed by alternately repeating the moving image scanning period T11 and the still image rest period T12 in units of one still image frame period. Here, a description will be given by taking an example of a still image frame period after the still image overwrite period. As shown in FIG. 2(B), during the 1st still image frame period, the operation for displaying the display image B is performed after the still image overwriting period. First, the gate lines GL1 to GLm are scanned once in the moving image scanning period T11 in the one-time still image frame period, and the image signals corresponding to the display image B are written in the respective pixel forming portions. The polarity of this image signal is negative compared to the period during which the still image is overwritten. After the moving image scanning period T11, the above-described operation in the still image rest period T12 is performed.

After the end of the 1 still image frame period, the positive image corresponding to the display image B is performed by the same action during the subsequent 1st still image frame period. The image signal is written in each pixel forming portion. In this way, in the normal operation, the image signal whose polarity is changed during each of the still image frames is written once to each pixel formation portion every one of the still image frames. In this normal operation, the polarity of the image signal is different during each static image frame, but the data (absolute value) itself is always corresponding to the display image B. Therefore, in this normal operation, the writing time of the image signal does not need to be ensured to be the same as that in the above-described still image overwriting period. Therefore, it is not necessary to write image signals of the same polarity twice during normal operation. That is, only one gate line GL1 to GLm may be scanned during each static image frame period.

<1.4 Change in panel brightness>

3 is a waveform diagram of panel luminance for three types of scanning periods (motion scanning period T11) in the case where a blinking pattern is displayed in the still image display mode. More specifically, Fig. 3(A) is a waveform diagram of the panel luminance in the case where the scanning period is A msec. Fig. 3(B) is a waveform diagram of the panel luminance in the case where the scanning period is 2A/3 msec. Fig. 3(C) is a waveform diagram of panel luminance in the case of A/2 msec during scanning.

The shorter the scanning period, the shorter the writing time of the image signal to each pixel forming portion. Therefore, as shown in FIGS. 3(A) to 3(C), the shorter the scanning period, the smaller the amplitude of the panel luminance waveform. Therefore, the shorter the scanning period (driving the gate lines GL1 to GLm at a high speed), the more difficult it is to recognize the flash (blinking) of the display image.

<1.5 Implementation Example>

A thin film transistor (hereinafter referred to as "a-SiTFT") using amorphous germanium (a-Si) in a semiconductor layer has been used as a thin film transistor in each pixel formation portion of a liquid crystal display device. This a-Si TFT is particularly commonly used in a liquid crystal display device in which a gate driver or the like is formed into a single integrated circuit. However, an oxide semiconductor is used for the semiconductor layer of the thin film transistor 80 in each pixel formation portion in the present embodiment. In addition, as the oxide semiconductor, InGaZnO _x (hereinafter referred to as "IGZO") which is an oxide semiconductor containing indium, gallium, zinc, and oxygen as a main component is typically used, but the present invention is not limited thereto. For example, it may be an oxide semiconductor containing at least one of indium, gallium, zinc, copper, antimony, tin, aluminum, calcium, strontium, and lead.

4 is a view showing a drain current-gate voltage characteristic of a TFT using an a-SiTFT and an IGZO (hereinafter referred to as "IGZOTFT") in a semiconductor layer. In FIG. 4, the horizontal axis represents the gate voltage Vg, and the vertical axis represents the drain current Ids. As shown in FIG. 4, the off leakage current of the IGZO TFT is 1/1000 or less of the off leakage current of the a-Si TFT, and the on current of the IGZO TFT is about 20 times the on current of the a-SiTFT.

Since the IGZOTFT has a small off-leakage current as described above, the case where the IGZOTFT is used as the thin film transistor 80 in the present embodiment can be maintained for a long time as compared with the case where the a-SiTFT is used as the thin film transistor 80. Pixel potential. Therefore, when the IGZOTFT is used as the thin film transistor 80 in the present embodiment, the rest period can be sufficiently set.

Further, since the IGZO TFT has a large on-current as described above, the IGZOTFT is used as the thin film transistor 80 in the present embodiment, and the a-Si TFT can be used as the thin film transistor 80. The writing of the image signal in the pixel formation portion is speeded up. That is, the scanning period can be shortened.

<1.6 effect>

According to the present embodiment, in the liquid crystal display device that performs low-frequency update driving, images are displayed in two driving modes of the moving image display mode and the still image display mode. The driving in the moving image display mode is the previous low frequency update driving. On the other hand, the driving in the still image display mode is realized by two operations of the overwriting operation and the normal operation. During the still image overwriting period during the overwrite operation, when the display image changes in the still image display mode, the image signals of the same polarity are tied to the second dynamic image scanning period T11 for each pixel. Provided by the formation department. Therefore, the writing of the image signal to each of the pixel forming portions can be sufficiently performed, so that the display of the afterimage can be eliminated. On the other hand, in the normal operation, only one dynamic image scanning period T11 is set for each static image frame period in the still image display mode, so that the driving of the gate lines GL1 to GLm can be reduced. Consume power. Furthermore, in this conventional operation, the data (absolute value) of the image signal itself is fixed, so the writing time of the image signal need not be ensured to be the same as that during the still image overwriting period. Even if an afterimage is generated, the display image is fixed and is not recognized as an afterimage.

Further, according to the present embodiment, since the still image rest period T2 is longer than the moving image rest period T12, it is possible to further reduce the power consumption in the still image display mode.

Moreover, according to the present embodiment, an IGZO TFT is used for the thin film transistor 80 in each pixel formation portion. Therefore, the pixel potential can be maintained for a long period of time, so that the rest period can be sufficiently set. Therefore, the drive frequency of the gate line is further reduced as compared with the previous low frequency update drive, so that further reduction in power consumption can be achieved. Moreover, since the image signal to the pixel forming portion can be written The speed is increased, that is, the scanning period can be shortened, so that the amplitude of the panel luminance waveform becomes small. As a result, it becomes difficult to recognize the flicker.

<1.7 Modifications>

Fig. 5 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the modification of the first embodiment. More specifically, FIG. 5(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 5(B) is a signal waveform diagram for explaining the operation in the still image display mode. In addition, the operation in the moving image display mode in the operation of the liquid crystal display device is the same as that of the above-described first embodiment, and thus the description thereof will be omitted.

In the still image overwriting period in the first embodiment, as shown in FIG. 2(B), the image signal written in each pixel forming portion is recorded during the first moving image scanning period T11. The polarities are the same as the polarities of the video signals written in the respective pixel forming portions in the second moving image scanning period T11 (positive polarity). However, in the present modification, as shown in FIG. 5(B), the polarity of the video signal written in each pixel forming portion during the first moving image scanning period T11 is positive. The polarity of the video signal written to each pixel forming portion in the second moving image scanning period T11 is negative. That is, in the present modification, the polarity inversion driving is performed even during the still image overwriting. In this case, even when the polarity inversion driving is performed during the still image overwriting period, the scanning period is sufficiently set (the secondary moving image scanning period T11) during the still image overwriting period to sufficiently perform and display. The writing of the image signal corresponding to the image B to each pixel forming portion is performed.

According to the present modification, the display image is changed in the still image display mode The image signals of the polarities different from each other are supplied to the respective pixel forming portions in the two-time moving image scanning period T11. Therefore, since the writing of the video signal to each of the pixel forming portions can be sufficiently performed, the display of the afterimage can be eliminated in the same manner as in the first embodiment.

<2. Second embodiment> <2.1 Action of Liquid Crystal Display Device>

Fig. 6 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the second embodiment of the present invention. More specifically, FIG. 6(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 6(B) is a signal waveform diagram for explaining the operation in the still image display mode. In addition, since the present embodiment is the same as the first embodiment except for the operation of the liquid crystal display device, the description of the same portions will be omitted. Further, as shown in FIGS. 6(A) and 6(B), the operation in the moving image display mode and the normal operation in the still image display mode in the operation of the liquid crystal display device are also the same as the above first Since the embodiments are the same, the description thereof will be omitted.

<2.1.1 Overwrite Action>

As shown in FIG. 6(B), the still image overwriting period in the present embodiment includes two moving image scanning periods T11 and a still image pause set after the two moving image scanning periods T11. Period T2. In other words, the still image overwriting period in the present embodiment includes one moving image scanning period T11 and one still image frame period set after the moving image scanning period T11. That is, the ratio of the scanning period during the still image overwriting period to the period of each of the still image frames including the moving image scanning period T11 and the still image rest period T12 is large. In order to display the image from the display image A In the case of the overwriting of B, first, the gate lines GL1 to GLm are scanned once in the moving image scanning period T11, and the image signals corresponding to the display image B (positive polarity) are written to the respective pixel forming portions. However, as described above, the gate lines GL1 to GLm are driven at high speed in the moving image scanning period T11, so that the writing of the image signals corresponding to the display image B to the respective pixel forming portions cannot be sufficiently performed.

Therefore, in the present embodiment, the moving image scanning period T11 (second time) is also provided after the moving image scanning period T11 (first time). Therefore, in the second moving image scanning period T11, the gate lines GL1 to GLm are scanned again, and the polarity (positive polarity) corresponding to the first moving image scanning period T11 is used. The video signal of the display image B is written again to each pixel forming portion. Therefore, the writing to the respective pixel forming portions of the image signal corresponding to the display image B is sufficiently performed. Thereby, the afterimage caused by insufficient writing time of the image signal can be eliminated. After the two moving image scanning periods T11, the still image rest period T2 for low frequency update driving is set.

Further, in the still image overwriting period in the present embodiment, after the panel luminance is increased in the first moving image scanning period T11, the panel luminance is further in the second moving image scanning period T11. Slightly improved. Next, the panel brightness is lowered during the still image rest period T2.

<2.2 effect>

According to the present embodiment, the moving image pause period T12 in the still image overwriting period in the first embodiment described above is not provided. Therefore, the number of times of switching between the operation during the scanning period and the rest period can be reduced, so that it is possible to achieve Further low power consumption.

<2.3 First Modification>

FIG. 7 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the first modification of the second embodiment. More specifically, FIG. 7(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 7(B) is a signal waveform diagram for explaining the operation in the still image display mode. In addition, the operation in the moving image display mode in the operation of the liquid crystal display device is the same as that of the second embodiment described above, and thus the description thereof will be omitted.

In the still image overwriting period in the second embodiment, as shown in FIG. 6(B), the image signal is written to each pixel forming portion during the first moving image scanning period T11. The polarities are the same as the polarities of the video signals written in the respective pixel forming portions in the second moving image scanning period T11 (positive polarity). However, in the present modification, as shown in FIG. 7(B), the polarity of the video signal written in each pixel forming portion during the first moving image scanning period T11 is positive. The polarity of the video signal written to each pixel forming portion in the second moving image scanning period T11 is negative. That is, in the present modification, the polarity inversion driving is performed even during the still image overwriting. In this case, even when the polarity inversion driving is performed during the still image overwriting period, the scanning period is sufficiently set (the dynamic image scanning period T11 of the second time) in the still image overwriting period. The writing of the video signal corresponding to the display image B to each pixel forming portion is performed.

According to the present modification, the image signals of mutually different polarities in the display image change in the still image display mode are subjected to two-time dynamic image scanning. A period T11 is supplied to each pixel forming portion. Therefore, since the writing of the image signal to each of the pixel forming portions is sufficiently performed, the display of the afterimage can be eliminated in the same manner as in the second embodiment.

<2.4 Second Modification>

FIG. 8 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the second modification of the second embodiment. More specifically, FIG. 8(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 8(B) is a signal waveform diagram for explaining the operation in the still image display mode. In addition, the operation in the still image display mode in the operation of the liquid crystal display device is the same as that in the second embodiment described above, and thus the description thereof will be omitted.

As shown in FIG. 8(A), the 1 moving image frame period in the present modification includes one moving image scanning period T11. That is, in the present embodiment, the low frequency update drive is performed only in the still image display mode, and the low frequency update drive is not performed in the moving image display mode. Therefore, the effect of reducing the power consumption is inferior to that of the second embodiment described above, but the display of the afterimage can be eliminated in the same manner as in the second embodiment.

<2.5 Third Modification>

FIG. 9 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the third modification of the second embodiment. More specifically, FIG. 9(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 9(B) is a signal waveform diagram for explaining the operation in the still image display mode. In the present modification, the operation in the moving image display mode is the operation in the second modification of the second embodiment, and the operation in the still image display mode is the first modification of the second embodiment. The action in the example. Again, by The detailed description of the above description is as shown in the second modification of the second embodiment and the first modification of the second embodiment, and therefore will not be described.

According to the present variation, the low frequency update driving is performed only in the still image display mode, and the low frequency update driving is not performed in the moving image display mode. Therefore, the effect of reducing the power consumption is inferior to that of the second embodiment described above, but the display of the afterimage can be eliminated in the same manner as in the second embodiment. Further, according to the present modification, the video signals having different polarities in the display image change in the still image display mode are supplied to the respective pixel forming portions in the two-time moving image scanning period T11. Thereby, the writing of the image signals to the respective pixel forming portions is sufficiently performed, so that the display of the afterimages can be eliminated in the same manner as in the second embodiment.

<3. Third embodiment> <3.1 Action of Liquid Crystal Display Device>

Fig. 10 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the third embodiment of the present invention. More specifically, FIG. 10(A) is a signal waveform diagram for explaining the operation in the moving image display mode. Fig. 10(B) is a signal waveform diagram for explaining the operation in the still image display mode. In addition, since the present embodiment is the same as the first embodiment except for the operation of the liquid crystal display device, the description of the same portions will be omitted. Further, as shown in FIGS. 10(A) and 10(B), the operation in the moving image display mode and the normal operation in the still image display mode in the operation of the liquid crystal display device are also the same as described above. Since the first embodiment is the same, its description will be omitted.

<3.1.1 Overwrite Action>

As shown in FIG. 10(B), during the still image overwriting in this embodiment A scanning period (hereinafter referred to as "long-term scanning period") having the same length as that of the above-described 1 moving image frame period and a still image inactivity period T2 set after the long-term scanning period are included. Hereinafter, the long-term scanning period is indicated by the symbol T10. The ratio of the scanning period during the still image overwriting period to the period of each of the still image frames including the moving image scanning period T11 and the still image rest period T12 is large. Since the long-term scanning period T10 is longer than the moving image scanning period T11, the selection period of each gate line in the long-term scanning period T10 becomes longer than the selection period of each gate line in the moving image scanning period T11.

In order to perform overwriting of the display image A from the display image B, first, the gate lines GL1 to GLm are scanned once in the long-term scanning period T10, and the image signal corresponding to the display image B is set (set as The positive polarity is written to each of the pixel formation portions. As described above, since the selection period of each gate line in the long-term scanning period T10 is longer than the selection period of each gate line in the moving image scanning period T12, the still image overwriting period in the present embodiment is Although the number of scanning times of the gate lines GL1 to GLm is one, the writing of the image signals corresponding to the display image B to the respective pixel forming portions can be sufficiently performed. After the long-term scanning period T10, the still image rest period T2 for the low-frequency update driving is set.

Further, in the still image overwriting period in the present embodiment, after the panel luminance is increased in the long-term scanning period T10, the panel luminance is lowered in the subsequent still image inactivity period T2.

<3.2 effect>

According to this embodiment, the overwrite is reduced by setting the long-term scanning period T10. Since the driving frequency of the gate lines GL1 to GLm at the time of writing is written, it is possible to further reduce the power consumption.

<4. Other>

In the still image overwriting period in the first embodiment, the modification, the second embodiment, and the modifications thereof, two moving image scanning periods T11 are provided, but three or more dynamic images may be provided. Like the scan period T11. Further, in the still image overwriting period in the third embodiment, only one long-term scanning period T10 is provided, but two or more long-term scanning periods T10 may be provided.

A relatively short period of time for performing various processes may be provided after each scanning period in each of the above embodiments.

In the above embodiments, the liquid crystal display device is described as an example, but the present invention is not limited thereto. When the present invention is applied to a display device other than a liquid crystal display device, the polarity inversion driving described above is not required. Further, various modifications may be made to the above-described embodiments without departing from the spirit and scope of the invention.

According to the above, according to the present invention, it is possible to provide a display device and a driving method thereof that suppress a decrease in display quality and lower power consumption than before.

[Industrial availability]

The present invention is applicable to a display device that performs low frequency update driving.

80‧‧‧Thin-film transistor (switching element)

200‧‧‧ display control circuit

300‧‧‧Source driver (image signal line driver circuit)

400‧‧‧ gate driver (scanning signal line driver circuit)

600‧‧‧Display Department

T2‧‧‧still image during rest period

T10‧‧‧Long-term scanning period

T11‧‧‧Dynamic image scanning period

T12‧‧‧Dynamic image rest period

Fig. 1 is a block diagram showing the overall configuration of a liquid crystal display device according to a first embodiment of the present invention.

Fig. 2 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the first embodiment. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

Figure 3 is a waveform diagram of panel brightness corresponding to scans of three lengths. (A) A waveform diagram of panel luminance in the case of A msec during scanning. (B) A waveform diagram of panel brightness in the case of 2A/3 msec during scanning. (C) is a waveform diagram of panel brightness in the case of A/2 msec during scanning.

Fig. 4 is a graph showing the drain current-gate voltage characteristics of the a-SiTFT and the IGZOTFT.

Fig. 5 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the modification of the first embodiment. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

Fig. 6 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the second embodiment of the present invention. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

FIG. 7 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the first modification of the second embodiment. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

FIG. 8 is a signal waveform diagram for explaining the operation of the liquid crystal display device according to the second modification of the second embodiment. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

Figure 9 is a view showing a liquid crystal display according to a third modification of the second embodiment; A signal waveform diagram showing the operation of the device. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

Fig. 10 is a signal waveform diagram for explaining the operation of the liquid crystal display device of the third embodiment of the present invention. (A) is a signal waveform diagram in the moving image display mode. (B) is a signal waveform diagram in the still image display mode.

FIG. 11 is a signal waveform diagram for explaining a driving method of the display device described in Patent Document 2.

T2‧‧‧still image during rest period

T11‧‧‧Dynamic image scanning period

T12‧‧‧Dynamic image rest period

Claims (14)

A display device, comprising: a display portion, comprising: a plurality of scanning signal lines; a plurality of image signal lines crossing the plurality of scanning signal lines; and respectively comprising corresponding plurality of scanning signal lines and the plurality of scanning lines a plurality of pixel forming portions of the switching elements arranged in a matrix on the image signal lines; and a scanning signal line driving circuit capable of driving the plurality of scanning signal lines in two driving modes of the first driving mode and the second driving mode; a signal line driving circuit for driving the plurality of image signal lines; and a display control circuit for controlling the scanning signal line driving circuit and the image signal line driving circuit; and the scanning signal line driving circuit: in the first driving mode And driving the plurality of scanning signal lines in a period including a first frame period of the scanning period in which the plurality of scanning signal lines are sequentially selected, and in the second driving mode, including the scanning period and the plurality of lines Whether any of the scanning signal lines should be displayed during the rest period of the non-selected state The plurality of scanning signal lines are driven such that the scanning period and the rest period alternately occur in a period including the scanning period and the second frame period of the rest period, in addition to the specific period immediately after the change, and And causing the length of the scanning period in the second frame period to be the same as the length of the scanning period in the first frame period, and causing the scanning period in the specific period The ratio between the two is greater than the ratio of the above scanning period in the second frame period. The display device of claim 1, wherein the first frame period further includes the rest period, and the scanning signal line drive circuit alternately displays the scan period and the pause period in a cycle of the first frame period The method drives the plurality of scanning signal lines. The display device of claim 2, wherein the scanning signal line driving circuit causes the rest period in the second frame period to be longer than the rest period in the first frame period. The display device of claim 3, wherein each of the pixel forming portions includes a liquid crystal layer, and the scanning period included in the specific period includes two scanning periods having the same length as the scanning period in the first frame period. The video signal line drive circuit drives the polarity inversion drive, and causes the signals applied to the respective video signal lines to have the same polarity in the two scanning periods in the specific period. The display device of claim 3, wherein each of the pixel forming portions includes a liquid crystal layer, and the scanning period included in the specific period includes two scanning periods having the same length as the scanning period in the first frame period. The image signal line drive circuit performs polarity inversion driving, and causes signals to be applied to the respective image signal lines to be performed on two of the specific periods. The polarity during the scanning period is different from each other. The display device according to claim 4 or 5, wherein the specific period includes a scanning period having the same length as the scanning period in the first frame period; and the rest period in the first frame period is a rest period of the same length; a scan period having the same length as the scan period in the first frame period; and a rest period having the same length as the rest period in the second frame period. The display device of claim 4 or 5, wherein the specific period includes two scan periods having the same length as the scan period in the first frame period and the pause in the second frame period The period is the rest period of the same length. The display device of claim 3, wherein the scanning period included in the specific period includes the scanning period having the same length as the first frame period, and the specific period sequentially includes the first frame period The scanning period of the same length and the rest period of the same length as the above-described rest period of the second frame period are the same length. The display device of claim 8, wherein each of the pixel forming portions includes a liquid crystal layer, and the image signal line driving circuit performs polarity inversion driving. The display device of claim 1, wherein each of the pixel forming portions includes a liquid crystal layer, wherein the first frame period includes the scanning period, and the scanning period included in the specific period includes two and The scanning period in the first frame period is a scanning period of the same length, and the specific period includes two scanning periods having the same length as the scanning period in the first frame period and the second frame. In the above-described rest period of the period, the video signal line drive circuit performs polarity inversion driving, and causes the signals applied to the respective video signal lines to have the same polarity in the two scanning periods in the specific period. The display device of claim 1, wherein each of the pixel forming portions includes a liquid crystal layer, wherein the one frame period includes the scanning period, and the scanning period included in the specific period includes two of the first and the first frame period The scan period is the same length of the scan period, and the specific period includes two scan periods having the same length as the scan period in the first frame period and the rest period in the second frame period. The video signal line drive circuit performs polarity inversion driving, and causes the signals supplied to the respective image signal lines to have mutually different polarities in the two scanning periods in the specific period. The display device according to any one of claims 1 to 11, wherein said display control circuit drives said scanning signal line drive circuit in said first driving mode when said display unit performs moving image display plural Controlling the scanning signal line driving circuit by scanning the signal line, and driving the scanning signal line driving circuit to drive the plurality of scanning signals in the second driving mode when the display unit performs static image display In the manner of a line, the above-mentioned scanning signal line drive circuit is controlled. The display device according to any one of claims 1 to 12, wherein the switching element is a thin film transistor in which a semiconductor layer is formed by an oxide semiconductor. A driving method for driving a display device including a display portion including a plurality of scanning signal lines, and capable of driving the plural in two driving modes of a first driving mode and a second driving mode a scanning signal line driving circuit for scanning the signal lines; and the driving method includes the steps of: in the first driving mode, the first frame period of the scanning period including the plurality of scanning signal lines sequentially selected as a period And driving the plurality of scanning signal lines; and in the second driving mode, the image to be displayed in the rest period including the scanning period and the plurality of scanning signal lines being in a non-selected state In addition to the specific period after the change, the plurality of scanning signal lines are driven such that the scanning period and the rest period alternately occur in a period including the scanning period and the second frame period of the rest period, and the The length of the scanning period in the second frame period and the length of the scanning period in the first frame period The same, and that the ratio of the above-described scanning period of the specific period is greater than the ratio of the information in the frame of the second period of the scanning period.