JP4149384B2 - Liquid crystal display method and liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal display method and a liquid crystal display device excellent in moving image display.

  Conventionally, there is an active matrix type liquid crystal display device. In this active matrix type liquid crystal display device, as shown in FIG. 31, every time one horizontal line of data is sampled from the video signal into the sampling memory 2 by the source driver 1, the sampled data is stored in the holding memory 3. store. On the liquid crystal panel side, a horizontal line consisting of picture element rows in which data is to be written is selected by a gate driver (not shown), and a TFT (thin film transistor) of the selected picture element is turned on. Thereafter, the data signal for one horizontal line stored in the holding memory 3 is DA-converted by the DA converter 4 and written via the source line 6 to all the picture elements constituting the selected horizontal line.

  The above-described operation is performed for all horizontal lines, and one screen image writing is completed. By repeating this as one frame, various images can be displayed. An active matrix liquid crystal display device that performs such a display operation is applied to a display unit of a word processor, a notebook personal computer, a television, or the like.

  By the way, in the conventional active matrix type liquid crystal display device, since the response speed of the liquid crystal, particularly the response speed between halftones, is slower than 16.7 ms which is the time of the one frame, an afterimage is generated in the case of moving image display. There is a problem of deterioration of display quality such as being seen.

  Further, while the TFT is not selected, the data signal written in the corresponding picture element is continuously held. For this reason, even if the response speed of the liquid crystal is increased, there is an afterimage on the retina because the human gaze tracks the moving image. As a result, there is a problem that display quality is lowered.

  In order to solve the above problems, the following liquid crystal display methods have been proposed (Patent Document 1 and Non-Patent Document 1). In Patent Document 1, the screen is divided into upper and lower parts, and in the first half of the frame time, the upper screen is scanned with a signal and simultaneously the lower screen is scanned with a black signal (blanking). In the second half of the frame time, the upper screen is scanned with a black signal (blanking) and simultaneously the lower screen is scanned with a signal.

  Further, in Non-Patent Document 1, the screen is divided into upper and lower parts and one frame time is divided into time slots of the number of lines of the entire screen. In the first slot, the upper screen is signal-scanned simultaneously with the lower screen. In the second slot, the upper screen is scanned with a black signal (blanking) and the lower screen is also scanned with a black signal (blanking). In this way, signal scanning and black signal (blanking) scanning are repeated sequentially for each slot.

According to each of the above liquid crystal display methods, when focusing on one picture element, there are always both an image display period and a black display period in one frame time, and the frame data before and after are mixed due to the presence of the black display period. An image can be displayed without any problem. Therefore, the display performance of moving images can be improved.
JP-A-11-109921 “LCD for new animation using pi-cell”, Journal of Japanese Liquid Crystal Society, 1999, vol. 3, No. 2

  However, the liquid crystal display method disclosed in Non-Patent Document 1 has the following problems. That is, one frame time is divided into time slots corresponding to the number of lines of the entire screen, and the screen is further divided into upper and lower parts. In the first slot, the upper screen is signal-scanned simultaneously with the lower screen. On the other hand, in the second slot, the upper screen is scanned with a black signal (blanking) and simultaneously the lower screen is scanned with a black signal (blanking). In this way, signal scanning and black signal (blanking) scanning are repeated sequentially for each slot. Therefore, when the upper screen starts to be scanned, the lower screen needs to be scanned at the same time, and it is necessary to store image data for one line once. Therefore, there is a problem that the circuit is complicated and the cost is increased.

  The liquid crystal display method disclosed in Patent Document 1 has the same problem. That is, one frame time is divided into the first half and the second half, and the screen is further divided into two parts. In the first half of one frame time, the upper screen is scanned with a signal and simultaneously the lower screen is scanned with a black signal (blanking). On the other hand, in the second half of one frame time, the upper screen is scanned with a black signal (blanking) and simultaneously the lower screen is scanned with a signal. In this case, it is not necessary to store image data as in Non-Patent Document 1, but problems such as circuit complexity and cost increase due to screen division still occur.

  Needless to say, dividing the screen requires, for example, twice as many source drivers as the top and bottom, resulting in an increase in cost.

  Therefore, an object of the present invention is not to perform screen division as in Patent Document 1 and Non-Patent Document 1, and without requiring a special screen storage device, and by using a minimal improvement of a conventional liquid crystal display device, a moving image is obtained. An object of the present invention is to provide a liquid crystal display method and a liquid crystal display device capable of improving display quality.

  In order to achieve the above object, the first invention supplies data signals to a plurality of column lines arranged in parallel to each other, and selects a plurality of row lines arranged in parallel to each other in a direction intersecting the column lines. A liquid crystal display method for supplying an image and displaying an image on a picture element composed of liquid crystal at or near an intersection position of a column line to which the data signal is supplied and a row line to which the selection signal is supplied. , N (n: positive integer) The selection signal is supplied to the row line and the data signal is supplied to the column line, and the picture relating to the intersection position of the n-th row line and each column line is supplied. A black display signal for displaying an image based on the data signal and then supplying the selection signal to the (n + m) th row line with m as a positive integer and displaying a black image on the pixel Is supplied to the column line, and the (n + m) th row line and each column line are The black image is displayed on the picture element related to the difference position, and the display signal and the black image display operation based on the data signal are repeated while sequentially shifting the row line supplying the selection signal, and the selection signal is displayed. When the (n + m) th row line to be supplied exceeds the last row line, the image is returned to the first row line, and an image based on the data signal and a black image are displayed for each of the picture elements within one frame period. It is characterized by that.

  According to the above configuration, unlike the case of Patent Document 1 and Non-Patent Document 1, the data signal supply and the black display signal supply to the column line are alternately performed, and the row line supplying the selection signal is In synchronization with the signal supply, n is sequentially increased as n, n + m, n + 1, n + m + 1, n + 2, n + m + 2,. In this way, after the data signal is written to all the picture elements without dividing the screen or using the circuit for storing the image data of one screen, and after a predetermined time corresponding to m has passed, The black display signal is supplied, and the state in which the black display signal is written is maintained until a new image data signal is written in the next frame, and a black image is displayed. Therefore, when the pixel displaying white changes to black display in the next frame, the black image is already displayed before the black display signal is written, and the backlight does not leak. It is.

  In addition, the edge of the video in the moving image moves at the frame change and stops during the frame period. However, since it is felt by humans that the video is moving smoothly, there are periods in which the edges of the video are ahead of and behind the human line of sight, and the edges of the video appear blurred. However, in the present invention, as described above, the picture element displaying the video is displayed black until the next data signal is applied, and the video disappears. The period before the line of sight and the period after the line of sight are shortened, and blurring of the edge of the video is reduced. Thus, the moving image display quality is improved.

  The second invention supplies a data signal to a plurality of column lines arranged in parallel to each other, and supplies a selection signal to a plurality of row lines arranged in parallel to each other in a direction intersecting the column lines. , A liquid crystal display method for displaying an image on a picture element made of liquid crystal at or near the intersection position of a column line supplied with the data signal and a row line supplied with the selection signal, the nth row Supplying the selection signal to the line and supplying the data signal to the column line, and displaying an image based on the data signal on the picture element at the intersection of the n-th row line and each column line; Next, the selection signal is simultaneously supplied to a plurality of row lines different from the n-th row line, and a black display signal for displaying a black image on the picture element is supplied to the column line. The black image is displayed on the picture element at the intersection of multiple row lines and column lines. The image display operation and the black image display operation based on the data signal are repeated while sequentially shifting the row line supplying the selection signal, and the plurality of row lines supplying the selection signal at the same time determine the final row line. In the case of exceeding the first row line, an image based on the data signal and a black image are displayed for each of all picture elements within one frame period.

  According to the above configuration, the black display signal is supplied to all the picture elements a plurality of times in the second half of one frame period. Therefore, even when the black display signal supply time is a time when black image display cannot be sufficiently performed only by one black display signal supply, black display is surely performed by repeating the black display signal supply a plurality of times. . Thus, even when the black display signal supply time is not sufficient because the pixel density of the display panel is high and the number of row lines is high, high-quality video display that does not cause backlight leakage is performed. .

  In the liquid crystal display method of the second invention, the plurality of row lines are set to the (n + α · m) (α = 1, 2,..., P (p: positive integer))-th row line. It is desirable.

  According to the above configuration, when attention is paid to a single horizontal line, black display is repeatedly performed every m scans. In this way, a higher quality display is performed without the influence of the dielectric constant of the liquid crystal due to the display contents of the immediately preceding frame.

  In the liquid crystal display method according to the second aspect of the invention, the plurality of row lines are arranged from the (n + α · m) th line to (n + α · m + k−1) (α = 1, 2,..., P (p, k: A positive integer)) It is desirable to make the line up to the actual line.

  According to the above configuration, when attention is paid to one horizontal line, black display is repeated k times every m scans, and the influence of the display content of the immediately preceding frame is further eliminated.

  In the liquid crystal display method of the first invention or the second invention, it is desirable that the data signal supply time and the black display signal supply time are equal.

  According to the above configuration, since the supply time of the data signal is equal to the supply time of the black display signal, the supply of the data signal and the supply of the black display signal can be switched by a very simple switching control process. .

  In the liquid crystal display method of the first invention or the second invention, it is preferable that the supply time of the data signal is longer than the supply time of the black display signal.

  According to the above configuration, since the pixel density of the display panel is high and the number of row lines is large, it is possible to cope with a case where the data signal supply time is not sufficient.

In the liquid crystal display method of the first invention or the second invention, it is desirable to set the value of m so as to satisfy the relationship of the following equation.
f × m / N> t
N: number of row lines f: 1 frame time t: response time of liquid crystal when white display is switched to black display

  According to the above configuration, the supply time of the black display signal in one frame period is set to be longer than the response time of the liquid crystal when white display is switched to black display. Thus, even for a picture element in which a white image is displayed based on the data signal, black display is reliably performed until the next data signal is applied.

In the liquid crystal display method of the first invention or the second invention, it is desirable to set the value of k so as to satisfy the relationship of the following equation.
T × k ≧ T ₀
However, T: Time for supplying black display signal once T ₀ : Shortest time for black display signal that can completely switch white display to black display

  According to the above configuration, the supply time of the black display signal in one frame period is set to be equal to or longer than the shortest time during which white display can be switched to black display by supplying black display signals k times. Thus, when the black display signal is repeatedly supplied k times because the supply time of the black display signal is insufficient, even if it is a pixel that displays a white image based on the data signal, the next data The black display is surely performed before the signal is applied.

In the liquid crystal display method of the first invention or the second invention, the voltage Vd when the data signal is a data signal for black display and the voltage Vr of the black display signal satisfy the following relationship. It is desirable to set as follows.
In the case of positive polarity with respect to the potential level of the counter electrode, Vd <Vr at normally white, Vd> Vr at normally black.
In the case of negative polarity with respect to the potential level of the counter electrode, Vd> Vr at normally white and Vd <Vr at normally black.

  According to the above configuration, even when the black display signal supply time is insufficient and sufficient black display cannot be performed, the black display signal voltage is set large (small) to ensure black display. Display is performed.

  Further, the third invention provides a plurality of column lines arranged in parallel to each other, a plurality of row lines arranged in parallel to each other in a direction intersecting with the column electrodes, the intersection positions of the column lines and the row lines, or In a liquid crystal display device having a display panel on which at least picture elements made of liquid crystal near the intersection position are formed, a column line driver for supplying a data signal to the column line, and a row line driver for supplying a selection signal to the row line Supplying a video signal and a control signal to the column line driver, and supplying a control signal to the row line driver to control an image display operation on the display panel; and a black image to the picture element. A black display signal generating means for generating a black display signal for display; a data signal provided on the column line driver based on the video signal from the display control section; and a black display signal from the black display signal generating means. The display control unit includes a changeover switch for alternately selecting and switching the display signal, and the display control unit supplies the control signal for sequentially selecting the row lines to the row line driver, and the changeover switch receives the data signal. While selecting, the selection signal is supplied to the nth row line, while when the changeover switch selects the black display signal, the selection signal is supplied to the (n + m) th row line. It is a feature.

  According to the above configuration, the row line driver and the column line driver are controlled as follows based on the control signal from the display control. That is, when a data signal is selected by the selector switch of the column line driver and supplied to the column line, the nth row line is selected by the row line driver. On the other hand, when the black display signal is selected by the changeover switch and supplied to the column line, the (n + m) th row line is selected. In this way, data signals are written to all picture elements, and a black display signal is supplied after a predetermined time corresponding to m has passed, and black display is performed until a new image data signal is written in the next frame. The state where the signal is written is maintained and a black image is displayed. Therefore, when the pixel displaying white changes to black display in the next frame, the black image is already displayed before the black display signal is written, and the backlight does not leak. It is.

  According to a fourth aspect of the present invention, there are provided a plurality of column lines arranged in parallel to each other, a plurality of row lines arranged in parallel to each other in a direction intersecting the column electrodes, the intersection positions of the column lines and the row lines, or In a liquid crystal display device having a display panel on which at least picture elements made of liquid crystal near the intersection position are formed, a column line driver for supplying a data signal to the column line, and a row line driver for supplying a selection signal to the row line Supplying a video signal and a control signal to the column line driver, and supplying a control signal to the row line driver to control an image display operation on the display panel; and a black image to the picture element. A black display signal generating means for generating a black display signal for display; a data signal provided on the column line driver based on the video signal from the display control section; and a black display signal from the black display signal generating means. The display control unit includes a changeover switch for alternately selecting and switching the display signal, and the display control unit supplies the control signal for sequentially selecting the row lines to the row line driver, and the changeover switch receives the data signal. While selecting, the selection signal is supplied to the nth row line, while when the changeover switch selects the black display signal, a plurality of row lines different from the nth row line are supplied. A selection signal is supplied.

  According to the above configuration, the row line driver and the column line driver are controlled as follows based on the control signal from the display control. That is, when a data signal is selected by the selector switch of the column line driver and supplied to the column line, the nth row line is selected by the row line driver. On the other hand, when the black display signal is selected by the changeover switch and supplied to the column line, a plurality of row lines different from the nth are selected. Therefore, even when the black display signal supply time is a time when black image display cannot be sufficiently performed only by one black display signal supply, black display is surely performed by repeating the black display signal supply a plurality of times. . Thus, even when the black display signal supply time is not sufficient because the pixel density of the display panel is high and the number of row lines is high, high-quality video display that does not cause backlight leakage is performed. .

  In the liquid crystal display device of the third invention or the fourth invention, the row line is divided into L (L: positive integer) blocks for every m lines, and the row line driver is divided into the row of each block. It is desirable to configure with L partial row line drivers that supply selection signals to the lines.

  According to the above configuration, when a data signal is supplied to the column line by the changeover switch, the nth row line connected to the partial row line driver is selected by a certain partial row line driver. . On the other hand, when the black display signal is supplied to the column line by the changeover switch, the n-th row line connected to the partial row line driver by the partial row line driver located in the subsequent column of the partial row line driver. Is selected. Thus, the selection operation of (n + m) row lines is performed by simple control.

  In the liquid crystal display device of the third invention or the fourth invention, the control signal from the display control unit to the column line driver includes a switching control signal for controlling the switching operation of the changeover switch, The switching control signal is preferably configured so that the selection time of the data signal is longer than the selection time of the black display signal.

  According to the above configuration, the supply time of the data signal is longer than the supply time of the black display signal. Therefore, it is possible to cope with a case where the data signal supply time is not sufficient because the picture element density of the display panel is high and the number of row lines is large.

  In the liquid crystal display device of the third invention or the fourth invention, the control signal from the display control unit to the column line driver includes a switching control signal for controlling the switching operation of the changeover switch, It is desirable that the selection time of the data signal is equal to the selection time of the black display signal in the switching control signal.

  According to the above configuration, since the supply time of the data signal is equal to the supply time of the black display signal, the supply of the data signal and the supply of the black display signal can be switched by a very simple switching control process. .

  In the liquid crystal display device of the fourth invention, the control signal from the display control unit to the row line driver is for identifying whether or not the black display signal supply period for supplying the black display signal. Based on the identification signal, the row line driver supplies the selection signal to the row lines from the (n + m) th to the (n + m + k−1) th in the black display signal supply period based on the identification signal. It is desirable that

  According to the above configuration, the black display signal is supplied to all the picture elements k times during a predetermined time corresponding to m until the next data signal is applied. Therefore, even when the black display signal supply time corresponding to m is insufficient for black image display, black display is reliably performed by repeating the black display signal supply k times. Thus, even when the black display signal supply time is not sufficient because the pixel density of the display panel is high and the number of row lines is high, high-quality video display that does not cause backlight leakage is performed. .

  According to the fourth aspect of the present invention, the control signal from the display control unit to the row line driver includes a scanning start signal, and the row line driver includes a shift register having a plurality of latch circuits; Based on the identification signal, the scan start signal is supplied to the first latch circuit of the shift register during the data signal supply period, while the scan start signal is supplied to the mth shift register of the shift register during the black display signal supply period. It is desirable to provide scanning start signal supply means for supplying k consecutive latch circuits from the latch circuit.

  According to the above configuration, the row line driver capable of supplying the black display signal k times before the next data signal is applied is realized with a simple configuration in which the scanning start signal supply means is provided in the row line driver having the shift register. The

  In the liquid crystal display device according to the fourth aspect of the present invention, it is preferable that the scanning start signal supply means can change the latch circuit number m and the latch circuit number k in the black display signal supply period.

According to the above configuration, by changing the latch circuit number m, the time for displaying a black image is changed until the next data signal is applied.
Further, by changing the number k of latch circuits, the number of times the black display signal is supplied before the next data signal is applied is changed.

  The liquid crystal display device according to the fourth aspect of the invention further comprises supply control means for controlling the operation of the scan start signal supply means, and the supply control means is configured to perform the above operation based on a scan start position designation signal from the outside. It is desirable to output a control signal for setting the latch circuit number m to the scanning start signal supply means.

  According to the above configuration, the time for displaying a black image is changed until the next data signal is applied based on an external signal.

  In the liquid crystal display device according to the third or fourth aspect of the invention, the display control unit performs a black display signal supply operation based on the operation of the changeover switch in response to a command signal from the outside. It is desirable to switch and output the display mode control signal and the control signal for the second display mode in which the operation of the changeover switch is stopped and the black display signal supply operation is not performed.

  According to the above configuration, the display mode is the first display mode in which the energy consumption increases because the black display signal is supplied to the column lines based on the operation of the changeover switch for each frame, and the energy consumption is usually low. By switching to the second display mode, it is possible to prevent energy from being wasted by constantly fixing the display mode to the first mode.

  The liquid crystal display device of the third or fourth aspect of the invention further comprises a signal reference power source for setting the voltage of the data signal supplied from the column line driver, and the voltage of the signal reference power source. Is preferably switchable between the first display mode and the second display mode.

  According to the above configuration, the black display signal is supplied after the data signal is written, and the transmittance of the liquid crystal is lowered to display the black image before the new image data signal is written in the next frame. In the first display mode, the voltage of the signal reference power supply is switched, and the voltage of the data signal is set according to the decrease in the transmittance of the liquid crystal. In this way, a constant gradation balance is maintained between the first display mode and the second display mode.

  The liquid crystal display device according to the third or fourth aspect of the invention monitors data related to the same position on the screen based on the video signal from the display control unit, and the image based on the video signal is a moving image. It is desirable to provide a moving image still image determining means for determining whether the image is a still image or not and outputting the command signal indicating the determination result to the display control unit.

According to the above configuration, the moving image still image determining unit determines whether the image is a moving image or a still image based on the video signal, and outputs a command signal representing the determination result to the display control unit.
Thus, when displaying a moving image whose display quality is likely to deteriorate, a control signal for the first display mode is automatically output from the display control unit, and a data signal is written in one frame period, and then data is transferred to the next frame. A black image is displayed before the signal is applied, and the display quality is improved.

  The liquid crystal display device according to the third or fourth aspect of the invention is based on the backlight that irradiates the display panel from the back side and the command signal, and the first display mode and the second display mode. It is desirable to provide backlight dimming means for switching the luminance of the backlight.

  According to the above configuration, in the first display mode in which the transmittance of the liquid crystal is low in order to display a black image until the data signal is applied to the next frame after the data signal is written in one frame period. In the case of the normal second display mode, the backlight brightness is lowered by the backlight dimming means. Thus, waste of energy due to constantly increasing the brightness of the backlight is prevented.

  In the liquid crystal display device according to the third or fourth aspect of the invention, the black display signal generating means is composed of a black display signal power supply, and the voltage of the black display signal power supply is set to the value in the first display mode. It is desirable to be able to switch between the second display mode and the second display mode.

  According to the above configuration, in the first display mode in which the black image is displayed until the data signal is applied to the next frame after the data signal is written in one frame period, the black display signal power supply is turned on. The voltage is switched to ensure black display.

  As apparent from the above, the liquid crystal display method according to the first aspect of the present invention supplies the selection signal to the nth row line and the data signal to the column line, and based on the data signal on the pixel of the selected row line. An image is displayed, and then the selection signal is supplied to the (n + m) th row line and a black display signal is supplied to the column line to display a black image on the picture element of the selection row line, and the selection row Since the image display operation and the black image display operation based on the data signal are repeated while sequentially shifting the line, the data signal is written to all the picture elements, and a predetermined time corresponding to m has elapsed. Then, a black display signal is supplied, and a black image can be displayed while maintaining a state in which the black display signal is written until a new image data signal is written in the next frame. Therefore, when changing a pixel that is displaying white to black display in the next frame, the black image is already displayed before the next data signal is written, preventing backlight leakage. it can.

  In addition, as described above, since the picture element displaying the video is displayed in black until the next data signal is applied and the video disappears, the edge of the video in the moving image exists before the human eyes. And the following period can be shortened. Therefore, blurring of the edge of the image can be reduced.

  That is, according to the present invention, the moving image display quality can be improved by the minimum change of supplying the black display signal to the column line and changing the selection method of the row line.

  Further, the liquid crystal display method of the second invention supplies a selection signal to the nth row line and a data signal to the column line to display an image based on the data signal on the picture element of the selection row line, Next, the selection signal is simultaneously supplied to a plurality of row lines different from the n-th row, and a black display signal is supplied to the column line to display a black image on the picture element of the selection row line. Since the image display operation and the black image display operation based on the data signal are repeated while sequentially shifting the image signal, the black display signal can be supplied a plurality of times until the next data signal is applied. Therefore, even when the black display signal supply time is insufficient for black image display, black display can be reliably performed by repeatedly supplying the black display signal a plurality of times.

  Therefore, according to the present invention, since the pixel density of the display panel is high and the number of row lines is large, even when the black display signal supply time is not sufficient, the light leakage of the backlight or the image edge portion can occur. High-quality moving image display that does not cause blurring of light can be performed with minimal changes.

  Further, in the liquid crystal display method of the second aspect of the invention, if the plurality of row lines are (n + α · m) (α = 1, 2,..., P) th row line, one horizontal line is related. Black display can be repeated every m scans. Therefore, it is possible to eliminate the variation in the dielectric constant of the picture element capacitance due to the display content in the immediately preceding frame and to perform a higher quality display.

  In the liquid crystal display method of the second invention, the plurality of row lines are arranged from the (n + α · m) th to (n + α · m + k−1) (α = 1, 2,..., P) th row lines. Then, black display can be performed by repeating k times for every m scans with respect to a certain horizontal line. Therefore, it is possible to further eliminate the influence of the display contents in the immediately preceding frame.

  In the liquid crystal display method according to the first or second invention, the data signal can be obtained by a very simple switching control process as long as the supply time of the data signal is equal to the supply time of the black display signal. And the supply of the black display signal can be switched.

  In the liquid crystal display method of the first invention or the second invention, if the supply time of the data signal is longer than the supply time of the black display signal, the pixel density of the display panel is high. Since the number of row lines is large, it is possible to cope with a case where a sufficient data signal supply time cannot be obtained.

In the liquid crystal display method of the first invention or the second invention, if the value of m is set so as to satisfy the relationship of the following equation, the supply time of the black display signal in one frame period is set to white display. Can be set longer than the response time of the liquid crystal when switching to black display. Therefore, even for a picture element in which a white image is displayed based on the data signal, black display can be reliably performed until the next data signal is applied.
f × m / N> t
N: number of row lines f: 1 frame time t: response time of liquid crystal when white display is switched to black display

In the liquid crystal display method of the first invention or the second invention, if the value of k is set so as to satisfy the relationship of the following equation, the supply time of the black display signal in one frame period is set to black display. The white display can be set longer than the shortest time that can be switched to black display by supplying the signal k times. Accordingly, when the black display signal supply is repeated k times because the supply time of the black display signal is insufficient, even if the pixel element displays a white image based on the data signal, The black display can be surely performed before the data signal is applied.
T × k ≧ T ₀
However, T: Time for supplying black display signal once T ₀ : Shortest time for black display signal that can completely switch white display to black display

In the liquid crystal display method of the first invention or the second invention, the voltage Vd when the data signal is a data signal for black display and the voltage Vr of the black display signal satisfy the following relationship. With this setting, even when the black display signal supply time is insufficient and sufficient black display cannot be performed, black display can be reliably performed.
In the case of positive polarity with respect to the potential level of the counter electrode, Vd <Vr at normally white, Vd> Vr at normally black.
In the case of negative polarity with respect to the potential level of the counter electrode, Vd> Vr at normally white and Vd <Vr at normally black.

  In the liquid crystal display device of the third invention, the row line driver selects the nth row line when the switch of the column line driver selects the data signal according to the control signal from the display control unit. While the signal is supplied, when the changeover switch selects the black display signal, the row line driver supplies the selection signal to the (n + m) th row line. Then, after writing a data signal and supplying a black display signal after a predetermined time corresponding to m has passed, the state in which the black display signal is written is maintained until a new image data signal is written in the next frame. A black image can be displayed. Therefore, when changing the picture element that is displaying white to black display in the next frame, the black image is already displayed before the next data signal is written, and the backlight leaks out. Can be prevented.

  That is, according to the present invention, the moving image display quality can be improved by a minimum change in which a changeover switch is provided in the column line driver and the control signal from the display control unit is changed.

  In the liquid crystal display device according to the fourth aspect of the invention, the row line driver selects the nth row line when the switch of the column line driver selects the data signal according to the control signal from the display control unit. While the signal is supplied, when the changeover switch selects the black display signal, the row line driver supplies the selection signal to a plurality of row lines different from the n-th line. Even when the supply time is not enough to display a black image only by supplying a black display signal only once, the black display can be reliably displayed by repeating the black display signal supply a plurality of times. Therefore, even when the black display signal supply time is not sufficient due to the high density of picture elements on the display panel and the large number of lines, it is possible to perform high-quality video display without backlight leakage. is there.

  In the liquid crystal display device of the third invention or the fourth invention, the row line is divided into L blocks for every m lines, and the row line driver supplies a selection signal to the row line of each block. If L partial row line drivers are used, when the data signal is supplied to the column line by the changeover switch, the nth row line in a partial row line driver is selected while the black display signal is supplied to the column line. In the case of supplying to the partial row line driver, the (n + m) row line selection operation is performed by a simple control of selecting the n-th row line in the partial row line driver located in the subsequent column of the partial row line driver. Can do.

  In the liquid crystal display device of the third or fourth aspect of the invention, the switch control signal of the changeover switch, which is one of the control signals from the display control unit to the column line driver, is selected as the data signal. If the time is set to be longer than the selection time of the black display signal, the supply time of the data signal can be made longer than the supply time of the black display signal. Therefore, even when the display panel has a high picture element density and a large number of row lines, it is possible to cope with a case where a sufficient data signal supply time cannot be obtained.

  In the liquid crystal display device of the third or fourth aspect of the invention, the switch control signal of the changeover switch, which is one of the control signals from the display control unit to the column line driver, is selected as the data signal. If the time and the black display signal selection time are set to be equal, the data signal supply time and the black display signal supply time can be made equal. Therefore, the supply of the data signal and the supply of the black display signal can be switched by a very simple switching control process.

  In the liquid crystal display device according to the fourth aspect of the invention, the row line driver supplies the black display signal during the black display signal supply period based on an identification signal which is one of control signals from the display control unit to the row line driver. If the selection signal is supplied to the (n + m) th to (n + m + k-1) th row lines, the black display signal can be supplied k times before the next data signal is applied. Therefore, even when the black display signal supply time is insufficient, black display can be reliably performed. Therefore, according to the present invention, since the pixel density of the display panel is high and the number of row lines is large, even when the black display signal supply time is not sufficient, the high-quality backlight does not leak. Video display.

  In the liquid crystal display device according to the fourth aspect of the invention, the row line driver supplies a scan start signal as one of the control signals to the first latch circuit of the shift register during the data signal supply period. In the black display signal supply period, the scan start signal supply means for supplying the scan start signal to the k latch circuits continuous from the mth latch circuit of the shift register is provided. A row line driver capable of supplying a black display signal k times before the next data signal is applied can be realized by simply changing the line driver to include a scanning start signal supply means.

  In the liquid crystal display device according to the fourth aspect of the present invention, if the scanning start signal supply means can change the latch circuit number m and the number k of latch circuits in the black display signal supply period, the latch circuit number can be changed. By changing m, the display time of the black image until the next data signal is applied can be changed. Further, by changing the number k of latch circuits, the number of black display signals supplied until the next data signal is applied can be changed. Therefore, according to the present invention, it is possible to easily cope with a change in pixel density of the display panel, a change in environmental temperature, and the like.

  In the liquid crystal display device according to the fourth aspect of the invention, the supply control means outputs a control signal for setting the latch circuit number m to the scan start signal supply means based on a scan start position designation signal from the outside. For example, the display time of the black image until the next data signal is applied can be changed based on an external signal.

  In the liquid crystal display device of the third or fourth aspect of the invention, the control signal for the first display mode in which the display control unit performs the supply operation of the black display signal in response to a command signal from the outside. And the control signal for the second display mode that does not perform the black display signal supply operation are compared with the case where the display mode is always fixed to the first mode that consumes a large amount of energy. Thus, waste of energy can be prevented.

  In the liquid crystal display device according to the third or fourth aspect of the present invention, the voltage of the signal reference power supply for setting the voltage of the data signal supplied from the column line driver is set to the second display mode and the second display mode. If switching between display modes is possible, in the first display mode in which the transmittance of the liquid crystal is low, the voltage of the data signal can be set according to the decrease in the transmittance of the liquid crystal. Therefore, a constant gradation balance can be maintained between the first display mode and the second display mode.

  In the liquid crystal display device according to the third or fourth aspect of the invention, the moving image / still image determining means determines whether the image is a moving image or a still image, and sends the command signal indicating the determination result to the display control unit. If output is performed, the control signal for the first display mode is automatically output from the display control unit at the time of moving image display whose display quality is likely to deteriorate, and the data signal is then output to all the picture elements. A black image can be displayed before is applied. Therefore, the display quality can be improved by automatically detecting that the display image has been changed to a moving image.

  In the liquid crystal display device of the third invention or the fourth invention, the backlight dimming means switches the backlight luminance between the first display mode and the second display mode based on the command signal. In this case, the luminance of the backlight can be increased in the first display mode in which the liquid crystal transmittance is low. Therefore, it is possible to prevent waste of energy in the second display mode as compared with the case where the luminance of the backlight is fixed in accordance with the first display mode.

  The liquid crystal display device according to the third or fourth aspect of the invention switches the voltage of the black display signal power source as the black display signal generating means between the first display mode and the second display mode. By doing so, it becomes possible to maintain a constant gradation balance between the first display mode and the second display mode.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

<First embodiment>
FIG. 1 is a schematic configuration diagram of an active matrix type liquid crystal display device as a liquid crystal display device in the present embodiment. The liquid crystal display device in the present embodiment includes a liquid crystal panel 11, a plurality of source drivers 12, and a plurality of gate drivers 13. The liquid crystal panel 11 includes a TFT substrate 14 and a counter substrate 15. On the TFT substrate 14, pixel electrodes 16 arranged in a matrix, and a TFT 17 having a drain connected to the pixel electrode 16, The gate lines G connected in parallel to the gates of the TFTs 17 in each row and the source lines S connected in parallel to the sources of the TFTs 17 in the respective columns are formed. A counter electrode 18 is formed on the counter substrate 15 that faces the TFT substrate 14 at a predetermined interval. The counter electrode 18 faces the pixel electrode 16. Although not shown, liquid crystal is sandwiched between the pixel electrode 16 and the counter electrode 18.

  Here, the liquid crystal panel 11 in the present embodiment has a VGA (video graphics array) in which the number of the gate lines G is 480 and the number of the source lines S is 640 (three times in the case of color display). A panel is used. The 480 gate lines G are divided into three groups of 160 lines and connected to the first gate driver 13a to the third gate driver 13c for each group. Similarly, the source line S is divided into a plurality of groups and connected to the source driver 12 for each group.

  The display control unit 20 includes clock signal generation means, and outputs the generated clock signal to the first source driver 12 together with the input video signal. Further, it has scanning start signal generation means and identification signal generation means, and outputs the generated scanning start signal and identification signal together with the clock signal to each gate driver 13. The moving image / still image discriminating circuit 21 determines whether the moving image is mainly a moving image or the still image mainly by monitoring several points of data on the screen based on the video signal received from the display control unit 20. To do. Then, the discrimination result is returned to the display control unit 20. Then, the display control unit 20 switches the switching clock signal, the identification signal, and the scanning start signal, which are one of the clock signals, to either a moving image or a still image based on the determination result.

  Further, the determination result from the moving image / still image determination circuit 21 is also output to the signal reference power supply 22, the black signal power supply 24 and the backlight dimming circuit 23. Then, the signal reference power supply 22 and the black signal power supply 24 send the data signal reference voltage and the black signal voltage to each source driver 12 according to the determination result. The backlight dimming circuit 23 dims a backlight (not shown) according to the determination result. The black signal power source 24 is a power source used when generating a reset signal (black signal), which will be described in detail later.

  FIG. 2 is a schematic configuration diagram of the source driver 12. However, a representative configuration is shown for one source line S, and the same configuration is provided for all source lines S. Data for one picture element (one horizontal line) is sampled in the sampling memory 31 from the video signal, and the sampled data is stored in the holding memory 32. Then, DA conversion is performed by the DA converter 33 using the signal reference voltage from the signal reference power supply 22, and the signal is sent to the changeover switch 34.

  The changeover switch 34 has a clock signal obtained by dividing the sampling clock signal supplied to the sampling memory 31, the holding memory 32 and the DA converter 33, and the sampling memories 31, 31 of all the source drivers 12, 12,. ,... Are input with the switching clock signal having a period of time during which data for one horizontal line is sampled. The changeover switch 34 selects the data signal from the DA converter 33 and outputs it to the corresponding source line S when the level of the changeover clock signal is “H”, for example. On the other hand, in the case of “L”, the black signal voltage from the black signal power supply 24 is selected and output to the corresponding source line S as the reset signal.

  The source driver 12 may be configured as shown in FIG. That is, in the source driver 12 shown in FIG. 2, the changeover switch 34 is positioned at the subsequent stage of the DA converter 33, but in FIG. 3, the changeover switch 35 is positioned at the front stage of the holding memory 38. The changeover switch 35 selects the video signal from the sampling memory 37 and sends it to the holding memory 38 when the level of the changeover clock signal is “H”, for example. On the other hand, in the case of “L”, the black signal data from the black signal data generation unit 36 is selected and sent to the holding memory 38. Then, DA conversion is performed by the DA converter 38 using the signal reference voltage from the signal reference power supply 22 and output to the corresponding source line S. Thus, the data signal based on the video signal is output to the source line S in the first half of the time when data for one horizontal line is sampled, while the reset signal based on the black signal data is output in the source line S in the second half. Is output.

  FIG. 4 is a schematic configuration diagram of the gate driver 13. However, the configuration of the gate driver 13 in the present invention is not limited to this. The gate driver 13 according to the present embodiment has a shift register 41, and output signals from latch circuits (not shown) constituting the shift register 41 are supplied to the output circuit 42. The output circuit 42 applies a gate voltage of level “H” or level “L” to the gate line G to select the gate line G.

  The shift register 41 sequentially shifts the scanning start signal supplied to the first latch circuit to the next latch circuit based on the clock signal from the display control unit 20, and sequentially selects the gate lines G. go. In this case, the scanning start signal is also input to the analog switch 43 that opens and closes using the identification signal from the display control unit 20 as a control signal. The level of the identification signal becomes “H”, for example, and the analog switch 43 By opening, the scanning start signal is also supplied to the second to fourth latch circuits in the shift register 41.

The liquid crystal display device having the above configuration operates as follows to display a moving image.
That is, FIG. 5 is a timing chart of drive signals relating to the three gate drivers 13a, 13b, and 13c and selection signals output to the gate lines G. As can be seen from FIG. 5, from the display control unit 20, the second gate driver 13b located at the center is supplied with a clock signal delayed by a half cycle from the clock signal supplied to the first gate driver 13a located at one end. Is done. Further, the third gate driver 13c located at the other end is supplied with a clock signal delayed by a half cycle from the clock signal supplied to the second gate driver 13b. The scanning start signal supplied from the display control unit 20 to the gate drivers 13a to 13c is a pulse signal in which one pulse exists at the first clock and the 321st clock. Input by shifting the phase. Further, the identification signal supplied from the display control unit 20 to each gate driver 13a to 13c has, for example, an “L” level for 320 clocks and an “H” level for 160 clocks. It is input with the phase shifted by 160 clocks.

As a result, first, the gate line G ₁ of the first by the first gate driver 13a is selected. After that, the first to fourth gate lines G, that is, the 161st to _164th gate lines G _{161 to} G ₁₆₄ as a whole are selected by the second gate driver 13b. Then, after the second gate line G ₂ is selected by the first gate driver 13a, gate lines G ₁₆₂ ~G ₁₆₅ of 162 th to 165 th by the second gate driver 13b (to 5 th second) is selected Is done. Thereafter, the selection is sequentially performed by the two gate drivers 13a and 13b, and the 320th (160th) gate line _G320 is selected by the second gate driver 13b.

Then, after the first gate line G, that is, the 161st gate line G ₁₆₁ as a whole is selected by the second gate driver 13b, the first to fourth gate lines G ₁₆₁ are then selected by the third gate driver 13c. , 321 th ～324 th gate driver G ₃₂₁ ~G ₃₂₄ is selected as a whole that is. Then after the gate line G ₁₆₂ 162-th (second) is selected by the second gate driver 13b, the gate lines G ₃₂₂ ~G of 322 th to 325 th the third gate driver 13c (to 5 th second) ₃₂₅ is selected. Thereafter, the selection is sequentially performed by the two gate drivers 13b and 13c in the same manner, and the 480th (160th) gate line G480 is eventually selected by the third gate driver 13c.

Then, after the first gate line G, that is, the 321st gate line G ₁₆₁ as a whole is selected by the third gate driver 13c, the first to fourth gates are again selected by the first gate driver 13a. Lines G _{1 to} G ₄ are selected.
After the gate line G ₄₈₀ 480-th through third gate driver 13c (160 th) is selected, the 160-th gate line G ₁₆₀ by the first gate driver 13a is selected, one frame scanning is ended To do.

  The timing chart shown in FIG. 5 is a case where an identification signal having “H” level for 160 clocks is sequentially given to each gate driver 13b to 13a as described above, and the level of the identification signal is “H”. ", The analog switch 43 of the gate driver 13 is turned on, so that the gate driver 13 selects four consecutive gate lines G. On the other hand, when the identification signals whose all levels are “L” are given to the gate drivers 13, the analog switches 43 of all the gate drivers 13 are off, so that they are adjacent as shown in FIG. The two gate drivers 13 select one gate line G alternately and while shifting.

  Hereinafter, the image display operation by the liquid crystal display device in this embodiment will be specifically described. As described above, the source driver 12 column alternately outputs the data signal stored in the holding memory 32 and the reset signal. In this case, the pulse width of the switching clock input to the changeover switch 34 is set so that the output time widths of both signals are equal to each other. The width of the output time in this embodiment is approximately 16.7 ms (one frame time) / 480 lines / 2≈about 17 μs.

The gate driver 13 that selects the horizontal line is input with the clock signal and the scan start signal as described above, and the identification signal whose level is “L”.
Then, as shown in FIG. 6, after the nth gate line G is selected, the (n + 160) th gate line G is selected. Further, after the (n + 1) th gate line G is selected, the (n + 161) th gate line G is selected. However, if (n + m) is larger than the number of lines, the selected line is obtained from the first line following the last line. The selection time width of each gate line G is about 17 μs, similar to the width of the signal output time to the source line S. In this case, the nth gate line G is selected when the source driver 12 outputs the data signal, and the (n + 160) th gate line G is selected when the source driver 12 outputs the reset signal. The timing between the switching clock and the scanning start signal is set in advance.

As described above, the reset signal is applied to the gate line G (m = 160) ahead of the gate line G that has output the data signal for the following reason. That is, the response time for the liquid crystal transmittance to change from 100% to 10% is about 4 ms. When a reset signal is applied to a pixel electrode of a certain pixel connected to a certain gate line G, it is necessary that the display is substantially black until the next data signal is applied. Therefore, the following relationship is established.
f × m / N> 4 ms
F: 1 frame time (16.7 ms)
N: Total number of gate lines (480)
Therefore, it is necessary that m> 115.

  Here, in this embodiment, three gate drivers 13 connected to 160 gate lines G are arranged in a straight line, and 480 are scanned. Therefore, if m = 160, the reset signal is sent from the gate driver 13 next to the gate driver 13 outputting the data signal to the gate line G having the same number as the gate line G outputting the data signal. The condition of m> 115 can be cleared by a very simple control of outputting.

  The display result by such an image display operation is compared with the display result by the conventional liquid crystal display device as follows. Here, in the image used for description, as shown in FIG. 7, a white belt 52 having a width corresponding to three picture elements is arranged in the center of a black background 51 in the vertical direction. The white band 52 is assumed to be a moving image that moves one picture element per frame as indicated by an arrow (A).

  First, an image display method using a conventional liquid crystal display device will be described. FIG. 8 shows an image display sequence in one frame period by a conventional liquid crystal display device. One horizontal line of the video signal sent one after another is sampled in the sampling memory 2 of the source driver 1 and temporarily stored in the holding memory 3. Then, the data signal for one horizontal line read from the holding memory 3 is written in the picture element row constituting one horizontal line selected by the gate driver. At the same time, the data signal of the second horizontal line is sampled in the sampling memory 2 and the contents of the holding memory 3 are rewritten. This is repeated for 480 horizontal lines to complete the data signal writing for one frame.

  The liquid crystal adopts a normally white type TN (twisted nematic) mode. The characteristic is that the time for the transmittance to reach 0% → 90% is about 20 ms, and the time for the transmittance to reach 100% → 10% is about 4 ms.

  When the moving image as described above is displayed by the image display sequence of the conventional liquid crystal display device, as shown in FIG. 9, an afterimage (image that is apparent in the picture element array 53 changed from the white belt 52 to the background 51 is displayed. Bleeding). The cause of this is explained as follows. That is, FIG. 10 shows the transmittance change for each frame in an arbitrary picture element 54 adjacent to the white band 52 in the forward direction of the white band 52 in FIG. Ideally, the change in transmittance is black display (transmittance <10%) in the first frame, white display (transmittance> 90%) from the second frame to the fourth frame, and the fifth frame. Then it should return to black again. However, as described above, the time until the transmittance reaches 0% to 90% is about 20 ms, and the time until the transmittance reaches 100% to 10% is about 4 ms. For this reason, when a white signal is written in the second frame to the picture element 54 that was black in the first frame, the liquid crystal of the picture element 54 cannot be completed within the frame time and is almost completed in the third frame. Will do. Therefore, the original white display is obtained in the fourth frame. In the fifth frame, a black signal is written, but since the time required for the transmittance to reach 100% to 10% is about 4 ms, a slight light leakage is observed as shown by the picture element row 53. It is. Therefore, in the conventional image display sequence, the width of the white band 52 cannot be clearly seen as three picture elements.

  Next, an image display operation in the liquid crystal display device of the present embodiment will be described. In the present liquid crystal display device, a reset signal having a voltage capable of achieving black display within one frame period is written between the data signal writing of each horizontal line. FIG. 11 shows an image display sequence in the liquid crystal display device of the present embodiment. FIG. 11B shows the specific contents of the write and reset periods in FIG. As shown in FIG. 11, in this embodiment mode, writing of a data signal and writing of a reset signal are alternately performed at a half cycle of the sampling cycle. In this case, the reset signal is written to the horizontal line 160 lines ahead of the data signal write horizontal line.

  In the present embodiment, by adopting such an image display sequence, as shown in FIG. 12, no afterimage (image blur) is confirmed in the picture element row 63 that has changed from the white belt 62 to the background 61. . The reason for this can be explained as follows. FIG. 13 shows the transmittance change for each frame in an arbitrary picture element 64 (corresponding to the picture element 54 in FIG. 7) adjacent to the white band 62 in the traveling direction of the white band 62 in FIG. This picture element 64 is displayed in black in the first frame. Then, the white signal is written in the second frame, but at a certain time point in the frame time (the next time when the white signal is written to the horizontal line 160 lines behind the horizontal line to which the picture element 64 belongs). A black signal is written at a. The voltage of the black signal is a voltage that can achieve black display within one frame period as described above, and the time point a is set so that the transmittance reaches 10% within the remaining time of the second frame. is there. Therefore, it is possible to return to black display by the next frame.

  The same applies to the third and fourth frames. Therefore, in the second to fourth frames, a white signal is written in the picture element 64 for the same time, and the maximum transmittance in each frame is the same. As a result, the same luminance can be displayed in the second to fourth frames. Further, in the fifth frame, since the black signal has already been written after the time point a of the fourth frame, the transmittance exhibits 10% or less at the start time, and no light leakage is observed.

  Further, the afterimage reduction by the image display sequence of the present embodiment can be explained also for the following reason. In order to simplify the description, a case where the response time of the liquid crystal is infinitely small will be described. The image used for the explanation is a moving image in which the white band having the width of three picture elements as described above moves in one direction by one picture element every frame. FIG. 14 shows the movement of the white band in an arbitrary horizontal line. Show the state. Further, the transmittance response waveform in infinitesimal response time is shown in FIG. 15 for the conventional image display sequence, and in FIG. 16 for the image display sequence of the present embodiment.

  FIG. 17 shows the movement of the white band on an arbitrary horizontal line according to the conventional image display sequence. Since the data signal written in an arbitrary picture element is held during the frame period, the white belt is stopped during one frame period. Then, when entering the next frame period, it moves by one picture element and stops again during one frame period. Thereafter, the above is repeated. Then, when a human observes the movement of the white band, it is recognized as a moving image in which the white band moves smoothly. In other words, it cannot be recognized that the white belt is stationary every frame. Therefore, as shown by broken arrows (B) and (C) in FIG. 17, the human viewpoint moves at a constant speed.

  Therefore, in the human retina, as shown in FIG. As a result, both edges appear to be duller than an actual white band image based on the data signal, and a blurred afterimage is felt. In other words, since the human eye feels that the white belt is moving smoothly even though the white belt is stationary for each frame, the white belt appears as indicated by the symbol “b” in the first half of one frame. Before the human line of sight, in the second half of one frame, the human line of sight overtakes the white band, so that a white band is present after the line of sight as indicated by the symbol “c”. Then, an image in which the “present / absent” of the white belt image is averaged is projected on the human retina, so that the white belt image blurred with a dull edge can be seen. As described above, in the conventional image display sequence, blurring of moving images is always felt.

  Next, the case of the image display sequence in the liquid crystal display device of the present embodiment will be described. FIG. 19 shows how the white belt moves along an arbitrary horizontal line according to the image display sequence of the present embodiment. In this image display sequence, “m”, which is the difference between the write line number of the reset signal and the write line number of the data signal, is set to “160”, so the data signal is only 2/3 in the first half of one frame period. Is held, and the black signal is held in the second half of the third half to display black. That is, the white band stops only in the first half 2/3 during one frame period, and the white band disappears in the second half 1/3. Therefore, the white band display period can be shortened to 2/3 of one frame period, and as is clear from comparison between FIG. 19 and FIG. 17, the white band indicated by the symbol “b” is ahead of the human line of sight. The existing period and the period after the line of sight indicated by the symbol “c” can be shortened. Therefore, as a result, as shown in FIG. 20, the blurring of the edge of the white belt image can be reduced.

  In the above description, for the sake of simplicity, it is assumed that the response time of the liquid crystal is infinitely small. However, if black display is performed for each frame, the same effect can be obtained even if the response time of the liquid crystal is not infinitely small. It is clear from the above description.

  By the way, as can be seen from the comparison between FIG. 15 and FIG. 16, in the present embodiment, for the display picture element, the process of changing the black transmittance to an arbitrary transmittance and the black from the arbitrary transmittance for each frame. Including the process of transmissivity, the transmissivity is substantially lower than when the conventional image display sequence is applied. Therefore, in order to obtain the same luminance as when the conventional image display sequence is applied, it is necessary to increase the luminance of the backlight.

  Therefore, in consideration of adopting this liquid crystal display device for mobile devices, several points on the screen are monitored, and whether the currently displayed image is an image mainly composed of moving images or images based on still images automatically. A moving image / still image discrimination circuit 21 for discrimination is provided. Then, according to the determination result of the moving image / still image determination circuit 21, when the backlight dimming circuit 23 determines that the image is a moving image, the luminance of the backlight is increased. Further, when it is determined that the image is a still image, the luminance of the backlight is lowered. In this way, the power consumption can be reduced compared to the case where the backlight brightness is always fixed to the moving image, and a portable liquid crystal display device excellent in moving picture display quality is minimized. It can be obtained with a limited increase in power consumption.

  Instead of providing the moving image / still image discriminating circuit 21, a switch for selecting the image display sequence of the present embodiment and the conventional image display sequence is provided so that one of the image display sequences can be selected by the user. There is no problem. When the switch is switched to the image display sequence side of the present embodiment, the backlight dimming circuit 23 increases the backlight brightness in synchronization. Also in this case, a liquid crystal display device excellent in moving image display quality can be obtained with a minimum increase in power consumption.

  Further, as described above, in the present embodiment, since a process of changing from black transmittance to an arbitrary transmittance and a process of changing from arbitrary transmittance to black transmittance are included for each frame, as shown in FIG. The relationship between the writing voltage and the transmittance is different from that in the conventional image display sequence. Further, as shown in FIG. 22, the temporal change in transmittance at each gradation also differs between the image display sequence of the present embodiment and the conventional image display sequence.

  Therefore, in consideration of these results, when the image display sequence according to the present embodiment is adopted, the write voltage at each gradation is determined by the signal reference power source 22 based on the determination result of the moving image / still image determination circuit 21. By re-adjusting the amplitude with respect to black display as a reference, it is possible to obtain a better gradation balance than when the conventional image display sequence is adopted.

  As described above, a VGA panel is used as the liquid crystal panel 11 in the present embodiment. The source driver 12 has a changeover switch 34 for switching and outputting both the data signal stored in the holding memory 32 and the reset signal based on the black signal voltage to the source line S during one horizontal line sampling period. Provide. The 480 gate lines G are divided into three groups of 160 lines, and the gate lines G of each group are connected to the first gate driver 13a to the third gate driver 13c.

  Then, the display control unit 20 supplies the first gate driver 13a to the third gate driver 13c with a clock signal whose phase is sequentially delayed by half a cycle. Further, a scanning start signal having one pulse at the first clock and the 321st clock is input from the display control unit 20 to the first gate driver 13a to the third gate driver 13c with phases shifted by 160 clocks. ing.

  Therefore, the gate driver 13 selects the nth gate line G when the source driver 12 outputs the data signal, and the (n + 160) th gate line when the source driver 12 outputs the reset signal. By setting the timing of the switching clock and the scanning start signal so as to select G, the picture element in which the data signal is written is displayed in the second half of the frame as shown in FIG. A reset signal is written in.

  At that time, if the voltage of the reset signal (that is, the voltage of the black signal power supply 24) is set to a voltage that can achieve black display within one frame period, the display can return to black display by the next frame. it can. That is, according to the present embodiment, when a black signal is written in the next frame with respect to a picture element in which a white signal is written, the black signal is already written in the second third of the previous frame. At the start of the frame, the transmittance is 10% or less, and no light leakage is observed.

  Furthermore, the edge portion of the video in the moving image repeats moving and stopping in each frame. In that case, since the human cannot visually recognize the stop of the edge portion, the edge portion seems to move smoothly. In this embodiment, a reset (black) signal is written in the second half of the frame for the picture element in which the data signal is written, and the video disappears. However, since a human cannot visually recognize that the video has disappeared, the period in which the edge portion of the video is before and after the human's line of sight is shortened, resulting in a moving image as shown in FIG. It is possible to reduce bleeding at the edge portion.

  In the present embodiment, a moving image / still image discrimination circuit 21 is provided that automatically determines whether the displayed image is a moving image-oriented image or a still image-oriented image. When the moving image / still image determining circuit 21 determines that the image is a moving image, the backlight dimming circuit 23 increases the luminance of the backlight. Therefore, it is possible to prevent a decrease in transmittance caused by writing a reset signal to 1/3 after one frame at the time of moving image display with a minimum increase in power consumption.

  In other words, according to the present embodiment, it is possible to improve the quality of moving picture display with a minimum increase in power consumption by performing a minimum improvement on a liquid crystal display device having a conventional VGA panel. is there.

  In the above description of the operation, the case of moving image display is taken as an example, but it goes without saying that still images can also be displayed. At the time of displaying a still image, the display control unit 20 outputs a switching clock signal for a still image having all levels of “H” to the source driver 12, and only the data signal is received over the entire sampling period of one horizontal line. Is output. Furthermore, a still image scanning start signal having one pulse is input to each of the gate drivers 13a to 13c with a phase difference of 160 clocks, while a still image identification signal having a level "L" is input to each gate driver. 13 is output. In this manner, as in the conventional liquid crystal display device, the image signal is displayed by outputting the data signal to all the source lines S while sequentially selecting 480 gate lines G from one end.

  In the above description, the voltage relationship between the signal reference power supply 22 and the black signal power supply 24 is not particularly described, but the display quality can be further improved by setting as follows. That is, when the black image reference voltage (black reference voltage) from the signal reference power supply 22 is Vd and the voltage of the black signal power supply 24 is Vr, the voltage level of the counter electrode 18 is positive. Sets both voltages so as to satisfy the relationship of Vd <Vr at normally white and Vd> Vr at normally black. On the other hand, in the case of negative polarity, both voltages are set so as to satisfy the relationship of Vd> Vr when normally white and Vd <Vr when normally black. By doing so, the shortage of the black display signal supply time can be compensated, and the display quality can be further improved.

Normally, the TFT (switching element) 17 requires a supply time of 20.5 μs at the shortest to reliably supply a signal voltage. On the other hand, as described above, when the VGA panel is driven at 16.7 ms (= 16700 μs), that is, when 480 gate lines G are driven at 60 Hz, one horizontal period is 10 times. ⁶ μs / 60 (Hz) / 480 (main) = 34.7 μs. Therefore, the data signal supply time and the black signal supply time are set as data signal supply time = 20.8 μs and black signal supply time = 34.7 μs−20.8 μs = 13.9 μs. FIG. 23 shows a timing chart of each drive signal and selection signal, and FIG. 24 shows an image display sequence.

  By setting each signal supply time in this way, data from the source drivers 13a to 13c can be reliably supplied to the pixel electrode 16. If the black signal supply time is shortened, it is considered that sufficient black signal supply (charging to the pixel capacity) is not performed. However, in the case of many liquid crystal display elements, when looking at the voltage-transmittance curve, the transmittance change is insensitive to the voltage near the black display (the transmittance is saturated to 0 near the black display). Therefore, a sufficient effect can be obtained even if the black signal supply is somewhat insufficient. In this embodiment, one frame time is defined as a time required to display an image of the entire screen of the liquid crystal display device regardless of the video signal system. For example, in the case of the interlace video signal system, one frame time is generally composed of two fields, and the entire screen of the liquid crystal display device is displayed in one field time corresponding to ½ of the frame time. In this case, the one field time is regarded as one frame time in the present embodiment. The same applies to other video signal systems. This is the same in the following embodiments.

<Second Embodiment>
The schematic configuration of the liquid crystal display device in the present embodiment is the same as that of the active matrix liquid crystal display device in the first embodiment shown in FIG. However, the liquid crystal display device in this embodiment uses an S-XGA (super XGA) panel for the liquid crystal display unit. The number of picture elements is 1280 (three times in the case of color display) × 1024, which is about twice as many as the number of gate lines G from the VGA panel in the first embodiment. Therefore, as in the case of the first embodiment, if the data signal and the reset signal are alternately output with the same output time width, the selection time of one horizontal line is approximately 16.7 ms (one frame time) / 1024 pieces / 2≈about 8.1 μs. Therefore, each signal writing (that is, charging) cannot be sufficiently performed on the picture element.

  In view of the ability of the TFT element to switch the connection between each pixel electrode and the source line S, the selection time of one horizontal line needs to be at least 12.0 μs. Therefore, in the present embodiment, the switching clock supplied to the changeover switch 34 in the source driver 12 is 16.7 ms (one frame time) / 1024 lines≈about 16.3 μs, out of the maximum selection time of one horizontal line. 12.0 μs is assigned to the data signal writing time, and the remaining 4.3 μs is assigned to the reset signal writing time.

  However, in such a reset signal writing time, it is impossible to sufficiently write the reset signal in one selection period. Therefore, in the present embodiment, as shown in FIGS. 25 and 26, the 1024 gate lines G are divided into four groups of 256, and four different gate drivers (hereinafter referred to as “first”) are divided for each group. 1 gate driver 13a to 4th gate driver 13d). However, the basic configuration of each gate driver 13 is the same as the configuration shown in FIG. When the image is displayed, the display control unit 20 sends an identification signal having “L” level for 768 clocks and “H” level for 256 clocks to each gate driver 13a. The phase is shifted by 256 clocks. Further, a scan start signal having one pulse at the first clock and the 769th clock is input to each gate driver 13 with a phase shift of 256 clocks.

  As a result, since the analog switch 43 of the gate driver 13 whose identification signal level is “H” is turned on, four consecutive gate lines G are selected in the gate driver 13 and are adjacent to each other. One gate line G and four gate lines G are alternately selected by the two gate drivers 13 while shifting.

  The image display sequence in the liquid crystal display device of the present embodiment is as shown in FIG. FIG. 27B shows the specific contents of the write and reset periods in FIG. As shown in FIG. 27, in this embodiment mode, writing of a data signal and writing of a reset signal are alternately performed with different time widths as described above. In this case, the reset signal is written simultaneously to four horizontal lines that are continuous from the data signal writing horizontal line 256 based on the identification signal and the scanning start signal as described above from the display control unit 20. It is done.

  By doing so, it is possible to write a reset signal to each horizontal line four times in one frame, and as shown in FIG. 28, sufficient black display is performed even if the reset signal writing time is 4.3 μs. Can be made. That is, according to the present embodiment, in an active matrix type liquid crystal display device using an S-XGA panel as the liquid crystal panel 11, blurring and afterimage of moving image display can be reduced.

In the present embodiment, as described above, the reset signal is applied to the gate line G (m = 256) ahead of the gate line G that has output the data signal for the following reason. That is, as described above, the response time for changing the transmittance of the liquid crystal from 100% to 10% is about 4 ms. When a reset signal is applied to a pixel electrode of a certain pixel connected to a certain gate line G, it is necessary that the display is substantially black until the next data signal is applied. Therefore, the following relationship is established.
f × m / N> 4 ms
F: 1 frame time (16.7 ms)
N: Total number of gate lines (1024)
Therefore, it is necessary that m> 246.

  Here, in the present embodiment, four gate drivers 13 connected to 256 gate lines G are arranged in a straight line, and 1024 are scanned. Therefore, if m = 256, the reset signal is sent from the gate driver 13 next to the gate driver 13 that is currently outputting the data signal to the gate line G having the same number as the gate line G that is outputting the data signal. Therefore, the condition of m> 246 can be cleared by a very simple control of outputting.

  Also in the case of this embodiment, the moving image / still image discriminating circuit 21 automatically determines whether the display image is a moving image-oriented image or a still image-oriented image. If the luminance of the backlight is increased by the circuit 23, a portable liquid crystal display device excellent in moving image display quality can be obtained with a minimum power consumption increase.

  In the above description, an example is described in which after a data signal is written to the nth gate line G, a reset signal is written to the k gate lines G continuously from the (n + m) th. However, the K gate lines G to which the reset signal is written may be divided into p groups every m lines. In this case, reset signals are simultaneously written in k (= K / p) continuous for each group.

FIG. 29 shows an example of a timing chart of each drive signal and selection signal (the gate driver 13d is omitted). FIG. 30 shows an image display sequence for one frame period.
FIG. 29 shows an example in the case of m = 256, p = 2, and k = 1.

  As described above, the following effects can be obtained by writing reset signals to the gate lines G after being distributed to p groups every m lines. That is, the liquid crystal has a characteristic that it starts to respond to black display when the reset signal is written and its dielectric constant gradually changes (due to the dielectric anisotropy of the liquid crystal). Therefore, even if a predetermined reset voltage is applied to the liquid crystal, the voltage actually applied to the liquid crystal changes due to the change in the dielectric constant.

  However, when a reset signal is supplied to k gate lines G by being distributed to p groups every other m lines, when attention is paid to one horizontal line, the reset signal is generated once every m lines are scanned. Will be supplied. That is, the liquid crystal responds to some extent by the first reset signal, and its dielectric constant changes. Then, after m scans, a second reset signal is supplied to the liquid crystal whose dielectric constant has changed. Therefore, more reliable black display can be obtained by repeating this operation p times.

  In other words, the signal supply to the liquid crystal element is an operation of applying a signal voltage to each pixel capacitor (that is, a charging operation). Therefore, the dielectric constant of the liquid crystal changes depending on the display content (alignment state), and the charge amount varies depending on the previous display content. Therefore, even if the same signal is supplied to the same picture element, a different display will occur if the previous display contents are different.

  However, as described above, the reset signal is repeatedly written p times after the time that the m gate lines G are scanned, so that the above-described problem of change in dielectric constant can be improved. A black display can be obtained.

<Third Embodiment>
In the liquid crystal display device according to the first embodiment, since the response speed of the liquid crystal becomes slow when used at a low temperature, the data signal of the next frame is written before the black display by the reset signal is completed. There is a problem that the amount of bleeding increases. This problem can be solved by applying the second embodiment, that is, by switching the identification signal from the display control unit 20, but from the transmittance corresponding to the data signal to the black transmittance. It can also be eliminated by controlling the response time so that it falls within the frame period. Hereinafter, a method for controlling the response time from the arbitrary transmittance corresponding to the data signal to the black transmittance will be described.

  As a method for controlling the response time, there are the following methods.

  (1) Increase “m”, which is the difference between the write line number of the reset signal and the write line number of the data signal, as the environmental temperature decreases. This makes it possible to lengthen the reset signal writing time so that the response time at the time of writing the reset signal is sufficiently within the frame period, and to compensate for a decrease in the response speed of the liquid crystal.

  (2) The black signal voltage (that is, the reset signal voltage) from the black signal power supply 24 is increased as the environmental temperature decreases. This makes it possible to increase the reset signal writing speed so that the response time at the time of reset signal writing is sufficiently within the frame period, and to compensate for a decrease in the response speed of the liquid crystal.

  Various methods of changing “m” in the above (1) are conceivable. For example, the method is as follows. That is, the shift register 41 of each gate driver 13 divided into a plurality is connected in series. An analog switch is connected to each of the input terminals of the m-th to (m + J) -th latch circuits among the latch circuits constituting all the shift registers 41, and any one of the (J + 1) analog switches is connected. The scanning start signal can be input to the input terminals of the mth to (m + J) th latch circuits. Further, a control circuit for the analog switch is provided, and the (m + j (j ≦ J))-th analog switch is turned on by this control circuit in accordance with the temperature drop.

  In the present embodiment, even if only one of the control methods (1) and (2) is performed, it is possible to avoid an increase in the amount of moving image blur due to a decrease in the response speed of the liquid crystal.

  In the second embodiment, the case where the reset signal is simultaneously written to four horizontal lines has been described as an example. However, the present invention is not limited to four horizontal lines. . Further, the reset signal writing is not limited to a fixed number of horizontal lines, and the number of reset signal writings can be changed. In this case, various methods for changing the number of reset signals written can be considered. For example, the following method may be used.

  That is, in FIG. 4, an analog switch is connected to each of the input terminals of the second to Kth latch circuits in each gate driver 13, and the analog switch 43 is connected via any one of the (K-1) analog switches. Can be supplied to the input terminals of the second to Kth latch circuits. Further, the control circuit for the analog switch is provided, and the second to k (k ≦ K) analog switches are turned on by the control circuit in accordance with the k signal from the outside. The k signal is a signal that specifies the number of reset signals to be written.

  In each of the above embodiments, the case where the present invention is applied to an active matrix liquid crystal display device has been described as an example, but it goes without saying that the present invention can also be applied to a duty type liquid crystal display device.

It is a figure which shows schematic structure in the liquid crystal display device of this invention. It is a figure which shows schematic structure of the source driver in FIG. FIG. 3 is a diagram showing a schematic configuration of a source driver different from FIG. 2. It is a figure which shows schematic structure of the gate driver in FIG. It is explanatory drawing when the analog switch in FIG. 4 operate | moves. 3 is a timing chart of three gate driver drive signals and selection signals output to each gate line in the first embodiment. It is explanatory drawing of the image used for description of a moving image display operation | movement. It is a figure which shows the conventional image display sequence. It is explanatory drawing of the blur which arises in the image shown in FIG. It is a figure which shows the transmittance | permeability change for every frame in the white belt picture element based on the conventional image display sequence. It is a figure which shows the image display sequence in the liquid crystal display device shown in FIG. It is a figure which shows the display result of the image shown in FIG. 7 based on the image display sequence shown in FIG. It is a figure which shows the transmittance | permeability change for every frame based on the image display sequence shown in FIG. It is a figure which shows the mode of the movement of the white belt in the arbitrary horizontal lines of the image shown in FIG. It is a figure which shows the response waveform of the transmittance | permeability in the conventional image display sequence at the time of making the response time of a liquid crystal into infinitesimal. It is a figure which shows the response waveform of the transmittance | permeability in the image display sequence shown in FIG. 11 when the response time of a liquid crystal is made into infinitesimal. It is a figure which shows the movement of the white belt | band | zone and the movement of a human viewpoint in the conventional image display sequence. It is a figure which shows the state which the brightness | luminance of both edges of a white belt falls due to the shift | offset | difference of the movement of a white belt shown in FIG. 17, and the movement of a human viewpoint. It is a figure which shows the movement of a white belt and the movement of a human viewpoint in the image display sequence shown in FIG. FIG. 20 is a diagram illustrating a state in which the luminance of both edges of the white belt is reduced due to the shift between the movement of the white belt and the movement of the human viewpoint shown in FIG. 19. It is a figure which shows the relationship between the write voltage and the transmittance | permeability in the image display sequence shown in FIG. 11, and the conventional image display sequence. It is a figure which shows the time-dependent change of the transmittance | permeability in each gradation in the image display sequence shown in FIG. 11, and the conventional image display sequence. 7 is a timing chart of drive signals and selection signals different from those in FIG. 6. It is a figure which shows the image display sequence different from FIG. It is a timing chart of a drive signal and a selection signal in a 2nd embodiment. It is a timing chart following FIG. FIG. 25 is a diagram showing an image display sequence different from those in FIGS. 11 and 24. It is a figure which shows the transmittance | permeability change for every frame based on the image display sequence shown in FIG. It is a timing chart different from FIG. It is a figure which shows the image display sequence of FIG. It is a schematic block diagram of the source driver in the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Liquid crystal panel 12 ... Source driver 13 ... Gate driver 20 ... Display control part 21 ... Movie / still image discrimination circuit,
DESCRIPTION OF SYMBOLS 22 ... Signal reference power supply 23 ... Backlight dimming circuit 24 ... Black signal power supply 31, 37 ... Sampling memory 32, 38 ... Holding memory 33, 38 ... DA converter 34, 35 ... Changeover switch 36 ... Black signal data generation part 41 ... Shift register 42 ... Output circuit 43 ... Analog switch

Claims (20)

A plurality of column lines arranged in parallel to each other, a plurality of row lines arranged in parallel to each other to intersect the plurality of column lines, and an intersection of the plurality of column lines and the plurality of row lines A method for displaying an image on a liquid crystal display device having a plurality of correspondingly provided picture elements,
(A) supplying a selection signal to one of the plurality of row lines from the n-th to the (n + m-1) -th row (n and m are positive integers), and Supplying a predetermined data signal to a picture element corresponding to the one row line among the plurality of picture elements by supplying a data signal to each of the column lines;
(B) Before or after the step (a), the first line of the plurality of row lines (l is a positive integer, l ≧ n + m or l + m ≦ n) to the l + m−1th row line. A selection signal is supplied to at least one row line, and a black display signal is supplied to each of the plurality of column lines, thereby corresponding to the at least one row line in the plurality of picture elements. Supplying a black display signal to the picture element to be processed,
The step of supplying the data signal to each of the plurality of column lines in the step (a) and the step of supplying the black display signal to each of the plurality of column lines in the step (b) include the data signal and Executed by switching between the black display signal and supplying one of the black display signals to the plurality of column lines,
By executing the steps (a) and (b) a plurality of times, the predetermined data signal and the black display signal are supplied for each of the plurality of picture elements in one frame period, and the plurality of pictures Each of the elements is a liquid crystal display method in which a state in which a black display signal is supplied for a time exceeding 4 / 16.7 of one frame period is maintained.
Including supplying a selection signal to two or more of the plurality of row lines and supplying a black display signal to each of the plurality of column lines;
The two or more row lines are (n + α · m) (α = 1, 2,..., P (p: a positive integer greater than or equal to 2)) or (n + α · m) -th row (n + α · m). m + k-1) (α = 1,2, ..., p (k: positive integer)) Ri row line der up to the present day,
A liquid crystal display method, wherein m> 115 and the value of m is set to satisfy the relationship of the following equation .
f × m / N> t
N: Number of row lines
f: 1 frame time
t: Response time of liquid crystal when switching from white display to black display   The liquid crystal display method according to claim 1, wherein the step (a) and the step (b) are alternately repeated. In the liquid crystal display method according to claim 1 or claim 2, a liquid crystal display wherein the equal to the supply time of the supply time and the black display signal of the data signal. In the liquid crystal display method according to claim 1 or claim 2, the supply time of the data signal, the liquid crystal display wherein the longer than the supply time of the black display signal. The liquid crystal display method according to any one of claims 1 to 4 ,
The two or more row lines are row lines from the (n + α · m) th to the (n + α · m + k−1 ) th , and the value of k is set so as to satisfy the relationship of the following equation. A liquid crystal display method characterized by the above.
T × k ≧ T ₀
However, T: Time for supplying black display signal once T ₀ : Shortest time for black display signal that can completely switch white display to black display In the liquid crystal display method according to any one of claims 1 to 5, and the voltage Vd when the data signal is a data signal for black display and a voltage Vr of the black display signal, the following A liquid crystal display method characterized by setting so as to satisfy the relationship.
In case of positive polarity with respect to the potential level of the counter electrode, Vd <Vr at normally white.
When normally black, Vd> Vr
In the case of negative polarity with respect to the potential level of the counter electrode, Vd> Vr during normally white.
Vd <Vr for normally black A plurality of column lines arranged in parallel to each other, a plurality of row lines arranged in parallel to each other to intersect the plurality of column lines, and an intersection of the plurality of column lines and the plurality of row lines A liquid crystal having a display panel having a plurality of correspondingly provided picture elements, a column line driver for supplying a data signal to the plurality of column lines, and a row line driver for supplying a selection signal to the plurality of row lines In the display device,
A video signal and a control signal are supplied to the column line driver, and a control signal is supplied to the row line driver to control an image display operation on the display panel, and a black image is applied to the plurality of picture elements. Black display signal generating means for generating a black display signal for displaying
Provided in the column line driver, comprising a changeover switch for switching and selecting one of a data signal based on a video signal from the display control unit and a black display signal from the black display signal generating means,
The display control unit supplies the control signal for selecting the row line to the row line driver, and when the changeover switch selects a data signal, the display control unit selects from the nth to the n + m−1th (n And m is a positive integer), a selection signal is supplied to one of the row lines, and when the changeover switch is selecting a black display signal, the selection signal is output from the plurality of row lines. The selection signal is supplied to at least one row line from the l-th row (l is a positive integer, l ≧ n + m or l + m ≦ n) to the l + m−1-th row, The data signal and the black display signal are supplied during one frame period, and the black display signal is supplied for each of the plurality of picture elements over a time period exceeding 4 / 16.7 of one frame period. Liquid crystal display device for maintaining state There,
When the changeover switch selects a black display signal, a selection signal is supplied to two or more row lines of the plurality of row lines, and the two or more row lines are (n + α · m). (Α = 1, 2,..., P (p: positive integer greater than or equal to 2)) From the first row line or (n + α · m) th to (n + α · m + k−1) (α = 1, 2,..., P (k: positive integer)) Ri row line der up to the present day,
m> 115 and the value of m is set so as to satisfy the relationship of the following equation .
f × m / N> t
N: Number of row lines
f: 1 frame time
t: Response time of liquid crystal when switching from white display to black display
The liquid crystal display device according to claim 7 , wherein the changeover switch alternately selects the data signal and the black display signal. 9. The liquid crystal display device according to claim 7, wherein the plurality of row lines are divided into L (L: a positive integer of 2 or more ) blocks every m lines, and the row line driver is A liquid crystal display device comprising L partial row line drivers for supplying selection signals to the row lines of each block. In the liquid crystal display according to any one of claims 7 to 9, the control signal to the column line driver from the display control unit, a switching control signal for controlling the switching operation of the changeover switch And the switching control signal is configured to make the selection time of the data signal longer than the selection time of the black display signal. In the liquid crystal display device according to any one of claims 7 to 9, the control signal to the column line driver from the display control unit, a switching control signal for controlling the switching operation of the changeover switch And the switching control signal is configured to make the selection time of the data signal equal to the selection time of the black display signal. 12. The liquid crystal display device according to claim 7 , wherein a control signal from the display control unit to the row line driver identifies whether or not a black display signal supply period for supplying the black display signal. The row line driver, based on the identification signal, outputs the (n + m) th to (n + m + k-1) th (k is a positive integer and k> 1 based on the identification signal. The liquid crystal display device is characterized in that the selection signal is supplied to the row lines up to. 13. The liquid crystal display device according to claim 12 , wherein a control signal from the display control unit to the row line driver includes a scanning start signal, and the row line driver includes a shift register having a plurality of latch circuits, and the identification signal. The scan start signal is supplied to the first latch circuit of the shift register during the data signal supply period, while the scan start signal is supplied to the mth latch circuit of the shift register during the black display signal supply period. A liquid crystal display device comprising scanning start signal supply means for supplying to k consecutive latch circuits. 14. The liquid crystal display device according to claim 13 , wherein the scanning start signal supply means can change the latch circuit number m and the number of latch circuits k in the black display signal supply period. . 15. The liquid crystal display device according to claim 14 , further comprising supply control means for controlling the operation of the scan start signal supply means, wherein the supply control means is based on a scan start position designation signal from the outside. A liquid crystal display device which outputs a control signal for setting a number m to the scanning start signal supply means. 16. The liquid crystal display device according to claim 7, wherein the display control unit performs a black display signal supply operation based on an operation of the changeover switch in response to a command signal from the outside. A control signal for the first display mode and a control signal for the second display mode in which the operation of the changeover switch is stopped and the black display signal supply operation is not performed are switched and output. A liquid crystal display device. 17. The liquid crystal display device according to claim 16 , further comprising a signal reference power source for setting a voltage of a data signal supplied from the column line driver, wherein the voltage of the signal reference power source is the first display mode. A liquid crystal display device that is switchable between the time and the second display mode. 17. The liquid crystal display device according to claim 16 , wherein data relating to the same position on the screen is monitored based on a video signal from the display control unit, and whether the image based on the video signal is a moving image or a still image. A liquid crystal display device comprising moving image still image discrimination means for discriminating between and outputting the command signal representing the discrimination result to the display control unit. In the liquid crystal display device according to any one of claims 16 to 18, a backlight for illuminating the display panel from the back side, based on the command signal, the first display mode and second display mode And a backlight dimming means for switching the luminance of the backlight. 20. The liquid crystal display device according to claim 7, wherein the black display signal generating means is a black display signal power supply, and the voltage of the black display signal power supply can be changed. A liquid crystal display device.

Images