JP2007240725A - Liquid crystal device and driving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which does nor cause flicker when displaying a still picture, having a quick response speed when displaying a dynamic picture, and having low power consumption. <P>SOLUTION: The liquid crystal display device comprises: a display part in which a plurality of pixels is arranged two-dimensionally, a plurality of scanning lines is arranged along the plurality of pixels, and also a plurality of signal lines is arranged along the plurality of pixels; a scanning line driver for driving the plurality of scanning lines; a signal line driver for driving the plurality of signal lines; a motion detection circuit for detecting a motion of an image displayed by the liquid crystal display part; and a control circuit for controlling the scanning driver and the signal line driver to perform non-interlace scanning when the motion is detected by the motion detection circuit, and to perform interlace scanning when the motion is not detected by the motion detection circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an OCB mode liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device and a driving method thereof that can suppress occurrence of flicker when displaying a still image.

  One of various techniques developed to improve the performance of liquid crystal display devices is OCB (Optically Compensated Bend) liquid crystal technology. In the OCB liquid crystal technology, liquid crystal molecules located between glass substrates are aligned in a bowed state (bend alignment) to improve response characteristics and viewing angle characteristics. In the present specification, a liquid crystal display device using OCB liquid crystal technology is referred to as an “OCB mode liquid crystal display device”.

  In the OCB mode liquid crystal display device, black display is temporarily inserted into the display image, thereby realizing high-speed display and maintaining the alignment of the liquid crystal. Black insertion is a method of providing a video display period and a black display period for each frame. In the OCB mode liquid crystal display device, moving image display performance is improved by performing black insertion.

  In general, in an OCB mode liquid crystal display device, scanning is performed one scanning line at a time from the top to the bottom of the liquid crystal display. In this way, one display screen is configured. Such scanning is called non-interlaced scanning.

Incidentally, for example, Patent Document 1 discloses a technique for realizing a good display of a liquid crystal display device. This document discloses a method of ensuring the brightness necessary for realizing a good display by increasing the proportion of light emission time in one frame period.
JP 2003-215535 A

  In an OCB mode liquid crystal display device that performs non-interlaced scanning, when performing television display mainly for moving image display, good characteristics have been obtained by performing black insertion. However, when it is necessary to display a still image on this liquid crystal display device, for example, when the liquid crystal display device is used as a monitor screen of a personal computer, problems such as flicker have occurred due to black insertion processing. Flicker means display flicker. In a liquid crystal display unit of a liquid crystal display device, rewriting is usually performed several tens of times per second. When the number of rewrites is small, that is, when the fresh rate of the liquid crystal display unit is low, the liquid crystal display unit may appear to flicker to the user.

  In order to suppress the occurrence of flicker, it is necessary to set the frame frequency to 70 Hz or higher. However, such setting causes an increase in data transfer speed and an increase in display rewriting frequency, resulting in an increase in power consumption of the liquid crystal display device. In addition, since the signal rewriting speed in the liquid crystal display portion is increased, a large thin film transistor must be used, and the transmittance of the panel (liquid crystal display portion) is also reduced.

  Accordingly, the present invention provides a liquid crystal display device capable of preventing occurrence of flicker when displaying a still image while suppressing power consumption and displaying a clear image with a high response speed when displaying a moving image, and a driving method thereof. For the purpose.

  In order to solve the above problem, according to one aspect of the present invention, a plurality of pixels are arranged two-dimensionally, a plurality of scanning lines are arranged in a row direction along the plurality of pixels, and the plurality of pixels are arranged. A liquid crystal display unit in which a plurality of signal lines are arranged in a column direction along the pixels, a scanning line driver that drives the plurality of scanning lines, a signal line driver that drives the plurality of signal lines, and the liquid crystal display A motion detection circuit that detects a motion of an image displayed on the screen, and a non-interlaced scan when the motion is detected by the motion detection circuit, and an interlace when the motion is not detected by the motion detection circuit. The scanning line driver and a control circuit for controlling the signal line driver are provided so as to perform race scanning.

  According to the present invention, it is possible to prevent occurrence of flicker when displaying a still image, and to obtain a clear image with a high response speed and a low power consumption when displaying a moving image, and a driving method thereof. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an OCB mode liquid crystal display device 100 according to an embodiment of the present invention. The liquid crystal display device 100 is a liquid crystal display device including a liquid crystal display unit such as a notebook computer.

  The liquid crystal display device 100 includes a liquid crystal display unit 10, a motion detection circuit 20, a control circuit 30, a scanning line driver 40, and a signal line driver 50.

  The liquid crystal display unit 10 displays characters, images (still images and moving images), and the like. The liquid crystal display unit 10 may be, for example, a TFT-LCD. In the liquid crystal display unit 10, a plurality of pixels are two-dimensionally arranged, and these pixels constitute a plurality of rows and a plurality of columns. In addition, a plurality of signal lines are arranged along a plurality of columns of pixels, and a plurality of scanning lines are arranged along a plurality of rows of pixels. More specifically, each of the plurality of signal lines is arranged along a corresponding column of the plurality of columns of pixels. Each of the plurality of scanning lines is arranged along a corresponding row of the plurality of rows of pixels.

  The image data and the synchronization signal are supplied to the signal line driver 50 via the control circuit 30. The control circuit 30 gives various timing signals synchronized with the image data to the signal line driver 50 and the scanning line driver 40. The image data is further used in the motion detection circuit 20, where the image motion is detected. The detection results (image motion detection signal, image motion non-detection signal (may be referred to as still image detection signal)) are supplied to the control circuit 30.

  The control circuit 30 controls the scanning line driver 40 and the signal line driver 50 according to the result detected by the motion detection circuit 20.

  The scanning line driver 40 drives a plurality of scanning lines of the liquid crystal display unit 10 according to control by the control circuit 30. The signal line driver 50 supplies display signals to a plurality of pixels via a plurality of signal lines of the liquid crystal display unit 10 according to control by the control circuit 30.

  Next, operations of the motion detection circuit 20 and the control circuit 30 will be described in more detail. As described above, the motion detection circuit 20 detects whether or not motion is included in the displayed image. Whether or not motion is included in the image can be determined by whether or not a motion vector is detected between successive frames, for example. Further, the magnitude of the motion can be determined based on the magnitude of the detected motion vector.

  If the displayed image does not include motion, it can be considered that the image is a still image. If non-interlaced scanning and black insertion are performed when displaying a still image, problems such as flicker may occur as described above.

  On the other hand, when a displayed image includes a motion, the image can be considered as a moving image. When displaying a moving image, non-interlaced scanning and black insertion are performed to obtain good characteristics such as improved moving image visibility and high-speed response characteristics. For this reason, it is desirable to divide the processing performed by the control circuit 30 depending on whether the image displayed on the liquid crystal display unit 10 is a still image or a moving image.

  Processing that can be applied when the displayed image is a still image will be described with reference to FIG. FIG. 2 is a waveform diagram for explaining a driving method of an OCB mode liquid crystal display device according to an embodiment of the present invention. FIG. 2 shows the case where the frame frequency is 60 Hz.

  In FIG. 2, VS is a vertical synchronization signal input, and X is a signal voltage output from the signal line driver 50 and supplied to the signal line of the liquid crystal display unit 10. Yn (n is a natural number. The uppermost scanning line Y1 of the liquid crystal display unit 10 and the subsequent scanning lines are Y2, Y3, Y4, and so on in order) is a scanning line. The scanning line voltage output from the line driver 40 is supplied. The scanning line voltages D1, D2, D3,... Are the signal writing timing voltages, and B1, B2, 3,. V represents a pixel electrode voltage at the intersection of the signal line and the scanning line in the liquid crystal display unit 10, and RES represents a display period in which the pixel responds.

  Here, when the scanning line voltage reaches the writing level (D1), the display voltage supplied to the signal line at that time is written and held in the pixel 1 at the intersection. As a result, the pixel 1 is in a voltage state corresponding to the display content. Next, when the scanning line reaches the writing level (B1), a display voltage corresponding to “black” display is supplied to the signal line, and a “black” display voltage is written and held in the pixel 1 (black). Insert). That is, after the display signal is written to the pixel, the “black” display signal is written.

  The above scanning is sequentially performed on odd-numbered scanning lines (Y1, Y3, Y5,...) From the upper part to the lower part of the liquid crystal display unit 10. When the scanning of the odd-numbered scanning lines on the liquid crystal display unit 10 is finished, the scanning is performed on the even-numbered scanning lines (Y2, Y4, Y6,...). That is, interlaced scanning is performed on the liquid crystal display unit 10.

  By performing such interlaced scanning, the apparent blinking frequency of the liquid crystal display unit 10 can be increased to twice the frame frequency (in this embodiment, 60 Hz × 2 = 120 Hz). Generally, when the frame frequency is 70 Hz or more, the user often does not visually recognize flicker. Therefore, by performing interlaced scanning as described above, it is possible to suppress the occurrence of flicker when displaying a still image.

  On the other hand, when displaying moving images, interlaced scanning may cause a change in visual resolution. For example, when an image having a different color or brightness from the background is moved on the liquid crystal display unit 10, the image quality may be deteriorated. For example, line interference may occur, or the boundary of the image may appear jagged. This is because the scanning lines updated in each field are thinned out. For example, in the case of 2: 1 interlace, the image is updated every other scanning line in each field. For this reason, when the image displayed on the liquid crystal display unit 10 is a moving image, it is preferable to perform non-interlaced scanning.

  Next, an OCB mode liquid crystal display device 200 according to another embodiment of the present invention will be described with reference to FIG.

  FIG. 3 is a block diagram illustrating a schematic configuration of the liquid crystal display device 200. The liquid crystal display device 200 includes a sensitivity adjustment input unit 60 that performs sensitivity adjustment of the motion detection circuit 20 in addition to the configuration of the liquid crystal display device 100 illustrated in FIG. 1. In FIG. 3, the same parts as those in FIG. As described above, the motion detection circuit 20 determines the motion of an image input to the liquid crystal display unit 10 and detects motion (output for moving image determination) or non-motion detection (still image) depending on the detection sensitivity. Judgment output). The control unit 30 controls the scanning line driver 40 and the signal line driver 50 so as to perform non-interlaced scanning when a motion detection output is obtained and to perform interlaced scanning when a motion non-detection output is obtained. To do. Here, the sensitivity adjustment input unit 60 can adjust the detection sensitivity of the motion detection circuit 20.

  In the liquid crystal display device 100 shown in FIG. 1, the motion detection circuit 20 detects whether an image displayed on the liquid crystal display unit 10 is a still image or a moving image. If the image is a still image, interlace scanning is performed. For moving images, non-interlaced scanning is performed. However, even if the displayed images are the same, the user may feel that interlaced scanning with less flicker is appropriate depending on the display content, usage status, usage environment, sensitivity of the user to flicker, etc. There may be cases where non-interlaced scanning capable of displaying a good moving image is appropriate.

  Therefore, the liquid crystal display device 200 is provided with a sensitivity adjustment input unit 60 so that the user can input sensitivity adjustment of the motion detection circuit 20. Therefore, the user can select or adjust the display state (scanning method) of the liquid crystal display unit 10, and can reduce the stress that can be felt by the display state.

  The sensitivity adjustment input unit 60 may be any input device that can input sensitivity adjustment, such as a push button, a knob, or a dial. Further, the sensitivity adjustment input unit 60 can be provided in any part of the liquid crystal display device 200. For example, when the liquid crystal display device 200 is a notebook personal computer, the sensitivity adjustment input unit 60 is provided in an arbitrary part such as a part close to the liquid crystal display part (screen), a part close to the keyboard part, or a side surface of the notebook personal computer body. it can. When the liquid crystal display device 200 is a desktop type liquid crystal display, the sensitivity adjustment input unit 60 may be provided in an arbitrary part such as a part close to the liquid crystal display part (screen), a side surface of the liquid crystal display, a support part in contact with a desk or the like. . When the liquid crystal display device is a portable terminal such as a PDA or an in-vehicle terminal, the sensitivity adjustment input unit 60 may be provided in an arbitrary part such as an input unit or a side surface of the portable terminal.

  Further, the sensitivity adjustment input unit 60 is not limited to a physical input device such as a push button. The sensitivity adjustment input unit 60 may be realized as a program that provides a sensitivity adjustment function. For example, when the liquid crystal display device is a portable terminal such as a PDA or an in-vehicle terminal, the sensitivity of the motion detection circuit 20 may be adjusted by calling the program from the touch screen of the portable terminal.

  Various methods can be adopted as a sensitivity adjustment method in the sensitivity adjustment input unit 60. For example, the ratio of the area of the moving part to the entire area of the liquid crystal display unit 10 (the area of the moving part / the area of the entire liquid crystal display unit 10) is set as the parameter P1, and the user can adjust the threshold Th1 of the parameter P1. May be. In this case, the motion detection circuit 20 compares the parameter P1 with the threshold Th1. As a result of comparison, when the parameter P1 is equal to or greater than the threshold value Th1, switching from interlaced scanning to non-interlaced scanning may be performed.

  In addition, a motion vector (Vx, Vy) may be detected between successive frames of an image displayed on the liquid crystal display unit 10, and the user may be able to adjust the threshold Th2 for the value. In this case, the motion detection circuit 20 compares the motion vector (Vx, Vy) with the threshold Th2. As a result of the comparison, when the motion vector (Vx, Vy) is greater than or equal to the threshold Th2, switching from interlaced scanning to non-interlaced scanning may be performed.

  Furthermore, the threshold value Th2 may be set as a fixed value so that the user can adjust the amplification degree of the motion vector (Vx, Vy). In this case, the motion detection circuit 20 compares the motion vector (Vx, Vy) whose amplification degree is adjusted with the threshold value Th2. As a result of the comparison, when the motion vector (Vx, Vy) whose amplification degree is adjusted is equal to or greater than the threshold value Th2, switching from interlaced scanning to non-interlaced scanning may be performed.

  In the above-described embodiment, a case where a 2: 1 interlace that scans every other scanning line is used has been described. However, interlaced scanning is not limited to this, and for example, a 3: 1 interlace that scans every other scanning line, a 4: 1 interlace that scans every other scanning line, etc., are used as appropriate. May be. In these cases, the same effect as in the present embodiment can be obtained.

  Further, the liquid crystal display device according to the present invention is not limited to a notebook personal computer, and various portable devices such as a mobile phone, a personal digital assistant (PDA), a portable game machine, an in-vehicle terminal, a portable TV, and a portable video player. You may apply to various fixed terminals, such as a terminal, a liquid crystal display, and a liquid crystal television.

  FIG. 4 is a waveform diagram for explaining a conventional driving method of an OCB mode liquid crystal display device (hereinafter referred to as “conventional driving method”) in order to clarify the difference from the embodiment of the present invention. is there. In FIG. 4, VS is a vertical synchronization signal input, X is a signal voltage output from the signal line driver and supplied to the signal line of the liquid crystal display unit, Yn (n is a natural number. The uppermost scanning line of the liquid crystal display unit is Y1 and subsequent scanning lines Y2, Y3, Y4, and so on in order) are output from the scanning line driver and supplied to the scanning lines of the liquid crystal display unit, and V is in the liquid crystal display unit The pixel electrode voltage RES at the intersection of the signal line and the scanning line, RES, indicates the response of the pixel. FIG. 2 shows the case where the frame frequency is 60 Hz.

  Looking at the driving waveform of the scanning line Y1, the scanning line voltage becomes the writing level, and the display voltage supplied to the signal line at that time is written and held in the pixel 1 at the intersection. As a result, the pixel 1 is in a voltage state corresponding to the display content. Next, when the scanning line reaches the writing level, the display voltage corresponding to the “black” display is supplied to the signal line, and the “black” display voltage is written and held in the pixel 1 (black insertion). That is, after the display signal is written to the pixel, the “black” display signal is written.

  In the conventional driving method, the operation as described for the scanning line Y1 is sequentially performed on the subsequent scanning lines Y2, Y3,..., Yn-2, Yn-1, and Yn. That is, non-interlaced scanning is performed. In the conventional driving method, non-interlaced scanning is performed regardless of whether the image displayed on the liquid crystal display unit is a still image or a moving image. For this reason, for example, when displaying a still image, problems such as flicker may occur.

  Therefore, in the above embodiment of the present invention, the motion detection circuit 20 detects whether or not the image displayed on the liquid crystal display unit 10 includes motion, and based on the detection result, interlaced scanning and non-interlaced scanning are performed. And switching. As shown in FIG. 3, when the liquid crystal display device 200 includes a sensitivity adjustment input 60, the user can adjust the detection sensitivity of the motion detection circuit 20. In this case, the motion detection circuit 20 detects whether or not the image displayed on the liquid crystal display unit 10 includes motion according to the adjusted detection sensitivity, and based on the detection result, interlace scanning and non-interlace are performed. Switching between scanning.

  In addition, this invention is not limited to the said embodiment as it is. In the implementation stage, the present invention can be embodied by changing the components without departing from the scope of the invention.

  Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a block diagram which shows schematic structure of the liquid crystal display device of OCB mode by one Embodiment of this invention. FIG. 5 is a waveform diagram for explaining a method of driving an OCB mode liquid crystal display device according to an embodiment of the present invention; It is a block diagram which shows schematic structure of the liquid crystal display device of OCB mode by another embodiment of this invention. It is a wave form diagram for demonstrating the drive method of the liquid crystal display device of the conventional OCB mode.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Liquid crystal display part, 20 ... Motion detection circuit, 30 ... Control circuit, 40 ... Scan line driver, 50 ... Signal line driver, 60 ... Sensitivity adjustment input part

Claims (7)

A liquid crystal display in which a plurality of pixels are two-dimensionally arranged, a plurality of scanning lines are arranged in a row direction along the plurality of pixels, and a plurality of signal lines are arranged in a column direction along the plurality of pixels And
A scanning line driver for driving the plurality of scanning lines;
A signal line driver for driving the plurality of signal lines;
A motion detection circuit for determining a motion of an image input to the liquid crystal display unit and obtaining a motion detection output or a motion non-detection output according to detection sensitivity;
A control circuit for controlling the scanning line driver and the signal line driver so as to perform non-interlace scanning when the motion detection output is obtained, and to perform interlace scanning when the motion non-detection output is obtained; ,
A liquid crystal display device comprising: A sensitivity adjustment input unit for adjusting the detection sensitivity of the motion detection circuit;
The liquid crystal display device according to claim 1, further comprising: The sensitivity adjustment input unit is configured such that a user can adjust the first threshold as the detection sensitivity,
The motion detection circuit obtains a ratio of the area of the image motion part to the area of the liquid crystal display unit, and compares the ratio with the first threshold value to obtain the motion detection output and the motion non-detection output. Configured to determine,
The liquid crystal display device (200) according to claim 1, characterized in that: The sensitivity adjustment input unit is configured so that a user can adjust a second threshold as the detection sensitivity,
The motion detection circuit obtains a vector value of a motion vector between successive frames of the image, and compares the vector value with a second threshold value in the previous period to obtain the motion detection output and the motion non-detection output. Configured to determine,
The liquid crystal display device according to claim 1. The sensitivity adjustment input unit
3. The liquid crystal display device according to claim 2, wherein when the motion detection circuit detects a motion vector between successive frames of the image, the amplification degree of the motion vector detection unit can be adjusted.   The liquid crystal display device according to claim 2, wherein the function of the sensitivity adjustment input unit is realized by a program. A liquid crystal display in which a plurality of pixels are two-dimensionally arranged, a plurality of scanning lines are arranged in a row direction along the plurality of pixels, and a plurality of signal lines are arranged in a column direction along the plurality of pixels A scanning line driver that drives the plurality of scanning lines, a signal line driver that drives the plurality of signal lines, a motion detection circuit that detects a motion of an image displayed on the liquid crystal display unit, and the motion A liquid crystal display device comprising: a sensitivity adjustment input unit that adjusts the detection sensitivity of a detection circuit; and a control circuit that controls the scanning line driver and the signal line driver based on a detection result of the motion detection circuit. Driving method,
When the motion is detected by the motion detection circuit, non-interlaced scanning is performed, and when the motion is not detected by the motion detection circuit, interlaced scanning is performed.
A driving method for a liquid crystal display device.

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