JP2005222011A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device whose moving picture performance can be improved further without lowering luminance and to provide a method of driving the same. <P>SOLUTION: The liquid crystal display includes: a liquid crystal display panel having a matrix of a plurality of pixels arrayed two dimensionally in a first direction and in a second direction crossing the first direction; and an illuminating device including a plurality of light sources facing the pixel matrix of the liquid crystal display panel. The plurality of light sources are arrayed in the first direction and grouped into a plurality of light source areas. The turn-on start timing of light sources in each light source area is set to a specified timing based on the input timing of the video signal to the selected pixel rows in the pixel matrix. Further, the turn-on and turn-off timings of the light source areas are set to specified conditions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a driving method of a liquid crystal display device, and more particularly to a liquid crystal display device having improved moving image performance when a moving image is displayed on a liquid crystal TV or the like and a driving method thereof.

Liquid crystal televisions (hereinafter referred to as liquid crystal TVs) using a TFT liquid crystal display module as a display unit are commercially available.
In general, the liquid crystal TV employs a display method in which the backlight is always on (hereinafter referred to as a hold-type display method). In this hold-type display method, the image quality appears blurred when displaying a moving image. It is known that.
As an improvement measure, it is known to insert black data between frames of video (hereinafter referred to as black insertion display method) (for example, refer to Patent Document 1 below). There is also known a technique for intermittently turning on a backlight of a liquid crystal display device and displaying an image formed on the liquid crystal display panel so as to resemble impulse emission of a cathode ray tube (for example, the following patents) Reference 2).

As prior art documents related to the invention of the present application, there are the following.
JP 11-109921 A Japanese National Patent Publication No. 08-500915 JP 2001-204049 JP 2003-280599 A

There is a demand for further improvement in moving image performance due to the increase in the size of liquid crystal TV displays. In order to meet this demand, the black data insertion amount may be increased in the black insertion display method.
However, in the above-described black insertion display method, the moving image performance can be improved as the amount of insertion of black data is increased, but conversely, the luminance is lowered.
Since brightness is an important characteristic for TVs, the amount of black data inserted cannot be increased due to the balance with the brightness. With the black insertion display method, the video performance increases as the LCD TV display size increases. Cannot be improved.
The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for driving a liquid crystal display device capable of further improving moving image performance without reducing luminance. Is to provide.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

The inventors of the present application have studied the case where the backlight is intermittently lit (hereinafter referred to as “blink”) within one frame in addition to the black insertion technique, but it has been found that the video performance greatly changes depending on the timing of the blink. .
The present invention has been made on the basis of the above knowledge, and the outline of typical ones of the inventions disclosed in the present application will be briefly described as follows.
That is, the present invention includes a liquid crystal display panel having a pixel matrix in which a plurality of pixels are two-dimensionally arranged along a first direction and a second direction intersecting the first direction, and the plurality of pixels And a plurality of pixel rows arranged in the first direction and sequentially selected from one end to the other end of the pixel matrix for each frame period. A plurality of light sources are arranged to face the pixel matrix of the liquid crystal display panel, and the plurality of light sources are arranged in the first direction and face at least three groups of the plurality of pixel rows, respectively. A liquid crystal display device having a lighting device divided into one light source region and a driving method thereof, wherein a plurality of lighting periods (in other words, turn-on periods) of the plurality of light source regions correspond to the plurality In response to the selection of the at least three groups of pixel rows and the start of capturing video signals by the group of the pixels belonging to the selected group of the plurality of pixel rows, sequentially starting for each frame period, The lighting periods of the plurality of light source regions end sequentially within each frame period, and the at least three light source regions are arranged in the first direction of the pixel matrix where the first group of the plurality of pixel rows is located. A first light source region facing the central region, and a second group of the plurality of pixel rows selected before the first group of pixel rows for each frame period, and the center along the first direction. A second light source region adjacent to the region of the pixel matrix adjacent to the region, a third group of the plurality of pixel rows selected after the first group of pixel rows for each frame period, and the second group One direction In other words, it is divided into a third light source region facing the other region of the pixel matrix adjacent to the central region, and a lighting period of the second light source region and a lighting period of the first light source region for each frame period. And the lighting period of the third light source region starts and ends in this order, the lighting period of the second light source region ends after the start of the lighting time of the first light source region, The lighting time starts after the lighting time of the first light source region starts and at or before the end of the lighting time of the second light source region.

The start time of the turn-on period of the third light source region may coincide with the end time of the turn-on period of the second light source region. In the frame period, the first light source region and the second light source The turn-on period of each of the region and the third light source region may be the same. In addition, one of the lighting periods of the first light source region, the second light source region, and the third light source region in the frame period may be different from at least one of the other, and the respective lighting periods may be different from each other. May be.
On the other hand, a tubular light source extending in the second direction may be used as the plurality of light sources, and the lighting device may be configured by arranging a plurality of the tubular light sources in parallel in the first direction, A plurality of tubular light sources may be juxtaposed in the first direction in at least one of the first light source region, the second light source region, and the third light source region.
Each of the plurality of pixels belonging to the first group of the plurality of pixel rows is in a first light source region, and each of the plurality of pixels belonging to the second group of the plurality of pixel rows is in a second light source region. Each of the plurality of pixels belonging to the third group of pixel rows may be opposed to a third light source region, and from the one end of the pixel matrix toward the other end, a second light source region, The first light source region and the third light source region may be arranged in this order.
In the frame period, after the video signal is captured in the plurality of pixel rows, the video signal may be selected again, and a voltage signal for reducing the luminance may be captured in each of the plurality of pixels belonging to the pixel row. The voltage signal may be used to display a pixel that captures the voltage signal in black.
The time (t _U ) from the start time of capturing the video signal by the second group of pixel rows to the start time of the lighting period of the second light source is defined as the time at which the video signal is captured by the first group of pixel rows. May be different from a time (t _M ) from the start time of the lighting period of the first light source to the start time of the first light source, and the lighting period of the third light source from the start time of capturing the video signal by the third group of pixel rows. The time (t _L ) until the start time of the first light source may be made different from the time (t _M ) from the start time of the video signal capture by the first group of pixel rows to the start time of the lighting period of the first light source. Good.

  Among the inventions of the driving method of the liquid crystal display device disclosed in the present application, an example other than the above is a pixel matrix in which a plurality of pixels are two-dimensionally arranged in a first direction and a second direction intersecting the first direction. A liquid crystal display panel having a plurality of pixels arranged in the second direction, arranged in the first direction in the pixel matrix, and sequentially selected from one end to the other end of the pixel matrix for each frame period And a plurality of light sources opposed to the pixel matrix of the liquid crystal display panel, and the light sources are arranged in at least three groups of the plurality of pixel rows side by side in the first direction. A liquid crystal display device including an illuminating device divided into at least three light source regions facing each other, and the at least three of the plurality of pixel rows corresponding to lighting periods of the plurality of light source regions, respectively. In response to the start of capturing video signals by the group of pixels belonging to the selected group of the plurality of pixel rows and the plurality of pixel rows thereby, the plurality of pixel rows are opposed to each other. A blanking signal for canceling the video signal is taken into a group of the plurality of pixels belonging to the reselected one of the plurality of pixel rows by sequentially selecting again after the lighting periods of at least three light source regions are started. A step of ending the lighting period of the at least three light source regions after one of the at least three groups of the plurality of pixel rows opposed to each of the light source areas starts to capture the blanking signal for each frame period. The at least three light source regions are repeated in (i) a central region in the first direction of the pixel matrix where the first group of the plurality of pixel rows is located. And (ii) a second group of the plurality of pixel rows for capturing the video signal before the first group of pixel rows for each frame period, and along the first direction. A second light source region facing the region of the pixel matrix adjacent to the central region; and (iii) a third of the plurality of pixel rows that captures the video signal after the first group of pixel rows for each frame period. A group of light sources and a third light source region facing the other region of the pixel matrix adjacent to the central region along the first direction, the lighting period of the second light source region (turn-on Period), a lighting period of the first light source region, and a lighting period of the third light source region are sequentially started and ended in this order, and the lighting period of the second light source region is turned on of the first light source region. After the start of the period, the third The lighting period of the light source area is started after the lighting period of the first light source area starts and before or after the lighting period of the second light source area ends, and the lighting of the first light source area in each frame period is started. Interrupting at least one of the lighting period of the second light source area and the lighting period of the third light source area after the end of the period and before the start of the lighting period of the first light source area in another subsequent frame period It is.

An example of the invention of the liquid crystal display device disclosed in the present application includes a pixel matrix in which a plurality of pixels are two-dimensionally arranged along a first direction and a second direction intersecting the first direction, A plurality of pixel rows each composed of a group of a plurality of pixels arranged in the second direction, arranged in the first direction in the pixel matrix, and sequentially selected from one end to the other end of the pixel matrix for each frame period. The formed liquid crystal display panel, a plurality of light sources are arranged to face the pixel matrix of the liquid crystal display panel, and the plurality of light sources are arranged in the first direction and at least three groups of the plurality of pixel rows. An illumination device divided into at least three light source regions facing each other, a display control circuit for supplying an image signal to the pixel matrix, and the plurality of the plurality of light sources in response to a control signal from the display control signal A control unit including a light source drive circuit for controlling the driving source, the control unit is for the following processing respectively executed.
(I) For each frame period, one of the at least three groups of the plurality of pixel rows corresponding to each of the plurality of light source regions is selected, and the group belonging to the selected group of the plurality of pixel rows When a plurality of pixels start to capture video signals, sequentially start lighting periods (turn-on periods) of the plurality of light source regions; and
(II) while the lighting period of the plurality of light source regions is sequentially terminated within the frame period,
(III) a first light source region facing the central region in the first direction of the pixel matrix in which the first group of the plurality of pixel rows is located, selected before the pixel row of the first group for each frame period A second light source region facing the pixel matrix region adjacent to the central region along the first direction, and the first group for each frame period. The third group of the plurality of pixel rows selected after the pixel row is located and includes a third light source region facing the other region of the pixel matrix adjacent to the central region along the first direction. Use at least three light source areas,
(IV) For each frame period, the lighting period of the second light source region, the lighting period of the first light source region, and the lighting period of the third light source region are sequentially started and ended in this order,
(V) ending the lighting period of the second light source region after the start of the lighting period of the first light source region; and
(VI) The lighting period of the third light source region is started after the lighting period of the first light source region is started and at or before the end of the lighting period of the second light source region.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the present invention, it is possible to further improve moving image performance without reducing luminance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.
<Basic configuration of a liquid crystal display module to which the driving method of the present embodiment is applied>
FIG. 16 is an exploded perspective view showing a schematic configuration of a liquid crystal display module to which the driving method of the present embodiment is applied.
The liquid crystal display module shown in FIG. 16 includes a frame-shaped upper frame 4 made of a metal plate, a liquid crystal display panel 5, and a direct type backlight unit.
The liquid crystal display panel 5 includes a TFT substrate on which pixel electrodes, thin film transistors, and the like are formed and a filter substrate on which counter electrodes, color filters, and the like are formed with a predetermined gap therebetween, and a peripheral portion between the two substrates. Both substrates are bonded together by a sealing material provided in the vicinity of a frame, and liquid crystal is sealed and sealed inside the sealing material between the substrates from a liquid crystal sealing port provided in a part of the sealing material. A polarizing plate is attached to the outside of the substrate.
Here, on the glass substrate of the TFT substrate, a plurality of drain drivers and gate drivers composed of a semiconductor integrated circuit device (IC) are mounted.
The drain driver is supplied with drive power, display data, and control signals through the flexible printed circuit board 1, and the gate driver is supplied with drive power and control signals through the flexible printed circuit board 1. .
The flexible printed wiring board 1 is connected to a drive circuit board (TCON board) 13 provided on the back side of the backlight unit.
The backlight unit of the liquid crystal display module according to the present embodiment includes a plurality of cold cathode fluorescent lamps (CFL) 2 and optical members (diffusion sheets, lenses) between a frame-shaped intermediate frame 6 made of a metal plate and the reflector 3. Sheet) 7 are arranged in the order shown in FIG.
In FIG. 16, 8 and 11 are holders for the cold cathode fluorescent lamp 2, 9 is a high voltage side cable connector, 10 is a rubber bush, 12 is a low voltage side connector, and 14 is an inverter circuit for driving the cold cathode fluorescent lamp 2. A substrate 15 is a low voltage side cable connector.
In the present embodiment, the reflector 3 whose inner surface is white or silver also serves as the lower frame.

FIG. 17 shows an example of the configuration of a liquid crystal display device (liquid crystal display module, also abbreviated as LCD) used in the embodiment of the present invention, and FIG. 18 shows a pixel array (display panel) provided in the liquid crystal display device. An example of the circuit configuration is shown respectively. Elements having the same reference numerals as those shown in FIG. 16 indicate elements having the same or substantially equivalent functions.
In FIG. 17, a portion surrounded by a broken-line frame indicates a liquid crystal display device 20 to which the present invention is applied. A liquid crystal display device 20 shown in FIG. 17 is mounted on a television receiver (not shown). The television receiver includes a receiving circuit 19 that receives a television broadcast as an external circuit of the liquid crystal display device 20. (Image signal source) is also installed. The receiving circuit 19 receives the video signal a that matches the received video signal of the television broadcast with the resolution of the liquid crystal display device 20 and the timing signal b for reproducing the video data on the liquid crystal display device 20. To enter. The timing signal b includes a display control signal, such as a vertical synchronization signal and a horizontal synchronization signal that control the transmission state of the video data a, and a display timing that is an external clock signal. A signal (Display Timing Signal) and a dot clock signal (Dot Clock Signal) are included.
The video data input to the liquid crystal display device 20 is stored in the frame memory 22 for each frame period through a display control circuit 21 (for example, a timing controller) provided in the liquid crystal display device 20. When the frame frequency of a television broadcast video signal is 60 Hz, one frame period is approximately 16.7 msec. (Milliseconds). The display control circuit 21 supplies the input video data a to each pixel of the pixel array 5 (liquid crystal display panel) of the liquid crystal display device 20 at a frequency higher than the vertical synchronization signal and horizontal synchronization signal received from the reception circuit 19. In order to do so, it has a function of generating its own clock. The video data stored in the frame memory 22 is transferred to the pixel array 5 according to the clock signal generated by the display control circuit 21.
Note that the scan clock, dot clock, frame start signal, and the like output from the display control circuit 21 are transmitted to the data signal drive circuit 24 via the data signal line control bus 28. In addition, a frame start signal, a scan clock, and the like output from the display control circuit 21 are transmitted to the scan drive circuit 23 via the scan line control bus 29.

In the pixel array 5 of the liquid crystal display device 20, as shown in FIG. 18, a plurality of pixels are two-dimensionally arranged along a vertical direction (arrow x) and a horizontal direction (arrow y) intersecting the vertical direction. In a pixel array having WXGA (Wide eXtended Graphics Array) standard resolution, 768 pixel rows are arranged in the vertical direction and 1280 pixel columns are arranged in the horizontal direction. Each pixel row is composed of a plurality of pixels arranged in the horizontal direction. Each of the pixel columns is composed of a plurality of pixels arranged in the vertical direction. When the pixel array displays a color image with three primary colors of R (red), G (green), and B (blue), since 1280 pixel columns are provided for each of the primary colors of R, G, and B, horizontal pixels There are 3840 rows in total. Accordingly, the pixel array 5 is formed with a display portion (effective display area) composed of 2949120 pixels determined by the product of ₇₆₈ pixel rows Y _{001 to} Y ₇₆₈ and 3840 pixel columns X _{0001 to} X _3840. The
The scanning lines 201 corresponding to the ₇₆₈ pixel rows Y _{001 to} Y 768 shown in FIG. 18 are drawn from one side (left side) extending in the vertical direction of the pixel array 5 shown in FIG. 23 (vertical scanning circuit). Data signal lines 203 respectively corresponding to 3840 pixel column X ₀₀₀₁ to X ₃₈₄₀ shown in Figure 18, drawn from the upper side extending in the horizontal direction of the pixel array 5 shown in FIG. 17, the data signal drive circuit 24 (horizontal scanning circuit). The scanning drive circuit 23 sequentially sends a scanning signal to ₇₆₈ scanning lines 201 from the scanning line 201 corresponding to the pixel row Y001 to the scanning line 201 corresponding to the pixel row Y768, and one 768 pixel row is obtained. Select one by one (or multiple). Depending on the choice of such a pixel row, the data signal drive circuit 24 outputs to the 3840 data signal lines 203 corresponding to the pixel columns X ₀₀₀₁ to X ₃₈₄₀ gradation voltages according to the video signal level. A video signal is written to each of the pixels 207 belonging to the selected pixel row, and a video is displayed.

The operation in which the pixel 207 provided in the liquid crystal display device 20 generates luminance in accordance with the video signal input thereto can be described as control of voltage to the capacitor 206 including a liquid crystal layer and a pair of electrodes sandwiching the liquid crystal layer. (See FIG. 18). The pixel 207 is provided with a switching element that is opened and closed by a scanning signal applied from the scanning line 201, for example, a thin film transistor 204, and a video signal (voltage signal) input from the data signal line 203 through the switching element 204 is Applied to one of the pair of electrodes forming the capacitor 206. Since a constant voltage is always applied to the other electrode of the capacitor 206 through the common signal line 202, the light transmittance of the liquid crystal layer forming the capacitor 206 changes according to the video signal. In principle, the light transmittance of the liquid crystal layer is maintained until the pixel 207 receives the next video signal, but in reality, the voltage applied to one electrode of the capacitor 206 gradually decreases. Because it changes. In order to prevent such a drop in the voltage applied to one electrode of the capacitor 206, the pixel 207 is provided with a storage capacitor 205.
The liquid crystal display device 20 shown in FIG. 17 is also provided with a lighting device 26 called a backlight unit (FIG. 16) for irradiating the pixel array 5 with light. Hereinafter, the backlight unit is simply referred to as a backlight. In the liquid crystal display device 20 to which the present invention is applied, a cold-cathode fluorescent lamp (Cold-cathode Fluorescent Lamp) 2 shown in FIG. 16, an external electrode fluorescent lamp (External Electrode Fluorescent Lamp), a light emitting diode (Light Emitting Diode), or the like. A backlight 26 (referred to as a direct type) is used in which a plurality of light sources such as two-dimensionally arranged facing the main surface of the liquid crystal display panel 5 are used. The structure of the liquid crystal display device provided with the direct type backlight 26 is as shown in FIG. The lighting of the plurality of light sources arranged in the backlight 26 is controlled by the backlight driving circuit 25, respectively. In the liquid crystal display device 20 according to the present invention, the timing signal c (scanning clock or the like) is input from the display control circuit 21 to the backlight driving circuit 25 through the backlight control bus 27.

FIG. 19 is a plan view showing a schematic configuration when the above-described direct type backlight 26 is incorporated in the liquid crystal display device 20. The outline of the pixel array of the liquid crystal display panel 5 is indicated by a broken line frame. Twelve fluorescent tubes 2 are arranged in the vertical scanning direction from the pixel row Y ₀₀₁ to the pixel row Y ₇₆₈ of the liquid crystal display panel 5. The twelve fluorescent tubes 2 are illustrated on the assumption that a cold-cathode fluorescent lamp 2 shown in FIG. 16 or a light source extending in a tubular shape such as an external electrode fluorescent lamp is used. Each of the light sources may be replaced with at least one row of light emitting diodes arranged in the horizontal scanning direction of the liquid crystal display panel 5 (including a light emitting diode array including two or more rows). Terminals are provided at both ends of each fluorescent tube 2, and a high voltage is applied from one of the terminals (right side in FIG. 19) from the backlight drive circuit 25 to start lighting. A reference voltage (for example, ground potential) is applied to the other terminal (left side in FIG. 19) of each fluorescent tube 2. When each fluorescent tube 2 is replaced with a light emitting diode row or a light emitting diode array comprising a plurality of light emitting diodes, a current is supplied from the backlight drive circuit 25 to each of the plurality of light emitting diodes. Both the application of a high voltage from the backlight driving circuit 25 to the fluorescent tube 2 and the current injection into the light emitting diode row or the light emitting diode array are performed from the display control circuit 21 through the backlight control bus 27 to the backlight driving circuit 25. Is performed in accordance with the timing signal input to.
When this direct type backlight 26 is combined with the liquid crystal display panel 5 having the WXGA standard pixel array (having 768 pixel rows) described above, one fluorescent tube 2 is arranged in the pixel array. Corresponds to a pixel row of books. For example, the fluorescent tube Lamp6 corresponds to the pixel row Y384 located in the center of the pixel array along the vertical scanning direction. However, since the fluorescent tube Lamp 6 corresponds to the pixel rows Y _{320 to} Y ₃₈₄ and the fluorescent tube Lamp 7 corresponds to the pixel rows Y _{385 to} Y ₄₄₈ , the luminance of 3840 pixels forming the pixel row Y ₃₈₄ is the same as that of the fluorescent tube Lamp 6 and It is determined by the lighting state of each fluorescent tube Lamp7. This relationship also holds when the fluorescent tube 2 is replaced with the light emitting diode row or the light emitting diode array. In the following description of the method for driving a liquid crystal display device according to the present invention, a liquid crystal display device including a direct type backlight in which a plurality of cold cathode fluorescent lamps are arranged as shown in FIG. 19 is exemplified.

<Driving Method of Liquid Crystal Display Device of Embodiment of the Present Invention>
A liquid crystal driving method according to an embodiment of the present invention will be described below. The plurality of cold cathode fluorescent lamps 2 of the direct type backlight 26 described above are divided into n groups (n is a natural number and satisfies n ≧ 3), and the cold cathode fluorescent lamps 2 of each group are intermittently lit within one frame period. The blinking sequence to be executed is executed.
Hereinafter, the driving method of the liquid crystal display device in this embodiment will be described more specifically.
An example in which the direct type backlight unit 26 of the liquid crystal display module shown in FIG. 16 is configured by arranging, for example, twelve cold cathode fluorescent lamps 2 as shown in FIG. In the present embodiment, the 12 cold cathode fluorescent lamps 2 (Lamp1 to Lamp12) are arranged in groups of three in groups of four in the vertical scanning direction of the pixel rows of the liquid crystal display panel 5 (hereinafter also referred to as display line selection direction). Divide into (n = 3). Accordingly, the twelve fluorescent lamps shown in FIG. 19 (in this description, cold cathode fluorescent lamps) are arranged in the first group (pixel rows Y _{001 to} Y ₂₅₆ ) of fluorescent lamps Lamp 1 to Lamp 4 as shown in FIG. corresponding) second group consisting of a fluorescent lamp Lamp5～Lamp8 (corresponding to the pixel row Y ₂₅₇ to Y _512), and divided into 3 groups of fluorescent lamps Lamp9～Lamp12 (corresponding to the pixel row Y ₅₁₃ to Y _768). Since the pixel row Y ₀₀₁ is located at the upper end and the pixel row Y ₇₆₈ is located at the lower end of the image (for example, television image) displayed on the liquid crystal display panel 5, four fluorescent lamps Lamp1 belonging to the first group are located. ~ Lamp4 is located at the top of the screen, the four fluorescent lamps Lamp5 to Lamp8 belonging to the second group are located at the center of the screen, and the four fluorescent lamps Lamp9 to Lamp12 belonging to the third group are located at the bottom of the screen The Thereafter, in the present embodiment, as described above, a plurality of light sources are divided into three groups (n = 3) along the selection direction of each display line when the video signal voltage is written to each pixel of the liquid crystal display panel 5. The case will be described.
The index of the moving image performance of the liquid crystal display device in the present embodiment will be described with reference to FIG. As shown in FIG. 1, when the background is displayed in white (example: 255 gradation), a black (example: 0 gradation) bar is displayed there, and the bar is moved in the horizontal direction, the edge portion is blurred. Looks. From the brightness profile at this time, the width between 10% and 90% of relative brightness is defined as BEW (Blurred Edge Width).
Since this BEW is proportional to the moving speed of the image, a value normalized by the moving speed is defined as N-BEW (Normalized-BEW; BEW / moving speed). The smaller the N-BEW value, the better the moving image performance.
Therefore, in the following description, this N-BEW is adopted as the moving image performance. The details of the evaluation method are described in Patent Document 3.

On the other hand, the driving sequence (Driving Sequence) of the liquid crystal display panel 5 in the evaluation of the moving image performance of the liquid crystal display device 20 described above will be described with reference to the waveform diagram of FIG. FIG. 21 will be described with reference to input waveform diagrams of voltage signals (video signals or alternatives) to main pixel rows of the liquid crystal display panel 5. The liquid crystal display device is mounted on a television receiver as shown in FIG.
The television broadcast video signal received by the television receiver is converted into video data in accordance with the resolution of the liquid crystal display panel, that is, the WXGA standard by the receiving circuit 19 (image signal source), and the liquid crystal is displayed for each frame period. This is input to the display control circuit 21 of the display device 20. The receiving circuit 19 also inputs a vertical synchronizing signal, a horizontal synchronizing signal, a display timing signal, and a dot clock signal that match the video data to the display control circuit 21 of the liquid crystal display device 20. The display control circuit 21 refers to the input signal and stores the video data in the frame memory 22. When a television broadcast video signal is input to the receiving circuit at a frame frequency of 60 Hz, the frequency of the vertical synchronizing signal is also 60 Hz. On the other hand, in the present embodiment, one frame period: 16.7 msec. Are divided into a video data transfer time to 768 pixel rows and a vertical blanking period corresponding to the video data transfer time to 32 pixel rows. Accordingly, the frequency of the horizontal synchronizing signal is 48 kHz in accordance with the video data transfer to 800 pixel rows. The dot clock signal (data signal line control bus 28) for sending video data (video signal) of 3840 pixels per pixel row is about 184 MHz, but is further increased by setting the horizontal blanking period. Note that the display timing signal prevents storage of the signal (fake video data) input to the display control circuit from the video data transmission path in the vertical blanking period or horizontal blanking period in the frame memory. Signal.

The video signal described with reference to FIG. 21 is read out by the display control circuit 21 and transferred to the data signal driving circuit 24 after the video data once stored in the frame memory 22 as described above. It is generated with reference to the video data. The signal waveform of each pixel row shown in FIG. 21 shows a rectangular wave surrounded by a dotted ellipse and a rectangular wave that is not. The rectangular wave not surrounded by the ellipse indicates the timing when the video signal is input to each of the 3840 pixels belonging to the pixel row, and the rectangular wave surrounded by the dotted ellipse indicates 3840 pixels that belong to the pixel row. The timing at which the blanking signal is input to each pixel is shown. The blanking signal is a signal for erasing the video signal already input to the pixel, and can be generated by, for example, the display control circuit 21 or the data signal driving circuit 24 regardless of the video data stored in the frame memory. Further, as is apparent from the waveform of the pixel row Y ₀₀₁ in FIG. 21, in this embodiment, the blanking signal is input to each pixel so as to follow the input of the video signal to each pixel every frame period. The
In such a drive sequence, when a voltage signal for reducing the luminance of the pixel to the lowest level (or the vicinity thereof) is generated as a blanking signal, the luminance of each pixel in the liquid crystal display panel 5 (pixel array) is set for one frame period. After reaching a predetermined brightness every time, it falls to the lowest level, so an image is displayed on the screen by impulse light emission such as CRT. In the liquid crystal display device, the blanking signal for reducing the luminance of the pixel to the lowest level is a voltage that minimizes the light transmittance of the liquid crystal layer corresponding to the pixel 207 in the equivalent circuit of the pixel 207 described with reference to FIG. It is also a signal. However, in the following description, such a blanking signal is also referred to as “black” or “black data”.

In the driving sequence of the liquid crystal display panel 5 in the present embodiment, the video signal is input to the 3840 pixels forming the pixel row for each pixel row four times, and then the four video signals to which these video signals are input are input. Four pixel rows (for example, Y _{005 to} Y ₀₀₈ ) other than the pixel row (for example, Y _{465 to} Y ₄₆₈ ) are selected, and blanking signals are input to a total of 15360 pixels included in the four pixel rows. To do. Following the blanking signal input, the video signal is input to a pixel row (for example, Y ₄₆₉ ) adjacent to the pixel row (for example, Y ₄₆₈ ) to which the video signal input has been input immediately before. Therefore, in the driving sequence of the liquid crystal display panel 5, every time a video signal is sequentially input to four pixel rows, a blanking signal is simultaneously input to another four pixel rows. In other words, in the driving sequence of the liquid crystal display panel 5 in the present embodiment, at least 960 times of video signal input to 768 pixel rows that can be completed by selecting 768 times of pixel rows every frame period. Need to be selected. Furthermore, in this embodiment, a margin of a period corresponding to 40 pixel row selection times is provided for each frame period, and a certain frame period (for example, Nth, N is a natural number) followed by the next frame period This prevents a malfunction between the storage of video data in the frame memory 22 and the reading of the video data from the frame memory 22 (for example, (N + 1) th). Therefore, in the driving sequence of the liquid crystal display panel 5 in the present embodiment, the frequency of the horizontal synchronizing signal (scanning clock) is set so that the pixel row can be selected 1000 times per frame period, and the value thereof is 60 kHz. . The horizontal synchronization signal, the corresponding dot clock (requires a frequency of at least 230.4 MHz), and the display timing signal for identifying the video signal input and the blanking signal input are used for display control of the liquid crystal display device. Generated by the circuit 21. Note that one of the two frame memories 22 (M1, M2) connected to the display control circuit 21 shown in FIG. 17 has video data of an odd-numbered frame period in one, and video data of an even-numbered frame period in the other. Are stored alternately.

The count number shown in FIG. 21 indicates the number of pulses of the horizontal synchronizing signal (scanning clock) generated 1000 times per frame period, and corresponds to the start of video signal input to the pixel row _Y001 . Is set to “0” as the start time of the frame period. The video signal input to the pixel array in this frame period ends with the 959th count when the video signal input to the pixel row Y ₇₆₈ is completed, and the 1000th count from the 959th count (in this frame period). In the period up to the 0th count of the subsequent next frame period), no video signal is input to the pixel array. On the other hand, the blanking signal input to the four pixel rows Y ₀₀₁ to Y ₀₀₄ including the pixel row Y ₀₀₁ is immediately after the video signal input to the pixel row Y 464 in response to the 579th count of the horizontal synchronization signal and This is performed immediately before the video signal is input to the pixel row Y ₄₆₅ . The blanking signal input to the next four pixel rows Y ₀₀₅ to Y ₀₀₈ is immediately after the video signal input to the pixel row Y ₄₆₈ and the pixel row Y in response to the 584th count of the horizontal synchronization signal. _This is performed immediately before video signal input to ₄₆₉ . Then, 427 pixel rows (Y _{341 and} later) positioned below the screen (pixel array) from the four pixel rows Y _{337 to} Y ₃₄₀ to which blanking signals are input in response to the 999th count. The blanking signal is input into the next frame period. Therefore, the blanking signal input to the pixel row Y _{768 in} the frame period ends at the 535th count in the next frame period following this. In FIG. 21, the blanking signal input to the pixel row Y ₇₆₈ in the frame period (previous frame period) _immediately before the frame period starting from the 0th count shown at the left end is the 535th count in the frame period. (In other words, immediately after the video signal input to the pixel row Y ₄₂₈ and immediately before the video signal input to the pixel row Y ₄₂₉ in the frame period).

In such a driving sequence of the liquid crystal display panel, the period in which each pixel belonging to the pixel rows Y _{001 to} Y ₀₀₄ holds the video signal in one frame period corresponds to 576 to 579 pulses of the horizontal synchronizing signal, and the remaining 421 to 424. The blanking signal is held for a period corresponding to the pulse. In each pixel belonging to a pixel row other than the pixel rows Y _{001 to} Y ₀₀₄ , the ratio between the period for holding the video signal and the period for holding the blanking signal in one frame period is the same for each pixel belonging to the pixel rows Y _{001 to} Y _004. It is similar to that. Therefore, if this blanking signal is a voltage signal that minimizes the light transmittance of the liquid crystal layer corresponding to each pixel, each pixel is related to the video signal over a period corresponding to about 42% of one frame period. Will be displayed in black. Hereinafter, in this specification, a driving mode in which each pixel constituting the pixel array is displayed in black by a blanking signal in a predetermined period within one frame period is referred to as “black insertion”, and the one frame period corresponding to the one frame period of that period is described. The ratio is noted as “black insertion rate”. The “black insertion” technique is described in Patent Document 4 above.
The video signal input and blanking signal input for each frame period shown in FIG. 21 are depicted macroscopically as shown in FIG. Since a pixel row to which a video signal is input and a pixel row to which a blanking signal is input are selected four times in a time corresponding to five pulses of a horizontal synchronization signal for starting selection of the pixel row five times, the time axis The gradient (number of pixel rows) in the vertical scanning direction with respect to (horizontal axis) is macroscopically equal between the video signal input and the blanking signal input. Further, assuming that the waveform shown in FIG. 21 is the Nth frame period (N is a natural number), it can be seen that the blanking signal input in the Nth frame period ends in the next (N + 1) th frame period. .

FIG. 2A shows a luminance response waveform depending on whether or not black data (hereinafter simply referred to as black) is inserted. This waveform is a waveform when the entire display screen of the liquid crystal display panel is displayed in white and the luminance of the screen is detected by a photo sensor.
As shown in FIG. 2A, by performing black insertion, an impulse-like luminance waveform is obtained, and the moving image performance is improved. However, the luminance decreases due to the black insertion period.
FIG. 2B shows the moving image performance and the luminance reduction rate with respect to the black insertion rate. This data drives the liquid crystal display panel at a black insertion rate of 0% (dots displayed as “none”), 33% (specification A), 42% (specification B), and 50% (specification C), respectively. Under each driving condition, the moving image performance was evaluated based on the width (BEW) in which the edge of the black bar moving in the horizontal direction on the white screen was blurred as described with reference to FIG. The numerical value (%) of the moving image performance is 100% of the reference measured in the driving state in which the liquid crystal display panel is driven at a black insertion rate of 0% and the backlight is continuously turned on. The value of BEW in the state is shown as a relative value from the case where BEW is 100% of the standard.
The evaluation of the luminance reduction rate is as described above with reference to FIG. The numerical value (%) of the luminance reduction rate defines the luminance measured at a black insertion rate of 0% as “reference luminance (luminance reduction rate = 0%)”, and the measured luminance at each black insertion rate from this reference luminance. Is calculated as a ratio (Percentage) to the reference luminance of the difference obtained by subtracting.
As shown in FIG. 2B, the video performance is improved by increasing the black insertion rate, but the luminance reduction rate is increased, so that the black insertion rate is easily obtained in the continuous light emission of the normal hold type display method. Can not increase.

Therefore, when driving with black insertion, the brightness of the display screen is maintained without being affected by the black insertion period by turning on the backlight at the timing when the luminance waveform becomes a high transmittance part. The inventors have thought to further increase the video performance by further increasing. As is apparent from FIG. 22, in one frame period started by the video signal input to the pixel row Y ₀₀₁ , black insertion is stopped in the middle (period extending from the 535th count to the 579th count). There is. In contrast, the lighting periods of the n groups of light sources described above are made different from each other in accordance with the timing of video signal input to the pixel rows corresponding to the respective groups (groups), and the lighting periods of these light sources are different from each other. The lighting start times of the light sources in each group are set so as to overlap with a period in which black insertion is not performed.
Hereinafter, in this specification, a case where the black insertion rate is 42% (specification B) will be described. FIG. 2B also shows data for a black insertion rate of 42% (specification B) for the specifications to be examined later, as well as data for a black insertion rate of 33% (specification A) for comparison. .
As described above, FIGS. 21 and 22 show a driving sequence of the liquid crystal display panel at a black insertion rate of 42%. Therefore, the video signal input timing and blanking signal input timing shown in each of them correspond to that of the black insertion rate B that can achieve both the brightness of the display screen and the moving image performance at a desired level. In the description of FIGS. 21 and 22, the input time of the video signal and the blanking signal to each pixel row in one frame period has been described by the pulse number of the horizontal synchronization signal. However, in the driving sequence of the liquid crystal display panel according to the present embodiment, a video signal is input from the pulse number of the horizontal synchronization signal in order to provide a margin of a period corresponding to 40 pixel row selection times for each frame period. It is difficult to specify the address of the pixel row: Y _xxx (xxx is a natural number of 3 digits, for example, Y ₇₆₈ ).

Therefore, in the following description, instead of the pulse number of the horizontal synchronization signal, the video signal input start time to the pixel row Y ₀₀₁ in a certain frame period (Nth frame period in FIG. 22) continues from that frame period. The time in the “time zone” over these two frame periods is specified at the address of the pixel row to which the video signal is input over the next frame period (the (N + 1) th frame period in FIG. 22). Several examples of the time display are shown in FIG. 22 as scanning line numbers corresponding to typical pulse numbers of the horizontal synchronizing signal. For example, the time when the input of the video signal to the pixel array in the Nth frame period is described as a scanning line number: 768 instead of the pulse number: 959 of the horizontal synchronization signal.
It should be noted in this time display that virtual scan line numbers 769 to 800 for expressing the above margin are added to 768 scan line numbers (pixel row addresses) to which video signals are actually input. It is being done. For example, after the video signal input to the pixel array in the Nth frame period is completed, the time when the video signal input to the pixel array in the (N + 1) th frame period starts is described as a scan line number: 800. Is done. In FIG. 22, the scanning line number with an asterisk is the virtual scanning line number or the line number in the (N + 1) th frame period counted including this. In the intermittent lighting operation of the light source, which will be described later, the lighting start time of the light source is indicated by the above scanning line number, so that the vertical scanning position of the pixel array at the lighting start time (address of the pixel row to which the video signal is input) is determined. A specific and desirable lighting start time will be described.

In the present embodiment, the start time of the intermittent lighting operation of the light source is the light source facing the central portion (hereinafter simply referred to as the central portion) in the vertical scanning direction (y) of the pixel array (display portion of the liquid crystal display panel 5). Set the lighting start time of the group as a reference. The light source group facing the central portion of the pixel array corresponds to the pixel row of the pixel array: Y ₃₈₄ or Y ₃₈₅ in the backlight facing the WXGA standard pixel array in which 768 pixel rows are arranged in the vertical direction. The second group (Middle) including the fluorescent tubes Lamp5 to Lamp8 in the direct type backlight shown in FIG. 20 corresponds to this. The address of the pixel row located in the center of the pixel array changes according to the resolution. For example, in an SXGA (Super eXtended Graphics Array) standard pixel array in which 1024 pixel rows are arranged in the vertical direction, Y ₅₁₂ and Y _{513 are obtained} . In a UXGA (Ultra eXtended Graphics Array) standard pixel array in which 1200 pixel rows are arranged in the vertical direction, Y ₆₀₀ and Y ₆₀₁ are obtained. Depending on the grouping of the plurality of light sources provided in the direct type backlight, the boundary between the light source of the y-th group (y is a natural number and satisfies the relationship of 1 <y <n) and the light source of the (y + 1) -th group It may be located in the center of the pixel array. In this case, as the light source facing the center of the pixel array, the lighting start time of either the y-th group light source or the (y + 1) -th group light source is used as a reference for the above “start time of intermittent light source lighting operation”.

In light of the essence of the present invention, it is not necessary to discuss the light source corresponding to the center along the “horizontal” scan direction of the pixel array, unless the positions of the scan drive circuit 23 and the data signal drive circuit 24 are interchanged in FIG. . Therefore, in the following description, “the center of the pixel array along the vertical scanning direction” is simply referred to as “the center of the pixel array” or “the center of the screen”. In the following description, the lighting start time of the light source (light source group) facing the center of the pixel array (the center of the screen) is referred to as “Blink Start Timing”. The blink start timing may be different from the start time of the intermittent lighting operation of the light source in the entire backlight in the backlight lighting sequence described later, but it remains the reference for the setting. Hereinafter, the present embodiment will be described by taking a liquid crystal display device having a backlight shown in FIG. 20 as an example.
FIG. 3 shows the measurement results of the moving image performance and the luminance reduction rate at the center of the screen of the liquid crystal display device using the driving method using both black insertion and the intermittent lighting operation of the backlight (light source). In this experiment, the lighting start times of the light source group (first group) facing the upper part of the screen and the light source group (third group) facing the lower part of the screen are used as the lighting start time of the light source group (second group) facing the center of the screen. The backlight “Simultaneous Blinking Operation” was adopted according to the time, that is, the blink start timing. The moving image performance was evaluated by the measurement method described with reference to FIG. 1, and the luminance reduction rate was evaluated by the measurement method described with reference to FIG.

  As described with reference to FIG. 1, the numerical value (%) of the moving image performance is “blurred” measured by a liquid crystal display device provided with a backlight that is continuously lit on a liquid crystal display panel driven at a black insertion rate of 0%. The “width” is based on the values measured on both sides along the moving direction of the black bar moving in the horizontal direction on the white screen. When the black bar moves from the left to the right of the screen, “blurring” generated in the process of changing the pixel (pixel array) displaying the vicinity from black to white is observed at the left end of the bar. The width of this “blurring” is denoted as “B → W” in FIG. In addition, “blurring” generated in the process of changing another pixel (pixel row) displaying the vicinity thereof from white to black is observed at the right end of the bar. The width of this “blurring” is denoted as “W → B” in FIG. In this experiment, each time the blink start timing is changed, the blur width: “B → W” and the blur width: “W → B” are measured, and each of the measured values is driven at a black insertion rate of 0%. 3 is plotted in the graph of FIG. 3 as a ratio (%) to a reference value of 100%.

The numerical value (%) of the luminance reduction rate is defined as the luminance measured by a liquid crystal display device that is driven at a black insertion rate of 0% and the backlight is continuously lit, as the reference luminance (luminance reduction rate = 0%). The ratio (Percentage) of the difference obtained by subtracting the measured brightness at each black insertion rate from the reference brightness with respect to the reference brightness is plotted in the graph of FIG.
Further, the line number of the blink start timing indicated on the horizontal axis corresponds to the time display “scan line number” described above with reference to FIG. Therefore, the dot indicated by 800 line has a blink start timing at the start time of the next frame period following the frame period after the video signal input to the pixel array in a certain frame period is completed (scan line number: 768 line). The result when combined. Note that “W → B” added to FIG. 3 and each drawing referred to thereafter is BEW shown in FIG. 1A, and “B → W” is BEW shown in FIG. Represents. Similarly, the “Blink ON Duty” additionally indicated indicates the ratio of the period during which each light source group is lit to the frame period (about 16.7 msec.). For example, when the blink start timing is 600 lines, each light source group is lit until the video signal input to 200 pixel rows in the next frame period following the frame period is completed.

As shown in FIG. 3, the moving image performance and the luminance reduction rate change depending on the blink start timing. As the dot values (%) of “W → B” and “B → W” are lower, the “blurring width” is narrowed and the moving image performance is better. Also, the lower the dot value (%) of the luminance reduction rate, the better the display quality of the moving image. As is apparent from the results of FIG. 3, depending on the blink start timing (scanning line number), it has been found that the moving image performance may not be improved as expected even if the backlight is intermittently turned on. In FIG. 3, the value of the moving image performance of the liquid crystal display device provided with the liquid crystal display panel driven at the above-described black insertion rate of 33% (specification A) and the continuously lit backlight is also indicated by a broken line. In a liquid crystal display device having a liquid crystal display panel driven with a black insertion rate of 42% (specification B) and a backlight that performs a blink operation, the blur width “B → W” when the blink start timing is 500 lines or earlier. Is wider than the case of the liquid crystal display device of specification A and the liquid crystal display device having a black insertion rate: 0% and a liquid crystal display device that is continuously lit, and lowers the moving image performance.
In view of the result of FIG. 3, in the present embodiment, the timing 600line at which the luminance decrease is small and the moving image performance is almost the best value is adopted as the blink start timing. When the blink start timing is set in this way, as is apparent from FIGS. 22 and 20, the light source group (second group) facing the center of the screen moves to the pixel rows Y ₂₅₇ to Y ₅₁₂ of the corresponding pixel array. After the video signal input is completed, lighting starts. When a liquid crystal display panel operation with a black insertion rate of 42% is used in combination with a collective blink operation of a backlight, a light source group that faces the pixel row (Y _{001 to} Y ₁₄₀ when a blanking signal is input) ( Lighting of the first group is started, and lighting of the light source group (third group) facing the pixel row is started before the video signal is input to the pixel rows: Y _{601 to} Y ₇₆₈ .

FIG. 4A shows the result of confirming the moving image performance and luminance at the top and bottom of the screen in this state.
As shown in FIG. 4A, the luminance is greatly reduced at the top of the screen, and there is no improvement effect on the moving image performance at the top and bottom of the screen. Further, as shown in FIG. 4B, the chromaticity value also changes greatly.
Such a result is due to the time difference of data writing in the screen, and the timing of data writing and blinking do not match.
5A to 5C show the relationship between the data writing time difference and the blink timing when black is inserted. In these figures, the hatched part is the period during which the light source is turned on, and the other part is the extinguishing period.
FIG. 5A shows the case of collective blink driving in which intermittent lighting of all light sources is performed simultaneously. In this case, the cold cathode fluorescent lamp 2 is turned on in the second half of the luminance waveform (that is, the video signal voltage is written and the transmittance characteristic of the liquid crystal) at the upper part of the screen, and the cold cathode fluorescent lamp is shown in the first half of the luminance waveform at the lower part of the screen. Since 2 lights up, the characteristics are not improved.
For this reason, in order to improve the display performance, as shown in FIG. 5B, in accordance with the data writing time difference between the pixel rows in the pixel array, for each light source group corresponding to each pixel row, the lighting start time and Blinking by the sequential lighting system with different lighting end times is required. FIG. 5C shows the relationship between the data write time difference and the blink timing at the time of black insertion in the blink operation of sequentially turning on the light source groups of the backlight in this embodiment to be described later.

FIG. 6 shows the timing of writing data to pixel rows arranged at the top, center, and bottom of the screen (pixel array) (pixel row: video signal input time to Y ₀₀₁ , Y ₂₅₇ , Y ₅₁₃ ). In addition, the evaluation results of the moving image performance when the cold cathode fluorescent lamps 2 arranged corresponding to the upper part, the center part, and the lower part of the screen are sequentially started at different times are shown.
As is apparent from the measurement results in FIG. 6, in the backlight operation of blinks (line graphs plotted by black circles and black squares) by sequential lighting, blinks by line lighting (line graphs plotted by white circles and white squares) Compared to that, the video performance at the top and bottom of the screen improved (15% at the top of the screen and 18% at the bottom of the screen), but the center of the screen deteriorates (-20%), and the center of the screen has the best video performance. It got worse.
The luminance response waveform at the center of the screen at this time is shown in FIG. 7 together with the luminance response waveform in the collective blink operation.
In contrast to the collective lighting blink, in the sequential lighting blink, the peak luminance decreases in the latter half of each frame period (around 10 msec. And 27 msec.), And the base luminance between the peaks increases, so the impulse waveform changes greatly. It was.
As this factor, light leakage from the top and bottom of the screen of the cold cathode fluorescent lamp 2 of the direct type backlight can be considered.

FIG. 8 shows the result of a light leakage confirmation experiment from the top and bottom of the screen of the liquid crystal display panel.
In this experiment, the screen of the liquid crystal display panel is virtually divided into an upper region, a central region, and a lower region, and the cold cathode fluorescent lamp 2 shown in FIG. 16 is opposed to the virtual three regions in the screen. The backlight was configured so that the cold cathode fluorescent lamp 2 could be turned on independently for each group. The three groups of the cold cathode fluorescent lamps 2 are named upper, middle, and lower in accordance with the upper area, the central area, and the lower area of the screen of the liquid crystal display panel, and the respective lighting waveforms are shown on the left side of FIG. A rectangular wave with a hatched waveform indicates a period in which the cold cathode fluorescent lamp 2 (light source) is turned on, and the cold cathode fluorescent lamp is kept off in other periods. Response waveforms when the upper, center, and lower cold cathode fluorescent lamps are lit in a lump (simultaneously) and when the upper or lower cold cathode fluorescent lamps are lit at a timing that reverses the central timing. As a result, the peak brightness decreased and the base brightness increased in the reverse lighting operation of the upper or lower cold-cathode fluorescent lamps as compared to the collective lighting operation, and the result was almost the same as the sequential blink operation shown in FIG. It became.
As a result, it was confirmed that light leakage from the top and bottom of the screen affected the center.

FIG. 9A shows a sequential lighting waveform for changing the lighting start time (blink timing) of each cold cathode fluorescent lamp 2 facing the upper and lower regions of the liquid crystal display panel screen. FIG. 9C shows the moving image performance in that case. In the waveform of FIG. 9A, the high level period is the lighting period, and the low level is the extinguishing period. The cold cathode fluorescent lamp 2 facing the central region of the WXGA-class liquid crystal display panel screen having 768 pixel rows has a data writing start time (pixel row: image to Y ₂₅₇₎ to a pixel row provided in the central region. Lights up at the signal input time.
As shown in FIGS. 9 (B) and 9 (C), the cold cathode fluorescent lamps 2 facing the center of the screen are positioned at the top and bottom of the screen with reference to the intermittent lighting start timing (hereinafter referred to as blink timing). When the blink timing of the cathode fluorescent lamp 2 is changed, the moving image performance deteriorates at the center of the screen, and at the upper and lower portions of the screen, the blink timing is at the data writing start time to the pixel row provided in each area. Improve as you get closer.
In the upper area, the central area, and the lower area of the WXGA standard liquid crystal display panel screen, 256 pixel rows (scanning lines) are arranged.
On the other hand, on the horizontal axis of the graphs of FIGS. 9B and 9C, the lighting start time and the central area of each of the cold cathode fluorescent lamps 2 facing the upper area and the lower area of the liquid crystal display panel screen are shown. The time difference from the lighting start time of the opposing cold cathode fluorescent lamp 2 is indicated by the scanning line number described with reference to FIG.
Therefore, at the time when the horizontal axis of the graphs of FIGS. 9B and 9C becomes 256 lines, the blink timing of the cold cathode fluorescent lamps 2 positioned at the upper and lower portions of the screen is the upper region of the liquid crystal display panel screen and Synchronized with the start of data writing to the pixel row in the lower region. From this, it is considered that the moving image performance in the upper area and the lower area of the liquid crystal display panel screen is the best in synchronism with data writing in each area.
In the upper and lower parts of the LCD panel screen, the video performance improves because the timing of blinking matches the data writing, but the video performance deteriorates in the center of the screen due to the light leakage from the top and bottom and the lighting timing in the center. It is thought that there is.

In FIG. 10A, the blink timing of the cold cathode fluorescent lamp 2 facing the upper and lower parts of the liquid crystal display panel screen is synchronized with the start of data writing to the pixel rows arranged at the upper and lower parts of the screen. Show the case. In this specification, such a backlight driving sequence is hereinafter referred to as “sequential blink of data write synchronization”. When the backlight is operated with sequential blinking of data writing, light leakage at the top and bottom of the screen concentrates in the central light-off period, and conversely, light leakage does not occur in the central light-up period.
For this reason, the luminance during the lighting period at the center of the screen decreases, and conversely, the luminance increases during the extinguishing period. Therefore, it is considered that the luminance response waveform is as shown in FIG.
Therefore, the moving image characteristics at the center of the screen are better when light leakage from above and below is concentrated in the lighting period at the center of the screen, and there is a trade-off relationship between the improvement of moving image characteristics at the top and bottom of the screen. .
For this reason, it is necessary to adjust the blink timing of the cold cathode fluorescent lamps 2 located at the upper and lower portions of the screen so as to minimize the deterioration at the center of the screen.
As shown in FIG. 10B, each cold cathode fluorescent lamp 2 is turned on so that the cold cathode fluorescent lamp 2 facing the lower part of the screen is turned on during the extinguishing period of the cold cathode fluorescent lamp 2 facing the upper part of the liquid crystal display panel screen. When the blink timing is adjusted, during the lighting period of the cold cathode fluorescent lamp 2 facing the center of the screen, from at least one of the cold cathode fluorescent tube 2 facing the top of the screen and the cold cathode fluorescent tube 2 facing the bottom of the screen to the center of the screen. Light leaks. Further, during the extinguishing period of the cold cathode fluorescent lamp 2 facing the center of the screen, light leakage to the center of the screen is caused by either the cold cathode fluorescent tube 2 facing the upper part of the screen or the cold cathode fluorescent tube 2 facing the lower part of the screen. It occurs only from one side, and no light leaks to the center of the screen from both sides.

The backlight driving sequence shown in FIG. 10B is a desirable driving method of the liquid crystal display device of this embodiment.
A luminance response waveform measured at the center of the screen of the liquid crystal display device according to this embodiment in which the backlight is operated in the drive sequence shown in FIG. 10B is shown by a waveform (a) in the graph of FIG. FIG. 11 shows a luminance response waveform (b) of the liquid crystal display device in which the backlight shown in FIG. 7 is blink-operated collectively, and a liquid crystal display device in which the backlight is sequentially blinked in synchronization with data writing (FIG. 10). The luminance response waveform (c) of (A)) is also shown for comparison. In the luminance response waveform in this embodiment, as shown in FIG. 11, the peak luminance is improved and the base luminance is decreased as compared with the case where the backlight is sequentially blinked in synchronization with data writing.
For this reason, the driving method of the liquid crystal display device according to the present embodiment can improve the moving image characteristics and suppress the display luminance as compared with the driving method of the liquid crystal display device in which the backlight is operated in a sequential blink synchronized with data writing. . In addition, the driving method of the liquid crystal display device according to the present embodiment is inferior to the driving method of the liquid crystal display device in which the backlight is operated in a collective blink at the peak luminance and base luminance at the center of the screen, but the luminance waveform is The aspect ratio is sufficient to maintain an impulse-like image display even in the center of the screen.
12 (A) to 12 (C), the moving image performance and brightness of images displayed by the driving method of the liquid crystal display device according to the present embodiment and the driving method of the liquid crystal display device in which the backlight is operated in a blinking manner, respectively. The reduction rate and chromaticity value change are compared at the top, center, and bottom of the screen.

FIG. 12A shows a comparison of moving image performance. As shown in FIG. 12A, the driving method of the liquid crystal display device according to the present embodiment (a line graph plotted with black circles and black squares) is a batch blink (white circles and white squares plotted with respect to moving image performance). Compared to the line graph), an improvement of 15% was observed at the top of the screen, but an improvement of 12% was observed at the bottom of the screen. Therefore, in the moving image characteristics, the driving method of the liquid crystal display device according to the present embodiment has almost reached the target level at the top and the center of the screen.
FIG. 12B shows a comparison of luminance reduction rates. As shown in FIG. 12B, the driving method of the liquid crystal display device according to the present embodiment (a line graph plotted with a square) is higher at the top of the screen than a collective blink (a line graph plotted with a rhombus). Although the luminance reduction rate was suppressed to 17%, no significant difference was observed in the luminance reduction rate at the center of the screen and at the bottom of the screen. However, in the method for driving the liquid crystal display device according to the present embodiment, by increasing the black insertion rate, it is possible to further suppress the luminance reduction rate at the center of the screen and at the bottom of the screen, compared to the collective blink. In addition, the luminance difference between the upper part of the screen and the center, which was a problem with collective blinking, can be reduced from 14.8% to 5.1%.
FIG. 12C shows a comparison of chromaticity value changes. As shown in FIG. 12 (C), the chromaticity value change of 0.013 at the maximum generated in the collective blink (a line graph plotted with white circles and white squares) is a driving method of the liquid crystal display device according to the present embodiment ( The maximum value was reduced to 0.005 by the black circles and the black line plots), and the target was achieved.
From the above results, the sequential blink when black is inserted turns on at least one of the light source facing the upper part of the screen and the light source facing the lower part of the screen and faces the center of the screen during the lighting period of the light source facing the center of the screen. By driving the backlight so that both the light source facing the upper part of the screen and the light source facing the lower part of the screen do not turn on at the same time during the light-off period, the degradation of video performance at the center of the screen is minimized and The moving image performance and luminance characteristics of the part can be improved.

With normal driving at fV = 60 Hz, a data writing time difference of about 16 ms occurs at the top and bottom of the screen.
When the upper, middle and lower parts of the screen are divided into three parts, if the cold cathode fluorescent lamps 2 located at the upper, middle and lower parts of the screen are blinked with a lighting period of 50% duty, the upper part of the screen is displayed. After the cold cathode fluorescent lamp 2 is turned off, the lower cold cathode fluorescent lamp 2 is turned on about 2 ms later.
For this reason, in the central portion of the screen, the period when the upper and lower cold cathode fluorescent lamps 2 are turned on is longer when the cold cathode fluorescent lamp 2 is turned off than when the cold cathode fluorescent lamp 2 is turned on.
Even when the cold cathode fluorescent lamp 2 is turned on only at the top or bottom of the screen, the light at the top and bottom of the screen affects the center of the screen due to light leakage from the backlight.
Since it is necessary to obtain the best moving image performance at the center of the screen, it is necessary to first adjust the cold cathode fluorescent lamp 2 at the center of the screen to be lit at an optimal timing.
However, with this adjustment alone, due to the light leakage from above and below, the impulse-like luminance waveform at the center of the screen changes, and the moving image performance deteriorates.
On the other hand, in the present embodiment, the lighting end time of the cold cathode fluorescent lamp 2 located at the upper part of the screen is matched with the lighting disclosure time of the cold cathode fluorescent lamp 2 located at the lower part of the screen, By avoiding a gap between the lighting period of the cold cathode fluorescent lamp 2 positioned and the lighting period of the cold cathode fluorescent lamp 2 positioned at the bottom of the screen, the influence on the center of the screen is minimized and the screen The characteristics at the top and bottom can be improved.
In the above-mentioned patent document 1, it is described in the prior art column that the moving image performance is improved by intermittently lighting the backlight in synchronization with the frame period. However, this patent document does not disclose any blinking sequence as in the present embodiment.

Video data is sent to the liquid crystal display device mounted on the television receiver at a frequency of 60 Hz. For this reason, the liquid crystal display device is normally driven with a vertical synchronizing signal: fV = 60 Hz. Therefore, between the video signal input (data writing) to the top (pixel row: Y ₀₀₁ ) of the screen and the video signal input to the bottom (pixel row: Y _MAX ... Y _{768 in the} WXGA standard) A time difference of about 16 ms occurs. Accordingly, when the screen is divided into the upper part, the center part, and the lower part, the cold cathode fluorescent lamps 2 (or a group thereof) disposed in the upper, middle, and lower areas of the screen according to the data writing timing difference of each part are turned on. When the blink operation is performed with 50% duty, the cold cathode fluorescent lamp 2 at the upper part of the screen is turned off, and the lower cold cathode fluorescent lamp 2 is turned on after about 2 ms. For this reason, in the center part of the screen, the lighting period of the cold cathode fluorescent lamp 2 at the upper part of the screen and the lower part of the screen becomes longer in the period when the cold cathode fluorescent lamp 2 in the central part is turned on.
Even when only one of the cold cathode fluorescent lamps 2 (or a group thereof) arranged at the upper part of the screen and the cold cathode fluorescent lamps 2 (or a group thereof) arranged at the lower part of the screen is lit, each cold cathode fluorescent lamp 2 The light leaking from the liquid crystal display panel to the center of the screen affects the quality of the display image at the center of the screen. When displaying moving images on a liquid crystal display device, it is necessary to obtain the best moving image performance at the center of the screen. Therefore, first, adjustment is made to light the cold cathode fluorescent lamp 2 arranged at the center of the screen at the optimal timing. There is a need to do. However, only with this adjustment, due to the influence of light leakage from the top and bottom of the center of the screen, the impulse-like luminance waveform at the center of the screen changes, and the moving image performance deteriorates.
On the other hand, in the present embodiment, the lighting end time of the cold cathode fluorescent lamp 2 located at the upper part of the screen is matched with the lighting disclosure time of the cold cathode fluorescent lamp 2 located at the lower part of the screen, so that In the lighting period of the cold cathode fluorescent lamp 2 positioned, the backlight is driven so that both the cold cathode fluorescent lamp 2 positioned at the upper part and the lower part of the screen are not turned off. In other words, during the lighting period of the light source in the center of the screen, the backlight is driven so that there is no time gap between the lighting time of the light source facing the upper part of the screen and the lighting time of the light source facing the lower part of the screen. Set the sequence.

In addition, from the essence of the present invention, only the lighting period of the light source facing the center of the screen may overlap the lighting period of the light source facing the upper part of the screen and the lighting period of the light source facing the lower part of the screen. When light enters the center of the screen from the surroundings during the lighting period of the light source facing the center of the screen, the peak luminance at the center of the screen is increased. However, in light of the improvement in video performance and suppression of luminance reduction at the top and bottom of the screen, which is the original purpose of the light source facing the top of the screen and the light source facing the bottom of the screen, these lighting periods face the center of the screen. The overlapping time in the lighting period of the light source is limited.
In the light source lighting operation according to the present embodiment described above, in the light extinguishing period of the light source facing the center of the screen, the overlap between the lighting time of the light source facing the upper part of the screen and the lighting time of the light source facing the lower part of the screen is avoided. It is important to suppress the base brightness at the center of the screen. In this way, the influence of the light source located at the top of the screen and the light source located at the bottom of the screen on the image display at the center of the screen is minimized, and the image display characteristics at the top and bottom of the screen are improved. .
In the above-mentioned patent document, it is described in the prior art column that the moving image performance is improved by intermittently lighting the backlight in synchronization with the frame period. However, this patent document does not disclose any backlight blinking sequence as in the present embodiment.

FIG. 23 shows the backlight driving sequence according to the present embodiment superimposed on the liquid crystal display panel driving sequence with a black insertion rate of 42% shown in FIG. In FIG. 23, the horizontal axis indicates a time axis, and the pixels are arranged in the order of addresses of pixel rows (scanning lines) vertically scanned along the vertical axis. 768 pixel rows: a liquid crystal display panel Y ₀₀₁ to Y ₇₆₈ are arranged in the vertical scanning direction, the pixel row: the top of the screen Y ₀₀₁ to Y ₂₅₆ is arranged, the pixel row: the Y ₂₅₇ to Y ₅₁₂ The center of the screen arranged side by side and the pixel rows: Y _{513 to} Y ₇₆₈ are divided into the lower part of the screen, and the upper light source (fluorescent tube Lamp 1 to Lamp 4) shown in FIG. Lamp5 to Lamp8) and the lower light source (fluorescent tubes Lamp9 to Lamp12) face each other.
The upper light source performs a so-called blinking operation in which the light is turned on in a period in which the “row” corresponding to the upper part of the screen in FIG. 23 is shaded and turned off in other periods. The central light source is turned on in a period in which “row” corresponding to the center of the screen in FIG. 23 is shaded, and is turned off in other periods. The lower light source is turned on in a period in which “row” corresponding to the lower part of the screen in FIG. 23 is shaded, and is turned off in other periods. For example, in the Nth frame period, the upper light source, the central light source, and the lower light source start lighting in this order in response to vertical scanning in which a video signal is input to the pixel row. Thus, the upper light source, the central light source, and blink timing BT U of the lower light _source, BT _M, BT _L is an upper light source, the central light source, and the left end of the lighting period of the lower light source becomes a time position.

In the backlight driving sequence, the blink timings BT _U , BT _M , and BT _L are set so that the lighting period of the upper light source overlaps the lighting period of the lower light source in the lighting period of the central light source. The lighting of the central light source as a reference for the driving sequence is started when the first 600line in the scanning line number after the video signal input to the screen center of the pixel rows of a predetermined time t _M has elapsed since the completion The In accordance with this, the lighting of the upper light source is started after a predetermined time t _U (where t _U > t _M ) has elapsed from the completion of the video signal input to the pixel row at the top of the screen. The processing is started after a predetermined time t _L (where t _M > t _L ) has elapsed since the completion of video signal input to the pixel row at the bottom of the screen. Each light source is sequentially blinked under the condition that the ratio (Duty) of the lighting period to the frame period is 50%. Accordingly, during the turn-off period of the central light source, only one of the upper light source and the lower light source is turned on, or both are turned off.
The backlight driving sequence shown in FIG. 23 pays attention to the fact that there is a delay in the response of the liquid crystal layer to the video signal and the blanking signal, and the blink timings BT _U , BT _M , BT _L of the respective light sources correspond to the pixel rows. The input of the blanking signal to the corresponding pixel row is started in each lighting period with a delay from the video signal input start time. Therefore, at the upper end of the screen (pixel row: Y ₀₀₁ ), the lighting start of the upper light source is delayed with respect to the video signal input, and the blanking signal is input while the upper light source is turned on. At the lower end of the screen (pixel row: Y ₇₆₈ ), the lower light source is turned off before the light transmittance of the liquid crystal layer reaches a value corresponding to the video signal. Therefore, although the image becomes dark at the upper and lower ends of the screen, it does not affect the display quality of the entire screen, and the peak luminance at the center of the screen is increased and the base luminance is suppressed.

When dividing the twelve fluorescent tubes shown in FIG. 20 (FIG. 19) into six light sources, two light sources (light sources including the fluorescent tubes 5 and 6 and the fluorescent tubes 7 and 8 are opposed to the center of the screen). For each of the included light sources), the two light sources sandwiching the light source are regarded as the upper light source and the lower light source described above, and the respective lighting periods are adjusted. Such adjustment of the lighting period is also performed when twelve fluorescent tubes are divided into four light sources by three.
Accordingly, a backlight having n light sources (n is a natural number and n ≧ 3) arranged in the scanning direction and extending in a direction crossing the scanning direction is provided opposite to the screen of the liquid crystal display panel. In the present embodiment, the liquid crystal display device is driven as follows.
(1) The n light sources arranged in the vertical scanning direction of the liquid crystal display panel are backlit according to sequential input of video signals (sequential selection of scanning lines) to pixel rows arranged along the vertical scanning direction of the liquid crystal display panel. The lighting is started sequentially from the light source provided in the upper area of the.
(2) The n light sources include a first light source opposed to the center of the screen of the liquid crystal display panel, a second light source and a third light source adjacent to each other above and below the first light source, and are arranged in a pixel row of the liquid crystal display panel. Lighting is started in the order of the second light source, the first light source, and the third light source within the frame period in which the video signal is input, and lighting is ended in this order.
(3) The lighting period of the second light source in the frame period ends during the lighting period of the first light source, and the lighting period of the first light source ends during the lighting period of the third light source. That is, the lighting period of the first light source overlaps with the lighting period of the second light source and the lighting period of the third light source on the time axis.
(4) The third light source starts lighting at or before the end of the lighting period of the second light source in the lighting period of the first light source.

FIGS. 13A to 13C show a variation of the blink timing sequentially as a variation of the present embodiment. A hatched rectangular wave period is a lighting period.
FIG. 13A has been described so far, and the blink interval (lighting period) of the cold cathode fluorescent lamps 2 located at the upper part, the center, and the lower part of the screen is constant.
However, when the cold cathode fluorescent lamp 2 located at the upper part of the screen and the cold cathode fluorescent lamp 2 located at the lower part of the screen are turned on without any interval, the light leakage to the center of the screen is uniform. As shown in B), the timing of the cold cathode fluorescent lamp 2 located at the center of the screen can be shifted.
As a result of FIG. 12 (B), the brightness at the top of the screen is lower than that at the center and the bottom, but it can be improved by shortening the blink timing (lighting disclosure time) of the cold cathode fluorescent lamp 2 located at the top of the screen. it can.
At this time, the lower part of the cold-cathode fluorescent lamp 2 located at the lower part of the screen also has a blink timing (lighting disclosure time) that is set earlier so that the lighting interval is not maintained, so that the characteristics at the center of the screen are maintained and the screen is maintained. The brightness gradient in the middle and lower can be adjusted.
In the above description, the blink ON duty is constant, but as shown in FIG. 13 (C), the blink on duty of the cold cathode fluorescent lamp 2 located at the top of the screen is lower than the screen. The blink ON duty (lighting period) of the cold-cathode fluorescent lamp 2 located in the position can be changed, and the brightness adjustment effect as in FIG. 13B can be obtained. Also, the adjustment can be made with emphasis on moving image performance instead of luminance.
As described above, in the present embodiment, when the plurality of cold-cathode fluorescent lamps 2 of the direct type backlight are divided into three groups and sequentially lit intermittently within one frame, the upper portion of the screen is not spaced. The cold-cathode fluorescent lamp 2 located at the bottom of the screen and the cold-cathode fluorescent lamp 2 located at the bottom of the screen are turned on, minimizing the degradation of video performance at the center of the screen due to light leakage from the top and bottom of the screen. The luminance gradient and chromaticity value change can be reduced.

In the present embodiment, the lighting disclosure time of the cold cathode fluorescent lamp 2 located at the lower part of the screen is the cold cathode located at the upper part of the screen after the lighting start time of the cold cathode fluorescent lamp 2 located at the upper part of the screen. By setting the time before the lighting end time of the fluorescent lamp 2 (that is, within the lighting period of the cold cathode fluorescent lamp 2 positioned at the upper part of the screen), the cold cathode fluorescent lamp 2 positioned at the upper part of the screen is not spaced apart The cold cathode fluorescent lamp 2 located at the bottom of the screen may be turned on.
Further, by combining the black insertion and the blinking backlight, it is possible to obtain a more impulsive display light such as a CRT and to improve the moving image performance.
In the above description, a case has been described in which a plurality of cold cathode fluorescent lamps 2 of a direct type backlight are divided into three groups and sequentially lighted intermittently within one frame, but the present invention is limited to this. Instead, the division number n of the plurality of cold cathode fluorescent lamps 2 of the direct type backlight may be 3 or more.
15 (A) to 15 (F), a plurality of cold cathode fluorescent lamps 2 of direct type backlights are arranged as shown in FIGS. 14 (A), 14 (B), and 14 (C). The moving image performance when dividing into 4, 4, and 6 and sequentially performing blinking is shown.
As shown in the figure, even when the plurality of cold cathode fluorescent lamps 2 of the direct type backlight are divided into 4 and 6, even when the plurality of cold cathode fluorescent lamps 2 of the direct type backlight is divided into 3, The result is almost the same.
Therefore, even when the number of divisions of the plurality of cold cathode fluorescent lamps 2 of the direct type backlight is increased, the uppermost portion and the lowermost portion in the selection direction of each display line when writing the video signal voltage to each pixel of the liquid crystal display panel 5 Then, it should be lit so that there is no interval.
Although the invention made by the present inventor has been specifically described based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. Of course.

It is a figure for demonstrating the parameter | index of the moving image performance in a liquid crystal display device. It is a graph which shows the relationship of (A) brightness | luminance response waveform at the time of black insertion, (B) black insertion rate, and moving image performance, respectively. It is a graph which shows the moving image performance by a blink start timing, and a luminance fall rate. It is a graph which shows (A) animation performance and brightness | luminance fall rate of black insertion + collective blink, and (B) chromaticity change. It is a figure which shows the relationship between the data writing time difference at the time of black insertion, and blink timing divided into (A) collective blink, (B) sequential blink, and (C) blink in this Embodiment. It is a graph which shows the moving image performance of an example of black insertion + sequential blink. It is a figure which shows the luminance response waveform in the case shown in FIG. It is a figure for demonstrating that the light leakage from the screen upper and lower sides influences display performance. (A) An explanatory diagram of the procedure for changing the blink timing at the upper and lower portions with reference to the blink timing at the center of the pixel array, and “shift (indicated by the number of scanning lines)” of the blink timing with respect to the center of the pixel array. And (C) a graph showing the results of evaluation of the relationship between the video performance and the case where the display color of each pixel is changed from white to black and the case where (C) the display color of each pixel is changed from black to white It is. The backlight lighting pattern 2 modes (A) and (B) for changing the blink timing at the upper and lower portions with reference to the blink timing at the center of the pixel array and the state of light leakage to the center of the pixel array in each of them. It is a figure explaining. 10A and 10B show luminance response waveforms (at the same time as (c) data writing and (a) equal light leakage) in the center of the pixel array when the backlight lighting patterns shown in FIGS. FIG. It is a graph which shows the moving image performance of the liquid crystal display device of the Example of this invention, a luminance fall rate, and a chromaticity change, (A) Moving image performance when adjusting up-and-down blink timing and equalizing up-and-down light leakage, B is a graph showing a luminance reduction rate and (C) a chromaticity change. It is a figure which shows three aspects (A), (B), (C) of the timing of blink sequentially as a modification of this Embodiment. It is a figure which shows the lighting state of each light source area when the several cold cathode fluorescent lamp of a direct type | mold backlight is divided into (A) 3 division, (B) 4 division, and (C) 6 division. In each of the three types of liquid crystal display devices having different divisions of the plurality of cold cathode fluorescent lamps in the direct type backlight shown in FIG. 14, the blink timings at the upper and lower portions are changed with respect to the blink timing at the center of the pixel array. The display performance of the screen is shown in (A) and (B) at the center of the screen (pixel array), (C) and (D) at the top of the screen, and (E) and (F) at the bottom of the screen. It is a graph which shows the result evaluated by the case where it changes from white to black, and the case where it changes from black to white. 1 is an exploded perspective view showing a schematic structure of a liquid crystal display module to which a characteristic structure of a liquid crystal display device according to the present invention and a characteristic driving method are applied. 1 shows an example of a configuration of a liquid crystal display device (liquid crystal display module) in which a driving method according to the present invention is used. FIG. 17 shows an example of a circuit configuration of a part of a pixel array provided in the liquid crystal display device. It is a top view which shows schematic structure when a direct type | mold backlight is integrated in a liquid crystal display device. The structure which divided | segmented the several cold cathode fluorescent lamp in a direct type | mold backlight unit into three groups (group) is shown. It is a wave form diagram of the input voltage signal to the main pixel row of a liquid crystal display panel. FIG. 22 is a signal diagram depicting the waveform diagram shown in FIG. 21 more macroscopically. FIG. 23 is a signal diagram in which the backlight driving sequence in the embodiment of the present invention is superimposed on the liquid crystal display panel driving sequence at a black insertion rate of 42% shown in FIG. 22.

Explanation of symbols

1 Flexible printed circuit board 2 Cold cathode fluorescent lamp 3 Reflector (lower frame)
4 Upper frame 5 Liquid crystal display panel 6 Intermediate frame 7 Optical member (diffusion sheet, lens sheet)
8, 11 Holding body 9 of cold cathode fluorescent lamp 2 High voltage side cable connector 10 Rubber bush 12 Low voltage side connector 13 Drive circuit board (TCON board)
14 Inverter circuit board 15 Low voltage side cable connector 19 Receiver circuit (image signal source)
20 Liquid crystal display device 21 Display control circuit 22 Frame memory 23 Scan driving circuit (vertical scanning circuit)
24 Data signal driving circuit (horizontal scanning circuit)
25 Backlight drive circuit 26 Backlight (lighting device)
201 Scanning line 202 Common signal line 203 Data signal line 204 Thin film transistor 205 Retention capacitor 206 Liquid crystal capacitor 207 Pixel

Claims (15)

A pixel matrix in which a plurality of pixels are two-dimensionally arranged in a first direction and a second direction crossing the first pixel, and a group of the plurality of pixels arranged in the second direction in the pixel matrix. A liquid crystal display panel having a plurality of pixel rows arranged in the first direction and sequentially selected from one end to the other end of the pixel matrix for each frame period, and facing the pixel matrix of the liquid crystal display panel; In a driving method of a liquid crystal display device comprising: an illumination device having a plurality of light sources divided into three light source regions arranged in the first direction and opposed to at least three groups of the pixel rows along the first direction,
The lighting period of the light source region for each frame period is selected when one of the at least three groups of the pixel row corresponding thereto is selected and the plurality of pixels belonging to the group of the pixel row receive a video signal. Starting sequentially,
The lighting period of the light source region for each frame period ends sequentially,
The at least three light source regions are a first light source region, a second light source region, and a third light source region, and the first light source region is the first direction of the pixel matrix in which the first group of the pixel rows is located. The second light source region is adjacent to the central portion in the first direction and is selected before the first group of pixel rows for each frame period. Opposite to the region of the pixel matrix in which two groups are located, the third light source region is selected adjacent to the central portion in the first direction and after the pixel row of the first group every frame period. Facing the other region of the pixel matrix where the third group of pixel rows is located,
The lighting period of the second light source region, the lighting period of the first light source region, and the lighting period of the third light source region start and end sequentially in this order,
The lighting period of the second light source region ends after the start of the lighting period of the first light source region, and the lighting period of the third light source region is after the start of the lighting period of the first light source region, and the first light source region 2. A driving method of a liquid crystal display device, which starts at or before the end of a lighting period of two light source regions.   2. The driving method of the liquid crystal display device according to claim 1, wherein a start time of a lighting period of the third light source region coincides with an end time of a lighting period of the second light source region.   2. The driving method of the liquid crystal display device according to claim 1, wherein lighting periods of the first light source region, the second light source region, and the third light source region in the frame period are the same.   2. The liquid crystal display according to claim 1, wherein one of the lighting periods of each of the first light source region, the second light source region, and the third light source region in the frame period is different from at least one of the other. Device driving method.   5. The driving method of the liquid crystal display device according to claim 4, wherein lighting periods of the first light source region, the second light source region, and the third light source region in the frame period are different from each other.   2. Each of the plurality of light sources is a tubular light source extending in the second direction, and the tubular light source is juxtaposed in the first direction in the lighting device. A method for driving a liquid crystal display device according to claim 1.   The plurality of tubular light sources are arranged in parallel in the first direction in at least one of the first light source region, the second light source region, and the third light source region. 7. A method for driving a liquid crystal display device according to 6.   Each of the plurality of pixels belonging to the first group of the plurality of pixel rows is in a first light source region, and each of the plurality of pixels belonging to the second group of the plurality of pixel rows is in a second light source region. 2. The driving method of the liquid crystal display device according to claim 1, wherein each of the plurality of pixels belonging to the third group of the pixel rows is opposed to the third light source region.   The plurality of light source regions are configured by arranging the second light source region, the first light source region, and the third light source region in this order from the one end to the other end of the pixel matrix. The method for driving a liquid crystal display device according to claim 1.   In the frame period, the plurality of pixel rows are selected again after capturing the video signal, and each of the plurality of pixels belonging to the reselected pixel row captures a voltage signal that reduces its luminance. The method for driving a liquid crystal display device according to claim 1.   11. The driving method of a liquid crystal display device according to claim 10, wherein the voltage signal causes each of the plurality of pixels belonging to the pixel row selected again to be displayed in black.   The time from the start time of capturing the video signal by the second group of pixel rows to the start time of the lighting period of the second light source is from the start time of capturing the video signal by the first group of pixel rows to the first time. The method for driving a liquid crystal display device according to claim 1, wherein the time is different from a time until a start time of a lighting period of the light source.   The time from the start time of capturing the video signal by the pixel row of the third group to the start time of the lighting period of the third light source is from the start time of capturing the video signal by the pixel row of the first group. The method for driving a liquid crystal display device according to claim 1, wherein the time is different from a time until a start time of a lighting period of the light source. A liquid crystal display panel having a pixel matrix in which a plurality of pixels are two-dimensionally arranged in a first direction and a second direction intersecting the first direction;
A plurality of pixel rows each composed of a group of the plurality of pixels arranged in the second direction, arranged in the first direction in the pixel matrix, and sequentially selected from one end to the other end of the pixel matrix for each frame period; ,
The liquid crystal display panel includes a plurality of light sources opposed to the pixel matrix, and the plurality of light sources are arranged in at least three light source regions arranged in the first direction and respectively opposed to at least three groups of the plurality of pixel rows. A method of driving a liquid crystal display device comprising a divided illumination device,
Selection of the at least three groups of the plurality of pixel rows corresponding to the lighting periods of the plurality of light source regions, respectively, and thereby an image of the group of pixels belonging to the selected group of the plurality of pixel rows In response to the start of signal acquisition, start sequentially
A group of the plurality of pixels belonging to the reselected one of the plurality of pixel rows by sequentially selecting the plurality of pixel rows again after the lighting period of the at least three light source regions facing each other is started. To capture the blanking signal to cancel the video signal,
The step of ending the lighting period of the at least three light source regions after each of the at least three groups of the plurality of pixel rows facing each of the light source areas starts to capture the blanking signal is repeated for each frame period. ,
The at least three light source regions are
(I) a first light source region facing a central region in the first direction of the pixel matrix in which a first group of the plurality of pixel rows is located;
(Ii) The pixels adjacent to the central region along the first direction, in which the second group of the plurality of pixel rows capturing the video signal is positioned before the first group of pixel rows every frame period. A second light source region facing the region of the matrix;
(Iii) The pixel matrix in which the third group of the plurality of pixel rows that captures the video signal after the first group of pixel rows is located in each frame period and is adjacent to the central region along the first direction. Divided into a third light source region facing the other region,
The lighting period of the second light source area, the lighting period of the first light source area, and the lighting period of the third light source area start and end sequentially in this order,
The lighting period of the second light source region ends after the start of the lighting period of the first light source region,
The lighting period of the third light source region starts after the lighting period of the first light source region and at or before the end of the lighting period of the second light source region, and the first light source in each frame period At least one of the lighting period of the second light source area and the lighting period of the third light source area after the end of the lighting period of the area and before the start of the lighting period of the first light source area in another subsequent frame period A driving method of a liquid crystal display device, wherein the driving method is interrupted. A plurality of pixels each having a pixel matrix that is two-dimensionally arranged along a first direction and a second direction intersecting the first direction; and from each group of the plurality of pixels arranged in the second direction. A plurality of pixel rows arranged in the first direction in the pixel matrix and sequentially selected from one end to the other end of the pixel matrix for each frame period; Illumination arranged opposite to the pixel matrix of the display panel, and the plurality of light sources divided into at least three light source regions arranged in the first direction and respectively opposed to at least three groups of the plurality of pixel rows. And a control unit including a display control circuit that supplies an image signal to the pixel matrix, and a light source drive circuit that controls driving of the plurality of light sources in response to a control signal from the display control signal. For example,
The control unit selects one of the at least three groups of the plurality of pixel rows corresponding to each of the plurality of light source regions for each frame period, and selects the selected group of the plurality of pixel rows. When the plurality of pixels to which the plurality of pixels start capturing video signals, the lighting periods of the plurality of light source regions are sequentially started, and the lighting periods of the plurality of light source regions are sequentially ended within the frame period, The first light source region facing the central region in the first direction of the pixel matrix where the first group of the plurality of pixel rows is located, the plurality selected before the first group of pixel rows for each frame period A second light source region that is located in the second direction of the pixel row and that faces the region of the pixel matrix adjacent to the central region along the first direction, and the pixel row of the first group for each frame period. later The at least three light source regions including a third light source region in which the third group of the plurality of selected pixel rows is located and facing the other region of the pixel matrix adjacent to the central region along the first direction. Use
For each frame period, the lighting period of the second light source region, the lighting period of the first light source region, and the lighting period of the third light source region are sequentially started and ended in this order,
The lighting period of the second light source region ends after the start of the lighting period of the first light source region, and the lighting period of the third light source region is set after the start of the lighting period of the first light source region and the second A liquid crystal display device that executes a process that starts at or before the end of the lighting period of the light source region.

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